Dicyandiamide cured ricinoleic acid modified epoxy glue

Abstract

The dicyandiamide-cured ricinoleic acid modified epoxy glue is prepared from the following components in parts by weight: 80 to 100 parts of ricinoleic acid modified epoxy resin, 10 to 40 parts of a core-shell structure rubber toughening agent, 5 to 15 parts of dicyandiamide, 0.1 to 5 parts of a curing accelerator, 0.1 to 1 part of an antioxidant, 0.1 to 4 parts of a coupling agent and 1 to 100 parts of filler, the ricinoleic acid modified epoxy resin is prepared by reacting 10 to 40 parts of ricinoleic acid, 80 to 100 parts of epoxy resin and 2 to 10 parts of diisocyanate. According to the dicyandiamide cured ricinoleic acid modified epoxy glue, hydrophobic ricinoleic acid is used for grafting and modifying epoxy resin, polyurethane is introduced to enhance the hydrogen bond effect so as to improve cohesion, meanwhile, the water resistance and peel strength of the epoxy glue are improved, and the dicyandiamide cured ricinoleic acid modified epoxy glue is used as a single-component latent epoxy glue with excellent performance.

Description

Technical Field

[0001] The invention relates to a dicyandiamide-cured ricinoleic acid-modified epoxy adhesive, belonging to the technical field of epoxy adhesives. Background Art

[0002] The single-component latent epoxy adhesive composed of epoxy resin, dicyandiamide, accelerator and various fillers has a certain storage stability at room temperature, can react quickly under heating conditions, and can form a high-strength, high-hardness cured product with excellent insulation and high temperature resistance. It has a wide range of applications in circuit board packaging, coatings, adhesives and composite materials. However, dicyandiamide as an epoxy resin curing agent also has some disadvantages, such as its insolubility in epoxy resin causes uneven cured coating, dicyandiamide is easy to absorb moisture, resulting in a higher water absorption rate of the cured material; the high degree of curing crosslinking leads to brittle adhesive, resulting in low bonding peel strength. Invention patent application CN113896861A discloses a dicyandiamide-cured epoxy resin suitable for can outside molding and a preparation method thereof, which comprises 100 parts by mass of epoxy resin, 2-20 parts by mass of dicyandiamide curing agent, 1-10 parts by mass of accelerator and 5-30 parts by mass of solubilizing and toughening agent, wherein the solubilizing and toughening agent comprises polyester-type thermoplastic polyester elastomer, polyether-type thermoplastic polyester elastomer, etc., so as to improve the compatibility between dicyandiamide and epoxy resin and increase the toughness of epoxy cured product. Invention patent application CN105176005A discloses a low water absorption dicyandiamide cured epoxy composite, which is prepared by adding a silicone modified epoxy compound containing 3-10 epoxy groups to a single-component epoxy resin system, including the following components measured by mass: 100 parts of resin, 2-20 parts of curing agent, 0.1-15 parts of latent accelerator, 0-20 parts of toughening agent, 0-5 parts of wetting agent, 0-10 parts of reactive dehydrating agent and 0-500 parts of filler, etc. Silicone is used to improve the hydrophobicity of the material, and a core-shell structure toughening agent improves the toughness and bonding properties.

[0003] In the existing technology of curing epoxy adhesive with dicyandiamide, there are technical difficulties in solving the problems of poor compatibility between dicyandiamide and epoxy resin, high water absorption of cured products and insufficient adhesive peeling force. For example, silicone rubber has good hydrophobicity, but its low strength will affect the adhesive performance; polyurethane elastomer modification can improve the compatibility between dicyandiamide and epoxy, but it fails to improve the problem of insufficient water resistance. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art, invent a dicyandiamide-cured ricinoleic acid-modified epoxy adhesive, and solve the technical problems of poor compatibility between dicyandiamide and epoxy resin, high water absorption of the cured product, insufficient bonding and peeling force, etc.

[0005] In order to solve the above technical problems, the present invention provides a technical solution: a dicyandiamide-cured ricinoleic acid-modified epoxy adhesive, comprising the following components in parts by weight: 80 to 100 parts of ricinoleic acid-modified epoxy resin, 10 to 40 parts of a core-shell structure rubber toughener, 5 to 15 parts of dicyandiamide, 0.1 to 5 parts of a curing accelerator, 0.1 to 1 part of an antioxidant, 0.1 to 4 parts of a coupling agent and 1 to 100 parts of a filler.

