A heat-sealing adhesive material for medical sterilization packaging and its aqueous dispersion preparation process.

Abstract

This invention relates to the field of medical packaging materials technology, specifically a heat-sealing adhesive material for medical sterilization packaging, comprising the following raw materials by weight: 25-50 parts medical-grade EVA, 5-25 parts bio-wax, 1-15 parts beeswax, 3-20 parts tackifying resin, 0.1-8 parts functional additives, and 30-120 parts deionized water. By introducing a compound combination of medical-grade EVA, beeswax, and bio-wax into an aqueous system, the heat-sealing and opening performance of the packaging material is improved. Beeswax and bio-wax provide excellent lubrication and internal plasticizing effects within the EVA matrix, enabling a smooth opening interface during coating peeling, effectively preventing fuzzing caused by excessive stretching of paper fibers, and ensuring a sterile opening environment. The aqueous preparation route replaces traditional solvent-based processes, eliminating the use of organic solvents at the source, preventing the volatilization of harmful gases, and eliminating the potential physicochemical effects of chemical residues.

Description

Technical Field

[0001] This invention relates to the field of medical packaging materials technology, specifically to a heat-sealing adhesive material for medical sterilization packaging and its aqueous dispersion preparation process. Background Technology

[0002] Medical sterilization packaging is a crucial barrier system for ensuring the safety of sterile medical devices, widely used in the protection of medical masks, surgical packs, medical syringes, artificial joints, and other sanitary materials and medical devices. These packaging systems are typically composed of dialysis paper, Tyvek (or similar breathable materials), and plastic films. They must allow sterilization media such as ethylene oxide, vapor, or plasma to effectively penetrate while ensuring that microorganisms cannot penetrate, thereby achieving terminal sterilization of the product.

[0003] Existing medical packaging heat-sealing materials largely rely on imports, with their main technical approaches including solvent-based adhesives or hot melt adhesive coatings. Traditional solvent-based products suffer from severe volatile organic compound (VOC) emissions during production, making it difficult to meet increasingly stringent environmental regulations. Furthermore, solvent residues can easily remain inside the packaging, posing a potential threat to the safety of precision medical devices. Ordinary hot melt adhesive materials often suffer from defects such as excessively high initial sealing temperatures, insufficient heat-sealing stability, and a tendency to tear paper fibers during peeling, making it difficult to maintain consistent sealing quality on high-efficiency automated packaging production lines.

[0004] Existing manufacturing processes typically require large amounts of organic solvents for dissolving high-viscosity polymers such as ethylene-vinyl acetate copolymer (EVA), resulting in high carbon emissions during production. Water-based solutions face technical bottlenecks such as difficulty in precisely controlling particle size, poor system storage stability, and susceptibility to cracking during sealing under harsh sterilization conditions. Developing a water-based heat-sealing material that balances environmental friendliness, excellent breathability and antibacterial properties, and stable peelability has become a critical challenge in the field of medical packaging materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a heat-sealing adhesive material for medical sterilization packaging and its aqueous dispersion preparation process. The aim is to prepare a heat-sealing adhesive material with solvent-free evaporation, high stability, and microporous breathable structure through specific component ratios and physical water dispersion processes.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a heat-sealing adhesive material for medical sterilization packaging, wherein the heat-sealing adhesive material is an aqueous dispersion system, comprising the following raw materials by weight: 25-50 parts of medical-grade EVA, 5-25 parts of bio-wax, 1-15 parts of beeswax, 3-20 parts of tackifying resin, 0.1-8 parts of functional additives, and 30-120 parts of deionized water; The tackifying resin is any one or a combination of rosin resin, modified rosin resin, hydrogenated rosin resin, terpene resin or terpene phenol resin. The heat-sealing adhesive has a viscosity of 100-3000 cps at 20-40°C, a solid content of 30%-45%, and a pH value of 7-11. After coating and drying, it forms a coating that combines a heat-sealing layer and a breathable and antibacterial microporous structure.

[0007] Preferably, by weight, it comprises: 30-45 parts medical-grade EVA, 8-18 parts bio-wax, 2-10 parts beeswax, 5-15 parts tackifying resin, 0.3-5 parts functional additives, and 45-90 parts deionized water; wherein the medical-grade EVA has a vinyl acetate content of 12wt%-40wt% and a melt index of 50-800g / 10min.

