Paper-plastic composite aqueous hot melt adhesive for medical packaging and preparation method therefor

Abstract

The present application relates to the field of aqueous hot melt adhesives and particularly discloses a paper-plastic composite aqueous hot melt adhesive for medical packaging and a preparation method therefor. The aqueous hot melt adhesive comprises the following raw materials in parts by weight: 50-80 parts of an aqueous polyolefin dispersion, 10-40 parts of an ethylene-acrylic acid copolymer emulsion, 2-10 parts of a wax emulsion, 5-20 parts of a filler, 0.5-2 parts of an anti-settling agent, 0.1-1 part of a microbicide, and 0.1-1 part of a defoaming agent. The preparation method therefor comprises the following steps: uniformly mixing and stirring the aqueous polyolefin dispersion, the ethylene-acrylic acid copolymer emulsion, the wax emulsion, the filler, the anti-settling agent, the microbicide, and the defoaming agent, filtering the mixture, and discharging the resulting material. The obtained aqueous hot melt adhesive can achieve bonding sealing between a plastic film and dialysis paper and has a good storage stability; and when the plastic film such as PE and the dialysis paper are peeled apart, the paper would not be torn, thereby effectively preventing medical supplies from being contaminated by impurities such as paper scraps and solving the problem of balance between bonding sealing and paper scraps not falling off during peeling.

Description

A paper-plastic composite water-based hot melt adhesive for medical packaging and its preparation method Technical Field

[0001] The present application relates to the field of water-based hot melt adhesives, and more specifically, to a paper-plastic composite water-based hot melt adhesive for medical packaging and a preparation method thereof. Background Art

[0002] The main materials of paper-plastic composite sterilization packaging bags used for disposable medical supplies such as surgical gowns, cotton swabs, syringes, catheters, tweezers, masks, gloves and respiratory masks include medical dialysis paper, laminated / laminated paper, Tyvek, PE, PP, PET, PVC, etc. Among them, the paper-based material is mainly medical dialysis paper, which is made from dehydrated wood pulp and mainly consists of wood cellulose. It has poor heat sealing properties. The currently used heat sealing adhesives are mostly made of thermoplastic polyurethane resin as the main raw material, supplemented by additives such as viscosity-enhancing agents and antioxidants. They need to be heated and melted when used. The pressing temperature must be above 150°C and the pressing time must be greater than 0.5s. In addition, the contents are easily adhered after gluing. When tearing apart the PE and other plastic films and dialysis paper, the paper is easily torn, which greatly increases the possibility of impurities such as paper scraps contaminating the packaging contents and damaging the cleanliness of medical supplies. Summary of the Invention

[0003] The present application provides a paper-plastic composite water-based hot melt adhesive for medical packaging and a preparation method thereof. The water-based hot melt adhesive has high thermal sensitivity when used for paper-plastic composite of sterilized packaging bags, and can achieve bonding and sealing between the plastic film and dialysis paper under low pressing temperature (100-110°C) and short pressing time (0.2-0.4s). The water-based hot melt adhesive has good storage stability and good aging resistance after gluing, preventing bacteria and other microorganisms from contaminating the contents. When PE and other plastic films and dialysis paper are torn apart, the paper will not be torn, effectively preventing impurities such as paper scraps from contaminating the packaging contents, thereby ensuring the cleanliness of medical supplies.

[0004] In the first aspect, the present application provides a paper-plastic composite water-based hot melt adhesive for medical packaging that adopts the following technical solution:

[0005] A paper-plastic composite water-based hot melt adhesive for medical packaging, comprising the following raw materials in parts by weight: 50-80 parts of water-based polyolefin dispersion, 10-40 parts of ethylene-acrylic acid copolymer emulsion, 2-10 parts of wax emulsion, 5-20 parts of filler, 0.5-2 parts of anti-settling agent, 0.1-1 parts of bactericide, and 0.1-1 parts of defoaming agent;

[0006] The solid content of the aqueous polyolefin dispersion is in the range of 20-40%, and the melting point of the dry film is in the range of 80-95°C; the solid content of the ethylene-acrylic acid copolymer emulsion is in the range of 25-50%, and the melting point of the dry film is in the range of 75-110°C.

