Modified dicyandiamide, single-component epoxy structural adhesive and preparation method thereof

Abstract

The invention discloses modified dicyandiamide, a single-component epoxy structural adhesive and a preparation method of the modified dicyandiamide and the single-component epoxy structural adhesive. The modified dicyandiamide is obtained by reaction of epoxy group terminated polyether and dicyandiamide, and the epoxy group terminated polyether is obtained by reaction of polyether polyol and epoxy chloropropane; the polyether polyol contains at least two hydroxyl groups. The single-component epoxy structural adhesive prepared by taking the modified dicyandiamide as the curing agent and matching the modified dicyandiamide with the epoxy resin, the nano calcium carbonate and other components not only has lower curing temperature, but also is remarkably improved in elongation at break and peel strength compared with an unmodified dicyandiamide system, and has better adhesive property with materials. Moreover, the single-component epoxy structural adhesive has higher glass transition temperature and body strength while the various properties are obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of sealants, in particular to epoxy sealants, and in particular to a modified dicyandiamide, single-component epoxy structural adhesive and a preparation method thereof. Background Art

[0002] Dicyandiamide is a widely used one-component epoxy latent curing agent. The one-component epoxy structural adhesive prepared by adding dicyandiamide has extremely high bulk strength and high glass transition temperature after curing, and is widely used.

[0003] However, the existing one-component epoxy structural adhesive with a dicyandiamide curing system has the following defects: on the one hand, the cured product is often hard and brittle, and usually needs to add a toughening agent to improve the brittleness, but the use of a flexible toughening agent often greatly reduces the glass transition temperature of the cured colloid, reducing its bulk strength and other properties; on the other hand, the curing temperature of the one-component epoxy structural adhesive with dicyandiamide as a curing agent is very high, often beyond the acceptable range of the production process, and curing at high temperature may damage the performance of the device.

[0004] How to improve the toughness and reduce the curing temperature of the one-component epoxy structural adhesive of the dicyandiamide curing system while maintaining its high glass transition temperature and bulk strength and other performance properties has become an urgent problem that needs to be solved in practical applications. Summary of the invention

[0005] Based on this, the object of the present invention is to provide a one-component epoxy structural adhesive with lower curing temperature and higher toughness, and the one-component epoxy structural adhesive also has higher glass transition temperature and bonding strength.

[0006] In order to achieve the above object, the present invention includes the following technical solutions.

[0007] In a first aspect, the present invention provides a modified dicyandiamide obtained by reacting an epoxy-terminated polyether with dicyandiamide, wherein the epoxy-terminated polyether is obtained by reacting a polyether polyol with epichlorohydrin;

[0008] The polyether polyol contains at least two hydroxyl groups.

[0009] In a second aspect, the present invention provides a method for preparing the modified dicyandiamide, comprising the following steps:

[0010] The polyether polyol and the catalyst are stirred evenly, heated to 30° C. to 50° C., and the epichlorohydrin is added dropwise, and reacted for 4 to 6 hours to obtain the epoxy-terminated polyether;

[0011] The epoxy-terminated polyether and dicyandiamide are refluxed for reaction at 130° C. to 150° C. for 3 to 5 hours to obtain the modified dicyandiamide.

[0012] In a third aspect, the present invention provides a one-component epoxy structural adhesive, which is obtained by mixing raw materials including the following components in parts by weight:

[0013]

[0014] In a fourth aspect, the present invention provides a method for preparing the one-component epoxy structural adhesive, comprising the following steps:

[0015] The epoxy resin, modified dicyandiamide, organic urea, nano calcium carbonate and heavy calcium carbonate are uniformly mixed to obtain the one-component epoxy structural adhesive.

