Wollastonite-starch slurry for paper surface sizing as well as preparation method and application of wollastonite-starch slurry

Abstract

The invention provides wollastonite-starch slurry for paper surface sizing as well as a preparation method and application of the wollastonite-starch slurry, and relates to the technical field of inorganic non-metallic materials. The preparation method of the wollastonite-starch slurry comprises the following steps: heating wollastonite particles, spraying the wollastonite particles with water, drying the wollastonite particles, and carrying out dry grinding to obtain wollastonite powder; mixing the wollastonite powder with water and a grinding aid, and performing wet grinding to obtain wollastonite slurry; and mixing and grinding the wollastonite slurry, the gelatinized starch liquid and a cationic modifier to obtain the wollastonite-starch slurry for paper surface sizing. After the wollastonite is subjected to high-temperature treatment, associated organic matters in the raw ore can be removed, and the purity is improved; the high-temperature wollastonite has a large number of cracks when encountering water, the grinding efficiency can be improved, and the needle-shaped structure of the wollastonite can be kept. The wollastonite-starch slurry prepared by the method is applied to surface sizing of paper, and the ring crush compression resistance and tensile strength of the paper can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic materials, in particular to a wollastonite-starch slurry for paper surface sizing, and a preparation method and application thereof. Background Art

[0002] In the papermaking industry, in addition to pulp board, fillers and starch are important components of raw materials. Among them, starch is an important functional additive in the papermaking industry and is widely used in multiple production links. The main applications include the following: 1. As a reinforcing agent (internal addition), starch combines with cellulose through hydrogen bonds, strengthening the bonding force between fibers, improving the tensile strength, burst resistance and folding resistance of paper, reducing the loss of fine fibers, and improving the uniformity of the finished paper; 2. Surface sizing, after starch is gelatinized, it is coated on the surface of paper and processed through a size press or membrane transfer sizer to improve the smoothness and gloss of the paper surface, enhance the surface strength, and reduce powder loss and hair pulling during the printing process; 3. Coating processing (pigment-coated paper), as an adhesive, it is used in combination with synthetic latex to improve the uniformity and printability of the coating layer and reduce costs. In short, starch has multiple functions in papermaking, such as reinforcement, sizing, coating and wet-end control, and is an indispensable key raw material in traditional and modern papermaking processes. However, starch is a food and is relatively expensive. In addition, the use of starch as sizing agent will generate a large amount of anionic waste during the waste paper recycling process, making wastewater treatment more difficult and requiring the addition of expensive anionic waste capture agents.

[0003] Wollastonite is a major new functional inorganic non-metallic filler material in the field of fine chemicals. Due to its unique needle-like structure, it has special uses in many fields. Due to the high whiteness and needle-like structure of wollastonite, the opacity, hiding power and printability of paper can be significantly improved. It is especially suitable for cultural paper, coated paper and other paper types with high optical performance requirements. Wollastonite can replace part of plant fibers in papermaking, reduce the use of wood, and comply with the concept of green environmental protection. In the existing technology, wollastonite and starch are often used together in the papermaking industry. However, the existing technology only uses mechanical force and simple chemical effects to prepare wollastonite-modified starch. It is impossible to achieve a close combination between organic starch and inorganic non-metallic powder wollastonite, which seriously limits the performance of the product. However, how to give full play to the needle-like structural characteristics of wollastonite, how to develop an enhanced modification scheme with a close combination of starch and wollastonite, and apply it to paper surface sizing are problems that need to be solved urgently by those skilled in the art. Summary of the Invention

[0004] The purpose of the present invention is to provide a wollastonite-starch slurry for paper surface sizing and its preparation method and application, so as to solve the problem in the prior art that organic starch and inorganic non-metallic powder wollastonite cannot be tightly combined by only using mechanical force and simple chemical effects.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a wollastonite-starch slurry for paper surface sizing, comprising the following steps:

[0007] 1) heating wollastonite particles and then spraying them with water, drying the wollastonite particles and then dry-grinding them to obtain wollastonite powder;

[0008] 2) mixing the wollastonite powder with water and a grinding aid and performing wet grinding to obtain a wollastonite slurry;

[0009] 3) mixing and grinding the wollastonite slurry, gelatinized starch solution, and a cationic modifier to obtain a wollastonite-starch slurry for paper surface sizing;

[0010] The preparation method of the gelatinized starch liquid comprises heating the starch liquid, adding a temperature-resistant amylase, and then obtaining the gelatinized starch liquid.

