A method for preparing a lignin-modified phenol-formaldehyde resin and a molding compound thereof

Abstract

The present application relates to the technical fields of high polymer synthesis and modification, in particular to a preparation method of lignin modified phenolic resin and its molding compound. The preparation method comprises the following steps: adding organic boron, lignin and acid catalyst, stirring and heating to boiling, refluxing for 1-6 hours; then adding phenol and formaldehyde, refluxing for 1-6 hours, and obtaining lignin modified phenolic resin after dehydration; the preparation method uses specific organic boron and lignin to modify phenolic resin together, compared with existing phenolic resin and lignin modified phenolic resin, it has better fluidity and heat resistance, and can overcome the shortcomings of existing lignin modified phenolic resin. The modified phenolic resin is used to prepare phenolic molding compound, which can effectively improve the processing fluidity of the molding compound, reduce the injection pressure, overcome the product defects, and also has good toughness and cost advantage.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis and modification technology, specifically a method for preparing lignin-modified phenolic resin and its molding compound. Background Technology

[0002] Phenolic resin is one of the earliest industrialized polymer materials, with a research history of nearly a century. It possesses excellent high-temperature resistance, high bonding strength, low cost, and superior chemical resistance, along with a high char residue rate. It is widely used in various sectors of the national economy, including molding compounds, friction materials, laminated sand, foamed materials, refractory materials, and electronic products. Phenolic molding compounds prepared using phenolic resin as a matrix exhibit good insulation, dimensional stability, and mechanical properties, and are widely used in related industries such as automotive, electronics, home appliances, steel, and housing.

[0003] Lignin, as a biomass resource second only to cellulose in terms of abundance in nature, is a renewable natural organic polymer with advantages such as rich resources, non-toxicity, renewability, and low cost. Molding plastics made from lignin-modified phenolic resins have a significant cost advantage. Chinese invention application number 201210557028.6 uses a high-pressure activation method to activate lignin and react it with formaldehyde to prepare lignin-modified phenolic resins. Chinese invention application number 201911277695.7 uses lignin to replace formaldehyde to prepare lignin-modified phenolic resins. Chinese invention application number 200810072174.3 uses enzymatic hydrolysis of lignin or its derivatives to prepare modified phenolic resins. In addition, numerous other processes for lignin-modified phenolic resins have been reported. However, directly using lignin to modify phenolic resins has several drawbacks: the special structure of lignin limits its usage; the strength of the modified phenolic resin is somewhat reduced; and its water resistance, high-temperature erosion resistance, anti-fading properties, abrasion resistance, and cut resistance are weakened.

[0004] To address the aforementioned issues, Chinese inventions with application numbers 201210492443.8 and 201610124004.X proposed using lignin and boron compounds to co-modify phenolic resins, thereby improving their heat resistance, water resistance, and ablation resistance. However, these boron compounds contain multiple active sites, which, after the reaction, form branched structures, reducing the resin's flowability and toughness, and easily leading to cross-linking and curing. The reaction is difficult to control, posing a significant risk of cross-linking. The flowability of phenolic molding compounds prepared using this resin as a matrix is ​​also significantly affected, causing product defects and injection molding machine barrel blockage, among other problems. Therefore, to avoid resin cross-linking and curing, the amount of boron-containing compounds added should not be too high, with priority given to improving the resin's heat resistance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a lignin-modified phenolic resin with excellent heat resistance and its molding compound.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing lignin-modified phenolic resin, comprising the following steps: adding organic boron, lignin and acidic catalyst, stirring and heating to boiling, reflux reaction for 1-6 hours; then adding phenol and formaldehyde, reflux reaction for 1-6 hours, and dehydration to obtain lignin-modified phenolic resin.

[0007] The organoboron is 4-hydroxyphenylboronic acid or 2-hydroxyphenylboronic acid.

