Preparation of polystyrene hollow microspheres with uniform size and application of polystyrene hollow microspheres in packaging paper

Abstract

The invention discloses preparation of polystyrene hollow microspheres with uniform size and application of the polystyrene hollow microspheres in packaging paper. The preparation method of the polystyrene hollow microspheres comprises the following steps: (1) adding ammonium persulfate and polyvinylpyrrolidone into an ethanol / water system, then adding styrene, and reacting to obtain polystyrene microspheres with uniform size; and (2) adding the polystyrene microspheres into an ethanol / water system, and heating and stirring for reaction to prepare the polystyrene hollow microspheres with uniform size. The prepared hollow polystyrene microspheres and coating emulsion are blended and applied to paper coating, and paper which is high in whiteness, high in brightness, high in opacity, good in glossiness, waterproof and oil-proof can be prepared and used for producing high-grade packaging paper.

Description

Technical Field

[0001] This invention belongs to the field of chemicals, and specifically relates to the preparation of uniformly sized polystyrene hollow microspheres and their application in packaging paper. Background Technology

[0002] Paper, as a non-toxic, harmless, and biodegradable high-value-added material, plays an irreplaceable role in the packaging industry. During packaging paper production, coating technology is often used to impart superior properties, such as water and oil resistance, and aesthetic appeal. In recent years, water-based coatings have received widespread attention as an environmentally friendly and safe alternative to solvent-based systems. In these water-based formulations, opacifying materials are a key component for optimizing optical properties (such as opacity and whiteness) and surface aesthetics. However, the poor compatibility of most opacifying materials with water-based matrices easily leads to film damage, reduced coating stability, and impaired adhesion, thus limiting their practical application. Therefore, there is an urgent need to develop green, cost-effective, efficient, and stable opacifying materials for the production of high-performance water-based coatings and high-grade packaging paper.

[0003] Polystyrene hollow microspheres, as a stable thermoplastic material, are highly regarded for their excellent mechanical strength and chemical resistance. Their molecular structure contains a large number of nonpolar phenyl and vinyl groups, exhibiting excellent compatibility with waterborne coatings containing nonpolar structural units (such as styrene-acrylic latex and styrene-butadiene latex). Due to the significant difference in refractive index between the shell material and the internal cavity (1.6 / 1.0), hollow microspheres exhibit strong refraction, reflection, and scattering of light, resulting in excellent light-blocking effects. Furthermore, the hollow internal structure of the microspheres allows for lower density, enabling lighter production and improved cost-effectiveness. These properties make polystyrene hollow microspheres one of the most promising masking materials for waterborne coatings.

[0004] Currently, the common preparation process for polystyrene hollow microspheres suffers from drawbacks such as complex processes, large amounts of chemical additives, high energy consumption, low strength, uncontrollable size, and non-uniform dimensions. Therefore, developing a novel preparation method to solve these problems is of great significance in the production of high-grade packaging paper. Summary of the Invention

[0005] The primary objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a method for preparing polystyrene hollow microspheres with uniform size.

[0006] Another object of the present invention is to provide polystyrene hollow microspheres prepared by the method described above.

[0007] Another object of the present invention is to provide the application of the aforementioned polystyrene hollow microspheres.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing uniformly sized polystyrene hollow microspheres includes the following steps:

[0010] (1) Preparation of polystyrene microspheres

[0011] Ammonium persulfate and polyvinylpyrrolidone were added to a mixed solvent of ethanol and water at a mass ratio of (0.03–0.15):(0.005–0.015) in a volume ratio of (4–9):1. The mixture was stirred until homogeneous to obtain an initiation solution. Styrene was then added at 60–75°C and the mixture was stirred at a speed of 100–600 rpm. After the reaction was completed, the synthesized microspheres were removed, centrifuged, washed, and dried to obtain solid polystyrene microspheres.

