A low-carbon, drainage-resistant polyurethane adhesive and its preparation method

Abstract

This invention discloses a low-carbon, water-repellent polyurethane adhesive and its preparation method, belonging to the field of polymer processing technology. The polyurethane adhesive, by weight, comprises the following raw materials: polyurethane prepolymer, modified silica, 1-butyl-3-methylimidazolium hydrogen sulfate, a water-repellent agent, an organobismuth catalyst, and a defoamer. First, the modified silica and 1-butyl-3-methylimidazolium hydrogen sulfate are ball-milled and mixed to obtain a modified silica pre-dispersion. Then, the polyurethane prepolymer is added dropwise to the modified silica pre-dispersion, followed by the addition of the defoamer and stirring to obtain a polyurethane-modified silica dispersion. Finally, the water-repellent agent and the organobismuth catalyst are added sequentially to the polyurethane-modified silica dispersion, and the mixture is filtered to obtain the final product. The polyurethane adhesive provided by this invention exhibits excellent water-repellent and hydrophobic properties, maintains adhesiveness and adhesive layer rigidity in humid environments, and meets low-carbon and environmentally friendly requirements.

Description

Technical Field

[0001] This invention belongs to the field of polymer processing technology, specifically relating to a low-carbon, water-repellent polyurethane adhesive and its preparation method. Background Technology

[0002] Polyurethane adhesives, as high-performance adhesives, are widely used in many fields such as construction, woodworking, shoemaking, packaging, automotive, aerospace, machinery, electronics, textiles and leather, and bookbinding. Their excellent bonding properties have also led to their increased application in areas such as building waterproofing and pipe repair.

[0003] With increasingly stringent environmental protection requirements, the high carbon emissions and environmental pollution problems of traditional adhesives are becoming increasingly prominent, leading to a growing market demand for low-carbon and environmentally friendly adhesives. Low-carbon, water-repellent polyurethane adhesives have emerged to address this need, aiming to reduce carbon emissions during production and use while meeting the performance requirements of adhesives in drainage applications. Ordinary polyurethane adhesives have poor water resistance; in humid environments, their bond strength decreases, and they are easily affected by water molecules, resulting in performance degradation.

[0004] While current polyurethane adhesives have many advantages, they still have some drawbacks that limit their application in specific fields. Therefore, it is essential to develop a high-performance, adaptable, low-carbon, and drainage-resistant polyurethane adhesive. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a low-carbon drainage polyurethane adhesive and its preparation method.

[0006] The first aspect of this invention is to provide a low-carbon, drainage-resistant polyurethane adhesive, comprising, by weight, the following raw materials: 100 parts of polyurethane prepolymer, 20-40 parts of modified silica, 2-8 parts of 1-butyl-3-methylimidazolium hydrogen sulfate, 6-12 parts of drainage agent, 0.05-0.7 parts of organic bismuth catalyst, and 0.01-0.5 parts of defoamer;

[0007] The polyurethane prepolymer is an isocyanate-terminated prepolymer; the drainage agent is a composite modified bentonite obtained by modifying bentonite with cationic surfactant.

[0008] In some embodiments, the low-carbon drainage polyurethane adhesive comprises, by weight, the following raw materials: 100 parts of polyurethane prepolymer, 25-35 parts of modified silica, 4-6 parts of 1-butyl-3-methylimidazolium hydrogen sulfate, 8-10 parts of drainage agent, 0.1-0.5 parts of organic bismuth catalyst, and 0.1-0.3 parts of defoamer.

[0009] In some embodiments, the composite modified bentonite is prepared by the following steps:

[0010] (1) Disperse calcium-based bentonite in deionized water, add hydrochloric acid dropwise to react, and obtain a wet filter cake after centrifugation and washing;

[0011] (2) Disperse the wet filter cake obtained in step (1) in deionized water, add sodium carbonate to adjust the pH value, and dry to obtain activated bentonite;

[0012] (3) Add octadecyltrimethylammonium chloride dropwise to the activated bentonite obtained in step (2), mix and react, then add isooctyltriethoxysilane and catalyst in sequence, and dry to obtain composite modified bentonite.

