Polyethylene glycol terephthalate foam material as well as preparation method and application thereof

Abstract

The invention relates to a polyethylene glycol terephthalate foam material, which is prepared from the following raw materials in percentage by mass: 91 to 99.9 percent of polyethylene glycol terephthalate and 0.1 to 9 percent of modified SiO2, the modified SiO2 comprises polysiloxane modified SiO2 and / or silane coupling agent modified SiO2, and the silane coupling agent modified SiO2 comprises polysiloxane modified SiO2 and / or silane coupling agent modified SiO2. The average cell size of the polyethylene glycol terephthalate foam material is smaller than or equal to 20 microns, the density is smaller than or equal to 0.35 g / cm < 3 >, and the light reflectivity is larger than or equal to 90%. The invention further provides a preparation method and application of the polyethylene glycol terephthalate foaming material. A light reflecting plate prepared from the polyethylene glycol terephthalate foaming material meets the requirements of low cost, light weight and high reflectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of foaming materials, and particularly to a polyethylene terephthalate foaming material, a preparation method thereof, and an application thereof. Background Art

[0002] Light reflectors are widely used in backlight modules of liquid crystal TVs, mobile phones, tablet computers, and LED lighting. Currently, light reflectors are mainly made of polyethylene terephthalate (PET) substrates, which are prepared by coating or biaxial stretching to form pores. However, the light reflectors prepared in this way have problems such as high cost, high density (usually above 0.8 g / cm 3 3), and insufficient reflectivity, and cannot meet the current requirements of low cost, light weight, and high reflectivity. Summary of the Invention

[0003] Based on this, in view of the above problems, it is necessary to provide a polyethylene terephthalate foaming material, a preparation method thereof, and an application thereof. The light reflector prepared by using the polyethylene terephthalate foaming material meets the requirements of low cost, light weight, and high reflectivity.

[0004] A polyethylene terephthalate foaming material, in terms of mass fraction, the raw materials for preparation include 91%-99.9% of polyethylene terephthalate and 0.1%-9% of modified SiO2. Among them, the modified SiO2 includes SiO2 modified by polysiloxane and / or SiO2 modified by a silane coupling agent. The average cell size of the polyethylene terephthalate foaming material is less than or equal to 20 μm, the density is less than or equal to 0.35 g / cm 3 , and the light reflectivity is greater than or equal to 90%.

[0005] In one embodiment, the mass fraction of the SiO2 modified by polysiloxane is 0.1%-7%;

[0006] And / or, the mass fraction of the SiO2 modified by the silane coupling agent is 2%-9%.

[0007] In one embodiment, the average particle size of the SiO2 modified by polysiloxane is 17 nm-80 nm;

[0008] And / or, the average particle size of the SiO2 modified by the silane coupling agent is 13 nm-55 nm.

[0009] In one embodiment, the grafting rate of the SiO2 modified by polysiloxane is 5%-30%;

[0010] And / or, the grafting rate of the SiO2 modified by the silane coupling agent is 5%-50%.

[0011] In one embodiment, the polysiloxane is selected from at least one of polydimethylsiloxane, hydroxypolysiloxane, or polyphenylmethylsiloxane;

[0012] And / or, the silane coupling agent is selected from at least one of hexamethyldisilazane, dodecyltrimethoxysilane, or octadecyltrimethoxysilane.

[0013] In one embodiment, the polyethylene terephthalate is selected from at least one of fiber grade, film grade, or carbonated bottle grade.

[0014] A method for preparing the polyethylene terephthalate foamed material as described above, comprising the following steps:

[0015] Melting and blending polyethylene terephthalate with modified SiO2 to form a sheet;

[0016] Placing the sheet in a high-pressure reactor for saturation to obtain a saturated sample;

[0017] Foaming the saturated sample to obtain a polyethylene terephthalate foamed material.

[0018] In one embodiment, in the saturation step, the saturation temperature is 20°C - 25°C, the saturation pressure is 4 MPa - 6 MPa, and the saturation time is 48 h - 72 h.

[0019] In one embodiment, in the foaming step, the foaming temperature is 80°C - 225°C, and the foaming time is 15 s - 30 s.

[0020] An application of the polyethylene terephthalate foamed material as described above in the preparation of a light reflecting plate.

[0021] In the present invention, polysiloxane and silane coupling agent are respectively used to modify the surface of SiO2, and the modified SiO2 is used as a heterogeneous nucleating agent for PET bubbles, which can enhance the melt strength of PET, enabling PET to rapidly form a large number of uniform bubble nuclei during the foaming process, thereby increasing the number of pores and reducing the pore size, and further forming a fine and uniform microporous structure with an average pore size less than or equal to 20 μm and a pore density greater than or equal to 10 8 cell / cm 3 such that the density of the finally prepared polyethylene terephthalate foamed material is less than or equal to 0.35 g / cm 3 , and the light reflectance is greater than or equal to 90%.

