Urushiol modified resorcinol-formaldehyde resin and preparation method thereof

Abstract

According to the urushiol-modified resorcinol-formaldehyde resin and the preparation method thereof, through chemical grafting of urushiol and a resorcinol-formaldehyde prepolymer, flexible chain segments and natural active sites of urushiol are combined, the high bonding strength of the resorcinol-formaldehyde resin is achieved, and the resin has the advantages of being high in mechanical strength, high in mechanical strength and good in mechanical property. The modified resin with excellent heat resistance, hydrophobicity, bonding strength and environmental friendliness is prepared, the modified resin is used for replacing resorcinol-formaldehyde resin to be applied to tire tread rubber, heat resistance, wear resistance, hydrophobicity and wet skid resistance can be remarkably improved, and the modified resin is suitable for manufacturing of high-performance tires.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, and in particular to a urushiol-modified resorcinol-formaldehyde resin and its preparation method. Background Technology

[0002] Resorcinol-formaldehyde resin (RF resin) is an important type of thermosetting phenolic resin, which is formed by the condensation polymerization of resorcinol and formaldehyde under acidic or alkaline conditions. Its molecular structure contains a highly active ortho- and para-hydroxymethyl and benzene ring conjugated system, which has the characteristics of fast curing speed, high bonding strength and good heat resistance. It is widely used in tire industry, adhesives, coatings, electronic packaging and friction materials. However, traditional RF resin has the following limitations: (1) the molecular chain is too rigid and brittle; (2) the UV aging resistance is insufficient, and it is easy to yellow and degrade when exposed to light for a long time; (3) some application scenarios (such as outdoor coatings) need to take into account both bio-based source and environmental protection.

[0003] Urushiol is the main active ingredient extracted from natural lacquer (content is about 40%-80%). Its molecular structure is characterized by: using catechol as the backbone, with long-chain aliphatic hydrocarbons (usually containing C15-C17 alkenyl groups) linked at the 3 position, exhibiting high reactivity (phenolic hydroxyl groups can condense and oxidatively polymerize) and unique self-crosslinking film-forming properties. Urushiol has unique performance advantages: (1) the long side chains give the molecule good flexibility and hydrophobicity; (2) the conjugated diene structure can form a crosslinking network through oxidative polymerization, improving heat resistance; (3) the ortho- and ortho-position hydroxyl groups on the benzene ring can react with multifunctional groups such as formaldehyde to achieve chemical grafting; (4) as a natural product, it conforms to the development direction of green chemistry.

[0004] Chemical grafting modification of urushiol and resorcinol-formaldehyde resin can combine the advantages of both: urushiol's long side chains improve the brittleness of RF resin, its conjugated structure enhances heat resistance, and chemical bonding improves interfacial compatibility. This approach retains the high crosslinking strength and reinforcing effect of RF resin while introducing flexible segments and active sites from urushiol, ultimately resulting in a high-performance modified resin. Currently, research on urushiol-modified phenolic resins mainly focuses on the direct polycondensation of urushiol with formaldehyde (such as urushiol-formaldehyde resin) or simple physical blending of RF resin and urushiol. However, systematic methods for chemical grafting modification have not yet been reported, especially selective modification techniques for resorcinol-formaldehyde resin, which remain a gap in research. Summary of the Invention

[0005] The purpose of this invention is to provide a urushiol-modified resorcinol-formaldehyde resin and its preparation method. By chemically grafting natural urushiol onto a resorcinol-formaldehyde prepolymer, a modified resin with excellent heat resistance, hydrophobicity, bonding strength, and environmental friendliness is obtained, which is suitable for tire adhesives, high-performance coatings, electronic packaging materials, and other fields. By controlling the synthesis of the resorcinol-formaldehyde prepolymer and the chemical grafting reaction of urushiol in a stepwise manner, a modified resin with controllable structure and excellent performance is obtained, solving the problems of high brittleness and insufficient heat resistance of traditional RF resins, while enhancing the application value of bio-based materials.

