PET-based flame-retardant high-temperature-resistant insulating adhesive for laminated busbar and preparation method thereof

Abstract

The invention discloses a PET-based flame-retardant high-temperature-resistant insulating adhesive for a laminated busbar and a preparation method thereof, and relates to the technical field of epoxy resin. The adhesive is composed of a component A and a component B. The component A is a blending system of four-functional-group resin and phenolic resin, and an antioxidant, a defoaming agent and an optional solvent are added; and the component B is a co-curing system of a curing agent and a flame retardant. The preparation method comprises the following steps: mixing the two components to prepare a glue solution, coating a PET film with the glue solution, and curing at 80-200 DEG C for 2-20 minutes. The flame retardance of the adhesive can reach UL-94 V-0 level, the adhesive can resist high temperature of 125 DEG C, the adhesive property and processability are excellent, the inherent mechanical property and transparency of resin are reserved, the raw materials are cheap, the process is simple, imported products can be replaced, and the industrial production requirement of the laminated busbar is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of epoxy resin, and particularly relates to a PET-based flame-retardant high-temperature-resistant insulating adhesive for a laminated busbar and a preparation method thereof. BACKGROUND

[0002] The PET insulating film for a laminated busbar is an insulating adhesive film taking polyester film (PET) as a base material and designed specially for interlayer insulation of a laminated busbar. The PET insulating film is combined with a conductor through a hot-pressing process and can provide effective electrical insulation, flame-retardant protection and mechanical support, and is a key material for manufacturing compact low-inductance laminated busbars.

[0003] The PET insulating film is usually made of flame-retardant PET film as a base material and polyurethane or epoxy resin adhesive. Figure 1 The structure of the PET insulating adhesive film is shown in the accompanying drawings. In order to meet the harsh working environment of power batteries, the product needs to meet the requirements of high-temperature and high-humidity resistance, high insulation, excellent peel strength and flame retardance. At present, although the quality of the insulating adhesive film products in China has been improved, the insulating films on the market are expensive, and therefore it is extremely crucial to develop an insulating adhesive film with high performance and applicable to laminated busbars. The adhesive of the PET adhesive film is mainly epoxy adhesive (EP). The EP is known for excellent adhesive strength, excellent mechanical properties, outstanding chemical corrosion resistance and stable electrical insulation, and is a material with extremely strong comprehensive performance. However, the EP itself is flammable, has low limiting oxygen index (LOI) and poor high-temperature resistance, cannot work for a long time at high temperature, does not meet the UL-94 combustion test standard, and greatly limits its practical application, and therefore the performance of the EP must be improved.

[0004] The national standard GB / T 37659-2019 Performance Requirements for Insulating Film for Laminated Busbars was promulgated in 2019, which promoted the development of high-efficiency flame retardants, including the manufacture of flame-retardant EP thermosetting materials. At the same time, environmental regulations on flame retardants are rapidly tightening worldwide, with the core trend being to limit traditional halogen-based flame retardants (especially bromine-based), which are extremely prone to generating dioxins and furans under incomplete combustion conditions, posing a serious risk to the environment and human health. And promote more environmentally friendly alternatives. Phosphorus-containing EP monomers and curing agents can both impart good flame retardancy to EP cured products, and have shown a relatively broad prospect in practical applications. However, due to the relatively poor processability and high cost of phosphorus-containing EP monomers, they cannot completely replace ordinary epoxy resins. In comparison, the use of P-containing curing agents seems to be a more feasible strategy, however, most of the phosphorus-containing curing agents reported so far tend to have low curing activity and adversely affect high-temperature resistance, which should be satisfactorily solved before actual application. For example, CN117229738A discloses a high-thermal-conductivity flame-retardant insulating epoxy resin pouring sealant and a preparation method thereof. The high-thermal-conductivity flame-retardant insulating epoxy resin pouring sealant selects a trifunctional epoxy resin bisphenol F epoxy resin. By adjusting the formula, the thermal conductivity of the epoxy resin pouring sealant is improved, and the heat dissipation performance is excellent, which can meet the pouring requirements of electronic product components. By using high-functionality resins and a large amount of functional fillers, the upper limit of the single performance (thermal conductivity, strength, heat resistance) of the pouring sealant is successfully improved, but these improvements often come at the expense of process friendliness, impact resistance, and high cost. For example, CN114634783B discloses a halogen-free flame-retardant high-temperature-resistant epoxy resin sealant and a preparation method thereof. The sealant includes A and B components, wherein the A component is a resin matrix, and the B component is a curing agent system. By adding modified graphene oxide and carbon nanotubes, and silane-modified magnesium-aluminum hydrotalcite, the mechanical properties of the sealant can be effectively improved. Although the introduction of complex and expensive nanocomposite systems can improve performance, it also brings a series of challenges in engineering and commercialization, such as high production cost, complex process, and long-term reliability risk.