[0022] In addition, the enhanced PET melt strength broadens the foaming temperature window of PET, enabling PET to foam within a wider temperature range and optimizing the preparation conditions. Furthermore, the polyethylene terephthalate foamed material is applied to a light reflecting plate, which can meet the requirements of low cost, light weight, and high reflectivity. Description of the Drawings

[0023] Figure 1 It is a pore morphology diagram of the polyethylene terephthalate foamed material of Example 1;

[0024] Figure 2 It is a pore morphology diagram of the polyethylene terephthalate foamed material of Example 4;

[0025] Figure 3 It is a pore morphology diagram of the polyethylene terephthalate foamed material of Example 5;

[0026] Figure 4 It is a pore morphology diagram of the polyethylene terephthalate foamed material of Example 6;

[0027] Figure 5 It is a pore morphology diagram of the polyethylene terephthalate foamed material of Example 9;

[0028] Figure 6 It is a pore morphology diagram of the polyethylene terephthalate foamed material of Example 10;

[0029] Figure 7 It is a pore morphology diagram of the polyethylene terephthalate foamed material of Comparative Example 1;

[0030] Figure 8 It is a pore morphology diagram of the polyethylene terephthalate foamed material of Comparative Example 2. Detailed Description of the Invention

[0031] For the convenience of understanding the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of this invention are for the purpose of describing specific embodiments or examples only, and are not intended to limit the invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The said any and all combinations include combinations of any two related listed items, any more related listed items, or all related listed items.

[0033] The present invention provides a polyethylene terephthalate foaming material. By mass fraction, the raw materials for preparation include 91%-99.9% of polyethylene terephthalate and 0.1%-9% of modified SiO2. Among them, the modified SiO2 includes SiO2 modified by polysiloxane and / or SiO2 modified by silane coupling agent. The average cell size of the polyethylene terephthalate foaming material is less than or equal to 20 μm, and the density is less than or equal to 0.35 g / cm 3 , and the light reflectivity is greater than or equal to 90%.

[0034] The present invention respectively uses polysiloxane and silane coupling agent to modify the surface of SiO2, and uses the modified SiO2 as a heterogeneous cell nucleating agent for PET, which can enhance the melt strength of PET, enabling PET to quickly form a large number of uniform cell nuclei during the foaming process, thereby increasing the number of cells and reducing the cell size, and further forming a fine and uniform microporous structure with an average cell size less than or equal to 20 μm and a density greater than or equal to 10 8 cell / cm 3 , so that the density of the finally prepared polyethylene terephthalate foaming material is less than or equal to 0.35 g / cm 3 , and the light reflectivity is greater than or equal to 90%.

[0035] In addition, the enhanced melt strength of PET broadens the foaming temperature window of PET, enabling PET to foam within a wider temperature range and optimizing the preparation conditions. Furthermore, when the polyethylene terephthalate foaming material is applied to a light reflector, the light reflector can meet the requirements of low cost, light weight, and high reflectivity.

[0036] Optionally, the mass fraction of the SiO2 modified by polysiloxane is 0.1%-7%, and / or the mass fraction of the SiO2 modified by silane coupling agent is 2%-9%, so as to be more conducive to enhancing the melt strength of PET and further forming more uniform and dense cell nuclei during the foaming process, and improving the cell structure of the polyethylene terephthalate foaming material.

[0037] In one embodiment, when only polysiloxane-modified SiO2 is added to PET and the mass fraction of the polysiloxane-modified SiO2 is 0.1%-7%, PET has a foaming temperature window of 85°C - 220°C and a good cell structure, with a foaming ratio of 5 - 12 times, a cell diameter of 2μm - 12μm, and a density as low as 0.1g / cm 3 , and the light reflectivity can reach over 93%.

[0038] In one embodiment, when only silane-coupling-agent-modified SiO2 is added to PET and the mass fraction of the silane-coupling-agent-modified SiO2 is 2%-9%, PET has a foaming temperature window of 85°C - 195°C and good foaming ability, with a foaming ratio of 6 - 9 times, a cell diameter of 13μm - 18μm, and a density as low as 0.16g / cm 3 , and the light reflectivity can reach over 91%.

