Janus nucleating agent and preparation method for supercritical foaming of Janus nucleating agent and polymer

Abstract

The invention discloses a Janus nucleating agent and a supercritical foaming preparation method of the Janus nucleating agent and a polymer. The preparation method of the Janus nucleating agent comprises the following steps: carrying out a sol-gel reaction on ethyl silicate and gamma-(methylacryloyloxy) propyl trimethoxy silane in a sodium dodecyl sulfate alkaline solution containing hexadecane; then, styrene and divinyl benzene are subjected to a polymerization reaction under the initiation of azodiisobutyronitrile in a nitrogen atmosphere, and a silicon dioxide coated polydivinyl benzene Janus nucleating agent is obtained; the preparation method comprises the following steps: blending and molding a Janus nucleating agent and a polymer matrix, and carrying out supercritical CO2 batch foaming in a foaming kettle. The Janus nucleating agent prepared by the method disclosed by the invention is easy for industrial production, has an anisotropic chemical structure, is good in dispersity in a polymer, and is beneficial to improving the cellular structure and compression strength of a polymer matrix.

Description

Technical Field

[0001] The invention relates to the preparation and application of a nucleating agent, and in particular to the preparation and application of a nucleating agent used in supercritical foaming of polymers. Background Art

[0002] According to the different ways of introducing gas, polymer foaming can be divided into mechanical foaming, chemical foaming and physical foaming. The mechanical method is to introduce gas into the foaming raw material through physical stirring. It has the advantages of green environmental protection, low cost and high efficiency, but it has high requirements on equipment and the pore structure is difficult to control. Chemical foaming refers to the formation of pore structure by generating gas through thermal decomposition or chemical reaction during the foaming process. However, traditional halogenated aliphatic hydrocarbon foaming agents are toxic, have safety hazards, and are difficult to remove from the matrix. Physical foaming is to change the physical state of the foaming agent during the foaming process to achieve the purpose of foaming. It has the advantages of low cost and controllable morphology. Green supercritical CO in physical foaming 2 Fluid foaming technology has attracted much attention due to its advantages such as low cost and high diffusion rate.

[0003] Green supercritical CO 2 Fluids have poor solubility in most polymers. The addition of inorganic particles can improve the polymer's solubility in CO. 2 The adsorption of Janus particles can reduce the size of the pores, increase the pore density, and improve the mechanical properties of the foamed material. However, inorganic nanoparticles have high polarity and are easy to agglomerate in the matrix, which is not conducive to obtaining foamed materials with uniform pores. Janus materials have directional forces or unilateral selective reactions due to different chemical compositions at both ends, and can achieve their respective functions without interfering with each other. Based on this, the present invention prepares a solvent-resistant and melt-resistant Janus particle as a nucleating agent, which is applied to the supercritical CO 2 Foaming is used to prepare polymer foam materials with low density and high compressive strength, and to promote the application of Janus nucleating agents in polymer foam materials.

[0004] Janus materials are a type of anisotropic, centrally asymmetric particles with different surface chemical compositions. The graduation thesis of Lin Jiahe, a master student in the research group of this invention, entitled "Janus particle interface-induced polymer bicontinuous phase, foaming and multiphase catalytic reaction", published a study on SiO 2 @PS The dispersion of Janus particles in the matrix and the effect on pore size during foaming. It is believed that one side of the Janus particles is inorganic SiO 2 , which can increase CO 2 The adsorption capacity of SiO2 is good for reducing the pore size and improving the pore uniformity; the other side of the Janus particle is PS, which has good compatibility with the PS matrix and is conducive to the uniform dispersion of the particles in the matrix. 2The PS end of the @PS Janus particles is a linear polymer, which has poor heat resistance and solvent resistance. It is easy to melt or dissolve in the subsequent blending molding, resulting in the disappearance of the Janus structure, leaving only residual SiO 2 The particles lose the anisotropic functionality of the Janus material. Therefore, it is very necessary to find a Janus foaming agent that is universal for polymer supercritical foaming technology. The cross-linked structure of the polydiene end of the present invention has better solvent resistance and heat resistance, and helps to maintain the anisotropic Janus structure of the nucleating agent during blending. Among them, the polydiene end has good compatibility with non-polar polymers, which is beneficial to the dispersion of the nucleating agent; in polar polymers, it is beneficial to the formation of bubbles. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of a Janus nucleating agent for supercritical foaming of polymers. The nucleating agent has wide applicability in supercritical foaming of polymers and expands the application range of Janus materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a Janus nucleating agent and a supercritical foaming method thereof with a polymer comprises the following steps:

