Naringenin modified lignin phenolic resin adhesive and preparation method thereof
By modifying lignin phenolic resin adhesive with naringenin, the environmental and performance problems of traditional phenolic resin adhesives are solved, the preparation of bio-based adhesives with high strength and high thermal stability is achieved, and its application range is expanded.
Patent Information
- Application Number
- CN202511108990.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-08
- Publication Date
- 2025-10-17
AI Technical Summary
Traditional phenolic resin adhesives use petroleum-based raw materials and may release formaldehyde during production and use, which is harmful to the environment and health. In addition, the large molecular weight and highly disordered structure of lignin itself lead to a decrease in mechanical and thermal properties.
By adding naringenin to modify the lignin phenolic resin adhesive, the phenolic hydroxyl groups in naringenin react with the aldehyde groups in the phenolic resin to form additional cross-linking points, thereby improving the cross-linking density and thermal stability, while using biomass resources to replace part of the petroleum-based raw materials.
The bonding strength and thermal performance are improved, formaldehyde emission is reduced, the preparation of environmentally friendly adhesives is realized, and the application field is broadened.
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Figure CN120795839A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of polymer adhesive materials, and particularly relates to a naringenin modified lignin phenol-formaldehyde resin adhesive and a preparation method thereof. BACKGROUND
[0002] The raw materials for preparing traditional phenol-formaldehyde resin adhesives include formaldehyde and phenol, both of which are petroleum-based raw materials. However, petroleum resources are limited and non-renewable. Moreover, traditional phenol-formaldehyde resin adhesives may release formaldehyde during production and use, which is harmful to human health and the environment. Bio-based phenol-formaldehyde resin adhesives partially replace phenol with biomass (such as lignin, starch, etc.), which are abundant and renewable. The development and utilization of these resources can help reduce dependence on petroleum resources and reduce environmental problems caused by the exploitation and use of petroleum resources. Moreover, bio-based phenol-formaldehyde resin adhesives can effectively reduce the release of formaldehyde and reduce indoor air pollution by using biomass raw materials and green synthesis processes, which meets people's pursuit of environmental protection and health.
[0003] Naringenin is a naturally occurring dihydroflavonoid and belongs to flavonoids. It mainly exists in the peel and pulp of citrus fruits (such as grapefruit, orange, lemon, etc.) and is also distributed in other plants such as tomatoes and Rosaceae plants. Its molecular formula is C 15 H 12 O5. In the chemical industry, naringenin can be used as a biomass resource to replace fossil raw materials and as a synthetic raw material for biomass benzoxazine resin and biomass epoxy resin.
[0004] Natural lignin is an aromatic compound widely present in plant cell walls, and its molecular structure has certain similarity with phenol. Through activation modification treatment (such as hydroxymethylation, demethylation or phenolation), lignin can replace part of the phenol for the preparation of phenol-formaldehyde resin. This new type of resin based on the combination of biological resources and chemical synthesis not only reduces the use of toxic substances such as phenol, but also effectively reduces the release of formaldehyde, providing new possibilities for the development of environmentally friendly adhesives. However, lignin itself has a large molecular weight, and its repeating unit has high structural disorder and large steric hindrance effect, which leads to a certain degree of decline in the mechanical properties and thermal properties of the prepared phenol-formaldehyde resin. SUMMARY
[0005] Therefore, the purpose of the present application is to provide a naringenin modified lignin phenol-formaldehyde resin adhesive and a preparation method thereof. The present application improves the thermal properties and bonding strength of lignin phenol-formaldehyde resin adhesive by adding naringenin, and prepares an environmentally friendly phenol-formaldehyde resin adhesive.
[0006] The application provides a naringenin modified lignin phenolic resin adhesive, which comprises the following preparation raw materials in mass fractions:
[0007] formaldehyde solution 60-70 parts, phenol 65-85 parts, naringenin 6-14 parts, lignin 10-20 parts, alkali metal hydroxide 12-18 parts and water 25-30 parts; the mass concentration of the formaldehyde solution is 35%-40%.
[0008] Preferably, the mass fraction of the phenol is 70-80 parts.
[0009] Preferably, the mass fraction of the naringenin is 8-12 parts.
