Improved resin composition, process for manufacturing such a resin, and object comprising a polyester derived from such a resin

Abstract

In order to provide an improved biobased resin composition that can be processed relatively quickly, a multi-curable liquid resin composition is provided comprising polyester derived from - multi-functional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond, - saturated aliphatic polyol monomer with 2-15 carbon atoms, - saturated aliphatic polycarboxylic acid monomer with 3 to 15 carbon atoms, and - a curing agent, wherein the amount of multi-functional monomers is in the range of 5-50 wt.% calculated on the total amount of monomer in the composition, and the ratio between the total number of hydroxy groups and the total number of carboxylic acid groups is between 3:1 and 1:3.

Description

[0001] IMPROVED RESIN COMPOSITION, PROCESS FOR MANUFACTURING SUCH A RESIN, AND OBJECT COMPRISING A POLYESTER DERIVED FROM SUCH A RESIN

[0002] The invention relates to a resin composition comprising a polyester derived from a saturated aliphatic polyol monomer with 2-15 carbon atoms and a saturated aliphatic poly carboxy lie acid with 3-15 carbon atoms. The invention relates in particular to a biobased resin composition having one or more of a relatively low activation energy, a relatively fast curing mechanism, and providing good shape stability. The invention also relates to a process for manufacturing a resin, and an object comprising a polyester derived from a resin composition.

[0003] Resins are solid or highly viscous substances that can typically be converted into polymers (e.g. thermoset polymers). Resins can be of plant origin, such as amber, balsam, and copal, of animal origin, such as lac, but can also be synthetic.

[0004] Synthetic resins are industrially produced resins that typically convert into cross-linked polymers by curing. Synthetic resins include e.g. phenolic resin, melamine, alkyd resin, polyurethane resin, epoxy resin, silicones, and polyester resin. In order to undergo curing, the monomers and / or oligomers of the resin composition typically contain reactive end groups, such as hydroxy groups and carboxyl groups in case of an alkyd resin or epoxy groups in case of epoxy resin.

[0005] Resins find application in a variety of fields. They can e.g. be used as adhesives, coating, or in the production of composite materials, laminates, wood panels, packaging material, and 3D-printed material. Curing can for example be induced by the addition of a hardener, by UV- light or by heating.

[0006] Conventional resins have a number of advantages. Depending on their nature, they may for example cause the slow release of formaldehyde, and unreacted monomers, oligomers and solvent carriers may be potential health hazards. Therefore, biobased resins, i.e. resins made completely or substantially from biological resources, are attractive from an environmental viewpoint.

[0007] The use of biobased resins comprising a polyester derived from a saturated aliphatic polyol monomer with 2-15 carbon atoms and a saturated aliphatic polycarboxylic acid with 3-15 carbon atoms has been described in the art. WO2012140237 describes a composite material comprising 10-98 wt. % of a bio-based particulate or fibrous filler and at least 2 wt. % of a polyester derived from an aliphatic polyalcohol with 2-15 carbon atoms and a polycarboxylic acid, wherein the polycarboxylic acid comprises at least 10 wt. % of tricarboxylic acid. In particular, the filler may be selected from wood chips, wood flakes, sawdust, pulp, e.g., pulp of (recycled) paper or other fiber pulp, and plant-derived fibers such as cotton, linen, flax, and hemp.

[0008] WO2012140239 describes a composite material which comprises the same polymer material as the composite of WO2012140237, but in this case a synthetic filler is used, preferably selected from one or more of ceramic, including glass, in particular glass fibers, polymer, in particular polymer fibers, and carbon, in particular carbon fibers.

[0009] WO2012052385 describes the same polymer, in the form of a foam.

[0010] W02020152082 describes the application of the same polymer in biodegradable containers or plate material. WO2021105143 describes a composition comprising a polyester derived from an aliphatic polyol with 2-15 carbon atoms and an aliphatic polycarboxylic acid with 3-15 carbon atoms for use in 3D printing, while W02022043330 describes a process for manufacturing a shaped object through a winding process using a resin comprising at least 50 wt.% of polyester derived from an aliphatic polyol with 2-15 carbon atoms and an aliphatic polycarboxylic acid with 3-15 carbon atoms.

[0011] Thus, it is clear that biobased resins comprising a polyester derived from a saturated aliphatic polyol monomer with 2-15 carbon atoms and a saturated aliphatic poly carboxy lie acid with 3-15 carbon atoms are used in a wide variety of applications. However, a problem of these biobased resins is that they generally have a relatively high activation energy and slow curing speed. Therefore, the curing of a biobased resin can be a relatively slow and energy consuming process.

[0012] Thus, there is a need for an improved biobased resin composition that can be processed relatively quickly. The present invention provides such a resin composition.

[0013] Summary of the invention

[0014] The present invention provides a multi-curable liquid resin composition comprising polyester derived from

[0015] - multi-functional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond,

[0016] - saturated aliphatic polyol monomer with 2-15 carbon atoms, and

[0017] - saturated aliphatic poly carboxylic acid monomer with 3 to 15 carbon atoms, and

[0018] - a curing agent wherein the amount of multi-functional monomers is in the range of 5-50 wt.% calculated on the total amount of monomer in the composition, and the ratio between the total number of hydroxy groups and the total number of carboxylic acid groups is between 3:1 and 1 :3, wherein the saturated aliphatic polycarboxylic acid monomer comprises at least 70 wt.% of tricarboxylic acid, calculated on the total amount of saturated aliphatic polycarboxylic acid monomer.

[0019] “Gel time” is the time required under specific conditions for a resin system to reach its gel point at which the system loses fluidity and forms a gel. Once the gel point has been reached, the gel is shape stable.

[0020] It was found that the gel time of the resin according to the invention was reduced compared to the resin known from e.g. WO2012140237. Thus, the processing time of the resin according to the invention is reduced, and a shape stable resin can be obtained faster. For example, pressing times or demoulding times can be reduced. Because the resin according to the invention can be processed quicker, products manufactured using this resin can also be manufactured faster. For instance, the pressing time of wood panels manufactured using the resin according to the invention can be reduced compared to wood panels manufacture using the resin described in WO2012140237.

[0021] Furthermore, when the bending strength and internal bond of plywood prepared using the resin according to the invention was higher than when the plywood was prepared using the reference resin known from WO2012140237 and under the same pressing times.

[0022] Finally, the resin according to the invention may be derived in its entirety from renewable vegetable resources. It does not have to rely on fossil fuels.

[0023] The present invention also provides a process for manufacturing a multi-curable resin composition, a process for manufacturing a solid cured resin composition, and an object comprising polyester.

[0024] Detailed description

[0025] The polyester

[0026] The present invention involves a polyester derived from (i) a multi-functional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond, (ii) a saturated aliphatic polyol monomer with 2-15 carbon atoms, and (iii) a saturated aliphatic polycarboxylic acid monomer with 3 to 15 carbon atoms, wherein the amount of multi-functional monomers is in the range of 5-50 wt.% calculated on the total amount of monomer in the composition.

[0027] (i) The multi-functional monomer

[0028] The multi-functional monomer comprises at least one reactive group selected from hydroxy groups and carboxyl groups, and at least one reactive unsaturated carbon-carbon bond. “Multi-functional” means that the monomer can take part in multiple curing reactions. At one hand the hydroxy group and / or the carboxyl group can react in an esterification reaction under the formation of a condensation product such as water, while on the other hand the unsaturated carbon-carbon bond can take part in a secondary curing mechanism, such as a radical-initiated reaction, UV curing, Michael addition reaction, or Diels-Alder reaction. The presence of the multi-functional monomer contributes to a reduced gel-time of the liquid resin composition, which can lead to a reduced processing time.