[0008] 1) Preparation of Janus nucleating agent:

[0009] Add ethyl silicate, γ-(methacryloyloxy)propyltrimethoxysilane and hexadecane to sodium dodecyl sulfonate solution, stir mechanically for 15 minutes to form an emulsion, adjust the pH of the emulsion to 9.0 with sodium hydroxide aqueous solution, and react at 50-90°C for 1-3 hours to fully hydrolyze ethyl silicate into a silica microsphere suspension. After the reaction, cool the silica microsphere suspension to room temperature, slowly add styrene, divinylbenzene and azobisisobutyronitrile under a nitrogen atmosphere, stir for 2 hours to fully diffuse the monomers, and then heat to 50-90°C for polymerization for 3-12 hours. After centrifugation, washing and drying, the product is obtained as silica@polydivinylbenzene Janus nucleating agent;

[0010] The mass ratio of ethyl silicate, γ-(methacryloyloxy)propyltrimethoxysilane, hexadecane, sodium dodecylsulfonate, styrene, divinylbenzene and azobisisobutylcyanide is 100:10-50:20:6:100-200:100-200:0.75;

[0011] 2) Supercritical foaming of polymer:

[0012] After the Janus nucleating agent and the polymer matrix in step 1 are blended and formed, they are placed in a foaming kettle for supercritical CO 2Intermittent foaming;

[0013] Wherein, the mass ratio of Janus nucleating agent to polymer is 100:1-10;

[0014] Furthermore, the washing method is washing three times with a 50wt% ethanol aqueous solution and then washing three times with water;

[0015] Furthermore, the blending method is solid high mixing, melt blending or solution blending; the molding method is extrusion molding, molding, casting molding or tape casting molding.

[0016] The silicon dioxide@polydivinylbenzene Janus nucleating agent obtained by the preparation method of the present invention and its application in supercritical foaming of polymers.

[0017] The present invention adopts the above technical scheme and utilizes a phase separation method to prepare a silicon dioxide@polydivinylbenzene Janus nucleating agent, which is applied to supercritical foaming of polymers to increase the cell density and improve the compressive strength of the foamed material.

[0018] The present invention adopts the above method to prepare a Janus nucleating agent with universality in supercritical foaming of polymer matrix, which has the following advantages:

[0019] 1. The preparation method of Janus nucleating agent by phase separation technology is simple and easy, and is suitable for industrial production.

[0020] 2. Janus nucleating agent has an anisotropic chemical structure, rich interfacial behavior, and good dispersion in the polymer matrix.

[0021] 3. The two ends of the Janus nucleating agent have different polarities. The end that is incompatible with the polymer plays a nucleating role, and the end that is compatible with the polymer enhances its dispersibility and the interaction force with the matrix. It is applied to supercritical foaming of polymers, which is beneficial to improve the physical and mechanical properties of the foamed materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the Janus nucleating agent prepared in Example 1 of the present invention.

[0023] Figure 2 This is a scanning electron microscope image of the polystyrene foam material prepared in Example 1 of the present invention under the action of a Janus nucleating agent. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments.

