Modified microsphere for foam molding of thick part, composition and application of composition

Abstract

The invention relates to a modified microsphere for foam molding of a thick part, a composition and application of the composition. The modified microspheres are prepared by the following steps: S1, polymerizing a microgel monomer to form microgel particles; s2, modifying the surfaces of the microgel particles by adopting maleic anhydride to obtain microgel particles with active sites; and S3, grafting infrared absorption molecules to the surface-modified microgel particles with the active sites to obtain the modified microspheres. According to the modified microsphere disclosed by the invention, the infrared absorption molecules are grafted on the surface of the microsphere, so that the absorption and scattering capabilities of the modified microsphere on infrared light are improved, laser can effectively penetrate through a foaming piece with a relatively thick or complex shape, and uniform heating is ensured; the modified microspheres are applied to a composition for foam forming of thick parts, and a laser forming process is combined, so that the accurate control of the foaming process can be ensured, the condition of overheating or nonuniform foaming is avoided, and the composition can be used for efficiently preparing a foam material.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and particularly to modified microspheres, compositions for thick-piece foam molding, and applications of the compositions. Background Art

[0002] In the fields of modern industry and materials science, foam materials are widely used in many key fields such as aerospace, building insulation, and packaging protection due to their excellent properties such as light weight, heat insulation, and buffering. For example, in aerospace, foam materials can reduce the weight of aircraft and improve fuel efficiency; in building insulation, they can effectively reduce energy consumption and maintain stable indoor temperature.

[0003] As an efficient heat source, a laser has significant advantages such as concentrated energy and fast heating speed, and is widely used in the forming and processing of various materials. Especially in the processing and forming of foam materials, laser heating can achieve rapid temperature rise, which helps to improve production efficiency and product quality.

[0004] Existing foam materials usually have weak infrared light absorption ability. When using a laser to heat and form thick-walled products of foam materials, the area near the surface can fully absorb the laser energy, rapidly heat up and reach the appropriate forming temperature. However, as the laser penetrates deeper into the material, the energy attenuation is obvious. This is mainly due to the complex interaction between the laser and the material, including processes such as absorption, scattering, and reflection. When the laser enters the material, photons collide with atoms and molecules in the material. Part of the energy is absorbed and converted into heat energy, part is scattered and changes the propagation direction, and part is reflected back to the outside. As the penetration depth increases, the laser energy is continuously lost, resulting in insufficient heating in some internal regions. This will cause the temperature in the deep part of the material not to reach the expected value. Therefore, when manufacturing with relatively thick foam materials, due to the hindrance of heat transfer, the heating during the forming process is uneven, which in turn leads to differences in the internal structure of the foam material. Specifically, in some regions, the temperature is too low, resulting in incomplete curing of the material, the material structure is loose and uneven, and the manufactured parts may not be able to withstand complex mechanical environments, seriously affecting the mechanical properties and overall quality of the products, and there are potential safety hazards; while in some regions, the surface may overheat, resulting in problems such as material decomposition and performance deterioration. Therefore, how to overcome the problem of laser energy attenuation in relatively thick materials and ensure that each region inside the material can obtain sufficient and uniform heating has become a key technical problem to be solved urgently in the current field of laser processing of foam materials. Summary of the Invention

[0005] Based on this, the object of the present invention is to provide a modified microsphere for thick-piece foam molding. By grafting infrared-absorbing molecules on the surface of the microsphere, the absorption and scattering ability of the modified microsphere to infrared light is improved, enabling the laser to effectively penetrate thicker or complex-shaped foam parts and ensuring uniform heating.

[0006] Another object of the present invention is to provide a composition. By adding the modified microsphere, the foam material formed by laser is made more uniform, improving the mechanical properties, elasticity and thermal stability of the material, solving the problem of uneven local foaming in traditional foaming processes, especially suitable for the preparation of foam parts with complex geometric shapes and uneven thicknesses, and having high energy efficiency and processing accuracy.

[0007] A modified microsphere for thick-piece foam molding provided by the present invention is prepared through the following steps:

[0008] S1, polymerize microgel monomers to form microgel particles;

[0009] S2, modify the surface of the microgel particles with maleic anhydride to obtain microgel particles with active sites;

[0010] S3, graft infrared-absorbing molecules onto the surface-modified microgel particles with active sites to obtain modified microspheres.

