Environment-friendly bio-based polyurethane adhesive and preparation method thereof

Abstract

The invention discloses an environment-friendly bio-based polyurethane adhesive, which is composed of the following raw materials: 35-55 parts of composite bio-based polyol with a hydroxyl value of 210-260 mgKOH / g; 25 to 40 parts of bio-based modified isocyanate with the NCO content of 28 to 34 weight percent; the mass ratio of acetyl tributyl citrate to epoxidized soybean oil in the composite environment-friendly plasticizer is 3: 1; the length-diameter ratio of the nanocellulose-silicon dioxide hybrid reinforcing agent is larger than or equal to 180, and the specific surface area of the nanocellulose-silicon dioxide hybrid reinforcing agent is larger than or equal to 200 m < 1-3 parts of a plant polyphenol-vitamin E composite antioxidant; the bio-based carbon content of the composite polyol and the modified isocyanate is greater than or equal to 60%; compared with a traditional petroleum-based system, the environment-friendly leap-type improvement is realized; and the acid value is less than or equal to 0.5 mgKOH / g in a molecular distillation purification technology, which is superior to 2.0 mgKOH / g required by the industrial standard.

Description

Technical Field

[0001] This invention relates to the field of adhesive preparation technology, and in particular to an environmentally friendly bio-based polyurethane adhesive and its preparation method. Background Technology

[0002] Currently, in the field of adhesive technology, polyurethane adhesives are one of the most promising areas for expansion and also one of the most widely used solvent-free adhesives. Polyurethane adhesives can produce excellent adhesion to porous surfaces such as ceramics, as well as smooth surfaces such as metal foils, glass, and polymer films, thus finding wide application in various fields. Polyurethane adhesives are mainly petroleum-based. Currently, petroleum-based polyurethane adhesives face three major technical bottlenecks: 1. Environmental defects: Traditional MDI systems contain benzene ring structures, which degrade to produce carcinogenic aromatic amines (meeting the detection limit requirements of GB / T 18448-2018); 2. Performance limitations: Bio-based products generally suffer from low initial tack (<3N / cm) and poor heat resistance (strength decay >40% at 80℃); 3. Complex processes: Nanomaterials are prone to agglomeration, leading to a reinforcement efficiency loss >30%. Summary of the Invention

[0003] Based on the aforementioned problems, this invention proposes an environmentally friendly bio-based polyurethane adhesive and its preparation method to solve these problems.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: An environmentally friendly bio-based polyurethane adhesive, composed of the following raw materials: 35-55 parts of a composite bio-based polyol with a hydroxyl value of 210-260 mg KOH / g; 25-40 parts of a bio-based modified isocyanate with an NCO content of 28-34 wt%; 8-18 parts of a composite environmentally friendly plasticizer consisting of tributyl acetylacetonate and epoxidized soybean oil in a mass ratio of 3:1; and an aspect ratio ≥180 and a specific surface area ≥200 m². 2 / g of nanocellulose-silica hybrid reinforcing agent 4-10 parts; plant polyphenol-vitamin E complex antioxidant 1-3 parts.

[0005] As a preferred embodiment of the present invention, the composite bio-based polyol is a mixture of castor oil-based polyol and cashew phenol-based polyol in a 7:3 ratio, and is purified by molecular distillation with an acid value ≤0.5mgKOH / g.

[0006] As a further preferred embodiment of the present invention, the bio-based modified isocyanate is a mixture of HDI trimer and IPDI derivative with bio-based carbon content ≥40% in a 6:4 ratio, and its free monomer content is ≤0.1%.

[0007] As a further preferred embodiment of the present invention, the nanocellulose-silica hybrid reinforcing agent is synthesized in situ via a sol-gel method, wherein nanocellulose serves as a template to guide the directional growth of silica, forming a three-dimensional network structure.

[0008] Furthermore, it also includes 0.5-2 parts of a light stabilizer composed of hindered amines and benzotriazoles, which can withstand 300 hours of UVB irradiation with a yellowing index ΔYI≤2.

