A high solid low gas calcium stearate aqueous dispersion and a method of making the same

Abstract

The present application relates to the field of aqueous functional dispersion, disclose a kind of high solid low bubble calcium stearate aqueous dispersion and its preparation method, the aqueous dispersion includes calcium stearate 40~55 parts, deionized water 43~58 parts, emulsifying system 2.5~5.5 parts, dispersant 0.25~2.5 parts, no silicon defoamer 0.15~1.0 parts, viscosity reducing aid 0.5~2.5 parts, bactericide 0.1~0.5 parts by mass parts;Emulsifying system includes branched low bubble type fatty acid methyl ester ethoxylate sodium sulfonate, Span 60 and Tween 20.The present application is carefully selected and designed dispersant and auxiliary stabilizer, so that calcium stearate particles realize long-term stable suspension in aqueous system, avoid settlement and stratification, with excellent storage stability.Solve the problem that calcium stearate is easily aggregated, settled and foamed in aqueous system in the prior art.

Description

Technical Field

[0001] This invention relates to the field of aqueous functional dispersions, specifically to an aqueous dispersion of calcium stearate with high solids content and low bubbles, and its preparation method. Background Technology

[0002] Calcium stearate is a water-insoluble metal soap fatty acid salt with a unique amphiphilic structure. One end is a hydrophilic inorganic calcium ion, and the other end is two hydrophobic long-chain alkyl groups, which endow it with excellent lubricity, hydrophobicity, and thermal stability, making it widely used in various industrial fields such as papermaking, coatings, plastics, and rubber. However, the strong hydrophobicity of calcium stearate makes it difficult to disperse stably in aqueous systems. It is prone to agglomeration, sedimentation, and the formation of unstable phenomena such as stratification, precipitation, and paste formation, which seriously affects the storage stability and application effect of the product. In addition, in the preparation and application of aqueous calcium stearate dispersions, the generation of bubbles is also a common and troublesome problem due to the high surfactant and high solids content of the system. Once formed, bubbles rise and escape slowly in high-viscosity systems, hindering bubble coalescence and collapse. This results in an abnormally stable foam structure that persists in the dispersion for a long time, affecting the appearance, flowability, and application performance of the product.

[0003] Currently, existing technologies commonly employ a two-step process of "solvent melting followed by emulsification" to prepare aqueous calcium stearate dispersions. This method has several drawbacks: firstly, it requires a large amount of organic solvent (VOC > 3%), which is environmentally restrictive; secondly, to address the issue of bubble formation, current defoamers often use siloxanes, posing a risk of silica spots in subsequent paper / food paper production. Therefore, there is an urgent need to develop a new process for preparing high-solids-content, low-bubble, silica-free, low-VOC aqueous calcium stearate dispersions. Summary of the Invention

[0004] The present invention aims to provide a high-solids-content, low-bubbling calcium stearate aqueous dispersion and its preparation method, so as to solve the problems of easy aggregation, sedimentation and foaming of calcium stearate in aqueous systems in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a high-solids-content, low-foaming calcium stearate aqueous dispersion, comprising, by mass, 40-55 parts calcium stearate, 43-58 parts deionized water, 2.5-5.5 parts emulsification system, 0.25-2.5 parts dispersant, 0.15-1.0 parts silicone-free defoamer, 0.5-2.5 parts viscosity reducer, and 0.1-0.5 parts bactericide; the emulsification system comprises branched low-foaming fatty acid methyl ester ethoxylate sodium sulfonate, Span 60, and Tween 20.

[0006] Preferably, as an improvement, the mass ratio of branched low-foaming fatty acid methyl ester ethoxylate sodium sulfonate, Span 60, and Tween 20 is 0.5~1.5:0.5~1.5:0.5~2.0.

[0007] Preferably, as an improvement, the dispersant is sodium polyacrylate or sodium salt of styrene-maleic anhydride copolymer with a weight average molecular weight of 3000-8000.

[0008] Preferably, as an improvement, the silicone-free defoamer is a paraffin oil emulsion or a naphthenic oil emulsion, and the particle size of the paraffin oil emulsion or naphthenic oil emulsion is <0.5μm.

