Secondary branched epoxy modified organic silicon resin as well as preparation method and application thereof

Abstract

The invention relates to the technical field of flexible die cutting circuit boards, and discloses secondary branched epoxy modified organic silicon resin and a preparation method and application thereof.The secondary branched epoxy modified organic silicon resin comprises a core R3, the core R3 is connected with three branched chains R2 through carbon bonds, each branched chain R2 is connected with two branched chains R1 through carbon bonds, and the tail ends of the branched chains R1 are epoxy groups; the used raw materials comprise a raw material A with three silicon-hydrogen bonds in the molecular structure, a raw material B with double bonds and epoxy groups in the molecular structure, and silicone oil C with three end-capped double bonds in the molecular structure, wherein the molar ratio of the raw material A to the raw material B to the silicone oil C is (2.97-3.03): (5.91-6.09): 1. Secondary branched epoxy terminated organic silicon resin is synthesized through a hydrosilylation reaction, a branched structure and a flexible Si-O-Si molecular chain are introduced into thermosetting epoxy resin, the low-temperature toughness of the epoxy resin is improved, the problem that the epoxy resin is poor in humidity and heat resistance is solved through the hydrophobic characteristic of organic silicon, and the epoxy resin can be better applied to a flexible die cutting circuit board covering film.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible die-cut circuit boards, and in particular to a secondary branched epoxy-modified silicone resin and a preparation method and application thereof. Background Art

[0002] Flexible die-cutting circuits (FDCs) are manufactured through a die-cutting process. The flexible circuits are then laminated using a lamination process to form a PET / PI cover film and die-cut copper or aluminum foil. With the development of new energy vehicles, FDCs are widely used in these vehicles, placing higher demands on these materials. In-vehicle FDCs must exhibit superior resistance to heat, cold, and humidity.

[0003] Epoxy resin is commonly used as an adhesive for flexible die-cut circuit boards in the prior art. However, the cured epoxy resin has a network structure with a high cross-linking density, which makes it brittle. In addition, epoxy adhesives easily absorb moisture, and react under the action of moisture, resulting in poor moisture and heat resistance. This greatly limits its application in flexible die-cut circuit boards.

[0004] Adding modifiers, such as rubber particles, nanomaterials, and thermoplastics, to an epoxy resin matrix to improve its toughness through physical modification is a simple and effective method for improving toughness. However, these modifiers have poor compatibility with the epoxy resin matrix and inevitably undergo phase separation before or during the curing process, making it difficult to ensure the performance of the modified epoxy resin at low temperatures. Furthermore, these modifiers cannot improve the epoxy's poor resistance to moisture and heat, making them unsuitable for use as cover films in flexible die-cut circuit boards. Summary of the Invention

[0005] In response to the above-mentioned defects, the purpose of the present invention is to propose a secondary branched epoxy modified silicone resin and its preparation method and application, so as to solve the problems of insufficient low-temperature toughness and moisture and heat resistance when conventional resins are used to prepare epoxy cover films for flexible die-cut circuit boards.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] A secondary branched epoxy modified silicone resin with a molecular structure of The core R3 is connected to three branches R2 through carbon bonds, and each branch R2 is connected to two branches R1 through carbon bonds, wherein the core R3 and the branch R2 both contain The structure of the branched chain R1 is an epoxy group at the end; the raw materials used include Raw material A has a structure and three silicon-hydrogen bonds, raw material B has a double bond and epoxy group in its molecular structure, and raw material B has The present invention relates to a silicone oil C having a structure and three end-capped double bonds, wherein the molar ratio of raw material A: raw material B: silicone oil C is 2.97-3.03:5.91-6.09:1.

[0008] Preferably, the raw material A is phenyltri(dimethylsiloxy)silane, tri(dimethylsiloxy)ethoxysilane, tri(dimethylsiloxy)methylsilane or a homologue thereof.