[0007] This application uses a water-based polyolefin aqueous dispersion, which has polar groups and is similarly compatible with PP / PE, which are also polyolefins, and has excellent adhesion. The molecular structure of the ethylene-acrylic acid copolymer emulsion has carboxyl groups randomly distributed on the ethylene main chain and side chains, and has excellent adhesion and toughness. It is easy to combine with polar substances and has excellent adhesion to materials such as metal foil, paper, nylon, polyolefin, and glass. The water-based polyolefin aqueous dispersion and the ethylene-acrylic acid copolymer emulsion are compounded to solve the problem of balancing bonding and sealing with paper tearing during packaging bag peeling, which is beneficial to reducing the phenomenon of paper tearing during peeling.

[0008] In addition, after the water-based polyolefin aqueous dispersion and ethylene-acrylic acid copolymer emulsion are compounded, the solid content and dry film melting point of each component are strictly controlled. This results in a water-based hot melt adhesive that not only has a fast heat sealing response speed and high thermal sensitivity, but also can adapt to less glue application, lower heat sealing temperatures, and shorter pressing times. It can melt when heated at lower temperatures during use, and has good heat sealing properties. The resulting water-based hot melt adhesive also has excellent mechanical stability and is adaptable to processes such as roller coating, spraying, scraping, and brushing. It can be evenly distributed on the surface of the substrate using the corresponding gluing tools. It can be pre-coated on paper during application and rolled up after drying, greatly reducing the difficulty of use. Experimental research has found that a bonding seal between the plastic film and the dialysis paper can be achieved under the conditions of a pressing temperature of 100-110°C and a pressing time of 0.2-0.4s, which has the advantages of reducing costs, saving energy, and improving production efficiency, bringing excellent economic benefits.

[0009] Components such as water-based polyolefin dispersion, ethylene-acrylic acid copolymer emulsion, wax emulsion, filler and anti-settling agent cooperate with each other to form an interpenetrating network, so that the water-based hot melt adhesive has good storage stability. At the same time, it has good anti-aging properties after gluing, so that the packaging bag will not debond during storage, which can effectively prevent bacteria and other microorganisms from contaminating the contents and ensure the cleanliness of medical supplies.

[0010] During the film-forming process of the aqueous polyolefin dispersion and ethylene-acrylic acid copolymer emulsion, the wax emulsion migrates to the surface of the polymer film. Combined with the anti-settling agent, it is evenly dispersed, forming a wax protective layer interspersed within the macromolecular polymer segments. This reduces the coefficient of friction and creates a release effect, preventing paper tearing and falling paper scraps during peeling. This ensures smoother peeling and effectively prevents contamination of the contents by impurities such as paper scraps. It also helps improve the stickiness of pre-coated paper, ensuring that the contents of the packaging bag will not adhere after gluing. It also helps improve the heat resistance of other raw materials in the finished product.

[0011] Preferably, the wax emulsion is one or more of PE wax emulsion, paraffin wax emulsion or aqueous wax dispersion.

[0012] Furthermore, as a preferred embodiment of the wax emulsion, the wax emulsion is PE wax emulsion.

[0013] Through experimental research, it was found that the use of PE wax emulsion can further improve the flexibility of the adhesive film after the water-based hot melt adhesive is applied, so that the plastic film and dialysis paper can be peeled off more smoothly when torn apart, effectively preventing impurities such as paper scraps from contaminating the contents.

[0014] Preferably, the filler includes one or more of calcium carbonate, titanium dioxide, starch, kaolin or talc.

[0015] Titanium dioxide has excellent hiding power and weather resistance, and can improve the whiteness and hiding power of the film. Starch has good adhesion and can improve the bonding strength of the colloid. Talc has excellent slipperiness and wear resistance, and can improve the wear resistance and fluidity of the colloid. Calcium carbonate can play a filling and thickening role, which can increase the strength and hardness of the film and improve its heat resistance. Kaolin can effectively improve the fluidity and coating performance of the colloid and improve the stability of the colloid.

[0016] Preferably, the filler comprises calcium carbonate and kaolin in a mass ratio of 1:(2-4).

[0017] Through experimental research, it was found that when calcium carbonate and kaolin are used as fillers and within the above-mentioned dosage range, the calcium carbonate and kaolin can be distributed in the polymer film after film formation, thereby reducing the density of the dry film and improving the air permeability of the dry film.

[0018] Preferably, the anti-settling agent includes one or more of fumed silica, bentonite, silicate or montmorillonite.

