Foaming box sealing hot melt adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of hot melt adhesives, and particularly relates to a foaming box sealing hot melt adhesive and a preparation method thereof. Comprising the following raw materials in parts by weight: 10 to 15 parts of PVB (Polyvinyl Butyral) resin, 15 to 20 parts of EVA (Ethylene-Vinyl Acetate) resin, 5 to 10 parts of EVA-g-MA (Ethylene-Vinyl Acetate) resin, 30 to 50 parts of tackifying resin, 15 to 25 parts of Fischer-Tropsch wax, 0.3 to 1 part of antioxidant and 1 to 3 parts of active silica powder. In order to further reduce the use cost on the premise of not influencing the adhesive property of the hot melt adhesive, the invention provides the foaming box sealing hot melt adhesive, PVB resin is added into an EVA hot melt adhesive system, so that the foaming rate of the hot melt adhesive system is remarkably increased, meanwhile, a certain amount of EVA-g-MA resin is compounded to adjust the overall adhesive force, and the service life of the foaming box sealing hot melt adhesive is prolonged. When the box sealing hot melt adhesive is applied to a product to be bonded, the bonding force is not influenced, and the use amount of the box sealing hot melt adhesive can be greatly reduced, so that the aim of reducing the cost of the hot melt adhesive is fulfilled.

Description

Technical Field

[0001] The invention belongs to the technical field of hot melt adhesives, and in particular relates to a foaming box sealing hot melt adhesive and a preparation method thereof. Background Art

[0002] EVA hot melt adhesive is a solvent-free, water-free, 100% solid fusible polymer adhesive. It is solid at room temperature, becomes a viscous liquid that can flow after heating, and is light brown translucent or white after melting. Its main component is a resin formed by the copolymerization of ethylene and vinyl acetate under high pressure, and is made of tackifiers, viscosity regulators, antioxidants, etc. EVA hot melt adhesive has the advantages of strong adhesion, affordable price, low pollution, and fast curing. It is widely used in packaging, woodworking, printing, medical, electronics, footwear, textiles and other industries. It can be used to seal boxes, stick labels, make sanitary disposable medical supplies, bond electronic components and wood products, etc. At the same time, EVA hot melt adhesive also has good flexibility, high and low temperature resistance, and environmental protection characteristics, which meets the requirements of green packaging and environmental protection standards.

[0003] EVA hot melt adhesive as a traditional carton sealing hot melt adhesive has the following disadvantages:

[0004] 1. The low temperature resistance of EVA hot melt adhesive is relatively poor;

[0005] 2. EVA hot melt adhesive has the problem of drawing during use, which seriously affects the neatness and beauty of the appearance of the sealing product;

[0006] 3. The cost of using EVA sealing glue is relatively high. Summary of the invention

[0007] The purpose of the present invention is to provide a foaming hot melt adhesive for sealing box and a preparation method thereof in view of the comprehensive problems of the prior art such as high cost, poor low temperature resistance, and adhesive wire drawing that affects the appearance of EVA-type sealing adhesives.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A foaming box sealing hot melt adhesive comprises the following raw materials in parts by weight: 10-15 parts of PVB resin, 15-20 parts of EVA resin, 5-10 parts of EVA-g-MA resin, 30-50 parts of tackifying resin, 15-25 parts of Fischer-Tropsch wax, 0.3-1 parts of antioxidant and 1-3 parts of active silicon micropowder.

[0010] In the technical scheme of the present invention, in order to further reduce the use cost without affecting the bonding performance of the hot melt adhesive, a foaming carton sealing hot melt adhesive is proposed. By adding PVB resin to the EVA hot melt adhesive system, the foaming rate is significantly increased. At the same time, a certain amount of EVA-g-MA resin is compounded to adjust the overall bonding force, so that the carton sealing hot melt adhesive of the present invention does not affect the bonding force on the product to be bonded, and can also greatly reduce its usage, thereby achieving the purpose of reducing the cost of the hot melt adhesive.

[0011] In the technical solution of the present invention, a small amount of branching (acetal between molecules) is formed in the PVB resin itself during the synthesis process, so that a small amount of PVB molecules cannot move freely when the PVB resin is melted. Therefore, when air is blown in, bubbles of various pore sizes are easily formed. The addition of active silicon micropowder and the PVB resin can produce a heterogeneous nucleation effect, thereby increasing the pore density. The synergistic effect of the branch locking in PVB and the heterogeneous nucleation of active silicon micropowder can significantly improve the foaming ratio.

