Hot melt adhesive, production method and application of hot melt adhesive in seamless bonding of cartons

Abstract

The invention discloses a hot melt adhesive, a production method and application of the hot melt adhesive in seamless bonding of cartons, and belongs to the field of cartons, and the production method comprises the following steps: S1, obtaining hydroxypropyl starch; s2, dispersing hydroxypropyl starch in water, and adding butyl acrylate and ammonium persulfate; introducing nitrogen to remove oxygen, heating to 70-90 DEG C, reacting for 2-5 hours to generate a starch poly (butyl acrylate) grafted copolymer, precipitating the reaction liquid with ethanol, filtering, drying at 60 DEG C, and crushing into 100-mesh powder to obtain modified grafted starch powder; s3, premixing 100 parts of modified grafted starch powder, hydrogenated rosin glyceride, sugarcane wax and 0.3 part of antioxidant 1010 in a high-speed mixer for 5-10 minutes to obtain a premixed material; s4, adding acetylated cellulose nanocrystal suspension and a zirconium-based catalyst into the premixed material, and performing melt extrusion; s5, the extruded strip-shaped colloid makes contact with cooling liquid to be cooled, and then the strip-shaped colloid is cut into particles; the hot melt adhesive disclosed by the invention has good heat resistance and has a wide application prospect in the fields of cartons and the like.

Description

Technical Field

[0001] This invention relates to the field of cardboard boxes, specifically to a hot melt adhesive, a production method thereof, and its application in seamless bonding of cardboard boxes. Background Technology

[0002] Hot melt adhesive is a type of malleable adhesive whose physical state changes with temperature within a certain temperature range, while its chemical properties remain unchanged. It is non-toxic, odorless, and an environmentally friendly chemical product. Because it is a solid, it is easy to package, transport, and store; it is solvent-free, pollution-free, and non-toxic; and it boasts advantages such as simple production processes, high added value, strong bonding strength, and fast processing speed.

[0003] Starch-based hot melt adhesives are environmentally friendly adhesives made primarily from natural starch (corn, cassava, potato, etc.), which are then modified through physical, chemical, or biological means to impart thermoplasticity. They are applied in a molten state, cooled, and then rapidly cured to form adhesive bonds.

[0004] Application No. 201410484739.4 discloses a preparation technology for a rosin / starch-based biodegradable hot melt adhesive. The method involves mixing starch and a plasticizer under high-speed stirring, allowing the mixture to stand for 24 hours, and then heating it at 120–140°C to form a molten gel. After cooling and pelletizing, thermoplastic starch granules are obtained for later use. Existing starch-based hot melt adhesives suffer from insufficient high-temperature resistance, limiting their application. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by disclosing a method for producing hot melt adhesive, comprising the following steps:

[0006] S1: Obtain hydroxypropyl starch;

[0007] S2: Disperse hydroxypropyl starch in water, add butyl acrylate and ammonium persulfate; purge with nitrogen to remove oxygen, heat to 70℃-90℃, react for 2-5 hours to generate starch-polybutyl acrylate graft copolymer, precipitate the reaction solution with ethanol, filter and dry at 60℃, pulverize into 100 mesh powder to obtain modified graft starch powder.

[0008] S3: Premix 100 parts of modified grafted starch powder, 40 parts of hydrogenated rosin glycerol ester, 10 parts of sugarcane wax, and 10100.3 parts of antioxidant in a high-speed mixer for 5-10 minutes to obtain a premixed material;

[0009] S4: Add the above premixed materials to an acetylated cellulose nanocrystal suspension and a zirconium-based catalyst, and then melt-extrude them;

[0010] S5: The extruded strip-shaped colloid is cooled by contact with coolant and then cut into granules.

[0011] In the preferred embodiment, a twin-screw extruder is used for melt extrusion. The temperatures of each zone of the twin-screw extruder are as follows: Zone 1: 90℃; Zone 2: 110℃; Zone 3: 140℃; Zone 4: 130℃, and the screw speed is 200-300 rpm.

[0012] In the preferred embodiment, 25 parts of liquid glycerin are added to zone two.

