Preparation method of a cellulose melamine resin composite material

Abstract

The present invention relates to the technical field of melamine resins, and discloses a preparation method of a cellulose melamine resin composite material. In the present invention, melamine resin and modified cellulose are added to a mixer for mixing, and after discharging and ball milling and pulverizing, the material is placed in a flat vulcanizing machine for hot pressing to obtain the cellulose melamine resin composite material. The diphenyl sulfone polymer containing a triazine structure introduced into the cellulose microcrystals in the present invention has good compatibility with the melamine resin containing a triazine structural unit, improves the dispersion of the cellulose microcrystals in the melamine resin, enables the cellulose microcrystals to play a good reinforcing role, and significantly improves the flexural strength and impact strength of the melamine resin material. Moreover, by introducing the heat-resistant diphenyl sulfone structure, the thermal decomposition temperature and mass residue rate of the resin material are also significantly increased, improving the heat resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of melamine resins, and specifically to a preparation method of a cellulose melamine resin composite material. Background Art

[0002] Melamine resin is a new type of high molecular resin material obtained by the polymerization reaction of melamine and formaldehyde as raw materials. It has high chemical activity, fast curing speed, high bonding strength, good water resistance, and excellent wear resistance, and is widely used in furniture, automobiles, building materials, etc. However, melamine resin has a large curing crosslinking density, high brittleness, and poor toughness, and the toughening modification of melamine resin is a research hotspot. As a natural green environmental protection material with excellent mechanical properties, cellulose is widely used in the toughening modification of polymer materials. The invention patent with the publication number CN113980421 B discloses an environmentally friendly melamine powder material and its preparation method. Using nanocrystalline cellulose, sodium periodate, 3-amino-4,4,4-trifluorocrotonic acid ethyl ester, 2,2-dimethylolbutyric acid, dibutyltin oxide, etc. as raw materials, modified nanocrystalline cellulose is prepared, and then mixed with melamine resin to obtain melamine powder with characteristics such as heat resistance and water resistance. However, the melamine powder material of this patent does not have good mechanical properties such as flexural strength and impact strength. Summary of the Invention

[0003] The technical problem solved by the present invention is: to provide a preparation method of a cellulose melamine resin composite material, which solves the mechanical strength and heat resistance of melamine resin.

[0004] The technical solution provided by the present invention is: a preparation method of a cellulose melamine resin composite material, comprising the following steps:

[0005] Step (1): Add triethylamine, 4,4'-dihydroxy diphenyl sulfone, and phenylalanyl chloride isocyanurate to N,N-dimethylformamide, stir and react at room temperature for 18-24 h, then add phenylalanyl chloride isocyanurate, react for 2-3 h, add acetone to the solution, filter, wash with acetone, and dry to obtain an acyl chloride isocyanurate diphenyl sulfone polymer.

[0006] Step (2): Add microcrystalline cellulose to N,N-dimethylformamide, stir, then add the acyl chloride isocyanurate diphenyl sulfone polymer and triethylamine, filter after reaction, wash successively with water and ethanol, and dry to obtain modified cellulose.

[0007] Step (3): Add melamine resin and modified cellulose with a mass ratio of 100:(20-40) to a mixer for mixing, discharge, ball mill and crush the material, and then place the material in a flat vulcanizing machine for hot pressing to obtain a cellulose melamine resin composite material.

[0008] Further, in step (1), the molar ratio of triethylamine, 4,4'-dihydroxydiphenyl sulfone, and phenylalanyl chloride isocyanurate is (1.5-1.8):1:(0.7-0.74).

[0009] Further, in step (2), the mass ratio of microcrystalline cellulose, acyl chloride isocyanurate diphenyl sulfone polymer added after stirring, and triethylamine is 1:(0.2-0.5):(0.03-0.08).

[0010] Further, the reaction in step (2) is carried out at room temperature for 6-10 h.

[0011] Further, in step (3), the temperature during mixing in the internal mixer is 70-80 °C, and the time is 30-60 min.

[0012] Further, in step (3), the temperature during hot pressing in the flat vulcanizer is 150-165 °C, the pressure is 15-20 MPa, and the time is 5-8 min.

[0013] Further, the preparation method of phenylalanyl chloride isocyanurate includes: adding DL-phenylalanine, N,N-diisopropylethylamine, and cyanuric chloride with a molar ratio of (3-3.3):(6-6.6):1 to a tetrahydrofuran or 1,4-dioxane solvent, heating to 60-85 °C in a nitrogen atmosphere, reacting for 12-18 h, performing vacuum distillation, recrystallizing the crude product with ethanol, adding the crystalline product to thionyl chloride, heating to 60-70 °C, reacting for 3-5 h, performing vacuum distillation, and drying to obtain phenylalanyl chloride isocyanurate.

