Barrier coating composition for paper-based material, barrier coating and paper substrate

Abstract

In order to overcome the problems of insufficient mechanical strength and easy breeding of bacteria in the existing acrylic polymer barrier coating for paper-based materials, the present invention provides a barrier coating composition for paper-based materials, a barrier coating and a paper substrate, wherein the barrier coating composition for paper-based materials comprises the following components: water-based acrylic prepolymer, chitosan grafted polyvinyl alcohol, inorganic filler, microcrystalline cellulose, water-based polyurethane, polysiloxane grafted acrylic monomer, epoxy-containing acrylic monomer, 1,4-butanediol diacrylate and solvent. The barrier coating composition for paper-based materials provided by the present invention has excellent water vapor barrier performance and grease barrier performance. More importantly, the barrier coating composition for paper-based materials provided by the present invention has good antibacterial performance while having excellent mechanical properties, and is suitable for a variety of paper-based food packaging products such as disposable paper cups, paper bowls, and food boxes, thereby improving their food safety performance.

Description

Technical Field

[0001] The invention belongs to the technical field of barrier coatings, and in particular relates to a barrier coating composition for paper-based materials, a barrier coating and a paper substrate. Background Art

[0002] At present, traditional paper packaging generally adopts polyethylene (PE) coating process to achieve waterproof and oil-proof effects. However, PE coating is non-degradable and difficult to re-pulp, which makes paper packaging materials difficult to recycle and increases the environmental burden. In addition, PE coating will produce volatile organic compounds (VOC) during production and use, which has adverse effects on the environment and human health.

[0003] As global environmental awareness increases, the market is in urgent need of environmentally friendly and biodegradable paper packaging materials. However, existing alternative materials, such as polylactic acid (PLA) coatings, are expensive and have insufficient barrier properties, making it difficult to meet actual application needs.

[0004] Acrylic polymers are used in barrier coatings for paper-based materials because of their good water vapor and oil barrier properties after film formation, as well as good adhesion to paper materials. However, acrylic polymers have deficiencies in mechanical properties, mainly in their insufficient toughness and tensile strength. When the paper-based material is folded, cracks are easily generated at the folded position due to stretching, which leads to the failure of the barrier properties. Furthermore, acrylic polymers do not have good antibacterial properties. When used as a barrier coating for food packaging, bacteria are easily grown under conditions of long-term contact with food.

[0005] Therefore, developing a low-cost, high-performance high-barrier water-based coating composition for paper packaging has become a technical problem that the industry urgently needs to solve. Summary of the invention

[0006] Aiming at the problems that the existing acrylic polymer barrier coating for paper-based materials has insufficient mechanical strength and is easy to breed bacteria, the present invention provides a barrier coating composition for paper-based materials, a barrier coating and a paper substrate.

[0007] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0008] In one aspect, the present invention provides a barrier coating composition for a paper-based material, comprising the following components:

[0009] The invention discloses a water-based acrylic prepolymer, chitosan grafted polyvinyl alcohol, an inorganic filler, microcrystalline cellulose, a water-based polyurethane, a polysiloxane grafted acrylic monomer, an epoxy-containing acrylic monomer, 1,4-butanediol diacrylate and a solvent, wherein the epoxy-containing acrylic monomer comprises glycidyl methacrylate.

[0010] Optionally, the barrier coating composition for paper-based materials comprises the following components by weight:

[0011] 20-25 parts of water-based acrylic prepolymer, 10-15 parts of chitosan grafted polyvinyl alcohol, 8-50 parts of inorganic filler, 8-12 parts of microcrystalline cellulose, 5-8 parts of water-based polyurethane, 1-5 parts of polysiloxane grafted acrylic monomer, 1-3 parts of epoxy-containing acrylic monomer, 2-4 parts of 1,4-butanediol diacrylate and 8-50 parts of solvent.

[0012] Optionally, the polymerizable monomers of the waterborne acrylic prepolymer include one or more of carboxyl-containing monomers, hydroxyl-containing monomers, acrylate monomers, amino-containing monomers, and styrene monomers;

[0013] The carboxyl group-containing monomer includes one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, glucaric acid monoacrylate, and allyl sulfonic acid; and / or

[0014] The hydroxyl-containing monomer includes one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate; and / or

[0015] The acrylic acid ester monomers include one or more of methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, isobornyl acrylate, isobornyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, and phenyl methacrylate; and / or

[0016] The amino-containing monomer includes one or more of dimethylaminoethyl methacrylate and dimethylaminoethyl acrylate; and / or

[0017] The styrene monomers include one or more of styrene and methyl styrene.

[0018] Optionally, in the chitosan-grafted polyvinyl alcohol, the mass ratio of the part derived from the chitosan to the part derived from the polyvinyl alcohol is 20:80 to 50:50.

