Modified phenolic resin adhesive and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, in particular to a modified phenolic resin adhesive and a preparation method thereof. The problems of excessive formaldehyde emission, long curing time, poor wear resistance, low bonding strength and poorer toughness of a phenolic resin adhesive are solved. By controlling the use amount of urea, urea reacts with formaldehyde to generate urea-formaldehyde resin, so that the content of free formaldehyde in the adhesive is reduced; the curing speed of the resin is increased by changing the dosage of the basic catalyst and the type and dosage of the curing agent; the chemical structure of the phenolic resin adhesive is changed by adding the cashew nut shell oil, and the crosslinking density and hardness of the phenolic resin adhesive are increased, so that the wear resistance of the adhesive is improved; by changing the dosage of formaldehyde and the type and dosage of the silane coupling agent, the binding force between the adhesive and a base material is enhanced, and the bonding strength is improved; vanadium pentoxide is modified by dioleoyl phosphatidyl ethanolamine, and the use amount of the modified vanadium pentoxide is changed, so that the toughness of the adhesive is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, in particular to a modified phenolic resin adhesive and a preparation method thereof. Background Art

[0002] Phenolic resin is a synthetic resin formed by the polycondensation of phenol and aldehyde in the presence of an acidic or alkaline catalyst. It is one of the earliest synthetic polymer materials and has been widely used in various industries for over 100 years. Phenolic resin can be used as a raw material to prepare inks, plastics, adhesives, wear-resistant materials, etc. In the adhesive field, phenolic resin adhesives are the most widely used adhesive type besides urea-formaldehyde resin adhesives.

[0003] Phenolic resin adhesives are widely used in the manufacture of outdoor wood-based panels. Multi-layer solid wood composite flooring, made by gluing and pressing multi-layer plywood as a base material and covering it with veneers of internationally popular precious woods, has gained widespread adoption in developed countries like Europe and the United States. Solid wood composite flooring requires high veneer bonding strength, especially in Japan, South Korea, and coastal cities in eastern Asia, where high humidity places even higher demands on flooring adhesives. Conventional urea-formaldehyde resins struggle to meet the required water and weather resistance, but using phenolic resin adhesives for veneer bonding can improve the product's bonding strength, water resistance, and weather resistance. Therefore, phenolic resin adhesives offer significant advantages in the production of water-resistant and weather-resistant wood products. Phenolic resin adhesives, produced by modifying phenolic resins, are poised to gradually become a superior alternative to urea-formaldehyde resin adhesives.

[0004] Chinese patent CN105368355A discloses a phenolic resin adhesive and its preparation method, the components and weight percentages of which are: 70-80 parts of phenolic resin, 2-3 parts of anti-aging agent, 3-4 parts of dispersant, 3-5 parts of compatibilizer, 1-2 parts of curing agent, 0.5-1.5 parts of plasticizer, 4-6 parts of flame retardant, 0.5-1 parts of accelerator, 6-8 parts of vanadium pentoxide, and 9-12 parts of SEBS. The phenolic resin adhesive prepared by this invention has good toughness, but poor tensile shear strength. When subjected to external force, the structure is easily damaged, causing the adhesive to lose its effectiveness. In addition, the phenolic resin adhesive prepared by this invention has poor high temperature resistance and is difficult to maintain its excellent bonding performance in high temperature environments.

[0005] Chinese patent CN113461886B discloses a fast-curing phenolic resin and its application. Thiourea and cellulose sulfate are applied to the phenolic resin system. The water-soluble, fast-curing modified phenolic resin prepared by this inventive method has a fast curing speed, which not only saves energy and improves production efficiency, but is also safe and environmentally friendly, and can be widely used on reconstituted wood, modified wood, or plywood. This invention has developed a novel phenolic resin adhesive with low toxicity and a fast curing speed. In the production of reconstituted wood, it can reduce curing time, save energy, reduce reconstituted wood production costs, and improve production efficiency. However, the modified phenolic resin prepared in this invention has poor wear resistance and is easily worn by external forces.

[0006] Chinese patent CN108314987B discloses a high-temperature resistant adhesive containing graphite powder and its preparation method. The preparation method of the adhesive in this invention is as follows: Step 1: Prepare a modified boron phenolic resin; Step 2: Weigh and grind a hydroxyl-containing methylphenyl silicone resin, a modified boron phenolic resin, a curing paste, graphite powder, a high-temperature resistant filler, a liquid toughening agent, an inorganic toughening agent, ethyl orthosilicate, and a filler; Step 3: Prepare a high-temperature resistant adhesive containing graphite powder. This invention uses a hydroxyl-containing methylphenyl silicone resin and a modified boron phenolic resin as the adhesive base materials, adds a high-temperature carbonization material graphite powder and a high-temperature resistant filler, and uses a crosslinking agent, ethyl orthosilicate, to crosslink the organic resin and the inorganic material at the curing temperature, thereby improving the bonding strength of the adhesive in both room temperature and high-temperature environments. The inorganic toughening agent and the liquid toughening agent are combined to give the adhesive higher toughness at room temperature. However, the curing paste used in the invention contains a large amount of free formaldehyde, resulting in excessive free formaldehyde content in the synthesized adhesive.