[0039] In one embodiment, polysiloxane-modified SiO2 and silane-coupling-agent-modified SiO2 are added to PET simultaneously, and the polysiloxane-modified SiO2 and the silane-coupling-agent-modified SiO2 can be compounded in any proportion. Preferably, the mass fractions of the polysiloxane-modified SiO2 and the silane-coupling-agent-modified SiO2 are 2%-5% and 0.5%-2% respectively, so that PET has a foaming temperature window of 90°C - 205°C and a good cell structure, with a foaming ratio of 7 - 9 times, a cell diameter as low as 2μm - 3μm, and a density as low as 0.17g / cm 3 , and the light reflectivity can reach over 96%.

[0040] Optionally, the average particle size of the unmodified SiO2 is 10nm - 40nm, so that the SiO2 has a large specific surface area and contains a large number of active silanol groups, which is beneficial to the modification of SiO2 by polysiloxane or silane coupling agent, thereby obtaining a high grafting rate. Further preferably, the average particle size of the unmodified SiO2 is 10nm - 20nm, which is more beneficial to improving the grafting rate.

[0041] Optionally, the grafting rate of the polysiloxane-modified SiO2 is 5%-30%, and the grafting rate of the silane-coupling-agent-modified SiO2 is 5%-50%. Further preferably, the grafting rate of the polysiloxane-modified SiO2 is 10%-20%, and the grafting rate of the silane-coupling-agent-modified SiO2 is 25%-40%. This is beneficial to improving the heterogeneous bubble nucleation ability of the modified SiO2 in the PET matrix, reducing the cell size, and increasing the light reflectivity of the polyethylene terephthalate foaming material.

[0042] Optionally, the average particle size of the polysiloxane-modified SiO2 is 17 nm - 80 nm; the average particle size of the silane coupling agent-modified SiO2 is 13 nm - 55 nm. Further preferably, the average particle size of the polysiloxane-modified SiO2 is 17 nm - 55 nm, and the average particle size of the silane coupling agent-modified SiO2 is 13 nm - 50 nm. The modified SiO2 has a larger particle size than the unmodified SiO2. Using the modified SiO2 is beneficial to improving the dispersion of nanoparticles in PET and is beneficial to increasing the melt strength of PET, and thus is beneficial to preparing a polyethylene terephthalate foaming material with smaller, more uniform cell sizes and higher light reflectivity.

[0043] Optionally, the polysiloxane is preferably at least one of polydimethylsiloxane, hydroxypolysiloxane or polyphenylmethylsiloxane.

[0044] Optionally, the silane coupling agent is preferably at least one of hexamethyldisilazane, dodecyltrimethoxysilane or octadecyltrimethoxysilane.

[0045] Optionally, the polyethylene terephthalate is preferably at least one of fiber grade, film grade or carbonated bottle grade. High-viscosity polyethylene terephthalate is beneficial to increasing the upper limit of the foaming temperature, and the cell size of the prepared foaming material is smaller and the light reflectivity is higher. The polyethylene terephthalate is preferably carbonated bottle grade.

[0046] The present invention also provides a method for preparing the above-mentioned polyethylene terephthalate foaming material, comprising the following steps:

[0047] S1, melting and blending polyethylene terephthalate and modified SiO2 and making into a sheet;

[0048] S2, placing the sheet in a high-pressure reactor for saturation to obtain a saturated sample;

[0049] S3, foaming the saturated sample to obtain a polyethylene terephthalate foaming material.

[0050] In step S1, the preparation method of the modified SiO2 comprises the following steps:

[0051] S11, preparing an SiO2 suspension;

[0052] S12, adding a polysiloxane or a silane coupling agent to the SiO2 suspension and reacting for 4 h - 12 h;

[0053] S13, after the reaction is completed, washing and centrifuging to obtain a precipitate, and drying the precipitate at 50 °C - 90 °C to obtain the modified SiO2.

[0054] In step S11, the SiO2 is preferably prepared by the vapor phase method.

[0055] Before preparing the SiO2 suspension, it also includes vacuum drying the SiO2 at 75°C - 85°C for more than 12 h to remove the moisture of the SiO2.

[0056] Considering the influence of the reaction temperature and reaction time on the grafting rate, in step S12, when modifying SiO2 with polysiloxane, the reaction conditions are: placing the SiO2 suspension at 70°C - 80°C, adjusting the pH value of the SiO2 suspension to 3 - 5 with a weak acid or adjusting the pH value of the SiO2 suspension to 9 - 11 with a weak base, adding a catalyst and polysiloxane to the SiO2 suspension, and carrying out a condensation reflux reaction for 8 h - 12 h; when modifying SiO2 with a silane coupling agent, the reaction conditions are: placing the SiO2 suspension at 60°C - 90°C, adding a weak acid to adjust the pH value to 3 - 5, then adding a silane coupling agent, and carrying out a condensation reflux reaction for 5 h - 7 h.