[0011] Further, in step S1, weigh microgel monomers proportionally and dissolve them in deionized water, then successively add an emulsifier, a buffer and an initiator. After sufficient polymerization, dialyze and dry the polymerization product to obtain microgel particles.

[0012] Among them, the microgel monomers are selected from two or more of acrylate, methacrylate, dimethacrylate, dimethylaminoethyl methacrylate, polyethylene glycol diacrylate, acrylic acid / acrylamide copolymers, vinyl amide compounds, and styrene maleic anhydride copolymers.

[0013] As an example, in step S1, the emulsifier is sodium dodecyl sulfate; the buffer is dipotassium hydrogen phosphate; the initiator is ammonium persulfate.

[0014] Further, the particle size of the microgel particles in step S1 is 0.1 - 100 μm.

[0015] Further, in step S2, dissolve the microgel particles prepared in step S1 in a mixed solvent of anhydrous chloroform and 1,4-dioxane to obtain a reaction solution, and then add maleic anhydride to react to obtain microgel particles with active sites (-R). Among them, the -R group is a carboxyl group or a hydroxyl group.

[0016] Further, in step S3, the infrared absorption molecules are dissolved in anhydrous toluene, the microgel particles with active sites obtained in step S2 are added, and then an acid catalyst is added for reaction to obtain modified microspheres.

[0017] Among them, the infrared absorption molecules are one of copper phthalocyanine, chromium phthalocyanine, polybenzothiophene, and azo dyes.

[0018] Further, in step S3, the acid catalyst is p-aminobenzoic acid and concentrated sulfuric acid.

[0019] A composition for thick-piece foaming molding provided by the present invention includes the following components in parts by weight:

[0020] 40 - 70 parts of a high molecular copolymer;

[0021] 2 - 10 parts of a foaming agent;

[0022] 0.5 - 2 parts of a crosslinking agent;

[0023] 1 - 3 parts of an auxiliary agent;

[0024] 5 - 30 parts of modified microspheres.

[0025] The components are melt-blended at a high temperature according to the ratio, and then the combined material particles are obtained by cooling and pelletizing.

[0026] Among them, the high molecular copolymer is a high molecular foaming material, and is selected from one or more of polyester rubber, polystyrene, polyurethane, polypropylene, polymethyl methacrylate, and ethylene-vinyl acetate copolymer.

[0027] The foaming agent is selected from one or more of diphenylsulfonylhydrazide ether, azodicarbonamide, diisopropyl azodicarboxylate, sodium bicarbonate, and ammonium carbonate.

[0028] The crosslinking agent is selected from one or more of dicumyl peroxide and di-tert-butyl peroxide diisopropylbenzene.

[0029] The auxiliary agent includes a lubricant, an antioxidant, and a dispersant, all of which are commonly used auxiliary agents in the art. By way of example, a stearate is used as the lubricant to improve the processing fluidity; 1010 is used as the antioxidant to improve the thermal stability of the material; white oil or low molecular weight polyethylene wax is used as the dispersant to promote the uniform dispersion of the modified microspheres.

[0030] Further, in some embodiments, the composition further includes 10 - 20 parts of PET as a toughening agent or reinforcing material to improve the mechanical properties of the composite material.

[0031] The composition for thick-piece foaming molding described in the present invention can be applied to the field of laser molding.

[0032] Specifically, during the laser injection molding process of the composition, an infrared light source is used in conjunction with a glass mold to precisely heat a specific area of the glass mold, causing the modified microspheres to expand and thereby forming a foamed structure in the polymer copolymer matrix. Among them, the high light transmittance of the glass mold enables infrared light to be effectively conducted into the interior of the composition material to heat the composition.

[0033] Furthermore, the material of the glass mold is quartz glass or aluminosilicate glass, which can meet higher processing temperatures, and at the same time has excellent light transmittance and is suitable for laser transmission in the infrared band. At the same time, the glass mold has a high thermal conductivity and can dissipate the heat generated during the injection molding process faster, realizing rapid cooling. Compared with traditional metal molds, the glass mold can significantly shorten the cooling time of the injection molded parts and shorten the production cycle. This characteristic of rapid cooling not only helps to improve production efficiency, but also reduces the deformation and stress problems caused by uneven cooling during the molding process and improves the quality of the finished product.