[0019] Fumed silica is highly dispersible and chemically stable, enhancing the thixotropy of colloids. This increases the fluidity of the colloid when subjected to shear forces and decreases when the shear forces cease. This allows the colloid to flow easily during the coating process while maintaining a certain degree of stability after application. Bentonite, with its excellent adsorption and thickening properties, increases the viscosity and thixotropy of the colloid, improving its tensile strength and crack resistance. Silicates act as reinforcing agents, increasing the strength and hardness of the colloid. Montmorillonite, with its unique layered structure and excellent adsorption properties, acts as a thickener and stabilizer, increasing the viscosity and stability of the colloid.

[0020] Preferably, the anti-settling agent comprises fumed silica and montmorillonite in a mass ratio of 1:(2-4).

[0021] Through experimental research, it was found that by using fumed silica and montmorillonite as anti-settling agents and within the above-mentioned dosage range, the water-based hot melt adhesive obtained has better storage stability.

[0022] Preferably, the fungicide is one or more of 5-chloro-2-methyl-4-isothiazoline-3-one, 2-methyl-4-isothiazoline-3-one, and 1,2-benzisothiazolin-3-one.

[0023] Preferably, the defoaming agent is one or more of an acetylene glycol defoaming agent, a mineral oil defoaming agent, a silicone defoaming agent, and a vegetable oil defoaming agent.

[0024] Optimize the component selection of fungicide and defoamer to help improve the overall performance of water-based hot melt adhesive.

[0025] In a second aspect, the present application provides a method for preparing a paper-plastic composite water-based hot melt adhesive for medical packaging, which adopts the following technical solution:

[0026] A method for preparing a paper-plastic composite water-based hot melt adhesive for medical packaging comprises the following steps: uniformly mixing a water-based polyolefin dispersion, an ethylene-acrylic acid copolymer emulsion, a wax emulsion, a filler, an anti-settling agent, a bactericide and a defoamer, and filtering the material.

[0027] Preferably, the aqueous polyolefin dispersion is stirred, and after the ethylene-acrylic acid copolymer emulsion is added, the stirring speed is increased and the dispersion is uniform;

[0028] Add the wax emulsion while stirring until evenly combined;

[0029] Then add filler and increase the stirring speed until the filler is completely and evenly dispersed;

[0030] Add anti-settling agent and mix evenly, reduce the stirring speed and add fungicide and defoamer and mix evenly, filter the material with a 100-200 mesh filter.

[0031] Mixing the raw material components in steps helps to better disperse them in the system, resulting in a water-based hot melt adhesive with good fluidity and better coating performance.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. This application uses a water-based polyolefin aqueous dispersion, which has polar groups and is similarly compatible with PP / PE, which are also polyolefins, and has excellent adhesion. The molecular structure of the ethylene-acrylic acid copolymer emulsion has carboxyl groups randomly distributed on the ethylene main chain and side chains, and has excellent adhesion and toughness. It is easy to combine with polar substances and has excellent adhesion to materials such as metal foil, paper, nylon, polyolefins, and glass. The water-based polyolefin aqueous dispersion and the ethylene-acrylic acid copolymer emulsion are compounded to solve the balance problem between bonding and sealing and paper tearing during packaging bag peeling, which is beneficial to reduce the phenomenon of paper tearing during peeling.

[0034] 2. After compounding the water-based polyolefin dispersion and ethylene-acrylic acid copolymer emulsion, the solid content and dry film melting point of each component are strictly controlled. This results in a water-based hot melt adhesive that not only has a fast heat-sealing response speed and high thermal sensitivity, but also can adapt to less glue application, lower heat-sealing temperatures, and shorter pressing times. It can melt when heated at lower temperatures during use, exhibiting good heat-sealing properties. Furthermore, the resulting water-based hot melt adhesive has excellent mechanical stability and is adaptable to processes such as roller coating, spraying, scraping, and brushing. It can be evenly distributed on the surface of the substrate using the corresponding gluing tools. It can be pre-coated on paper during application and rolled up after drying, greatly reducing the difficulty of use. Experimental studies have found that a bonding seal between the plastic film and the dialysis paper can be achieved under the conditions of a pressing temperature of 100-110°C and a pressing time of 0.2-0.4s, which reduces costs, saves energy, and improves production efficiency, resulting in excellent economic benefits.

