Adhesive compositions, process for obtaining adhesive compositions, and product.

Description

1 / 28 Adhesive compositions, process for obtaining adhesive compositions, and product.

[001] The present invention relates to adhesive compositions with lignin replacing starch, maintaining adequate bonding performance and increasing the moisture resistance of the adhesive composition. Adhesive compositions with a combination of lignin and microfibrillated cellulose (MFC) replacing starch are also provided. Processes for obtaining the aforementioned compositions are also provided. Description of the State of the Art

[002] The main non-food application of starch is as an adhesive in the paper and corrugated cardboard industry. In its application process, the aqueous starch-based adhesive is applied to the surface of the paper, where water migrates into the pores and retains the starch granules, which, through the application of heat and pressure, swell and gelatinize, acting as a fast and strong adhesive. After the gelatinization process, when heating ceases and the adhesive is left to rest and cool, the molecules re-approach each other, the amylose reorganizes and tends to return to the interior of the molecule, forming a network through association with chains surrounding the gelatinized granules, causing an increase in viscosity in this process, which is called retrogradation.

[003] Starch-based adhesives tend to have low water resistance due to the hydroxyl groups present in starch, which restricts the application of this type of adhesive. As an alternative to overcome this problem, coupled with the search for greener options, it is advantageous to explore the substitution of starch with renewable materials, such as different types of fiber and hemicellulose.

[004] It is estimated that in 2010, 50 million tons of lignin were extracted in the pulp industry, of which only 2% Petition 870250077529, dated 01 / 09 / 2025, page 7 / 83 2 / 28 were sold for use in chemical industries, such as in adhesive formulations, dispersants, surfactants, or as antioxidants, and the remainder was burned to generate energy for the pulp and paper industry. With technological advances and the growing demand for the use of raw materials from renewable sources, the use of lignin in new products for different industrial segments has been investigated.

[005] In this context, the present invention utilizes lignin, which contains several functional groups, has a good cost-benefit ratio and is also a biodegradable material, as a reinforcing substitute to improve or maintain the mechanical and adhesion properties of adhesive compounds, as well as to seek greater moisture resistance of the compound. Also in the context of obtaining renewable materials, the present invention proposes the substitution of part of the starch by MFC. Objectives of the Invention

[006] A primary objective of the present invention is to provide a renewable-based adhesive.

[007] A second objective of the present invention is to provide an adhesive that has lignin as a replacement component, preferably a major component, in the adhesive composition for application to paper substrates.

[008] A third objective of the present invention is to provide an adhesive with MFC added to a starch-lignin base to reduce the amount of starch required to obtain the adhesive.

[009] A fourth objective of the present invention is to provide a starch-lignin based adhesive, with or without MFC, which has superior moisture resistance compared to adhesives based solely on starch. Brief Description of the Invention Petition 870250077529, dated 01 / 09 / 2025, page 8 / 83 3 / 28

[0010] The present invention relates to an adhesive composition comprising lignin in a proportion of about 1% to about 4% by mass of the adhesive composition, and starch in a proportion of about 10% to about 30% by mass of the adhesive composition, preferably about 19% to about 21% by mass of the adhesive composition, or starch in a proportion of about 3% to about 22% by mass of the adhesive composition and microfibrillated cellulose (MFC) in a proportion of about 0.4% to about 0.6% by mass of the adhesive composition.

[0011] In one embodiment, the adhesive composition comprises borax in a proportion of about 0.05% to about 0.40% by mass of the adhesive composition, 50% sodium hydroxide solution in a proportion of about 0.8% to about 1.5% by mass of the adhesive composition, and water in a proportion of 35% to 70% by mass of the adhesive composition.

[0012] In another embodiment, the adhesive composition comprises a borax / starch ratio by mass of the adhesive composition between about 0.01 and about 0.040.

[0013] In another embodiment, the adhesive composition comprises a lignin solution in a proportion of about 22% to about 50% by mass of the adhesive composition.

[0014] In another embodiment, the lignin solution comprises moist lignin (40 to 60% solids) in a proportion of about 14% to about 19% by mass of the solution, sodium hydroxide in a proportion of about 1.5% to about 2.5% by mass of the solution, and water q.s.

[0015] The present invention also relates to a process for obtaining an adhesive composition such as that described above in any of its embodiments, comprising the steps of: - Mix in a container for 1 minute, approximately 50% of the water mass specified in the adhesive formulation, at a temperature of approximately Petition 870250077529, dated 01 / 09 / 2025, p. 9 / 83 4 / 28 30°C to approximately 42°C and 15% to 22% of the starch specified in the adhesive formulation; - Add the total mass of the 50% sodium hydroxide solution specified in the formulation and mix at a speed of approximately 480 rpm for about 3 minutes; Add the remaining water specified in the formulation at a temperature of approximately 30°C to approximately 42°C and mix for about 1 minute; - Add the lignin solution or the lignin specified in the formulation to the mixture and mix for about 3 minutes; - To add: the remaining starch mass specified in the adhesive composition; or the remaining starch mass specified in the adhesive composition and the total aqueous dispersion of MFC specified in the adhesive composition; Mix for about 3 minutes at a speed of about 1200 rpm; and - Add the total mass of borax specified in the adhesive composition, without stopping the stirring, and mix for about 3 minutes at a speed of about 2300 rpm. Brief Description of the Drawings

[0016] The present invention will now be described in more detail based on an exemplary embodiment shown in the drawings. The figures show:

[0017] Figure 1 - is an experimental setup for validating the present invention.