[0005] Therefore, how to maintain the comprehensive performance (such as mechanical performance, insulation performance, transparency, etc.) of the resin material while ensuring high flame retardance and high temperature resistance is still the current research focus. Instead of pursuing the extreme of a certain performance in isolation, the best balance point between various performances must be sought from the molecular structure design and the formulation system. The goal is to make different components work together rather than simply add up. It can mainly start from the resin matrix and the flame retardant, and consider their synergistic effect. Selecting appropriate flame retardants and high-temperature-resistant resin matrixes is an effective way to prepare flame-retardant and high-temperature-resistant resin adhesives for laminated buss bars. The present scheme uses a cheap high-temperature-resistant resin as the matrix, introduces a flame retardant with good compatibility as a co-curing agent, and can obtain a PET-based insulating adhesive for laminated buss bars with excellent comprehensive performance through a simple method. SUMMARY

[0006] The present application aims at the problems of poor flame retardance and insufficient high temperature resistance of the existing epoxy resin adhesives, and the problems of high cost, complex process and unbalanced comprehensive performance of the existing improved schemes, and provides a PET-based flame-retardant and high-temperature-resistant insulating adhesive for laminated buss bars with excellent comprehensive performance, low cost and simple process, and a preparation method thereof.

[0007] To solve the above technical problems, the present application is realized by the following technical scheme:

[0008] The preparation method of the PET-based flame-retardant and high-temperature-resistant insulating adhesive for laminated buss bars of the present application realizes the balance between flame retardance, high temperature resistance and comprehensive performance by reasonably selecting the resin matrix and the flame retardant and utilizing the synergistic effect of the two, and the specific technical scheme is as follows:

[0009] Adhesive composition

[0010] A component (resin matrix): tetrafunctional resin 10-80 parts, phenolic resin 10-80 parts (total of 100 parts), antioxidant 0.1-1 part, defoaming agent 0.5-1.5 parts, solvent 0-80 parts;

[0011] B component (curing system): curing agent 10-30 parts, flame retardant 5-10 parts.

[0012] Key component selection

[0013] The tetrafunctional resin is selected from any one of STREM-80, AG-80 and MY-720, the phenolic resin is selected from any one of F-51, F-48, YECN-195, YECN-200 and YECN-220, and the weight ratio of the two is preferably 2:8-8:2;

[0014] The antioxidant is selected from any one of the hindered phenols 2246 and 330, thioesters DLTP and DSTP, and compound antioxidants 225, 561, 900, and PW series.

[0015] The solvent is selected from one or more such as acetone and cyclohexanone, so that the solid content of the resin composition is 30-60 wt%, ensuring processability;

[0016] The flame retardant is preferably a phosphorus-containing flame retardant (one of DOPO-HQ, DOPO-ITA, Di-DOPO, DOPO-TMT), or a combination of a nitrogen-containing flame retardant and a metal oxide / hydroxide;

[0017] The curing agent is selected from one or more of the following: ethylenediamine, isophorone diamine, etc.

[0018] Preparation steps

[0019] (1) Preparation of matrix solution: Melt the curing agent and flame retardant in component B at 90-120℃ and 30-300rpm for 0.5-5h to prepare a homogeneous solution; mix the tetrafunctional resin and phenolic resin in component A and heat until homogeneous and transparent, add antioxidant and defoamer, then mix with component B evenly, and adjust the solid content with solvent.

[0020] (2) Coating and curing: Apply the adhesive to a PET film with a thickness of 100-250µm, and cure it in an oven at 120-180℃ for 2-20 minutes, and then let it cool naturally to room temperature.

[0021] The present invention has the following advantages over the prior art:

[0022] (1) Excellent high temperature resistance and flame retardant performance: The adhesive has a flame retardant rating of UL-94 V-0 and a relative temperature index of 125℃, which can meet the high temperature working requirements of the laminated busbar.

[0023] (2) Balanced overall performance: The flame retardant has good compatibility with the resin matrix and does not affect the inherent mechanical properties, transparency and insulation of the resin when used as a co-curing agent. The surface resistivity is >1.0×10 14 Ω;

[0024] (3) Processing and cost advantages: The preparation process is simple, the pressing temperature is low, and the raw materials are cheap and readily available, which can reduce production costs and replace imported products;

[0025] (4) Great industrialization potential: The product has high reliability and is suitable for large-scale production.

[0026] Attached image description.

[0027] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the PET insulating film structure corresponding to the present invention;

[0030] Figure 2 This is a process flow diagram of the preparation process of the flame-retardant, insulating, and high-temperature resistant resin adhesive for laminated busbars in an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 2 As shown: Specific Implementation Example 1

[0034] (1) Preparation of component A: Weigh 30 g of curing agent 4,4'-diaminodiphenylmethane (DDM) and 10 g of flame retardant DI-DOPO into a 100 mL beaker and heat to 120 °C to melt them. Stir until a homogeneous and transparent solution is formed.

