Adhesive additive for polyurethane adhesive, preparation method thereof, and polyurethane adhesive

Abstract

The present invention belongs to the field of polyurethane adhesive additives, specifically relating to an adhesive additive for polyurethane adhesive, a preparation method thereof, and the polyurethane adhesive. The adhesive additive for polyurethane adhesive provided by the present invention contains multiple hindered amine groups and terminal hydroxyl groups in its molecular structure. Compared with aminosilane coupling agents such as KH550, it has an increased number of reactive functional groups, effectively improving the adhesive properties of polyurethane adhesives. Furthermore, as a macromolecular polymer, the adhesive additive avoids the rapid reaction time and poor leveling associated with small-molecule aminosilane coupling agents. Therefore, it can be effectively used in polyurethane adhesives, comprehensively improving the adhesive's operational adaptability, adhesion, and self-leveling properties.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane bonding additives, and particularly relates to a bonding additive for polyurethane glue, a preparation method thereof, and the polyurethane glue. Background Art

[0002] Due to its excellent wear resistance and oil resistance, polyurethane sealants are widely used as caulking sealing materials in buildings, squares, and roads, as well as for sealing in automobile manufacturing, glass installation, electronic filling, submarines and rockets.

[0003] The most widely used A and B component polyurethane sealants on the market are mostly based on polyol and isocyanate components as the main film-forming substances, and then various fillers are added to achieve specific functions. For example, glass microbeads with low density and high strength characteristics are added to reduce density, improve thermal insulation performance, increase coating film thickness, and increase the frosted feel of the coating surface; the strength of polyurethane glue is increased by adding fumed silica, etc.

[0004] In order to further enhance the bonding performance of polyurethane adhesive, it is generally necessary to add an adhesion promoter (also known as an adhesion aid) to further improve substrate wetting and increase bonding strength. For example, the Chinese invention patent with authorization announcement number CN113462341B discloses a two-component polyurethane adhesive, which uses HDI trimer and polycarbonate polyol and polyester polyol as main raw materials. By adding 1 to 3% by weight of an epoxy group-containing silane compound of component B, the polyurethane adhesive has strong bonding strength at the initial stage of use.

[0005] Adhesion promoters are generally aminosilane coupling agents and epoxysilane coupling agents. The alkoxy groups contained in these silane coupling agents can improve the wettability of the substrate and the dispersion and interfacial bonding performance of the filler. Active hydrogen groups such as epoxy and amino groups can react with isocyanate components, thereby increasing the bonding performance to a certain extent.

[0006] If conventional polyether polyols and polyisocyanates are used directly as film-forming substances, the following problems may arise when using aminosilane coupling agents and epoxysilane coupling agents respectively:

[0007] Aminosilane coupling agents (such as KH550) are highly active and react quickly with isocyanate groups, which results in high viscosity and a short working period (the time interval for the glue to change from good fluidity to poor fluidity) of the polyurethane adhesive, making it difficult to meet industrial use requirements. At the same time, the urea group generated by the reaction of aminosilane coupling agents with isocyanate groups has very good thixotropy, which deteriorates the flow performance of the adhesive and its wettability to the substrate, making it unsuitable for some scenarios where the adhesive needs to be self-leveling.

[0008] If an epoxy silane coupling agent (such as KH560) is used, the reaction between the epoxy group and the isocyanate is relatively slow, and generally it takes a long time to achieve the bonding requirements.

[0009] In addition, both aminosilane coupling agents and epoxysilane coupling agents are small molecule coupling agents, and their effects on improving the bonding performance of polyurethane adhesives are extremely limited. Summary of the Invention

[0010] The purpose of the present invention is to provide an adhesive additive for polyurethane adhesive to solve the problems that aminosilane coupling agents such as KH550 react quickly with isocyanate groups, the viscosity of polyurethane adhesive is high, and the adhesive performance of polyurethane adhesive needs to be improved.

