A preparation method of rosin for toughening flux

Abstract

The present application relates to the technical field of soldering flux, and specifically discloses a method for preparing rosin for toughening soldering flux, comprising the following steps: mixing an alcohol-soluble resin with a solvent and adding a dissolving agent and stirring to obtain a mixed solution; adding rosin to the mixed solution, heating the mixture for reaction, and evaporating to obtain a solid as the rosin for soldering flux. The present application dissolves the alcohol-soluble resin in a solvent, and because it carries functional groups, the molecular chains are stretched out to react with the carboxyl groups of the rosin, and after chemical bonding, the molecular weight of the rosin becomes larger and the chain becomes longer, thereby improving the toughness of the rosin while maintaining its solubility and dissolution rate, avoiding the problem of rosin crystallization, and ensuring the soldering properties of the rosin itself.

Description

Technical Field

[0001] The present application relates to the technical field of soldering flux, and more specifically, to a method for preparing rosin for toughening soldering flux. Background Art

[0002] As an important natural resin, rosin is widely used in many fields such as electronic materials, especially in the welding materials industry. However, rosin itself has the defects of being brittle and easy to break, which limits its application in some occasions that require higher toughness.

[0003] At present, although there are some toughening technologies, the toughening effect is not significant, and it brings about the problem of greatly increased costs or decreased performance. Especially after being made into flux, due to its brittleness, after simple coating, it is affected by external environmental changes, and the rosin will be cracked due to external or internal stress, which will eventually cause the flux to fall off. This situation has a great negative impact on the operation and production efficiency of workers when using flux production.

[0004] Therefore, improving the toughness of rosin is of great significance to the development of flux. Summary of the invention

[0005] In order to improve the toughness of rosin for flux, the present application provides a method for preparing toughened rosin for flux.

[0006] The present application provides a method for preparing rosin for toughening flux, which adopts the following technical scheme: A method for preparing rosin for toughening flux comprises the following steps: (1) mixing an alcohol-soluble resin with a solvent and adding a solvent promoter and stirring to obtain a mixed solution; (2) Adding rosin to the mixed solution, heating for reaction and evaporating to dryness to obtain a solid, which is the rosin for soldering flux.

[0007] By adopting the above technical scheme, after the alcohol-soluble resin is dissolved in a solvent, because it has functional groups, the molecular chain is stretched and reacts with the carboxyl group of the rosin. After chemical bonding, the molecular weight of the rosin becomes larger and its chain becomes longer, thereby improving the toughness of the rosin while maintaining its solubility and dissolution rate, avoiding the problem of rosin crystallization and precipitation, and ensuring the fluxing properties of the rosin itself.

[0008] In a specific embodiment, the alcohol-soluble resin is polyvinyl butyral resin, polyvinyl pyrrolidone or polyethylene glycol resin.

[0009] By adopting the above technical scheme, the polyvinyl butyral resin contains longer side chains, has good flexibility, low glass transition temperature, high tensile strength and impact strength; has excellent transparency, good solubility, good light resistance, water resistance, heat resistance, cold resistance and film-forming properties; the hydroxyl groups contained in it can undergo esterification reaction with the carboxyl groups of rosin to increase the chain segments of the rosin, thereby improving the toughness of the rosin.

[0010] As a synthetic alcohol-soluble polymer compound, polyvinyl pyrrolidone has good colloid protection, film-forming, adhesive, hygroscopic, solubilizing or coagulating effects. It can react with rosin to increase the molecular weight of rosin and toughen it.

[0011] Polyethylene glycol has good solubility, hydration ability and surfactant properties. Its terminal hydroxyl group undergoes esterification reaction with the carboxyl group of rosin to lengthen the chain segment of rosin to improve the toughness of rosin.

[0012] In a specific embodiment, the average molecular weight of the alcohol-soluble resin is 200-10,000.

[0013] In a specific embodiment, the average molecular weight of the alcohol-soluble resin is 500-2000.