[0013] It should be noted that this invention first dissolves the Ca between the bentonite layers through acidification. 2+ Mg 2+ Fe 3+ Impurity ions are removed to eliminate ion bridging effects and promote interlayer separation. Simultaneously, acid etching removes alumina octahedrons from the mineral, increasing the specific surface area. Then, sodium carbonate is added to induce sodium ion hydration, and sodium carbonate replaces H₂. + Na-bentonite is produced, Na + A large hydration radius can expand the interlayer spacing of bentonite, which is beneficial for the subsequent insertion of quaternary ammonium salt macromolecules.

[0014] The quaternary ammonium cations of octadecyltrimethylammonium chloride (OTAC) are readily attracted to the interlayer region by negatively charged bentonite layers. Simultaneously, these quaternary ammonium cations can displace the original Na+ in the bentonite interlayer. + or H + By forming ionic bonds, OTAC, with its long molecular chain, expands the interlayer spacing of bentonite, providing nanochannels for drainage. After hydrolysis, isooctyltriethoxysilane covalently bonds with the hydroxyl groups on the bentonite surface to form a hydrophobic film. Because isooctyl has a highly branched carbon chain structure, it is easier to form a dense molecular arrangement than straight-chain alkyl, thereby reducing the surface energy of bentonite, making it difficult for water molecules to spread, and improving the hydrophobicity of the composite modified bentonite.

[0015] In some embodiments, the hydrochloric acid concentration is 25-35% by mass, and the amount of hydrochloric acid used is 10-20% of the mass of calcium-based bentonite; the pH value is 8-9.

[0016] In some embodiments, the mass ratio of octadecyltrimethylammonium chloride to activated bentonite is 1:18-22; the mass ratio of isooctyltriethoxysilane to octadecyltrimethylammonium chloride is 2-4:5; the catalyst is selected from at least one of acetic acid, hydrochloric acid, phosphoric acid, citric acid, and oxalic acid, and the amount of catalyst used is 3-4% of the amount of isooctyltriethoxysilane.

[0017] In some embodiments, the polyurethane prepolymer is an isocyanate-terminated prepolymer; the organic bismuth catalyst is selected from at least one of bismuth isopropoxide, bismuth monobutyl ether glycol, and bismuth acetylacetone; and the defoamer is selected from at least one of alkoxy-terminated polyether silicone oil and ethoxylated acetylenol.

[0018] A second aspect of this invention is to provide a method for preparing a low-carbon, water-repellent polyurethane adhesive, comprising the following steps:

[0019] S1: Pretreated modified silica and 1-butyl-3-methylimidazolium hydrogen sulfate were ball-milled and mixed to obtain a modified silica pre-dispersion.

[0020] S2: Add polyurethane prepolymer dropwise to the modified silica predispersant obtained in S1, then add defoamer and stir to mix, to obtain polyurethane-modified silica dispersion;

[0021] S3: Add a drainage agent and an organic bismuth catalyst sequentially to the polyurethane-modified silica dispersion obtained in S2, and then filter to obtain a low-carbon drainage polyurethane adhesive.

[0022] S1-S3 were all carried out under inert gas protection.

[0023] In some embodiments, in S1, the modified silica is obtained by hydrophobically modifying silica with silane coupling agent KH-570.

[0024] In some embodiments, in S2, the temperature of the modified silica predispersant is 5-8°C, the dropping rate of the polyurethane prepolymer is 1.5 parts / min, and the stirring speed is 700-900 rpm.

[0025] In some embodiments, in S3, the temperature of the polyurethane-modified silica dispersion is 35-45°C, and the filtration mesh size is 150-250 mesh.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention creatively incorporates composite modified bentonite as a drainage agent into polyurethane adhesives. Isooctylsilane forms a dense superhydrophobic film on the surface of bentonite particles. The interlayer domains expanded by quaternary ammonium salt intercalation generate strong capillary forces, actively drawing in residual micro-pore water films (such as pore water on the surface of modified silica) at the substrate interface. This water is then drained to the outside of the adhesive layer through nanochannels, ensuring that the interior of the adhesive is in a dry environment and enhancing the drainage performance of the polyurethane adhesive.