[0010] Preferably, the mass fraction of the lignin is 12-18 parts.
[0011] Preferably, the alkali metal hydroxide comprises sodium hydroxide and / or potassium hydroxide.
[0012] Preferably, the preparation raw materials comprise the following mass fractions: formaldehyde solution 64 parts, phenol 70 parts, naringenin 12 parts, lignin 18 parts, sodium hydroxide 15 parts and water 27 parts.
[0013] The application further provides a preparation method of the naringenin modified lignin phenolic resin adhesive.
[0014] Part of the formaldehyde solution, the phenol, the naringenin, the lignin, the alkali metal hydroxide and water are mixed to perform first stirring to obtain a first reaction liquid;
[0015] The first reaction liquid and another part of the formaldehyde solution are mixed to perform second stirring to obtain a second reaction liquid;
[0016] The second reaction liquid and the remaining formaldehyde solution are mixed to perform third stirring to obtain the naringenin modified lignin phenolic resin adhesive.
[0017] Preferably, the first stirring, the second stirring and the third stirring are all performed in a water bath, and the temperature of the water bath is 75-85 DEG C.
[0018] Preferably, the time of the first stirring, the second stirring and the third stirring is independently 0.5-2 hours.
[0019] Preferably, the part of the formaldehyde solution, the another part of the formaldehyde solution and the remaining formaldehyde solution are all one third of the total mass of the formaldehyde solution.
[0020] Compared with the prior art, the application has the following beneficial effects:
[0021] The present application provides a naringenin modified lignin phenol-formaldehyde resin adhesive, comprising the following raw materials in mass fraction: formaldehyde solution 60-70 parts, phenol 65-85 parts, naringenin 6-14 parts, lignin 10-20 parts, alkali metal hydroxide 12-18 parts and water 25-30 parts; the mass concentration of the formaldehyde solution is 35%-40%.
[0022] The present application adds naringenin in the preparation raw materials of the phenol-formaldehyde resin adhesive, the naringenin molecule contains multiple phenolic hydroxyl groups, these functional groups can react with the aldehyde groups in the phenol-formaldehyde resin to form additional crosslinking points, thereby enhancing the crosslinking density and thermal stability of the resin, improving the bonding strength, overcoming the negative impact of lignin on the performance of the phenol-formaldehyde resin after being introduced, and meeting the needs of practical application. At the same time, naringenin is a naturally derived compound, which has renewability and biodegradability, and can improve the environmental friendliness of the phenol-formaldehyde resin.
[0023] The present application uses lignin and naringenin to replace part of the petroleum raw material phenol to synthesize a biomass-based phenol-formaldehyde resin adhesive, which can make full use of renewable resources and reduce environmental pollution. The use of bio-phenol to replace phenol to synthesize phenol-formaldehyde resin has become an important direction to solve the environmental problem of the resin. Compared with the traditional phenol-formaldehyde resin adhesive, the biomass-based phenol-formaldehyde resin adhesive of the present application improves the bonding strength and thermal performance, and further widens the application field of the adhesive material.
[0024] The present application also provides a preparation method of the naringenin modified lignin phenol-formaldehyde resin adhesive described in the above technical solution, which prepares the phenol-formaldehyde resin adhesive by a three-step polymerization method using formaldehyde solution, phenol, naringenin, lignin, sodium hydroxide and water, and the method is simple and easy to industrialize. BRIEF DESCRIPTION OF DRAWINGS
[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.
[0026] Figure 1 The infrared spectra of the phenol-formaldehyde resin of Comparative Example 1 and the naringenin modified lignin phenol-formaldehyde resin of Example 2;
[0027] Figure 2 The infrared spectra of naringenin and lignin;
[0028] Figure 3 The relationship curve between the mass substitution rate of naringenin and lignin to phenol and the bonding strength;
[0029] Figure 4TG curves of the phenol-formaldehyde resin adhesives prepared by different naringenin and lignin mass substitution rates on phenol;
[0030] Figure 5 DTG curves of the phenol-formaldehyde resin adhesives prepared by different naringenin and lignin mass substitution rates on phenol. DETAILED DESCRIPTION
[0031] The present application provides a naringenin modified lignin phenol-formaldehyde resin adhesive, which comprises the following mass fractions of raw materials:
[0032] 60-70 parts of formaldehyde solution, 65-85 parts of phenol, 6-14 parts of naringenin, 10-20 parts of lignin, 12-18 parts of alkali metal hydroxide and 25-30 parts of water; the mass concentration of the formaldehyde solution is 35%-40%.
