Modified palm oil polyol and preparation method thereof, and polyurethane structural adhesive

Abstract

The application discloses modified palm oil polyol and a preparation method thereof, and polyurethane structural glue, and belongs to the field of high polymer chemistry. The preparation method comprises the following steps: (1) palm oil is subjected to saponification reaction by using lye to obtain mixed fatty acid salt; (2) the fatty acid salt crude product is subjected to acidification reaction by using acid liquor to obtain mixed fatty acid; (3) the mixed fatty acid is mixed with small-molecule polyhydric alcohol to perform esterification reaction to obtain palm oil-based polyhydric alcohol ester; and (4) the palm oil-based polyhydric alcohol ester is subjected to epoxidation reaction to obtain the modified palm oil polyol. The modified palm oil polyol obtained by the preparation method has the advantages of low viscosity, low hardness and high bonding strength for the polyurethane structural glue.

Description

Technical Field

[0001] This invention belongs to the field of polymer chemistry and relates to a modified palm oil polyol and its preparation method, as well as a polyurethane structural adhesive. Background Technology

[0002] Two-component polyurethane structural adhesives are indispensable key materials in modern industrial manufacturing, and their performance optimization has always been a research hotspot in the field of polymer materials. With the rapid development of new energy vehicles, flexible electronic devices, and lightweight structural materials, the market has placed more stringent comprehensive performance requirements on polyurethane structural adhesives: they need to have low viscosity to ensure good workability and substrate wettability, moderate hardness to absorb dynamic loads and thermal stress, and extremely high bond strength to meet the load-bearing requirements of structural components. For example, in the assembly of electric vehicle battery packs, structural adhesives need to meet the requirements of low viscosity for automated application, medium hardness to buffer driving vibrations, and extremely high bond strength to fix heavy battery modules. This comprehensive performance requirement poses a huge challenge to traditional formulation design; that is, balancing multiple performance indicators has become the main technical bottleneck in the current research and development of polyurethane structural adhesives.

[0003] Traditional two-component polyurethane structural adhesives typically control the performance of the final product by adjusting the molecular weight, functionality, and isocyanate type of the polyol. However, this conventional approach often faces a "performance seesaw" effect: reducing viscosity often leads to a decrease in cohesive strength, reducing hardness may sacrifice heat resistance and durability, while increasing crosslinking density to enhance bond strength will increase hardness and viscosity.

[0004] Modified polyol technology is considered an effective way to overcome this bottleneck. By introducing special structures or functional groups into polyols through molecular design, the cross-linking network structure of polyurethane can be controlled at the molecular level, thereby achieving synergistic optimization of viscosity, hardness, and strength. In recent years, the emergence of novel modified polyols such as bio-based polyols, fluorinated polyols, and nanocomposite polyols has provided new ideas for solving multi-objective optimization problems. In particular, block-modified polyols that precisely combine rigid and flexible segments, as well as topological polyols that introduce functional side chains through click chemistry, have shown excellent performance regulation potential.

[0005] CN115975586A discloses a two-component polyurethane structural adhesive that introduces a combination of bisphenol A-modified polyether polyol and castor oil-modified polyol. The rigid segments of bisphenol A provide strength, while the flexible segments of castor oil adjust the hardness, achieving high bonding strength (shear strength > 10 MPa) to aluminum and PET. However, it requires the use of a thermally activated catalyst, and the room temperature operation time is more than 60 minutes. Moreover, the hardness of the resulting structural adhesive is relatively high (Shore D > 50), and the contradiction between hardness and strength has not yet been resolved.

[0006] From the perspective of industry demand, the annual growth rate of demand for polyurethane structural adhesives exceeds 8%. At the same time, driven by strict environmental regulations (such as REACH and GB 33372-2020), the development of high-performance polyurethane structural adhesives that are free of organic solvents and have low V emissions has become an industry consensus.

[0007] Therefore, developing environmentally friendly structural adhesives based on modified polyols that simultaneously meet the requirements of low viscosity, low hardness, and high bond strength is not only of significant scientific importance, but also holds enormous market value. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a modified palm oil polyol, its preparation method, and a polyurethane structural adhesive.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing modified palm oil polyols, the method comprising:

[0011] (1) Palm oil is saponified using an alkaline solution to obtain a mixture of fatty acid salts;

[0012] (2) The crude fatty acid salts are acidified with acid to obtain mixed fatty acids;

[0013] (3) Mixed fatty acids and small molecule polyols are mixed and esterified to obtain palm oil-based polyol esters;

[0014] (4) The palm oil-based polyol ester undergoes an epoxidation reaction to obtain the modified palm oil polyol.