[0008] Another technical solution adopted in this invention is: a method for preparing phenolic molding compound, comprising the following steps: mixing lignin-modified phenolic resin, fiber, inorganic filler, hexamethylenetetramine and additives evenly; the mixed material is successively subjected to plasticizing, sheeting, cooling and pulverizing to obtain phenolic molding compound; wherein the lignin-modified phenolic resin is the lignin-modified phenolic resin prepared by the above preparation method.

[0009] The beneficial effects of this invention are as follows: The preparation method of this invention uses specific organic boron and lignin to co-modify phenolic resin. Compared with existing phenolic resins and lignin-modified phenolic resins, it has better flowability and heat resistance, overcoming the shortcomings of existing lignin-modified phenolic resins. The organic boron can improve the reactivity of lignin, which is beneficial to the condensation reaction between lignin and formaldehyde, increasing the lignin filling amount, thereby reducing costs and pollution. Phenolic molding compounds prepared with this modified phenolic resin can effectively improve the processing flowability of the molding compound, reduce injection pressure, overcome product defects, and also have good toughness and cost advantages. Attached Figure Description

[0010] Figure 1 The images show the TG test results of the lignin-modified phenolic resins prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0011] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0012] A method for preparing lignin-modified phenolic resin includes the following steps: adding organoboron, lignin and an acidic catalyst, stirring and heating to boiling, and refluxing for 1-6 hours; then adding phenol and formaldehyde, refluxing for 1-6 hours, and dehydrating to obtain lignin-modified phenolic resin.

[0013] The organoboron is 4-hydroxyphenylboronic acid or 2-hydroxyphenylboronic acid.

[0014] As can be seen from the above description, the beneficial effects of the present invention are as follows: The present invention uses lignin and specific organic boron to modify phenolic resin, resulting in better flowability and heat resistance. Phenolic molding compounds prepared using this modified phenolic resin exhibit better flowability and improved toughness after curing due to the unbranched structure of the boron-containing groups in the resin.

[0015] The preparation method of the present invention has the following advantages:

[0016] 1. Leveraging the resource advantages of lignin to significantly reduce costs;

[0017] 2. The boron compound of the present invention has a structure similar to phenol, has good reactivity, and can react with lignin and formaldehyde to be introduced into the molecular chain, thereby achieving the effects of in-situ modification and reactive introduction.

[0018] 3. Boric acid is commonly used to modify phenolic resins. However, boric acid (see Formula 1) and phenyl borate ester formed by boric acid and phenol (see Formula 2) contain three or more functionalities per molecule, which easily form branched structures with phenol, formaldehyde, etc., making it difficult for resin molecular chains to move and reducing fluidity. At the same time, due to its multifunctionality, the resin is prone to cross-linking in the reactor. Therefore, the amount of boric acid used cannot be too much, otherwise it may lead to production accidents. The amount of boric acid used also limits the improvement of the resin's heat resistance.

[0019]

[0020] This invention uses 4-hydroxyphenylboronic acid or 2-hydroxyphenylboronic acid as a common modifier. The boron compound has only two active sites on the benzene ring and is a difunctional monomer, which can limit the substitution reaction on the main chain, inhibit the formation of branched structures, and make the modified phenolic resin have good flowability and toughness.

[0021] Since 4-hydroxyphenylboronic acid or 2-hydroxyphenylboronic acid has an active site occupied at the ortho or para position, the functionality of the benzene ring is only 2. After participating in the reaction, it can only form a linear structure and will not produce a branched structure. Therefore, the synthesized resin molecules have better mobility and are less likely to form cross-links that would cause the reaction to run away from control. Therefore, the amount of this boron compound can be greatly increased, thereby better improving the heat resistance of the resin.

[0022] 4. 4-Hydroxyphenylboronic acid (see Formula 3) and 2-hydroxyphenylboronic acid (see Formula 4) have structures similar to phenol. The ortho and para positions of the hydroxyl groups are active sites, which can react with formaldehyde, hydroxymethyl and other groups, thereby improving the reactivity of lignin. This is beneficial to the condensation reaction of lignin and formaldehyde, improving the improvement effect of lignin and the amount of lignin filling, and reducing costs.

