Oxygen absorbing type polypropylene carbonate sacrificial binder for electronic or ceramic paste

Abstract

The present application relates to a kind of oxygen-absorbing type polypropylene carbonate sacrificial binder and its application in electronic paste or ceramic paste, the sacrificial binder is modified by molecular structure to polypropylene carbonate (PPC), covalently grafts allyl ether group (-O-CH2-CH=CH2) in its main chain portion propyl side chain site, so that it is based on the rheological regulation and low residual characteristics of traditional binder, new active oxygen-absorbing function is added.The beneficial effects of the present application are that in the pre-sintering stage of the paste, the allyl ether group consumes the residual oxygen in the system through thermal activation free radical chain reaction, effectively inhibits the oxidation of metal powder or ceramic functional phase, so that the resistivity of sintered body is significantly reduced.The present application realizes oxidation resistance from the material level, reduces the dependence on complex external atmosphere control, and widens the paste process window.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials or functional polymer materials technology, and particularly relates to an oxygen-absorbing polypropylene carbonate sacrificial binder for electronic pastes or ceramic pastes. Background Technology

[0002] Electronic pastes and ceramic pastes are key materials for electronic packaging, functional ceramics, and component fabrication. Their composition typically includes inorganic functional powders, organic carriers, solvents, and sacrificial binders. In the paste sintering process, the sacrificial binder primarily improves powder dispersibility, regulates rheology, and provides bonding during molding. Furthermore, during subsequent high-temperature sintering, the sacrificial binder undergoes thermal decomposition (decomposition or volatilization under elevated temperatures) to remove organic components from the product, thus preventing organic residues from adversely affecting its performance.

[0003] However, the sacrificial binders commonly used in existing technologies have significant limitations:

[0004] (1) The sacrificial binders used in the prior art mainly undertake the functions of physical rheological regulation and film formation, and lack the ability to actively regulate the atmosphere in the system before sintering. Especially under complex or dense packing conditions, the oxygen remaining in the slurry during drying and debinding can easily cause oxidation of metal powder (such as copper powder) or functional phase, resulting in the deterioration of the electrical properties of the sintered body;

[0005] (2) At present, the means of suppressing oxidation rely on external atmosphere control (such as introducing a reducing atmosphere), but this type of method has high requirements for equipment and process window, high equipment cost and difficulty in completely eliminating local oxygen in pores;

[0006] (3) Although there are oxygen-absorbing polymer materials (such as oxygen-absorbing polymer materials in the packaging field), they usually introduce functional groups that are easy to react with oxygen into the main chain or side chain of the polymer, so that the material can consume oxygen in the environment under certain conditions. However, their molecular structure has not been optimized for the special working conditions of electronic paste and ceramic paste in the process of heating, debinding and high-temperature sintering, and cannot meet the needs of staged oxygen absorption and low residual debinding at low temperature.

[0007] Therefore, developing a sacrificial binder that combines active oxygen absorption with low residue properties is key to improving the oxidation resistance of electronic and ceramic pastes. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide an oxygen-absorbing polypropylene carbonate sacrificial binder for electronic pastes or ceramic pastes.

[0009] This oxygen-extracting polypropylene carbonate is a modified polymer of polypropylene carbonate, which has the following repeating units of polypropylene carbonate:

[0010] ,

[0011] n is the number of repeating units;

[0012] The modified polymer of polypropylene carbonate has an allyl ether group R covalently bonded to some propyl side chain sites on the polypropylene carbonate backbone as a side chain (instead of introducing side chains through physical blending or simple doping as in the prior art). The structural formula of R is (–O–CH2–CH=CH2):

[0013] ;

[0014] The amount of allyl ether groups introduced into polypropylene carbonate is 0.5–15 mol% (the amount introduced refers to the molar percentage of allyl ether groups in polypropylene carbonate, i.e., the molar percentage of allyl ether groups introduced at the structural unit level, based on the number of moles of repeating units in polypropylene carbonate). The allyl ether groups are grafted onto the polypropylene carbonate backbone, which can endow it with oxygen absorption capacity without destroying the polypropylene carbonate backbone structure. Furthermore, the allyl ether group R does not participate in backbone construction or cross-linking reactions, allowing it to undergo thermal decomposition under further heating conditions and achieve low organic residues.

