CN111378261B - Processing method of disposable lunch box - Google Patents
Processing method of disposable lunch box Download PDFInfo
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- CN111378261B CN111378261B CN202010147026.4A CN202010147026A CN111378261B CN 111378261 B CN111378261 B CN 111378261B CN 202010147026 A CN202010147026 A CN 202010147026A CN 111378261 B CN111378261 B CN 111378261B
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- bagasse
- polylactic acid
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- disposable lunch
- vinyl acetate
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D22/00—Producing hollow articles
- B29D22/003—Containers for packaging, storing or transporting, e.g. bottles, jars, cans, barrels, tanks
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F212/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
- C08F212/02—Monomers containing only one unsaturated aliphatic radical
- C08F212/04—Monomers containing only one unsaturated aliphatic radical containing one ring
- C08F212/06—Hydrocarbons
- C08F212/08—Styrene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F218/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid
- C08F218/02—Esters of monocarboxylic acids
- C08F218/04—Vinyl esters
- C08F218/08—Vinyl acetate
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F222/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides, or nitriles thereof
- C08F222/04—Anhydrides, e.g. cyclic anhydrides
- C08F222/06—Maleic anhydride
- C08F222/08—Maleic anhydride with vinyl aromatic monomers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/06—Biodegradable
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
- C08L2205/035—Polymer mixtures characterised by other features containing three or more polymers in a blend containing four or more polymers in a blend
Abstract
The invention provides a processing method of a disposable lunch box, belonging to the technical field of degradable materials, comprising the following steps: mixing and granulating a polylactic acid composition containing polylactic acid, bagasse, a toughening agent and a slipping agent to obtain polylactic acid composition particles; carrying out injection molding on the polylactic acid composition particles, and demolding to obtain the disposable lunch box; wherein the toughening agent comprises acetyl tributyl citrate and fumaric acid-vinyl acetate copolymer; the bagasse is activated by using a styrene-maleic anhydride copolymer after being treated by a strong alkali solution. The processing method can reduce the surface viscosity of the polylactic acid composition particles in the injection molding process and reduce the using amount of the slipping agent in the polylactic acid composition particle molding process; the disposable lunch box obtained by the processing method has higher tensile strength, bending strength and impact strength, and the slipping agent in the disposable lunch box has low mobility to food and can be completely degraded in natural environment.
Description
Technical Field
The invention belongs to the technical field of degradable materials, and particularly relates to a processing method of a disposable lunch box.
Background
With the development of the novel consumption mode of O2O, the development mode of 'off-line physical store + network platform' provides a brand-new development opportunity for the catering industry, so that customers can really experience the convenience of enjoying services without going out of home, the take-away industry also obtains a great amount of economic benefits from the convenience, and online ordering becomes a new life style. The problem of disposable tableware gradually appears when taking out the convenience of people. According to statistics, by the end of 2018, 6 months, the scale of users ordering food through the network in China reaches 3.64 hundred million, and the number is increased by 6 percent compared with the end of the last year, and the number is continuously increased. A large consumer population inadvertently creates large quantities of disposable tableware waste. At present, domestic disposable tableware is mainly made of plastic products and paper products, wherein the plastic products are poor in degradability and high-temperature use safety, the paper products and the tableware need a large number of trees to provide raw materials, and meanwhile, the paper making industry is high in pollution and energy consumption. At the present stage, international calls for environmental protection, energy conservation, emission reduction and green manufacturing are higher and higher, the environmental protection supervision and inspection strength is continuously upgraded in recent years at home, and the development and utilization of harmless, pollution-free and renewable environment-friendly novel materials for preparing disposable tableware in the take-away catering industry has become a necessary trend.
At present, the degradable plastic materials mainly comprise polyvinyl alcohol (PVA) foaming materials, polybutylene succinate (PBS) foaming materials, polylactic acid (PLA) foaming materials, poly epsilon-caprolactone (PCL) foaming materials, thermoplastic starch foaming materials and the like. Polylactic acid (PLA) is a polymer formed by dehydrating and condensing lactic acid at high temperature under the action of a catalyst to form lactide, and then carrying out ring-opening polymerization on the lactide under the action of different catalysts. However, in the prior art, the cost of synthesizing polylactic acid is high, the yield is low, and the market demand is difficult to meet. Therefore, there is a need to find a new substance to replace polylactic acid completely or partially so as to reduce the production cost.
Disclosure of Invention
An object of the present invention is to provide a use of fumaric acid-vinyl acetate copolymer for reducing the surface viscosity of polylactic acid and/or polylactic acid composition.
The technical scheme adopted by the invention for realizing the purpose is as follows:
use of a fumaric acid-vinyl acetate copolymer for reducing the surface viscosity of a polylactic acid and/or polylactic acid composition.
