Anti-aging hot melt adhesive and preparation method thereof

Abstract

The invention provides an anti-aging hot melt adhesive and a preparation method thereof, and belongs to the technical field of hot melt adhesive preparation. The preparation process comprises the following steps: preparing the ultraviolet absorbent; preparing an anti-migration antioxidant; and preparing the hot melt adhesive. The preparation method comprises the following steps: adding anhydrous citric acid and cysteamine hydrochloride to carry out dehydration condensation reaction to produce a product, reacting the product with epoxy chloropropane, and then carrying out ring-opening polymerization reaction on the product and tetrahydrofuran; the hot melt adhesive prepared from the prepared ultraviolet absorbent and coupling agent modified montmorillonite loaded intramolecular synergistic macromolecular antioxidant containing thioether and aromatic secondary amine has good aging resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of hot melt adhesive preparation, and in particular to an aging-resistant hot melt adhesive and a preparation method thereof. Background Art

[0002] In modern industry and daily life, hot melt adhesives, as an important adhesive, are widely used in packaging, construction, automotive, electronics, textiles, and many other fields due to their advantages such as ease of use, fast curing speed, high bond strength, and reusability upon heating. However, when used in outdoor environments, hot melt adhesives often face severe aging challenges, such as degradation caused by UV radiation, performance degradation caused by thermal oxidation, and insufficient adhesion to various substrates. These problems seriously affect the service life and application range of hot melt adhesives.

[0003] Ultraviolet rays are a major factor contributing to the aging of hot-melt adhesives. Prolonged exposure to UV rays can cause the molecular structure of hot-melt adhesives to break and degrade, leading to a decrease in their physical and chemical properties, such as reduced bond strength and flexibility. To improve the UV resistance of hot-melt adhesives, the addition of UV absorbers is currently a common method. However, traditional UV absorbers are mostly small molecules that are prone to molecular migration within the hot-melt adhesive, leading to the loss of UV-absorbing groups and a gradual weakening of the UV resistance. This makes it difficult to effectively protect the hot-melt adhesive from UV rays over the long term, thus limiting its application in outdoor environments with high UV levels.

[0004] At the same time, thermal oxidative aging (OTA) is a significant issue during the high-temperature processing and use of hot-melt adhesives. This oxidative aging can cause oxidation reactions in the hot-melt adhesive molecules, generating free radicals that trigger a chain reaction, leading to molecular chain breakage and crosslinking, which in turn deteriorates the hot-melt adhesive's performance. Existing antioxidants in hot-melt adhesives lack sufficient anti-migration properties. Over time, antioxidants easily migrate out of the hot-melt adhesive, reducing their antioxidant efficiency and making them ineffective in effectively suppressing OTA reactions over the long term. This, in turn, impacts the hot-melt adhesive's stability and service life in high-temperature environments.

[0005] The present invention is based on the above-mentioned deficiencies of the prior art and provides a hot melt adhesive with excellent aging resistance and a preparation method thereof through innovative design of ultraviolet absorbers, antioxidants and resin systems. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide an aging-resistant hot melt adhesive and a preparation method thereof.

[0007] An aging-resistant hot melt adhesive comprises the following raw material components in parts by weight:

[0008] 30 - 50 parts by weight of graft - modified polyolefin, 20 - 30 parts by weight of graft - modified PPB resin, 25 - 30 parts by weight of tackifying resin, 2 - 3 parts by weight of anti - migration antioxidant, 5 - 8 parts by weight of ultraviolet absorber, 1 - 3 parts by weight of softener, 1 - 2 parts by weight of cross - linker and 1 - 2 parts by weight of initiator;

[0009] Among them, the graft - modified polyolefin is vinyltrimethoxysilane - modified α - polyolefin;

[0010] The graft - modified PPB resin is MAH - graft - modified PPB resin;

[0011] The anti - migration antioxidant is prepared by using pentaerythritol tetra(3 - mercaptopropionate), triethylamine, N-(4 - aminophenyl) maleimide, and tetrahydrofuran as raw materials to prepare an antioxidant and graft - loading it on coupling agent - modified montmorillonite to obtain the anti - migration antioxidant;

[0012] The ultraviolet absorber is an ultraviolet absorber prepared by reacting with anhydrous citric acid, cysteamine hydrochloride, epichlorohydrin, tetrabutylammonium bromide, tetrahydrofuran, dichloromethane, and boron trifluoride - diethyl ether complex as raw materials.

[0013] A preparation method of an aging - resistant hot - melt adhesive, comprising the following steps:

[0014] S1: Preparation of ultraviolet absorber

[0015] First, solid powder is prepared from anhydrous citric acid and cysteamine hydrochloride, and then it reacts with epichlorohydrin to obtain an intermediate product. Finally, it is mixed with tetrahydrofuran and dichloromethane to obtain mixture I. Dichloromethane and boron trifluoride - diethyl ether complex are mixed to obtain mixture II. The ultraviolet absorber is prepared by reacting mixture I and mixture II.

[0016] S2: Preparation of anti - migration antioxidant

[0017] Montmorillonite is modified with silane coupling agent KH570 to obtain coupling agent - modified montmorillonite. Then, N-(4 - aminophenyl) maleimide solution is added to the mixed solution of pentaerythritol tetra(3 - mercaptopropionate), triethylamine, and tetrahydrofuran. After reaction, coupling agent - modified montmorillonite and triethylamine are added, and the anti - migration antioxidant is obtained after further reaction.

