Double-sided coated paper as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of coated paper, and particularly discloses double-sided coated paper and a preparation method and application thereof.The double-sided coated paper comprises a first modified heat-sealing layer, a paper base layer and a second modified heat-sealing layer, the paper base layer is made of environment-friendly recycled paper pulp base materials, and the first modified heat-sealing layer and the second modified heat-sealing layer are both made of modified composite coatings. The modified composite coating comprises the following components in parts by weight: 60-70 parts of poly (butylene adipate-co-terephthalate); 10 to 15 parts of polylactic acid; 10 to 20 parts of a disintegrating agent; 1-2 parts of a slipping agent; 1-3 parts of an anti-blocking agent; and 0.2 to 0.5 part of a chain extender. According to the double-sided coated paper and the preparation method and application thereof, the double-sided heat sealability, the water and oil resistance, the printing adaptability and the environment-friendly recoverability are synergistically improved, and the use requirements of high-end environment-friendly packaging in multiple fields are met.

Description

Technical Field

[0001] This invention relates to the field of coated paper technology, and in particular to a double-sided coated paper, its preparation method, and its application. Background Technology

[0002] Coated paper is a composite material in which plastic particles are coated onto the surface of paper using a casting machine. Its main characteristics include oil and water resistance (relatively), and heat-sealing capability. Double-sided heat-sealable coated paper, with its advantages of double-sided heat sealing, water and oil resistance, and convenient forming, is widely used in disposable lunch boxes, food packaging bags, and aseptic packaging. In existing technologies, coated paper mostly uses single-sided heat sealing, i.e., one side is waterproof and the other is heat-sealed, which is convenient for printing, but the front and back must be distinguished during heat sealing. Conventional double-sided heat-sealable coated paper has a smooth surface and very low polarity, resulting in poor ink adhesion during printing and easily causing problems such as color fading, ink stripping, and blurred patterns. Furthermore, with increasing environmental protection requirements, the industry is evolving towards bio-based biodegradable materials, using biodegradable materials such as PLA and PBAT bio-based particles to achieve double-sided coating through casting composite processes. However, coated materials prepared with these biodegradable materials also present printing challenges, and are brittle and have poor heat-sealing performance. Therefore, there is an urgent need for a double-sided coated paper, its preparation method, and its applications that meet both environmental and printing requirements while also being practical. Summary of the Invention

[0003] The purpose of this invention is to provide a double-sided coated paper, its preparation method and application, which synergistically improves double-sided heat-sealing properties, water and oil resistance, printability and environmental recyclability, meeting the needs of high-end environmentally friendly packaging in multiple fields.

[0004] To achieve the above objectives, the present invention provides a double-sided coated paper, comprising a first modified heat-sealing layer, a paper base layer, and a second modified heat-sealing layer, wherein the paper base layer is made of environmentally friendly recycled pulp substrate, and both the first and second modified heat-sealing layers are modified composite coatings, the modified composite coating comprising the following components in parts by weight: 60-70 parts of polybutylene adipate-terephthalate; 10-15 parts of polylactic acid; 10-20 parts of disintegrant; 1-2 parts of slip agent; 1-3 parts of anti-blocking agent; Chain extender 0.2~0.5 parts.

[0005] Preferably, the environmentally friendly recycled pulp substrate is a mixture of recycled wood pulp and bamboo pulp in a mass ratio of 7:3.

[0006] Preferably, the basis weight of the paper base layer is controlled between 150 and 320 g / m². 2 The moisture content is <4.5%; the thickness of the first modified heat seal layer and the second modified heat seal layer is controlled at 12~15μm.

[0007] Preferably, the disintegrant is thermoplastic starch, the slip agent is bio-based fatty acid amide, the anti-blocking agent is silica masterbatch, and the chain extender is glycidyl methacrylate.

