Hydrophobic modified acrylic resin and flexible circuit board waterproof glue

Abstract

The hydrophobic modified acrylic resin and the flexible circuit board waterproof glue are prepared by mixing a soft monomer, a hard monomer, a hydrophobic modified monomer, a functional monomer, a solvent and an initiator and then heating to initiate polymerization, the composition comprises the following components in percentage by mass: 30-40% of a soft monomer; 8-15% of a hard monomer; 3-10% of a hydrophobic modified monomer; 1-5% of a functional monomer; 45-50% of a solvent; and 0.2-2% of an initiator.

Description

Technical Field

[0001] The invention relates to a surface material and a preparation technology thereof, in particular to a hydrophobic modified acrylic resin and a flexible circuit board waterproof glue. Background Art

[0002] Existing waterproof adhesives mainly use a two-component A agent + B agent pressure-sensitive adhesive system, where A agent is mainly an acrylic resin system and B agent is an isocyanate. After A and B agents are mixed, they are coated on the PET film by screen printing and bonded to the PET after baking. The performance requirements mainly include: being able to withstand immersion in room temperature water at 25°C for 2 hours and hot water at 60°C for 2 hours; the 180° peeling force on the PET substrate reaches 500gf; at the same time, under extreme conditions: high temperature and high humidity at 70°C, no obvious change in 90% HR within 240h, and no obvious heat diffusion phenomenon when baked at high temperature at 150°C for 30min.

[0003] The existing two-component A agent + B agent pressure-sensitive adhesive system contains fluorine and silicon additives in the colloid, which are used to adjust the system's leveling and defoaming properties. Such additives are easy to migrate to the surface of the colloid, resulting in insufficient and stable peeling force. It is easy to bounce off due to the tension of the circuit board structure, affecting waterproofing. Acrylic colloid contains a small amount of polar groups such as carboxyl and hydroxyl groups, and its water resistance is insufficient. Water vapor will enter after long-term immersion. It has poor pressure sensitivity and poor adhesion during bonding, resulting in bubbles on the appearance and poor waterproofing performance.

[0004] In addition, the market has increasingly higher requirements for the waterproof performance of flexible circuit boards such as computer keyboards and membrane switches. This puts forward higher requirements for the waterproof performance of waterproof adhesive products. The waterproof performance conditions are more stringent: soak in room temperature water at 25℃ for 24 hours, and soak in hot water at 60℃ for 6 hours.

[0005] Therefore, it is necessary to provide a hydrophobically modified acrylic resin and a flexible circuit board waterproof adhesive. Summary of the invention

[0006] The purpose of the present invention is to provide a hydrophobic modified acrylic resin and a waterproof adhesive for a flexible circuit board.

[0007] The present invention achieves the above object through the following technical solutions:

[0008] One of the technical solutions:

[0009] A hydrophobically modified acrylic resin is prepared by mixing a soft monomer, a hard monomer, a hydrophobically modified monomer, a functional monomer, a solvent, and an initiator and then heating and initiating polymerization;

[0010] In terms of mass percentage, the components are:

[0011] Soft monomer: 30-40%;

[0012] Hard monomer: 8-15%;

[0013] Hydrophobic modified monomer: 3-10%;

[0014] Functional monomer: 1-5%;

[0015] Solvent: 45-50%;

[0016] Initiator: 0.2-2%.

[0017] Further, the preparation process:

[0018] 1) preparing 10% of a monomer mixture solution and adding it to the bottom of a reaction kettle, wherein the monomer mixture solution is a mixture solution consisting of a soft monomer, a hard monomer, a hydrophobically modified monomer, a functional monomer, and a solvent;

[0019] 2) nitrogen was introduced for 10 minutes, and a 5% initiator solution was added; the initiator solution was a mixed solution of initiator and solvent, and nitrogen was continuously introduced;

[0020] 3) Raise the temperature to 80°C and keep warm for 0.5h;

[0021] 4) Add 90% of the monomer mixture and 90% of the initiator solution dropwise for 3-4 hours;

[0022] 5) Maintain constant temperature at 80°C for 1 hour;

[0023] 6) Add 5% initiator solution;

[0024] 7) Keep warm at 80℃ for 2-3h;

[0025] 8) Filter the material to obtain a hydrophobically modified acrylic resin.