[0006] One objective of this invention is to provide a urushiol-modified resorcinol-formaldehyde resin, wherein the urushiol-modified resorcinol-formaldehyde resin is end-capped with urushiol, and its structure is shown in the following formula (1): Equation (1) Wherein, R is one of C15~C17 mono-alkyl, C15~C17 diene alkyl, and C15~C17 tri-alkyl, and m is an integer from 1 to 50.

[0007] The second objective of this invention is to provide a method for preparing urushiol-modified resorcinol-formaldehyde resin, comprising the following steps: Step 1: Preparation of resorcinol-formaldehyde prepolymer. Resorcinol was added to a 250ml four-necked flask, heated to 110-150℃, stirred until melted, and then an acidic catalyst was added. The mixture was stirred for 10-20 minutes at a speed of 100-200 rpm. Subsequently, 37% formaldehyde solution was added dropwise. After the addition was complete, the mixture was refluxed and kept at the temperature for 30-60 minutes to obtain a reddish-brown resorcinol-formaldehyde prepolymer. Step 2: End-capping and grafting reaction of urushiol with resorcinol-formaldehyde prepolymer. The resorcinol-formaldehyde prepolymer obtained in step 1 is slowly added dropwise to urushiol at 90-130℃ with stirring. After the addition is completed, the pH value of the system is monitored. The pH of the system is controlled to 4-7 by pH adjuster and the reaction is kept at the temperature for 1-4 hours. Step 3: Condensation and dehydration to form resin, heating and vacuum distillation at a vacuum degree of -0.01 to -0.1 MPa for 10 to 20 minutes to remove water from the resin, thus obtaining reddish-brown to dark brown urushiol-modified resorcinol-formaldehyde resin.

[0008] Preferably, in the above method for preparing urushiol-modified resorcinol-formaldehyde resin, in step 1, the molar ratio of resorcinol to formaldehyde is 1:0.4~0.9, preferably 1:0.5~0.8.

[0009] Preferably, in the above-mentioned method for preparing urushiol-modified resorcinol-formaldehyde resin, in step 1, the acidic catalyst includes at least one of inorganic acid and organic acid, wherein the inorganic acid includes sulfuric acid, phosphoric acid, and hydrochloric acid, and the organic acid includes benzenesulfonic acid, dodecyl sulfonic acid, p-toluenesulfonic acid, oxalic acid, and glacial acetic acid, and the amount of the acidic catalyst is 0.1-2% of the mass of the resorcinol, preferably 0.5-1.5%.

[0010] Preferably, in the above method for preparing urushiol-modified resorcinol-formaldehyde resin, in step 2, the amount of urushiol used is 5%-20% of the amount of resorcinol used, preferably 8%-14%.

[0011] Preferably, in the above method for preparing urushiol-modified resorcinol-formaldehyde resin, the reaction temperature in step 2 is preferably 100-120℃.

[0012] Preferably, in the above method for preparing urushiol-modified resorcinol-formaldehyde resin, in step 2, the reaction pH value is 4-7, preferably 5-6.

[0013] Preferably, in the above-mentioned method for preparing urushiol-modified resorcinol-formaldehyde resin, in step 2, the pH adjuster is an organic base or hydroxide, including at least one of triethylamine, diethylamine, potassium hydroxide, sodium hydroxide, and calcium hydroxide, and the molar ratio of the amount of pH adjuster to the amount of catalyst is 0.8 to 1.3, preferably 1 to 1.2.

[0014] Preferably, in the above method for preparing urushiol-modified resorcinol-formaldehyde resin, the heat preservation reaction time in step 2 is preferably 1.5-2 hours.

[0015] The method for preparing urushiol-modified resorcinol-formaldehyde resin proposed in this invention uses natural urushiol as a modifier, reducing reliance on petrochemical raw materials and eliminating the use of toxic solvents in the preparation process, which aligns with the concept of green chemistry. By using directional chemical grafting technology, the resin structure is optimized, and the modified resin combines the high heat resistance of resorcinol-formaldehyde resin with the flexibility of urushiol. At the same time, the side chain structure of urushiol enhances the resin's moisture resistance and hydrophobicity, making it suitable for applications such as tire adhesives, high-performance coatings, and electronic packaging materials. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be described in detail below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1