[0009] Based on the above, the present invention further discloses a method for preparing an environmentally friendly bio-based polyurethane adhesive, comprising the following steps:

[0010] Step 1: Dehydrate the polyol under a vacuum of 0.095 MPa, with a final water content of ≤300 ppm;

[0011] Step 2: A microreactor is used for the prepolymerization reaction, with a reaction temperature of 75±0.5℃ and a residence time precisely controlled to the second level;

[0012] Step 3: The plasticizer is injected after being degassed by a molecular membrane;

[0013] Step 4: The enhancer is dispersed by ultrasonic-centrifugal coupling at a frequency of 28kHz and a centrifugal force of 2000g.

[0014] Preferably, step two employs near-infrared online monitoring, and the next process is automatically triggered when the -NCO conversion rate reaches 96.5±0.3%.

[0015] More preferably, the final product undergoes a three-stage molecular sieve dehumidification system to achieve a finished product moisture content of ≤0.02wt%.

[0016] Next, based on the above, this invention discloses a special application equipment for environmentally friendly bio-based polyurethane adhesives, which integrates: a two-component precision metering system with an error of ≤0.5%; a static mixer with a mixing efficiency of ≥98%; and a low-temperature plasma surface treatment module.

[0017] Next, based on the above, this invention discloses the application of an environmentally friendly bio-based polyurethane adhesive, which is mainly suitable for: sealing of new energy vehicle battery packs with electrolyte erosion resistance ≥500h; heat sealing of biodegradable food packaging with heat sealing strength ≥25N / 15mm; and coating of orthopedic implants with cytotoxicity rating of 0.

[0018] After adopting the above-mentioned technical improvements, the present invention mainly has the following advantages:

[0019] 1. Innovations in the material system: This invention achieves a breakthrough in increasing the bio-based content of the composite polyol (castor oil / cashew nut shell) and modified isocyanate (HDI / IPDI) to ≥60% bio-based carbon content, representing a significant improvement in environmental friendliness compared to traditional petroleum-based systems (typically ≤30%). Molecular distillation purification technology ensures an acid value ≤0.5mgKOH / g, exceeding the industry standard (GB / T12008.3-2009) requirement of 2.0mgKOH / g. Regarding the innovative reinforcing agent structure, the use of a three-dimensional network structure (aspect ratio ≥180) of nanocellulose-silica hybrids results in a tensile strength increase of over 200% compared to conventional fumed silica (aspect ratio ≤50). Furthermore, the sol-gel in-situ synthesis method effectively avoids the agglomeration problems caused by traditional mechanical mixing.

[0020] 2. Breakthrough in preparation process: This invention employs a microreactor for precise control, achieving a 10-fold improvement in precision compared to traditional batch reactors (±5℃) under constant temperature control of 75±0.5℃. Simultaneously, second-level residence time control reduces the standard deviation of -NCO conversion from ±2% to ±0.3%. Furthermore, in terms of dispersion technology upgrade, the use of ultrasonic-centrifugal coupled dispersion (28kHz / 2000g) achieves a nanoparticle dispersion of 98.7%, superior to single ultrasonic dispersion (typically ≤90%).

[0021] 3. Regarding the leap in performance indicators, the polyurethane adhesive of this invention exhibits significant improvements in environmental resistance, with a UVB irradiation ΔYI ≤ 2 after 300 hours, compared to commercially available light-stabilized systems (typically ΔYI ≥ 5); the bond strength retention rate after 500 hours of electrolyte erosion testing is ≥ 95%; and in terms of safety performance, the free monomer content is ≤ 0.1% (EU REACH standard requires ≤ 0.5%), and the cytotoxicity is grade 0 (the highest level of ISO 10993-5 standard).

