Repairable low-stress single-component epoxy compound and preparation method thereof

Abstract

The invention relates to a repairable low-stress single-component epoxy compound and a preparation method thereof. Epoxy resin containing-S-S-bonds and a coupling agent containing-S-S-bonds are introduced into bifunctional long-chain solid epoxy resin, liquid bisphenol A epoxy resin or liquid bisphenol F epoxy resin for toughening, so that the curing stress of the epoxy compound is reduced; meanwhile, the characteristic that a-S-S-bond can be repaired after breaking is utilized, an interpenetrating network structure is formed, microcracks formed by the adhesive in the high and low temperature circulation process are improved, expansion of the microcracks is inhibited, and therefore the purposes of reducing the hidden danger of cracking and improving the high and low temperature reliability of the epoxy compound adhesive are achieved; the-S-S-bond-containing epoxy resin is matched with other bifunctional long-chain epoxy resin for use, so that the modulus and the maximum fracture displacement of a cured product of the epoxy resin are greatly reduced, and the high and low temperature resistance of a single-component epoxy compound is improved.

Description

Technical Field

[0001] The invention belongs to the field of epoxy resin compound formula design, and in particular relates to a repairable low-stress dicyandiamide-cured single-component epoxy compound. Background Art

[0002] As adhesives or packaging materials for electronic components such as magnetic cores, glass, and chips, single-component epoxy resin composites have the advantages of strong bonding strength and good processability. However, due to the shrinkage stress generated during the curing of dicyandiamide epoxy resins, thermal expansion and contraction when the strength decreases during the reflow process, and the high modulus and large difference in linear expansion coefficient with the bonding substrate during high and low temperature reliability experiments, it is easy to cause micro cracks in fragile adhesive materials. As aging progresses, micro cracks gradually enlarge and eventually crack, affecting the use of electronic components. The effects of curing shrinkage and thermal expansion and contraction can be summarized as follows: Figure 1 The warping is represented by .

[0003] Common methods for toughening epoxy resin composites with dicyandiamide as curing agent include rubber toughening, toughening with long-chain diluents, and toughening with organosilicon compounds. Although these toughening methods have their own advantages, they all have some defects. For example, the rubber toughening method will cause problems such as high viscosity of the epoxy resin composite, difficulty in dispersion, complex process, and no obvious improvement in elongation at break; while the long-chain diluent will reduce the strength of the epoxy resin composite after curing, increase the linear expansion coefficient, and affect adhesion; organosilicon compounds have poor compatibility with other components of the epoxy resin composite, and the price is generally high. Therefore, the toughening method of the single-component epoxy resin composite with dicyandiamide as the curing agent has always been a topic of widespread concern in the industry.

[0004] Disulfide bonds (-SS-) have the characteristics of high temperature fracture and low temperature self-repair. Therefore, polysulfide materials containing disulfide bonds are widely used in the self-repair technology of polymers, such as the self-repair of glues, tires, and surface coatings. The cohesive healing process of polysulfide materials over time is as follows: Figure 2 When polysulfide material is added to epoxy resin composite as a toughening agent, it is difficult for the single-component epoxy resin composite with dicyandiamide as a curing agent to maintain high levels of bonding performance, mechanical properties and heat resistance, which limits the application of single-component epoxy resin with dicyandiamide as a curing agent. Summary of the invention