[0008] Polybutylene adipate terephthalate (PBAT) provides flexibility, heat-sealing properties, and melt stability, while also providing stiffness; polylactic acid (PLA) regulates melt strength and increases bio-based content; a disintegrant (thermoplastic starch) accelerates composting disintegration and reduces overall raw material costs; a chain extender (epoxypropyl methacrylate) improves PLA / PBAT compatibility and enhances melt strength; a slip agent (bio-based fatty acid amides, such as erucamide) ensures smooth winding; and an anti-blocking agent (silica masterbatch) prevents film roll adhesion. The thickness of the single-sided modified heat-sealing layer is controlled at 12~15μm, ensuring a double-sided heat-sealing strength ≥13N / 15mm, and widening the heat-sealing temperature range to 110~150℃, making it compatible with various heat-sealing equipment.

[0009] This double-sided coated paper consists of a first modified heat-sealing layer, a paper base layer, and a second modified heat-sealing layer, arranged from top to bottom. The three layers are co-extruded and bonded together simultaneously without additional adhesive, meeting food contact safety standards. The paper base layer uses FSC-certified recycled wood pulp, possessing high stiffness, tear resistance, and excellent toughness. This ensures product molding stability while also enabling the recycling of waste paper resources, reducing virgin wood pulp consumption, and aligning with environmental protection principles. The first modified heat-sealing layer combines heat-sealing properties with printability, while the second modified heat-sealing layer ensures double-sided heat sealing strength. Both heat-sealing layers utilize environmentally friendly, biodegradable, and easily separable modified coatings, abandoning traditional pure PE materials, enabling easy separation of paper and plastic after disposal and facilitating recycling and degradation.

[0010] This invention also provides a method for preparing double-sided coated paper, comprising the following steps: S1. Paper base pretreatment: The paper base prepared from the mixed pulp is dried with low-temperature hot air at 50~60℃ to remove surface moisture and dust, and the moisture content is controlled to <4.5%. Then, a primary corona treatment is performed to control the surface tension to 35~37 dynes, which improves the bonding force between the paper base and the heat-sealing layer, thus obtaining the paper base. In addition to the low-temperature drying treatment, the paper base pretreatment stage also includes slag removal and degreasing treatment, resulting in a surface free of impurities and high flatness, which improves the composite adhesion with the heat-sealing layer. S2. Modified heat-sealing layer raw material blending modification: PBAT, PLA, disintegrant, slip agent and anti-blocking agent are added into a high-speed mixer according to the ratio and mixed at 80~90℃ for 20~30min to obtain a mixture. Then the mixture is fed into a twin-screw extruder and melted and plasticized at 160~180℃. Then a chain extender is added in the middle and rear section of the twin-screw extruder to obtain a melt. S3, Double-sided synchronous co-extrusion coating: The molten material obtained in S2 is fed into the double-sided co-extrusion die head, and the die head temperature is controlled to be stable at 170~180℃. The paper base layer obtained in S1 is passed through the die head at a uniform speed, and the first modified heat-sealing layer and the second modified heat-sealing layer are extruded synchronously. The composite roller is pressed together to obtain a three-layer composite structure. S4. Segmented corona activation treatment: The first modified heat-sealing layer of the three-layer composite structure obtained in S3 is subjected to a second corona treatment to control the surface tension to 39~42 dynes, optimize the surface polarity, and improve the ink adhesion. The second modified heat-sealing layer is subjected to a light corona treatment to ensure heat-sealing performance while avoiding film damage, thus obtaining the intermediate product of coated paper. S5. Online cooling and curing: The intermediate coated paper obtained in S4 is fed into the cooling roller group and cooled by circulating cooling water at 15~20℃ to quickly set the heat-sealing layer and avoid delamination and wrinkling. Finally, it is rolled up to obtain the finished double-sided heat-sealed coated paper.

[0011] Preferably, in S1, the process parameters of the primary corona treatment are: electrode gap 1.0~2.0mm, frequency 10~25KHz, voltage 10~20kV, and time 15~30s.

[0012] Preferably, in S3, the relevant parameters for the composite roller pressing are: pressing pressure controlled at 0.4~0.6MPa, pressing temperature at 85~100℃, wherein the pressing temperature of the composite roller is specifically a gradient increase of 85, 90, 95, and 100℃. Observe whether the film surface sticks to the roller. If sticking occurs, decrease the temperature according to the gradient. If the composite strength is insufficient (low peel force), increase the temperature according to the gradient to achieve seamless composite of the three-layer structure.