The polylactic acid has the advantages of complete non-toxicity, no harm, high hardness, good compatibility and the like, but has the defects of poor toughness, difficult opening, large surface viscosity and the like, and in order to ensure the injection molding and improve the processability of the polylactic acid and the service performance of a polylactic acid product, a plasticizer, an opening agent or a slipping agent is required to be added, and the plasticizer, the opening agent or the slipping agent has potential toxicity and is very likely to migrate into food, so that the risk of safety to a human body exists. The fumaric acid-vinyl acetate copolymer can reduce the surface viscosity of polylactic acid, reduce the use amount of an opening agent or a slipping agent in the polylactic acid molding processing process and improve the safety of food; but also can improve the toughening effect of the toughening agent, reduce the using amount of the toughening agent and improve the impact strength of the polylactic acid product.
Preferably, the fumaric acid-vinyl acetate copolymer is prepared by the following steps: stirring fumaric acid and toluene at 60-80 ℃ until the fumaric acid is completely dissolved, adding vinyl acetate and benzoyl peroxide, wherein the toluene accounts for 1.0-2.0 wt% of the total mass of the fumaric acid and the vinyl acetate, and the benzoyl peroxide accounts for 1.0-2.0 wt% of the total mass of the fumaric acid and the vinyl acetate, continuing to react at constant temperature for 3.0-4.0h, then distilling the product under reduced pressure to remove the toluene, washing the product with absolute ethyl alcohol to be neutral, separating liquid, cooling and then carrying out suction filtration to obtain the final product of the fumaric acid-vinyl acetate copolymer. The mass ratio of fumaric acid to vinyl acetate is 1: 1.2-1.6.
The invention also aims to provide a processing method of the disposable lunch box for reducing the surface viscosity of the polylactic acid composition particles in the injection molding process and reducing the using amount of the slipping agent in the polylactic acid composition particle molding process, the disposable lunch box obtained by the processing method has higher tensile strength, bending strength and impact strength, the migration rate of the slipping agent to food in the disposable lunch box is low, and the disposable lunch box can be completely degraded in natural environment.
The technical scheme adopted by the invention for realizing the purpose is as follows:
The processing method of the disposable lunch box comprises the following steps:
mixing and granulating a polylactic acid composition containing polylactic acid, bagasse, a flexibilizer and a slipping agent to obtain polylactic acid composition particles;
carrying out injection molding on the polylactic acid composition particles, and demoulding to obtain the disposable lunch box;
wherein the toughening agent comprises acetyl tributyl citrate and the fumaric acid-vinyl acetate copolymer of claim 1.
The processing method can reduce the usage amount of acetyl tributyl citrate in the toughening agent, reduce the surface viscosity of polylactic acid composition particles in the injection molding process, reduce the usage amount of the slipping agent in the polylactic acid composition particle molding processing process, and obtain the disposable lunch box with higher impact strength and safety; in addition, the processing method can also improve the crystallinity of the polylactic acid, improve the migration resistance of the slipping agent in the disposable lunch box and reduce the migration rate of the slipping agent in the disposable lunch box, thereby reducing the migration of the slipping agent in the disposable lunch box to food and improving the safety of the food. The disposable lunch box obtained by the processing method has higher tensile strength, bending strength and impact strength, the migration rate of the slipping agent in the disposable lunch box to food is low, the disposable lunch box can be completely degraded in natural environment, the natural degradation rate reaches 89% in 30-50 days, and the natural degradation rate reaches 100% in 100-180 days.
In one embodiment, bagasse is subjected to a strong alkaline solution and then activated by using a styrene-maleic anhydride copolymer. Bagasse contains polar groups, interface compatibility is poor when polylactic acid and bagasse are compounded, and due to the fact that a large number of hydroxyl groups exist in bagasse, bagasse particles form hydrogen bonds to be aggregated, so that bagasse is difficult to disperse uniformly in polylactic acid, stress concentration is easy to generate when the bagasse is stressed, and the bagasse cannot effectively play a role. According to the invention, small molecular substances in bagasse are removed by using an alkali solution, then, the bagasse is subjected to activation treatment by using a styrene-maleic anhydride copolymer and subjected to esterification reaction with hydroxyl molecules on the surface of the bagasse, and a hydrophobic molecular chain segment is introduced to the surface of the bagasse, so that the polarity of the surface of the bagasse can be weakened, the interfacial compatibility when the bagasse and polylactic acid are compounded is improved, the bagasse is uniformly dispersed in the polylactic acid and is in a large amount, the interfacial force among the bagasse, the polylactic acid and the slipping agent can be improved, the mechanical property of the disposable lunch box is improved, the sufficient mechanical strength is ensured to meet the application requirement, and the migration of the slipping agent in the disposable lunch box is inhibited. In addition, the bagasse subjected to activation treatment by using the styrene-maleic anhydride copolymer can also improve the capacity of adsorbing the slipping agent, and further reduce the migration of the slipping agent in a food mold to a certain extent.
Preferably, the number average molecular weight of the styrene-maleic anhydride copolymer is 2500-7000 g/mol.
