Polypropylene hot-melt adhesive and method for producing the same

Abstract

The application discloses a polypropylene hot melt adhesive and a preparation method thereof, and belongs to the technical field of hot melt adhesives. The polypropylene hot melt adhesive comprises the following components in parts by weight: 10-20 parts of maleic anhydride modified polypropylene resin, 65-80 parts of polypropylene resin, 3-5 parts of a viscosity regulator, and 5-10 parts of modified montmorillonite. The polypropylene hot melt adhesive has good bonding performance, good aging resistance and good antibacterial property, and effectively avoids the agglomeration and migration of internal raw materials, so that the polypropylene hot melt adhesive can be applied to complex application scenarios.

Description

Technical Field

[0001] This invention relates to the field of hot melt adhesive technology, specifically to a polypropylene hot melt adhesive and its preparation method. Background Technology

[0002] Hot melt adhesive is a thermoplastic adhesive characterized by its reversible change in physical state with temperature within a specific temperature range, while its chemical properties remain stable. It is solid at room temperature, melts into a viscous liquid upon heating, and solidifies again upon cooling. Widely regarded as a "green" adhesive due to its solvent-free, pollution-free, rapid curing, and ease of application, it is widely used in packaging, automotive, and non-woven fabric industries.

[0003] Polypropylene hot melt adhesive is mainly composed of polyolefin resins, which have good thermal stability and corrosion resistance. It is particularly suitable for bonding non-polar substrates such as polypropylene and polyethylene, as well as composite materials such as paper and metal foil. Its excellent environmental properties and good mechanical properties make PP hot melt adhesive one of the mainstream products in the market.

[0004] However, existing polypropylene hot melt adhesives have significant shortcomings in terms of anti-aging performance. Under prolonged use or exposure to sunlight and high temperatures, the adhesive is prone to aging phenomena such as brittleness, peeling, loss of tack, and discoloration, leading to decreased bond strength and shortened service life. This problem is particularly prominent in outdoor applications, electronic device packaging, and solar modules, where high weather resistance is required, severely limiting the widespread application of traditional polypropylene hot melt adhesives. Chinese patent document CN103509494A discloses a high-viscosity hot melt adhesive, which is prepared from the following raw materials in parts by weight: Formosa Plastics 7240MEVA 80-90, polyolefin elastomer 20-30, antioxidant 1682-4, antioxidant 10761-2, antioxidant 10101-2, titanium dioxide 5-8, and composite filler 4-5. This invention provides a hot melt adhesive with good viscosity, excellent anti-aging effect, and long service life, making it suitable for applications in aviation, shipbuilding, and other fields with high requirements for hot melt adhesive performance. However, the antioxidant used in this patent is blended with the resin matrix. The antioxidant is prone to migration and loss during long-term use, which causes its anti-aging effect to gradually weaken over time, making it difficult to achieve long-lasting and stable anti-aging performance. Summary of the Invention

[0005] The main objective of this invention is to provide a polypropylene hot melt adhesive and its preparation method, which has good anti-aging properties, high bonding strength and long-lasting stability.

[0006] To achieve the above objectives, the present invention proposes a polypropylene hot melt adhesive comprising the following components by weight: 10-20 parts maleic anhydride modified polypropylene resin, 65-80 parts polypropylene resin, 3-5 parts viscosity modifier, and 5-10 parts modified montmorillonite.

[0007] This invention relates to a blend of maleic anhydride-modified polypropylene resin and polypropylene resin, which significantly improves the overall performance of the adhesive. By introducing polar maleic anhydride groups, the adhesion of the polypropylene matrix to the metal substrate is greatly improved. Simultaneously, it acts as a compatibilizer, promoting the uniform dispersion and interfacial bonding of polypropylene and modified montmorillonite, thus enhancing the mechanical properties of the adhesive. The viscosity modifier controls the melt index of the resin matrix, ensuring suitable flowability and substrate wettability of the molten adhesive, while avoiding adhesion failure caused by excessive flow at high temperatures. The modified montmorillonite is dispersed in the polypropylene matrix through intercalation or exfoliation, forming a nanocomposite structure. Its layers hinder the thermal motion of molecular chains, significantly improving the heat distortion temperature and dimensional stability of the adhesive. The adhesive maintains excellent shear strength and peel resistance even at high temperatures.

