A reinforcing resin, its preparation and use

Abstract

The application belongs to the technical field of phenolic resin, and particularly relates to a reinforcing resin and a preparation method and application thereof. The reinforcing resin comprises phenol, a phenolic compound A, methyl p-hydroxycinnamate, an acidic catalyst and an aldehyde compound; the molar ratio of the phenol, the phenolic compound A, the methyl p-hydroxycinnamate and the aldehyde compound is 1:(0.03-0.1):(0.02-0.05):(0.5-0.8); the amount of the acidic catalyst is 0.3-1 mol% of the total molar amount of the phenol, the phenolic compound A and the methyl p-hydroxycinnamate. The reinforcing resin of the application can significantly improve the tear resistance, hardness and aging resistance of rubber when applied to rubber products, and is suitable for rubber products such as tires and conveyor belts.

Description

Technical Field

[0001] This invention belongs to the field of phenolic resin technology, specifically relating to a reinforcing resin, its preparation method, and its application. Background Technology

[0002] Phenolic resins are a class of polymeric materials prepared through the condensation reaction between phenols and aldehydes. Their structure is primarily composed of benzene rings, connected by methylene bridges. In the rubber industry, phenolic resins can be used to reinforce and harden rubber, significantly increasing the hardness of vulcanized rubber and improving its overall performance. Commonly used reinforcing resins in the rubber industry include pure phenolic resins and phenolic resins modified with tall oil or cashew nutshell oil. These phenolic reinforcing agents effectively reduce the mixing difficulty and improve the plasticity of rubber compounds during the pre-vulcanization mixing stage. During vulcanization, they form an interpenetrating network structure with the rubber crosslinking network, utilizing the rigidity of the phenolic network and the interpenetrating superposition of the two networks to achieve reinforcement.

[0003] However, pure phenolic resins suffer from high brittleness and poor compatibility with rubber. While tall oil or cashew nutshell oil-modified phenolic resins reduce the polarity of the phenolic resin and improve its compatibility with rubber, their processing produces a strong odor, failing to meet environmental protection requirements. Furthermore, tire rubber has a complex composition, containing a large amount of fillers, sulfur, and other additives; the interactions between different additives can also affect the final properties of the rubber. Therefore, a reinforcing resin is needed to address these issues. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the present invention aims to provide a reinforcing resin, its preparation method, and its applications. Applying the reinforcing resin of the present invention to rubber products can significantly improve the tear resistance, hardness, and aging resistance of rubber, making it suitable for rubber products such as tires and conveyor belts.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A reinforcing resin comprises: phenol, phenolic compound A, methyl p-hydroxycinnamate, an acidic catalyst, and an aldehyde compound; the molar ratio of phenol, phenolic compound A, methyl p-hydroxycinnamate, and the aldehyde compound is 1:(0.03-0.1):(0.02-0.05):(0.5-0.8); the amount of the acidic catalyst is 0.3-1 mol% of the total molar amount of phenol, phenolic compound A, and methyl p-hydroxycinnamate; the structural formula of phenolic compound A is as follows: .

[0007] According to the above-mentioned reinforcing resin, preferably, the preparation process of the phenolic compound A is as follows:

[0008] (1) Under the action of an organic base, 3-(2-aminoethylamino)propylamine and cycloheptyl isothiocyanate were reacted in N,N-dimethylformamide to obtain intermediate 1; the structural formula of intermediate 1 is as follows:

[0009] (2) 4-(bromomethyl)phenol and intermediate 1 are reacted in acetonitrile under the action of an inorganic base to obtain the phenolic compound A.

[0010] The preparation process of phenolic compound A in this invention is as follows: First, a cycloheptyl group is introduced by reacting the amino group of 3-(2-aminoethylamino)propylamine with cycloheptyl isothiocyanate to obtain intermediate 1. Then, phenolic compound A is obtained by a substitution reaction between intermediate 1 and 4-(bromomethyl)phenol.