[0012] In the technical solution of the present invention, the hydroxyl groups of the PVB resin and the side chain carboxyl groups in the EVA-g-MA resin can form strong hydrogen bonds. The EVA-g-MA resin is maleic anhydride grafted EVA, and the strong polar bonds of the strong hydrogen bonds can increase the thickness of the interfacial liquid film between the foams, making the formed foams less likely to dissipate, and thus having a good foam stabilizing effect. Furthermore, the PVB resin side chains used in the hot melt adhesive of the present invention contain strongly polar hydroxyl groups, and the carboxyl groups in the EVA-g-MA resin can form strong hydrogen bonds with the surface of the bonding substrate, thereby increasing the bonding force with the substrate surface, which can effectively offset the technical defect of decreased bonding force caused by the reduced contact area between the adhesive and the substrate surface due to foaming.

[0013] In the technical solution of the present invention, since PVB molecules and EVA molecules are not completely miscible, there is a slight microscopic phase separation between the two, so that during the cooling process of the hot melt adhesive, the PVB molecules solidify first from the system, so that the adhesive filaments are quickly separated from the hot melt adhesive liquid, and the hot melt adhesive filament breaking performance is enhanced. When using the hot melt adhesive, there will be no serious wire drawing phenomenon that affects the appearance of the box.

[0014] As a preferred embodiment of the present invention, the butyral content of the PVB resin is 70%-90%, and the viscosity of the PVB resin in a 5% methanol solution is in the range of 100-150 mPa.s.

[0015] In order to achieve the foaming purpose of hot melt adhesive, a large number of foaming resins were tested and it was found that PVB resin is soluble at high temperature and its side chain has a highly polar hydroxyl group, which has a good bonding effect on various paper fiber substrates. PVB resin itself has a foam stabilizing effect and intermolecular branching can increase the formation of foams of various pore sizes.

[0016] In the hot melt adhesive of the present invention, the selected PVB resin has a moderate butyral group content, and the PVB resin has good low-temperature toughness. The synergistic effect of the PVB resin and a small amount of active silicon powder can effectively offset the internal silver streaks generated under low-temperature impact, thereby improving the low-temperature resistance of the hot melt adhesive. At the same time, the cross-linking of a small amount of molecular chains in the PVB resin can effectively limit the movement of low molecular weight molecular segments in the hot melt adhesive system at high temperatures, thereby improving the high-temperature resistance of the system.

[0017] As a preferred embodiment of the present invention, the melt index of the EVA-g-MA resin at 190° C. is in the range of 100-500 g / 10 min; the vinyl acetate content is in the range of 19%-33%; and the grafting rate is in the range of 1%-3%.

[0018] In the EVA hot melt adhesive system of the present invention, when the melt mass flow rate of the EVA-g-MA resin is 100-500 g / 10 min, the fluidity is good, which is conducive to the penetration and bonding of the box sealing hot melt adhesive.

[0019] EVA with a VA content of 19-33% has good compatibility with petroleum resin and rosin, which is beneficial to the fluidity of the hot melt adhesive product. The grafting rate range is 1%-3%. Within this grafting rate range, it has good compatibility with PVB resin and has little effect on the high-temperature aging effect of the entire system.

[0020] When the ratio of PVB resin to EVA-g-MA resin is too large (over 3:1), the prepared hot melt adhesive has a turbid appearance and the fluidity of the entire system is poor. When the ratio of PVB:EVA is lower than 1.5:1, the compatibility of the entire system becomes better, the hot melt adhesive becomes very clear and transparent, the wire breaking effect of the hot melt adhesive becomes worse, and the price of EVA-g-MA is relatively high. Excessive use will increase the cost of the hot melt adhesive. Therefore, as a more preferred technical solution of the present invention, the mass ratio between the PVB resin and the EVA-g-MA resin is (3-1.5):1.

[0021] As a preferred embodiment of the present invention, the melt index of the EVA resin at 190°C is in the range of 50-200 g / 10 min, and the vinyl acetate content of the EVA resin is in the range of 19-33%. In the EVA hot melt adhesive system of the present invention, selecting the EVA resin in this range can better control the overall viscosity and compatibility of the system.