[0015] Preferably, the amount of allyl ether groups introduced into polypropylene carbonate is 1–10 mol.

[0016] The preparation method of this oxygen-absorbing polypropylene carbonate includes the following steps:

[0017] Weigh out an average molecular weight of 5 × 10 4 ~15×10 4 5–20 g of poly(propylene carbonate) (PPC) per mol were dissolved in 50–300 mL of anhydrous tetrahydrofuran to obtain a mixed solution. The mixed solution was stirred at 20–40 °C for 0.5–2 h under a nitrogen atmosphere to obtain a homogeneous solution.

[0018] Hydroxylation treatment was performed on the molecular chain ends of polypropylene carbonate in a homogeneous solution to introduce hydroxyl active sites at some propyl side chain sites on the main chain of polypropylene carbonate. A basic alcohol solution, a weak base, or a nucleophilic reagent was added to the homogeneous solution, and the pH value of the homogeneous solution containing the basic alcohol solution, weak base, or nucleophilic reagent was controlled at 8-12. The reaction was carried out at a temperature of 20-60 °C for 0.5-6 h to form hydroxyl groups at the molecular chain ends or side positions of polypropylene carbonate without significantly reducing the molecular weight of the polymer.

[0019] Add an allylating agent to the reaction system after the above-mentioned hydroxylation treatment and introduction of hydroxyl active sites, mix at a temperature of 30-80 °C, and react for 4-24 h to introduce the allyl-containing ether bond structure into the polypropylene carbonate molecular chain in a side-linking manner.

[0020] After the reaction solution is completed, it is poured into a non-solvent for precipitation and then filtered. The resulting solid is placed in a vacuum environment and dried at a temperature of 30–60 °C to obtain oxygen-absorbing polypropylene carbonate that can be used as a sacrificial binder.

[0021] Preferably, the molecular chain ends of polypropylene carbonate in the homogeneous solution are hydroxylated to introduce hydroxyl active sites at some propyl side chain sites on the main chain of polypropylene carbonate: an alkaline alcohol solution with a concentration of 0.01-1.0 mol / L is added to the homogeneous solution, the pH value of the homogeneous solution with added alkaline alcohol solution is controlled at 8-12, and a reaction is carried out at a temperature of 20-60 °C to controllably open the ring or activate the chain ends of the polypropylene carbonate molecular chain, thereby forming hydroxyl groups at the molecular chain ends or side positions of polypropylene carbonate.

[0022] Preferably, the allylating agent is selected from at least one of the following: allyl halide, allyl sulfonate and allyl glycidyl ether; the amount of allylating agent added is 0.5 to 5 times the molar amount of hydroxyl groups in the reaction system.

[0023] Preferably, after completing the hydroxylation treatment and introducing hydroxyl active sites, the amount of allyl ether groups introduced into the obtained oxygen-absorbing polypropylene carbonate is adjusted by adjusting the amount of allylating agent added.

[0024] An oxygen-absorbing polypropylene carbonate electronic paste comprises: 50-90 wt% metal powder, 1-20 wt% organic carrier, 5-40 wt% solvent and 0.1-10 wt% oxygen-absorbing polypropylene carbonate;

[0025] Among them, oxygen-absorbing polypropylene carbonate is used as a sacrificial binder, and allyl ether oxygen-absorbing functional side chain is used to prevent the electronic paste from oxidizing before sintering.

[0026] In this slurry system, oxygen-absorbing polypropylene carbonate not only improves powder dispersion, adjusts slurry rheological properties, and provides film-forming adhesion, but the allyl ether oxygen-absorbing functional side chain can also actively consume residual oxygen inside the slurry system through its staged oxygen absorption behavior during the pre-sintering stage and during the thermal activation of free radical auto-oxidation under heating conditions.

[0027] In actual processes, oxygen-absorbing polypropylene carbonate maintains good storage stability and printability at room temperature to approximately 120°C, and no significant oxygen absorption reaction occurs within this temperature range.