[0011] The second object of the present invention is to provide a method for preparing the above-mentioned adhesive additive for polyurethane adhesive to solve the above-mentioned problems.

[0012] The third object of the present invention is to provide a polyurethane adhesive containing the above-mentioned bonding agent to improve the leveling performance of the polyurethane adhesive and further improve the bonding performance.

[0013] A polyurethane adhesive bonding agent having a structure shown in formula (1):

[0014]

[0015] In formula (1), R1 and R1′ are independently selected from C2 to C4 alkylene groups; one of R2 and R2′ is H and the other is in, represents the connection position, m=2~5, R3 is methyl or ethyl; n=5~20.

[0016] The present invention provides an adhesive additive for polyurethane adhesives. Its molecular structure contains multiple hindered amine groups and terminal hydroxyl groups. Compared to aminosilane coupling agents such as KH550, this additive has a higher number of reactive functional groups, effectively enhancing the adhesive properties of polyurethane adhesives. Furthermore, as a macromolecular polymer, it avoids the rapid reaction time associated with smaller aminosilane coupling agents. Therefore, it can be effectively incorporated into polyurethane adhesives, comprehensively improving their operational adaptability, adhesion, and substrate wettability.

[0017] In order to further simplify the structure of the bonding agent and reduce production costs, preferably, R1 and R1′ are each independently selected from a C3-C4 alkylene group; m=3-4.

[0018] The preparation method of the above-mentioned adhesive additive for polyurethane adhesive comprises the following steps: carrying out condensation reaction between unsaturated dibasic acid and diol to obtain alcoholic hydroxyl-terminated condensation polymer, and then carrying out addition reaction between the alcoholic hydroxyl-terminated condensation polymer and primary aminosilane coupling agent.

[0019] The present invention provides a method for preparing an adhesive additive for polyurethane adhesive, which comprises first preparing a polyester diol containing an unsaturated bond, and then subjecting the polyester diol to an addition reaction with a primary aminosilane coupling agent to prepare the adhesive additive. The two-step method can conveniently control the quality of the product, has high preparation efficiency, and is suitable for industrial production.

[0020] In order to further optimize the bonding performance of the auxiliary agent, preferably, the molar ratio of the unsaturated dibasic acid, the diol, and the primary aminosilane coupling agent is 100:(105-120):100.

[0021] To further improve the preparation efficiency of the bonding agent, preferably, the polycondensation reaction is first carried out at 160-170°C for 50-80 minutes, then heated to 190-200°C for 8-20 minutes, and after the system is cooled to 80-90°C, a solvent is added to dissolve the mixture, and then a primary aminosilane coupling agent is added for an addition reaction. The advantage of using the above two-step temperature-raising reaction for the polymerization reaction is that the unsaturated dibasic acid and diol are partially reacted first, and then the temperature is raised before the entire reaction is carried out to avoid excessively intense high-temperature reactions. The advantage of adding the solvent for the addition reaction after cooling to 80-90°C is that the viscosity of the first reaction product is adjusted, allowing the subsequent primary aminosilane coupling agent to fully react with it.

[0022] To ensure that the addition reaction occurs sufficiently, the addition reaction time is preferably 120 to 180 minutes, more preferably 130 to 150 minutes.

[0023] To facilitate the addition of the bonding agent and promote efficient addition reaction, the amount of the solvent is preferably 50-200% of the total mass of the unsaturated dibasic acid, diol, and primary aminosilane coupling agent, more preferably 80-150%.

[0024] In order to further reduce the cost of raw materials and facilitate the quality control of each reaction, preferably, the unsaturated dibasic acid is maleic acid and / or fumaric acid; the diol is selected from propylene glycol and / or butanediol; and the primary aminosilane coupling agent is selected from aminopropyltrimethoxysilane and / or aminopropyltriethoxysilane.

[0025] A polyurethane adhesive containing the above-mentioned adhesive auxiliary agent for polyurethane adhesive.