[0022] As a preferred embodiment of the present invention, the tackifying resin comprises 20-30 parts of C5 / C9 copolymerized petroleum resin and 10-20 parts of rosin pentaerythritol ester; the softening point temperature of the C5 / C9 copolymerized petroleum resin is 90-110° C., and the softening point temperature range of the rosin pentaerythritol ester resin is 90-110° C. C5 / C9 copolymerized petroleum resin is also called C5 / C9 composite petroleum resin, which has the excellent properties of both C5 petroleum resin and C9 petroleum resin, has good comprehensive performance, has a higher iodine value than C9 petroleum resin, and has good solubility, and is compatible with polar or non-polar polymers.

[0023] As a preferred embodiment of the present invention, the softening point temperature range of the Fischer-Tropsch wax is 80-120°C.

[0024] As a preferred embodiment of the present invention, the particle size of the active silicon powder is in the range of 1-3 μm. The active silicon powder mainly plays a role in increasing heterogeneous nucleation in the hot melt adhesive system of the present invention, thereby increasing the number of hot melt adhesive bubble points and further improving the foaming rate. At the same time, a small amount of silicon powder can effectively destroy the regularity of polymer crystallization, thereby reducing the low-temperature brittleness of the product.

[0025] As a preferred embodiment of the present invention, the antioxidant includes antioxidant 1010 and antioxidant 168. Antioxidant 1010 is a primary antioxidant, and 168 is a secondary antioxidant. In the hot melt adhesive system of the present invention, the antioxidant can be antioxidant 1010, or a combination of antioxidant 1010 and antioxidant 168.

[0026] On the other hand, the present invention provides a method for preparing a foaming hot melt adhesive for sealing a box, comprising the following steps:

[0027] Step 1, adding the raw materials of claim 1 to a reaction kettle in order, mixing, heating and melting to obtain a molten mixture liquid, keeping the temperature at 130° C. to 150° C. and evacuating the mixture; specifically, the melting temperature of the reaction kettle is 190° C., the stirring rate of the reaction kettle is 1000 to 1200 r / h, and the vacuuming pressure is -0.05 MPa to -0.08 MPa;

[0028] Specifically, the order of adding the raw materials is: first add Fischer-Tropsch wax and rosin pentaerythritol ester, then add antioxidant, PVB, EVA, EVA-g-MA after melting, and finally add C5 / C9 petroleum resin;

[0029] Step 2: filtering the molten mixture liquid in step 1, and then performing underwater extrusion granulation to form hot melt adhesive particles.

[0030] Specifically, the molten mixture liquid is filtered through a double-layer filter bag with a mesh size of 200 to 400, and then discharged into a single screw extruder for underwater granulation, wherein the screw speed is 90 r / h to 100 r / h, the pelletizing speed is 1300 r / h to 1500 r / h, the dehydrator speed is 600 r / h to 700 r / h, the cooling water is 5 to 10° C., and the screw and die head insulation temperature is 100 to 130° C.

[0031] Preferably, a water-soluble release agent is added to the cooling water, and the water-soluble release agent includes: modified water-soluble paraffin wax and modified water-soluble silicone oil.

[0032] Preferably, the amount of the water-soluble release agent used is 2‰ to 5‰ of the cooling water.

[0033] The hot melt adhesive prepared by the technical solution of the present invention is compounded with PVB resin, EVA resin and EVA-g-MA resin. By further optimizing the compounding ratio, the hot melt adhesive system has foaming characteristics, and the amount of hot melt adhesive is effectively saved during use. The overall bonding force is adjusted by compounding a certain amount of EVA-g-MA resin, so that the box sealing hot melt adhesive of the present invention does not affect the bonding force on the product to be bonded and can also greatly reduce its usage.

[0034] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0035] 1. In the technical solution of the present invention, a foaming hot melt adhesive for sealing boxes is compounded with PVB resin, EVA resin and EVA-g-MA resin. By further optimizing the compounding ratio, the hot melt adhesive system has foaming characteristics, and the amount of hot melt adhesive used is effectively saved during use. By compounding a certain amount of EVA-g-MA resin to adjust the overall bonding force, the hot melt adhesive for sealing boxes of the present invention does not affect the bonding force on the products to be bonded, and can also greatly reduce its usage, thereby achieving the purpose of reducing the cost of hot melt adhesive. Compared with the hot melt adhesive in the prior art, the foaming hot melt adhesive of the present invention can seal boxes more than twice at the same content.

[0036] 2. In the technical solution of the present invention, in the foaming hot melt adhesive system, the addition of active silicon powder and PVB resin can produce a heterogeneous nucleation effect, thereby increasing the cell density. The side chains in PVB play an important role in locking the cells and stabilizing the foam, thereby significantly improving the foaming ratio.

