FIELD OF THE INVENTION

The present invention relates to a synthetic resin, comprising at least one hydroxyl- aromatic compound, vinasse and an aldehyde. The invention further relates to the method of preparing said synthetic resin and to the use of said synthetic resin for coating a carrier material or preparing HPL or CPL.

BACKGROUND OF THE INVENTION

Phenol formaldehyde resins (PF) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Phenolic resins are mainly used in the production of circuit boards. They are better known however for the production of molded products including pool balls, laboratory countertops and as coatings and adhesives.

The industrial development of phenolic resins is still continuing despite the long history. Their importance is likely to remain considerable because the raw materials can be obtained at reasonable cost both from petroleum and from coal. Phenolic resins can be used as raw materials for synthetic fibers and in photoresists for the production of microchips which characterizes the continuing relevance of this group of resins. As an important application example, exterior grade composite and panel wood products are bonded with synthetic resins. Hereby, phenol-formaldehyde resins are used in more than 90% of exterior grade composite products. The use of phenol as a toxic chemical is aggravated by the fact that it possesses a relatively high vapor pressure. Hence, there is a need for reducing the phenol content in the respective synthetic resins.

Furthermore, the finite supply of fossil raw materials, associated with an increasing demand for resin-based products, has created a need for alternative, environmentally sound resin systems, which have to be produced as uniform and high quality products. This challenge has been addressed in the prior art in different ways.

Traditionally, reductions in free phenol levels have been most easily achieved by increasing the formaldehyde to phenol molar ratio. However, this usually tends to increase the level of free formaldehyde in the resin and thus increase the amount of formaldehyde released during processing and curing.

WO 1996/26164 A1 relates to a phenolic resin whereby the emission of phenol is reduced by an excess of formaldehyde, whose emission is reduced by an excess of ammonia which in turn is reacted with a sugar compound to reduce the ammonia emission.

For a reduction of free phenol WO 2008/141042 A1 teaches the preparation of a conventional phenolic resin in the first step followed by removal of the residual phenol (e.g. by heating under vacuum, azeotropic distillation or film evaporation) and subsequent addition of an organic solvent or a dibasic ester. As a result, this production process is still based on a phenol-enriched resin and requires further technical demanding and costly process steps.

Hence, there is still a need for an improved phenolic resin which overcomes at least one of the above mentioned disadvantages.

SUMMARY OF THE INVENTION This problem is solved by providing a synthetic resin composition that comprises at least one hydroxyl-aromatic compound, vinasse and at least one aldehyde. Specific embodiments of the invention are subject matter of further independent or dependent claims. The core aspect of the invention is the finding that the vinasse can be used to partially substitute the aromatic hydroxylic compounds within a phenolic resin. Vinasse is available e.g. as a byproduct of the sugar industry.

According to the invention, the proportion of aromatic hydroxylic compounds within the resin can be reduced which results in a resin composition which is considerably more environmentally-friendly. Since vinasse is less costly than the hydroxyl-aromatic compounds (whereby phenol is mostly used) the synthetic resin of the invention also exhibits lower production costs.

The inventors could show that the addition of vinasse does not have a negative impact on the quality of the resulting synthetic resin.

Furthermore, the addition of vinasse does not interfere with the well-established prior art production methods. Hence established materials, production machines and processes can be applied in the method according to the invention.

Besides, the inventors assume that vinasse may have certain properties of a flexibilizer in resins. This may possibly allow for some reduction in the amount of flexibilizers which are usually added depending on the kind of application and, thus, could probably further contribute to reduced production costs and further facilitate environmentally-friendly production. Besides, the inventors suppose that vinasse may have some catalytic activity on the condensation of components in resins which may further facilitate the preparation of a condensated resin and allow for a reduction of further catalytic compounds that may be added to initiate a condensation reaction.