[0028] Under thermally activated conditions (temperatures are raised to approximately 120–300 °C and heated at a rate of 0.5–10 °C / min (preferably 1–5 °C / min)), the oxygen-absorbing side chain of allyl ether undergoes a free radical auto-oxidation reaction under these conditions (the hydrogen at the allyl position breaks to generate allyl free radicals (the allyl ether side chain structure is thermally activated), the free radicals react with oxygen to generate peroxy free radicals, and further form hydroperoxides and other stable oxygen-containing compounds (including but not limited to alcohols, ketones, or carboxylic acid derivatives)), thereby consuming oxygen. This allows for staged oxygen absorption during the drying, heating, or debinding stages of the slurry, reducing the risk of oxidation before sintering, and even preventing oxidation before sintering.

[0029] During the process of further heating to 300-600 °C at a heating rate of 1-10 °C / min (preferably 2-5 °C / min), the carbonate bonds in the polypropylene carbonate backbone undergo thermal decomposition, and the oxygen-absorbing polypropylene carbonate decomposes or volatilizes, thereby essentially removing organic components before sintering or high-temperature treatment. After sintering, low organic residue can be achieved, maintaining its characteristic of low organic residue as a sacrificial binder, which is beneficial to reducing the impact of residual carbon on sintering densification and electrical properties.

[0030] As a preferred option:

[0031] It also includes additives, which are at least one of the following: plasticizers, dispersants, rheology modifiers, and wetting agents; the additives can improve the processing performance, dispersion stability, or printability of the slurry; the introduction of the additives does not change the molecular structure of the oxygen-absorbing polypropylene carbonate sacrificial binder, nor does it participate in its free radical self-oxidation oxygen absorption reaction process, and their type and dosage can be conventionally selected and adjusted by those skilled in the art according to the specific slurry system and process conditions;

[0032] The metal powder is copper powder.

[0033] A ceramic slurry comprising oxygen-extracting polypropylene carbonate includes: 50–90 wt% ceramic powder, 1–20 wt% organic carrier, 5–40 wt% solvent and 0.1–10 wt% oxygen-extracting polypropylene carbonate;

[0034] Among them, oxygen-absorbing polypropylene carbonate is used as a sacrificial binder, and allyl ether oxygen-absorbing side chain is used to prevent the ceramic slurry from oxidizing before sintering.

[0035] In this slurry system, oxygen-absorbing polypropylene carbonate not only improves powder dispersion, adjusts slurry rheological properties, and provides film-forming adhesion, but the allyl ether oxygen-absorbing functional side chain can also actively consume residual oxygen inside the slurry system through its staged oxygen absorption behavior during the pre-sintering stage and during the thermal activation of free radical auto-oxidation under heating conditions.

[0036] In actual processes, oxygen-absorbing polypropylene carbonate maintains good storage stability and printability at room temperature to approximately 120°C, and no significant oxygen absorption reaction occurs within this temperature range.

[0037] Under thermally activated conditions (temperatures are raised to approximately 120–300 °C and heated at a rate of 0.5–10 °C / min (preferably 1–5 °C / min)), the oxygen-absorbing side chain of allyl ether undergoes a free radical auto-oxidation reaction under these conditions (the hydrogen at the allyl position breaks to generate allyl free radicals (the allyl ether side chain structure is thermally activated), the free radicals react with oxygen to generate peroxy free radicals, and further form hydroperoxides and other stable oxygen-containing compounds (including but not limited to alcohols, ketones, or carboxylic acid derivatives)), thereby consuming oxygen. This allows for staged oxygen absorption during the drying, heating, or debinding stages of the slurry, reducing the risk of oxidation before sintering, and even preventing oxidation before sintering.

[0038] During the process of further heating to 300-600 °C at a heating rate of 1-10 °C / min (preferably 2-5 °C / min), the carbonate bonds in the polypropylene carbonate backbone undergo thermal decomposition, and the oxygen-absorbing polypropylene carbonate decomposes or volatilizes, thereby essentially removing organic components before sintering or high-temperature treatment. After sintering, low organic residue can be achieved, maintaining its characteristic of low organic residue as a sacrificial binder, which is beneficial to reducing the impact of residual carbon on sintering densification and electrical properties.