[0035] 3. The components such as water-based polyolefin dispersion, ethylene-acrylic acid copolymer emulsion, wax emulsion, filler and anti-settling agent cooperate with each other to form an interpenetrating network, so that the water-based hot melt adhesive has good storage stability. At the same time, it has good anti-aging properties after gluing, so that the packaging bag will not open during storage, which can effectively prevent bacteria and other microorganisms from contaminating the contents and ensure the cleanliness of medical supplies.

[0036] 4. During the film-forming process of the aqueous polyolefin dispersion and ethylene-acrylic acid copolymer emulsion, the wax emulsion migrates to the surface of the polymer film, regulating the colloid bonding strength. Combined with the anti-settling agent, it is evenly dispersed, forming a wax protective layer interspersed within the macromolecular polymer segments, reducing the coefficient of friction and creating a certain release effect. This prevents paper tearing and paper scraps from falling during peeling, making peeling smoother and effectively preventing contamination of the contents by impurities such as paper scraps. It helps improve the stickiness of pre-coated paper, ensuring that the contents of the packaging bag will not adhere after gluing, and helps other raw materials improve the heat resistance of the finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a picture of the product of Example 9 of the present application after storage for 6 months.

[0038] FIG2 is a physical picture of Example 9 of the present application after the paper tearing and peeling test.

[0039] FIG3 is a physical picture of comparative example 2 of the present application after the paper tearing and peeling test.

[0040] FIG4 is a physical picture of comparative example 3 of the present application after the paper tearing and peeling test. DETAILED DESCRIPTION

[0041] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0042] The model of PE wax emulsion is ULTRALUBE ® CT 1849; the model of acetylene glycol defoamer is Hydropala ® WE3650; paraffin emulsion model: LW-103; water-based wax dispersion model: Twax-2101; mineral oil defoamer model: Foamaster ® Mo 2111; the model of silicone defoamer is Defoamer 1903; the model of vegetable oil defoamer is Defoamer 1810.

[0043] During the heat-sealing composite of paper and plastic, it was discovered that the paper-based material of medical supplies is primarily medical dialysis paper, which cannot be heat-sealed with most plastic-based polymer materials. Experiments have shown that using solid hot-melt adhesives has the disadvantages of requiring a large amount of glue, slow coating speed, high cost, poor air permeability, and easy adhesion to the contents after application. Using water-based adhesives, however, can be applied using an anilox roller, requiring a small amount of glue and a fast coating speed, thus achieving cost reduction and energy conservation while also improving production efficiency. However, the stability and reliability of heat-sealing strength of current water-based adhesives have been unsatisfactory, and the heat-sealing strength of most water-based adhesive products is low, failing to meet industry standards. Finished bags made with water-based adhesives that offer high heat-sealing strength often suffer from paper scraps when torn, affecting the cleanliness of the medical supplies contained in the bags and seriously impacting the quality of sterilized packaging bags. This has long been a pain point and difficulty in the industry. In addition, in addition to being able to achieve the above-mentioned bonding requirements, water-based hot melt adhesives must also take into account their stability during storage to ensure that there will be no stratification, agglomeration, etc. during long-term storage, thereby ensuring the workability of the water-based hot melt adhesive.

[0044] Therefore, on this basis, it is urgent to develop a water-based hot melt adhesive with high thermal sensitivity, which can achieve sealing and bonding of plastic film and medical dialysis paper by applying lower heat sealing pressure and temperature, and has good storage stability; at the same time, when PE and other plastic films and dialysis paper are torn apart, the paper will not be torn, solving the balance problem between bonding and sealing and paper tearing when packaging bags are peeled off, avoiding impurities such as paper scraps from contaminating medical supplies, and ensuring the cleanliness of the contents of the packaging bag. Example

[0045] Example 1

[0046] A paper-plastic composite water-based hot melt adhesive for medical packaging, comprising the following raw materials: 5 kg of water-based polyolefin dispersion, 4 kg of ethylene-acrylic acid copolymer emulsion, 0.2 kg of wax emulsion, 0.5 kg of filler, 0.05 kg of anti-settling agent, 0.01 kg of bactericide, and 0.01 kg of defoaming agent;

[0047] The solid content of the waterborne polyolefin dispersion is 40%, and its dry film melting point ranges from 80-85°C; the solid content of the ethylene-acrylic acid copolymer emulsion is 25%, and its dry film melting point ranges from 75-80°C;

[0048] The wax emulsion is paraffin emulsion, the filler is titanium dioxide and starch in a mass ratio of 1:1, the anti-settling agent is bentonite, the fungicide is 5-chloro-2-methyl-4-isothiazoline-3-one, and the defoaming agent is acetylene glycol defoaming agent.