[0057] Preferably, the mass ratio of the SiO2 to the polysiloxane is 100:20 - 100:50.

[0058] Preferably, the mass ratio of the SiO2 to the silane coupling agent is 100:40 - 100:120.

[0059] Preferably, the catalyst is selected from dibutyltin dilaurate.

[0060] In step S1, poly(ethylene terephthalate) and the above-mentioned modified SiO2 are weighed according to mass fractions as the preparation raw materials and melt-blended. The manner of the melt-blending is not specifically limited, and it is preferably melt-blended using a mixer to obtain a mixture.

[0061] Optionally, after obtaining the mixture, the mixture can also be made into a powdery sample by a pulverizer, and then the powdery sample is made into a sheet. The manner of preparing the sheet is not specifically limited, and it is preferably using a flat vulcanizer to make the powdery sample into a sheet.

[0062] Optionally, in the step of melt-blending using a mixer, the parameters of the mixer are preferably: the temperature of the front plate is 280°C - 285°C, the temperature of the middle plate is 280°C - 290°C, the temperature of the rear plate is 280°C - 290°C, and the rotor speed is 50 rpm / min - 60 rpm / min.

[0063] Optionally, the thickness of the made sheet is preferably 0.5 mm - 2.0 mm.

[0064] In step S2, in the saturation step, the mixture is placed in a high-pressure reactor, and a foaming gas is charged. After purging the air in the reactor, saturation is carried out to obtain a saturated sample.

[0065] Optionally, the foaming gas is preferably carbon dioxide.

[0066] Optionally, the saturation temperature is preferably 20°C - 25°C, the saturation pressure is preferably 4 MPa - 6 MPa, and the saturation time is preferably 48 h - 72 h.

[0067] In step S3, after saturation is completed, the sample is quickly transferred to an oil bath at 80°C - 225°C for foaming for 15 s - 30 s to obtain a foamed sample. After foaming is completed, the foamed sample can also be quickly transferred to ice water for quenching to fix the cell morphology.

[0068] Optionally, the oil bath is preferably a glycerol bath or a silicone oil bath.

[0069] The present invention also provides an application of the above-mentioned polyethylene terephthalate foaming material in the preparation of a light reflector, and the light reflectivity of the light reflector is greater than or equal to 90%.

[0070] Hereinafter, the polyethylene terephthalate foaming material, its preparation method and application will be further described through the following specific examples.

[0071] Example 1

[0072] 20 g of hydrophilic nano-SiO2 with a particle size of 12 nm was dissolved in a three-necked flask containing 400 mL of n-heptane solution and mechanically stirred. Ammonia water was added to adjust the pH value of the solution to 10, and then it was transferred to an oil bath at 75°C. Nitrogen was introduced, and 0.048 g of dibutyltin dilaurate and 4 g of polydimethylsiloxane were added dropwise. Under a constant temperature magnetic stirrer, condensation reflux reaction was carried out for 12 h.

[0073] After the reaction was completed, it was centrifuged, washed, dried and ground repeatedly with absolute ethanol, and finally modified SiO2 powder was obtained. The average particle size of SiO2 modified with polydimethylsiloxane was 17 nm, and the grafting rate was 8.9%.

[0074] 0.75 g of the modified SiO2 powder and 149.25 g of fiber-grade polyethylene terephthalate were melt-blended in a mixer and then pressed into a circular sheet by a flat vulcanizer. Among them, the mass fraction of the modified SiO2 was 0.5%.

[0075] Then the circular sheet was placed in a high-pressure reactor at 25°C, and carbon dioxide was introduced to make it reach 4 MPa. After saturation for 72 h, the pressure was quickly released, and then the saturated sample was transferred to a dimethyl silicone oil bath at 120°C for foaming for 20 s to obtain a foamed sample.

[0076] Example 2

[0077] Dissolve 20 g of hydrophilic nano-SiO₂ with a particle size of 12 nm in a three-necked flask containing 400 mL of n-heptane solution, and carry out mechanical stirring. Add ammonia water to adjust the pH value of the solution to 10, then transfer it to an oil bath at 75 °C, introduce nitrogen gas, and dropwise add 0.048 g of dibutyltin dilaurate and 10 g of hydroxy polysiloxane. Under a constant-temperature magnetic stirrer, carry out condensation reflux reaction for 12 h.

[0078] After the reaction is completed, repeatedly centrifuge, wash, dry and grind with absolute ethanol, and finally obtain modified SiO₂ powder. The average particle size of SiO₂ modified by hydroxy polysiloxane is 20 nm, and the grafting rate is 28.8%.