[0028] 2. In addition to the composite modified bentonite, the present invention also adds ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate to the polyurethane adhesive. In a humid environment, the ionic liquid will catalyze the hydrolysis reaction between the terminal isocyanate group (-NCO) of the terminal isocyanate group prepolymer and the interfacial water molecules to generate a highly active primary amine. The newly generated primary amine will react with another -NCO group of the terminal isocyanate group prepolymer to form a high-strength urea bond to complete the cross-linking and curing, thereby maintaining the rigidity of the adhesive layer in a humid environment.

[0029] 3. The preparation method provided by this invention uses recycled plastics and natural minerals to replace petrochemical raw materials, reducing the carbon footprint. Room temperature curing eliminates the energy consumption of high-temperature baking, reducing carbon emissions and achieving environmental protection and low carbon emissions. The polyurethane adhesive prepared has excellent drainage and hydrophobicity, and can maintain adhesiveness and adhesive layer rigidity in humid environments, solving the technical problem of adhesives being prone to failure when wet. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments.

[0031] Example 1

[0032] A low-carbon, drainage-friendly polyurethane adhesive, by weight, comprises the following raw materials: 100 parts of terminal isocyanate-based prepolymer, 30 parts of modified silica, 5 parts of 1-butyl-3-methylimidazolium hydrogen sulfate, 8 parts of drainage agent, 0.3 parts of organic bismuth catalyst, and 0.2 parts of defoamer.

[0033] The drainage agent is a composite modified bentonite obtained by modifying bentonite with a cationic surfactant. The composite modified bentonite is prepared by the following steps:

[0034] (1) Disperse calcium-based bentonite in deionized water, add hydrochloric acid with a mass percentage concentration of 30% dropwise to react, and obtain a wet filter cake after centrifugation and washing; the amount of hydrochloric acid used is 15% of the mass of calcium-based bentonite;

[0035] (2) Disperse the wet filter cake obtained in step (1) in deionized water, add sodium carbonate to adjust the pH value to 8-9, and dry to obtain activated bentonite;

[0036] (3) Add octadecyltrimethylammonium chloride dropwise to the activated bentonite obtained in step (2), mix and react, then add isooctyltriethoxysilane and acetic acid in sequence, and dry to obtain composite modified bentonite; the mass ratio of octadecyltrimethylammonium chloride to activated bentonite is 1:20; the mass ratio of isooctyltriethoxysilane to octadecyltrimethylammonium chloride is 3:5; the amount of catalyst is 3.5% of the amount of isooctyltriethoxysilane.

[0037] The above-mentioned low-carbon, water-repellent polyurethane adhesive is prepared by the following steps:

[0038] S1: Modified silica obtained by hydrophobic modification of silica with silane coupling agent KH-570, and 1-butyl-3-methylimidazolium hydrogen sulfate are ball-milled and mixed to obtain modified silica pre-dispersion;

[0039] S2: Cool the modified silica predispersant obtained in S1 to 6°C, then add isocyanate-terminated prepolymer dropwise at a rate of 1.5 parts / min, and finally add alkoxy-terminated polyether silicone oil and stir at 800 rpm to obtain polyurethane-modified silica dispersion.

[0040] S3: The polyurethane-modified silica dispersion obtained in S2 is heated to 40°C, and then the drainage agent and bismuth isopropoxide are added in sequence. After filtration through a 200-mesh filter, a low-carbon drainage polyurethane adhesive is obtained.

[0041] S1-S3 were all carried out under inert gas protection.

[0042] Example 2

[0043] A low-carbon, drainage-resistant polyurethane adhesive, by weight, comprises the following raw materials: 100 parts of isocyanate-terminated prepolymer, 40 parts of modified silica, 8 parts of 1-butyl-3-methylimidazolium hydrogen sulfate, 12 parts of drainage agent, 0.7 parts of organic bismuth catalyst, and 0.5 parts of defoamer.

