Spherical silicon dioxide anti-blocking agent for plastic film as well as preparation method and application of spherical silicon dioxide anti-blocking agent

Abstract

The invention belongs to the technical field of silicon dioxide preparation, and particularly relates to a preparation method of a spherical silicon dioxide anti-blocking agent for a plastic film, and the method comprises the following steps: 1) preparing spherical silicon dioxide particles by a flame method; and 2) carrying out surface modification on silicon dioxide. According to the prepared silicon dioxide anti-blocking agent, the content of SiO2 is 90%-99.9%, the content of iron is smaller than or equal to 0.01 ppm, the content of sodium ions is smaller than or equal to 0.6 ppm, and the silicon dioxide anti-blocking agent has the advantages of being narrow in particle size distribution (D50: 150-1000 nm), excellent in dispersity, low in oil absorption value (15-30 mL / 100 g) and the like. The modified silicon dioxide is compounded with a plastic matrix to prepare a film, and compared with a plastic film without the silicon dioxide anti-blocking agent, the silicon dioxide anti-blocking agent can remarkably improve the anti-blocking performance and mechanical properties of the plastic film, for example, the tensile strength is improved by 10-30%, the elongation at break is improved by 10-30%, and the light transmittance is larger than 92%. Meanwhile, the thermal oxidation yellowing phenomenon caused by metal ions can be effectively inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon dioxide preparation, and specifically relates to a spherical silicon dioxide opening agent for plastic film and a preparation method and application thereof. The silicon dioxide opening agent can be used to improve the opening performance of the plastic film. Background Art

[0002] Under the action of atmospheric pressure and winding tension, film products tend to form a vacuum-tight state, resulting in close adhesion between film layers, making them difficult to separate and affecting their application. In the production and preparation process of plastic film products, an opening agent (also called an anti-blocking agent) is usually added to improve the opening performance of the film. There are three generations of plastic film opening agents: the first generation is talcum powder, diatomaceous earth, calcium hydrogen phosphate, etc., which have the disadvantages of poor opening performance and low transmittance, affecting the optical properties of the film; the second generation is oleamide, erucamide, etc., which have the disadvantages of easy precipitation and safety risks; the third generation is synthetic silica, which has the advantages of good opening performance and non-toxicity, but has the disadvantages of high oil absorption value (>150 mL / 100g), low transmittance (<90%), and metal ion residue (Fe 3+ >5 ppm) and other defects.

[0003] Chinese patent CN110229380B uses water glass as raw material and adopts liquid phase method to synthesize porous silica. The powder is collected through washing, atomization drying, crushing and other steps. The process is complicated and the oil absorption value is high (1.3-1.6cm 3 / g). Chinese patent CN114455597B uses solid sodium silicate as raw material to prepare low oil absorption silica by pH control, but the light transmittance is insufficient. Chinese patent application CN117586558A uses solid sodium silicate as raw material to prepare sodium silicate solution, which is added dropwise to sulfuric acid solution for reaction, and then filtered, washed, pulped, spray dried, air flow crushed and other steps to obtain the target product. It requires multiple post-processing steps and has low efficiency.

[0004] At present, most silica opening agents used in plastic films are liquid phase synthetic silica, which has many processing steps. Therefore, it is necessary to provide a preparation method of silica opening agent with low oil absorption value and simple process, so as to effectively improve the opening effect of the film, maintain high light transmittance and improve other properties such as mechanics. Summary of the invention

[0005] In order to solve the problems raised in the above background technology, the present invention provides a spherical silica opening agent for plastic film with low oil absorption value, low metal ion content, high dispersion and simple process. The silica opening agent can overcome the adhesion of plastic film, thereby effectively improving the opening performance of plastic film.

[0006] The present invention also provides a preparation method and application of the spherical silica opening agent for plastic film. The silica opening agent can be used to improve the opening performance of plastic film.

[0007] To achieve the above object, the present invention adopts the following technical solution: A method for preparing a spherical silica opening agent for plastic film with low oil absorption value, low metal ion content, high dispersion and simple process, comprising the following steps: S1. Preparation of spherical silica by flame method: by precisely controlling the gas flow rate, the combustible gas and the combustion-supporting gas are introduced into the spheroidizing furnace, the peroxygen atmosphere in the furnace is maintained, the flame is ignited and the temperature is raised to the target ambient temperature of 200-1000°C (preferably 400-800°C); the silicon source is transported to the high temperature zone for melting under the action of the carrier gas, and spherical particles are formed after cooling and collected to obtain spherical silica; S2, surface modification: react the silane coupling agent with the spherical silica obtained in step S1 at 20-100°C for 1-10 h to obtain surface-modified spherical silica (i.e., silica opening agent for plastic film). The surface-modified spherical silica has a particle size D50 of 150-1000 nm and a specific surface area of ​​10-25 m 2 / g, oil absorption value is 15-30 mL / 100g, bulk density is 0.5-0.8 g / cm³, Fe 3+ Content ≤0.01ppm, Na + Content ≤0.6ppm.