[0029] The amount of multi-functional monomer in the resin composition is in the range of 5-50 wt.%, calculated on the total amount of monomer in the composition. It was found that a minimum amount of 5 wt.% multi-functional monomer, calculated on the total amount of monomer in the composition, was required to obtain a reduced curing time compared to resin not comprising multi-functional monomer. An amount of more than 50 wt.% multi-functional monomer calculated on the total amount of monomer in the composition may lead to a polymer with different properties. Preferably, the multi-functional monomer is present in the range of 5-50, more preferable 7.5-40 wt.%, most preferably in the range of 10-20 wt.%, calculated on the total amount of monomer in the composition.

[0030] The multi-functional monomer may be aromatic or aliphatic. In some embodiments, the multifunctional monomer consists of carbon, oxygen and hydrogen atoms. In other embodiments, the multi-functional monomer comprises nitrogen atoms, sulfur atoms, or both.

[0031] Suitable multi-functional monomers for use in the present invention include multi-functional polycarboxylic acid monomers with 2 to 15 carbon atoms comprising at least one unsaturated carbon-carbon bond, and multi-functional hydroxy-functional monomers with 2- 15 carbon atoms comprising at least one unsaturated carbon-carbon bond, and combinations thereof. Suitable multi-functional polycarboxylic acid monomers include for example aconitic acid (both cis and trans), itaconic acid, citraconic acid, muconic acid, hydromuconic acid, fumaric acid, maleic acid, synaptic acid, ferulic acid, caffeic acid, coumaric acid, and anhydrides and alkylated variants thereof. Other suitable multi-functional polycarboxylic acid monomers are (meth)acrylic acids, such as (meth)acrylic acid, methyl (meth)acrylic acid, ethyl (meth)acrylic acid, butyl (meth)acrylic acid, hydroxyethyl (meth)acrylic acid, and fatty acids, such as oleic acid and linolenic acid.

[0032] Preferably, the multi-functional polycarboxylic acid is selected from aconitic acid, itaconic acid, citraconic acid, muconic acid, hydromuconic acid, 3-carboxy-cis,cis-muconic acid, maleic acid, and fumaric acid, and anhydrides and alkylated variants thereof. These are industrially available.

[0033] It is noted that under highly reactive conditions such as high temperature, high acidity, long processing times, and the presence of a catalyst such as p-toluene sulfonic acid (PTSA) up to 4 wt.%, calculated on the total amount of monomer in the composition, aconitic acid may also be formed in situ from dehydration of citric acid. Under milder conditions, attractive from an economical point of view, generally at most 2 wt.%, or even at most 1 wt.% or at most 0.5 wt.%, calculated on the total amount of monomer in the composition, aconitic acid is formed.

[0034] Suitable multi-functional hydroxy-functional monomers include for example hydroxy-ethyl acrylate, hydroxy-ethyl methacrylate, vinyl-alcohol, allyl-alcohol, glycerol-tri-(meth)acrylate, trimethylolpropane-trimethacrylate and 1 ,4-butynediol, N-hydroxyethyl citraconimide, N- carboxymethyl citraconimide, N-hydroxyethyl maleamic acid, N-hydroxyethyl methyl- maleamic acid.

[0035] (ii) The saturated aliphatic polyol monomer

[0036] In addition to the multi-functional monomer, the resin composition also comprises a saturated aliphatic polyol monomer with 2-15 carbon atoms, and a saturated aliphatic polycarboxylic acid monomer with 3-15 carbon atoms. The polyol and polycarboxylic acid can react in an esterification reaction under the formation of a condensation product such as water or alkylalcohol.

[0037] The saturated aliphatic polyalcohol does not comprise any aromatic moieties. In an embodiment the polyol is an aliphatic polyalkanol containing only C, H, and O atoms. In another embodiment, the polyol comprises one or more heteroatoms, such as one or more nitrogen atoms and / or one or more sulfur atoms.

[0038] The saturated aliphatic polyol monomer used in the present invention comprises at least two hydroxyl groups, in particular at least three hydroxyl groups. In general, the number of hydroxyl groups will be 10 or less, more in particular 8 or less, or even 6 or less, in particular two or three.

[0039] The saturated aliphatic polyol monomer comprises preferably at least 50 mole% of an aliphatic polyol monomer comprising at least three hydroxyl groups, calculated on the total amount of saturated aliphatic polyol monomer, whether or not in combination with a saturated aliphatic polyol comprising two hydroxyl groups, a second saturated aliphatic polyol monomer comprising three or more hydroxyl groups, and mixtures thereof. In one embodiment the saturated aliphatic polyol monomer comprises at least 70 mole% of polyol monomer comprising at least three hydroxyl groups, calculated on the total amount of saturated aliphatic polyol monomer, more in particular at least 90 mole%, or even at least 95 mole%, calculated on the total amount of saturated aliphatic polyol monomer. In one embodiment the saturated aliphatic polyol monomer consists essentially of saturated aliphatic polyol monomer comprising at least three hydroxyl groups, wherein the word “essentially” means that other saturated aliphatic polyols may be present in amounts that do not affect the properties of the material.

[0040] The polyalcohol has 2-15 carbon atoms. More in particular, the polyalcohol has 3-10 carbon atoms.

[0041] Examples of suitable aliphatic polyols are 1 ,2-propane diol, 1 ,3-propane diol, 1 ,2-ethane diol, 1 ,4-butanene diol, glycerol, sorbitol, xylitol, pentaerythritol, mannitol, glucose, fructose, mannose, galactose, hydroxyalkyl amides such as Prim id XL-552, isosorbide, isomannide, isoidide, and mixtures of two or more thereof. Glycerol, sorbitol, xylitol, and mannitol are preferred examples of suitable aliphatic polyols. Glycerol is the most preferred example of a suitable aliphatic polyalcohol. One reason for this is that glycerol has a melting point of 20 °C, which allows easy processing (compared to, e.g., xylitol, sorbitol, and mannitol, which all have melting points above 90 °C). Moreover, glycerol is easily accessible and results in polymers having desirable properties. Accordingly, it is preferred for the polyol to consist for at least 50 mole% of glycerol, xylitol, sorbitol, or mannitol, in particular of glycerol, preferably at least 70 mole%, more in particular at least 90 mole%, or even at least 95 mole%. In one embodiment the polyalcohol consists essentially of glycerol. As used herein, “consists essentially of” means that other components (here: other aliphatic polyols) may be present in amounts that do not detrimentally affect the properties of the material.

[0042] (Hi) The saturated aliphatic polycarboxylic acid

[0043] The polycarboxylic acid does not comprise aromatic moieties. In an embodiment the polycarboxylic acid is an aliphatic polycarboxylic acid containing only C, H, and O atoms. In another embodiment the polycarboxylic acid comprises one or more heteroatoms, such as one or more nitrogen atoms and / or one or more sulfur atoms.

[0044] The saturated aliphatic polycarboxylic acid monomer comprises at least two carboxylic groups, in particular at least three carboxylic groups. In general, the number of carboxylic acid groups will be 10 or less, more in particular 8 or less, or even 6 or less.

[0045] The polycarboxylic acid has 3-15 carbon atoms. More in particular, the polycarboxylic acid has 3-10 carbon atoms.

[0046] In one embodiment a dicarboxylic acid is used. The dicarboxylic acid, if used, may be any dicarboxylic acid which has two carboxylic acid groups and, in general, at most 15 carbon atoms. Examples of suitable dicarboxylic acids include malic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, oxalic acid, suberic acid, azelaic acid, and mixtures of two or more thereof.

[0047] In one embodiment a tricarboxylic acid is used. The tricarboxylic acid, if used, may be any tricarboxylic acid which has three carboxylic acid groups and, in general, at most 15 carbon atoms. Examples include citric acid, isocitric acid, and tricarballylic acid. The use of citric acid is considered preferred, both for reasons of costs and of availability.

[0048] In one embodiment a tetracarboxylic acid is used. The tetracarboxylic acid, if used, may be any tetracarboxylic acid which has four carboxylic acid groups and, in general, at most 15 carbon atoms. Examples include cyclobutene tetracarboxylic acid.

