Water-soluble resin and water-soluble aluminum sheet prepared from water-soluble resin
By introducing carboxyl groups into the water-soluble resin coating of polyurethane molecular chain, the problems of high energy consumption, poor environmental performance and weak adhesion of existing coated aluminum sheets and film-coated aluminum sheets for PCB drilling are solved, realizing high-precision drilling and environmentally friendly production, and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-07
- Publication Date
- 2026-03-27
AI Technical Summary
Existing coated aluminum sheets and film-coated aluminum sheets for PCB drilling suffer from high energy consumption, poor environmental performance, weak adhesion between the coating and aluminum foil, and insufficient heat resistance, leading to problems such as easy coating peeling and hole clogging during drilling, making it difficult to meet the requirements of high-precision PCB drilling.
A water-soluble resin based on polyurethane amine neutralization is used to prepare a water-soluble resin coating by introducing carboxyl groups into the polyurethane molecular chain to form stable hydrophilic groups. The coating has strong adhesion, good heat resistance, and can be completely washed and recycled. The preparation process is environmentally friendly and simple.
It improves the quality of PCB drilling, has strong adhesion between the coating and aluminum sheet, good heat resistance, and the coating can be completely washed and recycled, reducing production costs and environmental pressure. The process is simple and easy to industrialize.
Smart Images
Figure CN121736216A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of auxiliary materials for printed circuit board (PCB) processing, specifically to the synthesis of a water-soluble resin and the preparation of water-soluble aluminum sheets using the water-soluble resin. Background Technology
[0002] In the PCB mechanical drilling process, the drilling aluminum cover plate serves as a key auxiliary material for protecting the PCB board. Its performance directly affects the drilling accuracy, drill bit life, yield rate, and the reliability of the finished PCB product. Currently, the mainstream PCB drilling cover plates on the market include coated aluminum sheets, phenolic resin cover plates, ordinary aluminum foil cover plates, and film-coated aluminum sheets. Among them, coated aluminum sheets and film-coated aluminum sheets are increasingly widely used in high-end PCB micro-precision hole drilling scenarios because they combine the supporting rigidity of aluminum foil with the buffering and lubricating properties of polymer resin.
[0003] The current process for preparing coated aluminum sheets mostly involves dissolving polymer materials in a solvent, coating them onto aluminum foil, and then drying to remove the solvent. This process has significant drawbacks: firstly, the use of solvents and the drying process not only increase production energy consumption and process costs but may also lead to environmental problems due to solvent residues; secondly, while existing water-soluble coating materials (such as PEG) can be washed and recycled, they suffer from weak adhesion between the coating and the aluminum foil, easy detachment during drilling, and insufficient heat resistance leading to tool sticking during drilling. Although non-water-soluble coating materials (PE) can be produced using a coating method, problems such as wire entanglement and hole clogging during drilling make it difficult to meet the stringent requirements of high-precision PCB drilling.