[0018] S3: Preparation of hot - melt adhesive

[0019] First, α - polyolefin is modified with vinyltrimethoxysilane to obtain graft - modified polyolefin, and then PPB resin is modified with MAH to obtain graft - modified PPB resin. Then, the graft - modified polyolefin and the graft - modified PPB resin are first mixed, and then tackifying resin, anti - migration antioxidant, ultraviolet absorber, and softener are added. Finally, cross - linker and initiator are added to prepare the hot - melt adhesive.

[0020] Further, the preparation of the ultraviolet absorber in step S1 specifically includes the following steps:

[0021] S1.1: Add 18 - 23 parts by weight of anhydrous citric acid and 10 - 12 parts by weight of cysteamine hydrochloride to 100 - 120 parts by weight of deionized water. After stirring and mixing, react at 130 - 140 °C for 12 - 14 h. After grinding and pulverizing, wash with water, centrifuge, and dry in vacuum to obtain solid powder;

[0022] S1.2: Add 20 - 30 parts by weight of the solid powder to 30 - 40 parts by weight of sodium hydroxide solution. After fully shaking, let it stand for 4 - 5 h, and then dry at 80 - 82 °C. Mix 8 - 10 parts by weight of the dried product, 55 - 58 parts by weight of epichlorohydrin, and 0.2 - 0.3 parts by weight of tetrabutylammonium bromide catalyst, and place them in a beaker with condensable reflux. Then react at 105 - 110 °C for 4 - 5 h. Then add 30 - 50 parts by weight of neutral alumina, stir and mix, filter, and perform rotary evaporation. Add the product after rotary evaporation to a separatory funnel, add ethyl acetate and deionized water, mix evenly, let it stand, and take the upper clear liquid for rotary evaporation to obtain an intermediate product;

[0023] S1.3: Mix 2 - 3 parts by weight of the intermediate product, 5 - 8 parts by weight of tetrahydrofuran, and 50 - 80 parts by weight of dichloromethane to obtain mixture I. Mix 10 - 12 parts by weight of dichloromethane and 0.01 - 0.02 parts by weight of boron trifluoride - diethyl ether complex to obtain mixture II. Place mixture I in an ice bath, then dropwise add mixture II, and continuously stir for 12 - 14 h. After the reaction is completed, perform rotary evaporation to obtain the ultraviolet absorber.

[0024] Further, the preparation of the anti - migration antioxidant in step S2 specifically includes the following steps:

[0025] S2.1: Mix 20 - 30 parts by weight of montmorillonite, 650 - 670 parts by weight of ethanol, and 72 - 73 parts by weight of deionized water, stir at 300 - 500 r / min, and dropwise add hydrochloric acid solution to adjust the pH to 3 - 4. Then add 32 - 35 parts by weight of silane coupling agent KH570, stir at room temperature for 12 - 14 h, and then transfer to a three - necked flask equipped with a condenser reflux tube and a magnetic stirrer. Under the protection of a nitrogen atmosphere, heat to 60 - 65 °C and react for 12 - 14 h. Then cool to room temperature, filter, wash until neutral, and dry to obtain the coupling agent - modified montmorillonite;

[0026] S2.2: Add 1.23 - 1.34 parts by weight of pentaerythritol tetrakis(3 - mercaptopropionate) and 0.3 - 0.4 parts by weight of triethylamine to 100 - 120 parts by weight of tetrahydrofuran, and ultrasonically disperse for 10 - 12 min to obtain a mixed solution. Add 1.12 - 1.31 parts by weight of N-(4 - aminophenyl) maleimide to 100 - 120 parts by weight of tetrahydrofuran to obtain an N-(4 - aminophenyl) maleimide solution. Then, under a nitrogen atmosphere at 60 - 65 °C, drop the N-(4 - aminophenyl) maleimide solution into the mixed solution. The dropping time is 30 - 40 min, and then react for 2 - 3 h. Then add 5 - 8 parts by weight of coupling agent - modified montmorillonite and 1 - 2 parts by weight of triethylamine, and continue to react for 12 - 14 h. After the reaction is completed, cool to room temperature, filter, wash with tetrahydrofuran 3 - 5 times, and dry to obtain the anti - migration antioxidant.

[0027] Further, the preparation of the hot - melt adhesive in step S3 specifically includes the following steps:

[0028] S3.1: Add 0.5 - 0.8 parts by weight of diisopropylbenzene peroxide to 2 - 3 parts by weight of vinyltrimethoxysilane, mix and then add to 80 - 90 parts by weight of α - polyolefin. Then add 0.2 - 0.3 parts by weight of antioxidant 1010. After mixing, react at 130 - 135 °C for 10 - 12 min to obtain the graft - modified polyolefin.

[0029] S3.2: Mix 30 - 50 parts by weight of PPB resin with diisopropylbenzene peroxide and MAH in a high - speed mixer at 300 - 500 r / min and 190 - 200 °C for 20 - 30 min to obtain a mixed system. The mixed system is extruded through a twin - screw extruder to obtain the graft - modified PPB resin.

[0030] S3.3: Heat 30 - 50 parts by weight of the graft - modified polyolefin and 20 - 30 parts by weight of the graft - modified PPB resin to 160 - 180 °C, and then stir - mix at 300 - 400 r / min for 2 - 2.5 h. Then add 25 - 30 parts by weight of tackifying resin, 2 - 3 parts by weight of anti - migration antioxidant, 5 - 8 parts by weight of ultraviolet absorber, and 1 - 3 parts by weight of softener, stir - mix evenly at 100 - 120 r / min, and then transfer to an extruder. Add 1 - 2 parts by weight of cross - linker and 1 - 2 parts by weight of initiator, heat at 140 - 160 °C for 1 - 1.5 h and then melt - extrude to obtain the hot - melt adhesive.