[0011] According to the above-mentioned reinforcing resin, preferably, the organic base in step (1) is triethylamine, which has moderate catalytic activity and is easy to process afterward; the molar ratio of 3-(2-aminoethylamino)propylamine, cycloheptyl isothiocyanate and organic base is 1:(2.2-2.4):(2.2-2.4); this ratio can ensure the smooth progress of the dithiourea reaction, while avoiding waste caused by excessive raw materials and difficulties in subsequent purification.

[0012] According to the above-mentioned reinforcing resin, preferably, the reaction temperature in step (1) is 80-85℃ and the time is 12-16h. Under these conditions, the reaction rate is moderate and there are few side reactions.

[0013] According to the above-mentioned reinforcing resin, preferably, the inorganic base in step (2) is potassium carbonate, which is mildly alkaline and can effectively neutralize the hydrogen bromide generated in the reaction, while avoiding the oxidation of phenolic hydroxyl groups under strong alkaline conditions; the molar ratio of the intermediate 1,4-(bromomethyl)phenol and the inorganic base is 1:(1.1-1.2):(1.1-1.2).

[0014] According to the above-mentioned reinforcing resin, preferably, the reaction time in step (2) is 10-12 h.

[0015] According to the above-mentioned reinforcing resin, preferably, the acidic catalyst is p-toluenesulfonic acid, which has high catalytic efficiency and is easily volatilized and removed during the high-temperature dehydration stage, and will not remain in the resin to affect the rubber properties; the aldehyde compound is at least one of formaldehyde, acetaldehyde, and furfural. More preferably, the aldehyde compound is formaldehyde, which has high reactivity, and the resulting resin has the best reinforcing effect.

[0016] A second aspect of the present invention provides a method for preparing the above-mentioned reinforcing resin, comprising the following steps:

[0017] Phenol, phenolic compound A, and methyl p-hydroxycinnamate were mixed and completely melted. The mixture was then cooled to 100-110°C, and aldehydes and an acidic catalyst were added. The mixture was reacted for 2-4 hours. Subsequently, the free phenol was removed by dehydration and vacuum to obtain the reinforcing resin.

[0018] A third aspect of this invention provides the application of the above-mentioned reinforcing resin in rubber products. Applying this reinforcing resin to rubber products can significantly improve the tear resistance, hardness, and aging resistance of the products, thereby extending their service life.

[0019] The present invention has the following advantages over the prior art:

[0020] 1. This invention provides a reinforcing resin, which is prepared by polycondensation reaction of phenol, phenolic compound A, methyl p-hydroxycinnamate and aldehyde compounds. This reinforcing resin can significantly improve the tear resistance, hardness and aging resistance of rubber, and can be applied to rubber products such as tires and conveyor belts.

[0021] 2. This invention designs and synthesizes a phenolic compound A containing a bicyclic heptyl dithiourea structure as a modifying monomer. The two cyclic heptyl groups introduced into this molecular structure have significant steric hindrance and flexible segment characteristics, which can reduce the rigidity of phenolic resin and improve its flexibility on the one hand; on the other hand, it can reduce the polarity of the resin and improve its compatibility with the rubber matrix. In addition, the thiourea group in phenolic compound A can promote the activation of the vulcanization system during vulcanization, improve vulcanization efficiency, and optimize the crosslinking network structure, thereby improving the mechanical properties of the rubber.