In the context of the present invention the hydroxyl-aromatic compounds are synonymously determined as "phenolics". They are defined as chemical compounds comprising at least one hydroxyl group (-OH) bonded directly to an aromatic hydrocarbon group. Hereby, an aromatic hydrocarbon group (alternatively coined as "arene") is a cyclic hydrocarbon with 4n+2 delocalized electrons (n = 1 , 2, 3, 4, 5 etc.; Huckel ^' s rule)

Preferably, the arene is a hydrocarbon with alternating double and single bonds between the carbon atoms forming rings. The class hydroxyl-aromatic compounds encompasses inter alia substances such as substituted or unsubstituted phenol, bisnuclear phenol linked through a linking group, resorcinol, phenolic novolacs, and polyvinylphenols, pyrocatechol, pyrogallol, phloroglucinol, resveratrol, apigenein, cardanol and cardol. Also natural phenolic raw materials such as cashew nut shell liquid (CNSL) which contains mostly cardol, cardanol and anacardic acid can be used.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the invention the hydroxyl-aromatic compound of the synthetic resin composition is selected from the group consisting of substituted or unsubstituted mononuclear phenol, bisnuclear phenol linked through a linking group, resorcinol, phenolic novolacs, and polyvinylphenols, and preferably is phenol. Other possible hydroxyl-aromatic compounds include alpha-naphthol; phenylphenol, cresol, 2-methylphenol, 3-methylphenol, caffeic acid, ferulic acid, coniferyl alcohol, sinapyl alcohol, xylenol derivatives such as 2,5-dimethylphenol and 3,5-dimethylphenol further alkyl phenols, alkoxyphenols such as 2-methoxy- or 3-methoxyphenol, bisphenol- A and bisphenol-F.

In the context of the present invention the term "vinasse" refers to an effluent produced in distilleries of any type and, specifically, to an effluent obtained in the process of fermenting sugar cane or beet. Vinasse represents a highly viscous liquid with an organic dry matter content of at least 7%, preferably at least 30% and more preferably at least 50%. The organic dry matter comprises of raw protein, ash and sugar. The organic dry matter has a raw protein content between 10 wt.-% and 40 wt.-% and an ash content between 20 wt.-% and 40 wt.-%. The sugar content of the organic dry matter is between 1 wt.-% and 20 wt.-%.

Vinasse has a variable qualitative and quantitative composition, but generally contains water, metal ions, yeasts, remainders of non-fermentable sugars, lignin, sulfates and other sulfur compounds and mainly organic material composed of heterogeneous polymers.

The composition varies depending on the origin of the molasses (sugar cane, sugar beet) and fermentation process. Preferably, the following vinasse compositions are used for the resin of the invention.

Cane vinasse derived from the alcohol production process

Organic dry matter (DM): approx. 61 %

Raw protein (in % of DM): approx. 11 %

Ash content (in % of DM): approx. 29 %

Sugar content (in % of DM): approx. 13 %

Beet vinasse from the citric acid production process

Organic dry matter (DM): approx. 61 %

Raw protein (in % of DM): approx. 26 %

Ash content (in % of DM): approx. 39 %

Sugar content (in % of DM): approx. 7 %

Cane vinasse derived from the yeast production process

Organic dry matter (DM): approx. 54 %

Raw protein (in % of DM): approx. 36 %

Ash content (in % of DM): approx. 38 %

Sugar content (in % of DM): approx. 2 % Due to the presence of organic acids, vinasse has an acid pH value which is typically between pH 4.0 and 5.0.

In a further embodiment of the invention the vinasse is selected from the group consisting of cane-vinasse, beet-vinasse, sulfite-alcohol vinasse, wheat vinasse and potassium- reduced vinasse. Preferably a beet-vinasse is used.

In a preferred embodiment of the invention a liquid vinasse is used. The vinasse can be used in the form of the primary waste product, e.g. as an untreated vinasse. Alternatively, the vinasse can be pre-treated by physical or chemical reactions. Physical reactions include dilution, water removal, filtration, sonification or homogenization. Chemical reactions encompass inter alia oxidation, reduction or precipitation of ingredients by addition of further substances.

In one embodiment of the invention the pH value of the untreated vinasse is adjusted to the pH value needed for condensation and reactivity depending of amount and type of vinasse used and the pH value needed for condensation. In a preferred embodiment of the invention the pH value of the uncured resin composition comprising vinasse is adjusted to the pH value needed for condensation and reactivity depending of amount and type of vinasse used and the pH value needed for condensation. As a preferred base for pH adjustment an alkali metal hydroxide, an earth alkali metal hydroxide, an amine or an inorganic or organic ammonium compound can be used.