[0012] (2) Preparation of polystyrene hollow microspheres

[0013] Polystyrene microspheres were added to a mixed solution of ethanol and water at a volume ratio of (4-8):1, and the mixture was stirred at 70-100°C. After the reaction was completed, the synthesized hollow microspheres were taken out, centrifuged, washed, and dried to obtain polystyrene hollow microspheres. The amount of polystyrene microspheres accounted for 0.001 wt% to 20 wt% of the mixed solution.

[0014] The preferred mass ratio of ammonium persulfate and polyvinylpyrrolidone in step (1) is 0.1:0.01.

[0015] The average molecular weight of the polyvinylpyrrolidone mentioned in step (1) is 58,000 (K29-32).

[0016] The preferred volume ratio of ethanol to water in step (1) is 25:3.

[0017] The amount of mixed solvent used in step (1) is calculated as 0.03 to 0.15 g of ammonium persulfate per 28 ml of mixed solvent; preferably, it is calculated as 0.1 g of ammonium persulfate per 28 ml of mixed solvent.

[0018] In step (1), the time for stirring and mixing evenly is 10 to 20 minutes; preferably 15 minutes.

[0019] The preferred stirring speed in step (1) is 300 rpm.

[0020] The preferred temperature for the stirring reaction in step (1) is 70°C.

[0021] The stirring reaction time in step (1) is 6 to 12 hours; preferably 6 hours.

[0022] The amount of styrene used in step (1) is calculated as 1.6 to 2.8 ml of styrene per 28 ml of mixed solvent; preferably, it is calculated as 2.2 ml of styrene per 28 ml of mixed solvent.

[0023] The centrifugal washing described in steps (1) and (2) is achieved by the following steps: first, repeatedly centrifuging and washing with a solution obtained by mixing ethanol and water, and finally centrifuging and washing with water; preferably, first, repeatedly centrifuging and washing with a solution obtained by mixing ethanol and water at a volume ratio of (1-9):1, and finally centrifuging and washing with water; more preferably, first, repeatedly centrifuging and washing with a solution obtained by mixing ethanol and water at a volume ratio of 1:1, and finally centrifuging and washing with water.

[0024] The drying process described in steps (1) and (2) is performed using an oven.

[0025] The drying conditions described in steps (1) and (2) are: drying at 40-100°C for 5-8 hours; preferably: drying at 60°C for 6 hours.

[0026] The amount of polystyrene microspheres used in step (2) is preferably 0.001 wt% to 18 wt% of the mixed solution; more preferably 0.5 wt% to 18 wt% of the mixed solution; and even more preferably 1.6 wt% of the mixed solution.

[0027] The preferred volume ratio of ethanol to water in step (2) is 5:1.

[0028] The stirring speed in step (2) is 100 rpm to 800 rpm; preferably 300 rpm.

[0029] The preferred temperature for the reaction described in step (2) is 70°C.

[0030] In step (2), the heating reaction time depends on the proportion of polystyrene microspheres in the system and the reaction temperature, which can be adjusted according to the proportion of polystyrene microspheres in the system and the reaction temperature. The reaction time is preferably 6 to 30 hours; more preferably 24 hours.

[0031] A type of uniformly sized polystyrene hollow microsphere is prepared by any of the preparation methods described above.

[0032] The application of the uniformly sized polystyrene hollow microspheres in the preparation of packaging paper.

[0033] A method for preparing packaging paper includes the following steps: uniformly mixed polystyrene hollow microspheres with a coating emulsion, coated onto the surface of paper, and dried to obtain packaging paper.

[0034] One or both of the styrene-acrylic emulsion and acrylic resin emulsion mentioned above.

[0035] The mass ratio of the polystyrene hollow microspheres to the coating emulsion is (1:9) to (6:4); preferably (2:8) to (5:5).

[0036] The paper can be any coated base paper, and its basis weight and thickness can be selected according to actual needs; preferably, it is tracing paper (e.g., basis weight 40 g / m³). 2 (45μm thick tracing paper).