[0007] Phenolic resin adhesives have been widely used in industry. Phenolic resin adhesives have the advantages of good impact resistance, good water resistance, good heat resistance and good stability. Therefore, phenolic resin adhesives are widely used in the production of weather-resistant and heat-resistant wood products. However, due to their shortcomings such as poor wear resistance, long curing time, poor toughness, low bonding strength and excessive formaldehyde emission, they result in low production efficiency and high consumption of equipment, materials and energy, limiting the effective industrial application of phenolic resin adhesives.

[0008] Therefore, a modified phenolic resin adhesive and a preparation method thereof are proposed. Summary of the Invention

[0009] The present invention aims to provide a modified phenolic resin adhesive and a preparation method thereof. The modified vanadium pentoxide is prepared and phenol, formaldehyde, a curing agent, urea, cashew nut shell liquid, a silane coupling agent, an alkaline catalyst, the modified vanadium pentoxide and deionized water are mixed to obtain the modified phenolic resin adhesive, wherein the formaldehyde, the alkaline catalyst and the deionized water are added in three batches. By controlling the amount of urea, the amino groups in the urea molecules react with the aldehyde groups in the formaldehyde molecules to form urea-formaldehyde resin, thereby reducing the free formaldehyde content in the adhesive. By changing the amount of alkaline catalyst, the type and amount of curing agent, the resin molecules form a three-dimensional network structure in an alkaline environment, which can significantly increase the curing speed of the resin. By adding cashew nut shell oil, the chemical structure of the phenolic resin adhesive is changed, the cross-linking density and hardness are increased, thereby improving the wear resistance. By changing the amount of formaldehyde, the type and amount of silane coupling agent, the bonding force between the adhesive and the substrate is enhanced and the bonding strength is improved. By using dioleoylphosphatidylethanolamine to modify vanadium pentoxide and changing the amount of modified vanadium pentoxide, the toughness of the adhesive is improved.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] On one hand, the present invention provides a method for preparing a modified phenolic resin adhesive. The method for preparing the modified phenolic resin adhesive is as follows: phenol, a portion of an alkaline catalyst, cashew nut shell liquid, and a portion of deionized water are added to a reaction flask by weight and mixed uniformly to obtain a mixture A; a first batch of formaldehyde, a first batch of alkaline catalyst, and a first batch of deionized water are added to the mixture A, and the mixture is heated to 90° C. and reacted for 50 minutes to obtain a mixture B; a second batch of formaldehyde, a second batch of alkaline catalyst, and a second batch of deionized water are added to the mixture B, and the mixture is reacted at 90° C. for 50 minutes to obtain a mixture C; the remaining formaldehyde, the remaining alkaline catalyst, and the remaining deionized water are added to the mixture C, and the mixture is reacted at 90° C. for 60 minutes to obtain a mixture D; the mixture D is cooled to 70° C., urea, a curing agent, a silane coupling agent, and modified vanadium pentoxide are added, the mixture is cooled to 65° C. and reacted for 45 minutes, and the mixture is cooled and discharged to obtain the modified phenolic resin adhesive;

[0012] The raw materials for producing the modified phenolic resin adhesive include, in parts by weight, 100 parts of phenol, 40-70 parts of formaldehyde, 1-3 parts of a curing agent, 5-15 parts of urea, 15-30 parts of cashew nut shell liquid, 1-5 parts of a silane coupling agent, 1.6-6 parts of a basic catalyst, 5-8 parts of modified vanadium pentoxide, and 80 parts of deionized water.

[0013] Preferably, the formaldehyde is a formaldehyde aqueous solution with a concentration of 38 wt%.

[0014] Preferably, the amount of the partial alkaline catalyst used is 20% of the total amount of the alkaline catalyst used; the amount of the partial deionized water used is 30% of the total amount of the deionized water used.

[0015] Preferably, the first batch of formaldehyde, the first batch of alkaline catalyst and the first batch of deionized water are 50%, 40% and 40% of the total amount of formaldehyde, the alkaline catalyst and the deionized water used respectively.

[0016] Preferably, the second batch of formaldehyde, the second batch of alkaline catalyst and the second batch of deionized water are 25%, 20% and 15% of the total amount of formaldehyde, the alkaline catalyst and the deionized water used respectively.

[0017] Preferably, the curing agent is one of resorcinol, tannin, propylene carbonate, sodium carbonate, and isocyanate.

[0018] Preferably, the silane coupling agent is one of KH550 silane coupling agent, KH560 silane coupling agent, KH602 silane coupling agent, and KH792 silane coupling agent.

[0019] Silane coupling agents contain both organic and hydrolyzable silane functional groups in their molecular structure. This unique structure enables them to form a bridge between the phenolic resin adhesive and the substrate, thereby improving interfacial bonding. One end of the silane coupling agent reacts with the organic groups in the phenolic resin adhesive, while the other end chemically bonds or physically adsorbs with inorganic or organic matter on the substrate surface, thereby strengthening the bond between the adhesive and the substrate. Silane coupling agents can also reduce the surface tension of the phenolic resin adhesive, improving its wettability to the substrate, and helping the adhesive to more fully penetrate the tiny pores on the substrate surface, creating more contact points and bonding area, thereby increasing bonding strength.

