A polycarbonate laminated material with high seal strength

Abstract

The application discloses a polycarbonate lamination material with high sealing strength and belongs to the technical field of high polymer packaging materials. The material is composed of the following components in parts by weight: PPCP 50-95 parts, PBAT 5-50 parts, PLA 0-20 parts and lamination auxiliary agent 0.1-20 parts. The number average molecular weight of the PPCP is 5W-40W, and the number average molecular weight of the PBAT is 5W-8W. The technical scheme of the application forms the lamination material with excellent comprehensive performance by taking PBAT and PPCP as the basic composition and combining the synergistic effect of the functional auxiliary agent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high molecular packaging materials, and specifically relates to a polycarbonate coating material with high sealing strength. BACKGROUND

[0002] With the increasing environmental awareness and the growing demand for degradable materials, coating materials are increasingly widely used in the fields of packaging, sanitary products and the like. PBAT (polybutylene adipate terephthalate) as a common biodegradable plastic has become a research hotspot due to its good mechanical properties and processing properties. However, the existing PBAT coating material still has deficiencies in sealing strength, barrier performance and adhesion strength with the original paper layer, which limits its promotion in high-end application scenarios.

[0003] After searching, a preparation method and application of a PBAT coating composite material (CN104999609B) were disclosed on March 29, 2017. The patent prepared a composite material with excellent mechanical properties by mixing PBAT with other biodegradable plastics or ultrafine calcium carbonate and then coating. However, this technical solution mainly focuses on the mechanical properties and water and oil resistance of the material, and does not fully consider the optimization of sealing strength and barrier performance. In addition, the adhesion strength of PBAT with the original paper layer in this solution is limited, which may cause peeling risk in actual use and affect the overall performance of the product.

[0004] After searching, a fully biodegradable coating paper (CN111187494B) and a preparation method thereof were disclosed on April 1, 2022. The patent solved the problem of low heat distortion temperature of PBAT by coating with a biodegradable resin mainly composed of PBAT, and reduced the production cost. However, this technical solution has insufficient sealing strength, especially in high temperature or high humidity environments, and the sealing is prone to failure. At the same time, the adhesion strength between the coating layer and the original paper layer in this solution still has room for improvement, which may cause delamination problems under complex stress conditions.

[0005] The above problems show that the existing PBAT coating material still has certain limitations in sealing strength, barrier performance and adhesion strength with the original paper layer. Therefore, the present application provides a polycarbonate coating material with high sealing strength, which aims to significantly improve the sealing strength, barrier performance and adhesion strength with the original paper layer by using a combination of PBAT and polycarbonate material as the coating material, so as to meet the needs of high-end packaging and functional material fields. SUMMARY

[0006] The technical problem solved by the present application is to overcome the shortcomings of the prior art and provide a polycarbonate coating film material with good barrier performance, high adhesion strength to the original paper layer and high sealing strength.

[0007] The technical solution adopted by the present application to solve its technical problem is: a polycarbonate coating film material with high sealing strength, characterized by: the composition of the material includes: PPCP (a terpolymer of propylene oxide, phthalic anhydride and carbon dioxide) 50-95 parts, PBAT 5-50 parts, PLA 0-20 parts, and coating film additives 0.1-20 parts.

[0008] The technical solution of the present application uses PBAT and PPCP as the basic composition, and combines the synergistic effect of functional additives to form a coating film material with excellent comprehensive performance.

[0009] Preferably, the polycarbonate coating film material with high sealing strength, the number average molecular weight of the PPCP is 5W-40W, and the number average molecular weight of the PBAT is 5W-8W.

[0010] Selecting PPCP with a molecular weight range of 5W-60W can ensure that the material forms a dense and uniform film structure during the coating process. More preferably, the number average molecular weight of the PPCP is 20W-40W, which can maintain stable melt flowability during high-temperature coating (260-320℃), avoiding the mechanical property decline caused by molecular chain rupture. When the molecular weight of PBAT is in the range of 8W-10W, the ductility and rigidity of the molecular chain reach the best balance. More preferably, the number average molecular weight of the PBAT is 5.5W-6.5W, which can significantly improve the tensile strength and elongation at break of the material through molecular chain entanglement, thereby enhancing the tear resistance of the sealing part.