[0008] Preferably, the viscosity modifier is at least one of the following: naphthenic mineral oil, hydrogenated polybutadiene, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, oxidized polyethylene wax, polypropylene wax, and saxo-amyl wax.

[0009] Preferably, the modified montmorillonite is prepared as follows:

[0010] S1. Disperse montmorillonite in N,N-dimethylformamide, add dodecyl dimethylammonium chloride, stir to react, filter, collect the solid, wash and dry to obtain pretreated montmorillonite;

[0011] S2. Disperse the pretreated montmorillonite in a mixed solution of ethanol and water, add isocyanate-propyltriethoxysilane, heat to react, filter, collect the solid, wash and dry to obtain isocyanate-based montmorillonite;

[0012] S3. Disperse isocyanate-based montmorillonite in N,N-dimethylformamide, add 5-amino-2-mercaptobenzimidazole, heat the reaction, filter, collect the solid, wash and dry it, then disperse it in dimethyl sulfoxide, add 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate, D-limonene, and benzoin dimethyl ether, and carry out the ultraviolet light irradiation reaction, filter, collect the solid, wash and dry it to obtain modified montmorillonite.

[0013] Preferably, in step S1, the mass ratio of montmorillonite to dodecyl dimethyl ammonium chloride is 30-50:5-8; the stirring reaction temperature is 50-70℃, and the reaction time is 3-5h.

[0014] Preferably, in step S2, the mass ratio of pretreated montmorillonite to isocyanate-propyltriethoxysilane is 15-25:3-5; the heating reaction temperature is 40-60℃; and the reaction time is 4-6h.

[0015] Preferably, in step S3, the mass ratio of isocyanate-based montmorillonite, 5-amino-2-mercaptobenzimidazole, 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate, D-limonene, and benzoin dimethyl ether is 10-20:2.8-4.2:2-3:1-2:0.5-1.5; the heating reaction temperature is 30-50℃, and the reaction time is 1-2 hours.

[0016] The preparation of the modified montmorillonite of this invention first involves intercalation modification of the interlayer of montmorillonite with quaternary ammonium salts to increase the interlayer spacing and form a nanoscale layered barrier in the resin matrix. This barrier can be oriented to the bonding interface and extend the oxygen diffusion path, improving the aging resistance and antibacterial properties of the adhesive. Then, isocyanate groups are introduced on its surface to enhance its reactivity, which is beneficial for its reaction with 5-amino-2-mercaptobenzimidazole. The heteroatoms on 5-amino-2-mercaptobenzimidazole can coordinate with metals to form stable coordination bonds, improving the adhesion between the adhesive and the metal. Secondly, the benzimidazole ring system has excellent UV aging resistance, which helps to improve the aging resistance of the bonding interface and provides reaction sites for further functionalization. Finally, by UV-initiated grafting, benzotriazole UV-protective groups and antibacterial agents are introduced to the surface of montmorillonite, which are not easily migrated out, significantly improving the adhesiveness, antibacterial properties, and weather resistance of the adhesive.

[0017] The present invention also discloses a method for preparing the polypropylene hot melt adhesive, comprising the following steps:

[0018] Maleic anhydride modified polypropylene resin, polypropylene resin, viscosity modifier, and modified montmorillonite are mixed evenly and added to a high-speed mixer for uniform mixing. Then, the mixture is added to a melt extruder for melt extrusion and cooling, and granulation is performed to obtain a polypropylene hot melt adhesive.