[0018] In a 250mL four-necked round-bottom flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, add 110.0 g of resorcinol and 0.55 g of p-toluenesulfonic acid sequentially. Heat to 110-120℃ and stir until melted, maintaining stirring for 10-20 minutes. Add 47.5 g of 37% formaldehyde aqueous solution (2 drops / second). After addition, maintain the temperature at 100-110℃ for 45 minutes. While maintaining the temperature at 100-110℃, add 9.90 g of urushiol. Continue to maintain the temperature at 100-110℃ for 2 hours. At the end of the reaction, slowly add 0.40 g of sodium hydroxide solution to adjust the pH to 5.5. Heating and vacuum distillation are performed at a vacuum level of -0.01 to -0.1 MPa for 10 to 20 minutes. This removes moisture from the resin, thus obtaining the urushiol-modified resorcinol-formaldehyde resin of formula (1).

[0019] The resin has a sp. temperature of 111.6℃. Throughout the reaction, the molar ratio of resorcinol to formaldehyde is 1:0.59; the amount of p-toluenesulfonic acid used is 0.5% of the mass of resorcinol, and the amount of urushiol used is 9% of the mass of resorcinol.

[0020] Example 2

[0021] In a 250mL four-necked round-bottom flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, add 110.0 g of resorcinol and 0.55 g of p-toluenesulfonic acid sequentially. Heat to 110-120℃ and stir until melted, maintaining stirring for 10-20 minutes. Add 47.5 g of 37% formaldehyde aqueous solution (2 drops / second). After addition, maintain the temperature at 100-110℃ for 45 minutes. While maintaining the temperature at 100-110℃, add 12.1 g of urushiol. Continue to maintain the temperature at 100-110℃ for 2 hours. At the end of the reaction, slowly add 0.40 g of sodium hydroxide solution to adjust the pH to 5.5. Heating and vacuum distillation are performed at a vacuum level of -0.01 to -0.1 MPa for 10 to 20 minutes. This removes moisture from the resin, thus obtaining the urushiol-modified resorcinol-formaldehyde resin of formula (1).

[0022] The SP of this resin is 110.3℃. Throughout the reaction, the molar ratio of resorcinol to formaldehyde is 1:0.59; the amount of p-toluenesulfonic acid used is 0.5% of the mass of resorcinol, and the amount of urushiol used is 11% of the mass of resorcinol.

[0023] Example 3

[0024] In a 250mL four-necked round-bottom flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, add 110.0 g of resorcinol and 0.55 g of p-toluenesulfonic acid sequentially. Heat to 110-120℃ and stir until melted, maintaining stirring for 10-20 minutes. Add 56.7 g of 37% formaldehyde aqueous solution (2 drops / second). After addition, maintain the reaction temperature at 100-110℃ for 45 minutes. While maintaining the temperature at 100-110℃, add 9.90 g of urushiol. Continue to maintain the reaction temperature at 110-120℃ for 2 hours. At the end of the reaction, slowly add 0.48 g of sodium hydroxide solution to adjust the pH to 5.8. Heating and vacuum distillation are performed at a vacuum level of -0.01 to -0.1 MPa for 10 to 20 minutes. This removes moisture from the resin, thus obtaining the urushiol-modified resorcinol-formaldehyde resin of formula (1).

[0025] The SP of this resin is 115.3℃. Throughout the reaction, the molar ratio of resorcinol to formaldehyde is 1:0.7; the amount of p-toluenesulfonic acid used is 0.5% of the mass of resorcinol, and the amount of urushiol used is 9% of the mass of resorcinol.

[0026] Example 4

[0027] In a 250mL four-necked round-bottom flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, add 110.0 g of resorcinol and 0.55 g of p-toluenesulfonic acid sequentially. Heat to 110-120℃ and stir until melted, maintaining stirring for 10-20 minutes. Add 56.7 g of 37% formaldehyde aqueous solution (2 drops / second). After addition, maintain the reaction temperature at 100-110℃ for 45 minutes. While maintaining the temperature at 100-110℃, add 12.1 g of urushiol. Continue to maintain the reaction temperature at 110-120℃ for 2 hours. At the end of the reaction, slowly add 0.48 g of sodium hydroxide solution to adjust the pH to 6.0. Heating and vacuum distillation are performed at a vacuum level of -0.01 to -0.1 MPa for 10 to 20 minutes. This removes moisture from the resin, thus obtaining the urushiol-modified resorcinol-formaldehyde resin of formula (1).