[0011] Preferably, the polycarbonate coating film material with high sealing strength, the mole percentage of polypropylene carbonate (PC) repeating units on the molecular chain of the PPCP is 60%-95%, preferably 80%-90%, the mole percentage of propylene oxide-phthalic anhydride copolymer (PA) repeating units is 5%-40%, preferably 10%-20%, and the balance is polyether segment (PO) of propylene oxide self-polymerization.

[0012] The PPCP molecular structure of the present application has excellent tensile strength, thereby enhancing the tear resistance of the sealing part. The ester group of the appropriate PA segment can form hydrogen bonds or chemical bonds with the carboxyl group of PBAT, thereby enhancing the adhesion strength (peeling strength ≥ 3.5 N / mm) to the paper-based fiber. The polyether segment of propylene oxide self-polymerization acts as a flexible segment and is distributed between the rigid main chain to play a stress buffering role. The melt flow performance of the PPCP ensures the uniformity of the coating layer in the coating process.

[0013] Preferably, the polycarbonate coating material with high sealing strength, the weight part composition of the coating aid includes: 0.1-7 parts of a compatibilizer, 0-20 parts of a plasticizer, 0-2 parts of a coupling agent, 0-5 parts of an antioxidant, 0-3 parts of an ultraviolet stabilizer, 0-5 parts of an anti-hydrolysis agent, and 0-20 parts of a filler.

[0014] Preferably, in the coating aid, the compatibilizer is at least one of glycidyl methacrylate, ethylene-acrylate-glycidyl methacrylate, and maleic anhydride grafted PBAT (PBAT-g-MAH).

[0015] More preferably, the compatibilizer is maleic anhydride grafted PBAT, and the grafting rate of the maleic anhydride grafted PBAT is 0.8%-1.5%. The introduction of maleic anhydride grafted PBAT as a compatibilizer in the PBAT / PPCP system can better improve the compatibility of the two-phase interface, and the maleic anhydride grafted PBAT can form a stable network structure with the PBAT / PPCP matrix through chemical bonding.

[0016] When the grafting rate is 0.8%-1.5%, the PBAT-g-MAH promotes the formation of a more uniform dispersed phase of PBAT and PPCP during melt blending through the physical adsorption of polar groups. Experiments show that when the grafting rate is ≥0.8%, the size of the dispersed phase decreases from microns (>5 μm) to submicrons (<1 μm), which can reduce stress concentration caused by interface defects. PBAT-g-MAH with a grafting rate of 0.8%-1.5% can maintain the flexibility of PBAT and improve the overall tensile strength (≥33 MPa) through the reinforcing effect of rigid PPCP segments. Preferably, PBAT-g-MAH with a grafting rate can increase the initial thermal degradation temperature of the PPCP / PBAT system to above 240°C, which can adapt to higher coating processing temperatures. When the grafting rate is too low (<0.8%), the insufficient anhydride groups result in weak interfacial bonding; when the grafting rate is too high (>1.5%), the PBAT molecular chains are crosslinked, increasing the melt viscosity and reducing the processing efficiency (melt index decreases). A grafting rate of 0.8%-1.5% can balance the proportion of polar and flexible segments, maintaining the melt flowability of the material.

[0017] Preferably, in the coating aid, the compatibilizer is an isocyanate compatibilizer, including at least one of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexyl methane-4,4'-diisocyanate (HMDI), and diphenyl methane diisocyanate (MDI).

[0018] The isocyanate compatibilizer reacts with the hydroxyl or carboxyl groups of the PBAT / PPCP molecular chain through the isocyanate group to form a cross-linked structure, thereby improving the tensile strength and elongation at break of the lamination film material. More preferably, the compatibilizer is a composite compatibilizer of maleic anhydride grafted PBAT and isocyanate compatibilizer.