Preferably, the styrene-maleic anhydride copolymer is prepared by the following method: adding maleic anhydride into a mixed solvent of butyl acetate and n-heptane with the volume ratio of 1:2-4, stirring until the maleic anhydride is completely dissolved under the protection of nitrogen, then preheating for 10-15min at 60-80 ℃, adding azobisisobutyronitrile accounting for 3-6% of the total weight of monomers and 3-mercaptopropionic acid accounting for 2-4% of the total weight of the monomers, beginning to dropwise add styrene monomers, continuing to react for 2-4h after completing dropwise addition within 40-60min, cooling to room temperature, carrying out suction filtration, washing the obtained solid with absolute ethyl alcohol, and drying to constant weight. Wherein the mass ratio of the styrene to the maleic anhydride is 1: 0.8-1.2.
In one embodiment, the activation treatment temperature is 80-100 deg.C, and the time is 30-120 min.
Preferably, the specific steps of the bagasse activation treatment are as follows: placing bagasse with the grain size of 100 meshes and 300 meshes in an alkali solution with the mass concentration of 15-30 wt% for alkali treatment for 10-30min, removing small molecular substances, cleaning with clear water, drying, homogenizing under high pressure at 50-200MPa for 3-7 times, dispersing the bagasse in a 70-90% ethanol solution containing 0.4-0.8 wt% of styrene-maleic anhydride copolymer and 0.01-0.1 wt% of 4-dimethylaminopyridine at the weight ratio of 5-10:100, adjusting the pH value of the solution to 5.0-7.0 with glacial acetic acid, activating at 80-100 ℃ for 30-120min, cleaning with absolute ethanol, and drying.
In one embodiment, the content of the bagasse is 40-60 parts by weight, the content of the toughening agent is 0.5-2.5 parts by weight, and the content of the slipping agent is 0.05-0.35 part by weight, relative to 100 parts by weight of the polylactic acid resin.
Preferably, the polylactic acid composition further comprises a mold release agent with a melting point of 0.01-2 parts by weight relative to 100 parts by weight of the polylactic acid resin, wherein the mold release agent is one or more selected from the group consisting of sorbitol, pentaerythritol, myristic acid, palmitic acid, stearic acid, and behenic acid.
In one embodiment, the slip agent is selected from one or more of the group consisting of erucamide, behenamide, oleamide, and stearamide.
Preferably, the toughening agent is acetyl tributyl citrate and fumaric acid-vinyl acetate copolymer with the weight ratio of 1:0.05-0.2
In one embodiment, the mixing temperature is 70-100 ℃ and the mixing time is 20-30 min.
In one embodiment, the injection molding temperature is 160-; the temperature of the mould is 80-110 ℃.
The invention also aims to provide a disposable lunch box obtained by the processing method, wherein the maximum migration rate of the slipping agent to isooctane at 70 ℃ in the disposable lunch box is less than 0.43%.
It is still another object of the present invention to provide a use of a styrene-maleic anhydride copolymer in activating bagasse.
Compared with the prior art, the invention has the following beneficial effects: according to the invention, the bagasse is activated by the silane coupling agent and the polymaleic anhydride, so that the interface compatibility of the bagasse and the polylactic acid during compounding can be improved, the alternate combination capacity of the straw powder and the polylactic acid is enhanced, the mechanical property of the degradable composite packaging material is improved, and the melting temperature of the degradable composite packaging material is reduced; the method has good effect of removing small molecular substances in bagasse by using the alkali solution, and can enhance the alternate binding capacity of the straw powder and the polylactic acid; the degradable composite packaging material has higher tensile strength, bending strength and impact strength, lower surface viscosity and melting temperature, better processing performance, can be completely degraded in natural environment, the natural degradation rate reaches 89% in 30-50 days, and the natural degradation rate reaches 100% in 100-180 days.
The processing method of the disposable lunch box provided by the invention adopts the technical scheme, makes up for the defects of the prior art, and has the advantages of reasonable design and convenient operation.
Drawings
FIG. 1 shows the grafting yield of bagasse in test example 1 of the present invention;
FIG. 2 is a FTIR chart of bagasse in test example 1 of the present invention;
FIG. 3 is the result of the melt flow rate test of the pellets of the polylactic acid composition in test example 2 of the present invention;
FIG. 4 is a DSC curve of non-isothermal melting of the pellets of the polylactic acid composition of Experimental example 2 according to the present invention;
FIG. 5 shows the tensile strength of the disposable lunch box in test example 2 of this invention;
FIG. 6 shows the bending strength of the disposable lunch box in test example 2 of this invention;
FIG. 7 shows the impact strength of the disposable lunch box in test example 2 of this invention;
FIG. 8 is a standard curve for measuring the initial content of erucamide in the disposable lunch box in test example 3 of this invention;
FIG. 9 is a standard curve for measuring the transfer amount of erucamide in the disposable lunch box in test example 3 of this invention;
FIG. 10 shows the maximum migration rate of erucamide to isooctane at 70 ℃ in the disposable lunch box of the invention in test example 3.