[0033] In the present application, the materials and equipment used are commercially available in the art, unless otherwise specified.
[0034] In the present application, the mass concentration of the formaldehyde solution is preferably 37%.
[0035] In the present application, the mass fraction of the formaldehyde solution is preferably 63-65 parts, and specifically can be 64 parts.
[0036] Based on the mass fraction of the formaldehyde solution, the mass fraction of the phenol is preferably 70-80 parts, and specifically can be 70 parts or 80 parts.
[0037] Based on the mass fraction of the formaldehyde solution, the mass fraction of the naringenin is preferably 8-12 parts, and specifically can be 8 parts or 12 parts. The mass fraction of the naringenin in the present application is advantageous for improving the bonding strength and thermal stability of the phenol-formaldehyde resin.
[0038] Based on the mass fraction of the formaldehyde solution, the mass fraction of the lignin is preferably 12-18 parts, and specifically can be 12 parts or 18 parts.
[0039] In the present application, the alkali metal hydroxide preferably includes sodium hydroxide and / or potassium hydroxide.
[0040] Based on the mass fraction of the formaldehyde solution, the mass fraction of the alkali metal hydroxide is preferably 14-16 parts, and specifically can be 15 parts.
[0041] Based on the mass fraction of the formaldehyde solution, the mass fraction of the water is preferably 26-28 parts, and specifically can be 27 parts.
[0042] In the present application, the naringenin modified lignin phenolic resin adhesive preferably comprises the following mass fractions of raw materials for preparation: formaldehyde solution 64 parts, phenol 80 parts, naringenin 8 parts, lignin 12 parts, sodium hydroxide 15 parts and water 27 parts; or comprises the following mass fractions of raw materials for preparation: formaldehyde solution 64 parts, phenol 70 parts, naringenin 12 parts, lignin 18 parts, sodium hydroxide 15 parts and water 27 parts.
[0043] The present application also provides a preparation method of the naringenin modified lignin phenolic resin adhesive described in the above technical solution, comprising the following steps:
[0044] Part of the formaldehyde solution, phenol, naringenin, lignin, alkali metal hydroxide and water are mixed for first stirring to obtain a first reaction liquid;
[0045] The first reaction liquid and another part of the formaldehyde solution are mixed for second stirring to obtain a second reaction liquid;
[0046] The second reaction liquid and the remaining formaldehyde solution are mixed for third stirring to obtain the naringenin modified lignin phenolic resin adhesive.
[0047] In the present application, the part of the formaldehyde solution is preferably one third of the total mass of the formaldehyde solution.
[0048] In the present application, the first stirring, the second stirring and the third stirring are all preferably carried out in a water bath, and the temperature of the water bath is preferably 75-85℃, and can be specifically 80℃.
[0049] In the present application, the time of the first stirring is preferably 0.5-2 hours, and can be specifically 1 hour. The time of the first stirring in the present application can make the hydroxymethylation reaction of lignin and naringenin more thorough.
[0050] In the present application, the another part of the formaldehyde solution is preferably one third of the total mass of the formaldehyde solution.
[0051] In the present application, the time of the second stirring is preferably 0.5-2 hours, and can be specifically 1 hour. The time of the second stirring in the present application can promote the condensation reaction between the hydroxymethyl phenol molecules and between the hydroxymethyl phenol and the phenol to a higher degree of completion.
[0052] In the present application, the time of the third stirring is preferably 0.5-2 hours, and can be specifically 1 hour. The time of the third stirring in the present application can make further condensation reactions occur between the dimers, trimers and polymers.
[0053] In the present application, the third stirring preferably further comprises: the obtained third reaction solution is subjected to heat preservation and cooling. The heat preservation is preferably carried out in a water bath, the temperature of the water bath is preferably 65-75℃, and specifically can be 70℃, and the time is preferably 1 hour; the heat preservation can further improve the reaction degree. The cooling is preferably natural cooling.