[0031] Further, in step S3.2, diisopropylbenzene peroxide accounts for 1.2 - 1.8 wt% of the mixed system, and MAH accounts for 1.5 - 3 wt% of the mixed system.

[0032] Further, the tackifying resin in step S3.3 is styrene - modified C9 petroleum resin.

[0033] Furthermore, in step S3.3, the softening agent is cyclohexane oil 4006.

[0034] Furthermore, in step S3.3, the initiator is dicumyl peroxide.

[0035] Furthermore, in step S3.3, the cross-linking agent is maleic anhydride.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] 1. The present invention generates a product by a dehydration condensation reaction between anhydrous citric acid and cysteamine hydrochloride, which is then reacted with epichlorohydrin to generate an intermediate product. The intermediate product is then subjected to a ring-opening polymerization reaction with tetrahydrofuran. The prepared ultraviolet absorber exhibits excellent ultraviolet absorption performance even at extremely low concentrations. The cross-linked network formed by the reaction with epichlorohydrin can fix the ultraviolet absorption groups and reduce the performance loss caused by molecular migration, thereby significantly improving the anti-ultraviolet degradation ability of the hot melt adhesive and extending its service life in outdoor environments. In addition, the addition of the ultraviolet absorber to the hot melt adhesive can improve the stability of the hot melt adhesive during high-temperature processing and use, reduce thermal decomposition, and at the same time improve the bonding strength and flexibility of the hot melt adhesive, making it adaptable to more substrates.

[0038] 2. The present invention prepares an intramolecular synergistic macromolecular antioxidant containing sulfide and aromatic secondary amine, loads and grafts it onto coupling agent-modified montmorillonite, and then adds it to the preparation of hot melt adhesive. The aromatic secondary amine group in the anti-migration antioxidant can capture aging free radicals and inhibit the occurrence of oxidation reactions, while the sulfide group can effectively decompose ROOH and inhibit the occurrence of autocatalytic oxidation reactions. The two groups work synergistically to improve the thermal oxidation stability of the hot melt adhesive. Moreover, when loaded and grafted onto coupling agent-modified montmorillonite, it exhibits higher anti-migration performance, thereby reducing the reduction in antioxidant efficiency caused by the migration of the antioxidant and avoiding the attenuation of the antioxidant effect, thereby achieving long-term thermal oxidation stability of the hot melt adhesive.

[0039] 3. The present invention introduces silane polar groups through vinyltrimethoxysilane grafting, which significantly improves the adhesion between polyolefins and polar substrates. At the same time, the silane structure can enhance the interfacial bonding strength through cross-linking reaction. By grafting maleic anhydride, polar anhydride groups are introduced on the PPB main chain, further improving the adhesion to polar surfaces and broadening the applicable substrate range of the hot melt adhesive. After the two are compounded, a network structure of "non-polar main chain + multi-polar group" is formed, which takes into account the bonding ability to non-polar and polar substrates and achieves broad-spectrum bonding performance. In addition, α-polyolefin as the base resin provides the hot melt adhesive with flexibility and low-temperature crack resistance, while the PPB resin has both rigidity and elasticity. The combination of the two can balance the strength and toughness of the adhesive layer. Brief Description of the Drawings

[0040] The drawings incorporated herein and constituting a part of the specification illustrate embodiments of the present invention and, together with the specification, are further used to explain the principles of the present invention and enable those skilled in the relevant art to implement and use the present invention.

[0041] Figure 1 It is the FT-IR spectrum of the ultraviolet absorber in the embodiment of the present invention. Detailed Description of the Invention

[0042] The following describes in detail a method for preparing an anti-aging hot melt adhesive provided by the present invention in combination with the drawings and specific embodiments. At the same time, it should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; moreover, the drawing part is only for more specifically describing the embodiments and is not intended to specifically limit the present invention.

[0043] Embodiment 1

[0044] A method for preparing an anti-aging hot melt adhesive includes the following steps:

[0045] S1: Preparation of ultraviolet absorber

[0046] S1.1: Add 18 parts by weight of anhydrous citric acid and 10 parts by weight of cysteamine hydrochloride to 100 parts by weight of deionized water, stir and mix, then react at 130 °C for 12 h, grind and pulverize, wash with water, centrifuge, and vacuum dry to obtain solid powder;

[0047] S1.2: Add 20 parts by weight of the solid powder to 30 parts by weight of sodium hydroxide solution, fully shake and then let stand for 4 h, then dry at 80 °C. Mix 8 parts by weight of the dried product, 55 parts by weight of epichlorohydrin, and 0.2 parts by weight of tetrabutylammonium bromide catalyst in a beaker with condensable reflux, then react at 105 °C for 4 h. Then add 30 parts by weight of neutral alumina, stir and mix, filter, rotary evaporate. Add the product after rotary evaporation to a separatory funnel, add ethyl acetate and deionized water, mix evenly and let stand, take the upper clear liquid and perform rotary evaporation to obtain an intermediate product;

[0048] S1.3: Mix 2 parts by weight of the intermediate product, 5 parts by weight of tetrahydrofuran, and 50 parts by weight of dichloromethane to obtain mixture I. Mix 10 parts by weight of dichloromethane and 0.01 parts by weight of boron trifluoride-ether complex to obtain mixture II. Place mixture I in an ice bath, then dropwise add mixture II and continuously stir for 12 h. After the reaction is completed, perform rotary evaporation to obtain the ultraviolet absorber;