[0014] By adopting the above technical scheme, the size of the molecular weight plays a decisive role in the structure and performance of the alcohol-soluble resin. The increase in molecular weight increases the chain entanglement between crystals, thereby enhancing the connection between longitudinal and transverse microfibers. When performing a tensile test, the chain entanglement inhibits the relative sliding of the microfibers, thereby improving the tensile strength; on the contrary, if the molecular weight decreases, the entanglement between the molecular chains decreases, the force weakens, and the corresponding tensile strength also decreases. At the same time, the elongation at break increases rapidly to a maximum value as the molecular weight increases, and a further increase in the molecular weight will cause a gradual decrease in the elongation at break. Therefore, by optimizing the average molecular weight of the alcohol-soluble resin, the mechanical properties of the alcohol-soluble resin can be improved, thereby optimizing the mechanical properties of the rosin after the alcohol-soluble resin acts.

[0015] In a specific embodiment, the solvent is one or more of methanol, ethanol, isopropanol, N,N-dimethylformamide and N-methyl-2-pyrrolidone, and more preferably ethanol.

[0016] By adopting the above technical solution, ethanol has the advantages of being non-toxic and non-corrosive, can dissolve many inorganic substances and most organic substances, has a lower boiling point, lower viscosity and lower surface tension, and its ionic strength is also very low, which plays a good auxiliary role in the reaction.

[0017] In a specific embodiment, the dissolution agent is one or more of ethyl acetate, dichloromethane and carbon tetrachloride.

[0018] By adopting the above technical scheme, the solubility of the reactant can be increased by the dissolution promoter, which is beneficial to the preparation of the target product; ethyl acetate has excellent dissolving ability and is an excellent industrial solvent. Its physical properties are suitable for dissolving organic matter, and it has strong dissolving power, good volatility and low toxicity; dichloromethane is one of the few polar non-protonic non-nucleophilic solvents, and it has quite good solubility for many organic matters, and has the advantages of strong dissolving ability, low boiling point and low toxicity; carbon tetrachloride, due to its low boiling point and good melting point, can be used to dissolve and react substrates when used as a non-polar solvent, thereby promoting the reaction.

[0019] In a specific embodiment, the rosin is water-white rosin or natural rosin.

[0020] By adopting the above technical scheme, water-white rosin is made from natural rosin through refined decolorization, and has the properties of light color (close to white), low odor, good compatibility, good initial viscosity, and yellowing resistance; natural rosin has the advantages of viscosity enhancement, emulsification, softening, moisture resistance, corrosion resistance and insulation. Both water-white rosin and natural rosin are non-corrosive and non-hygroscopic, and have good insulation properties, and can remove metal oxides at welding temperature; secondly, rosin has film-forming properties, which can protect the metal surface from oxidation during the welding process, and form a dense hydrophobic organic film after welding, which has good electrical insulation and moisture-proof function, and can play a certain protective role on the welding point; in addition, rosin in a molten state has good fluidity and thermal conductivity, which can effectively promote heat transfer during the welding process and avoid poor welding.

[0021] In a specific embodiment, the rosin is acrylic rosin, and the preparation method of the propylene-modified rosin is: hydroquinone is added to the rosin, nitrogen is introduced for protection, acrylic acid is added dropwise after heating, and the reaction is carried out by heat preservation and cooling to obtain the acrylic rosin.

[0022] By adopting the above technical scheme, rosin is widely used in the field of electronic solder as the most important active agent. There are two easily oxidized double bonds in its structure, which is not conducive to long-term storage and use. Therefore, the rosin resin is subjected to a diene addition reaction by acrylic acid, and the carboxyl group and the conjugated double bond in the rosin resin are modified. The tricyclic phenanthrene skeleton of the resin acid has a hydrophobic group like the long-chain hydrocarbon group of the higher fatty acid, and the hydrophilic group can be introduced through the active groups such as the carboxyl group and the conjugated double bond, thereby increasing the number of carboxyl groups in the rosin, which is beneficial to the subsequent chemical and bonding with the hydroxyl group in the alcohol-soluble resin, and further increasing the molecular chain length of the rosin, thereby improving the toughness of the rosin used for the flux.

[0023] In a specific implementation manner, during the heating, the temperature is 230° C. and the reaction time is 3-4 hours; during the heat preservation, the dripping speed of the acrylic acid is 60 drops / min.