[0015] In the preparation method provided by the present invention, saponification, acidification, esterification and epoxidation reactions are carried out on palm oil as a substrate to obtain modified palm oil polyol rich in epoxy groups. Therefore, when the modified palm oil polyol of the present invention is used to prepare polyurethane structural adhesive, the adhesive performance of the polyurethane structural adhesive can be increased and the adhesive strength of the polyurethane structural adhesive can be improved.

[0016] Furthermore, in the process of modifying palm oil, the present invention specifies that the esterification reaction is carried out using small molecule polyols. The resulting palm oil-based polyol ester and the final modified palm oil polyol have multiple aliphatic long chains and have large steric hindrance. When added to polyurethane structural adhesives, their reactivity with isocyanates can be reduced, so that the polyurethane structural adhesives using them have the characteristic of low hardness.

[0017] Meanwhile, the modified palm oil polyol provided by this invention has a low viscosity. Therefore, when it is applied to polyurethane structural adhesives, it can reduce the viscosity of the polyurethane structural adhesives, giving them a low viscosity characteristic.

[0018] Therefore, the polyurethane structural adhesive prepared by the modified palm oil polyol obtained by the preparation method provided by the present invention has the advantages of low viscosity, low hardness and high bonding strength.

[0019] Furthermore, the presence of aliphatic long chains can increase the wettability of polyurethane structural adhesive and the substrate to be bonded, making it easier for the polyurethane structural adhesive to spread on the surface of the substrate to be bonded. Moreover, the palm oil provided by this invention is a vegetable oil, which has little impact on the environment and is safe and environmentally friendly.

[0020] Preferably, the melting point of the palm oil is 8-24℃, such as 8℃, 10℃, 12℃, 14℃, 16℃, 18℃, 20℃, 24℃, etc.

[0021] Preferably, the solutes contained in the alkaline solution in step (1) include sodium hydroxide and / or potassium hydroxide.

[0022] Preferably, the concentration of the alkaline solution is 20-30 wt%, such as 20 wt%, 22 wt%, 24 wt%, 25 wt%, 26 wt%, 28 wt%, 30 wt%, etc.

[0023] Preferably, the molar ratio of the palm oil and the solute contained in the alkali solution in step (1) is 1:(3.0-3.3), for example 1:3.0, 1:3.05, 1:3.1, 1:3.15, 1:3.2, 1:3.25, 1:3.3, etc.

[0024] Preferably, the reaction temperature of the saponification reaction in step (1) is 80-100℃, for example 80℃, 82℃, 85℃, 88℃, 90℃, 92℃, 95℃, 98℃, 100℃, and the time is 1-2 h, for example 1 h, 1.1 h, 1.2 h, 1.4 h, 1.5 h, 1.6 h, 1.8 h, 2 h, etc.

[0025] Preferably, step (1) further includes salting out the mixed fatty acid salt after the saponification reaction is completed.

[0026] Preferably, the pH value of the acidification reaction in step (2) is 2-3, such as 2, 2.1, 2.2, 2.4, 2.5, 2.6, 2.8, 3, etc.

[0027] Preferably, the acidification reaction temperature is ≤40℃, such as 40℃, 38℃, 35℃, 32℃, 30℃, 25℃, 20℃, etc., preferably room temperature, and preferably the time is 0.5-2 h, such as 0.5 h, 1 h, 1.5 h, 2 h, etc.

[0028] Preferably, the solute contained in the acid solution in step (2) includes hydrogen chloride, that is, the present invention uses a dilute hydrochloric acid solution to carry out the acidification reaction.

[0029] Preferably, the concentration of the hydrochloric acid solution is 10-20 wt%, such as 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 18 wt%, 20 wt%, etc.

[0030] Preferably, the small molecule polyol in step (3) includes a small molecule polyol with 3-5 functionality (e.g., 3, 4, 5, etc.), and the small molecule polyol with 3-5 functionality includes any one or a combination of at least two of glycerol, pentylenetetrol, trimethylolpropane or xylitol.

[0031] Preferably, the molar ratio of the carboxyl group of the mixed fatty acid and the hydroxyl group of the small molecule polyol in step (3) is 1:(1-3), such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc.

[0032] This invention selects small molecule polyols with a functionality of 3-5 and controls the molar amount of the small molecule polyols to ensure that the small molecule polyols are not fully capped after the reaction. That is, the reaction products obtained by the reaction of small molecule polyols with mixed fatty acids still retain some hydroxyl groups that have not participated in the reaction. At the same time, due to the steric hindrance of the reaction, the formation of fully capped products can be further avoided. This method can reduce the viscosity of modified palm oil polyols, thereby reducing the viscosity of polyurethane structural adhesives.

