An adhesive and its preparation method

Abstract

The present invention discloses an adhesive and a preparation method thereof, belonging to the technical field of adhesives. It includes component A and component B. Component A includes polyether polyol, castor oil, an auxiliary agent, and modified aluminum hydroxide, and component B is polymethylene polyphenyl polyisocyanate. The preparation method of the adhesive: Vacuum dehydrate the polyether polyol, castor oil, and modified aluminum hydroxide, then cool down and add the auxiliary agent, and stir for 30 minutes under this temperature condition, and discharge the material to obtain component A; Seal and discharge the polymethylene polyphenyl polyisocyanate under a vacuum state to obtain component B. In the present invention, through the addition of the auxiliary agent, not only organic flame retardant components are introduced, but also it can act with the modified aluminum hydroxide, so that the adhesive has both organic and inorganic flame retardant components, with a synergistic flame retardant effect, and both the organic component and the inorganic component can form chemical bonding with the polyurethane matrix, thereby overcoming the defects that traditional flame retardants are prone to migration and exudation, and achieving the effect of long-lasting flame retardancy.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesives, and specifically relates to an adhesive and a preparation method thereof. Background Art

[0002] Plywood is one of the commonly used materials in furniture and interior decoration, and is one of the three major artificial boards. Traditional plywood has problems of releasing aldehyde toxic compounds during preparation, curing and use, seriously polluting the environment and endangering human health. With the gradual enhancement of environmental protection awareness, developing non-toxic, pollution-free and green environmental protection adhesives for plywood has become an inevitable trend in the industry development. Polyurethane adhesives are a type of block copolymers prepared by the reaction of polyisocyanates and low molecular weight polyols. Polyurethane adhesives have a wide range of hardness, excellent wear resistance, good elasticity, chemical corrosion resistance and adhesiveness, low gas permeability, and excellent vibration absorption performance, and are more and more widely used in plywood.

[0003] In recent years, with the continuous improvement of people's living standards, plywood is widely used in construction, furniture, decoration and decoration industries. However, flammability is its fatal weakness, and its scope of use is necessarily limited. Therefore, it is necessary to carry out flame retardant treatment on plywood. And as the raw material adhesive of plywood, it is the key direction to be broken through. In the prior art, inorganic flame retardant fillers or organic flame retardants are mostly used to carry out flame retardant treatment on polyurethane adhesives. The inorganic flame retardant fillers can only play an effect when the dosage is high. Therefore, there are defects such as easy agglomeration and increased specific gravity of the board. The organic flame retardants have defects such as easy migration and exudation, and it is difficult to achieve long-term flame retardancy. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide an adhesive and a preparation method thereof.

[0005] In the present invention, through the addition of additives, not only organic flame retardant components are introduced, but also they can act with modified aluminum hydroxide, so that the adhesive has both organic and inorganic flame retardant components, has a synergistic flame retardant effect, and the organic components and inorganic components that play the flame retardant effect can both generate chemical bonding with the polyurethane matrix (that is, have strong interaction forces), thereby overcoming the defects of easy migration and exudation of traditional flame retardants and achieving the effect of long-term flame retardancy.

[0006] The purpose of the present invention can be realized by the following technical solutions:

[0007] An adhesive, comprising component A and component B;

[0008] Component A includes polyether polyol, castor oil, additives and modified aluminum hydroxide;

[0009] Component B is polymethylene polyphenyl polyisocyanate.

[0010] The preparation method of the adhesive is as follows:

[0011] Dehydrate polyether polyol, castor oil and modified aluminum hydroxide at 100 - 110 °C for 3 h, then cool down to 55 - 60 °C, add additives, and stir for 30 min under this temperature condition, then discharge to obtain Component A;

[0012] Seal and discharge polymethylene polyphenyl polyisocyanate under vacuum to obtain Component B;

[0013] During use, mix Component A and Component B evenly according to the mass ratio of 100:10 - 12, and then construction can be carried out.

[0014] Furthermore, the mass ratio of each raw material in Component A is 50:20 - 25:8 - 12:10 - 14.

[0015] Furthermore, the modified aluminum hydroxide is nano - aluminum hydroxide surface - treated with silane coupling agent KH550.

