Oil-proof and plastic-removing food-grade degradable paper and preparation method and application thereof

Abstract

This invention discloses an oil-resistant and plastic-removable food-grade biodegradable paper, its preparation method, and its application. The biodegradable paper includes a base paper and an aqueous oil-resistant coating applied to at least one surface of the base paper. The aqueous oil-resistant coating comprises the following raw material components in parts by weight: 30-48 parts of hybrid acrylic emulsion; 15-25 parts of polyacrylic acid emulsion; 1-3 parts of acetylation diol surfactant; 5-10 parts of wax component; 2-5 parts of cellulose nanocrystals; 1-3 parts of plant gum; and 0.5-2 parts of hydroxyethyl cellulose thickener. This invention achieves complete plastic removal, full biodegradability, excellent water and oil resistance, safety and non-toxicity, stable mechanical strength, and simple preparation of food-grade packaging paper.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly materials technology, and in particular to an oil-resistant and plastic-removing food-grade biodegradable paper, its preparation method, and its application. Background Technology

[0002] Food packaging paper must meet core requirements such as waterproofing, oil resistance, anti-sticking, and safety / non-toxicity, while also being adaptable to the specific needs of food storage, transportation, and consumption. Traditional food packaging paper (such as ordinary kraft paper and coated paper) often uses polyethylene (PE) or polypropylene (PP) lamination or adds fluorinated oil-resistant agents (such as PFOS / PFOA). Although this achieves waterproofing and oil resistance, the plastic components are non-degradable, the fluorinated additives pose potential health risks, and it does not comply with the plastic reduction policy. Existing biodegradable food paper is mostly based on starch and plant fibers, but it suffers from poor oil resistance (high oil penetration), insufficient mechanical strength (easily damaged), poor temperature resistance (easily softens above 60℃), and insufficient antibacterial effect (easily breeds bacteria leading to food spoilage), making it difficult to meet the packaging needs of meat, fried foods, and cooked foods. Therefore, there is an urgent need for a food-grade packaging paper that is completely plastic-free, fully biodegradable, has excellent waterproof and oil-resistant properties, is safe and non-toxic, has stable mechanical strength, and is easy to prepare. Summary of the Invention

[0003] This invention provides an oil-resistant and plastic-removable food-grade biodegradable paper, its preparation method, and its application, achieving complete plastic removal, full biodegradability, excellent water and oil resistance, safety and non-toxicity, stable mechanical strength, and simple preparation of food-grade packaging paper.

[0004] In a first aspect, the present invention provides an oil-resistant and plastic-repellent food-grade biodegradable paper, comprising a base paper and an aqueous oil-resistant coating applied to at least one surface of the base paper, wherein the aqueous oil-resistant coating comprises the following raw material components in parts by weight: 30 to 48 parts of hybrid acrylic emulsion; 15 to 25 parts of polyacrylic acid emulsion; 1 to 3 parts of acetylenic diol surfactant; 5 to 10 parts wax component; 2 to 5 parts of cellulose nanocrystals; 1 to 3 parts plant-based gum; Hydroxyethyl cellulose thickener: 0.5 to 2 parts.

[0005] In some embodiments, the wax component is a mixture of modified plant wax and chitosan-grafted fatty acid ester, wherein the mass ratio of the modified plant wax to the chitosan-grafted fatty acid ester is (1~3):1.

[0006] In some of the embodiments, the hybrid acrylic emulsion is a silicone-modified acrylic emulsion or an epoxy resin-modified acrylic emulsion, with a solid content of 40% to 50% and a glass transition temperature of -10°C to 10°C.

[0007] In some of the embodiments, the polyacrylic acid emulsion is a soap-free polymerized polyacrylic acid emulsion with a solid content of 30% to 35%.

[0008] In some of the embodiments, the acetylidene diol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol or its ethoxylated form.

[0009] In some of these embodiments, the cellulose nanocrystals have a diameter of 5 nm to 20 nm and a length of 100 nm to 500 nm, and their surfaces are modified by acetylation or carboxylation.