[0033] Preferably, the esterification reaction in step (3) is carried out under the catalysis of a catalyst selected from any one or at least a combination of two of tetraisopropyl titanate, tetrabutyl titanate, dibutyltin oxide, monobutyltin oxide, or p-toluenesulfonic acid.

[0034] Preferably, the amount of catalyst added in step (3) is 1-2 wt% of the total mass of the mixed fatty acids and small molecule polyols, such as 1 wt%, 1.2 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, etc.

[0035] Preferably, the temperature of the esterification reaction in step (3) is 120-180℃, such as 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, etc., and the time is 3-5 h, such as 3h, 3.5h, 4h, 4.5h, 5h, etc.

[0036] Preferably, step (4) includes: epoxidizing palm oil-based polyol esters with hydrogen peroxide under organic acid catalysis to obtain the modified palm oil polyol.

[0037] Preferably, the organic acid includes formic acid and / or acetic acid.

[0038] Preferably, the amount of organic acid added is such that the pH value of the epoxidation reaction system is 3-5, for example, 3, 3.5, 4, 4.5, 5, etc.

[0039] Preferably, the organic acid is generally an organic acid solution, and the concentration of the organic acid solution is preferably 30-50 wt%, such as 30 wt%, 32 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, 45 wt%, 48 wt%, 50 wt%, etc.

[0040] Preferably, the hydrogen peroxide is used in the form of hydrogen peroxide solution, the concentration of which is 30-50 wt%, such as 30 wt%, 32 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, 45 wt%, 48 wt%, 50 wt%, etc.

[0041] Preferably, the molar ratio of double bonds to hydrogen peroxide in the palm oil-based polyol ester is 1:(1-1.3), such as 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, etc.

[0042] Preferably, the epoxidation reaction is carried out at a temperature of 50-70°C, such as 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, etc., and for a time of 4-8 hours, such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, etc.

[0043] In this invention, sodium hydroxide solution is used as the alkaline solution and pentaerythritol is used as the small molecule polyol to explain the reaction process of the preparation method described in this invention.

[0044] The reaction equations for obtaining fatty acids from palm oil through saponification and acidification reactions according to this invention are as follows:

[0045] ;

[0046] in:

[0047] R1, R2, and R3 are each independently selected from: ; "This refers to the point where a chemical bond connects;

[0048] R represents R1, R2, or R3.

[0049] That is, the mixed fatty acids obtained through the acidification reaction include palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid.

[0050] The reaction equation for the esterification reaction described in this invention is as follows:

[0051] ;

[0052] The epoxidation equation described in this invention is as follows (using oleic acid residues as an example):

[0053] .

[0054] Therefore, the modified palm oil polyol obtained by the preparation method provided by the present invention is rich in epoxy groups, which can improve the adhesion of polyurethane structural adhesives. At the same time, it has aliphatic long chains with large steric hindrance, which can reduce the reactivity and crosslinking density with isocyanates. Moreover, it has low viscosity, thus endowing polyurethane structural adhesives with the advantages of low viscosity, low hardness and high adhesive strength.

[0055] In some embodiments of the present invention, the preparation method includes:

[0056] (1) Palm oil is mixed with 20-30 wt% sodium hydroxide solution and saponified at 80-100℃ for 1-2 h. After the reaction is completed, saturated sodium chloride solution is added for salting out, and the upper layer of sodium fatty acid mixture (upper oil layer) is taken.

[0057] (2) Mix the sodium fatty acid mixture with 10-20 wt% hydrochloric acid solution. The amount of hydrochloric acid solution added is to make the pH of the reaction system 2-3. The acidification reaction is carried out at room temperature for 0.5-2 h. After the reaction is completed, fatty acid mixture (oil layer) is obtained. The fatty acid mixture is washed with water and purified by dehydration under reduced pressure.

[0058] (3) The fatty acid mixture is mixed with a small molecule polyol, and 1-2 wt% catalyst is added. The mixture is subjected to esterification at 120-180℃ for 3-5 h. The catalyst is removed, the mixture is washed with water, and the mixture is distilled under reduced pressure to obtain palm oil-based polyol ester.

[0059] (4) Add a mixture of organic acid and hydrogen peroxide to the palm oil-based polyol ester and carry out an epoxidation reaction at 50-70℃ for 4-8 h. Remove excess organic acid (neutralize), wash with water, remove impurities by vacuum distillation, and obtain the modified palm oil polyol (which is an epoxy-modified palm oil polyol).