[0079] Place 0.15 g of modified SiO₂ powder and 149.85 g of carbonated bottle-grade polyethylene terephthalate in a mixer and carry out melt blending, and then use a flat vulcanizer to press into a circular sheet. Among them, the mass fraction of modified SiO₂ is 0.1%.

[0080] Then place the circular sheet in a high-pressure reactor at 25 °C, introduce carbon dioxide to make it reach 6 MPa, after saturation for 48 h, quickly release the pressure, and then transfer the saturated sample to a dimethyl silicone oil bath at 120 °C for foaming for 15 s to obtain a foamed sample.

[0081] Example 3

[0082] Dissolve 20 g of hydrophilic nano-SiO₂ with a particle size of 12 nm in a three-necked flask containing 400 mL of n-heptane solution, and carry out mechanical stirring. Add ammonia water to adjust the pH value of the solution to 10, then transfer it to an oil bath at 75 °C, introduce nitrogen gas, and dropwise add 0.048 g of dibutyltin dilaurate and 6 g of polyphenylmethylsiloxane. Under a constant-temperature magnetic stirrer, carry out condensation reflux reaction for 12 h.

[0083] After the reaction is completed, repeatedly centrifuge, wash, dry and grind with absolute ethanol, and finally obtain modified SiO₂ powder. The average particle size of SiO₂ modified by polyphenylmethylsiloxane is 23 nm, and the grafting rate is 5.3%.

[0084] Place 10.5 g of modified SiO₂ powder and 139.5 g of fiber-grade polyethylene terephthalate in a mixer and carry out melt blending, and then use a flat vulcanizer to press into a circular sheet. Among them, the mass fraction of modified SiO₂ is 7%.

[0085] Then, place the circular sheet in a high-pressure reactor at 20 °C, introduce carbon dioxide to reach 5 MPa, saturate for 60 h, then rapidly release the pressure, and then transfer the saturated sample to a dimethyl silicone oil bath at 150 °C for foaming for 30 s to obtain a foamed sample.

[0086] Example 4

[0087] The difference between Example 4 and Example 1 is that 7.5 g of modified SiO2 powder and 142.5 g of fiber-grade polyethylene terephthalate are melt-blended in a mixer. Among them, the mass fraction of modified SiO2 is 5%.

[0088] Example 5

[0089] The difference between Example 5 and Example 1 is that the PET is of carbonated bottle grade.

[0090] Example 6

[0091] The difference between Example 6 and Example 5 is that the mass fraction of modified SiO2 is 5%.

[0092] Example 7

[0093] The difference between Example 7 and Example 1 is that the particle size of hydrophilic nano-SiO2 is 40 nm. The average particle size of polydimethylsiloxane-modified SiO2 is 48 nm, and the grafting rate is 6.4%.

[0094] Example 8

[0095] The difference between Example 8 and Example 7 is that 7.5 g of modified SiO2 powder and 142.5 g of fiber-grade polyethylene terephthalate are melt-blended in a mixer. Among them, the mass fraction of modified SiO2 is 5%.

[0096] Example 9

[0097] Dissolve 15 g of hydrophilic nano-SiO2 with a particle size of 12 nm in a three-necked flask containing a mixed solution of 300 mL of absolute ethanol and water, stir mechanically, add acetic acid to adjust the pH value of the solution to 4, then transfer the obtained SiO2 suspension to an oil bath at 75 °C, introduce nitrogen, and dropwise add 3 g of hexamethyldisilazane. Under a constant-temperature magnetic stirrer, carry out a condensation reflux reaction for 6 h.

[0098] After the reaction is completed, repeatedly centrifuge, wash, dry and grind with absolute ethanol to finally obtain modified SiO2 powder. The average particle size of hexamethyldisilazane-modified SiO2 is 13 nm, and the grafting rate is 6.2%.

[0099] 9 g of modified SiO2 powder and 141 g of fiber-grade polyethylene terephthalate were melt-blended in a mixer, and then pressed into circular sheets using a flat vulcanizer. Among them, the mass fraction of modified SiO2 was 6%.

[0100] Then, the circular sheet was placed in a high-pressure reactor at 25 °C, and carbon dioxide was introduced to reach 4 MPa. After saturation for 72 h, the pressure was rapidly released, and then the saturated sample was transferred to a dimethyl silicone oil bath at 120 °C for foaming for 20 s to obtain a foamed sample.

