Preparation method of high-concentration cationic starch dispersion liquid
Cationic starch dispersions are prepared through micro-nano mechanical grinding, which solves the problems of low concentration and high viscosity of cationic starch after gelatinization. A high-concentration, low-viscosity, and non-gelatinizable cationic starch dispersion is achieved, which improves the sizing and coating effects and enhances paper performance.
Patent Information
- Application Number
- CN202410361491.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-27
- Publication Date
- 2025-09-30
AI Technical Summary
The existing cationic starch has low concentration and high viscosity after gelatinization, which affects the sizing effect and solid content of the coating. It is also easy to gel, which limits its application range and requires heat preservation and storage, which is inconvenient.
Cationic starch dispersion was prepared by micro-nano mechanical grinding. The starch crystallinity was reduced through two-stage grinding to expose hydroxyl groups, thereby preparing a high-concentration, low-viscosity, and non-gelatinizable dispersion.
The preparation of high-concentration cationic starch dispersion was achieved, the bonding strength and biodegradability of the coating were improved, the gas and oil barrier properties of the paper were enhanced, and the application limitations of gelatinized starch were solved.
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing a high-concentration cationic starch dispersion, and belongs to the technical field of pulping and papermaking. Background Art
[0002] With the increasing scarcity of petroleum resources and the increasingly serious harm caused by non-degradable plastic products, research into bio-based, biodegradable chemical raw materials, particularly relatively inexpensive starch and its derivatives, has been very active both domestically and internationally in recent years, opening up many new application areas. Cationic starch, a common modified starch, has a wide range of applications in various fields, including papermaking and water treatment, and holds great potential for development.
[0003] Cationic starch is a modified starch commonly used in the papermaking industry. Its preparation process is mature, and products with varying degrees of substitution can be prepared according to application requirements. Cationic starch carries a positive charge and has a strong adsorption capacity for negatively charged fibers, fine fibers, fillers, and other components in the pulp. Therefore, it is primarily used as a wet-end additive in the papermaking industry, aiding retention and drainage and improving paper strength. Furthermore, due to its high bonding strength, cationic starch can also be used in surface sizing to enhance the surface strength of paper and board and improve the printability of the finished paper. It can also be used as a coating adhesive in paper coating.
[0004] Currently, cationic starch is prepared through gelatinization to create a starch solution. During the gelatinization process, as the temperature rises, the starch granules absorb water and expand, destroying the crystalline regions within the granules and breaking the hydrogen bonds between the starch molecules. The starch molecules within the granules spread out in all directions, connecting and entangled with each other, forming a viscous colloid. However, gelatinized cationic starch solution has a high viscosity and a low gelatinization concentration (typically 1%-5%). This not only requires larger tanks for production, but also affects the sizing effect and the solid content of the coating when used in areas such as sizing and adhesive coating, thus limiting its application in certain areas. Furthermore, the gelatinized cationic starch solution ages upon cooling, increasing its viscosity and becoming a gelatinous state. This phenomenon is irreversible. Therefore, cationic starch currently requires thermal insulation for storage after gelatinization, which introduces significant production inconveniences. Summary of the Invention
[0005] To address the above-mentioned issues, the present invention provides a method for preparing a high-concentration cationic starch dispersion. This method is characterized by preparing a stable cationic starch dispersion using micro-nanomechanical grinding. During the micro-nano grinding process, friction, collision, and shear forces between the grinding media and the starch granules cause the starch granules to rapidly swell and rupture, reducing the crystallinity of the starch molecules and exposing more hydroxyl groups. This results in improved water retention and a uniformly dispersed, well-suspended starch dispersion.
[0006] The technical solution adopted by the present invention is to prepare a cationic starch dispersion by using a two-stage grinding method to achieve rapid swelling and high-speed dissociation of cationic starch at a certain dispersion concentration.
[0007] The concentration of the cationic starch aqueous dispersion is 5-20%, preferably 5-10%.
[0008] The grinding equipment is a bead mill or a sand mill, and the grinding medium is one of zirconia beads and stainless steel beads with a diameter of 0.2-1.2 mm.
[0009] The first stage of grinding is light grinding, with a grinding concentration of 5%-20%, a grinding bead-to-material ratio of 2:1-10:1, and a grinding time of 15-45 minutes.
[0010] The second stage grinding is heavy grinding, with a grinding concentration of 5%-20%, a grinding bead to material ratio of 2:1 to 10:1, and a grinding time of 30-240 minutes.
[0011] The median particle size of the ground cationic starch is 0.5-15 μm.
[0012] The viscosity of the ground cationic starch dispersion is 300-4000 mPa.s.
[0013] Compared to gelatinized cationic starch solutions, the cationic starch dispersion prepared using this method has the advantages of high concentration (up to 5%-20%, with gelatinized concentrations generally below 5%), significant shear thinning, low viscosity, and resistance to gelling. The cationic starch dispersion prepared using this method can be used for surface sizing and adhesive coating, providing excellent bond strength while also improving the biodegradability of the coating. Furthermore, it can be applied to paper or paperboard, either alone or in combination with other bio-based barriers, significantly improving the paper's gas and oil barrier properties. DETAILED DESCRIPTION
[0014] The present invention will be further described below with reference to examples, but the embodiments of the present invention are not limited thereto.