[0023]

[0024] Furthermore, the lignin is any one of lignin sulfonate, alkali lignin, enzymatically hydrolyzed lignin, acid-hydrolyzed lignin, and high-boiling-point alcohol lignin.

[0025] Furthermore, the mass of lignin is 5% to 40% of the mass of phenol. Preferably, the mass of lignin is 20% to 40% of the mass of phenol.

[0026] As can be seen from the above description, 4-hydroxyphenylboronic acid and 2-hydroxyphenylboronic acid can improve the reactivity of lignin, and the amount of lignin added can be significantly increased. High-filled lignin can better leverage the resource utilization advantages of lignin and significantly reduce the cost of resin.

[0027] Furthermore, the acidic catalyst includes at least one of oxalic acid, acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, phosphonic acid, benzenesulfonic acid, and p-toluenesulfonic acid.

[0028] As can be seen from the above description, the reaction between lignin and boron compounds is catalyzed by acid, thereby increasing the reactivity of lignin. At the same time, the acidity of the boron compounds themselves can also promote the reaction.

[0029] Furthermore, the phenol is any one of phenol, cresol, bisphenol A, and bisphenol F.

[0030] Furthermore, when synthesizing thermoplastic linear phenolic resin, phenol is preferably used.

[0031] Furthermore, when the phenol is phenol, the mass of the organoboron is 2% to 30% of the mass of the phenol.

[0032] As can be seen from the above description, the amount of boron compound can be significantly increased to 30% to obtain phenolic resin with better heat resistance and toughness.

[0033] Another technical solution adopted in this invention is: a method for preparing phenolic molding compound, comprising the following steps: mixing lignin-modified phenolic resin, fiber, inorganic filler, hexamethylenetetramine and additives evenly; the mixed material is successively subjected to plasticizing, sheeting, cooling and pulverizing to obtain phenolic molding compound; the lignin-modified phenolic resin is the lignin-modified phenolic resin prepared by the above preparation method.

[0034] As described above, the lignin-modified phenolic resin prepared using this invention exhibits superior heat resistance and flowability. As a matrix resin for preparing phenolic molding compounds, it significantly improves the processability and heat resistance of the molding compounds. During the injection molding stage, the third active site on the phenolic chain segment of the modified phenolic resin reacts and crosslinks, leading to resin curing and the acquisition of phenolic molding compound products. Molding compounds prepared from traditional phenolic resins have a high degree of crosslinking and are brittle. However, the boron-containing segments in the modified resin structure of this invention do not branch, resulting in more extended molecular chains, which helps improve the brittleness of the molding compounds.

[0035] Furthermore, the lignin-modified phenolic resin comprises 15-45 parts by weight, the inorganic filler comprises 10-30 parts by weight, the hexamethylenetetramine comprises 10-20 parts by weight, the fiber comprises 10-40 parts by weight, and the additives comprises 0.5-4 parts by weight.

[0036] As can be seen from the above description, the modified resin of the present invention has better processing performance and can appropriately reduce the amount of additives used.

[0037] Furthermore, the fiber is at least one of bamboo powder, wood powder, paper powder, polyester fiber, carbon fiber, basalt fiber, glass fiber, and alumina fiber.

[0038] Furthermore, the additive is at least one selected from ethylene monostearamide, polyethylene wax, ethylene bisstearamide, polyethylene glycol, calcium stearate, zinc stearate, magnesium stearate, titanate coupling agent, silane coupling agent, aluminate coupling agent, borate coupling agent, and phosphate coupling agent.

[0039] Furthermore, the inorganic filler is at least one of silica, magnesium oxide, calcium carbonate, talc, mica powder, silica fume, calcium oxide, and asbestos powder.

