A degradable plastic prepared from plant wood fiber and a preparation method thereof

Abstract

The invention discloses a degradable plastic prepared by using plant wood fiber and a preparation method thereof, belonging to the field of degradable plastic preparation, including a degradable plastic prepared by using plant wood fiber and a preparation method of the degradable plastic prepared by using plant wood fiber. After the plant wood fiber, high molecular weight polyethylene glycol and polyethyleneimine are dissolved in a plant wood fiber solution, water is added to precipitate a large amount of stable solid plastic particles containing cellulose lignin and high toughness. The regenerated solid plastic particles can be used to prepare degradable plastics. The prepared degradable plastics can be degraded by 74.40% after being buried in the soil for 180 days, and have strong degradation ability; the tensile strength can reach 59.31Mpa, and the elongation at break can reach 251.31%, with good tensile strength and elongation at break, and the water absorption rate is only 0.29% under the condition of 80% humidity, and the water resistance is good.

Description

Technical Field

[0001] The invention relates to the field of preparation of degradable plastics, and in particular to a degradable plastic prepared by using plant wood fibers and a preparation method thereof. Background Art

[0002] Today, about 140 million tons of synthetic plastics of various types are produced around the world each year, most of which enter the ecological environment in the form of industrial waste. Although some materials, such as polyester, are biodegradable, most plastic products in use are not biodegradable or take decades to degrade, and their accumulation will cause great harm to the environment. Therefore, the research, development and utilization of biodegradable plastics have received unprecedented attention and importance.

[0003] Due to different degradation mechanisms, degradable plastics can be classified into: photodegradable, biodegradable and photo-biodegradable plastics. After decades of development, biodegradable plastics have become the main form of degradable plastics. Lignin is a renewable plant resource, which together with cellulose and hemicellulose constitutes plant wood fiber. It is abundant and inexpensive, and widely exists in plant tissues. However, due to the poor processing performance and mechanical properties of plant wood fiber itself, it is rarely made into structural parts alone.

[0004] Lignin in plant wood fiber has highly cross-linked supramolecular structure and intermolecular interaction, such as hydrogen bond, dipole-dipole action and van der Waals force, and can be blended with different macromolecules (synthetic or natural macromolecules). After blending with macromolecule, the weakness in plant wood fiber performance can be eliminated, and the degradable plastic with good processing properties is obtained. But in order to improve the tensile strength and elongation at break of plant wood fiber, the high polymer ratio that needs to be added during blending is often higher, and the obtained plastics need a long time to degrade, and the degradable plastics prepared simultaneously are waterproof and heat-resistant. Therefore, it is urgent to find a new method to make high polymer and plant wood fiber interact and play the advantages of each component, and make the obtained plastics have good natural degradation, anti-deformation, waterproof effect, while tensile strength and high elongation at break of degradable plastics. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a degradable plastic prepared using plant wood fiber and a preparation method thereof, so as to solve the problems of low tensile strength and elongation at break of plant wood fiber, poor waterproof effect of the degradable plastic prepared after blending with polymers, and long natural degradation time.

[0006] The present invention solves the above technical problems by the following technical means:

[0007] A degradable plastic prepared from plant wood fiber. The raw materials for preparing the degradable plastic include: plant wood fiber solution, 4000-6000Da polyethylene glycol, and 30000-50000Da polyethyleneimine.

[0008] Furthermore, the raw material ratio of the degradable plastic is: the volume mass ratio of plant wood fiber solution, 4000-6000Da polyethylene glycol and 30000-50000Da polyethyleneimine is (0.8-1.2)L:(1-2)g:(1-3)g.

[0009] Furthermore, the plant wood fiber solution comprises the following raw materials: plant wood fiber powder, methyltriethylammonium hydroxide, 500-1500Da polyethylene glycol and 1 mol / L sodium hydroxide solution.

[0010] Furthermore, the raw material ratio of the plant wood fiber solution is: the mass volume ratio of methyltriethylammonium hydroxide, 500-1500Da polyethylene glycol and 1mol / L sodium hydroxide solution is (3-5): (1-2): (0.05-0.15).