[0015] Example 1 220g of cationic starch was dispersed in 2300g of water and ground using a bead mill. The diameter of the grinding beads was 0.3-0.4mm, the grinding beads were made of zirconium oxide, and the bead-to-material ratio was 5:1. The mill linear speed was first set to 8m / s and the feed flow rate was 1000ml / min. After grinding for 20min, the mill linear speed was adjusted to 13.0m / s and the grinding was continued for 2h. The obtained cationic starch liquid had a median particle size of 8.28μm and a viscosity of 890mPa.s. The cationic starch liquid was coated on the base paper at a coating amount of 4.0g / m 2, the air permeability is reduced from 1.11μm / Pa.s to 0.002μm / Pa.s, and the Kit oil resistance level is increased from level 0 to level 6.
[0016] Example 2 200g of cationic starch was dispersed in 2000g of water and ground using a bead mill. The diameter of the grinding beads was 0.4-0.6mm, the grinding beads were made of zirconium oxide, and the bead-to-material ratio was 4:1. The mill linear speed was first set to 8m / s and the feed flow rate was 1000ml / min. After grinding for 30min, the mill linear speed was adjusted to 12.5m / s and the grinding was continued for 4h. The obtained cationic starch liquid had a median particle size of 0.8μm and a viscosity of 750mPa.s. The cationic starch liquid was coated on the base paper at a coating amount of 4.0g / m 2 , the air permeability is reduced from 1.11μm / Pa.s to 0.0006μm / Pa.s, and the Kit oil resistance level is increased from level 0 to level 8.
[0017] Example 3 250g of cationic starch was dispersed in 2000g of water and ground using a bead mill. The diameter of the grinding beads was 0.3-0.6mm, the grinding beads were made of zirconium oxide, and the bead-to-material ratio was 4.5:1. The mill linear speed was first set to 6m / s and the feed flow rate was 900ml / min. After grinding for 40min, the mill linear speed was adjusted to 12.5m / s and the grinding was continued for 0.5h. The obtained cationic starch liquid had a median particle size of 14.2μm and a viscosity of 1920mPa.s. The cationic starch liquid was coated on the base paper at a coating amount of 4.0g / m 2 , the air permeability is reduced from 1.11μm / Pa.s to 0.016μm / Pa.s, and the Kit oil resistance level is increased from level 0 to level 6.
[0018] Example 4 300g of cationic starch was dispersed in 2000g of water and ground using a bead mill. The diameter of the grinding beads was 0.2-0.4mm, the grinding beads were made of zirconium oxide, and the bead-to-material ratio was 4:1. The mill linear speed was first set to 6m / s and the feed flow rate was 1000ml / min. After grinding for 30min, the mill linear speed was adjusted to 14.0m / s and the grinding was continued for 3h. The obtained cationic starch liquid had a median particle size of 5.4μm and a viscosity of 960mPa.s. The cationic starch liquid was coated on the base paper at a coating amount of 4.0g / m 2 , the air permeability is reduced from 1.11μm / Pa.s to 0.0009μm / Pa.s, and the Kit oil resistance level is increased from level 0 to level 7.
[0019] Example 5 200g of cationic starch was dispersed in 2000g of water and ground using a bead mill. The diameter of the grinding beads was 0.2-0.4mm, the grinding beads were made of zirconium oxide, and the bead-to-material ratio was 4:1. The mill linear speed was first set to 6m / s and the feed flow rate was 1000ml / min. After grinding for 40min, the mill linear speed was adjusted to 14.0m / s and the grinding was continued for 3h. The cationic starch liquid obtained had a median particle size of 2.4μm and a viscosity of 800mPa.s. The above cationic starch liquid was used to grind 80g / m 2 The corrugated base paper is sizing, and the sizing amount is 2.0g / m 2 , the lateral ring pressure index is from 3.94Nmg -1 Increased to 5.41Nmg -1 Comparative sample 1: 30g of cationic starch was dispersed in 600g of water, heated in a water bath, set at 95°C, stirred at 600r / min, and kept warm for 30min to obtain gelatinized cationic starch liquid. The obtained cationic starch liquid had a solid content of 5% and a viscosity of 3600mPa.s. The above cationic starch liquid was coated on the base paper at a coating amount of 4.0g / m 2 , the air permeability is reduced from 1.11μm / Pa.s to 0.008μm / Pa.s, and the Kit oil resistance level is increased from level 0 to level 5.
Claims
1. A method for preparing a high-concentration cationic starch dispersion, characterized in that: The method is to prepare a stable cationic starch dispersion by micro-nano mechanical grinding, specifically: the cationic starch is dispersed in water, and a two-stage grinding method is used at a certain dispersion concentration to respectively achieve rapid swelling and high-speed dissociation of the cationic starch; The first stage of grinding is light grinding, and the second stage of grinding is heavy grinding.
2. The method for preparing a cationic starch dispersion according to claim 1, wherein: The concentration of the cationic starch aqueous dispersion is 5-20%, preferably 5-10%.
3. The method for preparing a cationic starch dispersion according to claim 1, wherein: The grinding equipment is a bead mill or a sand mill, and the grinding medium is one of zirconia beads and stainless steel beads with a diameter of 0.2-1.2 mm.
4. The method for preparing a cationic starch dispersion according to claim 1, wherein: The first stage is light grinding, with a grinding concentration of 5%-20%, a grinding bead to material ratio of 2:1 to 10:1, and a grinding time of 15-45 minutes.
5. The method for preparing a cationic starch dispersion according to claim 1, wherein: The second stage of heavy grinding has a grinding concentration of 5%-20%, a grinding bead to material ratio of 2:1 to 10:1, and a grinding time of 30-240 minutes.
6. The method for preparing a cationic starch dispersion according to claim 1, wherein: The median particle size of the ground cationic starch is 0.5-15 μm.
7. The method for preparing a cationic starch dispersion according to claim 1, wherein: The viscosity of the ground cationic starch dispersion is 300-4000 mPa.s.