Biopolymer coating composition for forming multi-coating structure, multi-coating structure, and method for preparing multi-coating structure

Abstract

The invention discloses a biopolymer coating composition for forming a multi-coating structure, the multi-coating structure and a preparation method of the multi-coating structure. The biopolymer coating composition comprises polyhydroxyalkanoate and an alkaline substance, and a multi-coating structure formed by the biopolymer coating composition has excellent waterproof and oil-proof performance.

Description

Technical Field

[0001] This invention relates to a biopolymer coating composition, and more particularly to a biodegradable biopolymer coating composition for forming a multi-layer structure, as well as the multi-layer structure and its preparation method. Background Technology

[0002] Currently, most paper containers on the market use petroleum-based coatings such as PE film, water-based acrylic / styrene-acrylic resin, or polyolefin as barrier layers to prevent water and oil from penetrating the paper containers. After these coatings separate from the paper, they are eventually disposed of or landfilled as waste. However, because these coatings cannot degrade, they impose a significant burden on the environment.

[0003] Recently, in response to growing environmental awareness and demands, biodegradable aqueous polymer dispersions have become a research focus in search of more environmentally friendly materials. US Patent No. 11,866,606 discloses a biodegradable aqueous dispersion comprising about 35–75% by weight of water and about 25–65% by weight of polyhydroxyalkanoate, wherein the coating formed by the dispersion exhibits an optimal Cobb value of less than 10 g / m³. 2 Furthermore, its oil resistance Kit value is only greater than 9.

[0004] In view of the inadequacy of water and oil resistance, this invention provides a biodegradable biopolymer coating composition for forming a multi-layer structure. While satisfying biodegradability, it can also be coated onto paper for food packaging. Furthermore, the multi-layer structure of this invention exhibits excellent resistance to water and oil penetration into the paper. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a biopolymer coating composition, a multi-layer structure, and a method for preparing the multi-layer structure, so as to solve the problem of insufficient waterproof and oil-proof performance of biodegradable biopolymer coating compositions in the prior art.

[0006] The present invention provides a biopolymer coating composition for forming a multi-layer structure, the biopolymer coating composition comprising a polyhydroxyalkanoate and an alkaline substance; wherein the polyhydroxyalkanoate comprises a first polyhydroxyalkanoate and a second polyhydroxyalkanoate, and the weight ratio of the first polyhydroxyalkanoate to the second polyhydroxyalkanoate is in the range of 3:1 to 1:3.

[0007] In one embodiment of the present invention, the first polyhydroxyalkanoate comprises poly(hydroxybutyrate-co-hydroxyhexanoate), and the second polyhydroxyalkanoate comprises a first monomer and a second monomer, wherein the first monomer comprises hydroxybutyrate, and the second monomer comprises hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, or hydroxydecanoate.

[0008] In one embodiment of the present invention, the first polyhydroxyalkanoate is a poly(hydroxybutyrate-co-hydroxyhexanoate) containing 5-10 moles of hydroxyhexanoate, and the second polyhydroxyalkanoate contains 5-10 moles of a second monomer. Preferably, the second monomer is hydroxyhexanoate.

[0009] In one embodiment of the present invention, in the biopolymer coating composition for forming a multi-layer structure, the alkaline substance comprises sodium hydroxide, sodium bicarbonate, sodium carbonate, calcium hydroxide, or ammonia.

[0010] In one embodiment of the present invention, the biopolymer coating composition for forming a multi-layer structure further comprises an additive, which is a plasticizer, thickener, nucleating agent, bactericide, or surfactant.

[0011] In one embodiment of the present invention, the thickener comprises polyvinyl alcohol, starch, or acrylic acid.

[0012] On the other hand, the present invention also provides a multi-coating structure formed using the biopolymer coating composition described above, wherein the multi-coating structure comprises at least three layers.

[0013] In one embodiment of the present invention, the multi-coating structure includes a first coating, a second coating, and a third coating, wherein the coating amount of the first coating is at least 5 g / m². 2 The coating amount of the second coating is at least 2 g / m². 2 The coating amount of the third coating is at least 2 g / m². 2 .