[0018] Figure 2A - is a photo of the application of the adhesive of the present invention for preparation for bonding testing;

[0019] Figure 2B - is a photo of the adhesive being pressed in preparation for bonding testing;

[0020] Figure 3 - is a representative diagram of the Peel test. Petition 870250077529, dated 01 / 09 / 2025, page 10 / 83 5 / 28 Adhesion;

[0021] Figure 4 - is a set of photos of cover and interior samples transformed into strips for making the plates;

[0022] Figure 5 - is a photo of a single-wall corrugated cardboard sheet;

[0023] Figure 6 - is a set of photos of the adhesive application process and gluing of the inner pages and covers;

[0024] Figure 7 - is a photo of the lignin used in the tests, taken by stereomicroscope - 25x;

[0025] Figure 8A - is an image of the lignin used in the tests, by SEM - 500x;

[0026] Figure 8B - is an image of the lignin used in the tests, by SEM - 2000x;

[0027] Figure 9 - is a graph representing the contact angle obtained from the wetting test for the starch modality, measured in degrees [°] (vertical axis) for each sample (horizontal axis);

[0028] Figure 10 - is a graph representing viscosity in [mPa.s] (vertical axis) as a function of time in [s] (horizontal axis) for different samples;

[0029] Figure 11 - is a graph representing viscosity in [mPa.s] (vertical axis) as a function of time in [s] (horizontal axis) under different shear rates;

[0030] Figure 12 - is a graph representing viscosity in [mPa.s] (vertical axis) as a function of time in [s] (horizontal axis) for different samples under a constant shear rate equal to 500s-1;

[0031] Figure 13 - is a schematic of the experimental plan for evaluating the addition of MFC to starch-lignin adhesive;

[0032] Figure 14 - is a graph representing viscosity in [mPa.s] (vertical axis) as a function of time in [s] (horizontal axis) Petition 870250077529, dated 01 / 09 / 2025, page 11 / 83 6 / 28 different samples;

[0033] Figure 15A - is a photo of the bonding test specimens with 150μιτι spiral extender, used in the bonding test;

[0034] Figure 15B - is a photo of the bonding test specimens with 100μm spiral extender, used in the bonding test; and

[0035] Figure 16 - is a graph representing the contact angle measured in degrees [°] (vertical axis) as a function of time in [s] (horizontal axis) for each sample, obtained in the wetting test for the modality with starch and MFC. Detailed Description of the Figures

[0036] First, it should be noted that the preferred term used here refers to a particular embodiment of the invention's efficiency among the multiple possible embodiments. This preferred term should not be understood as limiting the possible embodiments of the present invention, that is, it should not be understood as imperative or mandatory for carrying out the present invention. It is defined that the expression "about" should be understood as a tolerance range of 10% more or less. Furthermore, when not expressly indicated or implied, the percentages of components mentioned here should be understood as percentages of the total mass of the composition.

[0037] Unless expressly stated otherwise, all quantities expressed as percentages refer to a weight / weight ratio (or mass / mass, used here as equivalents), in other words, the weight of the component in relation to the weight of the composition in which it is included.

[0038] The use of the verb to understand, as well as its conjugations, does not exclude the presence of elements other than those established.

[0039] The acronym qsp means sufficient quantity for, Petition 870250077529, dated 01 / 09 / 2025, page 12 / 83 7 / 28 should be understood as any quantity necessary to achieve the total weight or volume of the desired composition or solution.

[0040] The present invention relates to an adhesive composition comprising, in some embodiments, starch and lignin and, in some other embodiments, comprising starch, lignin and microfibrillated cellulose (MFC). The following are specifications of exemplary embodiments of the invention, as well as information on tests performed that demonstrate the superiority or satisfactoryness of the invention in relation to reference compositions. STARCH

[0041] The most widely used starch adhesive production process is the Stein Hall method, which consists of a two-phase preparation: the cooked and the raw phases. The first phase is responsible for the adhesive's viscosity and for preventing the sedimentation of ungelatinized starch granules from the raw phase. The cooked portion is prepared using, preferably, 15 to 22% of the total starch in the composition, heated with water in the presence of a strong base, more preferably 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, or any range within these values. In this phase, the starch is completely gelatinized and acquires a high viscosity, with a gel-like appearance. This phase will receive the remaining percentage of starch and water from the formulation, as well as a small amount of a boron compound, usually Borax, which will react by creating hydroxyl group bonds between the starch molecules, resulting in cross-linking, which increases the adhesive's stickiness and viscosity.In addition, borax is also responsible for binding the cellulose molecules in the paper to the adhesive, keeping the corrugated cardboard parts together before the adhesive cures.