[0037] The coating can be carried out using conventional coating methods in the art; preferably, a doctor blade (sizing stick) is used for coating, and the coating speed is 1m / s to 10m / s (preferably 2m / s to 5m / s; more preferably 3m / s).

[0038] The coating amount on the paper surface is 2-10 g / m². 2 Preferred concentration: 3-6 g / m 2 Further preferred is 3-5 g / m 2 .

[0039] The drying process is carried out using an oven, with the temperature controlled within 50°C.

[0040] A type of packaging paper, prepared by any of the preparation methods described above.

[0041] The present invention has the following advantages and effects compared with the prior art:

[0042] (1) This invention provides a method for preparing polystyrene hollow microspheres with uniform size. No toxic organic solvents or large amounts of toxic chemicals are used in the synthesis process. The preparation process is simple, green and environmentally friendly, and low in cost.

[0043] (2) In this invention, polystyrene hollow microspheres are blended with styrene-acrylic latex and applied to paper coating to prepare paper with high whiteness, high brightness, high opacity, good gloss, waterproof and oil-proof properties. It has excellent light-blocking effect and can be used in the production of high-grade packaging paper. Attached Figure Description

[0044] Figure 1 This is a field emission scanning electron microscope image of the polystyrene microspheres prepared in Comparative Example 1 of the present invention.

[0045] Figure 2 This is a field emission scanning electron microscope image of the polystyrene microspheres prepared in Comparative Example 2 of the present invention.

[0046] Figure 3 This is a field emission scanning electron microscope image of the polystyrene microspheres prepared in Comparative Example 3 of the present invention.

[0047] Figure 4This is a field emission scanning electron microscope image of the polystyrene microspheres prepared in Comparative Example 4 of the present invention.

[0048] Figure 5 This is a field emission scanning electron microscope image of the polystyrene microspheres prepared in Comparative Example 5 of the present invention.

[0049] Figure 6 This is a field emission scanning electron microscope image of the polystyrene microspheres prepared in Comparative Example 6 of the present invention.

[0050] Figure 7 This is a transmission scanning electron microscope image of the polystyrene microspheres prepared in Comparative Example 7 of the present invention.

[0051] Figure 8 This is a field emission scanning electron microscope image of the base paper in Comparative Example 8 of the present invention.

[0052] Figure 9 These are field emission scanning electron microscope (FESEM) and transmission scanning electron microscope (TEM) images of the polystyrene microspheres prepared in Example 1 of this invention; wherein, A is a field emission scanning electron microscope (FESEM) image; and B is a transmission scanning electron microscope (TEM) image.

[0053] Figure 10 This is a field emission scanning electron microscope image of the polystyrene microspheres prepared in Example 2 of the present invention.

[0054] Figure 11 This is a field emission scanning electron microscope image of the polystyrene microspheres prepared in Example 3 of the present invention.

[0055] Figure 12 These are field emission scanning electron microscope (FESEM) and transmission scanning electron microscope (TEM) images of the polystyrene hollow microspheres prepared in Example 4 of this invention; wherein, A is a field emission scanning electron microscope (FESEM) image; and B is a transmission scanning electron microscope (TEM) image.

[0056] Figure 13 These are field emission scanning electron microscope (FESEM) and transmission scanning electron microscope (TEM) images of the polystyrene hollow microspheres prepared in Example 5 of this invention; wherein, A is a field emission scanning electron microscope (FESEM) image; and B is a transmission scanning electron microscope (TEM) image.

[0057] Figure 14 This is a transmission scanning electron microscope image of the polystyrene hollow microspheres prepared in Example 6 of the present invention.

[0058] Figure 15 This is a field emission scanning electron microscope image of the polystyrene hollow microspheres prepared in Example 7 of the present invention.

[0059] Figure 16 This is a field emission scanning electron microscope image of the polystyrene hollow microspheres prepared in Example 8 of the present invention.

