Anti-edge-warping polyurethane foam dressing and preparation method thereof

Abstract

The invention relates to the field of dressings, in particular to an anti-edge-warping polyurethane foam dressing and a preparation method thereof. In the production process of the polyurethane foam, a layer of water-blocking material is sprayed on the surface of the foam after normal-temperature curing, and then the water-blocking material and the polyurethane foam are dried and shrunk together, so that a firmly-combined water-blocking layer is formed on the surface of the polyurethane foam, and the polyurethane foam prepared in the manner has good water-blocking property and air permeability; when the foam absorbs water and expands, the waterproof layer on the upper surface layer also expands, so that the problem that the edge of the foam dressing is warped due to imbibition expansion in the prior art is effectively solved, the risk that the dressing falls off due to the warped edge is reduced, the stability of the dressing is remarkably improved, and the service life of the dressing is remarkably prolonged.

Description

Technical Field

[0001] This invention relates to the field of dressings, and more particularly to an anti-curling polyurethane foam dressing and its preparation method. Background Technology

[0002] Foam dressings are an important product in modern wound care, widely used to treat wounds with moderate to large amounts of exudate, such as postoperative wounds, burns, and pressure ulcers. Their core function is to absorb and lock in exudate, providing a moist, sealed healing environment for the wound.

[0003] Traditional foam dressings typically employ a multi-layered structure, primarily consisting of an absorbent layer (usually polyurethane foam) in contact with the wound and an outer layer serving as a backing. Currently, the backing layer of most products is directly bonded to the foam layer using adhesives; while this mature process is simple, in practical clinical applications, especially when treating highly exudative wounds, some inherent technical limitations have gradually become apparent:

[0004] When foam materials absorb liquid, they inevitably expand in three dimensions. However, the backing film (commonly made of TPU, PU, ​​etc.) has limited stretchability. When absorbing a large amount of exudate, the expansion of the foam layer significantly exceeds the passive stretching limit of the backing layer. This mismatch in deformation causes the edges of the foam dressing to warp upwards, a phenomenon known as "edge lifting." Edge lifting not only disrupts the adhesion between the dressing and the skin, leading to premature dressing detachment, but also allows external contaminants to enter the wound, severely impacting the effective use time and care outcome of the dressing.

[0005] Therefore, there is an urgent clinical need for a new type of foam dressing structure that can fundamentally solve the problem of edge lifting caused by mismatch in deformation after liquid absorption, while taking into account both excellent breathability and reliable barrier function. Summary of the Invention

[0006] In order to reduce the curling of foam dressings after liquid absorption in the prior art, while maintaining good air permeability and mechanical strength, this application provides an anti-curling polyurethane foam dressing and its preparation method.

[0007] Technical solution:

[0008] In a first aspect, this application provides a method for preparing an anti-curling polyurethane foam dressing, comprising the following preparation process:

[0009] After high-speed blending of the aqueous phase and prepolymer, the mixture is foamed and cured in a room-temperature curing section to form hydrophilic polyurethane foam. Then, water-blocking material is sprayed onto the hydrophilic polyurethane foam after room-temperature curing. The dried polyurethane foam with water-blocking layer is then processed through slitting, packaging and sterilization to obtain anti-curling polyurethane foam dressing.

[0010] The water-blocking material is any one of TPU, PU, ​​PE, PET, PVC, acrylic resin, rubber, and silicone.

[0011] Furthermore, when spraying the water-blocking material, the hydrophilic polyurethane foam is cured at room temperature and before entering the oven.

[0012] The application of this hydrophilic polyurethane foam spraying water-blocking material is carried out after room temperature curing and before drying. At this time, the hydrophilic polyurethane foam contains a lot of water (water that has not participated in the reaction in the aqueous phase during the polyurethane foam synthesis process), and there is also some carbon dioxide that has not been removed from the foam after the reaction. At this stage, the foam is in a relaxed state.

[0013] Furthermore, when spraying the water-blocking material, the aforementioned stage occurs after the room temperature curing stage and before entering the oven.

[0014] Furthermore, the moisture content of the dried polyurethane foam with a water-blocking layer is controlled between 0.1% and 10%, preferably between 1% and 5%.

[0015] Secondly, this application provides an anti-curling polyurethane foam dressing, comprising a polyurethane foam layer and a water-blocking layer, wherein the thickness of the water-blocking layer is 10-110 μm.

[0016] Furthermore, the water-blocking layer is preferably 30-90 μm thick.

[0017] Furthermore, the anti-curling polyurethane foam dressing described in this application, when tested according to the method in Annex I of EN13726-2023, has a water vapor transmission rate (MVTR) of 1500-6500 g / m². 2 24h.

