Water-based bio-based waterproof and oil-proof barrier coating emulsion for pulp molding or paper products and preparation method of water-based bio-based waterproof and oil-proof barrier coating emulsion

Abstract

The invention discloses a water-based bio-based waterproof and oil-proof barrier coating emulsion for pulp molding or paper products and a preparation method thereof, and belongs to the technical field of environment-friendly packaging materials. The invention aims to solve the technical problems of toxicity, non-degradability, low bio-based content, poor water resistance, poor oil-proof performance and poor film-forming property of the existing paper pulp molded product coating. The coating emulsion disclosed by the invention is prepared from a non-grain-sourced bio-based emulsion, a nano modifier, a bio-based emulsifier, a bio-based wetting agent and water. The preparation method comprises the following steps: extracting and emulsifying from a non-grain source, and then sequentially adding the nano modifier, the bio-based emulsifier, the water and the bio-based wetting agent. The prepared coating emulsion endows a paper pulp molded product with excellent waterproof, oil-proof, barrier and degradable properties through bio-based material compounding, a nano-modification technology and an emulsification technology, can replace a traditional fluorine-containing coating and a petroleum-based plastic spraying film, and is widely applied to the fields of paper-plastic tableware, take-out boxes, paper-based food packaging and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental protection packaging materials, and particularly relates to a water-based bio-based waterproof and oil-proof barrier coating emulsion for pulp molding or paper products and a preparation method thereof. BACKGROUND

[0002] Pulp molding products are widely used in many fields such as catering, industrial packaging, agriculture, and medical treatment. In the field of catering, pulp molding tableware gradually replaces disposable plastic tableware. In the field of industrial packaging, pulp molding products are used as cushioning packaging materials to effectively protect precision devices and fragile products. In the field of agriculture, pulp molding products are used as fruit trays and vegetable trays. In the field of medical treatment, pulp molding products are used to make disposable medical bedpans.

[0003] Pulp molding products are made of plant fibers (such as bamboo pulp and sugarcane residue) and have the advantages of biodegradability and renewability. However, the porous fiber structure of pulp molding products can easily absorb liquid and oil, and therefore, a surface coating is needed to achieve barrier function. Current mainstream technologies include: 1. Fluorine-containing coating: a low-surface-energy layer is formed by a fluorocarbon chain, which has significant waterproof and oil-proof effects, but has environmental toxicity (bioaccumulation and carcinogenic risk), which has been gradually banned in the European Union. 2. Petroleum-based plastic film coating (such as PE and PP): barrier performance is achieved by hot pressing and film coating, but it is not biodegradable, which conflicts with the environmental properties of pulp molding. 3. Traditional bio-based coating (such as starch and cellulose-based): although it is environmentally friendly, it has the following defects: a certain amount of petroleum-based material is added to achieve better performance, the bio-based content is low; poor water resistance: swelling and coating falling off when exposed to water; insufficient oil-proof performance: oil can easily penetrate, especially poor high-temperature oil resistance; poor film-forming property: it is difficult to cover the rough and porous surface of pulp molding products, which can cause defects and result in a lack of barrier performance. SUMMARY

[0004] The present application is to solve the technical problems of toxicity, non-degradability, low bio-based content, poor water resistance, poor oil-proof performance, and poor film-forming property of existing pulp molding product coatings, and to provide a water-based bio-based waterproof and oil-proof barrier coating emulsion for pulp molding or paper products and a preparation method thereof.

[0005] The water-based bio-based waterproof and oil-proof barrier coating emulsion for pulp molding or paper products according to the present application is composed of 40% to 60% of non-food source bio-based emulsion, 30% to 50% of nano-modifier, 1% to 5% of bio-based emulsifier, 0.5% to 1% of bio-based wetting agent, and the balance of water.

[0006] Preferably, the non-food source bio-based emulsion is obtained by extracting and emulsifying non-food source bio-based materials.

[0007] Preferably, the non-food source bio-based material is agricultural and forestry waste, non-food plants, algae, and microbial fermentation products.

