High-softening-point low-VOC (volatile organic compound) monomer resin as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of tackifying resin, and particularly relates to high-softening-point low-VOC (volatile organic compound) monomer resin as well as a preparation method and application thereof. The preparation method comprises the following steps: adding hydroxybutyl vinyl ether, maleic anhydride, an initiator and isopropanol into a three-neck flask, introducing nitrogen to replace air in the flask, starting a stirrer, reacting in an oil bath pan, and quickly cooling in an ice bath; the preparation method comprises the following steps: adding methyl tert-butyl ether into a three-neck flask to obtain a polymer precipitate, carrying out centrifugal separation to obtain a hydroxybutyl vinyl ether grafted maleic anhydride oligomer, adding the oligomer, alpha-methyl styrene, a styrene derivative and an ionic liquid into the three-neck flask, introducing nitrogen to replace air in the flask, adding a low-temperature water bath kettle, adding an initiator, and carrying out vacuum pumping; carrying out cationic polymerization reaction; and stopping the reaction after the reaction, washing and drying to obtain the monomer resin. Applications include hot melt adhesives and composite materials. The prepared monomer resin has narrow molecular weight distribution, high softening point and low VOC (volatile organic compound) performance.

Description

Technical Field

[0001] The invention belongs to the technical field of tackifying resins, and more specifically relates to a high softening point low VOC monomer resin and a preparation method and application thereof. Background Art

[0002] Hot melt adhesive is an adhesive made of base resin with additives such as tackifying resin, viscosity regulator, antioxidant, etc. added through melt mixing. It has the advantages of simple operation, low production cost, fast bonding speed, and green environmental protection. It is widely used in the fields of tapes, packaging, construction, decoration, binding, etc.

[0003] Tackifying resin is a thermoplastic monomer with an aliphatic ring structure or a ring structure formed during the polymerization process. It has the characteristics of low molecular weight and low softening point. It can enhance the wettability of the hot melt adhesive to the substrate, making the two fully bonded, thereby improving the bonding strength of the material. Adding an appropriate amount of tackifying resin to the hot melt adhesive can also improve the impact strength, peel strength and other properties of the colloid, and extend the service life of the hot melt adhesive. It is an important additive.

[0004] Commonly used tackifying resins are mainly divided into rosin resin, terpene resin and petroleum resin. Rosin resin is mainly composed of resin acid, in addition to a small amount of fatty acids and neutral substances. It is the most widely used tackifying resin and can effectively improve the bonding strength, wetting performance and fluidity of hot melt adhesives; terpene resin is an oligomer obtained by polymerizing α-pinene or β-pinene. The pinene resin currently used has a high VOC content, a certain odor and poor stability; petroleum resin is a thermoplastic resin produced by pre-treatment, polymerization, distillation and other processes of C5 and C9 fractions produced by petroleum cracking. Its comprehensive performance is slightly worse than other tackifying resins, but it is cheaper.

[0005] SIS hot melt adhesive is an adhesive made of styrene-isoprene-styrene block copolymer with tackifiers, softeners, antioxidants and other additives. SIS hot melt adhesive has low modulus, low viscosity, excellent anti-aging performance and special rheological properties, and has a wide range of applications. Since SIS resin itself does not have bonding properties, it is necessary to add a variety of modifiers to improve the SIS bonding performance. Selecting a suitable tackifying resin is of great significance for the development of high-performance SIS hot melt adhesives.

[0006] Pure monomer resin is a non-polar oligomer with strong rigidity, which can be used as a tackifier to improve the bonding performance of hot melt adhesive. However, pure monomer resin is usually obtained by cationic polymerization, and chain transfer reaction is very likely to occur during the polymerization process. The molecular weight distribution of the obtained product is relatively wide, which has an adverse effect on the preparation of low-VOC hot melt adhesive; in addition, pure monomer resin contains a large amount of aromatic structure, which is not compatible with the soft segment of SIS hot melt adhesive, and has limited effect on improving the initial viscosity of hot melt adhesive.