[0049] S2: Preparation of Anti-Migration Antioxidant

[0050] S2.1: Mix 20 parts by weight of montmorillonite, 650 parts by weight of ethanol and 72 parts by weight of deionized water, stir at 300 r / min, and add hydrochloric acid solution dropwise to adjust the pH to 3. Then add 32 parts by weight of silane coupling agent KH570, stir at room temperature for 12 h, and then transfer to a three-necked flask equipped with a condenser reflux tube and a magnetic stirrer. Under the protection of a nitrogen atmosphere, heat to 60 °C and react for 12 h. Then cool to room temperature, filter, wash until neutral, and dry to obtain coupling agent-modified montmorillonite;

[0051] S2.2: Add 1.23 parts by weight of pentaerythritol tetrakis(3-mercaptopropionate) and 0.3 parts by weight of triethylamine to 100 parts by weight of tetrahydrofuran, ultrasonically disperse for 10 min to obtain a mixed solution. Add 1.12 parts by weight of N-(4-aminophenyl) maleimide to 100 parts by weight of tetrahydrofuran to obtain an N-(4-aminophenyl) maleimide solution. Then, under a nitrogen atmosphere at 60 °C, drop the N-(4-aminophenyl) maleimide solution into the mixed solution. The dropping time is 30 min, and then react for 2 h. Then add 5 parts by weight of coupling agent-modified montmorillonite and 1 part by weight of triethylamine, and continue to react for 12 h. After the reaction is completed, cool to room temperature, filter, wash with tetrahydrofuran 3 times, and dry to obtain the anti-migration antioxidant;

[0052] S3: Preparation of Hot Melt Adhesive

[0053] S3.1: Add 0.5 part by weight of diisopropylbenzene peroxide to 2 parts by weight of vinyltrimethoxysilane, mix and then add to 80 parts by weight of α-olefin. Then add 0.2 part by weight of antioxidant 1010, mix, and react at 130 °C for 10 min to obtain graft-modified polyolefin;

[0054] S3.2: Mix 30 parts by weight of PPB resin with diisopropylbenzene peroxide and MAH in a high-speed mixer at 300 r / min and 190 °C for 20 min to obtain a mixed system. The mixed system is extruded through a twin-screw extruder to obtain graft-modified PPB resin, where diisopropylbenzene peroxide accounts for 1.2 wt% of the mixed system and MAH accounts for 1.5 wt% of the mixed system;

[0055] S3.3: Heat 30 parts by weight of the graft-modified polyolefin and 20 parts by weight of the graft-modified PPB resin to 160 °C, then stir and mix at 300 r / min for 2 h. After that, add 25 parts by weight of the styrene-modified C9 petroleum resin, 2 parts by weight of the anti-migration antioxidant, 5 parts by weight of the ultraviolet absorber, and 1 part by weight of the naphthenic oil 4006, stir and mix evenly at 100 r / min, then transfer to an extruder, add 1 part by weight of maleic anhydride and 1 part by weight of diisopropylbenzene peroxide, heat at 140 °C for 1 h and then melt and extrude to obtain the hot melt adhesive.

[0056] Example 2

[0057] A preparation method of an anti-aging hot melt adhesive, comprising the following steps:

[0058] S1: Preparation of the ultraviolet absorber

[0059] S1.1: Add 23 parts by weight of anhydrous citric acid and 12 parts by weight of cysteamine hydrochloride to 120 parts by weight of deionized water, stir and mix, then react at 130 °C for 12 h. After grinding and pulverizing, wash with water, centrifuge, and dry in vacuum to obtain a solid powder;

[0060] S1.2: Add 30 parts by weight of the solid powder to 40 parts by weight of the sodium hydroxide solution, shake well and then let stand for 4 h, then dry at 80 °C. Mix 10 parts by weight of the dried product, 58 parts by weight of epichlorohydrin, and 0.3 parts by weight of tetrabutylammonium bromide catalyst, place them in a beaker with condensable reflux, then react at 105 °C for 4 h. After that, add 50 parts by weight of neutral alumina, stir and mix, then filter, perform rotary evaporation. Add the product after rotary evaporation to a separatory funnel, add ethyl acetate and deionized water, mix evenly and let stand, take the upper clear liquid for rotary evaporation to obtain an intermediate product;

[0061] S1.3: Mix 3 parts by weight of the intermediate product, 8 parts by weight of tetrahydrofuran, and 80 parts by weight of dichloromethane to obtain mixture I. Mix 12 parts by weight of dichloromethane and 0.02 parts by weight of boron trifluoride-ether complex to obtain mixture II. Place mixture I in an ice bath, then dropwise add mixture II and continuously stir for 12 h. After the reaction is completed, perform rotary evaporation to obtain the ultraviolet absorber;

[0062] S2: Preparation of the anti-migration antioxidant

[0063] S2.1: Mix 30 parts by weight of montmorillonite, 670 parts by weight of ethanol and 73 parts by weight of deionized water, stir at 300 r / min, and add hydrochloric acid solution dropwise to adjust the pH to 4. Then add 35 parts by weight of silane coupling agent KH570, stir at room temperature for 12 h, then transfer to a three-necked flask equipped with a condenser reflux tube and a magnetic stirrer, and react at 60 °C for 12 h under the protection of a nitrogen atmosphere. Then cool to room temperature, filter, wash until neutral, and dry to obtain coupling agent-modified montmorillonite;

