Distiller's grains self-adhesive board, and preparation method and application thereof

Abstract

This invention belongs to the field of engineered wood panel manufacturing technology, specifically relating to self-adhesive particleboard made from brewing lees, its preparation method, and its application. To address the difficulty in treating brewing solid waste lees and to solve the environmental problem of existing technologies that require external adhesives to prepare particleboard from lees, this invention provides a method for preparing self-adhesive particleboard made from lees. The method involves drying and crushing the lees, then mixing them with a volatile acid or alkali, and then, with or without adding uncrushed lees, hot-pressing the mixture. This invention utilizes the adhesiveness of the remaining protein in the lees to achieve board bonding. By combining volatile acids, alkalis, and hot-pressing, without adding additional adhesives, a particleboard with static bending strength, modulus of elasticity, and internal bonding strength that meets the basic requirements of the national standard P2 type particleboard is produced. Furthermore, the preparation method is environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of artificial board preparation technology, specifically relating to self-adhesive boards made from distiller's grains, their preparation methods, and applications. Background Technology

[0002] There are three most common ways to process distillers' grains: producing biomass natural gas, feed, or fertilizer. However, in recent years, with the continuous development of brewing technology, the starch and protein content in the distillers' grains after brewing is relatively low. As a result, the use of distillers' grains as a raw material in biomass natural gas, feed, or fertilizer has gradually decreased, and the demand for high-value and diversified utilization of distillers' grains has become increasingly significant.

[0003] Processing distiller's grains into boards is one way to diversify the use of distiller's grains. Currently, there are generally two methods for processing distiller's grains into boards. One method involves washing the distiller's grains to remove starch, sugars, proteins, and inorganic salts, and then gluing together the remaining material, mainly rice husks, similar to the method used for "rice husk board." This method generates a large amount of wastewater and wastes a significant amount of resources. The second method involves using external adhesives to bond all the distiller's grains together. For example, patent CN 107116659 A describes how dried distiller's grains and their soluble components are bonded to wood shavings using adhesives, then laid out to form boards, and finally hot-pressed to obtain formaldehyde-free composite particleboard. However, this method has a significant drawback: the use of adhesives makes it environmentally unfriendly. Summary of the Invention

[0004] To address the difficulty in treating brewing solid waste lees, and to resolve the environmental issues arising from the need for external adhesives in existing technologies for preparing particleboard from lees, this invention provides a self-adhesive lees board, its preparation method, and its application.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a self-adhesive board made of distiller's grains, comprising the following steps: drying and crushing the distiller's grains, then adding a volatile acid or alkali and mixing them, then adding or not adding uncrushed distiller's grains, and hot pressing.

[0007] The drying temperature of the distiller's grains is ≤120℃. Preferably, the drying temperature is 80~120℃.

[0008] The dried distiller's grains have a moisture content of 0-20%. Preferably, the moisture content of the dried distiller's grains is 3-20%.

[0009] The particle size of the pulverized distiller's grains is ≤800μm. Preferably, the particle size of the pulverized distiller's grains is 100-500μm.

[0010] The total amount of the lees used is 100 parts.

[0011] The acid is at least one of formic acid, acetic acid, or hydrochloric acid. The base is at least one of triethylamine, dipropylamine, sec-butylamine, or pentylamine.

[0012] Of which, based on 100 parts by weight of distiller's grains, volatile acids comprise 5 to 80 parts and volatile bases comprise 20 to 150 parts. Preferably, volatile acids comprise 5 to 20 parts and volatile bases comprise 20 to 50 parts.

[0013] The lees are a mixture of crushed and uncrushed lees, with a ratio of crushed to uncrushed lees of 0:10 to 10:0, excluding 0:10. Preferably, the ratio is 3:7 to 10:0. More preferably, the ratio is 5:5 to 7:3.

[0014] The hot-pressing temperature is 100–190°C. Preferably, the hot-pressing temperature is 120–190°C.

[0015] The hot-pressing pressure is ≥0.5 MPa. Preferably, the hot-pressing pressure is 2–7.5 MPa.

[0016] The hot pressing time is 8 min to 12 h.

[0017] Secondly, the present invention provides a self-adhesive board made of distiller's grains prepared by the above preparation method.