[0020] Preferably, the alkaline catalyst is sodium hydroxide.

[0021] Preferably, the preparation method of the modified vanadium pentoxide is as follows: adding vanadium pentoxide to water to prepare a 6wt% slurry; heating the slurry to 80°C, adding 10wt% dioleoylphosphatidylethanolamine solution, stirring at a constant temperature for 40 minutes, and then cooling to room temperature to obtain a mixed solution; centrifuging the mixed solution with deionized water and filtering to obtain a filter residue; placing the filter residue in a vacuum drying oven and drying it at 100°C for 12 hours to obtain a dry filter residue; and sieving the dry filter residue to obtain the modified vanadium pentoxide.

[0022] Vanadium pentoxide is an inorganic rigid particle that can toughen the phenolic resin matrix. However, the surface of vanadium pentoxide is highly hydrophilic, while the phenolic resin matrix is lipophilic, resulting in poor compatibility between the two. Dioleoylphosphatidylethanolamine (DPEA) possesses both hydrophilic and lipophilic groups. The hydrophilic groups can physically adsorb to the surface of vanadium pentoxide, while the lipophilic groups chemically react with the phenolic resin matrix. Modification of vanadium pentoxide with DPEA transforms the hydrophilicity of the vanadium pentoxide surface into lipophilicity, improving its compatibility and interfacial bonding strength with the phenolic resin matrix. When the adhesive is subjected to external forces, the vanadium pentoxide hinders and passivates crack propagation in the matrix resin, ultimately preventing the cracks from developing into destructive cracking. Simultaneously, the vanadium pentoxide acts as a stress concentrator, causing the surrounding matrix to yield, consuming a significant amount of energy and significantly improving the toughness of the adhesive.

[0023] Another aspect of the present invention provides a modified phenolic resin adhesive, wherein raw materials for producing the modified phenolic resin include phenol, formaldehyde, a curing agent, urea, cashew nut shell oil, a silane coupling agent, an alkaline catalyst, modified vanadium pentoxide and deionized water; the modified phenolic resin adhesive is prepared by any of the preparation methods described above; the free formaldehyde content of the modified phenolic resin adhesive is 0.028%; the curing time of the modified phenolic resin adhesive is 53 seconds; the wear rate of the modified phenolic resin adhesive is 0.18%; the bonding strength of the modified phenolic resin adhesive is 2.13 MPa; the elongation at break of the modified phenolic resin adhesive at 25°C is 24.6%, and the elongation at break at 300°C is 12.5%.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. Urea is an effective formaldehyde scavenger. The present invention controls the amount of urea used and utilizes the condensation reaction between the amino groups in the urea molecule and the aldehyde groups in the formaldehyde molecule to generate urea-formaldehyde resin, thereby reducing the free formaldehyde content in the adhesive. The formaldehyde release of the prepared modified phenolic resin adhesive is significantly reduced, and the free formaldehyde content is 0.028%.

[0026] 2. The curing agent reacts with the phenolic groups in the phenolic resin to form a three-dimensional network structure, thereby promoting the curing of the resin. The alkaline environment helps accelerate the cross-linking reaction between the resin molecules, allowing the resin to reach a cured state more quickly and reducing the curing time. By varying the amount of alkaline catalyst and the type and amount of curing agent used, the present invention can significantly increase the curing speed of the resin, with a curing time of 53 seconds.

[0027] 3. The present invention changes the chemical structure of the phenolic resin adhesive by adding cashew nut shell liquid, increases its crosslinking density and hardness, and thus improves wear resistance. By controlling the amount of cashew nut shell liquid, the phenolic resin adhesive is made more stable when subjected to friction and wear, reducing the amount of wear. The wear rate of the prepared modified phenolic resin adhesive is 0.18%, showing significantly improved wear resistance.

[0028] 4. The present invention increases the number of cross-linking points in the resin by changing the amount of formaldehyde, the type and amount of the silane coupling agent, and thus improves the cross-linking degree of the resin. One end of the silane coupling agent reacts with the organic group in the phenolic resin adhesive, and the other end chemically bonds or physically adsorbs with the inorganic or organic matter on the surface of the substrate, which can enhance the bonding force between the adhesive and the substrate. The resulting modified phenolic resin adhesive has a bonding strength of 2.13 MPa, showing significantly improved bonding strength.