[0060] In a second aspect, the present invention provides a modified palm oil polyol prepared by the preparation method described in the first aspect.

[0061] Preferably, the modified palm oil polyol has an epoxy value of 0.3-1.1%, such as 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.05%, 1.1%, etc., and a hydroxyl value of 200-250 mgKOH / g, such as 200 mgKOH / g, 205 mgKOH / g, 210 mgKOH / g, 215 mgKOH / g, 220 mgKOH / g, 225 mgKOH / g, 230 mgKOH / g, 235 mgKOH / g, 240 mgKOH / g, 245 mgKOH / g, 250 mgKOH / g, etc.

[0062] Thirdly, the present invention provides a two-component polyurethane structural adhesive, comprising component A and component B in a mass ratio of 1:1, by weight:

[0063] Component A comprises: 200-250 parts by weight of isocyanate, 200-250 parts by weight of calcium carbonate, 100-150 parts by weight of plasticizer, and 20-25 parts by weight of silica.

[0064] Component B comprises: 200-250 parts by weight of calcium carbonate, 150-200 parts by weight of the modified palm oil polyol described in the second aspect, 50-100 parts by weight of castor oil, 50-100 parts by weight of chain extender, and 0.1-1 parts by weight of catalyst.

[0065] In component A of this invention, the isocyanate, in quantities of 200-250 parts by weight, can be 200 parts by weight, 205 parts by weight, 210 parts by weight, 215 parts by weight, 220 parts by weight, 225 parts by weight, 230 parts by weight, 235 parts by weight, 240 parts by weight, 245 parts by weight, 250 parts by weight, etc., and the calcium carbonate, in quantities of 200-250 parts by weight, can be 200 parts by weight, 205 parts by weight, 210 parts by weight, 215 parts by weight, 220 parts by weight, 225 parts by weight, 230 parts by weight, etc., etc. 35 parts by weight, 240 parts by weight, 245 parts by weight, 250 parts by weight, etc.; plasticizer 100-150 parts by weight can be 100 parts by weight, 105 parts by weight, 110 parts by weight, 115 parts by weight, 120 parts by weight, 125 parts by weight, 130 parts by weight, 135 parts by weight, 140 parts by weight, 145 parts by weight, 150 parts by weight, etc.; 20-25 parts by weight of silica can be 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, etc.

[0066] In component B of this invention, the calcium carbonate 200-250 parts by weight can be 200 parts by weight, 205 parts by weight, 210 parts by weight, 215 parts by weight, 220 parts by weight, 225 parts by weight, 230 parts by weight, 235 parts by weight, 240 parts by weight, 245 parts by weight, 250 parts by weight, etc.; the modified palm oil polyol 150-200 parts by weight mentioned in the second aspect can be 150 parts by weight, 155 parts by weight, 160 parts by weight, 165 parts by weight, 170 parts by weight, 175 parts by weight, 180 parts by weight, 185 parts by weight, 190 parts by weight, 195 parts by weight, 200 parts by weight, etc.; and the castor oil 50-100 parts by weight can be 50 parts by weight. The quantities of the chain extender can be 50-100 parts by weight, such as 50 parts by weight, 55 parts by weight, 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, 85 parts by weight, 90 parts by weight, 95 parts by weight, and 100 parts by weight. The quantities of the catalyst can be 0.1-1 parts by weight, such as 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, and 1 part by weight.

[0067] Preferably, the isocyanate includes MDI (diphenylmethane diisocyanate), MDI-100L (4,4'-diphenylmethane diisocyanate modified with carbodiimide-urea ketimide), MDI-50 (a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate), and PM200 (polymethylene polyphenyl polyisocyanate, such as WANNATE).® any one or a combination of at least two of PM - 200), HDI (hexamethylene diisocyanate), or IPDI (isophorone diisocyanate).

[0068] Preferably, the plasticizer includes any one or a combination of at least two of dihexyl phthalate (DHP), diisodecyl phthalate (DIDP), diisononyl phthalate (DINP), dibutyl phthalate (DBP), or dioctyl phthalate (DOP / DEHP).

[0069] Preferably, the chain extender includes any one or a combination of at least two of 1,4 - butanediol, ethylene glycol, propylene glycol, glycerol, trimethylolpropane, or trimethylolethane.