[0014] The technical effect of the present invention is: The present invention uses 4,4'-dihydroxydiphenyl sulfone to carry out a polymerization reaction with phenylalanyl chloride isocyanurate to obtain an acyl chloride isocyanurate diphenyl sulfone polymer. Its terminal acyl chloride group reacts with the hydroxyl group of microcrystalline cellulose, thereby grafting the isocyanurate diphenyl sulfone polymer onto the matrix of microcrystalline cellulose, and then blending with melamine resin and hot pressing to form a cellulose melamine resin composite material.

[0015] The diphenyl sulfone polymer containing a triazine structure introduced into the cellulose microcrystals in the present invention has good compatibility with the melamine resin containing a triazine structural unit, improves the dispersion of cellulose microcrystals in the melamine resin, enables the cellulose microcrystals to play a good reinforcing role, and significantly improves the flexural strength and impact strength of the melamine resin material. And by introducing a heat-resistant diphenyl sulfone structure, the T 5％ , T 10％ and mass residue rate of the resin material also increase significantly, improving the heat resistance. Specific Embodiments

[0016] To make the objectives, technical solutions, and advantages of the present disclosure clearer, the technical solutions of the present disclosure will be clearly and completely described below in conjunction with the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present disclosure. It should be noted that, without conflict, the embodiments in the present disclosure and the features in the embodiments can be combined arbitrarily with each other.

[0017] Example 1

[0018] 15 mmol of DL-phenylalanine, 30 mmol of N,N-diisopropylethylamine, and 5 mmol of cyanuric chloride were added to 20 mL of 1,4-dioxane solvent. The mixture was heated to 85°C in a nitrogen atmosphere and reacted for 12 h. Then, it was distilled under reduced pressure. The crude product was recrystallized with ethanol. The crystalline product was added to 120 mmol of thionyl chloride, heated to 70°C, and reacted for 3 h. After distillation under reduced pressure and drying, phenylalanyl chloride-based s-triazine was obtained.

[0019] Example 2

[0020] 16.5 mmol of DL-phenylalanine, 33 mmol of N,N-diisopropylethylamine, and 5 mmol of cyanuric chloride were added to 20 mL of tetrahydrofuran solvent. The mixture was heated to 60°C in a nitrogen atmosphere and reacted for 18 h. Then, it was distilled under reduced pressure. The crude product was recrystallized with ethanol. The crystalline product was added to 120 mmol of thionyl chloride, heated to 60°C, and reacted for 5 h. After distillation under reduced pressure and drying, phenylalanyl chloride-based s-triazine was obtained.

[0021] Example 3

[0022] Step (1): 16 mmol of triethylamine, 10 mmol of 4,4'-dihydroxydiphenyl sulfone, and 6.7 mmol of phenylalanyl chloride-based s-triazine (prepared in Example 1) were added to 80 mL of N,N-dimethylformamide. The mixture was stirred at room temperature for 18 h, and then 0.7 mmol of phenylalanyl chloride-based s-triazine was added and reacted for 3 h. Acetone was added to the solution, and after filtration, it was washed with acetone and dried to obtain an acyl chloride-based s-triazine diphenyl sulfone polymer.

[0023] Step (2): 20 g of microcrystalline cellulose was added to 500 mL of N,N-dimethylformamide. After stirring, 6 g of acyl chloride-based s-triazine diphenyl sulfone polymer and 0.9 g of triethylamine were added, and the reaction was carried out at room temperature for 10 h. After filtration, it was washed successively with water and ethanol and dried to obtain modified cellulose.

[0024] Step (3): Add 2 kg of melamine resin and 0.4 kg of modified cellulose into a kneader, mix them at 75 °C for 60 min, discharge the material, ball-mill and crush it, then place the material in a flat vulcanizing machine, hot-press it at 165 °C under 15 MPa for 5 min to obtain a cellulose melamine resin composite material.

[0025] Example 4

[0026] Step (1): Add 18 mmol of triethylamine, 10 mmol of 4,4'-dihydroxy diphenyl sulfone, and 6.7 mmol of phenylalanyl chloride-based melamine (prepared in Example 1) into 70 mL of N,N-dimethylformamide, stir and react at room temperature for 18 h, then add an additional 0.3 mmol of phenylalanyl chloride-based melamine and react for 2 h. Add acetone to the solution, filter, wash with acetone, and dry to obtain an acyl chloride-based melamine diphenyl sulfone polymer.

[0027] Step (2): Add 20 g of microcrystalline cellulose into 400 mL of N,N-dimethylformamide, stir, then add 4 g of acyl chloride-based melamine diphenyl sulfone polymer and 0.6 g of triethylamine, react at room temperature for 6 h, filter, wash successively with water and ethanol, and dry to obtain modified cellulose.