[0019] This invention also discloses the application of the polypropylene hot melt adhesive in the fields of packaging, electronic products, solar cells, equipment care, household appliances, and road construction.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1) This invention provides a polypropylene hot melt adhesive that can ensure good adhesion performance, good weather resistance and antibacterial properties, and effectively avoid the agglomeration and migration of internal raw materials, so that the polypropylene hot melt adhesive can be applied in complex application scenarios.

[0022] 2) The preparation of the modified montmorillonite of the present invention firstly involves intercalation modification of montmorillonite with quaternary ammonium salt didodecyl dimethyl ammonium chloride, then treatment with isocyanate-propyltriethoxysilane to introduce the active isocyanate group on the surface of montmorillonite; then reaction with 5-amino-2-mercaptobenzimidazole to introduce the active mercapto group, and finally grafting 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate and D-limonene onto montmorillonite through a mercapto-olefin click reaction. Through modification, montmorillonite can be better dispersed in the resin matrix, forming a nanoscale layered barrier, which is oriented at the bonding interface and prolongs the oxygen diffusion path, thereby improving the aging resistance and antibacterial properties of the adhesive. Detailed Implementation

[0023] To avoid unnecessary details, unless otherwise specified, all items used in the following examples are commercially available products, and all methods used are conventional methods unless otherwise specified.

[0024] The sources of some of the raw materials used in this invention are as follows:

[0025] Maleic anhydride modified polypropylene resin, brand name Mitsui Japan, grade name QF551.

[0026] Polypropylene resin, brand Hanwha Total, grade HJ730, melt flow rate 2.1 g / 10 min.

[0027] Montmorillonite, sodium-based, 325 mesh, purchased from Jiayuan Mineral Products Processing Plant in Lingshou County.

[0028] Example 1

[0029] A method for preparing a polypropylene hot melt adhesive includes the following steps:

[0030] 45g of maleic anhydride modified polypropylene resin, 210g of polypropylene resin, 12g of paraffin wax, and 24g of modified montmorillonite were mixed evenly and then added to a high-speed mixer for even mixing. The mixture was then added to a melt extruder for melt extrusion and cooling, and granulated to obtain a polypropylene hot melt adhesive.

[0031] The modified montmorillonite is prepared as follows:

[0032] S1. Disperse 40g of montmorillonite into 200mL of N,N-dimethylformamide, add 7.2g of dodecyl dimethylammonium chloride, stir and react at 60℃ for 4h, filter, collect the solid, wash and dry to obtain pretreated montmorillonite;

[0033] S2. Disperse 20g of pretreated montmorillonite in a mixed solution of 100mL ethanol and 100mL water, add 4.1g of isocyanate-propyltriethoxysilane, heat at 50℃ for 5h, filter, collect the solid, wash and dry to obtain isocyanate-based montmorillonite.

[0034] S3. Disperse 15g of isocyanate-based montmorillonite in 200mL of N,N-dimethylformamide, add 3.5g of 5-amino-2-mercaptobenzimidazole, and react at 40℃ for 1.5h. Filter, collect the solid, wash, dry, and disperse in dimethyl sulfoxide. Add 2.5g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate, 1.5g of D-limonene, and 1g of benzoin dimethyl ether. Under ultraviolet light (UV intensity 500mW / cm²), react the mixture. 2 The reaction was carried out at a temperature of 45℃ for 25 minutes. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified montmorillonite.

[0035] Example 2

[0036] A method for preparing a polypropylene hot melt adhesive includes the following steps:

[0037] 30g of maleic anhydride modified polypropylene resin, 195g of polypropylene resin, 9g of paraffin wax, and 15g of modified montmorillonite were mixed evenly and then added to a high-speed mixer for even mixing. The mixture was then added to a melt extruder for melt extrusion and cooling, and granulated to obtain a polypropylene hot melt adhesive.