Detailed Description
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It is not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Example 1:
The preparation method of the fumaric acid-vinyl acetate copolymer comprises the following steps: stirring fumaric acid and toluene at 70 ℃ until the fumaric acid is completely dissolved, adding vinyl acetate and benzoyl peroxide, wherein the toluene accounts for 1.5 wt% of the total mass of the fumaric acid and the vinyl acetate, and the benzoyl peroxide accounts for 1.5 wt% of the total mass of the fumaric acid and the vinyl acetate, continuing to perform constant-temperature reaction for 4.0h, then distilling the product under reduced pressure to remove the toluene, washing the product with absolute ethyl alcohol to be neutral, separating liquid, cooling, and performing suction filtration to obtain the final product, namely the fumaric acid-vinyl acetate copolymer. The mass ratio of fumaric acid to vinyl acetate was 1: 1.4.
Mixing polylactic acid composition containing polylactic acid and fumaric acid-vinyl acetate copolymer, granulating to obtain polylactic acid composition granule, mixing at 85 deg.C for 30 min.
Example 2:
the preparation method of the styrene-maleic anhydride copolymer comprises the following steps: adding maleic anhydride into a mixed solvent of butyl acetate and n-heptane with the volume ratio of 1:3, stirring under the protection of nitrogen until the maleic anhydride is completely dissolved, then preheating for 12min at 80 ℃, adding azobisisobutyronitrile with the weight of 5% of the total weight of monomers and 3-mercaptopropionic acid with the weight of 2% of the total weight of the monomers, beginning to dropwise add styrene monomer, continuing to react for 3h after the dropwise addition is completed within 60min, cooling to room temperature, carrying out suction filtration, washing with absolute ethyl alcohol to obtain a solid, and drying to constant weight. Wherein the mass ratio of styrene to maleic anhydride is 1: 1; the number average molecular weight of the styrene-maleic anhydride copolymer was 5382g/mol
Example 3:
a) placing 200 mesh bagasse into 17 wt% sodium hydroxide solution, alkali treating for 15min, removing small molecular substances, cleaning with clear water, and drying;
b) mixing and granulating a polylactic acid composition containing polylactic acid, bagasse, a toughening agent and erucamide to obtain polylactic acid composition particles, wherein the mixing is carried out at 85 ℃ for 30 min; wherein, relative to 100 weight parts of the polylactic resin, the content of bagasse is 50 weight parts, the content of the toughening agent is 2.0 weight parts, and the content of erucamide is 0.28 weight parts; the toughening agent is acetyl tributyl citrate and the fumaric acid-vinyl acetate copolymer of example 1 in a weight ratio of 1: 0.12;
c) and (3) carrying out injection molding on the polylactic acid composition particles at the injection molding temperature of 163 ℃, the pressure of 45MPa and the speed of 45%, wherein the mold temperature is 85 ℃, and demolding to obtain the disposable lunch box.
Example 4:
the processing method of the disposable lunch box comprises the following steps:
a) placing 200-mesh bagasse into 17 wt% sodium hydroxide solution, performing alkali treatment for 15min to remove small molecular substances, cleaning with clear water, drying, homogenizing under 120MPa for 5 times, dispersing bagasse in 80% ethanol solution containing 0.5 wt% styrene-maleic anhydride copolymer (obtained in example 2) and 0.05 wt% 4-dimethylaminopyridine at high pressure, wherein the weight ratio of bagasse to ethanol solution is 8:100, adjusting the pH value of the solution to 5.6 with glacial acetic acid, performing activation treatment at 85 ℃ for 90min, cleaning with absolute ethanol, and drying;
b) Mixing and granulating a polylactic acid composition containing polylactic acid, bagasse, a flexibilizer and erucamide to obtain polylactic acid composition particles, and mixing at 85 ℃ for 30 min; wherein, relative to 100 weight parts of the polylactic resin, the content of bagasse is 50 weight parts, the content of toughening agent is 2.0 weight parts, and the content of erucamide is 0.28 weight parts; the toughening agent is acetyl tributyl citrate and the fumaric acid-vinyl acetate copolymer of example 1 in a weight ratio of 1: 0.12;
c) and (3) carrying out injection molding on the polylactic acid composition particles at an injection molding temperature of 163 ℃, a pressure of 45MPa and a speed of 45%, wherein the mold temperature is 85 ℃, and demolding to obtain the disposable lunch box.