[0101] Example 10

[0102] 15 g of hydrophilic nano-SiO2 with a particle size of 12 nm was dissolved in a three-necked flask containing a mixed solution of 300 mL of absolute ethanol and water, and mechanical stirring was carried out. Acetic acid was added to adjust the pH value of the solution to 4. Then, the obtained SiO2 suspension was transferred to an oil bath at 75 °C, nitrogen was introduced, and 6 g of hexamethyldisilazane was added dropwise. Under a constant-temperature magnetic stirrer, condensation reflux reaction was carried out for 6 h.

[0103] After the reaction was completed, the modified SiO2 powder was finally obtained by centrifuging, washing, drying, and grinding with absolute ethanol repeatedly. The average particle size of SiO2 modified by hexamethyldisilazane was 13 nm, and the grafting rate was 25.4%.

[0104] 12 g of modified SiO2 powder and 138 g of fiber-grade polyethylene terephthalate were melt-blended in a mixer, and then pressed into circular sheets using a flat vulcanizer. Among them, the mass fraction of modified SiO2 was 8%.

[0105] Then, the circular sheet was placed in a high-pressure reactor at 25 °C, and carbon dioxide was introduced to reach 4 MPa. After saturation for 72 h, the pressure was rapidly released, and then the saturated sample was transferred to a dimethyl silicone oil bath at 120 °C for foaming for 20 s to obtain a foamed sample.

[0106] Example 11

[0107] 10 g of hydrophilic nano-SiO2 with a particle size of 12 nm was dissolved in a three-necked flask containing a mixed solution of 200 mL of absolute ethanol and water, and mechanical stirring was carried out. Oxalic acid was added to adjust the pH value of the solution to 4. Then, the obtained SiO2 suspension was transferred to an oil bath at 75 °C, nitrogen was introduced, and 4 g of octadecyltrimethoxysilane was added dropwise. Under a constant-temperature magnetic stirrer, condensation reflux reaction was carried out for 12 h.

[0108] After the reaction was completed, the modified SiO2 powder was finally obtained by centrifuging, washing, drying, and grinding with absolute ethanol repeatedly. The average particle size of SiO2 modified by octadecyltrimethoxysilane was 19 nm, and the grafting rate was 13.1%.

[0109] 6 g of modified SiO2 powder and 144 g of fiber-grade polyethylene terephthalate were melt-blended in a mixer, and then pressed into a circular sheet using a flat vulcanizer. Among them, the mass fraction of modified SiO2 was 4%.

[0110] Then, the circular sheet was placed in a high-pressure reactor at 25 °C, and carbon dioxide was introduced to reach 4 MPa. After saturation for 72 h, the pressure was rapidly released. Then, the saturated sample was transferred to a dimethyl silicone oil bath at 120 °C and foamed for 20 s to obtain a foamed sample.

[0111] Example 12

[0112] 10 g of hydrophilic nano-SiO2 with a particle size of 12 nm was dissolved in a three-necked flask containing a mixed solution of 200 mL of absolute ethanol and water, and mechanical stirring was carried out. Oxalic acid was added to adjust the pH value of the solution to 4. Then, the obtained SiO2 suspension was transferred to an oil bath at 75 °C, nitrogen was introduced, and 10 g of octadecyltrimethoxysilane was added dropwise. Under a constant-temperature magnetic stirrer, a condensation reflux reaction was carried out for 6 h.

[0113] After the reaction was completed, the modified SiO2 powder was finally obtained by centrifuging, washing, drying, and grinding with absolute ethanol repeatedly. The average particle size of SiO2 modified with octadecyltrimethoxysilane was 21 nm, and the grafting rate was 46.5%.

[0114] 7.5 g of modified SiO2 powder and 142.5 g of fiber-grade polyethylene terephthalate were melt-blended in a mixer, and then pressed into a circular sheet using a flat vulcanizer. Among them, the mass fraction of modified SiO2 was 5%.

[0115] Then, the circular sheet was placed in a high-pressure reactor at 25 °C, and carbon dioxide was introduced to reach 4 MPa. After saturation for 72 h, the pressure was rapidly released. Then, the saturated sample was transferred to a dimethyl silicone oil bath at 120 °C and foamed for 20 s to obtain a foamed sample.

[0116] Example 13

[0117] The difference between Example 13 and Example 1 is that when modified SiO2 and fiber-grade polyethylene terephthalate were melt-blended and foamed, the raw material components were: 4 g of the modified SiO2 powder in Example 1, 1 g of the modified SiO2 powder in Example 9, and 145 g of fiber-grade polyethylene terephthalate were melt-blended in a mixer, and then pressed into a circular sheet using a flat vulcanizer.

[0118] Then, the circular sheet was placed in a high-pressure reactor at 25 °C, and carbon dioxide was introduced to reach 4 MPa. After saturation for 72 h, the pressure was rapidly released. Then, the saturated sample was transferred to a dimethyl silicone oil bath at 120 °C and foamed for 20 s to obtain a foamed sample.

