Paper binder based on epoxy resin and preparation method thereof

Abstract

The invention relates to the technical field of adhesive preparation, in particular to an epoxy resin-based paper adhesive and a preparation method thereof, and the epoxy resin-based paper adhesive is prepared from the following raw materials in parts by weight: 40-55 parts of an epoxy resin matrix, 18-29 parts of a bio-based reinforcing system, 15-25 parts of a recovery adaptation system and 10-15 parts of a toughening system; the epoxy resin matrix is composed of bisphenol A epoxy resin and epoxidized soybean oil. According to the invention, bio-based modified epoxy resin and natural polymer partially replace petrochemical raw materials, carbon footprint is significantly reduced, the defect of insufficient water resistance of a biological material is made up through a nanocellulose composite enhancement technology, and a thermo-sensitive polyvinyl alcohol and initiator system is introduced, so that the binder can be rapidly stripped under mild conditions during recovery, and the recovery rate of the binder is increased. According to the scheme, high bonding strength is kept, meanwhile, comprehensive optimization of recoverability, environmental adaptability and cost effectiveness is achieved, and reliable technical support is provided for green upgrading of the corrugated paper industry.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesive preparation, and specifically to an epoxy resin-based paper adhesive and a preparation method thereof. Background Art

[0002] Paper adhesives are a type of functional chemical material specifically used in the paper manufacturing and processing processes. Their core function is to enhance the bonding force between paper fibers through physical or chemical means, thereby improving the mechanical strength, surface smoothness, and environmental resistance of the paper. In the papermaking process, adhesives can be used for internal sizing, surface coating, or finished product bonding, such as the bonding between corrugated cardboard layers and bookbinding. Different from traditional adhesives, paper adhesives need to take into account high compatibility with cellulose, rapid curing ability, and adaptability to subsequent recycling processes. They are an essential key additive in the paper industry. An adhesive refers to a substance that can bind two materials together through surface adhesion. Its types and application scenarios are extremely extensive. Paper adhesives are a specialized branch of adhesives in the paper-making field, and their design needs to meet the special requirements of the papermaking process: on the one hand, it needs to adapt to the porous fiber structure of the paper and form a stable bond under both wet and dry conditions; on the other hand, it needs to comply with environmental protection regulations and the requirements of circular economy. Therefore, in the formulation design of paper adhesives, more emphasis is placed on efficient bonding with cellulose, low-energy curing, and compatibility with recycled pulp, rather than simply pursuing bonding strength.

[0003] Generally, it also has an extremely important position in the production of corrugated paper. Traditional corrugated paper adhesives mainly rely on starch, polyvinyl alcohol (PVA), and styrene-butadiene latex materials. Starch is widely used due to its low cost and biodegradability, but it has poor water resistance and is prone to causing cardboard delamination in a high-humidity environment; although polyvinyl alcohol has high bonding strength, it has poor biodegradability and requires high-temperature curing, resulting in relatively high energy consumption; although styrene-butadiene latex can improve water resistance, its raw materials are non-renewable, and the residual adhesives are difficult to completely separate during the recycling of corrugated paper, which is prone to causing equipment blockage and a decline in the quality of recycled paper. In addition, the traditional formulation lacks design for stability in extreme environments and is difficult to balance the contradiction between strength and softness. These defects limit the application of traditional adhesives in the production of corrugated paper.

[0004] Based on this, the present invention provides an epoxy resin-based paper adhesive and a preparation method thereof to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide an epoxy resin-based paper adhesive and a preparation method thereof to solve the problems mentioned in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] The present invention provides an epoxy resin-based paper binder, which is composed of the following raw materials in parts by weight:

[0008] including an epoxy resin matrix: 40 - 55 parts, a bio-based reinforcement system: 18 - 29 parts, a recycling adaptation system: 15 - 25 parts, and a toughening system: 10 - 15 parts;

[0009] The epoxy resin matrix is composed of bisphenol A epoxy resin and epoxy soybean oil. The bisphenol A epoxy resin: 35 - 45 parts, and the epoxy soybean oil: 5 - 10 parts;

[0010] The bio-based reinforcement system is composed of sodium lignosulfonate, chitosan-nanocellulose composite, polylactic acid microspheres, and KH-560 silane coupling agent. The sodium lignosulfonate: 8 - 12 parts, the chitosan-nanocellulose composite: 5 - 8 parts, the polylactic acid microspheres: 3 - 5 parts, and the KH-560 silane coupling agent: 2 - 4 parts;

[0011] The recycling adaptation system is composed of nano-silica, zirconium phosphate nanosheets, thermosensitive polyvinyl alcohol, and ammonium persulfate-urea composite initiator. The nano-silica: 6 - 10 parts, the zirconium phosphate nanosheets: 3 - 5 parts, the thermosensitive polyvinyl alcohol: 4 - 6 parts, and the ammonium persulfate-urea composite initiator: 2 - 4 parts;

[0012] The toughening system is composed of aqueous polyurethane emulsion and sodium carboxymethyl starch. The aqueous polyurethane emulsion: 7 - 10 parts, and the sodium carboxymethyl starch: 3 - 5 parts.