[0037] 3. In the technical solution of the present invention, since PVB resin and EVA resin are not completely miscible, there is a slight microscopic phase separation between the two, so that during the cooling process of the hot melt adhesive, the PVB resin solidifies first from the system and quickly separates from the hot melt adhesive liquid, thereby enhancing the wire breaking performance of the hot melt adhesive. When using the hot melt adhesive, the appearance of the box can be ensured to be clean and beautiful. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] Example 1

[0040] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight:

[0041] 8 parts of PVB resin (butyral content is 85%), 20 parts of EVA resin, 10 parts of EVA-g-MA resin (including 28% vinyl acetate and 2.5% maleic anhydride grafting rate), 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2.5 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0042] The foaming hot melt adhesive for sealing is prepared according to the following preparation method:

[0043] Step 1, setting the temperature of the reactor to 190°C, and when the temperature of the reactor rises to 100°C, adding Fischer-Tropsch wax and rosin pentaerythritol ester; controlling the speed of the reactor to about 1000-1200 r / h, stirring for 40-60 minutes until completely melted;

[0044] Step 2, adding antioxidant, PVB resin, EVA resin, and EVA-g-MA resin to the reaction kettle in sequence, stirring at a speed of 800 to 1000 r / h, and stirring and mixing for 2 to 2.5 hours until completely melted;

[0045] Step 3, adding C5 / C9 copolymerized petroleum resin into the reaction kettle of step 2, stirring for 30 to 40 minutes until it is completely melted to obtain a uniformly mixed liquid, and then vacuuming for 30 to 40 minutes after keeping warm at 130 to 150° C., with a vacuum pressure of -0.05 to -0.08 MPa;

[0046] Step 4: Filter the mixture liquid in step 3 through a double-layer filter bag with a mesh size of 200 to 400, and then discharge the mixture into a single screw extruder for underwater granulation (screw speed 90 to 100 r / h, pelletizing speed 1300 to 1500 r / h, dehydrator speed 600 to 700 r / h, cooling water 5 to 10°C, and screw and die insulation temperature 100 to 130°C).

[0047] Example 2

[0048] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight: (the types of raw materials are the same as those in embodiment 1, the only difference is the ratio)

[0049] 10 parts of PVB resin, 20 parts of EVA resin, 10 parts of EVA-g-MA resin, 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2.5 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0050] Please refer to Example 1 for the specific preparation steps.

[0051] Example 3

[0052] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight: (the types of raw materials are the same as those in Embodiment 1, the only difference being the ratio;)

[0053] 12.5 parts of PVB resin, 20 parts of EVA resin, 10 parts of EVA-g-MA resin, 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2.5 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0054] Please refer to Example 1 for the specific preparation steps.

[0055] Example 4

[0056] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight: (the types of raw materials are the same as those in embodiment 1, the only difference is the ratio)

[0057] 15 parts of PVB resin, 20 parts of EVA resin, 10 parts of EVA-g-MA resin, 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2.5 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0058] Please refer to Example 1 for the specific preparation steps.

[0059] Example 5

[0060] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight: (the types of raw materials are the same as those in embodiment 1, the only difference is the ratio)

[0061] 20 parts of PVB resin, 20 parts of EVA resin, 10 parts of EVA-g-MA resin, 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2.5 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0062] Please refer to Example 1 for the specific preparation steps.

[0063] Examples 1 to 5 are mainly about changing the weight of PVB and comparing the performance of the final hot melt adhesive.

[0064] The raw material contents of the hot melt adhesives of Examples 1 to 5 are summarized in Table 1:

[0065] Table 1 is a summary of the raw material contents of the hot melt adhesives of Examples 1-5

[0066]

[0067] 1. The hot melt adhesives of Examples 1-5 were tested for foaming rate:

[0068] The specific test method is: use the FoamMe1t200 foaming hot melt adhesive machine produced by Nordson Corporation of the United States to introduce air or nitrogen, so that the hot melt adhesive of the present invention becomes a colloid full of small bubbles in the hot melt adhesive machine. The foaming time is 5 minutes, and then the test is carried out according to the test method.

[0069] Foaming rate test method: Heat the unfoamed hot melt adhesive to 170°C, weigh 100g with a measuring cylinder, and measure the volume V1. At the same time, after the hot melt adhesive is foamed, let it stand for 5 minutes. When the foam is stable, weigh 100g with a measuring cylinder, and measure the system V2. The foaming rate = (V2-V1) / V1*100%.