[0042] There are variations in the Stein Hall process. One of them is related to the order of addition of Borax, which can be carried out in Petition 870250077529, dated 01 / 09 / 2025, page 13 / 83 8 / 28 first stage (cooked), before the addition of secondary starch, instead of being at the end of the process as the last ingredient. Other alternatives are also possible, such as modifying the order of addition of the soda ash (NaOH), adding it in the second stage, also altering the proportion of water and starch in the first and second stages, using all the water from the beginning of the process with half the total starch of the formula, with enough soda ash and borax solution to reach the desired final gel point, or even the process without 2 stages, in which all the water, starch, 50% soda ash and borax are mixed, using well-controlled heat for swelling of the starch granule and partial gelatinization. These are process possibilities, but they have limitations and greater difficulty in controlling to achieve the desired specifications.

[0043] In the bonding process using starch adhesive, only the secondary starch, that is, the non-gelatinized starch, will be responsible for bonding the paper or corrugated cardboard. This occurs by supplying heat to the adhesive, where the available starch granules will gelatinize rapidly and adhere to the paper.

[0044] An important parameter to be controlled in the adhesive is its viscosity, which should not be too low so that water does not diffuse into the paper fibers and remain away from the bonding line, impairing starch gelatinization and consequently the bonding properties, but also not too high, as this hinders its penetration into the paper, resulting in wide glue lines and thus an increase in adhesive consumption, as well as not penetrating the paper sufficiently, decreasing adhesion because the bond between glue and paper is superficial and weak. Therefore, it is important to follow strict controls both in the adhesive production process and after it is finished, such as temperature and shear, as the modifications suffered by these factors can be irreversible and make the use impossible. Petition 870250077529, dated 01 / 09 / 2025, page 14 / 83 9 / 28 glue application. KRAFT LIGNIN

[0045] Lignin is one of the main components of wood, present in varying levels, preferably from about 15 to about 35%, depending on the plant species, and is responsible for protecting plants against oxidation and the action of microorganisms, as well as providing them with strength and structure, more preferably 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any range within these values. In the lignin extraction process in the pulp and paper industry, the lignin structure is degraded to modify its solubility and make it compatible with the reaction medium and separate it from the cellulose. One of the lignin extraction processes is the Kraft Process, which involves dissolving lignin in a solution of sodium hydroxide and sodium sulfide, resulting in a solution called black liquor. The soluble part of this solution is called Kraft lignin and has a high content of phenolic hydroxyl groups.To separate Kraft lignin from the rest of the solution, the pH is adjusted to an acidic condition, causing the lignin to precipitate. GENERAL INFORMATION ABOUT THE TESTS PERFORMED

[0046] To define the compositions that best met the objectives of the invention, different proportions of lignin in the adhesive composition were analyzed, as well as the effects of different pH values ​​and the NaOH / starch, Borax / starch and Borax / NaOH ratios. Microscopic images of the lignin were obtained and tests were performed to measure viscosity, pH, contact angle, gel point, bonding and moisture resistance, and rheological study of the compositions. In addition, standardized CMT, PAT and water immersion tests were performed on the corrugated paper bonded with the compositions. Petition 870250077529, dated 01 / 09 / 2025, page 15 / 83 10 / 28

[0047] Tests for viscosity and pH measurement, according to ASTM D1084:2016 and ABNT NBR 7353:2019 standards, contact angle measurement using an optical tensiometer, and gel point determination according to internal operating procedure. The rheological study was performed using a parallel plate rheometer.

[0048] For the bonding and moisture resistance test, the bonding strength verification was performed under two temperature and humidity conditions: Temperature: 25°C and Relative Humidity: 65%; and Temperature: 25°C and Relative Humidity: 85%.

[0049] For the performance of the aforementioned multiple tests, the preparation was carried out in accordance with the steps indicated below: 1) Apply the adhesive, using a 150-micron spreader, to Kraft paper with a weight of 125 g / m², preheated to 5°C above the adhesive's gelation temperature, as shown in Figure 2A. 2) Join it to the other side of the paper. 3) Press with a 1 kg weight in an oven for 10 minutes, as shown in Figure 2B.

[0050] After gluing the test specimens, the following evaluations were performed:

[0051] a) Immediate bonding strength: After the specimens were removed from the oven, a 1-minute wait was observed, and manual peeling was performed as illustrated in Figure 3, pulling on the glued ends to separate them at an approximate angle of 180°, a movement called 'Peel'. For the evaluation of adhesion / cohesion, a scale of 0 to 5 was used, as per the legend: 0 No cohesion. No paper delamination. 2. More than 50% without cohesion. Significant paper delamination failure. 4. Less than 50% without cohesion. Some defects in paper delamination. Petition 870250077529, dated 01 / 09 / 2025, page 16 / 83 11 / 28 Total cohesion.

[0052] The term adhesion should be understood as the wetting capacity and affinity of the adhesive to the substrate to be bonded, and the term cohesion should be understood as the adhesive's own internal resistance to stress. The greater the intermolecular forces of the adhesive, the greater the cohesion and resistance to delamination.

[0053] b) Final bond strength: For this evaluation, after removing the test specimens from the oven, they were kept for 24 hours in a climate-controlled environment (25°C / 60% humidity), and manual debonding and bond strength evaluation were performed, in the same way as for the immediate strength.

[0054] c) Moisture resistance: After removing the specimens from the oven, they were kept for 24 hours in a climate-controlled environment (25°C / 60% humidity). Then, they were placed in a climate chamber at 25°C and 85% humidity. The bond strength of the specimens was evaluated after exposure for 24 hours and after 48 hours in the presence of moisture. The bond strength test followed the same procedure described for immediate strength.