[0013] Preferably, the bisphenol A epoxy resin is prepared by subjecting bisphenol A and epichlorohydrin to a condensation reaction after being catalyzed by sodium hydroxide at 60 - 80°C and then dehydrating under reduced pressure, with a purity ≥ 95%.

[0014] Preferably, the epoxy soybean oil is prepared by reacting soybean oil with peracetic acid in an acidic environment at 50 - 60°C under sulfuric acid catalysis and then neutralizing, washing, and drying, with an epoxy value ≥ 6.0%.

[0015] Preferably, the sodium lignosulfonate is prepared by acidifying paper-making black liquor with sulfuric acid to precipitate lignin, neutralizing with sodium hydroxide solution to pH 9 - 10, and spray-drying at 180 - 200°C, with a purity ≥ 90%.

[0016] Preferably, the chitosan-nanocellulose composite is prepared by dissolving chitosan in a 1% - 2% dilute acetic acid solution, stirring and mixing with a nanocellulose suspension with a mass ratio of 3:1 at pH 4 - 5, and freeze-drying in a -50°C environment, with the nanocellulose accounting for 30% - 40%.

[0017] Preferably, the polylactic acid microspheres are prepared by dissolving polylactic acid in dichloromethane to form an oil phase, emulsifying and dispersing it in a polyvinyl alcohol aqueous phase, stirring at 800 - 1000 rpm to volatilize the solvent, and then centrifuging to collect them. The particle size is 5 - 10 μm.

[0018] Preferably, the thermosensitive polyvinyl alcohol is prepared by free radical graft copolymerization of polyvinyl alcohol and N - hydroxymethylacrylamide in an aqueous solution at 70 - 80 °C, and the grafting rate is 15% - 20%.

[0019] Preferably, the ammonium persulfate - urea composite initiator is prepared by ball - milling ammonium persulfate and urea in a molar ratio of 1:1 in a dry nitrogen environment. The particle size is ≤200 mesh and the purity is ≥98%.

[0020] The present invention also provides a preparation method of an epoxy resin - based paper binder, which includes the following steps:

[0021] S1. Add 35 - 45 parts of bisphenol A epoxy resin and 5 - 10 parts of epoxy soybean oil to a planetary mixer, set the stirring speed at 200 - 400 revolutions per minute, the jacket temperature at 50 - 60 °C, and the mixing time at 20 - 30 minutes until a homogeneous transparent liquid is formed. Then, successively add 8 - 12 parts of sodium lignosulfonate, 5 - 8 parts of chitosan - nanocellulose composite, 3 - 5 parts of polylactic acid microspheres, and 2 - 4 parts of KH - 560 silane coupling agent. Increase the stirring speed to 600 - 800 revolutions per minute and continuously mix for 40 - 60 minutes. At the same time, turn on the ultrasonic disperser, set the parameters as a frequency of 20 - 40 kHz, a power of 500 - 800 W, and an intermittent operation of working for 5 minutes and stopping for 2 minutes to ensure that there is no agglomeration of nano - fillers, and achieve pre - mixing of the epoxy resin matrix and the bio - based reinforcement system;

[0022] S2. Successively add 6 - 10 parts of nano - silica, 3 - 5 parts of zirconium phosphate nanosheets, and 4 - 6 parts of thermosensitive polyvinyl alcohol to the mixed solution prepared in step S1. Start a high - shear emulsifier, set the rotation speed at 1200 - 1500 revolutions per minute, the shearing time at 30 - 40 minutes, and the temperature at 55 - 65 °C. Use 0.1 mol / L dilute hydrochloric acid or sodium hydroxide solution to adjust the pH of the system to 6.5 - 7.5 in real - time through a pH on - line monitor to avoid premature curing of the epoxy resin or degradation of the biological components, complete the main reaction mixing, and introduce the recycled adaptation system;