[0119] Example 14

[0120] The difference between Example 14 and Example 1 is that when the modified SiO2 and fiber-grade polyethylene terephthalate are melt-blended and foamed, the raw material components are as follows: 7.5 g of the modified SiO2 powder in Example 2, 3 g of the modified SiO2 powder in Example 10, and 139.5 g of fiber-grade polyethylene terephthalate are placed in a mixer and melt-blended, and then pressed into a circular sheet by a flat vulcanizing machine.

[0121] Then the circular sheet is placed in a high-pressure reactor at 25 °C, and carbon dioxide is introduced to reach 4 MPa. After saturation for 72 h, the pressure is quickly released, and then the saturated sample is transferred to a dimethyl silicone oil bath at 120 °C for foaming for 20 s to obtain a foamed sample.

[0122] Example 15

[0123] The difference between Example 15 and Example 1 is that when the modified SiO2 and fiber-grade polyethylene terephthalate are melt-blended and foamed, the raw material components are as follows: 4 g of the modified SiO2 powder in Example 3, 1 g of the modified SiO2 powder in Example 12, and 145 g of fiber-grade polyethylene terephthalate are placed in a mixer and melt-blended, and then pressed into a circular sheet by a flat vulcanizing machine.

[0124] Then the circular sheet is placed in a high-pressure reactor at 25 °C, and carbon dioxide is introduced to reach 4 MPa. After saturation for 72 h, the pressure is quickly released, and then the saturated sample is transferred to a dimethyl silicone oil bath at 120 °C for foaming for 20 s to obtain a foamed sample.

[0125] Comparative Example 1

[0126] The difference between Comparative Example 1 and Example 1 is that 0.75 g of unmodified SiO2 powder and 149.25 g of fiber-grade polyethylene terephthalate are placed in a mixer and melt-blended, and then pressed into a circular sheet by a flat vulcanizing machine. Among them, the mass fraction of unmodified SiO2 is 0.5%.

[0127] Comparative Example 2

[0128] The difference between Comparative Example 2 and Example 1 is that 7.5 g of unmodified SiO2 powder and 142.5 g of fiber-grade polyethylene terephthalate are placed in a mixer and melt-blended, and then pressed into a circular sheet by a flat vulcanizing machine. Among them, the mass fraction of unmodified SiO2 is 5%.

[0129] Comparative Example 3

[0130] The difference between Comparative Example 3 and Example 1 lies in that: 15 g of polydimethylsiloxane-modified SiO2 powder and 135 g of fiber-grade polyethylene terephthalate are placed in a mixer for melt blending, and then pressed into a sheet by a flat vulcanizing machine to form a circular sheet. Among them, the mass fraction of the modified SiO2 is 10%.

[0131] Comparative Example 4

[0132] The difference between Comparative Example 4 and Example 9 lies in that: 15 g of hexamethyldisilazane-modified SiO2 powder and 135 g of fiber-grade polyethylene terephthalate are placed in a mixer for melt blending, and then pressed into a sheet by a flat vulcanizing machine to form a circular sheet. Among them, the mass fraction of the modified SiO2 is 10%.

[0133] Comparative Example 5

[0134] The differences between Comparative Example 5 and Example 1 and Example 9 lie in that: 7.5 g of polydimethylsiloxane-modified SiO2 powder prepared in Example 1, 7.5 g of hexamethyldisilazane-modified SiO2 powder prepared in Example 9 and 135 g of fiber-grade polyethylene terephthalate are placed in a mixer for melt blending, and then pressed into a sheet by a flat vulcanizing machine to form a circular sheet. Among them, the mass fraction of the modified SiO2 is 10%.

[0135] Table 1 shows the properties of the polyethylene terephthalate foaming materials obtained in the above examples and comparative examples. Among them, the reflectance (105 °C) is the light reflectance measured on the foam sample foamed at 105 °C.

[0136] Table 1

[0137]

[0138]

[0139] Combined with Table 1 and Figure 1-8 It can be seen that, compared with Comparative Examples 1-5, the heterogeneous nucleation effect of the modified SiO2 in Examples 1-15 is more obvious, the cell size of the obtained foaming material is significantly reduced, all below 20 μm, the cell distribution is more uniform, and the density of the prepared PET foaming material is less than or equal to 0.35 g / cm 3 , the upper limit of the foaming temperature can be increased, and the light reflectance can reach more than 90%.