[0039] As a preferred option:

[0040] It also includes additives, which are at least one of the following: plasticizers, dispersants, rheology modifiers, and wetting agents; the additives can improve the processing performance, dispersion stability, or printability of the slurry; the introduction of the additives does not change the molecular structure of the oxygen-absorbing polypropylene carbonate sacrificial binder, nor does it participate in its free radical self-oxidation oxygen absorption reaction process, and their type and dosage can be conventionally selected and adjusted by those skilled in the art according to the specific slurry system and process conditions;

[0041] The ceramic powder is alumina ceramic powder.

[0042] The beneficial effects of this invention are:

[0043] This invention functionalizes the molecular structure of polypropylene carbonate (PPC) by covalently grafting allyl ether groups (-O-CH2-CH=CH2) onto the propyl side chain sites of its main chain. This results in an oxygen-absorbing sacrificial binder that retains the rheological control, film-forming properties, and low residue characteristics (residual rate ≤0.25% after sintering) of traditional binders, while adding an active oxygen absorption function (i.e., the ability to actively consume residual oxygen in the slurry system through its thermally activated staged oxygen absorption behavior before sintering). This endows it with oxygen absorption capacity without damaging the main chain structure of polypropylene carbonate.

[0044] This oxygen-absorbing polypropylene carbonate consumes residual oxygen in the system through a thermally activated free radical chain reaction of allyl ether before sintering (at temperatures of 120–300°C). This effectively inhibits the oxidation of metal powders (such as copper powder) or functional phases, reducing the resistivity of the sintered body to 6.5 μΩ·cm. The oxygen-absorbing behavior of the allyl ether group occurs before the thermal decomposition of the polypropylene carbonate main chain. As a side chain, the allyl ether group does not participate in the main chain construction and crosslinking reaction, thus not weakening the original low-temperature decomposition and easy-to-remove adhesive properties of polypropylene carbonate.

[0045] The oxygen-absorbing polypropylene carbonate sacrificial binder of the present invention can be used to improve powder dispersibility, adjust slurry rheological properties and provide film-forming bonding. It can reduce the risk of pre-sintering oxidation at the material level without relying on an external reducing atmosphere, significantly broadening the slurry process window and being applicable to a variety of electronic slurry and ceramic slurry systems, thereby improving the performance consistency and reliability of sintered products. Detailed Implementation

[0046] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0047] Example 1

[0048] A method for preparing oxygen-absorbing polypropylene carbonate includes the following steps:

[0049] Weigh out an average molecular weight of 5 × 10 4 ~15×10 4 5–20 g of poly(propylene carbonate) (PPC) per mol were dissolved in 50–300 mL of anhydrous tetrahydrofuran to obtain a mixed solution. The mixed solution was stirred at 20–40 °C for 0.5–2 h under a nitrogen atmosphere to obtain a homogeneous solution.

[0050] Hydroxylation treatment was performed on the molecular chain ends of polypropylene carbonate in a homogeneous solution to introduce hydroxyl active sites at some propyl side chain sites on the main chain of polypropylene carbonate. A basic alcohol solution with a concentration of 0.01-1.0 mol / L was added to the homogeneous solution, and the pH value of the homogeneous solution with added basic alcohol solution was controlled at 8-12. The reaction was carried out at a temperature of 20-60 °C for 0.5-6 h to controllably open the ring or activate the chain ends of polypropylene carbonate molecular chains or some carbonate bonds, so as to form hydroxyl groups at the molecular chain ends or side positions of polypropylene carbonate without significantly reducing the molecular weight of the polymer.

[0051] Allyl sulfonate was added to the reaction system after the above-mentioned hydroxylation treatment and introduction of hydroxyl active sites. The amount of allyl sulfonate added was 0.5 to 5 times the molar amount of hydroxyl groups in the reaction system. The mixture was mixed at a temperature of 30 to 80 °C and reacted for 4 to 24 h, so that the allyl-containing ether bond structure was introduced into the polypropylene carbonate molecular chain by side linking.

[0052] After the reaction solution is completed, it is poured into a non-solvent for precipitation and then filtered. The resulting solid is placed in a vacuum environment and dried at a temperature of 30-60 °C to obtain oxygen-absorbing polypropylene carbonate that can be used as a sacrificial binder.