[0026] Furthermore, the soft monomer used includes one or more of butyl acrylate, isooctyl acrylate, butyl methacrylate, and isooctyl methacrylate to provide flexibility to the resin molecular chain;

[0027] The hard monomer includes one or more of methyl acrylate, methyl methacrylate, and ethyl methacrylate, which provide the resin with strength and cohesion.

[0028] Further, the hydrophobic modified monomer includes one or more of hexafluorobutyl acrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl acrylate, and dodecafluoroheptyl methacrylate, and the fluorinated chain segment provides a strong hydrophobic effect;

[0029] The functional monomers include one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate, which provide hydroxyl and carboxyl functional groups required for molecular chain cross-linking and improve affinity with PET materials.

[0030] Further, the solvent includes one or more of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, and propylene glycol ethyl ether acetate;

[0031] The initiator includes one or more of dibenzoyl peroxide and di-tert-butyl peroxide, which initiates the polymerization of monomers to form the desired modified high molecular polymer.

[0032] Technical solution 2:

[0033] A waterproof adhesive for a flexible circuit board, comprising an agent A and an agent B; the agent A comprises a hydrophobically modified acrylic resin, a tackifying resin, a defoaming agent, and a solvent; the agent B comprises a blocked isocyanate, a multifunctional epoxy resin, and a solvent;

[0034] In terms of percentage, the composition of Agent A is as follows:

[0035]

[0036]

[0037] In terms of percentage, the composition of Agent B is as follows:

[0038] 30-50 parts of blocked isocyanate;

[0039] 1-10 parts of multifunctional epoxy resin;

[0040] 30-50 parts of diethylene glycol ethyl ether acetate.

[0041] Furthermore, the hydrophobically modified acrylic resin has a viscosity of 6000-9000 mps, which is conducive to screen printing. Too high viscosity can easily lead to wire drawing during printing, and low viscosity can easily cause line flow and diffusion during screen printing. The solid content is 45%-55%, which is mainly used to control the thickness of the printed product. The polymer contains -OH and -COOH, AN value is 13%-19%, and OHV value is 5%-10%. The purpose is to provide sufficient cross-linking sites during curing and cross-linking. Different from the common hydroxyl curing and cross-linking, this polymer also introduces a certain amount of carboxyl groups for carboxyl curing. The two curings cooperate with each other to improve the curing rate and stability.

[0042] Furthermore, the tackifying resin is one or more of rosin resin, hydrogenated rosin resin, and terpene resin. As the tackifying resin, it mainly provides additional bonding force and improves the lasting viscosity of the colloid.

[0043] Furthermore, the defoaming agent includes one or more of an organosilicon defoaming agent or a non-silicon cyclic hydrocarbon defoaming agent, which effectively eliminates bubbles generated during the glue production and printing process and provides a good printing appearance.

[0044] Furthermore, the solvent includes one or more of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, and propylene glycol ethyl ether acetate; the curing agent uses a mixed curing agent of blocked isocyanate and multifunctional epoxy resin, and simultaneously cross-links the hydroxyl and carboxyl groups to improve the curing speed and colloid strength.