[0054] In order to further illustrate the present application, the naringenin modified lignin phenol-formaldehyde resin adhesive and the preparation method thereof provided by the present application are described in detail below in combination with the drawings and examples, but they should not be understood as limiting the protection scope of the present application.
[0055] In the following comparative examples or examples, the parts of raw materials are all mass parts unless otherwise specified; the mass concentration of formaldehyde solution is all 37%.
[0056] Comparative Example 1
[0057] Take 64 parts of formaldehyde solution, 100 parts of phenol, 15 parts of sodium hydroxide and 27 parts of water.
[0058] Add one-third of the total mass of formaldehyde solution, phenol, sodium hydroxide and water into a three-necked flask, and stir under water bath condition (80℃) for 1 hour; add another one-third of formaldehyde solution dropwise into the reaction solution, and continue to stir under water bath condition (80℃) for 1 hour; add the remaining one-third of formaldehyde solution dropwise into the reaction solution, and continue to stir under water bath condition (80℃) for 1 hour; remove the condenser, and heat the obtained reaction solution under water bath condition (70℃) for 1 hour, and then let it cool naturally, to finally obtain a phenol-formaldehyde resin adhesive.
[0059] The phenol-formaldehyde resin adhesive prepared in Comparative Example 1 has a bonding strength of 0.76 MPa, and a carbon residue rate of 59.64% at 900℃.
[0060] Comparative Example 2
[0061] Take 64 parts of formaldehyde solution, 100 parts of phenol, 15 parts of sodium hydroxide and 27 parts of water.
[0062] Add one-third of the total mass of formaldehyde solution, phenol, sodium hydroxide and water into a three-necked flask, and stir under water bath condition (80℃) for 1 hour; add another one-third of formaldehyde solution dropwise into the reaction solution, and continue to stir under water bath condition (80℃) for 1 hour; add the remaining one-third of formaldehyde solution dropwise into the reaction solution, and continue to stir under water bath condition (80℃) for 1 hour; remove the condenser, and heat the obtained reaction solution under water bath condition (70℃) for 1 hour, and then let it cool naturally, to finally obtain a phenol-formaldehyde resin adhesive.
[0063] The phenolic resin adhesive prepared in Comparative Example 2 has a bonding strength of 0.72 MPa and a carbon residue rate of 51.36% at 900°C.
[0064] Comparative Example 3
[0065] Take formaldehyde solution 64 parts, phenol 90 parts, naringin 4 parts, lignin 6 parts, sodium hydroxide 15 parts, and water 27 parts.
[0066] One-third of the total mass of the formaldehyde solution, phenol, naringin, lignin, sodium hydroxide, and water are added to a three-necked flask and stirred for 1 hour under water bath conditions (80°C). Another one-third of the formaldehyde solution is added dropwise to the reaction liquid, and stirring is continued for 1 hour under water bath conditions (80°C). The remaining one-third of the formaldehyde solution is added dropwise to the reaction liquid, and stirring is continued for 1 hour under water bath conditions (80°C). The condenser is removed, and the obtained reaction liquid is incubated for 1 hour under water bath conditions (70°C) and then naturally cooled, to finally obtain a phenolic resin adhesive.
[0067] The phenolic resin adhesive prepared in Comparative Example 3 has a bonding strength of 0.29 MPa and a carbon residue rate of 58.00% at 900°C.
[0068] Example 1
[0069] Take formaldehyde solution 64 parts, phenol 80 parts, naringin 8 parts, lignin 12 parts, sodium hydroxide 15 parts, and water 27 parts.
[0070] One-third of the total mass of the formaldehyde solution, phenol, naringin, lignin, sodium hydroxide, and water are added to a three-necked flask and stirred for 1 hour under water bath conditions (80°C). Another one-third of the formaldehyde solution is added dropwise to the reaction liquid, and stirring is continued for 1 hour under water bath conditions (80°C). The remaining one-third of the formaldehyde solution is added dropwise to the reaction liquid, and stirring is continued for 1 hour under water bath conditions (80°C). The condenser is removed, and the obtained reaction liquid is incubated for 1 hour under water bath conditions (70°C) and then naturally cooled, to finally obtain a phenolic resin adhesive.