[0044] The drainage agent is a composite modified bentonite obtained by modifying bentonite with a cationic surfactant. The composite modified bentonite is prepared by the following steps:

[0045] (1) Disperse calcium-based bentonite in deionized water, add hydrochloric acid with a mass percentage concentration of 35% dropwise to react, and obtain a wet filter cake after centrifugation and washing; the amount of hydrochloric acid used is 20% of the mass of calcium-based bentonite;

[0046] (2) Disperse the wet filter cake obtained in step (1) in deionized water, add sodium carbonate to adjust the pH value to 8-9, and dry to obtain activated bentonite;

[0047] (3) Add octadecyltrimethylammonium chloride dropwise to the activated bentonite obtained in step (2), mix and react, then add isooctyltriethoxysilane and hydrochloric acid in sequence, and dry to obtain composite modified bentonite; the mass ratio of octadecyltrimethylammonium chloride to activated bentonite is 1:22; the mass ratio of isooctyltriethoxysilane to octadecyltrimethylammonium chloride is 4:5; the amount of catalyst is 4% of the amount of isooctyltriethoxysilane.

[0048] The above-mentioned low-carbon, water-repellent polyurethane adhesive is prepared by the following steps:

[0049] S1: Modified silica obtained by hydrophobic modification of silica with silane coupling agent KH-570, and 1-butyl-3-methylimidazolium hydrogen sulfate are ball-milled and mixed to obtain modified silica pre-dispersion;

[0050] S2: Cool the modified silica predispersant obtained in S1 to 5℃, then add terminal isocyanate prepolymer dropwise at a rate of 1.5 parts / min, and finally add ethoxylated acetylene glycol and stir at 900 rpm to obtain polyurethane-modified silica dispersion.

[0051] S3: The polyurethane-modified silica dispersion obtained in S2 is heated to 45°C, and then the drainage agent and ethylene glycol monobutyl ether bismuth are added in sequence. After filtration through a 250-mesh filter, a low-carbon drainage polyurethane adhesive is obtained.

[0052] S1-S3 were all carried out under inert gas protection.

[0053] Example 3

[0054] A low-carbon, drainage-resistant polyurethane adhesive, by weight, comprises the following raw materials: 100 parts of terminal isocyanate-based prepolymer, 20 parts of modified silica, 2 parts of 1-butyl-3-methylimidazolium hydrogen sulfate, 6 parts of drainage agent, 0.05 parts of organic bismuth catalyst, and 0.01 parts of defoamer.

[0055] The drainage agent is a composite modified bentonite obtained by modifying bentonite with a cationic surfactant. The composite modified bentonite is prepared by the following steps:

[0056] (1) Disperse calcium-based bentonite in deionized water, add hydrochloric acid with a mass percentage concentration of 25% dropwise to react, and obtain a wet filter cake after centrifugation and washing; the amount of hydrochloric acid used is 10% of the mass of calcium-based bentonite;

[0057] (2) Disperse the wet filter cake obtained in step (1) in deionized water, add sodium carbonate to adjust the pH value to 8-9, and dry to obtain activated bentonite;

[0058] (3) Add octadecyltrimethylammonium chloride dropwise to the activated bentonite obtained in step (2), mix and react, then add isooctyltriethoxysilane and phosphoric acid in sequence, and dry to obtain composite modified bentonite; the mass ratio of octadecyltrimethylammonium chloride to activated bentonite is 1:18; the mass ratio of isooctyltriethoxysilane to octadecyltrimethylammonium chloride is 2:5; the amount of catalyst is 3% of the amount of isooctyltriethoxysilane.

[0059] The above-mentioned low-carbon, water-repellent polyurethane adhesive is prepared by the following steps:

[0060] S1: Modified silica obtained by hydrophobic modification of silica with silane coupling agent KH-570, and 1-butyl-3-methylimidazolium hydrogen sulfate are ball-milled and mixed to obtain modified silica pre-dispersion;

[0061] S2: Cool the modified silica predispersant obtained in S1 to 8°C, then add isocyanate-terminated prepolymer dropwise at a rate of 1.5 parts / min, and finally add alkoxy-terminated polyether silicone oil and stir at 700 rpm to obtain polyurethane-modified silica dispersion.