[0053] The oxygen-absorbing polypropylene carbonate obtained by the method described in this embodiment is a modified polymer of polypropylene carbonate. The basic repeating structural unit of the modified polypropylene carbonate polymer is derived from polypropylene carbonate, that is, the modified polypropylene carbonate polymer has the following repeating units of polypropylene carbonate:

[0054] ,

[0055] n is the number of repeating units;

[0056] The modified polymer of polypropylene carbonate has an allyl ether group R covalently bonded to some propyl side chain sites on the polypropylene carbonate backbone as a side chain (instead of introducing side chains through physical blending or simple doping as in the prior art). The structural formula of R is (–O–CH2–CH=CH2):

[0057] ;

[0058] The amount of allyl ether groups introduced into polypropylene carbonate is 1–10 mol.

[0059] The residual rate, resistivity, and viscosity of the obtained oxygen-absorbing polypropylene carbonate were tested using the following methods. The test results are shown in Table 1:

[0060] (1) Residual percentage (TGA): Thermogravimetric analysis was used to record the percentage of mass remaining at the final temperature by heating from room temperature to 500 ℃ at a heating rate of 2 ℃ / min in air atmosphere.

[0061] (2) Resistivity: The corresponding paste is printed on the surface of the substrate. After drying, debinding and sintering, the volume resistivity is tested at room temperature using the four-probe method. The result is expressed in μΩ·cm.

[0062] (3) Viscosity: A rotational rheometer was used to measure the viscosity at 25 °C and a shear rate of 10 s. -1 The steady-state viscosity of the slurry was tested, and the results are expressed in Pa·s.

[0063] Example 2

[0064] Based on Example 1, this example, after completing the hydroxylation treatment and introducing hydroxyl active sites, adjusts the amount of allyl ether groups introduced into the oxygen-extracting polypropylene carbonate by adjusting the amount of allylating agent added, wherein:

[0065] When the amount of allylating agent added is 0.2 to 0.8 times the molar amount of hydroxyl groups in the reaction system, an oxygen-extracting polypropylene carbonate with an allyl ether group introduction amount of about 1 mol% is obtained.

[0066] When the amount of allylating agent added is 0.8 to 2.0 times the molar amount of hydroxyl groups in the reaction system, an oxygen-extracting polypropylene carbonate with an allyl ether group introduction amount of about 5 mol% is obtained.

[0067] When the amount of allylating agent added is 2.0 to 4.0 times the molar amount of hydroxyl groups in the reaction system, an oxygen-extracting polypropylene carbonate with an allyl ether group introduction amount of about 12 mol% is obtained.

[0068] The residual rate, resistivity, and viscosity of the obtained oxygen-absorbing polypropylene carbonate were tested using the following methods. The test results are shown in Table 1:

[0069] (1) Residual percentage (TGA): Thermogravimetric analysis was used to record the percentage of mass remaining at the final temperature by heating from room temperature to 500 ℃ at a heating rate of 2 ℃ / min in air atmosphere.

[0070] (2) Resistivity: The corresponding paste is printed on the surface of the substrate. After drying, debinding and sintering, the volume resistivity is tested at room temperature using the four-probe method. The result is expressed in μΩ·cm.

[0071] (3) Viscosity: A rotational rheometer was used to measure the viscosity at 25 °C and a shear rate of 10 s. -1 The steady-state viscosity of the slurry was tested, and the results are expressed in Pa·s.

[0072] The above tests show that oxygen-absorbing polypropylene carbonates with different amounts of oxygen introduced all maintain good solubility and film-forming properties at room temperature.

[0073] Example 3

[0074] In this embodiment, the oxygen-absorbing polypropylene carbonate prepared in Example 1 is used as a sacrificial binder to prepare an electronic paste. The formulation of the electronic paste is as follows, by mass percentage:

[0075] 70 wt% copper powder, 10 wt% organic carrier, 15 wt% solvent, and 5 wt% oxygen-absorbing polypropylene carbonate were mixed and dispersed to obtain a homogeneous slurry; the obtained homogeneous slurry was dried and heated in an air atmosphere.