[0009] Preferably, as an improvement, the viscosity reducing agent is propylene glycol methyl ether or dipropylene glycol methyl ether.

[0010] Preferably, as an improvement, the bactericide is glutaraldehyde or isothiazolinone.

[0011] Preferably, as an improvement, a method for preparing a high-solids-content, low-bubbling calcium stearate aqueous dispersion includes the following steps: Step 1, Feeding at room temperature: Add calcium stearate, deionized water, emulsion system, dispersant, and viscosity reducer to the high-pressure reactor; Step 2, Sealed heating: Heat to 160~190℃ and emulsify at a constant temperature for 45~60 min; Step 3, rapid cooling under pressure: maintain 0.4 MPa and cool; Step 4, Post-addition: Add silicone-free defoamer and bactericide and mix; Step 5: After filtration, the finished product is obtained.

[0012] Preferably, as an improvement, in step one, the cooling rate of the built-in coil in the high-pressure reactor is ≥3℃ / min, and the temperature control accuracy is ±2℃.

[0013] Preferably, as an improvement, in step two, after nitrogen is replaced to 0.4 MPa, the temperature is raised for emulsification. The emulsification stage is carried out under stirring conditions, with a stirring speed of 600~1000 rpm.

[0014] Preferably, as an improvement, in step four, when the temperature is <50℃, a silicone-free defoamer and a bactericide are added; in step five, the sample is first filtered through a 325-mesh vibrating screen and then through a 0.2 μm bag filter.

[0015] The principle and advantages of this solution are as follows: In practical applications, calcium stearate has strong hydrophobicity, and its molecular structure contains two long-chain alkyl groups, making it difficult to disperse stably in aqueous systems. Furthermore, high-solids-content (40-55%) aqueous dispersions, due to their high viscosity and high surfactant content, are difficult to eliminate once bubbles are generated. While traditional siloxane defoamers are effective, they can cause silica spot defects in applications such as polishing painted surfaces in papermaking, food paper, and sandpaper. This technical solution addresses the problems of calcium stearate's tendency to agglomerate, settle, and foam in aqueous systems by comprehensively optimizing the composition and preparation process of the calcium stearate aqueous dispersion. It constructs a technical system from two dimensions: interfacial chemical regulation and synergistic process physical field, aiming to achieve the core objective of "high solids content, low bubble size, and stable, non-stratifying" calcium stearate aqueous dispersion.

[0016] Regarding raw material composition, this solution is based on the DLVO theory and steric hindrance stability theory of colloid chemistry. Through the compound design of dispersants and emulsification systems, a three-dimensional stability barrier is constructed for calcium stearate particles. Regarding electrostatic stability: our team's previous research found that conventional emulsifiers cannot effectively prevent the Ostwald ripening phenomenon of calcium stearate particles. During storage, the particles gradually grow and eventually settle and stratify. Based on this, this technical solution uses sodium polyacrylate or sodium salt of styrene-maleic anhydride copolymer with a weight-average molecular weight of 3000-8000 as a dispersant. The carboxyl groups, sulfonic acid groups, and other anionic groups on their molecular chains can be adsorbed onto the surface of calcium stearate particles, causing the particles to form an electric double layer. When particles approach each other, the electrostatic repulsion of the electric double layer hinders particle aggregation, which is the basis for solving the "easy aggregation" problem. Regarding steric stabilization: In this scheme, the long polymer chains of the dispersant (molecular weight 3000~8000 is the optimal range; too short and the steric hindrance is insufficient, too long and it is prone to entanglement) extend into the aqueous phase, forming a three-dimensional steric hindrance layer. Simultaneously, the nonionic surfactant (Span 60 / Tween 20) in the emulsion system adsorbs at the particle interface, and its polyethylene oxide segments further enhance the steric hindrance effect. This dual steric hindrance can counteract the van der Waals forces between particles, preventing particle sedimentation and achieving long-term suspension stability.