[0038] The modified montmorillonite is prepared as follows:

[0039] S1. Disperse 30g of montmorillonite into 200mL of N,N-dimethylformamide, add 5g of dodecyl dimethylammonium chloride, stir and react at 50℃ for 5h, filter, collect the solid, wash and dry to obtain pretreated montmorillonite;

[0040] S2. Disperse 15g of pretreated montmorillonite in a mixed solution of 100mL ethanol and 100mL water, add 3.2g of isocyanate-propyltriethoxysilane, heat at 40℃ for 6h, filter, collect the solid, wash and dry to obtain isocyanate-based montmorillonite.

[0041] S3. Disperse 10g of isocyanate-based montmorillonite in 200mL of N,N-dimethylformamide, add 2.8g of 5-amino-2-mercaptobenzimidazole, heat at 30℃ for 2h, filter, collect the solid, wash, dry, and disperse in dimethyl sulfoxide, add 2g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate, 1g of D-limonene, and 0.5g of benzoin dimethyl ether, and react under ultraviolet light (UV intensity 500mW / cm²). 2 The reaction was carried out at a temperature of 45℃ for 25 minutes. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified montmorillonite.

[0042] Example 3

[0043] A method for preparing a polypropylene hot melt adhesive includes the following steps:

[0044] 60g of maleic anhydride modified polypropylene resin, 240g of polypropylene resin, 15g of paraffin wax, and 30g of modified montmorillonite were mixed evenly and then added to a high-speed mixer for even mixing. The mixture was then added to a melt extruder for melt extrusion and cooling, and granulated to obtain a polypropylene hot melt adhesive.

[0045] The modified montmorillonite is prepared as follows:

[0046] S1. Disperse 50g of montmorillonite in 200mL of N,N-dimethylformamide, add 8g of dodecyl dimethylammonium chloride, stir and react at 70℃ for 3h, filter, collect the solid, wash and dry to obtain pretreated montmorillonite;

[0047] S2. Disperse 25g of pretreated montmorillonite in a mixed solution of 100mL ethanol and 100mL water, add 5g of isocyanate-propyltriethoxysilane, heat at 60℃ for 4h, filter, collect the solid, wash and dry to obtain isocyanate-based montmorillonite.

[0048] S3. Disperse 20g of isocyanate-based montmorillonite in 200mL of N,N-dimethylformamide, add 4.2g of 5-amino-2-mercaptobenzimidazole, heat at 50℃ for 2h, filter, collect the solid, wash, dry, and disperse in dimethyl sulfoxide, add 3g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate, 2g of D-limonene, and 1.5g of benzoin dimethyl ether, and react under ultraviolet light (UV intensity 500mW / cm²). 2 The reaction was carried out at a temperature of 45℃ for 25 minutes. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified montmorillonite.

[0049] Comparative Example 1

[0050] A method for preparing a polypropylene hot melt adhesive specifically includes the following steps:

[0051] 45g of maleic anhydride modified polypropylene resin, 210g of polypropylene resin, 12g of paraffin wax, and 24g of modified montmorillonite were mixed evenly and then added to a high-speed mixer for even mixing. The mixture was then added to a melt extruder for melt extrusion and cooling, and granulated to obtain a polypropylene hot melt adhesive.

[0052] The modified montmorillonite is prepared as follows:

[0053] S1. Disperse 40g of montmorillonite into 200mL of N,N-dimethylformamide, add 7.2g of dodecyl dimethylammonium chloride, stir and react at 60℃ for 4h, filter, collect the solid, wash and dry to obtain pretreated montmorillonite;

[0054] S2. Disperse 20g of pretreated montmorillonite in a mixed solution of 100mL ethanol and 100mL water, add 4.1g of isocyanate-propyltriethoxysilane, heat at 50℃ for 5h, filter, collect the solid, wash and dry to obtain isocyanate-based montmorillonite.

[0055] S3. Disperse 15g of isocyanate-based montmorillonite in 200mL of N,N-dimethylformamide, add 3.5g of 5-amino-2-mercaptobenzimidazole, and react at 40℃ for 1.5h. Filter, collect the solid, wash and dry it, and disperse it in dimethyl sulfoxide. Add 2.5g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate and 1g of benzoin dimethyl ether, and react under ultraviolet light (UV intensity 500mW / cm). 2 The reaction was carried out at a temperature of 45℃ for 25 minutes. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified montmorillonite.