[0034] Furthermore, the infrared light source can select a semiconductor laser with a longer wavelength according to the molding requirements. As an example, a semiconductor laser of 808 nm or 1064 nm is used to precisely control the wavelength and power density of the laser to ensure effective local heating. For low-power heating or the processing of small molded parts, an infrared LED light source can be used for heating. As an example, an infrared LED light source in the 850 - 1000 nm band is used to heat and mold small sheet-shaped molded parts.

[0035] In the present invention, modified microspheres are prepared by emulsion polymerization and chemical modification grafting, and the modified microspheres are applied to the composition for thick-piece foaming molding, so that the composition can uniformly absorb the heat of the infrared light source. In addition, the present invention combines the laser molding process and can achieve multi-point synchronous heating or rapid heating of key areas by dynamically regulating the laser light field, greatly shortening the heating time; at the same time, by adjusting the power density, spot position and heating time of the infrared light source, precise control of the foaming process is ensured, avoiding overheating or uneven foaming, so that the composition can efficiently prepare foamed materials, especially suitable for the precise molding of thicker or complex geometric shape foamed parts, ensuring high energy efficiency and processing accuracy.

[0036] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of the preparation principle of the modified microspheres of the present invention;

[0038] Figure 2 is a schematic diagram of the structure of the laser forming device;

[0039] Figure 3Schematic structural diagram of the mold for laser forming;

[0040] Figure 4 Schematic diagram of laser energy distribution during the laser forming processes of the examples and the comparative examples. Specific embodiments

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0042] The experimental methods used in the embodiments are all conventional methods unless otherwise specified; the reagents, materials, etc. used in the embodiments can be obtained from commercial channels unless otherwise specified.

[0043] Example

[0044] I. Preparation of modified microspheres

[0045] The preparation method of the modified microspheres in this embodiment includes the following steps:

[0046] S1. Take ethyl acrylate (139 g, 1.52 mol), 2-vinylpyrrolidone (92 g, 0.74 mol), and 1,4-butanediol diacrylate (3 g, 0.012 mol), mix them in proportion to form a monomer solution (234 g in total). In a four-necked flask, add 520 g of deionized water and dissolve sodium dodecyl sulfate (1.5 g, 0.005 mol) to form an emulsion system. Add dipotassium hydrogen phosphate (3 g, 7 wt% aqueous solution) as a buffer system to the system, and add ammonium persulfate (9 g, 2 wt% solution) as an initiator. Under nitrogen protection, heat the mixture to 80 °C and stir for 30 minutes at 600 rpm mechanical stirring to uniformly disperse the monomers. Dropwise add the remaining monomer solution at a constant speed within 1.5 hours, and continue to react for 2 hours to ensure sufficient polymerization. After the reaction is completed, dialyze the product (dialysis bag MWCO 10 kDa, deionized water for 24 h), and then dry it under vacuum to obtain microgel particles.

[0047] S2. Take 10 g of microgel particles and dissolve them in 50 mL of anhydrous chloroform. Then add 10 mL of 1,4-dioxane to obtain a reaction solution. Add 5.0 g of maleic anhydride to the above solution and stir evenly. Install the three-necked flask containing the reaction solution in a nitrogen protection environment to ensure that there is no moisture and oxygen during the reaction. Heat the reaction system to 80 °C and stir the reaction at this temperature for 2 - 4 hours. After the reaction is completed, use a rotary evaporator to remove the solvent chloroform, and wash the reaction product with deionized water to remove the unreacted maleic anhydride. Obtain microgel particles with active sites through vacuum drying.

[0048] S3. Dissolve 3.0 g of copper phthalocyanine in 50 mL of anhydrous toluene. Add 10 g of microgel particles grafted with maleic anhydride to the above solution. Add 0.5 g of p-aminobenzoic acid and add 1 - 2 drops of concentrated sulfuric acid as an acid catalyst. Install the three-necked flask in a nitrogen protection environment and carry out a reflux reaction. Set the reaction temperature to 100 °C and stir the reaction for 2 - 4 hours. After the reaction is completed, use a rotary evaporator to remove the toluene solvent to obtain microgel particles grafted with copper phthalocyanine. Wash the product with deionized water to remove the residual reactants, and then vacuum dry the product to obtain modified microspheres.

[0049] II. Preparation of composite material particles

[0050] The high molecular copolymer in the embodiment of the present invention is TPEE;

[0051] The foaming agent in the embodiment of the present invention is diphenylsulfonyl hydrazide ether;

[0052] The crosslinking agent in the embodiment of the present invention is dicumyl peroxide.

