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CN-121407420-B - Double PHA barrier system for paper-based container and paperboard, and preparation method and application thereof

CN121407420BCN 121407420 BCN121407420 BCN 121407420BCN-121407420-B

Abstract

The invention discloses a double PHA barrier system for paper-based containers and paperboards, and a preparation method and application thereof, and belongs to the technical field of paper-based material surface engineering and green packaging. The system sequentially comprises a paper base material, a water-based PHA (polyhydroxyalkanoate) dispersed hole sealing layer and a PHA extruded compact layer from inside to outside. The invention utilizes micron PHA dispersoid without cell fragments, can realize the high-efficiency hole sealing effect which is difficult to achieve by the traditional process with high coating amount only by extremely low coating amount, and radically eliminates the pinhole defect of an extrusion layer. The modified PHA extrusion layer with specific crystallinity is matched, so that the microcrack problem of a single coating in roll forming is cooperatively solved. The system achieves excellent barrier properties with a thinner bio-based structure, while having a broad heat seal window and excellent repulping recovery. Compared with the prior art, the invention obviously reduces the consumption of packaging materials and the environmental burden on the premise of ensuring high performance.

Inventors

  • LIN FANQIU
  • ZHAO XUGUANG
  • Pang Dehan
  • CHEN YUEZHI
  • ZHAO LEI
  • DOU WANQIANG
  • KANG XUFENG

Assignees

  • 都佰城新材料技术（上海）有限公司
  • 环涂士涂料有限公司
  • 中科联化有限公司
  • 都佰城集团有限公司

Dates

Publication Date
20260508
Application Date
20251224

Claims (14)