[0009] Preferably, the raw material B is allyl glycidyl ether, 4-vinylbenzyl glycidyl ether, 4-vinyl cyclohexene oxide or a homologue thereof.

[0010] Preferably, the silicone oil C is tris(vinyldimethylsiloxy)phenylsilane (TVTS name to be confirmed), trivinylethoxysilane, triallyl(phenyl)silane or its homologues.

[0011] A method for preparing a secondary branched epoxy-modified silicone resin, for preparing the above-mentioned silicone resin, comprises the following steps:

[0012] S1. Raw material A was added to the reactor, stirred and heated to 100-110 ° C under a protective atmosphere and maintained for 30 minutes;

[0013] S2. Add 50-100 ppm (to be confirmed) of catalyst;

[0014] S3. Add raw material B dropwise, and then continue the reaction for 1 to 3 hours;

[0015] S4. Cooling to obtain intermediate D for standby use;

[0016] S5. The silicone oil C and intermediate D were added to another reactor and stirred at room temperature under a protective atmosphere to disperse evenly;

[0017] S6. The catalyst was added dropwise over 30 minutes (to be confirmed whether the addition temperature was room temperature or 60 ° C), heated to 50 ~ 70 ° C and kept stirring for 5 hours;

[0018] S7. Add a catalyst, heat to 70-90° C. and maintain the reaction for 2 hours to obtain a secondary branched epoxy-modified silicone resin.

[0019] Preferably, the catalyst is a platinum catalyst, the platinum concentration in the platinum catalyst is 5000 ppm, the amount of the catalyst used in step S2 is 1 to 2% of the total weight of raw materials A and raw material B, the amount of the catalyst used in step S6 is 1 to 2% of the total weight of raw materials A, raw material B and raw material C, and the amount of the catalyst used in step S7 is 1 to 2% of the total weight of raw materials A, raw material B and raw material C.

[0020] Preferably, in step S3, the dropping temperature is 105-115° C., and the time is 50 to 80 minutes.

[0021] Preferably, in step S4, the hydrogen content of the intermediate D is 0.15%-0.2%, and the viscosity is 130-160 cp; in step S7, the epoxy value of the secondary branched epoxy-modified silicone resin is 0.17±0.2 mol / g, and the viscosity is 1000±50 cp.

[0022] A flexible die-cut circuit board epoxy cover film uses materials including epoxy resin, toughening agent, curing agent, flame retardant, solvent and the above-mentioned secondary branched epoxy modified silicone resin. The preparation method comprises the following steps: mixing and uniformly dispersing the above-mentioned materials in a weight ratio of epoxy resin: toughening agent: curing agent: flame retardant: solvent: secondary branched epoxy modified silicone resin = 100:40-70:7-8:50:200-300:2-20; coating the film on a polyimide film of the circuit board at a coating speed of 8-10 m / min; drying and reacting the film at a temperature of 100°C±10°C for 2-4 minutes; and finally thermally compounding the film with a matte film or a release film at a temperature of 90°C to obtain the epoxy cover film.

[0023] Preferably, the epoxy resin is one of phenol biphenyl epoxy resin, o-cresol epoxy resin or dicyclopentadienol type epoxy resin;

[0024] The toughening agent is carboxyl modified nitrile rubber;

[0025] The curing agent is micro powder dicyandiamide, and the molar ratio of active hydrogen in the micro powder dicyandiamide to the total epoxy groups of the epoxy resin and the secondary branched epoxy modified silicone resin is 1:1;

[0026] The flame retardant is magnesium hydroxide or aluminum hypophosphite;

[0027] The solvent is butanone, methyl isobutyl ketone or ethyl acetate;

[0028] After the materials are mixed, they are dispersed evenly through a disperser and a sand mill in sequence;

[0029] The coating method adopts comma blade coating or slit coating process, and the coating thickness is 45μm.

