A method for preparing a high-temperature resistant carbon dioxide-based biodegradable foam material

Abstract

A method for preparing a high-temperature resistant carbon dioxide-based biodegradable foamed material belongs to the field of polymer foamed material technology. The raw materials, by weight, consist of: 60-99 parts PPCHC, 0.5-5 parts nucleating agent, 0.1-10 parts filler, 0.1-5 parts coupling agent, and 0.05-0.5 parts foaming agent. The above raw materials are mixed and extruded using a twin-screw extruder and a single-screw extruder in series to form beads. The beads are then further foamed and molded to obtain the final product. The foamed material of this invention exhibits excellent physical properties, including good toughness, strong puncture resistance, and a soft texture, providing better protection when packaging easily damaged materials such as fruits.

Description

Technical Field

[0001] This invention belongs to the field of polymer foaming materials technology, specifically relating to a method for preparing a high-temperature resistant carbon dioxide-based biodegradable foaming material. Background Technology

[0002] Polystyrene foam (EPS) is a lightweight polymer. It is made by adding a foaming agent to polystyrene resin, heating it to soften the resin and generate gas, forming a rigid, closed-cell foam plastic. However, the adhesion between EPS beads is poor, and after foaming, the beads are prone to detachment when the foam board is squeezed or impacted. Furthermore, it is difficult to clean due to electrostatic adsorption. Polystyrene (EPS) is commonly used as a cushioning foam material in packaging boxes during transportation. EPS has a high expansion ratio, capable of expanding 40-80 times its original volume; its softening temperature is above 70℃, meeting the temperature requirements of container transportation. However, EPS is not biodegradable. Cushioning foam materials are easily discarded after use, difficult to recycle, and cause serious environmental pollution after disposal. Finding biodegradable materials to replace EPS is urgently needed.

[0003] Traditional biodegradable bio-based foaming materials are mainly PLA, but PLA's poor heat resistance and low melt strength cause it to deform at 50℃~55℃, greatly limiting its application areas and scope. This means PLA foaming materials cannot yet replace EPS and cannot meet application requirements. For example, Chinese patent CN113214618B discloses a food-grade heat-resistant PLA foaming material. It uses a biodegradable co-solvent to blend polylactic acid (PLA), butylene adipate, and butylene terephthalate (PBAT) condensate to obtain a PLA / PBAT alloy; then, it uses polymerized amino acids to intercalate montmorillonite (MMT) to obtain organo-montmorillonite; finally, it mixes and extrudes the PLA / PBAT alloy and organo-montmorillonite and foams them. Although using polymerized amino acids as intercalating agents achieves uniform dispersion of MMT in the PLA / PBAT alloy and improves the melt strength and heat distortion temperature of PLA, its heat distortion temperature is still only between 50℃ and 58℃. However, during container shipping at sea, the temperature inside the container can reach close to 70°C, which PLA foam material obviously cannot meet the packaging requirements.

[0004] In the earlier Chinese patent application CN116444974A, PPCHC was used as a modifier for PPCCP material and blended with PBS as a foaming material. This resulted in a high foaming ratio and higher softening point and tensile strength. However, the high compressive strength of this material leads to excessive hardness in many applications. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a carbon dioxide-based biodegradable foam material that meets the temperature requirements during container transportation.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a method for preparing the high-temperature resistant carbon dioxide-based biodegradable foam material, characterized in that: the high-temperature resistant carbon dioxide-based biodegradable foam material is characterized in that the raw material weight composition is: 60-99 parts of PPCHC, 0.5-5 parts of nucleating agent, 0.1-10 parts of filler, 0.1-5 parts of coupling agent, and 0.05-0.5 parts of foaming agent.

[0007] The foaming material of this invention uses cyclohexene carbonate-propylene carbonate copolymer (PPCHC) as the main material for foaming. The foaming ratio of this material can reach 40-80 times, and the heat distortion temperature reaches 70°C. The foaming material of this invention has excellent physical properties, good toughness, strong puncture resistance, and a soft texture, providing better protection when packaging easily damaged materials such as fruits. Furthermore, if the foaming material of this invention is foamed with beads and the resulting boards have strong inter-bead adhesion, it is less prone to bead detachment.