[0060] Figure 17This is a field emission scanning electron microscope (FEM) image of the base paper coated with polystyrene hollow microspheres in Example 9 of the present invention (sizing amount: 5 g / m²). 2 ). Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be understood that the specific embodiments described are only used to explain this application and are not intended to limit this application.

[0062] Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Test methods in the following examples that do not specify specific experimental conditions are generally performed under conventional experimental conditions or according to the manufacturer's recommended experimental conditions. Unless otherwise specified, the reagents and raw materials used in this invention are commercially available.

[0063] To more clearly illustrate the method provided by the present invention, the following embodiments and comparative examples are provided. The testing methods for various indicators of the hollow microspheres with light-shielding properties prepared in the following embodiments and comparative examples are as follows:

[0064] 1. Field emission scanning electron microscopy: Provides a direct visual analysis of the microscopic morphology and size of materials.

[0065] 2. Transmission scanning electron microscopy: Allows for direct analysis of the internal structure of materials, especially cavity structures.

[0066] 3. According to the national standard GB / T 7974-2013, the whiteness, brightness, and opacity of the paper were measured using an L&W whiteness meter. The gloss of the paper was measured using a Novo-Gloss™ gloss meter at a measurement angle of 70°.

[0067] 4. The oil resistance of the paper samples was tested according to the standard TAPPI 559cm-12. Castor oil, toluene, and n-heptane were mixed in a certain proportion to form a test solution with an oil resistance rating of 1-12. The higher the Kit value of the paper, the better its oil resistance.

[0068] 5. The water resistance of paper can be tested using the Cobb value. The lower the Cobb value, the better the water resistance of the paper. This experiment was conducted according to GB / T 1540-2002 standard, using a paper and paperboard absorbency tester (J-CBY100) to test the Cobb value of the paper. The water resistance performance mentioned in the examples and comparative examples in this article is represented by Cobb60.

[0069] Example 1

[0070] This embodiment provides a simple method for preparing polystyrene microspheres with uniform size, specifically including the following steps:

[0071] (1) Preparation of initiation solution: Take 0.1g ammonium persulfate (Maclean) and 0.01g polyvinylpyrrolidone (average molecular weight of 58000) (Maclean), place them in a mixture of 25ml ethanol and 3ml water, stir continuously for 15 minutes and then pour into a round bottom flask.

[0072] (2) One-pot preparation of polystyrene microspheres: Place the above round-bottom flask in a 70°C water bath, add 2.2 ml of styrene (Maclean), and continue heating and stirring for 6 hours at a stirring speed of 300 rpm.

[0073] (3) Purification of microspheres: The synthesized microspheres were taken out and repeatedly washed by centrifugation with an ethanol / water system (volume ratio of 1:1), and finally washed by centrifugation with water. The centrifuged product was placed in a 60℃ oven and dried for 6 hours to obtain polystyrene microspheres with uniform size.

[0074] Example 2

[0075] By changing the amount of ammonium persulfate added, the 0.1g in step (1) of Example 1, "take 0.1g of ammonium persulfate", is changed to 0.03g. The remaining steps are the same as in Example 1, and polystyrene microspheres with uniform size are prepared.

[0076] Example 3

[0077] By changing the amount of ammonium persulfate added, the 0.1g in step (1) of Example 1, "take 0.1g of ammonium persulfate", is changed to 0.15g. The remaining steps are the same as in Example 1, and polystyrene microspheres with uniform size are prepared.

[0078] Example 4

[0079] This embodiment provides a simple method for preparing polystyrene hollow microspheres with uniform size, specifically including the following steps:

[0080] (1) Take 0.3g of the polystyrene microspheres obtained in Example 1 and place them in a round-bottom flask containing a composite system of ethanol and water, wherein the ethanol is 50ml and the water is 10ml (volume ratio of ethanol to water is 5:1). Then heat and stir the round-bottom flask at 70°C for 24 hours at a speed of 300rpm.