[0013] Preferably, in S4, the process parameters for the secondary corona treatment are: electrode gap 1.0~1.5mm, frequency 20~35KHz, voltage 15~25kV, and time 15~30s; The process parameters for the mild corona treatment are: electrode gap 2.0~2.5mm, frequency 10~20kHz, voltage 8~12kV, and time 15~30s.

[0014] Preferably, in S5, the cooling speed of the cooling roller group is controlled at 15~20m / min, and the overall production line speed is 100~120m / min.

[0015] This invention also provides an application of double-sided heat-sealed coated paper in recyclable and environmentally friendly food packaging paper.

[0016] Therefore, the present invention employs the above-mentioned double-sided coated paper, its preparation method, and its application, and the beneficial effects are as follows: Balanced overall performance: This invention adopts an integrated process of double-sided synchronous co-extrusion coating + segmented corona treatment + online drying and curing. The double-sided heat sealing strength is stable at 13~16N / 15mm, the heat sealing temperature range is wide, the printing surface is treated with segmented corona, it is compatible with water-based environmentally friendly inks, the printed pattern is clear, the adhesion is strong, and there is no color fading or ink peeling. At the same time, it is also waterproof and oil-proof.

[0017] Excellent environmental performance: Abandoning the traditional pure PE coating structure, this invention adopts a biodegradable modified composite coating + additives. After disposal, paper and plastic can be quickly separated under pulping conditions, with a paper fiber recovery rate of ≥88%, an industrial compost degradation rate of ≥90% in 180 days, and no plastic residue.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 This is a heat-sealing strength result diagram of a double-sided coated paper, its preparation method, and an application embodiment of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0022] Example 1 An environmentally friendly double-sided heat-sealing coated paper with a base layer weight of 200g / m² 2 It is prepared by mixing recycled wood pulp and bamboo pulp in a 7:3 ratio; the modified composite coating formula is: 65 parts poly(butylene adipate-terephthalate), 15 parts polylactic acid, 15 parts disintegrant, 2 parts slip agent, 2 parts anti-blocking agent, and 0.5 parts chain extender; the single-sided coating thickness is 13 μm.

[0023] Its preparation method is as follows: S1. Paper base pretreatment: The paper base prepared from the mixed pulp is dried with low temperature hot air at 55℃, and the moisture content is controlled to be <4.5%. Then, a primary corona treatment is performed with an electrode gap of 1.0~2.0mm, a frequency of 15KHz, a voltage of 10kV, and a time of 15s. The surface tension is controlled to 36 dynes to obtain the paper base. S2. Modified heat-sealing layer raw material blending modification: PBAT, PLA, disintegrant, slip agent and anti-blocking agent are added into a high-speed mixer according to the ratio and mixed at 85℃ for 30 minutes to obtain a mixture. Then the mixture is fed into a twin-screw extruder and melted and plasticized at 170℃. Then a chain extender is added in the middle and rear section of the twin-screw extruder to obtain a melt. S3, Double-sided synchronous co-extrusion coating: The molten material obtained in S2 is fed into the double-sided co-extrusion die, and the die temperature is controlled to be stable at 175℃. The paper base layer obtained in S1 is passed through the die at a uniform speed, and the first modified heat-sealing layer and the second modified heat-sealing layer are extruded synchronously. The composite roller is pressed together with a pressing pressure of 0.5MPa and a pressing temperature of 95℃ to obtain a three-layer composite structure. S4. Segmented corona activation treatment: The first modified heat-sealing layer of the three-layer composite structure obtained in S3 is subjected to a second corona treatment with an electrode gap of 1.0~1.5mm, a frequency of 20KHz, a voltage of 15kV, and a time of 15s; the surface tension is controlled to 40 dynes. The second modified heat-sealing layer is subjected to a light corona treatment with an electrode gap of 2.0~2.5mm, a frequency of 10kHz, a voltage of 8kV, and a time of 15s to obtain the intermediate product of the coated paper. S5. Online cooling and curing: The intermediate coated paper obtained in S4 is fed into the cooling roller group and cooled by circulating cooling water at 17°C. The cooling speed is controlled at 18m / min, and the overall production line speed is 110m / min. The paper is then wound up to obtain the finished double-sided heat-sealed coated paper.

