CN108587208A - A kind of method that GT plasticising DMSO/TEAC systems dissolving wood powder prepares injection grade bio-based plastics - Google Patents

Abstract

The invention discloses a method for preparing injection-grade bio-based plastics by using GT plasticized DMSO/TEAC system to dissolve wood powder. The obtained ball-ground wood powder is placed in a desiccator for subsequent use; (2) the ball-ground wood powder is added in dimethyl sulfoxide/tetraethylammonium chloride solution, mechanically stirred for a certain period of time in a constant temperature water bath, acetone is added, and the product is separated out by suction filtration, The product is placed in an oven and dried to a constant weight to obtain a dissolved modified product; (3) the dissolved modified product and glycerol triacetate are blended and circulated in a twin-screw extruder, and pelletized to obtain the final product lignocellulosic bio base plastic particles. The invention has the advantages of simple process, no chemical reaction, wide distribution of raw materials, environmental protection, better mechanical properties of the obtained injection-grade bio-based plastics, and lays a certain foundation for realizing resource utilization of agricultural and forestry wastes.

Description

Preparation of injection molding grade bio-based plastics by dissolving wood flour in a GT plasticized DMSO/TEAC system Methods

technical field

The invention belongs to the technical field of bio-based plastics development, and relates to a method for preparing injection-grade bio-based plastics by dissolving wood powder using a GT plasticized DMSO/TEAC system.

Background technique

With the continuous development of society, the petrochemical resources needed for production and life are increasingly scarce, and a series of environmental problems caused by petrochemical resources, it is urgent to find a type of renewable resources that can replace petrochemical resources. As a rich renewable resource, wood fiber has attracted more and more attention and attention from researchers, and the development of bio-based composite materials from wood fiber has become a new direction of the material industry.

my country is a large agricultural country, and the annual production of agricultural and forestry wastes such as straw, wood scraps and other wood fibers is about 900 million tons. Moreover, these lignocellulosic biomass can be continuously regenerated, which is the most abundant renewable green resource that can be utilized by human beings in the 21st century. Therefore, it has a good prospect to make bio-based plastics from lignocellulosic biomass such as straw and forest trees. At present, the utilization of biomass raw materials is basically concentrated in the field of composite materials. Many scholars study lignocellulosic raw materials and polymer composite materials and interface modification. The materials prepared are biomass and polymer composite materials, and the biomass content is not high. .

Chemical modification can transform lignocellulosic materials into thermoplastic new polymer materials, such as esterification, etherification, graft copolymerization, etc., but at the cost of molecular structure changes caused by chemical modification, the material loses some inherent properties. Excellent properties, but at the same time the cost is very high, so far it has not been industrialized.

In recent years, a new research system—lignocellulose total soluble system—was proposed in the world for structural identification, chemical modification and efficient utilization of lignocellulose. The characteristic of this system is that it can break the hydrogen bonds in lignocellulose molecules and between molecules, thereby causing its dissolution. The main reason why wood fiber cannot be thermoplastically processed is the hydrogen bond in the cellulose molecule and between molecules in wood fiber. The DMSO/TEAC system is often reported as a good cellulose solvent system, and the tetraethylammonium ion [(C ₂ H ₅ ) ₄ N ⁺ ] in tetraethylammonium chloride can combine with the cellulose chain, thereby shielding Intramolecular and intermolecular hydrogen bonding of cellulose.

Contents of the invention

Purpose of the invention: Aiming at the deficiencies in the prior art, the purpose of the invention is to provide a method for preparing injection-grade bio-based plastics by dissolving wood powder using GT plasticized DMSO/TEAC system, reducing the cost of modification and realizing the reduction of agricultural and forestry wastes. resource utilization.

Technical solution: In order to realize the above-mentioned purpose of the invention, the technical solution adopted in the present invention is:

A kind of method utilizing GT plasticized DMSO/TEAC system to dissolve wood powder to prepare injection-grade bio-based plastics, comprises the following steps:

1) Take lignocellulosic raw material and pulverize it, then adopt planetary ball mill to carry out ball milling process to it, and the ball milled wood powder obtained is placed in drier for subsequent use;

2) Add the ground wood powder into the tetraethylammonium chloride/dimethyl sulfoxide solvent system, stir mechanically in a constant temperature water bath for a certain period of time, add acetone, and precipitate the product after suction filtration, put the product in an oven and dry it to constant weight obtain modified products;

3) The modified product and glycerol triacetate are blended and circulated in a twin-screw extruder, extruded, and granulated to obtain the final product lignocellulosic bio-based plastic particles.