[0029] 5. The present invention modifies vanadium pentoxide by using dioleoylphosphatidylethanolamine to change the hydrophilicity of the surface of vanadium pentoxide to lipophilicity, thereby improving the compatibility and interfacial bonding strength between the vanadium pentoxide and the phenolic resin matrix. When the adhesive is subjected to external effects, the vanadium pentoxide will not produce significant deformation. By changing the amount of modified vanadium pentoxide, the toughness of the adhesive is improved. The obtained modified phenolic resin adhesive has an elongation at break of 24.6% at 25°C and an elongation at break of 12.5% at 300°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a graph showing the test results of the free formaldehyde content of the modified phenolic resin adhesive of Example 8 of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] See also Figure 1 The present invention provides a modified phenolic resin adhesive and a preparation method thereof, and the technical solution is as follows:

[0033] The substance information involved in the present invention is as follows:

[0034] Dioleoylphosphatidylethanolamine CAS: 4004-05-1; Vanadium pentoxide CAS: 1314-62-1; Phenol CAS: 108-95-2; Formaldehyde CAS: 50-00-0; Resorcinol CAS: 108-46-3; Tannin CAS: 1401-55-4; Propylene carbonate CAS: 108-32-7; Sodium carbonate CAS: 497-19-8; Isocyanate CAS: 75- 13-8; urea CAS: 57-13-6; KH550 silane coupling agent CAS: 919-30-2; KH560 silane coupling agent CAS: 2530-83-8; KH602 silane coupling agent CAS: 3069-29-2; KH792 silane coupling agent CAS: 1760-24-3; sodium hydroxide CAS: 1310-73-2; cashew nut shell liquid was purchased from Jinan Renyuan Chemical Co., Ltd.

[0035] Example 1

[0036] The modified vanadium pentoxide is prepared by adding vanadium pentoxide to water to form a 6wt% slurry; heating the slurry to 80°C, adding a 10wt% dioleoylphosphatidylethanolamine solution, stirring at a constant temperature for 40 minutes, and then cooling to room temperature to obtain a mixed solution; centrifuging the mixed solution with deionized water and filtering to obtain a filter residue; placing the filter residue in a vacuum drying oven and drying it at 100°C for 12 hours to obtain a dry filter residue; and sieving the dry filter residue to obtain the modified vanadium pentoxide.

[0037] Preparation of modified phenolic resin adhesive: 100 parts of phenol, 0.32 parts of a portion of alkaline catalyst, 15 parts of cashew nut shell oil, and 24 parts of a portion of deionized water were added to a reaction flask by weight and mixed uniformly to obtain a mixture A; 20 parts of the first batch of formaldehyde, 0.64 parts of the first batch of alkaline catalyst, and 32 parts of the first batch of deionized water were added to the mixture A, and the mixture was heated to 90° C. and reacted for 50 minutes to obtain a mixture B; 10 parts of the second batch of formaldehyde, 0.32 parts of the second batch of alkaline catalyst, and 12 parts of the second batch of deionized water were added to the mixture B, and the mixture was reacted at 90° C. for 50 minutes to obtain a mixture The present invention relates to a process for preparing a modified phenolic resin adhesive comprising: a mixture of 10 parts of residual formaldehyde, 0.32 parts of residual alkaline catalyst and 12 parts of residual deionized water, and reacting the mixture at 90° C. for 60 minutes to obtain a mixture D; the mixture D is cooled to 70° C., 3 parts of urea, 1 part of curing agent, 1 part of silane coupling agent and 5 parts of modified vanadium pentoxide are added, the mixture is cooled to 65° C. and reacted for 45 minutes, and the material is cooled and discharged to obtain the modified phenolic resin adhesive; the alkaline catalyst is sodium hydroxide; the formaldehyde is a formaldehyde aqueous solution having a concentration of 38 wt %; the curing agent is resorcinol; and the silane coupling agent is KH550 silane coupling agent.

[0038] Examples 2-7

[0039] Refer to the preparation method and parameter conditions of Example 1, the specific differences are shown in Table 1.

[0040] Comparative Example 1

[0041] A modified phenolic resin adhesive was prepared according to the method of Example 1, except that urea was not added.

[0042] Example 8 Free Formaldehyde Content Test

[0043] The test was carried out in accordance with 3.16 of GB / T 14074-2017; the results are shown in Table 1.

[0044] Table 1 Free formaldehyde content test of Examples 1-7 and Comparative Example 1

[0045] Example Urea dosage / portion Free formaldehyde content / % Example 1 3 0.120 Example 2 5 0.074 Example 3 7 0.044 Example 4 9 0.032 Example 5 11 0.028 Example 6 13 0.028 Example 7 15 0.029 Comparative Example 1 0 0.260

[0046] From Table 1 and Figure 1 It can be seen that in Examples 1-7 and Comparative Example 1, as the amount of urea increases, the free formaldehyde content shows a downward trend. When the urea addition reaches a certain level, the rate of reduction of the free formaldehyde content slows down and even tends to be stable. In Example 5, when the urea addition is 11 parts, the free formaldehyde content is a minimum of 0.028%, and thereafter the free formaldehyde content remains essentially unchanged. This is because urea reacts with free formaldehyde to form urea-formaldehyde resin. When the free formaldehyde absorption is almost complete, the effect of the amount of urea added on the free formaldehyde is relatively small. In Comparative Example 1, urea modification is not added to the phenolic resin, and the free formaldehyde content of the obtained adhesive is 0.260%, which is much higher than the free formaldehyde content in the modified phenolic resin adhesive prepared by the present invention.

[0047] Example 9

[0048] Modified vanadium pentoxide was prepared according to the method of Example 1 above.