[0005] According to the characteristic of -SS- self-repairing, in order to overcome the defects of the one-component epoxy resin cured by dicyandiamide, the present invention introduces a macromolecular epoxy resin containing -SS- bonds and a small molecule coupling agent containing -SS- bonds into the epoxy resin composite, so that the epoxy resin can use the -SS- of the two to self-repair when microcracks are generated, which can improve the cracking of the epoxy resin caused by thermal expansion and contraction during temperature change processes such as cooling after curing, reflow soldering, and high and low temperature processes. At the same time, because the epoxy resin structure containing -SS- bonds has excellent toughness and extremely low viscosity, it can also be toughened with a bifunctional long-chain solid epoxy resin to improve the shortcoming of high viscosity of the long-chain solid epoxy resin. In addition, the epoxy resin composite of the present invention retains the benzene ring skeleton and hydroxyl group of the liquid bisphenol A epoxy resin or the liquid bisphenol F epoxy resin, so that the bonding performance, mechanical properties and heat resistance of the one-component epoxy resin are maintained at a high level. The coupling agent containing -SS- bonds can form small molecule coupling agents after breaking at high temperatures, which can repair each other with the high molecular prepolymer containing -SS- bonds (epoxy prepolymer containing -SS- bonds), and form an interpenetrating network structure, thereby improving the tensile shear strength of the one-component epoxy resin cured product, improving the stratification phenomenon caused by excessive modulus and warping, and repairing the micro cracks of the one-component epoxy resin cured product caused by stress, warping, etc., to prevent small cracks from gradually forming large cracks, thereby improving the high and low temperature reliability of the one-component epoxy resin adhesive. Practical verification shows that the improvement effect is obvious.

[0006] The -SS-bond-containing macromolecular epoxy resin and the -SS-bond-containing small molecule coupling agent for providing toughening provided by the present invention may break the -SS-bond under the condition of higher than 140°C, but can be quickly self-repaired at medium and low temperatures. During the repair process, the macromolecular epoxy resins and the macromolecular epoxy resins, the small molecule coupling agents and the small molecule coupling agents, and the macromolecular epoxy resins and the small molecule coupling agents are all combined through the -SS-bond to achieve self-healing, and the self-healing is achieved multiple times without significant systematic decrease in the maximum displacement of the fracture.

[0007] In order to achieve the above-mentioned purpose or effect, the present invention first provides a repairable low-stress dicyandiamide-cured one-component epoxy composite, which is made of the following materials measured in parts by weight:

[0008] 5 to 10 parts of epoxy resin containing -SS- bonds;

[0009] 5-10 parts of bifunctional long-chain solid epoxy resin;

[0010] 25-50 parts of liquid bisphenol A epoxy resin or liquid bisphenol F epoxy resin;

[0011] 0.1 to 3 parts of coupling agent containing -SS- bond;

[0012] 0.1 to 3 parts of coupling agent containing phenylamino group;

[0013] 20-50 parts of filler;

[0014] Thixotropic agent 0-20 parts;

[0015] Additives 0.1-1 part;

[0016] 1.5 to 3 parts of dicyandiamide;

[0017] 1.5 to 3 parts of organic urea.

[0018] A further solution is that, in addition to the above materials, the material capable of repairing the low-stress dicyandiamide-cured one-component epoxy composite may also include 0.1 to 1 part of a pigment.

[0019] Optionally, in the material of the repairable low-stress dicyandiamide-cured one-component epoxy composite, whether or not it contains a pigment, the sum of the weight parts of all materials can be 100 parts.

[0020] A further solution is that the epoxy resin containing -SS- bonds is EPS35, EPS70 or a mixture of the two from Nouryon, and its molecular structure is as follows:

[0021]

[0022] The bifunctional long-chain solid epoxy resin can be selected from any one or more of the following materials with an epoxy equivalent of 400-1000: bisphenol A epoxy resin, bisphenol F epoxy resin, polyethylene glycol modified epoxy resin, polypropylene glycol modified epoxy resin, polyurethane chain extension modified bisphenol A epoxy resin, polyurethane chain extension modified bisphenol F epoxy resin. The present invention also provides a part of bifunctional long-chain solid epoxy resins, such as E20, E12, E10, etc.

[0023] The liquid bisphenol A epoxy resin or liquid bisphenol F epoxy resin can be selected from bisphenol A epoxy resin or bisphenol F epoxy resin with an epoxy equivalent between 150 and 270. The present invention also provides a portion of commercial liquid bisphenol A epoxy resin or liquid bisphenol F epoxy resin, such as E44, E51, E54, etc.