In a more preferred embodiment, NaOH is used for pH adjustment. The amount of the base (which is preferably NaOH) which is required for preparation of the resin depends on the target pH value and the ratio of the different components. The amount of the base especially depends on the amount of the acidic component vinasse: The more vinasse is given the more of the base has to be added to the resin composition.

In another embodiment of the invention the aldehyde of the synthetic resin composition is selected from the group consisting of formaldehyde or a formaldehyde precursor, in particular paraformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, glyoxal, malondialdehyde and succindialdehyde; and preferably is formaldehyde.

In one aspect of the invention the synthetic resin composition comprises the vinasse in a proportion of between 10 to 30 wt.-%, preferably of between 12 to 28 wt.-%, further preferably of between 15 and 25 wt.-% and more preferably of 20 wt.-% as related to the phenolic compound. Especially amounts of between 10 to 30 wt.-% of vinasse as related to the phenolic compound allow for a high reduction of phenolic compound and have no negative impact on the quality and properties of the resulting condensated resin. Said synthetic resin compositions can be produced and processed by means of well- established production methods.

In one embodiment of the invention an alcohol is added to the resin in order to increase the shelf life and/or the improvement of penetration. As defined in the context of the present invention, the term "alcohol" includes aromatic and alkyl alcohols, mono _^ alcohols, diols, triols and polyols and also oligomeric or polymeric alcohols.

In a preferred embodiment an alkyl alcohol is used such as methanol, ethanol or isopropyl alcohol.

In one embodiment of the invention the synthetic resin has a basic phenolic to formaldehyde ratio of between 1 :1 to 1 :4.5, preferably of between 1 :1 to 1 :4.2, more preferably of between 1 : 1 to 1 :2.5 on a molar basis. In the context of the present invention a "basic phenolic to formaldehyde ratio" is defined as the ratio of the resin before addition of the vinasse, meaning that up to 30 wt.-% of the phenolic proportion as given by the above described ratio can be substituted by vinasse.

In a further embodiment of the invention, the synthetic resin composition being preferably a phenolic resin composition is a resol or a novolac.

In the context of the present invention a resol is defined as a base-catalysed synthetic resin with an aldehyde to hydroxyl-aromatic compound ratio of greater than one. Preferably it denotes to a phenol-formaldehyde resin with a formaldehyde to phenol ratio of greater than one (usually around .5).

As used herein, the term "novolac" is used a synthetic resin with an aldehyde to hydroxyl- aromatic compound ratio of less than one. Preferably it denotes to a phenol- formaldehyde resin with a formaldehyde to phenol ratio of less than one (usually around 0.8:1 ). Hereby the polymerization is brought to completion using acid-catalysis such as oxalic acid, hydrochloric acid or sulfonate acids. Hexamethylenetetramine can be added as a hardener in order to crosslink the novolac. At a temperature above 90°C, it forms methylene and dimethylene amino bridges. In a first embodiment, the synthetic resin is a novolac, which is preferably a phenolic resin which is not inherently reactive. It is prepared by reacting phenol with formaldehyde under acidic conditions at a formaldehyde/phenol molar ratio of below 1 :1. The majority of commercial formulations operate at a molar ratio in the range from 0.75 to 0.85:1. The usually result in a linear polymer of molecular weight of 1000 to 1500. Further cross- linking can only take place by the addition of more formaldehyde, usually in the form of hexamine.

In another embodiment, the resin is a resol which is preferably formed from the base catalysed reaction of phenol and formaldehyde and requires an excess of formaldehyde. For solution resin, they are reacted to a low molecular weight of 300 to 700, so that the polymer is still soluble. Further heating will cause condensation reactions and result in a high molecular weight cross-linked polymer.

In a further embodiment of the invention the synthetic resin further comprises a condensation partner of the group consisting of melamine, urea and dicyandiamide, preferably melamine and/or urea.

In a further embodiment of the invention the vinasse-containing resin can be mixed with one or more resins before curing such as e.g. a melamine, urea or dicyandiamide- containing resin, preferably a melamine containing resin and/or urea containing resin. In a preferred embodiment, the phenol-formaldehyde resin containing the vinasse is mixed with a melamine-formaldehyde resin before condensation and/or curing.