[0022] 3. This invention also introduces methyl p-hydroxycinnamate as a functional modifying monomer. The side chain of this molecule contains carbon-carbon double bonds, which can inhibit vulcanization reversion and thus improve the aging resistance of rubber. At the same time, the ester group in its molecule is a polar group, which can enhance the interaction between the resin and fillers (such as silica, carbon black, etc.) and other polar additives, promote the uniform dispersion of fillers and additives in the rubber compound, reduce agglomeration, and thus improve the comprehensive mechanical properties of rubber. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0024] Preparation Example 1

[0025] The specific steps for preparing phenolic compound A are as follows:

[0026] (1) 3-(2-aminoethylamino)propylamine (CAS: 13531-52-7, 10 mmol) was dissolved in 40 mL of N,N-dimethylformamide, and cycloheptayl isothiocyanate (23 mmol) and triethylamine (23 mmol) were added. After reacting at 80 °C for 14 h, the mixture was cooled to room temperature, and dilute hydrochloric acid (0.5 mol / L) and water were added to precipitate the product. The product was filtered, and the obtained solid product was purified by column chromatography (eluent was dichloromethane / methanol, volume ratio 15:1~10:1) to obtain intermediate 1 (yield 62.4%). 1 H NMR (C 21 H 41 S2N5, 400MHz, DMSO-d6) δ: 9.53 (s, 2H), 7.64 (s, 2H), 3.80 (t, 2H), 3.71 (t, 2H), 2.6 8 (t, 2H), 2.55 (t, 2H), 2.45-2.41 (m, 2H), 1.74-1.70 (m, 2H), 1.59-1.30 (m, 25H); MS (ESI) m / z=427.28[M].

[0027] (2) 4-(bromomethyl)phenol (CAS: 81542-16-7, 11.5 mmol) and potassium carbonate (11.5 mmol) were added to 45 mL of acetonitrile and stirred thoroughly. Intermediate 1 (10 mmol) was added in 3 batches. After stirring at room temperature for 11 h, the mixture was filtered and the acetonitrile was removed by rotary evaporation. The residue was purified by column chromatography (eluent was dichloromethane / methanol, volume ratio 10:1~8:1) to obtain phenolic compound A (yield 81.6%). 1 HNMR: (C 28 H 47 OS2N5, 400MHz, DMSO-d6) δ: 9.56 (s, 1H), 9.49 (s, 2H), 7.61 (s, 2H), 7.08 (d, 2H), 6.78 (d, 2H) , 3.78 (t, 2H), 3.69-3.64 (m, 4H), 2.53-2.38 (m, 6H), 1.73-1.69 (m, 2H), 1.60-1.32 (m, 24H). MS (ESI) m / z=533.32 [M].

[0028] Preparation Example 2

[0029] The specific steps for preparing phenolic compound A are as follows:

[0030] (1) 3-(2-aminoethylamino)propylamine (CAS: 13531-52-7, 10 mmol) was dissolved in 30 mL of N,N-dimethylformamide, and cycloheptayl isothiocyanate (22 mmol) and triethylamine (22 mmol) were added. After reacting at 85 °C for 12 h, the mixture was cooled to room temperature, and dilute hydrochloric acid (0.5 mol / L) and water were added to precipitate the product. The product was filtered, and the resulting solid product was purified by column chromatography (eluent was dichloromethane / methanol, volume ratio 15:1~10:1) to obtain intermediate 1 (yield 61.0%).

[0031] (2) 4-(bromomethyl)phenol (CAS: 81542-16-7, 11 mmol) and potassium carbonate (11 mmol) were added to 40 mL of acetonitrile and stirred thoroughly. Intermediate 1 (10 mmol) was added in 3 batches. After stirring at room temperature for 10 h, the mixture was filtered and the acetonitrile was removed by rotary evaporation. The residue was purified by column chromatography (eluent was dichloromethane / methanol, volume ratio 10:1~8:1) to obtain phenolic compound A (yield 80.8%).

[0032] Preparation Example 3

[0033] The specific steps for preparing phenolic compound A are as follows:

[0034] (1) 3-(2-aminoethylamino)propylamine (CAS: 13531-52-7, 10 mmol) was dissolved in 50 mL of N,N-dimethylformamide, and cycloheptayl isothiocyanate (24 mmol) and triethylamine (24 mmol) were added. After reacting at 80 °C for 16 h, the mixture was cooled to room temperature, and dilute hydrochloric acid (0.5 mol / L) and water were added to precipitate the product. The product was filtered, and the obtained solid product was purified by column chromatography (eluent was dichloromethane / methanol, volume ratio 15:1~10:1) to obtain intermediate 1 (yield 60.8%).