[0053] The preparation method of the composition for thick-piece foaming molding in the embodiment of the present invention includes the following steps:

[0054] Weigh each component according to Table 1, and then put all the components on a high-speed mixer and set the rotation speed to 60 revolutions per minute and mix for 20 minutes to mix evenly; then put the mixed material into a twin-screw extruder, set the melting temperature to 120 °C, the rotation speed to 60 revolutions per minute, and the residence time to 300 s, and carry out melt blending and granulation to obtain composite material particles for thick-piece foaming molding.

[0055] Table 1 Dosage table of each component of the composition in Examples 1 - 5

[0056]

[0057] III. Laser forming

[0058] Please refer to Figure 2, the laser forming device in this embodiment includes: a laser 1, a spatial light modulator 2, a lens 4, a mold 5, a radiator 6, a heat dissipation channel 7, and a feed port 8. The laser 1 generates laser light, and by controlling the scanning path and heating area of the laser light, the heating and melting of the plastic are precisely controlled. Then, the spatial light modulator 2 performs real-time dynamic modulation on the laser light field, and adjusts the position, energy distribution, and scanning path of the laser spot in real time to ensure uniform temperature distribution within the mold 5 and further optimize the melting state. It can be understood that during the laser forming process, the molten plastic is injected into the mold 5 through the feed port 8 under pressure for forming. It is also possible to pour the plastic raw material into the mold 5 and then form it.

[0059] Please refer to Figure 3 , in this embodiment, the mold selects quartz glass with high heat resistance and high light transmittance as the mold material, manufactures the upper mold and the lower mold, and coats an anti-adhesion coating on the surface of the mold to facilitate demolding. The inner cavity shape of the glass mold is a complex geometric shape with uneven thickness.

[0060] The laser forming of the combined material particles in the embodiment of the present invention is specifically carried out according to the following steps:

[0061] Parameter setting of the laser forming device: Use a fiber laser with a wavelength of 1064 nm as the heat source, set the laser power to 300 W, adjust the spot diameter to 2 mm, and adopt a scanning mode to gradually cover the injection area of the mold, with an irradiation time of 1 s. The laser light path enters the outside of the mold after being collimated by the lens and directly acts on the combined material particles through the transparent glass mold. The parameters of the spatial light modulator are set as: 1920×1080 pixels; the refresh rate is 500 Hz, which is used to dynamically adjust the shape of the light field.

[0062] Laser forming: Place the combined material particles in the inner cavity of the glass mold, turn on the laser to heat the combined material, and quickly heat the material particles to the molten state. Stop the laser heating, start the built-in cooling system of the mold, and quickly remove the heat of the mold through the circulating coolant, and reduce the temperature of the inner cavity of the mold to below 60 °C. After the mold is cooled, take out the sample.

[0063] Comparative Example

[0064] The difference between Comparative Example 1 and Example 1 is that the modified microspheres in the composition of Example 1 are replaced with unmodified grafted microgel particles, and other components and preparation methods are the same as those in Example 1.

[0065] The difference between Comparative Example 2 and Example 1 is that the modified microspheres in the composition of Example 1 are not added, and other components and preparation methods are the same as those in Example 1.

[0066] The difference between Comparative Example 3 and Comparative Example 2 is only that PET components are added in Comparative Example 3.

[0067] The dosages of the components in the compositions of Comparative Examples 1-3 are shown in Table 2 in detail.

[0068] Table 2 Dosage table of each component in the compositions of Comparative Examples 1-3

[0069]

[0070] Performance Test

[0071] The samples prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to the following performance tests.

[0072] (1) Foaming ratio;

[0073] (2) Compression performance test (ASTM D695 / ISO604);

[0074] The test results are shown in Table 3 in detail.

[0075] Table 3 Performance data table of the samples prepared in Examples and Comparative Examples

[0076] Sample Foaming Ratio (times) Compression Modulus (MPa) Example 1 5.1 5.2 Example 2 5.1 5.1 Example 3 4.9 5.5 Example 4 4.9 5.4 Example 5 4.7 5.8 Comparative Example 1 3.7 8.1 Comparative Example 2 3.8 8.1 Comparative Example 3 3.5 8.5

[0077] As can be seen from Table 3, the compositions of Examples 1-5 were added with modified microspheres, and the samples obtained had a higher foaming ratio, more pores, and a significantly lower compression modulus compared with the samples obtained in the comparative examples, showing excellent mechanical properties.