[0022] 4. In terms of application scalability, the heat-sealing strength of 25N / 15mm (2.5 times the ASTM F88 standard value) can simultaneously meet the requirements of automotive battery packs (-40℃~150℃) and food packaging (FDA 21CFR 175.105). Furthermore, in terms of intelligent manufacturing support, the metering accuracy of the dedicated sizing equipment is 0.5%, which is 6 times higher than that of traditional equipment (±3%). In addition, the low-temperature plasma treatment can increase the surface energy of the substrate to 72mN / m (compared to about 50mN / m for conventional treatment). Attached Figure Description

[0023] Figure 1 The diagram shown is a flowchart of the preparation process of this invention; Detailed Implementation

[0024] The present invention will be further described below using specific embodiments.

[0025] An environmentally friendly bio-based polyurethane adhesive is composed of the following raw materials: 35-55 parts of a composite bio-based polyol with a hydroxyl value of 210-260 mg KOH / g; 25-40 parts of a bio-based modified isocyanate with an NCO content of 28-34 wt%; 8-18 parts of a composite environmentally friendly plasticizer consisting of acetylated tributyl citrate and epoxidized soybean oil in a mass ratio of 3:1; and an aspect ratio ≥180 and a specific surface area ≥200 m². 2 / g of nanocellulose-silica hybrid reinforcing agent 4-10 parts; plant polyphenol-vitamin E complex antioxidant 1-3 parts.

[0026] In this invention, the preferred composite bio-based polyol is a mixture of castor oil-based polyol and cashew phenol-based polyol in a 7:3 ratio, purified by molecular distillation with an acid value ≤0.5mgKOH / g.

[0027] In this invention, the preferred bio-based modified isocyanate is a mixture of HDI trimer and IPDI derivative with bio-based carbon content ≥40% in a 6:4 ratio, with a free monomer content ≤0.1%.

[0028] In this invention, the preferred nanocellulose-silica hybrid reinforcing agent is synthesized in situ via a sol-gel method, wherein nanocellulose serves as a template to guide the directional growth of silica, forming a three-dimensional network structure.

[0029] The above-mentioned formulation of the present invention also includes 0.5-2 parts of a light stabilizer composed of hindered amines and benzotriazoles, which can withstand 300 hours of UVB irradiation with a yellowing index ΔYI≤2.

[0030] Based on the above, the present invention further discloses a method for preparing an environmentally friendly bio-based polyurethane adhesive, comprising the following steps:

[0031] Step 1: Dehydrate the polyol under a vacuum of 0.095 MPa, with a final water content of ≤300 ppm;

[0032] Step 2: A microreactor is used for the prepolymerization reaction, with a reaction temperature of 75±0.5℃ and a residence time precisely controlled to the second level;

[0033] Step 3: The plasticizer is injected after being degassed by a molecular membrane;

[0034] Step 4: The enhancer is dispersed by ultrasonic-centrifugal coupling at a frequency of 28kHz and a centrifugal force of 2000g.

[0035] In step two, near-infrared online monitoring is used, and the next process is automatically triggered when the -NCO conversion rate reaches 96.5±0.3%.

[0036] The final product of this invention undergoes a three-stage molecular sieve dehumidification system to achieve a moisture content of ≤0.02wt%.

[0037] Next, based on the above, this invention discloses a special application equipment for environmentally friendly bio-based polyurethane adhesives, which integrates: a two-component precision metering system with an error of ≤0.5%; a static mixer with a mixing efficiency of ≥98%; and a low-temperature plasma surface treatment module.

[0038] Next, based on the above, this invention discloses the application of an environmentally friendly bio-based polyurethane adhesive, which is mainly suitable for: sealing of new energy vehicle battery packs with electrolyte erosion resistance ≥500h; heat sealing of biodegradable food packaging with heat sealing strength ≥25N / 15mm; and coating of orthopedic implants with cytotoxicity rating of 0.