[0011] The present invention also provides a method for preparing degradable plastics, the specific steps of which are as follows:

[0012] S1. Preparation of degradable plastic stock solution: adding 4000-6000Da polyethylene glycol and 30000-50000Da polyethyleneimine to the plant wood fiber solution, stirring and heating, and stirring at a constant temperature to obtain a degradable plastic stock solution;

[0013] S2. Preparation of degradable plastics: The degradable plastic stock solution is cooled to room temperature, and water is added to precipitate a colloid. When the colloid no longer precipitates, the solid is separated by filtration. The solid is dried at 50-60°C, and then fed into a twin-screw extruder for melt blending, extrusion and granulation at a temperature of 180°C-220°C and a screw speed of 40-60r / min to obtain a degradable plastic.

[0014] Furthermore, in step S1, the temperature of the constant temperature stirring is 60-80° C., and the time is 1-2 h.

[0015] Further, the preparation method of the plant wood fiber solution:

[0016] A. Preparation of plant wood fiber dissolving agent: 500-1500Da polyethylene glycol and methyl triethyl ammonium hydroxide are mixed and stirred evenly, 1 mol / L sodium hydroxide solution is added and stirred for 5-15 minutes, and then stirred at a constant temperature of 40-50°C for 20-30 minutes, poured into a reactor, heated under reflux and stirred to obtain a plant wood fiber dissolving agent;

[0017] B. Preparation of plant wood fiber solution: Add plant wood fiber powder into plant wood fiber dissolving agent, raise the temperature to 50-60° C. while stirring, continue stirring for 20-30 minutes, and then filter and separate to obtain plant wood fiber solution.

[0018] Furthermore, in step A, the heating reflux stirring time is 1-2h and the temperature is 85-95°C.

[0019] Furthermore, in step B, the mass volume ratio of the plant wood fiber powder to the plant wood fiber dissolving agent is (1-2) kg: (3-5) L.

[0020] Plant wood fibers can be made into lignocellulosic biomass plastics, but they have the disadvantages of low tensile strength, elongation at break, and poor heat and water resistance. In order to improve the tensile strength, elongation at break, and water resistance of lignocellulosic biomass plastics, plant wood fibers can be blended with polyethylene glycol and polyethylene imine to obtain modified lignocellulosic biomass plastics. However, high molecular weight polyethylene glycol and polyethylene imine are difficult to dissolve at room temperature and cannot be well blended with lignocellulose. After high-temperature melting, polyethylene glycol and polyethylene imine are prone to uneven distribution, resulting in the tensile strength, elongation at break, and water resistance of the formed lignocellulosic biomass plastics not being well improved.

[0021] The invention uses plant wood fiber, 4000-6000Da polyethylene glycol and 30000-50000Da polyethylene imine as raw materials, and mixes methyl triethyl ammonium hydroxide, 500-1500Da polyethylene glycol and 1 mol / L sodium hydroxide solution to dissolve plant wood fiber powder to prepare a plant wood fiber solution. Subsequently, 4000-6000Da polyethylene glycol and 30000-50000Da polyethylene imine are added and dissolved, and then water is added to quickly regenerate lignin from the plant wood fiber solution. The regenerated lignin is mutually entangled and cross-linked with the 4000-6000Da polyethylene glycol and the 30000-50000Da polyethylene imine, and is filled in a cellulose nano-network structure, so that a large number of stable solid plastic particles containing cellulose lignin and high toughness can be obtained. The biodegradable plastic produced by extrusion and granulation of recycled solid plastic particles has good tensile strength, elongation at break and waterproof ability, and has a short natural degradation time. It can be used to prepare disposable plastic bags and packaging boxes.

[0022] Beneficial effects:

[0023] 1. The present invention dissolves plant wood fiber solution, 4000-6000Da polyethylene glycol and 30000-50000Da polyethyleneimine, and then adds water to successfully precipitate a biodegradable material with good tensile strength, elongation at break and waterproof performance.