[0004] Polyurethane resins have potential applications in PCB cover materials due to their excellent film-forming properties, adhesion, and mechanical properties. However, conventional polyurethane resins have poor water solubility, requiring modification by introducing hydrophilic groups to achieve water solubility. High-acid-value polyurethanes, by introducing a large number of carboxyl hydrophilic groups, can form a stable water-soluble system after amine neutralization. Furthermore, the presence of carboxyl groups enhances the interaction with the aluminum foil surface, improving coating adhesion. The resulting water-soluble polyurethane coating can be washed away to eliminate residue issues, having no negative impact on subsequent PCB processing steps. This process is environmentally friendly and simple. Summary of the Invention
[0005] To address the shortcomings of existing coated and film-coated aluminum sheets for PCB drilling, such as high energy consumption, poor environmental performance, weak adhesion and insufficient heat resistance of existing water-soluble coating materials to aluminum foil, and the problem of PE residue clogging in non-water-soluble coating materials, this invention provides a water-soluble resin and a method for preparing water-soluble aluminum sheets using this resin. This water-soluble resin is prepared based on the neutralization of polyurethane amine, exhibiting excellent environmental performance. Furthermore, the water-soluble aluminum sheets prepared using this resin possess strong coating adhesion, good heat resistance, and are completely washable and recyclable, effectively improving the quality of PCB drilling. The technical solution provided in this application is as follows:
[0006] In a first aspect, the present invention provides a water-soluble resin, which is prepared by neutralizing polyurethane with an amine, and the preparation steps include:
[0007] (1) Synthesis of polyurethane prepolymer: Polyol, hydrophilic chain extender and diacid anhydride are added to the reactor, inert gas is introduced for protection, the temperature is raised to 120~140℃ and stirred to dissolve, and then the temperature is raised to 170~190℃ for esterification reaction until the acid value reaches 120~185mg KOH / g, to obtain polyol prepolymer containing carboxyl groups; the temperature is lowered to 80~90℃, acetone is added for dilution, and then diisocyanate is slowly added dropwise, controlling the molar ratio of NCO to OH to be 1.2~1.3:1, and the reaction is carried out at 70~80℃ for 3~4h to obtain polyurethane prepolymer;
[0008] (2) Amine neutralization reaction: The polyurethane prepolymer obtained in step (1) is cooled to 40~50℃, neutralizing amine is added, the pH value of the system is adjusted to 7.5~8.5, and the reaction is stirred for 30~60 min to obtain the neutralized product;
[0009] (3) Preparation of water-soluble resin: Deionized water is slowly added to the neutralization product of step (2) while stirring at high speed to disperse the water. Then, acetone in the system is removed by vacuum to obtain a water-soluble resin emulsion with a solid content of 40-50%.
[0010] Preferably, the polyol in step (1) is selected from one or more of neopentyl glycol, pentaerythritol, and castor oil fatty acids; the hydrophilic chain extender is 2,2-dimethylolpropionic acid (DMPA); the dicarboxylic acid anhydride is selected from one of benzotricarboxylic anhydride and adipic anhydride; and the diisocyanate is selected from one or a mixture of two of toluene diisocyanate (TDI) and isophorone diisocyanate (IPDI).
[0011] Preferably, the neutralizing amine in step (2) is selected from one or more of dodecylamine and AMP-95.
[0012] Preferably, during the esterification reaction in step (1), the acid value is sampled and tested every 30 minutes to ensure that the final acid value is stable within the range of 120~185mg KOH / g; the dropping rate of diisocyanate is 1~3 drops / second to avoid excessive reaction leading to local overheating.
[0013] Preferably, in step (3), the high-speed stirring speed is 500~800 r / min, the water dispersion temperature is controlled at 40~50℃, the temperature for vacuum removal of acetone is 50~60℃, and the vacuum degree is -0.08~-0.09 MPa.
[0014] Secondly, the present invention provides a method for preparing water-soluble aluminum sheets for PCB drilling using the above-mentioned water-soluble resin, comprising the following steps:
[0015] (1) Pretreatment of aluminum sheet: Select aluminum foil with a thickness of 0.03~0.2mm, and successively clean it with sodium thiosulfate solution, activate it with aluminum passivating agent, neutralize it with water, and dry it to obtain pretreated aluminum sheet;
[0016] (2) Coating preparation: Add wetting and leveling agent, defoamer and other additives to the water-soluble resin emulsion and stir evenly. Then, coat the resin emulsion mixture evenly on one side of the pretreated aluminum sheet. The coating thickness (dry film) is 20~120μm.
[0017] (3) Curing and molding: The coated aluminum sheet is placed in an oven at 100~180℃ and dried for 1~5 minutes to cure and mold, thus obtaining water-soluble aluminum sheet for PCB drilling.
[0018] Preferably, in step (2), the coating method is selected from either blade coating or roller coating, and the aluminum coil running speed is 10-20m / min.
[0019] Preferably, in step (3), the three-stage oven for curing adopts a stepped heating method. First, it is dried at a low temperature of 100~120℃, then heated to 120~130℃ for baking, and finally thoroughly dried in an oven at 130-180℃. The stepped heating helps the moisture to evaporate fully and avoid defects such as blistering on the coating surface, ensuring that the coating is dense and bubble-free.
