Graphene-organic silicon core-shell defoaming agent and preparation method thereof

Abstract

The invention discloses a graphene-organic silicon core-shell defoaming agent and a preparation method thereof.The defoaming agent is of a core-shell structure with graphene as a core and organic silicon as a shell, and the graphene and the organic silicon have a synergistic effect, so that the defoaming agent is good in monodispersity and can stably play a defoaming role at the high temperature. Preparing a graphene oxide dispersion liquid; meanwhile, a PDMS prepolymer is prepared, and the graphene oxide dispersion liquid is dropwise added into a PDMS prepolymer system, so that the organic silicon monomer is subjected to graft polymerization reaction on the surface of the graphene oxide. And then carrying out reduction treatment on the reaction product to convert the graphene oxide into reduced graphene oxide to form a core-shell structure, and carrying out centrifugal separation, washing and vacuum drying to obtain the graphene-organic silicon core-shell defoaming agent. The problems that an existing defoaming agent is poor in dispersity, weak in interface bonding force and insufficient in high temperature resistance in the high polymer material forming process are solved, and the defoaming efficiency and the product quality are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material additive preparation, in particular to a graphene-organic silicon core-shell defoamer and a preparation method thereof. Background Art

[0002] In the field of polymer molding, such as the production of rotomolded nylon products, air bubbles have always been a key factor affecting product quality. The presence of air bubbles not only reduces the product's appearance but also reduces its mechanical properties, such as strength and toughness. To address this issue, the use of defoaming agents is crucial.

[0003] While traditional silicone defoamers offer excellent defoaming effects, they suffer from poor dispersibility, migration, and insufficient high-temperature resistance in polymer systems, making them difficult to meet the demands of high-temperature molding processes like rotational molding. Graphene, a novel nanomaterial, possesses excellent mechanical properties, thermal conductivity, and a large specific surface area. Combining it with silicones could potentially lead to the development of even more effective defoamers.

[0004] At present, the method of preparing defoaming agents by compounding graphene with silicone has the following main shortcomings: first, graphene easily agglomerates and is difficult to disperse evenly in silicone; second, the interfacial bonding force between the two is weak, resulting in unstable performance of the composite defoaming agent. Summary of the Invention

[0005] In response to the above-mentioned shortcomings, the present invention proposes a graphene-silicone core-shell defoamer and a preparation method thereof to solve the problems of poor dispersibility, weak interfacial bonding force, and insufficient high temperature resistance of existing defoamers in the polymer material molding process, thereby improving the defoaming efficiency and product quality.

[0006] The present invention provides the following technical solution: a graphene-organic silicone core-shell defoamer, the defoamer having a core-shell structure with a particle size of 50-100 nm. The core-shell structure uses graphene as the core to puncture bubbles and silicone as the shell to reduce surface tension. The two act synergistically, making the defoamer well monodispersible and able to stably exert a defoaming effect at a rotational molding temperature of 240-260°C.

[0007] As an improvement, the amount of the defoaming agent added for eliminating bubbles during the polymer material molding process is 0.1-0.5% of the mass of the polymer material, so that the defoaming agent eliminates bubbles, making the bubble rate in the polymer material no more than 3.8%, while also increasing the tensile strength of the polymer material by 20%-30% compared to the system without addition, and the impact strength is increased by 15%-25%.

[0008] As an improvement, the polymer material is nylon and the molding process is rotational molding.

[0009] As an improvement, as in any of the above-mentioned methods for preparing the graphene-organic silicon core-shell defoamer, the defoamer preparation method comprises the following steps: S1: preparing a graphene oxide dispersion by using a modified Hummers method, dispersing graphene oxide in deionized water, and obtaining a graphene oxide dispersion with a concentration of 1-2 mg / mL by ultrasonic dispersion; S2: Prepare polydimethylsiloxane prepolymer with a viscosity of 500-1500 mPa·s and perform degassing before use to prevent air bubbles from entering the prepolymer during preparation or storage, which may affect the performance and quality of the product. S3: In a reaction vessel equipped with a condensation reflux device and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote a graft polymerization reaction of the organosilicon monomer on the surface of the graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is evenly dispersed in the organosilicon. The mass ratio of the polydimethylsiloxane prepolymer to the graphene oxide is controlled to be 10:1-20:1, and the reaction is stirred at 60-80° C. under inert gas protection for 2-4 hours; S4: adding a reducing agent to the reaction system and performing stirring reduction, wherein the mass ratio of the reducing agent to graphene oxide is 1:1-2:1, centrifuging, washing and drying the reduced product to obtain graphene-organic silicon core-shell composite particles.