[0017] Furthermore, while traditional siloxane defoamers are effective at suppressing foaming, they can cause silicone spot defects in applications such as papermaking, food paper, and sandpaper finishing. This solution addresses the pain point of high-solids-content systems where foam is easily generated and difficult to eliminate. It employs a synergistic approach of formula control and process adaptation, differing from the passive method of simply adding a defoamer. 1. Low-foaming design at the source (emulsion system optimization): The core emulsifier is branched-chain low-foaming fatty acid methyl ester ethoxylate sodium sulfonate. Its branched groups disrupt the ordered arrangement of surfactant molecules at the gas-liquid interface, reducing the strength and mechanical stability of the foam film, thus fundamentally reducing foam generation. Simultaneously, the combination of Span 60 (lipophilic) and Tween 20 (hydrophilic) precisely adjusts the HLB value of the system to the optimal range for calcium stearate emulsification, ensuring emulsification while avoiding excessive foaming due to HLB value imbalance. During the technology development phase, the mixing ratio of Span 60 (HLB≈4.7) to Tween 20 (HLB≈16.7) directly affected the emulsification effect. Initial experiments revealed that using either Span 60 or Tween 20 alone could not achieve the desired emulsification effect: too much Span 60 resulted in high emulsion viscosity and easy separation; too much Tween 20 resulted in excessive foaming and poor stability. Through systematic research, the team determined the optimal mixing ratio of Span 60:Tween 20:FMES = 0.5-1.5:0.5-1.5:0.5-2.0, adjusting the HLB value of the system to the optimal range for calcium stearate emulsification. 2. Synergistic Defoaming: The added paraffin oil / naphthenic oil emulsion viscosity reducer (silicone-free defoamer, particle size <0.5μm) can quickly diffuse to the surface of the foam liquid film, replacing surfactant molecules in the film layer, causing the liquid film to thin and break down. Meanwhile, the viscosity reducer (propylene glycol methyl ether / dipropylene glycol methyl ether) reduces the viscosity of the system, decreasing the space for bubble retention and accelerating bubble rise and escape, creating a synergistic effect with the defoamer. Furthermore, the silicone-free design avoids the "silicone spot" defect that silicone-based defoamers produce in subsequent applications, making it suitable for high-end application scenarios.

[0018] In optimizing the preparation process, to achieve nanoscale dispersion of calcium stearate, it is necessary to heat it to 160-190℃ to melt it and then rapidly cool and solidify it. Controlling the process parameters is extremely critical: too low a temperature results in incomplete melting and a wide particle size distribution; too high a temperature leads to oxidative degradation of calcium stearate; and too slow a cooling rate causes Ostwald ripening, resulting in particle growth. This scheme optimizes the microstructure of calcium stearate particles through precise control of physical field conditions. High-pressure melting followed by instantaneous pressurized cooling forms "core-shell" microspheres, reducing high-temperature droplet agglomeration. During the high-pressure melting and dispersion stage, calcium stearate is completely melted at 160-190℃ under a 0.4MPa nitrogen atmosphere. High-speed stirring (600-1000rpm) breaks the molten calcium stearate into tiny droplets. Nitrogen replacement prevents oxidative degradation of calcium stearate at high temperatures, while the high-pressure environment inhibits premature droplet nucleation. During the pressurized rapid cooling nucleation stage, rapid cooling was achieved by maintaining a pressure of 0.4 MPa through an internal coil (cooling rate ≥3℃ / min, temperature control accuracy ±2℃). The molten droplets solidified instantly, forming dense "core-shell" structured microspheres—the core being calcium stearate crystals, and the outer shell being an interface layer adsorbed with emulsifiers / dispersants. The rapid cooling process avoids particle agglomeration caused by slow crystal growth, while the "core-shell" structure further enhances the dispersion stability of the particles in the aqueous phase, providing process support for achieving a high solids content of 40-55%. Through extensive experiments, the team determined the optimal process window of 0.4 MPa nitrogen atmosphere, isothermal temperature of 160-190℃ for 45-60 min, and cooling rate ≥3℃ / min, which yielded core-shell structured microspheres with a particle size of approximately 0.6 μm.

[0019] In summary, the beneficial effects of the present invention are as follows: 1. High solid content: The calcium stearate dispersion of the present invention has a solid content of up to 40-50%, which allows for higher addition and cost-effectiveness in application.

[0020] 2. Low foam content: By selecting low-foaming emulsifiers and adding viscosity-reducing agents, the generation of bubbles is effectively suppressed and bubble breakage is promoted, solving the problem of difficult foam control in high-solids-content aqueous dispersions.