[0019] Preferably, in the above-mentioned lamination film aid, the plasticizer comprises a main plasticizer and an auxiliary plasticizer, the main plasticizer is epoxidized soybean oil, and the auxiliary plasticizer is glycerol or tributyl citrate.

[0020] The main plasticizer is epoxidized soybean oil, and the epoxy group thereof is coupled with the surface of the filler to further enhance the interfacial bonding force. Its flexibility and processing fluidity are significantly improved. The auxiliary plasticizer is glycerol or tributyl citrate, which can reduce the melt viscosity, but the amount needs to be controlled to avoid excessive reduction of thermal stability. Preferably, the mass ratio of the main plasticizer to the auxiliary plasticizer in the plasticizer is 10:0.8~2.4.

[0021] Preferably, in the above-mentioned lamination film aid, the coupling agent is a silane coupling agent. The silane coupling agent (such as KH550) is used for surface treatment of each material, and the wettability of the aid with the PBAT / PPCP matrix is improved through chemical bonding, and the agglomeration phenomenon is reduced.

[0022] Preferably, in the above-mentioned lamination film aid, the antioxidant is 1010 or 168, and the ultraviolet stabilizer is a benzotriazole ultraviolet stabilizer. UV-531, UV-326, UV-384. The antioxidant is a compound of 1010 and 168 with a mass ratio of 1:1~2. These aids delay the aging process of the material by capturing free radicals and absorbing ultraviolet rays, thereby prolonging the service life.

[0023] In terms of process parameters, the melt blending temperature is controlled at 150℃~180℃, the lamination temperature is controlled at 260℃~320℃, and the speed is controlled at 50m / min~80m / min. The above-mentioned process conditions ensure uniform dispersion of the aid and form a firm bond between the coating and the substrate.

[0024] Compared with the prior art, the poly carbonate lamination film material with high sealing strength has the following beneficial effects: the sealing strength, barrier property and bonding force with the paper base material are comprehensively improved through the above technical means. Specifically, the synergistic effect of maleic anhydride grafted PBAT and MDI chain extender significantly enhances the interfacial bonding force between PBAT and PPCP, so that the material can still maintain excellent sealing performance in high temperature or high humidity environment. The lamellar structure of nano calcium carbonate prolongs the penetration path of gas and water vapor, thereby significantly improving the barrier property of the material. The introduction of PVA / borax composite coating further reduces the oxygen transmission rate, making it suitable for application scenarios with high barrier property requirements.

[0025] The present application provides a poly carbonate lamination film material with high sealing strength, excellent barrier property and firm adhesion to the base material by scientific and reasonable component ratio and process optimization, which can meet the needs of high-end packaging and functional material field.

[0026] In actual application, for example in the field of high-end food packaging, the lamination film material can significantly improve the sealing strength and barrier property, ensuring that the packaged contents can still maintain good sealing performance and shelf life in high temperature or high humidity environment. At the same time, firm adhesion to the paper base material avoids the risk of peeling, meeting the use requirements under complex stress conditions. DETAILED DESCRIPTION

[0027] The present application will be described in detail below by examples. If there is no other description, the raw materials used are commercially available.

[0028] The present application provides a poly carbonate lamination film material with high sealing strength, which structure design and preparation process are carried out around improving sealing performance, barrier property and bonding force with paper base material.

[0029] PBAT / PPCP is the basic component of the material, which is mixed by PBAT and PPCP according to the weight ratio of 20-35 / 65-80. In actual operation, PBAT and PPCP are first dried to a moisture content of less than 0.05% to avoid hydrolysis reaction during processing and affect the material performance. Then, they are placed in a high-speed mixer and pre-mixed at 70℃~90℃ for 5~10 minutes to make the two polymers preliminarily uniformly dispersed to obtain the base material. At this time, the amount of maleic anhydride grafted PBAT is added, which is 5%~7% of the total weight. Maleic anhydride grafted PBAT as a compatibilizer can improve the interfacial compatibility between PBAT and PPCP through chemical bonding, thereby forming a stable two-phase system. In the subsequent melt blending process, maleic anhydride grafted PBAT is preferentially distributed at the interface between PBAT and PPCP.

