Preparation method of cashew phenol and boron synergistically modified phenolic resin and its molding compound

Abstract

The present application relates to the technical fields of high polymer synthesis and modification, in particular to a preparation method of cashew phenol and boron synergistically modified thermoplastic phenolic resin and its molding compound. The preparation method comprises the following steps: adding phenol, cashew phenol and formaldehyde, stirring uniformly, then adding organic boron and oxalic acid, stirring uniformly again, then heating to 95-105 DEG C, refluxing for 1-5 hours, and then dehydrating to obtain cashew phenol and boron synergistically modified thermoplastic phenolic resin; the organic boron is 4-aminobenzoic acid or 2-aminobenzoic acid. The present application uses a special structure of organic boron and cashew phenol to synergistically modify the phenolic resin, and the modified phenolic resin prepared has good heat resistance and toughness, the cashew phenol replacement amount in the resin is high, the reaction is mild, the resin softening point is controllable, and the modified phenolic resin has good environmental protection benefits; the phenolic molding compound prepared by using the modified phenolic resin has the advantages of low cost, good impact resistance and heat resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis and modification technology, specifically to a method for preparing a thermoplastic phenolic resin and its molding compound synergistically modified with cashew nut shell phenol and boron. Background Technology

[0002] Phenolic resin is a high-performance polymer material with good heat resistance, flame retardancy, and electrical insulation. It is mainly used in the preparation of molding compounds, refractory materials, and coated sand, and is also a raw material for copper-clad laminates, coatings, and photoresists. According to curing characteristics, phenolic resins are mainly divided into two categories: thermoplastic and thermosetting. Among them, the largest application of thermoplastic phenolic resin is in the preparation of phenolic molding compounds.

[0003] Traditional phenolic resins use phenol and formaldehyde as their main raw materials. These resins have the following drawbacks: 1. The raw materials are all petrochemical products, posing a risk of non-renewable energy and environmental pollution, and are expensive and subject to price fluctuations; 2. They are rigid but brittle, as the structure of phenolic resins is mostly composed of benzene rings and methylene groups, resulting in insufficient toughness; 3. They have poor heat resistance. Therefore, with rapid industrial development, higher requirements are being placed on phenolic resins, such as higher heat resistance, better mechanical properties, and superior frictional properties.

[0004] Modification is an important method to solve the above problems. Cashew nut shell oil (CDPO) is an agricultural byproduct of cashew nut processing. It has advantages such as being natural and renewable, readily available raw materials, abundant resources, low price, and unique properties. CDPO has a similar chemical structure to phenol and can (partially) replace phenol in the synthesis of phenolic resins. Chinese invention patent application No. 201210027577.2 discloses the use of CDPO to modify phenolic paper-based copper-clad laminates; Chinese invention patent application No. 201210576483.0 discloses CDPO-modified phenolic foam; and Chinese invention patent applications Nos. 201110223037.7, 201110177345.0, and 200710129766.X all disclose the use of CDPO to modify phenolic resins. All of the above patent documents report methods for modifying phenolic resins using CDPO / cashew shell oil. Existing cashew nut shell phenolic resins still suffer from the following technical drawbacks: 1. Low cashew nut shell phenol substitution: Cashew nut shell phenol has a similar structure and properties to phenol, and its side chains can improve flexibility. However, excessive cashew nut shell phenol content leads to a lower softening point, making the resin difficult to store and pulverize, which is detrimental to downstream processing; 2. Poor reactivity of cashew nut shell phenol, requiring strong acid catalysis, making the reaction difficult to control and posing safety hazards; 3. Decreased temperature resistance of cashew nut shell phenolic resins. These drawbacks can be overcome by employing a cashew nut shell phenol-boric acid dual modification method.