[0024] 2. The plant wood fiber solution is prepared from plant wood fiber powder, methyltriethylammonium hydroxide, 500-1500Da polyethylene glycol and 1 mol / L sodium hydroxide solution. It can simultaneously dissolve plant wood fiber, high molecular weight polyethylene glycol and polyethyleneimine and fully mix the three. The obtained degradable plastic structure has a tight tensile strength, elongation at break and waterproof performance that are effectively improved.

[0025] 3. The prepared plant wood fiber solution is a green solvent and is degradable. It can be added to the plant wood fiber powder again for recycling. The whole synthesis process is mild and green. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to embodiments:

[0027] Example 1: Preparation of degradable plastic

[0028] Before preparing degradable plastics, plant wood fiber solution should be prepared. The specific method is as follows:

[0029] A. Preparation of plant wood fiber dissolving agent: 1.5 L of polyethylene glycol with a molecular weight of 1000 Da and 4 L of methyltriethylammonium hydroxide were respectively weighed and mixed and stirred evenly, 0.1 L of 1 mol / L sodium hydroxide solution was added and stirred for 10 min, and then stirred at a constant temperature of 45° C. for 25 min, and then poured into a reactor, heated and stirred under reflux at 90° C. for 1.5 h to obtain a plant wood fiber dissolving agent;

[0030] B. Preparation of plant wood fiber solution: Weigh 1.5 kg of plant wood fiber powder and add it into 1 L of plant wood fiber dissolving agent. After heating to 55° C. while stirring, continue stirring for 25 minutes, and then filter and separate to obtain the plant wood fiber solution.

[0031] Preparation of degradable plastics:

[0032] S1. Preparation of biodegradable plastic stock solution: 1.5 g of polyethylene glycol with a molecular weight of 5000 Da and 2 g of polyethyleneimine with a molecular weight of 40000 Da were added to 1 L of plant wood fiber solution, heated to 70 ° C while stirring, and stirred at a constant temperature for 1.5 h to obtain a biodegradable plastic stock solution;

[0033] S2. Preparation of degradable plastics: The degradable plastic stock solution is cooled to room temperature, and water is added to precipitate a colloid. When the colloid no longer precipitates, the solid is separated by filtration. The solid is dried at 55°C and sent to a twin-screw extruder for melt blending, extrusion and granulation at a temperature of 200°C and a screw speed of 50r / min to obtain a degradable plastic.

[0034] Example 2: Preparation of biodegradable plastic

[0035] Before preparing degradable plastics, plant wood fiber solution should be prepared. The specific method is as follows:

[0036] A. Preparation of plant wood fiber dissolving agent: 1 L of 500 Da molecular weight polyethylene glycol and 3 L of methyl triethyl ammonium hydroxide were respectively weighed and mixed and stirred evenly, 0.05 L of 1 mol / L sodium hydroxide solution was added and stirred for 5 min, and then stirred at a constant temperature of 40° C. for 30 min, and then poured into a reactor, heated and stirred under reflux at 85° C. for 2 h to obtain a plant wood fiber dissolving agent;

[0037] B. Preparation of plant wood fiber solution: Weigh 1 kg of plant wood fiber powder and add it into 0.5 L of plant wood fiber dissolving agent. After heating to 50° C. while stirring, continue stirring for 30 minutes, and then filter and separate to obtain the plant wood fiber solution.

[0038] Preparation of degradable plastics:

[0039] S1. Preparation of biodegradable plastic stock solution: add 1 g of polyethylene glycol with a molecular weight of 6000 Da and 1 g of polyethyleneimine with a molecular weight of 50000 Da to 0.8 L of plant wood fiber solution, heat to 60 ° C while stirring, and stir at a constant temperature for 2 h to obtain a biodegradable plastic stock solution;

[0040] S2. Preparation of degradable plastics: The degradable plastic stock solution is cooled to room temperature, and water is added to precipitate a colloid. When the colloid no longer precipitates, the solid is separated by filtration. The solid is dried at 50°C and sent to a twin-screw extruder for melt blending, extrusion and granulation at a temperature of 220°C and a screw speed of 40r / min to obtain a degradable plastic.