[0016] Furthermore, the additive is prepared through the following steps:

[0017] S1. Add ethylenediamine, sodium bicarbonate, 1,3 - dinitrobenzene and tetrahydrofuran into a dry three - necked flask, place the flask in an ice bath, stir and mix. When the system temperature is stable at 0 - 2 °C, slowly drip 3 - chloro - 1,2 - propanediol dropwise through a constant - pressure dropping funnel under stirring. After the dropping is completed, react at 0 - 2 °C for 3 h, filter to remove salts, rotary evaporate under reduced pressure to remove most of the tetrahydrofuran, then recrystallize and purify with a methanol - chloroform mixed solvent (the volume ratio of the two is 11:9), and dry under vacuum to obtain Intermediate 1; the dosage ratio of ethylenediamine, sodium bicarbonate, 1,3 - dinitrobenzene and 3 - chloro - 1,2 - propanediol is 0.105 mol:8.4 g:0.24 g:0.1 mol;

[0018] Under the action of sodium bicarbonate and 1,3 - dinitrobenzene, the - NH on the ethylenediamine molecule 2 and the - Cl on the 3 - chloro - 1,2 - propanediol molecule undergo a nucleophilic substitution reaction. By controlling the molar ratio of the two to be close to 1:1 and with ethylenediamine being slightly in excess, under the steric hindrance effect, only one - end - NH of ethylenediamine 2 undergoes a mono - substitution reaction, and the process is as shown below to obtain Intermediate 1;

[0019]

[0020] S2. Add intermediate 1 and DMSO (dimethyl sulfoxide) into a three-necked flask equipped with a condensing reflux device and a stirring device. After stirring and dissolving evenly, slowly dropwise add the DMSO solution of terephthalaldehyde into the flask at room temperature. After the addition is completed, continue stirring and reacting for 3 h. After distilling off most of the DMSO under reduced pressure, add hot water (distilled water at 65 - 70 °C) and mix evenly. Extract with ethyl acetate, take the organic phase, dry with anhydrous sodium sulfate, filter, and rotary evaporate to remove ethyl acetate to obtain intermediate 2. The dosage ratio of intermediate 1 to terephthalaldehyde is 13.4 g:14.2 g;

[0021] -NH on the molecule of intermediate 1 2 and -CHO on the molecule of terephthalaldehyde undergo a Schiff base reaction. By controlling the molar ratio of the two to be close to 1:1 and terephthalaldehyde being slightly in excess, only one end of -CHO of terephthalaldehyde participates in the reaction to generate intermediate 2. The reaction process is as follows:

[0022]

[0023] S3. Add dimethyl phosphite, CCl 4 and tetrahydrofuran into a three-necked flask with a stirring device in sequence. Transfer the flask to an ice bath and stir. Dropwise add triethylamine and the ethyl acetate solution of intermediate 2 into the flask simultaneously. After the addition is completed, transfer the three-necked flask to room temperature and continue stirring and reacting for 10 h. After the reaction is completed, perform suction filtration, take the filtrate, and rotary evaporate (remove tetrahydrofuran, ethyl acetate, and CCl 4 ) to obtain the additive. The dosage ratio of dimethyl phosphite, CCl 4 , tetrahydrofuran, triethylamine, and intermediate 2 is 11 g:15.4 g:20 mL:10.1 g:25 g;

[0024] -NH- on intermediate 2 reacts with dimethyl phosphite in an Atherton-Todd reaction. The reaction process is as follows to obtain the additive:

[0025]

[0026] The obtained additive molecule contains multiple alcohol hydroxyl groups, aldehyde groups directly connected to the benzene ring, and P-N components. The presence of multiple alcohol hydroxyl groups enables the additive to replace part of the polyol and participate in the crosslinking and curing process with isocyanate, enabling the additive to bind to the polyurethane molecular chain in a chemical bonding manner, thereby introducing the additive molecule into the polyurethane molecular structure. On the one hand, the presence of aldehyde groups enables the polyurethane molecular chain to react with -NH on the surface of modified aluminum hydroxide 2Chemical bonding is generated, thereby enhancing the interaction force between the modified aluminum hydroxide and the matrix, promoting the uniform dispersion of the modified aluminum hydroxide in the adhesive while improving the mechanical properties of the cured adhesive film (nano-aluminum hydroxide belongs to inorganic reinforcing filler), and also enabling the modified aluminum hydroxide to better exert the flame retardant effect. In addition, the benzene ring is connected to the aldehyde group, and the benzene ring has large rigidity and steric hindrance effects, making the aluminum hydroxide particles more dispersed, thereby further improving the dispersion effect; on the other hand, the P-N component introduced into the polyurethane molecular chain belongs to the phosphorus-nitrogen synergistic flame retardant component and has various organic flame retardant mechanisms. Therefore, this organic component and inorganic aluminum hydroxide can also produce a synergistic effect, greatly improving the flame retardant performance of the adhesive; it should be added that both the organic component and the inorganic component that exert the flame retardant effect can form chemical bonds with the polyurethane matrix (that is, have strong interaction forces), thereby overcoming the defects of traditional flame retardants being prone to migration and exudation and achieving the effect of long-term flame retardancy.