[0008] Preferably, the biowax is selected from any one or more combinations of Fischer-Tropsch wax, polyethylene wax, plant-based modified wax, and oxidized wax; the functional additives include any one or more combinations of dispersant stabilizers, rheology modifiers, defoamers, wetting agents, pH adjusters, antioxidants, and preservatives; wherein the dispersant stabilizer is nonionic or anionic, and its addition amount is 0.1% to 3.0% of the total weight.

[0009] Preferably, the volume average particle size (D50) of the dispersed particles of the heat-sealing adhesive material is 0.2–8 μm, and the volatile organic compounds (VOCs) are less than 5.0 mg / m³ based on the total residual solvent. 2 .

[0010] This invention also provides an aqueous dispersion preparation process for a heat-sealing adhesive material for medical sterilization packaging, comprising the following steps: S1. Medical-grade EVA, bio-wax, beeswax, tackifying resin and functional additives are put into a heating and stirring device with a precision heating system for premixing; S2. The premix is ​​heated stepwise to 160-220°C to melt the components and form a homogeneous molten phase; S3. Under the condition of maintaining the temperature of the molten phase, deionized water is introduced and mechanical shearing is applied to cause physical water dispersion of the molten phase, thus obtaining a primary dispersion system; S4. Homogenize the primary dispersion system to reduce the particle size of the dispersed particles; S5. After cooling to 40-90℃, filter to remove impurities.

[0011] Preferably, the stepwise heating in step S2 is as follows: first, the temperature is raised to 80-130°C to soften the low-melting-point components, then the temperature is raised to 140-180°C to melt the wax phase and the tackifying resin, and then the temperature is raised to 180-210°C to completely melt the EVA; in step S3, the deionized water is added by atomization, fine stream or multiple intermittent additions, and the shear rate is controlled at 500-6000 rpm.

[0012] Preferably, the homogenization process in step S4 adopts one or at least a combination of two of the following methods: high-shear homogenization, colloid mill homogenization, and high-pressure homogenization, and the D90 of the dispersion system after homogenization is not greater than 15 μm; the cooling rate in step S5 is controlled at 0.5 to 10 °C / min.

[0013] The present invention also provides a medical sterilization packaging material, comprising a substrate layer and a heat-sealable coating disposed on the surface of the substrate layer, wherein the heat-sealable coating is formed by coating and drying a heat-sealable adhesive material; the substrate layer is one or at least two of dialysis paper, medical paper, Tyvek, non-woven fabric, polyethylene film, polypropylene film, polyester film, co-extruded film, and paper-plastic composite substrate.

[0014] Preferably, the dry coating weight of the heat-sealing coating is 2-30 g / m². 2 It is formed by drying at 60-140℃; the coating contains a microporous channel structure formed by water dispersion and volatilization and wax / EVA phase rearrangement, which allows ethylene oxide, plasma or steam sterilization media to pass through.

[0015] Preferably, a medical sterilization packaging bag is made of medical sterilization packaging material, wherein the packaging bag is any one of paper-plastic bag, easy-peel combination bag, sterilization paper bag, top bag, formed / filled / sealed bag, four-side sealed bag, blister box lid material bag; after the packaging bag is subjected to ethylene oxide, radiation, plasma or high temperature steam sterilization, the heat seal strength decreases by no more than 20% of the initial value.

[0016] This invention provides a heat-sealing adhesive material for medical sterilization packaging and its aqueous dispersion preparation process. It has the following beneficial effects: 1. This invention significantly improves the heat-sealing and opening performance of packaging materials by introducing a compound combination of medical-grade EVA, beeswax, and bio-wax into an aqueous system. Beeswax and bio-wax act as excellent lubricants and internal plasticizers within the EVA matrix, enabling a smooth opening interface during coating peeling. This effectively prevents fuzzing caused by excessive stretching of paper fibers, ensuring a sterile opening environment.

[0017] 2. This invention achieves ultrafine dispersion of high molecular weight resin in an aqueous phase through precise stepwise heating and high-temperature physical shear water dispersion technology. By controlling the D50 particle size within the range of 0.2–8 μm, the adhesive material exhibits excellent spreading and permeability during coating, enabling it to uniformly cover the surface of dialysis paper or Tyvek. After drying and curing, the microporous structure formed between the particles in this ultrafine dispersion system can both block the invasion of external microorganisms and ensure efficient penetration of sterilizing gases, achieving a dynamic balance between air permeability and antibacterial properties.

[0018] 3. This invention replaces the traditional solvent-based process with an aqueous preparation route, eliminating the use of organic solvents at the source. The entire production process is carried out in a normal temperature and pressure environment, with no carbon emissions or harmful gas volatilization, and the total VOC residue in the finished product is far below industry standards. This ensures that the packaging materials meet the most stringent biocompatibility requirements for medical devices, eliminating the potential physicochemical effects of chemical residues on sensitive drugs and medical devices.