[0023] S3. Premix 7 - 10 parts of aqueous polyurethane emulsion and 3 - 5 parts of sodium carboxymethyl starch, and then add them to a twin - screw extruder through a side - feeding port. Set the extrusion temperature gradient in zones, the screw speed at 80 - 120 revolutions per minute, and monitor the viscosity target range of the mixed solution at 1500 - 2500 mPa·s in real - time. Control the rheological properties by adjusting the screw speed or adding deionized water. The added deionized water does not exceed 5 parts, and implement the blending of the toughening system and viscosity regulation;

[0024] S4. Dissolve 2 - 4 parts of ammonium persulfate - urea composite initiator in 5 times the mass of deionized water, and inject it into the main reaction system through an in - line static mixer with a flow rate of 10 - 15 L / min to ensure uniform dispersion. Set the pressure of the high - pressure homogenizer at 15 - 20 MPa and the temperature at 60 - 65 °C, and circulate and process 3 - 5 times to fully embed nano - silica and zirconium phosphate nanosheets into the resin network to form an intercalated structure, completing the addition of the curing agent and homogenization treatment;

[0025] S5. Transfer the mixed solution to a vacuum degassing tank, evacuate to - 0.08 to - 0.1 MPa, maintain the temperature at 50 - 55 °C, and stir and degas at a low speed at a rotation speed of 50 - 100 r / min for 30 - 40 minutes until no visible bubbles are present. After degassing, the binder is filtered through a 200 - mesh stainless - steel filter screen, filled into a light - proof and sealed container, and stored at a temperature of 10 - 25 °C and a relative humidity of ≤60%, avoiding phase separation of components caused by high temperature or freezing, completing degassing and finished product packaging.

[0026] Preferably, the extrusion temperature gradients in step S3 are respectively:

[0027] Zone 1: 50 °C, Zone 2: 60 °C, Zone 3: 65 °C, Zone 4: 70 °C.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] The present invention uses bio - based modified epoxy resin and natural polymers to partially replace petrochemical raw materials, significantly reducing the carbon footprint. At the same time, the nano - cellulose composite reinforcement technology is used to make up for the deficiency of the water resistance of biological materials. A temperature - sensitive polyvinyl alcohol and initiator system are introduced, enabling the binder to be quickly peeled off under mild conditions during recycling, completely avoiding the pollution of recycled pulp by adhesives. In addition, the intercalated structure design of nano - silica and zirconium phosphate endows the product with excellent heat - humidity resistance and high - temperature resistance, adapting to diverse application scenarios. Also, through segmented temperature control, high - shear homogenization, and low - pressure degassing technologies, the uniform dispersion and stable combination of each component are ensured, taking into account production efficiency and product consistency. Compared with traditional binders, the solution of the present invention comprehensively optimizes recyclability, environmental adaptability, and cost - effectiveness while maintaining high bond strength, providing reliable technical support for the green upgrade of the corrugated paper industry. Specific Embodiments

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] I. Materials:

[0032] The components of the paper binder formula of the present invention are all commercially available without special instructions;

[0033] The present invention provides an epoxy resin-based paper binder, which is composed of the following raw materials in parts by weight:

[0034] Including an epoxy resin matrix: 40 - 55 parts, a bio-based reinforcement system: 18 - 29 parts, a recycling adaptation system: 15 - 25 parts, and a toughening system: 10 - 15 parts;

[0035] Among them, the epoxy resin matrix is composed of bisphenol A epoxy resin and epoxy soybean oil. The bisphenol A epoxy resin: 35 - 45 parts, and the epoxy soybean oil: 5 - 10 parts;

[0036] Among them, the bio-based reinforcement system is composed of sodium lignosulfonate, chitosan-nanocellulose composite, polylactic acid microspheres, and KH-560 silane coupling agent. The sodium lignosulfonate: 8 - 12 parts, the chitosan-nanocellulose composite: 5 - 8 parts, the polylactic acid microspheres: 3 - 5 parts, and the KH-560 silane coupling agent: 2 - 4 parts;

[0037] Among them, the recycling adaptation system is composed of nano-silica, zirconium phosphate nanosheets, temperature-sensitive polyvinyl alcohol, and ammonium persulfate-urea composite initiator. The nano-silica: 6 - 10 parts, the zirconium phosphate nanosheets: 3 - 5 parts, the temperature-sensitive polyvinyl alcohol: 4 - 6 parts, and the ammonium persulfate-urea composite initiator: 2 - 4 parts;

[0038] Among them, the toughening system is composed of aqueous polyurethane emulsion and sodium carboxymethyl starch. The aqueous polyurethane emulsion: 7 - 10 parts, and the sodium carboxymethyl starch: 3 - 5 parts.

[0039] It should also be noted that bisphenol A epoxy resin is prepared by subjecting bisphenol A and epichlorohydrin to a condensation reaction under the catalysis of sodium hydroxide at 60 - 80°C and then dehydrating under reduced pressure. The purity is ≥95%.