[0049] Where applicable the saturated aliphatic polycarboxylic acid may be provided completely or in part in the form of an anhydride, e.g., citric acid anhydride, or in the form of an alkyl-ester, e.g. tri-methyl citrate. It has been found that the use of tricarboxylic acid results in a polyester with attractive properties. Therefore, in one embodiment, the polycarboxylic acid comprises at least 10 wt.% of tricarboxylic acid, calculated on the total amount of saturated aliphatic polycarboxylic acid, whether or not in combination with dicarboxylic acids, other tricarboxylic acids, and mixtures thereof. In one embodiment the poly carboxylic acid comprises at least 30 wt.% of tricarboxylic acid, calculated on the total amount of saturated aliphatic polycarboxylic acid, preferably at least 50 wt.%. In one embodiment the amount of tricarboxylic acid is at least 70 wt.%, more in particular at least 90 wt.%, or even at least 95 wt.%, calculated on the total amount of saturated aliphatic poly carboxy lie acid. In one embodiment the polycarboxylic acid consists essentially of tricarboxylic acid, wherein the word essentially means that other acids may be present in amounts that do not affect the properties of the material.

[0050] In another embodiment of the invention the polycarboxylic acid comprises at least 10 wt.% of dicarboxylic acid, calculated on the total amount of acid, preferably at least 30 wt.%, more preferably at least 50 wt.%. In one embodiment the amount of dicarboxylic acid is at least 70 wt.%.

[0051] In one embodiment the saturated aliphatic polycarboxylic acid comprises a combination of at least 10 wt.% of tricarboxylic acid and at least 2 wt.% of dicarboxylic acid, more in particular at least 10 wt.% of tricarboxylic acid and at least 5 wt.% of dicarboxylic acid, or at least 10 wt.% of tricarboxylic acid and at least 10 wt.% of dicarboxylic acid. In this embodiment the weight ratio between the two types of acid may vary within wide ranges, depending on the properties of the desired material. In one embodiment, the dicarboxylic acid makes up between 2 and 90 wt.% of the total of dicarboxylic and tricarboxylic acid, in particular between 5 and 90 wt.%, more in particular between 10 and 90 wt.%, depending on the properties of the desired material. It is noted that the preferred ranges for the tricarboxylic acid specified above are also applicable to this embodiment. It has been found that the use of a tricarboxylic acid, in particular citric acid, results in the formation of a high-quality composite material, in particular in combination with the use of a triol such as glycerol.

[0052] The molar ratio between the multi-functional monomer, saturated aliphatic polyol monomer and the saturated aliphatic polycarboxylic acid monomer in the resin composition is governed by the ratio between the number of hydroxyl and carboxylic acid groups. In general, the ratio between the total number of hydroxyl groups and the total number of carboxylic acid groups is between 3:1 and 1 :3 to support the formation of a polymer from the monomers. More in particular, the ratio may be between 2:1 and 1 :2, more specifically between 1.5:1 and 1 :1.5, more preferably between 1.1 :1 and 1 :1.1. Most preferably the molar ratio is about 1 :1. The molar ratio between the multi-functional monomer, saturated aliphatic polyol monomer and the saturated aliphatic polycarboxylic acid monomer in the resin composition is also governed by the ratio between the total number of reactive unsaturated carbon-carbon bonds and the total number of hydroxyl groups. In general, the ratio between the total number of reactive unsaturated carbon-carbon bonds and the total number of hydroxyl groups is between 1 :2 and 1 :65. More in particular, the ratio may be between 1 :5 and 1 :60, preferably between 1 :7.5 and 1 :40, more preferably between 1 :10 and 1 :30, even more preferably between 1 :10 and 1 :20.

[0053] (iv) Curing agents

[0054] In an embodiment, the resin composition comprises a curing agent. The curing agent is added to promote a crosslinking reaction with the unsaturated bond of the multi-functional monomer, via, for example, radical curing, Dielz-Alder reaction, or Michael addition (e.g. thio-, aza-, oxo-, carba-Michael) reaction. Preferably, the curing agent is selected from a curing agent comprising at least one unsaturated carbon-carbon bond, a curing agent comprising at least one thiol group, a radical initiator, and combinations thereof. The molar ratio between the curing agent and the total number of reactive unsaturated carbon-carbon bonds is preferably between 3:1 and 1 :3. More in particular, the ratio may be between 2:1 and 1 :2, more specifically between 1.5:1 and 1 :1.5, more preferably between 1.1 :1 and 1 :1.1. The ideal molar ratio is about 1 :1.

[0055] The curing agent comprising at least one unsaturated carbon-carbon bond promotes the crosslinking of unsaturated carbon-carbon bonds via Diels-Alder cross-coupling reaction. Suitable curing agents comprising at least one unsaturated carbon-carbon bond include for example furfural and 2-hydroy methyl furfural.

[0056] A curing agent comprising at least one unsaturated carbon-carbon bond such as furfural and 2- hydroxy methyl furfural is in particular preferred when a (thermo)reversible crosslinking of the unsaturated carbon-carbon bonds of the multi-functional monomers is desired. Furfural is preferred for its general availability.

[0057] The curing agent comprising at least one thiol group can promote the crosslinking between unsaturated carbon-carbon double bonds via Thio-Michael addition reactions. The curing agent comprising at least one thiol group may be a monothiol-compound or a dithiol- compound. The curing agent comprising at least one thiol group may also have other functional groups, such as a hydroxy group, a carboxylic acid group, an ester group, an amine group, or a combination of one or more thereof.

[0058] Suitable curing agents comprising at least one thiol group are 1 ,4-butanedithiol, 1 ,6- hexanedithiol, cysteamine, mercapto-ethanol, mercapto-acetic acid, mercapto-propionic acid, glyceryl-mono-, bis-, and tri-thioglycolate.

[0059] The total amount of curing agent comprising at least one unsaturated carbon-carbon bond and the curing agent comprising at least one thiol group is generally about half the mole amount of the multi-functional monomer. Preferably, the total amount of curing agent comprising at least one unsaturated carbon-carbon bond and the curing agent comprising at least one thiol group is in the range of 2.5-25 wt.%, calculated on the total resin composition. More preferably, the amount of curing agent is in the range of 3.5-20 wt.%, even more preferably in the range of 5-10 wt.%, calculated on the total resin composition.

[0060] The radical initiator supports the crosslinking of unsaturated carbon-carbon bonds. Suitable radical initiators are for example a peroxide, a hydroperoxide, a ketonperoxide, an azoinitiator, an alkylperoxide, a dialkylperoxide, a di-acylperoxide, a per-acid, a per-ester, percarbonate, a persulphate, or an initer. Optionally, the peroxide is used as an encapsulated peroxide. Optionally, a co-promotor is used in combination with a peroxide, for example a metal-complex (e.g. cobalt, copper, iron) or amine (e.g. di-methylaniline). Preferably, the radical initiator is hydrogen peroxide, 2,5-dimethyl-2,5-di(tertbutylperoxy) hexane, or dilauroyl peroxide.

[0061] Preferably the radical initiator is present in an amount of 0.01-5 wt.% of the total resin composition. More preferably, the radical initiator is present in an amount of 0.025-2.5 wt.%, even more preferably in an amount of 0.05-1 wt.%, and most preferably in an amount of 0.05-0.75 wt.% of the total resin composition.

[0062] (v) Further optional components of the liquid resin

[0063] In an embodiment, the resin composition further comprises a radical scavenger (inhibitor). The radical scavenger inhibits or prevents premature curing by scavenging radicals, such as oxygen radicals, which may e.g. be formed in a hot and acidic environment, or by sunlight, or specific UV wavelengths and may promote premature crosslinking of unsaturated carboncarbon bonds. Examples of suitable radical scavengers are ascorbic acid, phenolic antioxidants such as butylated hydroxytoluene (BHT), 4-tert-buty I catechol, 4- methoxy phenol, disodium 4,5-dihydroxy-1 ,3-benzenedisulfonate, 2,2,4-trimethyl-1 ,2- dihydroquinoline (TMQ), hydroquinone, (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO), and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-hydroxy-TEMPO).