[0030] A proportion of MDI chain extender is further introduced into the PBAT / PPCP substrate. The MDI chain extender reacts with the active end groups in PBAT and PPCP during melt blending to form cross-linking. This cross-linking structure not only enhances the interfacial bonding force between PBAT and PPCP, but also improves the overall mechanical properties of the substrate. In actual production, the MDI chain extender needs to be added in the last stage of melt blending to avoid premature reaction leading to uneven molecular weight distribution. Through dynamic rheological testing, it is found that the occurrence of cross-linking significantly improves the storage modulus and loss modulus of the material, improving its deformation ability at high temperatures.

[0031] Epoxidized soybean oil is added as the main plasticizer to the substrate. The epoxy groups in epoxidized soybean oil can chemically bond with hydroxyl groups and form hydrogen bonds with the polar groups in PBAT and PPCP, thereby enhancing the interfacial bonding force. In actual production, epoxidized soybean oil needs to be added in the initial stage of melt blending to ensure its full dispersion in the substrate.

[0032] The addition amount of antioxidant and ultraviolet stabilizer is 0.5-1% of the total weight. The antioxidant is selected as a 1010 and 168 compound system, with a weight ratio of 1:1~2. The ultraviolet stabilizer is preferably selected as UV-531, which contains a benzotriazole group in its molecular structure and can effectively absorb ultraviolet light energy. In actual operation, the antioxidant and ultraviolet stabilizer need to be added in the last stage of melt blending to avoid the influence of high temperature degradation on their performance. Through accelerated aging test, it is found that the synergistic effect of antioxidant and ultraviolet stabilizer significantly delays the aging process of the material, prolonging its service life in natural environment to more than 5 years.

[0033] The process parameters of the entire preparation process are optimized to ensure uniform dispersion of the auxiliary agent and the bonding strength of the coating. The melt blending temperature is controlled within the range of 150℃~180℃ (preferably 165℃), and the specific temperature is adjusted according to the thermal stability of the material. The film coating temperature is set to 260℃~320℃ (preferably 295℃), and the film coating speed is 50m / min~80m / min (preferably 65m / min. In actual production, the melt blending equipment uses a double-screw extruder, and the screw rotation speed is controlled within the range of 200rpm~300rpm (250rpm) to ensure sufficient mixing of the materials. The film coating equipment preferably uses a multi-roller calender, and the gap between the rollers can be adjusted according to the thickness requirement of the coating. Through strict control of the above process parameters, the final film-coated material has excellent sealing performance, barrier properties, and bonding strength with the paper substrate, and is suitable for high-end packaging and functional material fields.

[0034] In order to make the relevant person in the art fully understand and realize the present application, the present application is further described below in combination with specific examples. The processing technology is the same as the above-mentioned preferred process parameters, and the material formula is shown in the examples. In order to facilitate the performance comparison of the main materials, some functional auxiliary materials are not embodied in the examples.

[0035] Example 1

[0036] The materials are prepared according to parts by weight: PPCP 70 parts, PBAT 30 parts, maleic anhydride grafted PBAT 4 parts, MDI 1.5 parts, plasticizer 4.5 parts, KH550 1.0 part, antioxidant 2 parts and UV-531 2 parts.

[0037] The number average molecular weight of PPCP is 18W, the number average molecular weight of PBAT is 6W; the mole percentage of PC repeating units in the molecular chain of PPCP is 83%, the mole percentage of PA repeating units is 12%, and the rest is PO; the grafting rate of maleic anhydride grafted PBAT is 1.1%, the plasticizer is a plasticizer compounded by epoxidized soybean oil and tributyl citrate at a mass ratio of 10:1.5, and the antioxidant is a compound of 1010 and 168 at a mass ratio of 1:1.2.

[0038] Example 2

[0039] The materials are prepared according to parts by weight: PPCP 70 parts, PBAT 30 parts, maleic anhydride grafted PBAT 4 parts, MDI 1.5 parts, plasticizer 4.5 parts, KH550 1.0 part, antioxidant 2 parts and UV-531 2 parts.