[0024] Performance testing: Double-sided heat seal strength 14.5N / 15mm, excellent performance; paper fiber recovery rate 89.2%; 180-day composting organic component degradation rate 91.5%; ink adhesion on printed surface meets standards, with no ink fading or color loss.

[0025] Example 2 The difference from Example 1 is that the modified composite coating formulation is as follows: 67 parts of polybutylene adipate-terephthalate, 13 parts of polylactic acid, 15 parts of disintegrant, 2 parts of slip agent, 2 parts of anti-blocking agent, and 0.5 parts of chain extender.

[0026] Performance testing: Double-sided heat seal strength is 14.2N / 15mm, which is excellent. Paper fiber recovery rate is 89.5%. The organic component degradation rate after 180 days of composting is 91.0%. The ink adhesion on the printed surface meets the standard, and there is no ink fading or color loss.

[0027] Example 3 The difference from Example 1 is that the modified composite coating formulation is as follows: 70 parts of polybutylene adipate-terephthalate, 10 parts of polylactic acid, 15 parts of disintegrant, 2 parts of slip agent, 2 parts of anti-blocking agent, and 0.5 parts of chain extender.

[0028] Performance testing: Double-sided heat seal strength is 13.7N / 15mm, which is excellent. The paper fiber recovery rate is 88.9%, the organic component degradation rate after 180 days of composting is 90.5%, the ink adhesion on the printed surface meets the standard, and there is no ink removal or color fading.

[0029] Example 4 The difference from Example 1 is that its preparation method is as follows: S1. Paper base pretreatment: The paper base prepared from the mixed pulp is dried with low temperature hot air at 55℃, and the moisture content is controlled to be <4.5%. Then, a primary corona treatment is performed with an electrode gap of 1.0~2.0mm, a frequency of 15KHz, a voltage of 20kV, and a time of 30s. The surface tension is controlled to 37 dynes to obtain the paper base. S2. Modified heat-sealing layer raw material blending modification: PBAT, PLA, disintegrant, slip agent and anti-blocking agent are added into a high-speed mixer according to the ratio and mixed at 85℃ for 30 minutes to obtain a mixture. Then the mixture is fed into a twin-screw extruder and melted and plasticized at 170℃. Then a chain extender is added in the middle and rear section of the twin-screw extruder to obtain a melt. S3, Double-sided synchronous co-extrusion coating: The molten material obtained in S2 is fed into the double-sided co-extrusion die, and the die temperature is controlled to be stable at 175℃. The paper base layer obtained in S1 is passed through the die at a uniform speed, and the first modified heat-sealing layer and the second modified heat-sealing layer are extruded synchronously. The composite roller is pressed together with a pressing pressure of 0.5MPa and a pressing temperature of 95℃ to obtain a three-layer composite structure. S4. Segmented corona activation treatment: The first modified heat-sealing layer of the three-layer composite structure obtained in S3 is subjected to a second corona treatment with an electrode gap of 1.0~1.5mm, a frequency of 20KHz, a voltage of 25kV, and a time of 30s; the surface tension is controlled to 42 dynes. The second modified heat-sealing layer is subjected to a light corona treatment with an electrode gap of 2.0~2.5mm, a frequency of 10kHz, a voltage of 12kV, and a time of 30s to obtain the intermediate product of the coated paper. S5. Online cooling and curing: The intermediate coated paper obtained in S4 is fed into the cooling roller group and cooled by circulating cooling water at 17°C. The cooling speed is controlled at 18m / min, and the overall production line speed is 110m / min. The paper is then wound up to obtain the finished double-sided heat-sealed coated paper.