[0021] 3. Stable and non-stratified: Through careful selection and design of dispersants and auxiliary stabilizers, calcium stearate particles can achieve long-term stable suspension in aqueous systems, avoiding sedimentation and stratification, and have excellent storage stability.

[0022] 4. Environmental performance: The formula design follows the principle of low VOC emission, selects environmentally friendly raw materials, and complies with the relevant environmental regulations on VOC restrictions. Attached Figure Description

[0023] Figure 1 This is a process flow diagram for preparing a high-solids-content, low-bubbling calcium stearate aqueous dispersion in an embodiment of the present invention. Detailed Implementation

[0024] The following detailed description provides further details on specific embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials and reagents used are all commercially available.

[0025] Overview of the plan: A high-solids, low-foaming aqueous dispersion of calcium stearate, comprising, by weight, 40-55 parts calcium stearate, 43-58 parts deionized water, 2.5-5.5 parts emulsion system, 0.25-2.5 parts dispersant, 0.15-1.0 parts silicone-free defoamer, 0.5-2.5 parts viscosity reducer, and 0.1-0.5 parts bactericide.

[0026] The emulsion system includes 0.5-1.5 parts of branched-chain low-foaming fatty acid methyl ester ethoxylate sodium sulfonate, 0.5-1.5 parts of Span60, and 0.5-2.0 parts of Tween 20.

[0027] The dispersant is sodium polyacrylate or sodium salt of styrene-maleic anhydride copolymer with a weight average molecular weight of 3000~8000.

[0028] The silicone-free defoamer is a paraffin oil emulsion or naphthenic oil emulsion with a particle size of <0.5μm.

[0029] The viscosity reducer is propylene glycol methyl ether or dipropylene glycol methyl ether.

[0030] The bactericide is glutaraldehyde or isothiazolinone.

[0031] like Figure 1 As shown, a method for preparing a high-solids-content, low-bubbling calcium stearate aqueous dispersion includes the following steps: Step 1, Feeding at room temperature: Add calcium stearate, deionized water, emulsion system, dispersant, and viscosity reducer to the high-pressure reactor at one time. The high-pressure reactor has an internal coil cooling rate of ≥3℃ / min and a temperature control accuracy of ±2℃. Step 2, Sealed heating: Replace with nitrogen to 0.4 MPa, heat to 160~190℃, and emulsify at a constant temperature of 600~1000 rpm for 45~60 min; Step 3, rapid cooling under pressure: maintain 0.4 MPa and cool to <50℃ within 30 min; Step 4, Post-addition: When the temperature is <50℃, add silicone-free defoamer and bactericide, and mix at 400 rpm for 15 min; Step 5, Filtration: First pass through a 325-mesh vibrating screen, then through a 0.2 μm bag filter to obtain the finished product.

[0032] Examples 1-5 are embodiments of the present invention, and Comparative Examples 1-3 are comparative examples of the present invention. The raw material composition and key process parameters of each embodiment and comparative example are detailed in Table 1. Table 1 Components Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Calcium stearate (D50=10µm) 50 45 40 52 45 52 45 45 45 45 45 Deionized water 44 49.2 54.2 40.4 47.7 40.4 47.7 49.2 47.7 48.9 49.3 Span 60 1.5 1.2 — 1 1.2 1 1.2 1.2 1.2 — 1.2 Tween 20 2 1.8 — 1.4 1.6 1.4 1.6 1.8 1.6 1.6 — FMES (branched sulfonates) — — 3 2.5 2 2.5 2 — 2 2 2 Sodium polyacrylate (Mw7000) 1 0.8 1 1.2 — 1.2 — 0.8 — — — Sodium styrene-maleic anhydride — — — — 1 — 1 — 1 1 1 Silicone-free paraffin oil emulsion 0.3 0.3 0.4 0.3 — 0.3 — 0.3 — — — Silane-free naphthenic oil emulsion — — — — 0.3 — — — 0.3 0.3 0.3 Modified polysiloxane defoamer 0 0 0 0 0 0 0.3 — — — — Propylene glycol methyl ether 1 — 1.2 — 1 — 1 — 1 1 1 Dipropylene glycol methyl ether — 1.5 — 1 — 1 — 1.5 — — — glutaraldehyde 0.2 — 0.2 — 0.2 — 0.2 — 0.2 0.2 0.2 Isothiazolinone — 0.2 — 0.2 — 0.2 — 0.2 — — — Key processes Standard process Standard process Standard process Standard process Standard process Natural cooling at atmospheric pressure for 120 minutes (rapid cooling without pressure) The standard process was modified by replacing the defoamer with 0.3 wt% polyether-modified silicone oil emulsion. <![CDATA[Mechanical grinding at room temperature: 1 mm ZrO2 beads, 25 °C, 1800 rpm, 30 min, without temperature rise - pressure - rapid cooling]]> Standard process Standard process Standard process Note: "Standard process" refers to: one-step high-pressure emulsification-pressurized rapid cooling (N20.4 MPa, 160~190 ℃, 45~60 min, cooling to <5℃ within 30 min).

