A hyperbranched polyether dispersant for capacitive inductive nickel powder and a preparation method and application thereof

Abstract

This invention relates to the field of electronic materials technology, specifically to a special dispersant for nickel-based conductive or magnetic pastes used in electronic components such as capacitors and inductors. The purpose of this invention is to overcome the shortcomings of existing technologies and provide a "nanoscale steric spherical" dispersant based on a hyperbranched polyether framework. The invention adopts the following technical solutions: First, it provides a hyperbranched polyether dispersant for nickel powder. Second, it provides a method for preparing the above-mentioned hyperbranched polyether dispersant. Third, it provides the application of the above-mentioned hyperbranched polyether dispersant in the preparation of nickel-based electronic pastes. Fourth, it provides a nickel-based electronic paste comprising nickel powder, an organic carrier, and an effective amount of the above-mentioned hyperbranched polyether dispersant. The hyperbranched polyether dispersant provided by this invention, with its unique three-dimensional structure and multifunctional ends, significantly reduces the viscosity of high-solids-content nickel pastes while providing excellent long-term dispersion stability.

Description

Technical Field

[0001] This invention relates to the field of electronic materials technology, specifically to a special dispersant for nickel-based conductive or magnetic pastes used in electronic components such as capacitors and inductors. In particular, it relates to a hyperbranched polyether polymeric dispersant with a three-dimensional spherical structure and containing multiple anchoring functional end groups, its preparation method, and its application in achieving high-concentration, low-viscosity, and highly stable dispersion of nickel powder, ultimately obtaining sintered bodies with high electrical / magnetic properties. Background Technology

[0002] In the manufacture of multilayer ceramic capacitors (MLCCs), inductors, and other passive components, nickel (Ni) is widely used as a key functional phase in internal electrode pastes or magnetic pastes due to its excellent electrical conductivity, magnetic permeability, and low cost. To achieve miniaturization and high performance of devices, the paste is required to have extremely high solids content (>80 wt%), excellent rheological properties (suitable for fine screen printing), and dispersion stability (preventing sedimentation and agglomeration).

[0003] However, nickel powder, especially submicron nickel powder, has a large specific surface area, high surface energy, and is easily oxidized. It readily agglomerates in organic carriers (such as ethyl cellulose / terpineol systems), leading to a sharp increase in slurry viscosity, poor leveling, and decreased printing line resolution. More seriously, the agglomerates form pores and defects after sintering, significantly reducing the conductivity of the electrodes and the reliability of the components.

[0004] Currently, dispersants used in nickel slurries are mostly traditional linear polymers (such as ammonium polyacrylate and phosphate esters) or small molecule surfactants. They have the following inherent drawbacks: 1. Insufficient steric hindrance: Linear molecules are mostly adsorbed "lying flat" on the particle surface, providing limited steric hindrance, making it difficult to prevent particles from getting close together at high solid content.

[0005] 2. Weak anchoring strength: It has a weak affinity for nickel surfaces and is prone to desorption under high shear or long-term storage, leading to the collapse of the dispersion system and thickening of the slurry.

[0006] 3. Thermal decomposition residue: Many dispersants cannot be completely decomposed during sintering under a nitrogen / hydrogen protective atmosphere, leaving behind impurities such as carbon, which increases electrode resistance and may even cause component cracking or delamination.

[0007] 4. Affects slurry rheology: Some dispersants have poor compatibility with organic carriers or high viscosity, which is not conducive to obtaining the ideal slurry state of high solids and low viscosity.