[0040] It should also be noted that epoxy soybean oil is prepared by subjecting soybean oil and peracetic acid to sulfuric acid catalysis in an acidic environment at 50 - 60°C and then neutralizing, washing, and drying. The epoxy value is ≥6.0%.

[0041] It should also be noted that sodium lignosulfonate is prepared by acidifying paper-making black liquor with sulfuric acid to precipitate lignin, neutralizing with sodium hydroxide solution to pH 9 - 10, and spray-drying at 180 - 200°C. The purity is ≥90%.

[0042] It should also be noted that the chitosan-nanocellulose composite is prepared by dissolving chitosan in a 1%-2% dilute acetic acid solution, stirring and mixing it with a nanocellulose suspension with a mass ratio of 3:1 at pH 4-5, and freeze-drying in an environment of -50°C. The proportion of nanocellulose is 30%-40%.

[0043] It should also be noted that the polylactic acid microspheres are prepared by dissolving polylactic acid in dichloromethane to form an oil phase, emulsifying and dispersing it in a polyvinyl alcohol aqueous phase, centrifuging and collecting it after stirring and volatilizing the solvent at 800-1000 rpm. The particle size is 5-10 μm.

[0044] It should also be noted that the temperature-sensitive polyvinyl alcohol is prepared by free radical graft copolymerization of polyvinyl alcohol and N-hydroxymethylacrylamide in an aqueous solution at 70-80°C, and the grafting rate is 15%-20%.

[0045] It should also be noted that the ammonium persulfate-urea composite initiator is prepared by ball milling and mixing ammonium persulfate and urea in a molar ratio of 1:1 in a dry nitrogen environment. The particle size is ≤200 mesh and the purity is ≥98%.

[0046] The present invention also proposes a preparation method of an epoxy resin-based paper binder, including the following steps:

[0047] S1. Add 35-45 parts of bisphenol A epoxy resin and 5-10 parts of epoxy soybean oil to a planetary mixer, set the stirring speed at 200-400 revolutions per minute, the jacket temperature at 50-60°C, and the mixing time at 20-30 minutes until a homogeneous transparent liquid is formed. Then, sequentially add 8-12 parts of sodium lignosulfonate, 5-8 parts of chitosan-nanocellulose composite, 3-5 parts of polylactic acid microspheres, and 2-4 parts of KH-560 silane coupling agent. Increase the stirring speed to 600-800 revolutions per minute and continuously mix for 40-60 minutes. At the same time, turn on the ultrasonic disperser, set the parameters as a frequency of 20-40 kHz, a power of 500-800 W, and an intermittent operation of working for 5 minutes and stopping for 2 minutes to ensure that there is no agglomeration of nano-fillers, so as to achieve the pre-mixing of the epoxy resin matrix and the bio-based reinforcement system;

[0048] S2. Sequentially add 6-10 parts of nano-silica, 3-5 parts of zirconium phosphate nanosheets, and 4-6 parts of temperature-sensitive polyvinyl alcohol to the mixed solution prepared in step S1. Start a high-shear emulsifier, set the rotation speed at 1200-1500 revolutions per minute, the shearing time at 30-40 minutes, and the temperature at 55-65°C. Use a 0.1 mol / L dilute hydrochloric acid or sodium hydroxide solution to adjust the pH of the system to 6.5-7.5 in real time through a pH on-line monitor to avoid premature curing of the epoxy resin or degradation of the biological components, complete the main reaction mixing, and introduce the recycled adaptation system;

[0049] S3. Premix 7 - 10 parts of aqueous polyurethane emulsion with 3 - 5 parts of sodium carboxymethyl starch, and then add them into a twin - screw extruder through the side - feeding port. Set the extrusion temperature gradient in zones, with the screw speed at 80 - 120 revolutions per minute. Real - time monitor the target viscosity range of the mixed liquid at 1500 - 2500 mPa·s. Control the rheological properties by adjusting the screw speed or adding deionized water. The added deionized water does not exceed 5 parts, and implement toughening system blending and viscosity regulation;

[0050] S4. Dissolve 2 - 4 parts of ammonium persulfate - urea composite initiator in 5 times the mass of deionized water, and inject it into the main reaction system through an online static mixer with a flow rate of 10 - 15 L / min to ensure uniform dispersion. Set the pressure of the high - pressure homogenizer at 15 - 20 MPa and the temperature at 60 - 65 °C, and cycle and process 3 - 5 times to fully embed nano - silica and zirconium phosphate nanosheets into the resin network to form an intercalated structure, and complete the addition of the curing agent and homogenization treatment;

[0051] S5. Transfer the mixed liquid to a vacuum degassing tank, evacuate to - 0.08 to - 0.1 MPa, maintain the temperature at 50 - 55 °C, and stir and degas at a low speed at a rotation speed of 50 - 100 revolutions per minute for 30 - 40 minutes until no visible bubbles are present. After degassing, the binder is filtered through a 200 - mesh stainless - steel filter screen, filled into a light - proof and sealed container, and stored at a temperature of 10 - 25 °C and a relative humidity of ≤60%, to avoid component phase separation caused by high temperature or freezing, and complete degassing and finished product packaging.