[0049] A method for preparing a paper-plastic composite water-based hot melt adhesive for medical packaging comprises:

[0050] Step 1: Add the aqueous polyolefin dispersion into a stirring tank, adjust the stirring speed to 200 rpm, and stir for 10 minutes;

[0051] Step 2: Add ethylene-acrylic acid copolymer emulsion while stirring, adjust the stirring speed to 250 rpm, and stir for 20 minutes;

[0052] Step 3: Add wax emulsion while stirring, maintain stirring speed at 250 rpm, and stir for 20 minutes;

[0053] Step 4: Slowly add the filler into the stirring kettle while stirring. After all the filler is added, increase the stirring speed to 350 rpm and continue stirring for 50 minutes until the filler is completely and evenly dispersed.

[0054] Step 5: Add anti-settling agent while stirring, maintain stirring speed at 350 rpm, and stir for 20 minutes;

[0055] Step 6: Add the fungicide and defoamer while stirring, adjust the stirring speed to 300 rpm, and stir for 20 minutes;

[0056] Step 7: After all the raw materials are completely mixed, filter the material with a 150-mesh filter.

[0057] Example 2

[0058] A paper-plastic composite water-based hot melt adhesive for medical packaging, comprising the following raw materials: 8 kg of water-based polyolefin dispersion, 1 kg of ethylene-acrylic acid copolymer emulsion, 1 kg of wax emulsion, 2 kg of filler, 0.2 kg of anti-settling agent, 0.1 kg of bactericide, and 0.1 kg of defoaming agent;

[0059] The solid content of the waterborne polyolefin dispersion is 20%, and its dry film melting point ranges from 90-95°C; the solid content of the ethylene-acrylic acid copolymer emulsion is 50%, and its dry film melting point ranges from 100-110°C;

[0060] The wax emulsion is an aqueous wax dispersion, the filler is titanium dioxide, starch and kaolin in a mass ratio of 1:1:2, the anti-settling agent is fumed silica and montmorillonite in a mass ratio of 1:2, the fungicide is 2-methyl-4-isothiazoline-3-one, and the defoamer is a mineral oil defoamer.

[0061] Example 3

[0062] The difference from Example 2 is that a paper-plastic composite water-based hot melt adhesive for medical packaging includes the following raw materials: 6 kg of water-based polyolefin dispersion, 3 kg of ethylene-acrylic acid copolymer emulsion, 0.7 kg of wax emulsion, 1.2 kg of filler, 0.1 kg of anti-settling agent, 0.05 kg of bactericide, and 0.06 kg of defoaming agent;

[0063] The solid content of the aqueous polyolefin dispersion is 30%, and the melting point of the dry film thereof is in the range of 85-90°C; the solid content of the ethylene-acrylic acid copolymer emulsion is 35%, and the melting point of the dry film thereof is in the range of 90-95°C; and the rest are the same as in Example 2.

[0064] Example 4

[0065] The difference from Example 3 is that the wax emulsion is PE wax emulsion, and the rest is the same as Example 3.

[0066] Example 5

[0067] The difference from Example 4 is that the filler is calcium carbonate, starch and talc in a ratio of 1:4:0.7, and the rest is the same as Example 4.

[0068] Example 6

[0069] The difference from Example 4 is that the filler is calcium carbonate and kaolin in a ratio of 1:3, and the rest is the same as Example 4.

[0070] Example 7

[0071] The difference from Example 6 is that the anti-settling agent is fumed silica and bentonite in a ratio of 2:0.7, and the rest is the same as Example 6.

[0072] Example 8

[0073] The difference from Example 7 is that the anti-settling agent is fumed silica and montmorillonite in a ratio of 1:3.5, and the rest is the same as Example 6.