[0010] In some of these embodiments, the plant gum is guar gum, locust bean gum, or konjac glucomannan.

[0011] In some embodiments, the base paper is a food-grade plant fiber of 65 g / m² to 230 g / m², wherein the plant fiber is one or more of bamboo pulp, sugarcane pulp, or reed pulp.

[0012] Secondly, the present invention also provides a method for preparing the above-mentioned oil-resistant and plastic-removing food-grade biodegradable paper, comprising the following steps: Add the polyacrylic acid emulsion to the mixing tank and adjust the stirring speed to 100 rpm to 200 rpm; Add acetylation diol surfactant to the stirred tank and control the feeding time to 5 min to 10 min. After the feeding is completed, continue stirring for 8 min to 12 min. Slowly add the wax component to the mixing vessel and continue stirring for 15 to 20 minutes; Add hybrid acrylic emulsion to the stirred tank at a feed rate of 13 kg / h to 17 kg / h, and continue stirring for 20 min to 30 min after the addition is complete. Add the premix of cellulose nanocrystals and plant gum to the stirred tank and continue stirring for 10 to 20 minutes. Add hydroxyethyl cellulose thickener to the mixing tank, adjust the viscosity of the system to 250 mPa·s to 350 mPa·s, filter, and obtain the finished water-based oil-resistant coating; The finished water-based waterproof coating is applied to the surface of the base paper by scraping, with a coating amount of 8±1 g / m² of dry film weight. After coating, it is dried and cured at 75℃~85℃ for 30s~120s, and then the coated surface is heat-sealed at 145℃~155℃ and 0.3Mpa~0.5MPa for 1s~2s to obtain the finished degradable paper.

[0013] Thirdly, the present invention also provides an application of the above-mentioned oil-resistant and plastic-removing food-grade biodegradable paper in food packaging.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a blend of hybrid acrylic emulsion and polyacrylic acid emulsion as the main film-forming substances. The hybrid acrylic emulsion imparts flexibility and weather resistance to the coating, while the polyacrylic acid emulsion enhances cohesion and anchors the paper fibers. A wax component acts as the main hydrophobic and oil-repellent agent, forming a dense, low-surface-energy barrier on and within the coating surface. Alkyne diol surfactants effectively reduce the surface tension of the system, ensuring uniform coating spread on the paper substrate. The nanoscale effect and high crystallinity of cellulose nanocrystals create a labyrinthine physical barrier within the coating, significantly extending the penetration path of oil molecules. Plant gums act as natural dispersants and network enhancers, promoting the uniform dispersion of nanocellulose and synergistically constructing a three-dimensional network structure. Through the synergistic effect of these components, this invention achieves high-level oil resistance, excellent heat-sealing strength, and complete biodegradability without the use of fluorides or plastic coatings, effectively solving the dilemma of balancing environmental protection and high performance.

[0015] When a mixture of modified plant wax and chitosan-grafted fatty acid esters is used as the wax component, the modified plant wax provides a basic hydrophobic barrier. Chitosan-grafted fatty acid esters, due to their molecular structure containing both hydrophilic chitosan backbone and hydrophobic fatty acid long chains, can act as macromolecular emulsifiers to promote the uniform dispersion of the plant wax. Furthermore, their fatty acid chains can co-crystallize with the plant wax, constructing a denser, defect-free hydrophobic network, exhibiting a significant synergistic effect. Simultaneously, the introduction of chitosan also endows the coating with additional antibacterial properties, further enhancing the safety of food packaging.

[0016] Surface-acetylated or carboxylated cellulose nanocrystals, when combined with plant gums, form a more stable nanocomposite network through hydrogen bonding and physical entanglement. This not only further improves the oil resistance level but also significantly enhances the mechanical properties and water resistance of the coating.