[0026] By adding the above-mentioned bonding additives to polyurethane glue, commercially available conventional isocyanates and polyols can be used to prepare polyurethane glue with excellent performance in operational adaptability, adhesion and self-flowing properties. There is no need for complex isocyanate and polyol component design, and no need for complex polyurethane glue component design, which reduces the design cost of polyurethane glue and expands the application scenarios and adaptability of polyurethane glue.

[0027] Preferably, the polyurethane adhesive comprises components A and B. Component A comprises polymethylene polyphenyl isocyanate, and component B comprises polyether polyol and the aforementioned bonding agent. The mass ratio of polyether polyol to bonding agent is 100:(0.5-5). When used as a sealant, an addition amount of 0.5-5% combined with conventional isocyanate components (polymethylene polyphenyl isocyanate, or PAPI) and polyether polyol can achieve excellent results. DETAILED DESCRIPTION

[0028] The present invention provides the following adhesive additive having multiple hindered amines and containing hydroxyl groups, which solves the problems that aminosilane coupling agents have a fast reaction rate and high viscosity of the resulting polyurethane, while epoxysilane coupling agents have a slow reaction rate and both have limited improvement in adhesive performance.

[0029] The general structural formula of the bonding agent of the present invention is:

[0030]

[0031] In formula (1), R1 and R1′ are independently selected from C2 to C4 alkylene groups; one of R2 and R2′ is H and the other is in, represents the connection position, m=2~5, R3 is methyl or ethyl; n=5~20.

[0032] The C2-C4 alkylene group may be a linear or branched alkylene group. For example, the C2-C4 alkylene group may be an ethylene group, a propylene group, a butylene group, or an isomer thereof.

[0033] The bonding agent is prepared by the following method: unsaturated dibasic acid and diol are subjected to polycondensation reaction to obtain an alcoholic hydroxyl-terminated polycondensate, and then the alcoholic hydroxyl-terminated polycondensate is subjected to addition reaction with a primary aminosilane coupling agent.

[0034] Typical reaction materials are as follows:

[0035] The unsaturated dibasic acid is maleic acid and / or fumaric acid; the diol is selected from propylene glycol and / or butylene glycol; and the primary aminosilane coupling agent is selected from aminopropyltrimethoxysilane and / or aminopropyltriethoxysilane.

[0036] The amount of the solvent used is 50-200% of the total mass of the unsaturated dibasic acid, diol and primary aminosilane coupling agent. The solvent can be toluene, xylene or the like.

[0037] During the polycondensation reaction, the temperature is raised to 160-170°C under stirring and the reaction is carried out for 50-80 minutes, and then the temperature is raised to 190-200°C and the reaction is carried out for 8-20 minutes. The temperature is then lowered to 80-90°C and the above-mentioned solvent is added, and a primary aminosilane coupling agent is added. The mixture is kept at 80-90°C and stirred for 120-180 minutes to obtain an adhesive agent. The above reaction conditions are further preferably: the temperature is raised to 165-170°C under stirring and the reaction is carried out for 50-80 minutes, and then the temperature is raised to 190-200°C and the reaction is carried out for 10-20 minutes. The temperature is then lowered to 85-90°C and the above-mentioned solvent is added. The primary aminosilane coupling agent is added, and the mixture is kept at 85-90°C and stirred for 130-150 minutes to obtain an adhesive agent.

[0038] The above-mentioned adhesive additive can be used to produce conventional polyurethane adhesives such as polyurethane sealants. Taking the A and B component sealants as an example, polyurethane sealants with excellent performance can be easily produced without complex design of the polyether polyol and isocyanate components.

[0039] For example, component A of the polyurethane sealant can be PAPI (polymethylene polyphenyl isocyanate). Component B is the active hydrogen component, which is composed of the following components in parts by weight: 100 parts polyether polyol, 0.5-5 parts adhesion promoter, 5-30 parts glass microspheres, 2-5 parts fumed silica, and 0.05-0.2 parts catalyst.