[0019] Optionally, the inorganic filler includes talcum powder, and the D50 particle size of the talcum powder is less than or equal to 2 μm.

[0020] Optionally, the molecular weight of the waterborne polyurethane is in the range of 40,000 to 60,000, and the molecular weight is determined by gel permeation chromatography (GPC).

[0021] Optionally, the barrier coating composition for paper-based materials further comprises 0.1 to 10 parts by weight of an auxiliary agent, wherein the auxiliary agent comprises one or more of a thickener, a dispersant, a wetting agent, a leveling agent, and a defoaming agent.

[0022] In another aspect, the present invention provides a barrier coating for paper-based materials, which is obtained by curing the barrier coating composition for paper-based materials as described above.

[0023] In yet another aspect, the present invention provides a paper substrate, comprising a paper base material and the barrier coating for the paper base material as described above disposed on at least a portion of the surface of the paper base material.

[0024] According to the barrier coating composition for paper-based materials provided by the present invention, a water-based acrylic prepolymer, chitosan grafted polyvinyl alcohol, inorganic filler, microcrystalline cellulose, water-based polyurethane, polysiloxane grafted acrylic monomer, epoxy-containing acrylic monomer, and 1,4-butanediol diacrylate are used to obtain the barrier coating composition, wherein the added chitosan grafted polyvinyl alcohol, inorganic filler, microcrystalline cellulose, water-based polyurethane and polysiloxane grafted acrylic monomer effectively improve the water vapor barrier performance and grease barrier performance of the barrier coating composition. At the same time, the barrier coating composition for paper-based materials has excellent antibacterial properties and is suitable for a variety of paper-based food packaging products such as disposable paper cups, paper bowls, and food boxes, improving their food safety performance. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] The embodiment of the present invention provides a barrier coating composition for paper-based materials, comprising the following components:

[0027] The invention discloses a water-based acrylic prepolymer, chitosan grafted polyvinyl alcohol, an inorganic filler, microcrystalline cellulose, a water-based polyurethane, a polysiloxane grafted acrylic monomer, an epoxy-containing acrylic monomer, 1,4-butanediol diacrylate and a solvent, wherein the epoxy-containing acrylic monomer comprises glycidyl methacrylate.

[0028] The added chitosan grafted polyvinyl alcohol, inorganic filler, microcrystalline cellulose, waterborne polyurethane and polysiloxane grafted acrylic monomer effectively improve the water vapor barrier and grease barrier properties of the barrier coating composition. At the same time, the barrier coating composition for paper-based materials has excellent antibacterial properties and is suitable for a variety of paper-based food packaging products such as disposable paper cups, paper bowls, and food boxes, thereby improving their food safety performance.

[0029] Chitosan grafted polyvinyl alcohol:

[0030] The chitosan grafted polyvinyl alcohol added to the barrier coating composition is grafted to form an interpenetrating network in the barrier coating composition, thereby improving the barrier properties and mechanical properties of the barrier coating composition; furthermore, the chitosan grafted polyvinyl alcohol itself has antibacterial properties, and the amino groups in the chitosan destroy the bacterial cell membrane through electrostatic action, inhibiting bacterial growth, thereby improving the safety of application in the field of food paper packaging.

[0031] It should be noted that compared with chitosan without grafting modification, when polyvinyl alcohol is grafted on chitosan, the hydroxyl and amino groups in the chitosan molecules are bonded to polyvinyl alcohol through hydrogen bonds. At the same time, chitosan grafting forms an IPN structure, which enhances the intermolecular force, fills the brittle defects of polyvinyl alcohol molecules, improves the flexibility and durability of the coating, and is conducive to the formation of a high-density hydrogen bond network and an interpenetrating network, reducing the penetration path of water vapor and oil, enhancing the intermolecular force, improving the toughness and tensile resistance of the coating, and avoiding the generation of cracks during the folding process.

[0032] The chitosan grafted polyvinyl alcohol can be prepared by the following method:

[0033] Free radical initiated graft copolymerization includes the following steps:

[0034] Pretreatment: Dissolve chitosan in an appropriate solvent (such as dilute acid solution) to ensure that it is fully dissolved.

[0035] Mixing: Mix the dissolved chitosan solution with the polyvinyl alcohol solution, and add an initiator (such as ammonium persulfate, azobisisobutyronitrile, etc.).

[0036] Reaction: Heat the mixture to react.

[0037] Post-treatment: After the reaction is completed, the product is washed, dried, and other treatments are performed to remove unreacted raw materials and other impurities.

[0038] Microcrystalline Cellulose:

[0039] In the barrier coating composition, the microcrystalline cellulose can improve the rheological properties of the coating system, improve the dispersion uniformity of other components in the barrier coating composition, prevent component sedimentation, and ensure coating uniformity. In addition, the microcrystalline cellulose, as a physical filler, is beneficial to enhancing the tensile strength and elongation at break of the coating and reducing drying cracking.