[0040] Example 1 of the present invention is as follows: A method for preparing lignin-modified phenolic resin, comprising the following steps: 250g of 4-hydroxyphenylboronic acid, 300g of alkali lignin, and 15g of oxalic acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 4 hours; then 1000g of phenol and 621g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 2 hours, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0041] The properties of the lignin-modified phenolic resin were measured as follows: softening point 94.6℃, flowability 80mm.

[0042] Example 2 of the present invention is as follows: a method for preparing lignin-modified phenolic resin, comprising the following steps: 50g of 4-hydroxyphenylboronic acid, 100g of alkali lignin, and 7.5g of oxalic acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 3 hours; then 500g of phenol and 323g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 2.5 hours, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0043] The properties of the lignin-modified phenolic resin were measured as follows: softening point 95.9℃, flowability 82mm.

[0044] Example 3 of the present invention is as follows: a method for preparing lignin-modified phenolic resin, comprising the following steps: 240g of 4-hydroxyphenylboronic acid, 200g of alkali lignin, and 16g of oxalic acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 3 hours; then 800g of phenol and 504g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 2.5 hours, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0045] The properties of the lignin-modified phenolic resin were measured as follows: softening point 98.5℃, flowability 75mm.

[0046] Example 4 of the present invention is a method for preparing lignin-modified phenolic resin, comprising the following steps: 375g of 4-hydroxyphenylboronic acid, 600g of enzymatically hydrolyzed lignin, and 15g of oxalic acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 3.5h; then 1500g of phenol and 931g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 2.5h, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0047] The properties of the lignin-modified phenolic resin were measured as follows: softening point 93.4℃, flowability 80mm.

[0048] Example 5 of the present invention is as follows: a method for preparing lignin-modified phenolic resin, comprising the following steps: 120g of 4-hydroxyphenylboronic acid, 240g of alkali lignin, and 9.6g of oxalic acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 4 hours; then 600g of phenol and 362g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 3 hours, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0049] The properties of the lignin-modified phenolic resin were measured as follows: softening point 91.5℃, flowability 96mm.

[0050] Example 6 of the present invention is as follows: a method for preparing lignin-modified phenolic resin, comprising the following steps: 135g of 2-hydroxyphenylboronic acid, 225g of alkali lignin, and 10.8g of oxalic acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 4 hours; then 900g of phenol and 543g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 3 hours, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0051] The properties of the lignin-modified phenolic resin were measured as follows: softening point 92.4℃, flowability 95mm.

[0052] Example 7 of the present invention is a method for preparing lignin-modified phenolic resin, comprising the following steps: 80g of 4-hydroxyphenylboronic acid, 80g of enzymatically hydrolyzed lignin, and 8g of oxalic acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 2.5h; then 800g of phenol and 504g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 2h, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0053] The properties of the lignin-modified phenolic resin were measured as follows: softening point 90.9℃, flowability 102mm.

[0054] Example 8 of the present invention is a method for preparing lignin-modified phenolic resin, comprising the following steps: 2g of 2-hydroxyphenylboronic acid, 5g of lignin sulfonate, 0.5g of acetic acid, 0.2g of hydrochloric acid and 0.3g of sulfuric acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 1 hour; then 100g of phenol and 504g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 1 hour, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0055] The properties of the lignin-modified phenolic resin were measured as follows: softening point 90.9℃, flowability 102mm.

[0056] Example 9 of the present invention is as follows: A method for preparing lignin-modified phenolic resin, comprising the following steps: 80g of 4-hydroxyphenylboronic acid, 80g of acid-hydrolyzed lignin, 2g of phosphoric acid, 2g of phosphonic acid, 2g of benzenesulfonic acid and 2g of p-toluenesulfonic acid are added to a reactor, stirred and heated to 100°C, the solution is boiled and refluxed for 6h; then 800g of cresol and 504g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 6h, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0057] The properties of the lignin-modified phenolic resin were measured as follows: softening point 90.9℃, flowability 102mm.