[0030] The technical solution provided by the present invention can have the following beneficial effects:

[0031] 1. A secondary branched epoxy-terminated silicone resin is synthesized through a hydrosilylation reaction, and the branched structure and "flexible Si-O-Si" molecular chain are introduced into the thermosetting epoxy resin to improve the low-temperature toughness of the epoxy resin. The hydrophobic properties of silicone are also used to improve the poor moisture and heat resistance of the epoxy resin, making it better suitable for use in flexible die-cut circuit board cover films.

[0032] 2. Phenyl tris (dimethylsiloxy) silane is used, which contains a benzene ring. While ensuring low-temperature resistance, it can improve the heat resistance of the secondary branched epoxy modified silicone resin and the epoxy covering film prepared therefrom. In addition, the benzene ring provides a relatively large steric hindrance, reduces the production of by-products caused by the addition of three silicon-hydrogen bonds, and improves the purity of the secondary branched epoxy modified silicone resin and the performance of the epoxy covering film prepared therefrom.

[0033] 3. The use of allyl glycidyl ether, which has low cost, high double bond reactivity, and high hydrosilylation conversion rate, can improve reaction efficiency, reduce reaction time, and reduce the amount of monomer residue after the reaction, thereby improving the purity of the secondary branched epoxy-modified silicone resin and the performance of the epoxy covering film prepared therefrom (to be confirmed).

[0034] 4. Tris(vinyldimethylsiloxy)phenylsilane, which contains a benzene ring, is used to further improve the heat resistance of the secondary branched epoxy-modified silicone resin and the epoxy covering film prepared therefrom. It contains a silicon-oxygen bond and increases the flexibility of the epoxy covering film.

[0035] 5. By adding the catalyst in two steps and adjusting the temperature and addition time, the reaction rate can be controlled to avoid excessive or slow reaction, thereby improving the purity of the secondary branched epoxy-modified silicone resin. Using a higher platinum concentration increases the number of active sites per unit volume, improving reaction efficiency and shortening reaction time.

[0036] 6. Use viscosity to roughly indicate the formation of compounds and predict the degree of reaction. Observing viscosity facilitates monitoring of the reaction process.

[0037] 7. By applying secondary branched epoxy modified silicone resin to the epoxy cover film of flexible die-cut circuit boards, the low temperature performance and moisture and heat resistance of the epoxy adhesive layer of the cover film are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the synthesis of epoxy-modified silane containing silicon-hydrogen bonds according to Example 1 of the present invention.

[0039] Figure 2 Schematic diagram of the synthesis of the secondary branched epoxy-modified silicone resin of Example 1 of the present invention. DETAILED DESCRIPTION

[0040] For ease of understanding of the present invention, the present invention will be described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0041] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] The following describes embodiments of the present invention in conjunction with the accompanying drawings.

[0044] A secondary branched epoxy modified silicone resin with a molecular structure of The core R3 is connected to three branches R2 through carbon bonds, and each branch R2 is connected to two branches R1 through carbon bonds, wherein the core R3 and the branch R2 both contain The structure of the branched chain R1 is an epoxy group at the end; the raw materials used include Raw material A has a structure and three silicon-hydrogen bonds, raw material B has a double bond and epoxy group in its molecular structure, and raw material B has The present invention relates to a silicone oil C having a structure and three end-capped double bonds, wherein the molar ratio of raw material A: raw material B: silicone oil C is 2.97-3.03:5.91-6.09:1.

[0045] like Figure 1 and Figure 2 As shown, two of the silicon-hydrogen bonds in raw material A react with the double bonds of two raw materials B to form a molecular structure in which branch R2 connects two branches R1, forming a primary branched structure. At the same time, raw material B introduces an epoxy group, and the other silicon-hydrogen bonds in the three raw materials A react with the three end-capping double bonds of silicone oil C to form a molecular structure in which core R3 connects three branches R2, forming a secondary branched structure. A secondary branched epoxy-terminated silicone resin is synthesized through a silicon-hydrogen addition reaction. The branched structure and "flexible Si-O-Si" molecular chain are introduced into the thermosetting epoxy resin, improving the low-temperature toughness of the epoxy resin. The hydrophobic properties of silicone are used to improve the poor moisture and heat resistance of the epoxy resin, making it more suitable for use in flexible die-cut circuit board cover films.