[0052] It should also be noted that the extrusion temperature gradients in step S3 are as follows:

[0053] Zone 1: 50 °C, Zone 2: 60 °C, Zone 3: 65 °C, Zone 4: 70 °C.

[0054] Example 1. In this example, a preparation method of an epoxy - resin - based paper binder includes the following steps:

[0055] S1. Add 40 parts of bisphenol A epoxy resin and 8 parts of epoxy soybean oil into a planetary mixer, set the rotation speed at 200 revolutions per minute, mix for 25 minutes until it becomes a transparent liquid, and then add 10 parts of sodium lignosulfonate, 6 parts of chitosan - nanocellulose composite, 4 parts of polylactic acid microspheres, and 3 parts of KH - 560 silane coupling agent in sequence. Increase the rotation speed to 600 revolutions per minute, mix for 50 minutes, and simultaneously turn on the ultrasonic disperser, operating intermittently;

[0056] S2. Add 8 parts of nano - silica, 4 parts of zirconium phosphate nanosheets, and 5 parts of thermosensitive polyvinyl alcohol, start the high - shear emulsifier, shear for 35 minutes, and adjust the pH to 7.0 with 0.1 mol / L dilute hydrochloric acid;

[0057] S3. Premix 8 parts of aqueous polyurethane emulsion with 4 parts of sodium carboxymethyl starch, and then add them into the extruder through the side feeding port, and monitor the viscosity in real time until it reaches 2000 mPa·s;

[0058] S4. Dissolve 3 parts of ammonium persulfate-urea composite initiator in 15 parts of water, inject it into the system at a flow rate of 12 L / min, set the pressure of the high-pressure homogenizer to 18 MPa, and perform cyclic treatment 4 times;

[0059] S5. Defoam for 35 minutes, filter and then fill;

[0060] Example 2: In this example, bisphenol A epoxy resin: 45 parts; epoxy soybean oil: 5 parts; other components and processes are the same as those in Example 1;

[0061] Example 3: In this example, sodium lignosulfonate: 12 parts; chitosan-nanocellulose composite: 5 parts; polylactic acid microspheres: 3 parts; KH-560 silane coupling agent: 4 parts; the mixing speed in step S1 is 800 rpm; the shearing temperature in step S2 is 60 °C; the extrusion temperature gradients in step S3 are 50 °C, 60 °C, 65 °C, and 70 °C respectively; other components and processes are the same as those in Example 1;

[0062] Example 4: In this example, nano-silica: 6 parts; zirconium phosphate nanosheets: 5 parts; temperature-sensitive polyvinyl alcohol: 4 parts; ammonium persulfate-urea composite initiator: 4 parts; the mixing speed in step S1 is 600 rpm; the shearing temperature in step S2 is 65 °C; the extrusion temperature gradients in step S3 are 50 °C, 60 °C, 65 °C, and 70 °C respectively; other components and processes are the same as those in Example 1;

[0063] Example 5: In this example, aqueous polyurethane emulsion: 10 parts; sodium carboxymethyl starch: 3 parts; other components and processes are the same as those in Example 1.

[0064] The components and process parameters of Examples 1-5 are shown in Table 1:

[0065] Table 1 Component and process parameter table of Examples 1-5

[0066]

[0067]

[0068]

[0069] Prepare paper binders according to the components and process parameters of Examples 1-5, and conduct performance tests on the prepared paper binders, including bonding strength, water resistance, recycling peel rate, thermal stability and cost:

[0070] a. Bond strength test standard: Modified with reference to GB / T6548-2011 "Test Method for Edgewise Compressive Strength of Corrugated Fiberboard" and ASTM D828 "Standard Test Method for Tensile Strength of Paper and Paperboard";

[0071] The test method includes the following steps:

[0072] Sample preparation: Coat the adhesive between the corrugated paper core and the face paper (coating amount 20±2 g / m 2 ), and make a standard specimen (size 25mm×100mm) by hot pressing at 80°C for 5 minutes;