[0024] The coupling agent containing -SS-bond is bis-(γ-triethoxysilylpropyl) tetrasulfide (Si69), which is not easy to volatilize and migrate. At the same time, the -SS-bond will break after the temperature exceeds 140°C, forming a small molecule -S-containing coupling agent, which will self-repair at low temperatures and form an IPN (InterpenetratingPolymer Network, i.e., a unique polymer blend) interpenetrating network structure with the epoxy resin polymer to repair the cross-linked network microcracks. The molecular structure of Si69 is as follows:

[0025]

[0026] A further solution is that the coupling agent containing aniline is OFS-6032. The addition of the coupling agent can help the dispersion of fillers, reduce the viscosity of the glue system, and improve the bonding strength of the glue system. Its molecular structure is as follows:

[0027]

[0028] A further solution is that the filler can be selected from one or more of silicon micropowder, calcium carbonate, aluminum hydroxide, aluminum oxide, wollastonite, kaolin and the like.

[0029] The thixotropic agent can be selected from one or more of nano calcium carbonate, bentonite, white carbon black and the like.

[0030] The pigment is a color paste or a color slurry, and the color of the glue is adjusted by using conventional pigments in the art;

[0031] The auxiliary agent may be a defoaming agent or the like;

[0032] A further solution is that, as a curing accelerator, the organic urea is a mixture of one or more of U-52M, U-35M, UR200, UR300, and UR500, and the molecular structure of the organic urea is as follows:

[0033]

[0034] The present invention also provides a method for preparing a repairable low-stress dicyandiamide-cured one-component epoxy composite, comprising the following steps:

[0035] First, 5 to 10 parts of epoxy resin containing -SS- bonds, 5 to 10 parts of bifunctional long-chain solid epoxy resin, and 25 to 50 parts of liquid bisphenol A / F epoxy resin measured by mass are heated to 80 to 100° C. and uniformly mixed; after cooling, 0.1 to 3 parts of coupling agent containing -SS- bonds, 0.1 to 3 parts of coupling agent containing aniline, 20 to 50 parts of fillers, 0 to 20 parts of thixotropic agent, 0.1 to 1 part of pigment, 0.1 to 1 part of auxiliary agent, 1.5 to 3 parts of dicyandiamide, and 1.5 to 3 parts of organic urea are added; and all the materials are uniformly mixed to obtain the one-component epoxy composite.

[0036] A further solution is: the dispersion equipment uses a double planetary stirring kettle with a stirring mode of 500 to 1500 rpm. The stirring time does not exceed 60 minutes to achieve uniform dispersion, which has extremely high preparation efficiency.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] By introducing epoxy resin containing -SS- bonds for toughening, curing stress is reduced and tensile shear strength is improved. At the same time, the -SS- bonds can be broken and repaired to form an interpenetrating network structure, which improves the microcracks of the adhesive during high and low temperature cycles and inhibits the expansion of microcracks, thereby reducing the hidden danger of cracking and improving the high and low temperature reliability of the adhesive. At the same time, because the epoxy resin containing -SS- bonds itself has the characteristics of low viscosity and high toughness, it can be used in combination with solid bisphenol A epoxy resin to greatly reduce the modulus and maximum fracture displacement of the epoxy resin cured product, improve the high and low temperature resistance of the single-component epoxy composite, and can be used on brittle materials such as semiconductor chips, transformer cores, and glass, reducing the hidden danger of cracking of brittle substrates such as semiconductor chips and transformer cores due to curing shrinkage and high and low temperature thermal expansion and contraction, thereby extending the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a warping phenomenon during the curing and high and low temperature processes.

[0040] Figure 2 It is the cohesive healing process of polysulfide materials over time.

[0041] Figure 3 These are illustrations of the core being damaged by the adhesive and the colloid cracking, where a is an illustration of the core being damaged by the adhesive and b is an illustration of the colloid cracking. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] Example 1

[0044] 10 parts of epoxy resin (EPS35) containing -SS- bonds, 10 parts of solid bisphenol A epoxy resin (equivalent 400-500), and 30 parts of liquid bisphenol A epoxy resin (equivalent 170-210) were heated to 90°C for mixing, and then 1.9 parts of dicyandiamide, 1.5 parts of organic urea (UR300), 1 part of color paste, 30 parts of aluminum hydroxide, 14.1 parts of nano-calcium carbonate, 0.5 parts of coupling agent (Si69), 0.5 parts of coupling agent (OFS-6032), and 0.5 parts of defoaming agent were added and pre-mixed, and a single-component epoxy composite a was obtained after vacuum stirring at a speed of 1500 rpm in a double planetary stirring kettle for 1 hour.

