WO2024219983A1 - Process for obtaining a biologically based bioadhesive from industrial waste - Google Patents

Abstract

The present invention relates to a process for obtaining a bioadhesive from the processing of oilcake from the extraction of oil from seeds of the genus Plukenetia. The process includes the steps of degreasing, modifying pH, double filtering, double centrifuging, mixing soluble and insoluble carbohydrates, carrying out hydrolysis, neutralising, denaturing protein, mixing the denatured protein and the hydrolysed and neutralised carbohydrates, adding essential oil and drying. The technical effect achieved is to make use of oilcake from the extraction of oil from seeds of the genus Plukenetia, by means of a method that does not have toxicity, both in the intermediate steps and in the final product, with curing at room temperature, without needing to be mixed with other additives, among other advantages detailed in the description.

Description

PROCESS FOR OBTAINING A BIOLOGICALLY BASED BIOADHESION FROM INDUSTRIAL WASTE

TECHNICAL FIELD

The present invention relates to obtaining a bio-based adhesive from industrial waste with a high protein content, as an alternative to the use of raw materials of fossil origin conventionally used for the production of adhesives for, for example, wood, paper and cardboard.

The adhesive can be used, for example, for bonding paper and cardboard surfaces, and in the manufacture of laminates and wood products such as plywood, oriented strand board (OSB), laminated veneer lumber (LVL), medium-density fiberboard (MDF), high-density fiberboard (HDF), wooden flooring, curved plywood, particle board, chipboard veneer or MDF.

STATE OF THE ART (OR BACKGROUND OF THE INVENTION)

Currently, there are formaldehyde-based resins, mainly urea-formaldehyde (UF) and phenol-formaldehyde (PF) (M., 1998), for the manufacture of chipboard, medium-density fiberboard (MDF), oriented strand board (OSB), plywood and particle board.

The usual technique for the industrial production of urea-formaldehyde (UF) resins is from the condensation of formaldehyde and urea in an aqueous solution, using ammonia as an alkaline catalyst. The subsequent drying and spraying has applications as coatings and adhesives, and can also be mixed with cellulose as a filler. Under the application of temperature and pressure, the resin, composed of low molecular weight prepolymers, is cured forming a three-dimensional network of interrelated polymers. Phenol-formaldehyde (PF) resins are conventionally obtained from the reaction of phenols and aldehydes. During synthesis, temperature has a major effect on the characteristics of the final product, so that chain growth by condensations and alternative additions at temperatures below 100 ^s C, and cross-linking and hardening of the resins at temperatures above 100 ^s C, result in two types of PF resins: novolac and resoles.

The usual technique for the industrial production of novolac is the reaction of phenol and formaldehyde under acidic conditions with a molar excess of phenol with a phenol-formaldehyde molar ratio of 1 :(0.75-0.85), using oxalic acid as catalyst, while resols are obtained by the reaction of phenol and formaldehyde under basic conditions with a molar excess of formaldehyde. The phenol-formaldehyde molar ratio is 1 :(1 .2-3) using NaOH (sodium hydroxide) as catalyst.

These adhesives have advantages such as high profitability and fast curing. However, they also have some disadvantages, such as their origin from fossil raw materials and the need for high curing temperatures. Additionally, it has been proven that these resins have drawbacks in relation to their toxicity and serious health problems as a result of their continuous use (Park, Kang, Park, & Park, 201 1) (Ferguson, Mendon, Rawlins, & Thames, 2014).

This has encouraged the development of adhesives from various renewable sources that can replace or substitute conventional adhesives in the wood industry (Antov, Savov, & Neykov, 2020). Some of the raw materials that have been highlighted in recent years include the synthesis of bioadhesives from lignin, tannins, starch and proteins (Hemmilá, Adamopoulos, Karlsson, & Kumar, 2017), (Antov et al., 2020). Protein-based adhesives have traditionally been obtained from milk casein, collagen from animal skins, waste from the fishing industry and soybeans, because proteins of both animal and plant origin have functional groups with ideal characteristics for use as a base for wood adhesives.