[0013] In a preferred embodiment, the method for obtaining hydroxypropyl starch is as follows: corn starch is dispersed in water with a solid content of 30%, and 5% NaOH solution is added to adjust the pH to 10–11. The temperature is raised to 50°C and stirred for 30–50 minutes. Then, 20 parts of propylene oxide are slowly added dropwise while maintaining the temperature at 50–55°C for 4–6 hours. After the etherification reaction is completed, the solution is neutralized to pH 6.5–7.0 with dilute hydrochloric acid, centrifuged, washed, and dried to obtain hydroxypropyl starch.

[0014] In the preferred embodiment, the etherification reaction is controlled at 0.3-0.4. In the preferred embodiment, the grafting rate of the modified grafted starch powder is 40%-50%.

[0015] In a preferred embodiment, the acetylated cellulose nanocrystal suspension is prepared as follows: cellulose nanocrystals are added to a solution of acetic anhydride and pyridine, reacted at 60℃-80℃ for 2-4 hours, washed and dried, then dispersed in epoxidized soybean oil, and ultrasonically treated to form an acetylated cellulose nanocrystal suspension. The volume ratio of acetic anhydride to pyridine in the acetic anhydride-pyridine solution is 3:1.

[0016] This application also discloses a hot melt adhesive prepared according to the method described.

[0017] This application also discloses the application of hot melt adhesive in seamless bonding of cardboard boxes. When the hot melt adhesive of this invention is used in seamless bonding of cardboard boxes, the heat resistance is significantly improved at high temperatures. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0019] Example 1:

[0020] 100 parts of high amylose corn starch (purchased from Shandong Jurong Bioengineering Co., Ltd.) were dispersed in water with a solid content of 20%. The mixture was stirred, and a 5% NaOH solution was added to adjust the pH to 10. The temperature was raised to 50°C and stirred for 50 minutes. Then, 20 parts of propylene oxide were slowly added dropwise while maintaining the temperature at 50–53°C for 6 hours. After the etherification reaction was completed, the mixture was neutralized to pH 6.5 with dilute hydrochloric acid, centrifuged, washed, and dried to obtain hydroxypropyl starch. The degree of substitution of hydroxypropyl starch was found to be 0.4.

[0021] 100 parts of hydroxypropyl starch were dispersed in 500 ml of water, and 20 parts of butyl acrylate, 1.5 parts of ammonium persulfate, and 0.1 parts of hydroquinone were added. Nitrogen gas was introduced to remove oxygen, and the temperature was raised to 70°C. The reaction was carried out for 2 hours to generate starch-polybutyl acrylate graft copolymer. The reaction solution was precipitated with ethanol, filtered, dried at 60°C, and pulverized into 100-mesh powder to obtain modified graft starch powder.

[0022] 100 parts of modified grafted starch powder, 40 parts of hydrogenated rosin glycerol ester, 10 parts of sugarcane wax, and 0.3 parts of antioxidant 1010 were premixed in a high-speed mixer for 10 minutes to obtain a premixed material.

[0023] Cellulose nanocrystals (70% crystallinity) were dehydrated using a gradient of ethanol (50%, 70%, and 100%, respectively), each time soaking for 30 minutes, followed by centrifugation to remove the ethanol. For every 10 g of nanocrystals, 100 ml of DMSO was added to induce swelling for 2 hours. 50 ml of pyridine was added, the mixture was pre-cooled to 3°C, and 120 ml of acetic anhydride was slowly added dropwise. The mixture was then heated to 65°C and reacted for 3 hours. The nanocrystals were washed and dried.

[0024] The above premixed materials, acetylated cellulose nanocrystal mixture (modified grafted starch: acetylated cellulose nanocrystals = 100:14), zirconium-based catalyst (added in zone four), and epoxidized soybean oil (added in zone two; for example, 20 parts of modified grafted starch are added for 100 parts) are melt-extruded. The extruded strip-shaped colloid is cooled by contact with a coolant and then cut into granules. The melt extrusion is carried out using a twin-screw extruder, and the temperatures of each zone of the twin-screw extruder are as follows: Zone 1: 90℃; Zone 2: 110℃; Zone 3: 140℃; Zone 4: 130℃, and the screw speed is 300 rpm.