[0008] Preferably, the raw material composition by weight is: 70-85 parts PPCHC, 1.5-2.5 parts nucleating agent, 0.5-3 parts filler, 1-2.5 parts coupling agent, and 0.1-0.5 parts foaming agent. This preferred weight composition ensures a high foaming ratio, maintains the advantage of lightweight, and also meets the requirements of toughness and elasticity.

[0009] A preferred method for preparing PPCHC involves adding propylene oxide, cyclohexane oxide, and a catalyst into a reactor, introducing carbon dioxide to achieve a reaction pressure of 1.0 MPa to 2.0 MPa, and heating to maintain the reaction temperature at 60°C to 80°C. Ring-opening polymerization is then performed to generate the PPCHC. The resulting adhesive is then washed, devolatilized, and dried to obtain the final product. The PPCHC prepared using this preferred process exhibits excellent foaming performance, resulting in a material with lower hardness after foaming.

[0010] Specifically, the nucleating agent is one or more of talc, calcium carbonate, silicon dioxide, alum, calcium oxide, magnesium oxide, carbon black, and mica. The above-mentioned nucleating agents can meet the basic nucleation requirements of this invention and improve processing performance.

[0011] Preferably, the nucleating agent is acrylic acid-modified titanium dioxide. Immersing the titanium dioxide fractions in an acrylic acid solution for a short time (10s~20s) can better ensure the toughening effect of this soft foam material and improve its puncture resistance.

[0012] The foaming material of the present invention is compatible with most existing foaming processes and foaming agents. Preferably, the foaming agent is carbon dioxide or azodicarbonamide.

[0013] Specifically, the filler is one or more of the following: silica, heavy calcium carbonate, nano calcium carbonate, light calcium carbonate, and zinc oxide. Adding an appropriate amount of the above filler can maintain the uniformity of foaming, thereby ensuring the toughness of the foamed material.

[0014] Specifically, the coupling agents mentioned are silane coupling agents, titanate coupling agents, and chromium complex coupling agents. Adding an appropriate amount of coupling agent can promote the uniform distribution of the above-mentioned fillers, nucleating agents, etc. in the material, ensuring the performance of the foamed material.

[0015] Preferably, the coupling agent is a composite titanate coupling agent, which is a combination of a monoalkoxyphosphate phthalate coupling agent and a monoalkoxy fatty phthalate coupling agent. Using a monoalkoxy phthalate coupling agent in PPCHC can better promote the uniform dispersion of the above raw materials, and the effect is even better when two or more monoalkoxy phthalate coupling agents are used in combination.

[0016] A method for preparing the above-mentioned high-temperature resistant carbon dioxide-based biodegradable foamed material is characterized in that the above-mentioned raw materials are mixed and then extruded and foamed into beads using a twin-screw extruder and a single-screw extruder in series. The beads are then further foamed and molded to obtain the final product. The foamed material of this invention is extruded using a twin-screw and single-screw extruder in series, which ensures uniform mixing of the materials.

[0017] Preferably, in the above preparation method, the length-to-diameter ratio of the twin-screw extruder is 36:1, and the length-to-diameter ratio of the single-screw extruder is 30:1. Adjusting the length-to-diameter ratios of the twin-screw and single-screw extruders controls the front and rear extrusion rates, achieving a better mixing effect.

[0018] Preferably, in the above preparation method, the foaming ratio is 40 to 80 times.

[0019] Preferably, the temperature settings of the twin-screw extruder are: zone 1 50℃~100℃, zone 2 155℃~165℃, zone 3 160℃~170℃, and zone 4 170℃~180℃; the temperature settings of the single-screw extruder are: zone 1 170℃~180℃, zone 2 165℃~175℃, zone 3 160℃~170℃, and zone 4 160℃~170℃. By adjusting the temperature settings, the softening or melting state of the material in the extruder is adjusted, allowing for more uniform mixing, more complete reaction of the chain extender and crosslinking agent, and a more ideal foaming effect.