[0062] S3: The polyurethane-modified silica dispersion obtained in S2 is heated to 35°C, and then the drainage agent and organic bismuth acetylacetone bismuth are added in sequence. After filtration through a 150-mesh filter, a low-carbon drainage polyurethane adhesive is obtained.

[0063] S1-S3 were all carried out under inert gas protection.

[0064] Example 4

[0065] It is basically the same as Example 1, except that:

[0066] The low-carbon, drainage-resistant polyurethane adhesive provided in this embodiment comprises the following raw materials by weight: 100 parts of terminal isocyanate-based prepolymer, 35 parts of modified silica, 6 parts of 1-butyl-3-methylimidazolium hydrogen sulfate, 10 parts of drainage agent, 0.5 parts of organic bismuth catalyst, and 0.3 parts of defoamer.

[0067] Example 5

[0068] It is basically the same as Example 1, except that:

[0069] The low-carbon, drainage-resistant polyurethane adhesive provided in this embodiment comprises the following raw materials by weight: 100 parts of terminal isocyanate-based prepolymer, 25 parts of modified silica, 4 parts of 1-butyl-3-methylimidazolium hydrogen sulfate, 8 parts of drainage agent, 0.1 parts of organic bismuth catalyst, and 0.1 parts of defoamer.

[0070] Comparative Example 1

[0071] It is basically the same as Example 1, except that 1-butyl-3-methylimidazolium hydrogen sulfate is not added.

[0072] Comparative Example 2

[0073] It is basically the same as Example 1, except that the composite modified bentonite is replaced with the same amount of ordinary bentonite.

[0074] To demonstrate the excellent drainage properties of the low-carbon, water-repellent polyurethane adhesive provided by this invention, performance tests were conducted on Examples 1-5 and Comparative Examples 1-2, and the test results are shown in Table 1.

[0075] (1) Peel strength test: Polyurethane adhesive was applied to the surface of a rigid PVC sheet, and the coated surface was bonded to another rigid PVC sheet. The sheet was dried at 50°C and then pressed at 1.2 MPa for 10 seconds. After 24 hours at 25°C and 90% humidity, the peel strength was measured using a tensile testing machine at 200 mm / min. -1 The data is recorded by pulling at a certain speed.

[0076] (2) Water absorption test: Pour the adhesive into a container, let it cure and then demold it. Weigh the mass of the sample as w1, then soak it in deionized water. After 72 hours, take it out, blow dry the surface moisture, weigh the mass of the sample as w2, and calculate the water absorption rate of the adhesive = (w2-w1) / w1×100%.

[0077] (3) Contact angle test: The water contact angle was tested using the KrassDSA100 surface contact angle meter and the pendant drop method. The test temperature was 25℃. Five different locations of the same sample were selected for measurement, and the average value was taken as the final result of the contact angle.

[0078] Table 1

[0079]

[0080] As shown in Table 1, the low-carbon, drainage-resistant polyurethane adhesive prepared in the embodiments of the present invention exhibits excellent peel strength and hydrophobic drainage properties. Compared to Comparative Examples 1-2, the adhesives of Comparative Examples 1-2 show a decrease in both bonding strength and drainage / hydrophobicity due to the absence of retro-modified bentonite and 1-butyl-3-methylimidazolium hydrogen sulfate.

[0081] The low-carbon, water-repellent polyurethane adhesive prepared in Example 1 was tested. The test results for the total volatile organic compounds were in accordance with ISO 12219-2-2012, the test results for the total aldehydes and ketones were in accordance with ISO 12219-2-2012, and the test results for TVOC (total volatile organic compounds) were in accordance with ISO 12219-2-2012. The test results are shown in Table 2.

[0082] Table 2

[0083]

[0084] As can be seen from Table 2, the low-carbon drainage polyurethane adhesive prepared in Example 1 of the present invention has the characteristics of low VOC and zero formaldehyde. The composition of Examples 2-5 is basically the same as that of Example 1, and all meet the requirements of low-carbon and environmental protection.