[0049] Preparation of modified phenolic resin adhesive: 100 parts of phenol, 0.32 parts of a portion of alkaline catalyst, 15 parts of cashew nut shell liquid, and 24 parts of a portion of deionized water were added to a reaction flask by weight and mixed uniformly to obtain a mixture A; 20 parts of the first batch of formaldehyde, 0.64 parts of the first batch of alkaline catalyst, and 32 parts of the first batch of deionized water were added to the mixture A, and the mixture was heated to 90° C. and reacted for 50 minutes to obtain a mixture B; 10 parts of the second batch of formaldehyde, 0.32 parts of the second batch of alkaline catalyst, and 12 parts of the second batch of deionized water were added to the mixture B, and the mixture was reacted at 90° C. for 50 minutes to obtain a mixture mixture C; adding 10 parts of remaining formaldehyde, 0.32 parts of remaining alkaline catalyst and 12 parts of remaining deionized water to the mixture C, and reacting at 90° C. for 60 minutes to obtain a mixture D; cooling the mixture D to 70° C., adding 11 parts of urea, 1 part of curing agent, 1 part of silane coupling agent and 5 parts of modified vanadium pentoxide, and cooling the mixture to 65° C. for 45 minutes, and cooling the material to obtain the modified phenolic resin adhesive; the alkaline catalyst is sodium hydroxide; the formaldehyde is a formaldehyde aqueous solution with a concentration of 38 wt%; the curing agent is tannin; and the silane coupling agent is KH550 silane coupling agent.

[0050] Examples 10-20

[0051] Refer to the preparation method and parameter conditions of Example 9, the specific differences are shown in Table 2.

[0052] Comparative Example 2

[0053] A modified phenolic resin adhesive was prepared according to the method of Example 9, except that no curing agent was added.

[0054] Example 21 Curing time test

[0055] A 1.5g adhesive sample was weighed and placed on a hot plate. Its curing time was measured at 120°C. The molten material was stirred in a small circular motion with a stirrer. When the molten material began to thicken, while continuing to stir, the stirrer was raised approximately 8mm from the molten material every 2 seconds and its state was observed. If the strands formed during the raising of the stirrer became brittle and fractured and could no longer be pulled from the molten material into a filament, the timer was stopped and the time recorded. The recorded time was the curing time of the sample. The results are shown in Table 2.

[0056] Table 2 Curing time test of Examples 5, 9-20 and Comparative Example 2

[0057] Example Type of curing agent Curing agent dosage / part Amount of alkaline catalyst / part Curing time / s Example 5 Resorcinol 1.0 1.6 75 Example 9 Tannins 1.0 1.6 80 Example 10 Propylene carbonate 1.0 1.6 82 Example 11 sodium carbonate 1.0 1.6 80 Example 12 Isocyanates 1.0 1.6 76 Example 13 Resorcinol 1.5 1.6 73 Example 14 Resorcinol 2.0 1.6 68 Example 15 Resorcinol 2.5 1.6 60 Example 16 Resorcinol 3.0 1.6 62 Example 17 Resorcinol 2.5 3.0 57 Example 18 Resorcinol 2.5 4.0 53 Example 19 Resorcinol 2.5 5.0 55 Example 20 Resorcinol 2.5 6.0 60 Comparative Example 2 / / 4.0 140

[0058] Adding resorcinol can make phenolic resin form more cross-linking points, promote the cross-linking reaction between resin molecules, thereby accelerate the curing process, when the addition of resorcinol reaches a certain proportion, the synthetic phenolic resin can be fast-cured at a lower temperature, as shown in Table 2, in Examples 5, 9-12, when the curing agent is selected for use by resorcinol, the curing time is the shortest. The consumption of the curing agent is also an important factor affecting the curing time of the phenolic resin adhesive. In Examples 13-15, increasing the consumption of the curing agent within a suitable range can accelerate the curing reaction and shorten the curing time. Alkaline catalysts can reduce the activation energy required for the reaction, so that the reaction can also be carried out quickly at a lower temperature. Therefore, in Examples 16-18, increasing the consumption of the catalyst can improve reaction rate, and then shorten the curing time. In Example 18, using resorcinol as a curing agent, the curing agent addition is 2.5 parts, and when the alkaline catalyst addition is 4 parts, the curing time is the shortest at 53s. In Comparative Example 2, no curing agent was added to the modified phenolic resin adhesive, so the curing speed was greatly reduced, and the curing time reached 140 seconds.

[0059] Example 22

[0060] Modified vanadium pentoxide was prepared according to the method of Example 1 above.