[0020] Thirdly, the present invention provides a water-soluble aluminum sheet for PCB drilling prepared by the above method. The water-soluble aluminum sheet includes an aluminum sheet substrate and a water-soluble resin coating coated on the surface of the aluminum sheet substrate. The adhesion between the water-soluble resin coating and the aluminum sheet substrate is ≥0 grade (100-cross cross-cut adhesion test), the dissolution time of the coating in water at 25°C is ≤10min, and the heat resistance temperature is ≥150°C.
[0021] The beneficial effects of this invention are as follows: The water-soluble resin of this invention is prepared based on polyurethane through amine neutralization. By introducing a large number of carboxyl groups into the polyurethane molecular chain, stable hydrophilic groups are formed after amine neutralization. Water dispersion can be achieved without adding a large amount of organic solvent. The preparation process is environmentally friendly and pollution-free, and the resin emulsion has good stability and a shelf life of more than 6 months. The water-soluble aluminum sheet prepared using the water-soluble resin of this invention has strong adhesion between the coating and the pretreated aluminum sheet substrate, achieving a cross-cut adhesion test grade of 0 or higher, effectively preventing coating peeling during PCB drilling. The coating has a heat resistance temperature ≥150℃, which can withstand the heat generated by the high-speed rotation of the drill bit during drilling, preventing the coating from softening and sticking to the drill bit, thus improving efficiency. The invention improves drilling accuracy; after PCB drilling is completed, the water-soluble aluminum sheet can be separated from the coating simply by rinsing with water. The aluminum sheet is recyclable and reusable, and residues can be washed away without clogging the holes or negatively impacting copper plating. The coating solution contains no harmful substances and is easy to handle, significantly reducing subsequent cleaning costs and environmental pressure. The preparation process of this invention is simple. The vacuum removal of acetone during the preparation of the water-soluble resin has low energy consumption. The water-soluble aluminum sheet coating and curing process is easy to achieve industrial mass production. Compared with existing solvent-based coated aluminum sheet and film-coated aluminum sheet production processes, the production line length can be shortened by more than 60%, and the production cost can be reduced by 20-30%, which has significant economic advantages. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the structure of a water-soluble aluminum sheet according to the present invention. 10 represents a polyurethane water-soluble coating, and 20 represents aluminum foil. Detailed Implementation
[0023] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.
[0024] Example 1
[0025] Preparation of a water-soluble resin:
[0026] (1) Synthesis of polyurethane prepolymer: 20g of neopentyl glycol, 15g of 2,2-dimethylolpropionic acid (DMPA) and 25g of benzotricarboxylic anhydride were added to the reactor. Nitrogen gas was introduced for protection, and the temperature was raised to 130℃ and stirred to dissolve. The temperature was then raised to 180℃ for esterification reaction. The acid value was measured every 30 minutes. After 2.5h of reaction, the acid value reached 175mg KOH / g, and a carboxyl-containing polyol prepolymer was obtained. The temperature was lowered to 85℃, 50g of acetone was added for dilution, and then 38g of toluene diisocyanate (TDI) was added dropwise at a rate of 1.5 drops / second. The molar ratio of NCO to OH was controlled to be 1.2:1. The reaction was carried out at 75℃ for 4h to obtain polyurethane prepolymer.
[0027] (2) Amine neutralization reaction: The above high acid value polyurethane prepolymer was cooled to 45°C, 12g of dodecylamine was added, the pH of the system was adjusted to 8.0, and the reaction was stirred for 45min to obtain the neutralized product;
[0028] (3) Preparation of water-soluble resin: 180g of deionized water was slowly added to the neutralization product, and water was dispersed by stirring at a high speed of 600r / min. Then, acetone was removed under vacuum at 55℃ and -0.085MPa to obtain a water-soluble resin emulsion with a solid content of 45%. No stratification was observed after 6 months of storage.