[0041] Example 3: Preparation of degradable plastic

[0042] Before preparing degradable plastics, plant wood fiber solution should be prepared. The specific method is as follows:

[0043] A. Preparation of plant wood fiber dissolving agent: 2L of 1500Da molecular weight polyethylene glycol and 5L of methyltriethylammonium hydroxide were respectively weighed and mixed and stirred evenly, 0.15L of 1mol / L sodium hydroxide solution was added and stirred for 15min, and then stirred at a constant temperature of 50°C for 20min, and then poured into a reactor, heated and stirred under reflux at 95°C for 1h to obtain a plant wood fiber dissolving agent;

[0044] B. Preparation of plant wood fiber solution: Weigh 2 kg of plant wood fiber powder and add it into 1.5 L of plant wood fiber dissolving agent. After heating to 50° C. while stirring, continue stirring for 30 minutes, and then filter and separate to obtain the plant wood fiber solution.

[0045] Preparation of degradable plastics:

[0046] S1. Preparation of biodegradable plastic stock solution: 0.8L of plant wood fiber solution was added with 2g of polyethylene glycol with a molecular weight of 4000Da and 3g of polyethyleneimine with a molecular weight of 30000Da, heated to 60°C while stirring, and stirred at a constant temperature for 2h to obtain the biodegradable plastic stock solution;

[0047] S2. Preparation of degradable plastics: The degradable plastic stock solution is cooled to room temperature, and water is added to precipitate a colloid. When the colloid no longer precipitates, the solid is separated by filtration. The solid is dried at 50°C and sent to a twin-screw extruder for melt blending, extrusion and granulation at a temperature of 220°C and a screw speed of 40r / min to obtain a degradable plastic.

[0048] Comparative Example 1:

[0049] This comparative example is in contrast to Example 1, the difference being that, in the preparation of the plant wood fiber solution in the preparation of the degradable plastic, no 1 mol / L sodium hydroxide solution is added in step A, and the remaining steps are the same. The preparation of the plant wood fiber solution is specifically as follows:

[0050] A. Preparation of plant wood fiber dissolving agent: 2 L of polyethylene glycol with a molecular weight of 1500 Da and 5 L of methyltriethylammonium hydroxide were respectively weighed and mixed and stirred evenly, and then stirred at a constant temperature of 50° C. for 20 minutes to obtain a plant wood fiber dissolving agent.

[0051] Comparative Example 2:

[0052] This comparative example is in contrast to Example 1, the difference being that, in the preparation of the degradable plastic, no 1000Da polyethylene glycol is added in step A of preparing the plant wood fiber solution, and the remaining steps are the same. The preparation of the plant wood fiber solution is specifically as follows:

[0053] A. Preparation of plant wood fiber dissolving agent: Measure 5.5 L of methyltriethylammonium hydroxide and stir evenly, add 0.1 L of 1 mol / L sodium hydroxide solution and continue stirring for 10 min, then stir at a constant temperature of 45 ° C for 25 min, then pour into a reactor, heat and stir under reflux at 90 ° C for 1.5 h to obtain a dissolving agent.

[0054] The prepared solvent cannot dissolve plant wood fibers, so the subsequent steps cannot be carried out and the degradable plastic cannot be produced.

[0055] Comparative Example 3:

[0056] This comparative example is in contrast to Example 1, the difference being that methyltriethylammonium hydroxide is not added in step A of preparing the plant wood fiber solution when preparing the degradable plastic, and the remaining steps are the same. The preparation of the plant wood fiber solution is specifically as follows:

[0057] A. Preparation of plant wood fiber dissolving agent: 5.5 L of polyethylene glycol with a molecular weight of 1000 Da was measured, 0.1 L of 1 mol / L sodium hydroxide solution was added, and the mixture was stirred for 10 min, and then stirred at a constant temperature of 45° C. for 25 min, and then poured into a reactor, and heated and stirred under reflux at 90° C. for 1.5 h to obtain a plant wood fiber dissolving agent;

[0058] The prepared solvent cannot dissolve plant wood fibers, so the subsequent steps cannot be carried out and the degradable plastic cannot be produced.