[0061] Preparation of modified phenolic resin adhesive: 100 parts of phenol, 0.8 parts of a portion of alkaline catalyst, 18 parts of cashew nut shell liquid, and 24 parts of a portion of deionized water were added to a reaction flask by weight and mixed uniformly to obtain mixture A; 20 parts of the first batch of formaldehyde, 1.6 parts of the first batch of alkaline catalyst, and 32 parts of the first batch of deionized water were added to the mixture A, and the mixture was heated to 90° C. and reacted for 50 minutes to obtain mixture B; 10 parts of the second batch of formaldehyde, 0.8 parts of the second batch of alkaline catalyst, and 12 parts of the second batch of deionized water were added to the mixture B, and the mixture was reacted at 90° C. for 50 minutes to obtain mixture C. ; Add 10 parts of remaining formaldehyde, 0.8 parts of remaining alkaline catalyst and 12 parts of remaining deionized water to the mixture C, and react at 90°C for 60 minutes to obtain a mixture D; cool the mixture D to 70°C, add 11 parts of urea, 2.5 parts of curing agent, 1 part of silane coupling agent and 5 parts of modified vanadium pentoxide, cool to 65°C and react for 45 minutes, cool and discharge to obtain the modified phenolic resin adhesive; the alkaline catalyst is sodium hydroxide; the formaldehyde is a formaldehyde aqueous solution with a concentration of 38wt%; the curing agent is resorcinol; and the silane coupling agent is KH550 silane coupling agent.

[0062] Examples 23-27

[0063] Referring to the preparation method and parameter conditions of Example 22, the specific differences are shown in Table 3.

[0064] Comparative Example 3

[0065] A modified phenolic resin adhesive was prepared according to the method of Example 22, except that cashew nut shell liquid was not added.

[0066] Example 28 Wear resistance test

[0067] The wear resistance of the adhesive was tested using a Taber 5900 reciprocating abrader; the results are shown in Table 3.

[0068] Table 3 Wear resistance test of Examples 18, 22-27 and Comparative Example 3

[0069] Example Cashew nut shell liquid dosage / portion Wear rate / % Example 18 15 0.32 Example 22 18 0.20 Example 23 20 0.18 Example 24 22 0.22 Example 25 25 0.25 Example 26 27 0.27 Example 27 30 0.31 Comparative Example 3 0 0.41

[0070] The addition of cashew nut shell liquid can change the chemical structure of the phenolic resin adhesive, increase its cross-linking density and hardness, thereby improving wear resistance. This change makes the phenolic resin adhesive more stable when subjected to friction and wear, reducing the amount of wear. As shown in Table 3, in Examples 18, 22-27, as the amount of cashew nut shell liquid continues to increase, the wear of the modified phenolic resin adhesive obtained first increases and then gradually decreases. This is because when the amount of cashew nut shell liquid is too little as a modifier, its modifying effect cannot be fully exerted, thereby significantly improving the wear resistance of the adhesive; when the amount of cashew nut shell liquid is too much, the softening point of the modified phenolic resin will be caused to decrease. The low softening point means that the material is easily softened at high temperatures, thereby affecting its wear resistance. In Example 23, when the amount of cashew nut shell liquid is 20 parts, the wear rate is as low as 0.18%. In Comparative Example 3, cashew nut shell liquid was not added to the modified phenolic resin adhesive. In this case, the stability of the phenolic resin adhesive was reduced when subjected to friction and wear, and the wear rate reached 0.41%.

[0071] Example 29

[0072] Modified vanadium pentoxide was prepared according to the method of Example 1 above.

[0073] Preparation of modified phenolic resin adhesive: 100 parts of phenol, 0.8 parts of a portion of alkaline catalyst, 20 parts of cashew nut shell liquid, and 24 parts of a portion of deionized water were added to a reaction flask by weight and mixed uniformly to obtain mixture A; 20 parts of the first batch of formaldehyde, 1.6 parts of the first batch of alkaline catalyst, and 32 parts of the first batch of deionized water were added to the mixture A, and the mixture was heated to 90° C. and reacted for 50 minutes to obtain mixture B; 10 parts of the second batch of formaldehyde, 0.8 parts of the second batch of alkaline catalyst, and 12 parts of the second batch of deionized water were added to the mixture B, and the mixture was reacted at 90° C. for 50 minutes to obtain mixture C. ; Add 10 parts of remaining formaldehyde, 0.8 parts of remaining alkaline catalyst and 12 parts of remaining deionized water to the mixture C, and react at 90° C. for 60 minutes to obtain a mixture D; cool the mixture D to 70° C., add 11 parts of urea, 2.5 parts of curing agent, 1 part of silane coupling agent and 5 parts of modified vanadium pentoxide, cool to 65° C. and react for 45 minutes, cool and discharge to obtain the modified phenolic resin adhesive; the alkaline catalyst is sodium hydroxide; the formaldehyde is a formaldehyde aqueous solution with a concentration of 38wt%; the curing agent is resorcinol; and the silane coupling agent is KH560 silane coupling agent.

[0074] Examples 30-39

[0075] Referring to the preparation method and parameter conditions of Example 29, the specific differences are shown in Table 4.

[0076] Comparative Example 4

[0077] A modified phenolic resin adhesive was prepared according to the method of Example 29, except that no silane coupling agent was added.

[0078] Example 40 Bonding Strength Test

[0079] According to GB / T 9846-2004, Class I plywood was prepared. The specimens were placed in boiling water for 4 hours, then dried in a 60°C air drying oven for 20 hours, immersed in boiling water for 4 hours, and finally placed in cold water for 2 hours before the bonding strength test. The bonding strength was calculated according to the following formula: Where P is the maximum failure load, A is the width of the shear section of the specimen, B is the length of the shear section of the specimen, and 0.9 is the correction factor. The results are shown in Table 4.