[0064] S2.2: Add 1.34 parts by weight of pentaerythritol tetra(3-mercaptopropionate) and 0.4 parts by weight of triethylamine to 120 parts by weight of tetrahydrofuran, ultrasonically disperse for 10 min to obtain a mixed solution. Add 1.31 parts by weight of N-(4-aminophenyl) maleimide to 120 parts by weight of tetrahydrofuran to obtain an N-(4-aminophenyl) maleimide solution. Then, under a nitrogen atmosphere at 60 °C, drop the N-(4-aminophenyl) maleimide solution into the mixed solution, with a dropping time of 30 min. Then react for 2 h, then add 8 parts by weight of coupling agent-modified montmorillonite and 2 parts by weight of triethylamine, and continue to react for 12 h. After the reaction is completed, cool to room temperature, filter, wash 3 times with tetrahydrofuran, and dry to obtain an anti-migration antioxidant;

[0065] S3: Preparation of hot melt adhesive

[0066] S3.1: Add 0.8 parts by weight of dicumyl peroxide to 3 parts by weight of vinyltrimethoxysilane, mix and add to 90 parts by weight of α-olefin. Then add 0.3 parts by weight of antioxidant 1010, mix, and react at 130 °C for 10 min to obtain a graft-modified polyolefin;

[0067] S3.2: Mix 50 parts by weight of PPB resin with dicumyl peroxide and MAH in a high-speed mixer at 300 r / min and 190 °C for 20 min to obtain a mixed system. The mixed system is extruded through a twin-screw extruder to obtain a graft-modified PPB resin, where dicumyl peroxide accounts for 1.8 wt% of the mixed system and MAH accounts for 3 wt% of the mixed system;

[0068] S3.3: Heat 50 parts by weight of graft-modified polyolefin and 30 parts by weight of graft-modified PPB resin to 160 °C, then stir and mix at 300 r / min for 2 h. Then add 30 parts by weight of styrene-modified C9 petroleum resin, 3 parts by weight of anti-migration antioxidant, 8 parts by weight of ultraviolet absorber and 3 parts by weight of naphthenic oil 4006, stir and mix evenly at 100 r / min, then transfer to an extruder, add 2 parts by weight of maleic anhydride and 2 parts by weight of dicumyl peroxide, heat at 140 °C for 1 h and then melt and extrude to obtain a hot melt adhesive.

[0069] Example 3

[0070] A preparation method of an anti-aging hot melt adhesive, comprising the following steps:

[0071] S1: Preparation of ultraviolet absorber

[0072] S1.1: Add 18 parts by weight of anhydrous citric acid and 10 parts by weight of cysteamine hydrochloride to 100 parts by weight of deionized water, stir and mix, then react at 140 °C for 14 h, grind and pulverize, wash with water, centrifuge, and dry in vacuum to obtain solid powder;

[0073] S1.2: Add 20 parts by weight of the solid powder to 30 parts by weight of sodium hydroxide solution, shake well and let stand for 5 h, then dry at 82 °C. Mix 8 parts by weight of the dried product, 55 parts by weight of epichlorohydrin and 0.2 part by weight of tetrabutylammonium bromide catalyst, place them in a beaker with condensable reflux, then react at 110 °C for 5 h. Then add 30 parts by weight of neutral alumina, stir and mix, filter, perform rotary evaporation. Add the product after rotary evaporation to a separatory funnel, add ethyl acetate and deionized water, mix evenly and let stand, take the upper clear liquid for rotary evaporation to obtain an intermediate product;

[0074] S1.3: Mix 2 parts by weight of the intermediate product, 5 parts by weight of tetrahydrofuran and 50 parts by weight of dichloromethane to obtain mixture I. Mix 10 parts by weight of dichloromethane and 0.01 part by weight of boron trifluoride-ether complex to obtain mixture II. Place mixture I in an ice bath, then dropwise add mixture II and continuously stir for 14 h. After the reaction is completed, perform rotary evaporation to obtain the ultraviolet absorber;

[0075] S2: Preparation of anti-migration antioxidant

[0076] S2.1: Mix 20 parts by weight of montmorillonite, 650 parts by weight of ethanol and 72 parts by weight of deionized water, stir at 500 r / min, and dropwise add hydrochloric acid solution to adjust the pH to 3. Then add 32 parts by weight of silane coupling agent KH570, stir at room temperature for 14 h, then transfer to a three-necked flask equipped with a condenser reflux tube and a magnetic stirrer, and react at 65 °C for 14 h under the protection of a nitrogen atmosphere. Then cool to room temperature, filter, wash until neutral, and dry to obtain coupling agent-modified montmorillonite;

[0077] S2.2: Add 1.23 parts by weight of pentaerythritol tetrakis(3-mercaptopropionate) and 0.3 parts by weight of triethylamine to 100 parts by weight of tetrahydrofuran, and ultrasonically disperse for 12 min to obtain a mixed solution. Add 1.12 parts by weight of N-(4-aminophenyl) maleimide to 100 parts by weight of tetrahydrofuran to obtain an N-(4-aminophenyl) maleimide solution. Then, under a nitrogen atmosphere at 65 °C, dropwise add the N-(4-aminophenyl) maleimide solution to the mixed solution over 40 min, and then react for 3 h. Then add 5 parts by weight of coupling agent-modified montmorillonite and 1 part by weight of triethylamine, and continue to react for 14 h. After the reaction is completed, cool to room temperature, filter, wash with tetrahydrofuran 5 times, and dry to obtain an anti-migration antioxidant;