[0035] (2) 4-(bromomethyl)phenol (CAS: 81542-16-7, 12 mmol) and potassium carbonate (12 mmol) were added to 50 mL of acetonitrile and stirred thoroughly. Intermediate 1 (10 mmol) was added in 3 batches. After stirring at room temperature for 12 h, the mixture was filtered and the acetonitrile was removed by rotary evaporation. The residue was purified by column chromatography (eluent was dichloromethane / methanol, volume ratio 10:1~8:1) to obtain phenolic compound A (yield 79.5%).

[0036] Example 1

[0037] A reinforcing resin comprises: phenol, phenolic compound A (Preparation Example 1), methyl p-hydroxycinnamate, p-toluenesulfonic acid, and formaldehyde; wherein the molar ratio of phenol, phenolic compound A, methyl p-hydroxycinnamate, and formaldehyde is 1:0.06:0.03:0.65, and the amount of p-toluenesulfonic acid is 0.6 mol of the total molar amount of phenol, phenolic compound A, and methyl p-hydroxycinnamate.

[0038] This embodiment also provides a method for preparing the above-mentioned reinforcing resin, including:

[0039] Phenol, phenolic compound A, and methyl p-hydroxycinnamate were mixed and heated to a complete melt. The mixture was then cooled to 105°C, and a 37% (w / w) aqueous solution of formaldehyde and p-toluenesulfonic acid were added. After reacting for 3 hours, the mixture was heated to 160°C to dehydrate. The mixture was then evacuated to a relative vacuum of -0.098 MPa to remove free phenol, thus obtaining the reinforcing resin.

[0040] The specifications of this reinforcing resin are as follows: the free phenol content is 0.62% as determined by the gas phase method according to GB / T 30773-2014, and the softening point is 100℃ as determined by the ring and ball method according to GB / T 4507-2014.

[0041] Example 2

[0042] A reinforcing resin comprises: phenol, phenolic compound A (Preparation Example 1), methyl p-hydroxycinnamate, p-toluenesulfonic acid, and formaldehyde; wherein the molar ratio of phenol, phenolic compound A, methyl p-hydroxycinnamate, and formaldehyde is 1:0.03:0.02:0.5, and the amount of p-toluenesulfonic acid is 0.3 mol of the total molar amount of phenol, phenolic compound A, and methyl p-hydroxycinnamate.

[0043] This embodiment also provides a method for preparing the above-mentioned reinforcing resin, including:

[0044] According to the above dosage ratio, phenol, phenolic compound A and methyl p-hydroxycinnamate were mixed, heated to full melting, cooled to 100°C, and a 37% (w / w) formaldehyde aqueous solution and p-toluenesulfonic acid were added. After reacting for 4 h, the temperature was raised to 160°C to dehydrate, and the vacuum was drawn to a relative vacuum of -0.098 MPa to remove free phenol, thus obtaining the reinforcing resin.

[0045] The specifications of this reinforcing resin are as follows: the free phenol content is 0.55% as determined by the gas phase method according to GB / T 30773-2014, and the softening point is 101℃ as determined by the ring and ball method according to GB / T 4507-2014.

[0046] Example 3

[0047] A reinforcing resin comprises: phenol, phenolic compound A of Preparation Example 1, methyl p-hydroxycinnamate, p-toluenesulfonic acid, and formaldehyde; wherein the molar ratio of phenol, phenolic compound A, methyl p-hydroxycinnamate, and formaldehyde is 1:0.1:0.05:0.8, and the amount of p-toluenesulfonic acid is 1 mol of the total molar amount of phenol, phenolic compound A, and methyl p-hydroxycinnamate.