[0014] In one embodiment of the present invention, in the multi-coating structure, the total coating amount of the biopolymer coating composition is at least 13 g / m². 2 .

[0015] On the other hand, the present invention also provides a method for preparing a multi-layered structure, which includes forming at least three layers by applying and drying the biopolymer coating composition as described above layer by layer.

[0016] This invention provides a biodegradable biopolymer coating composition for forming a multi-layer structure. While satisfying biodegradability, it can also be coated onto paper for food packaging. Furthermore, the multi-layer structure of this invention exhibits excellent resistance to water and oil penetration into the paper. Detailed Implementation

[0017] The purpose of this invention is to provide a biopolymer coating composition, a multi-layer structure, and a method for preparing the multi-layer structure, so as to solve the problem of insufficient waterproof and oil-proof properties of biodegradable biopolymer coating compositions in the prior art.

[0018] [Biopolymer Coating Composition]

[0019] The biopolymer coating composition of the present invention comprises polyhydroxyalkanoate and alkaline substances.

[0020] [Polyhydroxyalkanoate]

[0021] Polyhydroxyalkanoates are naturally occurring biodegradable polymers, bio-based polymers produced by bacteria through fermentation on a carbon source; therefore, they are biogenerated, not industrially synthesized. Due to their excellent biodegradability and biocompatibility, they are gradually replacing traditional petrochemical materials and can be used in packaging and biomedical applications. The polyhydroxyalkanoates of this invention are composed of hydroxyalkanoate monomers. Suitable hydroxyalkanoate monomers include, but are not limited to, hydroxybutyrate, hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, and / or hydroxydecanoate.

[0022] In a preferred embodiment, the polyhydroxyalkanoate comprises 50 to 95 moles of hydroxybutyrate; more preferably, the polyhydroxyalkanoate comprises 80 to 95 moles of hydroxybutyrate; even more preferably, the polyhydroxyalkanoate comprises 90 to 95 moles of hydroxybutyrate.

[0023] In a preferred embodiment, the polyhydroxyalkanoate comprises a first polyhydroxyalkanoate and a second polyhydroxyalkanoate, wherein the weight ratio of the first polyhydroxyalkanoate to the second polyhydroxyalkanoate ranges from 3:1 to 1:3.

[0024] In a preferred embodiment, the first polyhydroxyalkanoate comprises poly(hydroxybutyrate-co-hydroxyhexanoate), and the second polyhydroxyalkanoate comprises a first monomer and a second monomer, wherein the first monomer comprises hydroxybutyrate, and the second monomer comprises hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, or hydroxydecanoate. Preferably, the first polyhydroxyalkanoate is a poly(hydroxybutyrate-co-hydroxyhexanoate) containing 5-10 mol% hydroxyhexanoate, and the second polyhydroxyalkanoate contains 5-10 mol% of the second monomer. In a preferred embodiment, the second monomer is hydroxyhexanoate.

[0025] In a preferred embodiment, the first polyhydroxyalkanoate is a poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) containing 5-10 mol% hydroxyhexanoate; the second polyhydroxyalkanoate is a poly(hydroxybutyrate-co-hydroxyhexanoate) containing 5-10 mol% hydroxyhexanoate; and the first polyhydroxyalkanoate is different from the second polyhydroxyalkanoate. The hydroxybutyrate can be 2-hydroxybutyrate (2-HB), 3-hydroxybutyrate (3-HB), or 4-hydroxybutyrate (4-HB); the hydroxyhexanoate (HHx) can be 3-hydroxyhexanoate or 6-hydroxyhexanoate.

[0026] In a preferred embodiment, the first polyhydroxyalkanoate used in the biopolymer coating composition of the present invention is a poly(hydroxybutyrate-co-hydroxyhexanoate) containing 5 moles of hydroxyhexanoate, and the second polyhydroxyalkanoate is a poly(hydroxybutyrate-co-hydroxyhexanoate) containing 10 moles of hydroxyhexanoate.