[0046] Preferably, the raw material A is phenyltri(dimethylsiloxy)silane, tri(dimethylsiloxy)ethoxysilane, tri(dimethylsiloxy)methylsilane or a homologue thereof.

[0047] Preferably, the raw material A is phenyltris(dimethylsiloxy)silane, which contains a benzene ring. While ensuring low-temperature resistance, it can improve the heat resistance of the secondary branched epoxy-modified silicone resin and the epoxy covering film prepared therefrom. In addition, the benzene ring provides a relatively large steric hindrance, reduces the production of by-products resulting from the addition of three silicon-hydrogen bonds, and improves the purity of the secondary branched epoxy-modified silicone resin and the performance of the epoxy covering film prepared therefrom.

[0048] Preferably, the raw material B is allyl glycidyl ether, 4-vinylbenzyl glycidyl ether, 4-vinyl cyclohexene oxide or a homologue thereof.

[0049] Preferably, the raw material B is allyl glycidyl ether, which has low cost, high double bond reactivity, and high hydrosilylation conversion rate, can improve reaction efficiency, reduce reaction time, and reduce the amount of monomer residue after the reaction, thereby improving the purity of the secondary branched epoxy-modified silicone resin and the performance of the epoxy covering film prepared therefrom.

[0050] Preferably, the silicone oil C is tris(vinyldimethylsiloxy)phenylsilane, trivinylethoxysilane, triallyl(phenyl)silane or a homologue thereof.

[0051] Preferably, the silicone oil C is tris(vinyldimethylsiloxy)phenylsilane, which contains a benzene ring, further improving the heat resistance of the secondary branched epoxy-modified silicone resin and the epoxy covering film prepared therefrom, and contains a silicon-oxygen bond, increasing the flexibility of the epoxy covering film.

[0052] In one embodiment, the preparation method of the above-mentioned secondary branched epoxy-modified silicone resin can be as follows: Method 1: Raw materials A and B are mixed at one time, dispersed evenly, a catalyst is added at one time, heated and subjected to a primary branching reaction, and then raw material C is added, mixed and dispersed, and a secondary branching reaction is carried out to obtain the secondary branched epoxy-modified silicone resin.

[0053] Although this preparation method can obtain a secondary branched epoxy-modified silicone resin, adding all the catalysts at once will cause the primary branching reaction rate to be too fast and difficult to control, the catalyst activity in the secondary branching reaction is insufficient, the secondary branching reaction efficiency is low, and the overall reaction efficiency is not high. At the same time, the purity of the secondary branched epoxy-modified silicone resin obtained is low.

[0054] In another embodiment, the preparation method of the above-mentioned secondary branched epoxy-modified silicone resin can be, method 2: raw materials A and B are mixed at one time, and after uniform dispersion, a catalyst required for the primary branching reaction is first added, heated and a primary branching reaction is carried out, and then raw material C is added and mixed and dispersed uniformly, and then a catalyst required for the secondary branching reaction is added, and a secondary branching reaction is carried out to prepare the secondary branched epoxy-modified silicone resin.

[0055] Although this preparation method adds the catalyst separately on both sides, the instantaneous reaction rate after each addition of the catalyst is still relatively fast, resulting in more by-products and the purity of the prepared secondary branched epoxy-modified silicone resin is not high.