[0045] Compared with the prior art, the present invention starts with the design of the resin structure, introduces hydrophobic modified monomers, improves the water resistance of the colloidal resin itself, and further improves the waterproof performance of the colloid; by adjusting the combination of soft and hard monomers, the pressure sensitivity of the system is improved, the adhesion is improved, and the waterproof performance is improved; finally, a hydrophobic modified acrylic resin is used to improve the water resistance of the colloidal resin body, and significantly improve the waterproof performance of the glue, from the original immersion in room temperature water at 25°C for 2h, immersion in hot water at 60°C for 2h, and a pass rate of 85%, to immersion in room temperature water at 25°C for 24h, immersion in hot water at 60°C for 6h, and a pass rate of 90%; by matching soft and hard monomers, the pressure sensitivity of the system is adjusted, the adhesion of the glue is improved, and the appearance of the bonding is smooth and free of bubbles. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of an application product of Example 2 of the present invention. DETAILED DESCRIPTION

[0047] Embodiment 1:

[0048] This embodiment shows a hydrophobically modified acrylic resin, which is prepared by mixing a soft monomer, a hard monomer, a hydrophobically modified monomer, a functional monomer, a solvent, and an initiator, and then heating to initiate polymerization.

[0049] In terms of mass percentage, the components are:

[0050] Soft monomer: 30-40%;

[0051] Hard monomer: 8-15%;

[0052] Hydrophobic modified monomer: 3-10%;

[0053] Functional monomer: 1-5%;

[0054] Solvent: 45-50%;

[0055] Initiator: 0.2-2%.

[0056] in:

[0057] The soft monomers used include one or more of butyl acrylate, isooctyl acrylate, butyl methacrylate, and isooctyl methacrylate, which provide the resin molecular chain with flexibility;

[0058] The hard monomer includes one or more of methyl acrylate, methyl methacrylate, and ethyl methacrylate, which provide resin strength and cohesion;

[0059] The hydrophobic modified monomer includes one or more of hexafluorobutyl acrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl acrylate, and dodecafluoroheptyl methacrylate, and the fluorinated chain segment provides a strong hydrophobic effect;

[0060] The functional monomers include one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate, which provide hydroxyl and carboxyl functional groups required for molecular chain cross-linking and improve affinity with PET materials.

[0061] The solvent includes one or more of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, and propylene glycol ethyl ether acetate;

[0062] The initiator includes one or more of dibenzoyl peroxide and di-tert-butyl peroxide, which initiates the polymerization of monomers to form the desired modified high molecular polymer.

[0063] The preparation process is:

[0064] Step 1. Weigh the soft monomer, hard monomer, hydrophobic modified monomer, functional monomer and solvent in proportion in a configuration cylinder, stir and mix them evenly to obtain a monomer mixed solution for standby use;

[0065] Step 2. Add the initiator and solvent into the batching tank, dissolve and mix them evenly to obtain the initiator solution for later use;

[0066] Step 3. Nitrogen was introduced into the bottom of the reactor for 10 min, and 10% of the monomer mixture and 5% of the initiator solution were added in sequence, and the nitrogen was continuously introduced, and the temperature was raised to 80°C and kept warm for 0.5 h;

[0067] Step 4. Add 90% of the monomer mixture and 90% of the initiator solution dropwise at the same time for 3-4 hours, and keep the temperature at 80°C during the addition;

[0068] Step 5. After the dropwise addition is completed, the temperature is kept at 80°C for 1 hour, the remaining initiator solution is added at once, the temperature is kept at 80°C for 2-3 hours, and the material is filtered to obtain a hydrophobically modified acrylic resin;

[0069] Embodiment 2:

[0070] A waterproof adhesive for a flexible circuit board, comprising an agent A and an agent B; the agent A comprises a hydrophobically modified acrylic resin, a tackifying resin, a defoaming agent, and a solvent; the agent B comprises a blocked isocyanate, a multifunctional epoxy resin, and a solvent;

[0071] In terms of percentage, the composition of Agent A is as follows:

[0072]

[0073] In terms of percentage, the composition of Agent B is as follows:

[0074] 30-50 parts of blocked isocyanate;

[0075] 1-10 parts of multifunctional epoxy resin;

[0076] 30-50 parts of diethylene glycol ethyl ether acetate.