[0028] The resin has a sp. temperature of 114.8℃. Throughout the reaction, the molar ratio of resorcinol to formaldehyde is 1:0.7; the amount of p-toluenesulfonic acid used is 0.5% of the mass of resorcinol, and the amount of urushiol used is 11% of the mass of resorcinol.

[0029] Example 5

[0030] In a 250mL four-necked round-bottom flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, add 110.0 g of resorcinol and 0.55 g of p-toluenesulfonic acid sequentially. Heat to 110-120℃ and stir until melted, maintaining stirring for 10-20 minutes. Add 56.7 g of 37% formaldehyde aqueous solution (2 drops / second). After addition, maintain the temperature at 100-110℃ for 45 minutes. While maintaining the temperature at 100-110℃, add 9.90 g of urushiol and continue the reaction at 110-120℃ for 1.5 hours. At the end of the reaction, slowly add 0.4 g of potassium hydroxide solution to adjust the pH to 5.4. Heating and vacuum distillation are performed at a vacuum level of -0.01 to -0.1 MPa for 10 to 20 minutes. This removes moisture from the resin, thus obtaining the urushiol-modified resorcinol-formaldehyde resin of formula (1).

[0031] The SP of this resin is 115.5℃. Throughout the reaction, the molar ratio of resorcinol to formaldehyde is 1:0.7; the amount of p-toluenesulfonic acid used is 0.5% of the mass of resorcinol, and the amount of urushiol used is 9% of the mass of resorcinol.

[0032] Example 6

[0033] In a 250mL four-necked round-bottom flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, add 110.0 g of resorcinol and 0.55 g of p-toluenesulfonic acid sequentially. Heat to 110-120℃ and stir until melted, maintaining stirring for 10-20 minutes. Add 56.7 g of 37% formaldehyde aqueous solution (2 drops / second). After addition, maintain the reaction temperature at 100-110℃ for 45 minutes. While maintaining the temperature at 100-110℃, add 12.1 g of urushiol and continue the reaction at 110-120℃ for 1.5 hours. At the end of the reaction, slowly add 0.4 g of potassium hydroxide solution to adjust the pH to 5.6. Heating and vacuum distillation are performed at a vacuum level of -0.01 to -0.1 MPa for 10 to 20 minutes. This removes moisture from the resin, thus obtaining the urushiol-modified resorcinol-formaldehyde resin of formula (1).

[0034] The SP of this resin is 114.1℃. Throughout the reaction, the molar ratio of resorcinol to formaldehyde is 1:0.7; the amount of p-toluenesulfonic acid used is 0.5% of the mass of resorcinol, and the amount of urushiol used is 11% of the mass of resorcinol.

[0035] The urushiol-modified resorcinol-formaldehyde resin prepared in the examples was compared with commercially available resorcinol-formaldehyde resin products in rubber application tests.

[0036] The rubber application test formulations are shown in the table below:

[0037] Example 4: Application in rubber products: The first step is to mix the rubber components at about 150°C using a Banbury internal mixer to obtain the masterbatch.

[0038] The second step involves mixing B-20-S, the urushiol-modified resorcinol-formaldehyde resin sample prepared in Example 4, and cobalt salt into the masterbatch obtained by mixing in a Banbury internal mixer at a temperature of approximately 145°C.

[0039] The third step involves adding the insoluble sulfur, accelerator TBBS, and HMMM listed in the table above to the mixture at 90-100°C. The resulting product is then left overnight in an environment with a constant temperature of approximately 23°C and a relative humidity of 50%. Finally, its sulfurization, shape, and optimal degree of sulfurization are determined at 160°C using a sulfur reversion apparatus.

[0040] The test data for the rubber composition are shown in the table below. Tensile properties were tested according to GB / T528-2009. The vulcanization conditions for the steel cord bonding performance were 155℃ x 40 min, and the steel cord specifications were 3+9+15*0.22+1, tested according to standard ASTM DI871-2004.