[0074] Example 9

[0075] The difference from Example 8 is that the fungicide is 1,2-benzisothiazolin-3-one, the defoaming agent is an organosilicon defoaming agent, and the rest are the same as Example 8. Comparative Example

[0076] Comparative Example 1

[0077] The difference from Example 9 is that the aqueous polyolefin dispersion is replaced by a polyurethane emulsion, and the rest is the same as Example 9.

[0078] Comparative Example 2

[0079] The difference from Example 9 is that the ethylene-acrylic acid copolymer emulsion is replaced by polyethylene-vinyl acetate emulsion, and the rest is the same as Example 9.

[0080] Comparative Example 3

[0081] The difference from Example 9 is that wax emulsion is not added, and the rest is the same as Example 9. Performance testing

[0082] The water-based hot melt adhesive prepared in Examples 1-9 and Comparative Examples 1-3 was pre-coated on dialysis paper using a roller coating method to achieve sealing and bonding between the hot melt adhesive and the plastic film. Each group of packaging bags had 10 bags. The specific steps were as follows:

[0083] 1. Use a 15-mesh wire rod to apply water-based hot melt adhesive to the dialysis paper;

[0084] 2. Dry in a 55°C oven;

[0085] 3. Remove the dialysis paper from the oven and cool to room temperature;

[0086] 4. The plastic film and paper were heat-pressed on a heat sealer with a set pressing pressure of 0.5 MPa, a pressing temperature of 105°C, and a pressing time of 0.3 s.

[0087] The peel force was measured according to YY / T 0698.5-2009 “Packaging materials for terminally sterilized medical products – Part 5: Requirements and test methods for sealable combination bags and rolls composed of breathable materials and plastic films”. The average value of each group was recorded in Table 1.

[0088] The water-based hot melt adhesives prepared in Examples 1-9 and Comparative Examples 1-3 were subjected to a storage stability test: they were stored in a constant temperature chamber at a temperature of 23°C and a humidity of 50% for 6 months, and the product appearance and viscosity changes were observed to see whether stratification and sedimentation occurred. The results are recorded in Table 1.

[0089] The paper-plastic packaging bags for medical supplies coated with the water-based hot melt adhesives prepared in Examples 1-9 and Comparative Examples 1-3 were subjected to a paper tearing and peeling test, and the paper tearing conditions were recorded. The results are recorded in Table 1.

[0090] Table 1 Peeling force / N Storage stability Paper tearing condition Example 13.7 No significant change in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling Example 23.5 No significant change in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling Example 34.3 No significant change in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling Example 44.6 No significant change in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling Example 54.4 No significant change in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling Example 64.9: No significant changes in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling off Example 74.7: No significant changes in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling off Example 85.1: No significant changes in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling off Example 95.2: No significant changes in appearance and viscosity, no delamination and sedimentation, smooth peeling, no paper scraps and other impurities falling off Comparative Example 11.2: Delamination and sedimentation, weak peeling force, no paper scraps and other impurities falling off Comparative Example 24.7: No significant changes in appearance, significant increase in viscosity, no delamination and sedimentation, peeling jam, and more paper scraps falling off Comparative Example 36.2: No significant changes in appearance and viscosity, no delamination and sedimentation, peeling jam, and a few paper scraps falling off

[0091] When the water-based hot melt adhesive prepared in Examples 1-9 is heat-sealed by a heat sealer, it can be seen that the water-based hot melt adhesive has high thermal sensitivity when used for paper-plastic composite of sterilized packaging bags, and can achieve bonding and sealing between the plastic film and the dialysis paper under low pressing temperature (100-110°C) and short pressing time (0.2-0.4s). Combined with Table 1 and Figure 1, it can be seen that the prepared water-based hot melt adhesive has good storage stability and good aging resistance after gluing, preventing bacteria and other microorganisms from contaminating the contents. It can be seen from Example 9 and Figure 2 that when plastic films such as PE and dialysis paper are torn apart, the paper will not be torn, effectively preventing impurities such as paper scraps from contaminating the contents, thereby ensuring the cleanliness of medical supplies.