[0020] Carbon dioxide is introduced at the junction of the twin-screw extruder and the single-screw extruder. This carbon dioxide gas provides protection against the release of any residual flammable monomers, preventing potential hazards.

[0021] Compared with existing technologies, the high-temperature resistant carbon dioxide-based biodegradable foaming material and preparation method of the present invention have the following beneficial effects: The present invention uses cyclohexene carbonate-propylene carbonate copolymer (PPCHC) as the main material. PPCHC itself has high strength and good barrier properties. After adding modifying components, the overall toughness of the material is better. As the main material of the foaming material, the toughness and strength of the foaming material are both very ideal, and the foaming ratio is high. The PPCHC of the present invention has a high foaming ratio. Compared with PBS blending foaming, PPCHC has a glass transition temperature of 80℃~100℃, making it easier to foam. Using PPCHC as the main material results in better foaming effect, better degradability, and high temperature resistance. The large foaming ratio results in a high softening point and large tensile deformation of the material, as well as good dimensional stability. After adjusting the properties with the above-mentioned additives, the composite material has better processing performance and more uniform foaming. Detailed Implementation

[0022] The present invention will now be described in detail through examples. Unless otherwise stated, all raw materials used are commercially available.

[0023] Example 1

[0024] Preparation method of PPCHC: The 5L high-pressure reactor was purged with high-purity carbon dioxide to remove moisture and oxygen. One part propylene oxide, two parts cyclohexane oxide, and 0.006 parts catalyst were added to the reactor. The catalyst was a composite catalyst of tetrabutylammonium halide and triethylboron in a molar ratio of 1:2.5. Carbon dioxide was introduced to bring the reaction pressure to 1.5 MPa, and the reaction was maintained at 70℃ for 8 hours. The reaction was then cooled, depressurized, and terminated. The gel was dissolved in chloroform, precipitated with ethanol, and the product was devolatilized and dried to obtain pure PPCHC. GPC analysis showed that the molecular weight of PPCHC was 9.5 × 10⁻⁶. 4 g / mol.

[0025] Raw materials are prepared in parts by weight: 78 parts PPCHC, 2.0 parts acrylic acid modified titanium dioxide, 1.3 parts nano calcium carbonate, 1.7 parts coupling agent composed of monoalkoxy phosphate phthalate coupling agent and monoalkoxy fatty phthalate coupling agent in a mass ratio of 1:1, and 0.3 parts carbon dioxide.

[0026] First, PPCHC is extruded and granulated at 165℃ using a twin-screw extruder. Then, it is mixed evenly with other additives and extruded and foamed into beads using a twin-screw extruder and a single-screw extruder in series. The beads are transferred to a foaming tank and heated to 135℃ for foaming. The foamed material is then transferred to a fluidized bed and cured for 90 minutes using 70℃ hot air to obtain a cured material. The cured material is then transferred to a forming machine and heated to 110℃ to form foamed sheets. The twin-screw extruder has an L / D ratio of 36:1, and the single-screw extruder has an L / D ratio of 30:1. The temperature settings for the twin-screw extruder are: Zone 1 50℃~100℃, Zone 2 155℃~165℃, Zone 3 160℃~170℃, and Zone 4 170℃~180℃; the temperature settings for the single-screw extruder are: Zone 1 170℃~180℃, Zone 2 165℃~175℃, Zone 3 160℃~170℃, and Zone 4 160℃~170℃; the carbon dioxide charging pressure is 2MPa.

[0027] Example 2

[0028] PPCHC prepared in Example 1.

[0029] Raw materials are prepared in parts by weight: 85 parts PPCHC, 1.5 parts acrylic acid modified titanium dioxide, 3 parts light calcium carbonate, 1 part coupling agent composed of monoalkoxy phosphate phthalate coupling agent and monoalkoxy fatty phthalate coupling agent in a mass ratio of 3:1, and 0.3 parts carbon dioxide.

[0030] The foamed board molding process of Example 1.

[0031] Example 3

[0032] PPCHC prepared in Example 1.