[0041] Rubber compound performance table:

[0042] Compared with B-20-S, urushiol-modified resorcinol-formaldehyde resin exhibits good mechanical properties, while its steel wire bonding performance is also significantly improved.

[0043] This embodiment is merely an illustrative description of the present patent and does not limit its scope of protection. Those skilled in the art may make partial modifications to it. As long as they do not exceed the spirit and essence of the present patent, they shall be regarded as equivalent substitutions to the present patent and shall be within the scope of protection of the present patent.

Claims

1. A urushiol-modified resorcinol-formaldehyde resin, characterized in that, The urushiol-modified resorcinol-formaldehyde resin is end-capped with urushiol, and its structure is shown in formula (1) below: Equation (1) Wherein, R is one of C15~C17 mono-alkyl, C15~C17 diene alkyl, and C15~C17 tri-alkyl, and m is an integer from 1 to 50.

2. The method for preparing urushiol-modified resorcinol-formaldehyde resin according to claim 1, characterized in that, The steps are as follows: Step 1: Preparation of resorcinol-formaldehyde prepolymer. Resorcinol was added to a 250ml four-necked flask, heated to 110-150℃, stirred until melted, and then an acidic catalyst was added. The mixture was stirred for 10-20 minutes at a speed of 100-200 rpm. Subsequently, 37% formaldehyde solution was added dropwise. After the addition was complete, the mixture was refluxed and kept at the temperature for 30-60 minutes to obtain a reddish-brown resorcinol-formaldehyde prepolymer. Step 2: End-capping and grafting reaction of urushiol with resorcinol-formaldehyde prepolymer. The resorcinol-formaldehyde prepolymer obtained in step 1 is slowly added dropwise to urushiol at 90-130℃ with stirring. After the addition is completed, the pH value of the system is monitored. The pH of the system is controlled to 4-7 by pH adjuster and the reaction is kept at the temperature for 1-4 hours. Step 3: Condensation and dehydration to form resin, heating and vacuum distillation at a vacuum degree of -0.01 to -0.1 MPa for 10 to 20 minutes to remove water from the resin, thus obtaining reddish-brown to dark brown urushiol-modified resorcinol-formaldehyde resin.

3. The method for preparing urushiol-modified resorcinol-formaldehyde resin according to claim 2, characterized in that, In step 1, the molar ratio of resorcinol to formaldehyde is 1:0.4~0.9, preferably 1:0.5~0.

8.

4. The method for preparing urushiol-modified resorcinol-formaldehyde resin according to claim 2, characterized in that, In step 1, the acidic catalyst includes at least one of inorganic acid and organic acid. The inorganic acid includes sulfuric acid, phosphoric acid, and hydrochloric acid. The organic acid includes benzenesulfonic acid, dodecyl sulfonic acid, p-toluenesulfonic acid, oxalic acid, and glacial acetic acid. The amount of the acidic catalyst is 0.1-2% of the mass of the resorcinol, preferably 0.5-1.5%.

5. The method for preparing urushiol-modified resorcinol-formaldehyde resin according to claim 2, characterized in that, In step 2, the amount of urushiol used is 5%-20% of the amount of resorcinol used, preferably 8%-14%.

6. The method for preparing urushiol-modified resorcinol-formaldehyde resin according to claim 2, characterized in that, In step 2, the reaction temperature is preferably 100-120℃.

7. The method for preparing urushiol-modified resorcinol-formaldehyde resin according to claim 2, characterized in that, In step 2, the reaction pH is 4-7, preferably 5-6.

8. The method for preparing urushiol-modified resorcinol-formaldehyde resin according to claim 2, characterized in that, In step 2, the pH adjuster is an organic base or hydroxide, including at least one of triethylamine, diethylamine, potassium hydroxide, sodium hydroxide, and calcium hydroxide. The molar ratio of the pH adjuster to the catalyst is 0.8 to 1.3, preferably 1 to 1.

2.

9. The method for preparing urushiol-modified resorcinol-formaldehyde resin according to claim 2, characterized in that, In step 2, the heat preservation reaction time should preferably be 1.5-2 hours.

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