Casein is the main protein in milk and its use as glue in wooden frames has been documented since the Renaissance. Casein-based glues were already being marketed at the beginning of the 19th century and a century later, the first adhesive mixtures containing dry casein, lime and sodium salts were patented. From the 1930s onwards, it began to be replaced by adhesives with greater water resistance such as phenolic resins (1931-1935), urea-formaldehyde (1937), resorcinol (1943) and polyvinyl acetate copolymers (1970) (Bye, 1990).

The use of animal waste to obtain low-cost adhesives has also been considered, such as the synthesis of adhesives from hydrolyzed collagen from leather industry waste as an initiator and silane coupling agent (SCA) as a cross-linking agent (Zhou et al., 2017).

There are adhesives based on mussel proteins (MAPs) whose properties have been evaluated in recent years, due to their great adhesive strength and water resistance (Kord Forooshani & Lee, 2017). However, this raw material is not widely available and therefore its cost is high, additionally due to the high cost of adhesives obtained from mussels, this process is not profitable for applications in the wood industry (Song et al., 2016). However, based on these results, studies have been carried out for the modification of proteins from other sources, in order to increase tolerance to humidity (Y. Liu & L¡, 2004).

In recent years, attention has focused on soy flour proteins. (SF), a by-product of soybean oil extraction, is a by-product of soybean oil extraction due to its low price, easy availability and easy handling (Wescott et al. 2006). Obtaining adhesives from the proteins present in SF has been widely studied for its extensive advantages (US2010/0035098 A1 ) (Vnucec, Kutnar, & Gorsek, 2017). On the one hand, the abundance of this resource since it is known that for each ton of crude soybean oil, about 5 tons of soybean meal with approximately 50% protein by weight can be obtained (Berk, 1992), (Fhhart & Birkeland, 2014). Additionally, products with a higher protein content can also be obtained from residual soy, such as soy protein concentrates (SPC) with approximately 65% protein (Lusas & Rhee, 1995), and soy protein isolate (SPI) which can have a protein content of 90% on a moisture-free basis (Frihart & Birkeland, 2014).

Hybrid protein adhesives that include a certain percentage of conventional adhesives (US2006/0234077 A1 ) (WO201 1/156380) and bioadhesives with additional fillers (D. Liu et al., 2010) have also been studied. Likewise, the obtaining of bioadhesives from mixtures of different renewable raw materials has been evaluated, such as the case of an adhesive composition that comprises the reaction of functional groups from lignin and soy protein, together with curing agents of the amine, amide, iminate or imide type with a heterocyclic functional group (Grot, 2009). In addition, it is also possible to obtain a wood adhesive from depolymerized lignin together with a by-product of biodiesel production (Zhu, Wang, Li, & Sun, 2017). Wheat gluten (WG) is a by-product of wheat starch processing and bioethanol production that has also been used together with soy protein to obtain bioadhesives that can be applied in the manufacture of particle boards (Khosravi, Khabbaz, Nordqvist, & Johansson, 2010).

Likewise, in the state of the art there is patent document US8057892B2, which discloses a bioadhesive for wood which mainly comprises a protein material, an acidity regulator, an aromatic compound, a curing agent and a preservative, where the adhesive has the advantage that It can be stored at room temperature and its shelf life can last for one year without cold storage, no or almost no formaldehyde is released during production, the wood adhesive has high water resistance and can even reach the standard of Grade I and Grade II; the curing temperature of wood adhesive is 1-10°C or higher, which is beneficial to its use. However, this background requires its mixing with various additives to be functional.

DESCRIPTION OF THE INVENTION

As a solution to the aforementioned problems, the present invention was developed, which comprises the use of an industrial residue originating from the extraction of products of the Plukenetia genus, as an alternative to the use of raw materials of fossil origin conventionally used for the production of adhesives for wood, paper and cardboard.

The cold pressing or extrusion process is currently the most widely used for the extraction of virgin seed oil, which is valued for its nutritional properties both in Peru and abroad. During this process, a residual cake of low commercial value is obtained as a by-product, which has a high protein content, which could be used through the proposed procedure.