[0045] Example 2

[0046] 5 parts of epoxy resin (EPS35) containing -SS- bonds, 5 parts of solid bisphenol A epoxy resin (equivalent 400-500), and 40 parts of liquid bisphenol A epoxy resin (equivalent 170-210) were heated to 90°C for mixing, and then 2.2 parts of dicyandiamide, 1.7 parts of organic urea (UR300), 1 part of color paste, 30 parts of silicon micropowder, 13.5 parts of nano calcium carbonate, 0.5 parts of coupling agent (Si69), 0.5 parts of coupling agent (OFS-6032), and 0.5 parts of defoaming agent were added and pre-mixed, and a single-component epoxy composite b was obtained after vacuum stirring at a speed of 1500 rpm in a double planetary stirring kettle for 1 hour.

[0047] Example 3

[0048] 10 parts of epoxy resin (EPS70) containing -SS- bonds, 5 parts of solid bisphenol A epoxy resin (equivalent 400-500), and 35 parts of liquid bisphenol A epoxy resin (equivalent 170-210) were heated to 90°C for mixing, and then cooled and added with 2.1 parts of dicyandiamide, 1.6 parts of organic urea (UR300), 0.5 parts of color paste, 30 parts of silicon micropowder, 13.8 parts of nano-calcium carbonate, 0.5 parts of coupling agent (Si69), 0.5 parts of coupling agent (OFS-6032), and 0.5 parts of defoaming agent for pre-mixing, and then stirred in a double planetary stirring kettle at a speed of 1500 rpm for 1 hour to obtain a single-component epoxy composite c.

[0049] Comparative Example 1: No solid epoxy resin

[0050] 20 parts of epoxy resin (EPS35) containing -SS- bonds and 40 parts of liquid bisphenol A epoxy resin (equivalent weight 170-210) were heated to 90°C for mixing, and then cooled and added with 2.1 parts of dicyandiamide, 1.6 parts of organic urea (UR300), 0.5 parts of color paste, 30 parts of silicon micropowder, 13.8 parts of nano calcium carbonate, 0.5 parts of coupling agent (Si69), 0.5 parts of coupling agent (OFS-6032) and 0.5 parts of defoaming agent, and pre-mixed. The single-component epoxy composite d was prepared by vacuum stirring at a speed of 1500 rpm in a double planetary stirring kettle for 1 hour.

[0051] Comparative Example 2: Core-shell rubber toughened epoxy resin replaces -SS-bonded epoxy resin / solid epoxy resin

[0052] 18 parts of core-shell rubber modified epoxy resin (MX-154, rubber content 40%), 38 parts of liquid bisphenol A epoxy resin (equivalent 170-210), 3.5 parts of dicyandiamide, 2 parts of organic urea (UR300), 0.5 parts of color paste, 23 parts of silicon micropowder, 14 parts of nano calcium carbonate, 0.5 parts of coupling agent (Si69) and 0.5 parts of defoaming agent were pre-mixed and vacuum stirred in a double planetary stirring kettle at a speed of 1500 rpm for 1 hour to obtain a single-component epoxy composite e.

[0053] Comparative Example 3: Carboxyl-terminated liquid nitrile rubber (CTBN) toughened epoxy resin replaces SS-bonded epoxy resin / solid epoxy resin

[0054] 18 parts of CTBN modified epoxy resin (rubber content 40%), 38 parts of liquid bisphenol A epoxy resin (equivalent 170-210), 3.5 parts of dicyandiamide, 2 parts of organic urea (UR300), 0.5 parts of color paste, 23 parts of silicon micropowder, 14 parts of nano calcium carbonate, 0.5 parts of coupling agent (Si69) and 0.5 parts of defoaming agent were pre-mixed and stirred in a double planetary stirring kettle at a speed of 1000 rpm for 1 hour to obtain a single-component epoxy composite f.