[0039] Example 1

[0040] An environmentally friendly bio-based polyurethane adhesive is composed of the following raw materials: 35 parts of a composite bio-based polyol with a hydroxyl value of 210 mg KOH / g; 25 parts of a bio-based modified isocyanate with an NCO content of 28 wt%; 8 parts of a composite environmentally friendly plasticizer consisting of tributyl acetylacetonate and epoxidized soybean oil in a mass ratio of 3:1; and an aspect ratio ≥180 and a specific surface area ≥200 m². 2 The formula of this invention includes 4 parts of nanocellulose-silica hybrid reinforcing agent ( / g) and 1 part of plant polyphenol-vitamin E complex antioxidant. The above formulation also includes 0.5 parts of a light stabilizer composed of hindered amines and benzotriazoles, which can withstand 300 hours of UVB irradiation with a yellowing index ΔYI ≤ 2.

[0041] Example 2

[0042] An environmentally friendly bio-based polyurethane adhesive is composed of the following raw materials: 55 parts of a composite bio-based polyol with a hydroxyl value of 260 mg KOH / g; 40 parts of a bio-based modified isocyanate with an NCO content of 34 wt%; 18 parts of a composite environmentally friendly plasticizer consisting of tributyl acetylacetonate and epoxidized soybean oil in a mass ratio of 3:1; and an aspect ratio ≥180 and a specific surface area ≥200 m². 2 The formulation of this invention includes 10 parts of a nanocellulose-silica hybrid reinforcing agent (per g); and 3 parts of a plant polyphenol-vitamin E complex antioxidant. The formulation also includes 2 parts of a light stabilizer composed of hindered amines and benzotriazoles, which can withstand 300 hours of UVB irradiation with a yellowing index ΔYI ≤ 2.

[0043] Example 3

[0044] An environmentally friendly bio-based polyurethane adhesive is composed of the following raw materials: 40 parts of a composite bio-based polyol with a hydroxyl value of 240 mg KOH / g; 30 parts of a bio-based modified isocyanate with an NCO content of 31 wt%; 14 parts of a composite environmentally friendly plasticizer consisting of tributyl acetylacetonate and epoxidized soybean oil in a mass ratio of 3:1; and an aspect ratio ≥180 and a specific surface area ≥200 m². 2 The formulation of this invention includes 7 parts of nanocellulose-silica hybrid reinforcing agent ( / g) and 2 parts of plant polyphenol-vitamin E complex antioxidant. The above formulation also includes 1 part of a light stabilizer composed of hindered amines and benzotriazoles, which can withstand 300 hours of UVB irradiation with a yellowing index ΔYI ≤ 2.

[0045] Example 4: Sealant for battery packs in new energy vehicles;

[0046] I. Raw material composition:

[0047] 1. Compound bio-based polyols: 45 parts of castor oil-based (70wt%) + cashew phenol-based (30wt%), hydroxyl value 238mgKOH / g (determined according to GB / T 12008.3-2023);

[0048] 2. Isocyanate: 35 parts of HDI trimer (60%) + IPDI bio-based derivative (40%), NCO content 31.5% (ASTM D5155-19);

[0049] 3. Plasticizer: Tributyl acetylacetonate: Epoxidized soybean oil = 3:1, 10 parts in total;

[0050] 4. Reinforcing agent: Nanocellulose-SiO2 hybrid material (BET specific surface area 215m²) 2 8 portions (g);

[0051] 5. Antioxidant: Rosemary extract + Vitamin E (2:1) 2 parts;

[0052] II. Preparation process:

[0053] 1. Dehydration treatment: The polyol was dehydrated at 115℃±1℃ and vacuum degree 0.098MPa for 3 hours, and the moisture content was monitored in real time until it reached 280ppm (Karl Fischer process);

[0054] 2. Prepolymerization reaction: A microchannel reactor (channel diameter 500μm) was used, with the following control: temperature 78.0℃±0.3℃ (three-stage PID temperature control), residence time 137 seconds, and nitrogen flow rate 0.8L / min; the reaction was terminated when the NCO conversion rate reached 96.8% as monitored by online FTIR.

[0055] 3. Plasticizer injection: After preheating to 65℃±1℃, degas through a 0.2μm filter and inject at a rate of 2mL / s;

[0056] 4. Dispersion process: Ultrasonic-centrifugal coupling system parameters: ultrasonic power 400W (frequency 28kHz); centrifugal acceleration 2000g, dispersion time 18min, temperature control ≤45℃.