[0056] Comparative Example 2

[0057] A method for preparing a polypropylene hot melt adhesive specifically includes the following steps:

[0058] 45g of maleic anhydride modified polypropylene resin, 210g of polypropylene resin, 12g of paraffin wax, and 24g of modified montmorillonite were mixed evenly and then added to a high-speed mixer for even mixing. The mixture was then added to a melt extruder for melt extrusion and cooling, and granulated to obtain a polypropylene hot melt adhesive.

[0059] The modified montmorillonite is prepared as follows:

[0060] S1. Disperse 40g of montmorillonite into 200mL of N,N-dimethylformamide, add 7.2g of dodecyl dimethylammonium chloride, stir and react at 60℃ for 4h, filter, collect the solid, wash and dry to obtain pretreated montmorillonite;

[0061] S2. Disperse 20g of pretreated montmorillonite in a mixed solution of 100mL ethanol and 100mL water, add 4.1g of isocyanate-propyltriethoxysilane, heat at 50℃ for 5h, filter, collect the solid, wash and dry to obtain isocyanate-based montmorillonite.

[0062] S3. Disperse 15g of isocyanate-based montmorillonite in 200mL of N,N-dimethylformamide, add 3.5g of 5-amino-2-mercaptobenzimidazole, and react at 40℃ for 1.5h. Filter, collect the solid, wash and dry it, and disperse it in dimethyl sulfoxide. Add 1.5g of D-limonene and 1g of benzoin dimethyl ether, and react under ultraviolet light (UV intensity 500mW / cm²). 2 The reaction was carried out at a temperature of 45℃ for 25 minutes. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified montmorillonite.

[0063] Comparative Example 3

[0064] A method for preparing a polypropylene hot melt adhesive includes the following steps:

[0065] 45g of maleic anhydride modified polypropylene resin, 210g of polypropylene resin, 12g of paraffin wax, and 24g of modified montmorillonite were mixed evenly and then added to a high-speed mixer for even mixing. The mixture was then added to a melt extruder for melt extrusion and cooling, and granulated to obtain a polypropylene hot melt adhesive.

[0066] The modified montmorillonite is prepared as follows:

[0067] S1. Disperse 40g of montmorillonite into 200mL of N,N-dimethylformamide, add 7.2g of dodecyl dimethylammonium chloride, stir and react at 60℃ for 4h, filter, collect the solid, wash and dry to obtain pretreated montmorillonite;

[0068] S2. Disperse 20g of pretreated montmorillonite in a mixed solution of 100mL ethanol and 100mL water, add 4.1g of isocyanate-propyltriethoxysilane, heat at 50℃ for 5h, filter, collect the solid, wash and dry to obtain isocyanate-based montmorillonite.

[0069] S3. Disperse 15g of isocyanate-based montmorillonite in dimethyl sulfoxide, add 2.5g of 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate, react at 45℃ for 25min, filter after reaction, collect the solid, wash and dry to obtain modified montmorillonite.

[0070] Performance testing

[0071] Aluminum / copper foil adhesion test: Using aluminum foil and copper foil as substrates, a 30µm thick adhesive film was prepared on a 170℃ film scraper and cut into 20mm×100mm strips. The strips were fixed on the backing plate, with the adhesive layer and the double-sided adhesive layer attached. The samples were peeled 180° at a peeling speed of 50mm / min. Five samples were tested for each strip, and the average value of the test results was taken.

[0072] Anti-aging test: The hot melt adhesives prepared in the examples and comparative examples were pressed into 1mm thick films at 160℃. The films were cut to size 25×150mm to make film samples. The samples were placed in a constant temperature chamber at 65℃ and 75% humidity for accelerated aging for 30 days. The peel strength of the samples before and after aging was tested respectively. The peel strength retention rate after aging was calculated. Peel strength retention rate % = peel strength after test / peel strength before test × 100%.