[0070] Preferably, the calcium carbonate in component A and component B independently includes any one or a combination of at least two of white stone calcium carbonate CCR, bamboo - original calcium carbonate SP, Omya calcium carbonate 1T - JI, Omya calcium carbonate 2T - JI, Omya calcium carbonate 5T - JI, Omya calcium carbonate 1 - JI, Omya calcium carbonate 2 - JI, or Omya calcium carbonate 5 - JI.

[0071] Preferably, the silica includes any one or a combination of at least two of Evonik R202, Evonik R974, Wacker H18, or Anhui Zaisheng KS - 180.

[0072] The present invention only lists the calcium carbonate and silica that can be used, and does not mean that the present invention can only use the materials listed above.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] (1) The modified palm oil polyol obtained by the preparation method provided by the present invention can endow the polyurethane structural adhesive with the advantages of low viscosity, low hardness, and high bonding strength;

[0075] (2) The modified palm oil polyol obtained by the preparation method provided by the present invention has good wettability for the substrate to be bonded;

[0076] (3) Palm oil is a vegetable oil, which is safe and environmentally friendly. Detailed Embodiments

[0077] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0078] Unless otherwise specified, the raw materials involved in the following specific embodiments of the present invention are all conventional materials in the art, and can be purchased from commercially available products. Some raw material information is as follows:

[0079] 8℃ palm oil and 16℃ palm oil: both were purchased from Shandong Wantai Chemical Co., Ltd.

[0080] Castor oil: purchased from Nanjing Qianyue Chemical Co., Ltd.;

[0081] Isocyanate: MDI-100L, purchased from Wanhua Chemical;

[0082] PM200: Purchased from Wanhua Chemical, brand name WANNATE ® PM-200;

[0083] Polyester polyol: purchased from Asahikawa Chemical XCPA-320.

[0084] Preparation Example 1

[0085] This preparation example provides a method for preparing modified palm oil polyols and the modified palm oil polyols obtained therefrom, including:

[0086] (1) The palm oil and the alkali solution are mixed at 8°C with sodium hydroxide solution (concentration 25 wt%) and saponified at 90°C for 1.5 h. After the reaction is completed, saturated sodium chloride solution is added for salting out and the upper layer of fatty acid sodium mixture (upper oil layer) is separated.

[0087] (2) The sodium fatty acid mixture was mixed with hydrochloric acid solution (15 wt%). The amount of hydrochloric acid solution added was to make the pH of the reaction system 2.5. The acidification reaction was carried out at room temperature for 1 h. After the reaction was completed, the water layer and the oil layer were separated to obtain the fatty acid mixture (oil layer). The fatty acid mixture was washed with water until neutral and purified by dehydration under reduced pressure.

[0088] (3) According to the molar ratio of the carboxyl group of the mixed fatty acid and the hydroxyl group of the small molecule polyol, the purified fatty acid mixture was mixed with pentaerythritol, 1.5 wt% p-toluenesulfonic acid was added and esterification reaction was carried out at 140℃ for 4h. Sodium bicarbonate solution was added to remove the catalyst, the mixture was washed with water until neutral, and unreacted small molecule polyol and water were removed by vacuum distillation to obtain palm oil-based polyol ester.

[0089] (4) Mix formic acid solution (40 wt%) and hydrogen peroxide (34 wt%). The molar ratio of double bonds and hydrogen peroxide in palm oil-based polyol ester is 1:1.2. Slowly add the mixture to palm oil-based polyol ester and carry out epoxidation reaction at pH 4 and 60°C for 6 h. After the reaction is completed, remove excess organic acid (neutralize with sodium carbonate), wash with water until neutral, and remove impurities by vacuum distillation to obtain the modified palm oil polyol.

[0090] Performance testing

[0091] The modified palm oil polyols obtained were structurally characterized, and the results are as follows:

[0092] (1) Determination of epoxy group content: The test shall be conducted in accordance with the test standard of Method B in ASTM D1652 "Standard Test Method for Epoxy Content of Epoxy Resins";

[0093] (2) Hydroxyl value determination: The test shall be performed in accordance with the test method provided in DIN 53240-2;

[0094] The test results showed that the modified palm oil polyol obtained by the preparation method provided in Example 1 of this invention had an epoxy content of 0.9% and a hydroxyl value of 220 mgKOH / g.

[0095] Preparation Example 2

[0096] This preparation example provides a method for preparing modified palm oil polyols and the modified palm oil polyols obtained therefrom, including:

[0097] (1) The solute contained in palm oil and alkali solution is 1:3.1. Palm oil at 24℃ is mixed with sodium hydroxide solution (concentration 20 wt%) and saponified at 80℃ for 2 h. After the reaction is completed, saturated sodium chloride solution is added for salting out, and the upper layer of fatty acid sodium mixture (upper oil layer) is separated.