[0040] The number average molecular weight of PPCP is 18W, the number average molecular weight of PBAT is 6W; the mole percentage of PC repeating units in the molecular chain of PPCP is 83%, the mole percentage of PA repeating units is 12%, and the rest is PO; the grafting rate of maleic anhydride grafted PBAT is 3%, the plasticizer is a plasticizer compounded by epoxidized soybean oil and tributyl citrate at a mass ratio of 10:1.5, and the antioxidant is a compound of 1010 and 168 at a mass ratio of 1:1.2.

[0041] Example 3

[0042] The materials are prepared according to parts by weight: PPCP 70 parts, PBAT 30 parts, maleic anhydride grafted PBAT 4 parts, MDI 1.5 parts, plasticizer 4.5 parts, KH550 1.0 part, antioxidant 2 parts and UV-531 2 parts.

[0043] The number average molecular weight of PPCP is 18W, the number average molecular weight of PBAT is 6W; the mole percentage of PC repeating units in the molecular chain of PPCP is 83%, the mole percentage of PA repeating units is 12%, and the balance is PO; the plasticizer is a plasticizer compounded by epoxidized soybean oil and tributyl citrate at a mass ratio of 10:1.5, and the antioxidant is a compound of 1010 and 168 at a mass ratio of 1:1.2.

[0044] Example 4

[0045] The raw materials are prepared according to parts by weight: PPCP 70 parts, PBAT 30 parts, maleic anhydride grafted PBAT 4 parts, MDI 1.5 parts, plasticizer 4.5 parts, KH550 1.0 part, antioxidant 2 parts and UV-531 2 parts.

[0046] The number average molecular weight of PPCP is 18W, the number average molecular weight of PBAT is 6W; the mole percentage of PC repeating units in the molecular chain of PPCP is 83%, the mole percentage of PA repeating units is 12%, and the balance is PO; the plasticizer is a plasticizer compounded by epoxidized soybean oil and tributyl citrate at a mass ratio of 10:1.5, and the antioxidant is a compound of 1010 and 168 at a mass ratio of 1:1.2.

[0047] Example 5

[0048] The raw materials are prepared according to parts by weight: PPCP 70 parts, PBAT 30 parts, maleic anhydride grafted PBAT 4 parts, MDI 1.5 parts, plasticizer 4.5 parts, KH550 1.0 part, antioxidant 2 parts and UV-531 2 parts.

[0049] The number average molecular weight of PPCP is 18W, the number average molecular weight of PBAT is 6W; the mole percentage of PC repeating units in the molecular chain of PPCP is 83%, the mole percentage of PA repeating units is 12%, and the balance is PO; the plasticizer is a plasticizer compounded by epoxidized soybean oil and tributyl citrate at a mass ratio of 10:1.5, and the antioxidant is a compound of 1010 and 168 at a mass ratio of 1:1.2.

[0050] Example 6

[0051] The raw materials are prepared according to parts by weight: PPCP 70 parts, PBAT 30 parts, maleic anhydride grafted PBAT 4 parts, MDI 1.5 parts, plasticizer 4.5 parts, KH550 1.0 part, antioxidant 2 parts and UV-531 2 parts.

[0052] The number average molecular weight of PPCP is 5W, and the number average molecular weight of PBAT is 8W; the mole percentage of PC repeating units in the molecular chain of PPCP is 89.6%, the mole percentage of PA repeating units is 9.8%, and the balance is PO; the plasticizer is a plasticizer compounded by epoxidized soybean oil and tributyl citrate at a mass ratio of 10:2.4.

[0053] The performance test of the laminated film material of each embodiment is carried out, and the test results are shown in Table 1.