[0076] The residual rate, resistivity, and viscosity of the obtained electronic paste were tested using the following methods. The test results are shown in Table 1:

[0077] (1) Residual percentage (TGA): Thermogravimetric analysis was used to record the percentage of mass remaining at the final temperature by heating from room temperature to 500 ℃ at a heating rate of 2 ℃ / min in air atmosphere.

[0078] (2) Resistivity: The corresponding paste is printed on the surface of the substrate. After drying, debinding and sintering, the volume resistivity is tested at room temperature using the four-probe method. The result is expressed in μΩ·cm.

[0079] (3) Viscosity: A rotational rheometer was used to measure the viscosity at 25 °C and a shear rate of 10 s. -1 The steady-state viscosity of the slurry was tested, and the results are expressed in Pa·s.

[0080] Experimental results show that the copper powder oxidation phenomenon in the electronic paste of this embodiment is significantly reduced in the pre-sintering stage.

[0081] Example 4

[0082] This embodiment uses the same slurry formulation as Example 3, except that the copper powder in the slurry formulation is replaced with alumina ceramic powder, while the other conditions remain unchanged, to prepare a ceramic slurry.

[0083] The residual rate, resistivity, and viscosity of the obtained ceramic slurry were tested using the following methods. The test results are shown in Table 1:

[0084] (1) Residual percentage (TGA): Thermogravimetric analysis was used to record the percentage of mass remaining at the final temperature by heating from room temperature to 500 ℃ at a heating rate of 2 ℃ / min in air atmosphere.

[0085] (2) Resistivity: The corresponding paste is printed on the surface of the substrate. After drying, debinding and sintering, the volume resistivity is tested at room temperature using the four-probe method. The result is expressed in μΩ·cm.

[0086] (3) Viscosity: A rotational rheometer was used to measure the viscosity at 25 °C and a shear rate of 10 s. -1 The steady-state viscosity of the slurry was tested, and the results are expressed in Pa·s.

[0087] Experimental results show that during the pre-sintering heating stage, the ceramic slurry system exhibits phased oxygen absorption behavior, which helps reduce the oxidation risk caused by oxygen retention in the ceramic slurry.

[0088] Example 5

[0089] In this embodiment, the oxygen-absorbing polypropylene carbonate obtained in Example 1 is introduced as a sacrificial binder into the same electronic paste system as in Example 3. The paste formulation and process conditions in this embodiment are the same as in Example 3, and a uniform electronic paste is obtained.

[0090] The residual rate, resistivity, and viscosity of the obtained electronic paste were tested using the following methods. The test results are shown in Table 1:

[0091] (1) Residual percentage (TGA): Thermogravimetric analysis was used to record the percentage of mass remaining at the final temperature by heating from room temperature to 500 ℃ at a heating rate of 2 ℃ / min in air atmosphere.

[0092] (2) Resistivity: The corresponding paste is printed on the surface of the substrate. After drying, debinding and sintering, the volume resistivity is tested at room temperature using the four-probe method. The result is expressed in μΩ·cm.

[0093] (3) Viscosity: A rotational rheometer was used to measure the viscosity at 25 °C and a shear rate of 10 s. -1 The steady-state viscosity of the slurry was tested, and the results are expressed in Pa·s.

[0094] The electronic paste was heated to 400 °C in air at a heating rate of 2 °C / min. The electronic paste was able to absorb oxygen before sintering and fully decompose during the subsequent heating process. No obvious organic residue was observed after sintering.

[0095] Comparative Example 1

[0096] Electronic paste without oxygen-extracting polypropylene carbonate: This comparative example uses the exact same paste formulation and process conditions as Example 3, except that the sacrificial binder is replaced with unmodified polypropylene carbonate.

[0097] The residual rate, resistivity, and viscosity of the obtained electronic paste were tested using the following methods. The test results are shown in Table 1:

[0098] (1) Residual percentage (TGA): Thermogravimetric analysis was used to record the percentage of mass remaining at the final temperature by heating from room temperature to 500 ℃ at a heating rate of 2 ℃ / min in air atmosphere.

[0099] (2) Resistivity: The corresponding paste is printed on the surface of the substrate. After drying, debinding and sintering, the volume resistivity is tested at room temperature using the four-probe method. The result is expressed in μΩ·cm.