[0019] 4. This invention, by adding a specific proportion of tackifying resin and multifunctional additives, endows the heat-sealable layer with an extremely wide process window. The material can achieve initial sealing at 95°C, while maintaining the stability of its physical structure even under high-temperature sterilization environments up to 160°C. This wide temperature range adaptability allows the product to be compatible with various high-speed automated bag-making equipment. Furthermore, after sterilization with ethylene oxide, radiation, plasma, or high-temperature steam, the decrease in heat-seal strength is controlled within 20%, ensuring the integrity of the packaging throughout its sterilization lifecycle. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation process of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0022] Example 1: like Figure 1 As shown, this embodiment of the invention provides a heat-sealing adhesive material for medical sterilization packaging, comprising the following raw materials by weight: 30 parts of medical-grade EVA with 18% VA content, 8 parts of bio-wax, 2 parts of beeswax, 5 parts of hydrogenated rosin resin, 1 part of nonionic dispersant, 0.2 parts of defoamer, and 45 parts of deionized water.

[0023] The preparation process steps are as follows: EVA, bio-wax, beeswax, hydrogenated rosin resin, and additives are added to a special heating and stirring equipment. The precision heating system is started. In the first stage, the temperature is raised to 110°C and stirred for 20 minutes to soften the wax phase and resin. In the second stage, the temperature is raised to 160°C, at which point the system is in a semi-fluid state. In the third stage, the temperature is precisely raised to 200°C and maintained at a constant temperature to allow the EVA to completely melt and interpenetrate with other components at the molecular level, forming a uniform and transparent molten phase.

[0024] At a constant temperature of 200℃ and a shear rate of 3000rpm, deionized water is slowly introduced into the molten material through a thin stream. At this time, a phase transformation occurs, the molten phase is mechanically sheared and broken up, and is coated with a charged dispersant stabilizer to form a primary emulsion.

[0025] The primary emulsion was introduced into a high-pressure homogenizer and homogenized twice under a pressure of 30 MPa to reduce the D50 particle size to 1.2 μm.

[0026] The precise control cooling system is activated to reduce the system temperature to 50°C at a rate of 3°C / min, and then the material is filtered through a 200-mesh filter before being discharged.

[0027] Testing revealed that the material obtained in Example 1 had a solid content of 42%, a pH value of 9.2, and a viscosity of 850 cps. It was coated onto 60g medical dialysis paper, with a dry coating weight controlled at 8g / m². 2 When sealed with PE composite film at 120℃ and 0.3MPa pressure for 2 seconds, the heat seal strength reaches 3.5N / 15mm, and the peeling interface is smooth with no paper debris peeling off.

[0028] Example 2: This invention provides a heat-sealing adhesive material for medical sterilization packaging, comprising the following raw materials by weight: 45 parts of medical-grade EVA with 28% VA content, 18 parts of bio-wax, 10 parts of beeswax, 15 parts of terpene resin, 0.5 parts of anionic dispersant, 0.3 parts of wetting agent, and 90 parts of deionized water.

[0029] The preparation process is the same as in Example 1, except that the step-by-step heating endpoint in step S2 is set to 210°C, and the shear rate in step S3 is increased to 5000 rpm.

[0030] The material obtained in Example 2 exhibits stronger mechanical stability due to its higher EVA content. When coated onto the surface of Tyvek material and dried, the resulting coating has excellent microporosity. After ethylene oxide sterilization, its air permeability loss rate is less than 5%, demonstrating extremely high process adaptability.

[0031] The packaging material prepared in the above embodiments was made into four-side-seal bags, which were then placed inside simulated surgical instruments and sterilized by high-temperature steam (121°C, 30 min). Experimental results showed that all sealed areas of the packaging bags exhibited no cracking or shrinkage, and the seal strength retention rate was over 85%. VOC testing showed that the total residual solvent was only 1.2 mg / m³. 2 It is far superior to the standard requirements of similar solvent-based products.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A heat-sealing adhesive material for medical sterilization packaging, characterized in that, The heat-sealing adhesive material is an aqueous dispersion system, comprising the following raw materials by weight: 25-50 parts medical-grade EVA, 5-25 parts biological wax, 1-15 parts beeswax, 3-20 parts tackifying resin, 0.1-8 parts functional additives, and 30-120 parts deionized water; The tackifying resin is any one or a combination of rosin resin, modified rosin resin, hydrogenated rosin resin, terpene resin or terpene phenol resin. The heat-sealing adhesive has a viscosity of 100-3000 cps at 20-40°C, a solid content of 30%-45%, and a pH value of 7-11. After coating and drying, it forms a coating that combines a heat-sealing layer and a breathable and antibacterial microporous structure.