[0064] The radical scavenger may be present in an amount of 0.001 -2.5 wt.% based on the total weight of the liquid resin composition, preferably in an amount of 0.005-1 wt.%, and most preferably in an amount of 0.01-0.25 wt.% of the liquid resin composition.

[0065] In an embodiment, the resin further comprises a chelating agent. Examples of suitable chelating agents include ethylenediaminetetraacetic acid (EDTA), nitriloacetic acid (NTA), polyphosphate chelating agents, and others known in the art.

[0066] The chelating agent may be present in an amount of 0.001-5 wt.% based on the total weight of the liquid resin composition, preferably in an amount of 0.01 -2.5 wt.%, and most preferably in an amount of 0.1-1 wt.% of the liquid resin composition.

[0067] Optionally a suitable catalyst can be used for catalyzing the esterification reaction between hydroxy groups and acid groups. Such suitable catalysts are known in the art. Preferred catalysts are those that do not contain heavy metals. Useful catalysts are for example sodium hypophosphite and strong acids such as, but not limited to, hydrochloric acid, hydroiodic acid and hydrobromic acid, sulfuric acid (H2SO4), methanesulf one acid, nitric acid (HNO3), chloric acid (HCIO3), boric acid, perchloric acid (HCIO4), trifluoroacetic acid, p- toluenesulfonic acid, pyridinium p-tolenesulfonic acid and trifluoromethanesulfonic acid. Optionally blocked catalysts can be used as is known in the industry, for example NACURE blocked acid catalysts. Catalysts such as iron chloride, Zn-chloride, Zn-acetate, Mn-acetate, Sn(ll)2-ethylhexanoate, and Ti(IV)isopropoxide can also be used, although they may be less preferred.

[0068] The catalyst may be present in an amount of 0.01 -5 wt.% based on the total weight of the liquid resin composition, preferably in an amount of 0.05-2.5 wt.%, and most preferably in an amount of 0.1-1 wt.% based on the total weight of the liquid resin composition.

[0069] In an embodiment, the resin comprises an hydroxy carboxylic acid, such as an alpha hydroxy carboxylic acid or a beta hydroxy carboxylic acid. An hydroxy carboxylic acid comprises both a hydroxy group and a carboxyl group. It can therefore form an ester bond with the saturated multi-functional monomer, the polyol monomer and the polycarboxylic acid monomer. Suitable hydroxy acids are for example glycolic acid, lactic acid, tartaric acid, malic acid, hydroxypropionic acid, (beta-)hydroxypropionic butyric acid, (beta-)hydroxybutyric acid, (beta-) hydroxy valeric acid, (beta-)hydroxy caproic acid, 12-hydroxy stearic acid and cyclic esters thereof, such as lactide and eta-caprolactone.

[0070] The hydroxy carboxylic acid may be present in an amount of 0.1-20 wt.% based on the total weight of the liquid resin composition, preferably in an amount of 0.5-15 wt.%, and most preferably in an amount of 1-10 wt.%, based on the total weight of the liquid resin composition.

[0071] Process for manufacturing a multi-curable liquid resin composition

[0072] The invention also relates to a process for manufacturing a multi-curable liquid resin composition. The process comprises combining (i) multi-functional monomer, (ii) saturated aliphatic polyol monomer, and (iii) saturated aliphatic polycarboxylic monomer to form a reaction mixture, and subjecting the mixture to a reaction to form a multi-curable liquid resin composition. The process may be performed as a one-step synthesis, or as a two-step synthesis.

[0073] An advantage of a one-step synthesis is that it is relatively fast to perform with relatively low handling costs. In the one-step synthesis, the multi-functional monomer, the saturated aliphatic polyol monomer, and the saturated aliphatic polycarboxylic monomer are combined together in a single reaction mixture, which is then subjected to a reaction to form the multi- curable liquid resin composition.

[0074] An advantage of the two-step synthesis is an improved incorporation of the multi-functional monomer into the multi-curable liquid resin composition. In the two-step synthesis, the multifunctional monomer is combined with either the saturated aliphatic polyol monomer or the saturated aliphatic polycarboxylic acid monomer into a first reaction mixture. The first reaction mixture is subjected to a first reaction to form a first reacted mixture. Then, respectively the saturated aliphatic polycarboxylic acid or the saturated aliphatic polyol is added to the first reacted mixture to form a second reaction mixture, and the second reaction mixture is subjected to a second reaction to form the multi-curable liquid resin composition comprising a polyester derived from the multi-functional monomer, saturated aliphatic polyol monomer, and the saturated aliphatic polycarboxylic acid.

[0075] Whether the first reaction mixture of the two-step synthesis comprises saturated aliphatic polyol or saturated aliphatic polycarboxylic acid is determined by the nature of the multifunctional monomer. In an embodiment the multi-functional monomer comprises a carboxylic acid group, and is combined with the saturated aliphatic polyol monomer to form the first reaction mixture. In another embodiment the multi-functional monomer comprises a hydroxy group and is combined with the saturated aliphatic polycarboxylic acid monomer to form the first reaction mixture.

[0076] Both in the one-step synthesis and in the two-step synthesis, a liquid phase is formed out of the reaction mixture(s), e.g. by the addition of a suitable solvent such as water, methanol, ethanol, iso-propyl alcohol, butanol, dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), or dimethylacetamide (DMA). Alternatively, the mixture is heated to a temperature where the components of the reaction mixture form a solution. Depending on the nature of the compounds this may be, e.g., at a temperature in the range of 20-250°C, e.g., 40-200°C, e.g. 60-200°C, or 90-200°C. Depending on the nature of the monomers and the scale (gram, kilogram, ton, kiloton) of the reaction, the reaction mixture may be heated and mixed for a period of between 5 minutes and 12 hours to form the multi-curable resin composition comprising the polyester. The temperature and time are chosen such that esterification of the monomers is promoted. In one embodiment, the mixture may be heated at a temperature of 80-220°C, in particular 100-180°C, more in particular at a temperature in the range of 100- 160°C. It is within the ability of the skilled person to set the appropriate reaction time for a reaction of a given scale.

[0077] During the reaction step to form a polyester, a condensation product may be formed such as water or alkylalcohol as a result of the esterification reaction between hydroxy groups and carboxylic groups which may limit the extent of polymerization and / or the reaction rate of the reaction step. Therefore, the condensation product is preferably removed during the reaction step. This may be done by methods known in the art, such as through evaporation, using reduced pressure, using a gas-purge-line (e.g. nitrogen), or using a co-solvent (e.g. azeotrope with toluene).

[0078] After the reaction step, a solvent (e.g. water) or reactive diluent (e.g. an ester such as ethyl lactate, butyl lactate, or mono-, di- and tri-acetin, or other reactive diluents such as styrene, tri-allylcyanurate, tri-allyl isocyanurate) may be added to dilute the multi-curable resin composition to obtain a resin composition with a desired viscosity.

[0079] The multi-curable liquid resin composition

[0080] The multi-curable resin composition may be in the form of for example a solution, an emulsion or a dispersion in a solvent such as water or glycerol. Furthermore, the multi- curable resin composition is still below its theoretical gel point, i.e. liquid of nature. “Liquid” as used herein refers to a viscosity at 20°C of between 1 mPa s and 200 Pa s. Preferably, the liquid composition has a viscosity of at least 500 mPa s, more preferably a viscosity of at least 1 Pa s. The liquid composition has preferably a viscosity of at most 100 Pa s, more preferably 50 Pa s, even more preferably at most 20 Pa s, and most preferably at most 10 Pa s.