[0033] Raw materials are prepared in parts by weight: 70 parts PPCHC, 2.5 parts acrylic acid-modified titanium dioxide, 0.5 parts silica, 2.5 parts coupling agent composed of monoalkoxy phosphate phthalate coupling agent and monoalkoxy fatty phthalate coupling agent in a mass ratio of 1:3, and 0.3 parts carbon dioxide.

[0034] Foamed boards were manufactured using the process described in Example 1.

[0035] Example 4

[0036] PPCHC prepared in Example 1.

[0037] Raw materials are prepared in parts by weight: 78 parts PPCHC, 2.0 parts acrylic acid modified titanium dioxide, 1.3 parts nano calcium carbonate, 1.7 parts monoalkoxy phosphate phthalate coupling agent, and 0.3 parts carbon dioxide.

[0038] Foamed boards were manufactured using the process described in Example 1.

[0039] Example 5

[0040] Preparation method of PPCHC: The 5L high-pressure reactor was purged with high-purity carbon dioxide to remove moisture and oxygen. One part propylene oxide, 2.5 parts cyclohexane oxide, and 0.008 parts catalyst (a composite catalyst of tetrabutylammonium halide and triethylboron in a molar ratio of 1:3) were added to the reactor. Propylene oxide, cyclohexane oxide, and catalyst were added to the reactor, and carbon dioxide was introduced to reach a reaction pressure of 3.0 MPa. The reaction was heated to 60℃ for 8 hours, then cooled, depressurized, and the reaction was terminated. The gel was dissolved in chloroform, precipitated with ethanol, and after devolatilization and drying, pure PPCHC was prepared. GPC analysis showed that the molecular weight of PPCHC was 8.6 × 10⁻⁶. 4 g / mol.

[0041] The raw material ratio and process of Example 1 were used to produce foamed boards.

[0042] Example 6

[0043] Preparation method of PPCHC: The 5L high-pressure reactor was purged with high-purity carbon dioxide to remove moisture and oxygen. One part propylene oxide, 1.5 parts cyclohexane oxide, and 0.003 parts catalyst (a composite catalyst of tetrabutylammonium halide and triethylboron in a molar ratio of 1:2) were added to the reactor. Propylene oxide, cyclohexane oxide, and catalyst were added to the reactor, and carbon dioxide was introduced to reach a reaction pressure of 1.0 MPa. The reaction was heated to 80℃ for 8 hours. The temperature was then lowered, the pressure released, and the reaction terminated. The gel was dissolved in chloroform, precipitated with ethanol, and the product was devolatilized and dried to obtain pure PPCHC. GPC analysis showed that the molecular weight of PPCHC was 9.7 × 10⁻⁶. 4 g / mol.

[0044] The raw material ratio and process of Example 1 were used to produce foamed boards.

[0045] Example 7

[0046] Preparation method of PPCHC: The 5L high-pressure reactor was purged with high-purity carbon dioxide to remove moisture and oxygen. One part propylene oxide, two parts cyclohexane oxide, and 0.006 parts catalyst (a composite catalyst of tetrabutylammonium halide and triethylboron in a molar ratio of 1:2.5) were added to the reactor. Propylene oxide, cyclohexane oxide, and catalyst were added to the reactor, and carbon dioxide was introduced to reach a reaction pressure of 3.5 MPa. The reaction was heated to 50℃ for 8 hours, then cooled, depressurized, and the reaction was terminated. The gel was dissolved in chloroform, precipitated with ethanol, and after devolatilization and drying, pure PPCHC was prepared. GPC analysis showed that the molecular weight of PPCHC was 1.2 × 10⁻⁶. 5 g / mol.

[0047] The raw material ratio and process of Example 1 were used to produce foamed boards.

[0048] Example 8

[0049] PPCHC prepared in Example 1.

[0050] Raw materials are prepared in the following proportions by weight: 60 parts PPCHC, 5 parts talc, 0.1 parts heavy calcium carbonate, 5 parts bis-(3-ethoxysilanepropyl)-tetrasulfide, and 0.5 parts azodicarbonamide.

[0051] Foamed sheets were produced using the process described in Example 1, with the twin-screw extruder having an aspect ratio of 33:1 and the single-screw extruder having an aspect ratio of 31:1.