[0029] A method for preparing water-soluble aluminum sheets for PCB drilling using the above-mentioned water-soluble resin:
[0030] (1) Pretreatment of aluminum foil: Select aluminum foil with a thickness of 0.13 mm, put it into a 6% sodium thiosulfate solution, wash and degrease it at 55°C for 20 seconds, then put it into a 6% passivating agent solution for 30 seconds, then wash it with deionized water to neutralize it to a pH value of 7.0, and finally dry it in a 90°C oven for 1 minute to obtain pretreated aluminum foil;
[0031] (2) Coating preparation: The mixture of the above water-soluble resin emulsion, wetting leveling agent and defoamer is applied to one side of the pretreated aluminum sheet using a roller coating machine. The speed of the plate feed is controlled at 15m / min and the dry film thickness is 50um.
[0032] (3) Curing and molding: The coated aluminum sheet is placed in a 110℃ oven to dry for 1 min, then in a second-stage oven at 140℃ for 1.5 min, and finally in a third-stage oven at 160℃ for 50 s to dry, thus obtaining water-soluble aluminum sheet for PCB drilling.
[0033] The performance of the prepared water-soluble aluminum sheet was tested: the adhesion between the coating and the aluminum substrate was grade 0 (100-cross test), the dissolution time in water at 25℃ was 8 minutes, and the heat resistance temperature was 220℃; when used for drilling small holes (0.2mm) in PCBs, the hole position accuracy CPK was greater than 1.33 (±2mil), the hole wall was burr-free, and the drill bit life was increased by 35% compared with ordinary coated aluminum foil.
[0034] Example 2
[0035] Preparation of a water-soluble resin:
[0036] (1) Synthesis of polyurethane prepolymer: 18g of pentaerythritol, 12g of 2,2-dimethylolpropionic acid (DMPA) and 22g of adipic anhydride were added to the reactor. Nitrogen gas was introduced for protection, and the temperature was raised to 125℃ and stirred to dissolve. The temperature was then raised to 175℃ for esterification reaction. After 3 hours of reaction, the acid value reached 180mg KOH / g, and a polyol prepolymer containing carboxyl groups was obtained. The temperature was lowered to 80℃, 45g of acetone was added for dilution, and then 42g of isophorone diisocyanate (IPDI) was added dropwise at a rate of 1 drop / second. The molar ratio of NCO to OH was controlled to be 1.2:1. The reaction was carried out at 70℃ for 5 hours to obtain polyurethane prepolymer.
[0037] (2) Amine neutralization reaction: The above high acid value polyurethane prepolymer was cooled to 40°C, 10g of AMP-95 was added, the pH of the system was adjusted to 7.5, and the reaction was stirred for 30min to obtain the neutralized product;
[0038] (3) Preparation of water-soluble resin: 160g of deionized water was slowly added to the neutralization product, and water was dispersed by stirring at a high speed of 800r / min. Then, acetone was removed under vacuum at 50℃ and -0.08MPa to obtain a water-soluble resin emulsion with a solid content of 42%.
[0039] A method for preparing water-soluble aluminum sheets for PCB drilling using the above-mentioned water-soluble resin:
[0040] (1) Pretreatment of aluminum foil: Select aluminum foil with a thickness of 0.1 mm, put it into 5% sodium thiosulfate solution, wash and degrease it at 50°C for 20 seconds, then put it into 6% passivating agent solution for 30 seconds, then wash it with deionized water to neutralize it to pH 7.0, and finally dry it in an oven at 90°C for 1 minute to obtain pretreated aluminum foil.
[0041] (2) Coating preparation: The mixture of the above water-soluble resin emulsion, wetting leveling agent and defoamer is applied to one side of the pretreated aluminum sheet using a roller coating machine. The speed of the plate feed is controlled at 17m / min and the dry film thickness is 70um.
[0042] (3) Curing and molding: The coated aluminum sheet is placed in a 100℃ oven to dry for 1 minute, then in a second-stage oven at 135℃ for 1.5 minutes, and finally in a third-stage oven at 160℃ for 60 seconds to dry, thus obtaining water-soluble aluminum sheet for PCB drilling.