[0056] A method for preparing a secondary branched epoxy-modified silicone resin, for preparing the above-mentioned silicone resin, comprises the following steps:

[0057] S1. Raw material A was added to the reactor, stirred and heated to 100-110 ° C under a protective atmosphere and maintained for 30 minutes;

[0058] S2. Adding a catalyst;

[0059] S3. Add raw material B dropwise, and then continue the reaction for 1 to 3 hours;

[0060] S4. Cooling to obtain intermediate D for standby use;

[0061] S5. The silicone oil C and intermediate D were added to another reactor and stirred at room temperature under a protective atmosphere to disperse evenly;

[0062] S6. After the catalyst was added dropwise over 30 minutes, the mixture was heated to 50-70°C and stirred for 5 hours;

[0063] S7. Add a catalyst, heat to 70-90° C. and maintain the reaction for 2 hours to obtain a secondary branched epoxy-modified silicone resin.

[0064] The catalyst is added twice in S6 and S7 to control the reaction rate so that it is not too intense or too slow, thereby improving the purity of the product.

[0065] Specifically, the protective atmosphere may be nitrogen, helium or argon.

[0066] Preferably, the catalyst is a platinum catalyst, the platinum concentration in the platinum catalyst is 5000 ppm, the amount of the catalyst used in step S2 is 1 to 2% of the total weight of raw materials A and raw material B, the amount of the catalyst used in step S6 is 1 to 2% of the total weight of raw materials A, raw material B and raw material C, and the amount of the catalyst used in step S7 is 1 to 2% of the total weight of raw materials A, raw material B and raw material C.

[0067] Using a higher platinum concentration will result in more active sites per unit volume, which can improve reaction efficiency and shorten reaction time.

[0068] Preferably, in step S3, the dropping temperature is 105-115° C., and the time is 50 to 80 minutes.

[0069] If the temperature is too low, the reaction will be too slow or non-existent. If the temperature is too high, byproducts with all three Si-H bonds added will be easily formed. If the addition time exceeds 80 minutes, the AGE concentration will be relatively low, the reaction speed will be relatively slow, and production efficiency will be affected. If the addition time is less than 50 minutes, byproducts with all three Si-H bonds added will be easily formed.

[0070] Preferably, in step S4, the hydrogen content of the intermediate D is 0.15%-0.2%, and the viscosity is 130-160 cp; in step S7, the epoxy value of the secondary branched epoxy-modified silicone resin is 0.17±0.2 mol / g, and the viscosity is 1000±50 cp.

[0071] The molecular weight of the raw material is relatively small, and the viscosity will be lower. The molecular weight of the product will be relatively large, and the viscosity will be higher. Viscosity can be used to roughly indicate the formation of the compound and predict the degree of reaction. Observing viscosity is convenient for monitoring the reaction process.

[0072] For intermediate D, hydrogen content indicates product conversion and the presence of residual Si-H bonds, which can subsequently react with silicone oil C to form a secondary branched structure. A low hydrogen content suggests an overdose of raw material B or oxidation of some Si-H bonds in raw material A. A high hydrogen content indicates that many Si-H bonds remain unreacted, leading to a low conversion rate.

[0073] The epoxy value is an important performance indicator of epoxy resins and can be used to identify the quality of epoxy resins or calculate the amount of curing agent used. A high or low epoxy value or viscosity of a secondary branched epoxy-modified silicone resin indicates low purity.

[0074] Example 1

[0075] S1. 3 parts of phenyltris(dimethylsiloxy)silane were added to the reaction vessel in a molar ratio, stirred and heated to 110 ° C under a nitrogen atmosphere and maintained for 30 minutes;

[0076] S2. Add 2% by weight of the total weight of raw material A and raw material B to the platinum catalyst PT-5000;

[0077] S3 according to the molar ratio of 6 parts of allyl glycidyl ether were added dropwise within 60 minutes, and then the reaction was continued for 2 hours;

[0078] S4 cooling to obtain epoxy-modified silane containing silicon-hydrogen bonds for use;

[0079] The obtained epoxy-modified silane had a hydrogen content of 0.1774 wt %, a viscosity of 148.08 cp, and a silicon-hydrogen conversion rate of 99.80%.