[0007] At present, there are few reports on the bonding performance of monomer resin modified hot melt adhesives. The patent application with application number CN202211663074.4 discloses a laminated hot melt adhesive for soft-pack batteries and its preparation method. SEBS rubber, SIS rubber, cyclopentane oil, pure monomer resin and other raw materials are melted and stirred in a certain proportion, which solves the problems of low adhesion and low peeling force of conventional hot melt adhesives. The patent application with application number CN202311671136.0 discloses a hot melt adhesive with high bonding performance and its preparation method. By adding monomer resin, the disadvantage of too fast penetration of hot melt adhesive is improved, and the adhesion and weather resistance of the finished coated product are improved.

[0008] In the prior art, the modification of hot melt adhesives by pure monomer resins has the following deficiencies: (1) The molecular weight distribution of the monomer resin is relatively wide and the content of small molecules is relatively high, resulting in a relatively high VOC content in the hot melt adhesive; (2) There is a critical polymerization temperature in the polymerization process of the pure monomer resin and the molecular weight is relatively low, resulting in a low softening point of the hot melt adhesive; (3) The monomer resin has limited effect on improving the wetting performance of the interface between the hot melt adhesive and the substrate, resulting in a low initial viscosity of the hot melt adhesive. Summary of the invention

[0009] 1. Technical issues to be resolved The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a high softening point low VOC monomer resin and a preparation method and application thereof.

[0010] (II) Technical solution In order to achieve the above-mentioned object and other related objects, the present invention provides the following technical solutions: The first aspect of the present invention provides a high softening point low VOC monomer resin, and the preparation method of the monomer resin comprises the following steps: Step 1: Add hydroxybutyl vinyl ether, maleic anhydride, initiator, and isopropanol into a three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath, and place the three-necked beaker in an ice bath for rapid cooling to terminate the reaction; add methyl tert-butyl ether into the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain a hydroxybutyl vinyl ether grafted maleic anhydride oligomer; Step 2: Add hydroxybutyl vinyl ether grafted maleic anhydride oligomer, α-methylstyrene, and styrene derivatives into a three-necked flask, add ionic liquid, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add initiator, evacuate the three-necked flask, and perform cationic polymerization under low temperature and low pressure conditions; after reacting for a period of time, add methanol to terminate the reaction, wash the product, and dry it to obtain a monomer resin.

[0011] Preferably, in step 1, the stirrer is turned on, the reaction is carried out in an oil bath at 90-120° C. for 1-5 hours, and the three-necked beaker is placed in an ice bath for rapid cooling to terminate the reaction; the initiator includes one or more of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), and dibenzoyl peroxide (BPO).

[0012] Preferably, in step 1, the mass ratio of hydroxybutyl vinyl ether, maleic anhydride, initiator and isopropanol is: 70-100:1-5:0.1-0.3:200.

[0013] Preferably, in step 2, the styrene derivative includes one or more of p-chloromethylstyrene, p-methylstyrene and vinyltoluene.

[0014] Preferably, in step 2, the mass ratio of α-methylstyrene, hydroxybutyl vinyl ether grafted maleic anhydride oligomer, and styrene derivative is 2-6:3:2-6.

[0015] Preferably, in step 2, the ionic liquid includes one or more of 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-vinyl-3-butylimidazolium bromide.

[0016] Preferably, in step 2, the initiator includes boron trifluoride etherate initiator added in an amount of 0.1 to 0.5 g.

[0017] Preferably, in step 2, the low temperature and low pressure conditions are: the reaction temperature is -20~0°C, the reaction pressure is 0.01~0.05MPa; and the reaction time is 0.5-3 hours.

[0018] A second aspect of the present invention provides a hot melt adhesive, and a preparation method of the hot melt adhesive comprises the following steps: weighing SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to a mass ratio of 40:15:30:1, adding them into a three-necked flask, introducing nitrogen to replace the air in the flask, heating and controlling the temperature to 100-200°C, turning on a mechanical stirrer and continuously stirring until the product forms a uniform molten state, to obtain a hot melt adhesive; wherein the monomer resin is the aforementioned high softening point low VOC monomer resin.

[0019] The third aspect of the present invention provides a composite material, and the preparation method of the composite material comprises the following steps: applying hot melt adhesive on a film, and controlling the coating layer thickness to be 20-50 μm, wherein the film comprises a PET film; and the hot melt adhesive is the aforementioned hot melt adhesive.