[0040] Waterborne polyurethane:

[0041] The flexible segments (such as polyether or polyester) in the waterborne polyurethane impart excellent crack resistance and ductility to the coating, making it very suitable for paper-based materials that need to be bent or deformed. This property not only improves the tensile strength and elongation at break of the coating, but also effectively prevents cracks after folding. In addition, the polar groups (such as hydroxyl and carboxyl) in the waterborne polyurethane molecules can be tightly bonded to the surface of the paper-based material through hydrogen bonding or electrostatic adsorption, thereby significantly enhancing the adhesion between the coating and the substrate. The waterborne polyurethane also exhibits excellent chemical stability, can resist the erosion of acids, alkalis and greases, and prolongs the service life of the packaging material, and is particularly suitable for the requirements for grease resistance in food packaging. At the same time, the waterborne polyurethane provides excellent gloss and smooth surface, enhances the wear resistance of the coating, and thus improves the overall appearance quality and touch of the packaging material. The coating surface is smoother and the wear resistance is also significantly improved.

[0042] Polysiloxane grafted acrylic monomer:

[0043] The polysiloxane grafted acrylic monomer is obtained by grafting acrylic groups on polysiloxane, wherein the main component of the polysiloxane part is a long-chain polymer containing a dimethylsiloxane structure, which provides the coating with flexibility, hydrophobicity and low surface energy characteristics; wherein, the flexible chain segment of the polysiloxane grafted acrylic monomer enhances the ductility and impact resistance of the coating, reduces the cracking problem during the drying process, improves the mechanical strength and flexibility of the coating, and avoids brittle cracking. Hydrophobicity can reduce the infiltration of water vapor and liquid, block the penetration path of grease, enhance the grease barrier performance, and improve the water vapor barrier performance (reducing WVTR) and Cobb value of the coating. The flexibility and lubricity of the polysiloxane chain segment improve the scratch resistance of the coating surface, while providing a smoother feel and appearance quality. The low surface energy characteristics of polysiloxane make water droplets roll on the surface in a spherical shape, take away dirt, achieve surface anti-fouling, and are suitable for the high hygiene requirements of food packaging. The acrylic group part is a methacrylate or acrylate structure, which can form a chemical bond with the water-based acrylic prepolymer in the coating, increase the cross-linking density and the dispersibility of the polysiloxane chain segment, improve the uniformity of the material system, and avoid the problem of material stratification. As a bridging group between the polysiloxane and acrylic groups, amino, hydroxyl or carboxyl groups can be selected.

[0044] Epoxy-containing acrylic monomers:

[0045] The epoxy-containing acrylic monomer has epoxy groups and acrylate groups, and can be grafted between different water-based acrylic prepolymer segments and other components through ring-opening reaction and addition polymerization to form a three-dimensional cross-linked network, effectively improving the cross-linking density of the barrier coating composition, thereby improving the mechanical properties of the coating.

[0046] 1,4-Butanediol diacrylate:

[0047] 1,4-Butanediol diacrylate is a bifunctional acrylic monomer that can undergo polymerization reaction with waterborne acrylic prepolymer segments to form a three-dimensional network structure, thereby increasing the crosslinking density of the coating film, which helps to enhance the hardness and wear resistance of the coating film.

[0048] In some embodiments, the barrier coating composition for paper-based materials includes the following components by weight:

[0049] 20-25 parts of water-based acrylic prepolymer, 10-15 parts of chitosan grafted polyvinyl alcohol, 8-50 parts of inorganic filler, 8-12 parts of microcrystalline cellulose, 5-8 parts of water-based polyurethane, 1-5 parts of polysiloxane grafted acrylic monomer, 1-3 parts of epoxy-containing acrylic monomer, 2-4 parts of 1,4-butanediol diacrylate and 8-50 parts of solvent.

[0050] In a specific embodiment, in the barrier coating composition for paper-based materials, the weight proportions of the water-based acrylic prepolymer can be 20 parts, 20.5 parts, 20.7 parts, 21 parts, 21.3 parts, 22 parts, 22.4 parts, 23 parts, 23.6 parts, 23.9 parts, 24 parts, 24.2 parts, 24.5 parts, 24.8 parts, and 25 parts; the weight proportions of the chitosan grafted polyvinyl alcohol can be 10 parts, 10.3 parts, 10.6 parts, The weight parts of the inorganic filler can be 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 36 parts, 40 parts, 45 parts, 50 parts; the weight parts of the microcrystalline cellulose can be 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 36 parts, 40 parts, 45 parts, 50 parts. The weight parts of the aqueous polyurethane can be 8 parts, 8.2 parts, 8.4 parts, 8.6 parts, 8.8 parts, 9 parts, 9.2 parts, 9.4 parts, 9.6 parts, 9.8 parts, 10 parts, 10.2 parts, 10.4 parts, 11.6 parts, and 12 parts; the weight parts of the aqueous polyurethane can be 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, 6 parts, 6.2 parts, 6.4 parts, 6.6 parts, 6.8 parts, 7 parts, 7.2 parts, 7.4 parts, and 7.6 parts. , 8 parts; the weight parts of the polysiloxane grafted acrylic monomer can be 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 36 parts, 40 parts, 45 parts, 50 parts; the weight parts of the solvent can be 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 23 parts, 25 parts, 28 parts, 30 parts, 33 parts, 36 parts, 40 parts, 45 parts, 50 parts.