[0018] Thirdly, the present invention also provides the application of the above-mentioned self-adhesive distillers' grains board in the preparation of engineered wood panels.

[0019] The artificial board is prepared by compounding and mixing the above-mentioned self-adhesive board made from distiller's grains with traditional particleboard and fiberboard.

[0020] Beneficial Effects: This invention utilizes the adhesiveness of residual protein in the brewing lees to achieve board bonding. Combined with volatile acids, alkalis, and hot-pressing processes, boards with a static bending strength of 12–17.5 MPa, an elastic modulus of 1.9–2.5 GPa, and an internal bonding strength of 0.45–0.8 MPa are successfully prepared without adding additional adhesives. The boards of this invention, as particleboard, fully meet the basic requirements of the national standard GB / T4897.1-7 2015 Particleboard Type P2. Furthermore, this invention achieves the resource utilization of brewing solid waste; the board preparation process does not generate new waste liquid, the boards do not introduce new adhesives, and there is no risk of VOC release. Attached Figure Description

[0021] Figure 1 This is a cross-sectional optical microscope photograph of Example 1;

[0022] Figure 2 A cross-sectional optical microscope image of a blank example. Detailed Implementation

[0023] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0024] In a specific embodiment of the present invention, a method for preparing a self-adhesive board made of distiller's grains is provided, comprising the following steps: drying and crushing the distiller's grains, then adding volatile acid or alkali and mixing well, then adding or not adding uncrushed distiller's grains, and hot pressing.

[0025] In the above preparation method, the purpose of drying the lees is to control the moisture content. Conventional drying equipment, including ovens, fluidized bed dryers, rotary dryers, and freeze dryers, is used to control the moisture content of the lees to 0-20%, preferably 3-20%, at a temperature not exceeding 120°C. Temperatures exceeding 120°C cause some easily decomposable functional groups on the proteins to decompose, losing their pH responsiveness and affecting subsequent adhesion.

[0026] In the above preparation method, the dried lees are pulverized. The purpose of pulverization is to increase the bulk density of the lees particles. After pulverization, the lees particle size is ≤800μm, preferably 100~500μm.

[0027] In the above preparation method, the addition of volatile acids or bases to the lees for mixing and modification is to impart viscosity to the proteins. The working principle is that the pH of the lees is adjusted using volatile acids or bases. Under the action of strong ions, the proteins denature, the molecular chains unfold, and they exhibit viscosity. The acid is preferably at least one of formic acid, acetic acid, or hydrochloric acid. The base is preferably at least one of triethylamine, dipropylamine, sec-butylamine, or pentylamine.

[0028] Of which, based on 100 parts by weight of distiller's grains, volatile acids comprise 5 to 80 parts and volatile bases comprise 20 to 150 parts. Preferably, volatile acids comprise 5 to 20 parts and volatile bases comprise 20 to 50 parts.

[0029] In the above preparation method, after adding volatile acids or alkalis, uncrushed distiller's grains can be added. Due to the support of rice husks, the bulk density of uncrushed distiller's grains is low, resulting in poor mechanical properties of the board, but it still meets basic requirements. Crushing some of the distiller's grains powder can increase the bulk density of the system, facilitating board molding. However, using only crushed distiller's grains powder will result in insufficient skeletal structure and reduced strength. Therefore, the ratio of crushed to uncrushed distiller's grains is 0:10 to 10:0, excluding 0:10. Preferably, the ratio is 3:7 to 10:0. More preferably, the ratio is 5:5 to 7:3.

[0030] In the above preparation method, the material is vibrated before hot pressing to level it, so as to maintain the uniformity of properties of all parts of the sheet during subsequent hot pressing. The vibrating equipment used is a flat plate vibrator.

[0031] In the above preparation method, the hot pressing parameters are: temperature 100–190℃, pressure ≥0.5MPa, and time 8 min–12 h. Preferably, the temperature is 120–190℃ and the pressure is 2–7.5MPa.