Example 5:
the processing method of the disposable lunch box comprises the following steps:
a) placing bagasse with the particle size of 100 meshes into a sodium hydroxide solution with the mass concentration of 15 wt% for alkali treatment for 10min, removing small molecular substances, cleaning with clear water, drying, homogenizing under high pressure at 50MPa for 7 times, dispersing the bagasse into a 70% ethanol solution containing 0.4 wt% of styrene-maleic anhydride copolymer (obtained in example 2) and 0.01 wt% of 4-dimethylaminopyridine, wherein the weight ratio of the bagasse to the ethanol solution is 5:100, adjusting the pH value of the solution to 5.0 with glacial acetic acid, performing activation treatment at 80 ℃ for 30min, cleaning with absolute ethanol, and drying to obtain the bagasse;
b) Mixing and granulating a polylactic acid composition containing polylactic acid, bagasse, a toughening agent and erucamide to obtain polylactic acid composition particles, and mixing at 70 ℃ for 20 min; wherein, relative to 100 weight parts of the polylactic resin, the content of bagasse is 40 weight parts, the content of the toughening agent is 0.5 weight part, the content of erucamide is 0.05 weight part and the content of release agent sorbitol is 0.01 weight part; the toughening agent is acetyl tributyl citrate and the fumaric acid-vinyl acetate copolymer in the embodiment 1 in a weight ratio of 1: 0.05;
c) and (3) carrying out injection molding on the polylactic acid composition particles at the injection molding temperature of 160 ℃, the pressure of 42MPa and the speed of 43 percent, and demoulding at the mould temperature of 80 ℃ to obtain the disposable lunch box.
Example 6:
in order to further inhibit the migration of erucamide in the disposable lunch box and improve the use safety of the disposable lunch box, the ethanol solution for bagasse activation treatment also contains 0.1-0.5 wt% of N-vinyl pyrrolidone, which is probably because the existence of the N-vinyl pyrrolidone can improve the grafting rate of bagasse and reduce the polarity of the bagasse surface, thereby further improving the compatibility of the bagasse and polylactic acid, promoting the interfacial force between the bagasse, polylactic acid and erucamide, finally reducing the migration rate of the erucamide in the disposable lunch box to food, improving the mechanical property of the disposable lunch box, and also improving the use amount of the bagasse in the polylactic acid composition and reducing the cost of the disposable lunch box. Therefore, this example is different from example 4 in that the ethanol solution contains 0.3 wt% of N-vinylpyrrolidone in the step a).
Comparative example 1:
the difference from example 3 is that: b) in the procedure, the fumaric acid-vinyl acetate copolymer of example 1 was not added.
Comparative example 2:
the difference from example 3 is that: b) in the step, acetyl tributyl citrate is not added.
Comparative example 3:
the difference from example 3 is that: b) in the step, no toughening agent is added.
Test example 1:
1. graft ratio of bagasse
Drying the pretreated bagasse in an oven to constant weight, and weighing m0(ii) a Drying the activated bagasse in an oven to constant weight, and weighing the weight m1(ii) a For a total of 3 replicates, the grafting was calculated by the following formula:
fig. 1 shows the grafting ratio of bagasse, and it can be seen that the grafting ratio of example 6 is higher than that of examples 4 and 5, which is probably because the presence of N-vinyl pyrrolidone facilitates the swelling of bagasse, so that the styrene-maleic anhydride copolymer can be in contact with bagasse over a large area to perform esterification reaction and grafted on the fiber surface of bagasse, thereby improving the grafting ratio.
2. FTIR analysis of bagasse
The bagasse and bagasse after activation in example 4 were characterized by a Fourier transform infrared spectrometer, and a small amount of freeze-dried samples of activated bagasse and bagasse were taken, mixed with KBr and tabletted, with a scanning range of 400-4000 cm –1Resolution of 4cm-1The number of scans was 32.
The FTIR diagram of the bagasse is shown in fig. 2, wherein 1 is bagasse and 2 is activated bagasse of example 4, it can be seen that the FTIR diagram of the activated and modified bagasse is obviously changed, specifically: example 4 bagasse after activation at 1720cm-1New absorption peaks appear at the positions, and the absorption peaks belong to the stretching vibration absorption peaks of ester groups, which shows that hydroxyl groups on the surface of bagasse fibers and a styrene-maleic anhydride copolymer are subjected to chemical reaction to form ester bonds, and can qualitatively prove that the styrene-maleic anhydride copolymer is successfully grafted to bagasse fibers; example 4 bagasse after activation at 1500cm-1And 1459cm-1New absorption peaks appear at the positions, and the absorption peaks belong to the vibration absorption peaks of the benzene ring framework, so that the styrene-maleic anhydride copolymer is further shown to be successfully grafted to the bagasse fibers; example 4 bagasse at 768cm after activation-1And 700cm-1And new absorption peaks appear at the positions, belong to C-H out-of-plane bending vibration absorption double peaks on a single substituted benzene ring, and further indicate that the styrene-maleic anhydride copolymer is successfully grafted to the bagasse fibers.