[0008] Preferably, the nano-modifier is composed of 30% to 50% nano-silicon dioxide, 20% to 40% polydimethylsiloxane, and 20% to 30% nano-silicon carbide by mass fraction, which builds a micro-nano rough structure, enhances the "lotus effect" hydrophobic effect, wear resistance, and filling effect to enhance adhesion.

[0009] Preferably, the bio-based emulsifier is alkyl polyglycoside or lecithin, which improves the storage stability of the system.

[0010] Preferably, the bio-based wetting agent is sorbitol ester or sophorolipid, which improves the spreading property of the coating on pulp molding or paper-based surfaces.

[0011] The preparation method of the water-based bio-based waterproof and oil-proof barrier coating emulsion for pulp molding or paper products of the present application is as follows:

[0012] I. Extraction and emulsification from non-food sources:

[0013] ①, raw material pretreatment: the non-food source bio-based material is physically crushed, then a eutectic solvent is added, and the temperature is kept at 60℃ to 100℃ for 20 minutes, and then it is cooled to room temperature;

[0014] ②, directional enzymolysis: a composite cellulase is added to the system at the end of ① to degrade cellulose into nano-cellulose and soluble sugar; the temperature is 40℃ to 50℃, the time is 48h, and the stirring speed is 400r / min; the composite cellulase accounts for 0.5% to 3% of the mass of the system at the end of ①;

[0015] ③, hydrophobic modification of nano-cellulose: a hydrophobic group is introduced into the system at the end of ② to improve its interfacial activity, and a bio-based hydrophobic active ingredient is obtained; the hydrophobic group is an acetyl group;

[0016] ④, emulsion preparation: the oil phase is the bio-based hydrophobic active ingredient prepared in ③ above, the water phase is a CNF dispersion liquid, an emulsifier is added, and high-speed stirring is performed to form a non-food source bio-based emulsion;

[0017] The mass ratio of the water phase and the oil phase is 7:3, and the emulsifier addition amount is 1% to 3%;

[0018] II. Nano-modifier is added to the non-food source bio-based emulsion prepared in step I, and stirring is performed at a speed of 500 to 700rpm for 10 to 20 minutes to obtain a master emulsion;

[0019] The nano modifier is mixed by 30-50% nano silicon dioxide, 20-40% polydimethylsiloxane and 20-30% nano silicon carbide according to mass fraction;

[0020] III. Slowly add the bio-based emulsifier in the main emulsion prepared in step II, emulsify at a speed of 2000-3000 rpm for 20-30 min to form a stable emulsion;

[0021] IV. Add water and bio-based wetting agent in the stable emulsion of step III, stir at a speed of 500-700 rpm for 20-30 min to obtain a coating emulsion;

[0022] The coating emulsion comprises 40-60% non-grain source bio-based emulsion, 30-50% nano modifier, 1-5% bio-based emulsifier, 0.5-1% bio-based wetting agent and the balance of water according to mass fraction.

[0023] The coating emulsion prepared by the application is applied to the spraying and spin coating process in the pulp molding sizing process, the spin coating process parameters can be adjusted, the initial speed is 100-400 rpm, the high speed is 500-1000 rpm, and then low-temperature curing is carried out: the drying temperature is ≤80℃, the existing equipment of the pulp molding production line is adapted, and the deformation of the substrate caused by high temperature is avoided.

[0024] The coating emulsion prepared by the application is prepared by compounding bio-based materials, nano modification technology and emulsification technology, and has excellent waterproof, oil-proof, barrier and degradable properties, can replace traditional fluorine-containing coating and petroleum-based plastic film, and is widely applied to the fields of paper and plastic tableware, take-out boxes and paper-based food packaging.

[0025] The nano modifier added in step II of the application adopts the lotus leaf structure biomimetic concept, constructs the nano modifier of nano SiO2 / polydimethylsiloxane / nano silicon carbide, organically combines the low surface energy of polysiloxane polymer, the dense structure of the composite coating, the nano-scale papillary low contact surface structure formed by SiO2 and the high hardness and high wear resistance of nano silicon carbide, and realizes the unity of high hydrophobic oil-proof property, wear resistance and high temperature resistance through synergistic effect.