[0033] illustrate: Comparative Example 2 The difference between this comparative example and Example 5 is that 0.3% of modified polysiloxane defoamer was added to this comparative example.

[0034] Comparative Example 4 The difference between this comparative example and Example 5 is that the dispersant in this comparative example is sodium polyacrylate with a molecular weight of 2000.

[0035] Comparative Example 5 The difference between this comparative example and Example 5 is that Span 60 was not added in this comparative example.

[0036] Comparative Example 6 The difference between this comparative example and Example 5 is that Tween 20 was not added in this comparative example.

[0037] Experimental Example The aqueous dispersions of calcium fatty acid prepared in the above embodiments and comparative examples were tested, and the test indicators and test methods are shown in the table below: Table 2 Performance indicators Test methods Instrument / Model Standards / Specifications Remark Solid content Drying method DHG-9070A forced-air drying oven GB / T 2793-1995 105℃±2℃, 2 h, aluminum foil dish, constant weight difference ≤0.5 mg Viscosity Rotational viscometer Brookfield DV2T, #2 rotor, 25°C, 20 rpm GB / T 2794-2013 Readings were taken after the sample had been left to stand for 10 minutes, and the average of the readings was calculated. Centrifugal stability high-speed centrifuge Xiangyi H1650, 50 mL centrifuge tubes, 25℃, 3000 rpm × 15 min Internal regulations Record the height of the bottom sediment layer in mm; <1 mm indicates "no visible sediment". Storage stability Observe after standing 250 mL stoppered graduated cylinder, 25℃ incubator Internal regulations 0, 7, 14, 30, 90, and 180 days of photographic recording of stratification, sedimentation, and flocculation. Foam height Shaking method A 250 mL stoppered graduated cylinder, containing 100 mL of liquid, was used for 30 up-and-down measurements, each measuring 30 cm. ASTM D3601-07 Immediately read the foam height in mm, and record the residual foam height at 30s, 1 min, and 3 min. Defoaming time Stopwatch Same as above Internal regulations Time required for foam height to be ≤1mm after shaking stops pH Electrode method Mettler-Toledo FE28, 25℃ GB / T 6920-1986 Three-point calibration (4.00 / 6.86 / 9.18) VOC Difference method The mass loss of a 1 g sample after drying at 105℃ for 1 h is the VOC equivalent. GB / T 23984-2009 Results are expressed as a percentage (%), with ≤0.5% considered "low VOC". Volatile organic matter is calculated after deducting moisture. Silicon content ICP-OES method Thermo iCAP 7200, detection limit ≤5ppm Internal regulations Results are expressed in ppm; ≤5 ppm is considered "silicone-free". D50 particle size Laser diffraction Malvern Mastersizer 3000, deionized water dispersion, sonicated for 5 min, refractive index 1.52, absorption coefficient 0.1 GB / T 19077-2016 Results are expressed in μm, D50 ≤ 1.0 μm Each example and comparative example underwent three repeated experiments, and the specific test results are shown in Table 3: Table 3

[0038] Note: All data were measured at room temperature (25 ℃) and centrifuged at 3000 rpm for 15 min.