[0058] Comparative Example 1 of the present invention is a conventional method for preparing lignin-modified phenolic resin, comprising the following steps: 300g of alkali lignin and 15g of oxalic acid are added to a reactor, stirred and heated to 100°C, the solution boils, and refluxed for 4 hours; then 1000g of phenol and 621g of formaldehyde (a 37% formaldehyde aqueous solution by volume) are added, refluxed for 2 hours, and dehydrated at 160°C (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0059] The properties of the lignin-modified phenolic resin were measured as follows: softening point 97.6℃, flowability 55mm.

[0060] Comparative Example 2 of the present invention is a method for preparing phenolic resin synergistically modified with boric acid and lignin, comprising the following steps:

[0061] 250g boric acid, 300g alkali lignin, and 15g oxalic acid were added to a reactor, stirred, and heated to 100℃. The solution was boiled and refluxed for 4 hours. Then, 1000g phenol and 621g formaldehyde (37% formaldehyde aqueous solution by volume) were added, and the mixture was refluxed for 2 hours. Dehydration was carried out at 160℃ (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0062] The crosslinking of lignin-modified phenolic resin was measured.

[0063] Comparative Example 3 of the present invention is a method for preparing phenolic resin synergistically modified with boric acid and lignin, the steps of which are as follows:

[0064] 50g boric acid, 400g alkali lignin, and 8g oxalic acid were added to a reactor, stirred, and heated to 100℃. The solution was boiled and refluxed for 4 hours. Then, 1000g phenol and 621g formaldehyde (37% formaldehyde aqueous solution by volume) were added, and the mixture was refluxed for 2 hours. Dehydration was carried out at 160℃ (vacuum degree -0.09MPa) to obtain lignin-modified phenolic resin.

[0065] The lignin-modified phenolic resin was measured to have a softening point of 102.2℃ and a flowability of 34 mm.

[0066] The TG test results of the lignin-modified phenolic resins prepared using the methods of Example 1 and Comparative Example 1 are shown in the figure. Figure 1 .Depend on Figure 1 It is known that the phenolic resin prepared by the preparation method of the present invention has high thermal stability and is suitable for preparing phenolic film materials.

[0067] Examples 10 to 15 describe methods for preparing phenolic molding compounds, with the following steps:

[0068] The lignin-modified phenolic resin (any one of Examples 1, 3, 5, 7 and Comparative Examples 1 and 3), fiber, inorganic filler, hexamethylenetetramine and additives were mixed evenly; the mixed material was fed into a two-roll mill, and after plasticizing, pressing, cooling and crushing, phenolic molding compound was obtained. The preparation formulas and test results of Examples 10 to 15 are shown in Table 1.

[0069] Table 1

[0070]

[0071]

[0072] Comparing Examples 14 and 15, it is evident that excessive lignin filling leads to a decrease in the mechanical properties and heat distortion temperature of the modified phenolic resin. Examples 1-15 show that the modified phenolic resin prepared by the method of this invention exhibits good flowability and heat resistance, with a high lignin content, and the resin meets the requirements for molding compound preparation. Phenolic molding compounds prepared with this resin possess good plasticity and processing flowability, low injection pressure, high product yield, and performance comparable to molding compounds prepared with unmodified resin. Furthermore, they exhibit good heat resistance and mechanical properties, and possess significant cost, resource, and environmental advantages.

[0073] In summary, the preparation method provided by this invention uses lignin and specific organic boron to modify phenolic resin, resulting in better flowability and heat resistance. Phenolic molding compounds prepared using this modified phenolic resin exhibit better flowability and improved toughness after curing.

[0074] The preparation method of the present invention has the following advantages:

[0075] 1. 4-hydroxyphenylboronic acid and 2-hydroxyphenylboronic acid have structures similar to phenol. The ortho and para positions of the hydroxyl groups are active sites, which can react with groups such as formaldehyde and hydroxymethyl groups, thereby improving the reactivity of lignin. This is beneficial for the condensation reaction of lignin and formaldehyde, promoting the improvement effect of lignin, and increasing the filling amount of lignin, which helps to reduce costs.