[0070] Wire breaking performance test method: add 100g of hot melt adhesive into a constant temperature tank (the tank is kept at 170℃), pick up the liquid with a glass rod, the liquid is 40cm above the tank mouth, and measure the length of the wire (from the glass rod to the end of the wire) after the first drop of glue falls.

[0071] Test method for low temperature and high temperature resistance: Carton sealing is carried out on a beer production line equipped with a FoamMe1t200 foaming hot melt adhesive machine from Nordson Corporation of the United States. After sealing, the finished product is placed in a -18°C cold storage for 24 hours, and then placed in a 60°C high temperature box for insulation for 24 hours. Then, the beer box is torn open to observe the broken area.

[0072] Adhesion test method: Carton sealing is carried out on a beer production line equipped with a FoamMe1t 200 foaming hot melt adhesive machine from Nordson Corporation of the United States. After the sealing is completed, the finished product is kept warm at 25°C for 24 hours, and the side cover of the beer box is pulled with a tensile testing machine to test the tensile force.

[0073] Glue transparency test: Use a glass rod to pick up the glue and visually inspect its transparency.

[0074] The hot melt adhesive expansion rate data of Examples 1-5 obtained through testing are shown in Table 2 below:

[0075] Table 2 is the hot melt adhesive foaming rate data of Examples 1-5

[0076] Example 1 Example 2 Example 3 Example 4 Example 5 Foaming rate (%) 26％ 47％ 75％ 112％ 103％

[0077] 2. Test the viscosity of the hot melt adhesives of Examples 1-5 respectively:

[0078] The test method is carried out according to the method in GB / T 2794. The hot melt adhesive viscosity data of Examples 1-5 are shown in Table 3 below:

[0079] Table 3 is the hot melt adhesive viscosity data of Examples 1-5

[0080]

[0081] 3. Wire breaking performance test, specific test method: test results are shown in Table 4:

[0082] Table 4 is the hot melt adhesive broken wire performance data of Examples 1-5

[0083]

[0084] 4. Low temperature and high temperature resistance: Specific test methods, test data table 5:

[0085] Table 5 shows the high temperature and low temperature resistance data of the hot melt adhesives of Examples 1-5.

[0086]

[0087]

[0088] 5. Adhesion performance test: Specific test method, test data table 6:

[0089] Table 6 is the hot melt adhesive bonding test data of Examples 1-5

[0090]

[0091] By testing various properties of the hot melt adhesive samples prepared in the above Examples 1-5, it can be seen that as the amount of PVB used increases, the foaming rate of the hot melt adhesive increases and its viscosity gradually increases. This is mainly because the branched structure in the PVB can fix the movement of the PVB molecular chain, playing a role in stabilizing the foam, locking the foam, and heterogeneous nucleation and foaming. In Examples 1-4, as the content of PVB increases, the filament breaking effect of the hot melt adhesive is significantly improved. This is mainly because the increase in PVB causes the compatibility in the system to gradually deteriorate. When the hot melt adhesive cools, the PVB branched structure solidifies and cools first, causing the hot melt adhesive system to be micro-phased, so that the filaments of the hot melt adhesive are broken.

[0092] After the hot melt adhesive in Examples 1-4 was sealed, its high temperature resistance and low temperature resistance gradually improved. This was mainly because an appropriate amount of PVB was added. The hydroxyl groups in PVB could form hydrogen bonds with the paper to enhance the bonding effect. However, a large area of ​​peeling occurred in Example 5. This was mainly because the excessive addition of PVB caused a sharp change in the compatibility of the entire system, resulting in a significant increase in the viscosity of the hot melt adhesive, poor fluidity, and failure to penetrate into the pores of the carton when sealing. It can be seen from Table 6 that in the hot melt adhesive samples in Examples 1-4, the foaming rate is increasing, the amount of hot melt adhesive is decreasing, but the bonding strength with the carton is increasing. This is mainly because the PVB content increases, and the increase in the number of hydrogen bonds causes the bonding strength to increase, which can effectively offset the decrease in bonding caused by the reduction in contact area.

[0093] Example 6

[0094] In order to study the interaction between active silica powder and PVB resin, the following hot melt adhesive samples Example 6-1 to Example 6-5 were prepared by changing the weight fraction of active silica powder; the specific raw material contents are summarized in Table 7:

[0095] Table 7 is a summary of raw materials for Example 6-1 to Example 6-5

[0096]

[0097] The foaming rate of the hot melt adhesive samples was tested; the test results are summarized in Table 8:

[0098] Table 8 is a table showing the foaming properties of the hot melt adhesive samples of Examples 6-1 to 6-5.