[0005] Chinese invention patent application number 201110325197.2 reports a method for dual-modified phenolic resin using cashew nut shell and boric acid. Specifically, phenol, formaldehyde, and cashew nut shell react under a catalyst for 2-3 hours, followed by the addition of boric acid and reaction for 0.5-1 hour. The resin is then dehydrated under reduced pressure to obtain cashew nut shell modified boron phenolic resin. However, the boric acid in this method has poor reactivity, resulting in low boron content in the resin and limited heat resistance. Chinese invention patent application number 201410802979.4 uses organic boron and cashew nut shell as modifiers to prepare cashew nut shell / boron modified phenolic resin. However, the benzene ring of this organic boron compound has multiple reaction sites. Increased amounts of cashew nut shell and organic boron easily form branched structures, causing resin cross-linking and making the reaction difficult to control. This limits the increase in cashew nut shell content and also limits the improvement in heat resistance. Furthermore, the boron element is directly bonded to oxygen, resulting in lower temperature resistance compared to the BC structure. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a thermoplastic phenolic resin and its molding compound synergistically modified with cashew phenol and boron, thereby improving the defects of low cashew phenol substitution and limited temperature resistance in existing resins.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a thermoplastic phenolic resin synergistically modified with cashew phenol and boron includes the following steps: adding phenol, cashew phenol and formaldehyde, stirring evenly, then adding organic boron and oxalic acid, stirring evenly again, then heating to 95-105℃, refluxing for 1-5 hours, and dehydrating after reaction to obtain the thermoplastic phenolic resin synergistically modified with cashew phenol and boron.

[0009] The organoboron is 4-aminophenylboronic acid or 2-aminophenylboronic acid.

[0010] Another technical solution adopted in this invention is: a method for preparing phenolic molding compound, which uses the above-mentioned cashew nut phenol and boron synergistic modified thermoplastic phenolic resin as the matrix, including the following steps: mixing cashew nut phenol and boron synergistic modified thermoplastic phenolic resin, fiber, inorganic filler, hexamethylenetetramine and additives evenly; the mixed material is then subjected to plasticizing, sheeting, cooling and pulverizing in sequence to obtain phenolic molding compound.

[0011] The beneficial effects of this invention are as follows: The preparation method of this invention first involves uniformly stirring phenol, cashew nut shell powder, and formaldehyde to improve dispersibility, then adding a specially structured organic boron and oxalic acid for polymerization to obtain a cashew nut shell powder and boron synergistically modified thermoplastic phenolic resin. This preparation method uses a specially structured organic boron and cashew nut shell powder to synergistically modify the phenolic resin. The resulting modified phenolic resin exhibits good heat resistance and toughness, with a high cashew nut shell powder substitution rate, mild reaction, controllable resin softening point, and excellent environmental benefits. Phenolic molding compounds prepared using this modified phenolic resin have the advantages of low cost, good impact resistance, and good heat resistance. Attached Figure Description

[0012] Figure 1 The images show the TG test results of the phenolic resins prepared in Examples 1, 1, and 2 of this invention. Detailed Implementation

[0013] 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.

[0014] A method for preparing a thermoplastic phenolic resin synergistically modified with cashew phenol and boron includes the following steps: adding phenol, cashew phenol and formaldehyde, stirring evenly, then adding organic boron and oxalic acid, stirring evenly again, then heating to 95-105℃, refluxing for 1-5 hours, and dehydrating after reaction to obtain the thermoplastic phenolic resin synergistically modified with cashew phenol and boron.

[0015] The organic boron is 4-aminophenylboronic acid or 2-aminophenylboronic acid.

[0016] As can be seen from the above description, the beneficial effects of this invention are: it prepares phenolic resins with high cashew nut phenol substitution, controllable softening point, and high heat resistance, and uses these resins to prepare phenolic molding compounds. To achieve the above objectives, this invention employs a specially structured organic boron compound, which, in combination with cashew nut phenol, synergistically modifies the phenolic resin.

[0017] Choosing 4-aminophenylboronic acid or 2-aminophenylboronic acid as a synergistic modifier of phenolic resins with organoboron and cashew phenol has the following advantages:

[0018] 1. The main chain of this organoboron has only two active sites, which can limit the reaction of the main chain and inhibit the formation of branched structures on the main chain. Therefore, increasing the amount of this organoboron can improve the heat resistance of the resin while making it less prone to crosslinking. At the same time, the boron element of this organoboron is directly connected to the carbon element of the benzene ring, which can better improve the thermal stability of the resin compared with the BO group.

[0019] 2. Although the active sites on the benzene ring of this organoboron are suppressed, the side chain contains amino groups, which can react with formaldehyde to form a hydroxymethyl structure, thereby forming certain branching on the side chain, increasing the resin softening point, reducing the problem of low softening point caused by excessive cashew phenol, increasing the amount of cashew phenol that can be replaced, and the reactivity of the side chain is limited, so even if the amount used is increased, cross-linking will not occur, and the reaction is controllable; increasing the resin softening point is also beneficial for storage and crushing, making it easier for subsequent processing and use;

[0020] 3. The organic boron of the present invention has a certain degree of acidity, which can play a certain role in autocatalysis, providing a basis for using weak acid as a catalyst. Therefore, the present invention can synthesize resin under oxalic acid catalysis, the reaction is mild and the process is easy to control.