[0025] Example 1

[0026] 1) Preparation of Janus nucleating agent:

[0027] 2g of ethyl silicate, 0.6g of γ-(methacryloyloxy)propyltrimethoxysilane, and 0.4g of hexadecane were added to 40mL of an aqueous solution containing 0.012g of sodium dodecyl sulfonate, and mechanically stirred for 15 minutes to form an emulsion, and the pH of the emulsion was adjusted to 9.0 with an aqueous sodium hydroxide solution. The reaction was carried out at 60°C for 2 hours to fully hydrolyze the ethyl silicate. After the reaction, the solution was cooled to room temperature, and 3g of styrene, 3g of divinylbenzene, and 0.015g of azobisisobutyronitrile were slowly added under a nitrogen atmosphere, stirred for 2 hours to fully diffuse the monomers, and then heated to 70°C for polymerization for 10 hours. The product was centrifuged, washed three times with a 50wt% ethanol aqueous solution and distilled water, respectively, and dried to obtain a silica@polydivinylbenzene Janus nucleating agent.

[0028] 2) Supercritical foaming of polymer:

[0029] The Janus nucleating agent obtained in step 1) and polystyrene (PS) were extruded and granulated in a twin-screw extruder at a ratio of 3:100 (mass ratio), injection molded, and placed in a foaming kettle for supercritical CO 2 Foaming to obtain PS foamed material.

[0030] Figure 1 This is a scanning electron microscope image of the Janus nucleating agent prepared in Example 1. Figure 1 It can be seen that the Janus nucleating agent is white particles with uniform particle size and a snowman-shaped structure with a certain aspect ratio. This structure is conducive to the two anisotropic ends of the Janus nucleating agent to play their respective roles.

[0031] Example 2

[0032] 1) Preparation of Janus nucleating agent:

[0033] 20g of ethyl silicate, 6g of γ-(methacryloyloxy)propyltrimethoxysilane, and 4g of hexadecane were added to 400mL of an aqueous solution containing 0.12g of sodium dodecyl sulfonate, mechanically stirred for 15 minutes to form an emulsion, and the pH of the emulsion was adjusted to 9.0 with an aqueous sodium hydroxide solution. The reaction was carried out at 70°C for 1 hour to fully hydrolyze the ethyl silicate. After the reaction, the solution was cooled to room temperature, and 30g of styrene, 30g of divinylbenzene and 0.15g of azobisisobutyronitrile were slowly added under a nitrogen atmosphere, stirred for 2 hours to fully diffuse the monomers, and then heated to 70°C for polymerization for 6 hours. The product was centrifuged, washed three times with a 50wt% ethanol aqueous solution and distilled water, respectively, and dried to obtain a silica@polydivinylbenzene Janus nucleating agent.

[0034] 2) Supercritical foaming of polymer:

[0035] 2.33 g of the Janus nucleating agent obtained in step 1) and 46.55 g of ethylene-vinyl acetate copolymer (EVA) were mixed and molded, and then placed in a foaming kettle for supercritical CO 2 Foaming to obtain EVA foam material.

[0036] Example 3

[0037] 1) Preparation of Janus nucleating agent:

[0038] 200g of ethyl silicate, 60g of γ-(methacryloyloxy)propyltrimethoxysilane, and 40g of hexadecane were added to 4000mL of an aqueous solution containing 1.2g of sodium dodecylsulfonate, and mechanically stirred for 15 minutes to form an emulsion, and the pH of the emulsion was adjusted to 9.0 with an aqueous sodium hydroxide solution. The reaction was carried out at 50°C for 3 hours to fully hydrolyze the ethyl silicate. After the reaction, the solution was cooled to room temperature, and 300g of styrene, 300g of divinylbenzene and 1.5g of azobisisobutyronitrile were slowly added under a nitrogen atmosphere, stirred for 2 hours to fully diffuse the monomers, and then heated to 80°C for polymerization for 6 hours. The product was centrifuged, washed three times with a 50wt% ethanol aqueous solution and distilled water, respectively, and dried to obtain a silica@polydivinylbenzene Janus nucleating agent.