[0085] The above descriptions are merely some embodiments of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A low carbon emission polyurethane adhesive, characterized by, By weight parts, including the following raw materials: polyurethane prepolymer 100 parts, modified silica 20-40 parts, 1-butyl-3-methyl imidazole hydrogen sulfate 2-8 parts, drainage agent 6-12 parts, organic bismuth catalyst 0.05-0.7 parts, defoaming agent 0.01-0.5 parts; Wherein, the polyurethane prepolymer is an isocyanate-terminated prepolymer; the drainage agent is a composite modified bentonite obtained by modifying bentonite with a cationic surfactant; The composite modified bentonite is prepared by the following steps: (1) Disperse calcium-based bentonite in deionized water, add hydrochloric acid dropwise and react, then wash by centrifugation to obtain a wet cake; (2) Disperse the wet cake obtained in step (1) in deionized water, add sodium carbonate to adjust the pH value, and dry to obtain activated bentonite; (3) Add octadecyl trimethyl ammonium chloride dropwise to the activated bentonite obtained in step (2), mix and react, then add isooctyl triethoxysilane and a catalyst in sequence, and dry to obtain the composite modified bentonite.

2. The low carbon emission polyurethane adhesive according to claim 1, characterized in that, By weight parts, the low-carbon drainage polyurethane adhesive comprises the following raw materials: polyurethane prepolymer 100 parts, modified silica 25-35 parts, 1-butyl-3-methyl imidazole hydrogen sulfate 4-6 parts, drainage agent 8-10 parts, organic bismuth catalyst 0.1-0.5 parts, defoaming agent 0.1-0.3 parts.

3. The low carbon emission polyurethane adhesive according to claim 1, characterized in that, The mass percentage concentration of the hydrochloric acid is 25-35%, and the amount of the hydrochloric acid is 10-20% of the mass of the calcium-based bentonite; the pH value is 8-9.

4. The low carbon emission polyurethane adhesive according to claim 1, characterized in that, The mass ratio of the octadecyl trimethyl ammonium chloride to the activated bentonite is 1:18-22; the mass ratio of the isooctyl triethoxysilane to the octadecyl trimethyl ammonium chloride is 2-4:5; the catalyst is selected from at least one of acetic acid, hydrochloric acid, phosphoric acid, citric acid, and oxalic acid, and the amount of the catalyst is 3-4% of the amount of the isooctyl triethoxysilane.

5. The low carbon emission polyurethane adhesive according to claim 2, wherein, The organic bismuth catalyst is selected from at least one of bismuth isopropyl alcohol, bismuth ethylene glycol monobutyl ether, and bismuth acetylacetone; the defoaming agent is selected from at least one of an alkoxy-terminated polyether silicone oil and an ethoxylated alkyne diol.

6. A process for the production of a low-emission polyurethane adhesive according to any one of claims 1 to 5, characterized in that The method comprises the following steps: S1: Ball-mill mix modified silica and 1-butyl-3-methyl imidazole hydrogen sulfate to obtain a modified silica pre-dispersion; S2: Add polyurethane prepolymer dropwise to the modified silica pre-dispersion obtained in S1, then add a defoaming agent and stir to mix, to obtain a polyurethane-modified silica dispersion; S3: Add a drainage agent and an organic bismuth catalyst in sequence to the polyurethane-modified silica dispersion obtained in S2, and filter to obtain a low-carbon drainage polyurethane adhesive; Wherein, S1-S3 are all carried out under inert gas protection.

7. The method for preparing the low-carbon, drainage-resistant polyurethane adhesive according to claim 6, characterized in that, In S1, the modified silica is obtained by hydrophobic modification of silica with silane coupling agent KH-570.

8. The method for preparing the low-carbon, drainage-resistant polyurethane adhesive according to claim 6, characterized in that, In S2, the temperature of the modified silica pre-dispersion is 5-8℃, the dropwise adding speed of the polyurethane prepolymer is 1.5 parts / min, and the stirring speed is 700-900 rpm.

9. The method for preparing the low-carbon, drainage-resistant polyurethane adhesive according to claim 6, characterized in that, In S3, the temperature of the polyurethane-modified silica dispersion is 35-45℃, and the filter mesh number is 150-250.

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