[0081] Preferably, the resin composition has an extent of polymerization in the range of 0.1 -0.6 after the one-step or two-step synthesis. The extent of polymerization is the ratio of the fraction of carboxylic acid groups that have reacted to the maximum of carboxylic acid groups that can react. In other words, other functionalities such as the unsaturated carbon-carbon bond are not relevant for determining the extent of polymerization. The extent of polymerization is determined by acid value titration.

[0082] If the extent of polymerization is above 0.6, the processability of the multi-curable resin composition may decrease and, in some embodiments, an unacceptably large amount of solvent may be required to keep the viscosity of the composition sufficiently low for further processing of the resin composition. The extent of polymerization of the multi-curable resin composition may be preferred to be at most 0.6, more preferably at most 0.55, even more preferably at most 0.5, in particular at most 0.4. Preferably the extent of polymerization of the multi-curable resin composition is at least 0.1 , in particular at least 0.2, more in particular at least 0.25, more in particular at least 0.3. A higher extent of polymerization of the multi- curable resin composition ensures that less curing after further processing of the resin composition is required.

[0083] In an embodiment, the multi-curable liquid resin composition is a one-component system (1 K-system) where all elements of the final multi-curable liquid resin composition are combined in one mixture. For the sake of clarity, this does not mean that the multi-curable liquid resin composition is prepared in a single step by combining all elements. For example, the polyester derived from (i) the multi-functional monomer, (ii) the saturated aliphatic polyol monomer and (iii) the saturated aliphatic polycarboxylic acid may be manufactured in a first step, and other elements such as a curing agent can be added when diluting the polyester to a desired concentration or viscosity. Preferably, the other elements such as the curing agent are added at a temperature of 50°C or less.

[0084] An advantage of using a one-component system is that it facilitates the use of the resin composition by a user without the need for having mixing capacities. In another embodiment, the multi-curable liquid resin composition is a two-component system (2K-system) wherein a first component comprises polyester derived from (i) the multifunctional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond, (ii) the saturated aliphatic polyol monomer with 2-15 carbon atoms, and (iii) the saturated aliphatic polycarboxylic acid monomer with 3 to 15 carbon atoms, and wherein a second component comprises at least one curing agent.

[0085] The two-component system allows for a physical separation of on the one hand the polyester derived from the multi-functional monomer, saturated aliphatic polyol monomer and the saturated aliphatic polycarboxylic acid monomer, and on the other hand components such as a curing agent. Therefore, the resin composition is more stable and can be stored over a longer period of time. In addition to this, a two-component system also leaves the choice for the desired curing system.

[0086] Both in the 1 K-system and the 2K-system the component or components of the multi-curable resin composition may be in the form of for example a solution, an emulsion or a dispersion in a solvent such as water or glycerol.

[0087] Manufacturing a solid cured resin composition

[0088] The multi-curable resin composition can be used in a process for manufacturing a solid cured resin composition. Therefore, the present invention also relates to a process for manufacturing a solid cured resin composition com prises the steps of

[0089] - providing a multi-curable liquid resin composition comprising polyester,

[0090] - combining the multi-curable liquid resin composition with a filler, and

[0091] - subjecting the combined multi-curable resin composition to a curing step under such conditions that a solid product is obtained, the product having an extent of polymerization of at least 0.7, wherein the curing step effects a reaction involving the reactive unsaturated carbon-carbon bond and an esterification reaction.

[0092] The curing step increases the extent of polymerization of the multi-curable resin composition. In this way, a composite of solid cured resin and filler is obtained. Curing can be performed by e.g. pressing or heating the multi-curable liquid resin composition comprising polyester. Depending on the nature of the monomers in the multi-curable resin composition, the multi- curable resin composition may e.g. be heated at a temperature in the range of 20-250°C, e.g., 40-230°C, e.g. 60-225°C, or 90-220°C. The curing step generally takes place at an internal temperature of at least 80°C, in particular at least 100°C, more in particular at least 120°C, even more in particular at least 130°C. An internal temperature which is very high results in increased side reactions. It is therefore preferred for the internal temperature not to reach values above 250°C. It may be preferred for the internal temperature to be in the range of 130-200°C. The internal temperature is measured during curing or immediately after the article is removed from a means for curing, such as an oven or a press.

[0093] Depending on the thickness of the layer of the multi-curable resin composition, the multi- curable resin composition may be heated for a period of 10 seconds to 3 hours. In one embodiment, the mixture may be heated and mixed for a period of 30 seconds to 2 hours, more specifically 1 minute to 45 minutes, at a temperature of 40-220°C, in particular 100- 200°, more in particular at a temperature in the range of 120-180°C. It is within the abilities of the skilled person to select the appropriate temperature and time for a given layer of multi- curable resin composition.

[0094] The curing step may be carried out in multiple substeps, wherein the substeps are carried out under different conditions. In this way, the reaction conditions may be selected to favour the esterification reaction or the cross-linking of the unsaturated carbon-carbon bonds. In other words, a substep may be carried out under conditions directed to preferentially promote the reaction involving the reactive unsaturated carbon-carbon bond and a further substep may be carried out under conditions directed to preferentially promote the esterification reaction.

[0095] In an embodiment, a first substep is carried out under conditions directed to promote the reaction involving the reactive unsaturated carbon-carbon bond and a second substep is carried out under conditions directed to promote the esterification reaction. The first substep is for example performed at a temperature in the range of 40-160°C, preferably at a temperature in the range of 60-140°C. The second substep is for example performed at a temperature in the range of 80-200°C, preferably at a temperature in the range of 100-180°C.

[0096] Curing can be carried out using heating technology known in the art, e.g., in in an oven with an oven temperature from 80°C up to 450°C. Different types of ovens may be used, including but not limited to belt ovens, convection ovens, microwave ovens, infra-red ovens, hot-air ovens, conventional baking ovens and combinations thereof. Vacuum ovens are also considered attractive. The curing step may for example be performed employing wave heating such as micro wave heating or high-frequency heating. Within the context of the present investigation, high- frequency heating, also indicated as HF heating, is subjecting an object to an alternating electromagnetic field with a frequency in the range of 3-100 MHz, in particular 10-50 MHz. Frequencies used for industrial purposes are 13.56 MHz, 27.12 MHz, and 40.68 MHz, with 27.12 MHz being used in particular. The energy provided depends on the field strength of the electromagnetic field. The desired energy input depends on the size of the object to be cured and on the nature of the apparatus. A value in the range of 1000 to 20.000 V may be mentioned as a general guideline, but it is within the scope of the skilled person to select a suitable voltage.

[0097] Depending on the size and shape of the object to be cured and the power provided, the HF heating step may be carried out for a period of 10 seconds to 30 minutes. Periods below 10 seconds are generally insufficient to achieve the desired temperature in the core of the object. Periods above 30 minutes are generally not required. It may be preferred for the heating to be carried out for a period of 10 seconds to 20 minutes, in particular 20 seconds to 10 minutes, more in particular 20 seconds to 5 minutes, or even 20 seconds to 3 minutes.

[0098] Preferably, the process for manufacturing a solid cured resin composition further encompasses a step of combining the multi-curable liquid resin composition with one or more further components, such as a stabilizer, a pigment, a dye, fire retardants, viscosity modifiers, anti-tacking agents, wetting agents, impact modifiers, defoamers, release agents, or biocides. Viscosity modifiers, or gelling agents or thickeners, are for example starch (e.g. corn starch, potato starch), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), chitosan, and gums (e.g. guar gum, Arabic gum).

[0099] In particular, the multi-curable liquid resin composition is preferably combined with a solid filler. The presence of filler may provide shapeability to the resin composition. The solid filler may also give specific properties to the end product, such as a desirable look and feel, or a particular texture. The presence of a filler can also increase the strength of the product. By selecting the density of the filler it is possible to influence the density of the final product.