[0071] The phenolic resin adhesive prepared in Example 1 has a bonding strength of 0.83 MPa and a carbon residue rate of 58.85% at 900°C.
[0072] Example 2
[0073] Take formaldehyde solution 64 parts, phenol 70 parts, naringin 12 parts, lignin 18 parts, sodium hydroxide 15 parts, and water 27 parts.
[0074] One third of the total mass of formaldehyde solution, phenol, naringenin, lignin, sodium hydroxide and water were added to a three-necked flask, and stirred for 1 hour under water bath condition (80°C); another one third of the formaldehyde solution was added dropwise to the reaction liquid, and stirred for 1 hour under water bath condition (80°C); the remaining one third of the formaldehyde solution was added dropwise to the reaction liquid, and stirred for 1 hour under water bath condition (80°C); the condenser was removed, and the obtained reaction liquid was kept under water bath condition (70°C) for 1 hour, and then naturally cooled, to finally obtain the phenol-formaldehyde resin adhesive.
[0075] The phenol-formaldehyde resin adhesive prepared in Example 2 had a bonding strength of 1.02 MPa, and a carbon residue rate of 62.00% at 900°C.
[0076] Comparative Example 4
[0077] Take formaldehyde solution 64 parts, phenol 60 parts, naringenin 16 parts, lignin 24 parts, sodium hydroxide 15 parts, and water 27 parts.
[0078] One third of the total mass of formaldehyde solution, phenol, naringenin, lignin, sodium hydroxide and water were added to a three-necked flask, and stirred for 1 hour under water bath condition (80°C); another one third of the formaldehyde solution was added dropwise to the reaction liquid, and stirred for 1 hour under water bath condition (80°C); the remaining one third of the formaldehyde solution was added dropwise to the reaction liquid, and stirred for 1 hour under water bath condition (80°C); the condenser was removed, and the obtained reaction liquid was kept under water bath condition (70°C) for 1 hour, and then naturally cooled, to finally obtain the phenol-formaldehyde resin adhesive.
[0079] The phenol-formaldehyde resin adhesive prepared in Comparative Example 4 had a bonding strength of 0.48 MPa, and a carbon residue rate of 61.91% at 900°C.
[0080] Comparative Example 5
[0081] Take formaldehyde solution 64 parts, phenol 50 parts, naringenin 20 parts, lignin 30 parts, sodium hydroxide 15 parts, and water 27 parts.
[0082] One third of the total mass of formaldehyde solution, phenol, naringenin, lignin, sodium hydroxide and water were added to a three-necked flask, and stirred for 1 hour under water bath condition (80°C); another one third of the formaldehyde solution was added dropwise to the reaction liquid, and stirred for 1 hour under water bath condition (80°C); the remaining one third of the formaldehyde solution was added dropwise to the reaction liquid, and stirred for 1 hour under water bath condition (80°C); the condenser was removed, and the obtained reaction liquid was kept under water bath condition (70°C) for 1 hour, and then naturally cooled, to finally obtain the phenol-formaldehyde resin adhesive.
[0083] The phenolic resin adhesive prepared in Comparative Example 5 has a bonding strength of 0.45 MPa and a carbon residue rate of 50.29% at 900°C.
[0084] Comparative Example 6
[0085] Take formaldehyde solution 64 parts, phenol 40 parts, naringin 24 parts, lignin 36 parts, sodium hydroxide 15 parts, and water 27 parts.
[0086] One-third of the total mass of the formaldehyde solution, phenol, naringin, lignin, sodium hydroxide, and water are added to a three-necked flask and stirred for 1 hour under water bath conditions (80°C); one-third of the remaining formaldehyde solution is added dropwise to the reaction liquid, and stirring is continued for 1 hour under water bath conditions (80°C); the remaining one-third of the formaldehyde solution is added dropwise to the reaction liquid, and stirring is continued for 1 hour under water bath conditions (80°C); the condenser is removed, and the obtained reaction liquid is incubated for 1 hour under water bath conditions (70°C) and then allowed to cool naturally, and finally the phenolic resin adhesive is obtained.
[0087] The phenolic resin adhesive prepared in Comparative Example 6 has a bonding strength of 0.69 MPa and a carbon residue rate of 54.98% at 900°C.