[0021] Furthermore, the mass of cashew phenol is 20-70% of the sum of the masses of phenol and cashew phenol. Preferably, the mass of cashew phenol is 20-30% of the sum of the masses of phenol and cashew phenol.

[0022] As described above, replacing part of the phenol with cashew nut shellac can reduce costs and improve the toughness of phenolic resins. In traditional processes for preparing cashew nut shellac-modified phenolic resins, the resin's heat resistance and softening point decrease with increasing cashew nut shellac content, making it difficult to store, pulverize, and process. The organoboron side chain of this invention contains amino groups, exhibiting a certain degree of reactivity. This increases the resin's molecular weight and softening point, while its reactivity is limited, making it less prone to cross-linking and curing, thus ensuring a controllable reaction. By increasing the amount of organoboron shellac used, the shortcomings of decreased softening point and heat resistance caused by increased cashew nut shellac content are overcome. The cashew nut shellac content of this invention can be significantly increased, achieving excellent synergistic modification. Even when the cashew nut shellac content reaches 70% of the combined mass of phenol and cashew nut shellac, the resin softening point remains controllable, meeting downstream application requirements.

[0023] Furthermore, the molar amount of formaldehyde is 0.7 to 0.95 times the sum of the molar amounts of phenol and cashew phenol.

[0024] As can be seen from the above description, the softening point of the resin can be adjusted by changing the molar number of formaldehyde. However, the molar number should not be too low or too high. Too low a number will lead to incomplete reaction and poor resin performance, while too high a number will result in poor environmental performance.

[0025] Furthermore, the formaldehyde is an aqueous solution of formaldehyde or paraformaldehyde.

[0026] Furthermore, the softening point of the thermoplastic phenolic resin synergistically modified with cashew phenol and boron is ≥90℃.

[0027] As can be seen from the above description, phenolic resin has a very low softening point, which is not conducive to processing and use.

[0028] Further, the mass of oxalic acid is 0.4% to 4% of the sum of the masses of phenol and cashew phenol. Preferably, the mass of acid is 1% to 2% of the sum of the masses of phenol and cashew phenol.

[0029] As described above, conventional cashew nut shell phenol-modified phenolic resins require strong acids, such as sulfuric acid, hydrochloric acid, or nitric acid, resulting in a vigorous, difficult-to-control, and high-risk reaction process. The organoboron compound of this invention can effectively adjust the resin's softening point and is inherently acidic, allowing the reaction to proceed under weakly acidic conditions with high safety.

[0030] Further, the mass of the organoboron is 0.2% to 10% of the mass of phenol. Preferably, the mass of the organoboron is 1% to 2% of the mass of phenol.

[0031] As can be seen from the above description, the softening point can be controlled by increasing the amount of 4-aminophenylboronic acid or 2-aminophenylboronic acid.

[0032] Another technical solution adopted in this invention is: a method for preparing phenolic molding compound, which uses the above-mentioned cashew nut phenol and boron synergistic modified thermoplastic phenolic resin as the matrix, including the following steps: mixing cashew nut phenol and boron synergistic modified thermoplastic phenolic resin, fiber, inorganic filler, hexamethylenetetramine and additives evenly; the mixed material is then subjected to plasticizing, sheeting, cooling and pulverizing in sequence to obtain phenolic molding compound.

[0033] As can be seen from the above description, the cashew phenol and boron synergistic modified thermoplastic phenolic resin of the present invention has good heat resistance and toughness, and its softening point is controllable and meets the requirements for use in molding compounds. Therefore, molding compounds prepared using this resin as a matrix have good impact resistance and heat resistance, and are low in cost, and have broad application prospects.

[0034] Furthermore, the weight parts of the cashew phenol synergistic modified thermoplastic phenolic resin are 15-45 parts, the weight parts of the fiber are 10-40 parts, the weight parts of the inorganic filler are 10-30 parts, the weight parts of the hexamethylenetetramine are 10-20 parts, and the weight parts of the additives are 0.5-4 parts.