[0080] S5 according to the molar ratio of 1 part of tri (vinyldimethylsilyloxy) phenyl silane and 3 parts of epoxy-modified silane containing silicon-hydrogen bonds were added to another reaction vessel and stirred at room temperature under a protective atmosphere;

[0081] S6. After 2% of the total weight of raw material A, raw material B and raw material C was added dropwise to a platinum catalyst PT-5000 within 30 minutes, the reaction was heated to 60 ° C and stirred for 5 hours;

[0082] S7. Add 2% of the total weight of raw material A, raw material B and raw material C of platinum catalyst PT-5000, heat to 80 ° C and keep the reaction for 2 hours to obtain a secondary branched epoxy modified silicone resin.

[0083] The epoxy content of the obtained secondary branched epoxy-modified silicone resin was 0.1714 mol / 100 g, the viscosity was 1017.75 cp, and the conversion rate of silicon hydrogen was 99.70%.

[0084] A flexible die-cut circuit board epoxy cover film uses materials including epoxy resin, toughening agent, curing agent, flame retardant, solvent and the above-mentioned secondary branched epoxy modified silicone resin. The preparation method comprises the following steps: mixing and uniformly dispersing the above-mentioned materials in a weight ratio of epoxy resin: toughening agent: curing agent: flame retardant: solvent: secondary branched epoxy modified silicone resin = 100:40-70:7-8:50:200-300:2-20; coating the film on a polyimide film of the circuit board at a coating speed of 8-10 m / min; drying and reacting the film at a temperature of 100°C±10°C for 2-4 minutes; and finally thermally compounding the film with a matte film or a release film at a temperature of 90°C to obtain the epoxy cover film.

[0085] By applying secondary branched epoxy modified silicone resin to the epoxy cover film of flexible die-cut circuit boards, the low temperature performance and moisture and heat resistance of the epoxy adhesive layer of the cover film are improved.

[0086] The Flexible Printed Circuit (FPC) process is relatively complex and uses a flat pressing process with relatively high pressure. The penetration depth of the adhesive layer of the cover film needs to be relatively small. However, silicone resin is relatively soft, which will increase the penetration depth of the adhesive film and easily cause adhesive overflow. To avoid adhesive overflow, the curing degree of the adhesive film needs to be increased, but this will lead to a decrease in the adhesion to metal.

[0087] The process of flexible die-cutting circuit (FDC) is very simple, but it uses a roller pressing process. The roller pressing pressure is relatively low, which requires the adhesive layer of the cover film to have a relatively high fluidity, and the needle penetration depth of the adhesive layer must be relatively large. The secondary branched epoxy modified silicone resin prepared by silicone modification is used in the cover film of flexible die-cutting circuit boards to achieve better results.

[0088] Preferably, the epoxy resin is one of phenol biphenyl epoxy resin, o-cresol epoxy resin or dicyclopentadienol type epoxy resin. These epoxy resins have relatively high epoxy functionality, which can increase the crosslinking density of the cured film, improve heat resistance and reduce water absorption;

[0089] The toughening agent is a carboxyl-modified nitrile rubber. The carboxyl group reacts with the epoxy group, and the nitrile rubber molecular chain and the epoxy resin form an interpenetrating network structure, which improves the impact toughness and flexural resistance of the epoxy resin.

[0090] The curing agent is micropowder dicyandiamide, and the molar ratio of active hydrogen in the micropowder dicyandiamide to the total epoxy groups of the epoxy resin and the secondary branched epoxy-modified silicone resin is 1:1. Since the micropowder dicyandiamide is incompatible with the epoxy resin, its reaction with epoxy is slow, thereby improving the storage stability of the film;

[0091] The flame retardant is magnesium hydroxide or aluminum hypophosphite. Preferably, aluminum hypophosphite is selected, as aluminum hypophosphite has a good flame retardant effect and does not promote epoxy reaction, thereby improving the storage stability of the coating and film.