[0020] 3. Beneficial technical effects Advantages of the present invention: (1) The hard segment of styrene derivatives is introduced through controlled cationic polymerization to effectively increase the softening point of the monomer resin.

[0021] (2) Using ionic liquids as solvents and reduced pressure polymerization can effectively regulate the reaction activity of carbon cations and promptly remove small molecules produced during the polymerization process, thereby reducing the VOC content of the monomer resin.

[0022] (3) The soft segment hydroxybutyl vinyl ether grafted maleic anhydride in the monomer resin copolymer gives the monomer resin a higher polarity, which can effectively improve the wettability of the hot melt adhesive and the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below through examples and drawings. The following examples are only exemplary descriptions of the specific technical solutions of the present invention and do not limit the scope of the present invention. That is, it should be understood that non-essential simple corrections, adjustments and combinations made by those skilled in the art according to the inventive concept of the present invention are within the scope of protection claimed by the present invention. In the following examples and comparative examples, unless otherwise specified, all raw materials can be obtained from commercial sources. Among them, SIS is polystyrene-isoprene-styrene. The manufacturer model of SIS is Kraton, D1117. The manufacturer model of polyethylene wax is Euroceras, CP15M. The purity of all raw materials or reagents is 99%.

[0025] It should be noted that the purpose of "excess" in the following description is to completely precipitate the polymer or terminate the reaction, and the amount of reagent used can ensure that the aforementioned purpose is achieved, and does not affect the preparation of the technical solution of the present application or is not a key influencing factor, which can be understood by those skilled in the art.

[0026] Example 1 Reference Figure 1 , a method for preparing a high softening point low VOC monomer resin, the specific steps are as follows: Step 1: Weigh 70g of hydroxybutyl vinyl ether, 1g of maleic anhydride, 0.1g of initiator AIBN, and 200g of isopropanol, add them to a 500 mL three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath at a temperature of 105°C for 3 hours, and place the beaker in an ice bath for rapid cooling to terminate the reaction. Add excess methyl tert-butyl ether to the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain hydroxybutyl vinyl ether grafted maleic anhydride oligomer D-1.

[0027] Step 2: Weigh 20g of α-methylstyrene, 30g of hydroxybutyl vinyl ether grafted maleic anhydride oligomer D1, and 60g of p-chloromethylstyrene, add them into a 250 mL three-necked flask in sequence, add 100mL of 1-ethyl-3-methylimidazolium acetate ionic liquid, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add 0.1g of boron trifluoride ether initiator, evacuate the three-necked flask, and carry out cationic polymerization at -20°C and 0.01MPa. After reacting for 0.5 hours, add excess methanol to terminate the reaction, wash the product repeatedly with anhydrous ethanol, and place it in an 85°C forced air drying oven for use to obtain a monomer resin.

[0028] The prepared monomer resin is applied as follows: Step 3: Weigh SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to the mass ratio of 40:15:30:1, add them into a 500mL three-necked flask, introduce nitrogen to replace the air in the flask, heat and control the temperature to about 160°C, turn on the mechanical stirrer and continue stirring until the product forms a uniform molten state to obtain a hot melt adhesive, and apply the hot melt adhesive evenly on the PET film with a coater. The coating layer thickness is controlled to be about 30μm, and the performance test is carried out.

[0029] Example 2 Reference Figure 1 , a method for preparing a high softening point low VOC monomer resin, the specific steps are as follows: Step 1: Weigh 75g of hydroxybutyl vinyl ether, 2g of maleic anhydride, 0.15g of initiator ABVN, and 200g of isopropanol, add them to a 500 mL three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath at a temperature of 105°C for 3 hours, and place the beaker in an ice bath for rapid cooling to terminate the reaction. Add excess methyl tert-butyl ether to the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain hydroxybutyl vinyl ether grafted maleic anhydride oligomer D-2.

[0030] Step 2: Weigh 30g of α-methylstyrene, 30g of hydroxybutyl vinyl ether grafted maleic anhydride oligomer D2, and 50g of p-methylstyrene, add them into a 250 mL three-necked flask in sequence, add 100mL of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add 0.2g of boron trifluoride ether initiator, evacuate the three-necked flask, and carry out cationic polymerization at -15°C and 0.02MPa. After reacting for 1.0 hour, add excess methanol to terminate the reaction, wash the product repeatedly with anhydrous ethanol, and place it in an 85°C forced air drying oven for use to obtain a monomer resin.