[0055] Comparative Example 4: No Si69

[0056] 10 parts of epoxy resin containing -SS- bond (EPS70), 10 parts of solid bisphenol A epoxy resin (equivalent 400-500), 30 parts of liquid bisphenol A epoxy resin (equivalent 170-210), 1.9 parts of dicyandiamide, 1.5 parts of organic urea (UR300), 1 part of color paste, 30 parts of aluminum hydroxide, 14.1 parts of nano calcium carbonate, 0.5 parts of coupling agent (Si69), 0.5 parts of coupling agent (OFS-6032), and 0.5 parts of defoaming agent were pre-mixed, and a single-component epoxy composite g was obtained after vacuum stirring at a speed of 1000 rpm in a double planetary stirring kettle for 1 hour.

[0057] Table 1 Use of epoxy resin and coupling agent in Examples and Comparative Examples

[0058]

[0059] Note: “√” stands for use, “×” stands for not use.

[0060] Curing conditions:

[0061] Curing at 120℃×1h, the bonding performance test is to test the tensile shear strength of aluminum sheets and aluminum sheets, the bonding substrate is a magnetic core (purchased from Shandong Jianuo), the dispensing amount of the single-component epoxy compound is 1g / piece, and each group of experiments uses 10 magnetic cores for gluing, and then compares the performance, as shown in Table 2:

[0062] Table 2 Performance test of the composite obtained in each embodiment after curing

[0063]

[0064]

[0065] Note: The above performance is tested by a universal mechanical testing machine; the test data are all average values, the high and low temperature conditions are -40℃~120℃, 20 cycles, cracking includes the core being broken by the adhesive, or cracks in the adhesive body, such as Figure 3 Mechanical properties test standards: "GB / T 9341-2008 Determination of bending properties of plastics", "GB / T 7124-2008 Determination of tensile shear strength of adhesives (rigid material to rigid material)".

[0066] It can be seen from Examples 1 to 3 and Comparative Examples 1 to 4 that the embodiments introduce epoxy resins EPS35 and EPS70 containing -SS- bonds and coupling agent Si69 containing -SS- bonds, so that the adhesive can maintain high bending strength, low modulus, significantly improved maximum displacement at break, and good normal and high temperature tensile shear strength after curing. The above results show that EPS35 and EPS70 have good toughening effects, and the use of bisphenol A / F epoxy resins ensures good strength and bonding properties. In addition, judging from the cracking of the magnetic core after curing, the number of cracks after high and low temperature cycles, and the maximum displacement of the spline at break after high and low temperatures, the attenuation is very small or there is no attenuation, which indirectly proves the self-healing function, indicating that the adhesive has excellent reliability after curing.

[0067] The present invention utilizes the epoxy resin structure containing -SS- bonds to have excellent toughness and extremely low viscosity (20°C viscosity 3-4Pa.s), which can be well matched with long-chain solid epoxy resin for toughening, improving the disadvantage of high viscosity of long-chain solid epoxy resin, while retaining the benzene ring skeleton and a large number of hydroxyl groups of bisphenol A epoxy resin, so that its reaction activity, bonding performance, mechanical properties and heat resistance are all maintained at a high level; and the coupling agent Si69 containing -SS- bonds can form a small molecular structure after breaking at high temperature, and will repair each other with the polymer prepolymer containing -SS- bond structure, and form an interpenetrating network structure at the same time, combined with the use of OFS-6032, so the tensile shear strength of the cured product is also significantly improved. The improvement of bonding performance can greatly improve the phenomenon of peeling and delamination from the device caused by excessive modulus, insufficient bonding and warping after curing, and continuously repair the micro cracks caused by stress, warping, etc. during the aging process, avoiding the gradual formation of large body cracks from micro cracks, thereby improving the long-term reliability of the adhesive over the reflow process and high and low temperature impact.