[0025] Example 2:

[0026] 100 parts of high amylose corn starch were dispersed in water with a solid content of 20%, stirred, and the pH was adjusted to 10 with 5% NaOH solution. The temperature was raised to 50°C and stirred for 50 minutes. Then, 20 parts of propylene oxide were slowly added dropwise while maintaining the temperature at 50–55°C for 6 hours. After the etherification reaction was completed, the solution was neutralized to pH 6.5 with dilute hydrochloric acid, centrifuged, washed and dried to obtain hydroxypropyl starch. The degree of substitution of hydroxypropyl starch was found to be 0.4.

[0027] 100 parts of hydroxypropyl starch were dispersed in 500 ml of water, and 20 parts of butyl acrylate, 1.5 parts of ammonium persulfate, and 0.1 parts of hydroquinone were added. Nitrogen gas was introduced to remove oxygen, and the mixture was heated to 70°C and reacted for 2 hours to generate a starch-polybutyl acrylate graft copolymer. The reaction solution was precipitated with ethanol, filtered, dried at 60°C, and pulverized into 100-mesh powder to obtain modified graft starch powder. 100 parts of modified graft starch powder, 40 parts of hydrogenated rosin glycerol ester, 10 parts of sugarcane wax, and 0.3 parts of antioxidant 1010 were premixed in a high-speed mixer for 10 minutes to obtain a premixed material.

[0028] Cellulose nanocrystals (70% crystallinity) were dehydrated using a gradient of ethanol (50%, 70%, and 100%, respectively), each time soaking for 30 minutes, followed by centrifugation to remove the ethanol. For every 10 g of nanocrystals, 100 ml of DMSO was added to induce swelling for 2 hours. 50 ml of pyridine was added, the mixture was pre-cooled to 3°C, and 120 ml of acetic anhydride was slowly added dropwise. The mixture was then heated to 65°C and reacted for 3 hours. The nanocrystals were washed and dried.

[0029] The above premixed materials, acetylated cellulose nanocrystal mixture (modified grafted starch: acetylated cellulose nanocrystals = 100:12), zirconium-based catalyst (added in zone four, 0.5% of total mass), and epoxidized soybean oil (added in zone two, 20 parts for 100 parts of modified grafted starch) were melt-extruded. The extruded strip-shaped colloid was cooled by contact with a coolant and then cut into granules. The melt extrusion was carried out using a twin-screw extruder, and the temperatures of each zone of the twin-screw extruder were as follows: Zone 1: 90℃; Zone 2: 110℃; Zone 3: 140℃; Zone 4: 130℃, and the screw speed was 300 rpm.

[0030] Example 3:

[0031] 100 parts of high amylose corn starch were dispersed in water with a solid content of 20%, stirred, and the pH was adjusted to 10 with 5% NaOH solution. The temperature was raised to 50°C and stirred for 50 minutes. Then, 20 parts of propylene oxide were slowly added dropwise while maintaining the temperature at 50–55°C for 6 hours. After the etherification reaction was completed, the solution was neutralized to pH 6.5 with dilute hydrochloric acid, centrifuged, washed and dried to obtain hydroxypropyl starch. The degree of substitution of hydroxypropyl starch was found to be 0.4.

[0032] 100 parts of hydroxypropyl starch were dispersed in 500 ml of water, and 20 parts of butyl acrylate, 1.5 parts of ammonium persulfate, and 0.1 parts of hydroquinone were added. Nitrogen gas was introduced to remove oxygen, and the mixture was heated to 70°C and reacted for 2 hours to generate a starch-polybutyl acrylate graft copolymer. The reaction solution was precipitated with ethanol, filtered, dried at 60°C, and pulverized into 100-mesh powder to obtain modified graft starch powder. 100 parts of modified graft starch powder, 40 parts of hydrogenated rosin glycerol ester, 10 parts of sugarcane wax, and 0.3 parts of antioxidant 1010 were premixed in a high-speed mixer for 10 minutes to obtain a premixed material.

[0033] Cellulose nanocrystals (70% crystallinity) were dehydrated using a gradient of ethanol (50%, 70%, and 100%, respectively), each time soaking for 30 minutes, followed by centrifugation to remove the ethanol. For every 10 g of nanocrystals, 100 ml of DMSO was added to induce swelling for 2 hours. 50 ml of pyridine was added, the mixture was pre-cooled to 3°C, and 120 ml of acetic anhydride was slowly added dropwise. The mixture was then heated to 65°C and reacted for 3 hours. The nanocrystals were washed and dried.