[0031] The prepared monomer resin is applied as follows: Step 3: Weigh SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to the mass ratio of 40:15:30:1, add them into a 500mL three-necked flask, introduce nitrogen to replace the air in the flask, heat and control the temperature to about 160°C, turn on the mechanical stirrer and continue stirring until the product forms a uniform molten state to obtain a hot melt adhesive, and apply the hot melt adhesive evenly on the PET film with a coater. The coating layer thickness is controlled to be about 30μm, and the performance test is carried out.

[0032] Example 3 Reference Figure 1 , a method for preparing a high softening point low VOC monomer resin, the specific steps are as follows: Step 1: Weigh 80g of hydroxybutyl vinyl ether, 3g of maleic anhydride, 0.20g of initiator BPO, and 200g of isopropanol, add them to a 500 mL three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath at a temperature of 105°C for 3 hours, and place the beaker in an ice bath for rapid cooling to terminate the reaction. Add excess methyl tert-butyl ether to the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain hydroxybutyl vinyl ether grafted maleic anhydride oligomer D-3.

[0033] Step 2: Weigh 40g of α-methylstyrene, 30g of hydroxybutyl vinyl ether grafted maleic anhydride oligomer D3, and 40g of vinyltoluene, add them into a 250 mL three-necked flask in sequence, add 100mL of 1-vinyl-3-butylimidazolium bromide ionic liquid, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add 0.3g of boron trifluoride ether initiator, evacuate the three-necked flask, and carry out cationic polymerization at -10°C and 0.03MPa. After reacting for 1.5 hours, add excess methanol to terminate the reaction, wash the product repeatedly with anhydrous ethanol, and place it in an 85°C forced air drying oven for use to obtain a monomer resin.

[0034] The prepared monomer resin is applied as follows: Step 3: Weigh SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to the mass ratio of 40:15:30:1, add them into a 500mL three-necked flask, introduce nitrogen to replace the air in the flask, heat and control the temperature to about 160°C, turn on the mechanical stirrer and continue stirring until the product forms a uniform molten state to obtain a hot melt adhesive, and apply the hot melt adhesive evenly on the PET film with a coater. The coating layer thickness is controlled to be about 30μm, and the performance test is carried out.

[0035] Example 4 Reference Figure 1, a method for preparing a high softening point low VOC monomer resin, the specific steps are as follows: Step 1: Weigh 90g of hydroxybutyl vinyl ether, 4g of maleic anhydride, 0.25g of initiator AIBN, and 200g of isopropanol, add them to a 500 mL three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath at a temperature of 105°C for 3 hours, and place the beaker in an ice bath for rapid cooling to terminate the reaction. Add excess methyl tert-butyl ether to the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain hydroxybutyl vinyl ether grafted maleic anhydride oligomer D-4.

[0036] Step 2: Weigh 50g of α-methylstyrene, 30g of hydroxybutyl vinyl ether grafted maleic anhydride oligomer D4, and 30g of p-chloromethylstyrene, add them into a 250 mL three-necked flask in sequence, add 100mL of 1-ethyl-3-methylimidazole acetate, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add 0.4g of boron trifluoride ether initiator, evacuate the three-necked flask, and carry out cationic polymerization at -5°C and 0.04MPa. After reacting for 2.0 hours, add excess methanol to terminate the reaction, wash the product repeatedly with anhydrous ethanol, and place it in an 85°C forced air drying oven for drying for use to obtain a monomer resin.

[0037] The prepared monomer resin is applied as follows: Step 3: Weigh SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to the mass ratio of 40:15:30:1, add them into a 500mL three-necked flask, introduce nitrogen to replace the air in the flask, heat and control the temperature to about 160°C, turn on the mechanical stirrer and continue stirring until the product forms a uniform molten state to obtain a hot melt adhesive, and apply the hot melt adhesive evenly on the PET film with a coater. The coating layer thickness is controlled to be about 30μm, and the performance test is carried out.