[0017] The method of this invention first disperses polyacrylic acid emulsion and wax components, and then introduces hybrid acrylic emulsion at a specific rate, which effectively avoids phase inversion and flocculation, and ensures the stability of the multiphase system; it precisely controls the coating amount and heat sealing conditions to ensure the uniformity of the coating morphology and the strong bond with the paper base, thereby obtaining stable high oil resistance and heat sealing strength. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0019] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0020] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0021] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity (i.e., number of occurrences) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available industrial products. The hybrid acrylic emulsion is a silicone-modified acrylic ester emulsion (45% solids content, Tg=0℃); the polyacrylic acid emulsion is a soap-free polymerized polyacrylic acid emulsion (32% solids content); the acetylenol surfactant is 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate (Surfynol 104E); the cellulose nanocrystals are surface-acetylated modified products (10-15 nm diameter, 200-300 nm length); the hydroxyethyl cellulose thickener is commercially available HS30000; and the base paper is 80 g / m² food-grade bamboo pulp kraft paper. Example 1

[0024] An oil-resistant, plastic-repellent, food-grade biodegradable water-based oil-resistant coating is composed of the following raw materials in parts by weight: 40 parts of hybrid acrylic emulsion; 20 parts of polyacrylic acid emulsion; Two parts of acetylenic diol surfactant; Wax component: 8 parts of a mixture of modified plant wax and chitosan grafted fatty acid esters (mass ratio 2:1); 3 parts of cellulose nanocrystals; 2 parts of konjac glucomannan; 1.2 parts of hydroxyethyl cellulose thickener.

[0025] The preparation method includes the following steps: (1) Add the polyacrylic acid emulsion to the mixing tank and adjust the stirring speed to 150 rpm; (2) Control the feeding time to 8 min, add acetylation diol surfactant to the stirred tank, and continue stirring for 10 min after the feeding is completed; (3) Slowly add the wax component to the stirred tank and continue stirring for 18 minutes to form a uniform milky white dispersion; (4) Control the feeding rate to 15 kg / h, add hybrid acrylic emulsion to the mixing tank, and continue stirring for 25 min after the feeding is completed; (5) Add the premix of cellulose nanocrystals and plant gum to the mixing vessel and continue stirring for 15 min; (6) Add hydroxyethyl cellulose thickener to the mixing tank, adjust the viscosity of the system to 300 mPa·s, filter through a 100-mesh sieve to obtain the finished water-based oil-proof coating; (7) The finished coating is applied to the surface of the base paper by scraping, and the dry film weight is controlled to be 8g / m². After coating, it is dried and cured at 80℃ for 60s, and then the coated surface is heat-sealed at 150℃ and 0.4MPa for 1.5s to obtain the finished degradable paper. Example 2

[0026] An oil-resistant, plastic-repellent, food-grade degradable coating is prepared using the same method as in Example 1. Its water-based oil-resistant coating is composed of the following raw materials in parts by weight: 30 parts of hybrid acrylic emulsion; 15 parts of polyacrylic acid emulsion; One part of an acetylenic diol surfactant; Wax component: 5 parts of a mixture of modified plant wax and chitosan grafted fatty acid esters (mass ratio 1:1); Two parts of cellulose nanocrystals; 1 part guar gum; 0.5 parts of hydroxyethyl cellulose thickener. Example 3

[0027] An oil-resistant, plastic-repellent, food-grade degradable coating is prepared using the same method as in Example 1. Its water-based oil-resistant coating is composed of the following raw materials in parts by weight: 48 parts of hybrid acrylic emulsion; 25 parts of polyacrylic acid emulsion; 3 parts of acetylacetonate diol surfactant; Wax component: 5 parts of a mixture of modified plant wax and chitosan grafted fatty acid esters (mass ratio 3:1); 5 parts of cellulose nanocrystals; 3 parts locust bean gum; Two parts of hydroxyethyl cellulose thickener.

[0028] The preparation method is the same as in Example 1.

[0029] Comparative Example 1: Compared with Example 1, Comparative Example 1 uses an equal amount of hybrid acrylic emulsion instead of polyacrylic acid emulsion, and the rest is the same as Example 1.

[0030] Comparative Example 2: Compared with Example 1, Comparative Example 2 uses an equal amount of polyacrylic acid emulsion instead of hybrid acrylic emulsion, and the rest is the same as Example 1.