[0011] Preferably, the particle size of the wollastonite particles in step 1) is 3 to 6 cm;

[0012] The content of calcium silicate in the wollastonite ore is ≥95%;

[0013] The heating is to make the temperature of the wollastonite ore reach 700-850°C.

[0014] Preferably, the particle size of the wollastonite powder in step 1) is 325-425 mesh.

[0015] Preferably, the amount of the grinding aid added in step 2) is 0.5-0.8% of the mass of the wollastonite powder;

[0016] The solid content of the wollastonite slurry is 45-55%;

[0017] The particle size of the wollastonite in the wollastonite slurry is D97=6-8 μm.

[0018] Preferably, the grinding aid in step 2) includes one or more of sodium polyacrylate, sodium hexametaphosphate, and sodium dodecylbenzenesulfonate.

[0019] Preferably, the mass ratio of the wollastonite slurry to the gelatinized starch solution in step 3) is 1:8-10;

[0020] The mass concentration of the gelatinized starch solution is 5-7%;

[0021] The amount of the cationic modifier added is 0.2-0.3% of the mass of wollastonite in the wollastonite slurry;

[0022] The cationic modifier is 2,3-epoxypropyltrimethylammonium chloride and / or sodium secondary alkyl sulfonate.

[0023] Preferably, the temperature of the starch solution after heating is 45-55°C, and the viscosity of the starch solution is 4-6 Pa·s when the temperature-resistant amylase is added;

[0024] The viscosity of the gelatinized starch liquid is 7-9 Pa·s.

[0025] Preferably, the particle size of the wollastonite in the wollastonite-starch slurry for paper surface sizing is D97=4-5 μm.

[0026] The present invention provides a wollastonite-starch slurry for paper surface sizing, which is prepared by the above-mentioned method for preparing the wollastonite-starch slurry for paper surface sizing.

[0027] The present invention also provides an application of the wollastonite-starch slurry for paper surface sizing in papermaking, and the application method is as follows:

[0028] Applying wollastonite-starch slurry on the surface of paper for surface sizing;

[0029] The coating rate is 6-7 m / min, and the coating amount is 2.5-3.5 g / m 2 .

[0030] The present invention has at least the following beneficial effects:

[0031] 1. After high temperature treatment, wollastonite can not only remove the organic matter associated with the original ore and improve its purity, but also make the heat-treated original ore appear a large number of cracks when it comes into contact with water, thereby improving the grinding efficiency and better maintaining the original needle-like structure of wollastonite.

[0032] 2. A sizing agent prepared by further mixing wollastonite modified with cationic starch with cationic starch can reduce the problem of excessive anionic waste in wastewater during paper recycling, which increases the difficulty and cost of treatment.

[0033] 3. Applying wollastonite-starch slurry to the surface sizing of paper can improve the ring crush strength and tensile strength of paper. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing a wollastonite-starch slurry for paper surface sizing, comprising the following steps:

[0035] 1) heating wollastonite particles and then spraying them with water, drying the wollastonite particles and then dry-grinding them to obtain wollastonite powder;

[0036] 2) mixing the wollastonite powder with water and a grinding aid and performing wet grinding to obtain a wollastonite slurry;

[0037] 3) mixing and grinding the wollastonite slurry, starch solution, and cationic modifier to obtain wollastonite-starch slurry for paper surface sizing;

[0038] The preparation method of the gelatinized starch liquid comprises heating the starch liquid, adding a temperature-resistant amylase, and then obtaining the gelatinized starch liquid.

[0039] In the present invention, the particle size of the wollastonite particles in step 1) is 3 to 6 cm, preferably 3.5 to 5.5 cm, more preferably 4 to 5 cm, and even more preferably 4.2 to 5.8 cm.

[0040] In the present invention, the content of calcium silicate in the wollastonite ore is ≥95%, 95-99.5%, more preferably 96-99%, and even more preferably 97-98%.

[0041] In the present invention, the heating is to make the temperature of the wollastonite ore reach 700-850°C, preferably 720-820°C, more preferably 750-800°C, and even more preferably 760-780°C.

[0042] In the present invention, the particle size of the wollastonite powder in step 1) is 325-425 mesh, preferably 340-410 mesh, more preferably 350-400 mesh, and even more preferably 370-380 mesh.