[0032] In the above preparation method, hot pressing works in conjunction with volatile acids or alkalis. The working principle is as follows: due to the volatilization of acids and alkalis caused by high temperatures, protein molecules tend to contract and entangle, forming entanglements with cellulose and other substances. This improves the bonding strength between the lees, resulting in ideal board properties. If the acid or alkali is non-volatile, it does not contribute to further entanglement, and the strength will decrease. Higher temperatures will lead to the decomposition of the lees. The hot pressing time of this invention is 8 minutes to 12 hours. In some embodiments of this invention, the board properties stabilize after 12 hours. Extending the hot pressing time further will not improve the board properties and will only waste energy and resources.

[0033] This invention utilizes the adhesive properties of residual protein in distiller's grains to bond boards. This aspect may be similar to conventional protein-based board bonding methods, which could affect the innovation of the solution. Here, the technical differences between the two solutions are explained in detail.

[0034] The principle behind conventional multilayer protein adhesives is that the molecular chain structure is disrupted under the influence of heat, acid, alkali, and denaturing agents, causing protein denaturation and thus producing adhesiveness. According to the textbook *Protein Chemistry and Technology* (edited by Mo Chongwen, Chemical Industry Press), the denaturing effect of heat on proteins manifests in the increased molecular vibration caused by heat, weakening various intramolecular and intermolecular forces. The originally regular and dense protein molecular structure is disrupted, and the orderly coiled and folded polypeptide chains unfold to form linear molecules. Treating proteins with strong acids or alkalis can improve protein adhesiveness, but these primarily disrupt secondary bonds such as salt bonds and ester bonds, causing denaturation due to the disruption of the protein's secondary and tertiary structures. Surfactants, such as sodium dodecyl sulfate, disrupt the hydrophobic interactions within protein molecules, exposing the hydrophobic side chains that were originally inside the molecule. This weakens intramolecular water transport interactions and increases intermolecular water transport interactions, causing protein molecules to aggregate and form larger molecular aggregates. In other words, traditional single-protein adhesives work by opening up the folded molecular chains of proteins, resulting in stronger adhesion and increasing the contact area with cellulose-based materials (wood, straw, etc.), thereby achieving material bonding. However, because the bonding between protein adhesives and cellulose-based materials involves only simple van der Waals forces, the adhesive effect is not ideal, often requiring the use of substances such as polyacrylamide and zinc oxide.

[0035] In this invention, the technical method used in the first step of protein processing (before hot pressing) is similar: using acid or alkali to open the folded molecular chains of the protein, increasing its contact with the distiller's grains particles. The difference lies in the use of volatile acid or alkali. Because the acid or alkali used in this invention is volatile, it will evaporate during the second step of hot pressing, causing the damaged secondary and tertiary structures of the protein to spontaneously recover (i.e., protein renaturation). During protein renaturation, the protein molecular chains tend to fold in a regular pattern. However, because the protein molecules and distiller's grains are intertwined at this point, the contraction and folding of the protein molecular chains further strengthens the entanglement between the protein molecules and the distiller's grains, further enhancing the interaction between them. Therefore, this invention can achieve stronger adhesiveness of protein molecules without using other substances, enabling the preparation of distiller's grain particle boards. In other words, the purpose of hot pressing in this invention is not merely to bond the distiller's grains together under high pressure, but more importantly, to utilize high temperature to volatilize acids or alkalis, causing the secondary and tertiary structures of proteins to spontaneously recover. This allows the proteins to further entangle with the cellulose and other particulate matter in the distiller's grains, enhancing intermolecular adhesion and thus improving the bonding strength of the board. Therefore, the self-adhesive mechanism of this invention is completely different from existing technologies.

[0036] The present invention also provides a self-adhesive board made of distiller's grains prepared by the above preparation method.

[0037] The above-mentioned board material of the present invention fully meets the basic requirements of the national standard GB / T 4897.1-7 2015 Particleboard P2 type: static bending strength 12MPa, elastic modulus 1.9GPa, and internal bonding strength 0.45MPa.

[0038] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0039] The lees used in this example are from Luzhou Laojiao Co., Ltd. The lees contain approximately 22.88% protein, approximately 7.88% oil, 47.70% crude fiber, and the remainder consists of soluble sugars and small to medium molecular weight esters.

[0040] The thickness of the prepared plates is 6mm.