[0039] "Silicone spots" refer to visible silicone oil pinholes / bright spots on the PET coated film after drying, counted according to GB / T 30696-2015, with a coating weight of 2 g / m². 2 Dry at 105℃ for 2 min, then at 23℃ and 50%RH, use a white LED table at 1000 lx to visually count bright spots with a diameter ≥ 0.1 mm. The testing area is 0.1 m². 2 Detection limit 5 per m 2When the number of observations is less than 5 / m 2 The time is recorded as 0 (not detected). When the number of observations > 200 / m 2 Stop counting when the time is >200.

[0040] As can be seen from the data in Table 3, all embodiments used "high-pressure melting-rapid cooling" to instantly form core-shell microspheres of about 0.6 µm from CaSt2. The particles are small, the interfacial energy is high, and the flow resistance is low under the same solid content.

[0041] Comparative Example 1 lacked rapid cooling, resulting in significant Ostwald ripening, with particle size increasing to 1.45 µm. Large particles easily formed a "particle network," leading to a sharp increase in the zero-shear viscosity of the system.

[0042] Comparative Example 3, which uses ball milling at room temperature, can only break down the original 10 µm particles to 1.5 µm with irregular shapes. The specific surface area increases, the free volume of the aqueous phase decreases, and the viscosity is the highest (320 mPa·s).

[0043] Example 1 uses a linear Span / Tween as the main emulsifier with HLB≈11, resulting in a foam film with high elasticity. The initial foam is 30 mm and the defoaming time is 45 s, which is still better than the industry standard (≤25 mm / 30 s) but worse than the subsequent examples.

[0044] Examples 2-5 introduce branched FMES or increase the proportion of FMES, which disrupts the tightly packed foam structure and reduces film strength; at the same time, dipropylene / propylene glycol methyl ether reduces surface tension and bulk viscosity, increases bubble rise-breakage speed, reduces foam height to 16-22 mm, and defoaming time to 12-21 s.

[0045] Comparative Example 1 has coarse particle size and high viscosity, resulting in slow bubble rise and foam up to 35 mm in diameter; the defoamer is the same, but the defoaming efficiency is inhibited by high viscosity, and the defoaming time is 65 s.

[0046] Comparative Example 2 added 0.3% modified polysiloxane defoamer. This silicone-containing defoamer showed excellent immediate defoaming efficiency, low foam height, and fast defoaming, but it produced severe "silicone spot" defects after coating. Compared with other examples, it had obvious coating appearance defects.

[0047] Comparative Example 3: The ball milling process introduced a large amount of air, and the high viscosity hindered the merging and rupture of bubbles. The initial foam was 55 mm and remained >40 mm after 30 minutes, indicating "unable to defoam".

[0048] In Comparative Example 4, as the molecular weight of the dispersant decreased from 7000 to 2000, the steric hindrance effect was significantly reduced, leading to an increase in particle size from 0.59 μm to 0.85 μm. Slight stratification of 2 mm appeared after 180 days. This indicates that a dispersant molecular weight of 3000-8000 is a key parameter for achieving long-term stability.

[0049] Comparative Example 5, lacking Span 60, had a higher HLB value, resulting in a decrease in emulsification effect: particle size 0.78 μm, foam 24 mm, defoaming time 28 s, and stratification of 5 mm at 180 days.

[0050] Comparative Example 6, lacking Tween 20, had a low HLB value and incomplete emulsification: particle size 0.92 μm, foam 32 mm, difficult defoaming (42 s), severe stratification (8 mm) at 180 days, accompanied by bottom paste formation.

[0051] In summary: (1) Microstructure of particles High pressure (0.4 MPa) and 160-190℃ completely melt CaSt2; instantaneous rapid cooling under pressure leads to supercooling and nucleation of molten droplets, generating 0.6 µm spherical particles with a narrow particle size distribution. In contrast, rapid cooling is not applied, allowing sufficient time for droplets to grow to 1.4-1.5 µm with irregular shapes, decreased specific surface area, increased interparticle contact points, and increased viscosity.

[0052] (2) Foam control Branched FMES form a loose adsorption layer at the gas-liquid interface, reducing the membrane elastic modulus E' by 40-50% and the initial foam height by ≥40%. Propylene glycol ethers both reduce viscosity and increase the liquid film drainage rate, causing the bubble half-life to change from 45 s to 12-18 s.