[0028] Step (3): Add 2 kg of melamine resin and 0.55 kg of modified cellulose into a kneader, mix them at 80 °C for 30 min, discharge the material, ball-mill and crush it, then place the material in a flat vulcanizing machine, hot-press it at 160 °C under 20 MPa for 5 min to obtain a cellulose melamine resin composite material.

[0029] Example 5

[0030] Step (1): Add 15 mmol of triethylamine, 10 mmol of 4,4'-dihydroxy diphenyl sulfone, and 6.7 mmol of phenylalanyl chloride-based melamine (prepared in Example 1) into 80 mL of N,N-dimethylformamide, stir and react at room temperature for 24 h, then add an additional 0.7 mmol of phenylalanyl chloride-based melamine and react for 2 h. Add acetone to the solution, filter, wash with acetone, and dry to obtain an acyl chloride-based melamine diphenyl sulfone polymer.

[0031] Step (2): Add 20 g of microcrystalline cellulose into 500 mL of N,N-dimethylformamide, stir, then add 10 g of acyl chloride-based melamine diphenyl sulfone polymer and 1.6 g of triethylamine, react at room temperature for 10 h, filter, wash successively with water and ethanol, and dry to obtain modified cellulose.

[0032] Step (3): Add 2 kg of melamine resin and 0.7 kg of modified cellulose into a kneader, mix at 70 °C for 60 min, discharge the material. After ball milling and pulverizing, place the material in a flat vulcanizing machine, hot press at 15 MPa and 150 °C for 8 min to obtain a cellulose melamine resin composite material.

[0033] Example 6

[0034] Step (1): Add 15 mmol of triethylamine, 10 mmol of 4,4'-dihydroxy diphenyl sulfone, and 6.7 mmol of phenylalanyl chlorotriazine (prepared in Example 1) to 70 mL of N,N-dimethylformamide, stir and react at room temperature for 24 h. Then add an additional 0.5 mmol of phenylalanyl chlorotriazine and react for 2 h. Add acetone to the solution, filter, wash with acetone, and dry to obtain an acyl chloride group triazine diphenyl sulfone polymer.

[0035] Step (2): Add 20 g of microcrystalline cellulose to 500 mL of N,N-dimethylformamide, stir, then add 8 g of acyl chloride group triazine diphenyl sulfone polymer and 1.3 g of triethylamine, react at room temperature for 8 h, filter, wash successively with water and ethanol, and dry to obtain modified cellulose.

[0036] Step (3): Add 2 kg of melamine resin and 0.8 kg of modified cellulose into a kneader, mix at 80 °C for 60 min, discharge the material. After ball milling and pulverizing, place the material in a flat vulcanizing machine, hot press at 15 MPa and 160 °C for 6 min to obtain a cellulose melamine resin composite material.

[0037] Comparative Example 1

[0038] Step (1): Add 2 kg of melamine resin into a kneader, mix at 75 °C for 60 min, discharge the material. After ball milling and pulverizing, place the material in a flat vulcanizing machine, hot press at 15 MPa and 165 °C for 5 min to obtain a melamine resin material.

[0039] Comparative Example 2

[0040] Step (1): Add 2 kg of melamine resin and 0.4 kg of cellulose into a kneader, mix at 75 °C for 60 min, discharge the material. After ball milling and pulverizing, place the material in a flat vulcanizing machine, hot press at 15 MPa and 165 °C for 5 min to obtain a cellulose melamine resin composite material.

[0041] Comparative Example 3

[0042] Step (1): Add 16 mmol of triethylamine, 10 mmol of 4,4'-dihydroxydiphenyl sulfone, and 6.7 mmol of phenylalanyl chloride isocyanuric acid (prepared in Example 1) to 80 mL of N,N-dimethylformamide. Stir and react at room temperature for 18 h, then add an additional 0.7 mmol of phenylalanyl chloride isocyanuric acid and react for 3 h. Add acetone to the solution, filter, wash with acetone, and dry to obtain the acyl chloride isocyanuric acid diphenyl sulfone polymer.

[0043] Step (2): Add 2 kg of melamine resin and 0.4 kg of acyl chloride isocyanuric acid diphenyl sulfone polymer to a kneader. Mix at 75 °C for 60 min, discharge, ball mill and crush the material, then place the material in a flat vulcanizer. Hot press at 15 MPa and 165 °C for 5 min to obtain the melamine resin composite material.

[0044] The flexural properties of the melamine resin composite material were tested according to the method of GB / T 9341-2008. The impact properties were tested according to the method of GB / T 1043.1-2008.

[0045] Weigh 6 mg of the melamine resin composite material and place it in a thermogravimetric analyzer for thermal performance analysis. Under a nitrogen atmosphere, the heating rate is 10 °C / min, and the test temperature is 20 - 800 °C.

[0046] The test results are shown in Table 1.