[0038] Example 5 Reference Figure 1 , a method for preparing a high softening point low VOC monomer resin, the specific steps are as follows: Step 1: Weigh 100g of hydroxybutyl vinyl ether, 5g of maleic anhydride, 0.30g of initiator AIBN, and 200g of isopropanol, add them to a 500 mL three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath at 105°C for 3 hours, and place the beaker in an ice bath for rapid cooling to terminate the reaction. Add excess methyl tert-butyl ether to the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain hydroxybutyl vinyl ether grafted maleic anhydride oligomer D-5.

[0039] Step 2: Weigh 60g of α-methylstyrene, 30g of hydroxybutyl vinyl ether grafted maleic anhydride oligomer D4, and 20g of p-chloromethylstyrene, add them into a 250 mL three-necked flask in sequence, add 100mL of 1-butyl-3-methylimidazolium tetrafluoroborate, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add 0.5g of boron trifluoride ether initiator, evacuate the three-necked flask, and carry out cationic polymerization at 0°C and 0.05MPa. After reacting for 3.0 hours, add excess methanol to terminate the reaction, wash the product repeatedly with anhydrous ethanol, and place it in an 85°C forced air drying oven for drying for use to obtain a monomer resin.

[0040] The prepared monomer resin is applied as follows: Step 3: Weigh SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to the mass ratio of 40:15:30:1, add them into a 500mL three-necked flask, introduce nitrogen to replace the air in the flask, heat and control the temperature to about 160°C, turn on the mechanical stirrer and continue stirring until the product forms a uniform molten state to obtain a hot melt adhesive, and apply the hot melt adhesive evenly on the PET film with a coater. The coating layer thickness is controlled to be about 30μm, and the performance test is carried out.

[0041] Comparative Example 1 The preparation method of the monomer resin comprises the following specific steps: Step 1: Weigh 70g of hydroxybutyl vinyl ether, 1g of maleic anhydride, 0.1g of initiator AIBN, and 200g of isopropanol, add them to a 500 mL three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath at 105°C for 3 hours, and place the beaker in an ice bath for rapid cooling to terminate the reaction. Add excess methyl tert-butyl ether to the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain hydroxybutyl vinyl ether grafted maleic anhydride oligomer DB-1.

[0042] Step 2: Weigh 30g of hydroxybutyl vinyl ether grafted maleic anhydride oligomer DB-1 and 80g of α-methylstyrene, add them into a 250 mL three-necked flask in sequence, add 100mL of 1-ethyl-3-methylimidazolium acetate ionic liquid, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add 0.1g of boron trifluoride ether initiator, evacuate the three-necked flask, and carry out cationic polymerization at -20°C and 0.01MPa. After reacting for 0.5 hours, add excess methanol to terminate the reaction, wash the product repeatedly with anhydrous ethanol, and place it in an 85°C forced air drying oven for use to obtain a monomer resin.

[0043] The prepared monomer resin is applied as follows: Step 3: Weigh SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to the mass ratio of 40:15:30:1, add them into a 500mL three-necked flask, introduce nitrogen to replace the air in the flask, heat and control the temperature to about 160°C, turn on the mechanical stirrer and continue stirring until the product forms a uniform molten state to obtain a hot melt adhesive, and apply the hot melt adhesive evenly on the PET film with a coater. The coating layer thickness is controlled to be about 30μm, and the performance test is carried out.

[0044] Comparative Example 2 The preparation method of the monomer resin comprises the following specific steps: Step 1: Weigh 75g of hydroxybutyl vinyl ether, 2g of maleic anhydride, 0.15g of initiator ABVN, and 200g of isopropanol, add them to a 500 mL three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath at a temperature of 105°C for 3 hours, and place the beaker in an ice bath for rapid cooling to terminate the reaction. Add excess methyl tert-butyl ether to the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain hydroxybutyl vinyl ether grafted maleic anhydride oligomer DB-2.

[0045] Step 2: Weigh 30g of hydroxybutyl vinyl ether grafted maleic anhydride oligomer DB-2, 30g of α-methylstyrene, and 50g of p-methylstyrene, and add them to a 250 mL three-necked flask in sequence, add 100mL of dichloromethane solvent, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add 0.2g of boron trifluoride ether initiator, and carry out cationic polymerization at -15°C and normal pressure. After reacting for 1.0 hour, add excess methanol to terminate the reaction, wash the product repeatedly with anhydrous ethanol, and place it in an 85°C forced air drying oven for use to obtain a monomer resin.