[0027] Preferably, the polyhydroxyalkanoate of the present invention has a high molecular weight, ranging from about 300,000 to 800,000 Daltons.

[0028] [Alkaline substances]

[0029] The alkaline substance includes, but is not limited to, sodium hydroxide, sodium bicarbonate, sodium carbonate, calcium hydroxide, ammonia, etc. Preferably, the alkaline substance is sodium hydroxide. In one embodiment, based on 100 parts by weight of polyhydroxyalkanoate, the alkaline substance is 0.00005 to 10 parts by weight, preferably 0.00005 to 5 parts by weight. The alkaline substance is used to adjust the pH value of the biopolymer coating composition of the present invention to be between 7.5 and 12.

[0030] [additive]

[0031] Without affecting the waterproof and oil-repellent properties, the biopolymer coating composition of the present invention may further include additives, such as plasticizers, thickeners, nucleating agents, bactericides, and surfactants. The types of additives can be those commonly used in the relevant technical field and are not limited herein. The range of addition ratios for each additive is not limited, provided it does not affect the waterproof and oil-repellent properties of the present invention.

[0032] In one embodiment, the plasticizer includes phthalic acid compounds (including but not limited to dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, dioctyl phthalate, dinonyl phthalate, diisononyl phthalate, didecyl phthalate, teicoplaninyl phthalate, dilauryl phthalate, trialkyl phthalate, dibenzyl phthalate). Dicyclohexyl phthalate, phthalate esters, butyl beryllium phthalate, octyl decyl phthalate, butyl octyl phthalate, octyl beryllium phthalate, n-hexyl n-decyl phthalate, n-octyl phthalate and n-decyl phthalate), phosphorus compounds (including but not limited to tricresyl phosphate), trioctyl phosphate, triphenyl phosphate, octyl diphenyl phosphate, toluene diphenyl phosphate and trichloroethyl phosphate), adipic acid compounds (including but not limited to dibutoxyethoxyethyl adipic acid (DBEEA)). (including, but not limited to, dioctyl adipate, diisooctyl adipate, di-n-octyl adipate, didecyl adipate), adipic acid, diisodecyl adipate, n-octyl adipate, n-heptyl adipate, and n-nonyl adipate), sebacic acid compounds (including but not limited to dibutyl sebacate, dioctyl sebacate, diisooctyl sebacate, and butyl benzoate sebacate), azelaic acid compounds, citric acid compounds (including but not limited to triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, and acetyl trioctyl citrate), glycolic acid) Compounds (including but not limited to ethyl methyl phthaloyl glycolate, ethyl phthaloyl glycolate, ethyl glycolate, and butyl phthaloyl glycolate), trimellitic acid compounds (including but not limited to trioctyl trimellitate, tri-n-octyl trimellitate, and n-decyl trimellitate), phthalic acid isomers (including but not limited to dioctyl isophthalate and dioctyl terephthalate), castor oil acid compounds (including but not limited to methyl acetyl laurate, methyl acetyl laurate, and butyl acetyl laurate), polyester compounds, or polyethylene glycol, etc. Plasticizers can be used alone or in combination.

[0033] Examples of thickeners include acrylics, polyvinyl alcohol, fatty acid soaps, polyvinylpyrrolidone, ethylene oxide-propylene oxide nonionic surfactants, polymer dispersants with free carboxylic acid side chains, methylcellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose, starch and mixtures thereof.

[0034] Nucleating agents include, but are not limited to, sulfur, erythritol, pentaerythritol, dipentaerythritol, artificial sweeteners, stearates, sorbitol, mannitol, polyester waxes, and mixtures thereof. Bactericides include, but are not limited to, ethylenediaminetetraacetic acid (EDTA) or benzisothiazolinone.