[0016] The present invention has the following beneficial effects:

[0017] The invention adopts multifunctional polyether polyol and epichlorohydrin to synthesize epoxy-terminated polyether of specific molecular weight, and modifies dicyandiamide by epoxy-terminated polyether, so as to prepare a modified dicyandiamide containing polyether segment and hydroxyl group. The modified dicyandiamide can not only reduce the curing temperature of the one-component epoxy structural adhesive by using the modified dicyandiamide as a curing agent, but also play the role of a toughening agent, and can make the one-component epoxy structural adhesive maintain a high glass transition temperature, storage stability and bulk strength while improving the toughness of the one-component epoxy structural adhesive. In addition, the flexible segment and hydroxyl group in the modified dicyandiamide can also improve the bonding strength and peeling strength between the one-component epoxy adhesive and the substrate.

[0018] The one-component epoxy structural adhesive prepared by using the modified dicyandiamide of the present invention as a curing agent in combination with epoxy resin, nano calcium carbonate and other components not only has a lower curing temperature, is convenient for application in more occasions, but also has better toughness, and the elongation at break is significantly improved compared with the unmodified dicyandiamide system, while the bonding strength and peel strength are also significantly improved compared with the unmodified dicyandiamide system, and the bonding performance between materials is better. In addition, the one-component epoxy structural adhesive of the present invention has a higher glass transition temperature and bulk strength while the above-mentioned various properties are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the infrared spectrum of epoxy-terminated polyether.

[0020] Figure 2 This is the infrared spectrum of modified dicyandiamide. DETAILED DESCRIPTION

[0021] The technical scheme of the present invention is further illustrated by specific examples below. Those skilled in the art should understand that the examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0023] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products or equipment.

[0024] In the present invention, the term "multiple" refers to two or more than two. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0025] Some embodiments of the present invention relate to a modified dicyandiamide obtained by reacting an epoxy-terminated polyether with dicyandiamide, wherein the epoxy-terminated polyether is obtained by reacting a polyether polyol with epichlorohydrin;

[0026] The polyether polyol contains at least two hydroxyl groups.

[0027] The polyether polyol described in the present invention refers to a polyether polymer having two or more hydroxyl groups (-OH) at the end or side groups, and is prepared by polyaddition reaction of diols such as propylene glycol and ethylene glycol, triols such as glycerol and trimethylolpropane, or polyols such as pentaerythritol as initiators with ethylene oxide, propylene oxide, etc. in the presence of a catalyst.

[0028] In some of the embodiments, the molar ratio of the epoxy-terminated polyether to dicyandiamide is 0.5-0.7:1.

[0029] In some embodiments, the molar ratio of the polyether polyol to epichlorohydrin is 1:1-3, preferably 1:1.5-2.3.

[0030] In some embodiments, the number average molecular weight of the polyether polyol is 300-2200, preferably 300-800, and more preferably 300-600.

[0031] In some embodiments, the number average molecular weight of the epoxy-terminated polyether is 400-2300, preferably 400-900.

[0032] In some embodiments, the epoxy content of the epoxy-terminated polyether is 3-24%, preferably 12-20%.

[0033] In some embodiments, the active hydrogen equivalent of the modified dicyandiamide is 80-200, preferably 100-150, more preferably 110-120; the hydroxyl content is 2-12%, preferably 5-9%, more preferably 7-8%.

[0034] In some embodiments, the polyether polyol is selected from any one polyether polyol or a combination of multiple polyether polyols in formula (I) or formula (II):

[0035]

[0036] Among them, n=2-25, x+y+z=2-25.

[0037] In some of these embodiments, n is 4, 5, 6, 7, or 8.

[0038] In some embodiments, x+y+z=4, 5, 6, 7 or 8

[0039] In some embodiments, the polyether polyol is one or more combinations of polyether polyol N204, polyether polyol N303F and polyether polyol N306.

[0040] In some embodiments, the polyether polyol is a combination of polyether polyol N303F and polyether polyol N306.

[0041] In some embodiments, the molar ratio of the polyether polyol N303F to the polyether polyol N306 is preferably 2-3:1.