[0046] The prepared monomer resin is applied as follows: Step 3: Weigh SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to the mass ratio of 40:15:30:1, add them into a 500mL three-necked flask, introduce nitrogen to replace the air in the flask, heat and control the temperature to about 160°C, turn on the mechanical stirrer and continue stirring until the product forms a uniform molten state to obtain a hot melt adhesive, and apply the hot melt adhesive evenly on the PET film with a coater. The coating layer thickness is controlled to be about 30μm, and the performance test is carried out.

[0047] Comparative Example 3 The preparation method of the monomer resin comprises the following specific steps: Step 1: Weigh 40g of isoprene, 30g of α-methylstyrene, and 40g of vinyltoluene, add them into a 250mL three-necked flask in sequence, add 100mL of 1-vinyl-3-butylimidazolium bromide ionic liquid, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add 0.3g of boron trifluoride ether initiator, evacuate the three-necked flask, and carry out cationic polymerization reaction at -10°C and 0.03MPa. After reacting for 1.5 hours, add excess methanol to terminate the reaction, wash the product repeatedly with anhydrous ethanol, and place it in an 85°C forced air drying oven for drying for use to obtain a monomer resin.

[0048] The prepared monomer resin is applied as follows: Step 2: Weigh SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to the mass ratio of 40:15:30:1, add them into a 500mL three-necked flask, introduce nitrogen to replace the air in the flask, heat and control the temperature to about 160°C, turn on the mechanical stirrer and continue stirring until the product forms a uniform molten state to obtain a hot melt adhesive, and apply the hot melt adhesive evenly on the PET film with a coater. The coating layer thickness is controlled to be about 30μm, and the performance test is carried out.

[0049] Performance testing: 1. First, the monomer resins prepared in Examples 1-5 and Comparative Examples 1-3 were tested. The testing method was as follows: The relative molecular weight and relative molecular weight distribution were obtained by PL-GPC50 gel permeation chromatography with tetrahydrofuran as the mobile phase.

[0050] The softening point is tested according to GB / T 4507-2014 Determination of softening point of asphalt (ring and ball method).

[0051] The VOC content is tested according to "T / CSTM 00636-2022 (Air Bag Method)".

[0052] The evaluation results are shown in Table 1.

[0053] Table 1 Evaluation results of monomer resins obtained in various examples and comparative examples

[0054] It can be seen from Table 1 that the monomer resin prepared in the present invention has the properties of narrow molecular weight distribution, higher softening point and lower VOC.

[0055] 2. Then, the monomer resin modified SIS hot melt adhesive (i.e., hot melt adhesive) prepared in Examples 1-5 and Comparative Examples 1-3 was tested. The testing method is as follows: (1) Initial adhesion is tested according to GB / T 31125-2014 Test method for initial adhesion of adhesive tapes - Ring method.

[0056] (2) The holding force is tested according to GB / T 4851-2014 Test method for holding force of adhesive tapes.

[0057] (3) 180° peel strength is tested according to GB / T 27792-2014 Test method for peel strength of adhesive tapes.

[0058] It should be noted that the hot melt adhesive was evenly coated on the PET film using an applicator, and the coating layer thickness was controlled to be about 30 μm, and then the tests (1) to (3) were performed.

[0059] (4) The softening point is tested according to GB / T 4507-2014 Determination of softening point of asphalt (ring and ball method).

[0060] (5) VOC content is tested according to T / CSTM 00636-2022 (Air Bag Method).

[0061] It should be noted that (4)-(5) are for hot melt adhesive testing and do not require coating it on PET film first.

[0062] The evaluation results are shown in Table 2.