[0073] Test conditions: Use a universal material testing machine (Instron 3365), tensile speed 50mm / min, and fixture spacing 50mm;

[0074] Calculation method: Divide the peak force value (N) by the bonding surface width (m), that is:

[0075] Bond strength = F_max / W (N / m);

[0076] b. Water resistance test standard: Adjusted according to GB / T1034-2008 "Determination of Water Absorption of Plastics" and ISO 287:2017 "Determination of Moisture Content in Paper and Board";

[0077] The test method includes the following steps:

[0078] Sample treatment: Dry the bonded paper sample (50mm×50mm) to a constant weight (in an oven at 105°C for 2h), and weigh (m0);

[0079] Immersion conditions: Immerse in distilled water at 23±1°C for 24 hours, take out and dry the surface moisture with filter paper, and weigh immediately (m1);

[0080] Calculation method: Water absorption rate = [(m1 - m0) / m0]×100%;

[0081] c. Recycling peel rate test standard: Refer to TAPPIT 275sp-02 "Determination of Adhesives in Recycled Pulp" and the in-house method of the laboratory;

[0082] The test method includes the following steps:

[0083] Simulated recycling: Crush the bonded paper sample into 2cm×2cm fragments, soak in hot water at 60°C (pH 7) with a pulp consistency of 10% for 30 minutes, and mechanically stir (500 rpm) for 10 minutes;

[0084] Separation and detection: Sieve the pulp (pore size 0.15mm), collect the unpeeled adhesives on the sieve and dry and weigh (m2);

[0085] Calculation method: Stripping rate = [1 - (m2 / m0)] × 100%, where m0 is the mass of the original binder;

[0086] d. Thermal stability (°C)

[0087] Test standard: According to ISO11358-1:2014 "General Principles of Thermogravimetric Analysis (TGA) for Plastics";

[0088] The test method includes the following steps:

[0089] Instrument parameters: Thermogravimetric analyzer (TA Q50), nitrogen atmosphere (flow rate 50 mL / min), heating rate 10 °C / min, temperature range 30 - 600 °C;

[0090] Judgment index: Take the temperature (T5%) corresponding to a 5% weight loss in the thermogravimetric curve as the thermal stability threshold;

[0091] e. Cost calculation standard: Based on the "Chemical Raw Material Market Price Database" and the energy consumption accounting of the production process;

[0092] Raw material cost: According to the mass fraction ratio of the formula components, combined with the market price for weighted summation;

[0093] Energy consumption cost: Includes the electricity consumption (calculated at 0.8 yuan / kWh) and equipment depreciation allocation for the mixing, shearing, and extrusion processes;

[0094] Total cost: Raw material cost + energy consumption cost + labor cost (at 5 yuan / kg);

[0095] The test data of the paper binder prepared according to the components and process parameters of Examples 1 - 5 are shown in Table 2:

[0096] Table 2 Performance data of the paper binder prepared according to the components and process parameters of Examples 1 - 5

[0097] Performance indicators Example 1 Example 2 Example 3 Example 4 Example 5 Bonding strength (N / m) 420 450 390 410 430 Water resistance (24h water absorption rate %) 1.2 1.8 1.5 1.3 1.4 Recovery peel rate (%) 92 88 85 90 89 Thermal stability (°C) 220 210 215 225 218 Cost (yuan / kg) 25.5 27.2 26.8 26.0 28.1

[0098] To verify the rationality of the paper binder formula range set in the above Examples 1 - 5, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were designed for verification;

[0099] Comparative Example 1: In this comparative example, 50 parts of bisphenol A epoxy resin, and the other components and processes are the same as those in Example 1;

[0100] Comparative Example 2: In this comparative example, 3 parts of chitosan-nanocellulose composite, and the other components and processes are the same as those in Example 1;

[0101] Comparative Example 3: In this comparative example, there is no thermosensitive polyvinyl alcohol, and the other components and processes are the same as those in Example 1;

[0102] The test data of preparing the paper binder according to the components and process parameters of Comparative Examples 1-3 are shown in Table 3:

[0103] Table 3 Performance data of the paper binder prepared according to the components and process parameters of Comparative Examples 1-3

[0104] Performance indicators Comparative example 1 Comparative example 2 Comparative example 3 Bonding strength (N / m) 380 360 300 Water resistance (24h water absorption rate %) 3.5 4.2 5.8 Recovery peel rate (%) 70 65 40 Thermal stability (°C) 180 170 160 Cost (yuan / kg) 22.0 20.5 18.0

[0105] As can be seen from Table 3, 50 parts of bisphenol A epoxy resin in Comparative Example 1 exceeded the range, resulting in excessive resin crosslinking and poor flexibility. In Comparative Example 2, 3 parts of chitosan-nanocellulose composite had insufficient bio-based reinforcement, and the bonding strength was only 360 N / m with poor water resistance. In Comparative Example 3, the recovery peeling rate of the thermosensitive polyvinyl alcohol dropped sharply to 40%, which could not meet the environmental protection requirements. Therefore, the paper binders prepared by the formulations and processes of Examples 1 to 5 of the present invention are all within the qualified range.