[0057] 5. Performance testing: Electrolyte resistance: After immersion in LiPF6 electrolyte at 60℃ for 504 hours, the tensile strength retention rate is 92.1% (initial value 4.8MPa); Flame retardancy: Self-extinguishing time in UL94 vertical burning test is <3s (thickness 2mm).

[0058] 6. Process window: Pot life (25℃) up to 6 hours (viscosity increase <10%).

[0059] Example 5: Biodegradable heat-sealing adhesive for food packaging;

[0060] I. Raw material adjustment:

[0061] 1. Replace the polyol with 40 parts of 100% soybean oil-based (hydroxyl value 225mgKOH / g);

[0062] 2. Isocyanate was used only in 30 parts of IPDI bio-based derivative (NCO2 9.8%);

[0063] 3. Add 3 parts of polylactic acid microspheres (particle size 5-8μm) as a pore-opening agent;

[0064] II. Key Processes:

[0065] 1. Low-temperature reaction: Prepolymerization at 66℃±0.5℃, with NCO conversion rate controlled at 95.2%;

[0066] 2. Stepwise dispersion: First, mechanically stir at 1500 rpm for 10 minutes, then process three times using a high-pressure homogenizer (80 MPa);

[0067] 3. Film formation process: Slit coating (gap 200μm) is used, and the film is cured at 80℃ for 20min.

[0068] III. Food contact performance:

[0069] 1. Migration test (GB 31604.8-2023): Total migration value 2.1 mg / dm³ 2 (far below 10 mg / dm) 2 (Limit)

[0070] 2. Heat seal strength: 28.3 N / 15 mm at 130℃ / 0.3 MPa (ASTM F88).

[0071] Example 6: Orthopedic implant coating adhesive;

[0072] I. Medical-grade modification:

[0073] 1. All raw materials comply with USP Class VI standards;

[0074] 2. Add 1.5 parts of hydroxyapatite nanowires (aspect ratio > 50);

[0075] 3. Sterilization process: γ-ray irradiation dose 25kGy.

[0076] II. Biological Evaluation:

[0077] 1. Cytotoxicity (ISO 10993-5): L929 cells showed a relative proliferation rate of 98.7%;

[0078] 2. In vivo degradation: 9.3% mass loss rate after 12 months (rabbit femoral implantation model);

[0079] 3. Bond strength: The bonding strength with the titanium alloy substrate reaches 15.2 MPa (ISO 527).

[0080] Example 7: Application of automotive interior trim

[0081] 1. Application Scenario: Leather-wrapped dashboard technology for a new energy vehicle brand (Model: 2025 Model E);

[0082] 2. Technical Implementation:

[0083] (1) Substrate treatment: Using the special adhesive application equipment of claim 9, the microfiber leather (thickness 1.2mm) and modified PP honeycomb panel (density 0.6g / cm³) are treated. 3 Low-temperature plasma surface treatment was performed, which increased the surface energy to 58 mN / m;

[0084] (2) Application process: The two-component metering system is sprayed at a mass ratio of 20:1 (polyol component: isocyanate component). The temperature of the adhesive outlet of the static mixer is controlled at 45±2℃, and the amount of adhesive applied is 100~120g / m². During construction, the adhesive is evenly brushed onto the surface to be bonded of the sample, and the amount of adhesive applied is 100~120g / m². The amount of adhesive on the bonded surface is uniform, without insufficient adhesive or adhesive accumulation.

[0085] 3. Performance Verification:

[0086] (1) Environmental friendliness: According to VOC testing (ISO 12219-3), the acetaldehyde emission is 0.008 mg / m³. 3 It is 90% better than the national standard limit;

[0087] (2) Durability: After aging test at 85℃ / 85%RH for 1000h, the peel strength retention rate is ≥92% (initial value 28.6N / 25mm);

[0088] (3) Safety certification: Passed the FMVSS 302 combustion test (burning speed ≤100mm / min), and the cytotoxicity test complies with the ISO 10993-5 standard.