[0077] in:

[0078] Hydrophobically modified acrylic resin, viscosity 6000-9000mps, is conducive to screen printing. Too high viscosity can easily lead to wire drawing during printing. Low viscosity can easily cause line flow and diffusion during screen printing. Solid content 45%-55%, mainly controlling the thickness of the printed product. The polymer contains -OH and -COOH, AN value 13%-19%, OHV value 5%-10%, the purpose of which is to provide sufficient cross-linking sites during curing and cross-linking. Different from the common hydroxyl curing and cross-linking, this polymer also introduces a certain amount of carboxyl groups for carboxyl curing. The two curings cooperate with each other to improve the curing rate and stability.

[0079] The tackifying resin is one or more of rosin resin, hydrogenated rosin resin and terpene resin. As the tackifying resin, it mainly provides the supplement of the adhesive force and improves the lasting viscosity of the colloid.

[0080] The defoaming agent includes one or more of silicone defoaming agents or non-silicon cyclic hydrocarbon defoaming agents, which can effectively eliminate bubbles generated during the glue production and printing process and provide a good printing appearance.

[0081] The solvent includes one or more of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, and propylene glycol ethyl ether acetate; the curing agent adopts a mixed curing agent of blocked isocyanate and multifunctional epoxy resin, and cross-linking reaction is carried out on hydroxyl and carboxyl groups at the same time to improve the curing speed and colloid strength.

[0082] The preparation process is:

[0083] Step S1. Disperse one or more tackifying resins with diethylene glycol ethyl ether acetate as solvent at a solid content of 50-60% at a speed of 800-1000 rpm for 3-4 hours until they are completely dissolved and set aside.

[0084] Step S2. Add the mixture in step 6 to the above hydrophobically modified acrylic resin, disperse at a speed of 500 rpm for 10 minutes, then add a defoamer and a solvent in sequence, disperse for 60 minutes, and stir evenly to obtain Agent A.

[0085] Step S3. Add the isocyanate curing agent, multifunctional epoxy resin and solvent into the mixing tank in sequence, stir at 200 rpm for 30 minutes, and stir evenly to obtain Agent B.

[0086] Step S4. Mix the agent A prepared in step S2 and the agent B prepared in step S3 in proportion and stir them evenly to obtain a waterproof adhesive for a flexible circuit board.

[0087] The waterproof adhesive for flexible circuit board prepared in Example 2, the application product diagram can be found in Figure 1 .

[0088] Embodiment 3:

[0089] The performance of the hydrophobically modified acrylic resin prepared in Example 1 and the waterproof adhesive for flexible circuit boards prepared in Example 2 were tested. For specific tests, please refer to the following table:

[0090]

[0091] Compared with the prior art, the present invention starts with the design of the resin structure, introduces hydrophobic modified monomers, improves the water resistance of the colloidal resin itself, and further improves the waterproof performance of the colloid; by adjusting the combination of soft and hard monomers, the pressure sensitivity of the system is improved, the adhesion is improved, and the waterproof performance is improved; finally, a hydrophobic modified acrylic resin is used to improve the water resistance of the colloidal resin body, and significantly improve the waterproof performance of the glue, from the original immersion in room temperature water at 25°C for 2h, immersion in hot water at 60°C for 2h, and a pass rate of 85%, to immersion in room temperature water at 25°C for 24h, immersion in hot water at 60°C for 6h, and a pass rate of 90%; by matching soft and hard monomers, the pressure sensitivity of the system is adjusted, the adhesion of the glue is improved, and the appearance of the bonding is smooth and free of bubbles.

[0092] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A hydrophobically modified acrylic resin, characterized in that: It is formed by mixing soft monomer, hard monomer, hydrophobic modified monomer, functional monomer, solvent and initiator and then heating to initiate polymerization; In terms of mass percentage, the components are: Soft monomer: 30-40%; Hard monomer: 8-15%; Hydrophobic modified monomer: 3-10%; Functional monomer: 1-5%; Solvent: 45-50%; Initiator: 0.2-2%.