[0100] (3) Viscosity: A rotational rheometer was used to measure the viscosity at 25 °C and a shear rate of 10 s. -1 The steady-state viscosity of the slurry was tested, and the results are expressed in Pa·s.

[0101] Test results show that the slurry system did not exhibit significant oxygen absorption behavior during the pre-sintering heating stage, and obvious oxidation occurred on the surface of the copper powder.

[0102] Comparative Example 2

[0103] Electronic paste of physically blended allyl ether small molecules: This comparative example uses the same paste formulation as Example 3, except that the oxygen-extracting polypropylene carbonate is replaced with unmodified polypropylene carbonate, and an equal amount of allyl ether small molecules is added as a control.

[0104] The residual rate, resistivity, and viscosity of the obtained electronic paste were tested using the following methods. The test results are shown in Table 1:

[0105] (1) Residual percentage (TGA): Thermogravimetric analysis was used to record the percentage of mass remaining at the final temperature by heating from room temperature to 500 ℃ at a heating rate of 2 ℃ / min in air atmosphere.

[0106] (2) Resistivity: The corresponding paste is printed on the surface of the substrate. After drying, debinding and sintering, the volume resistivity is tested at room temperature using the four-probe method. The result is expressed in μΩ·cm.

[0107] (3) Viscosity: A rotational rheometer was used to measure the viscosity at 25 °C and a shear rate of 10 s. -1 The steady-state viscosity of the slurry was tested, and the results are expressed in Pa·s.

[0108] Test results show that the reaction of the slurry system is uncontrollable during the heating process, and the residue increases significantly after the glue is removed.

[0109] Comparative Example 3:

[0110] Electronic paste of polypropylene carbonate with high grafting amount leading to crosslinking: In this comparative example, polypropylene carbonate with an allyl ether grafting amount of more than 20 mol% was used as a sacrificial binder. The other paste formulations and process conditions of this comparative example are the same as those of Example 3.

[0111] The residual rate, resistivity, and viscosity of the obtained electronic paste were tested using the following methods. The test results are shown in Table 1:

[0112] (1) Residual percentage (TGA): Thermogravimetric analysis was used to record the percentage of mass remaining at the final temperature by heating from room temperature to 500 ℃ at a heating rate of 2 ℃ / min in air atmosphere.

[0113] (2) Resistivity: The corresponding paste is printed on the surface of the substrate. After drying, debinding and sintering, the volume resistivity is tested at room temperature using the four-probe method. The result is expressed in μΩ·cm.

[0114] (3) Viscosity: A rotational rheometer was used to measure the viscosity at 25 °C and a shear rate of 10 s. -1 The steady-state viscosity of the slurry was tested, and the results are expressed in Pa·s.

[0115] Test results show that the electronic paste system in this comparative example undergoes significant cross-linking during the heating process, with insufficient debinding and organic residues after sintering.

[0116] Table 1. Comparison of test results for residual rate, resistivity, and viscosity of materials in Examples 1-5 and Comparative Examples 1-3.

[0117] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Residual percentage (TGA, wt%) 0.25 0.25 0.25 0.25 0.25 0.35 1.2 3.5 Resistivity (μΩ·cm) - - 6.5 8.0 6.0 18.0 30.0 45.0 Viscosity (Pa·s) - - 85 90 88 82 140 220

[0118] Note: Except for the type or structure of the sacrificial binder, the slurry formulation, solid content, dispersion process and heating regime are the same in each embodiment and comparative example.

Claims

1. An oxygen-absorbing polypropylene carbonate, characterized in that: The modified polymer is a polypropylene carbonate, wherein the modified polypropylene carbonate has the following repeating units of polypropylene carbonate: ， n is the number of repeating units; The modified polypropylene carbonate polymer has an allyl ether group R covalently bonded to some propyl side chain sites on the polypropylene carbonate backbone as a side chain. The structural formula of R is (–O–CH2–CH=CH2): ； The amount of the allyl ether group introduced into the polypropylene carbonate is 0.5–15 mol.