[0010] As an improvement, the reaction temperature in step S3 is 70-80°C.

[0011] As an improvement, the reducing agent in step S4 is one of hydrazine hydrate, ascorbic acid or sodium borohydride.

[0012] As an improvement, the reduction reaction in step S4 is carried out for 22-26 hours.

[0013] As an improvement, in step S4, ethanol is used for washing 3-5 times and vacuum drying is performed for 12-24 hours.

[0014] Compared with the prior art, the advantages of the present invention are: Through a unique core-shell structure design, with graphene as the core and silicone as the shell, this structure combines the high surface activity of graphene with the low surface tension characteristics of silicone to achieve an excellent defoaming effect. The graphene core can quickly puncture bubbles, while the silicone shell can effectively reduce the surface tension of the liquid and prevent bubbles from forming again. The synergistic effect of the two significantly improves the defoaming efficiency. Moreover, due to the good high-temperature resistance of the silicone shell layer, the defoamer can stably exert its defoaming effect at a rotational molding temperature of 240-260°C, making the defoamer particularly suitable for high-temperature processing processes such as rotational molding, ensuring the durability and stability of the defoaming effect in high-temperature environments. At the same time, the defoamer has a core-shell structure with a particle size of 50-100nm and good monodispersity, which means that the defoamer particles can be evenly distributed in the liquid and are not easy to agglomerate, thereby improving the utilization rate of the defoamer and the defoaming effect.

[0015] The amount of defoamer added to polymer materials (such as nylon) is only 0.1-0.5% of the material mass, which can achieve a significant bubble elimination effect. This not only reduces production costs, but also avoids the problem of material performance degradation caused by excessive addition of defoamer. After adding the defoamer, the bubble rate of polymer materials, which are particularly suitable for nylon and other polymer materials in the molding process, can be reduced to below 3.8%, while the tensile strength is increased by 20%-30%, and the impact strength is increased by 15%-25%. This means that while the defoamer eliminates bubbles, it can also optimize the characteristics of the nylon material to achieve a better bubble elimination effect, significantly improve the mechanical properties of the material, and broaden the application field of the material. At the same time, this limitation is due to the polarity of nylon (polyamide) and the high temperature characteristics of the rotational molding process are highly matched with the defoamer structure. Since nylon The molecular chain contains amide bonds (-CONH-) with polarity, which matches the small amount of oxygen-containing functional groups remaining on the surface of graphene oxide (increasing polarity) and the moderate compatibility of the silicone shell (weak interaction between the siloxane chain and nylon), ensuring uniform dispersion of the defoamer; at the same time, the rotational molding temperature (240-260°C) is consistent with the high temperature resistance of the silicone shell (stable function), while traditional silicone defoamers are prone to volatility and failure at this temperature, while the graphene core further enhances its stability due to its high temperature resistance (>300°C); and for non-polar polymer materials (such as polyethylene), the defoamer may agglomerate due to its excessive compatibility with the silicone shell; for low-temperature molding processes (such as injection molding below 200°C), such high temperature resistance is not required, and traditional defoamers can meet it, so this defoamer is targeted at optimizing nylon rotational molding scenarios, reflecting application focus.

[0016] The preparation method utilizes conventional chemical synthesis steps, eliminating the need for complex equipment and conditions, making it easy to scale up for industrial production. Furthermore, the readily available raw materials, such as graphene oxide and polydimethylsiloxane (PDMS) prepolymer, are relatively low in cost and offer excellent economic benefits. Pretreatment steps, such as vacuum drying, ensure stable initial raw material properties, enhancing process controllability and product purity. Precise control of reaction temperature, stirring speed, and reducing agent type and dosage ensures sufficient reaction and uniform dispersion between graphene oxide and PDMS prepolymer, forming a stable core-shell structure. Post-treatment steps, including centrifugation, washing, and drying, completely remove unreacted reducing agent and impurities, yielding high-purity graphene-organic silicone core-shell composite particles. These particles exhibit excellent defoaming properties, dispersibility, and high-temperature resistance. Furthermore, the green reducing agent (such as ascorbic acid) used in the preparation process is suitable for safety-critical preparation scenarios. The entire preparation process is conducted in a fume hood, minimizing the risk of hazardous gas emissions and exposure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 Schematic diagram of the graphene-silicon core-shell structure of the defoaming agent; Figure 2 The graphene-organic silicon core-shell structure SEM images of the defoaming agent, where (a) is the SEM image of the graphene-organic silicon core-shell structure before it is broken, and (b) is the SEM image of the graphene-organic silicon core-shell structure after it is broken. DETAILED DESCRIPTION