[0031] Comparative Example 3: Compared with Example 1, Comparative Example 3 used an equal amount of modified plant wax instead of chitosan grafted fatty acid ester, and the rest was the same as in Example 1.

[0032] Comparative Example 4: Compared with Example 1, Comparative Example 4 uses an equal amount of chitosan grafted fatty acid ester instead of modified plant wax, and the rest is the same as Example 1.

[0033] Comparative Example 5: Compared with Example 1, Comparative Example 5 uses an equal amount of paraffin emulsion to replace the wax component, and the rest is the same as Example 1.

[0034] Comparative Example 6: Compared with Example 1, Comparative Example 6 uses an equal amount of cellulose nanocrystals instead of plant gum, and the rest is the same as Example 1.

[0035] Comparative Example 7: Compared with Example 1, Comparative Example 7 uses an equal amount of plant gum instead of cellulose nanocrystals, and the rest is the same as Example 1.

[0036] Comparative Example 8: Compared with Example 1, Comparative Example 8 removed cellulose nanocrystals and plant gums, and was otherwise the same as Example 1.

[0037] Comparative Example 9: Compared with Example 1, all raw materials in Comparative Example 9 were added to the mixing tank at one time, stirred at high speed of 500 rpm for 30 min, and then filtered to obtain the coating. The rest was the same as in Example 1.

[0038] Performance testing: 1. Oil resistance rating: According to the TAPPI T-559 cm-02 standard, the Kit test method is used. The higher the rating (maximum 12), the better the oil resistance.

[0039] 2. Heat seal strength: The peel strength (N / 15mm) of the heat seal layer shall be tested in accordance with GB / T 2358-1998 standard.

[0040] 3. Cobb value: According to GB / T 1540-2002 standard, the water absorption of paper in 60 seconds (g / m²) is tested, reflecting its water resistance.

[0041] 4. Biodegradation rate: The percentage of biodegradation under controlled composting conditions for 180 days was tested in accordance with GB / T 19277.1-2011 standard.

[0042] Table 1 Performance data of Examples 1 to 3 and Comparative Examples 1 to 9 Test sample Oil resistance rating (level) Heat seal strength (N / 15mm) Cobb value (g / m²) Biodegradation rate (%) Example 1 12 5.2 11.9 94.9 Example 2 11 4.9 14.8 96.2 Example 3 12 5.1 11.1 93.7 Comparative Example 1 8 3.5 25.4 95.1 Comparative Example 2 7 2.7 30.3 96.3 Comparative Example 3 9 4.1 18.7 95.4 Comparative Example 4 8 3.3 22.5 96.3 Comparative Example 5 11 4.6 10.1 89.6 Comparative Example 6 9 4.2 16.5 93.5 Comparative Example 7 8 3.7 20.6 95.2 Comparative Example 8 7 2.4 28.7 96.1 Comparative Example 9 5 1.2 40.9 91.1 As shown in Table 1, Examples 1 to 3 exhibit high-level oil resistance, excellent heat-sealing strength, hot water resistance, and biodegradability. Compared to Example 1, Comparative Example 1 lacks the fiber anchoring and cohesive enhancement provided by polyacrylic acid emulsion, resulting in weak bonding between the coating and the paper base; Comparative Example 2 lacks the flexibility provided by hybrid acrylic acid, making the coating brittle and prone to microcracks during drying or use; Comparative Example 3 lacks the synergistic effect of chitosan derivative macromolecular emulsification and co-crystallization, leading to uneven wax distribution; Comparative Example 4 shows that chitosan derivative has better film-forming properties than plant waxes, but it cannot form a highly dense hydrophobic network when used alone; Comparative Example 5 shows strong hydrophobicity of paraffin wax, but its compatibility with acrylic resin and synergistic effect with nanocrystals are not as good as composite waxes. Comparative Example 6 lacks the dispersing and network-reinforcing effects of plant gums, making cellulose nanocrystals prone to aggregation and weakening the maze effect; Comparative Example 7 lacks the maze effect, shortening the oil penetration path and significantly reducing oil resistance; Comparative Example 8 lacks both the maze effect and network reinforcement, relying solely on wax components and acrylic resin, resulting in a significant decrease in oil resistance; Comparative Example 9 suffers from high-speed shearing that disrupts emulsion stability, leading to demulsification and flocculation; uneven component dispersion prevents the formation of a continuous and dense coating, resulting in varying degrees of decrease in oil resistance, heat-sealing strength, and water resistance in Comparative Examples 1 to 9.