[0024] By adopting the above technical scheme, when heating, as the reaction temperature increases, the thermal isomerization of rosin resin is promoted, the diene addition reaction between rosin resin and acrylic acid is accelerated, and the content of adduct in the product is continuously increased. However, as the temperature continues to rise, the thermal isomerization of rosin resin reaches equilibrium, and decarboxylation reaction begins to occur. In addition, acrylic acid continues to evaporate and condense at high temperature, which accelerates its self-polymerization process, resulting in a downward trend in the content of adduct in the product. Therefore, it is more appropriate to control the reaction temperature at 230° C. The content of adduct in the reaction product generally increases with the extension of reaction time, but when the time is extended to a certain extent, the content of adduct decreases, which may be due to the increase of side reactions with the extension of time, so the optimal reaction time is the time point before the content of adduct begins to decrease.

[0025] During heat preservation, if the acceleration of acrylic acid droplet is too fast, the temperature will drop rapidly and it will be very slow to reach the specified reaction temperature, which will waste energy. At the same time, the acrylic acid concentration will be too high and it will easily volatilize. If the acceleration of acrylic acid droplet is too slow, the reaction time will be prolonged and the side reactions will increase.

[0026] In a specific embodiment, the mass ratio of rosin, hydroquinone and acrylic acid is 1:(0.02-0.04):(0.2-0.25).

[0027] By adopting the above technical scheme, when the mass of the catalyst hydroquinone is less than 2% of the rosin, the acid value of the system is low, indicating that the catalytic activity of the catalyst is insufficient and some acrylic acid still does not participate in the reaction; and when the mass of the catalyst is more than 4% of the rosin, the acid value of the system does not change much, so the use range of hydroquinone is 2-4% of the mass of the rosin.

[0028] When the amount of rosin is insufficient relative to acrylic acid, the acrylic acid content is higher than that of rosin, and acrylic acid will continue to evaporate, condense, and self-polymerize, resulting in a downward trend in the content of adducts in the product; and as the amount of rosin added increases, the content of adducts increases, but when the rosin is added in excess, the softening point of the obtained product is significantly reduced, which does not meet the requirements of the product technical indicators.

[0029] In summary, this application has the following beneficial effects: 1. In the present application, after the alcohol-soluble resin is dissolved in a solvent, the molecular chain of the alcohol-soluble resin is stretched out because of its functional groups, and then reacts with the carboxyl group of the rosin. After chemical bonding, the molecular weight of the rosin becomes larger and the chain becomes longer, thereby improving the toughness of the rosin while maintaining its solubility and dissolution rate, avoiding the problem of rosin crystallization, and ensuring the flux property of the rosin itself; 2. In the present application, the rosin is modified by acrylic acid to obtain polypropylene rosin, and the process parameters in the preparation process are controlled at the same time. The obtained acrylic rosin is not easy to oxidize, which is conducive to long-term storage and use. More importantly, the number of carboxyl groups in the rosin is increased, which is conducive to the subsequent chemical bonding with the hydroxyl groups in the alcohol-soluble resin, further increasing the molecular chain length of the rosin, thereby improving the toughness of the rosin for flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the infrared spectrum of the rosin for toughening flux prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0031] The present application is further described in detail below in conjunction with embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0032] Preparation Example 1 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0033] Preparation Example 2 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 2 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 20 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0034] Preparation Example 3 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 4 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 25 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 4 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0035] Preparation Example 4 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of water-white rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230° C. while N2 was introduced, and 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170° C. to obtain acrylic rosin.

[0036] Preparation Example 5 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 1 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0037] Preparation Example 6 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 5 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0038] Preparation Example 7 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 33.3 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0039] Preparation Example 8 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 16.7 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0040] Preparation Example 9 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 220°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0041] Preparation Example 10 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 240°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0042] Preparation Example 11 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 2 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0043] Preparation Example 12 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 60 drops / min. After the reaction was kept warm for 5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0044] Preparation Example 13 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 55 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin.