[0100] Preferably, the mixture comprises at least 10 wt.% of filler. If less than 10 wt.% of filler is present, forming a shaped object will be difficult. It may be preferred for the composition to contain at least 20 wt.% filler. The composition generally comprises at most 98 wt.% of filler. If more than 98 wt.% of filler is present, there will be insufficient room for the further components of the composition. It may be preferred for the composition to contain at most 80 wt.% of filler, in particular at most 70 wt.% of filler, in some embodiments at most 60 wt.% of filler or even at most 50 wt.% of filler.

[0101] The filler used in the composition according to the invention may be any solid material. Generally, the filler will be a particulate material such as flakes or granules, but the use of yarn-type fibers or plate material (e.g. in wood veneer) is also possible.

[0102] In one embodiment, the filler comprises a natural material such as a material derived from plants or animals.

[0103] Examples of plant-based materials include cellulose-based material such as fresh or used paper, fresh or used cardboard, wood or other plant material in any form, or combinations thereof. In one embodiment, a cellulose-based material is used derived from so-called virgin pulp which is obtained directly from the wood pulping process. This pulp can come from any plant material but mostly from wood. Wood pulp comes from softwood trees such as spruce, pine, fir, larch and hemlock, and hardwoods such as eucalyptus, popular, aspen and birch. In one embodiment, the cellulose-based material comprises cellulose material derived from recycled paper, such as cellulose pulp obtained from regenerated books, papers, newspapers and periodicals, egg cartons, and other recycled paper or cardboard products. A particular source is the use of reject paper fiber, which is paper fiber which is too short to be suitable for use in the manufacture of paper. Combinations of cellulose sources may also be used. Further examples of plant-derived material are cotton, flax, hemp, grass, reed, bamboo, coffee grounds, seed shells, e.g., from rice, burlap, kenaf, ramie, sisal, etc. and materials derived therefrom. In general plant material which has been comminuted to a suitable particle size, and where necessary dried to a suitable water content may be used. Examples of animal-derived materials include feathers, down, hair and derivatives thereof such as wool, but also bone meal.

[0104] The use of cellulose-based materials such as wood dust, wood pulp, and dust and pulp derived from other cellulose-based materials such as hemp has been found to give particularly attractive results.

[0105] Further examples of suitable fillers include fillers of ceramic materials, including oxides, e.g. alumina, beryllia, ceria, zirconia, silica, titania, and mixtures and combinations thereof, and non-oxides such as carbide, boride, nitride, silicide, and mixtures and combinations thereof such as silicium carbide. For the purposes of the present specification glass is considered a ceramic material. Glass may, e.g., be used in the form of long or short fibers, glass beads, whether solid or hollow, and ground glass particles. Suitable fillers further include materials like micaceaous fillers, calcium carbonate, and minerals such as phyllosilicates. Clay, sand, etc. may also be used.

[0106] Suitable fillers also include polymer fillers, such as particles or short fibers of polyethylene, polypropylene, polystyrene, polyesters such as polyethylene terephthalate, polyvinylchloride, polyamide (e.g., nylon-6, nylon 6.6 etc.), polyacrylamide, and arylamide polymers such as aramid. Suitable fillers also include carbon fibers and carbon particulate materials. Comminuted cured polyester resin as used in the present invention may also be used as filler. Comminuted cured polyester resin containing a filler may also be used. This makes it possible to recycle used articles according to the invention to new articles.

[0107] In general, composites may also be used as filler, e.g., polymer particles provided with a filler.

[0108] Suitable further fillers encompass materials like starch which in lower concentrations can dissolve in the polyester composition. If materials of this type are used, they should be used in an amount sufficient to ensure that the material is also present in solid form.

[0109] Combinations of different types and materials of fillers may also be used.

[0110] The process for manufacturing a solid cured resin composition may also comprise a shaping step in order to give the resin composition a desired shape. Furthermore, the solid cured resin composition can be submitted to after-treatments known in the art, e.g., sanding, coating, or polishing, painting or other surface treatments.

[0111] Object

[0112] Finally, the present invention relates to an object comprising polyester derived from

[0113] - multi-functional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond,

[0114] - saturated aliphatic polyol monomer with 2-15 carbon atoms,

[0115] - saturated aliphatic polycarboxylic acid monomer with 3 to 15 carbon atoms, and

[0116] - a curing agent, wherein the amount of multi-functional monomers is in the range of 5-40 wt.% calculated on the total amount of monomer in the polyester, wherein the polyester has an extent of polymerization of at least 0.7. Objects include e.g. containers such as plant pots, foams, and plate material such as chip board, fiber board, MDF, glass-fiber products, and 2D and 3D shaped products from natural fibers such as hemp fibers and flax fibers. As will be evident to the skilled person, preferred embodiments of various aspects of the present invention can be combined, unless they are mutually exclusive.

[0117] The present invention will be elucidated by the following examples, without being limited thereto or thereby.

[0118] Example 1 : preparation of comparative resin composition

[0119] Glycerol (1.0 kg, 10.8 mol, >99% purity), citric acid (2.0 kg, 10.4 mol, >99% purity), and a catalyst (boric acid, 9.0 gram) were combined in a reactor vessel that was stirred and heated. The reaction mixture was stirred and heated to boil between 120-150 °C under the constant removal of water until a desired rate of esterification was reached. The reaction mixture was cooled down by addition of water, after which the water content of the comparative resin composition was ca. 20 w%, with a conversion of ca. 40% (based on AV).

[0120] Example 2: preparation of multi-curable resin composition

[0121] Two-step synthesis :

[0122] Glycerol (412.2g, 4.48mol), itaconic acid (174.4 g, 1.34 mol), a radical scavenger (BHT, 1.3 gram, 5.90x103mol), and a catalyst (boric acid, 4.0 gram, 0.06 mol, and PTSA, 3.6 gram, 0.02 mol) were combined in a reactor vessel that was stirred and heated. The reaction mixture was heated to 150 °C for 2 hours under reflux. After a suitable rate of esterification of the itaconic acid was obtained the reaction mixture was cooled down to ca. 100 °C. Next, citric acid (661 .8 g, 3.44 mol) was added to the mixture, and the mixture was stirred and heated to boil between 120-150 °C. The mixture was kept boiling between 1 - 5 hours under the constant removal of water until a desired esterification rate was obtained. The reaction mixture was cooled down by addition of distilled water, after which the water content of the liquid multi-curable resin composition was ca 20 wt.%, with a conversion of ca. 40% (based on AV).

[0123] One- step synthesis:

[0124] Glycerol (412.2 g, 4.48 mol), citric acid (661.8 g, 3.44 mol), itaconic acid (174.4 g, 1.34 mol), a radical scavenger (BHT, 1.3gram, 5.9x103mol), and a catalyst (boric acid, 4.0 gram, 0.06mol, and PTSA, 3.6 gram, 0.02 mol) were combined in a reactor vessel that was stirred and heated to boil between 120 - 150 °C. The reaction mixture was heated for approximately 1 - 5 hours under constant removal of water until a desired esterification rate was obtained. The reaction mixture was cooled down by addition of distilled water, after which the water content of the liquid multi-curable resin composition was ca 20 wt.%, with a conversion of ca. 40% (based on AV).

[0125] Example 3: curing times of resins with peroxide curing

[0126] The two-step synthesis protocol was followed with varying amounts of added itaconic acid, as described in Table 1 . The multi-curable resin with itaconic acid was diluted with distilled water to a water content of 25 wt.%. In addition to demiwater, and 0 - 1 wt.% of hydrogen peroxide solution (50 wt.% in water) was added as initiator. Ca. 8.5 g of multi-curable resin was weighed in glass vessel. The gel time (i.e. the time required for the resin to turn from a liquid into a gel) of the multi-curable resin was determined at 150 °C using an oil bath.

[0127] Table 1

[0128] The two-step synthesis protocol was also followed, replacing itaconic acid with maleic anhydride (131.5 g, 1.34 mol). The gel time of multi-curable resin with maleic anhydride was determined at 150 °C using an oil bath. The results are shown in Table 2.