[0006] The ricinoleic acid modified epoxy resin is prepared by reacting 10 to 40 parts of ricinoleic acid, 80 to 100 parts of epoxy resin and 2 to 10 parts of diisocyanate by weight.

[0007] The preparation method of the ricinoleic acid modified epoxy resin comprises the following steps: weighing 10 to 40 parts of ricinoleic acid and 80 to 100 parts of epoxy resin in a container according to a proportion, reacting at 120 to 150° C. for 8 to 12 hours under nitrogen protection, then vacuum dehydrating at 100 to 120° C. for 1 hour to further promote the reaction, then cooling to 50 to 60° C., adding 2 to 10 parts of diisocyanate, reacting for 5 to 8 hours, and obtaining the ricinoleic acid modified epoxy resin. The epoxy resin is a mixture of one or more of bisphenol A epoxy resin, bisphenol F epoxy resin and phenolic epoxy resin.

[0008] The diisocyanate is preferably isophorone diisocyanate (IPDI) or toluene diisocyanate (TDI).

[0009] The curing accelerator is an organic urea, preferably one of N,N″-(4-methyl-1,3-phenylene)bis(N′,N′-dimethylurea), 3-phenyl-1,1-dimethylurea and 3-(3,4-dichlorophenyl)-1,1-dimethylurea.

[0010] The core-shell structure rubber toughening agent is a stable translucent dispersion formed by uniformly dispersing nano core-shell rubber particles in epoxy resin, wherein the nano core-shell rubber particles account for 25-30%. The nano core-shell rubber particles are one of polybutadiene core-shell rubber, styrene-butadiene core-shell rubber, and silicone core-shell rubber. The toughening agent further reduces the stress of the epoxy adhesive and improves the bonding and peeling force of the epoxy adhesive with the interface after curing.

[0011] The antioxidant is a mixture of one or more of antioxidant 168, antioxidant 1010 and antioxidant DLTP.

[0012] The coupling agents are KH560 and KH570 silane coupling agents.

[0013] The filler is selected and added according to the needs, and can be one or a mixture of silicon micropowder, alumina, silicon dioxide, iron oxide red, and aluminum powder.

[0014] Compared with the prior art, the principles and beneficial effects of the present invention are as follows:

[0015] The present invention adopts ricinoleic acid to modify epoxy resin, and the carboxyl group of hydrophobic ricinoleic acid is grafted with the epoxy group of epoxy resin to enhance the compatibility of low-polarity ricinoleic acid and high-polarity epoxy resin, and avoid phase separation of each component; the introduction of hydrophobic and flexible ricinoleic acid molecules reduces the water absorption of the adhesive on the one hand, and is also conducive to improving toughness; another group hydroxyl of ricinoleic acid is coupled with the diisocyanate added subsequently to form a polyurethane bond, thereby enhancing the bonding cohesion of the epoxy adhesive; the polyurethane in the modified epoxy resin forms a mutual hydrogen bond with dicyandiamide, thereby improving the compatibility of dicyandiamide with epoxy resin. Thus, polyurethane-modified epoxy resin is formed by grafting ricinoleic acid, which has the multiple effects of simultaneously improving the compatibility of dicyandiamide and epoxy in dicyandiamide-cured epoxy adhesive, toughness of the cured product, bonding strength and water resistance.

[0016] Reaction formula of ricinoleic acid modified epoxy resin:

[0017] DETAILED DESCRIPTION

[0018] Example 1

[0019] A dicyandiamide-cured ricinoleic acid-modified epoxy adhesive comprises the following components in parts by weight: 100 parts of ricinoleic acid-modified epoxy resin, 20 parts of a core-shell structure rubber toughener, 9 parts of dicyandiamide, 1 part of a curing accelerator N,N″-(4-methyl-1,3-phenylene)bis(N′,N′-dimethylurea), 0.2 parts of an antioxidant 168, 0.2 parts of an antioxidant 1010, 1 part of a KH560 coupling agent, 10 parts of silicon dioxide and 20 parts of aluminum powder.

[0020] The preparation steps of the ricinoleic acid modified epoxy resin are as follows: 20 parts of ricinoleic acid, 100 parts of bisphenol A epoxy resin (epoxy value 0.54) and 6 parts of isophorone diisocyanate are reacted by weight. The preparation method is as follows: 20 parts of ricinoleic acid and 100 parts of epoxy resin are weighed in a container, reacted at 130°C for 12 hours under nitrogen protection, then vacuum dehydrated at 100°C for 1 hour, then cooled to 50-60°C, 6 parts of diisocyanate are added, reacted for 8 hours, and the product is obtained.