[0081] (2) Purification of hollow microspheres: The synthesized hollow microspheres were taken out and repeatedly centrifuged and washed with an ethanol / water system (volume ratio of 1:1), and finally washed with water. The centrifuged product was placed in a 60℃ oven and dried for 6 hours to obtain polystyrene hollow microspheres with uniform size.

[0082] Example 5

[0083] By changing the amount of polystyrene microspheres added, the 0.3g in step (1) of Example 4, "take 0.3g and place it in a round-bottom flask containing a composite system of ethanol and water", was changed to 1g. The remaining steps were the same as in Example 2, and hollow polystyrene microspheres with uniform size were prepared.

[0084] Example 6

[0085] By changing the amount of polystyrene microspheres added, the 0.3g in step (1) of Example 4, "take 0.3g and place it in a round-bottom flask containing a composite system of ethanol and water", was changed to 10.8g. The remaining steps were the same as in Example 2, and hollow polystyrene microspheres with uniform size were prepared.

[0086] Example 7

[0087] By changing the reaction time in the preparation process of hollow microspheres, the 24 hours in step (1) of Example 4, "then heat and stir the round bottom flask at 70°C for 24 hours", was changed to 6 hours. The remaining steps were the same as in Example 2, and uniformly sized polystyrene hollow microspheres were prepared.

[0088] Example 8

[0089] By changing the reaction time in the preparation process of hollow microspheres, the 24 hours in step (1) of Example 4, "then heat and stir the round bottom flask at 70°C for 24 hours", was changed to 30 hours. The remaining steps were the same as in Example 2, and uniformly sized polystyrene hollow microspheres were prepared.

[0090] Example 9

[0091] (1) The polystyrene hollow microspheres obtained in Example 5 were thoroughly mixed with styrene-acrylic latex (neutralized BS-104, 50wt%) at a mass ratio of 2:8, and then coated onto base paper (commercially available tracing paper, 40g / m²) using a sizing stick at a speed of 3m / s. 2 The surface area (45μm) was controlled with a sizing amount of 3g / m. 2 and 5g / m2 Place it in an oven to dry thoroughly (temperature controlled below 50℃) to obtain packaging paper.

[0092] Comparative Example 1

[0093] By changing the preparation conditions of polystyrene microspheres, "0.1g ammonium persulfate" in step (1) of Example 1 was replaced with "0.18g ammonium persulfate", and the remaining steps were the same as those in Example 1, polystyrene microspheres with non-uniform size were obtained.

[0094] Comparative Example 2

[0095] The preparation conditions for polystyrene microspheres were changed by replacing "0.1g ammonium persulfate" in step (1) of Example 1 with "0.01g ammonium persulfate". The remaining steps were the same as those in Example 1, resulting in polystyrene microspheres with non-uniform sizes.

[0096] Comparative Example 3

[0097] The preparation conditions of polystyrene microspheres were changed by replacing "0.01g polyvinylpyrrolidone" in step (1) of Example 1 with "0.02g polyvinylpyrrolidone". The remaining steps were the same as those in Example 1, resulting in polystyrene microspheres with non-uniform size.

[0098] Comparative Example 4

[0099] By changing the preparation conditions of polystyrene microspheres, the phrase "placed in a mixture of 25 ml ethanol and 3 ml water" in step (1) of Example 1 was changed to "a mixture of 22 ml ethanol and 6 ml water". The remaining steps were the same as those in Example 1, resulting in polystyrene microspheres with non-uniform size.

[0100] Comparative Example 5

[0101] The preparation conditions for polystyrene microspheres were changed by replacing "placed in a 70°C water bath" in step (2) of Example 1 with "placed in a 90°C oil bath". The remaining steps were the same as those in Example 1, resulting in polystyrene microspheres with non-uniform sizes.