[0059] Comparative Example 4:

[0060] This comparative example is in contrast to Example 1, the difference being that polyethyleneimine is not added in the preparation of the degradable plastic stock solution in step S2, and the remaining steps are the same. The preparation of the degradable plastic stock solution in step S2 is specifically as follows:

[0061] S1. Preparation of biodegradable plastic stock solution: 3.5 g of polyethylene glycol with a molecular weight of 5000 Da was added to 1 L of plant wood fiber solution, heated to 70° C. while stirring, and stirred at a constant temperature for 1.5 h to obtain the biodegradable plastic stock solution;

[0062] Comparative Example 5:

[0063] This comparative example is in contrast to Example 1, the difference being that polyethylene glycol is not added in the preparation of the degradable plastic stock solution in step S2, and the remaining steps are the same. The preparation of the degradable plastic stock solution in step S2 is specifically as follows:

[0064] S2. Preparation of biodegradable plastic stock solution: add 3.5 g of 40,000 Da polyethyleneimine to 1 L of plant wood fiber solution, heat to 70 ° C while stirring, and stir at constant temperature for 1.5 h to obtain the biodegradable plastic stock solution;

[0065] Comparative Example 6:

[0066] This comparative example is in contrast to Example 1, the difference being that the degradable plastic is directly mixed with plant wood fiber powder, 5000Da polyethylene glycol and 40000Da polyethyleneimine and then melt-drawn. The preparation of the degradable plastic is as follows:

[0067] 1.5 kg of plant wood fiber powder, 1.5 g of 5000 Da polyethylene glycol and 2 g of 40000 Da polyethylene imine were weighed respectively, mixed evenly and sent into a twin-screw extruder for melt blending, extrusion and granulation at a temperature of 200° C. and a screw speed of 50 r / min to obtain a degradable plastic.

[0068] 1. Mechanical properties test of biodegradable plastics

[0069] The test was carried out in accordance with GB / T1040.1-2018 "Determination of tensile properties of plastics". The biodegradable plastics prepared in Example 1, Comparative Example 1 and Comparative Examples 4-6 were injection molded according to a standard type I sample mold. Five groups of each sample were tested, and the tensile strength, flexural strength and elongation at break were recorded. The average values ​​were then calculated. The results are shown in Table 1.

[0070] Table 1

[0071] Tensile strength / (Mpa) Elongation at break % Example 1 59.31 251.31 Comparative Example 1 41.52 177.45 Comparative Example 4 32.16 112.34 Comparative Example 5 33.61 124.59 Comparative Example 6 50.23 204.67

[0072] 2. Test of Waterproof Capacity of Degradable Plastics

[0073] The degradable plastics prepared in Example 1, Comparative Example 1 and Comparative Examples 4-6 were injection molded according to a standard I-type sample mold to obtain samples. The water resistance is reflected by the water absorption rate of the plastic. The lower the water absorption rate, the better the water resistance. The test method of water absorption rate is: place the sample in a 50°C oven and dry it for 24 hours, and record the mass as m 1 Then place the samples at 25℃, 50%, 65% and 80% humidity for 24h, and record the mass as m 2 , the water absorption rate of the sample was calculated according to the following formula, and the test results are shown in Table 2 below:

[0074] Water absorption rate = ((m 2 -m 1 ) / m 1 )×100%

[0075] Table 2

[0076]

[0077]

[0078] 3. Degradable plastic degradation ability test

[0079] The degradable plastics prepared in Example 1, Comparative Example 1 and Comparative Examples 4-6 were injection molded according to a standard type I sample mold to obtain samples. The degradation performance test was carried out according to GB / T 20197-2006, and the results are shown in Table 3.

[0080] Table 3

[0081]

[0082]

[0083] Data Analysis:

[0084] It can be seen from the data in Tables 1-3 that the degradable plastics prepared from plant wood fibers within the protection scope of the present invention have good tensile strength and elongation at break. The tested tensile strength can reach 59.31 MPa, and the elongation at break can reach 251.31%; the water resistance is good, and the water absorption rates under humidity conditions of 50%, 65% and 80% are 0.14%, 0.21% and 0.29% respectively; the degradation ability is strong, and the weight loss rates after burial for 30 days, 90 days and 180 days are 20.00%, 45.90% and 74.40% respectively.