[0078] S3: Preparation of hot melt adhesive

[0079] S3.1: Add 0.5 parts by weight of dicumyl peroxide to 2 parts by weight of vinyltrimethoxysilane, mix and then add to 80 parts by weight of α-olefin. Then add 0.2 parts by weight of antioxidant 1010. After mixing, react at 135 °C for 12 min to obtain a graft-modified polyolefin;

[0080] S3.2: Mix 30 parts by weight of PPB resin with dicumyl peroxide and MAH in a high-speed mixer at 500 r / min and 200 °C for 30 min to obtain a mixed system. The mixed system is extruded through a twin-screw extruder to obtain a graft-modified PPB resin, where dicumyl peroxide accounts for 1.2 wt% of the mixed system and MAH accounts for 1.5 wt% of the mixed system;

[0081] S3.3: Heat 30 parts by weight of the graft-modified polyolefin and 20 parts by weight of the graft-modified PPB resin to 180 °C, then stir and mix at 400 r / min for 2.5 h. Then add 25 parts by weight of styrene-modified C9 petroleum resin, 2 parts by weight of the anti-migration antioxidant, 5 parts by weight of the ultraviolet absorber, and 1 part by weight of naphthenic oil 4006 and mix evenly at 120 r / min. Then transfer to an extruder, add 1 part by weight of maleic anhydride and 1 part by weight of dicumyl peroxide, heat at 160 °C for 1.5 h and then melt and extrude to obtain a hot melt adhesive.

[0082] Comparative example 1

[0083] Compared with Example 1, the difference in Comparative Example 1 is that the ultraviolet absorber in Steps S1 and S3.3 is removed, and the remaining steps remain unchanged to prepare the hot melt adhesive, denoted as Comparative Example 1.

[0084] Comparative example 2

[0085] Compared with Example 1, the difference in Comparative Example 2 is that Comparative Example 2 removes step S2, replaces the anti-migration antioxidant in step S3.3 with antioxidant 1010, and prepares the hot melt adhesive with the remaining steps unchanged, denoted as Comparative Example 2.

[0086] Comparative Example 3

[0087] Compared with Example 1, the difference in Comparative Example 3 is that Comparative Example 3 removes "then add 5 parts by weight of coupling agent-modified montmorillonite and 1 part by weight of triethylamine, and continue to react for 12 h. After the reaction is completed," in steps S2.1 and S2.2, and prepares the hot melt adhesive with the remaining steps unchanged, denoted as Comparative Example 3.

[0088] Comparative Example 4

[0089] Compared with Example 1, the difference in Comparative Example 4 is that Comparative Example 4 replaces "5 parts by weight of coupling agent-modified montmorillonite and 1 part by weight of triethylamine, continue to react for 12 h. After the reaction is completed, cool to room temperature" in S2.2 with "5 parts by weight of coupling agent-modified montmorillonite are stirred and mixed. After mixing is completed," and prepares the hot melt adhesive with the remaining steps unchanged, denoted as Comparative Example 4.

[0090] Comparative Example 5

[0091] Compared with Example 1, the difference in Comparative Example 5 is that Comparative Example 6 removes the graft-modified polyolefin in steps S3.1 and S3.3, and prepares the hot melt adhesive with the remaining steps unchanged, denoted as Comparative Example 5.

[0092] Comparative Example 6

[0093] Compared with Example 1, the difference in Comparative Example 6 is that Comparative Example 6 removes the graft-modified PPB resin in steps S3.2 and S3.3, and prepares the hot melt adhesive with the remaining steps unchanged, denoted as Comparative Example 6.

[0094] The hot melt adhesives prepared in Examples 1-3 and Comparative Example 1 were cured to obtain 2 cm × 2 cm × 0.2 cm specimens, which were placed in a fluorescent ultraviolet lamp aging chamber with a wavelength of 340 nm and an irradiation intensity of 100 W / m 2 , stored at 23 ± 2 °C and 50 ± 5% RH for 8 months. After 3 months, record whether there are yellowing, oxidation, cracking, blistering and damage phenomena on the specimens. If so, it is recorded as unqualified, otherwise it is qualified. After 8 months, record again. The qualification rate of the specimens was recorded for 100 specimens in each group, and the results are shown in Table 1.

[0095] Table 1. Results of anti-ultraviolet and aging resistance determination

[0096] Qualified rate (%) after 3 months Qualified rate (%) after 8 months Example 1 100 100 Example 2 100 100 Example 3 100 100 Comparative Example 1 73 23

[0097] It can be seen from the data in Table 1 that adding the ultraviolet absorber prepared by the present invention can effectively improve the ultraviolet resistance of the hot melt adhesive and extend the time of ultraviolet resistance. Therefore, the aging resistance of the hot melt adhesive is effectively improved, and its service life in the outdoor environment is extended.

[0098] After curing the hot melt adhesives prepared in Examples 1-3 and Comparative Examples 1-4, samples with a size of 2 cm × 2 cm × 0.2 cm were prepared, placed in a constant temperature and humidity chamber at 75 ± 2 °C and 75 ± 3% relative humidity, and the air was kept flowing. After storing for 8 months, after 3 months, record whether there are phenomena such as yellowing, oxidation, cracking, blistering and damage on the samples. If so, record it as unqualified, otherwise it is qualified. After 8 months, record again. The qualification rate of 100 specimens in each group was recorded, and the results were recorded in Table 2.