[0055] Test specimens were then prepared for tests based on the following standards: CMT (ABNT NBR ISO 7263), PAT (ABNT NBR 14972) and water immersion for corrugated paper (ABNT NBR 10530). The cover paper and core paper samples, illustrated in Figure 4, were cut into strips measuring 14.7 mm wide x 152 mm long, and then conditioned at a temperature of 23°C and 50% relative humidity for 4 hours, in accordance with the ABNT NBR NM ISO 187 standard for testing paper, cardboard and corrugated paperboard.

[0056] During the plate making process, each component (covers and core) was heated on plates to 180°C, which gave the paper a Petition 870250077529, dated 01 / 09 / 2025, page 17 / 83 12 / 28 temperature around 90°C depending on the contact time with the hot plate.

[0057] After acclimatization, a laboratory corrugator transformed the strips into single-wall corrugated cardboard, as seen in Figure 5. This corrugation was carried out at a temperature between 175 and 180°C, corresponding to the temperatures used in industrial corrugators.

[0058] The sequence shown in Figure 6 demonstrates the process: (1) The sample is corrugated; (2) The sample is positioned on a rack to receive the adhesive and covers; (3) An adhesive film is applied using a ruler containing a groove with standard depth; (4) The sample is positioned with the adhesive; (5) The first kraft paper covers are placed over each corrugated and glued core; (6) A plate preheated to 180°C and a standard weight of 2kg are placed on the covers for 1 min; (7) The rack containing the core and the first cover already glued is inverted and adhesive is added to the other face; and (8) The second cover is glued on and the heated plate and the 2kg standard weight are placed on the samples to allow the glue to dry.

[0059] The finished corrugated cardboard samples are removed from the support and kept in climate control before performing the bond strength tests (PAT and immersion) and the corrugation crush resistance test (CMT). LIGNIN

[0060] The lignin sample used in the tests performed, illustrated in Figure 7, is derived from Pinus and has its characteristics listed Petition 870250077529, dated 01 / 09 / 2025, page 18 / 83 13 / 28 of those in Table 1 below. The visual aspect of this lignin was investigated by optical microscopy and scanning electron microscopy (SEM), as illustrated in Figure 8A and Figure 8B. Table 1: Characteristics of the lignin used. FINISHED PRODUCT Solids content (%) Ash content (%) L* a* b* Insoluble Lignin (%) Soluble Lignin (%) Purity (%) Calorific Value PCS MJ / kg Average 53.92 0.73 50.04 8.39 25.71 96.9 2.94 99.84 27.448 METALS Na K Mg Ca Fe Al Mn Cu (g / ton) (g / ton) (g / ton) (g / ton) (g / ton) (g / ton) (g / ton) (g / ton) 1868.6 239.05 56.54 60.66 57.31 138.9 19.02 2.96 ELEMENTAL ANALYSIS N (%) C (%) H (%) S (%) 0.235 64.415 5.583 2.507 PDI CHEMICAL ANALYSIS Phenol + Carboxylic OH (mmol / g) MW 4.2 3.4 6.6 INCORPORATION OF LIGNIN INTO STARCH SOLUTION

[0061] As a result of a preliminary investigation of the lignin addition process, it was concluded that the best addition method was that in which the lignin is prepared in solution with pH correction above 10, preferably using a paddle or Cowles type propeller. This result is consistent with the solubility of lignin at different pH scales, as tested and verified in Table 2 below. Solubility was defined by visual observation, when Petition 870250077529, dated 01 / 09 / 2025, page 19 / 83 14 / 28 showed homogeneity of the solution, without the presence of lignin particles. The fact that the lignin is added previously solubilized (in solution form) in the adhesive formulation favors its incorporation. It was observed that, without pH correction or if the addition occurs in solid form, the lignin does not completely solubilize, a situation that can generate instability in the medium. Table 2: Solubility of lignin at different pH levels. pH Solubility 3.37 Insoluble 8 Insoluble 9.9 Insoluble 10.21 Soluble 11.1 Soluble 11.5 Soluble 11.86 Soluble 12 Soluble 12.03 Soluble 12.07 Soluble 12.12 Soluble

[0062] At the end of the investigations, the preferred parameters for using the paddle-type propeller for shearing were defined, and the addition of lignin in the form of an aqueous solution with pH correction to the range of 10 to 11.

[0063] An investigation was also carried out into the incorporation of solid lignin in cake and powder form. The pH above 10 of the glue favors the solubilization of lignin, requiring only a longer stirring time for lignin solubilization in the formulation. The required stirring time was 10 to 30 minutes, preferably 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, or whichever was required. Petition 870250077529, dated 01 / 09 / 2025, page 20 / 83 15 / 28 requires a value within this range, using a paddle or Cowles type propeller. In this case, the solubility of lignin in the formulation was also evaluated visually, observing the homogeneity of the formulation, without the presence of lignin particles. Bonding and moisture resistance tests