[0008] Therefore, there is an urgent need to develop a nickel powder dispersant with strong anchoring, large steric hindrance, good thermal cleanability, and high compatibility with organic carriers. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a "nanoscale sterically hindered sphere" dispersant based on a hyperbranched polyether skeleton. This design achieves multi-point strong anchoring and all-round spatial protection of nickel powder particles through the three-dimensional structure of hyperbranched molecules and highly functionalized end groups, thereby solving the problems of dispersion stability and rheological properties of high solids content nickel slurry.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a hyperbranched polyether dispersant for nickel powder, characterized in that it is a highly branched polymer with a three-dimensional spherical structure, the structure of which comprises: (1) a hyperbranched polyether core: using a polyol (such as pentaerythritol, trimethylolpropane, glycerol) as the starting core, and through anionic ring-opening polymerization of epoxides (preferably propylene oxide PO, or copolymerized with a small amount of ethylene oxide EO) to form a highly branched polyether dendritic molecule with a narrow molecular weight distribution (Ð<1.5). The number average molecular weight (Mn) of the core is 2,000-15,000 g / mol, and the branching generation is 3-5 generations (with the starting core as generation 0). Its three-dimensional structure provides a rigid, incompressible "sphere" in space, which is the basis for generating strong entropy repulsion (steric hindrance).

[0011] (2) Multifunctional end groups: The vast majority of the terminal hydroxyl groups of the hyperbranched polyether molecule are modified into a combination of two or three of the following functional groups: - A. Strong coordination anchoring groups: accounting for 30% - 70% of the total number of terminal groups. Selected from phosphonate groups (-PO(OR)2, R=H or C1-C4 alkyl), carboxyl groups (-COOH), acetylacetonate groups (-COCH2COCH3), or primary / secondary amino groups (-NH2, -NHR). These groups can form stable chemical coordination bonds or ionic bonds with nickel atoms or nickel oxide layers on the surface of nickel powder, achieving "multi-point anchoring" of dispersant molecules on the particle surface, resulting in strong adsorption and resistance to desorption.

[0012] - B. Spatially Stable and Compatible Segments: These comprise 30%–70% of the total terminal groups. They are long-chain alkyl groups (C12–C18) or low-polyoxypropylene chains (PPO, Mn = 200–600) linked by ether or ester bonds. These hydrophobic / oleophilic segments extend into the organic support phase, providing an additional solvation layer and significantly improving the compatibility of the dispersant with the organic support (such as terpineol or butyl carbitol), thus contributing to reduced slurry viscosity.

[0013] - C. Electrostatic auxiliary group (optional): A small amount (<10%) of sulfonic acid group (-SO3H) or quaternary ammonium salt group may be introduced to provide a weak electrostatic stabilizing effect in non-aqueous media as a supplement.

[0014] Preferably, the weight-average molecular weight (Mw) of the hyperbranched polyether dispersant is 5,000-30,000 g / mol, and its hydrodynamic radius is equivalent to that of a nanoparticle.

[0015] Preferably, the strong coordination anchoring group is diisopropylphosphonate group or acetylacetone group, because it has excellent selective coordination ability to nickel.

[0016] Secondly, the present invention provides a method for preparing the above-mentioned hyperbranched polyether dispersant, characterized by employing a synthesis strategy of "core-first, arm-later, stepwise growth, and terminal functionalization," the specific steps of which are as follows: Step S1: Synthesis of hyperbranched polyether polyol (HBPE-OH) Starting with trimethylolpropane (TMP) as the core, anionic ring-opening polymerization is carried out stepwise with propylene oxide (PO) in the presence of a highly efficient bimetallic cyanide (DMC) catalyst. By controlling the feed ratio of PO to the core and the feeding procedure, hyperbranched polyether polyols with a generation number of 3-5 and a large number of primary hydroxyl groups at the ends are synthesized. This step yields products with narrow molecular weight distribution and well-defined structures.

[0017] Step S2: Partial esterification / etherification of terminal hydroxyl groups to introduce compatible segments The HBPE-OH obtained in step S1 is partially esterified or etherified with long-chain fatty acids (such as lauric acid, stearic acid) or their acyl chlorides, or long-chain alkyl glycidyl ethers, in the presence of a catalyst (such as p-toluenesulfonic acid). By controlling the acid / alcohol molar ratio, 30%-70% of the terminal hydroxyl groups are converted into esters or ethers with long-chain alkyl groups, introducing sterically stable and compatible segments (the aforementioned type B groups).