In an alternative embodiment, melamine-phenol-co-condensate with formaldehyde is formed, whereby up to 30 wt.-% Of the phenol is substituted by vinasse.

In a preferred embodiment the synthetic resin is used for preparation of a high pressure laminate (HPL) or continuous pressure laminate (CPL).

As used herein, the term "high pressure laminate" (HPL) refers to a laminate comprising of laminates moulded and cured at pressures not lower than 70 kg/cm ² . More commonly pressures in the range of 84 to 140 bar are used. The pressing is performed as hot pressing with temperatures ranging from 100 to 200°C, preferably from 120 to 180°C and more preferably from 150°C to 170°C. Depending on the press feed and the maximum temperature, the entire press cycle, including re-cooling, ranges between 30 and 240 minutes, preferably between 60 and 120 minutes and more preferably between 90 and

120 minutes. Typically, the HPL laminate is pressed with press pressures of between 40 and 20 bars, preferably between 50 and 100 bar and more preferably between 70 and 80 bar. For HPL preparation it is most preferably to use a discontinuously operating presses with press pressures of between 70 and 80 bar, temperatures in excess of 120°C and a press cycle time of approx. 100 min.

In the context of the present invention the term continuous pressure laminate (CPL) is defined as a laminate produced by hot pressing of the resin coated/saturated laminate sheets in continuously operating presses. Typically the laminate is pressed with a pressure of between 10 bar and 100 bar, preferably with a pressure between 15 and 75 bar and more preferably with a pressure between 25 bar and 50 bar. The pressing is performed as hot pressing with temperatures ranging from 100 to 200°C, preferably from

120 to 180°C and more preferably from 150°C to 170°C. Depending on the laminate thickness and the length of the pressing zone, the feed rate varies from 4 to 50 m/min, preferably from 8 to 40 m/min and more preferably from 8 to 30 m/min. A most preferred CPL production process is characterized by a press pressure between 25 and 50 bar, a press temperature between 150 and 170°C and a feed rate between 8 and 30 m/min.

Both qualities, CPL and HPL, are classified and tested in accordance with EN 438-1 and EN 438-2 (2005). The table below provides an excerpt of preferred CPL and HPL properties (as e.g. requested for kitchen worktops).

Preferably, a phenol-formaldehyde-melamine resin, whereby up to 30 wt.-% of the phenol is substituted by vinasse is used for preparing CPL or HPL. The invention further relates to a synthetic resin composition comprising phenol, formaldehyde and vinasse, whereby the basic phenol to formaldehyde molar ratio is between 1 :1 and 1 :2.5 and whereby up to 30 wt.-% of the phenol is substituted by vinasse. A substitution of up to 30% of phenol by vinasse proves to have no negative impact on the quality and properties of the resulting condensated resin and resulting resin could be produced and processed by means of well-established production methods.

In a preferred embodiment said synthetic resin composition comprises phenol, formaldehyde, vinasse and NaOH solution in a basic molar ratio of phenol to formaldehyde of between 1 :1 and 1 :2, whereby up to 30 wt.-% of the phenol is substituted by vinasse.

The invention also relates to a synthetic resin composition, especially used for CPL, comprising phenol, formaldehyde, melamine, vinasse and NaOH solution in a basic molar ratio of phenol to formaldehyde to melamine of 1 to between 2.0 and 4.5 to between 0.1 and 1 .0 whereby up to 30 wt.-% of the phenol is substituted by vinasse.

In a preferred embodiment said synthetic CPL resin composition comprises phenol, formaldehyde, melamine, vinasse and NaOH solution in a basic molar ratio of phenol to formaldehyde to melamine of 1 to 3.05 to 0.6 or 1 to 2.51 to 0.41 , whereby up to 30 wt.- % of the phenol is substituted by vinasse.

In another aspect the invention relates to the use of the synthetic resin composition of the invention for coating a carrier material, being preferably a board and more preferably a wood-based board.

In a preferred embodiment, a paper impregnated with the synthetic resin of the invention can then be attached under pressure and heat to a panel or board in order to provide a coated board or coated panel. In this embodiment the board or panel serves as a support layer. Possible support layers to be coated with an impregnated paper according to the invention are plywood, chipboard, fibre board, oriented strand board (OSB), glue wood, laminated veneer lumber (LVL), parallel strand lumber (PSL) and oriented strand lumber (OSL). The most preferred embodiment is plywood panel. The coated board or panel can be applied in the wood working industry, in particular in construction industry for concrete shuttering.