[0088] The naringin-modified lignin phenolic resin adhesives prepared in Comparative Examples 1-6 and Examples 1-2 are tested, and the specific results are shown in Table 1 and FIG. 1. Figures 1 to 5
[0089] Figure 1 FIG. 1 is an infrared spectrum of the phenolic resin (Comparative Example 1) and the naringin-modified lignin phenolic resin (Example 2); Figure 2 FIG. 2 is an infrared spectrum of naringin and lignin.
[0090] Figure 3 FIG. 3 is a relationship curve between the mass substitution rate of naringin and lignin to phenol and the bonding strength; Figure 4 FIG. 4 is a TG curve of the phenolic resin adhesives prepared with different mass substitution rates of naringin and lignin to phenol; Figure 5 FIG. 5 is a DTG curve of the phenolic resin adhesives prepared with different mass substitution rates of naringin and lignin to phenol; wherein 0:100, 1:9, 2:8, 3:7, 4:6, 5:5, and 6:4 correspond to Comparative Example 1, Comparative Example 3, Example 1, Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 6, respectively.
[0091] Table 1 Test results of the phenolic resin adhesives prepared in Comparative Examples 1-6 and Examples 1-2
[0092] Formulation Solids content / % Free phenol content / % Free aldehyde content / % Bonding strength / MPa Carbon residue at 900°C Comparative Example 1 47.01 4.9 0.15 0.76 59.64％ Comparative Example 2 46.32 4.6 0.17 0.72 51.36％ Comparative Example 3 23.58 3.79 0.19 0.29 58.00％ Example 1 38.43 2.54 0.2 0.83 58.85％ Example 2 50.36 2.3 0.21 1.02 62.00％ Comparative Example 4 40.72 1.88 1.4 0.48 61.91％ Comparative Example 5 39.11 1.92 1.6 0.45 50.29％ Comparative Example 6 46.65 2.05 2.55 0.69 54.98％
[0093] From Figure 1 , 2 It can be seen that in the naringenin modified lignin phenol-formaldehyde resin, there is a hydroxyl stretching vibration absorption peak near 3400-3200 cm -1 The absorption peak of the phenolic hydroxyl group in the phenol-formaldehyde resin, the hydroxyl group in the lignin and the hydroxyl group in the naringenin may jointly cause the absorption peak. In the region of 1680-1600 cm -1 The naringenin has a clear carbonyl absorption peak near 1680-1600 cm -1 The benzene ring skeleton vibration absorption peak near 1600-1450 cm -1 The naringenin modified lignin phenol-formaldehyde resin has a peak shape change in the benzene ring skeleton vibration absorption peak. This is because the chemical environment of the benzene ring changes after the combination of the naringenin, the lignin and the phenol-formaldehyde resin, resulting in a change in the vibration absorption peak, which indicates that the introduction of the naringenin and the lignin has an impact on the benzene ring structure. In the region of 1250-1000 cm
[0094] It can be seen from Table 1 that with the increase of the amount of the lignin and the naringenin, the solid content first decreases, then increases, then decreases and then increases. At a lower mass substitution rate, the addition of the naringenin may affect the crosslinking efficiency of the resin and reduce the solid content. With the increase of the mass substitution rate, the synergistic effect of the naringenin and the lignin may improve the crosslinking efficiency and increase the solid content. However, at a high mass substitution rate, too much naringenin may cause part of the components not to participate in the crosslinking reaction and reduce the solid content. The free phenol content first decreases and then increases with the increase of the common mass substitution rate of the naringenin and the lignin, and reaches the minimum of 1.88% when the common mass substitution rate is 4:6. At the initial stage, with the increase of the mass substitution rate of the naringenin, the phenolic hydroxyl group in the naringenin participates in the reaction and reduces the free phenol content. With the further increase of the mass substitution rate, the synergistic effect of the naringenin and the lignin may cause part of the phenolic hydroxyl group not to fully participate in the reaction and increase the free phenol content. The free aldehyde content gradually increases with the increase of the common mass substitution rate of the naringenin and the lignin. This may be because the introduction of the naringenin destroys the original crosslinking structure and causes part of the aldehyde groups not to fully react, thereby increasing the free aldehyde content.