[0026] The coating emulsion prepared by the application has the following beneficial effects:

[0027] 1. Environmental protection: the main emulsion is a natural non-grain source plant-based material, does not depend on food crops as raw materials, avoids competition with people for food, reduces land pressure, and the non-grain source is more in line with the sustainable development direction; the total bio-based content is zero VOC emission, can be completely degraded (180-day degradation rate ≥90%), and can replace fluorine-containing coating to avoid the pollution risk of "permanent chemicals";

[0028] 2. Performance improvement:

[0029] High barrier to hot water (100℃, 30min no penetration point) and hot oil (120℃, 30min no penetration point), Kit value up to 12; wide temperature resistance range (-30~130℃), suitable for cold storage and hot drink packaging, high temperature sterilization demand; good heat sealing performance, while achieving water and oil resistance barrier properties; meet the requirements of anti-back sticking; resistant to alcohol, good acid and alkali resistance;

[0030] 3. Process adaptability: adapt to existing pulp molding production line, low temperature curing (≤80℃), reduce energy consumption; process compatible with existing coating equipment, no need to add large investment; production cost is reduced by 30-40% compared with similar bio-based coating. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The photo of the product bottom under hot oil test in Test One;

[0032] Figure 2 The photo of the product front under hot oil test in Test One;

[0033] Figure 3 The photo of the product front under hot water test in Test One. DETAILED DESCRIPTION

[0034] Embodiment One: The embodiment is a water-based bio-based water and oil resistant barrier coating emulsion for pulp molding or paper products, which is composed of non-food source bio-based emulsion 40%~60%, nano modifier 30%~50%, bio-based emulsifier 1%~5%, bio-based wetting agent 0.5%~1%, and the balance of water, by mass fraction.

[0035] Embodiment Two: The difference between this embodiment and Embodiment One is that the non-food source bio-based emulsion is obtained by extracting and emulsifying non-food source bio-based materials.

[0036] Embodiment Three: The difference between this embodiment and Embodiment Two is that the non-food source bio-based material is agricultural and forestry waste, non-food plants, algae, and microbial fermentation products. Other aspects are the same as Embodiment Two.

[0037] Embodiment Four: The difference between this embodiment and Embodiment One is that the nano modifier is composed of 30%~50% nano silicon dioxide, 20%~40% polydimethylsiloxane, and 20%~30% nano silicon carbide, by mass fraction. Other aspects are the same as Embodiment One.

[0038] Embodiment five: this embodiment is different from embodiment one in that the bio-based emulsifier is alkyl polyglycoside or lecithin. Other aspects are the same as embodiment one.

[0039] Embodiment six: this embodiment is different from embodiment one in that the bio-based wetting agent is sorbitol ester or sophorolipid. Other aspects are the same as embodiment one.

[0040] Embodiment seven: this embodiment is a method for preparing a water-based bio-based emulsion for a waterproof and oil-proof barrier coating of pulp molding or paper products in embodiment one, and the specific process is as follows:

[0041] I. Extraction and emulsification from non-food sources:

[0042] ①, raw material pretreatment: the non-food source bio-based material is physically crushed, then a eutectic solvent is added, and the temperature is kept at 60-100°C for 20 min, and then cooled to room temperature;

[0043] ②, directional enzymatic hydrolysis: a complex cellulase is added to the system at the end of ① to degrade cellulose into nanocellulose and soluble sugar; the temperature is 40-50°C, the time is 48h, and the stirring speed is 400r / min; the complex cellulase accounts for 0.5-3% of the mass of the system at the end of ①;

[0044] ③, hydrophobic modification of nanocellulose: introduce a hydrophobic group into the system at the end of ② to improve its interfacial activity and obtain a bio-based hydrophobic active ingredient; the hydrophobic group is acetyl;

[0045] ④, emulsion preparation: the oil phase is the bio-based hydrophobic active ingredient prepared in ③ above, the water phase is a CNF dispersion liquid, an emulsifier is added, and high-speed stirring is performed to form a non-food source bio-based emulsion;

[0046] The mass ratio of the water phase and the oil phase is 7:3, and the amount of emulsifier added is 1-3%;