In a further aspect the invention relates to a wood-based board, an HPL or a CPL prepared with the synthetic resin of the invention.

In another aspect the invention provides a method for preparing a condensated resin from the components of the synthetic resin composition. The method for preparing the condensated resin preferably comprises the condensation of the hydroxyl aromatic compound and the aldehyde, wherein vinasse is added before or during said condensation, i.e. before said condensation is completed.

The method for preparing a condensed resin of the invention comprises the following steps in a preferred aspect of the invention: a) providing a mixture of the phenolic compound, preferably phenol, and the vinasse; b) applying a base to adjust the pH value to more than 7.0 and preferably between 8.5 and 10;

c) initiating the polycondensation by addition of a aqueous solution comprising an aldehyde, preferably formaldehyde.

In another preferred aspect the invention provides a method for preparing a condensed resin of the invention comprising the following steps: a) providing the phenolic compound, preferably phenol;

b) applying a base to adjust the pH value to between 7 and 1 1 ;

c) initiating the polycondensation by addition of a solution comprising an aldehyde, preferably formaldehyde

d) adding the pH-adjusted vinasse before the reaction mixture of c) is condensated completely.

The term "condensated resin" as used herein denotes to a resin formed by polycondensation.

In the context of the present invention the term "condensation" or "condensate" is synonymous to the term "curing" and refers to the toughening or hardening of the synthetic resin by polymerization of the monomers. For phenolic resins said polymerization represents a condensation reaction, since two molecules or moieties (functional groups) combine to form a larger molecule, together with the loss of water. The cross-linking of polymer chains can be initiated by chemical additives, ultraviolet radiation, electron beam or heat.

The coated articles according to the invention are described with the following illustrative figures and examples, which should not be interpreted in order to limit the scope of protection.

EXAMPLES

Example 1 : Preparation of a phenolic resin suitable as surface resin or glue resin

1000 kg phenol is added to the reaction vessel following by the addition of 330 kg vinasse. The pH value is adjusted to 10 by addition of NaOH. 1000 kg of an aqueous 37% formaldehyde solution are slowly added over 15 min to keep the temperature at 64 to 85°C. The condensation is than kept for 10 min at 85 °C. After 10 min additional 1000 kg of an aqueous 37% formaldehyde solution are added within 24 min to keep temperature at 85°C. The condensation is kept for 50 min at 87°C to achieve the end viscosity. When reaching a viscosity of 42 sec at 20°C (as determined according DIN EN ISO 2431 ), the resin is cooled down to room temperature. The resulting resin has a kinematic viscosity of 42 sec when using a viscosity cup with a orifice diameter of 4 mm (acc. DIN EN ISO 2431 ), a volatile content of 52%, a curing time of 176 sec (so called B- time as determined according DIN 16916) and a pH value of 9.8.

Before impregnation additives such as antifoaming, colorants, release agents and levelling agents, wetting agents are added to the resin.

PF products are pressed on plywood surface and film tested for curing, for generation of a closed surface, for water penetration, in the boiling test, for suitability as concrete shuttering or for the appearance of cracks.

Example 2: Preparation of a phenolic resin suitable for a high pressure laminate (HPL)

The HPL-resin is prepared according the procedure of Example 1 , whereby the basic phenol to formaldehyde ratio is 1 to 1.5 or 1 :2.5 and whereby 20 wt.-% of said phenol is substituted by vinasse. The amount of vinasse is 25 wt.-% relating to phenol. The final resin is used to generate a high pressure laminate which is tested according HPL norm DIN EN 438.

Example 3: Preparation of a phenolic resin suitable for continuous pressure laminate iCPL)

The CPL resin is prepared according the procedure of Example 1 , whereby the basic phenol to formaldehyde to melamine ratio is 1 to 3.05 to 0.6 or 1 to 2.51 to 0.41 and whereby 20 wt.-% of said phenol is substituted by vinasse. The amount of vinasse is 25 wt.-% relating to phenol. The final resin is used to generate a continuous pressure laminate.