[0008] Specifically, in step S1, the combustible gas flow rate can be 1-20m 3 / h (preferably 5-15m 3 / h), the combustible gas may include but is not limited to at least one of natural gas, acetylene gas, etc.; the combustion-supporting gas flow rate may be 10-50m 3 / h (preferably 15-35m 3 / h), and the combustion-supporting gas includes but is not limited to oxygen, etc.

[0009] Furthermore, in step S1, the carrier gas flow rate may be 1-50m 3 / h (preferably 10-30m 3 / h), the carrier gas includes but is not limited to at least one of argon, nitrogen, oxygen, etc. In step S1, the silicon source used can be metallic silicon powder, and the average particle size can be 5-20 μm; the delivery frequency of the silicon source can be 1-45 Hz.

[0010] Specifically, the amount of the silane coupling agent used for surface modification in step S2 can be 0.1wt%-10wt% of the mass of spherical silica, and the reaction temperature is 20-80°C; the silane coupling agent includes at least one of alkoxysilane, silazane, chlorosilane, etc., and its carbon chain has one or more groups of amino, epoxy, vinyl, methyl, etc. Silane coupling agent coating is used to improve compatibility with the plastic matrix. Silane coupling agents include but are not limited to silane coupling agents containing amino, epoxy, double bonds and one or more silane coupling agents with different carbon chain lengths.

[0011] The invention provides a spherical silicon dioxide opening agent for plastic film prepared by the preparation method.

[0012] The invention provides application of the spherical silicon dioxide opening agent for plastic film in the preparation of plastic film.

[0013] The invention provides a plastic film, which comprises the spherical silicon dioxide opening agent for the plastic film.

[0014] The present invention provides a method for preparing the above-mentioned plastic film, which comprises mixing the spherical silica opening agent for plastic film with plastic particles, and preparing the plastic film containing the spherical silica opening agent through melt blending, extrusion, granulation and film forming processes; wherein the amount of the spherical silica opening agent for plastic film added is 0.1-20 wt% of the mass of the plastic particles. The prepared plastic film has a light transmittance of ≥90%, a tensile strength increased by 10-30%, and an elongation at break increased by 10-30%.

[0015] Specifically, the plastic particles include but are not limited to at least one of polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyamide, polyester and polyoxymethylene; the melt blending adopts a twin-screw extruder, the screw temperature is 120-200°C, and the speed is 100-500 rpm. When preparing the composite film, the silicon dioxide is evenly dispersed through twin-screw extrusion (120-200°C), and the final film has a light transmittance of ≥90%, and the mechanical properties are significantly improved.

[0016] The surface-modified spherical silica prepared by the present invention is amorphous silica, has a narrow particle size distribution, and is simple in process. The surface of the silica prepared by the present invention is coated with a silane coupling agent, which effectively prevents the aggregation of particles, increases its dispersibility in polymer materials, and has good transparency and dispersibility in the field of thin films.

[0017] The innovations of the present invention are: 1) the spherical silica is prepared in one step by flame method, which is simple and does not require complicated post-processing steps; 2) the dispersibility of silica in the plastic particle matrix is ​​enhanced by surface modification technology, light scattering is reduced, and a high light transmittance of more than 90% is maintained; 3) the ultra-low metal ion content (Fe 3+ <0.1 ppm) can inhibit yellowing and extend the service life of the film.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Spherical silica nanoparticles generated by high-temperature spheroidization process have a large stacking density and are easier to mix with plastic materials. To a certain extent, they can improve the tensile strength and elongation at break of plastic films, thereby improving the performance and physical properties of plastic films.

[0019] (2) The spherical silica modified by silane coupling agent has good compatibility with plastic materials and can be evenly dispersed in the plastic, forming uniform small protrusions on the surface of the film, thereby improving the opening performance of the silica opening agent in the plastic film and maintaining the high transparency of the film.

[0020] (3) The iron ion content of silica prepared by the flame method is extremely low, which reduces the possibility of film oxidation and discoloration, and effectively improves the "yellow edge" phenomenon of plastic films.