[0064] Bonding and moisture resistance tests were performed on samples of adhesive compositions shown in Table 3. The first and second columns (Ref1) are reference compositions with starch, without the use of lignin, and the others (Compl to Comp4) are exemplary compositions of the present invention. Among these samples, those that showed the best performance in bonding to paper substrates were those with the addition of 25% and 45% lignin solution by total mass of the adhesive composition, as indicated in Table 4 below. Table 3: Formulas for starch (reference) and starch adhesives with added lignin. Raw Material Ref1 Compl Comp2 Comp3 Comp4 % (m / m) 0 / / 0 (m / m) 0 / / 0 (m / m) 0 / / 0 (m / m) 0 / / 0 (m / m) Primary Water 35.45 35.45 35.45 35.45 35.45 Primary Starch 3.06 3.06 3.06 3.06 3.06 NaOH 50% 1.1 1.1 1.1 1.1 1.1 Secondary Water 36.67 16.1 10.96 5.81 0.67 Lignin Solution 18.5% - 25.24 31.55 37.86 44.18 Secondary Starch 23.35 18.68 17.51 16.34 15.18 Borax 0.37 0.37 0.37 0.37 0.37 % Total (m / m) 100 100 100 100 100

[0065] The results of the investigated properties are shown in Table 4 below and refer to:

[0066] - Performance of sizing on paper substrate: samples with added lignin at levels of 25% and 45% solution Petition 870250077529, dated 01 / 09 / 2025, p. 21 / 83 16 / 28 of lignin were the ones that presented the best results in comparison to the reference composition (Ref1).

[0067] - Moisture resistance: all samples with added lignin showed superior resistance compared to the reference composition (Ref1), in the presence of moisture for 24h and 48h. Advantageously, the presence of Kraft pine lignin conferred increased moisture resistance, this being an innovative and unexpected result of the application of lignin for this purpose.

[0068] - Production feasibility: with pH adjustment for prior dissolution of lignin (optimal pH value above 10), it was possible to add it to the adhesives without the formation of lumps. In this way, it was possible to incorporate the lignin homogeneously into the adhesive formulations, without the need for additional chemical modification. Table 4: Results obtained for the bonding performance and moisture resistance experiments. SAMPLE COLLAGE MOISTURE RESISTANCE (24H / 48H) Ref1 5.0 1.0 2.0 Compl 4.5 3.0 2.0 Comp2 5.0 4.0 4.0 Comp3 4.7 2.7 3.0 Comp4 4.7 2.0 3.0 [I069] It can be observed, from the results above, that the bonding performance of the compositions of the present invention containing lignin remains adequate compared to the reference composition, and the moisture resistance is even superior to that of Ref1, which demonstrates that the substitution of starch by lignin is possible without substantially impairing the efficiency of the adhesive composition and allows for greater moisture resistance. STARCH-LIGNIN ADHESIVE COMPOSITION

[0070] Based on the tests performed and the intervals of Petition 870250077529, dated 01 / 09 / 2025, page 22 / 83 17 / 28 components identified as suitable for obtaining the intended advantages, the starch and lignin-containing adhesive of the present invention preferably comprises the following composition: - lignin, preferably in a proportion of about 1% to about 4% by mass of the adhesive composition, preferably from about 2.5% to about 3.5%, more preferably 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5% or any range within these values ​​by mass of the adhesive composition; and - starch, preferably in a proportion of about 10% to about 30% by mass of the adhesive composition, preferably from about 19% to about 21%, more preferably from 19.1%, 19.2%, 19.3%, 19.4%, 19.5%, 19.6%, 19.7%, 19.8%, 19.9%, 20%, 20.1%, 20.2%, 20.2%, 20.3%, 20.4%, 20.5%, 20.6%, 20.7%, 20.8%, 20.9%, 21% or any range within these values ​​by mass of the adhesive composition.

[0071] Preferably, the other components may be present in the adhesive composition in the following quantities: - borax in a proportion of about 0.05% to about 0.40%, preferably 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40% or any range within these values ​​by mass of the adhesive composition; - Sodium hydroxide in a proportion of about 0.40% to about 0.70%, preferably 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70% or any range within these values ​​by mass of the adhesive composition; - water qsp PRODUCTION PROCESS

[0072] In accordance with the adhesive compositions proposed herein, the present invention further contemplates a process for producing an adhesive comprising starch and lignin, as set forth below. Petition 870250077529, dated 01 / 09 / 2025, page 23 / 83 18 / 28

[0073] The lignin solution to be added in the raw stage of the process has its composition described in Table 5. Its preparation can preferably be carried out according to the process below: 1. Add water to a container; 2. Add the previously macerated lignin and mix for 3 minutes in a disperser using a Cowles-type propeller. 3. Add the soda solution and mix for 10 minutes with a mechanical stirrer; 4. Check the pH, which should be above 10, using a pH meter. If it is not within the ideal range, add more soda to adjust. Also check if the lignin has been completely dispersed; otherwise, stir for longer. Table 5: Composition of the lignin solution. Soluble Lignin 18.5% Raw materials % (w / w) Water 77.6 Wet Lignin (~50% solids) * 18.5 Soda 50% 3.9 Total 100 Solids content of the formulation 11.22% Dry basis lignin added to the formulation 9.25%

[0074] The process for producing a starch-lignin adhesive of the present invention preferably comprises the following steps: COOKED STAGE: - Add primary water, preferably at a temperature of about 30°C to about 42°C, more preferably at a temperature of 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, or any range within these values, and primary starch to a container and mix for about 1 minute; Add the refrigerant solution and mix at a speed of approximately 480. Petition 870250077529, dated 01 / 09 / 2025, p. 24 / 83 19 / 28 rpm for about 3 minutes; RAW STAGE: - Add secondary water, preferably at a temperature of about 30°C to about 42°C, more preferably at a temperature of 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, or any range within these values, and mix for about 1 minute; Add lignin solution and mix for about 3 minutes; Add secondary starch and mix for 3 minutes at approximately 1200 rpm; Add borax while continuing to stir and mix for 3 minutes at approximately 2300 rpm.