[0099] Table 2. Determination results of heat and oxygen resistance, humidity resistance and aging resistance

[0100] Qualified rate (%) after 3 months Qualified rate (%) after 8 months Example 1 100 100 Example 2 100 100 Example 3 100 100 Comparative Example 1 95 90 Comparative Example 2 84 52 Comparative Example 3 92 74 Comparative Example 4 93 78

[0101] It can be seen from the data in Table 2 that the antioxidant effect of the added anti-migration antioxidant is significantly higher than that of the existing antioxidant 1010, and it is loaded and grafted on the montmorillonite modified by the coupling agent, which prolongs the time of the antioxidant effect.

[0102] Put the hot melt adhesives prepared in Examples 1-3 and Comparative Examples 5-6 into an oven at 170 °C to melt, press them into specimens with a thickness of 1 mm, after cooling, cut specimens with a size of 100 mm × 25 mm, place them on an aluminum foil (0.1 mm) with a size of 250 mm × 25 mm, then put them into an oven at 170 °C to melt again, immediately paste a PP board with a size of 150 mm × 25 mm, roll it back and forth 3 times with a 2 kg roller, after cooling to room temperature, place it at room temperature for 24 h, and measure the peel strength. The measurement results are shown in Table 3 for reference.

[0103] Put the hot melt adhesives prepared in Examples 1-3 and Comparative Examples 5-6 into an oven at 170 °C to melt, press them into specimens with a thickness of 1 mm, after cooling, cut specimens with a size of 100 mm × 25 mm, place them on an aluminum foil (0.1 mm) with a size of 250 mm × 25 mm, then put them into an oven at 170 °C to melt again, immediately paste an aluminum plate with a size of 150 mm × 25 mm, roll it back and forth 3 times with a 2 kg roller, after cooling to room temperature, place it at room temperature for 24 h, and measure the peel strength. The measurement results are shown in Table 3 for reference.

[0104] Table 3. Determination of peel strength

[0105]

[0106] It can be seen from the data in Table 3 that the hot melt adhesives prepared in Examples 1-3 broaden the applicable substrate range of the hot melt adhesive, take into account the bonding ability to non-polar and polar substrates, and achieve broad-spectrum bonding performance.

[0107] The characteristic absorption peaks of the monomer and the product before and after the ring-opening polymerization reaction were tested by FT-IR. From Figure 1 it can be seen that the reaction was successfully carried out and the ultraviolet absorber was successfully synthesized.

[0108] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An anti-aging hot melt adhesive, characterized in that, By weight parts, it includes the following raw material components: 30 - 50 parts by weight of graft-modified polyolefin, 20 - 30 parts by weight of graft-modified PPB resin, 25 - 30 parts by weight of tackifying resin, 2 - 3 parts by weight of anti-migration antioxidant, 5 - 8 parts by weight of ultraviolet absorber, 1 - 3 parts by weight of softener, 1 - 2 parts by weight of crosslinking agent and 1 - 2 parts by weight of initiator; Among them, the graft-modified polyolefin is vinyltrimethoxysilane-modified α-polyolefin; The graft-modified PPB resin is MAH-grafted PPB resin; The anti-migration antioxidant is prepared by using pentaerythritol tetrakis(3-mercaptopropionate), triethylamine, N-(4-aminophenyl) maleimide, and tetrahydrofuran as raw materials to prepare an antioxidant and graft-loading it on the coupling agent-modified montmorillonite to obtain the anti-migration antioxidant; The ultraviolet absorber is prepared by reacting with anhydrous citric acid, cysteamine hydrochloride, epichlorohydrin, tetrabutylammonium bromide, tetrahydrofuran, dichloromethane, and boron trifluoride-ether complex as raw materials.

2. A method for preparing the aging-resistant hot melt adhesive according to claim 1, characterized in that: It includes the following steps: S1: Preparation of ultraviolet absorber First, prepare a solid powder from anhydrous citric acid and cysteamine hydrochloride, then react it with epichlorohydrin to obtain an intermediate product. Finally, mix it with tetrahydrofuran and dichloromethane to obtain mixture I. Mix dichloromethane and boron trifluoride-ether complex to obtain mixture II. React mixture I and mixture II to prepare the ultraviolet absorber; S2: Preparation of anti-migration antioxidant Modify montmorillonite with silane coupling agent KH570 to obtain coupling agent-modified montmorillonite. Then add N-(4-aminophenyl) maleimide solution to the mixed solution of pentaerythritol tetrakis(3-mercaptopropionate), triethylamine, and tetrahydrofuran. After reaction, add coupling agent-modified montmorillonite and triethylamine, and react again to obtain the anti-migration antioxidant; S3: Preparation of hot melt adhesive First, modify α-polyolefin with vinyltrimethoxysilane to obtain graft-modified polyolefin. Then modify PPB resin with MAH to obtain graft-modified PPB resin. Then mix the graft-modified polyolefin and the graft-modified PPB resin first, and then add tackifying resin, anti-migration antioxidant, ultraviolet absorber, and softener. Finally, add crosslinking agent and initiator to prepare the hot melt adhesive. In step S1, the preparation of the ultraviolet absorber specifically includes the following steps:

3. The preparation method of an anti-aging hot melt adhesive according to claim 2, characterized in that, S1.1: Add 18 - 23 parts by weight of anhydrous citric acid and 10 - 12 parts by weight of cysteamine hydrochloride to 100 - 120 parts by weight of deionized water, stir and mix, then react at 130 - 140 °C for 12 - 14 h. Grind and crush, then wash, centrifuge, and vacuum dry to obtain the solid powder; ​ S1.2: Add 20-30 parts by weight of solid powder to 30-40 parts by weight of sodium hydroxide solution, shake thoroughly, let stand for 4-5 hours, and then dry at 80-82°C. Mix 8-10 parts by weight of the dried product, 55-58 parts by weight of epichlorohydrin and 0.2-0.3 parts by weight of tetrabutylammonium bromide catalyst, place in a beaker with condensable reflux, and then react at 105-110°C for 4-5 hours. Then add 30-50 parts by weight of neutral alumina, stir and mix, filter, and rotary evaporate. Add the product after rotary evaporation to a separatory funnel, add ethyl acetate and deionized water, mix well, let stand, and take the supernatant for rotary evaporation to obtain an intermediate product; S1.3: Mix 2-3 parts by weight of the intermediate product, 5-8 parts by weight of tetrahydrofuran and 50-80 parts by weight of dichloromethane to obtain mixture I, mix 10-12 parts by weight of dichloromethane and 0.01-0.02 parts by weight of boron trifluoride-ether complex to obtain mixture II, place mixture I in an ice bath, then add mixture II dropwise and stir continuously for 12-14 hours. After the reaction is completed, perform rotary evaporation to obtain a UV absorber.

4. The preparation method of an anti-aging hot melt adhesive according to claim 3, characterized in that Step S2 is the preparation of an anti-migration antioxidant, specifically comprising the following steps: S2.1: 20-30 parts by weight of montmorillonite, 650-670 parts by weight of ethanol, and 72-73 parts by weight of deionized water are mixed, stirred at 300-500 r / min, and hydrochloric acid solution is added dropwise to adjust the pH to 3-4. Then, 32-35 parts by weight of silane coupling agent KH570 are added and stirred at room temperature for 12-14 hours. The mixture is then transferred to a three-necked flask equipped with a reflux tube and a magnetic stirrer. Under a nitrogen atmosphere, the mixture is heated to 60-65°C and reacted for 12-14 hours. The mixture is then cooled to room temperature, filtered, washed until neutral, and dried to obtain coupling agent-modified montmorillonite; S2.2: 1.23-1.34 parts by weight of pentaerythritol tetrakis(3-mercaptopropionic acid) ester and 0.3-0.4 parts by weight of triethylamine are added to 100-120 parts by weight of tetrahydrofuran, and ultrasonically dispersed for 10-12 minutes to obtain a mixed solution; 1.12-1.31 parts by weight of N-(4-aminophenyl)maleimide are added to 100-120 parts by weight of tetrahydrofuran to obtain N-(4-aminophenyl)maleimide. Amine solution, then in a nitrogen atmosphere, at 60-65 ° C, N- (4-aminophenyl) maleimide solution is added dropwise to the mixed solution for 30-40 minutes, followed by reaction for 2-3 hours, and then 5-8 parts by weight of coupling agent modified montmorillonite and 1-2 parts by weight of triethylamine are added, and the reaction is continued for 12-14 hours. After the reaction is completed, it is cooled to room temperature, filtered, washed with tetrahydrofuran 3-5 times, and dried to obtain an anti-migration antioxidant.

5. The preparation method of an anti-aging hot melt adhesive according to claim 4, characterized in that, Step S3: Preparation of hot melt adhesive, specifically including the following steps: S3.1: Add 0.5-0.8 parts by weight of dicumyl peroxide to 2-3 parts by weight of vinyltrimethoxysilane, mix, and add to 80-90 parts by weight of α-polyolefin. Then, add 0.2-0.3 parts by weight of antioxidant 1010. After mixing, react at 130-135°C for 10-12 minutes to obtain a graft-modified polyolefin. S3.2: Mix 30-50 parts by weight of PPB resin with dicumyl peroxide and MAH in a high-speed mixer at 300-500 rpm and 190-200°C for 20-30 minutes to obtain a mixed system. Extrude the mixed system through a twin-screw extruder to obtain a graft-modified PPB resin. S3.3: Heat 30-50 parts by weight of grafted modified polyolefin and 20-30 parts by weight of grafted modified PPB resin to 160-180°C, then stir and mix at 300-400 r / min for 2-2.5 hours, then add 25-30 parts by weight of tackifying resin, 2-3 parts by weight of anti-migration antioxidant, 5-8 parts by weight of UV absorber and 1-3 parts by weight of softener, stir and mix evenly at 100-120 r / min, then transfer to an extruder, add 1-2 parts by weight of cross-linking agent and 1-2 parts by weight of initiator, heat at 140-160°C for 1-1.5 hours, and then melt and extrude to obtain a hot melt adhesive.

6. The method for preparing an aging-resistant hot melt adhesive according to claim 5, characterized in that: In step S3.2, dicumyl peroxide accounts for 1.2-1.8 wt% of the mixed system, and MAH accounts for 1.5-3 wt% of the mixed system.

7. A weather-resistant hot melt adhesive and its preparation method according to claim 5, characterized in that, The tackifying resin in step S3.3 is styrene-modified C9 petroleum resin.

8. The method for preparing an aging-resistant hot melt adhesive according to claim 5, characterized in that: The softening agent in step S3.3 is naphthenic oil 4006.

9. The preparation method of an anti-aging hot melt adhesive according to claim 5, characterized in that, In step S3.3, the initiator is dicumyl peroxide.

10. The preparation method of an anti-aging hot melt adhesive according to claim 5, characterized in that, In step S3.3, the cross-linking agent is maleic anhydride.

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