[0054] Table 1 Performance test results

[0055] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Seal strength N / mm 3.5 3.1 3.2 3.0 3.2 2.7 Oxygen transmission rate cc / m2 day atm 19.1 21.4 21.6 17.8 22.6 17.6 Peel strength N / mm 3.7 3.2 3.1 3.1 3.5 2.9 Hygrothermal aging retention rate 89 84 81 89 81 78 Tensile strength MPa 34 33 32 42 30 31 Elongation at break % 435 387 376 298 452 274

[0056] Comparative Example 1

[0057] The formula and blending, laminating process are the same as Example 1, except that PBAT of equal mass is used instead of PPCP.

[0058] Performance comparison:

[0059] The sealing strength (ASTM F88) is only 1.8 N / mm, which is lower than 3.5 N / mm of Example 1 of the application;

[0060] The oxygen transmission rate (ASTM D3985) reaches 125 cc / m²·day·atm;

[0061] The peeling strength with the original paper (GB / T 2790) is only 1.2 N / mm, and the interface shows obvious delamination.

[0062] Comparative Example 2

[0063] The formula and blending, laminating process are the same as Example 1, except that PBAT of equal mass is used instead of maleic anhydride grafted PBAT.

[0064] Performance defects:

[0065] The melt flow index (230℃ / 2.16kg) decreases to 5g / 10min (Example 1 is 9g / 10min);

[0066] The interface compatibility is poor, and the DSC test shows that the separation degree of the melting peak of PBAT and PPCP increases by 35%;

[0067] The hygrothermal aging retention rate is 58% (85℃ / 85%RH, 500h).

[0068] Comparative Example 3

[0069] The formula and blending, laminating process are the same as Example 1, except that PPCP with a number average molecular weight of 80W and PBAT with a number average molecular weight of 15W are used.

[0070] Processing problems:

[0071] The melt blending temperature needs to be raised to above 200℃, which causes thermal degradation of PPCP (TGA shows weight loss 30℃ earlier);

[0072] Sharkskin defects occur in the lamination process, and the surface roughness (Ra) reaches 1.2μm (0.4μm for Example 1);

[0073] Melt fracture causes lamination thickness fluctuation of ±15% (Example controlled at ±5%).

[0074] The above description is only the preferred embodiment of the present application, and is not intended to limit the other forms of the present application. Any skilled person in the art can use the disclosed technical content to make changes or modifications to equivalent embodiments. However, any simple modification, equivalent change and modification made to the above embodiments without departing from the technical solution of the present application, and in accordance with the technical essence of the present application, still falls within the protection scope of the present application.

Claims

1. A high-seal-strength polycarbonate-coated film material, characterized by: The composition of the material includes: PPCP 50-95 parts, PBAT 5-50 parts, PLA 0-20 parts, and film forming aid 0.1-20 parts by weight; The mole percentage of polypropylene carbonate repeating units in the molecular chain of the PPCP is 60-95%, the mole percentage of propylene oxide-phthalic anhydride copolymer repeating units is 5-40%, and the rest is polyether segment of propylene oxide self-polymerization; The weight composition of the film forming aid includes: compatibilizer 0.1-7 parts, plasticizer 0-20 parts, coupling agent 0-2 parts, antioxidant 0-5 parts, ultraviolet stabilizer 0-3 parts, anti-hydrolysis agent 0-5 parts, and filler 0-20 parts; The compatibilizer is a composite compatibilizer of maleic anhydride grafted PBAT and MDI, and the grafting rate of the maleic anhydride grafted PBAT is 0.8-1.5%.

2. The high seal strength polycarbonate cast film material according to claim 1, wherein, The number average molecular weight of the PPCP is 5W-40W, and the number average molecular weight of the PBAT is 5W-8W.

3. The high seal strength polycarbonate cast film material of claim 1, wherein, The plasticizer includes a main plasticizer and an auxiliary plasticizer, the main plasticizer is epoxidized soybean oil, and the auxiliary plasticizer is glycerol or tributyl citrate.

4. The high seal strength polycarbonate cast film material of claim 1, wherein, The coupling agent is a silane coupling agent.

5. The high seal strength polycarbonate cast film material of claim 1, wherein, The antioxidant is 1010 or 168, and the ultraviolet stabilizer is a benzotriazole ultraviolet absorber.