The lignocellulosic raw material described in step 1) includes all lignocellulosic biomass such as wood, mulberry branch, reed, rice husk, straw and bagasse.

The ball milling treatment time described in step 1) is 4 hours, the forward and reverse are alternated every 30 minutes, and the rotating speed is 516r/min.

In step 2), the temperature of the constant temperature water bath is 50-80° C., the stirring time is 2-4 hours, and the rotational speed of the mechanical stirring is about 200 r/min.

In step 2), the amount of ball-milled wood powder is 12.5g-15g, the amount of tetraethylammonium chloride is 7.5g-22.5g, and the amount of dimethyl sulfoxide is 40g.

In step 3), the amount of triacetin accounts for 0-15% of the total amount of the DMSO/TEAC solvent modified product and triacetin.

In step 3), the extrusion temperature is 120-160° C., and the screw speed is 40-80 r/min.

Beneficial effect: compared with the prior art, the advantages of the present invention include:

(1) The raw materials used come from a large amount of renewable lignocellulosic biomass in nature, which has multiple advantages of environmental protection and low cost, and can lay a certain foundation for the resource utilization of agricultural and forestry waste.

(2) The bio-based plastic prepared in the present invention has good mechanical properties, good plasticity, and broad application prospects.

(3) The acetone used in the present invention can be recycled after the experiment ends, without causing environmental pollution and resource waste, and realizing resource recycling.

(4) In the present invention, wood powder is dissolved in DMSO/TEAC system, does not involve chemical reaction, utilizes DMSO/TEAC system to destroy the hydrogen bond of cellulose in wood fiber, then adds plasticizer to prepare injection molding grade material, method operation Simple, easy to realize industrialization.

Description of drawings

Fig. 1 is the infrared spectrogram comparison figure of the ball-milled wood powder, modified product and extrusion product of embodiment 2, and curve a is the infrared spectrogram of ball-milled wood powder, and curve b is that the addition amount of tetraethylammonium chloride is 12.5g When the infrared spectrum of the modified product is shown, the curve c is the infrared spectrum of the extruded product blended with 5% triacetin when the added amount of tetraethylammonium chloride is 12.5g.

Fig. 2 is that embodiment 2 is the XRD comparison figure of ball-milled wood flour, modified product, extruded product and tetraethylammonium chloride, curve a is the XRD figure of ball-milled wood flour, and curve b is the addition of tetraethylammonium chloride The XRD pattern of the modified product when the amount is 12.5g, the curve c is the XRD pattern of the extruded product blended with 5% triacetin when the added amount of tetraethylammonium chloride is 12.5g, and the curve d is the tetraethylammonium chloride XRD pattern of ammonium chloride.

Fig. 3 is the scanning electron micrograph of modified product and glyceryl triacetate extruded product after injection molding, and the scanning electron microscope picture of bending section is enlarged 500 times, and 3-A is the scanning electron microscope picture of modified product when tetraethylammonium chloride addition is 15g, 3-B is a scanning electron micrograph of the extruded product blended with 5% triacetin when the added amount of tetraethylammonium chloride is 12.5g.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Example 1

A method for dissolving wood powder by GT plasticized DMSO/TEAC system to prepare injection-grade bio-based plastics, comprising the steps of:

1) Take the sage bark as raw material, peel off the bark, dry it in the air, crush it mechanically and then dry it.

2) Take 8g of dried wood flour raw material and place it in a 200mL agate ball mill jar, add zirconia balls of different diameters (Φ10mm:Φ7mm:Φ5mm, 20:40:120), and mill in a planetary ball mill for 4h, every 30min Alternate forward and reverse once, the speed is 516r/min. The ball-ground wood powder is placed in a desiccator for later use.