[0075] In the steps of adding secondary water, adding lignin solution and adding secondary starch, mixing is temporarily stopped for the addition of the respective raw materials. In the step of adding borax, stirring or mixing is not stopped.

[0076] It was also observed that it was possible to modify the amount of sodium hydroxide added without significantly altering the desired results when combined with lignin solutions of different concentrations. The formulations below, named Sd1 (prepared without the addition of soda in the lignin solution with a 18.5% lignin solution) and Sd2 (prepared with the addition of soda in the lignin solution with a 31.5% lignin solution). In both formulations, water was added to maintain the desired starch and lignin solids contents, as per the formulas presented in Table 6. Table 6: Adhesive formulations with different amounts of added soda. Raw material Sd1 (% m / m) Sd2 (% m / m) Primary water 35.45 35.45 Petition 870250077529, dated 01 / 09 / 2025, page 25 / 83 20 / 28 Primary starch 3.06 3.06 NaOH 50% 1.1 1.1 Secondary water 10.96 10.96 Water for solids correction 22.14 20.91 NaOH 50% (added to Lignin Solution) - 1.23 Lignin Solution 9.41 (18.5%) 9.41 (31.5%) Secondary starch 17.51 ​​17.51 ​​Borax decahydrate 0.37 0.37 Total 100 100 Solids content 24.45% 25.07% Lignin dry basis 2.92% 2.92% Addition of MFC to Starch-Lignin Adhesive

[0077] A study was conducted on reducing the percentage of starch in the starch-lignin adhesive formulation and adding unbleached microfibrillated cellulose (MFC). The experimental plan developed proposed replacing part of the secondary starch added to the raw phase with MFC (4% w / w dispersion).

[0078] The experimental plan began with the reduction of 30% of the amount of secondary starch from the raw phase and the addition of two different percentages of unbleached microfibrillated cellulose (MFC) in this same phase. The formulations are presented in Table 7, noting that the amounts of MFC were: - 0.25% MFC, considering the solid content, calculated on the total formula, or 6.25% MFC as a percentage of the total formula mass (0.25 - MFC); and - 0.50% MFC, considering the solid content, calculated on the total formula, or 12.5% ​​MFC as a percentage of the total formula mass (0.50 - MFC). Petition 870250077529, dated 01 / 09 / 2025, p. 26 / 83 21 / 28 Table 7: Formulation of starch-lignin adhesives with the addition of unbleached MFC. Raw Material 0.25-MFC (%m / m) 0.50MFC (%m / m) Primary Water 35.45 35.45 Primary Starch 3.06 3.06 50% NaOH 1.1 1.1 Secondary Water 9.96 3.71 Lignin Solution 31.55 31.55 Secondary Starch 12.26 12.26 4% MFC 6.25 12.5 Borax Decahydrate 0.37 0.37 Total 100 100 Solids Content 20.02% 20.27% Lignin Dry Basis 2.92% 2.92%

[0079] After verifying the amount of MFC that showed the best bonding performance, this content was fixed (0.5% MFC) and a greater reduction in the percentage of secondary starch was carried out, where the secondary starch content of the raw phase was decreased by 60%. In this phase, adjustments to the proportions of soda and borax were also evaluated in order to determine a preferred proportion of these components. The description of the formulas is presented in Table 8. Table 8: Adhesive formulations with a 60% reduction in starch in the raw phase and adjustment of the soda / borax and borax / starch ratios. Item Raw Material 0.5-MFC60-1 (%m / m) 0.5-MFC60-2 (%m / m) 0.5-MFC60-3 (%m / m) 1 Primary water 35.45 35.45 35.45 2 Primary starch 3.06 3.06 3.06 3 NaOH 50% 1.1 0.54 1.1 4 Secondary water 8.97 9.71 9.15 Petition 870250077529, dated 01 / 09 / 2025, page 27 / 83 22 / 28 5 Lignin Solution 31.55 31.55 31.55 6 Secondary Starch 7 7 7 7 MFC 4% 12.5 12.5 12.5 8 Borax Decahydrate 0.37 0.181 0.181 Total 100 100 100 Solids Content 15.01% 14.51% 14.81% Lignin Dry Basis 2.92% 2.92% 2.92% Soda / Starch Proportions 5.47 2.68 5.47 Borax / Starch 3.68 1.8 1.8 Borax / Soda 67.27 67.04 31.91