  1. 1. The utility model provides a double polyhydroxyalkanoate separation system for paper-based container and cardboard, its characterized in that includes paper substrate, waterborne polyhydroxyalkanoate dispersion hole sealing layer and polyhydroxyalkanoate extrusion compact layer that sets gradually from inside to outside, wherein: The aqueous polyhydroxyalkanoate dispersion hole sealing layer is derived from an aqueous polyhydroxyalkanoate dispersion which is prepared by a melt dispersion or solvent extraction re-emulsification process and does not contain cell debris, and polyhydroxyalkanoate in the dispersion is selected from one or more of short-chain polyhydroxyalkanoate, medium-long-chain polyhydroxyalkanoate or a copolymer between monomers forming short-chain and medium-long-chain polyhydroxyalkanoate; The short-chain polyhydroxyalkanoate is selected from one or more of poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and poly (3-hydroxybutyrate-co-4-hydroxybutyrate); the medium-long chain polyhydroxyalkanoate is selected from one or more of poly (3-hydroxycaproic acid ester), poly (3-hydroxyheptanoate), poly (3-hydroxyoctanoate), poly (3-hydroxynonanoate), poly (3-hydroxydecanoate), poly (3-hydroxydodecanoate) and poly (3-hydroxytetradecanoate); The solid content of the dispersion is 25% -50%, the median diameter D 50 of the particle size is 0.20-2.00 mu m, the 90% cumulative distribution particle size D 90 is less than or equal to 3.00 mu m, the dry coating amount of the dispersed hole sealing layer is 2-10g/m < 2 >, and the total water content of the paper base material and the dispersed hole sealing layer after multistage drying is less than or equal to 3.0%; The polyhydroxyalkanoate extruded compact layer is a blend of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) in a mass ratio of 75 to 25 to 82 to 18, a mole fraction of 3-hydroxyvalerate units in the poly (3-hydroxybutyrate-co-3-hydroxyvalerate) of 5 to 12%, a mole fraction of 3-hydroxyhexanoate units in the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) of 6 to 15%, the polyhydroxyalkanoate extruded compact layer has a melt flow rate of 2 to 5g/10min at 170 to 190 ℃ and a 2.16kg load, a secondary temperature rise differential scanning calorimetric crystallinity of 33 to 37%, and a thickness of 20 to 30 μm or an areal density of 24 to 39g/m2; corona or plasma treatment is carried out on the interface to be covered before extruding the polyhydroxyalkanoate extruded compact layer to ensure that the surface energy is more than or equal to 42mN/m, coating or compounding is completed within 30min after the treatment, the interval time from the water-based polyhydroxyalkanoate dispersed hole sealing layer to the extrusion line is less than or equal to 10min, the preheating temperature is 60-110 ℃ before the line is fed, and the preheating time is 5-30s.
  2. 2. The barrier system of claim 1, wherein the polyhydroxyalkanoate extruded densified layer further comprises one or more selected from the group consisting of poly 3-hydroxybutyrate, poly (3-hydroxybutyrate-co-4-hydroxybutyrate) and medium-long chain polyhydroxyalkanoates such that the total polyhydroxyalkanoate content of the extruded densified layer is greater than or equal to 95%.
  3. 3. The dihydroxyfatty acid ester barrier system for paper-based containers and paperboard according to claim 1, wherein at least two of the following conditions are satisfied when the dry coating amount of the aqueous polyhydroxyfatty acid ester dispersion sealing layer is 2-10g/m 2: The paper base material is subjected to sizing and calendaring treatment, the Benthsen roughness of the paper base material is less than or equal to 200mL/min or the surface smoothness of PPS is less than or equal to 1.2 mu m; The median diameter D 50 of the particle size of the aqueous polyhydroxyalkanoate dispersion is less than or equal to 2.0 mu m, and the viscosity at 25 ℃ is 400-1200 mPa.s; adopting a double micro-coating process or a slit head micro-coating process; the relative humidity of the dry tail section is less than 25 percent and is discharged the total water content in the drying box is less than or equal to 3.0 percent.
  4. 4. The dihydroxyfatty acid ester barrier system for paper-based containers and paperboard according to claim 1, further comprising a functional barrier layer that is a thin oxygen barrier layer or a carbon dioxide barrier layer, wherein: The thin oxygen-blocking interlayer is arranged between the water-based polyhydroxyalkanoate dispersion hole sealing layer and the polyhydroxyalkanoate extrusion compact layer, is a water-dispersible oxygen-blocking polymer coating, has a dry coating amount of 2-6g/m <2 >, and is one or more of the following types: Polyvinyl alcohols, including polyvinyl alcohols composed of vinyl alcohol units and polyvinyl alcohols obtained by partial or complete saponification of vinyl acetate; ethylene-vinyl alcohol copolymers obtained by copolymerizing an ethylene monomer and a vinyl alcohol unit; Polysaccharides and derivatives thereof, including carboxymethyl cellulose, hydroxypropyl