[0051] Waterborne acrylic prepolymer:

[0052] The water-based acrylic prepolymer is the main resin of the barrier coating composition, and its own properties have a great influence on the water vapor and grease barrier properties, anti-blocking properties and heat sealing strength of the coating.

[0053] In some embodiments, the polymerizable monomers of the waterborne acrylic prepolymer include one or more of carboxyl-containing monomers, hydroxyl-containing monomers, acrylate monomers, amino-containing monomers, and styrene monomers.

[0054] In some embodiments, the carboxyl group-containing monomer includes one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, glucarboxylic acid monoacrylate, and allyl sulfonic acid.

[0055] In some embodiments, the hydroxyl-containing monomer includes one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

[0056] In some embodiments, the acrylic ester monomer includes one or more of methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, isobornyl acrylate, isobornyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, and phenyl methacrylate.

[0057] In some embodiments, the amino-containing monomer includes one or more of dimethylaminoethyl methacrylate and dimethylaminoethyl acrylate.

[0058] In some embodiments, the styrene monomer includes one or more of styrene and methyl styrene.

[0059] In some embodiments, the waterborne acrylic prepolymer includes an acid-rich copolymer present in an amount of about 5 wt % to about 60 wt %; and an acid-free copolymer present in an amount of about 40 wt % to about 95 wt %.

[0060] The polymerizable monomers of the acid-rich copolymer include carboxyl-containing monomers, and optionally one or more of hydroxyl-containing monomers, acrylic ester monomers, amino-containing monomers, and styrene monomers.

[0061] The polymerized monomers of the acid-free copolymer include one or more of hydroxyl-containing monomers, acrylate monomers, amino-containing monomers, and styrene monomers.

[0062] In some embodiments, the acid-rich copolymer contains the carboxyl-containing monomer in an amount from about 5 wt % to about 25 wt %.

[0063] The water-based acrylic prepolymer obtained by using the acid-rich copolymer and the acid-free copolymer has good anti-blocking and heat-sealing strength.

[0064] In some embodiments, in the chitosan-grafted polyvinyl alcohol, the mass ratio of the chitosan portion to the polyvinyl alcohol portion is 20:80 to 50:50.

[0065] If the mass proportion of the chitosan part is too high, it is difficult to form a high-density hydrogen bond network and an interpenetrating network, which may easily lead to insufficient mechanical strength of the coating; if the mass proportion of the chitosan part is too low, it is also not conducive to improving the mechanical strength of the coating, and the antibacterial properties and toughness improvement effects produced by chitosan will also be weakened.

[0066] In some embodiments, the inorganic filler includes talc powder, and the D50 particle size of the talc powder is less than or equal to 2 μm.

[0067] Choosing talcum powder with a D50 particle size of less than or equal to 2 μm as an inorganic filler can fill the micropores in the coating, reduce the molecular diffusion path, and significantly reduce the water vapor transmission rate (WVTR) and grease penetration. At the same time, talcum powder has high mechanical strength and can provide mechanical support when evenly dispersed in the barrier coating composition, significantly increasing the impact strength of the coating.

[0068] In some embodiments, the inorganic filler may further include one or more of heavy calcium carbonate, light calcium carbonate, kaolin, silica, barium sulfate, mica powder, titanium dioxide, alumina, bentonite, glass microspheres, and aluminum hydroxide.

[0069] In some embodiments, the waterborne polyurethane has a molecular weight ranging from 40,000 to 60,000, as measured by gel permeation chromatography (GPC).

[0070] In some embodiments, the barrier coating composition for paper-based materials further comprises 0.1 to 10 parts by weight of an auxiliary agent, wherein the auxiliary agent comprises one or more of a thickener, a dispersant, a wetting agent, a leveling agent, and a defoaming agent.

[0071] In some embodiments, the thickener includes one or more of a HASE thickener (hydrophobically modified alkali swellable thickener), a HEUR thickener (hydrophobically modified polyurethane thickener), a cellulose ether thickener (such as carboxymethyl cellulose), and a polyacrylate thickener.

[0072] In some embodiments, the dispersant includes one or more of anionic dispersants (e.g., polycarboxylates, lignin sulfonates, naphthalenesulfonic acid formaldehyde condensates), nonionic dispersants (e.g., polyethylene glycol (PEG), modified polyurethane, block copolymers), cationic dispersants (quaternary ammonium salt compounds), and zwitterionic dispersants (betaine-type surfactants).