[0099] Example 6-1 Example 6-2 Example 6-3 Example 6-4 Example 6-5 Foaming rate (%) 85％ 98％ 103％ 112％ 110％

[0100] The present invention also conducts a low temperature resistance test on the hot melt adhesive samples of the above embodiment. The specific test method is shown in Table 9:

[0101] Table 9 is a table showing the low temperature resistance of the hot melt adhesive samples of Examples 6-1 to 6-5.

[0102]

[0103] From the data in Table 8, it can be seen that the addition of silicon micropowder has a certain auxiliary effect on improving the foaming rate of hot melt adhesive. When silicon micropowder is added to a certain amount, its effect on the foaming rate tends to be stable, because the marginal effect of heterogeneous nucleation of the system is decreasing. At the same time, with the increase of silicon micropowder content, its low-temperature adhesion also increases to a certain extent, but when it increases to 4%, its low-temperature resistance decreases instead, mainly because with the increase of silicon micropowder content, its silicon micropowder partially agglomerates and causes microscopic phase separation, the fluidity of the adhesive solution decreases, and the low-temperature brittleness of the hot melt adhesive increases, so the adhesion becomes worse.

[0104] Example 7

[0105] In order to adjust the overall adhesion of the system, a certain amount of EVA-g-MA resin was compounded. Furthermore, the embodiments of the present invention further studied the regulatory effect of the ratio between EVA-g-MA resin and PVB resin on the adhesion performance of the hot melt adhesive system. In order to compare the optimal compounding ratio, the hot melt adhesives with different contents of EVA-g-MA resin were tested for adhesion, peeling force after sealing, and wire breaking effect. The specific test results are shown below:

[0106] Specifically, the following hot melt adhesive samples Example 7-1 to Example 7-5 were prepared;

[0107] Table 10 is a list of ingredients for the hot melt adhesive samples of Examples 7-1 to 7-5

[0108]

[0109] Examples 7-1 to 7-6 provide hot melt adhesive samples with different ratios of PVB resin and EVA-g-MA resin to investigate the effects on the hot melt adhesive system. The hot melt adhesive samples of Examples 7-1 to 7-6 were subjected to the following performance tests:

[0110] Table 11 is a summary of the properties of the hot melt adhesive samples of Examples 7-1 to 7-5

[0111]

[0112] It can be seen from Table 11 that when PVB:EVA-g-MA is greater than 3:1, the compatibility of the entire hot melt adhesive system is poor, the viscosity of the hot melt adhesive is relatively large, the fluidity of the hot melt adhesive is poor, and the curing speed is very fast. The hot melt adhesive has no time to penetrate into the corrugated paper to form an effective physical bond, which causes its bonding force to deteriorate. When PVB:EVA-g-MA=3~1.5:1, the compatibility of its hot melt adhesive has undergone a significant change, from slightly turbid and translucent to transparent. This is mainly because EVA-g-MA plays a solubilizing role in the system, making the compatibility of the system gradually better. When PVB:EVA-g-MA reaches 1.875:1, the length of the hot melt adhesive drawing is only 15cm. The liquid is similar to a Bingham fluid, and its silk has good retraction performance, so that when 2-3 drops are picked up with a glass rod, basically no silk can be seen. When the amount of EVA-g-MA continues to increase, the compatibility of the system becomes very good, and the hot melt adhesive's wire breaking property becomes worse. When PVB:EVA-g-MA=1.25:1, its tensile force value decreases instead. This is mainly because after the amount of EVA-g-MA is greatly increased, the viscosity increases, the hot melt adhesive's fluidity deteriorates, and its physical anchoring bonding effect deteriorates.

[0113] Example 8

[0114] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight:

[0115] 15 parts of PVB resin (butyral content is 70%), 20 parts of EVA resin, 10 parts of EVA-g-MA resin (including 33% vinyl acetate and 2.5% maleic anhydride grafting rate), 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0116] The raw material ratio of this embodiment is consistent with that of embodiment 7-5, and the only difference is the change of the butyral content of the PVB resin and the vinyl acetate content and grafting rate of the EVA-g-MA resin.