[0043] In the present invention, the amount of the grinding aid added in step 2) is 0.5-0.8% of the mass of the wollastonite powder, preferably 0.55-0.75%, more preferably 0.6-0.7%, and even more preferably 0.65%.

[0044] In the present invention, the grinding agent in step 2) is preferably added in part before grinding, with the remainder added during the grinding process. The mass ratio of the two parts of grinding agent is 1:1. The staged addition of the additive can better control particle dispersion and grinding efficiency during the grinding process. The additive plays different roles at different stages. The additive added in the early stage can prevent particle agglomeration, while the additive added in the later stage can further refine the particles, improving the fineness and uniformity of the product.

[0045] In the present invention, the solid content of the wollastonite slurry is 45-55%, preferably 47-53%, and more preferably 48-50%.

[0046] In the present invention, the particle size of the wollastonite in the wollastonite slurry is D97=6-8 μm, preferably D97=6.2-7.8 μm, more preferably D97=6.5-7.5 μm, and even more preferably D97=6.8-7.2 μm.

[0047] In the present invention, the grinding aid in step 2) includes one or more of sodium polyacrylate, sodium hexametaphosphate, and sodium dodecylbenzenesulfonate.

[0048] During the grinding process, the surface of wollastonite becomes negatively charged due to the action of the grinding aid. Then, when it is co-blended with the cationic starch solution and ground, the surface charges of wollastonite and starch are opposite, which makes it easier for the cationic starch and wollastonite to combine in the later co-blending and grinding modification process. Compared with the wollastonite-modified starch prepared by only using mechanical force and simple chemical effects, the combination cannot be tighter.

[0049] In the present invention, the mass ratio of the wollastonite slurry to the starch solution in step 3) is 1:8-10, preferably 1:8.5-9.5, more preferably 1:8.8-9.2, and more preferably 1:9.

[0050] In the present invention, the mass concentration of the starch solution is 5-7%, preferably 5.5-6.5%, more preferably 5.8-6.8%, and even more preferably 6%.

[0051] In the present invention, the amount of the cationic modifier added is 0.2-0.3% of the mass of the wollastonite in the wollastonite slurry, preferably 0.22-0.28%, and more preferably 0.25%.

[0052] In the present invention, the cationic modifier is 2,3-epoxypropyltrimethylammonium chloride and / or sodium secondary alkyl sulfonate.

[0053] In the present invention, the temperature of the starch liquid after heating is 45-55°C, preferably 47-53°C, and more preferably 50°C; the viscosity of the starch liquid when the temperature-resistant amylase is added is 4-6 Pa·s, preferably 4.5-5.5 Pa·s, more preferably 4.8-5.2 Pa·s, and more preferably 5 Pa·s.

[0054] In the present invention, the viscosity of the gelatinized starch liquid is 7 to 9 Pa·s, preferably 7.5 to 8.5 Pa·s, more preferably 7.8 to 8.2 Pa·s, and even more preferably 8 Pa·s.

[0055] Starch begins to gelatinize at 60-70°C, so the first heating to 45-55°C can disperse the starch granules, making it easier to gelatinize in the subsequent heating process.

[0056] In the present invention, the particle size of the wollastonite in the wollastonite-starch slurry for paper surface sizing is D97=4-5 μm, preferably D97=4.2-4.8 μm, and more preferably D97=4.5 μm.

[0057] The present invention provides a wollastonite-starch slurry for paper surface sizing, which is prepared by the above-mentioned method for preparing the wollastonite-starch slurry for paper surface sizing.

[0058] The present invention also provides an application of the wollastonite-starch slurry for paper surface sizing in papermaking, and the application method is as follows:

[0059] Applying wollastonite-starch slurry on the surface of paper for surface sizing;

[0060] The coating rate is 6-7 m / min, preferably 6.2-6.8 m / min, more preferably 6.5 m / min, and the coating amount is 2.5-3.5 g / m 2 , preferably 2.7 to 3.3 g / m 2 , more preferably 3g / m 2 .