[0045] Preparation Example 14 In this preparation example, acrylic rosin was prepared according to the following method: 100 g of natural rosin and 3 g of hydroquinone were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a thermometer, and the temperature was slowly raised to 230°C while N2 was introduced. 22.2 g of acrylic acid was added dropwise from the feeding funnel at a rate of 65 drops / min. After the reaction was kept warm for 3.5 hours, the temperature was lowered to 170°C to obtain acrylic rosin. Example

[0046] Example 1 In this embodiment, rosin for toughening flux is prepared according to the following steps: at 25°C, 5g of polyvinyl butyral resin with a number average molecular weight of 2000 and 95g of ethanol are added to a three-necked flask, and 20g of ethyl acetate is added to stir to completely dissolve the solid in the liquid, and then 15g of natural rosin is added and heated to 50°C for dissolution. After complete dissolution, the stirring speed is set to 300r / min and the reaction is carried out for 20min. The solution after the reaction is poured into a leveling machine and evaporated in a water bath at 85°C. The solid product on the ground is the rosin for flux.

[0047] Example 2 In this embodiment, the toughened rosin for soldering flux is prepared according to the following steps: at 25°C, 5g of polyvinyl butyral resin with a number average molecular weight of 2000 and 95g of ethanol are added to a three-necked flask, and 20g of ethyl acetate is added and stirred to completely dissolve the solid in the liquid, and then 15g of acrylic rosin is added and heated to 50°C for dissolution. After complete dissolution, the stirring speed is set to 300r / min, and the reaction is carried out for 20min. The solution after the reaction is poured into a leveling machine, and evaporated to dryness in a water bath at 85°C. The solid product on the flat ground is rosin for soldering flux, and its infrared spectrum is as shown in Figure 1 As shown; wherein the acrylic rosin is obtained from Preparation Example 1.

[0048] Example 3 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 2.

[0049] Example 4 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 3.

[0050] Example 5 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 4.

[0051] Example 6 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 5.

[0052] Example 7 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 6.

[0053] Example 8 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 7.

[0054] Example 9 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 8.

[0055] Example 10 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 9.

[0056] Embodiment 11 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 10.

[0057] Example 12 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 11.

[0058] Example 13 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 12.

[0059] Embodiment 14 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 13.

[0060] Embodiment 15 The difference between this embodiment and embodiment 1 is that the acrylic rosin is obtained from preparation example 14.

[0061] Example 16 In this embodiment, rosin for toughening flux is prepared according to the following steps: at 25°C, 5g of polyvinyl pyrrolidone resin with a number average molecular weight of 2000 and 95g of ethanol are added to a three-necked flask, and 20g of ethyl acetate as a promoter is added and stirred to make the solid completely dissolved in the liquid, and then 15g of acrylic rosin is added and heated to 50°C for dissolution. After complete dissolution, the stirring speed is set to 300r / min, and the reaction is carried out for 20min. The solution after the reaction is poured into a leveling machine and evaporated in a water bath at 85°C. The solid product on the ground is the rosin for flux; wherein the acrylic rosin is obtained in Preparation Example 1.

[0062] Embodiment 17 In this embodiment, rosin for toughening flux is prepared according to the following steps: at 25°C, 5g of polyethylene glycol resin with a number average molecular weight of 2000 and 95g of ethanol are added to a three-necked flask, and 20g of ethyl acetate as a promoter is added and stirred to make the solid completely dissolved in the liquid, and then 15g of acrylic rosin is added and heated to 50°C for dissolution. After complete dissolution, the stirring speed is set to 300r / min, and the reaction is carried out for 20min. The solution after the reaction is poured into a selected leveler and evaporated in a water bath at 85°C. The solid product on the ground is the rosin for flux; wherein the acrylic rosin is obtained in Preparation Example 1.

[0063] Embodiment 18 In this embodiment, rosin for toughening flux is prepared according to the following steps: at 25°C, 5g of polyvinyl butyral resin with a number average molecular weight of 500 and 95g of ethanol are added to a three-necked flask, and 20g of ethyl acetate as a promoter is added and stirred to make the solid completely dissolved in the liquid, and then 15g of acrylic rosin is added and heated to 50°C for dissolution. After complete dissolution, the stirring speed is set to 300r / min, and the reaction is carried out for 20min. The solution after the reaction is poured into a leveling machine, evaporated to dryness at 85°C in a water bath, and the solid product on the ground is the rosin for flux; wherein the acrylic rosin is obtained by Preparation Example 1.