2. A hydrophobically modified acrylic resin according to claim 1, characterized in that: Preparation process: 1) preparing 10% of a monomer mixture solution and adding it to the bottom of a reaction kettle, wherein the monomer mixture solution is a mixture solution consisting of a soft monomer, a hard monomer, a hydrophobically modified monomer, a functional monomer, and a solvent; 2) nitrogen was introduced for 10 minutes, and a 5% initiator solution was added; the initiator solution was a mixed solution of initiator and solvent, and nitrogen was continuously introduced; 3) Raise the temperature to 80°C and keep warm for 0.5h; 4) Add 90% of the monomer mixture and 90% of the initiator solution dropwise for 3-4 hours; 5) Maintain constant temperature at 80°C for 1 hour; 6) Add 5% initiator solution; 7) Keep warm at 80℃ for 2-3h; 8) Filter the material to obtain a hydrophobically modified acrylic resin.

3. A hydrophobically modified acrylic resin according to claim 2, characterized in that: The soft monomers used include one or more of butyl acrylate, isooctyl acrylate, butyl methacrylate, and isooctyl methacrylate, which provide the resin molecular chain with flexibility; The hard monomer includes one or more of methyl acrylate, methyl methacrylate, and ethyl methacrylate, which provide the resin with strength and cohesion.

4. A hydrophobically modified acrylic resin according to claim 3, characterized in that: The hydrophobic modified monomer includes one or more of hexafluorobutyl acrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl acrylate, and dodecafluoroheptyl methacrylate, and the fluorinated chain segment provides a strong hydrophobic effect; The functional monomers include one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate, which provide hydroxyl and carboxyl functional groups required for molecular chain cross-linking and improve affinity with PET materials.

5. A hydrophobically modified acrylic resin according to claim 4, characterized in that: The solvent includes one or more of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, and propylene glycol ethyl ether acetate; The initiator includes one or more of dibenzoyl peroxide and di-tert-butyl peroxide, which initiates the polymerization of monomers to form the desired modified high molecular polymer.

6. A waterproof adhesive for a flexible circuit board, characterized in that: It is composed of agent A and agent B; agent A includes hydrophobically modified acrylic resin, tackifying resin, defoaming agent, and solvent; agent B includes blocked isocyanate, multifunctional epoxy resin, and solvent; In terms of percentage, the composition of Agent A is as follows: In terms of percentage, the composition of Agent B is as follows: 30-50 parts of blocked isocyanate; 1-10 parts of multifunctional epoxy resin; 30-50 parts of diethylene glycol ethyl ether acetate.

7. The waterproof adhesive for flexible circuit board according to claim 6, characterized in that: Hydrophobically modified acrylic resin, viscosity 6000-9000mps, is conducive to screen printing. Too high viscosity can easily lead to wire drawing during printing. Low viscosity can easily cause line flow and diffusion during screen printing. Solid content 45%-55%, mainly controlling the thickness of the printed product. The polymer contains -OH and -COOH, AN value 13%-19%, OHV value 5%-10%, the purpose of which is to provide sufficient cross-linking sites during curing and cross-linking. Different from the common hydroxyl curing and cross-linking, this polymer also introduces a certain amount of carboxyl groups for carboxyl curing. The two curings cooperate with each other to improve the curing rate and stability.

8. The waterproof adhesive for flexible circuit board according to claim 7, characterized in that: The tackifying resin is one or more of rosin resin, hydrogenated rosin resin and terpene resin. As the tackifying resin, it mainly provides the supplement of the adhesive force and improves the lasting viscosity of the colloid.

9. The waterproof adhesive for a flexible circuit board according to claim 8, characterized in that: The defoaming agent includes one or more of silicone defoaming agents or non-silicon cyclic hydrocarbon defoaming agents, which can effectively eliminate bubbles generated during the glue production and printing process and provide a good printing appearance.

10. The waterproof adhesive for a flexible circuit board according to claim 9, characterized in that: The solvent includes one or more of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, and propylene glycol ethyl ether acetate; the curing agent adopts a mixed curing agent of blocked isocyanate and multifunctional epoxy resin, and cross-linking reaction is carried out on hydroxyl and carboxyl groups at the same time to improve the curing speed and colloid strength.

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