[0034] The above premixed materials and acetylated cellulose nanocrystals were mixed (modified grafted starch: acetylated cellulose nanocrystals = 100:10), zirconium-based catalyst (added in zone four), and epoxidized soybean oil (added in zone two; for example, 20 parts of modified grafted starch were added for 100 parts). The mixture was then melt-extruded. The extruded strip-shaped colloid was cooled by contact with a coolant and then cut into granules. The melt extrusion was performed using a twin-screw extruder. The temperatures of each zone of the twin-screw extruder were as follows: Zone 1: 90℃; Zone 2: 110℃; Zone 3: 140℃; Zone 4: 130℃, and the screw speed was 300 rpm.

[0035] Example 4:

[0036] 100 parts of high amylose corn starch were dispersed in water with a solid content of 20%, stirred, and the pH was adjusted to 10 with 5% NaOH solution. The temperature was raised to 50°C and stirred for 50 minutes. Then, 20 parts of propylene oxide were slowly added dropwise while maintaining the temperature at 50–55°C for 6 hours. After the etherification reaction was completed, the solution was neutralized to pH 6.5 with dilute hydrochloric acid, centrifuged, washed and dried to obtain hydroxypropyl starch. The degree of substitution of hydroxypropyl starch was found to be 0.4.

[0037] 100 parts of hydroxypropyl starch were dispersed in 500 ml of water, and 20 parts of butyl acrylate, 1.5 parts of ammonium persulfate, and 0.1 parts of hydroquinone were added. Nitrogen gas was introduced to remove oxygen, and the mixture was heated to 70°C and reacted for 2 hours to generate a starch-polybutyl acrylate graft copolymer. The reaction solution was precipitated with ethanol, filtered, dried at 60°C, and pulverized into 100-mesh powder to obtain modified graft starch powder. 100 parts of modified graft starch powder, 40 parts of hydrogenated rosin glycerol ester, 10 parts of sugarcane wax, and 0.3 parts of antioxidant 1010 were premixed in a high-speed mixer for 10 minutes to obtain a premixed material.

[0038] Cellulose nanocrystals (70% crystallinity) were dehydrated using a gradient of ethanol (50%, 70%, and 100%, respectively), each time soaking for 30 minutes, followed by centrifugation to remove the ethanol. For every 10 g of nanocrystals, 100 ml of DMSO was added to induce swelling for 2 hours. 50 ml of pyridine was added, the mixture was pre-cooled to 3°C, and 120 ml of acetic anhydride was slowly added dropwise. The mixture was then heated to 65°C and reacted for 3 hours. The nanocrystals were washed and dried.

[0039] The above premixed materials and acetylated cellulose nanocrystals were mixed (modified grafted starch: acetylated cellulose nanocrystals ratio was 100:9), a zirconium-based catalyst was added (in zone four), and epoxidized soybean oil was added (in zone two; for example, 20 parts of modified grafted starch were added for 100 parts). The mixture was then melt-extruded. The extruded strip-shaped colloid was cooled by contact with a coolant and then cut into granules. The melt extrusion was performed using a twin-screw extruder. The temperatures of each zone of the twin-screw extruder were as follows: Zone 1: 90℃; Zone 2: 110℃; Zone 3: 140℃; Zone 4: 130℃, and the screw speed was 300 rpm.

[0040] The performance of each hot melt adhesive is shown in Table 1 below:

[0041] Table 1

[0042] ;

[0043] Comparative Example 1-1: Based on Example 1, without the addition of acetylated cellulose nanocrystals and epoxidized soybean oil, the properties of the prepared hot melt adhesive were determined as follows:

[0044] Comparative Examples 1-2: Based on Example 1, the difference is that acetylated cellulose nanocrystals were not added. The performance of the prepared hot melt adhesives was measured as follows:

[0045] Table 2

[0046] ;

[0047] A comparison of Tables 1 and 2 shows that the addition of acetylated cellulose nanocrystals and epoxidized soybean oil significantly improved the softening point, high-temperature melt viscosity, and thermogravimetric initiation temperature. Without the addition of acetylated cellulose nanocrystals, the addition of epoxidized soybean oil did not significantly improve the performance. The addition of epoxidized soybean oil had a relatively small impact on the performance. The inventors analyzed that the reason for this is that the cellulose nanocrystals restricted the movement of starch chains, and acetylation enhanced interfacial compatibility.