[0092] As can be seen from Example 9 and Comparative Examples 1-3, combined with Table 1, Comparative Example 1 replaces the aqueous polyolefin dispersion with a polyurethane emulsion. Under the prescribed low lamination temperature and short lamination time, the product fails to activate effectively, resulting in excessively low peel force and ineffective sealing of medical packaging bags. Furthermore, the water-based hot melt adhesive exhibits poor storage stability, with delamination and sedimentation. Comparative Example 2 replaces the ethylene-acrylic acid copolymer emulsion with a polyethylene-vinyl acetate emulsion. While the resulting water-based hot melt adhesive exhibits moderate peel force, its strong permeability to paper causes sticking during the peeling process, resulting in significant paper fragmentation (as shown in Figure 3). The product also exhibits poor storage stability and a significant increase in viscosity. Comparative Example 3, which lacks a wax emulsion, exhibits excessively high peel force and sticking during the peeling process, with minor paper fragmentation (as shown in Figure 4). This is due to the combination of the aqueous polyolefin dispersion and the ethylene-acrylic acid copolymer emulsion, which balances adhesive sealing with paper breakage during packaging bag peeling and reduces paper breakage during peeling. The wax emulsion is then used to adjust the colloid bonding strength. During the film-forming process of the water-based polyolefin dispersion and the ethylene-acrylic acid copolymer emulsion, it will migrate to the surface of the polymer film to form a wax protective layer interspersed in the macromolecular polymer chain segments, reducing the friction coefficient and forming a certain release effect, thereby preventing the paper from being torn and paper scraps from falling during peeling, making the peeling smoother and effectively preventing impurities such as paper scraps from contaminating the contents.

[0093] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A paper-plastic composite water-based hot melt adhesive for medical packaging, characterized in that, It comprises the following raw materials in parts by weight: 50 - 80 parts of aqueous polyolefin dispersion, 10 - 40 parts of ethylene-acrylic acid copolymer emulsion, 2 - 10 parts of wax emulsion, 5 - 20 parts of filler, 0.5 - 2 parts of anti-settling agent, 0.1 - 1 part of bactericide, and 0.1 - 1 part of defoamer; The solid content of the aqueous polyolefin dispersion ranges from 20% to 40%, and the dry film melting point ranges from 80°C to 95°C; the solid content of the ethylene-acrylic acid copolymer emulsion ranges from 25% to 50%, and the dry film melting point ranges from 75°C to 110°C.

2. The water-based hot melt adhesive for medical packaging paper-plastic composite according to claim 1, wherein: The wax emulsion is one or more of PE wax emulsion, paraffin wax emulsion or aqueous wax dispersion.

3. The water-based hot melt adhesive for medical packaging paper-plastic composite according to claim 1, characterized in that: The filler includes one or more of calcium carbonate, titanium dioxide, starch, kaolin or talc powder.

4. The water-based hot melt adhesive for medical packaging paper-plastic composite according to claim 3, wherein: The filler includes calcium carbonate and kaolin in a mass ratio of 1:(2 - 4).

5. The water-based hot melt adhesive for medical packaging paper-plastic composite according to claim 1, wherein: The anti-settling agent includes one or more of fumed silica, bentonite, silicate or montmorillonite.

6. The water-based hot melt adhesive for medical packaging paper-plastic composite according to claim 5, characterized in that: The anti-settling agent includes fumed silica and montmorillonite in a mass ratio of 1:(2 - 4).

7. The water-based hot melt adhesive for medical packaging paper-plastic composite according to claim 1, characterized in that: The bactericide is one or more of 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one.

8. The water-based hot melt adhesive for medical packaging paper-plastic composite according to claim 1, wherein: The defoamer is one or more of acetylenic glycol defoamer, mineral oil defoamer, silicone defoamer, vegetable oil defoamer.

9. The preparation method of the medical packaging paper-plastic composite water-based hot melt adhesive according to any one of claims 1-8, characterized in that: It includes the following steps: Mix and stir evenly the aqueous polyolefin dispersion, ethylene-acrylic acid copolymer emulsion, wax emulsion, filler, anti-settling agent, bactericide and defoamer, and then filter and discharge the material.

10. The preparation method of the medical packaging paper-plastic composite water-based hot-melt adhesive according to claim 9, wherein: Stir the aqueous polyolefin dispersion, add the ethylene-acrylic acid copolymer emulsion, then increase the stirring speed and disperse evenly; While stirring, add the wax emulsion and stir evenly; Then add the filler and increase the stirring speed until the filler is completely and evenly dispersed; Add the anti-settling agent and mix evenly, reduce the stirring speed, add the bactericide and defoamer and mix evenly, and filter and discharge the material through a 100 - 200 mesh filter screen.

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