[0098] (2) The sodium fatty acid mixture was mixed with hydrochloric acid solution (10 wt%). The amount of hydrochloric acid solution added was to make the pH of the reaction system 2. The acidification reaction was carried out at 35℃ for 0.5 h. After the reaction was completed, the water layer and the oil layer were separated to obtain the fatty acid mixture (oil layer). The fatty acid mixture was washed with water until neutral and purified by dehydration under reduced pressure.

[0099] (3) According to the molar ratio of the carboxyl group of the mixed fatty acid and the hydroxyl group of the small molecule polyol being 1:1, the purified fatty acid mixture was mixed with trimethylolpropane, 2 wt% p-toluenesulfonic acid was added and esterification was carried out at 180°C for 3 h, sodium bicarbonate solution was added to remove the catalyst, the mixture was washed with water until neutral, and unreacted small molecule polyol and water were removed by vacuum distillation to obtain palm oil-based polyol ester.

[0100] (4) Mix acetic acid solution (50 wt%) and hydrogen peroxide (40 wt%). The molar ratio of double bonds and hydrogen peroxide in palm oil-based polyol ester is 1:1.3. Slowly add the mixture to palm oil-based polyol ester and carry out epoxidation reaction at pH 3 and 50℃ for 8 h. After the reaction is completed, remove excess organic acid (neutralize with sodium carbonate), wash with water until neutral, remove impurities by vacuum distillation, and obtain the modified palm oil polyol with epoxy content of 0.6% and hydroxyl value of 250 mgKOH / g.

[0101] Preparation Example 3

[0102] This preparation example provides a method for preparing modified palm oil polyols and the modified palm oil polyols obtained therefrom, including:

[0103] (1) The molar ratio of the solutes in palm oil and alkali solution is 1:3.3. The palm oil at 24℃ is mixed with sodium hydroxide solution (concentration 30 wt%) and saponified at 100℃ for 1 h. After the reaction is completed, saturated sodium chloride solution is added for salting out, and the upper layer of fatty acid sodium mixture (upper oil layer) is separated.

[0104] (2) The sodium fatty acid mixture was mixed with hydrochloric acid solution (20 wt%). The amount of hydrochloric acid solution added was to make the pH of the reaction system 3. The acidification reaction was carried out at room temperature for 2 h. After the reaction was completed, the water layer and the oil layer were separated to obtain the fatty acid mixture (oil layer). The fatty acid mixture was washed with water until neutral and purified by dehydration under reduced pressure.

[0105] (3) According to the molar ratio of the carboxyl group of the mixed fatty acid and the hydroxyl group of the small molecule polyol, the purified fatty acid mixture was mixed with glycerol, 1 wt% p-toluenesulfonic acid was added and esterification reaction was carried out at 120℃ for 5 h, sodium bicarbonate solution was added to remove the catalyst, water was washed until neutral, and unreacted small molecule polyol and water were removed by vacuum distillation to obtain palm oil-based polyol ester.

[0106] (4) Mix formic acid solution (30 wt%) and hydrogen peroxide (50 wt%). The molar ratio of double bonds and hydrogen peroxide in palm oil-based polyol ester is 1:1. Slowly add the mixture to palm oil-based polyol ester and carry out epoxidation reaction at pH 5 and 70℃ for 4 h. After the reaction is completed, remove excess organic acid (neutralize with sodium carbonate), wash with water until neutral, remove impurities by vacuum distillation, and obtain the modified palm oil polyol with epoxy content of 0.6% and hydroxyl value of 240 mgKOH / g.

[0107] Comparative Preparation Example 1

[0108] This preparation example provides a method for preparing epoxy-modified palm oil polyol and the modified palm oil polyol obtained therefrom. The modification is carried out according to Route 1 provided in "Preparation and Performance Analysis of Industrial Palm Oil Polyols and Their Polyurethanes". The molar ratio of epoxy groups and amino groups of EXPO-P to diethanolamine is 1:1.

[0109] Comparative Preparation Example 2

[0110] This preparation example provides a method for preparing epoxy-modified palm oil polyol and the modified palm oil polyol obtained therefrom. The modification is carried out according to Route 2 provided in "Preparation and Performance Analysis of Industrial Palm Oil Polyols and Their Polyurethanes", with a mass ratio of EXPO to diethanolamine of 1.5:1.