[0043] The performance of the prepared water-soluble aluminum sheet was tested: the adhesion between the coating and the aluminum substrate was grade 0 (100-cross test), the dissolution time in water at 25℃ was 6 minutes, and the heat resistance temperature was 220℃. When used for drilling small holes (0.2mm) in PCBs, the hole position accuracy CPK was greater than 1.33 (±2mil), the hole wall was burr-free, and the drill bit life was increased by 30% compared with ordinary coated aluminum foil.
[0044] Example 3
[0045] Preparation of a water-soluble resin:
[0046] (1) Synthesis of polyurethane prepolymer: 25g of castor oil fatty acid, 18g of 2,2-dimethylolpropionic acid (DMPA) and 28g of benzotricarboxylic acid anhydride were added to the reactor. Nitrogen gas was introduced for protection, and the temperature was raised to 135℃ and stirred to dissolve. The temperature was then raised to 185℃ for esterification reaction. After 2 hours of reaction, the acid value reached 160mg KOH / g, and a carboxyl-containing polyol prepolymer was obtained. The temperature was lowered to 90℃, 55g of acetone was added for dilution, and then 45g of a mixed diisocyanate of TDI and IPDI (mass ratio 1:1) was added dropwise at a rate of 2 drops / second. The molar ratio of NCO to OH was controlled to be 1.3:1. The reaction was carried out at 80℃ for 3 hours to obtain the polyurethane prepolymer.
[0047] (2) Amine neutralization reaction: The above high acid value polyurethane prepolymer was cooled to 50°C, 15g of dodecylamine was added, the pH of the system was adjusted to 8.5, and the reaction was stirred for 60min to obtain the neutralized product;
[0048] (3) Preparation of water-soluble resin: 200g of deionized water was slowly added to the neutralization product, and water dispersion was carried out by high-speed stirring at 800r / min. Then, acetone was removed under vacuum at 60℃ and -0.09MPa to obtain a water-soluble resin emulsion with a solid content of 48%.
[0049] A method for preparing water-soluble aluminum sheets for PCB drilling using the above-mentioned water-soluble resin:
[0050] (1) Pretreatment of aluminum foil: Select aluminum foil with a thickness of 0.07 mm, put it into 8% sodium thiosulfate solution, wash and degrease it at 50°C for 20 seconds, then put it into 6% passivating agent solution for 40 seconds, then wash it with deionized water to neutralize it to pH 7.5, and finally dry it in an oven at 90°C for 1 minute to obtain pretreated aluminum foil.
[0051] (2) Coating preparation: The mixture of the above water-soluble resin emulsion, wetting leveling agent and defoamer is applied to one side of the pretreated aluminum sheet using a roller coating machine. The feed speed is controlled at 12m / min and the dry film thickness is 30um.
[0052] (3) Curing and molding: The coated aluminum sheet is placed in a 100℃ oven to dry for 1 minute, then in a second-stage oven at 125℃ for 1.5 minutes, and finally in a third-stage oven at 170℃ for 60 seconds to dry, thus obtaining water-soluble aluminum sheet for PCB drilling.
[0053] The performance of the prepared water-soluble aluminum sheet was tested: the adhesion between the coating and the aluminum substrate was grade 0 (100-cross test), the dissolution time in water at 25℃ was 6 minutes, and the heat resistance temperature was 220℃; when used for drilling small holes (0.2mm) in PCBs, the hole position accuracy CPK was greater than 1.33 (±2mil), the hole wall was burr-free, and the drill bit life was increased by 40% compared with ordinary coated aluminum foil.
[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. The scope of the invention is defined by the appended claims rather than the foregoing description, and any reference numerals in the claims should not be construed as limiting the scope of the claims. Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. The description is merely for clarity, and those skilled in the art should consider the specification as a whole. Technical solutions in specific embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. Those skilled in the art can make corrections or modifications based on the foregoing description, but all such improvements and modifications should fall within the protection scope of the appended claims.