This represents an improvement in the state of the art, since the final product produced with this process does not present toxicity or health problems as a result of its continuous use. In addition, it will not be mixed with conventional adhesives, being entirely derived from natural sources, specifically, the residual cake. Another important improvement is that the curing of the bioadhesive occurs at room temperature.

The inclusion of carbohydrate hydrolysis influences the improvement of the process, since it allows a comprehensive use of the residual cake. This allows obtaining a higher yield, taking into account that there is a large amount of carbohydrates present in the composition of the cake formed by cold pressing of seeds of the Plukenetia genus. It is possible to use strong inorganic acids in low concentrations, which ionize in aqueous solution, such as HNO3, H2SO40 HCI, among others.

Additionally, since water-based bioadhesives such as the one proposed may have conservation problems after storage, additives are used, such as essential oils with known antimicrobial power that would act as a natural preservative of the bioadhesive or other synthetic additives.

The adhesive obtained from residual cake has a similar performance and adhesive power to other natural adhesives, however, to obtain other natural adhesives, inputs that compete with food production are used, while to obtain the bioadhesive from Plukenetia products, the residual cake left over after the extraction of oil from Plukenetia products is used. For human food and protein supplements from this residual cake, there is the problem that toxic solvents are required in the procedures and an effective removal of 100% of the solvent in the final product cannot be guaranteed, which is not attractive to consumers. Therefore, the proposed bioadhesive would not conflict with food production given the limitations of producing quality protein for human consumption from the residual cake, since although it is possible to isolate the protein, it is very difficult for it to be suitable for consumption and free of traces of solvents used during its extraction, such as hexane. Furthermore, this residual cake has been attempted to be used for animal feed with little success due to a high content of antinutritional factors and a low added value of the final product.

The procedure starts from the residual cake obtained as a residue of the cold extraction of the oil from products of the Plukenetia genus by using an expeller. The procedure consists of removing the residual oil from the cake formed, subsequently extract the proteins contained in the residual cake and carry out a hydrolysis process of the carbohydrates present in the cake, to finally obtain the bioadhesive from the mixture of the proteins together with the hydrolyzed carbohydrates.

Specifically, to obtain the bio-based bioadhesive from industrial waste, the following steps are carried out:

- Degreasing a residual cake obtained from the extraction of oil from seeds of the Plukenetia genus to obtain a degreased cake;

- Prepare a solution by mixing the degreased cake in distilled water at a concentration of 10 to 30% w/w;

- Adjust the pH of the solution from the previous step to between 7.5 and 9.0 with a pH modifying agent, such that a solution with adjusted pH is obtained;

- Centrifuge the pH-adjusted solution so that a centrifuged solution is obtained;

- Perform a first vacuum filtration of the centrifuged solution to separate it into two phases, obtaining a supernatant containing soluble carbohydrates and a precipitate containing insoluble carbohydrates;

- Adjust the pH of the supernatant until reaching the isoelectric point, such that a supernatant with adjusted pH is obtained;

- Centrifuge the pH-adjusted supernatant so that a centrifuged supernatant is obtained;

- Perform a second vacuum filtration of the centrifuged supernatant to separate two phases, obtaining a precipitated protein and soluble carbohydrates;

- Mix soluble and insoluble carbohydrates, in such a way that mixed carbohydrates are obtained;

- Perform an acid hydrolysis of the mixed carbohydrates, in a range between 1 M to 4M, and between 80 and 150°C for a time between 1 and 5 hours, in such a way that hydrolyzed carbohydrates are obtained;

- Neutralize hydrolyzed carbohydrates by slowly adding a alkaline solution, such that hydrolyzed and neutralized carbohydrates are obtained;

- Denature the protein present in the precipitate formed after the second vacuum filtration, using an alkalizing agent until reaching a pH of 1.1, in such a way that denatured protein is obtained;

- Mix the denatured protein and the hydrolyzed and neutralized carbohydrates, maintaining the pH, in such a way that a mixture of proteins and carbohydrates is obtained; and,

- Add between 1 to 5% v/v of essential oil or synthetic preservatives under stirring to the mixture of proteins and carbohydrates, in such a way that the bioadhesive is obtained.