[0018] Example 1 S1: Prepare graphene oxide dispersion. Graphene oxide was prepared using the modified Hummers method. 1 g of graphene oxide powder was added to 1000 mL of deionized water and ultrasonically dispersed for 2 hours to obtain a graphene oxide dispersion with a concentration of 1 mg / mL. S2: Prepare polydimethylsiloxane prepolymer. Select 10g of polydimethylsiloxane prepolymer with a viscosity of 500mPa·s and degas it before use to prevent air bubbles from being mixed into the prepolymer during preparation or storage, which may affect the performance and quality of the product. S3: In a reaction vessel equipped with a condenser reflux device and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote a graft polymerization reaction of the organosilicon monomer on the surface of the graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is evenly dispersed in the organosilicon. The mass ratio of the polydimethylsiloxane prepolymer to the graphene oxide is controlled to be 10:1, and the reaction is stirred at 70° C. under an inert gas, i.e., nitrogen, atmosphere for 2 hours; S4: Add 1 g of hydrazine hydrate to the reaction system and stir and reduce at room temperature for 24 hours, wherein the mass ratio of the reducing agent to graphene oxide is 1:1. The reduced product is centrifuged, washed with ethanol three times, and vacuum dried for 12 hours to obtain graphene-organic silicon core-shell composite particles with a particle size of 50-80 nm.

[0019] The defoamer was added to nylon 6 raw materials at a dosage of 0.3%, mixed evenly and then subjected to rotational molding. The product had a bubble rate of 3.8%, a tensile strength of 85 MPa, and an impact strength of 55 kJ / m².

[0020] Example 2 S1: Prepare graphene oxide dispersion. Graphene oxide was prepared using a modified Hummers method. 2 g of graphene oxide powder was added to 1000 mL of deionized water and ultrasonically dispersed for 3 hours to obtain a graphene oxide dispersion with a concentration of 2 mg / mL. S2: Prepare 20 g of polydimethylsiloxane prepolymer with a viscosity of 1000 mPa·s and perform degassing before use to prevent air bubbles from entering the prepolymer during preparation or storage, which could affect product performance and quality. S3: In a reaction vessel equipped with a condenser reflux device and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote a graft polymerization reaction of the organosilicon monomer on the surface of the graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is evenly dispersed in the organosilicon. The mass ratio of the polydimethylsiloxane prepolymer to the graphene oxide is controlled to be 10:1, and the reaction is stirred at 80° C. under an inert gas, i.e., nitrogen, atmosphere for 3 hours; S4: Add 2 g of ascorbic acid to the reaction system and reduce with stirring at room temperature for 24 hours, wherein the mass ratio of reducing agent to graphene oxide is 1:1. The reduced product is centrifuged, washed with ethanol five times, and vacuum dried for 24 hours to obtain graphene-organic silicon core-shell composite particles with a particle size of 80-100 nm.

[0021] The defoamer was added to nylon 66 raw materials at a dosage of 0.5%, mixed evenly and then subjected to rotational molding. The product had a bubble rate of 3.2%, a tensile strength of 90 MPa, and an impact strength of 60 kJ / m².

[0022] Example 3 S1: Prepare graphene oxide dispersion. Graphene oxide was prepared using a modified Hummers method. 1.5 g of graphene oxide powder was added to 1000 mL of deionized water and ultrasonically dispersed for 2.5 hours to obtain a graphene oxide dispersion with a concentration of 1.5 mg / mL. S2: Prepare polydimethylsiloxane prepolymer. Select 15g of polydimethylsiloxane prepolymer with a viscosity of 800mPa·s and degas it before use to prevent air bubbles from being mixed into the prepolymer during preparation or storage, which may affect the performance and quality of the product. S3: In a reaction vessel equipped with a condenser reflux device and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote a graft polymerization reaction of the organosilicon monomer on the surface of the graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is evenly dispersed in the organosilicon. The mass ratio of the polydimethylsiloxane prepolymer to the graphene oxide is controlled to be 10:1, and the reaction is stirred at 75° C. under an inert gas, i.e., nitrogen, atmosphere for 2.5 hours; S4: 3 g of sodium borohydride was added to the reaction system and reduced with stirring at room temperature for 24 hours, wherein the mass ratio of reducing agent to graphene oxide was 2:1. The reduced product was centrifuged, washed four times with ethanol, and vacuum dried for 18 hours to obtain graphene-organic silicon core-shell composite particles with a particle size of 60-90 nm.