[0035] (2) Preparation of component B: Weigh 80 g of F-51 and 20 g of SRTEM-80 and place them in a flask. Then mix at 90 °C with stirring at 300 r / min until the mixture becomes a homogeneous and transparent solution.

[0036] (3) Dilution and mixing: Add 0.1g of antioxidant 225 and 2g of defoamer to the above epoxy resin blend. Then, add component A and stir for 5 minutes to ensure that all components are fully mixed.

[0037] (4) Adjust the dispersion of components A and B (solid content of 30%) with acetone, mix them to form a resin composition, and apply the resin composite to the insulating film for laminated busbars.

[0038] (5) The adhesive is uniformly coated on one side of a 125µm thick PET insulating film using a coating machine, and the dry adhesive thickness is controlled to be 40µm. The coated PET film is placed in a 100℃ oven for 8 minutes to allow the solvent to evaporate. A solid adhesive layer is formed on the PET insulating film.

[0039] (6) After the curing process is completed, allow the sample to cool naturally to room temperature with the oven.

[0040] (7) Obtain a No. 1 epoxy resin composite material sample with a smooth surface and a dense interior without bubbles.

[0041] (8) Table 1 presents the performance data of epoxy resin composite material No. 1. Specific Implementation Example 2

[0043] (1) Preparation of component A: Weigh 32 g of curing agent 4,4'-diaminodiphenylmethane (DDM) and 10 g of flame retardant DI-DOPO into a 100 mL beaker and heat to 120 °C to melt them. Stir until a homogeneous and transparent solution is formed.

[0044] (2) Preparation of component B: Weigh 60g of F-51 and 40g of SRTEM-80 and place them in a flask. Then mix at 90℃ for 3 h with a stirring rate of 300r / min until the mixture becomes a transparent solution.

[0045] (3) Dilution and mixing: Add 0.1g of antioxidant 225 and 2g of defoamer to the above epoxy resin blend. Then, add component A and stir for 5 minutes to ensure that all components are fully mixed.

[0046] (4) Adjust the dispersion of components A and B (solid content of 30%) with acetone, mix them to form a resin composition, and apply the resin composite to the insulating film for laminated busbars.

[0047] (5) The adhesive is uniformly coated on one side of a 125µm thick PET insulating film using a coating machine, and the dry adhesive thickness is controlled to be 40µm. The coated PET film is placed in a 100℃ oven for 8 minutes to allow the solvent to evaporate and form a solid adhesive layer on the PET insulating film.

[0048] (6) After the curing process is completed, allow the sample to cool naturally to room temperature with the oven.

[0049] (7) Obtain a No. 2 epoxy resin composite material sample with a smooth surface and a dense interior without bubbles.

[0050] (8) Table 1 presents the performance data of epoxy resin composite material No. 2. Specific Implementation Example 3

[0052] (1) Preparation of component A: Weigh 34 g of curing agent 4,4'-diaminodiphenylmethane (DDM) and 10 g of flame retardant DI-DOPO into a 100 mL beaker and heat to 120 °C to melt them. Stir until a homogeneous and transparent solution is formed.

[0053] (2) Preparation of component B: Weigh 50g of F-51 and 50g of SRTEM-80 and place them in a flask. Then mix at 90℃ for 3h with a stirring rate of 300r / min until the mixture becomes a transparent solution.

[0054] (3) Dilution and mixing: Add 10 g of 1,4-butanediol diglycidyl ether as an active diluent to the above epoxy resin blend, and then add 0.1 g of antioxidant 225 and 2 g of defoamer. Then, add component A and stir for 5 minutes to ensure that all components are fully mixed.

[0055] (4) Adjust the dispersion of components A and B (solid content of 30%) with acetone, mix them to form a resin composition, and apply the resin to the insulating film for laminated busbars.

[0056] (5) The adhesive is uniformly coated on one side of a 125µm thick PET insulating film using a coating machine, and the dry adhesive thickness is controlled to be 40µm. The coated PET film is placed in a 100℃ oven for 8 minutes to allow the solvent to evaporate. A solid adhesive layer is formed on the PET insulating film.

[0057] (6) After the curing process is completed, allow the sample to cool naturally to room temperature with the oven.

[0058] (7) Obtain a No. 3 epoxy resin composite material sample with a smooth surface and a dense interior without bubbles.

[0059] (8) Table 1 presents the performance data of epoxy resin composite material No. 3.

[0060]

[0061] The above performance data was obtained from tests conducted in accordance with the following specifications;

[0062] (1) Flame retardancy is in accordance with UL-94.