[0040] The polyether polyol is preferably composed of a small molecule polyether polyol and polyether polyol 330N. Polyether polyol 330N accounts for 91-97% of the total mass of the small molecule polyether polyol and polyether polyol 330N. The small molecule polyether polyol is one or a combination of two or more of YD303, YD304, and YD305.

[0041] The catalyst can be selected from dibutyltin dilaurate or dibutyltin dichloride.

[0042] Component B should be dehydrated during preparation. Specifically, the polyether polyol is first dehydrated, and then an adhesive additive is added to remove the solvent therein. Finally, the dehydrated glass microbeads, fumed silica and catalyst are mixed evenly.

[0043] The polyether polyol dehydration conditions can be selected to be dehydrated at a temperature below -0.095 MPa and 80-100° C. for 2-3 hours, then cooled to 30-40° C. and added with the bonding agent, and vacuum stirred for 0.5-1 hour to remove the solvent therein; and the dehydrated glass beads, fumed silica and catalyst are added and stirred for 10-20 minutes.

[0044] When in use, the components A and B in the polyurethane sealant are uniformly mixed according to the molar ratio of the isocyanate group in the component A to the hydroxyl group in the component B (0.98-1.05):1 and then cured.

[0045] The implementation process of the present invention is described in detail below with reference to specific embodiments.

[0046] 1. Specific examples of the polyurethane adhesive additive and its preparation method of the present invention are as follows:

[0047] Example 1

[0048] The adhesive additive for urethane adhesive in this embodiment has the following general structural formula:

[0049]

[0050] Among them, R1 and R1' are both propyl groups, that is, R2 is H, R2′ is in, represents the connection position, m=3, R5 is methyl; n=5.

[0051] The preparation method of the bonding agent of this embodiment is as follows:

[0052] Place maleic acid and 1,3-propylene glycol in a reflux four-necked flask, heat to 165°C with stirring for 50 minutes, then heat to 196°C for 10 minutes, then cool to 85°C and add solvent to dissolve, then add aminopropyltrimethoxysilane, and continue stirring at this temperature for 150 minutes to obtain the bonding agent.

[0053] In this embodiment, the molar ratio of maleic acid, 1,3-propylene glycol, and aminopropyltrimethoxysilane is 100:120:100, the solvent is toluene, and the amount of solvent used is 80% of the total mass of maleic acid, 1,3-propylene glycol, and aminopropyltrimethoxysilane.

[0054] Example 2

[0055] The preparation method of the adhesive additive for urethane adhesive of this embodiment comprises the following steps:

[0056] Place maleic acid and 1,3-propylene glycol in a reflux four-necked flask, heat to 170°C with stirring and react for 80 minutes, then heat to 200°C for 10 minutes, lower to 90°C and add solvent to dissolve, then add aminopropyltrimethoxysilane, and continue stirring at this temperature for 130 minutes to obtain the bonding agent.

[0057] In this embodiment, the molar ratio of maleic acid, 1,3-propylene glycol, and aminopropyltrimethoxysilane is 100:105:100, the solvent is xylene, and the amount of solvent used is 150% of the total mass of maleic acid, 1,3-propylene glycol, and aminopropyltrimethoxysilane.

[0058] The general structural formula of the adhesive agent for urethane adhesive in this embodiment is shown in formula (1). The specific structure of the adhesive agent can be determined according to the reaction raw materials of Example 2 with reference to Example 1, wherein the value of n is 20.

[0059] Example 3

[0060] The preparation method of the adhesive additive for urethane adhesive of this embodiment comprises the following steps:

[0061] Place maleic acid and 1,3-propylene glycol in a reflux four-necked flask, heat to 170°C with stirring for 60 minutes, then heat to 190°C for 18 minutes, then cool to 88°C and add solvent to dissolve, then add aminopropyltrimethoxysilane, and continue stirring at this temperature for 140 minutes to obtain the bonding agent.