[0023] The defoamer was added to nylon 1010 raw material at a dosage of 0.1%, mixed evenly and then subjected to rotational molding. The product had a bubble rate of 3.5%, a tensile strength of 88 MPa, and an impact strength of 58 kJ / m².

[0024] Comparative Example 1 Using a traditional silicone defoamer (polydimethylsiloxane) at a dosage of 0.3% added to nylon 6 raw material for rotational molding, the product has a bubble rate of 10%, a tensile strength of 65MPa, and an impact strength of 40kJ / m².

[0025] Comparative Example 2 Graphene oxide was directly mixed with PDMS prepolymer without reaction or reduction treatment, and then added to nylon 6 raw material at a dosage of 0.3% for rotational molding. The product had a bubble rate of 8%, a tensile strength of 70MPa, and an impact strength of 45kJ / m².

[0026] By comparing the examples with the comparative examples, it can be seen that the graphene-silicone core-shell defoamer prepared by the present invention has excellent defoaming performance and product performance improvement effect, which is significantly better than traditional silicone defoamers and untreated mixtures of graphene oxide and polydimethylsiloxane, fully demonstrating the innovation and practicality of the present invention.

[0027] The above description is merely a description of the preferred embodiment of the present invention and is not to be construed as limiting the scope of the claims. The present invention is not limited to the above embodiment, and variations in the specific structure are permitted. Any variations within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

Claims

1. A graphene-organic silicon core-shell defoamer, characterized in that: The defoamer has a core-shell structure with a particle size of 50-100 nm. The core-shell structure uses graphene as the core to puncture bubbles and silicone as the shell to reduce surface tension. The two work synergistically, making the defoamer well monodispersible and able to stably exert a defoaming effect at a rotational molding temperature of 240-260°C.

2. A graphene-organic silicon core-shell defoamer according to claim 1, characterized in that: The defoaming agent used to eliminate bubbles during the molding process of polymer materials is added in an amount of 0.1-0.5% of the mass of the polymer material, so that the defoaming agent eliminates bubbles, making the bubble rate in the polymer material no more than 3.8%, and at the same time can increase the tensile strength of the polymer material by 20%-30% compared with the system without addition, and increase the impact strength by 15%-25%.

3. A graphene-organic silicon core-shell defoamer according to claim 2, characterized in that: The polymer material is nylon, and the molding process is rotational molding.

4. The method for preparing a graphene-organic silicon core-shell defoamer according to any one of claims 1 to 3, wherein: The defoamer preparation method comprises the following steps: S1: preparing a graphene oxide dispersion by using a modified Hummers method, dispersing graphene oxide in deionized water, and obtaining a graphene oxide dispersion with a concentration of 1-2 mg / mL by ultrasonic dispersion; S2: Prepare polydimethylsiloxane prepolymer with a viscosity of 500-1500 mPa·s and perform degassing before use to prevent air bubbles from entering the prepolymer during preparation or storage, which may affect the performance and quality of the product. S3: In a reaction vessel equipped with a condensation reflux device and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote a graft polymerization reaction of the organosilicon monomer on the surface of the graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is evenly dispersed in the organosilicon. The mass ratio of the polydimethylsiloxane prepolymer to the graphene oxide is controlled to be 10:1-20:1, and the reaction is stirred at 60-80° C. under inert gas protection for 2-4 hours; S4: adding a reducing agent to the reaction system and performing stirring reduction, wherein the mass ratio of the reducing agent to graphene oxide is 1:1-2:1, centrifuging, washing and drying the reduced product to obtain graphene-organic silicon core-shell composite particles.

5. The method for preparing a graphene-organic silicon core-shell defoamer according to claim 4, wherein: The reaction temperature in step S3 is 70-80°C.

6. The method for preparing a graphene-organic silicon core-shell defoamer according to claim 4, wherein: The reducing agent in step S4 is one of hydrazine hydrate, ascorbic acid or sodium borohydride.

7. The method for preparing a graphene-organic silicon core-shell defoamer according to claim 4, wherein: The reduction reaction in step S4 lasts for 22-26 hours.

8. The method for preparing a graphene-organic silicon core-shell defoamer according to claim 4, wherein: In step S4, the product is washed with ethanol for 3-5 times and vacuum dried for 12-24 hours.

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