[0053] Silicone-free mineral oil emulsions (particle size 0.3 µm) added below 50°C can spread rapidly on foam liquid films, locally reducing surface tension to 28-30 mN / m. -1 This enables "rapid bubble breaking".

[0054] (3) Storage stability Electrostatic-steric-vacancy triple stability: Sodium polyacrylate (Mw 5-7 k) provides A zeta potential above 40 mV; Span / Tween forms a 3-5 nm adsorption layer; excess polymer generates vacancy repulsion, which together inhibits Ostwald ripening.

[0055] Comparative Example 1 has large particle size and low absolute value of zeta potential ( (25 mV), the vacancy layer is thin, and 12 mm of paste appears after 4 weeks.

[0056] Comparative Example 3 showed irregular particle shapes, and ball milling introduced metal debris (Ca). 2+ (Release), compress the double layer, the zeta potential is only 20mV indicates the worst stability.

[0057] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A high-solids-content, low-bubbling calcium stearate aqueous dispersion, characterized in that: By weight, it comprises 40-55 parts calcium stearate, 43-58 parts deionized water, 2.5-5.5 parts emulsification system, 0.25-2.5 parts dispersant, 0.15-1.0 parts silicone-free defoamer, 0.5-2.5 parts viscosity reducer, and 0.1-0.5 parts bactericide; the emulsification system comprises branched low-foaming fatty acid methyl ester ethoxylate sodium sulfonate, Span 60, and Tween 20.

2. The high-solids-content, low-bubbling calcium stearate aqueous dispersion according to claim 1, characterized in that: The mass ratio of branched-chain low-foaming fatty acid methyl ester ethoxylate sodium sulfonate, Span 60, and Tween 20 is 0.5~1.5:0.5~1.5:0.5~2.

0.

3. The high-solids-content, low-bubbling calcium stearate aqueous dispersion according to claim 2, characterized in that: The dispersant is sodium polyacrylate or sodium salt of styrene-maleic anhydride copolymer with a weight average molecular weight of 3000-8000.

4. The high-solids-content, low-bubbling calcium stearate aqueous dispersion according to claim 3, characterized in that: The silicone-free defoamer is a paraffin oil emulsion or a naphthenic oil emulsion, and the particle size of the paraffin oil emulsion or naphthenic oil emulsion is <0.5μm.

5. The high-solids-content, low-bubbling calcium stearate aqueous dispersion according to claim 4, characterized in that: The viscosity-reducing agent is propylene glycol methyl ether or dipropylene glycol methyl ether.

6. The high-solids-content, low-bubbling calcium stearate aqueous dispersion according to claim 5, characterized in that: The bactericide is glutaraldehyde or isothiazolinone.

7. A method for preparing a high-solids-content, low-bubbling calcium stearate aqueous dispersion according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1, Feeding at room temperature: Add calcium stearate, deionized water, emulsion system, dispersant, and viscosity reducer to the high-pressure reactor; Step 2, Sealed heating: Heat to 160~190℃ and emulsify at a constant temperature for 45~60 min; Step 3, rapid cooling under pressure: maintain 0.4 MPa and cool; Step 4, Post-addition: Add silicone-free defoamer and bactericide and mix; Step 5: After filtration, the finished product is obtained.

8. The method for preparing a high-solids-content, low-bubbling calcium stearate aqueous dispersion according to claim 7, characterized in that: In step one, the cooling rate of the built-in coil in the high-pressure reactor is ≥3℃ / min, and the temperature control accuracy is ±2℃.

9. A method for preparing a high-solids-content, low-bubbling calcium stearate aqueous dispersion according to claim 8, characterized in that: In step two, nitrogen is used to purge to 0.4 MPa, and then the temperature is raised for emulsification. The emulsification stage is carried out under stirring conditions, with a stirring speed of 600~1000 rpm.

10. A method for preparing a high-solids-content, low-bubbling calcium stearate aqueous dispersion according to claim 9, characterized in that: In step four, when the temperature is <50℃, add silicone-free defoamer and bactericide; in step five, first pass through a 325-mesh vibrating screen, then through a 0.2 μm bag filter.

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