[0052] Example 9

[0053] PPCHC prepared in Example 1.

[0054] Raw materials are prepared in parts by weight: 99 parts PPCHC, 0.5 parts magnesium oxide, 10 parts zinc oxide, 0.1 parts chromium chloride methacrylate, and 0.05 parts pentane.

[0055] Foamed sheets were produced using the process described in Example 1, with the twin-screw extruder having an aspect ratio of 38:1 and the single-screw extruder having an aspect ratio of 28:1.

[0056] The performance test results of each embodiment are shown in Table 1. Water resistance is defined as the mass loss rate after immersing the sample in water at 25°C for 12 hours and then drying. Dimensional stability was tested according to GB / T 8811-2008. Threshing rate refers to the mass loss rate of a 1 dm³ cubic sample with a 0.5 kg weight on top, dragged for 10 m on a pine board with a friction coefficient of 0.2.

[0057] Foaming ratio Water resistance % Dimensional stability% Softening temperature (°C) threshing rate % Compressive strength kPa Shore A hardness Example 1 73 0.71 0.91 71.3 2.2 33 18 Example 2 73 0.73 0.92 73.4 2.4 33 18 Example 3 74 0.75 0.91 70.1 2.3 35 19 Example 4 71 0.89 1.11 66.6 2.4 36 20 Example 5 72 0.73 0.92 68.7 2.3 32 17 Example 6 72 0.76 0.93 70.1 2.1 43 22 Example 7 67 0.78 1.08 66.8 2.7 56 24 Example 8 78 0.93 1.23 61.7 3.3 42 20 Example 9 41 0.99 1.34 63.4 3.4 48 21

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high temperature resistant, carbon dioxide based biodegradable foamed material, characterized in that, The raw material weight percentage composition is: PPCHC 60~99 parts, nucleating agent 0.5~5 parts, filler 0.1~10 parts, coupling agent 0.1~5 parts, foaming agent 0.05~0.5 parts; The nucleating agent is acrylic acid modified titanium dioxide; the acrylic acid modified titanium dioxide is prepared by soaking titanium dioxide powder in an acrylic acid solution for 10s~20s; The coupling agent is a composite titanate coupling agent, and the composite titanate coupling agent is a coupling agent composed of a single alkoxyl phosphate ester type phthalate coupling agent and a single alkoxyl fatty ester type phthalate coupling agent.

2. The high temperature resistant carbon dioxide based biodegradable foamed material according to claim 1, characterized in that, The raw material weight percentage composition is: PPCHC 70~85 parts, nucleating agent 1.5~2.5 parts, filler 0.5~3 parts, coupling agent 1~2.5 parts, foaming agent 0.1~0.5 parts. 3.The high-temperature-resistant carbon dioxide-based biodegradable foamed material according to claim 1 or 2, characterized in that, The preparation method of PPCHC is as follows: propylene oxide, cyclohexene oxide and a catalyst are put into a reactor, carbon dioxide is filled to make the reaction pressure reach 1.0MPa~2.0MPa, heating is performed to keep the reaction temperature at 60℃~80℃, and then ring-opening polymerization is performed to generate a glue liquid, which is washed, devolatilized and dried to obtain a finished product. 4.The high-temperature-resistant carbon dioxide-based biodegradable foamed material according to claim 1 or 2, characterized in that, The filler is one or more of silica, heavy calcium carbonate, nano calcium carbonate, light calcium carbonate and zinc oxide.

5. A process for the preparation of the high temperature resistant carbon dioxide based biodegradable foamed material according to any one of claims 1 to 4, characterized in that, The above raw materials are mixed and then extruded by a double-screw extruder and a single-screw extruder in series to form beads, and then the beads are further foamed and molded to obtain the product.

6. The method of claim 5, wherein the method is characterized by: The length-diameter ratio of the double-screw extruder is 36:1, and the length-diameter ratio of the single-screw extruder is 30:

1.

7. The method according to claim 5, wherein the method is characterized by: The foaming ratio is 40~80 times.