[0047] II. Add a nanometer modifier to the non-food source bio-based emulsion prepared in step I and stir at a speed of 500-700 rpm for 10-20 min to obtain a main emulsion;

[0048] The nanometer modifier is a mixture of 30-50% nanometer silicon dioxide, 20-40% polydimethylsiloxane, and 20-30% nanometer silicon carbide according to mass fraction;

[0049] III. Slowly add a bio-based emulsifier to the main emulsion prepared in step II and emulsify at a speed of 2000-3000 rpm for 20-30 min to form a stable emulsion;

[0050] Four, adding water and bio-based wetting agent in the stable emulsion of step three, stirring at 500-700 rpm for 20-30 min to obtain a coating emulsion;

[0051] The coating emulsion consists of 40-60% bio-based emulsion from non-food sources, 30-50% nano-modifier, 1-5% bio-based emulsifier, 0.5-1% bio-based wetting agent, and the balance of water.

[0052] Specific embodiment eight: this embodiment is different from specific embodiment seven in that the eutectic solvent in step one ① is composed of choline chloride and urea in a molar ratio of 1:2. The others are the same as specific embodiment seven.

[0053] Specific embodiment nine: this embodiment is different from specific embodiment eight in that the composite cellulase in step one ② consists of 40-50% endo-enzyme and 50-60% exo-enzyme by mass fraction. The others are the same as specific embodiment eight.

[0054] Specific embodiment ten: this embodiment is different from specific embodiment nine in that the acetyl group source in step one ③ is acetic anhydride, acetic acid or long-chain alkyl. The others are the same as specific embodiment nine.

[0055] The following tests are used to verify the present application:

[0056] Test one: this test is a preparation method of a water-based bio-based waterproof and oil-proof barrier coating emulsion for pulp molding or paper products, the specific process is as follows:

[0057] I. Extraction and emulsification from non-food sources:

[0058] ①, raw material pretreatment: the non-food source bio-based material palm is physically crushed, then low eutectic solvent is added, and the temperature is kept at 80℃ for 20min, and then it is cooled to room temperature; the eutectic solvent is composed of choline chloride and urea in a molar ratio of 1:2;

[0059] ②, directional enzymolysis: adding composite cellulase to the system at the end of ① to degrade cellulose into nanocellulose and soluble sugar; the temperature is 50℃, the time is 48h, and the stirring speed is 400r / min; the composite cellulase accounts for 1% of the mass of the system at the end of ①; the composite cellulase consists of 45% endo-enzyme and 55% exo-enzyme by mass fraction;

[0060] ③, nanocellulose hydrophobic modification: introducing hydrophobic groups into the system at the end of ② to improve its interfacial activity and obtain bio-based hydrophobic active ingredients; the hydrophobic group is acetyl group, the source is acetic anhydride, and the addition amount is 20%.

[0061] IV. Emulsion preparation: the oil phase is the bio-based hydrophobic active ingredient prepared in III above, the water phase is a CNF dispersion (mass fraction of 30%), an emulsifier (soy lecithin) is added, and high-speed stirring is performed to form a non-grain source bio-based emulsion;

[0062] The mass ratio of the water phase and the oil phase is 7:3, and the amount of the emulsifier added is 2%;

[0063] II. A nano-modifier is added to the non-grain source bio-based emulsion prepared in step I, and stirring is performed at a speed of 600 rpm for 20 min to obtain a main emulsion;

[0064] The nano-modifier is composed of 35% nano-silicon dioxide, 40% polydimethylsiloxane, and 25% nano-silicon carbide according to the mass fraction;

[0065] III. A bio-based emulsifier alkyl polyglycoside is slowly added to the main emulsion prepared in step II, and emulsification is performed at a speed of 3000 rpm for 20 min to form a stable emulsion;

[0066] IV. Water and a bio-based wetting agent sorbitol ester are added to the stable emulsion of step III, and stirring is performed at a speed of 700 rpm for 30 min to obtain a coating emulsion;

[0067] The coating emulsion is composed of 50% non-grain source bio-based emulsion, 40% nano-modifier, 2.5% bio-based emulsifier, 1% bio-based wetting agent, and the balance of water according to the mass fraction.