[0030] Performance testing: Double-sided heat seal strength 14.0N / 15mm, excellent performance; paper fiber recovery rate 88.3%; 180-day composting organic component degradation rate 92.5%; ink adhesion on printed surface meets standards, with no ink fading or color loss.

[0031] Comparative Example 1 A traditional pure PE double-sided heat-sealed coated paper.

[0032] Performance testing: Double-sided heat seal strength 14.7N / 15mm, excellent performance, large area ink removal occurs after only one application of the tape.

[0033] Comparative Example 2 The difference from Example 1 is that its preparation method is as follows: S1. Paper base pretreatment: The paper base prepared from the mixed pulp is dried with low temperature hot air at 55℃, and the moisture content is controlled to be <4.5%. Then, a primary corona treatment is performed with an electrode gap of 1.0~2.0mm, a frequency of 25KHz, a voltage of 25kV, and a time of 30s. The surface tension is controlled to 42 dynes to obtain the paper base. S2. Modified heat-sealing layer raw material blending modification: PBAT, PLA, disintegrant, slip agent and anti-blocking agent are added into a high-speed mixer according to the ratio and mixed at 85℃ for 30 minutes to obtain a mixture. Then the mixture is fed into a twin-screw extruder and melted and plasticized at 170℃. Then a chain extender is added in the middle and rear section of the twin-screw extruder to obtain a melt. S3, Double-sided synchronous co-extrusion coating: The molten material obtained in S2 is fed into the double-sided co-extrusion die, and the die temperature is controlled to be stable at 175℃. The paper base layer obtained in S1 is passed through the die at a uniform speed, and the first modified heat-sealing layer and the second modified heat-sealing layer are extruded synchronously. The composite roller is pressed together with a pressing pressure of 0.5MPa and a pressing temperature of 95℃ to obtain a three-layer composite structure. S4. Online cooling and curing: The intermediate coated paper obtained in S4 is fed into the cooling roller group and cooled by circulating cooling water at 17°C. The cooling speed is controlled at 18m / min, and the overall production line speed is 110m / min. The paper is then wound up to obtain the finished double-sided heat-sealed coated paper.

[0034] Performance testing: Double-sided heat seal strength 12.6N / 15mm, paper fiber recovery rate 87.7%, 180-day compost degradation rate 89.0%, and large-area deinking after one application of tape.

[0035] Test Industrial composting tests were conducted on the products from Examples 1 to 4, and the test results are shown in Table 1.

[0036] Table 1 Industrial composting test results

[0037] In an industrial composting environment at 58±2℃, the organic components degrade by ≥90% within 180 days and disintegrate into fragments ≤2mm within 12 weeks. The compost products do not inhibit plant growth, and heavy metals such as lead, cadmium, and mercury are not detected, meeting the EN 13432 compostability certification standard.

[0038] Printing tests, heat seal strength tests, and waterproof and oil-proof tests were conducted on the products of Examples 1 and 4, as well as Comparative Examples 1 and 2. Water-based environmentally friendly inks were used for all printing tests. The results of ink adhesion (5 repeated applications of 3M tape) and waterproof and oil-proof (Kit method) are shown in Table 2. The heat seal strength results are as follows: Figure 1 As shown.

[0039] Table 2 Test results of printing ink adhesion, water resistance, and oil resistance.

[0040] The products in the examples all showed synergistic improvements in printing tests, heat seal strength tests, and waterproof and oil-proof tests. In Comparative Example 1, the polarity of the printed surface was too low, preventing effective ink adhesion; in Comparative Example 2, excessive corona discharge resulted in defects in ink adhesion, affecting appearance and barrier properties, while micro-cracks reduced waterproof and oil-proof performance.