3) Dissolve 15g of tetraethylammonium chloride in 40g of dimethyl sulfoxide to obtain a composite solvent, weigh 6g of ball-milled wood powder and add it to the composite solvent, mechanically stir at 60°C for 2 hours, add acetone, and obtain a modified product after suction filtration.

4) Injection molding of the modified product (using a MiniJet micro injection molding machine (Thermo Fisher), the injection molding conditions are: injection pressure 750bar, holding pressure 600bar, injection temperature 170°C, mold temperature 75°C, injection time 12s, holding time 8s, the same below) Afterwards, it was determined by electronic universal testing machine (mechanical performance test was carried out on electronic universal testing machine (SANS UTM6503, Shenzhen Sansi Zongheng), the reference standard was GB/T 1040-1992 (test method for plastic tensile properties) and GB/T 9341 -2000 (test method for plastic bending performance). The same below), the bending strength is 26.28MPa, and the tensile strength is 9.63MPa.

Example 2

A method for dissolving wood powder by GT plasticized DMSO/TEAC system to prepare injection-grade bio-based plastics, comprising the steps of:

1) Take the sage bark as raw material, peel off the bark, dry it in the air, crush it mechanically and then dry it.

2) Take 8g of dried wood flour raw material and place it in a 200mL agate ball mill jar, add zirconia balls of different diameters (Φ10mm:Φ7mm:Φ5mm, 20:40:120), and mill in a planetary ball mill for 4h, every 30min Alternate forward and reverse once, the speed is 516r/min. The ball-ground wood powder is placed in a desiccator for later use.

3) Dissolve 17.5g of tetraethylammonium chloride in 40g of dimethyl sulfoxide to obtain a composite solvent, weigh 6g of ball-milled wood powder and dissolve it in the composite solvent, stir mechanically at 60°C for 2 hours, add acetone, and obtain a modified product after suction filtration .

4) The extruded product obtained after injection molding of the modified product was measured by an electronic universal testing machine, and the flexural strength was 5.38 MPa, and the tensile strength was 2.76 MPa.

The infrared spectrogram comparison chart of ball-milled wood flour, modified product and extruded product is shown in Figure 1. Curve a is the infrared spectrogram of ball-milled wood flour, and curve b is when the addition of tetraethylammonium chloride is 12.5g. The infrared spectrogram of the neutral product, the curve c is the infrared spectrogram of the extruded product blended with 5% glycerol triacetate when the addition of tetraethylammonium chloride is 12.5g, and no new characteristic absorption peak is shown in the spectrogram , which indicated that almost no chemical reaction occurred during the modification and extrusion process, and there was no increase of chemical bonds in the cellulose macromolecular chains. Curve a shows the characteristic peaks of lignocellulose, including the OH stretching vibration peak at 3424 cm ^-1 , the CH stretching vibration peak at 2922 cm ^-1 , and the peak at 1633 cm ^-1 related to crystal water. Compared with the original ball-ground wood flour (curve a), the hydroxyl peak between cellulose molecules in the GT extruded product (curve c) shifted to a higher wave number, which indicated that the hydrogen bond interaction on the cellulose molecular chain was weakened. In addition, the absorption peak at 1727cm ^-1 is the C=O stretching vibration peak of acetyl group and uronic acid group in hemicellulose, and the characteristic peak of CO stretching vibration at 1048cm ^-1 is cellulose. After adding TEAC and GT, the absorption peak at 1727cm ^-1 disappeared, and the absorption peak at 1048cm ^-1 was obviously weakened, indicating that the hydrogen bond formed between the hydroxyl groups on the cellulose molecular chain was broken. At the same time, it also shows that in the process of dissolution reaction and blending and extrusion with GT, the system has a certain damage effect on hemicellulose and cellulose.