[0106] Combining Table 1 and Table 2 for data analysis of Examples 1 to 5 of the present invention, it can be seen that increasing the proportion of bisphenol A epoxy resin in Example 2 improved the bonding strength, but the water resistance decreased and the cost increased. In Example 3, adding sodium lignosulfonate reduced the recovery peeling rate to 85% because the water absorption of lignin increased. In Example 4, increasing the zirconium phosphate nanosheets to 5 parts had the best thermal stability, but the shear temperature increased to 65 °C, slightly affecting the bonding strength. In Example 5, adjusting the toughening system significantly increased the cost and the comprehensive cost performance was low. While in Example 1, the bonding strength was 420 N / m, the water resistance was 1.2%, the recovery peeling rate was 92%, and the thermal stability was 220 °C. The comprehensive index was the best, 25.5 yuan / kg, lower than that of Examples 2 to 5, and the process parameters strictly matched the component synergistic effect, with the whole process temperature fluctuation ≤ ±1 °C and the shear energy input of 6.5 kW·h / t, avoiding material denaturation.

[0107] In summary, Example 1 of the present invention realizes the best balance of high strength, recyclability and low cost of the binder through the optimization of the component range and the precise control of the process parameters, and adapts to the industrial production requirements of corrugated paper.

[0108] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0109] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. An epoxy resin-based paper binder, characterized in that, It is composed of the following raw materials in parts by weight: Including epoxy resin matrix: 40 - 55 parts, bio-based reinforcement system: 18 - 29 parts, recycling adaptation system: 15 - 25 parts, toughening system: 10 - 15 parts; The epoxy resin matrix is composed of bisphenol A epoxy resin and epoxy soybean oil. The bisphenol A epoxy resin: 35 - 45 parts, and the epoxy soybean oil: 5 - 10 parts; The bio-based reinforcement system is composed of sodium lignosulfonate, chitosan-nanocellulose composite, polylactic acid microspheres and KH-560 silane coupling agent. The sodium lignosulfonate: 8 - 12 parts, chitosan-nanocellulose composite: 5 - 8 parts, polylactic acid microspheres: 3 - 5 parts, KH-560 silane coupling agent: 2 - 4 parts; The recycling adaptation system is composed of nano-silica, zirconium phosphate nanosheets, thermosensitive polyvinyl alcohol and ammonium persulfate-urea composite initiator. The nano-silica: 6 - 10 parts, the zirconium phosphate nanosheets: 3 - 5 parts, the thermosensitive polyvinyl alcohol: 4 - 6 parts, the ammonium persulfate-urea composite initiator: 2 - 4 parts; The toughening system is composed of aqueous polyurethane emulsion and sodium carboxymethyl starch. The aqueous polyurethane emulsion: 7 - 10 parts, and the sodium carboxymethyl starch: 3 - 5 parts.

2. The paper binder based on epoxy resin according to claim 1, characterized in that, The bisphenol A epoxy resin is prepared by reacting bisphenol A with epichlorohydrin under the catalysis of sodium hydroxide at 60 - 80 °C, followed by polycondensation reaction and then vacuum dehydration.

3. The paper binder based on epoxy resin according to claim 2, wherein, The epoxy soybean oil is prepared by reacting soybean oil with peracetic acid in an acidic environment at 50 - 60 °C under the catalysis of sulfuric acid, followed by neutralization, washing with water.

4. The paper binder based on epoxy resin according to claim 3, characterized in that, The sodium lignosulfonate is prepared by acidifying the paper-making black liquor with sulfuric acid to precipitate lignin, and then neutralizing it with sodium hydroxide solution to pH 9 - 10, and spray drying at 180 - 200 °C.

5. The paper binder based on epoxy resin according to claim 4, characterized in that, The chitosan-nanocellulose composite is prepared by dissolving chitosan in 1% - 2% dilute acetic acid solution, stirring and mixing it with a nanocellulose suspension with a mass ratio of 3:1 at pH 4 - 5, and freeze-drying in a -50 °C environment.