[0080] Table 4 Bonding strength test of Examples 23, 29-39 and Comparative Example 4

[0081]

[0082]

[0083] As shown in Table 4, the modified phenolic resin adhesives produced in Examples 23, 29-31 using KH550 silane coupling agent exhibited the best bonding strength to the substrate, with a bond strength of 1.26 MPa. Silane coupling agents in adhesives can form "molecular bridges" at the interface between inorganic and organic materials, thereby enhancing their bond strength. However, when the amount of silane coupling agent is too low, the number of these "molecular bridges" is insufficient to fully connect the two materials, resulting in lower bond strength. When the amount of silane coupling agent is excessive, hydrolyzed silanols accumulate on the surface, forming isolated zones that are unable to fully react with the adhered surface. This hinders recoupling of the silane coupling agent already bound to the surface with the adhesive, thereby reducing bond strength. In Examples 23, 32-35, as the amount of silane coupling agent increases, the bond strength of the adhesives initially increases and then decreases. In Examples 34, 36-39, as the formaldehyde dosage increases, the bonding strength of the adhesive first increases. When the formaldehyde dosage reaches 60 parts, the bonding strength is maximum. Then, as the aldehyde dosage continues to increase, the bonding strength begins to decrease. The increase in the formaldehyde to phenol ratio can promote polycondensation, thereby making the bonding performance of the adhesive better. However, when the formaldehyde ratio is too large, as the polycondensation reaction proceeds, the viscosity of the resin will increase, gelation will occur easily, and the bonding strength will decrease. In Example 37, when 4 parts of KH550 silane coupling agents are added to the adhesive and the formaldehyde dosage is 40 parts, the bonding strength of the modified phenolic resin adhesive obtained reaches a maximum of 2.13MPa. In Comparative Example 4, no silane coupling agent is added, and the modified phenolic resin adhesive obtained has a bonding strength of only 1MPa.

[0084] Example 41

[0085] Modified vanadium pentoxide was prepared according to the method of Example 1 above.

[0086] Preparation of modified phenolic resin adhesive: 100 parts of phenol, 0.8 parts of a portion of alkaline catalyst, 20 parts of cashew nut shell liquid, and 24 parts of a portion of deionized water were added to a reaction flask by weight and mixed uniformly to obtain mixture A; 30 parts of the first batch of formaldehyde, 1.6 parts of the first batch of alkaline catalyst, and 32 parts of the first batch of deionized water were added to the mixture A, and the mixture was heated to 90° C. and reacted for 50 minutes to obtain mixture B; 15 parts of the second batch of formaldehyde, 0.8 parts of the second batch of alkaline catalyst, and 12 parts of the second batch of deionized water were added to the mixture B, and the mixture was reacted at 90° C. for 50 minutes to obtain mixture C ; 15 parts of remaining formaldehyde, 0.8 parts of remaining alkaline catalyst and 12 parts of remaining deionized water were added to the mixture C, and the mixture was reacted at 90° C. for 60 minutes to obtain a mixture D; the mixture D was cooled to 70° C., 11 parts of urea, 2.5 parts of curing agent, 4 parts of silane coupling agent and 5 parts of modified vanadium pentoxide were added, and the mixture was cooled to 65° C. and reacted for 45 minutes, and the material was cooled and discharged to obtain the modified phenolic resin adhesive; the alkaline catalyst was sodium hydroxide; the formaldehyde was a formaldehyde aqueous solution with a concentration of 38wt%; the curing agent was resorcinol; and the silane coupling agent was KH550 silane coupling agent.

[0087] Examples 42-46

[0088] Referring to the preparation method and parameter conditions of Example 41, the specific differences are shown in Table 5.

[0089] Comparative Example 5

[0090] A modified phenolic resin adhesive was prepared according to the method of Example 41, except that modified vanadium pentoxide was not added.

[0091] Comparative Example 6

[0092] A modified phenolic resin adhesive was prepared according to the method of Example 41, except that dioleoylphosphatidylethanolamine was not used to modify the vanadium pentoxide.

[0093] Example 47 Toughness Test

[0094] The elongation at break was tested in accordance with GB / T 30776-2014; the results are shown in Table 5.

[0095] Table 5 Toughness test of Examples 37, 41-46 and Comparative Example 5

[0096]

[0097] As can be seen from Table 5, in Examples 37, 41-46, as the amount of modified vanadium pentoxide increases, the toughness of the adhesive shows a trend of first increasing and then decreasing. When the amount of modified vanadium pentoxide added is too small, its dispersion in the adhesive is not uniform, making it difficult to achieve a good toughening effect. When the amount of modified vanadium pentoxide added is too large, agglomeration between particles is likely to occur. The agglomerated modified vanadium pentoxide particles not only fail to effectively exert their reinforcing effect in the adhesive, but may also become stress concentration points, causing the adhesive to be more prone to fracture when subjected to stress, thereby reducing its toughness. In Example 44, when the amount of modified vanadium pentoxide added was 7 parts, the modified phenolic resin adhesive produced had the best toughness, with an elongation at break of 24.6% at 25°C and 12.5% at 300°C. In Comparative Example 5, modified vanadium pentoxide was not added to the adhesive, and the toughness was poor, with an elongation at break of only 6.1% at 25°C and an elongation at break of only 3.8% at 300°C. In Comparative Example 6, unmodified vanadium pentoxide was used to prepare a phenolic resin adhesive. Since the surface of vanadium pentoxide is highly hydrophilic, while the phenolic resin matrix is lipophilic, the compatibility between the two is poor, with an elongation at break of 7.8% at 25°C and 5.2% at 300°C, which are not much different from the results measured when no modified vanadium pentoxide was added to the adhesive.