[0068] A 9-inch natural paper plastic disc is used as a substrate, and the coating emulsion prepared in test I is applied to the surface of the substrate by spraying and spinning coating processes. The spinning coating process parameters can be adjusted, the initial speed is 300 rpm, the high speed is 800 rpm, and then low-temperature curing is performed: the drying temperature is 60°C, which is suitable for the existing equipment of the paper pulp molding production line to avoid deformation of the substrate caused by high temperature. Then the sample is tested as follows:

[0069] 1. Environmental protection: the main emulsion of test I is a natural non-grain source plant-based material, which is environmentally friendly and fluorine-free, and realizes the biodegradability of the coating and the paper pulp molding and paper-based substrate; the coating does not contain fluorine compounds, and halogen detection is performed.

[0070] The degradation test is shown in Table 1 (the test sample is a paper plastic product after coating).

[0071] Table 1

[0072]

[0073] 2. Performance improvement:

[0074] ①High barrier to hot water (100℃, 30min no penetration point) and hot oil (120℃, 30min no penetration point), Kit value up to 12.

[0075] Table 2 Figure 1 , Figure 2 and Figure 3 .

[0076] Table 2

[0077]

[0078] Figure 1 The left side is coated, and the right side is uncoated. It can be seen that the hot oil of the coated product has not penetrated to the bottom, while the hot oil of the uncoated product has penetrated to the bottom.

[0079] Figure 2 The left side is coated, and the right side is uncoated. It can be seen that the hot oil of the coated product has not penetrated to the bottom, while the hot oil of the uncoated product has penetrated to the bottom.

[0080] Figure 3 The left side is coated, and the right side is uncoated. Figure 3 The left side is coated, and the right side is uncoated. It can be seen that the hot oil of the coated product has not penetrated to the bottom, while the hot oil of the uncoated product has penetrated to the bottom.

[0081] ②Kit value test: after the paper sample with a grammage of 60g is finished with sizing, 0.05mL of No. 12 test liquid is added to the surface, and no penetration is observed within 30S of starting the timer.

[0082] ③Wide temperature resistance range (-30~130℃), suitable for cold storage and hot drink packaging, high-temperature sterilization requirements.

[0083] ④Take 9-inch natural paper plastic disc as substrate (substrate is not waterproof and not oiled), test after completing the coating on the surface, and observe the appearance and test the performance (waterproof and oil-proof) after high and low temperature storage. The results are shown in Table 3.

[0084] Table 3

[0085]

[0086] ⑤Good heat sealing performance, can achieve waterproof and oil-proof barrier while having heat sealing performance: take 60g paper sample to complete coating, dry weight 7g, set heat sealing instrument temperature 110℃, time 2S, pressure 2MP to test heat sealing strength, and the heat sealing paper peeling strength is qualified.

[0087] (6) The anti-back-sticking requirement of the stack is met: simulate the actual stacking environment, 9-inch disc test, after the coating is completed, the number of stacked layers is set to 5, 10, 20 and 50, the temperature is 30℃, 50℃, and the static test is 48h, the standard environment is restored for 30 minutes, and whether the disc is easy to separate and whether there is adhesion is tested, and the results are shown in Table 4.

[0088] Table 4

[0089]

[0090] (7) Good resistance to alcohol, acid and alkali: 95% alcohol detection GB31604.8-2021, test results are qualified.

[0091] (8) Acid and alkali resistance test: acid / alkali solution (1% citric acid, 1% NaOH) is prepared according to the standard concentration, the acid / alkali solution is poured into the coated disc, and whether there is dissolution, peeling, foaming, discoloration and wrinkling is observed after 1h and 4h respectively. Test results: after 4h acid and alkali test, the coating surface is intact, without dissolution, peeling, foaming, discoloration and wrinkling.

Claims

1. An aqueous bio-based emulsion for a water- and oil-repellent barrier coating for pulp-molded or paper articles, characterized in that The waterproof and oil-proof barrier coating emulsion is composed of 40-60% of non-food source bio-based emulsion, 30-50% of nano modifier, 1-5% of bio-based emulsifier, 0.5-1% of bio-based wetting agent, and the balance of water.