[0061] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0062] Example 1

[0063] High-purity wollastonite ore with a calcium silicate content of 95% is selected as raw material, and is coarsely broken into wollastonite particles with a particle size of 3 to 6 cm by a crusher. The wollastonite particles are transported to a high-temperature furnace, heated to 800°C, and then quickly sprayed with water to cause cracks in the high-temperature stones when exposed to water. The wollastonite, which has been subjected to high-temperature cooling treatment, is dried at 50°C for 0.5 h and then transported to a ceramic-lined horizontal ball mill. The grinding media (zirconia balls) and material account for 40% of the entire cavity and are ground into 400-mesh wollastonite powder. 1.5 tons of wollastonite powder are mixed with water and 52.5 kg of sodium polyacrylate to form a slurry with a solid content of 50%. The slurry is transported to a ceramic-lined vertical wet stirred mill and wet-processed ultrafine grinding is performed to a slurry particle size D97 of 8 μm. The remaining sodium polyacrylate grinding aid is added, and the total amount of grinding aid is 0.7% of the mass of the wollastonite powder. Grinding is continued until the D97 reaches 6 μm to obtain a wollastonite slurry.

[0064] 6 kg of starch (Jiangxi Boda Chemical, whiteness 83%, pH 7) was mixed with water to prepare a starch solution with a mass concentration of 6%. The solution was heated at 45°C for the first time until the viscosity of the starch solution reached 5 Pa·s. Then, 240 g of temperature-resistant amylase (purchased from Shengxia Group, model: Xiasheng FDY-2215) was added and continued to heat until the viscosity reached 8 Pa·s to obtain a gelatinized starch solution.

[0065] 100 L of a cationic gelatinized starch solution having a viscosity of 8 Pa·s was added to 2000 L of the above-mentioned wollastonite slurry and continued grinding. During the grinding process, a 50% by mass concentration of sodium secondary alkyl sulfonate (Hostapur SAS60) solution was added dropwise. The amount of sodium secondary alkyl sulfonate added was 0.2% by mass of the wollastonite powder. The wollastonite in the slurry was ground until the particle size of the wollastonite was D97 = 4 μm, thereby obtaining a wollastonite-starch slurry for paper surface sizing.

[0066] Example 2

[0067] High-purity wollastonite ore with a calcium silicate content of 95% is selected as raw material. It is crushed into 3-6 cm wollastonite particles by a crusher, transported to a high-temperature furnace, heated to 750°C, and then quickly sprayed with water to cause cracks to appear in the high-temperature stone when it comes into contact with water. The wollastonite after high-temperature cooling treatment is dried at 50°C for 0.5 hours and then transported to a ceramic-lined horizontal ball mill. The grinding media (wear-resistant zirconia balls) and the material account for 40% of the entire cavity. It is ground into 40 0 mesh wollastonite powder, 1.5 tons of wollastonite powder and water, 45Kg of sodium dodecylbenzene sulfonate are formulated into a slurry with a solid content of 45%, the slurry is transported to a vertical wet stirred mill lined with ceramic treatment, and wet ultrafine grinding is carried out to the slurry particle size D97 reaches 7μm, the remaining sodium dodecylbenzene sulfonate grinding aid is added, the total amount of grinding aid is 0.6% of the mass of the wollastonite powder, and grinding is continued until D97 reaches 6μm to obtain a wollastonite slurry.

[0068] 7 kg of starch was mixed with water to prepare a starch solution with a mass concentration of 7%. The solution was heated at 50°C for the first time until the viscosity of the starch solution reached 5 Pa·s. Then, 280 g of temperature-resistant amylase was added and the solution was heated again until the viscosity reached 7 Pa·s to obtain a gelatinized starch solution.

[0069] 100 L of cationic gelatinized starch liquid with a viscosity of 7 Pa·s was added to 2000 L of the above-mentioned wollastonite slurry and continued grinding. During the grinding process, a 50% mass concentration of 2,3-epoxypropyltrimethylammonium chloride solution was added dropwise, and the amount of 2,3-epoxypropyltrimethylammonium chloride added was 0.3% of the mass of the wollastonite powder. The wollastonite in the slurry was ground until the particle size of the wollastonite was D97 = 4 μm, thereby obtaining a wollastonite-starch slurry for paper surface sizing.