[0064] Embodiment 19 In this embodiment, rosin for toughening flux is prepared according to the following steps: at 25°C, 5g of polyvinyl butyral resin with a number average molecular weight of 200 and 95g of ethanol are added to a three-necked flask, and 20g of ethyl acetate as a promoter is added and stirred to make the solid completely dissolved in the liquid, and then 15g of acrylic rosin is added and heated to 50°C for dissolution. After complete dissolution, the stirring speed is set to 300r / min, and the reaction is carried out for 20min. The solution after the reaction is poured into a leveling machine, evaporated to dryness in a water bath at 85°C, and the solid product on the ground is the rosin for flux; wherein the acrylic rosin is obtained by Preparation Example 1.

[0065] Embodiment 20 In this embodiment, rosin for toughening flux is prepared according to the following steps: at 25°C, 5g of polyvinyl butyral resin with a number average molecular weight of 10,000 and 95g of ethanol are added to a three-necked flask, and 20g of ethyl acetate as a promoter is added and stirred to make the solid completely dissolved in the liquid, and then 15g of acrylic rosin is added and heated to 50°C for dissolution. After complete dissolution, the stirring speed is set to 300r / min, and the reaction is carried out for 20min. The solution after the reaction is poured into a leveling machine, evaporated to dryness at 85°C in a water bath, and the solid product on the ground is the rosin for flux; wherein the acrylic rosin is obtained by Preparation Example 1.

[0066] Comparative Example Comparative Example 1 In this comparative example, the rosin used as soldering flux is natural rosin.

[0067] Performance testing methods A 0.2 mm × 40 mm × 40 mm PCB board was used as a welding board, the solder was Sn99.3Cu0.7, and the flux used was that of each embodiment and comparative example. The welding board was welded using the solder and the flux, and the mechanical properties of the solder joints were tested according to the test method of JIS-Z3197. The test results are shown in Table 1.

[0068] Table 1 Performance test data of Examples 1-20 and Comparative Example 1 It can be seen from Example 1 and Comparative Example 1 and Table 1 that the present application dissolves the alcohol-soluble polymer polyvinyl butyral resin in alcohol, and the alcohol-soluble polymer generally carries a hydroxyl group whose molecular chain stretches out to react with the carboxyl group in the rosin. After chemical bonding, the toughness of the rosin is improved while the fluxing property of the rosin itself is lost.

[0069] Combining Example 1 and Example 2 with Table 1, it can be seen that the flux prepared by modifying rosin with acrylic acid to obtain acrylic rosin and then reacting it with an alcohol-soluble polymer polyvinyl butyral resin has better mechanical properties. This is because the acrylic modified rosin is prepared by the addition reaction of rosin as a raw material with acrylic acid, so that they have two or more carboxyl groups in each molecule, which increases the number of carboxyl groups in the rosin, is conducive to the subsequent chemical and bonding with the hydroxyl groups in the alcohol-soluble resin, and further increases the molecular chain length of the rosin, thereby improving the toughness of the rosin used in the flux.

[0070] Combining Example 2 and Example 6-7 with Table 1, it can be seen that the present application can further improve the mechanical properties of the obtained flux by optimizing the mass ratio of acrylic rosin to hydroquinone; when the mass of the catalyst hydroquinone is less than 2% of the rosin, the acid value of the system is low, indicating that the catalytic activity of the catalyst is insufficient and some acrylic acid still does not participate in the reaction; and when the mass of the catalyst is more than 4% of the rosin, the acid value of the system does not change much, so the use range of hydroquinone is 2-4% of the mass of the rosin.

[0071] It can be seen from Example 2 and Example 8-9 and Table 1 that the present application can further improve the mechanical properties of the obtained flux by optimizing the mass ratio of acrylic rosin to acrylic acid; when the amount of rosin is insufficient relative to acrylic acid, the amount of acrylic acid is relatively high relative to rosin, and acrylic acid will continue to evaporate, condense, and self-polymerize, resulting in a downward trend in the content of the adduct in the product; and as the amount of rosin added increases, the content of the adduct increases, but when the rosin is added in excess, the softening point of the obtained product is significantly reduced, which does not meet the requirements of the product technical indicators.