[0027] Advantages of the present invention:

[0028] In the present invention, through the addition of additives, not only organic flame retardant components are introduced, but also they can act on the modified aluminum hydroxide, so that the adhesive contains both organic and inorganic flame retardant components, with a synergistic flame retardant effect. Moreover, both the organic component and the inorganic component that exert the flame retardant effect can form chemical bonds with the polyurethane matrix (that is, have strong interaction forces), thereby overcoming the defects of traditional flame retardants being prone to migration and exudation and achieving the effect of long-term flame retardancy. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0030] Example 1

[0031] Preparation of modified aluminum hydroxide:

[0032] 60 mL of 3-aminopropyltrimethoxysilane and 150 mL of an ethanol aqueous solution (the volume fraction of the ethanol aqueous solution is 50%) were added to a round-bottom flask. After mixing and dissolving evenly, 10 g of nano-aluminum hydroxide was added. After ultrasonic treatment for 10 min, the mixture was refluxed and stirred at 82 °C for 2 h, filtered by suction, and the product was washed 3 times with ethanol and deionized water respectively, dried in vacuum, and ground to obtain modified aluminum hydroxide.

[0033] Example 2

[0034] Preparation of additives:

[0035] S1. Add 0.105 mol of ethylenediamine, 8.4 g of sodium bicarbonate, 0.24 g of 1,3-dinitrobenzene and 150 mL of tetrahydrofuran into a dry three-necked flask. Place the flask in an ice bath, stir and mix. When the system temperature stabilizes at 0 - 2 °C, slowly drip 0.1 mol of 3-chloro-1,2-propanediol dropwise through a constant pressure dropping funnel under stirring. After the dropping is completed, react at 0 °C for 3 h. Filter to remove the salt, rotary evaporate under reduced pressure to remove most of the tetrahydrofuran, then recrystallize and purify with a methanol-chloroform mixed solvent (volume ratio of the two is 11:9), and dry in vacuum to obtain intermediate 1;

[0036] S2. Add 13.4 g of intermediate 1 and 100 mL of DMSO (dimethyl sulfoxide) into a three-necked flask equipped with a condensing reflux device and a stirring device. After stirring and dissolving evenly, slowly drip 50 mL of a DMSO solution containing 14.2 g of terephthalaldehyde into the flask at room temperature. After the dropping is completed, continue to stir and react for 3 h. Distill off most of the DMSO under reduced pressure, then add 150 mL of hot water (distilled water at 65 °C) and mix evenly. Extract with ethyl acetate, take the organic phase, dry with anhydrous sodium sulfate, filter, and rotary evaporate to remove ethyl acetate to obtain intermediate 2;

[0037] S3. Add 11 g of dimethyl phosphite, 15.4 g of CCl 4 and 20 mL of tetrahydrofuran into a three-necked flask with a stirring device in sequence. Transfer the flask to an ice bath and stir. Dropwise add 10.1 g of triethylamine and 50 mL of an ethyl acetate solution containing 25 g of intermediate 2 into the flask simultaneously. After the dropping is completed, transfer the three-necked flask to room temperature and continue to stir and react for 10 h. After the reaction is completed, perform suction filtration, take the filtrate, and rotary evaporate (remove tetrahydrofuran, ethyl acetate and CCl 4 ) to obtain the auxiliary agent.