[0035] Surfactants are commonly used in this technical field. They include ionic and nonionic surfactants, such as aliphatic carboxylic acids like lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid; N-acyl-N-methylglycine salts, N-acyl-N-methyl β-propanine salts, N-acylglutamate salts, polyoxyethylene alkyl ether carboxylates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, dialkyl sulfosuccinates, alkyl sulfosuccinate disalts, polyoxyethylene alkyl sulfosuccinate disalts, alkyl sulfoacetates, N-acylmethyl taurate, sodium dimethyl 5-sulfoisophthalate, sulfated oils, higher alcohol sulfates, polyoxyethylene alkyl ether sulfates, secondary higher alcohol ethoxylates, and polyoxyethylene alkylphenyl ether sulfates. The surfactants, including salts, monoglycyrrhizic acid sulfates, sulfated salts of fatty acid alkanolamides, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkylphenyl ether phosphates, alkyl phosphates, alkylamine oxides, sodium didecyl sulfosuccinate, sodium dioctyl sulfosuccinate, sodium dihexyl sulfosuccinate, sodium dicyclohexyl sulfosuccinate, sodium dipentyl sulfosuccinate, sodium diisobutyl sulfosuccinate, sulfosuccinate ethoxylated alcohol half ester, disodium sulfosuccinate ethoxylated nonylphenol half ester, sodium isodecyl sulfosuccinate, disodium octadecyl sulfosuccinate, disodium monododecyl diphenyl ether disulfonate or disodium dodecyl diphenyl ether disulfonate, sodium diisopropyl naphthalene sulfonate, and neutralization condensation products of sodium naphthalene sulfonate, can be used alone or in combination without restriction.

[0036] [water]

[0037] The biopolymer coating composition of the present invention is an aqueous coating, that is, the biopolymer coating composition of the present invention further includes water as a coating matrix. After mixing with an appropriate proportion of water, an aqueous coating for application can be formed. The proportion of water is not particularly limited here, as long as it can be coated. Preferably, the weight percentage of water is about 30% to 60% of the total coating composition.

[0038] Furthermore, the biopolymer coating composition of the present invention is used to form a multi-layer structure. The multi-layer structure formed by the biopolymer coating composition of the present invention has excellent water and oil repellency, preferably reaching Cobb's level. 30min <5gsm(g / m 2 ), and Kit≧10.

[0039] [Multi-coating structure]

[0040] On the other hand, the present invention also provides a multi-coating structure formed using the biopolymer coating composition described above, wherein the multi-coating structure comprises at least three layers. Specifically, the multi-coating structure may have four, five, or other layers. The multi-coating structure of the present invention achieves excellent waterproof and oil-repellent properties with only at least three layers.

[0041] Furthermore, the multi-coating structure may include a first coating, a second coating, and a third coating, wherein the coating amount of the first coating is at least 5 g / m³. 2 The coating amount of the second coating is at least 2 g / m². 2 The coating amount of the third coating is at least 2 g / m². 2 Furthermore, the total coating amount of the multi-coating structure only needs to be at least 13 g / m². 2 This achieves excellent waterproof and oil-proof performance. It is understood that, here, the first coating refers to the coating that is in contact with the substrate (e.g., paper).

[0042] [Preparation method of multi-coating structure]

[0043] The method for preparing the multi-layered structure of the present invention includes applying and drying the biopolymer coating composition as described above layer by layer. Specifically, an aqueous coating formed by homogenizing the biopolymer coating composition with water is applied to a paper card that needs to be waterproofed and oil-proofed, forming a first coating and then undergoing a first drying. A second coating is then applied and dried a second time, followed by a third coating and a third drying. If more layers are required, the process is continued to obtain the multi-layered structure of the present invention.

[0044] [Example]

[0045] Example 1: 11.74 g of PHBHHx (5% HHx), 35.21 g of PHBHHx (10% HHx), 2.35 g of sodium hydroxide, and 50.7 g of water were placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.2. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2 The coating amount is applied to the paper card and then dried in an oven at 180°C to form the first coating, the second coating and the third coating respectively.

[0046] The resulting Cobb coating structure 30min The value is 0.96, and the Kit value is 12. Cobb 30minThe test method for the kit is based on the standard method of TAPPI T441, extending the test time to 30 minutes. The lower the value, the better the waterproof performance. The test method for the kit is based on the standard method of TAPPI T559, and is divided into 1 to 12 levels. The higher the value, the better the oil resistance.