[0035] Furthermore, the fiber is at least one of wood flour, paper flour, bamboo flour, carbon fiber, basalt fiber, polyester fiber, alumina fiber, and glass fiber.

[0036] Furthermore, the inorganic filler is at least one of silica, magnesium oxide, calcium carbonate, talc, mica powder, silica fume, calcium oxide, and asbestos powder.

[0037] Furthermore, the additive is at least one selected from ethylene monostearamide, ethylene bisstearamide, polyethylene wax, polyethylene glycol, zinc stearate, calcium stearate, magnesium stearate, titanate coupling agent, aluminate coupling agent, silane coupling agent, borate coupling agent, and phosphate coupling agent.

[0038] Example 1 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0039] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0040] S2. Next, add 4-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0041] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0042] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0043] The mass of cashew phenol is 30% of the sum of the masses of phenol and cashew phenol.

[0044] The number of moles of formaldehyde is 0.85 times the sum of the number of moles of phenol and cashew phenol;

[0045] The mass of oxalic acid is 1% of the sum of the masses of phenol and cashew phenol;

[0046] The mass of 4-aminophenylboronic acid is 1.5% of the mass of phenol.

[0047] Example 2 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0048] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0049] S2. Next, add 4-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0050] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0051] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0052] The mass of cashew phenol is 20% of the sum of the masses of phenol and cashew phenol.

[0053] The number of moles of formaldehyde is 0.85 times the sum of the number of moles of phenol and cashew phenol;

[0054] The mass of oxalic acid is 1% of the sum of the masses of phenol and cashew phenol;

[0055] The mass of 4-aminophenylboronic acid is 1% of the mass of phenol.

[0056] Example 3 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0057] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0058] S2. Next, add 4-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0059] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0060] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0061] The mass of cashew phenol is 40% of the sum of the masses of phenol and cashew phenol.

[0062] The number of moles of formaldehyde is 0.85 times the sum of the number of moles of phenol and cashew phenol;

[0063] The mass of oxalic acid is 1.5% of the sum of the masses of phenol and cashew phenol;

[0064] The mass of 4-aminophenylboronic acid is 2% of the mass of phenol.

[0065] Example 4 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0066] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0067] S2. Next, add 4-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0068] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0069] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0070] The mass of cashew phenol is 30% of the sum of the masses of phenol and cashew phenol.

[0071] The number of moles of formaldehyde is 0.85 times the sum of the number of moles of phenol and cashew phenol;

[0072] The mass of oxalic acid is 1% of the sum of the masses of phenol and cashew phenol;

[0073] The mass of 4-aminophenylboronic acid is 2% of the mass of phenol.

[0074] Example 5 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0075] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0076] S2. Next, add 4-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0077] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0078] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0079] The mass of cashew phenol is 30% of the sum of the masses of phenol and cashew phenol.

[0080] The number of moles of formaldehyde is 0.86 times the sum of the number of moles of phenol and cashew phenol;

[0081] The mass of oxalic acid is 1% of the sum of the masses of phenol and cashew phenol;

[0082] The mass of 4-aminophenylboronic acid is 1.5% of the mass of phenol.

[0083] Example 6 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0084] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0085] S2. Next, add 4-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0086] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0087] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0088] The mass of cashew phenol is 30% of the sum of the masses of phenol and cashew phenol.

[0089] The number of moles of formaldehyde is 0.85 times the sum of the number of moles of phenol and cashew phenol;

[0090] The mass of oxalic acid is 1.2% of the sum of the masses of phenol and cashew phenol;

[0091] The mass of 4-aminophenylboronic acid is 1.5% of the mass of phenol.

[0092] Example 7 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0093] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0094] S2. Next, add 4-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0095] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0096] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0097] The mass of cashew phenol is 30% of the sum of the masses of phenol and cashew phenol.

[0098] The number of moles of formaldehyde is 0.85 times the sum of the number of moles of phenol and cashew phenol;

[0099] The amount of oxalic acid used is 1% of the sum of the masses of phenol and cashew phenol;

[0100] The amount of 4-aminophenylboronic acid used is 1% of the amount of phenol used.

[0101] Example 8 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0102] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0103] S2. Next, add 2-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0104] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0105] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0106] The mass of cashew phenol is 30% of the sum of the masses of phenol and cashew phenol.