[0076] 2. This invention uses 4-hydroxyphenylboronic acid or 2-hydroxyphenylboronic acid as a common modifier. The boron compound has only 2 active sites on the benzene ring and is a difunctional monomer, which can limit the substitution reaction on the main chain, inhibit the formation of branched structures, and make the modified phenolic resin have good flowability and toughness.

[0077] 3. Since one active site of 4-hydroxyphenylboronic acid or 2-hydroxyphenylboronic acid is occupied at the ortho or para position, the functionality of the benzene ring is only 2. After participating in the reaction, it can only form a linear structure and will not produce a branched structure. Therefore, the synthesized resin molecules have better mobility and are less likely to form cross-links that would cause the reaction to run away from control. Therefore, the amount of boron compound can be greatly increased, thereby improving the heat resistance of the resin.

[0078] 4. Leveraging the resource advantages of lignin, costs can be significantly reduced;

[0079] 5. The boron compound of the present invention has a structure similar to phenol, has good reactivity, and can react with lignin and formaldehyde to be introduced into the molecular chain, thereby achieving the effects of in-situ modification and reactive introduction.

[0080] The above description is merely an embodiment of the present invention and does not limit the scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the protection scope of the present invention.

Claims

1. A method for preparing lignin-modified phenolic resin, characterized in that, Includes the following steps: Organic boron, lignin and acidic catalyst were added, stirred and heated to boiling, and refluxed for 1-6 hours; then phenol and formaldehyde were added, refluxed for 1-6 hours, and dehydrated to obtain lignin-modified phenolic resin. The organic boron is 4-hydroxyphenylboronic acid or 2-hydroxyphenylboronic acid; The phenol is any one of phenol, cresol, bisphenol A and bisphenol F; The lignin is 5% to 40% of the mass of the phenol; When the phenol is phenol, the mass of the organoboron is 2% to 30% of the mass of the phenol.

2. The method for preparing lignin-modified phenolic resin according to claim 1, characterized in that, The lignin is any one of lignin sulfonate, alkali lignin, enzymatically hydrolyzed lignin, acid-hydrolyzed lignin, and high-boiling-point alcohol lignin.

3. The method for preparing lignin-modified phenolic resin according to claim 1, characterized in that, The acidic catalyst includes at least one of oxalic acid, acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, phosphonic acid, benzenesulfonic acid, and p-toluenesulfonic acid.

4. A method for preparing a phenolic molding compound, characterized in that, The process includes the following steps: lignin-modified phenolic resin, inorganic filler, hexamethylenetetramine, fiber, and additives are mixed evenly; the mixed material is then subjected to plasticizing, sheeting, cooling, and pulverizing to obtain a phenolic molding compound; the lignin-modified phenolic resin is... The lignin-modified phenolic resin prepared by the preparation method according to any one of claims 1-3.

5. The method for preparing phenolic molding compound according to claim 4, characterized in that, The lignin-modified phenolic resin has a weight ratio of 15-45, the inorganic filler has a weight ratio of 10-30, the hexamethylenetetramine has a weight ratio of 10-20, the fiber has a weight ratio of 10-40, and the additives have a weight ratio of 0.5-4.

6. The method for preparing phenolic molding compound according to claim 4, characterized in that, The fiber is at least one of bamboo powder, wood powder, paper powder, polyester fiber, carbon fiber, basalt fiber, glass fiber, and alumina fiber.

7. The method for preparing phenolic molding compound according to claim 4, characterized in that, The additive is at least one selected from ethylene monostearamide, polyethylene wax, ethylene bisstearamide, polyethylene glycol, calcium stearate, zinc stearate, magnesium stearate, titanate coupling agent, silane coupling agent, aluminate coupling agent, borate coupling agent, and phosphate coupling agent.

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