[0129] Table 2 A multi-curable resin with 14.2 mol% of itaconic acid was prepared following the two-step synthesis protocol and the one step synthesis protocol. The gel times of the resulting multi- curable resin with 14.2 mol% of itaconic acid was determined at 150 °C using an oil bath. The results are shown in see Table 3.

[0130] Table 3

[0131] Example 5: bending strength, internal bond, and thickness swelling of chipboard composites To obtain a multi-curable resin with 14.2 mol% of itaconic acid the two-step synthesis protocol. The multi-curable resin for surface chips was diluted with distilled water to a water content of 30 wt.%. In addition to demiwater, 4 wt.% of hydrogen peroxide solution (50 wt.% in water) was added as initiator. The multi-curable resin for core chips was diluted with distilled water to a water content of 25 wt.%. In addition to demiwater, 4 wt.% of hydrogen peroxide solution (50 wt.% in water) was added as initiator. Furthermore, 0.3 wt.% of p- toluenesulfonic acid (PTSA) was added as additional catalyst.

[0132] The comparative resin was prepared as described above in example 1 . The comparative resin was diluted with water to a water content of 25 wt.% for use with core chips, or to 30 wt.% for used with surface chips.

[0133] The core chips (10 - 1.4 mm, spruce) and surface chips (< 1.4 mm, spruce) were dried at 110 °C in an oven until moisture content of 2 - 3%. Core chips were mixed with the comparative or multi-curable resin for core chips. Surface chips were mixed with the comparative or multi-curable resin for surface chips.

[0134] The amount of resin added was 15% on dry weight. The chips were poured in a 20*20 cm mold and pre-pressed using a manual hydraulic press, to obtain a so-called cake. Subseguently, the cake was pressed at 200°C with 19 mm thickness control for variation in time. The panels (density of 650 - 750 kg / m3) were then cured in an oven for 90 min at 180°C. The samples were climatized at 20°C and 65% relative humidity and tested according to EN 310 (bending strength), EN 319 (Internal bond), EN 317-1996 (thickness swelling). The results are shown in Table 4.

[0135] Table 4

[0136] 5

[0137] Example 6: strength of plywood composites

[0138] To obtain a multi-curable resin with 14,2 mol% of itaconic acid the synthesis protocol as described in the two-step synthesis protocol. The multi-curable resin for plywood was diluted with distilled water to a water content of 30 wt.%. In addition to demiwater, 4 wt.% of

[0139] 10 hydrogen peroxide solution (50 wt.% in water) was added as initiator.

[0140] The comparative resin for plywood was prepared as described above in example 1 .

[0141] The comparative and multi-curable resin was applied to wood veneer (20*20cm) using an 15 roller. The amount of applied resin was 150 - 200 g / m2. Layers of wood veneer (7,5 mm, birch) were stacked on top of each other (with the wood fibers perpendicular to each other) to form a plywood (5 ply). The plywood samples were first pre-pressed for 5 minutes at 0 - 1 bar. The plywood samples were then pressed with variation in time at 11 bars. The plywood was then cured for 90 min at 170°C using an oven. Strength of the glue bond of plywood with 20 comparative or multi-curable resin determined according to class 1 ; dry interior (EN 314-2).

[0142] The results are shown in Table 5.

[0143] Table 5

[0144] Example 7: swelling of hemp composites

[0145] To obtain a multi-curable resin with 14.2 mol% of itaconic acid the synthesis protocol as described in the two-step synthesis protocol. The multi-curable resin for plywood was diluted with distilled water to a water content of 50 wt.%. In addition to demiwater 6 wt.% of hydrogen peroxide solution (50 wt.% in water) was added as initiator.

[0146] The hemp mats (20*25 cm, 1.25 kg / m3) were impregnated with (multi-curable) resin using a waltz. The impregnated hemp mats were dried for 120 min at 90 °C. The dried resin content was 46 - 47 wt.%. 4 hemp mats were stacked on top of each other. The hemp mats were pressed for 6 - 8 minutes as indicated in Table 6 at 160 °C with 8 mm thickness controls. The pressed plates were then cured for 2h at 160°C. The samples were climatized at 20°C and 65% relative humidity and tested according to ASTM D 7264 (bending strength) and EN 319 (thickness swelling). The results are shown in Table 6.

[0147] Table 6

[0148] Example 8: suitability of different peroxides for multi-curable resin

[0149] The two-step synthesis protocol was followed with 14,2 mol% of added itaconic acid, as described in Table 1. The multi-curable resin with itaconic acid was diluted with distilled water to a water content of 25 wt.%. As indicated in Table 8, 0 - 2.15 wt.% of peroxide was added as initiator. Ca. 8.5 g of multi-curable resin was weighed in glass vessel. The gel time (i.e. the time required for the resin to turn from a liquid into a gel) of the multi-curable resin was determined at 150 °C using an oil bath. The stability of the multi-curable resin was determined at room temperature. To be suitable as a 1 K curing system, the resin must remain stable for at least 30 days. The results are shown in Table 7.

[0150] Table 7 Example 9: Radical scavengers for multi-curable resin

[0151] The two-step synthesis protocol was followed with 14,3 mol% of added itaconic acid with varying radical scavengers at a concentration of 0.1 wt.%, as described in Table 8. The effect of the radical scavenger is tested two-fold: on one hand it must have a shelf-stable product without initiator (30+ days), on the other hand it should not inhibit the increased curing rate after addition of initiator. The multi-curable resin with itaconic acid was diluted with distilled water to a water content of 25 wt.%. In addition to demi water, 0 - 1 wt.% of hydrogen peroxide was added as initiator. Ca. 8.5 g of multi-curable resin was weighed in glass vessel. The gel time (i.e. the time required for the resin to turn from a liquid into a gel) of the multi- curable resin was determined at 150 °C using an oil bath. The results are shown in Table 8.

[0152] Table 8

[0153] All radical scavengers result in a minimum shelf-life extension of 30 days before addition of the initiator hydrogen peroxide.

[0154] Example 10: Curing times of resins with peroxide curing with acrylates as second multifunctional monomer

[0155] The two-step synthesis protocol was followed to produce a multi-curable resin with 13.64 wt.% of itaconic acid. The multi-curable resin with itaconic acid was diluted with distilled water to a water content of 25 wt.%. In addition to demiwater, 1 .17 wt.% (molar ratio itaconic acid : H2O2 is 3.02 : 1) of pure hydrogen peroxide (50 wt.% in water) was added as initiator. Methacrylic acid and 2-hydroxyethyl methacrylatewere added as second multifunctional monomer at molar ratios ranging from 1 :1 to 3:1 with respect to itaconic acid. Ca. 8.5 g of multi-curable resin was weighed in glass vessels. The gel time (i.e. the time required forthe resin to turn from a liquid into a gel) of the multi-curable resin was determined at 150 °C using an oil bath. The results are shown in Table 9.

[0156] ★Table 9

[0157] Example 11 : Curing times of multi-curable resins with aconitic acid peroxide curing The two-step synthesis protocol was followed to obtain a multi-curable resin with 14.25 mol% of added trans-aconitic acid. The multi-curable resin with aconitic acid was diluted with distilled water to a water content of 25 wt.%. In addition to demiwater, 0 - 2.17 wt.% (molar ratio aconitic acid : H2O2 is 3.02 : 1) of pure hydrogen peroxide (50 wt.% in water) was added as initiator. Ca. 8.5 g of multi-curable resin was weighed in glass vessels. The gel time (i.e. the time required for the resin to turn from a liquid into a gel) of the multi-curable resin was determined at 150 °C using an oil bath. The results are shown in table 10.