methylcellulose, and starch or starch esters; The aqueous composite of the buccal tablet layer nano material comprises a composite of nano cellulose or montmorillonite and a water-soluble polymer; The carbon dioxide-blocking interlayer is arranged between the water-based polyhydroxyalkanoate dispersion hole sealing layer and the polyhydroxyalkanoate extrusion compact layer, and is a thermoplastic gas-blocking polymer layer at the inner side or the outer side of the polyhydroxyalkanoate extrusion compact layer, and the polymer is one or more selected from polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyglycolic acid, polylactic acid, polyethylene terephthalate and aliphatic-aromatic copolyester, wherein the aliphatic-aromatic copolyester comprises a copolymer obtained by polycondensation of terephthalic acid, aliphatic dibasic acid and dihydric alcohol, and the dry coating amount or the surface density of the carbon dioxide-blocking interlayer is 2-8g/m < 2 >.
  5. 5. The barrier system of claim 1, wherein the polyhydroxyalkanoate extruded densified layer comprises 0-5% plasticizer selected from one or more of the group consisting of citric acid esters and polyethylene glycols; And a bonding transition phase is arranged between the water-based polyhydroxyalkanoate dispersion hole sealing layer and the polyhydroxyalkanoate extrusion compact layer or inside the polyhydroxyalkanoate extrusion compact layer, the bonding transition phase is a bonding resin layer, the resin is one or more selected from modified polyhydroxyalkanoate, degradable aliphatic or aliphatic-aromatic copolymerized polyester, polybutylene succinate obtained by polycondensation of succinic acid and 1, 4-butanediol and polybutylene adipate obtained by polycondensation of adipic acid and 1, 4-butanediol, polylactic acid obtained by ring-opening polymerization of lactic acid monomers, ethylene-vinyl acetate copolymer obtained by copolymerization of ethylene and vinyl acetate monomers, polyvinyl alcohol obtained by hydrolysis of vinyl alcohol units, and the water-based polyurethane adhesive, and the thickness of the bonding transition phase is 1-10 mu m or the dry coating amount is 1-5g/m < 2 >.
  6. 6. The dihydroxyl fatty acid ester barrier system for paper-based containers and paperboard according to claim 1, wherein an aqueous top coat layer with a dry coating amount of 3-8g/m2 is arranged outside the polyhydroxyalkanoate extrusion compact layer, the aqueous top coat layer at least comprises an aqueous polyhydroxyalkanoate and can further comprise an aqueous film forming polymer selected from one or more of an aqueous acrylate resin, an aqueous polyurethane and a polyvinyl alcohol or ethylene-vinyl alcohol copolymer.
  7. 7. A dihydroxyfatty acid ester barrier system for paper based containers and paperboard according to claim 1, wherein the system is adapted for heat sealing with a heat sealing window covering at least 20 ℃ in the range of 130-170 ℃.
  8. 8. The dihydroxyfatty acid ester barrier system for paper based containers and paperboard according to claim 1, wherein the paper substrate is a vegetable fiber based paper, paperboard or molded pulp board having a basis weight of 150-400g/m2.
  9. 9. A method of preparing a dihydroxyfatty acid ester barrier system for paper-based containers and paperboard as recited in claim 1, comprising the steps of: Step 1, applying aqueous polyhydroxyalkanoate dispersion on the surface of a paper or paperboard substrate, wherein the dispersion is prepared by a melt dispersion or solvent extraction and re-emulsification process, the wall-broken suspension of fermentation liquor is not used as a raw material, the solid content of the dispersion is 25% -50%, the median diameter D 50 in the particle size is 0.20-2.00 mu m, the dry coating amount is controlled to be 2-10g/m < 2 >, and the aqueous polyhydroxyalkanoate dispersion hole sealing layer is obtained after drying; Step 2, drying the paper or paperboard substrate obtained in the step 1 and the water-based polyhydroxyalkanoate dispersion hole sealing layer formed on the paper or paperboard substrate by adopting zoned hot air or infrared drying, wherein the drying comprises a first section, a middle section and a tail section, the drying temperature of the first section is 60-90 ℃, the drying temperature of the middle section is 80-110 ℃, the drying temperature of the tail section is 70-90 ℃, the relative humidity of the drying area of the tail section is less than or equal to 25%, and the total water content of the paper or paperboard substrate and the water-based polyhydroxyalkanoate dispersion hole sealing layer after drying is less than or equal to 3.0%, so that the water-based polyhydroxyalkanoate dispersion hole sealing layer after drying is obtained; Step 3, balancing the dried water-based polyhydroxyalkanoate dispersion hole sealing layer obtained in the step 2 and a paper or paperboard substrate for 2-10min under the conditions of 23 ℃ and 50% relative humidity, preheating to 60-110 ℃ before feeding, keeping for 5-30s, adopting corona or plasma treatment before extrusion to ensure that the