[0047] Example 2: 35.21 g of PHBHHx (5% HHx), 11.74 g of PHBHHx (10% HHx), 2.35 g of sodium hydroxide, and 50.7 g of water were placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.7. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 2.58, and the Kit value is 12.

[0048] Example 3: 35.19 g of PHBHHx (5% HHx), 10.73 g of PHBHHx (10% HHx), 2.15 g of sodium hydroxide, 46.35 g of water, and 8.58 g of polyethylene glycol (PEG200) with an average molecular weight of 200 were placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.6. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 4.37, and the Kit value is 12.

[0049] Example 4: 32.89 grams of PHBHHx (5% HHx), 10.96 grams of PHBHHx (10% HHx), and 2.19 x 10 -5 47.37 g of sodium hydroxide, 47.37 g of water, and 8.77 g of PEG200 were placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and homogenized at 300 bar to form a coating solution with a pH of 7.6. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 1.95, and the Kit value is 12.

[0050] Example 5: The coating liquid prepared as in Example 2 was sequentially applied at 7 g / m³. 2 3g / m 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, third, and fourth coatings, respectively. The resulting Cobb coating structure... 30min The value is 2.7, and the Kit value is 12.

[0051] Example 6: The coating liquid prepared as in Example 2 was sequentially applied at a concentration of 7 g / m³. 2 3g / m 2 3g / m 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, third, fourth, and fifth coatings, respectively. The resulting Cobb coating structure... 30min The value is 3.9, and the Kit value is 12.

[0052] Example 7: 35.21 g of PHBHHx (5% HHx), 11.74 g of PHBHHx (10% HHx), 2.35 g of sodium hydroxide, 50.7 g of water, and 7.04 x 10 -5 Acrylic acid was placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.8. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 1.96, and the Kit value is 10.

[0053] Example 8: 23.47 g of PHBHHx (5% HHx), 23.47 g of PHBHHx (10% HHx), 2.35 g of sodium hydroxide, 50.7 g of water, and 7.04 x 10 -5Acrylic acid was placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.9. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 4.7, and the Kit value is 10.

[0054] Example 9: The coating liquid prepared as in Example 2 was sequentially applied at a concentration of 5 g / m³. 2 4g / m 2 4g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 3.91, and the Kit value is 12.

[0055] Example 10: The coating liquid prepared as in Example 2 was sequentially applied at 7 g / m³. 2 2g / m 2 4g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 4.22, and the Kit value is 12.

[0056] Example 11: The coating liquid prepared as in Example 2 was sequentially applied at 7 g / m³. 2 4g / m 2 2g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 3.36, and the Kit value is 12.

[0057] Example 12: 35.21 g of PHBHHx (5% HHx), 11.74 g of PHBHHx (10% HHx), 2.35 g of sodium hydroxide, 50.7 g of water, and 0.0045 g of starch were placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and homogenized at 300 bar to form a coating solution with a pH of 11.7. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 3.36, and the Kit value is 12.

[0058] Comparative Example 1: 42.25 g of PHBHHx (5% HHx), 4.69 g of PHBHHx (10% HHx), 2.35 g of sodium hydroxide, 50.7 g of water, and 7.04 x 10 -5 Acrylic acid was placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.9. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 8.63, and the Kit value is 8.

[0059] Comparative Example 2: 46.95 g of PHBHHx (10% HHx), 2.35 g of sodium hydroxide, and 50.7 g of water were placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.6. The coating solution was then sequentially mixed with 7 g / m³ of water. 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 9.56, and the Kit value is less than 3.

[0060] Comparative Example 3: 46.94 g of PHBHHx (5% HHx), 2.35 g of sodium hydroxide, 50.7 g of water, and 0.013 g of starch were placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.6. The coating solution was then sequentially mixed with 7 g / m³ of water. 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 26.8, and the Kit value is less than 3.

[0061] Comparative Example 4: 46.95 g of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) (5% 4HB), 2.35 g of sodium hydroxide, 50.7 g of water, and 7.04 x 10 -5 Acrylic acid was placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and dispersed and homogenized at 300 bar to form a coating solution with a pH of 11.7. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 42.44, and the Kit value is less than 3.