[0092] The solvent is butanone, methyl isobutyl ketone or ethyl acetate. Preferably, butanone is selected because it has a low boiling point, small solvent residue, and good solubility for nitrile rubber and epoxy resin. At the same time, the carbonyl group has the effect of inhibiting the ring-opening reaction of the epoxy group, thereby improving the stability of the coating.

[0093] After the materials are mixed, they are dispersed evenly through a disperser and a sand mill in sequence;

[0094] The coating method adopts comma blade coating or slit coating process, and the coating thickness is 45μm.

[0095] Examples 2-9 are the preparation of epoxy cover films for flexible die-cut circuit boards, all of which use the secondary branched epoxy-modified silicone resin prepared in Example 1.

[0096] The preparation methods of Examples 2-9 and Comparative Example 1 are as follows:

[0097] Table 1 Raw materials and their weight parts of Examples 2-7 and Comparative Example 1

[0098]

[0099] Table 2 Raw materials and their weight parts of Example 8

[0100]

[0101] Table 3 Raw materials and their weight parts of Example 9

[0102]

[0103] According to the weight proportions in Tables 1-3, all the materials were mixed and dispersed evenly, and then coated on a circuit board made of polyimide film using a slit coating process at a coating speed of 9m / min. The reaction was dried at a temperature of 100°C for 3 minutes, and finally the release film was thermally composited at a temperature of 90°C to obtain an epoxy cover film. The softening point, needle penetration depth, room temperature bonding strength, room temperature bonding strength after 1000h of 85°C / 85%RH wet heat aging, and low temperature (5°C) bonding strength were tested respectively. Low temperature bonding strength is correlated with low temperature toughness. If the low temperature toughness is poor, the bonding strength will deteriorate. Therefore, the low temperature toughness can be characterized by the low temperature bonding strength. Compared with Comparative Example 1, the low temperature performance and wet heat resistance of Examples 2-9 are significantly improved.

[0104] Table 4 Performance test of Examples 2-9 and Comparative Example 1

[0105]

[0106] Room temperature bond strength test method, according to IPC-TM650 "Test Method Manual" 2.4.9 Peel Strength, Flexible Dielectric Material Method Determination.

[0107] Low temperature (5°C) bond strength test method: use a high and low temperature peel tester with the temperature set to 5°C and measure according to IPC-TM650 "Test Method Manual" 2.4.9 Peel Strength, Flexible Dielectric Materials Method.

[0108] Room-temperature bond strength test method after 1000h of 85°C / 85% RH damp heat aging: After aging the sample at 85°C / 85% RH for 1000h, the peel strength of the flexible dielectric material is measured according to IPC-TM650 "Manual of Test Methods", 2.4.9.

[0109] Low-temperature bonding strength is correlated with low-temperature toughness. If the low-temperature toughness is poor, the bonding strength will deteriorate. Therefore, low-temperature toughness can be characterized by low-temperature bonding strength.

[0110] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A secondary branched epoxy modified silicone resin, characterized in that: The molecular structure is The core R3 is connected to three branches R2 through carbon bonds, and each branch R2 is connected to two branches R1 through carbon bonds, wherein the core R3 and the branch R2 both contain The structure of the branched chain R1 is an epoxy group at the end; the raw materials used include Raw material A has a structure and three silicon-hydrogen bonds, raw material B has a double bond and epoxy group in its molecular structure, and raw material B has The present invention relates to a silicone oil C having a structure and three end-capped double bonds, wherein the molar ratio of raw material A: raw material B: silicone oil C is 2.97-3.03:5.91-6.09:

1.

2. A secondary branched epoxy-modified silicone resin according to claim 1, characterized in that: The raw material A is phenyltri(dimethylsiloxy)silane, tri(dimethylsiloxy)ethoxysilane, tri(dimethylsiloxy)methylsilane or its homologues.