[0042] In some of the embodiments, the polyether polyol and epichlorohydrin are reacted in the presence of a catalyst, the catalyst is preferably boron trifluoride ethyl ether, and the molar ratio of the polyether polyol to the catalyst is preferably 1:0.1-0.3.

[0043] In some embodiments of the present invention, the preparation method of the modified dicyandiamide comprises the following steps:

[0044] The polyether polyol and the catalyst are stirred evenly, heated to 30° C. to 50° C., and the epichlorohydrin is added dropwise, and reacted for 4 to 6 hours to obtain the epoxy-terminated polyether;

[0045] The epoxy-terminated polyether and dicyandiamide are refluxed for reaction at 130° C. to 150° C. for 3 to 5 hours to obtain the modified dicyandiamide.

[0046] In some embodiments, the preparation method of the modified dicyandiamide comprises the following steps:

[0047] The polyether polyol and the catalyst are stirred evenly, heated to 35° C. to 45° C., the epichlorohydrin is added dropwise, reacted for 4 to 6 hours, and distilled under reduced pressure to separate the reaction product, and then the reaction product is washed with a saturated aqueous solution of NaOH at a temperature of 25° C. to 35° C., the oil layer is separated, and the water is removed to obtain the epoxy-terminated polyether;

[0048] The epoxy-terminated polyether and dicyandiamide are refluxed for reaction at 135° C. to 145° C. for 3 to 5 hours, and the modified dicyandiamide is separated by distillation.

[0049] In some embodiments of the present invention, a one-component epoxy structural adhesive is provided, which is obtained by mixing raw materials including the following components in parts by weight:

[0050]

[0051] In some embodiments, the one-component epoxy structural adhesive is obtained by mixing raw materials including the following components, in parts by weight:

[0052]

[0053] In some embodiments, the one-component epoxy structural adhesive is obtained by mixing raw materials including the following components, in parts by weight:

[0054]

[0055]

[0056] Some embodiments of the present invention relate to a method for preparing a one-component epoxy structural adhesive, comprising the following steps:

[0057] The epoxy resin, modified dicyandiamide, organic urea, nano calcium carbonate and heavy calcium carbonate are uniformly mixed to obtain the one-component epoxy structural adhesive.

[0058] The following are specific embodiments.

[0059] The "parts" described in the following examples refer to parts by weight unless otherwise specified.

[0060] Example 1

[0061] (1) Preparation of epoxy-terminated polyether

[0062]

[0063] Weigh 1.6 mol of polyether polyol (N204, difunctional, number average molecular weight 400), 0.2 mol of boron trifluoride ether catalyst, add to a three-necked flask, stir evenly, heat to 40°C, slowly drop 3 mol of epichlorohydrin, drip it all within 0.5 hour, react for 5 hours, and separate the reaction product by vacuum distillation. The reaction product is washed with a saturated aqueous solution of NaOH at a temperature of 30°C, the oil layer is separated, and the water is removed by vacuum distillation to obtain an epoxy-terminated polyether, the number average molecular weight is 508, and the epoxy content is 16.2%.

[0064] The infrared spectrum of the epoxy-terminated polyether is as follows Figure 1 Shown: 3467cm -1 The characteristic absorption peak of hydroxyl group is 838cm -1 The characteristic absorption peak of epoxy group is 2868cm -1 The methylene absorption peak is at 1373 cm -1 It is the polyoxypropyl absorption peak at 1092cm -1 The peak at the center is the asymmetric stretching vibration peak of the COC bond.

[0065] (2) Preparation of modified dicyandiamide

[0066]

[0067] Weigh 1.2 mol of epoxy-terminated polyether and 2 mol of dicyandiamide (DYHARD 100S, active hydrogen equivalent 21, particle size 8.1-9.1 μm), add them into a three-necked flask equipped with a condenser, a stirrer and an electric heating jacket in sequence, pass condensed water, turn on the stirrer and the electric heating jacket, reflux at 140° C. for 4 hours, then replace the reduced pressure distillation apparatus, turn on the vacuum pump and the electric heating jacket for distillation, the external temperature is 135° C., until no liquid is extracted, and the product is a modified dicyandiamide epoxy curing agent with an active hydrogen equivalent of 108 and a hydroxyl content of 5.4%.