[0117] Example 9

[0118] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight:

[0119] 15 parts of PVB resin (butyral content is 90%), 20 parts of EVA resin, 10 parts of EVA-g-MA resin (including 33% vinyl acetate and 2.5% maleic anhydride grafting rate), 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0120] Example 10

[0121] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight:

[0122] 15 parts of PVB resin (butyral content is 80%), 20 parts of EVA resin, 10 parts of EVA-g-MA resin (including 33% vinyl acetate and 1.0% maleic anhydride grafting rate), 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0123] Embodiment 11

[0124] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight:

[0125] 15 parts of PVB resin (butyral content is 80%), 20 parts of EVA resin, 10 parts of EVA-g-MA resin (including 33% vinyl acetate and 3.0% maleic anhydride grafting rate), 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0126] Example 12

[0127] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight:

[0128] 15 parts of PVB resin (butyral content is 80%), 20 parts of EVA resin, 10 parts of EVA-g-MA resin (including 19% vinyl acetate and 1.0% maleic anhydride grafting rate), 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0129] Embodiment 13

[0130] This embodiment provides a foaming box sealing hot melt adhesive, comprising the following raw materials in parts by weight:

[0131] 15 parts of PVB resin (butyral content is 80%), 20 parts of EVA resin, 10 parts of EVA-g-MA resin (including 19% vinyl acetate and 3.0% maleic anhydride grafting rate), 20 parts of Fischer-Tropsch wax, 0.5 parts of antioxidant 1010, 2 parts of active silica powder; 25 parts of C5 / C9 copolymer petroleum resin and 15 parts of rosin pentaerythritol ester.

[0132] Among them, the ingredient lists of Examples 8 to 12 are summarized in Table 12:

[0133] Table 12 is a summary of the ingredients of Example 8 to Example 12

[0134]

[0135] The hot melt adhesive samples of Examples 8-12 were tested for foaming rate and bonding performance. The specific test results are shown in Table 13:

[0136] Table 13 shows the foaming rate and bonding performance test data of the hot melt adhesive samples of Examples 8-12

[0137]

[0138] From the data in Table 13, it can be seen that when the butyral group increases, the viscosity of the hot melt adhesive increases, and its foaming rate increases, while the tensile test value decreases. This is mainly because when the amount of acetal groups increases, the acetal between PVB molecules will increase rapidly to produce more branched structures, so the viscosity of the hot melt adhesive increases, and its foam stabilizing effect is also better during the foaming process, and the foaming rate increases. With the increase of acetal degree, the hydroxyl group in its PVB decreases, the hydrogen bonds formed decrease, and thus the tensile force decreases. It can be seen from the comparative examples 10 and 11 that within the range of 1-3% grafting rate, the grafting rate increases, the lower the viscosity, and the greater the tensile force of the hot melt adhesive paper box. This is mainly because the higher the grafting rate, the higher the proportion of carboxyl groups in its MA, and thus the more hydrogen bonds formed with the paper surface, and thus the better the adhesion. A comprehensive comparison of Examples 10, 11, 12, and 13 found that the VA content in the range of 19-28% has little effect on the bonding strength, foaming rate, and viscosity of the hot melt adhesive. Therefore, the acetal content of PVB and the MA grafting rate in EVA-g-MA given in the patent of this invention have an impact on each other. To achieve ideal box sealing performance, these two key parameters need to be comprehensively considered.

[0139] Comparative Example 1

[0140] This comparative example provides a hot melt adhesive, comprising the following raw materials in parts by weight:

[0141] Referring to the raw material ratio of Example 7-5, other ingredients remain unchanged, and only the PVB resin is replaced with SIS (styrene-butadiene rubber, S segment <20%).

[0142] Comparative Example 2

[0143] This comparative example provides a hot melt adhesive, comprising the following raw materials in parts by weight:

[0144] Referring to the raw material ratio of Example 7-5, the other ingredients remain unchanged, and only the PVB resin is replaced with POE (melt index: 30-50 (190° C.).

[0145] Comparative Example 3

[0146] This comparative example provides a hot melt adhesive, comprising the following raw materials in parts by weight:

[0147] Referring to the raw material ratio of Example 7-5, the other ratios remain unchanged, and only the EVA-g-MA resin is replaced by EVA-Cl (chlorinated EVA, chlorination value: 18-24%, VA content 19-33%).