[0098] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a modified phenolic resin adhesive, characterized in that: The preparation method of the modified phenolic resin adhesive is as follows: phenol, a portion of an alkaline catalyst, cashew nut shell oil, and a portion of deionized water are added to a reaction flask in parts by weight and mixed uniformly to obtain a mixture A; a first batch of formaldehyde, a first batch of alkaline catalyst, and a first batch of deionized water are added to the mixture A, and the mixture is heated to 90° C. and reacted for 50 minutes to obtain a mixture B; a second batch of formaldehyde, a second batch of alkaline catalyst, and a second batch of deionized water are added to the mixture B, and the mixture is reacted at 90° C. for 50 minutes to obtain a mixture C; the remaining formaldehyde, the remaining alkaline catalyst, and the remaining deionized water are added to the mixture C, and the mixture is reacted at 90° C. for 60 minutes to obtain a mixture D; the mixture D is cooled to 70° C., urea, a curing agent, a silane coupling agent, and modified vanadium pentoxide are added, the mixture is cooled to 65° C. and reacted for 45 minutes, and the mixture is cooled and discharged to obtain the modified phenolic resin adhesive; The raw materials for producing the modified phenolic resin adhesive include, in parts by weight, 100 parts of phenol, 40-70 parts of formaldehyde, 1-3 parts of a curing agent, 3-15 parts of urea, 15-30 parts of cashew nut shell liquid, 1-5 parts of a silane coupling agent, 1.6-6 parts of a basic catalyst, 5-8 parts of modified vanadium pentoxide, and 80 parts of deionized water.

2. The method for preparing a modified phenolic resin adhesive according to claim 1, wherein: The formaldehyde is a formaldehyde aqueous solution with a concentration of 38 wt%.

3. The method for preparing a modified phenolic resin adhesive according to claim 1, wherein: The amount of the partial alkaline catalyst used is 20% of the total amount of the alkaline catalyst used; the amount of the partial deionized water used is 30% of the total amount of the deionized water used.

4. The method for preparing a modified phenolic resin adhesive according to claim 1, wherein: The first batch of formaldehyde, the first batch of alkaline catalyst and the first batch of deionized water are 50%, 40% and 40% of the total amount of formaldehyde, alkaline catalyst and deionized water used respectively.

5. The method for preparing a modified phenolic resin adhesive according to claim 1, wherein: The second batch of formaldehyde, the second batch of alkaline catalyst and the second batch of deionized water are respectively 25%, 20% and 15% of the total amount of formaldehyde, the alkaline catalyst and the deionized water used.

6. The method for preparing a modified phenolic resin adhesive according to claim 1, wherein: The curing agent is one of resorcinol, tannin, propylene carbonate, sodium carbonate and isocyanate.

7. The method for preparing a modified phenolic resin adhesive according to claim 1, wherein: The silane coupling agent is one of KH550 silane coupling agent, KH560 silane coupling agent, KH602 silane coupling agent and KH792 silane coupling agent.

8. The method for preparing a modified phenolic resin adhesive according to claim 1, wherein: The alkaline catalyst is sodium hydroxide.

9. The method for preparing a modified phenolic resin adhesive according to claim 1, wherein: The preparation method of the modified vanadium pentoxide is as follows: adding vanadium pentoxide to water to prepare a 6wt% slurry; heating the slurry to 80°C, adding a 10wt% dioleoylphosphatidylethanolamine solution, stirring at a constant temperature for 40 minutes, and then cooling to room temperature to obtain a mixed solution; centrifuging the mixed solution with deionized water and filtering to obtain a filter residue; placing the filter residue in a vacuum drying oven and drying it at 100°C for 12 hours to obtain a dry filter residue; and sieving the dry filter residue to obtain the modified vanadium pentoxide.

10. A modified phenolic resin adhesive, characterized in that: The raw materials for producing the modified phenolic resin include phenol, formaldehyde, a curing agent, urea, cashew nut shell oil, a silane coupling agent, an alkaline catalyst, modified vanadium pentoxide and deionized water; the modified phenolic resin adhesive is prepared by the preparation method described in any one of claims 1 to 9; the free formaldehyde content of the modified phenolic resin adhesive is 0.028%; the curing time of the modified phenolic resin adhesive is 53s; the wear rate of the modified phenolic resin adhesive is 0.18%; the bonding strength of the modified phenolic resin adhesive is 2.13MPa; the elongation at break of the modified phenolic resin adhesive at 25°C is 24.6%, and the elongation at break at 300°C is 12.5%.

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