[0140] It can be known from Table 1 that polydimethylsiloxane-modified SiO2 was selected in Examples 1-8, and silane coupling agent-modified SiO2 was selected in Examples 9-12. Among them, polydimethylsiloxane-modified SiO2 is more conducive to preparing foaming materials with small cell size, high light reflectance and wide foaming temperature window, which is beneficial to expanding the application in the field of PET light reflection.

[0141] As can be seen from Examples 13 - 15 in Table 1, when compounding the polysiloxane - modified SiO2 and the silane coupling agent - modified SiO2 in a suitable ratio, not only can small - sized cell holes similar to those added with polysiloxane - modified SiO2 be prepared, but also it is beneficial to increase the expansion ratio. For example, when the foaming pore diameter is also 2 μm - 3 μm, the expansion ratio of Examples 13 - 15 is greater than 7 times, thus further meeting the requirements of current PET foaming materials for low cost, lightweight, and high reflectivity.

[0142] As can be seen from Table 1, the PETs in Examples 5 and 6 are carbonated bottle - grade. Compared with the fiber - grade PETs in Examples 1 and 4 respectively, the cell hole size of the obtained foaming materials decreases and the light reflectivity increases.

[0143] As can be seen from Table 1, the particle size of SiO2 in Examples 7 - 8 is 40 nm. Compared with the SiO2 with a particle size of 12 nm in Examples 1 and 4 respectively, the grafting rate of the modified SiO2 decreases. Therefore, a smaller SiO2 particle size is beneficial to increasing the grafting rate, thus being beneficial to improving the heterogeneous nucleation ability of uniform bubbles of the modified SiO2 in the PET matrix, reducing the cell hole size, and increasing the light reflectivity of the polyethylene terephthalate foaming material.

[0144] As can be seen from Table 1, in Comparative Examples 3 - 5, when the content of the modified SiO2 is too large, it is very difficult to obtain a PET nanocomposite by melt - blending, and thus a PET foaming sample cannot be obtained.

[0145] The technical features of the above - described embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above - described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0146] The above - described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting 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 deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A polyethylene terephthalate foamed material, characterized in that, By mass fraction, the preparation raw materials include 91%-99.9% of polyethylene terephthalate and 0.1%-9% of modified SiO2. Among them, the modified SiO2 includes SiO2 modified by polysiloxane and / or SiO2 modified by silane coupling agent. The average cell size of the polyethylene terephthalate foam material is less than or equal to 20 μm, and the density is less than or equal to 0.35 g / cm 3 , and the light reflectance is greater than or equal to 90%.

2. The polyethylene terephthalate foamed material according to claim 1, characterized in that, The mass fraction of the polysiloxane-modified SiO2 is 0.1% - 7%; and / or, the mass fraction of the silane coupling agent-modified SiO2 is 2% - 9%.

3. The polyethylene terephthalate foamed material according to claim 1, characterized in that, The average particle size of the polysiloxane-modified SiO2 is 17 nm - 80 nm; and / or, the average particle size of the silane coupling agent-modified SiO2 is 13 nm - 55 nm.

4. The polyethylene terephthalate foamed material according to claim 1, characterized in that, The grafting rate of the polysiloxane-modified SiO2 is 5% - 30%; and / or, the grafting rate of the silane coupling agent-modified SiO2 is 5% - 50%.

5. The polyethylene terephthalate foamed material according to claim 1, characterized in that, The polysiloxane is selected from at least one of polydimethylsiloxane, hydroxypolysiloxane or polyphenylmethylsiloxane; and / or, the silane coupling agent is selected from at least one of hexamethyldisilazane, dodecyltrimethoxysilane or octadecyltrimethoxysilane.

6. The polyethylene terephthalate foamed material according to claim 1, characterized in that, The polyethylene terephthalate is selected from at least one of fiber grade, film grade or carbonated bottle grade.

7. A preparation method of the polyethylene terephthalate foamed material according to any one of claims 1 - 6, characterized in that, It includes the following steps: Melting and blending polyethylene terephthalate with modified SiO2 to form a sheet; Placing the sheet in a high-pressure reactor for saturation to obtain a saturated sample; Foaming the saturated sample to obtain a polyethylene terephthalate foam material.

8. The preparation method of the polyethylene terephthalate foamed material according to claim 7, characterized in that, In the saturation step, the saturation temperature is 20°C - 25°C, the saturation pressure is 4 MPa - 6 MPa, and the saturation time is 48 h - 72 h.

9. The preparation method of the polyethylene terephthalate foamed material according to claim 7, characterized in that, In the foaming step, the foaming temperature is 80°C - 225°C, and the foaming time is 15 s - 30 s.

10. An application of the polyethylene terephthalate foamed material according to any one of claims 1 - 6 in the preparation of a light reflecting plate.

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