2. The oxygen-absorbing polypropylene carbonate according to claim 1, characterized in that: The amount of the allyl ether group introduced into the polypropylene carbonate is 1 to 10 mol.

3. A method for preparing oxygen-extracting polypropylene carbonate as described in claim 2, characterized in that, Includes the following steps: Weigh out an average molecular weight of 5 × 10 4 ~15×10 4 5–20 g of polypropylene carbonate (g / mol) was dissolved in 50–300 mL of anhydrous tetrahydrofuran to obtain a mixed solution, and the mixed solution was stirred at 20–40 °C for 0.5–2 h under a nitrogen atmosphere to obtain a homogeneous solution. The ends of the polypropylene carbonate molecular chains in the homogeneous solution are hydroxylated to introduce hydroxyl groups at some propyl side chain sites on the main chain of the polypropylene carbonate: an alkaline alcohol solution, a weak base, or a nucleophilic reagent is added to the homogeneous solution, the pH of the homogeneous solution containing the alkaline alcohol solution, weak base, or nucleophilic reagent is controlled at 8-12, and the reaction is carried out at a temperature of 20-60 °C for 0.5-6 h to form hydroxyl groups at the ends or side positions of the polypropylene carbonate molecular chains; Add an allylating agent to the reaction system after the hydroxylation treatment and introduction of hydroxyl groups, mix at a temperature of 30–80°C, and react for 4–24 h. After the reaction solution is completed, it is poured into a non-solvent for precipitation and then filtered. The resulting solid is placed in a vacuum environment and dried at a temperature of 30–60 °C to obtain oxygen-absorbing polypropylene carbonate.

4. The method for preparing oxygen-extracting polypropylene carbonate according to claim 3, characterized in that, The ends of the polypropylene carbonate molecular chains in the homogeneous solution are hydroxylated. When introducing hydroxyl groups at some propyl side chain sites on the main chain of the polypropylene carbonate: an alkaline alcohol solution with a concentration of 0.01-1.0 mol / L is added to the homogeneous solution, the pH value of the homogeneous solution with added alkaline alcohol solution is controlled at 8-12, and a reaction is carried out at a temperature of 20-60 °C to open the ring or activate the chain ends of the polypropylene carbonate molecular chains, thereby forming hydroxyl groups at the ends or side positions of the polypropylene carbonate molecular chains.

5. The method for preparing oxygen-extracting polypropylene carbonate according to claim 4, characterized in that: The allylating agent is selected from at least one of the following: allyl halides, allyl sulfonates, and allyl glycidyl ethers; the amount of the allylating agent added is 0.5 to 5 times the molar amount of hydroxyl groups in the reaction system.

6. The method for preparing oxygen-extracting polypropylene carbonate according to claim 5, characterized in that: After the hydroxylation treatment is completed and hydroxyl groups are introduced, the amount of allyl ether groups introduced into the obtained oxygen-absorbing polypropylene carbonate is adjusted by adjusting the amount of allylating agent added.

7. An electronic paste comprising oxygen-extracting polypropylene carbonate as described in any one of claims 1-2, characterized in that, include: 50–90 wt% metal powder, 1–20 wt% organic carrier, 5–40 wt% solvent and 0.1–10 wt% oxygen-extracting polypropylene carbonate; The oxygen-absorbing polypropylene carbonate serves as a sacrificial binder to prevent oxidation of the electronic paste during the pre-sintering stage.

8. The electronic paste according to claim 7, characterized in that: It also includes additives, said additives being at least one of the following: plasticizers, dispersants, rheology modifiers, and wetting agents; The metal powder is copper powder.

9. A ceramic slurry comprising oxygen-absorbing polypropylene carbonate as described in any one of claims 1-2, characterized in that, include: 50–90 wt% ceramic powder, 1–20 wt% organic carrier, 5–40 wt% solvent and 0.1–10 wt% oxygen-absorbing polypropylene carbonate; The oxygen-absorbing polypropylene carbonate serves as a sacrificial binder to prevent oxidation of the ceramic slurry before sintering.

10. The ceramic slurry according to claim 9, characterized in that: It also includes additives, said additives being at least one of the following: plasticizers, dispersants, rheology modifiers, and wetting agents; The ceramic powder is alumina ceramic powder.

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