[0158] ★Table 10 Example 12: Curing times of multi-curable with Oxo- Michael curing

[0159] The two-step synthesis protocol was followed to produce a multi-curable resin with 13.64 wt.% of itaconic acid. The multi-curable resin with itaconic acid was diluted with distilled water to a water content of 25 wt.%. In addition to demiwater, p-Toluenesulfonic acid (PTSA) was added as an additional catalyst to promote the Oxo-Michael addition. Ca. 8.5 g of multi-curable resin was weighed in glass vessels. The gel time (i.e. the time required for the resin to turn from a liquid into a gel) of the multi-curable resin was determined at 150 °C using an oil bath. The results are shown in table 11 .

[0160] ★Table 11

Claims

CLAIMS1. Multi-curable liquid resin composition comprising polyester derived from- multi-functional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond,- saturated aliphatic polyol monomer with 2-15 carbon atoms,- saturated aliphatic polycarboxylic acid monomer with 3 to 15 carbon atoms, and- a curing agent, wherein the amount of multi-functional monomers is in the range of 5-50 wt.% calculated on the total amount of monomer in the composition, and the ratio between the total number of hydroxy groups and the total number of carboxylic acid groups is between 3:1 and 1 :3, wherein the saturated polycarboxylic acid monomer comprises at least 70 wt.% of tricarboxylic acid, calculated on the total amount of saturated aliphatic polycarboxylic acid monomer.

2. Multi-curable resin composition according to claim 1 , wherein the multi-functional monomer is selected from the group of carboxylic acid monomers with 3 to 15 carbon atoms, in particular aliphatic polycarboxylic acid monomers with 3 to 15 carbon atoms e.g., aconitic acid, itaconic acid, citraconic acid, muconic acid, hydromuconic acid, fumaric acid, maleic acid, synaptic acid, ferulic acid, caffeic acid, coumaric acid, and anhydrides and alkylated variants thereof, (meth)acrylic acids, such as (meth)acrylic acid, methyl (meth)acrylic acid, ethyl (meth)acrylic acid, butyl (meth)acrylic acid, hydroxyethyl (meth)acrylic acid, and fatty acids, such as oleic acid and linolenic acid, or a combination of two or more thereof.

3. Multi-curable resin composition according to any one of the preceding claims, wherein the multi-functional monomer is selected from the group of hydroxy -functional monomers with 2-15 carbon atoms, in particular aliphatic polyol acid monomers with 2 to 15 carbon atoms e.g., hydroxy-ethyl acrylate, hydroxy-ethyl methacrylate, vinyl-alcohol, allyl-alcohol, glycerol-tri-(meth)acrylate, trimethylolpropane-trimethacrylate and 1 ,4-butynediol, N- hydroxyethyl citraconimide, N -carboxy methyl citraconimide, N-hydroxyethyl maleamic acid, N-hydroxyethyl methyl-maleamic acid, or a combination of two or more thereof.

4. Multi-curable resin composition according to any one of the preceding claims, wherein the saturated aliphatic polyol monomer is selected from the group of 1 ,2-propane diol, 1 ,3- propane diol, 1 ,2-ethane diol, 1 ,4-butanene diol, glycerol, sorbitol, xylitol, pentaerythritol, mannitol, hydroxyalkyl amides, or a combination of two or more thereof, in particular glycerol.

5. Multi-curable resin composition according to any one of the preceding claims, wherein the saturated aliphatic polycarboxylic acid monomer is selected from the group of dicarboxylic acids selected from malic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, oxalic acid, suberic acid, azelaic acid, and mixtures of two or more thereof, in particular succinic acid, tricarboxylic acids selected from citric acid, and isocitric acid, and tetracarboxylic acids such as cyclobutene tetracarboxylic acid.

6. Multi-curable resin composition according to any one of the preceding claims wherein the ratio between the multi-functional monomer, the saturated aliphatic polyol monomer, and the saturated aliphatic polycarboxylic acid monomer is such that the ratio between the total number of hydroxy-groups and the total number of carboxylic acid groups is in the range of 3:1 to 1 :3, in particular in the range of 2:1 to 1 :2, more in particular between 1.5:1 to 1 :1.5, even more in particular between 1.1 :1 and 1 :1.1.

7. Multi-curable resin composition according to any one of the preceding claims wherein the ratio between the multi-functional monomer, the saturated aliphatic polyol monomer, and the saturated aliphatic polycarboxylic acid monomer is such that the ratio between the total number of reactive unsaturated carbon-carbon bonds and the total number of hydroxygroups is in the range of 1 :2 to 1 :65, more in particular 1 :5 to 1 :60, even more in particular 1 :7.5 and 1 :40, even more in particular 1 :10 and 1 :30, and most in particular 1 :10 and 1 :20.

8. Multi-curable resin composition according to any one of the preceding claims, wherein the curing agent is a radical initiator, a diene curing agent, a curing agent comprising a thiol group, or a combination of two or more thereof.

9. Multi-curable resin composition according to any one of claims any of the preceding claims wherein the multi-curable resin composition is a two-component system, wherein a first component comprises polyester comprising multi-functional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond, saturated aliphatic polyol monomer with 2-15 carbon atoms, and saturated aliphatic polycarboxylic acid monomer with 3 to 15 carbon atoms, and wherein a second component comprises at least one curing agent; or wherein the multi-curable resin composition is a one-component system, which comprises polyester comprising multi-functional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond, saturated aliphatic polyol monomer with 2-15 carbon atoms, andsaturated aliphatic polycarboxylic acid monomer with 3 to 15 carbon atoms, and a curing agent.

10. Process for manufacturing a multi-curable resin composition according to any one of the preceding claims, comprising the steps of combining multi-functional monomer, saturated aliphatic polyol monomer, and saturated aliphatic polycarboxylic acid monomer to form a reaction mixture, subjecting the mixture to a reaction step, and after performing the reaction step, adding a curing agent to form a multi-curable resin composition.11 . Process according to claim 10, wherein the curing agent is a catalyst for catalyzing an esterification in the reaction step and / or a compound selected from a radical initiator, a diene curing agent, and a curing agent comprising a thiol group and one or m ore of a hydroxy group and a carboxylic acid group.

12. Process according to any one of claims 10 or 11 , comprising the steps of- combining the multi-functional monomer with the saturated aliphatic polyol monomer into a first reaction mixture and subjecting the first reaction mixture thus obtained to a first reaction step to form a first reacted mixture,- adding the saturated aliphatic polycarboxylic acid monomer to the first reacted mixture to form a second reaction mixture, and subjecting the second reaction mixture thus obtained to a second reaction step to form the multi-curable resin composition.

13. Process according to any one of claims 10-12 wherein a reaction product is removed during the reaction step, e.g., through evaporation, and / or wherein water is added to the reaction mixture after the reaction.

14. Process for manufacturing a solid cured resin composition comprising the steps of- providing a multi-curable liquid resin composition comprising polyester according to any one of claims 1-9, and- subjecting the multi-curable liquid resin composition to a curing step under such conditions that a solid product is obtained, the product having a ratio of the fraction of carboxylic acid groups that have reacted to the maximum of carboxylic acid groups that can react of at least 0.7, wherein the curing step effects a reaction involving the reactive unsaturated carboncarbon bond and an esterification reaction.

15. Object com prising polyester derived from- multi-functional monomer comprising at least one reactive group selected from hydroxy groups and carboxyl groups and at least one reactive unsaturated carbon-carbon bond,- saturated aliphatic polyol monomer with 2-15 carbon atoms, - saturated aliphatic polycarboxylic acid monomer with 3 to 15 carbon atoms, and- a curing agent, wherein the amount of multi-functional monomers is in the range of 5-50 wt.% calculated on the total amount of monomer in the polyester, and wherein the saturated polycarboxylic acid monomer comprises at least 70 wt.% of tricarboxylic acid, calculated on the total amount of saturated aliphatic polycarboxylic acid monomer, wherein the polyester has a ratio of the fraction of carboxylic acid groups that have reacted to the maximum of carboxylic acid groups that can react of at least 0.7.

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