[0021] (4) The spherical silica opening agent prepared by the present invention is amorphous silica, does not contain organic matter, does not contain any silicon crystals, is stable in nature in plastics, will not have precipitates attached to the surface of the film, and is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The XRD pattern of the spherical silicon dioxide prepared in Example 1 (amorphous structure); Figure 2 The particle size distribution (left) and SEM morphology (right) of the spherical silica opening agent prepared in Example 1 (sphericity > 95%); Figure 3 The particle size distribution (left) and SEM morphology (right) of the spherical silica opening agent prepared in Example 2 (sphericity > 95%); Figure 4 The particle size distribution (left) and SEM morphology (right) of the spherical silica opening agent prepared in Example 3 (sphericity > 95%). DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0024] In the following examples, the silicon source used is metallic silicon powder with an average particle size of 5-20 μm, which can be directly purchased from ordinary commercial products or prepared using conventional techniques in the art.

[0025] In the embodiments, the processes not described in detail, such as extrusion, granulation, film-forming process, etc., can be carried out by conventional techniques in the art, and they are not the innovation of the present application and are not described in detail.

[0026] Example 1 The method for preparing the spherical silica opening agent for plastic film comprises the following steps: (1) Set the flow rate to 5m 3 / h of natural gas and a flow rate of 12m 3 / h of oxygen was introduced into the spheroidizing furnace and the temperature was raised to an ambient temperature of 400°C; a flow rate of 5m 3 / h argon gas and a feeding motor with a frequency of 4Hz transport the silicon source metal silicon powder into the high temperature zone of the furnace for melting, and form spherical particles after cooling; the recovery motor with a frequency of 20Hz collects the particles to obtain spherical silicon dioxide; (2) 5 g of silane coupling agent KH570 and 100 g of spherical silica in step (1) are reacted at 60° C. for 2 h to obtain surface-modified spherical silica, which is a spherical silica opening agent for plastic film.

[0027] 10g of surface-modified spherical silica is mixed with 500g of polypropylene plastic particles, and subjected to melt blending (melt blending is carried out using a twin-screw extruder, the screw temperature is 130-150°C, and the rotation speed is 200 rpm), extrusion, granulation and film preparation processes to obtain a plastic film (thickness is about 35μm) containing a silica opening agent.

[0028] Figure 1 This is the XRD diagram of the surface-modified spherical silica product prepared in this example. It can be seen from the diagram that the product is amorphous.

[0029] Figure 2 The particle size distribution diagram and SEM photograph of the surface-modified spherical silica prepared in this example show that the product has good sphericity and a particle size of about 800 nm.

[0030] Example 2 The method for preparing the spherical silica opening agent for plastic film comprises the following steps: (1) Set the flow rate to 8m 3 / h of natural gas and a flow rate of 17m 3 / h of oxygen was introduced into the spheroidizing furnace and the temperature was raised to an ambient temperature of 500°C; a flow rate of 10m 3 / h argon gas and a feeding motor with a frequency of 7Hz transport the silicon source metal silicon powder into the high temperature zone of the furnace for melting, and form spherical particles after cooling; the recovery motor with a frequency of 15Hz collects the spherical silicon dioxide; (2) 6 g of silane coupling agent KH570 and 100 g of spherical silica in step (1) are reacted at 70° C. for 2 h to obtain surface-modified silica, which is a silica opening agent for plastic film.

[0031] 10g of surface-modified spherical silica is mixed with 500g of polypropylene plastic particles, and subjected to melt blending (melt blending is carried out using a twin-screw extruder, the screw temperature is 160-180°C, and the rotation speed is 300 rpm), extrusion, granulation and film preparation processes to obtain a plastic film (thickness is about 35μm) containing a silica opening agent.

[0032] Figure 3 The particle size distribution diagram and SEM photograph of the surface-modified spherical silica prepared in this example show that the product has good sphericity and a particle size of about 500 nm.

[0033] Example 3 The method for preparing the spherical silica opening agent for plastic film comprises the following steps: (1) Set the flow rate to 11m 3 / h of natural gas and a flow rate of 22m 3 / h of oxygen was introduced into the spheroidizing furnace and the temperature was raised to an ambient temperature of 600°C; the flow rate was 15m 3 / h argon gas and a feeding motor with a frequency of 10Hz are used to transport the silicon source metal silicon powder into the high temperature zone of the furnace for melting, and then spherical particles are formed after cooling; the spherical silicon dioxide is obtained by collecting the spherical silicon dioxide with a recovery motor with a frequency of 10Hz; (2) 7 g of silane coupling agent n-dodecyltrimethoxysilane and 100 g of spherical silica in step (1) are reacted at 80° C. for 2 h to obtain surface-modified silica, which is a silica opening agent for plastic film.