BRIEF DESCRIPTION OF THE FIGURES

FIGURE NO. 1: An operations diagram of the production process is shown.

FIGURE N°2: Comparison between FTIR spectra obtained from the cake of products of the Plukenetia genus and the bioadhesive obtained.

FIGURE N°3: A) Thermogravimetric curve of the bioadhesive and B) its derivative.

FIGURE No. 4: Identification table of characteristic peaks of the FTIR spectra obtained from the residual cake of products of the Plukenetia genus.

DETAILED DESCRIPTION AND/OR PREFERRED EMBODIMENTS

Figure 1 shows an operation diagram of the production process, where upon reaching the first stage of centrifugation, on the right side soluble carbohydrates are mixed with HCl, and the proteins are precipitated and denatured; while on the left side, insoluble and soluble carbohydrates are mixed, and hydrolyzed carbohydrates are neutralized. Characterization of the residual cake of products of the Plukenetia genus and the bioadhesive obtained:

The result of the determination of the amount of proteins present in the raw material (residual cake of Plukenetia genus product) is attached. The FTIR spectrum of the bioadhesive was obtained using a Shimadzu IR Tracer-100 model FTIR spectrophotometer. This analysis was carried out in order to understand the reaction mechanism between the hydrolyzed carbohydrates and the protein residue of the defatted cake to form the bioadhesive. Table 1 summarizes the peaks identified in the residual cake, with the bond vibration of functional groups characteristic of carbohydrates, proteins and fats. On the other hand, characteristic peaks of the functional groups Amide I, II and III are observed, which are characteristic of proteins, this predicts that the residual cake of Plukenetia genus products is a protein-rich residue.

The FTIR assay performed on the obtained product was intended to evaluate the reaction mechanism between the hydrolyzed carbohydrates and the protein residue of the defatted waste cake to form the bioadhesive (Figure 2). The FTIR spectra obtained from the cake and the bioadhesive were compared, as shown in Figure 2. The results show differences in both spectra in the range of 1000 to 1700 cm ¹ . Generally, the Maillard reaction refers to the interaction initiated between the amino groups of proteins and the aldehyde groups of reducing sugars, this reaction leads to the loss of NH2 bonds and the formation of compounds with (CO bonds), (CN bonds) and (CN bonds). This is demonstrated in the FTIR spectrum obtained from the bioadhesive, since it is observed that the intensity of the characteristic peaks of the NH2 bonds present in the Amide groups I, II and III of the protein (located at 1652, 1545 and 1244 cnr ¹ respectively), is reduced compared to the FTIR spectrum of the Cake. In addition, the formation of a new peak at 1048 cm ^-1 is observed, which is characteristic of the C-0 bonds originated by the reaction. On the other hand, the intensity of the characteristic peaks of the CN bonds (located at 1085 and 1 158 cm-1 ) increases in the spectrum of the bioadhesive. Therefore, these results validate the mechanism of the Maillard reaction that gave rise to the formation of the bioadhesive.

On the other hand, the thermal stability of the bioadhesive was analyzed at the Renewable Energy Laboratory of the National Agrarian University La Molina. The equipment used was a thermogravimetric analyzer model TGA701 from the LECO brand. The sample was heated from 25 to 600 °C at a heating rate of 10 °C/min under a nitrogen flow of 20 mL/min. In this test, the thermogravimetric curve of the sample and its derivative were obtained and analyzed. The TGA was carried out in order to evaluate the influence of the binding between proteins and reducing sugars, responsible for the formation of the bioadhesive, on its thermal stability. The thermogravimetric curve obtained and its derivative are shown in Figure 3. These were divided into 3 regions: 25-107 °C (Region I), 107-300 °C (Region II) and 300-500 °C (Region III). In the first region, the weight loss of the bioadhesive is attributed to the evaporation of residual moisture, which represents 4.26%. In the second region, the weight loss is considerable, reaching 30.47% due to the loss of protein micromolecules and, therefore, to the decomposition of the chemical bond that unites the proteins and reducing sugars responsible for the formation of the bioadhesive. In the third and last region there is a weight loss of 23.84%, which corresponds to the degradation of the bioadhesive. Therefore, the bioadhesive does not undergo significant changes at temperatures below 107°C, however, when this temperature is exceeded its behavior can vary significantly since the proteins, essential components for the formation of the bioadhesive, begin to degrade.