[0038] Example 3

[0039] Preparation of the auxiliary agent:

[0040] S1. Add 0.21 mol of ethylenediamine, 16.8 g of sodium bicarbonate, 0.48 g of 1,3-dinitrobenzene and 300 mL of tetrahydrofuran into a dry three-necked flask. Place the flask in an ice bath, stir and mix. When the system temperature stabilizes at 0 - 2 °C, slowly drip 0.2 mol of 3-chloro-1,2-propanediol dropwise through a constant pressure dropping funnel under stirring. After the dropping is completed, react at 2 °C for 3 h. Filter to remove the salt, rotary evaporate under reduced pressure to remove most of the tetrahydrofuran, then recrystallize and purify with a methanol-chloroform mixed solvent (volume ratio of the two is 11:9), and dry in vacuum to obtain intermediate 1;

[0041] S2. Add 26.8 g of Intermediate 1 and 200 mL of DMSO (dimethyl sulfoxide) to a three-necked flask equipped with a condenser reflux device and a stirring device. After stirring and dissolving evenly, slowly drop 100 mL of a DMSO solution containing 28.4 g of terephthalaldehyde into the flask at room temperature. After the dropping is completed, continue stirring and reacting for 3 h. After removing most of the DMSO by vacuum distillation, add 300 mL of hot water (distilled water at 70 °C), mix well, extract with ethyl acetate, take the organic phase, dry over anhydrous sodium sulfate, filter, and rotary evaporate to remove ethyl acetate to obtain Intermediate 2;

[0042] S3. Add 22 g of dimethyl phosphite, 30.8 g of CCl 4 and 40 mL of tetrahydrofuran to a three-necked flask with a stirring device in sequence. Transfer the flask to an ice bath and stir. Dropwise add 20.2 g of triethylamine and 100 mL of an ethyl acetate solution containing 50 g of Intermediate 2 into the flask simultaneously. After the dropping is completed, transfer the three-necked flask to room temperature and continue stirring and reacting for 10 h. After the reaction is completed, filter by suction, take the filtrate, and rotary evaporate (remove tetrahydrofuran, ethyl acetate, and CCl 4 ) to obtain the additive.

[0043] Example 4

[0044] Preparation of Adhesive:

[0045] Dehydrate 100 g of polyether polyol (produced by Shandong Bluestar Dongda, 220), 40 g of castor oil, and 20 g of the modified aluminum hydroxide prepared in Example 1 at 100 °C for 3 h, then cool to 55 °C, add 16 g of the additive prepared in Example 2, and stir at this temperature for 30 min, then discharge to obtain Component A;

[0046] Seal and discharge polymethylene polyphenyl polyisocyanate under vacuum to obtain Component B;

[0047] Mix 100 g of Component A and 10 g of Component B evenly to obtain the adhesive.

[0048] Example 5

[0049] Preparation of Adhesive:

[0050] Dehydrate 100 g of polyether polyol (produced by Shandong Bluestar Dongda, 220), 45 g of castor oil, and 24 g of the modified aluminum hydroxide prepared in Example 1 at 105 °C for 3 h, then cool to 58 °C, add 20 g of the additive prepared in Example 3, and stir at this temperature for 30 min, then discharge to obtain Component A;

[0051] Seal and discharge polymethylene polyphenyl polyisocyanate under vacuum to obtain Component B;

[0052] Mix 100 g of Component A and 11 g of Component B evenly to obtain the adhesive.

[0053] Example 6

[0054] Prepare the adhesive:

[0055] Mix 100 g of polyether polyol (produced by Shandong Bluestar Dongda, 220), 50 g of castor oil, and 28 g of the modified aluminum hydroxide prepared in Example 1 and dehydrate at 110 °C for 3 h. Then, cool down to 60 °C and add 24 g of the auxiliary agent prepared in Example 2, and stir for 30 min under this temperature condition, then discharge to obtain Component A;

[0056] Seal and discharge the polymethylene polyphenyl polyisocyanate under vacuum to obtain Component B;

[0057] Mix 100 g of Component A and 12 g of Component B evenly to obtain the adhesive.

[0058] Comparative Example 1

[0059] Replace the modified aluminum hydroxide in Example 4 with ordinary aluminum hydroxide, and keep the other raw materials and preparation process unchanged to obtain the adhesive.

[0060] Comparative Example 2

[0061] Replace the auxiliary agent in Example 4 with the same amount of polyether diol, and keep the other raw materials and preparation process unchanged to obtain the adhesive.