[0034] 10g of surface-modified spherical silica is mixed with 500g of low-density polyethylene plastic masterbatch, and melt blending (melt blending is carried out using a twin-screw extruder, the screw temperature is 180-200°C, and the rotation speed is 400 rpm), extrusion, granulation and film preparation process to obtain a plastic film (thickness is about 35μm) containing a silica opening agent.

[0035] Figure 4 The particle size distribution diagram and SEM photograph of the surface-modified spherical silica prepared in this example show that the product has good sphericity and a particle size of about 300 nm.

[0036] Table 1 shows the physicochemical properties of the silica opening agents prepared in the above examples, and Table 2 shows the properties of the plastic films prepared using the silica opening agents in the examples.

[0037] Table 1 Physical and chemical properties of the silica opening agent obtained in Examples 1-3 Table 2 Performance of silica anti-blocking agent applied to plastic film It can be seen from Table 1 and Table 2 that the SiO2 content in the silica opening agent prepared by the present invention is 90%-99.9%, the iron content is ≤0.01ppm, the sodium ion content is ≤0.6ppm, and it has the characteristics of narrow particle size distribution (D50: 150-1000 nm), excellent dispersibility, low oil absorption value (15-30mL / 100g), etc. Compared with the plastic film without the silica opening agent of the present invention, the silica opening agent can significantly improve the opening performance of the plastic film, the mechanical properties of the plastic film, such as tensile strength increased by 10-30%, elongation at break increased by 10-30%, light transmittance>92%, and can also effectively inhibit the thermal oxidation yellowing phenomenon caused by metal ions.

[0038] The above descriptions are only some preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a spherical silica opening agent for plastic film, characterized in that: The steps include: S1. Pass combustible gas and combustion-supporting gas into the spheroidizing furnace, maintain an oxygen atmosphere in the furnace, ignite the flame and heat up to the target ambient temperature of 200-1000°C; transport the silicon source to the high temperature zone for melting under the action of the carrier gas, form spherical particles after cooling and collect to obtain spherical silicon dioxide; S2. reacting the silane coupling agent with the spherical silica obtained in step S1 at 20-100° C. for 1-10 h to obtain the product.

2. The method for preparing the spherical silica opening agent for plastic film according to claim 1, characterized in that: In step S1, the combustible gas flow rate is 1-20m 3 / h, the combustible gas may include but is not limited to at least one of natural gas and acetylene gas; the flow rate of the combustion-supporting gas is 10-50m 3 / h, the combustion-supporting gas includes but is not limited to oxygen.

3. The method for preparing a silicon dioxide opening agent for plastic film according to claim 1, wherein in step S1, the flow rate of the carrier gas is 1-50m 3 / h, the carrier gas includes but is not limited to at least one of argon, nitrogen and oxygen.

4. The method for preparing the spherical silica opening agent for plastic film according to claim 1, characterized in that: In step S1, the silicon source used is metallic silicon powder with an average particle size of 5-20 μm; the delivery frequency of the silicon source is 1-45 Hz.

5. The method for preparing the silicon dioxide opening agent for plastic film according to claim 1, characterized in that: In step S2, the amount of the silane coupling agent added is 0.1wt%-10wt% of the mass of the spherical silica; the silane coupling agent includes at least one of alkoxysilane, silazane, and chlorosilane.

6. Spherical silica opening agent for plastic film prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the spherical silica opening agent for plastic film according to claim 6 in the preparation of plastic film.

8. A plastic film, characterized in that: The invention comprises the spherical silica opening agent for plastic film according to claim 6.

9. A method for preparing the plastic film according to claim 8, characterized in that: The spherical silica opening agent for plastic film according to claim 6 is mixed with plastic particles, and subjected to melt blending, extrusion, granulation and film forming processes to obtain a plastic film containing the spherical silica opening agent; wherein the addition amount of the spherical silica opening agent for plastic film is 0.1-20 wt% of the mass of the plastic particles.

10. The method for preparing a plastic film according to claim 9, characterized in that: The plastic particles in step S3 include but are not limited to at least one of polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyamide, polyester and polyoxymethylene; the melt blending is performed using a twin-screw extruder with a screw temperature of 120-200° C. and a rotation speed of 100-500 rpm.

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