[0080] In order to verify the feasible limit for reducing the amount of starch in the raw phase, formulations were prepared with different percentages of secondary starch reduction, maintaining the MFC content of 0.5%, and adjusting the preferred borax / starch ratio to 1.8, as shown in Table 9. Table 9: Adhesive formulations with 70, 80, 90 and 100% reduction of starch in the raw phase with adjustment of the borax / starch ratio. Item Raw Material 0.5-MFC70 (%m / m) 0.5-MFC80 (%m / m) 0.5-MFC90 (%m / m) 0.5MFC100 (%m / m) 1 Primary water 35.45 35.45 35.45 35.45 2 Primary starch 3.06 3.06 3.06 3.06 3 NaOH 50% 1.1 1.1 1.1 1.1 4 Secondary water 10.94 12.72 14.50 16.28 5 Lignin solution 31.55 31.55 31.55 31.55 Petition 870250077529, dated 01 / 09 / 2025, p. 28 / 83 23 / 28 6 Secondary starch 5.25 3.50 1.75 0 7 MFC 4% 12.5 12.5 12.5 12.5 8 Borax decah id rattado 0.15 0.12 0.09 0.06 Total 100 100 100 100 Solids content 13.01% 11.21% 9.51% 7.71% Lignin dry basis 2.92% 2.92% 2.92% 2.92% Soda / starch ratios 6.62 8.38 11.43 17.97 Borax / starch 1.8 1.8 1.8 1.8 Borax / soda 27.21 21.48 15.75 10.01

[0081] In order to evaluate the inclusion of MFC in the starch-lignin adhesive formulation, bonding performance analyses were carried out on paper substrates and the results obtained are presented in Table 10: Table 10: Results of tests performed on starch-lignin adhesive formulations with added MFC. Bonding Performance Formula 0.25-MFC 3.5 0.50-MFC 4.5 0.5-MFC60-1 4 0.5-MFC60-2 0 0.5-MFC60-3 5 0.5-MFC70 5 0.5-MFC80 4 0.5-MFC90 5 0.5-MFC100 1.7

[0082] It is observed that the bonding performance of the 0.5-MFC60-2 sample was substantially lower than the others, indicating that Petition 870250077529, dated 01 / 09 / 2025, page 29 / 83 24 / 28 that specific combination of borax / soda / starch ratio is unfavorable to the bonding efficiency of the compound. It was also observed that the bonding performance of a compound with 100% removal of secondary starch is substantially lower than the others with 60% and 90% of secondary starch removed, indicating that secondary starch removal can be achieved with good efficiency in proportions from 50% to 90%. MEASURING THE CONTACT ANGLE

[0083] To evaluate the difference in contact angle with the insertion of microfibrillated cellulose and reduction of starch content, the following adhesives were analyzed:

[0084] - Ref1: reference starch-lignin adhesive; and

[0085] - 0.5-MFC60-3; 0.5-MFC70 and 0.5-MFC80: starch-lignin adhesive formulations with reduced starch content and added MFC.

[0086] Figure 16 shows the graph with the results of the contact angle measurements as a function of time for the four samples analyzed. Among the formulations analyzed, the Ref1 adhesive showed the smallest contact angle, i.e., the most hydrophilic characteristic. It was possible to verify that, with the reduction of the starch content in the raw phase and the addition of MFC, there is an increase in the hydrophobic character of the adhesive (lower surface wettability), proven by the result obtained for the 0.5MFC80 formulation, which, among the tests performed, is the adhesive with the lowest starch content.

[0087] According to the analysis of the contact angle results, there was an indication of increased hydrophobicity with the reduction of starch content in the raw phase. This behavior can be evidenced according to the data in the graph for samples 0.5-MFC60-3, 0.5MFC70, 0.5MFC80. This behavior can be evidenced according to the data in the graph for samples 0.5-MFC6-3 and 0.5-MFC70. Petition 870250077529, dated 01 / 09 / 2025, page 30 / 83 25 / 28 respectively. Composition of starch-lignin-MFC adhesive

[0088] Based on the tests performed and the component ranges identified as suitable for obtaining the intended advantages, the adhesive containing starch, lignin and MFC of the present invention preferably comprises the following composition: - lignin, preferably in a proportion of about 1% to about 4% by mass of the adhesive composition, preferably about 2.5% to 3.5%, more preferably 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5% or any range within these values ​​by mass of the adhesive composition; - starch, preferably in a proportion of about 3% to about 22%, more preferably 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, or any range within these values ​​by mass of the adhesive composition; and - Microfibrillated cellulose (MFC), preferably in a proportion of about 0.4% to about 0.6%, more preferably 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.50%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, 0.60%, or any range within these values, by mass of the adhesive composition, preferably in the form of an aqueous dispersion (MFC-4%) in a proportion of about 10% to about 15%, preferably 10.00%, 10.25%, 10.50%, 10.75%, 11.00% 11.25%, 11.50%, 11.75%, 12.00%, 12.25%, 12.50%, 12.75%, 13.00%, 13.25%, 13.50%, 13.75%, 14.00%, 14.25%, 14.50%, 14.75%, 15.00%, or any range within these values ​​by mass of the adhesive composition.