[0018] Step S3: Phosphonate / functionalization of the remaining hydroxyl groups to introduce anchoring groups The modified product obtained in step S2 is reacted with an excess of a phosphonate esterifying agent (such as diethylvinylphosphonate) or acetoacetate under mild conditions via Michael addition or transesterification to convert most of the remaining hydroxyl groups into phosphonate groups or acetylacetone groups (the aforementioned type A groups). This ultimately yields a terminally multifunctional hyperbranched polyether dispersant.

[0019] Thirdly, the present invention provides the application of the above-mentioned hyperbranched polyether dispersant in the preparation of nickel-based electronic pastes.

[0020] The nickel-based electronic paste comprises: - Nickel powder: Solid content** 70 - 92 wt% - Organic carrier: composed of organic solvents (terpineol, butyl carbitol, etc.) and resins (ethyl cellulose, etc.); - Dispersant: The above hyperbranched polyether dispersant is added at a rate of 0.3% - 3.0% of the weight of nickel powder.

[0021] Fourthly, the present invention provides a nickel-based electronic paste comprising nickel powder, an organic carrier, and an effective amount of the above-mentioned hyperbranched polyether dispersant.

[0022] The beneficial effects of this invention are: 1. Superior steric stabilization: The three-dimensional nanosphere structure of hyperbranched molecules forms a thick, incompressible three-dimensional barrier on the surface of nickel powder. Through a strong entropy repulsion effect, it can effectively prevent van der Waals attraction of particles even at high solid content, thus preventing agglomeration, which is unmatched by linear molecules.

[0023] 2. Strong multi-point anchoring: The densely functionalized ends on the molecular surface can simultaneously interact strongly with multiple sites on the surface of a single nickel powder particle, forming a "multi-claw anchoring" with high adsorption energy, shear resistance, storage resistance, and excellent dispersion stability.

[0024] 3. Excellent viscosity reduction and rheological control capabilities: The spherical structure of the molecules and the compatible chain segments introduced therein act as a "ball bearing" lubrication between particles, and can effectively destroy the network structure between particles, significantly reduce the viscosity of the paste, improve fluidity, and obtain rheological properties (high shear thinning) suitable for fine printing.

[0025] 4. Good thermal cleanliness: The polyether backbone and most functional groups can be basically decomposed into volatile small molecules under an inert / reducing sintering atmosphere, with extremely low residual ash content, which is conducive to obtaining a highly dense and highly conductive sintered nickel layer.

[0026] 5. High versatility: This structural design has good effects on various types of nickel powder (carbonyl nickel, reduced nickel, and different particle sizes), and can be extended to the dispersion of other easily oxidized metal powders (such as copper powder and iron powder).

[0027] Detailed Implementation Methods and Examples Example 1: Synthesis of Phosphonate / Long-Chain Alkyl Co-Modified Hyperbranched Polyether Dispersant (HBPE-P / C18)** 1. Using TMP as the core and DMC as the catalyst, HBPE-OH (G4) with Mn≈8000 and hydroxyl value of about 140 mgKOH / g was synthesized through 4 generations of PO growth.

[0028] 2. Take 100g of the above HBPE-OH and 35g of stearic acid, and react at 140℃ for 6 hours under the catalysis of p-toluenesulfonic acid to esterify about 50% of the hydroxyl groups, thus obtaining HBPE-C18.

[0029] 3. 80 g of HBPE-C18 and 25 g of diethylvinylphosphonate were reacted at 80 °C for 8 hours under the catalysis of a small amount of sodium methoxide, so that most of the remaining hydroxyl groups were converted into diethylphosphonate groups. A pale yellow viscous liquid, HBPE-P / C18, was obtained, and the phosphonate esterification was confirmed to be successful by 31P-NMR.