[0018] Furthermore, the anti-curling polyurethane foam dressing described in this application will not have its water-blocking layer peel off during the product's shelf life under normal temperature conditions.

[0019] Furthermore, when the anti-curling polyurethane foam dressing described in this application is placed in water and shaken on a shaker, the time for the water-blocking layer to fall off is greater than 7 days.

[0020] Furthermore, the anti-curling polyurethane foam dressing described in this application, when tested according to YY / T 0471.1-2004 "Test Methods for Contact Wound Dressings - Part 1: Liquid Absorbency", shows no curling in purified water.

[0021] Beneficial effects: 1. In the production process of polyurethane foam, after curing at room temperature, a layer of water-blocking material is sprayed onto the surface of the foam. After drying and shrinking together with the polyurethane foam, a firmly bonded water-blocking layer is formed on the surface of the polyurethane foam. The polyurethane foam produced in this way has good water resistance and air permeability. When the foam absorbs water and expands, the water-blocking layer on the upper surface will also expand. This effectively solves the problem of foam dressings curling up due to liquid absorption and expansion in the prior art, which leads to the dressing falling off. It significantly improves the stability and service life of the dressing.

[0022] 2. The polyurethane foam coating of the present invention has good water resistance and air permeability, which effectively improves the problem of low air permeability of dressings in the prior art, meets the management of dressing air permeability and exudate, and is conducive to promoting wound healing; by forming a water-resistant layer on the surface of polyurethane foam, the occurrence of skin allergies caused by adhesive components is effectively avoided, and the safety and applicability of the dressing are improved.

[0023] 3. By spraying a layer of water-blocking material onto the surface after natural curing and drying and shrinking it together with polyurethane foam, the preparation method of the present invention can effectively control the thickness and distribution of the water-blocking layer, ensuring a tight bond between the water-blocking layer and the foam, and improving the overall performance of the dressing. Attached Figure Description

[0024] Figure 1 The process flow diagram of the preparation method in Example 2 of this application. Detailed Implementation

[0025] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1, a method for preparing an anti-curling polyurethane foam dressing, comprising the following preparation process:

[0027] Step 1: Prepare the hydrophilic polyurethane foam prepolymer and aqueous phase material, and prepare the water-blocking spray coating material for spraying after room temperature curing.

[0028] Step 2: Pump the aqueous phase and prepolymer into their respective tanks. Once the aqueous phase and prepolymer reach the required temperatures (aqueous phase temperature 5~10℃, prepolymer temperature 35~50℃), set the production speed (4m / min), the prepolymer:aqueous phase mass ratio (prepolymer:aqueous phase = 1.2:1), the mixing speed (3000-5000rpm), and the discharge rate (1.0kg / min), and pour it between the two layers of release paper.

[0029] Step 3: Disperse the mixture using a dispersing roller, and then allow the dispersed mixture to naturally foam and cure in a room-temperature curing section.

[0030] Step 4: Release paper peeling. After curing at room temperature, peel off the top and bottom layers of release paper from the polyurethane foam.

[0031] Step 5: Spray water-blocking material. The water-blocking material can be TPU, PU, ​​PE, PET, PVC, acrylic resin, rubber, or silicone, with TPU being the preferred choice.

[0032] The spraying liquid prepared in step 1 is uniformly sprayed onto the surface of the foam that has cured at room temperature through an atomizing nozzle. The spraying amount is calculated using Formula 1 to control the spraying and prepare foams with TPU layer thicknesses of 10μm, 30μm, 50μm, 70μm, 90μm and 110μm.

[0033] Step 6: Drying. Place the polyurethane foam with water-resistant material sprayed on the surface into an oven to dry.

[0034] Step 7: Trim the edges, removing the edges of the dried foam;

[0035] Step 8: After winding, it is used in subsequent processes to prepare polyurethane foam dressings;

[0036] The aforementioned method for producing medical polyurethane foam:

[0037] The water-blocking spray coating in step 1 is composed of solvent-based TPU resin and solvent, and can be formulated with optional leveling agents and defoamers.

[0038] In step 1, some functional additives, such as silver powder, can be added during the preparation of the water-blocking spray coating to increase its antibacterial effect.

[0039] The formula for calculating the amount of water-blocking material sprayed in step 5 is as follows:

[0040] M = v × L × h × ρ / (108 × k1 × k2) Formula 1

[0041] M represents the spraying rate per minute, expressed in kg / min.

[0042] v represents the speed of the foam production line, in m / min;

[0043] L represents the spray width, in cm;

[0044] h represents the thickness of the pre-sprayed water-blocking film after drying, in μm.