[0068] The infrared spectrum of the modified dicyandiamide is as follows: Figure 2 As shown, in the infrared spectrum of the modified dicyandiamide, 3469cm -1 The characteristic absorption peak of hydroxyl group is 2865cm -1 The methylene absorption peak is at 2187cm -1 The cyanide absorption peak is at 1373 cm -1 It is the polyoxypropyl absorption peak at 1094cm -1 The peak at 1565cm is the asymmetric stretching vibration peak of the COC bond. -1 It is the nitrogen-hydrogen absorption peak.

[0069] (3) Preparation of one-component epoxy structural adhesive

[0070] Weigh 43 parts of epoxy resin (NPEL-128), 25 parts of modified dicyandiamide (active hydrogen equivalent 108), 0.25 parts of organic urea accelerator (DYHARD UR500, particle size 8.5-9.5 μm), 10 parts of nano calcium carbonate (CCS-25i, 70 nm) and 21.75 parts of heavy calcium carbonate (1250 mesh), mix well to obtain a one-component epoxy structural adhesive.

[0071] Example 2

[0072] (1) Preparation of epoxy-terminated polyether

[0073]

[0074] Where x+y+z=4.

[0075] Weigh 1.6 mol of polyether polyol (N303F, trifunctionality, number average molecular weight 340), add 0.2 mol of boron trifluoride ether catalyst into a three-necked flask, stir evenly, heat to 40°C, slowly drop 3 mol of epichlorohydrin, drip it all within 0.5 hours, react for 5 hours, and separate the reaction product by vacuum distillation. Wash the reaction product with a saturated aqueous solution of NaOH at a temperature of 30°C, separate the oil layer, and remove the water by vacuum distillation to obtain an epoxy-terminated polyether. The number average molecular weight is 451, and the epoxy content is 19.1%.

[0076] (2) Preparation of modified dicyandiamide

[0077]

[0078] Where x+y+z=4.

[0079] Weigh 1.2 mol of epoxy-terminated polyether and 2 mol of dicyandiamide (DYHARD 100S, active hydrogen equivalent 21, particle size 8.1-9.1 μm), add them into a three-necked flask equipped with a condenser, a stirrer and an electric heating jacket in sequence, pass condensed water, turn on the stirrer and the electric heating jacket, reflux at 140° C. for 4 hours, then replace the reduced pressure distillation apparatus, turn on the vacuum pump and the electric heating jacket for distillation, the external temperature is 135° C., until no liquid is extracted, and the product is a modified dicyandiamide epoxy curing agent with an active hydrogen equivalent of 102 and a hydroxyl content of 8.1%.

[0080] (3) Preparation of one-component epoxy structural adhesive

[0081] Weigh 43 parts of epoxy resin (NPEL-128), 24 parts of modified dicyandiamide (active hydrogen equivalent 102), 0.25 parts of organic urea accelerator (DYHARD UR500, particle size 8.5-9.5 μm), 10 parts of nano calcium carbonate (CCS-25i, 70 nm) and 22.75 parts of heavy calcium carbonate (1250 mesh), mix well to obtain a one-component epoxy structural adhesive.

[0082] Example 3

[0083] (1) Preparation of epoxy-terminated polyether

[0084]

[0085] Where x+y+z=8.