[0095] It can be seen from Table 1 and Figure 3It can be seen that the introduction of a small amount of naringenin leads to a significant decrease in the bonding strength, and naringenin may destroy the synergy between lignin and phenolic resin. Lignin contains phenolic hydroxyl and methoxyl groups, which form good cross-linking with phenolic resin; while the flavonoid structure of naringenin may lead to a loose network structure due to poor compatibility or competition for reaction sites. When the mass substitution ratio increases from 1:9 to 3:7, the bonding strength gradually increases and reaches a maximum of 1.02 MPa at a mass substitution ratio of 3:7. This may be because the hydroxyl and carbonyl groups of naringenin synergize with the phenolic hydroxyl groups of lignin to form a more dense three-dimensional cross-linked network. Subsequently, the bonding strength decreases again, which may be because the rigid structure of excessive naringenin may limit the flowability of the resin, leading to an increase in the porosity of the glue layer, while the cross-linking efficiency of flavonoids is lower than that of lignin, and excessive mass substitution ratio weakens the overall network strength.
[0096] It can be seen from Table 1, Figure 4 and Figure 5 With the increase of lignin and naringenin, the thermal performance of the phenolic resin adhesive shows a trend of first increasing and then decreasing. Lignin contains more phenylpropane units and phenolic hydroxyl groups, and has better reactivity with phenolic resin, but is prone to form free radicals during thermal decomposition, resulting in relatively low thermal stability. The flavonoid structure of naringenin contains multiple hydroxyl groups and conjugated double bonds, which can form hydrogen bonds and covalent bonds with lignin and phenolic resin, enhancing the intermolecular forces. An appropriate amount of naringenin can fill the defects between lignin and phenolic resin, improving the thermal stability.
[0097] Although the above embodiments have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the embodiments of the present application without creative labor, which are within the protection scope of the present application.
Claims
1. A naringenin-modified lignin phenolic resin adhesive, characterized in that: The preparation comprises the following raw materials in parts by weight: 60-70 parts of formaldehyde solution, 65-85 parts of phenol, 6-14 parts of naringenin, 10-20 parts of lignin, 12-18 parts of alkali metal hydroxide and 25-30 parts of water; the mass concentration of the formaldehyde solution is 35%-40%.
2. The naringenin-modified lignin phenolic resin adhesive according to claim 1, characterized in that: The mass fraction of the phenol is 70 to 80 parts.
3. The naringenin-modified lignin phenolic resin adhesive according to claim 1, characterized in that: The mass fraction of the naringenin is 8 to 12 parts.
4. The naringenin-modified lignin phenolic resin adhesive according to claim 1, characterized in that: The mass fraction of the lignin is 12 to 18 parts.
5. The naringenin-modified lignin phenolic resin adhesive according to claim 1, characterized in that: The alkali metal hydroxide includes sodium hydroxide and / or potassium hydroxide.
6. The naringenin-modified lignin phenolic resin adhesive according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following raw materials in parts by weight: 64 parts of formaldehyde solution, 70 parts of phenol, 12 parts of naringenin, 18 parts of lignin, 15 parts of sodium hydroxide and 27 parts of water.
7. The method for preparing the naringenin-modified lignin phenolic resin adhesive according to any one of claims 1 to 6, characterized in that: The following steps are involved: mixing a portion of the formaldehyde solution, phenol, naringenin, lignin, an alkali metal hydroxide, and water and performing a first stirring to obtain a first reaction solution; mixing the first reaction solution and another portion of the formaldehyde solution and performing a second stirring to obtain a second reaction solution; The second reaction liquid and the remaining formaldehyde solution are mixed and stirred for a third time to obtain a naringenin-modified lignin phenolic resin adhesive.
8. The preparation method according to claim 7, characterized in that The first stirring, the second stirring and the third stirring are all performed in a water bath, and the temperature of the water bath is 75-85°C.
9. The preparation method according to claim 7 or 8, characterized in that The time for the first stirring, the second stirring and the third stirring is independently 0.5 to 2 hours.
10. The preparation method according to claim 7, characterized in that The partial formaldehyde solution, the other partial formaldehyde solution and the remaining formaldehyde solution are all one-third of the total mass of the formaldehyde solution.