[0072] It can be seen from Example 2 and Example 8-9 and Table 1 that the present application can further improve the mechanical properties of the obtained flux by optimizing the reaction temperature for preparing acrylic rosin; as the reaction temperature increases, the thermal isomerization of the rosin resin is promoted, and the diene addition reaction between the rosin resin and acrylic acid is accelerated, and the content of the adduct in the product continues to increase. However, as the temperature continues to increase, the thermal isomerization of the rosin resin reaches equilibrium, and a decarboxylation reaction begins to occur. In addition, acrylic acid continues to evaporate and condense at high temperature, which accelerates its self-polymerization process, resulting in a downward trend in the content of the adduct in the product. Therefore, it is more appropriate to control the reaction temperature at 230°C.

[0073] It can be seen from Example 2 and Examples 8-9 and Table 1 that the present application can further improve the mechanical properties of the obtained flux by optimizing the reaction time for preparing acrylic rosin; the adduct content of the reaction product generally increases with the extension of the reaction time, but when the time is extended to a certain extent, the adduct content decreases, which may be due to the increase in side reactions as the time is extended, so the optimal reaction time is the time point before the adduct content begins to decrease.

[0074] It can be seen from Example 2 and Examples 8-9 and Table 1 that the present application can further improve the mechanical properties of the obtained flux by optimizing the dropping speed of acrylic acid when preparing acrylic rosin; if the dropping speed of acrylic acid is too fast, the temperature drops rapidly and it is very slow to rise to the specified reaction temperature, which wastes energy. At the same time, the acrylic acid concentration is too high and it is easy to volatilize; and when the dropping speed of acrylic acid is too slow, the reaction time is prolonged and the side reactions increase.

[0075] The main embodiments are merely explanations of the present application and are not limitations of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiments without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing rosin for toughening flux, characterized in that: The following steps are involved: Mixing an alcohol-soluble resin with a solvent and adding a solvent promoter and stirring to obtain a mixed solution; Rosin is added into the mixed solution, heated for reaction and evaporated to obtain a solid, which is the rosin for soldering flux.

2. The method for preparing rosin for toughening flux according to claim 1, characterized in that: The alcohol-soluble resin is polyvinyl butyral resin, polyvinyl pyrrolidone or polyethylene glycol resin.

3. The method for preparing rosin for toughening flux according to claim 2, characterized in that: The average molecular weight of the alcohol-soluble resin is 200-10000.

4. The method for preparing rosin for toughening flux according to claim 3, characterized in that: The average molecular weight of the alcohol-soluble resin is 500-2000.

5. The method for preparing rosin for toughening flux according to claim 1, characterized in that: The solvent is one or more of methanol, ethanol, isopropanol, N,N-dimethylformamide and N-methyl-2-pyrrolidone.

6. The method for preparing rosin for toughening flux according to claim 1, characterized in that: The dissolution promoter is one or more of ethyl acetate, dichloromethane and carbon tetrachloride.

7. The method for preparing rosin for toughening flux according to claim 1, characterized in that: The rosin is water-white rosin or natural rosin.

8. The method for preparing rosin for toughening flux according to claim 1, characterized in that: The rosin is acrylic rosin, and the preparation method of the propylene-modified rosin is as follows: hydroquinone is added to the rosin, nitrogen is introduced for protection, acrylic acid is added dropwise after heating, and the reaction is carried out by heat preservation and cooling to obtain the acrylic rosin.

9. The method for preparing rosin for toughening flux according to claim 8, characterized in that: During the heating, the temperature is 230° C. and the reaction time is 3-4 hours; during the heat preservation, the dripping speed of the acrylic acid is 60 drops / min.

10. The method for preparing rosin for toughening flux according to claim 8, characterized in that: The mass ratio of the rosin, hydroquinone and acrylic acid is 1: (0.02-0.04): (0.2-0.25).

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