Test example 2:
1. melt flow Rate testing of polylactic acid composition pellets
The melt flow rate, abbreviated as MFR, is a value which characterizes the viscous behavior of the plastic in the melt state. When the melt flow rate test is performed, the test is performed according to GBT 3682.1-2018. And testing five cut samples in each group of experiment, selecting the cut samples meeting the testing requirements, and calculating a mass average value, wherein the calculation formula of the melt flow rate is as follows:
MFR (θ, m (nom)) t (ref) × m/n, wherein:
θ -Experimental temperature (. degree. C.);
m (nom) -nominal load (g);
m-average mass of cut (g);
t (ref) -reference time (10min), s (600 s);
t-time interval for switching off, s;
MFR-melt flow rate, g/10 min.
Fig. 3 is a result of a melt flow rate test of the polylactic acid composition pellets, and it can be seen that the melt flow rate of the polylactic acid composition pellets obtained in example 1 is greater than that of the polylactic acid, which indicates that the fumaric acid-vinyl acetate copolymer can increase the melt flow rate of the polylactic acid, thereby reducing the surface tackiness of the polylactic acid. The melt flow rate of the polylactic acid composition particles obtained in examples 4 to 6 and comparative example 1 is higher than that of the polylactic acid composition particles obtained in comparative example 1 to comparative example 2, which shows that the fumaric acid-vinyl acetate copolymer can improve the melt flow rate of the polylactic acid composition, thereby reducing the surface viscosity of the polylactic acid composition and reducing the use amount of the opening agent or the slipping agent in the polylactic acid molding process; meanwhile, the fumaric acid-vinyl acetate copolymer and acetyl tributyl citrate can synergistically improve the melt flow rate of the polylactic acid composition, thereby reducing the surface viscosity of the polylactic acid composition and reducing the use amount of the opening agent or the slipping agent in the polylactic acid forming process. In addition, example 6 does not adversely affect the effect of the ethanol solution on the "fumaric acid-vinyl acetate copolymer capable of reducing the surface tackiness of the polylactic acid".
3. Non-isothermal melting DSC curve of polylactic acid composition particles
The thermal property of the polylactic acid composition particles is tested by a Differential Scanning Calorimetry (DSC) analyzer, about 7.0mg of sample is weighed and put into an aluminum crucible for sample preparation, and then the test is carried out under the condition of nitrogen protection. Firstly, heating to 200 ℃ from room temperature at a speed of 10 ℃/min, staying for 5min to eliminate thermal history and other influencing factors, and then cooling to 70 ℃ at a temperature speed of 5 ℃/min to obtain the non-isothermal melting DSC curve of the polylactic acid composition particles.
FIG. 4 is a non-isothermal melting DSC curve of the polylactic acid composition granule, and it can be seen from FIG. 7 that the crystallization peak of the pure polylactic acid is very small, but the crystallization peak of the polylactic acid in the polylactic acid composition granule obtained in example 4 is more obvious, which indicates that the processing method of example 4 promotes the crystallization of the polylactic acid; and compared with pure polylactic acid, the crystallization peaks of the polylactic acid composition particles obtained by the processing method of the embodiment 4 are all shifted to high temperature directions, which shows that the processing method of the embodiment 4 improves the non-isothermal melt crystallization temperature of the polylactic acid, so that the crystallization of the polylactic acid can be started at higher temperature. In addition, the crystallization peak of the particle sample of the polylactic acid composition obtained by the processing method of the example 4 is obviously narrower than that of the pure polylactic acid, which shows that the processing method of the example 4 improves the non-isothermal melt crystallization rate of the polylactic acid. The obvious crystallization peak, the improvement of the crystallization peak temperature and the crystallization rate fully indicate that the substances in the polylactic acid composition particles obtained by the processing method of the example 4 have obvious heterogeneous nucleation effect on the polylactic acid.
Test example 3:
1. mechanical property of disposable lunch box
A test sample is prepared by using the disposable lunch box, the sample is kept for 48 hours in a standard environment with the temperature of (23 +/-2) DEG C and the relative humidity of (50 +/-5%), the balance state is adjusted, and then the tensile strength, the bending strength and the impact strength of the sample are measured according to GB/T29418-2012. The stretching speed is 50mm/min, and the three-point bending speed is 2 mm/min.
FIGS. 5 to 7 show the tensile strength, bending strength and impact strength of the disposable cutlery box, respectively, and it can be seen that the tensile strength, bending strength and impact strength of the disposable cutlery box of example 4 are all higher than those of comparative examples 1 to 3, especially the impact strength, which shows that the fumaric acid-vinyl acetate copolymer can improve the toughening effect of the toughening agent tributyl acetylcitrate, and improve the impact strength of the polylactic acid product; the tensile strength, the bending strength and the impact strength of the disposable lunch boxes in the examples 4 and 5 are higher than those of the disposable lunch box in the example 3, which shows that the bagasse activated by the styrene-maleic anhydride copolymer in the examples 4 and 5 can improve the interfacial force among the bagasse, the polylactic acid and the slipping agent and improve the mechanical property of the disposable lunch box; the tensile strength, the bending strength and the impact strength of the disposable lunch box in the embodiment 6 are all higher than those of the disposable lunch box in the embodiment 4, which shows that the activation treatment in the embodiment 6 can further improve the compatibility of bagasse and polylactic acid and improve the mechanical property of the disposable lunch box.