[0073] It should be noted that the dispersant includes a surfactant, and other types of existing surfactants can also be used as the dispersant in the present invention.

[0074] In some embodiments, the wetting agent includes one or more of an organosilicon wetting agent, a non-ionic wetting agent, and a multifunctional polyether wetting agent.

[0075] In a preferred embodiment, the wetting agent includes one or more of BYK-348 (BYK Chemical), TEGO Wet 270 (Evonik), and Dynol™ 980 (Evonik).

[0076] In some embodiments, the leveling agent includes one or more of an organic silicone leveling agent (e.g., polydimethylsiloxane, modified silicone oil), an acrylate leveling agent (e.g., fluorinated acrylate copolymer, long-chain alkyl acrylate copolymer), a polyether-modified polysiloxane (e.g., polyether-modified polydimethylsiloxane), a fluorocarbon leveling agent, an amide leveling agent, and a mineral oil leveling agent.

[0077] In some embodiments, the defoaming agent includes one or more of polyether-modified siloxanes and silicones.

[0078] In a preferred embodiment, the defoaming agent includes one or more of BYK-024 (BYK Chemicals), TEGO Foamex 805 (Evonik), and FoamStar® SI 2240 (BASF).

[0079] In some embodiments, the solvent is selected from water, more preferably deionized water.

[0080] Another embodiment of the present invention provides a barrier coating for paper-based materials, which is obtained by curing the barrier coating composition for paper-based materials as described above.

[0081] The barrier coating for the paper-based material has a Cobb value of no more than 15 g / m² and a KIT value of no less than 10.

[0082] Cobb value is mainly used to measure the water absorption of paper or paperboard, that is, the amount of water absorbed per unit area of ​​the material under specific conditions. It reflects the water vapor barrier performance of the material. Test method: According to international standards ISO 535 or TAPPI T441, place the sample in a certain amount of water and take it out after a specified time (usually 10 minutes or 60 minutes). Then measure the excess moisture on the surface of the sample and calculate the amount of water absorbed per square meter (in grams).

[0083] KIT value (Kleinert-Ihde Test) is an indicator used to evaluate the material's ability to resist grease penetration, especially in the paper and paperboard industry. It reflects the grease barrier properties of the material. Test method: According to TAPPI T559 standard, a specific grease solution (such as mineral oil) is dripped onto the surface of the sample. Observe and record the number of the last grease solution on the sample surface that does not produce stains or penetration, and record it as the KIT value.

[0084] In some embodiments, the barrier coating composition for paper-based materials is cured by applying it to the surface of the paper-based material by blade coating or roller coating, and drying it at 80° C. to 100° C. for 3 to 5 minutes to complete the curing.

[0085] Another embodiment of the present invention provides a paper substrate, comprising a paper-based material and the barrier coating for the paper-based material as described above disposed on at least a portion of the surface of the paper-based material.

[0086] The heat sealing strength of the paper substrate is ≥1.5 N / cm.

[0087] In some embodiments, the paper substrate is a disposable paper cup, a paper bowl, a food packaging box, or an industrial moisture-proof packaging paper.

[0088] Another embodiment of the present invention provides a method for preparing the barrier coating composition for paper-based materials as described above, comprising the following steps:

[0089] S1. Mix the aqueous acrylic prepolymer emulsion and deionized water and stir evenly;

[0090] S2. Chitosan grafted polyvinyl alcohol was dispersed in deionized water and then added to the mixture of S1 and stirred for 10-15 minutes;

[0091] S3. The talc and redispersible microcrystalline cellulose were dispersed in deionized water, and the mixture was added to S2 after being treated by a high shear disperser;

[0092] S4. Gradually add epoxy-containing acrylic monomer, 1,4-butanediol diacrylate, polysiloxane-grafted acrylic monomer and aqueous polyurethane dispersion, stirring at low speed;

[0093] S5. Adjust the coating viscosity to 200-500 mPa·s, stir evenly until completely dispersed, and obtain a barrier coating composition.

[0094] The present invention is further described below by way of examples.

[0095] In the examples and comparative examples of the present invention, chitosan grafted polyvinyl alcohol was purchased from Q-0200121 (Xi'an Qiyue Biological), waterborne acrylic prepolymer was purchased from BASF Joncryl® HPB 4110, waterborne polyurethane was purchased from Covestro Bayhydur® XP 2755, and polysiloxane grafted acrylic acid was purchased from Dow SILASTIC™ 3661 (acrylatesilicone).

[0096] Example 1

[0097] This example is used to illustrate the barrier coating composition, paper-based material and preparation method thereof disclosed in the present invention.