[0048] This embodiment also provides a method for preparing the above-mentioned reinforcing resin, including:

[0049] Phenol, phenolic compound A, and methyl p-hydroxycinnamate were mixed and heated to a complete melt. The mixture was then cooled to 110°C, and a 37% (w / w) aqueous solution of formaldehyde and p-toluenesulfonic acid were added. After reacting for 2 hours, the mixture was heated to 160°C to remove water. The mixture was then evacuated to a relative vacuum of -0.098 MPa to remove free phenol, thus obtaining the reinforcing resin.

[0050] The specifications of this reinforcing resin are as follows: the free phenol content is 0.67% as determined by the gas phase method according to GB / T 30773-2014, and the softening point is 99℃ as determined by the ring and ball method according to GB / T 4507-2014.

[0051] Comparative Example 1

[0052] The content of Comparative Example 1 is basically the same as that of Example 1, except that phenolic compound A is omitted.

[0053] The resin obtained in Comparative Example 1 has the following properties: the free phenol content is 0.45% as determined by the gas phase method according to GB / T 30773-2014, and the softening point is 103℃ as determined by the ring and ball method according to GB / T 4507-2014.

[0054] Comparative Example 2

[0055] The content of Comparative Example 2 is basically the same as that of Example 1, except that methyl hydroxycinnamate is omitted.

[0056] The resin obtained in Comparative Example 2 has the following properties: the free phenol content is 0.52% as determined by the gas phase method according to GB / T 30773-2014, and the softening point is 99℃ as determined by the ring and ball method according to GB / T 4507-2014.

[0057] Test case

[0058] To verify the application effect of the reinforcing resin of the present invention, the resins obtained in Examples 1-3 and Comparative Examples 1-2 were used in the preparation of rubber products and their performance was tested.

[0059] 100 g of natural rubber, 57 g of carbon black N330, 2 g of stearic acid, and 4 g of zinc oxide were added to a mixing mill at 45 rpm and mixed until the rubber was discharged at 155°C. After cooling to room temperature, the mixture was transferred to a two-roll mill and then rolled. 10 g of the reinforcing resin obtained in Examples 1-3 or Comparative Examples 1-2, 3 g of antioxidant (antioxidant 4020: antioxidant RD = 1:1), 1 g of protective wax, 0.3 g of scorch inhibitor CTP, and 0.8 g of hexamethylenetetramine were added sequentially. After mixing evenly, 4.5 g of sulfur (ordinary sulfur: insoluble sulfur = 2:1), 1.2 g of accelerator NS, and 3.2 g of accelerator DM were added. The mixture was mixed at 20°C for 6 min, passed through a thin pass 6 times, and formed into triangular sheets 3 times. After cooling, the sheets were vulcanized at 151°C for 40 min to obtain various rubber products.

[0060] Tensile properties: The tensile properties of each rubber product were tested in accordance with GB / T 528-2009;

[0061] Tear resistance: The tear strength of each rubber product was tested according to GB / T 529-2008;

[0062] Hardness: The Shore A hardness of each rubber product was determined according to GB / T 531.1-2008;

[0063] Thermo-oxidative aging test: Thermo-oxidative aging test was conducted on each rubber product according to GB / T 3512-2014. A type 1 laminar flow air aging chamber was used with an air flow rate of 1 m / s. After treatment at 100℃ for 48 h, the tensile strength and tear strength of each sample were tested again, and the tensile retention rate and tear retention rate were calculated.

[0064] The test results are shown in Table 1.

[0065] Table 1 Tensile strength (MPa) 20.7 19.9 20.3 17.2 17.5 Tear strength (kN / m) 49.5 47.5 48.7 42.5 45.1 Shore A hardness 92 91 91 89 86 Tensile retention rate after 100℃×48 h heat aging (%) 79.1 77.8 78.3 73.5 62.7 Tear retention rate after 100℃×48 h heat aging (%) 81.1 79.3 80.4 74.8 63.2

[0066] As can be seen from Table 1, the reinforcing resins obtained in Examples 1-3 of the present invention exhibit excellent reinforcing effects and aging resistance when applied to general rubber reinforcing formulations. Their overall performance is significantly better than that of the comparative examples, and they fully meet the requirements of high-requirement rubber products.