[0107] The number of moles of formaldehyde is 0.85 times the sum of the number of moles of phenol and cashew phenol;

[0108] The amount of oxalic acid used is 1% of the sum of the masses of phenol and cashew phenol;

[0109] The amount of 2-aminophenylboronic acid used is 1.5% of the amount of phenol used.

[0110] Example 9 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0111] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0112] S2. Next, add 4-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0113] S3. Gradually increase the temperature to 95℃ and reflux for 5 hours;

[0114] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0115] The mass of cashew phenol is 70% of the sum of the masses of phenol and cashew phenol.

[0116] The number of moles of formaldehyde is 0.7 times the sum of the number of moles of phenol and cashew phenol;

[0117] The amount of oxalic acid used is 0.4% of the sum of the masses of phenol and cashew phenol;

[0118] The amount of 4-aminophenylboronic acid used is 0.2% of the amount of phenol used.

[0119] Example 10 of the present invention is a method for preparing thermoplastic phenolic resin synergistically modified with cashew phenol and boron, the steps of which are as follows:

[0120] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0121] S2. Next, add 2-aminophenylboronic acid and oxalic acid, and stir until well mixed.

[0122] S3. Gradually increase the temperature to 105℃ and reflux for 1 hour;

[0123] S4. After dehydration, a thermoplastic phenolic resin synergistically modified with cashew phenol and boron is obtained.

[0124] The mass of cashew phenol is 30% of the sum of the masses of phenol and cashew phenol.

[0125] The number of moles of formaldehyde is 0.95 times the sum of the number of moles of phenol and cashew phenol;

[0126] The amount of oxalic acid used is 4% of the sum of the masses of phenol and cashew phenol;

[0127] The amount of 2-aminophenylboronic acid used is 10% of the amount of phenol used.

[0128] Comparative Example 1 of the present invention is a method for preparing ordinary thermoplastic phenolic resin, comprising the following steps:

[0129] S1. Add phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0130] S2. Next, add oxalic acid and stir well.

[0131] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0132] S4. After dehydration, thermoplastic phenolic resin is obtained;

[0133] The molar amount of formaldehyde is 85% of the molar amount of phenol;

[0134] The mass of oxalic acid is 1% of the mass of phenol.

[0135] Comparative Example 2 of the present invention is a method for preparing cashew phenol-modified thermoplastic phenolic resin, the steps of which are as follows:

[0136] S1. Add phenol, cashew phenol and a 37% (v / v) formaldehyde aqueous solution to the reaction vessel and stir until homogeneous;

[0137] S2. Next, add oxalic acid and stir well.

[0138] S3. Gradually increase the temperature to 100℃ and reflux for 3 hours;

[0139] S4. After dehydration, cashew phenol-modified thermoplastic phenolic resin is obtained;

[0140] The mass of cashew phenol is 30% of the sum of the masses of phenol and cashew phenol.

[0141] The number of moles of formaldehyde is 0.85 times the sum of the number of moles of phenol and cashew phenol;

[0142] The mass of oxalic acid is 1% of the sum of the masses of phenol and cashew phenol.

[0143] Phenolic resins were prepared using the methods described in Examples 1 to 8, and Comparative Examples 1 and 2, respectively. The phenolic resins were tested, and the results are shown in Table 1. The TG test results of the phenolic resins from Example 1, Comparative Example 1, and Comparative Example 2 are shown in Table 1. Figure 1 .

[0144] Table 1

[0145]

[0146]

[0147] As shown in Table 1, the modified phenolic resin prepared using the method of this invention has a high and controllable softening point, combined with... Figure 1 It is evident that this resin also possesses high thermal stability, making it suitable for preparing phenolic molding compounds. In contrast, the phenolic resin prepared directly from cashew nut shells in Comparative Example 2 has lower viscosity and softening point, making it difficult to pulverize and store, which is detrimental to the production of phenolic molding compounds.

[0148] Examples 11 to 16 describe methods for preparing phenolic molding compounds, comprising the following steps:

[0149] Thermoplastic phenolic resin (any one of Examples 1 to 4, Comparative Examples 1 and 2), 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 formula and test results of Examples 9 to 14 are shown in Table 2.