[0098] The following components are prepared into a barrier coating composition according to weight:

[0099] 23 parts of water-based acrylic prepolymer, 12 parts of chitosan grafted polyvinyl alcohol, 18 parts of talc (D50≤2μm), 10 parts of microcrystalline cellulose, 7 parts of water-based polyurethane, 1 part of polysiloxane grafted acrylic monomer, 2 parts of 1,4-butanediol diacrylate, 2 parts of glycidyl methacrylate, 2 parts of carboxymethyl cellulose, 0.5 parts of BYK-024 (BYK Chemical), 0.5 parts of BYK-348 (BYK Chemical) and 17 parts of deionized water.

[0100] The preparation method comprises the following steps:

[0101] S1. Mix the aqueous acrylic prepolymer emulsion, deionized water, BYK-024 (BYK Chemical) and BYK-348 (BYK Chemical), and stir at room temperature at a speed of about 300-500 rpm for 8 minutes to mix evenly;

[0102] S2. Chitosan grafted polyvinyl alcohol was dispersed in deionized water, stirred at room temperature for 10 minutes, and then added to the mixture of S1 and stirred for about 15 minutes;

[0103] S3. The talc and microcrystalline cellulose were dispersed in deionized water, respectively, and added to the mixture of S2 after being treated by a high shear disperser (about 5000-8000 rpm, 5 minutes);

[0104] S4. Gradually add glycidyl methacrylate, 1,4-butanediol diacrylate, polysiloxane grafted acrylic monomer and aqueous polyurethane dispersion, stir at 100-200 rpm for 10 minutes and stir evenly;

[0105] S5. Add carboxymethyl cellulose, adjust the coating viscosity to 200-500 mPa·s (measured at 25°C), stir evenly until completely dispersed, and obtain a barrier coating composition.

[0106] S6. Filter the barrier coating composition through a 100-200 mesh filter to remove impurities and undispersed particles. Spray the barrier coating composition evenly on the surface of the surface-treated paper substrate, and control the coating thickness to be 10-20 microns.

[0107] S7. Place the coated paper substrate in an oven at 60-80° C. and cure for 15 minutes to form a dense cross-linked network structure to obtain a paper-based material with a barrier coating.

[0108] Example 2

[0109] This example is used to illustrate the barrier coating composition, paper-based material and preparation method thereof disclosed in the present invention.

[0110] The barrier coating composition comprises the following components by weight:

[0111] 25 parts of water-based acrylic prepolymer, 10 parts of chitosan grafted polyvinyl alcohol, 15 parts of talc, 12 parts of microcrystalline cellulose, 5 parts of water-based polyurethane, 2 parts of polysiloxane grafted acrylic monomer, 4 parts of 1,4-butanediol diacrylate, 1 part of glycidyl methacrylate, 3 parts of carboxymethyl cellulose, 0.3 parts of BYK-024 (BYK Chemical), 0.2 parts of BYK-348 (BYK Chemical) and 15 parts of deionized water.

[0112] The preparation method is the same as that in Example 1.

[0113] Comparative Example 1

[0114] This comparative example is used to illustrate the barrier coating composition, paper-based material and preparation method thereof disclosed in the present invention.

[0115] The barrier coating composition comprises the following components by weight:

[0116] 23 parts of water-based acrylic prepolymer, 12 parts of chitosan grafted polyvinyl alcohol, 18 parts of talc, 10 parts of microcrystalline cellulose, 7 parts of water-based polyurethane, 1 part of polysiloxane grafted acrylic monomer, 2 parts of 1,4-butanediol diacrylate, 2 parts of carboxymethyl cellulose, 0.5 parts of BYK-024 (BYK Chemical), 0.5 parts of BYK-348 (BYK Chemical) and 17 parts of deionized water.

[0117] The preparation method is largely the same as Example 1, except that glycidyl methacrylate is not added.

[0118] Comparative Example 2

[0119] This comparative example is used to illustrate the barrier coating composition, paper-based material and preparation method thereof disclosed in the present invention.

[0120] The barrier coating composition comprises the following components by weight:

[0121] 23 parts of water-based acrylic prepolymer, 12 parts of chitosan grafted polyvinyl alcohol, 18 parts of talc, 10 parts of microcrystalline cellulose, 7 parts of water-based polyurethane, 1 part of polysiloxane grafted acrylic monomer, 2 parts of glycidyl methacrylate, 2 parts of carboxymethyl cellulose, 0.5 parts of BYK-024 (BYK Chemical), 0.5 parts of BYK-348 (BYK Chemical) and 17 parts of deionized water.

[0122] The preparation method is mostly the same as Example 1, except that 1,4-butanediol diacrylate is not added.

[0123] Comparative Example 3

[0124] This comparative example is used to illustrate the barrier coating composition, paper-based material and preparation method thereof disclosed in the present invention.