interfacial surface energy is more than or equal to 42mN/m, finishing extrusion within 30min after treatment, extruding and coating a polyhydroxyalkanoate melt on the surface of the dried water-based polyhydroxyalkanoate dispersion hole sealing layer to form an extrusion compact layer within no more than 10min after the drying box is discharged, controlling extrusion parameters to be that the melt temperature is 150-200 ℃, the air gap is 80-150mm, the pressure of a press roll is 4-8bar, the temperature of a cooling roll is 10-25 ℃, the linear speed is 60-250m/min, the melt shearing rate is 50-500s -1 , wherein the melt is a blend of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) with the mass ratio of 75-to 25-82, the melt flow rate is 2-5g/10m, the differential crystallization rate is 20-37 mu m, and the extrusion compact layer is formed by scanning the thickness of the extrusion compact layer to be 20-30 mu m; And 4, cooling and shaping the polyhydroxyalkanoate extruded compact layer and the paper or paperboard substrate at the inner side of the polyhydroxyalkanoate extruded compact layer and the water-based polyhydroxyalkanoate dispersed hole sealing layer, and slitting and rolling or directly shaping the polyhydroxyalkanoate extruded compact layer to form a paper-based product to obtain the double polyhydroxyalkanoate barrier system.
  10. 10. The method of claim 9, comprising one or both of the following steps: After the step 2 and before the step 3, applying a blocking interlayer on the surface of the dried water-based polyhydroxyalkanoate dispersion hole sealing layer obtained in the step 2, wherein the blocking interlayer is a thin oxygen blocking interlayer or a carbon dioxide blocking interlayer, and controlling the dry coating amount of the blocking interlayer to be 2-8g/m2 to obtain a blocking interlayer; After the step 3, an aqueous top coating is applied to the outside of the polyhydroxyalkanoate extrusion compact layer obtained in the step 3, wherein the dry coating amount of the aqueous top coating is 3-8g/m2, and the aqueous top coating is obtained.
  11. 11. The method according to claim 9, wherein when the dry coating amount of the hole sealing layer is 2 to 5g/m2, a double micro coating process or a slit head micro coating process is used, and the viscosity of the dispersion at 25 ℃ is controlled to be 400 to 800 mPa-s.
  12. 12. The method of manufacturing according to claim 9, further comprising the step of forming the paper cup with a heat seal temperature of 140-170 ℃ for 0.2-1.0s, creasing, hemming or locking the cutlery box or tray, or die cutting and attaching the dry liner.
  13. 13. Use of the dihydroxyfatty acid ester barrier system for paper based containers and paperboard according to claim 1 in paper cups, take-away cutlery boxes, baking trays, cold drink cups and dry liner packaging, characterized in that said use meets at least three combination performance requirements: The water vapor transmittance is less than or equal to 50 g/(m2.d) under the conditions of ASTM F1249-25 standard and 23 ℃ and 50% relative humidity; the grease blocking grade is more than or equal to grade 9 according to TAPPI T559 cm-22 standard; the microcrack rate of the rolling opening or the rib folding area is less than or equal to 1 percent; the repulping rejection rate measured according to the PTS-RH 021:2012 type II method is less than or equal to 10%; the 180-degree peel strength of the polyhydroxyalkanoate extruded compact layer and the water-based polyhydroxyalkanoate dispersed hole sealing layer or the paper base material is more than or equal to 1.0N/15mm.
  14. 14. Use according to claim 13, characterized in that one of the following conditions is fulfilled: When used in a non-aerated beverage paper cup or cold drink cup, the water vapor transmittance under the conditions of ASTM F1249-25 standard, 23 ℃ and 50% relative humidity is less than or equal to 30 g/(m 2. D), the microcracking rate of a rolling mouth or a rib folding area is less than or equal to 1%, and the 180 DEG peel strength of the polyhydroxyalkanoate extrusion compact layer and the aqueous polyhydroxyalkanoate dispersion hole sealing layer or paper substrate is more than or equal to 1.0N/15mm; When the packaging material is used for packaging dairy products or dry goods with a shelf life of 3 months or more, the oxygen transmittance is less than or equal to 30cm < 3 >/(m < 2 >. D) under the conditions of ASTM D3985-24 standard and 23 ℃ and 0% relative humidity; When the sealing fatigue test is used for a carbon dioxide-containing beverage paper cup inner liner or a paper shell and inner liner packaging structure, the sealing fatigue test proves that after the carbon dioxide-containing beverage is filled, the sealing fatigue test proves that the sealing fatigue test is carried out for 100 times under the internal pressure of 0.25-0.60MPa, wherein the carbon dioxide retention rate is more than or equal to 95%, the leakage rate after the internal pressure circulation is less than or equal to 2%, and the sealing fatigue qualification rate is more than or equal to 95%.