[0043] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0044] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. An oil-resistant and plastic-removing food-grade biodegradable paper, characterized in that, The material includes a base paper and an aqueous oil-resistant coating applied to at least one surface of the base paper, the aqueous oil-resistant coating comprising the following raw material components in parts by weight: 30 to 48 parts of hybrid acrylic emulsion; 15 to 25 parts of polyacrylic acid emulsion; 1 to 3 parts of acetylacetonate diol surfactant; 5 to 10 parts wax component; 2 to 5 parts of cellulose nanocrystals; 1 to 3 parts plant-based gum; Hydroxyethyl cellulose thickener: 0.5 to 2 parts.

2. The oil-resistant and plastic-removing food-grade biodegradable paper as described in claim 1, characterized in that, The mixture of modified plant wax and chitosan grafted fatty acid ester has a mass ratio of (1~3):

1.

3. The oil-resistant and plastic-removing food-grade biodegradable paper as described in claim 1, characterized in that, The hybrid acrylic emulsion is a silicone-modified acrylic emulsion or an epoxy resin-modified acrylic emulsion, with a solid content of 40%~50% and a glass transition temperature of -10℃~10℃.

4. The oil-resistant and plastic-removing food-grade biodegradable paper as described in claim 1, characterized in that, The polyacrylic acid emulsion is a soap-free polymerized polyacrylic acid emulsion with a solid content of 30% to 35%.

5. The oil-resistant and plastic-removing food-grade biodegradable paper as described in claim 1, characterized in that, The acetylenic diol surfactant is 2,4,7,9-tetramethyl-5-decyn-4,7-diol or its ethoxylated derivative.

6. The oil-resistant and plastic-removing food-grade biodegradable paper as described in claim 1, characterized in that, The cellulose nanocrystals have a diameter of 5nm~20nm and a length of 100nm~500nm, and their surfaces are modified by acetylation or carboxylation.

7. The oil-resistant and plastic-removing food-grade biodegradable paper as described in claim 1, characterized in that, The plant gum is guar gum, locust bean gum, or konjac glucomannan.

8. The oil-resistant and plastic-removing food-grade biodegradable paper as described in claim 1, characterized in that, The base paper is food-grade plant fiber with a density of 65 g / m² to 230 g / m².

9. A method for preparing the oil-resistant and plastic-removing food-grade biodegradable paper as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Add the polyacrylic acid emulsion to the mixing tank and adjust the stirring speed to 100 rpm to 200 rpm; Add acetylation diol surfactant to the stirred tank and control the feeding time to 5 min to 10 min. After the feeding is completed, continue stirring for 8 min to 12 min. Slowly add the wax component to the mixing vessel and continue stirring for 15 to 20 minutes; Add hybrid acrylic emulsion to the stirred tank at a feed rate of 13 kg / h to 17 kg / h, and continue stirring for 20 min to 30 min after the addition is complete. Add the premix of cellulose nanocrystals and plant gum to the stirred tank and continue stirring for 10 to 20 minutes. Add hydroxyethyl cellulose thickener to the mixing tank, adjust the viscosity of the system to 250 mPa·s to 350 mPa·s, filter, and obtain the finished water-based oil-resistant coating; The finished water-based waterproof coating is applied to the surface of the base paper by scraping, with a coating amount of 8±1 g / m² of dry film weight. After coating, it is dried and cured at 75℃~85℃ for 30s~120s, and then the coated surface is heat-sealed at 145℃~155℃ and 0.3Mpa~0.5MPa for 1s~2s to obtain the finished degradable paper.

10. The application of an oil-resistant and plastic-removing food-grade biodegradable paper as described in any one of claims 1 to 8 in food packaging.