[0041] Example 1: Self-adhesive board made of distiller's grains

[0042] (1) Dry the lees in an oven at 105°C until the moisture content is 10%;

[0043] (2) Crush the dried lees to a particle size of 100μm;

[0044] (3) Add 5 parts of acetic acid to 100 parts of crushed lees powder, stir and mix well in a mixer, and then pour into a mold;

[0045] (4) Place the mold with the material on a flat vibrator and flatten it. Then place it on a 120℃ hot press and press it at 6MPa for 20 minutes to obtain the hot-pressed plate.

[0046] Example 2: Self-adhesive board made of distiller's grains

[0047] (1) Dry the lees in a fluidized bed dryer at 80℃ until the moisture content is 20%;

[0048] (2) Crush the dried lees to a particle size of 500μm;

[0049] (3) Add 20 parts of acetic acid to 50 parts of crushed lees powder, and mix them together with 50 parts of uncrushed lees in a mixer. Then pour the mixture into a mold.

[0050] (4) Place the mold with the material on a flat vibrator and flatten it. Then place it on a 170℃ hot press and press it at 5MPa for 8 minutes to obtain the hot-pressed plate.

[0051] Example 3: Self-adhesive board made of distiller's grains

[0052] (1) Dry the lees in an oven at 120°C until the moisture content is 3%;

[0053] (2) Crush the dried lees to a particle size of 800 μm;

[0054] (3) Add 80 parts of acetic acid to 20 parts of crushed lees powder, and mix them together with 80 parts of uncrushed lees in a mixer and then pour the mixture into a mold.

[0055] (4) Place the mold with the material on a flat vibrator and flatten it. Then place it on a 100℃ hot press and press it at 3MPa for 1 hour to obtain the hot-pressed plate.

[0056] Example 4: Self-adhesive board made of distiller's grains

[0057] (1) Dry the lees in an oven at 120°C until the moisture content is 7%;

[0058] (2) Crush the dried lees to a particle size of 300μm;

[0059] (3) Add 80 parts of triethylamine to 80 parts of crushed lees powder, and mix it with 20 parts of uncrushed lees in a mixer. Then pour the mixture into a mold.

[0060] (4) Place the mold with the material on a flat vibrator and flatten it. Then place it on a 120℃ hot press and press it at 0.5MPa for 12 hours to obtain the hot-pressed plate.

[0061] Example 5: Self-adhesive board made of distiller's grains

[0062] (1) Dry the lees in an oven at 120°C until the moisture content is 7%;

[0063] (2) Crush the dried lees to a particle size of 300μm;

[0064] (3) Add 20 parts of triethylamine to 60 parts of crushed lees powder, and mix them together with 40 parts of uncrushed lees in a mixer before pouring the mixture into a mold.

[0065] (4) Place the mold with the material on a flat vibrator and flatten it. Then place it on a 190℃ hot press and press it at 7.5MPa for 1 hour to obtain the hot-pressed plate.

[0066] Example 6: Self-adhesive board made of distiller's grains

[0067] (1) Dry the lees in an oven at 120°C until the moisture content is 3%;

[0068] (2) Crush the dried lees to a particle size of 300μm;

[0069] (3) Add 50 parts of triethylamine to 70 parts of crushed lees powder, and mix them together with 30 parts of uncrushed lees in a mixer and then pour the mixture into a mold.

[0070] (4) Place the mold with the material on a flat vibrator and flatten it. Then place it on a 170℃ hot press and press it at 4.5MPa for 3 hours to obtain a hot-pressed plate.

[0071] Comparative Example 1

[0072] Compared to Example 1, 100 parts of crushed lees were replaced with 100 parts of uncrushed lees.

[0073] Comparative Example 2

[0074] Compared to Example 5, the variable is that the hot-pressing temperature is increased to 200°C.

[0075] Comparative Example 3

[0076] Compared to Example 6, the variable is that the alkali used is 5 parts NaOH.

[0077] Comparative Example 4

[0078] Compared to Example 3, the variable was the use of 100 parts of acetic acid.

[0079] Comparative Example 5

[0080] Compared to Example 1, the variable is that acetic acid is not used.

[0081] Blank example

[0082] Compared to Example 1, the distiller's grains were not crushed and acetic acid was not used.