Claims
1. A water-soluble resin, characterized in that, It is prepared by neutralizing polyurethane with amines, and the preparation steps include: (1) Synthesis of polyurethane prepolymer: Polyol, hydrophilic chain extender and diacid anhydride are added to the reactor, inert gas is introduced for protection, the temperature is raised to 120~140℃ and stirred to dissolve, and then the temperature is raised to 170~190℃ for esterification reaction until the acid value reaches 120~185mg KOH / g, to obtain polyol prepolymer containing carboxyl groups; the temperature is lowered to 80~90℃, acetone is added for dilution, and then diisocyanate is slowly added dropwise, controlling the molar ratio of NCO to OH to be 1.2~1.3:1, and the reaction is carried out at 70~80℃ for 3~4h to obtain polyurethane prepolymer; (2) Amine neutralization reaction: The polyurethane prepolymer obtained in step (1) is cooled to 40~50℃, neutralizing amine is added, the pH value of the system is adjusted to 7.5~8.5, and the reaction is stirred for 30~60 min to obtain the neutralized product; (3) Preparation of water-soluble resin: Deionized water is slowly added to the neutralization product of step (2) while stirring at high speed to disperse the water. Then, acetone in the system is removed by vacuum to obtain a water-soluble resin emulsion with a solid content of 40-50%. The hydrophilic chain extender is 2,2-dimethylolpropionic acid (DMPA); the neutralizing amine is selected from one or more of dodecylamine and AMP-95.
2. The water-soluble resin according to claim 1, characterized in that, The polyol mentioned in step (1) is selected from one or more of neopentyl glycol, pentaerythritol, and castor oil fatty acids; the dicarboxylic acid anhydride is selected from one of benzotricarboxylic anhydride and adipic anhydride; the diisocyanate is selected from one or a mixture of two of toluene diisocyanate (TDI) and isophorone diisocyanate (IPDI).
3. The water-soluble resin according to claim 1, characterized in that, During the esterification reaction in step (1), the acid value was measured every 30 minutes; the dropping rate of diisocyanate was 1~3 drops / second.
4. The water-soluble resin according to claim 1, characterized in that, In step (3), the high-speed stirring speed is 500~800 r / min, the water dispersion temperature is controlled at 40~50℃, the temperature for vacuum removal of acetone is 50~60℃, and the vacuum degree is -0.08~-0.09MPa.
5. A method for preparing water-soluble aluminum sheets for PCB drilling using the water-soluble resin according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Pretreatment of aluminum sheet: Select aluminum foil with a thickness of 0.03~0.2mm, and successively clean it with sodium thiosulfate solution, activate it with aluminum passivating agent, neutralize it with water, and dry it to obtain pretreated aluminum sheet; (2) Coating preparation: Add wetting and leveling agent, defoamer and other additives to the water-soluble resin emulsion and stir evenly. Then, coat the resin emulsion mixture evenly on one side of the pretreated aluminum sheet. The coating thickness (dry film) is 20~120μm. (3) Curing and molding: The coated aluminum sheet is placed in an oven at 100~180℃ and dried for 1~5 minutes to cure and mold, thus obtaining water-soluble aluminum sheet for PCB drilling.
6. The method according to claim 5, characterized in that, In step (2), the coating method is selected from either blade coating or roller coating, and the aluminum coil running speed is 10-20m / min.
7. The method according to claim 5, characterized in that, In step (3), the curing process of the three-stage oven adopts a stepped heating method. First, it is dried at a low temperature of 100~120℃, then heated to 120~130℃ for baking, and finally thoroughly dried in an oven at 130-180℃. The stepped heating helps the moisture to evaporate fully and avoids defects such as blistering on the coating surface.
8. A water-soluble aluminum sheet for drilling PCBs prepared by the method according to any one of claims 5 to 7, characterized in that, It includes an aluminum sheet substrate and a water-soluble resin coating applied to the surface of the aluminum sheet substrate. The adhesion between the water-soluble resin coating and the aluminum sheet substrate is ≥0 grade (cross-cut adhesion test), the dissolution time of the coating in water at 25°C is ≤10min, and the heat resistance temperature is ≥150°C.