[0086] Weigh 1.6 mol of polyether polyol (N306, trifunctionality, number average molecular weight 600), add 0.2 mol of boron trifluoride ether catalyst into a three-necked flask, stir evenly, heat to 40°C, slowly drop 3 mol of epichlorohydrin, drip it all within 0.5 hours, react for 5 hours, and separate the reaction product by vacuum distillation. Wash the reaction product with a saturated aqueous solution of NaOH at a temperature of 30°C, separate the oil layer, and remove the water by vacuum distillation to obtain an epoxy-terminated polyether. The number average molecular weight is 708, and the epoxy content is 12.1%.

[0087] (2) Preparation of modified dicyandiamide

[0088]

[0089] Where x+y+z=8.

[0090] Weigh 1.2 mol of epoxy-terminated polyether and 2 mol of dicyandiamide (DYHARD 100S, active hydrogen equivalent 21, particle size 8.1-9.1 μm), add them into a three-necked flask equipped with a condenser, a stirrer and an electric heating jacket in sequence, pass condensed water, turn on the stirrer and the electric heating jacket, reflux at 140° C. for 4 hours, then replace the reduced pressure distillation apparatus, turn on the vacuum pump and the electric heating jacket for distillation, the external temperature is 135° C., until no liquid is extracted, and the product is a modified dicyandiamide epoxy curing agent with an active hydrogen equivalent of 142 and a hydroxyl content of 5.9%.

[0091] (3) Preparation of one-component epoxy structural adhesive

[0092] Weigh 43 parts of epoxy resin (NPEL-128), 33 parts of modified dicyandiamide (active hydrogen equivalent 142), 0.25 parts of organic urea accelerator (DYHARD UR500, particle size 8.5-9.5 μm), 10 parts of nano calcium carbonate (CCS-25i, 70 nm) and 13.75 parts of heavy calcium carbonate (1250 mesh), mix well to obtain a one-component epoxy structural adhesive.

[0093] Example 4

[0094] (1) Preparation of modified dicyandiamide

[0095] Weigh 0.8 mol of the epoxy-terminated polyether prepared in Example 2, 0.4 mol of the epoxy-terminated polyether prepared in Example 3, and 2 mol of dicyandiamide, and add them sequentially into a three-necked flask equipped with a condenser, a stirrer and an electric heating jacket, pass condensed water, turn on the stirrer and the electric heating jacket, reflux at 140° C. for 4 hours, then replace the reduced pressure distillation apparatus, turn on the vacuum pump and the electric heating jacket for distillation, the external temperature is 135° C., until no liquid is extracted, and the product is a modified dicyandiamide epoxy curing agent with an active hydrogen equivalent of 113 and a hydroxyl content of 7.1%.

[0096] (2) Preparation of one-component epoxy structural adhesive

[0097] Weigh 43 parts of epoxy resin (NPEL-128), 30 parts of modified dicyandiamide (active hydrogen equivalent 113), 0.25 parts of organic urea accelerator (DYHARD UR500, particle size 8.5-9.5 μm), 10 parts of nano calcium carbonate (CCS-25i, 70 nm) and 16.75 parts of heavy calcium carbonate (1250 mesh), mix well to obtain a one-component epoxy structural adhesive.

[0098] Comparative Example 1 Preparation of one-component epoxy structural adhesive

[0099] Weigh 43 parts of epoxy resin (NPEL-128), 4.3 parts of dicyandiamide (DYHARD 100S, active hydrogen equivalent 21, particle size 8.1-9.1 μm), 0.25 parts of organic urea accelerator (DYHARD UR500, particle size 8.5-9.5 μm), 10 parts of nano calcium carbonate (CCS-25i, particle size 70 nm) and 42.45 parts of heavy calcium carbonate (1250 mesh), mix well to obtain a one-component epoxy structural adhesive.

[0100] Comparative Example 2 Preparation of one-component epoxy structural adhesive

[0101] Weigh 43 parts of epoxy resin (NPEL-128), 19.7 parts of epoxy-terminated polyether (prepared in Example 1), 4.3 parts of dicyandiamide (DYHARD 100S, active hydrogen equivalent 21, particle size 8.1-9.1 μm), 0.25 parts of organic urea accelerator (DYHARD UR500, particle size 8.5-9.5 μm), 10 parts of nano calcium carbonate (CCS-25i, particle size 70 nm) and 22.75 parts of heavy calcium carbonate (1250 mesh), mix well to obtain a one-component epoxy structural adhesive.