[0062] In this embodiment, the molar ratio of maleic acid, 1,3-propylene glycol, and aminopropyltrimethoxysilane is 100:110:100, the solvent is toluene, and the amount of solvent used is 100% of the total mass of maleic acid, 1,3-propylene glycol, and aminopropyltrimethoxysilane.

[0063] The general structural formula of the adhesive agent for urethane adhesive in this embodiment is shown in formula (1). The specific structure of the adhesive agent can be determined according to the reaction raw materials of Example 3 with reference to Example 1, wherein the value of n is 10.

[0064] 2. Specific embodiments of the polyurethane adhesive of the present invention are as follows:

[0065] Example 4

[0066] The polyurethane adhesive of this embodiment is a polyurethane sealant, comprising components A and B. Component A is PAPI (polymethylene polyphenyl isocyanate), and component B is composed of the following components by weight: 100 parts polyether polyol, 3 parts bonding agent obtained by the method of Example 1, 10 parts glass microspheres (HL40), 5 parts fumed silica, and 0.1 part dibutyltin dilaurate. The polyether polyol is composed of polyether polyol YD303 and polyether polyol 330N in a mass ratio of 5:95.

[0067] When in use, mix the isocyanate group in component A and the hydroxyl group in component B in a molar ratio of 1:1.

[0068] In other implementation situations, the amount of the bonding agent added can be selected according to the application scenario. Relative to 100 parts of polyether polyol, the amount of the bonding agent added is 0.5 parts, 1 parts, 2 parts, 4 parts, and 5 parts, respectively, which can achieve corresponding improvement effects.

[0069] Examples 5-6

[0070] The polyurethane sealants of Examples 5 and 6 differ from those of Example 4 in that the bonding aids are replaced by the bonding aids obtained by the methods of Examples 2 and 3 with the same total solid content, respectively.

[0071] 3. Comparative Example

[0072] Comparative Examples 1 to 3

[0073] The polyurethane sealant of Comparative Example 1 differs from that of Example 4 in that the bonding aid is replaced by KH560 having the same solid content.

[0074] The polyurethane sealant of Comparative Example 2 differs from that of Example 5 in that the bonding aid is replaced by KH550 having the same solid content.

[0075] The polyurethane sealant of Comparative Example 3 differs from that of Example 6 in that the bonding aid is replaced by KH560 with the same solid content.

[0076] IV. Experimental Examples

[0077] Experimental Example 1

[0078] This experimental example evaluates the surface drying time, self-leveling, adhesion and other properties of the polyurethane sealants of various embodiments and comparative examples. The evaluation method for each item is as follows:

[0079] Surface drying time test: Components A and B in Examples 4, 5, and 6 and Comparative Examples 1, 2, and 3 were mixed uniformly according to a certain ratio, and the surface drying time was tested with a glass rod under standard conditions of 23° C. and 50% RH.

[0080] Self-leveling test: Components A and B of Examples 4, 5, and 6 and Comparative Examples 1, 2, and 3 were mixed uniformly in the appropriate proportions. Under standard conditions of 23°C and 50% RH, 400 ml of the mixture was poured from the center into a mold measuring 20 cm long, 20 cm wide, and 3 cm long. The time was recorded until the adhesive completely flowed to all four sides.

[0081] Adhesion Performance Test: Components A and B from Examples 4, 5, and 6 and Comparative Examples 1, 2, and 3 were mixed uniformly in the appropriate proportions and then bonded to an anodized aluminum sheet (25 mm × 100 mm × 2 mm) and glass (50 mm × 40 mm × 6 mm). The anodized aluminum sheet and glass were pre-treated with KH560 toluene dilution. The adhesive was applied to a 1 mm thick layer on the anodized aluminum sheet, leaving a bonding area of ​​25 mm × 12.5 mm. The sheet was then bonded to the glass and cured for 7 days under standard conditions of 23°C and 50% RH. Shear strength was then tested.

[0082] The comparative results of the adhesive properties of the polyurethane sealants of the embodiments and comparative examples are shown in Table 1.