The XRD comparison chart of ball-milled wood flour, modified product, extruded product and tetraethylammonium chloride is shown in Figure 2. Curve a is the XRD figure of ball-milled wood flour, and curve b is the amount of tetraethylammonium chloride added. The XRD pattern of the modified product at 12.5g, the curve c is the XRD pattern of the extruded product blended with 5% triacetin when the added amount of tetraethylammonium chloride is 12.5g, and the curve d is the tetraethylammonium chloride XRD pattern. It can be seen from the figure that the characteristic peak of the cellulose I crystal form in the ball-milled wood flour (a) basically disappears, which indicates that the ball milling has destroyed the crystalline form of cellulose in the wood flour. Compared with curve a, curve d has the characteristic diffraction peaks of TEAC at 2θ=18.0°, 26.0°, 30.2° and many other places. From the curves b and c, it can be seen that there is no diffraction peak of TEAC crystal in the XRD pattern of the modified product and GT extrusion product, and TEAC does not exist in the form of crystals, but exists in the form of ion pairs in the fiber Compared with the ball-milled wood flour, its crystallinity is also greatly reduced among the molecular chains of the element, so its thermoplasticity is significantly improved.

Example 3

A method for dissolving wood powder by GT plasticized DMSO/TEAC system to prepare injection-grade bio-based plastics, comprising the steps of:

1) 1) Take the sage bark as raw material, peel it off, dry it in the air, crush it mechanically and then dry it.

2) Take 8g of dried wood flour raw material and place it in a 200mL agate ball mill jar, add zirconia balls of different diameters (Φ10mm:Φ7mm:Φ5mm, 20:40:120), and mill in a planetary ball mill for 4h, every 30min Alternate forward and reverse once, the speed is 516r/min. The ball-ground wood powder is placed in a desiccator for later use.

3) Dissolve 12.5g of tetraethylammonium chloride in 40g of dimethyl sulfoxide to obtain a composite solvent. Weigh 6g of ball-milled wood powder and add it to the composite solvent. Stir mechanically in a water bath at 60°C for 2 hours, add acetone, and obtain a modified solution after suction filtration. product.

4) The modified product and glyceryl triacetate (the amount of glycerol triacetate accounts for 5% of the total amount of the modified product and glyceryl triacetate) is blended and extruded in a twin-screw extruder, and the extruder speed is 60r/ min, the extrusion temperature is 120°C.

5) The extruded product was crushed and granulated with a grinder, and tested by an electronic universal testing machine after injection molding. The bending strength was 24.91 MPa, and the tensile strength was 8.39 MPa.

Example 4

A method for dissolving wood powder by GT plasticized DMSO/TEAC system to prepare injection-grade bio-based plastics, comprising the steps of:

1) Take the sage bark as raw material, peel off the bark, dry it in the air, crush it mechanically and then dry it.

2) Take 8g of dried wood flour raw material and place it in a 200mL agate ball mill jar, add zirconia balls of different diameters (Φ10mm:Φ7mm:Φ5mm, 20:40:120), and mill in a planetary ball mill for 4h, every 30min Alternate forward and reverse once, the speed is 516r/min. The ball-ground wood powder is placed in a desiccator for later use.

3) Weigh 6g of ball-milled wood powder, dissolve 12.5g of tetraethylammonium chloride in 40g of dimethyl sulfoxide, stir mechanically in a water bath at 60°C for 2 hours, add acetone, and obtain a modified product after suction filtration.

4) The modified product and glyceryl triacetate (the amount of glycerol triacetate accounts for 5% of the total amount of the modified product and glyceryl triacetate) is blended and extruded in a twin-screw extruder, and the extruder speed is 60r/ min, the extrusion temperature is 140°C.

5) The extruded product was pulverized and granulated with a grinder, and tested by an electronic universal testing machine after injection molding. The bending strength was 34.71 MPa and the tensile strength was 16.33 MPa.

Example 5

A method for dissolving wood powder by GT plasticized DMSO/TEAC system to prepare injection-grade bio-based plastics, comprising the steps of:

1) Take the sage bark as raw material, peel off the bark, dry it in the air, crush it mechanically and then dry it.

2) Take 8g of dried wood flour raw material and place it in a 200mL agate ball mill jar, add zirconia balls of different diameters (Φ10mm:Φ7mm:Φ5mm, 20:40:120), and mill in a planetary ball mill for 4h, every 30min Alternate forward and reverse once, the speed is 516r/min. The ball-ground wood powder is placed in a desiccator for later use.