[0150] Table 2

[0151]

[0152]

[0153] As shown in Table 2, the tensile strength, flexural strength, impact strength, and heat distortion temperature of Examples 11, 14, 15, and 16 are all improved compared to Examples 12 and 13. This indicates that using the resin of the present invention to prepare molding compounds can significantly improve the mechanical properties and heat resistance of phenolic molding compounds. Furthermore, the high amount of cashew phenol in the present invention results in lower production costs for the molding compounds.

[0154] In summary, the preparation method provided by this invention uses a special structure of organic boron and cashew phenol to synergistically modify phenolic resin. The modified phenolic resin obtained has good heat resistance and toughness, and the cashew phenol substitution in the resin is high. The reaction is mild, the resin softening point is controllable, and it also has good environmental benefits. The phenolic molding compound prepared using this modified phenolic resin has the advantages of low cost, good impact resistance and heat resistance.

[0155] This preparation method has the following advantages:

[0156] 1. The organoboron (4-aminophenylboronic acid or 2-aminophenylboronic acid) of this invention has two active sites on its main chain, which can participate in the reaction of phenol, cashew nut shell powder, and formaldehyde, thereby connecting to the phenolic resin main chain and achieving the purpose of in-situ introduction of boron. Simultaneously, the two active sites can inhibit branching reactions on the main chain, preventing cross-linking even with increased dosage. This ensures that increasing the amount of organoboron used will improve the heat resistance of the resin. The boron element in this organoboron is directly connected to the carbon element of the benzene ring, which, compared to BO groups, can better improve the thermal stability of the resin.

[0157] When 2-aminophenylboronic acid or 4-aminophenylboronic acid is crosslinked, branched structures of a certain length can grow on the side chains, which can increase the softening point of the resin. By increasing the amount of organoboron, the problem of decreased softening point and heat resistance caused by increased cashew phenol content can be overcome, achieving a good synergistic modification effect.

[0158] 3, 4-aminophenylboronic acid or 2-aminophenylboronic acid have autocatalytic properties, which solves the problem of insufficient reactivity of cashew phenol and provides a basis for the catalysis of the reaction under weak acid, making the production process more stable and controllable.

[0159] The above description is merely an embodiment of the present invention and does not limit the patent 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 patent protection scope of the present invention.

Claims

1. A method for preparing a thermoplastic phenolic resin synergistically modified with cashew phenol and boron, characterized in that, Includes the following steps: Phenol, cashew nut phenol and formaldehyde are added and stirred evenly. Then organic boron and oxalic acid are added and stirred evenly again. The temperature is then raised to 95~105℃ and refluxed for 1~5 hours. After the reaction, the product is dehydrated to obtain cashew nut phenol and boron synergistic modified thermoplastic phenolic resin. The organic boron is 4-aminophenylboronic acid or 2-aminophenylboronic acid; The mass of the cashew phenol is 20-70% of the sum of the masses of phenol and cashew phenol; The mass of the organoboron is 0.2% to 10% of the mass of phenol.

2. The method for preparing the cashew phenol and boron synergistic modified thermoplastic phenolic resin according to claim 1, characterized in that, The molar amount of formaldehyde is 0.7 to 0.95 of the sum of the molar amounts of phenol and cashew phenol.

3. The method for preparing the cashew phenol and boron synergistic modified thermoplastic phenolic resin according to claim 1, characterized in that, The mass of the oxalic acid is 0.4% to 4% of the sum of the masses of phenol and cashew phenol.

4. A method for preparing a phenolic molding compound, comprising using the cashew phenol and boron synergistic modified thermoplastic phenolic resin as described in any one of claims 1-3 as the matrix, characterized in that, The process includes the following steps: mixing cashew phenol with boron-modified thermoplastic phenolic resin, fiber, inorganic filler, hexamethylenetetramine and additives until homogeneous; the mixed material is then subjected to plasticizing, tableting, cooling and pulverizing to obtain phenolic molding compound.

5. The method for preparing phenolic molding compound according to claim 4, characterized in that, The cashew phenol and boron synergistic modified thermoplastic phenolic resin comprises 15-45 parts by weight, the fiber comprises 10-40 parts by weight, the inorganic filler comprises 10-30 parts by weight, the hexamethylenetetramine comprises 10-20 parts by weight, and the additive comprises 0.5-4 parts by weight.

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

7. The method for preparing phenolic molding compound according to claim 4, characterized in that, The inorganic filler is at least one of the following: silica, magnesium oxide, calcium carbonate, talc, mica powder, silica fume, calcium oxide, and asbestos powder.

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

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