[0048] Comparative Example 2, based on Comparative Example 1, replaced the linear starch with conventional corn starch (Comparative Example 2) and branched corn starch (Comparative Example 3).

[0049] Table 3

[0050] ;

[0051] As can be seen from Table 3, the hot melt adhesive prepared from amylose has a lower softening point and poorer heat resistance.

[0052] Based on Examples 1 and 2, Examples 5 and 6 replaced the cellulose nanocrystals with 85% cellulose nanocrystals with 55% crystallinity, each by half the weight, while maintaining the same total weight. Example 7 consisted entirely of cellulose nanocrystals with 55% crystallinity, and Example 8 consisted entirely of cellulose nanocrystals with 85% crystallinity. The hot melt adhesive properties were measured as follows:

[0053] Table 4

[0054] ;

[0055] As can be seen from Table 4, after replacing the cellulose nanocrystals with two different crystallinities (high and low), the softening point and viscosity of the product were significantly improved. The inventors analyzed that cellulose with different crystallinities has both rigidity and toughness, and at the same time, cellulose also has good interfacial bonding properties, which better restricts the movement of starch chains.

Claims

1. A method for producing hot melt adhesive, characterized in that, Includes the following steps: S1: Obtain hydroxypropyl starch; S2: Disperse hydroxypropyl starch in water, add butyl acrylate and ammonium persulfate; purge with nitrogen to remove oxygen, heat to 70℃-90℃, react for 2-5 hours to generate starch-polybutyl acrylate graft copolymer, precipitate the reaction solution with ethanol, filter and dry at 60℃, pulverize into 100 mesh powder to obtain modified graft starch powder. S3: Premix the modified grafted starch powder, hydrogenated rosin glycerol ester, sugarcane wax, and antioxidant in a high-speed mixer for 5-10 minutes to obtain the premixed material; S4: Add the above premixed materials to acetylated cellulose nanocrystals and zirconium-based catalyst, and then melt-extrude them; S5: The extruded strip-shaped colloid is cooled by contact with coolant and then cut into granules.

2. The hot melt adhesive production method according to claim 1, characterized in that, The melt extrusion uses a twin-screw extruder, and the temperatures of each zone of the twin-screw extruder are as follows: Zone 1: 90℃; Zone 2: 110℃. Zone 3: 140℃; Zone 4: 130℃, screw speed 200-300 rpm.

3. The hot melt adhesive production method according to claim 2, characterized in that, Add 25 parts liquid glycerin to zone two.

4. The hot melt adhesive production method according to claim 1, characterized in that, The method for obtaining hydroxypropyl starch is as follows: Disperse corn starch in water with a solid content of 30%, add 5% NaOH solution to adjust the pH to 10–11, heat to 50°C and stir for 30–50 minutes; then slowly add 20 parts of propylene oxide, maintain the temperature at 50–55°C and react for 4–6 hours. After the etherification reaction is complete, neutralize with dilute hydrochloric acid to pH 6.5–7.0, centrifuge, wash and dry to obtain hydroxypropyl starch.

5. The hot melt adhesive production method according to claim 4, characterized in that, The etherification reaction was controlled at 0.3-0.

4.

6. The hot melt adhesive production method according to claim 5, characterized in that, In step S2, the grafting rate of the modified grafted starch powder is 40%-50%.

7. The hot melt adhesive production method according to claim 1, characterized in that, The preparation method of the acetylated cellulose nanocrystal suspension is as follows: cellulose nanocrystals are added to acetic anhydride pyridine solution and reacted at 60℃-80℃ for 2-4 hours. After washing and drying, the nanocrystals are dispersed in epoxidized soybean oil and ultrasonically treated to form an acetylated cellulose nanocrystal suspension.

8. The hot melt adhesive production method according to claim 7, characterized in that, The volume ratio of acetic anhydride to pyridine is 3:

1.

9. A hot melt adhesive, characterized in that, Prepared according to the method of any one of claims 1-7.

10. The application of the hot melt adhesive of claim 9 in seamless bonding of cardboard boxes.