[0102] Comparative Example 3 Preparation of one-component epoxy structural adhesive

[0103] Weigh 43 parts of epoxy resin (NPEL-128), 19.7 parts of modified nitrile rubber (WD-510), 4.3 parts of dicyandiamide (DYHARD100S, active hydrogen equivalent 21, particle size 8.1-9.1 μm), 0.25 parts of organic urea accelerator (DYHARD UR500, particle size 8.5-9.5 μm), 10 parts of nano calcium carbonate (CCS-25i, particle size 70 nm) and 22.75 parts of heavy calcium carbonate (1250 mesh), mix well to obtain a one-component epoxy structural adhesive.

[0104] The one-component epoxy structural adhesives prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to the following performance tests:

[0105] 1. Glass transition temperature: Determine the glass transition temperature in accordance with GB / T 19466.2-2004 Plastics Differential Scanning Calorimetry (DSC) Part 2: Determination of glass transition temperature.

[0106] 2. Tensile shear strength test: Test according to GB / T 7124 (aluminum-aluminum).

[0107] 3. T peel strength: Determine according to the requirements of GB / T 2791-1995 Adhesive T peel strength test method.

[0108] 4. Tensile elastic modulus and elongation at break: measured in accordance with the provisions of GB / T 1040.2-2006.

[0109] 5. Storage stability test: Place the sample in a constant temperature control box at 40±2℃, keep it for 168 hours, then take it out to measure the viscosity and tensile shear strength. The viscosity is measured according to the single cylinder rotation viscometer method of GB / T 2794-2013 Adhesive Viscosity Determination. The tensile shear strength is measured according to GB / T 7124 (aluminum-aluminum).

[0110] Among them, the one-component epoxy structural adhesive test sample prepared in Comparative Example 1 was cured at 170° C. for 20 min, and the one-component epoxy structural adhesive test samples prepared in Examples 1-4 and Comparative Examples 2-3 were cured at 150° C. for 20 min, and the samples were tested after returning to room temperature.

[0111] The test results are shown in Table 1:

[0112] Table 1 Performance parameters of the one-component epoxy structural adhesive prepared in Examples 1-4 and Comparative Examples 1-3

[0113]

[0114] According to the above results, the one-component epoxy structural adhesives of Examples 1-4 prepared using the modified dicyandiamide synthesized by the present invention all have lower curing temperatures, higher glass transition temperatures, better tensile shear strength, T peel strength, tensile elastic modulus, and elongation at break, as well as good storage stability and excellent overall performance.

[0115] Among them, compared with Example 1, in Comparative Example 1, no modified dicyandiamide curing agent is used, and no toughening agent is added, and the peel strength and elongation at break of the obtained one-component epoxy structural adhesive are far inferior to those of Example 1. Compared with Example 1, in Comparative Example 2, the epoxy-terminated polyether (flexible toughening agent) prepared in Example 1 is added, and the glass transition temperature of the obtained one-component epoxy structural adhesive is significantly reduced, and its peel strength and elongation at break are improved compared with Comparative Example 1, but not as good as Example 1. Comparative Example 3 uses modified nitrile rubber as a toughening agent, and the glass transition temperature of the obtained one-component epoxy structural adhesive is also significantly reduced, while the peel strength and elongation at break are far inferior to those of Example 1.

[0116] Compared with Example 1, Example 2 uses a tri-functionality polyether polyol to prepare an epoxy-terminated polyether, and the dicyandiamide modified with it has an increased hydroxyl content. The resulting one-component epoxy structural adhesive has improved tensile shear strength and T-peel strength compared to Example 1. Compared with Example 1, the flexible segment is slightly shorter and the elongation at break is reduced.