[0063] Table 2 Performance test results of monomer resin modified SIS hot melt adhesive

[0064] It can be seen from Example 1 and Comparative Example 1 that the present invention prepares a narrow molecular weight distribution monomer resin by introducing a styrene derivative hard segment, which can effectively improve the softening point of the monomer resin and the SIS hot melt adhesive; it can be seen from Example 2 and Comparative Example 2 that the present invention uses an ionic liquid as a solvent and can prepare a low-VOC content monomer resin by vacuum treatment, thereby effectively reducing the VOC content of the SIS hot melt adhesive; it can be seen from Example 3 and Comparative Example 3 that the present invention introduces a hydroxybutyl vinyl ether grafted maleic anhydride oligomer soft segment to give the monomer resin a higher polarity, which can effectively improve the initial adhesion and 180° peel strength of the SIS hot melt adhesive, and improve the SIS hot melt adhesive's holding performance to a certain extent.

[0065] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A high softening point low VOC monomer resin, It is characterized in that The preparation method of the monomer resin comprises the following steps: Step 1: Add hydroxybutyl vinyl ether, maleic anhydride, initiator, and isopropanol into a three-necked flask with a thermometer and mechanical stirring, introduce nitrogen to replace the air in the flask, turn on the stirrer, react in an oil bath, and place the three-necked beaker in an ice bath for rapid cooling to terminate the reaction; add methyl tert-butyl ether into the three-necked flask to obtain a polymer precipitate, and centrifuge to obtain a hydroxybutyl vinyl ether grafted maleic anhydride oligomer; Step 2: Add hydroxybutyl vinyl ether grafted maleic anhydride oligomer, α-methylstyrene, and styrene derivatives into a three-necked flask, add ionic liquid, introduce nitrogen to replace the air in the flask, place the three-necked flask in a low-temperature water bath, add initiator, evacuate the three-necked flask, and perform cationic polymerization under low temperature and low pressure conditions; after reacting for a period of time, add methanol to terminate the reaction, wash the product, and dry it to obtain a monomer resin.

2. The high softening point low VOC monomer resin according to claim 1, It is characterized in that In step 1, the stirrer is turned on, and the reaction is carried out in an oil bath at 90-120° C. for 1-5 hours, and the three-necked beaker is placed in an ice bath for rapid cooling to terminate the reaction; the initiator includes one or more of AIBN, ABVN, and BPO.

3. The high softening point low VOC monomer resin according to claim 1, It is characterized in that In step 1, the mass ratio of hydroxybutyl vinyl ether, maleic anhydride, initiator and isopropanol is: 70~100:1~5:0.1~0.3:

200.

4. The high softening point low VOC monomer resin according to claim 1, It is characterized in that In step 2, the styrene derivative includes one or more of p-chloromethylstyrene, p-methylstyrene and vinyltoluene.

5. The high softening point low VOC monomer resin according to claim 1, It is characterized in that In step 2, the mass ratio of α-methylstyrene, hydroxybutyl vinyl ether grafted maleic anhydride oligomer, and styrene derivative is 2~6:3:2~6.

6. The high softening point low VOC monomer resin according to claim 1, It is characterized in that In step 2, the ionic liquid includes one or more of 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-vinyl-3-butylimidazolium bromide.

7. The high softening point low VOC monomer resin according to claim 1, It is characterized in that In step 2, the initiator includes boron trifluoride etherate initiator added in an amount of 0.1 to 0.5 g.

8. The high softening point low VOC monomer resin according to claim 1, It is characterized in that In step 2, the low temperature and low pressure conditions are: the reaction temperature is -20~0°C, the reaction pressure is 0.01~0.05MPa; the reaction time is 0.5-3 hours.

9. Hot melt adhesive, It is characterized in that The preparation method of the hot melt adhesive comprises the following steps: weighing SIS, polyethylene wax, monomer resin and antioxidant 1010 in sequence according to a mass ratio of 40:15:30:1, adding them into a three-necked flask, introducing nitrogen to replace the air in the flask, heating and controlling the temperature to 100-200° C., turning on a mechanical stirrer and continuously stirring until the product forms a uniform molten state, so as to obtain the hot melt adhesive; wherein the monomer resin is the high softening point and low VOC monomer resin according to any one of claims 1 to 8.

10. Composite materials, It is characterized in that The preparation method of the composite material comprises the following steps: coating the hot melt adhesive on a film, and controlling the coating layer thickness to be 20-50 μm, wherein the film comprises a PET film; and the hot melt adhesive is the hot melt adhesive described in claim 9.

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