Description

Double PHA barrier system for paper-based container and paperboard, and preparation method and application thereof Technical Field The invention belongs to the technical field of paper-based material surface engineering and green packaging, and particularly relates to a double PHA barrier system for paper-based containers and paperboards, and a preparation method and application thereof. Background With the deep implementation of plastic limiting and plastic prohibiting in the global scope, the consumer environmental protection consciousness is obviously improved, and the search for green substitutes of the traditional petroleum-based plastics has become an urgent need of the packaging industry. Paper and paperboard are widely used in the field of food and beverage packaging as a natural, renewable and biodegradable material. However, paper-based materials themselves have porosity, hydrophilicity, and fibrous moisture-absorbing swelling properties, and lack effective barrier capability to water, water vapor, grease, and gases, which greatly limit their immediate use in liquid containers, high humidity environments, or long shelf life food packaging. In order to impart the necessary barrier properties to paper-based materials, the prior art generally employs a film-casting or coating process. The main solution in the market at present is to extrude and laminate polyethylene, PE for short, or polyethylene terephthalate, PET for short, and other petroleum-based plastics. Although the traditional laminated paper has excellent waterproof and oil-proof performance and heat sealing performance, the plastic coating is tightly combined with the paper base, and is difficult to realize effective separation by a conventional pulping process after being abandoned, and is often classified as non-recyclable garbage to be buried or burned, so that serious resource waste and environmental pollution are caused. Another common oil-repellent treatment is sizing or coating with fluorochemical substances, but with perfluorinated and polyfluoroalkyl substances, PFAS for short, development of fluorine-free oil-repellent replacement techniques has been hampered due to increasingly stringent regulatory restrictions on bioaccumulation and potential toxicity worldwide. In the field of biodegradable polymers, polylactic acid (PLA) is a paper laminating material which is widely applied at present. Although PLA has industrial compost degradation capability, it is poor in heat resistance, has a narrow heat sealing temperature window, and is hard and brittle in texture, and is extremely susceptible to brittle fracture when paper cup is rolled or paper box is folded and molded. In addition, the barrier properties of PLA are highly sensitive to environmental humidity, and it is difficult to meet the high standard requirements of cold chain or hot beverage packaging. Polyhydroxyalkanoates (PHA), which are intracellular polyesters synthesized by fermentation of microorganisms using various carbon sources, have not only thermoplastic processability similar to petroleum-based plastics, but also excellent hydrophobicity, gas barrier property and completely biodegradability in soil, fresh water or even marine environments, and are considered as ideal green packaging materials. However, the application of PHA to paper-based packaging still faces a number of technical bottlenecks: Firstly, the fiber network structure on the paper surface is rough and porous, and when a single PHA melt extrusion lamination process is adopted, a higher coating thickness is often required for covering capillary pores on the paper surface and eliminating pinhole defects, which not only greatly increases the raw material cost, but also can lead to curling and stiffness reduction. If the thickness is reduced, pinholes are very likely to be generated due to melt film rupture, resulting in barrier failure. Second, the existing PHA aqueous dispersion coating technology has significant drawbacks. In the prior art, as in the schemes of patent EP4166716A1 and Chinese patent CN115698427B, attempts are made to directly prepare aqueous paint by using crude extract obtained after breaking wall of fermentation broth, or to stabilize dispersion by relying on a large amount of emulsifying agent and water-soluble polymer binder such as polyvinyl alcohol. The PHA dispersion based on fermentation stock solution often has a large amount of cell fragments, proteins and residual culture medium components remained, and the impurities can not only cause peculiar smell and color browning of the coating, but also have extremely strong hygroscopicity, and seriously destroy the hydrophobic barrier advantage of PHA. At the same time, the introduction of a large amount of hydrophilic auxiliary agent makes the coating easy to swell, sticky and even disintegrate when contacting water or high humidity environment. Furthermore, single component PHA materials present inherent contradictions in processin