[0117] Compared with Example 2, Example 3 uses a longer chain trifunctional polyether polyol to prepare an epoxy-terminated polyether, and the dicyandiamide modified with it has a hydroxyl content similar to that of Example 2. Compared with Example 2, the obtained one-component epoxy structural adhesive has similar tensile shear strength and T-peel strength, and improved elongation at break.

[0118] Example 4 uses a trifunctional polyether polyol with a reasonable combination of long and short chains to prepare epoxy-terminated polyether, and uses it to modify dicyandiamide to prepare a one-component epoxy structural adhesive, which has the best comprehensive performance compared to other examples.

[0119] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0120] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A modified dicyandiamide, characterized in that: The epoxy-terminated polyether is obtained by reacting with dicyandiamide, wherein the epoxy-terminated polyether is obtained by reacting with polyether polyol and epichlorohydrin; The polyether polyol contains at least two hydroxyl groups.

2. The modified dicyandiamide according to claim 1, characterized in that The molar ratio of the epoxy-terminated polyether to dicyandiamide is 0.5-0.7:1; and / or, The molar ratio of the polyether polyol to epichlorohydrin is 1:1-3, preferably 1:1.5-2.3; and / or, The number average molecular weight of the polyether polyol is 300 to 2200, preferably 300 to 800, more preferably 300 to 600; and / or, The number average molecular weight of the epoxy-terminated polyether is 400 to 2300, preferably 400 to 900; and / or The epoxy group content of the epoxy-terminated polyether is 3 to 24%, preferably 12 to 20%.

3. The modified dicyandiamide according to claim 1, characterized in that The polyether polyol is selected from any one polyether polyol or a combination of multiple polyether polyols in formula (I) or formula (II): Wherein, n=2-25, preferably 4, 5, 6, 7 or 8; x+y+z=2-25, preferably 4, 5, 6, 7 or 8.

4. The modified dicyandiamide according to claim 3, characterized in that The polyether polyol is one or more of polyether polyol N204, polyether polyol N303F and polyether polyol N306; Preferably, the polyether polyol is a combination of polyether polyol N303F and polyether polyol N306, and the molar ratio of polyether polyol N303F to polyether polyol N306 is preferably 2-3:

1.

5. The modified dicyandiamide according to claim 1, characterized in that The active hydrogen equivalent of the modified dicyandiamide is 80-200, preferably 100-150, more preferably 110-120; the hydroxyl content is 2-12%, preferably 5-9%, more preferably 7-8%.

6. The modified dicyandiamide according to any one of claims 1 to 5, characterized in that: The polyether polyol and epichlorohydrin react in the presence of a catalyst, the catalyst is preferably boron trifluoride ethyl ether, and the molar ratio of the polyether polyol to the catalyst is preferably 1:0.1-0.

3.

7. A method for preparing the modified dicyandiamide according to any one of claims 1 to 6, characterized in that: The steps include: The polyether polyol and the catalyst are stirred evenly, heated to 30° C. to 50° C., and the epichlorohydrin is added dropwise, and reacted for 4 to 6 hours to obtain the epoxy-terminated polyether; The epoxy-terminated polyether and dicyandiamide are refluxed for reaction at 130° C. to 150° C. for 3 to 5 hours to obtain the modified dicyandiamide.

8. A one-component epoxy structural adhesive, characterized in that: The mixture is prepared by mixing the following raw materials in parts by weight:

9. The one-component epoxy structural adhesive according to claim 8, characterized in that: In parts by weight, it is obtained by mixing the following components:

10. A method for preparing the one-component epoxy structural adhesive according to claim 8 or 9, characterized in that: The steps include: The epoxy resin, modified dicyandiamide, organic urea, nano calcium carbonate and heavy calcium carbonate are uniformly mixed to obtain the one-component epoxy structural adhesive.

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