[0148] Table 14 is a material list of hot melt adhesive samples of Comparative Examples 1-3

[0149]

[0150] The hot melt adhesive samples of Comparative Examples 1-3 were subjected to the following performance tests, and the test results are shown in Table 15 below:

[0151] Table 15 shows the performance data of hot melt adhesive samples

[0152]

[0153] It can be seen from the above comparative examples that the foaming rate of the hot melt adhesive using SIS (S segment <20%) in comparative example 1 is significantly lower than that of the hot melt adhesive using PVB resin. At the same time, its viscosity is relatively high, and its peeling force is relatively weak. Its stringing is abnormally serious. This is mainly because after the addition of SIS (styrene-isoprene-styrene (SIS) block copolymer), the open time of the hot melt adhesive is extended and it takes longer to solidify. Therefore, SIS cannot play a nucleation role during the foaming process, and the stringing becomes more severe. Comparative example 2 uses POE, which has relatively good foaming and wire breaking effects, but poor peeling force. This is mainly because POE is a non-polar polymer that cannot form polar bonding or hydrogen bonding with the surface of paper, resulting in reduced peeling force. Comparative example 3 uses chlorinated EVA, which is much weaker in polarity than EVA-MA, so its solubilization effect becomes worse, resulting in increased viscosity. At the same time, chlorine atoms cannot form hydrogen bonds with the bonded substrate, resulting in reduced adhesion of the hot melt adhesive.

[0154] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A foaming hot melt adhesive for sealing a box, characterized in that: The invention comprises the following raw materials in parts by weight: 10-15 parts of PVB resin, 15-20 parts of EVA resin, 5-10 parts of EVA-g-MA resin, 30-50 parts of tackifying resin, 15-25 parts of Fischer-Tropsch wax, 0.3-1 parts of antioxidant and 1-3 parts of active silicon micropowder.

2. The foaming hot melt adhesive for sealing a box according to claim 1, characterized in that: The butyral content of the PVB resin is 70%-90%, and the viscosity of the PVB resin in a 5% methanol solution is in the range of 100-150 mPa.s.

3. The foaming hot melt adhesive for sealing a box according to claim 2, characterized in that: The EVA-g-MA resin has a melting index range of 100-500 g / 10 min at 190° C., a vinyl acetate content range of 19%-33%, and a grafting rate range of 1%-3%.

4. The foaming hot melt adhesive for sealing a box according to claim 3, characterized in that: The mass ratio between the PVB resin and the EVA-g-MA resin is (3-1.5):

1.

5. The foaming hot melt adhesive for sealing a box according to claim 1, characterized in that: The melting index of the EVA resin at 190° C. is in the range of 50-200 g / 10 min. The vinyl acetate content of the EVA resin is in the range of 19-33%.

6. The foaming hot melt adhesive for sealing a box according to claim 1, characterized in that: The tackifying resin comprises 20-30 parts of C5 / C9 copolymerized petroleum resin and 10-20 parts of rosin pentaerythritol ester; the softening point temperature range of the C5 / C9 copolymerized petroleum resin is 90-110°C, and the softening point temperature range of the rosin pentaerythritol ester resin is 90-110°C.

7. The foaming hot melt adhesive for sealing a box according to claim 1, characterized in that: The softening point temperature range of the Fischer-Tropsch wax is 80-120°C.

8. The foaming hot melt adhesive for sealing a box according to claim 1, characterized in that: The particle size of the active silicon powder is in the range of 1-3 μm.

9. The foaming hot melt adhesive for sealing a box according to claim 1, characterized in that: The antioxidants include antioxidant 1010 and antioxidant 168.

10. A method for preparing the foaming hot melt adhesive for sealing box according to any one of claims 1 to 9, characterized in that: The steps include: Step 1, adding the raw materials described in claim 1 to a reaction kettle in order, mixing, heating and melting to obtain a molten mixture liquid, keeping the temperature at 130° C. to 150° C. and evacuating; the order of adding the raw materials is: first adding Fischer-Tropsch wax and rosin pentaerythritol ester, then adding antioxidant, PVB, EVA, EVA-g-MA after melting, and finally adding C5 / C9 copolymer petroleum resin; Step 2: Filter the molten mixture liquid in step 1, and then extrude and granulate it underwater to form hot melt adhesive particles, wherein the molten mixture liquid is filtered through a double-layer filter bag with a mesh size of 200 to 400, and then discharged into a single screw extruder for extrusion and underwater granulation, wherein the screw speed is 90 r / h to 100 r / h, the pelletizing speed is 1300 r / h to 1500 r / h, the dehydrator speed is 600 r / h to 700 r / h, the cooling water is 5 to 10°C, and the screw and die head insulation temperature is 100 to 130°C.

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