2. The heat-sealing adhesive material for medical sterilization packaging according to claim 1, characterized in that, The composition by weight is as follows: 30-45 parts medical-grade EVA, 8-18 parts bio-wax, 2-10 parts beeswax, 5-15 parts tackifying resin, 0.3-5 parts functional additives, and 45-90 parts deionized water; the medical-grade EVA has a vinyl acetate content of 12wt%-40wt% and a melt index of 50-800g / 10min.

3. The heat-sealing adhesive material for medical sterilization packaging according to claim 1, characterized in that, The bio-wax is selected from any one or more combinations of Fischer-Tropsch wax, polyethylene wax, plant-based modified wax, and oxidized wax; the functional additives include any one or more combinations of dispersant stabilizers, rheology modifiers, defoamers, wetting agents, pH adjusters, antioxidants, and preservatives; wherein the dispersant stabilizer is nonionic or anionic, and its addition amount is 0.1% to 3.0% of the total weight.

4. The heat-sealing adhesive material for medical sterilization packaging according to claim 1, characterized in that, The dispersed particles of the heat-sealing adhesive have a volume average particle size (D50) of 0.2–8 μm and volatile organic compounds (VOCs) of less than 5.0 mg / m³ based on total solvent residue. 2 .

5. The aqueous dispersion preparation process of a heat-sealing adhesive material for medical sterilization packaging according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Medical-grade EVA, bio-wax, beeswax, tackifying resin and functional additives are put into a heating and stirring device with a precision heating system for premixing; S2. The premix is ​​heated stepwise to 160-220°C to melt the components and form a homogeneous molten phase; S3. Under the condition of maintaining the temperature of the molten phase, deionized water is introduced and mechanical shearing is applied to cause physical water dispersion of the molten phase, thus obtaining a primary dispersion system; S4. Homogenize the primary dispersion system to reduce the particle size of the dispersed particles; S5. After cooling to 40-90℃, filter to remove impurities.

6. The aqueous dispersion preparation process of a heat-sealing adhesive material for medical sterilization packaging according to claim 5, characterized in that, The stepwise heating in step S2 is as follows: first, the temperature is raised to 80-130℃ to soften the low-melting-point components, then the temperature is raised to 140-180℃ to melt the wax phase and the tackifying resin, and then the temperature is raised to 180-210℃ to completely melt the EVA; in step S3, the deionized water is added by atomization, fine stream or multiple intermittent additions, and the shear rate is controlled at 500-6000 rpm.

7. The aqueous dispersion preparation process of a heat-sealing adhesive material for medical sterilization packaging according to claim 5, characterized in that, The homogenization process in step S4 adopts one or more of the following methods: high shear homogenization, colloid mill homogenization, and high pressure homogenization, or a combination of two of them. After homogenization, the D90 of the dispersion system is not greater than 15 μm. In step S5, the cooling rate is controlled at 0.5 to 10 °C / min.

8. A medical sterilization packaging material, characterized in that, The material includes a substrate layer and a heat-sealable coating disposed on the surface of the substrate layer, wherein the heat-sealable coating is formed by coating and drying the heat-sealable adhesive material as described in any one of claims 1-4; the substrate layer is one or at least two of dialysis paper, medical paper, Tyvek, nonwoven fabric, polyethylene film, polypropylene film, polyester film, co-extruded film, and paper-plastic composite substrate.

9. A medical sterilization packaging material according to claim 8, characterized in that, The dry coating weight of the heat-sealing coating is 2-30 g / m². 2 It is formed by drying at 60-140℃; the coating contains a microporous channel structure formed by water dispersion and volatilization and wax / EVA phase rearrangement, which allows ethylene oxide, plasma or steam sterilization media to pass through.

10. A medical sterilization packaging bag, characterized in that, Made of the medical sterilization packaging material as described in claim 8 or 9, the packaging bag is any one of paper-plastic bag, easy-peel combination bag, sterilization paper bag, top bag, formed / filled / sealed bag, four-side sealed bag, blister box lid material bag; after being subjected to ethylene oxide, radiation, plasma or high-temperature steam sterilization, the heat seal strength of the packaging bag decreases by no more than 20% of the initial value.

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