[0063] (2) Surface resistance shall conform to the requirements of GB / T1410.

[0064] (3) The relative temperature index shall be in accordance with UL 746B.

[0065] (4) Peel strength shall be in accordance with the provisions of GB / T 37659-2019 at room temperature.

[0066] (5) Tensile strength shall be in accordance with the provisions of GB / T 13542.2-2009.

[0067] According to the data in Table 1, compared with commercially available products, the resin composites of Examples 1, 2, and 3 exhibit comprehensive advantages in flame retardancy, insulation, thermal properties, and mechanical properties. Although their tensile strength is relatively low, this can be compensated for by increasing the material thickness. Overall, the key performance indicators of these three composite materials meet the standard requirements for insulating films for laminated busbars.

[0068] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A preparation method of a PET-based flame-retardant high-temperature-resistant insulating adhesive for laminated busbars, characterized in that, The method comprises the following steps: (1) Preparation of base solution: two components A and B are prepared, wherein the component A is a resin base, and the component B is a curing agent system, and the specific composition of each component is as follows according to weight: The component A comprises 10-80 parts of tetrafunctional resin, 10-80 parts of phenolic resin, 0.1-1 part of antioxidant, 0.5-1.5 parts of defoaming agent, and 0-80 parts of solvent; the total amount of the tetrafunctional resin and the phenolic resin is 100 parts; The component B comprises 10-30 parts of curing agent and 5-10 parts of flame retardant; the two components A and B are mixed to prepare a glue solution; (2) Film coating and curing: the glue solution is uniformly coated on a 100-250µm thick PET insulating film by using a coating machine, and the coating thickness is 10-60µm; the PET film coated with glue is placed in an oven at 80-200℃ for curing for 2-20min to obtain the target adhesive.

2. The preparation method of the PET-based flame-retardant high-temperature-resistant insulating adhesive for laminated busbars according to claim 1, characterized in that, The tetrafunctional resin in the component is selected from any one of STREM-80, AG-80, and MY-720, and the phenolic resin is selected from any one of F-51, F-48, YECN-195, YECN-200, and YECN-.

3. The preparation method of the PET-based flame-retardant high-temperature-resistant insulating adhesive for laminated busbars according to claim 1, characterized in that, The weight ratio of the tetrafunctional resin to the phenolic resin is 2:8-8:

2.

4. The preparation method of the PET-based flame-retardant high-temperature-resistant insulating adhesive for laminated busbars according to claim 1, characterized in that, The antioxidant is selected from any one of hindered phenol 2246, 330, thioester DLTP, DSTP, and composite antioxidants 225, 561, 900, and PW series.

5. The method for preparing the PET-based flame-retardant and high-temperature-resistant insulating adhesive for laminated busbar according to claim 1, characterized in that, The solvent is selected from at least one of acetone, cyclohexanone, methanol, ethanol, ethyl acetate, methyl ethyl ketone, benzyl alcohol, toluene, and xylene, and the solvent makes the solid content of the resin composition to be 30-60wt%.

6. The method for preparing the PET-based flame-retardant and high-temperature-resistant insulating adhesive for laminated busbar according to claim 1, characterized in that, The flame retardant is selected from one or a combination of two of phosphorus-containing flame retardant, nitrogen-containing flame retardant, metal oxide, or metal hydroxide, wherein the phosphorus-containing flame retardant is one of DOPO-HQ, DOPO-ITA, Di-DOPO, and DOPO-TMT.

7. The method for preparing the PET-based flame-retardant and high-temperature-resistant insulating adhesive for laminated busbar according to claim 1, characterized in that, The curing agent is selected from at least one of ethylenediamine, isophorone diamine, 2-ethyl-4-methylimidazole, methyltetrahydrophthalic anhydride, methyl nadic anhydride, m-phenylenediamine, diaminodiphenyl sulfone, and diaminodiphenyl methane.

8. The method for preparing the PET-based flame-retardant and high-temperature-resistant insulating adhesive for laminated busbar according to claim 1, characterized in that, The high-temperature melting conditions of the flame retardant and the curing agent in the component B are as follows: temperature 90-120℃, stirring rate 30-300rpm, and treatment time 0.5-5h.

9. The method for preparing the PET-based flame-retardant and high-temperature-resistant insulating adhesive for laminated busbar according to claim 1, characterized in that, The coating thickness is 10-50µm, and the curing temperature is 120-180℃.

10. A PET based flame retardant heat resistant insulating adhesive for laminated busbar characterized in that, The PET-based flame-retardant high-temperature-resistant insulating adhesive for the laminated busbar is prepared by the preparation method of the PET-based flame-retardant high-temperature-resistant insulating adhesive for the laminated busbar according to any one of claims 1-9.

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