[0021] Example 2

[0022] A dicyandiamide-cured ricinoleic acid-modified epoxy adhesive comprises the following components in parts by weight: 100 parts of ricinoleic acid-modified epoxy resin, 20 parts of a core-shell structure rubber toughener, 9 parts of dicyandiamide, 1 part of a curing accelerator N,N″-(4-methyl-1,3-phenylene)bis(N′,N′-dimethylurea), 0.2 parts of an antioxidant 168, 0.2 parts of an antioxidant 1010, 1 part of a KH560 coupling agent, 10 parts of silicon dioxide and 20 parts of aluminum powder.

[0023] The difference between the ricinoleic acid modified resin in Example 2 and Example 1 is that the modified epoxy resin is different, and the preparation steps are as follows: 25 parts of ricinoleic acid, 100 parts of bisphenol A epoxy resin (epoxy value 0.54) and 5 parts of toluene diisocyanate are reacted by weight. The preparation method is as follows: 25 parts of ricinoleic acid and 100 parts of epoxy resin are weighed in a container, reacted at 130°C for 12 hours under nitrogen protection, then vacuum dehydrated at 100°C for 1 hour, then cooled to 50-60°C, 5 parts of diisocyanate are added, reacted for 5 hours, and the product is obtained.

[0024] Comparative Example 1

[0025] A dicyandiamide-cured epoxy adhesive comprises the following components in parts by weight: 100 parts of bisphenol A epoxy resin (epoxy value 0.54), 20 parts of a core-shell structure rubber toughener, 9 parts of dicyandiamide, 1 part of a curing accelerator N,N″-(4-methyl-1,3-phenylene)bis(N′,N′-dimethylurea), 0.2 parts of an antioxidant 168, 0.2 parts of an antioxidant 1010, 1 part of a KH560 coupling agent, 10 parts of silicon dioxide and 30 parts of aluminum powder.

[0026] Comparative Example 2

[0027] A dicyandiamide-cured epoxy adhesive comprises the following components in parts by weight: 100 parts of bisphenol A epoxy resin (epoxy value 0.44), 20 parts of a core-shell structure rubber toughener, 9 parts of dicyandiamide, 1 part of a curing accelerator N,N″-(4-methyl-1,3-phenylene)bis(N′,N′-dimethylurea), 0.2 parts of an antioxidant 168, 0.2 parts of an antioxidant 1010, 1 part of a KH560 coupling agent, 10 parts of silicon dioxide and 30 parts of aluminum powder.

[0028] The ricinoleic acid modified epoxy adhesive prepared in Example 1 and Example 2, and the epoxy adhesive prepared in Comparative Example 1 and Comparative Example 2, were cured at 170° C. for 40 minutes to prepare test samples, and the water absorption rate and aluminum-aluminum peel strength performance tests were performed. The results are shown in the following table:

[0029] Test items Example 1 Example 2 Comparative Example 1 Comparative Example 2 Water absorption rate (%, soaking for 24 hours) 0.72 0.75 1.35 1.43 Aluminum-aluminum T peel strength (N / mm) 10.8 10.6 7.4 8.1

[0030] It can be seen from the test results that the epoxy adhesive prepared in Examples 1 and 2 of the present invention has a 30% higher T peel strength and a 40% lower water absorption rate than that of Comparative Examples 1 and 2. That is, the present invention adopts the grafted ricinoleic acid polyurethane modification technology to simultaneously improve the bonding strength and water resistance of the dicyandiamide-cured epoxy adhesive, and the effect of the invention is remarkable.

Claims

1. A dicyandiamide-cured ricinoleic acid-modified epoxy adhesive, comprising the following components in parts by weight: 10 to 40 parts of a core-shell rubber toughener, 5 to 15 parts of dicyandiamide, 0.1 to 5 parts of a curing accelerator, 0.1 to 1 part of an antioxidant, 0.1 to 4 parts of a coupling agent, and 1 to 100 parts of a filler, characterized in that There are also 80-100 parts of ricinoleic acid modified epoxy resin; the ricinoleic acid modified epoxy resin is a product of the reaction of 10-40 parts of ricinoleic acid, 80-100 parts of epoxy resin and 2-10 parts of diisocyanate.

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