2. Migration volume and migration rate of erucamide in disposable lunch box
2.1 chromatographic and Mass Spectrometry conditions
Chromatographic conditions are as follows: a chromatographic column: AgilentHP-5MS (30.0 m.times.250 μm.times.0.25 μm); temperature rising procedure: the initial temperature is 60 ℃, the temperature is increased to 200 ℃ at the speed of 40 ℃/min, then the temperature is increased to 280 ℃ at the speed of 20 ℃/min, the temperature is kept for 5min, the flow rate of carrier gas (He) is 1mL/min, and the sample injection amount is 1 muL; the split ratio was 20: 1.
Mass spectrum conditions: electron bombardment ion source; electron energy 70 eV; the transmission line temperature was 275 ℃; the ion source temperature is 235 ℃; the ion scanning mode was selected, the quantitative ions were 59, 72, 55, and the retention time was 8.63 min.
2.2 initial erucamide content in Disposable cutlery Box
Establishment of a standard curve: 0.01g of erucamide is weighed and dissolved by a solution of 10mLV (dichloromethane) and V (methanol) 1:2 to prepare a standard stock solution with the mass concentration of 1000 mg/L. The standard stock solution was diluted with a solution of V (dichloromethane) ═ V (methanol) ═ 1:2 to working solutions with mass concentrations of 1.5, 3, 6, 15, 30mg/L and 60 mg/L. Putting the sample into a sample bottle for on-machine detection. And (3) corresponding the detected peak area y to the concentration x to draw a standard curve (as shown in figure 8), wherein the standard equation is as follows: 3013.63582x-3710.8228, R2＝0.99994。
Cutting lunch box into pieces, weighing 0.1g, placing in a 50mL triangular flask with a stopper, adding 10mL dichloromethane, shaking to dissolve completely, adding 20mL methanol to precipitate high polymer, standing for 24h until the supernatant is clear, collecting appropriate amount of supernatant, filtering with 0.22 μm filter membrane, testing on a machine, and taking 3 parallels.
2.3 migration volume and migration rate of erucamide in Disposable lunch Box
Establishment of a standard curve: in the experimental example, isooctane was used as a food simulant, 0.01g of erucamide was weighed and dissolved in 10mL of isooctane to prepare a standard stock solution with a mass concentration of 1000 mg/L. And diluting the standard stock solution into working solution with mass concentration of 1.5, 3, 6, 15, 30 and 60mg/L by using isooctane. Putting the sample into a sample bottle for on-machine detection. And (3) corresponding the detected peak area y to the concentration x to draw a standard curve (as shown in FIG. 9), wherein the standard equation is as follows: 2487.076x-876.076, R2＝0.99827。
Cutting the disposable lunch box into 1 × 1cm2Taking 6 sample blocks, placing the sample blocks into a 20mL test tube, adding 10mL of food simulant, fully mixing and shaking uniformly, covering a test tube plug, sealing the test tube plug with a preservative film, placing the test tube plug into a 70 ℃ oven for a migration experiment, taking out the test tube plug after 2 hours, sucking supernatant, filtering the supernatant through a 0.22 mu m filter membrane, and detecting by GC-MS to obtain the mass concentration (rho) of erucamide; each sample was run in 3 replicates.
Migration volume in food simulantsMeasured mass of erucamide (m)1) Mass (m) with food simulant2) Is calculated according to the following formula:
the migration volume (mg/kg) ═ m1/m2＝(ρ×V×N)/m2(ii) a In the formula (I), the compound is shown in the specification,
m1-mass of erucamide in food simulant, mg;
m2-mass of food simulant, mg;
the mass concentration of rho-erucamide;
v-volume of food simulant, L;
n-dilution factor (if the food simulant is directly put on the machine, N equals 1).
The mobility is expressed as the ratio of the transport of erucamide measured in the food simulant to the initial content of erucamide in the disposable cutlery box, calculated according to the following formula:
mobility is M/M0＝(ρ×V×N)/m2(ii) a In the formula (I), the compound is shown in the specification,
the migration amount of the M-erucamide is mg/kg;
M0initial content of erucamide in disposable lunch boxes, mg/kg.
FIG. 10 shows the maximum migration rate of erucamide to isooctane at 70 ℃ in the disposable lunch box, and it can be seen that the maximum migration rate of the slipping agent to isooctane at 70 ℃ in the disposable lunch boxes of examples 4-6 is less than 0.43%; example 4 the maximum migration rate of the slipping agent in the disposable lunch box to isooctane at 70 ℃ is less than that in example 3, which shows that the bagasse in example 4 can be treated in a way that the interfacial force between bagasse and polylactic acid and the slipping agent can be improved, and the migration of the slipping agent in the disposable lunch box can be inhibited; example 6 the maximum migration rate of the slipping agent in the disposable meal box to isooctane at 70 ℃ is higher than that in example 4, which shows that the bagasse treatment mode in example 6 can further inhibit the migration of erucamide in the disposable meal box, and improve the use safety of the disposable meal box.