[0111] Comparative preparation example 3

[0112] This preparation example provides a method for preparing modified palm oil polyols and the modified palm oil polyols obtained therefrom.

[0113] The difference from Preparation Example 1 is that, in this comparative preparation example, the small molecule polyol was replaced with pentaerythritol (2,2-dimethyl-1,3-propanediol).

[0114] Comparative preparation example 4

[0115] This preparation example provides a method for preparing modified palm oil polyols and the modified palm oil polyols obtained therefrom.

[0116] The difference from Preparation Example 1 is that the epoxidation reaction in step (4) is not carried out in this comparative preparation example.

[0117] Example 1

[0118] This embodiment provides a two-component polyurethane structural adhesive, consisting of component A and component B in a 1:1 mass ratio, wherein:

[0119] Component A: 200 parts by weight of isocyanate (MDI-100L), 200 parts by weight of calcium carbonate (Omia 2T-JI), 100 parts by weight of plasticizer (DHP), and 20 parts by weight of silica (Evonik R202).

[0120] Component B: 200 parts by weight of calcium carbonate (Omia 2T-JI), 150 parts by weight of modified palm oil polyol provided in Preparation Example 1, 50 parts by weight of castor oil, 50 parts by weight of propylene glycol, and 0.1 parts by weight of dioctyltin dilaurate.

[0121] The preparation method is as follows:

[0122] (1) Dehydrate castor oil, modified palm oil polyol, calcium carbonate, silica and chain extender;

[0123] (2) The catalyst was pre-dispersed in the chain extender, and the filler and modified palm oil polyol were mixed (dispersed at 2000 rpm for 30 min), and then mixed with the remaining components in component A (homogenization, 60℃, 1 h) to obtain component A;

[0124] (3) Mix each component in component B at high speed (disperse at 2000 rpm for 30 min) to obtain component B.

[0125] Example 2

[0126] This embodiment provides a two-component polyurethane structural adhesive, consisting of component A and component B in a 1:1 mass ratio, wherein:

[0127] Component A: 250 parts by weight of isocyanate (PM200), 250 parts by weight of calcium carbonate (White Stone CCR), 150 parts by weight of plasticizer (DBP), and 25 parts by weight of silica (Black Wacker H18).

[0128] Component B: 250 parts by weight of calcium carbonate (white stone CCR), 200 parts by weight of modified palm oil polyol provided in Preparation Example 2, 100 parts by weight of castor oil, 100 parts by weight of ethylene glycol, and 1 part by weight of dioctyltin dilaurate.

[0129] The preparation method is the same as in Example 1.

[0130] Example 3

[0131] This embodiment provides a two-component polyurethane structural adhesive, consisting of component A and component B in a 1:1 mass ratio, wherein:

[0132] Component A: 220 parts by weight of isocyanate (HDI), 220 parts by weight of calcium carbonate (Omia 2T-JI), 120 parts by weight of plasticizer (DINP), and 22 parts by weight of silica (Evonik R202);

[0133] Component B: 220 parts by weight of calcium carbonate (Omia 2T-JI), 180 parts by weight of modified palm oil polyol provided in Preparation Example 3, 80 parts by weight of castor oil, 80 parts by weight of 1,4-butanediol, and 0.5 parts by weight of dibutyltin dilaurate.

[0134] The preparation method is the same as in Example 1.

[0135] Example 4

[0136] This embodiment provides a two-component polyurethane structural adhesive, consisting of component A and component B in a 1:1 mass ratio, wherein:

[0137] Component A: 220 parts by weight of isocyanate (MDI-50), 220 parts by weight of calcium carbonate (Omia 5T-JI), 120 parts by weight of plasticizer (DINP), and 22 parts by weight of silica (Evonik R202).

[0138] Component B: 220 parts by weight of calcium carbonate (Omia 5T-JI), 180 parts by weight of modified palm oil polyol provided in Preparation Example 1, 50 parts by weight of castor oil, 80 parts by weight of trimethylolpropane, and 0.7 parts by weight of dibutyltin dilaurate.

[0139] The preparation method is the same as in Example 1.

[0140] Comparative Examples 1-4

[0141] This comparative example provides a two-component polyurethane structural adhesive.

[0142] The difference from Example 1 is that, in this comparative example, the modified palm oil polyol provided in Preparation Example 1 is replaced with the modified polyol provided in Comparative Preparation Examples 1-4.

[0143] Comparative Example 5

[0144] This comparative example provides a two-component polyurethane structural adhesive.

[0145] The difference from Example 1 is that, in this comparative example, the modified palm oil polyol provided in Preparation Example 1 is replaced with a polyester polyol.