[0078] Combined with Figure 4 , see Figure 4 (a), it can be seen that in the comparative examples, the microgel particles without modified graft treatment were used, or the compositions without adding modified microspheres were used. After laser forming, the samples obtained had uneven foaming due to slow heat transfer inside and heat concentration at the central position; due to the lower foaming ratio, the cell structure was denser, and thus the compression modulus was higher. See Figure 4 (b), in Examples 1-5, due to the addition of modified microspheres in the composition, it can accurately absorb laser heat during the laser forming process, and the heat is evenly dispersed, enabling uniform foaming of thick parts, and finally the cells are more uniform and the density is lower.

[0079] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0080] (1) Modified microspheres were prepared by emulsion polymerization and chemical modification grafting, improving the absorption and scattering ability of the microspheres to infrared light, enabling the modified microspheres to be widely used in the field of laser forming, especially suitable for the forming and foaming of thick parts or complex foamed parts, ensuring high energy efficiency and processing accuracy;

[0081] (2) Apply the modified microspheres to the composition for thick-piece foam molding, enabling the composition to uniformly absorb the heat of the infrared light source, making the molded foam material more uniform, improving the mechanical properties, elasticity, and thermal stability of the material, and solving the problem of uneven local foaming in the traditional foaming process;

[0082] (3) By configuring a laser forming device equipped with a spatial light modulator to dynamically control the laser light field, multi-point synchronous heating or rapid heating of key areas can be achieved, ensuring uniform temperature distribution within the mold, further optimizing the molten state, significantly shortening the heating time, and improving production efficiency.

[0083] The above embodiments only represent several implementation modes of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these changes and modifications.

Claims

1. A modified microsphere for thick foaming, characterized in that: Prepared by the following steps: S1, polymerizing microgel monomers to form microgel particles; S2, modifying the surface of microgel particles with maleic anhydride to obtain microgel particles with active sites; S3, grafting infrared absorbing molecules onto microgel particles with active sites to obtain modified microspheres.

2. The modified microsphere for thick-piece foaming molding according to claim 1, characterized in that: In step S1, microgel monomers are weighed in proportion and dissolved in deionized water, and then an emulsifier, a buffer and an initiator are added in sequence. After sufficient polymerization, the polymer product is dialyzed and dried to obtain microgel particles; The microgel monomer is selected from two or more of acrylate, methacrylate, dimethacrylate, dimethylaminoethyl methacrylate, polyethylene glycol diacrylate, acrylic acid / acrylamide copolymers, vinylamide compounds, and styrene maleic anhydride copolymers.

3. The modified microsphere for thick-piece foaming molding according to claim 2, characterized in that: In step S1, the emulsifier is sodium lauryl sulfate; The buffer is dipotassium hydrogen phosphate; The initiator is ammonium persulfate.

4. The modified microsphere for thick-piece foaming molding according to claim 2, characterized in that: In step S1, the particle size of the microgel particles is 0.1-100 μm.

5. The modified microsphere for thick-piece foaming molding according to claim 1, characterized in that: In step S2, the microgel particles prepared in step S1 are dissolved in a mixed solvent of anhydrous chloroform and 1,4-dioxane to obtain a reaction solution, and then maleic anhydride is added to react to obtain microgel particles with active sites.

6. The modified microsphere for thick-piece foaming molding according to claim 1, characterized in that: In step S3, the infrared absorbing molecules are dissolved in anhydrous toluene, the microgel particles with active sites obtained in step S2 are added, and then an acid catalyst is added to react to obtain modified microspheres; Wherein, the infrared absorbing molecule is one of copper phthalocyanine, chromium phthalocyanine, polybenzothiophene and azo dyes.

7. The modified microsphere for thick-piece foaming molding according to claim 6, characterized in that: The acid catalyst is p-aminobenzoic acid and concentrated sulfuric acid.

8. A composition for thick foam molding, characterized in that: The composition comprises the following components in parts by weight: 40-70 parts of high molecular copolymer; 2-10 parts of foaming agent; Cross-linking agent 0.5-2 parts; 1-3 parts of additives; 5-30 parts of the modified microspheres according to any one of claims 1-7; The composition is prepared by melt-blending the components according to a proportion.

9. A composition for thick-piece foaming molding according to claim 8, characterized in that: Also included is 10-20 parts of PET.

10. Use of the composition for thick-piece foaming molding according to any one of claims 8 or 9 in the field of laser molding.

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