[0089] 4. Innovation effect:

[0090] 1. It reduces weight by 17% compared to traditional solvent-based adhesives, contributing to a 2.3% increase in vehicle range;

[0091] 2. The bio-based carbon content reaches 43%, meeting the requirements of the EU ELV Directive for renewable materials;

[0092] 3. Zero solvent evaporation during construction, no explosion-proof modification required for the production line.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An environmentally friendly bio-based polyurethane adhesive, characterized in that, Composed of the following raw materials: 35-55 parts of a composite bio-based polyol with a hydroxyl value of 210-260 mg KOH / g; 25-40 parts of a bio-based modified isocyanate with an NCO content of 28-34 wt%; 8-18 parts of a composite environmentally friendly plasticizer consisting of acetylated tributyl citrate and epoxidized soybean oil in a mass ratio of 3:1; and an aspect ratio ≥180 and a specific surface area ≥200 m². 2 / g of nanocellulose-silica hybrid reinforcing agent 4-10 parts; plant polyphenol-vitamin E complex antioxidant 1-3 parts.

2. The environmentally friendly bio-based polyurethane adhesive according to claim 1, characterized in that, The composite bio-based polyol is a mixture of castor oil-based polyol and cashew phenol-based polyol in a 7:3 ratio, and is purified by molecular distillation with an acid value ≤0.5mgKOH / g.

3. The environmentally friendly bio-based polyurethane adhesive according to claim 1, characterized in that, The bio-based modified isocyanate is a compound of HDI trimer and IPDI derivative with bio-based carbon content ≥40% in a 6:4 ratio, with a free monomer content ≤0.1%.

4. The environmentally friendly bio-based polyurethane adhesive according to claim 1, characterized in that, The nanocellulose-silica hybrid reinforcing agent is synthesized in situ via a sol-gel method, in which nanocellulose serves as a template to guide the directional growth of silica, forming a three-dimensional network structure.

5. The environmentally friendly bio-based polyurethane adhesive according to claim 1, characterized in that, It also includes 0.5-2 parts of a light stabilizer composed of hindered amines and benzotriazoles, which can withstand 300 hours of UVB irradiation with a yellowing index ΔYI≤2.

6. A method for preparing an environmentally friendly bio-based polyurethane adhesive as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Dehydrate the polyol under a vacuum of 0.095 MPa, with a final water content of ≤300 ppm; Step 2: A microreactor is used for the prepolymerization reaction, with a reaction temperature of 75±0.5℃ and a residence time precisely controlled to the second level; Step 3: The plasticizer is injected after being degassed by a molecular membrane; Step 4: The enhancer is dispersed by ultrasonic-centrifugal coupling at a frequency of 28kHz and a centrifugal force of 2000g.

7. The method for preparing an environmentally friendly bio-based polyurethane adhesive according to claim 6, characterized in that, Step two employs near-infrared online monitoring, and automatically triggers the next process when the -NCO conversion rate reaches 96.5±0.3%.

8. The method for preparing an environmentally friendly bio-based polyurethane adhesive according to claim 6, characterized in that, The final product undergoes a three-stage molecular sieve dehumidification system to ensure that the moisture content of the finished product is ≤ 0.02 wt%.

9. A dedicated applicator for the environmentally friendly bio-based polyurethane adhesive as described in claim 1, characterized in that, Integration: a two-component precision metering system with an error of ≤0.5%; a static mixer with a mixing efficiency of ≥98%; and a low-temperature plasma surface treatment module.

10. The application of the environmentally friendly bio-based polyurethane adhesive according to any one of claims 1-9, characterized in that, Suitable for: sealing of new energy vehicle battery packs with electrolyte corrosion resistance ≥500h; heat sealing of biodegradable food packaging with heat sealing strength ≥25N / 15mm; and coating of orthopedic implants with cytotoxicity rating of 0.

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