[0089] Preferably, the other components may be present in the composition in the following quantities: Petition 870250077529, dated 01 / 09 / 2025, page 31 / 83 26 / 28 - borax in a proportion of about 0.05% to about 0.40%, preferably 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40% or any range within these values ​​by mass of the adhesive composition; - Sodium hydroxide in a proportion of about 0.4% to about 0.7%, preferably 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70% or any range within these values ​​by mass of the adhesive composition; - water qsp

[0090] In particular, the adhesive composition of the present invention (starch-lignin composition or starch-lignin-MFC composition) can preferably be obtained by the following process: - mixing in a container for 1 minute, about 50% of the mass of water provided for in the adhesive formulation, preferably at a temperature of about 30°C to about 42°C, more preferably at a temperature of 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, or any range within these values, and preferably from 15% to 22%, more preferably 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, or any range within these values, of the starch specified in the adhesive formulation; - Add the total mass of the 50% sodium hydroxide solution specified in the formulation and mix at a speed of approximately 480 rpm for about 3 minutes; - Add the remaining water specified in the formulation, preferably at a temperature of about 30°C to about 42°C, more preferably at a temperature of 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, or any range within these values, and mix for about 1 minute; - Add the lignin solution specified in the formulation to the product and mix for approximately 3 minutes; Petition 870250077529, dated 01 / 09 / 2025, p. 32 / 83 27 / 28 - to add: the remaining starch mass specified in the adhesive composition; or the remaining starch mass specified in the adhesive composition and, sequentially, the total aqueous dispersion of MFC specified in the adhesive composition; - Mix for about 3 minutes at a speed of about 1200 rpm; and - Add the total mass of borax specified in the adhesive composition, without stopping the stirring, and mix for about 3 minutes at a speed of about 2300 rpm.

[0091] It makes clear that the adhesive compositions proposed here allow the use of raw materials other than starch (lignin, combined or not with MFC) to produce adhesives with mechanical properties similar to compositions with starch alone, while exhibiting superior moisture resistance properties. The addition of MFC, in particular, demonstrated an effect of increasing the hydrophobicity of the composition. Therefore, compositions with a significant reduction in starch (50 to 90% of the starch in the raw phase) are obtained compared to prior art compositions, used here as a reference. As an additional advantage, a reduction in solids content of at least 10% is observed, directly derived from the reduction in the amount of starch used, which is reflected in reduced production costs.

[0092] The present invention also contemplates a product comprising a substrate, preferably cellulose-based, to which the aforementioned adhesive composition is applied in any of its possible forms, considering the most varied configurations and applicators, including, but not limited to, the following products: corrugated cardboard boxes, corrugated cardboard sheets, slip sheets, sacks, and other materials. Petition 870250077529, dated 01 / 09 / 2025, page 33 / 83 28 / 28 similar, where the adhesive is applied in different ways and using different applicators to provide adequate adhesion, as needed for the application. Petition 870250077529, dated 01 / 09 / 2025, page 34 / 83

Claims

1 / 2 CLAIMS 1. Adhesive composition characterized in that it comprises: - lignin solution in a proportion of 22% to 50% by mass of the adhesive composition; - borax in a proportion of 0.05% to 0.40% by mass of the adhesive composition; - a composition selected from the group comprising: a. starch in a proportion of 10% to 30%, preferably 19% to 21%, by mass of the adhesive composition; or b. starch in a proportion of 3% to 22% by mass of the adhesive composition, and microfibrillated cellulose (MFC) in a proportion of 0.4% to 0.6% by mass of the adhesive composition; wherein the adhesive composition comprises a borax / starch ratio by mass of the adhesive composition between 0.01 and 0.04; wherein the lignin solution comprises: - wet lignin (40 to 60% solids) in a proportion of 14% to 19% by mass of the solution; - sodium hydroxide in a proportion of 1.5% to 2.5% by mass of the solution; and - water.

2. Process for obtaining an adhesive composition such as that defined in claim 1, characterized in that it comprises the following steps: - Mixing in a container for 1 minute, 50% of the mass of water provided for in the adhesive formulation, at a temperature of 30°C to 42°C and 15% to 22% of the starch provided for in the adhesive formulation; - Adding the total mass of the 50% sodium hydroxide solution provided for in the formulation and mixing at a speed of approximately 480 rpm for 3 minutes; Petition 870260055100, dated 08 / 06 / 2026, p.11 / 22 2 / 2 - Add the remaining water specified in the formulation at a temperature of 30°C to 42°C and mix for 1 minute; - Add the lignin solution or the lignin specified in the formulation to the formulation and mix for 3 minutes; - Add: the remaining mass of starch specified in the adhesive composition; or the remaining mass of starch specified in the adhesive composition and the total aqueous dispersion of MFC specified in the adhesive composition; - Mix for 3 minutes at a speed of 1200 rpm; and - Add the total mass of borax specified in the adhesive composition, without stopping the agitation, and mix for 3 minutes at a speed of 2300 rpm.

3. A process for producing a lignin solution to be used in a process for obtaining an adhesive composition as defined in claim 2, characterized in that it comprises the following steps: - Adding water to a container; - Adding previously macerated lignin and mixing for 3 minutes in a disperser, preferably using a Cowles-type propeller; - Adding soda solution and mixing for 10 minutes, preferably with a mechanical stirrer; - Checking if the pH of the solution is above 10 and, if not, adding more soda until the pH is above 10; and - Checking if there has been complete dispersion of the lignin and, if not, stirring until there is complete dispersion of the lignin.

4. Product characterized by comprising a substrate, preferably cellulose-based, to which an adhesive composition is applied, as defined in claim 1. Petition 870260055100, dated 08 / 06 / 2026, page 12 / 22

Images