[0045] ρ is the density of the pre-sprayed water-blocking film after drying, in kg / m3;

[0046] K1 is the transverse shrinkage coefficient after foam drying. The specific calculation method is: k1=L1 / L2, which is obtained by preparing conventional hydrophilic polyurethane foam of the corresponding specifications (K1 can be obtained by preparing uncoated foam in steps 1, 2, 3, 4, and 6, and measuring the width before and after drying).

[0047] L1 is the width of the foam before drying;

[0048] L2 is the width of the foam after drying;

[0049] K2 is the film-forming coefficient of the sprayed water-blocking material, which is the weight ratio of the amount of sprayed material to the amount of film formed per unit time.

[0050] In the above formula, ρ can be referenced to the density of solvent-based TPU particles;

[0051] In step 6, the drying temperature is 60~90℃. During the drying process, the foam shrinks along with the water-blocking layer as the moisture evaporates. After drying, the moisture content of the foam with the water-blocking layer is controlled between 0.1% and 10%, preferably between 1% and 5%.

[0052] Step 7 is an optional step; you can choose to trim the edges or not, depending on whether the actual spray width covers the foam width.

[0053] The thickness of the polyurethane foam water-blocking layer with water-blocking layer obtained in step 8 is 10~110μm, preferably 30~90μm, and more preferably 30~70μm.

[0054] Example 2, a method for preparing an anti-curling polyurethane foam dressing, comprising the following preparation process:

[0055] Step 1: Prepare the prepolymer and aqueous phase material for hydrophilic polyurethane foam, see Table 1 and Table 2 for details;

[0056] Table 1. List of raw materials using prepolymer and aqueous phase

[0057]

[0058] Table 2. Water-blocking spray coating materials available for use:

[0059]

[0060] Step 2: Pump the aqueous phase and prepolymer into their respective tanks. Once the aqueous phase and prepolymer reach the required temperatures (aqueous phase temperature 8℃, prepolymer temperature 40℃), set the production speed (4m / min), the prepolymer:aqueous phase ratio (prepolymer:aqueous phase = 1.2:1), the mixing speed (4000rpm), and the discharge rate (1.0kg / min), and pour the mixture between the two layers of release paper.

[0061] Step 3: Disperse the mixture using a dispersing roller, and then allow the dispersed mixture to naturally foam and cure in a room-temperature curing section.

[0062] Step 4: Release paper peeling. After curing at room temperature, peel off the upper and lower layers of release paper to obtain hydrophilic polyurethane foam.

[0063] Step 5: Apply the water-blocking spraying material prepared in Step 1 evenly to the surface of the foam after it has cured at room temperature through an atomizing nozzle; use Formula 1 to calculate the spraying amount and control the thickness of the water-blocking layer to prepare foams with thicknesses of 10 μm, 30 μm, 50 μm, 70 μm, 90 μm and 110 μm.

[0064] Step 6: Drying. The polyurethane foam with water-resistant material sprayed on the surface is sent into an oven with a conveyor belt to dry, so as to obtain polyurethane foam with a water-resistant layer on the surface.

[0065] Preferably, the drying temperature in step 6 is 80°C. During the drying process, the foam shrinks along with the water-blocking material as the water evaporates.

[0066] Step 7: Trim the edges, cut off the edges of the dried foam.

[0067] Optionally, step 7 can be omitted. You can choose to trim the edge or not, depending on whether the actual spray width covers the foam width.

[0068] Preferably, the water-blocking spray coating is composed of solvent-based TPU resin and solvent, and leveling agents and defoamers may be selectively added.

[0069] The formula for calculating the amount of water-blocking material sprayed in step 5 is as follows:

[0070] M=v×L×h×ρ / (108×k1×k2);

[0071] M represents the spraying rate per minute, expressed in kg / min.

[0072] v represents the speed of the foam production line, in m / min;

[0073] L represents the spray width, in cm;

[0074] h represents the thickness of the pre-sprayed water-blocking film after drying, in μm.

[0075] ρ represents the density of the pre-sprayed water-blocking film after drying, in kg / m³. 3 ;

[0076] K1 is the transverse shrinkage coefficient after foam drying. The specific calculation method is: k1=L1 / L2, which is obtained by preparing conventional hydrophilic polyurethane foam of the corresponding specifications (K1 can be obtained by preparing uncoated foam in steps 1, 2, 3, 4, and 6, and measuring the width before and after drying).

[0077] L1 is the width of the foam before drying;

[0078] L2 is the width of the foam after drying;

[0079] K2 is the film-forming coefficient of the sprayed water-blocking material, which is the weight ratio of the amount of sprayed material to the amount of film formed per unit time.

[0080] In the above formula, ρ represents the density of solvent-based TPU particles.