[0102] Comparative Example 6

[0103] By changing the preparation conditions of polystyrene microspheres, the "stirring speed of 300 rpm" in step (2) of Example 1 was changed to "stirring speed of 800 rpm", and the remaining steps were the same as the preparation steps of Example 1, polystyrene microspheres with non-uniform size were obtained.

[0104] Comparative Example 7

[0105] By changing the preparation conditions of polystyrene hollow microspheres, the 0.3g in step (1) of Example 2, "take 0.3g and place it in a round-bottom flask containing a composite system of ethanol and water", was changed to 15g. The remaining steps were the same as in Example 2, but the hollow microsphere structure could not be obtained.

[0106] Comparative Example 8

[0107] The base paper (same as in Example 9) is not treated.

[0108] Comparative Example 9

[0109] The polystyrene microspheres obtained in Comparative Example 1 were thoroughly mixed with styrene-acrylic latex at a mass ratio of 2:8, and then applied to the surface of the base paper (same as in Example 9) using a sizing stick at a speed of 3 m / s, with the sizing amount controlled at 3 g / m. 2 and 5g / m 2 Place it in an oven to dry thoroughly (temperature controlled below 50℃) to obtain packaging paper.

[0110] Comparative Example 10

[0111] The polystyrene microspheres obtained in Comparative Example 3 were thoroughly mixed with styrene-acrylic latex at a mass ratio of 2:8, and then applied to the surface of the base paper (same as in Example 9) using a sizing stick at a speed of 3 m / s, with the sizing amount controlled at 3 g / m. 2 and 5g / m 2 Place it in an oven to dry thoroughly (temperature controlled below 50℃) to obtain packaging paper.

[0112] Effect Example

[0113] The products prepared in Examples 1-9 and Comparative Examples 1-10 were characterized and tested:

[0114] 1. Field emission scanning electron microscopy and transmission scanning electron microscopy analysis:

[0115] Field emission scanning electron microscope (FEM) images and transmission electron microscope (TEM) images of different comparative examples and embodiments are as follows: Figures 1 to 17 As shown.

[0116] Examples 1, 2, and 3 successfully synthesized polystyrene microspheres with uniform size. However, in Comparative Example 1, the amount of ammonium persulfate added was too high; in Comparative Example 2, the amount of ammonium persulfate added was too low; in Comparative Example 3, the amount of polyvinylpyrrolidone added was too high; in Comparative Example 4, the proportion of water in the reaction system was too high; in Comparative Example 5, the reaction temperature was too high; and in Comparative Example 6, the stirring was too vigorous. The synthesis reaction conditions of the polystyrene microspheres in the above comparative examples were all outside the set range, and it was impossible to synthesize polystyrene microspheres with uniform size. This directly led to the inability to synthesize polystyrene hollow microspheres with uniform size in the subsequent process (for ease of comparison, the differences between Comparative Examples 1-6 and Examples 1-3 of the present invention are listed in Table 1 below).

[0117] Table 1

[0118]

[0119]

[0120] Based on the polystyrene microspheres synthesized in Example 1, uniformly sized hollow polystyrene microspheres can be synthesized further. Examples 4, 5, and 6 are hollow polystyrene microspheres synthesized with different amounts of polystyrene microspheres, exhibiting uniform size and inner diameter. It is noted that the increased microsphere size indicates the formation of a hollow structure. In Comparative Example 7, the amount of polystyrene microspheres added exceeded the preset range, preventing the formation of a hollow structure. Examples 7 and 8 show the microscopic morphology of microspheres at different reaction times at 70°C; the increased microsphere size indicates the formation of a hollow structure with uniform size (for ease of comparison, the differences between Examples 4-8 and Comparative Example 7 are listed in Table 2 below).

[0121] Table 2

[0122]

[0123] Comparative Example 8 is an uncoated base paper. Its microstructure reveals numerous pores on its surface, which is highly detrimental to the waterproof and oil-resistant design of the packaging paper. Example 9 is the prepared packaging paper. Its microstructure shows that microspheres and latex form a dense film on the paper, which is beneficial for the paper's waterproof and oil-resistant properties.