[0085] From the data of Example 1, Comparative Example 1 and Comparative Examples 4-5 in Comparative Tables 1-3, it can be seen that the plant wood fiber solution prepared by not adding 1 mol / L sodium hydroxide solution in Comparative Example 1 is used for the preparation of degradable plastics, and Comparative Examples 4-5 do not add 30000-50000Da polyethyleneimine and 4000-6000Da polyethylene glycol in the preparation process of degradable plastics, which reduces the tensile strength, elongation at break and water resistance, narrowing the application scope of degradable plastics. From the data of Example 1 and Comparative Example 6 in Comparative Tables 1-3, it can be seen that the tensile strength, elongation at break and water resistance of the plastic obtained by melting and drawing the plant wood fiber powder, 5000Da polyethylene glycol and 40000Da polyethyleneimine after mixing in Comparative Example 6 have been improved to a certain extent, but its degradation performance is extremely poor, and it does not belong to degradable plastics.

[0086] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.

Claims

1. A degradable plastic prepared from plant wood fiber, characterized in that: The raw materials of the degradable plastic include: plant wood fiber solution, 4000-6000 Da polyethylene glycol, 30000-50000 Da polyethylene imine; The raw material ratio of the degradable plastic is plant wood fiber solution, 4000-6000 Da polyethylene glycol and 30000-50000 Da polyethylene imine, and the volume mass ratio is (0.8-1.2) L: (1-2) g: (1-3) g; The preparation method of the degradable plastic is as follows: S1. Preparation of biodegradable plastic stock solution: adding 4000-6000 Da polyethylene glycol and 30000-50000 Da polyethyleneimine to the plant wood fiber solution, heating while stirring, and stirring at a constant temperature to obtain a biodegradable plastic stock solution; S2. Preparation of degradable plastic: The degradable plastic stock solution is cooled to room temperature, and water is added to precipitate a colloid. When the colloid no longer precipitates, the solid is separated by suction filtration, and the solid is dried and sent to a twin-screw extruder for melt blending, extrusion and granulation to obtain a degradable plastic; The plant wood fiber solution comprises the following raw materials: plant wood fiber powder, methyl triethyl ammonium hydroxide, 500-1500Da polyethylene glycol and 1 mol / L sodium hydroxide solution; the raw material ratio of the plant wood fiber solution is methyl triethyl ammonium hydroxide, 500-1500Da polyethylene glycol and 1 mol / L sodium hydroxide solution in a volume ratio of (3-5): (1-2): (0.05-0.15); The preparation method of the plant wood fiber solution: A. Preparation of plant wood fiber dissolving agent: 500-1500 Da polyethylene glycol and methyl triethyl ammonium hydroxide are mixed and stirred evenly, 1 mol / L sodium hydroxide solution is added and stirred for 5-15 min, and then stirred at a constant temperature of 40-50° C. for 20-30 min, poured into a reactor, heated under reflux and stirred to obtain a plant wood fiber dissolving agent; B. Preparation of plant wood fiber solution: Add plant wood fiber powder into plant wood fiber dissolving agent, raise the temperature to 50-60° C. while stirring, continue stirring for 20-30 minutes, and then filter and separate to obtain plant wood fiber solution.

2. The degradable plastic prepared from plant wood fiber according to claim 1, characterized in that: In step S1, the temperature of the constant temperature stirring is 60-80° C., and the time is 1-2 hours.

3. The degradable plastic prepared from plant wood fiber according to claim 2, characterized in that: The heating reflux stirring time in step A is 1-2h, and the temperature is 85-95°C.

4. The degradable plastic prepared from plant wood fiber according to claim 3, characterized in that: In the step B, the mass volume ratio of the plant wood fiber powder to the plant wood fiber dissolving agent is (1-2) kg: (3-5) L.

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