[0070] Comparative Example 1

[0071] Selecting calcium silicate content is that 96% high-purity wollastonite ore is a raw material, by the coarse broken wollastonite particle diameter of crusher at 3~6cm size, be transported in the horizontal ball mill of lining ceramics, grinding medium (wear-resistant zirconium oxide ball) and material account for 40% of whole cavity, be ground into 400 purpose wollastonite powder, 1.5 tons of wollastonite powders and water, 45Kg sodium dodecylbenzene sulfonate are deployed into solid content and be 45% slurry, slurry is transported in the vertical wet stirred mill that lining ceramics handles, carry out wet method ultrafine grinding to slurry particle diameter D97 and reach 7 μ m, add and remain sodium dodecylbenzene sulfonate grinding aid, the grinding aid total consumption is 0.6% of a wollastonite powder quality, continue to grind to D97 and reach 6 μ m, obtain wollastonite slurry.

[0072] 6 kg of starch was mixed with water to prepare a starch solution with a mass concentration of 6%. The solution was heated at 45°C for the first time until the viscosity of the starch solution reached 4 Pa·s. Then, 240 g of temperature-resistant amylase was added and the solution was heated again until the viscosity reached 7 Pa·s to obtain a gelatinized starch solution.

[0073] 100 L of cationic gelatinized starch liquid with a viscosity of 7 Pa·s was added to 2000 L of the above-mentioned wollastonite slurry and continued grinding. During the grinding process, a 50% mass concentration of 2,3-epoxypropyltrimethylammonium chloride solution was added dropwise, and the amount of 2,3-epoxypropyltrimethylammonium chloride added was 0.3% of the mass of the wollastonite powder. The wollastonite in the slurry was ground until the particle size of the wollastonite was D97 = 4 μm, thereby obtaining a wollastonite-starch slurry for paper surface sizing.

[0074] Comparative Example 2

[0075] High-purity wollastonite ore with a calcium silicate content of 95% is selected as raw material. It is crushed into 3-6 cm wollastonite particles by a crusher, transported to a high-temperature furnace, heated to 800°C, and then quickly sprayed with water to cause cracks to appear in the high-temperature stone when it comes into contact with water. The wollastonite after high-temperature cooling treatment is dried at 50°C for 0.5 hours and then transported to a ceramic-lined horizontal ball mill. The grinding media (wear-resistant zirconia balls) and the material account for 40% of the entire cavity. It is ground into 40 0 mesh wollastonite powder, 1.5 tons of wollastonite powder and water, 45Kg of sodium dodecylbenzene sulfonate are formulated into a slurry with a solid content of 45%, the slurry is transported to a vertical wet stirred mill lined with ceramic treatment, and wet ultrafine grinding is carried out to the slurry particle size D97 reaches 7μm, the remaining sodium dodecylbenzene sulfonate grinding aid is added, the total amount of grinding aid is 0.6% of the mass of the wollastonite powder, and grinding is continued until D97 reaches 6μm to obtain a wollastonite slurry.

[0076] 7 kg of starch was mixed with water to prepare a starch solution with a mass concentration of 7%. The solution was heated at 50°C for the first time until the viscosity of the starch solution reached 5 Pa·s. Then, 280 g of temperature-resistant amylase was added and the solution was heated again until the viscosity reached 7 Pa·s to obtain a gelatinized starch solution.

[0077] 100 L of cationic gelatinized starch solution with a viscosity of 7 Pa·s was added to 2000 L of the above wollastonite slurry and ground continuously until the particle size of the wollastonite in the slurry was D97=4 μm, thereby obtaining wollastonite-starch slurry for paper surface sizing.

[0078] Comparative Example 3

[0079] High-purity wollastonite ore with a calcium silicate content of 96% is selected as raw material, which is coarsely crushed into wollastonite particles with a particle size of 3 to 6 cm by a crusher. The wollastonite particles are transported to a high-temperature furnace, heated to 750°C, and then quickly sprayed with water to cause cracks in the high-temperature stones when exposed to water. The wollastonite, which has been subjected to high-temperature cold treatment, is dried at 50°C for 0.5 h and then transported to a ceramic-lined horizontal ball mill. The grinding medium (wear-resistant zirconia balls) and the material account for 40% of the entire cavity and are ground into 400-mesh wollastonite powder. 1.5 tons of the wollastonite powder are mixed with water and 45 kg of sodium dodecylbenzene sulfonate to form a slurry with a solid content of 45%. The slurry is transported to a ceramic-lined vertical wet stirred mill and subjected to wet ultrafine grinding to a slurry particle size D97 of 4 μm to obtain a wollastonite slurry.