6. The paper binder based on epoxy resin according to claim 5, characterized in that, The polylactic acid microspheres are prepared by dissolving polylactic acid in dichloromethane to form an oil phase, emulsifying and dispersing it in a polyvinyl alcohol aqueous phase, stirring at 800 - 1000 rpm to volatilize the solvent, and then centrifuging and collecting them with a particle size of 5 - 10 μm.

7. A paper binder based on epoxy resin according to claim 6, characterized in that, The thermosensitive polyvinyl alcohol is prepared by free radical graft copolymerization of polyvinyl alcohol and N-hydroxymethylacrylamide in an aqueous solution at 70 - 80 °C.

8. The paper binder based on epoxy resin according to claim 7, characterized in that, The ammonium persulfate-urea composite initiator is prepared by ball milling ammonium persulfate and urea in a molar ratio of 1:1 in a dry nitrogen environment.

9. The preparation method of an epoxy resin-based paper binder according to any one of claims 1 to 8, characterized in that, Including the following steps: S1. Add 35 - 45 parts of bisphenol A epoxy resin and 5 - 10 parts of epoxy soybean oil into a planetary mixer. Set the stirring speed at 200 - 400 revolutions per minute, the jacket temperature at 50 - 60 °C, and the mixing time at 20 - 30 minutes until a homogeneous and transparent liquid is formed. Then, sequentially add 8 - 12 parts of sodium lignosulfonate, 5 - 8 parts of chitosan - nanocellulose composite, 3 - 5 parts of polylactic acid microspheres, and 2 - 4 parts of KH - 560 silane coupling agent. Increase the stirring speed to 600 - 800 revolutions per minute and continuously mix for 40 - 60 minutes. Simultaneously, turn on the ultrasonic disperser with the set parameters of frequency 20 - 40 kHz and power 500 - 800 W, operating in an intermittent mode of working for 5 minutes and stopping for 2 minutes to ensure that there is no agglomeration of nano - fillers, achieving a pre - mixed epoxy resin matrix and bio - based reinforcement system; S2. Sequentially add 6 - 10 parts of nano - silica, 3 - 5 parts of zirconium phosphate nanosheets, and 4 - 6 parts of thermosensitive polyvinyl alcohol into the mixed solution prepared in step S1. Start the high - shear emulsifier, set the rotation speed at 1200 - 1500 revolutions per minute, the shearing time at 30 - 40 minutes, and control the temperature at 55 - 65 °C. Use 0.1 mol / L dilute hydrochloric acid or sodium hydroxide solution to adjust the pH of the system to 6.5 - 7.5 in real - time through a pH on - line monitor to avoid premature curing of epoxy resin or degradation of biological components, complete the main reaction mixing, and introduce the recycled adaptation system; S3. Premix 7 - 10 parts of aqueous polyurethane emulsion and 3 - 5 parts of sodium carboxymethyl starch, and then add them into a twin - screw extruder through the side - feeding port. Set the extrusion temperature gradient in zones, the screw speed at 80 - 120 revolutions per minute, and continuously monitor the target viscosity range of the mixed solution at 1500 - 2500 mPa·s. Control the rheological properties by adjusting the screw speed or adding deionized water. The added deionized water does not exceed 5 parts, and implement the blending of the toughening system and viscosity regulation; S4. Dissolve 2 - 4 parts of ammonium persulfate - urea composite initiator in 5 times the mass of deionized water, and inject it into the main reaction system through an on - line static mixer with a flow rate of 10 - 15 L / min to ensure uniform dispersion. Set the pressure of the high - pressure homogenizer at 15 - 20 MPa and the temperature at 60 - 65 °C, and cycle and process 3 - 5 times to make the nano - silica and zirconium phosphate nanosheets fully embed in the resin network to form an intercalated structure, completing the addition of the curing agent and homogenization treatment; S5. Transfer the mixed solution to a vacuum degassing tank, evacuate to - 0.08 to - 0.1 MPa, maintain the temperature at 50 - 55 °C, and stir and degas at a low speed at 50 - 100 revolutions per minute for 30 - 40 minutes until no visible bubbles are present. After degassing, the binder is filtered through a 200 - mesh stainless - steel filter screen, filled into a light - proof and sealed container, and stored at a temperature of 10 - 25 °C and a relative humidity of ≤60%, avoiding phase separation of components caused by high temperature or freezing, and completing degassing and finished product packaging.

10. The preparation method of an epoxy resin-based paper binder according to claim 9, characterized in that, In step S3, the extrusion temperature gradient is as follows: Zone 1: 50 °C, Zone 2: 60 °C, Zone 3: 65 °C, Zone 4: 70 °C.

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