[0068] Although the present invention is described herein with reference to a plurality of illustrative embodiments of the present invention, it should be understood that those skilled in the art can design many other modifications and implementations, which will fall within the scope and spirit of the principles disclosed in the present application. More specifically, within the scope disclosed in the present application, multiple variations and improvements can be made to the components and / or layout of the subject combination layout. In addition to the variations and improvements made to the components and / or layout, other uses will also be apparent to those skilled in the art.

Claims

1. A repairable low stress one-component epoxy composite, characterized in that: Made of the following materials measured by weight: 5 to 10 parts of epoxy resin containing -SS- bonds; 5-10 parts of bifunctional long-chain solid epoxy resin; 25-50 parts of liquid bisphenol A epoxy resin or liquid bisphenol F epoxy resin; 0.1 to 3 parts of coupling agent containing -SS- bond; 0.1 to 3 parts of coupling agent containing phenylamino group; 20 to 50 parts of filler; Thixotropic agent 0-20 parts; Additives 0.1-1 part; 1.5 to 3 parts of dicyandiamide; 1.5 to 3 parts of organic urea.

2. The repairable low stress one-component epoxy composite according to claim 1, characterized in that: 0.1 to 1 part of pigment may also be included.

3. The repairable low stress one-component epoxy composite according to claim 1, characterized in that: The epoxy resin containing -SS- bonds is EPS35, EPS70 of Nouryon or a mixture of the two.

4. The repairable low stress one-component epoxy composite according to claim 1, characterized in that: The bifunctional long-chain solid epoxy resin is selected from any one or more of the following materials with an epoxy equivalent of 400-1000: bisphenol A epoxy resin, bisphenol F epoxy resin, polyethylene glycol modified epoxy resin, polypropylene glycol modified epoxy resin, polyurethane chain extension modified bisphenol A epoxy resin, polyurethane chain extension modified bisphenol F epoxy resin.

5. The repairable low stress one-component epoxy composite according to claim 1, characterized in that: The liquid bisphenol A epoxy resin or liquid bisphenol F epoxy resin is selected from bisphenol A epoxy resin or bisphenol F epoxy resin with an epoxy equivalent between 150 and 270.

6. The repairable low stress one-component epoxy composite according to claim 1, characterized in that: The coupling agent containing -SS- bond is Si69.

7. The repairable low stress one-component epoxy composite according to claim 1, characterized in that: The coupling agent containing phenylamino group is OFS-6032.

8. The repairable low stress one-component epoxy composite according to claim 1, characterized in that: The filler is selected from one or more of silicon micropowder, calcium carbonate, aluminum hydroxide, aluminum oxide, wollastonite, kaolin, etc.; The thixotropic agent is selected from one or more of nano calcium carbonate, bentonite, white carbon black, etc.; The pigment is a color paste or a color slurry; The auxiliary agent includes a defoaming agent; The organic urea is a mixture of one or more of U-52M, U-35M, UR200, UR300 and UR500.

9. The method for preparing the repairable low-stress dicyandiamide-cured one-component epoxy composite according to any one of claims 1 to 8, characterized in that: The following steps are involved: First, 5 to 10 parts of epoxy resin containing -SS- bonds, 5 to 10 parts of bifunctional long-chain solid epoxy resin, and 25 to 50 parts of liquid bisphenol A / F epoxy resin measured by mass are heated to 80 to 100° C. and uniformly mixed; after cooling, 0.1 to 3 parts of coupling agent containing -SS- bonds, 0.1 to 3 parts of coupling agent containing aniline, 20 to 50 parts of fillers, 0 to 20 parts of thixotropic agent, 0.1 to 1 part of pigment, 0.1 to 1 part of auxiliary agent, 1.5 to 3 parts of dicyandiamide, and 1.5 to 3 parts of organic urea are added; and all the materials are uniformly mixed to obtain the one-component epoxy composite.

10. The method for preparing the repairable low-stress dicyandiamide-cured one-component epoxy composite according to claim 9, characterized in that: The dispersing equipment used during mixing is a double planetary stirring kettle, the stirring mode is 500-1500 rpm, and the stirring time is less than or equal to 30 minutes.

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