[0039] 2) Supercritical foaming of polymer:

[0040] The Janus nucleating agent obtained in step 1) and the polymerized waterborne polyurethane were placed in a foaming kettle at a ratio of 1:100 (mass ratio) for supercritical CO 2 Foaming to obtain a polyurethane foam material.

[0041] Example 4

[0042] 1) Preparation of Janus nucleating agent:

[0043] 4g of ethyl silicate, 2g of γ-(methacryloyloxy)propyltrimethoxysilane, and 0.8g of hexadecane were added to 80mL of an aqueous solution containing 0.024g of sodium dodecylsulfonate, and mechanically stirred for 15 minutes to form an emulsion, and the pH of the emulsion was adjusted to 9.0 with an aqueous sodium hydroxide solution. The reaction was carried out at 90°C for 1 hour to fully hydrolyze the ethyl silicate. After the reaction, the solution was cooled to room temperature, and 4g of styrene, 4g of divinylbenzene, and 0.020g of azobisisobutyronitrile were slowly added under a nitrogen atmosphere, stirred for 2 hours to fully diffuse the monomers, and then heated to 90°C for polymerization for 4 hours. The product was centrifuged, washed three times with a 50wt% ethanol aqueous solution and distilled water, respectively, and dried to obtain a silica@polydivinylbenzene Janus nucleating agent.

[0044] 2) Supercritical foaming of polymer:

[0045] The Janus nucleating agent obtained in step 1) and polycaprolactam (PA6) were extruded and granulated in a twin-screw extruder at a ratio of 4:100 (mass ratio), cast into a film, and placed in a foaming kettle for supercritical CO 2 Foaming to obtain PA6 nylon foam material.

Claims

1. A Janus nucleating agent and a method for preparing the same with a polymer by supercritical foaming, characterized in that: The steps include: 1) Preparation of Janus nucleating agent: Add ethyl silicate, γ-(methacryloyloxy)propyltrimethoxysilane and hexadecane to the sodium dodecyl sulfonate solution, stir mechanically for 15 minutes to form an emulsion, and adjust the pH of the emulsion to 9.0 with sodium hydroxide aqueous solution, 50-90 o C for 1-3 hours to fully hydrolyze ethyl silicate into a silica microsphere suspension; after the reaction, the silica microsphere suspension was cooled to room temperature, styrene, divinylbenzene and azobisisobutyronitrile were slowly added under a nitrogen atmosphere, stirred for 2 hours to fully diffuse the monomers, and then heated to 50-90 o C is polymerized for 3-12 hours to form a product; the product is centrifuged, washed and dried to obtain a silica@polydivinylbenzene Janus nucleating agent; The mass ratio of ethyl silicate, γ-(methacryloyloxy)propyltrimethoxysilane, hexadecane, sodium dodecylsulfonate, styrene, divinylbenzene and azobisisobutylcyanide is 100:10~50:20:6:100~200:100~200:0.75; 2) Supercritical foaming of polymer: After the Janus nucleating agent and the polymer matrix in step 1) are blended and formed, the mixture is placed in a foaming kettle for intermittent foaming with supercritical CO2; Among them, the mass ratio of Janus nucleating agent to polymer matrix is ​​100:1~10.

2. The preparation method according to claim 1, characterized in that: The product was washed three times with a 50 wt% ethanol aqueous solution and then washed three times with water.

3. The preparation method according to claim 2, characterized in that: The blending method of the Janus nucleating agent and the polymer matrix is ​​melt blending or solution blending; the molding method of the Janus nucleating agent and the polymer matrix is ​​extrusion molding, molding molding, casting molding or tape casting molding.

4. Use of the silicon dioxide@polydivinylbenzene Janus nucleating agent obtained according to the preparation method of claim 1, 2 or 3 in supercritical foaming of polymers.

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