[0041] Therefore, the present invention adopts the above-mentioned double-sided coated paper and its preparation method and application, which synergistically improves double-sided heat sealability, water and oil resistance, printability and environmental recyclability, and meets the use needs of high-end environmentally friendly packaging in multiple fields.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A double-sided coated paper, characterized in that, It includes a first modified heat-sealing layer, a paper base layer, and a second modified heat-sealing layer, wherein the paper base layer uses environmentally friendly recycled pulp as the substrate, and both the first and second modified heat-sealing layers use a modified composite coating. The modified composite coating includes the following components in parts by weight: 60-70 parts of polybutylene adipate-terephthalate; 10-15 parts of polylactic acid; 10-20 parts of disintegrant; 1-2 parts of slip agent; 1-3 parts of anti-blocking agent; Chain extender 0.2~0.5 parts.

2. The double-sided coated paper according to claim 1, characterized in that: The environmentally friendly recycled pulp base material is specifically a mixture of recycled wood pulp and bamboo pulp in a mass ratio of 7:

3.

3. The double-sided coated paper according to claim 1, characterized in that: The basis weight of the paper base layer is controlled between 150 and 320 g / m². 2 The moisture content is <4.5%; the thickness of the first modified heat seal layer and the second modified heat seal layer is controlled at 12~15μm.

4. The double-sided coated paper according to claim 1, characterized in that: The disintegrant is thermoplastic starch, the slip agent is bio-based fatty acid amide, the anti-blocking agent is silica masterbatch, and the chain extender is glycidyl methacrylate.

5. A method for preparing double-sided coated paper as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Paper base pretreatment: The paper base prepared from the mixed pulp is dried with low temperature hot air at 50~60℃, and the moisture content is controlled to <4.5%. Then, a primary corona treatment is performed to control the surface tension to 35~37 dynes to obtain the paper base. S2. Modified heat-sealing layer raw material blending modification: PBAT, PLA, disintegrant, slip agent and anti-blocking agent are added into a high-speed mixer according to the ratio and mixed at 80~90℃ for 20~30min to obtain a mixture. Then the mixture is fed into a twin-screw extruder and melted and plasticized at 160~180℃. Then a chain extender is added in the middle and rear section of the twin-screw extruder to obtain a melt. S3, Double-sided synchronous co-extrusion coating: The molten material obtained in S2 is fed into the double-sided co-extrusion die head, and the die head temperature is controlled to be stable at 170~180℃. The paper base layer obtained in S1 is passed through the die head at a uniform speed, and the first modified heat-sealing layer and the second modified heat-sealing layer are extruded synchronously. The composite roller is pressed together to obtain a three-layer composite structure. S4. Segmented corona activation treatment: The first modified heat-sealing layer of the three-layer composite structure obtained in S3 is subjected to a second corona treatment to control the surface tension to 39~42 dynes. The second modified heat-sealing layer is subjected to a light corona treatment to obtain the intermediate product of coated paper. S5. Online cooling and curing: The intermediate coated paper obtained in S4 is fed into the cooling roller group and cooled by circulating cooling water at 15~20℃ to obtain the finished double-sided heat-sealed coated paper.

6. The method for preparing a double-sided coated paper according to claim 5, characterized in that, In S1, the process parameters for the primary corona treatment are: electrode gap 1.0~2.0mm, frequency 10~25KHz, voltage 10~20kV, and time 15~30s.

7. The method for preparing a double-sided coated paper according to claim 5, characterized in that, In S3, the relevant parameters for the composite roller pressing are: pressing pressure controlled at 0.4~0.6MPa, and pressing temperature at 85~100℃.

8. The method for preparing a double-sided coated paper according to claim 5, characterized in that, In S4, the process parameters for the secondary corona treatment are: electrode gap 1.0~1.5mm, frequency 20~35KHz, voltage 15~25kV, and time 15~30s. The process parameters for the mild corona treatment are: electrode gap 2.0~2.5mm, frequency 10~20kHz, voltage 8~12kV, and time 15~30s.

9. The method for preparing a double-sided coated paper according to claim 5, characterized in that, In S5, the cooling speed of the cooling roller assembly is controlled at 15~20m / min, and the overall production line speed is 100~120m / min.

10. The application of a double-sided heat-sealed coated paper product prepared by the method of preparing double-sided coated paper according to any one of claims 5 to 9 in recyclable and environmentally friendly food packaging paper.

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