[0125] The barrier coating composition comprises the following components by weight:

[0126] 23 parts of water-based acrylic prepolymer, 12 parts of chitosan, 18 parts of talc, 10 parts of microcrystalline cellulose, 7 parts of water-based polyurethane, 1 part of polysiloxane grafted acrylic monomer, 2 parts of 1,4-butanediol diacrylate, 2 parts of glycidyl methacrylate, 2 parts of carboxymethyl cellulose, 0.5 parts of BYK-024 (BYK Chemical), 0.5 parts of BYK-348 (BYK Chemical) and 17 parts of deionized water.

[0127] The preparation method is mostly the same as that of Example 1, except that chitosan is used instead of chitosan-grafted polyvinyl alcohol.

[0128] Comparative Example 4

[0129] This comparative example is used to illustrate the barrier coating composition, paper-based material and preparation method thereof disclosed in the present invention.

[0130] The barrier coating composition comprises the following components by weight:

[0131] 23 parts of water-based acrylic prepolymer, 12 parts of polyvinyl alcohol, 18 parts of talc, 10 parts of microcrystalline cellulose, 7 parts of water-based polyurethane, 1 part of polysiloxane grafted acrylic monomer, 2 parts of 1,4-butanediol diacrylate, 2 parts of glycidyl methacrylate, 2 parts of carboxymethyl cellulose, 0.5 parts of BYK-024 (BYK Chemical), 0.5 parts of BYK-348 (BYK Chemical) and 17 parts of deionized water.

[0132] The preparation method is mostly the same as that of Example 1, except that polyvinyl alcohol is used instead of chitosan grafted polyvinyl alcohol.

[0133] Comparative Example 5

[0134] This comparative example is used to illustrate the barrier coating composition, paper-based material and preparation method thereof disclosed in the present invention.

[0135] The barrier coating composition comprises the following components by weight:

[0136] 23 parts of water-based acrylic prepolymer, 12 parts of chitosan grafted polyvinyl alcohol, 18 parts of talc, 7 parts of water-based polyurethane, 1 part of polysiloxane grafted acrylic monomer, 2 parts of 1,4-butanediol diacrylate, 2 parts of glycidyl methacrylate, 2 parts of carboxymethyl cellulose, 0.5 parts of BYK-024 (BYK Chemical), 0.5 parts of BYK-348 (BYK Chemical) and 17 parts of deionized water.

[0137] The preparation method is mostly the same as Example 1, except that no microcrystalline cellulose is added.

[0138] Comparative Example 6

[0139] This comparative example is used to illustrate the barrier coating composition, paper-based material and preparation method thereof disclosed in the present invention.

[0140] The barrier coating composition comprises the following components by weight:

[0141] 23 parts of water-based acrylic prepolymer, 12 parts of chitosan grafted polyvinyl alcohol, 18 parts of talc, 10 parts of microcrystalline cellulose, 7 parts of water-based polyurethane, 2 parts of 1,4-butanediol diacrylate, 2 parts of glycidyl methacrylate, 2 parts of carboxymethyl cellulose, 0.5 parts of BYK-024 (BYK Chemical), 0.5 parts of BYK-348 (BYK Chemical) and 17 parts of deionized water.

[0142] The preparation method is mostly the same as Example 1, except that no polysiloxane-grafted acrylic monomer is added.

[0143] Performance Testing

[0144] The paper-based material prepared above was subjected to the following performance tests:

[0145] 1. Cut 10 samples from the paper-based material prepared above, test the Cobb value according to the international standard ISO 535, and calculate the average value of all samples.

[0146] 2. Cut 10 samples from the paper-based material prepared above, perform KIT value test according to TAPPI T559 standard, and calculate the average value of all samples.

[0147] 3. Cut samples from the paper-based material prepared above, fold the samples 180° at intervals of 10 mm, apply a weight to the folded position, let stand for 20 minutes, and then test the Cobb value using the international standard ISO 535.

[0148] 4. Cut out samples from the paper-based materials prepared above and test their antibacterial properties in the following ways:

[0149] (1) Sample preparation:

[0150] Cut 10 samples of the same size (5 cm × 5 cm) from the paper-based material prepared above and keep them in a sterile environment for later use. Dry the samples at 105°C ± 2°C to constant weight and place them in a sterile environment to ensure that they are not contaminated by the outside.

[0151] (2) Preparation of bacterial strains and bacterial solution:

[0152] Escherichia coli ATCC 8739 was selected as the test strain. The strain was cultured on a suitable medium (nutrient agar) until the logarithmic growth phase, and the concentration of the bacterial suspension was adjusted to about 10 with sterile phosphate buffer. 5 ~10 6 CFU / mL. The bacterial concentration is confirmed by standard plate count or spectrophotometry.