[0080] The wollastonite-starch slurry or wollastonite slurry prepared in Examples 1, 2 and Comparative Examples 1 to 3 was applied at a sizing rate of 6 m / min and 3 g / m 2 Unsized base paper was surface-sized with a sizing dosage of 1000 g / m2. The coated paper's performance was tested. Tensile strength was measured according to GB / T 12914-2008, and ring crush strength was measured according to GB / T 2679.8-1995. Grinding energy consumption was measured directly from the grinding equipment. The test results are shown in Table 1.

[0081] Table 1 Energy consumption of dry grinding when preparing wollastonite-starch slurry or wollastonite slurry in Examples 1, 2 and Comparative Examples 1 to 3 and performance test results of paper after sizing

[0082]

[0083]

[0084] In the dry grinding stage of wollastonite, compared with Comparative Example 1, the high-temperature heating followed by cooling treatment in other cases can reduce grinding energy consumption and shorten the grinding time; by comparing the performance of the paper coated with the wollastonite-starch slurry prepared in Examples 1 and 2 with that in Comparative Examples 2 and 3, it can be seen that the cationically modified wollastonite is used for sizing, which can improve the ring crush strength and tensile strength indicators of the paper.

[0085] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing wollastonite-starch slurry for paper surface sizing, characterized in that: The following steps are involved: 1) heating wollastonite particles and then spraying them with water, drying the wollastonite particles and then dry-grinding them to obtain wollastonite powder; 2) mixing the wollastonite powder with water and a grinding aid and performing wet grinding to obtain a wollastonite slurry; 3) mixing and grinding the wollastonite slurry, gelatinized starch solution, and a cationic modifier to obtain a wollastonite-starch slurry for paper surface sizing; The preparation method of the gelatinized starch liquid comprises heating the starch liquid, adding a temperature-resistant amylase, and then obtaining the gelatinized starch liquid.

2. The method for preparing a wollastonite-starch slurry for paper surface sizing according to claim 1, characterized in that: The particle size of the wollastonite particles in step 1) is 3 to 6 cm; The content of calcium silicate in the wollastonite ore is ≥95%; The heating is to make the temperature of the wollastonite ore reach 700-850°C.

3. The method for preparing a wollastonite-starch slurry for paper surface sizing according to claim 2, characterized in that: The particle size of the wollastonite powder in step 1) is 325-425 mesh.

4. The method for preparing a wollastonite-starch slurry for paper surface sizing according to any one of claims 1 to 3, characterized in that: The amount of the grinding aid added in step 2) is 0.5-0.8% of the mass of the wollastonite powder; The solid content of the wollastonite slurry is 45-55%; The particle size of the wollastonite in the wollastonite slurry is D97=6-8 μm.

5. The method for preparing a wollastonite-starch slurry for paper surface sizing according to claim 4, characterized in that: The grinding aid in step 2) includes one or more of sodium polyacrylate, sodium hexametaphosphate, and sodium dodecylbenzenesulfonate.

6. The method for preparing a wollastonite-starch slurry for paper surface sizing according to claim 5, characterized in that: The mass ratio of the wollastonite slurry to the gelatinized starch solution in step 3) is 1:8-10; The mass concentration of the gelatinized starch solution is 5-7%; The amount of the cationic modifier added is 0.2-0.3% of the mass of wollastonite in the wollastonite slurry; The cationic modifier is 2,3-epoxypropyltrimethylammonium chloride and / or sodium secondary alkyl sulfonate.

7. The method for preparing a wollastonite-starch slurry for paper surface sizing according to claim 6, characterized in that: The temperature of the starch solution after heating is 45-55°C, and the viscosity of the starch solution when the temperature-resistant amylase is added is 4-6 Pa·s; The viscosity of the gelatinized starch liquid is 7-9 Pa·s.

8. The method for preparing a wollastonite-starch slurry for paper surface sizing according to claim 7, characterized in that: The particle size of the wollastonite in the wollastonite-starch slurry for paper surface sizing is D97=4-5 μm.

9. Wollastonite-starch slurry for paper surface sizing prepared by the method for preparing wollastonite-starch slurry for paper surface sizing according to any one of claims 1 to 8.

10. Use of the wollastonite-starch slurry for paper surface sizing according to claim 9 in papermaking, characterized in that: The application method is as follows: Applying wollastonite-starch slurry on the surface of paper for surface sizing; The coating rate is 6-7 m / min, and the coating amount is 2.5-3.5 g / m 2 .

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