[0062] Comparative Example 5: The coating liquid prepared as in Example 2 was sequentially applied at 7 g / m³. 2 6g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first and second coatings, respectively. The resulting Cobb coating structure... 30min The value is 27.45, and the Kit value is less than 3.

[0063] Comparative Example 6: The coating liquid prepared as in Example 2 was applied at 18 g / m³. 2 The coating is applied to the paper card and then dried in an oven at 180°C to form the first coating. The resulting Cobb coating structure... 30min The value is 7.15, and the Kit value is less than 3.

[0064] Comparative Example 7: 36.06 g of PHBHHx (5% HHx), 12.02 g of PHBHHx (10% HHx), 51.92 g of water, and 7.21 x 10 -5 Acrylic acid was placed in a container and mixed at 1000 rpm for 60 minutes. The mixture was then poured into a high-pressure homogenizer and homogenized at 300 bar to form a coating solution with a pH of 6.9. The coating solution was then sequentially added at 7 g / m³... 2 3g / m 2 3g / m 2 The coating was applied to the paper card and then dried in an oven at 180°C to form the first, second, and third coatings, respectively. The resulting Cobb coating structure... 30min The value is 4.46, and the Kit value is 4.

[0065] As can be seen from the above embodiments, the multi-layer structure formed by the biopolymer coating composition according to the present invention, while satisfying biodegradability, also has excellent waterproof and oil-repellent properties, making it a superior Cobb coating.30min Less than 5g / m 2 Furthermore, the Kit value can reach 10 to 12.

[0066] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A biopolymer coating composition for forming a multi-layered structure, characterized in that, include: The polyhydroxyalkanoate and an alkaline substance; wherein the polyhydroxyalkanoate comprises a first polyhydroxyalkanoate and a second polyhydroxyalkanoate, and the weight ratio of the first polyhydroxyalkanoate to the second polyhydroxyalkanoate is in the range of 3:1 to 1:

3.

2. The biopolymer coating composition for forming a multi-layered structure according to claim 1, characterized in that, The first polyhydroxyalkanoate includes poly(hydroxybutyrate-co-hydroxyhexanoate), and the second polyhydroxyalkanoate includes a first monomer and a second monomer. The first monomer includes hydroxybutyrate, and the second monomer includes hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, or hydroxydecanoate.

3. The biopolymer coating composition for forming a multi-layered structure according to claim 2, characterized in that, The first polyhydroxyalkanoate is a poly(hydroxybutyrate-co-hydroxyhexanoate) containing 5-10 moles of hydroxyhexanoate, and the second polyhydroxyalkanoate contains 5-10 moles of a second monomer.

4. The biopolymer coating composition for forming a multi-layer structure according to claim 1, characterized in that, The alkaline substance includes sodium hydroxide, sodium bicarbonate, sodium carbonate, calcium hydroxide, or ammonia.

5. The biopolymer coating composition for forming a multi-layered structure according to claim 1, characterized in that, It further includes additives, which are plasticizers, thickeners, nucleating agents, bactericides, or surfactants.

6. The biopolymer coating composition for forming a multi-layered structure according to claim 5, characterized in that, The thickener comprises polyvinyl alcohol, starch, or acrylic acid.

7. A multi-coating structure, characterized in that, It is formed using the biopolymer coating composition as described in claim 1, wherein the multi-coating structure comprises at least three layers.

8. The multi-coating structure according to claim 7, characterized in that, It includes a first coating, a second coating, and a third coating, wherein the coating amount of the first coating is at least 5 g / m². 2 The coating amount of the second coating is at least 2 g / m². 2 The coating amount of the third coating is at least 2 g / m². 2 .

9. The multi-coating structure according to claim 7, characterized in that, The total coating weight of the biopolymer coating composition is at least 13 g / m². 2 .

10. A method for preparing a multi-coating structure, characterized in that, This includes forming at least three layers by applying and drying the biopolymer coating composition as described in claim 1, one layer at a time.