[0124] 2. Optical properties of paper:

[0125] Table 3 shows the changes in the optical properties of the paper after coating the base paper with a single styrene-acrylic latex (same as in Example 9). When the sizing amount is 5 g / m²... 2 At that time, its whiteness, brightness, and opacity were all lower than the original paper, while the gloss increased by 50.53%, which would give users a dazzling feeling. Tables 4 and 5 show the coating effect of the paper after being compounded with styrene-acrylic latex in Comparative Examples 1 and 3 (i.e., Comparative Examples 9 and 10). As the amount of sizing increases, the whiteness, brightness, and opacity of the paper increase slowly, while the gloss remains high. Table 6 shows the optical performance of the paper coated after being compounded with styrene-acrylic latex in Example 5 (i.e., Example 9). As the amount of sizing increases, the whiteness, brightness, and opacity of the paper are comprehensively improved, and the gloss increases only slightly, so as not to cause strong discomfort to users. Therefore, the paper based on polystyrene hollow microsphere coating has a higher texture.

[0126] Table 3 Effect of Single Styrene-Acrylic Latex Coating

[0127] <![CDATA[施胶量(g / m 2 )]]> Whiteness (%) brightness(%) Opacity (%) Gloss (%) 0 56.55 79.48 69.94 11.67 5 52.73 77.28 66.84 50.53

[0128] Table 4. Coating effect of polystyrene microspheres (Comparative Example 1) and styrene-acrylic latex composite.

[0129] <![CDATA[施胶量(g / m 2 )]]> Whiteness (%) brightness(%) Opacity (%) Gloss (%) 0 56.55 79.48 69.94 11.67 3 56.74 79.48 70.34 30.54 5 57.31 80.42 71.75 40.56

[0130] Table 5. Coating effect of polystyrene microspheres (Comparative Example 3) and styrene-acrylic latex composite.

[0131] <![CDATA[Size application amount (g / m 2 )]]> Whiteness (%) brightness(%) Opacity (%) Gloss (%) 0 56.55 79.48 69.94 11.67 3 56.94 79.52 70.42 29.43 5 57.36 80.52 71.94 38.43

[0132] Table 6. Coating effect of polystyrene hollow microspheres (Example 5) and styrene-acrylic latex composite coating

[0133] <![CDATA[施胶量(g / m 2 )]]> Whiteness (%) brightness(%) Opacity (%) Gloss (%) 0 56.55 79.48 69.94 11.67 3 57.34 80.42 71.56 22.00 5 59.80 81.24 74.18 27.43

[0134] 3. Water and oil repellency of the paper:

[0135] Table 7 shows the oil-repellent properties of the packaging paper prepared in Example 9. As the sizing amount increases, the oil-repellent effect of the packaging paper rapidly improves. When the sizing amount is 3 g / m², the oil-repellent effect reaches its maximum. 2 At that time, the paper's oil resistance rating reached level 10, fully meeting daily use needs. When the sizing amount was 5g / m²... 2 At that time, the oil resistance rating of the packaging paper reached the maximum level of 12. Table 8 shows the waterproof performance of Example 9. As the amount of sizing agent increased, the Cobb60 value decreased rapidly, indicating a significant improvement in waterproof effect. Based on the above performance, the coated paper based on polystyrene hollow microspheres, with its appearance and barrier effect, is suitable for the preparation of high-grade packaging paper.