[0081] Example 3: The polyurethane foam with different water-blocking layer thicknesses prepared in Example 2 was further cut, bagged and sterilized to make anti-curling polyurethane foam dressing. The water-blocking, MVTR, TPU film peeling and curling performance were tested; the test results are shown in Table 3.

[0082] Table 3 lists the performance changes of foam dressing samples prepared by further processing hydrophilic polyurethane foam with different water-blocking layer thicknesses as described in Example 1.

[0083]

[0084] Note: The control sample foam dressing (non-adhesive type) is made by fixing a TPU backing film (water-resistant layer) onto a polyurethane foam (prepared in steps 1, 2, 3, 4, and 6 of Example 2) with solvent adhesive, followed by cutting, bagging, and sterilization.

[0085] 1) Water-blocking performance:

[0086] Samples of the foam dressings from the examples and comparative examples were taken in 10cm×10cm sizes. Water resistance was tested according to YY / T 0471.3-2004 "Test Methods for Contact Wound Dressings Part 3: Water Resistance". Except for the foam sample with a TPU film thickness of 10μm, the results of the other samples all met the test requirements. The test results are shown in Table 1.

[0087] 2) Water vapor transmission rate (MVTR):

[0088] Samples with a diameter of 5 cm were taken from the foam dressings of the examples and comparative examples; the water vapor transmission rate (MVTR) was tested according to the method in Annex I of EN13726-2023 standard, and the test results are shown in Table 1.

[0089] 3) TPU film peeling status:

[0090] Take 5cm×5cm samples of the foam dressings from the examples and comparative examples; place the samples into an Erlenmeyer flask, add 50ml of purified water, and stopper the flask; then place the Erlenmeyer flask on a shaker, set the temperature to 37℃ and the rotation speed to 120rpm;

[0091] Observe daily for 7 consecutive days and record the number of days it takes for the TPU film on the sample to begin to peel off.

[0092] 4) Edge curling:

[0093] Samples of the foam dressings from the examples and comparative examples were taken at 10cm×10cm. According to YY / T 0471.1-2004 "Test Methods for Contact Wound Dressings - Part 1: Liquid Absorbency", the samples were placed flat in purified water with the foam side down. The presence of any curling at the edges during the water absorption process of the foam dressing was observed and recorded.

[0094] Results: TPU film thicknesses of 10μm, 30μm, 50μm, 70μm and 90μm showed no edge curling during water absorption, while foam dressings with a TPU film thickness of 110μm showed slight edge curling during water absorption.

[0095] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing an anti-curling polyurethane foam dressing, characterized in that, The preparation process includes the following: After high-speed blending of the aqueous phase and prepolymer, the mixture is foamed and cured in a room-temperature curing section to form hydrophilic polyurethane foam. Then, water-blocking material is sprayed onto the hydrophilic polyurethane foam after room-temperature curing. The dried polyurethane foam with water-blocking layer is then processed through slitting, packaging and sterilization to obtain anti-curling polyurethane foam dressing. The water-blocking material is any one of TPU, PU, ​​PE, PET, PVC, acrylic resin, rubber, and silicone.

2. The method for preparing an anti-curling polyurethane foam dressing according to claim 1, characterized in that, When spraying water-blocking materials, the aforementioned stage occurs after the room temperature curing stage and before entering the oven.

3. The method for preparing an anti-curling polyurethane foam dressing according to claim 2, characterized in that, The moisture content of the dried polyurethane foam with a water-blocking layer is controlled between 0.1% and 10%, preferably between 1% and 5%.

4. A polyurethane foam dressing for preventing edge curling obtained by the preparation method according to any one of claims 1-3, characterized in that, It includes a polyurethane foam layer and a water-blocking layer, wherein the thickness of the water-blocking layer is 10-110 μm.

5. The anti-curling polyurethane foam dressing according to claim 4, characterized in that, The water-blocking layer is preferably 30-90 μm thick.

6. The anti-curling polyurethane foam dressing according to claim 4 or 5, characterized in that, According to the Annex I method in EN13726-2023, the water vapor transmission rate (MVTR) is 1500-6500 g / m³. 2 24h.

7. The anti-curling polyurethane foam dressing according to claim 6, characterized in that, Under normal temperature conditions, the water-blocking layer will not fall off during the product's shelf life.

8. A polyurethane foam dressing for preventing edge curling according to any one of claims 4-5 and 7, characterized in that, The anti-curling polyurethane foam dressing is placed in water and shaken on a shaker, and the water-blocking layer takes more than 7 days to fall off.

9. The anti-curling polyurethane foam dressing according to claim 8, characterized in that, According to YY / T 0471.1-2004 "Test Methods for Contact Wound Dressings - Part 1: Liquid Absorbency", the dressing showed no edge curling in purified water.

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