[0047] Table 1: Performance Test

[0048]

[0049] T 5％ is the thermal decomposition temperature at a 5% mass loss. T 10％ is the thermal decomposition temperature at a 10% mass loss. Weight is the mass residue rate at 800 °C.

[0050] After testing, compared with Comparative Example 1, cellulose microcrystals were added to the melamine resin in Comparative Example 2. Due to the poor compatibility between the two, the dispersion of cellulose microcrystals in the melamine resin was not good, resulting in a poor strengthening effect of cellulose microcrystals, and the increase in the flexural strength and impact strength of the melamine resin material was relatively small. And after adding cellulose microcrystals, T 5％ and T 10％ showed a downward trend, and the heat resistance decreased.

[0051] Compared with Comparative Example 1, an acyl chloride group melamine resin was added to the melamine resin of Comparative Example 3. The polymer contains a triazine structure and has good compatibility with the melamine resin containing a triazine structural unit. When added to the resin material, it has little effect on its flexural strength and impact strength. Moreover, the polymer contains a heat-resistant diphenyl sulfone structure, which can be introduced into the resin material matrix to increase the T 5％ , T 10％ and mass residue rate, and the heat resistance is significantly improved.

[0052] Microcrystalline cellulose modified with melamine resin was added to the melamine resins of Examples 4-6. The diphenyl sulfone polymer containing a triazine structure introduced into the microcrystalline cellulose has good compatibility with the melamine resin containing a triazine structural unit, improving the dispersibility of the microcrystalline cellulose in the melamine resin and enabling the microcrystalline cellulose to play a good reinforcing role. The flexural strength and impact strength of the melamine resin material are significantly improved. Moreover, by introducing the heat-resistant diphenyl sulfone structure, the T 5％ , T 10％ and mass residue rate of the resin material also increase significantly, improving the heat resistance.

Claims

1. A method for preparing a cellulose melamine resin composite material, characterized in that, The preparation method includes the following steps: Step (1): Triethylamine, 4,4'-dihydroxydiphenyl sulfone, and phenylalanyl chloride isocyanurate are added to N,N-dimethylformamide, and stirred at room temperature for 18 - 24 h. Then, phenylalanyl chloride isocyanurate is added and the reaction proceeds for 2 - 3 h. Acetone is added to the solution, followed by filtration, washing, and drying to obtain the acyl chloride isocyanurate diphenyl sulfone polymer. Step (2): Microcrystalline cellulose is added to N,N-dimethylformamide, and after stirring, the acyl chloride isocyanurate diphenyl sulfone polymer and triethylamine are added. After the reaction, filtration, washing, and drying are carried out to obtain the modified cellulose. Step (3): Melamine resin and modified cellulose with a mass ratio of 100:(20 - 40) are added to a mixer for mixing. After discharging, the material is ball-milled and then placed in a flat vulcanizing machine for hot pressing to obtain the cellulose melamine resin composite material. In step (1), the molar ratio of triethylamine, 4,4'-dihydroxydiphenyl sulfone, and phenylalanyl chloride isocyanurate is (1.5 - 1.8):1:(0.7 - 0.74). In step (2), the mass ratio of microcrystalline cellulose, acyl chloride isocyanurate diphenyl sulfone polymer, and triethylamine is 1:(0.2 - 0.5):(0.03 - 0.08).

2. The preparation method of the cellulose melamine resin composite material according to claim 1, characterized in that, In step (2), the reaction is carried out at room temperature for 6 - 10 h.

3. The preparation method of the cellulose melamine resin composite material according to claim 1, characterized in that, In step (3), the temperature during mixing in the mixer is 70 - 80 °C, and the time is 30 - 60 min.

4. The preparation method of the cellulose melamine resin composite material according to claim 1, characterized in that, In step (3), the temperature during hot pressing in the flat vulcanizing machine is 150 - 165 °C, the pressure is 15 - 20 MPa, and the time is 5 - 8 min.

5. The preparation method of the cellulose melamine resin composite material according to claim 1, characterized in that, The preparation method of phenylalanyl chloride isocyanurate is as follows: DL-phenylalanine, N,N-diisopropylethylamine, and cyanuric chloride are added to a solvent, heated to 60 - 85 °C in a nitrogen atmosphere, and reacted for 12 - 18 h. Then, vacuum distillation and recrystallization are carried out. The crystalline product is added to thionyl chloride, heated to 60 - 70 °C, and reacted for 3 - 5 h. After vacuum distillation and drying, phenylalanyl chloride isocyanurate is obtained.

6. The preparation method of the cellulose melamine resin composite material according to claim 5, characterized in that, The solvent is tetrahydrofuran or 1,4-dioxane.

7. The preparation method of the cellulose melamine resin composite material according to claim 5, characterized in that, The molar ratio of DL-phenylalanine, N,N-diisopropylethylamine, and cyanuric chloride is (3 - 3.3):(6 - 6.6):1.

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