[0067] Compared to Example 1, Comparative Example 1 omitted phenolic compound A and only retained methyl p-hydroxycinnamate for modification. As a result, the mechanical properties of the rubber compound decreased across the board. This indicates that phenolic compound A improves the compatibility between the resin and the rubber matrix through its flexible segments, optimizes the uniformity of the crosslinking network, thereby improving the basic mechanical properties of the rubber compound. It can also synergistically enhance the interfacial bonding force with methyl p-hydroxycinnamate and further improve the thermal stability of the system.

[0068] Comparative Example 2 omitted methyl p-hydroxycinnamate and retained only phenolic compound A for modification. As a result, the thermal aging performance of the rubber compound was significantly reduced, and the hardness was significantly decreased. This indicates that methyl p-hydroxycinnamate is the core component for improving aging resistance. Its side chain double bonds can participate in the vulcanization reaction to form a resin-rubber covalent bond network, effectively inhibiting high-temperature vulcanization reversion. The ester group can form hydrogen bonds with the carbon black surface, enhancing the stability of the filler-rubber interface and delaying the interface aging process.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A reinforcing resin, characterized in that, include: Phenol, phenolic compounds A, methyl p-hydroxycinnamate, acidic catalysts, and aldehydes; The molar ratio of phenol, phenolic compound A, methyl p-hydroxycinnamate, and aldehydes is 1:(0.03-0.1):(0.02-0.05):(0.5-0.8); the amount of acidic catalyst is 0.3-1 mol% of the total molar amount of phenol, phenolic compound A, and methyl p-hydroxycinnamate; the structural formula of phenolic compound A is as follows: 。 2. The reinforcing resin according to claim 1, characterized in that, The preparation process of the phenolic compound A is as follows: (1) Under the action of an organic base, 3-(2-aminoethylamino)propylamine and cycloheptyl isothiocyanate were reacted in N,N-dimethylformamide to obtain intermediate 1; the structural formula of intermediate 1 is as follows: (2) 4-(bromomethyl)phenol and intermediate 1 are reacted in acetonitrile under the action of an inorganic base to obtain the phenolic compound A.

3. The reinforcing resin according to claim 2, characterized in that, The organic base mentioned in step (1) is triethylamine; the molar ratio of 3-(2-aminoethylamino)propylamine, cycloheptyl isothiocyanate and organic base is 1:(2.2-2.4):(2.2-2.4).

4. The reinforcing resin according to claim 2, characterized in that, The reaction in step (1) is carried out at a temperature of 80-85℃ for 12-16 h.

5. The reinforcing resin according to claim 2, characterized in that, The inorganic base mentioned in step (2) is potassium carbonate; the molar ratio of the intermediate 1,4-(bromomethyl)phenol and the inorganic base is 1:(1.1-1.2):(1.1-1.2).

6. The reinforcing resin according to claim 2, characterized in that, The reaction time in step (2) is 10-12 hours.

7. The reinforcing resin according to claim 1, characterized in that, The acidic catalyst is p-toluenesulfonic acid; the aldehyde compound is at least one of formaldehyde, acetaldehyde, and furfural.

8. A method for preparing the reinforcing resin according to any one of claims 1-7, characterized in that, Includes the following steps: Phenol, phenolic compound A, and methyl p-hydroxycinnamate were mixed and completely melted. The mixture was then cooled to 100-110°C, and aldehydes and an acidic catalyst were added. The mixture was reacted for 2-4 hours. Subsequently, the free phenol was removed by dehydration and vacuum to obtain the reinforcing resin.

9. The use of the reinforcing resin according to any one of claims 1-7 in the preparation of rubber products.

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