3) Dissolve 12.5g of tetraethylammonium chloride in 40g of dimethyl sulfoxide to obtain a composite solvent, weigh 6g of ball-milled wood powder and add it to the composite solvent, mechanically stir in a water bath at 60°C for 2 hours, add acetone, and obtain a modified solution after suction filtration. sexual product.

4) The modified product and glyceryl triacetate (the amount of glycerol triacetate accounts for 5% of the total amount of the modified product and glyceryl triacetate) is blended and extruded in a twin-screw extruder, and the extruder speed is 60r/ min, the extrusion temperature is 160°C.

5) The extruded product was crushed and granulated with a grinder, and tested by an electronic universal testing machine after injection molding. The bending strength was 33.66 MPa and the tensile strength was 15.12 MPa.

The SEM image of the modified product and triacetin extruded product after injection molding is magnified 500 times of the curved section as shown in Figure 3, 3-A is the SEM of the modified product when the addition of tetraethylammonium chloride is 15g Figure 3-B is a scanning electron microscope image of the extruded product blended with 5% triacetin when the amount of tetraethylammonium chloride added is 12.5g. The curved section of Figure 3-B is very flat and smooth, and the intermolecular combination is dense , the fiber structure disappears, which means that the small GT molecules penetrate into the cellulose macromolecular chains and play a plasticizing role, making the injection molded splines smoother, tighter and better in mechanical properties. From Figure 3-A, it can be seen that when the amount of TEAC added is 15g, a large number of holes appear in the curved section of the modified product, resulting in a decrease in mechanical properties.

Claims (7)

1. A method utilizing GT plasticized DMSO/TEAC system to dissolve wood powder to prepare injection-grade bio-based plastics, is characterized in that, comprising the following steps: 1) Take lignocellulosic raw material and pulverize it, then adopt planetary ball mill to carry out ball milling process to it, and the ball milled wood powder obtained is placed in drier for subsequent use; 2) Add the ground wood powder into the tetraethylammonium chloride/dimethyl sulfoxide solution, mechanically stir and dissolve in a constant temperature water bath for a certain period of time, add acetone, and precipitate the product after suction filtration, put the product in an oven and dry it to constant weight obtain modified products; 3) The modified product and glycerol triacetate are blended and circulated in a twin-screw extruder, extruded, and granulated to obtain the final product lignocellulosic bio-based plastic particles. 2. the method for utilizing GT plasticized DMSO/TEAC system to dissolve wood powder according to claim 1 to prepare injection-grade bio-based plastics, characterized in that, the lignocellulosic raw material described in step 1) contains wood, mulberry branches , reed, rice husk, straw and bagasse and all lignocellulosic biomass. 3. The method for dissolving wood powder by GT plasticized DMSO/TEAC system according to claim 1 to prepare injection-grade bio-based plastics, characterized in that, the ball milling treatment time described in step 1) is 4h, every 30min front and back Alternate once, the speed is 516r/min. 4. The method for dissolving wood powder by GT plasticized DMSO/TEAC system to prepare injection-grade bio-based plastics according to claim 1, characterized in that, the temperature of the constant temperature water bath in step 2) is 50-80°C, and the stirring time For 2-4h, the speed of mechanical stirring is about 200r/min. 5. The method for preparing injection-grade bio-based plastics by using GT plasticized DMSO/TEAC system to dissolve wood powder according to claim 1, characterized in that the amount of ball-ground wood powder in step 2) is 12.5g to 15g, tetraethyl The consumption of ammonium chloride is 7.5g～22.5g, and the consumption of dimethyl sulfoxide is 40g. 6. the method utilizing GT plasticized DMSO/TEAC system dissolving wood flour according to claim 1 to prepare injection molding grade bio-based plastics, it is characterized in that, in step 3), the consumption of triacetin accounted for DMSO/TEAC solvent modification 0-15% of the total amount of non-toxic wood flour and glycerol triacetate. 7. The method for preparing injection-grade bio-based plastics by using GT plasticized DMSO/TEAC system to dissolve wood powder according to claim 1, characterized in that, in step 3), the extrusion temperature is 120-160°C, and the screw speed is 40～80r/min.