[0062] Stack three layers of poplar veneers in a staggered and crisscross pattern. Apply the adhesives obtained in Examples 4 - 6 and Comparative Examples 1 - 2 evenly on one side of the first and second layers respectively. The double-sided glue application amount is 320 g / m 2 , let it stand and age for 8 min, then perform hot pressing under the conditions of a hot pressing temperature of 110 °C and a hot pressing time of 180 s. Cut the plywood according to the size requirements in the GB / T 9846 - 2015 standard and conduct the following performance tests:

[0063] Gluing strength: Test according to GB 9846.12 - 2015;

[0064] Combustion performance: Test with reference to GB 12441 - 2005;

[0065] Combustion performance classification: Test with reference to GB 8624 - 2006;

[0066] The measured results are shown in the following table:

[0067]

[0068] As can be seen from the data in the above table, the adhesive obtained by the present invention has high bonding strength and excellent flame retardant properties; combined with the data of Comparative Example 1, it can be seen that after the aluminum hydroxide is modified, it can interact with the additives to improve the mechanical strength and flame retardant effect; combined with the data of Comparative Example 2, it can be seen that the addition of the additives can synergistically interact with the modified aluminum hydroxide to greatly improve the flame retardant effect.

[0069] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0070] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. An adhesive, comprising component A and component B, characterized in that, component A includes polyether polyol, castor oil, an auxiliary agent and modified aluminum hydroxide, and component B is polymethylene polyphenyl polyisocyanate; wherein, the auxiliary agent is prepared by the following steps: S1. Add ethylenediamine, sodium bicarbonate, 1,3-dinitrobenzene and tetrahydrofuran into a dry three-necked flask, place the flask in an ice bath, stir and mix. When the system temperature is stable at 0-2°C, slowly drip 3-chloro-1,2-propanediol dropwise through a constant pressure dropping funnel under stirring. After the dropping is completed, react at 0-2°C for 3 h, filter to remove the salt, remove most of the tetrahydrofuran by rotary evaporation under reduced pressure, recrystallize and purify with a methanol-chloroform mixed solvent, and vacuum dry to obtain intermediate 1; S2. Add intermediate 1 and DMSO into a three-necked flask equipped with a condensing reflux device and a stirring device, stir and dissolve evenly, and then slowly drip a DMSO solution of terephthalaldehyde into the flask at room temperature. After the dropping is completed, continue to stir and react for 3 h. After removing most of the DMSO by distillation under reduced pressure, add hot water and mix well, extract with ethyl acetate, take the organic phase, dry over anhydrous sodium sulfate, filter, and rotary evaporate to remove ethyl acetate to obtain intermediate 2; S3. Add dimethyl phosphite, CCl 4 and tetrahydrofuran into a three-necked flask equipped with a stirring device in sequence. Transfer the flask to an ice bath and stir. Slowly add triethylamine and an ethyl acetate solution of intermediate 2 dropwise into the flask simultaneously. After the addition is completed, transfer the three-necked flask to room temperature and continue stirring for reaction for 10 h. After the reaction is completed, perform suction filtration, take the filtrate, and rotary evaporate to obtain an auxiliary agent; The modified aluminum hydroxide is nano-aluminum hydroxide surface-treated with silane coupling agent KH550.

2. An adhesive according to claim 1, characterized in that, In step S1, the dosage ratio of ethylenediamine, sodium bicarbonate, 1,3-dinitrobenzene and 3-chloro-1,2-propanediol is 0.105 mol: 8.4 g: 0.24 g: 0.1 mol.

3. An adhesive according to claim 1, characterized in that, In step S2, the dosage ratio of intermediate 1 and terephthalaldehyde is 13.4 g: 14.2 g.

4. An adhesive according to claim 1, characterized in that, In step S3, the dosage ratio of dimethyl phosphite, CCl 4 , tetrahydrofuran, triethylamine, and intermediate 2 is 11 g: 15.4 g: 20 mL: 10.1 g: 25 g.

5. An adhesive according to claim 1, characterized in that, The mass ratio of each raw material in component A is 50: 20-25: 8-12: 10-14.

6. A preparation method of the adhesive according to claim 1, characterized in that, specifically as follows: Dehydrate polyether polyol, castor oil and modified aluminum hydroxide at 100-110°C for 3 h, then cool down to 55-60°C, add the auxiliary agent, and stir at this temperature for 30 min, then discharge to obtain component A; Seal and discharge polymethylene polyphenyl polyisocyanate under a vacuum state to obtain component B.

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