2. An aqueous bio-based emulsion for water and oil barrier coating of pulp molded or paper articles according to claim 1, characterized in that The non-food source bio-based emulsion is obtained by extraction and emulsification of non-food source bio-based materials.

3. An aqueous bio-based emulsion for water and oil barrier coating of pulp molded or paper articles according to claim 2, characterized in that The non-food source bio-based materials are agricultural and forestry wastes, non-food plants, algae, and microbial fermentation products.

4. An aqueous bio-based emulsion for water and oil barrier coating of pulp molded or paper articles according to claim 1, characterized in that The nano modifier is composed of 30-50% of nano silicon dioxide, 20-40% of polydimethylsiloxane, and 20-30% of nano silicon carbide.

5. An aqueous bio-based emulsion for water and oil barrier coating of pulp molded or paper articles according to claim 1, characterized in that The bio-based emulsifier is alkyl polyglycoside or lecithin.

6. An aqueous bio-based emulsion for water and oil barrier coating of pulp molded or paper articles according to claim 1, characterized in that The bio-based wetting agent is sorbitol ester or sophorolipid.

7. A process for the preparation of an aqueous bio-based emulsion for water and oil repellent barrier coating of pulp molded or paper articles according to claim 1, characterized in that The preparation method is as follows: I. Extraction and emulsification from non-food sources: ①, raw material pretreatment: the non-food source bio-based materials are physically crushed, then a eutectic solvent is added, and the temperature is kept at 60-100℃ for 20min, and then it is cooled to room temperature; ②, directional enzymolysis: add a complex cellulase to the system of ① to degrade cellulose into nano cellulose and soluble sugar; the temperature is 40-50℃, the time is 48h, and the stirring speed is 400r / min; the complex cellulase accounts for 0.5-3% of the mass of the system of ①; ③, hydrophobic modification of nano cellulose: introduce a hydrophobic group to improve the interfacial activity of the system of ② to obtain a bio-based hydrophobic active ingredient; the hydrophobic group is acetyl; ④, emulsion preparation: the oil phase is the bio-based hydrophobic active ingredient prepared in ③, the water phase is a CNF dispersion liquid, an emulsifier is added, and high-speed stirring is performed to form a non-food source bio-based emulsion; The mass ratio of the water phase to the oil phase is 7:3, and the addition amount of the emulsifier is 1-3%; II. Add nano modifier to the non-food source bio-based emulsion prepared in step I, stir at a speed of 500-700rpm for 10-20min to obtain a main emulsion; The nano modifier is composed of 30-50% of nano silicon dioxide, 20-40% of polydimethylsiloxane, and 20-30% of nano silicon carbide; III. Slowly add bio-based emulsifier to the main emulsion prepared in step II, emulsify at a speed of 2000-3000rmp for 20-30min to form a stable emulsion; IV. Add water and bio-based wetting agent to the stable emulsion of step III, stir at a speed of 500-700rpm for 20-30min to obtain a coating emulsion; The coating emulsion is composed of 40-60% of non-food source bio-based emulsion, 30-50% of nano modifier, 1-5% of bio-based emulsifier, 0.5-1% of bio-based wetting agent, and the balance of water.

8. A process for the preparation of an aqueous bio-based emulsion for water and oil repellent barrier coating of pulp molded or paper articles according to claim 7, characterized in that The solute of the eutectic solvent in step I ① is a mixture of choline chloride and urea in a molar ratio of 1:2, and the solvent is water.

9. A process for the preparation of an aqueous bio-based emulsion for water and oil repellent barrier coating of pulp molded or paper articles according to claim 7, characterized in that The complex cellulase in step one ② is composed of 40% to 50% endo-enzyme and 50% to 60% exo-enzyme by mass fraction.

10. A process for the preparation of an aqueous bio-based emulsion for water and oil repellent barrier coating of pulp molded or paper articles according to claim 7, characterized in that The acetyl source in step one ③ is acetic anhydride, acetic acid or long-chain alkyl.

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