In a preferred embodiment, before starting the bioadhesive synthesis process, the residual cake is degreased by Soxhlet extraction to remove the remaining oil. There are different solvents that can be used in this stage, such as petroleum ether or hexane.

In a preferred embodiment, some curing agents could be added. which could increase the storage properties of the adhesive, for example, ammonium chloride, potassium pyrosulfate, sodium sulfite, sodium dihydrogen phosphate, sodium tetraborate, sodium hypophosphite, sodium bisulfate, ferric sulfate, sodium silicate, triethylamine, 3, 3 ', 4,4'- benzophenonetetracarboxylic dianhydride, 2-dodecen -1-ylsuccinic anhydride, decanedihydrazide, chlorendic anhydride, ammonium perchlorate or a mixture thereof. On the other hand, after adding between 1 to 5% v / v of essential oil or synthetic preservatives under stirring, the bioadhesive obtained can be filtered, dried or freeze-dried and then the product can be stored in a cool, dry place at room temperature.

It can also be stored in gel form at room temperature as long as it is kept sealed, and once opened it is recommended to keep it refrigerated.

Claims

1.- A process for obtaining a bio-based bioadhesive from industrial waste, characterized in that it comprises: - Degreasing a residual cake obtained from the extraction of oil from seeds of the Plukenetia genus to obtain a degreased cake; - Prepare a solution by mixing the degreased cake in distilled water at a concentration of 10 to 30% w/w; - Adjust the pH of the solution from the previous step to between 7.5 and 9.0 with a pH modifying agent, such that a solution with adjusted pH is obtained; - Centrifuge the pH-adjusted solution so that a centrifuged solution is obtained; - Perform a first vacuum filtration of the centrifuged solution to separate it into two phases, obtaining a supernatant containing soluble carbohydrates and a precipitate containing insoluble carbohydrates; - Adjust the pH of the supernatant until reaching the isoelectric point, such that a supernatant with adjusted pH is obtained; - Centrifuge the pH-adjusted supernatant so that a centrifuged supernatant is obtained; - Perform a second vacuum filtration of the centrifuged supernatant to separate two phases, obtaining a precipitated protein and soluble carbohydrates; - Mix soluble and insoluble carbohydrates, in such a way that mixed carbohydrates are obtained; - Perform an acid hydrolysis of the mixed carbohydrates, in a range between 1 M to 4M, and between 80 and 150°C for a time between 1 and 5 hours, in such a way that hydrolyzed carbohydrates are obtained; - Neutralize the hydrolyzed carbohydrates by slowly adding an alkaline solution, in such a way that hydrolyzed and neutralized carbohydrates are obtained; - Denature the protein present in the precipitate formed after the second vacuum filtration, using an alkalizing agent until reaching a pH of 11, such that denatured protein is obtained; - Mix the denatured protein and the hydrolyzed and neutralized carbohydrates, maintaining the pH, in such a way that a mixture of proteins and carbohydrates is obtained; and, - Add between 1 to 5% v/v of essential oil or synthetic preservatives under stirring to the mixture of proteins and carbohydrates, in such a way that the bioadhesive is obtained. 2.- The process for obtaining a biologically-based bioadhesive, according to claim 1, characterized in that the bioadhesive obtained after adding the essential oil or synthetic preservatives is filtered. 3.- The process for obtaining a biologically-based bioadhesive, according to claim 1, characterized in that the bioadhesive obtained after adding the essential oil or synthetic preservatives is dried. 4.- The process to obtain a biologically based bioadhesive, according to claim 1, characterized in that the bioadhesive obtained after adding the essential oil or synthetic preservatives is lyophilized.