[0073] The test results are shown in Table 1:

[0074] Table 1 Performance test results of polypropylene hot melt adhesive

[0075]

[0076] Antibacterial performance test: The antibacterial performance was verified by the inhibition zone test. The cured adhesive layer was cut into small pieces of 0.5×0.5cm. The bacterial suspension was evenly spread on the surface of a sterilized agar plate. The adhesive layer was placed on the agar plate and incubated at 37℃ for 24 hours. The size of the inhibition zone was then measured. The test strain was Escherichia coli ATCC25922. The test results are shown in Table 2.

[0077] Table 2. Test results of antibacterial properties of polypropylene hot melt adhesives

[0078]

[0079]

[0080] As can be seen from the experimental results in Tables 1 and 2, the polypropylene hot melt adhesive prepared by this invention has good metal bonding performance, aging resistance and antibacterial properties.

[0081] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A polypropylene hot melt adhesive, characterized in that, It includes the following components by weight: 10-20 parts maleic anhydride modified polypropylene resin, 65-80 parts polypropylene resin, 3-5 parts viscosity modifier, and 5-10 parts modified montmorillonite. The modified montmorillonite is prepared as follows: S1. Disperse montmorillonite in N,N-dimethylformamide, add dodecyl dimethylammonium chloride, stir to react, filter, collect the solid, wash and dry to obtain pretreated montmorillonite; S2. Disperse the pretreated montmorillonite in a mixed solution of ethanol and water, add isocyanate-propyltriethoxysilane, heat to react, filter, collect the solid, wash and dry to obtain isocyanate-based montmorillonite; S3. Disperse isocyanate-based montmorillonite in N,N-dimethylformamide, add 5-amino-2-mercaptobenzimidazole, heat the reaction, filter, collect the solid, wash and dry it, then disperse it in dimethyl sulfoxide, add 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate, D-limonene, and benzoin dimethyl ether, and carry out the ultraviolet light irradiation reaction, filter, collect the solid, wash and dry it to obtain modified montmorillonite.

2. The adhesive according to claim 1, characterized in that: The viscosity modifier is at least one of the following: naphthenic mineral oil, hydrogenated polybutadiene, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, oxidized polyethylene wax, polypropylene wax, and saxo-amyl wax.

3. The adhesive according to claim 1, characterized in that: In step S1, the mass ratio of montmorillonite to dodecyl dimethyl ammonium chloride is 30-50:5-8.

4. The adhesive according to claim 1, characterized in that: In step S1, the stirring reaction temperature is 50-70℃ and the reaction time is 3-5h.

5. The adhesive according to claim 1, characterized in that: In step S2, the mass ratio of pretreated montmorillonite to isocyanate-propyltriethoxysilane is 15-25:3-5.

6. The adhesive according to claim 1, characterized in that: In step S2, the heating reaction temperature is 40-60℃ and the reaction time is 4-6h.

7. The adhesive according to claim 1, characterized in that, In step S3, the mass ratio of isocyanate-based montmorillonite, 5-amino-2-mercaptobenzimidazole, 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl-2-methacrylate, D-limonene, and benzoin dimethyl ether is 10-20:2.8-4.2:2-3:1-2:0.5-1.

5.

8. A method for preparing the adhesive according to any one of claims 1-7, characterized in that, Includes the following steps: Maleic anhydride modified polypropylene resin, polypropylene resin, viscosity modifier, and modified montmorillonite are mixed evenly and added to a high-speed mixer for uniform mixing. Then, the mixture is added to a melt extruder for melt extrusion and cooling, and granulation is performed to obtain a polypropylene hot melt adhesive.

9. The application of the adhesive according to any one of claims 1-7, characterized in that, The adhesive is applied in the fields of packaging, electronic products, solar cells, equipment care, household appliances, and road construction.

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