[0146] Performance testing:

[0147] The performance of the two-component polyurethane structural adhesives provided in the examples and comparative examples was tested using the following methods:

[0148] (1) Viscosity: The viscosity was tested using a Brookfield DV2 RV rotational viscometer, with a 7# rotor, 20-40 rpm, and 25℃.

[0149] (2) Hardness: Tested using a Shore D hardness tester.

[0150] (3) Adhesion performance: 3003 aluminum was used as the base material, and the sample was prepared and tested in accordance with GB / T 7124-2008 standard.

[0151] The results are shown in Table 1:

[0152] Table 1

[0153]

[0154] As can be seen from the examples and performance tests, adding the modified palm oil polyol prepared by the preparation method provided by the present invention to the polyurethane structural adhesive can give the polyurethane structural adhesive the advantages of low viscosity, low hardness and high bonding strength. The viscosity of the polyurethane structural adhesive is ≤80000 cps, the hardness is ≤50 D, and the bonding strength with aluminum is about 9-12 MPa.

[0155] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A two-component polyurethane structural adhesive, characterized in that, Including component A and component B in a mass ratio of 1:1, by weight: Component A comprises: 200-250 parts by weight of isocyanate, 200-250 parts by weight of calcium carbonate, 100-150 parts by weight of plasticizer, and 20-25 parts by weight of silica. Component B comprises: 200-250 parts by weight of calcium carbonate, 150-200 parts by weight of modified palm oil polyol, 50-100 parts by weight of castor oil, 50-100 parts by weight of chain extender, and 0.1-1 parts by weight of catalyst. The method for preparing the modified palm oil polyol includes: (1) Palm oil is saponified using an alkaline solution to obtain a mixture of fatty acid salts; (2) The crude fatty acid salts are acidified with acid to obtain mixed fatty acids; (3) Mixed fatty acids and small molecule polyols are mixed and subjected to esterification reaction to obtain palm oil-based polyol esters. The small molecule polyols are selected from any one or at least two of glycerol, pentaerythritol, trimethylolpropane or xylitol. The molar ratio of the carboxyl group of the mixed fatty acids to the hydroxyl group of the small molecule polyols is 1:(1-3). (4) The palm oil-based polyol ester undergoes an epoxidation reaction to obtain the modified palm oil polyol; The isocyanate is selected from any one or a combination of at least two of MDI, HDI or IPDI; The plasticizer is selected from any one or a combination of at least two of dihexyl phthalate, diisodecyl phthalate, diisononyl phthalate, dibutyl phthalate or dioctyl phthalate; The chain extender is selected from any one or a combination of at least two of 1,4-butanediol, ethylene glycol, propylene glycol, glycerol, trimethylolpropane, or trimethylolethane.

2. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The solutes contained in the alkaline solution in step (1) include sodium hydroxide and / or potassium hydroxide; In step (1), the molar ratio of the solute contained in the palm oil and the alkali solution is 1:(3.0-3.3); The saponification reaction in step (1) is carried out at a temperature of 80-100℃ for 1-2 hours. Step (1) also includes salting out the mixed fatty acid salt after the saponification reaction is completed.

3. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The pH value of the acidification reaction in step (2) is 2-3; The solutes contained in the acid solution in step (2) include hydrogen chloride.

4. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The esterification reaction in step (3) is carried out under the catalysis of a catalyst selected from any one or a combination of at least two of tetraisopropyl titanate, tetrabutyl titanate, dibutyltin oxide, monobutyltin oxide, or p-toluenesulfonic acid. The amount of catalyst added is 1-2 wt% of the total mass of the mixed fatty acids and small molecule polyols. The esterification reaction in step (3) is carried out at a temperature of 120-180℃ for 3-5 hours.

5. The two-component polyurethane structural adhesive according to claim 1, characterized in that, Step (4) includes: epoxidizing palm oil-based polyol esters with hydrogen peroxide under organic acid catalysis to obtain the modified palm oil polyol.

6. The two-component polyurethane structural adhesive according to claim 5, characterized in that, The organic acids include formic acid and / or acetic acid; The amount of organic acid added makes the pH of the epoxidation reaction system 3-5; The palm oil-based polyol ester contains a double bond and hydrogen peroxide in a molar ratio of 1:(1-1.3). The epoxidation reaction is carried out at a temperature of 50-70℃ for 4-8 hours.

7. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The modified palm oil polyol has an epoxy value of 0.3-1.1% and a hydroxyl value of 200-250 mgKOH / g.

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