[0136] Table 7. Oil-resistant properties of polystyrene hollow microspheres and styrene-acrylic latex composite coated paper (Example 9)

[0137] <![CDATA[施胶量(g / m 2 )]]> Oil resistance rating 0 0 3 10 5 12

[0138] Table 8 Waterproof performance of polystyrene hollow microspheres and styrene-acrylic latex composite coated paper (Example 9)

[0139] <![CDATA[施胶量(g / m 2 )]]> <![CDATA[Cobb60(g / m 2 )]]> 0 12.43 3 4.45 5 1.12

[0140] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing uniformly sized polystyrene hollow microspheres, characterized in that, Includes the following steps: (1) Preparation of polystyrene microspheres Ammonium persulfate and polyvinylpyrrolidone were added to a mixed solvent of ethanol and water at a mass ratio of 0.03–0.15:0.005–0.015 in a volume ratio of 4–9:

1. The mixture was stirred until homogeneous to obtain an initiation solution. Styrene was then added at 60–75°C and the mixture was stirred at a speed of 100–600 rpm. After the reaction was completed, the synthesized microspheres were removed, centrifuged, washed, and dried to obtain polystyrene microspheres. (2) Preparation of polystyrene hollow microspheres Polystyrene microspheres were added to a mixed solution of ethanol and water at a volume ratio of 4–8:1 and stirred at 70–100°C. After the reaction was completed, the synthesized hollow microspheres were taken out, centrifuged, washed, and dried to obtain polystyrene hollow microspheres. The amount of polystyrene microspheres accounted for 0.001 wt%–20 wt% of the mixed solution.

2. The method according to claim 1, characterized in that: The average molecular weight of the polyvinylpyrrolidone mentioned in step (1) is 58,000; The amount of mixed solvent used in step (1) is calculated based on 0.03 to 0.15 g of ammonium persulfate per 28 ml of mixed solvent. The amount of styrene used in step (1) is calculated as 1.6 to 2.8 ml of styrene per 28 ml of mixed solvent.

3. The method according to claim 1, characterized in that: The mass ratio of ammonium persulfate and polyvinylpyrrolidone mentioned in step (1) is 0.1:0.01; The volume ratio of ethanol to water in step (1) is 25:3; The amount of polystyrene microspheres used in step (2) is 0.001 wt% to 18 wt% of the mixed solution; The volume ratio of ethanol to water in step (2) is 5:

1.

4. The method according to claim 1, characterized in that: The centrifugal washing described in steps (1) and (2) is achieved by the following steps: first, repeatedly centrifuging and washing with a solution obtained by mixing ethanol and water, and finally centrifuging and washing with water; further, first, repeatedly centrifuging and washing with a solution obtained by mixing ethanol and water at a volume ratio of 1 to 9:1, and finally centrifuging and washing with water; and even further, first, repeatedly centrifuging and washing with a solution obtained by mixing ethanol and water at a volume ratio of 1:1, and finally centrifuging and washing with water.

5. The method according to claim 1, characterized in that: In step (1), the time for stirring and mixing evenly is 10 to 20 minutes; The stirring reaction time described in step (1) is 6 to 12 hours; The drying conditions described in steps (1) and (2) are 40–100°C for 5–8 hours; The stirring speed mentioned in step (2) is 100 rpm to 800 rpm; The reaction time described in step (2) is 6 to 30 hours.

6. A type of uniformly sized hollow polystyrene microsphere, characterized in that: It is prepared by the method described in any one of claims 1 to 5.

7. The application of the uniformly sized polystyrene hollow microspheres of claim 6 in the preparation of packaging paper.

8. A method for preparing packaging paper, characterized in that, The specific steps are as follows: uniformly sized polystyrene hollow microspheres as described in any one of claims 1 to 5 are mixed with a coating emulsion, coated onto the surface of paper, and dried to obtain packaging paper.

9. The method according to claim 8, characterized in that: One or both of the styrene-acrylic emulsion and acrylic resin emulsion mentioned above; The mass ratio of the polystyrene hollow microspheres to the coating emulsion is 1:9 to 6:4; The coating amount on the paper surface is 2-10 g / m². 2 .

10. A type of packaging paper, characterized in that: It is prepared by the preparation method described in claim 8 or 9.

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