[0153] (3) Inoculation and culture conditions:

[0154] In a sterile operating table, evenly inoculate about 0.1 mL of bacterial suspension on the surface of the sample to ensure that the bacterial suspension fully contacts the sample. Place the inoculated sample in a sterile culture dish and culture it at 35℃±2℃ for 24 hours.

[0155] At the same time, a control group (paper-based material not coated with the barrier coating of the present invention) was set up and inoculated and cultured under the same conditions.

[0156] (4) Colony count:

[0157] After the incubation, rinse the sample surface with sterile phosphate buffer to suspend the bacteria attached to the surface. Dilute the resulting suspension by an appropriate multiple and inoculate it on a nutrient agar plate, and incubate it at 35℃±2℃ for 24 hours.

[0158] The control group was operated in parallel with the test group, and the colonies grown in the plate were counted, and the number of colonies in the control group (C) and the number of colonies in the test group (T) were recorded.

[0159] (5) Calculation of antibacterial rate:

[0160] Inhibition rate (%) = [(C - T) / C] × 100%

[0161] Among them, C is the average number of colonies in the control sample, and T is the average number of colonies in the test sample.

[0162] The test results obtained are entered in Table 1.

[0163] Table 1

[0164]

[0165] It can be seen from the test results in Table 1 that the paper-based material with a barrier coating prepared by the preparation method of the present invention has excellent water-blocking, oil-resistant and flexibility properties.

[0166] It can be seen from the test results of Examples 1 and 2 and Comparative Examples 1 and 2 that 1,4-butanediol diacrylate and glycidyl methacrylate play a role in increasing the crosslinking density in the barrier coating composition provided by the present invention. When any one of them is removed, the Cobb value will increase, indicating that the crosslinking density of the barrier coating has a certain correlation with its water vapor barrier performance.

[0167] It can be seen from the test results of Example 1 and Comparative Examples 1 to 4 that, compared with Example 1, Comparative Example 3 (chitosan replacing chitosan grafted polyvinyl alcohol), Comparative Example 4 (polyvinyl alcohol replacing chitosan grafted polyvinyl alcohol), Comparative Example 5 (no addition of microcrystalline cellulose) and Comparative Example 6 (no addition of polysiloxane grafted acrylic monomer) all showed obvious performance degradation of the barrier coating, and the Cobb value, Cobb value after folding, KIT value and antibacterial performance all showed significant decreases, indicating that the chitosan grafted polyvinyl alcohol, microcrystalline cellulose and polysiloxane grafted acrylic monomer in the barrier coating composition have a synergistic effect in improving the barrier properties, folding resistance and antibacterial properties of the barrier coating.

[0168] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A barrier coating composition for paper-based materials, characterized in that: It consists of the following components by weight: 20-25 parts of water-based acrylic prepolymer, 10-15 parts of chitosan grafted polyvinyl alcohol, 8-50 parts of inorganic filler, 8-12 parts of microcrystalline cellulose, 5-8 parts of water-based polyurethane, 1-5 parts of polysiloxane grafted acrylic monomer, 1-3 parts of epoxy-containing acrylic monomer, 2-4 parts of 1,4-butanediol diacrylate and 8-50 parts of solvent; The polymerizable monomers of the waterborne acrylic prepolymer include one or more of carboxyl-containing monomers, hydroxyl-containing monomers, acrylate monomers, amino-containing monomers, and styrene monomers; The carboxyl group-containing monomer includes one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, glucaric acid monoacrylate, and allyl sulfonic acid; The hydroxyl-containing monomer includes one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate; The acrylic acid ester monomers include one or more of methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, isobornyl acrylate, isobornyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, and phenyl methacrylate; The amino-containing monomer includes one or more of dimethylaminoethyl methacrylate and dimethylaminoethyl acrylate; The styrene monomers include one or more of styrene and methyl styrene; In the chitosan-grafted polyvinyl alcohol, the mass ratio of the chitosan portion to the polyvinyl alcohol portion is 20:80 to 50:50; The inorganic filler includes talcum powder, and the D50 particle size of the talcum powder is less than or equal to 2 μm.

2. The barrier coating composition for paper-based materials according to claim 1, characterized in that: The molecular weight of the waterborne polyurethane is in the range of 40,000 to 60,000, as determined by gel permeation chromatography (GPC).

3. The barrier coating composition for paper-based materials according to claim 1, characterized in that: The barrier coating composition for paper-based materials further comprises 0.1 to 10 parts by weight of an auxiliary agent, wherein the auxiliary agent comprises one or more of a thickener, a dispersant, a wetting agent, a leveling agent, and a defoaming agent.

4. A barrier coating for paper-based materials, characterized in that: The paper-based material barrier coating composition is obtained by curing the paper-based material barrier coating composition as claimed in any one of claims 1 to 3.

5. A paper substrate, characterized in that The invention comprises a paper-based material and the barrier coating for the paper-based material as claimed in claim 4 which is arranged on at least a part of the surface of the paper-based material.

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