3. A secondary branched epoxy-modified silicone resin according to claim 1, characterized in that: The raw material B is allyl glycidyl ether, 4-vinylbenzyl glycidyl ether, 4-vinyl cyclohexene oxide or a homologue thereof.

4. A secondary branched epoxy-modified silicone resin according to claim 1, characterized in that: The silicone oil C is tris(vinyldimethylsiloxy)phenylsilane, trivinylethoxysilane, triallyl(phenyl)silane or a homologue thereof.

5. A method for preparing a secondary branched epoxy-modified silicone resin, characterized in that: The method for preparing the organic silicone resin according to any one of claims 1 to 4 comprises the following steps: S1. Raw material A was added to the reactor, stirred and heated to 100-110 ° C under a protective atmosphere and maintained for 30 minutes; S2. Adding a catalyst; S3. Add raw material B dropwise, and then continue the reaction for 1 to 3 hours; S4. Cooling to obtain intermediate D for standby use; S5. The silicone oil C and intermediate D were added to another reactor and stirred at room temperature under a protective atmosphere to disperse evenly; S6. After the catalyst was added dropwise over 30 minutes, the mixture was heated to 50-70°C and stirred for 5 hours; S7. Add a catalyst, heat to 70-90° C. and maintain the reaction for 2 hours to obtain a secondary branched epoxy-modified silicone resin.

6. The method for preparing a secondary branched epoxy-modified silicone resin according to claim 5, wherein: The catalysts are all platinum catalysts, the platinum concentration in the platinum catalyst is 5000ppm, the amount of the catalyst used in step S2 is 1-2% of the total weight of raw materials A and raw material B, the amount of the catalyst used in step S6 is 1-2% of the total weight of raw materials A, raw material B and raw material C, and the amount of the catalyst used in step S7 is 1-2% of the total weight of raw materials A, raw material B and raw material C.

7. The method for preparing a secondary branched epoxy-modified silicone resin according to claim 5, wherein: In step S3, the dropping temperature is 105-115° C. and the time is 50 to 80 minutes.

8. The method for preparing a secondary branched epoxy-modified silicone resin according to claim 5, wherein: In step S4, the hydrogen content of the intermediate D is 0.15%-0.2%, and the viscosity is 130-160 cp; in step S7, the epoxy value of the secondary branched epoxy-modified silicone resin is 0.17±0.2 mol / g, and the viscosity is 1000±50 cp.

9. A flexible die-cut circuit board epoxy cover film, characterized by: The materials used include epoxy resin, toughening agent, curing agent, flame retardant, solvent and the secondary branched epoxy modified silicone resin according to any one of claims 1 to 4. The preparation method is as follows: the above materials are mixed and dispersed uniformly in a weight ratio of epoxy resin: toughening agent: curing agent: flame retardant: solvent: secondary branched epoxy modified silicone resin = 100:40-70:7-8:50:200-300:2-20, and then coated on the polyimide film of the circuit board at a coating speed of 8-10m / min, dried and reacted at a temperature of 100℃±10℃ for 2-4 minutes, and finally thermally composited with a matte film or release film at a temperature of 90℃ to obtain the epoxy cover film.

10. The epoxy cover film for a flexible die-cut circuit board according to claim 9, characterized in that: The epoxy resin is one of phenol biphenyl epoxy resin, o-cresol epoxy resin or dicyclopentadienol type epoxy resin; The toughening agent is carboxyl modified nitrile rubber; The curing agent is micro powder dicyandiamide, and the molar ratio of active hydrogen in the micro powder dicyandiamide to the total epoxy groups of the epoxy resin and the secondary branched epoxy modified silicone resin is 1:1; The flame retardant is magnesium hydroxide or aluminum hypophosphite; The solvent is butanone, methyl isobutyl ketone or ethyl acetate; After the materials are mixed, they are dispersed evenly through a disperser and a sand mill in sequence; The coating method adopts comma blade coating or slit coating process, and the coating thickness is 45μm.

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