[0083] Table 1. Materials and parameters of the sheet materials prepared in the examples and comparative examples.

[0084]

[0085]

[0086] The experimental examples were conducted according to the method of GB / T 17657-2013 to test the mechanical properties of the boards, and the results are shown in Table 2 below. The basic requirements for P2 boards are: static bending strength 12 MPa, elastic modulus 1.9 GPa, and internal bond strength 0.45 MPa. In the comparative examples, some individual properties meet the standards, but not all three.

[0087] Table 2 Mechanical properties of the plates prepared in the examples and comparative examples

[0088] sample Static bending strength (MPa) Elastic modulus (GPa) Internal bond strength (MPa) Example 1 16.30 2.26 0.78 Example 2 14.66 2.13 0.52 Example 3 12.44 1.91 0.48 Example 4 13.45 2.03 0.51 Example 5 17.21 2.33 0.65 Example 6 17.41 2.46 0.76 Comparative Example 1 7.65 1.32 0.37 Comparative Example 2 8.65 3.23 0.28 Comparative Example 3 11.04 1.77 0.46 Comparative Example 4 9.02 1.56 0.42 Comparative Example 5 4.74 0.86 0.22 Blank example 2.11 0.42 ～0.02

Claims

1. A method for preparing a self-adhesive board made of distiller's grains, characterized in that: Includes the following steps: After drying the lees, crush them, then add volatile acids or alkalis and mix well. Add or not add uncrushed lees, and then heat press. The drying temperature of the lees is ≤120℃. Based on 100 parts by weight of lees, the volatile acids are 5-80 parts and the volatile alkalis are 20-150 parts.

2. The method for preparing the self-adhesive board made of distiller's grains according to claim 1, characterized in that: The drying temperature for distiller's grains is 80–120℃.

3. The method for preparing the self-adhesive board made of distiller's grains according to claim 1, characterized in that: The moisture content of the dried lees is 0-20%.

4. The method for preparing the self-adhesive board made of distiller's grains according to claim 3, characterized in that: The moisture content of the dried distiller's grains is 3-20%.

5. The method for preparing the self-adhesive board made of distiller's grains according to claim 1, characterized in that: The particle size of the pulverized distiller's grains is ≤800 μm.

6. The method for preparing the self-adhesive board made of distiller's grains according to claim 5, characterized in that: The particle size of the pulverized distiller's grains is 100–500 μm.

7. The method for preparing the self-adhesive board made of distiller's grains according to claim 1, characterized in that: The total amount of the lees used is 100 parts; the lees are a mixture of crushed and uncrushed lees, and the ratio of crushed to uncrushed lees is 0:10 to 10:0, excluding 0:

10.

8. The method for preparing the self-adhesive board made of distiller's grains according to claim 7, characterized in that: The ratio of crushed to uncrushed lees is 3:7 to 10:

0.

9. The method for preparing the self-adhesive board made of distiller's grains according to claim 8, characterized in that: The ratio of crushed to uncrushed lees is 5:5 to 7:

3.

10. The method for preparing the self-adhesive board made of distiller's grains according to claim 1, characterized in that: The acid is at least one of formic acid, acetic acid, or hydrochloric acid; the base is at least one of triethylamine, dipropylamine, sec-butylamine, or pentylamine.

11. The method for preparing the self-adhesive board made of distiller's grains according to claim 1, characterized in that: The volatile acid content is 5-20 parts, and the volatile base content is 20-50 parts.

12. The method for preparing the self-adhesive board made of distiller's grains according to any one of claims 1 to 11, characterized in that: Hot pressing parameters must meet at least one of the following: The hot pressing temperature is 100–190°C; The hot-pressing pressure is ≥0.5 MPa; The hot pressing time is 8 min to 12 h.

13. The method for preparing the self-adhesive board made of distiller's grains according to claim 12, characterized in that: The hot pressing temperature is 120–190℃; the hot pressing pressure is 2–7.5 MPa.

14. The self-adhesive board made of distiller's grains prepared by the preparation method according to any one of claims 1 to 13.

15. The application of the self-adhesive board made of distiller's grains as described in claim 14 in the preparation of engineered wood panels.

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