[0083] Table 1 Comparison of the adhesive properties of the polyurethane sealants of the embodiment and the comparative example

[0084] Example No. Bond strength (MPa) Leveling(s) Surface drying time (min) Example 4 5.1 22 33 Comparative Example 1 3.9 23 35 Example 5 5.2 24 32 Comparative Example 2 4.2 56 29 Example 6 5.0 23 32 Comparative Example 3 3.7 23 34

[0085] As shown in Table 1, the curing time of the adhesives prepared with KH560 (Comparative Examples 1 and 3) is slightly slower than that of the adhesives prepared with Examples 1 and 3. The curing time of the adhesive prepared with KH550 (Comparative Example 2) is faster than that of the adhesive prepared with Example 2. In terms of self-leveling performance, the flow properties of the polyurethane adhesive prepared with KH550 are poor, while the flow properties of the polyurethane adhesive prepared with KH560 are comparable to those of the present invention. In terms of bond strength, the adhesive prepared with the present invention significantly outperforms both KH560 and KH550 in polyurethane adhesive application.

[0086] From the above experimental results, it can be seen that after using the bonding agent of this embodiment, compared with small molecule bonding agents such as KH550 and KH560, the comprehensive performance in terms of curing time, self-leveling, bonding performance, etc. is further improved, the adaptability of the polyurethane sealant during use is increased, and the comprehensive performance of the polyurethane sealant is improved.

Claims

1. An adhesive additive for polyurethane adhesive, characterized in that: It has the structure shown in formula (1): In formula (1), R1 and R1′ are the same and are both selected from C2 to C4 alkylene groups; one of R2 and R2′ is H and the other is in, represents the connection position, m=2~5, R3 is methyl or ethyl; n=5~20.

2. The adhesive additive for polyurethane adhesive according to claim 1, characterized in that: R1 and R1' are each independently selected from a C3-C4 alkylene group; m=3-4.

3. A method for preparing the adhesive additive for polyurethane adhesive according to claim 1 or 2, characterized in that: The following steps are involved: The unsaturated dibasic acid and the diol undergo a condensation polymerization reaction to obtain an alcoholic hydroxyl-terminated condensation polymer, and then the alcoholic hydroxyl-terminated condensation polymer and a primary aminosilane coupling agent undergo an addition reaction.

4. The method for preparing the adhesive additive for polyurethane adhesive according to claim 3, wherein: The molar ratio of the unsaturated dibasic acid, the diol and the primary aminosilane coupling agent is 100:(105-120):

100.

5. The method for preparing the adhesive additive for polyurethane adhesive according to claim 3, wherein: The polycondensation reaction is first reacted at 160-170°C for 50-80 minutes, then heated to 190-200°C for 8-20 minutes, and after the system is cooled to 80-90°C, a solvent is added to dissolve the mixture, and then a primary aminosilane coupling agent is added to carry out an addition reaction.

6. The method for preparing the adhesive additive for polyurethane adhesive according to claim 5, wherein: The addition reaction time is 120 to 180 minutes.

7. The method for preparing the adhesive additive for polyurethane adhesive according to claim 5, wherein: The amount of the solvent used is 50-200% of the total mass of the unsaturated dibasic acid, diol and primary aminosilane coupling agent.

8. The method for preparing the adhesive additive for polyurethane adhesive according to any one of claims 3 to 7, characterized in that: The unsaturated dibasic acid is maleic acid or fumaric acid; the diol is selected from propylene glycol or butylene glycol; and the primary aminosilane coupling agent is selected from aminopropyltrimethoxysilane or aminopropyltriethoxysilane.

9. A polyurethane adhesive containing the adhesive additive for polyurethane adhesive according to claim 1 or 2.

10. The polyurethane adhesive according to claim 9, characterized in that The polyurethane glue is divided into components A and B. Component A is polymethylene polyphenyl isocyanate, and component B contains polyether polyol and the bonding agent. The mass ratio of polyether polyol to bonding agent is 100:(0.5-5).

Images