[0030] Example 2: Synthesis of acetylacetone-modified hyperbranched polyether dispersant (HBPE-AA) Take 100g of HBPE-OH synthesized in step 1, 40g of ethyl acetoacetate and catalyst, and reflux in toluene to dehydrate and convert more than 80% of the hydroxyl groups to acetylacetone groups to obtain the product HBPE-AA.

[0031] Application test case: - Slurry formulation: 85g of nickel carbonyl powder (D50=0.8 μm), 15g of organic carrier (10% ethyl cellulose terpineol solution), and a variable amount of dispersant.

[0032] - Preparation process: Premix in a planetary mixer for 30 minutes, and roll in a three-roll mill for 5 passes until the fineness meets the requirements.

[0033] - Evaluation metrics: 1. Slurry viscosity: The viscosity at 10 rpm was measured using a rotational viscometer.

[0034] 2. Dispersion stability: After the slurry has been left to stand for 7 days, the volume percentage of the bottom sediment is measured.

[0035] 3. Sintering performance: The slurry was cast into a film and sintered at 900℃ in a N2 / H2 atmosphere. The surface resistivity of the sintered film was measured. Conclusion: The hyperbranched polyether dispersant provided by this invention, with its unique three-dimensional structure and multifunctional ends, significantly reduces the viscosity of high-solids-content nickel slurry while providing excellent long-term dispersion stability. More importantly, its use helps to obtain sintered electrodes with lower resistance, which is crucial for improving the performance of components such as capacitors and inductors, demonstrating significant industrial application value.

Claims

1. A hyperbranched polyether dispersant for nickel powder, characterized in that, It is a hyperbranched polyether structure formed by the polymerization of epoxides with polyols as the core, and its terminal groups include: (i) Strongly coordinating anchoring groups, selected from phosphonate, carboxyl, acetylacetone, or amino groups, comprising 30%–70% of the total number of terminal groups; and (ii) Spatially stable and compatible segments comprising long-chain alkyl or low-polyoxypropylene chains, accounting for 30%-70% of the total number of terminal groups.

2. The dispersant according to claim 1, characterized in that, The hyperbranched polyether has a branching generation of 3-5 and a number average molecular weight of 2,000-15,000 g / mol.

3. The dispersant according to claim 1, characterized in that, The strong coordination anchoring group is a dialkylphosphonate group or an acetylacetone group.

4. The dispersant according to claim 1, characterized in that, The spatially stable and compatible segments are connected to the ends of the hyperbranched polyether via ester or ether bonds, and their long-chain alkyl groups are C12-C18 alkyl groups.

5. A method for preparing the dispersant according to any one of claims 1-4, characterized in that, Including the following steps: (a) Using polyols as initiators, ring-opening polymerization of epoxides is catalyzed to synthesize hyperbranched polyether polyols with hydroxyl terminals; (b) Reacting some of the terminal hydroxyl groups with long-chain alkyl compounds to introduce sterically stable and compatible segments; (c) The remaining terminal hydroxyl groups are reacted with a phosphonate esterifying agent or an acetoacetate ester reagent to introduce a strongly coordinating anchoring group.

6. The method according to claim 5, characterized in that, A bimetallic cyanide (DMC) catalyst is used in step (a).

7. The use of the hyperbranched polyether dispersant as described in any one of claims 1-4 in the preparation of nickel-based conductive or magnetic pastes for capacitors or inductors.

8. A nickel-based electronic paste, characterized in that, It comprises nickel powder, an organic carrier, and a hyperbranched polyether dispersant as described in any one of claims 1-4.

9. The nickel-based electronic paste according to claim 8, characterized in that, Based on the weight of nickel powder, the amount of dispersant added is 0.3% - 3.0%.

10. The nickel-based electronic paste according to claim 8 or 9, characterized in that, The slurry has a solids content of 70-92 wt% and a settling rate of less than 5% after standing for 7 days.