Conventional techniques in the above embodiments are known to those skilled in the art, and therefore, will not be described in detail herein.
The above embodiments are merely illustrative, and not restrictive, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the protection scope of the present invention should be defined by the claims.
Claims (8)
1. Use of a fumaric acid-vinyl acetate copolymer to increase the melt flow rate of a polylactic acid or a polylactic acid composition; the preparation method of the fumaric acid-vinyl acetate copolymer comprises the following steps: stirring fumaric acid and toluene at 60-80 ℃ until the fumaric acid is completely dissolved, adding vinyl acetate and benzoyl peroxide, wherein the toluene accounts for 1.0-2.0 wt% of the total mass of the fumaric acid and the vinyl acetate, the benzoyl peroxide accounts for 1.0-2.0 wt% of the total mass of the fumaric acid and the vinyl acetate, the mass ratio of the fumaric acid to the vinyl acetate is 1:1.2-1.6, continuously reacting at constant temperature for 3.0-4.0h, removing the toluene from the product by reduced pressure distillation, washing the product with absolute ethyl alcohol until the product is neutral, separating the solution, cooling and performing suction filtration to obtain the final product, namely the fumaric acid-vinyl acetate copolymer.
2. The processing method of the disposable lunch box comprises the following steps:
mixing and granulating a polylactic acid composition containing polylactic acid, bagasse, a flexibilizer and a slipping agent to obtain polylactic acid composition particles;
carrying out injection molding on the polylactic acid composition particles, and demoulding to obtain the disposable lunch box;
wherein, relative to 100 weight parts of polylactic resin, the content of bagasse is 40 to 60 weight parts, the content of toughener is 0.5 to 2.5 weight parts, and the content of slipping agent is 0.05 to 0.35 weight part;
the toughening agent is acetyl tributyl citrate with the weight ratio of 1:0.05-0.2 and the fumaric acid-vinyl acetate copolymer as defined in claim 1;
the bagasse is subjected to activation treatment by using a styrene-maleic anhydride copolymer after being subjected to a strong alkali solution, and the method specifically comprises the following steps: placing 100-mesh and 300-mesh bagasse into an alkali solution with the mass concentration of 15-30 wt% for alkali treatment for 10-30min, removing small molecular substances, cleaning with clear water, drying, homogenizing under high pressure at 50-200MPa for 3-7 times, dispersing the bagasse into a 70-90% ethanol solution containing 0.4-0.8 wt% of styrene-maleic anhydride copolymer, 0.01-0.1 wt% of 4-dimethylaminopyridine and 0.1-0.5 wt% of N-vinylpyrrolidone at a weight ratio of 5-10:100, adjusting the pH value of the solution to 5.0-7.0 with glacial acetic acid, activating at 80-100 ℃ for 30-120min, cleaning with absolute ethanol, and drying; the number average molecular weight of the styrene-maleic anhydride copolymer was 2500-7000 g/mol.
3. A method for processing a disposable lunch box as claimed in claim 2, characterized in that: the activating treatment temperature is 80-100 ℃, and the time is 30-120 min.
4. A method for processing a disposable lunch box as claimed in claim 2, characterized in that: the slipping agent is selected from one or more of the group consisting of erucamide, behenamide, oleamide and stearamide.
5. A method for processing a disposable lunch box as claimed in claim 2, characterized in that: the mixing temperature is 70-100 ℃, and the mixing time is 20-30 min.
6. A method for processing a disposable lunch box as claimed in claim 2, characterized in that: the injection molding temperature is 160-180 ℃, the pressure is 42-47MPa, and the speed is 43-47%; the temperature of the mould is 80-110 ℃.
7. A disposable cutlery box obtained by the process according to any of claims 2 to 6, wherein the slip agent has a maximum mobility towards isooctane at 70 ℃ of less than 0.43%.
8. A method for activating bagasse comprises the steps of putting bagasse with a particle size of 100 meshes and 300 meshes into an alkali solution with a mass concentration of 15-30 wt% for alkali treatment for 10-30min, removing small molecular substances, cleaning with clear water, drying, homogenizing for 3-7 times under high pressure at 50-200MPa, dispersing the bagasse into a 70-90% ethanol solution containing 0.4-0.8 wt% of styrene-maleic anhydride copolymer, 0.01-0.1 wt% of 4-dimethylaminopyridine and 0.1-0.5 wt% of N-vinyl pyrrolidone, wherein the weight ratio of the bagasse to the ethanol solution is 5-10:100, adjusting the pH value of the solution to 5.0-7.0 with glacial acetic acid, activating at 80-100 ℃ for 30-120min, cleaning with absolute ethanol, and drying; the number average molecular weight of the styrene-maleic anhydride copolymer was 2500-7000 g/mol.
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