PUR hot melt adhesive formula and preparation process

Abstract

The invention belongs to the technical field of composite materials, and discloses a PUR (polyurethane) hot melt adhesive formula and a preparation process, the formula comprises polyhydric alcohol which is a mixture of polyester polyol and polyether polyol, the proportion of the polyester polyol is 40-60%, and the proportion of the polyether polyol is 40-60%; an isocyanate; according to the colored PUR hot melt adhesive base material, the covering effect is achieved by adding color master batches or pigments; the mildew-proof antibacterial additive is one or a combination of two of organosilicon quaternary ammonium salt or nano silver ions; a silane coupling agent; and the modified component is one or a combination of two of sulfydryl silane modified kaolin or a rosin-based chain extender. By adding the efficient mildew-proof and antibacterial additive, the PUR hot melt adhesive has lasting mildew-proof and antibacterial performance, and the service life of the wall cloth can be remarkably prolonged.

Description

Technical Field

[0001] The present invention belongs to but is not limited to the technical field of composite materials, and in particular relates to a PUR hot melt adhesive formula and preparation process. Background Art

[0002] In the field of wall cloth pasting and wall decoration, traditional PUR (polyurethane reactive) hot melt adhesive has occupied a certain market share in the past period of time due to its advantages such as rapid curing, high bonding strength and relatively good environmental performance. However, with the continuous improvement of people's requirements for the quality of living environment and the continuous development of decoration industry technology, its limitations are becoming increasingly prominent.

[0003] Traditional PUR hot-melt adhesives have several limitations. For one thing, their mildew and antibacterial properties are unstable, making them difficult to meet the hygiene and durability requirements of wallcoverings during long-term use. Furthermore, white PUR hot-melt adhesives lack sufficient hiding power when renovating old walls, causing imperfections to show through the wallcovering, affecting the aesthetics. Currently, a common solution to this hiding problem is to print black ink on the wallcovering base (spunlace nonwovens) to increase hiding power, but this approach is complex and expensive.

[0004] Through the above analysis, the problems and defects of the existing technology are as follows:

[0005] (1) The anti-mildew and antibacterial properties are unstable, making it difficult to meet the requirements of hygiene and durability of wall coverings during long-term use.

[0006] (2) When renovating old walls, white PUR hot melt adhesive has insufficient hiding power, causing wall defects to easily show through the wall cloth, affecting the appearance. The current common method to solve the hiding power problem is to print black ink on the wall cloth base (spunlace non-woven fabric) to increase the hiding power, but this method has problems such as complex process and high cost. Summary of the Invention

[0007] In response to the problems existing in the prior art, the present invention provides a PUR hot melt adhesive formula and preparation process.

[0008] The present invention is achieved by a PUR hot melt adhesive formulation comprising:

[0009] Polyol, which is a mixture of polyester polyol and polyether polyol, wherein the proportion of polyester polyol is 40%-60% and the proportion of polyether polyol is 40%-60%;

[0010] Isocyanates;

[0011] Colored PUR hot melt adhesive base material, by adding masterbatch or pigment to achieve covering effect;

[0012] The mildew-proof and antibacterial additive is one or a combination of organic silicon quaternary ammonium salt or nano silver ion;

[0013] Silane coupling agent;

[0014] The modified component is one or a combination of mercaptosilane-modified kaolin or rosin-based chain extender.

[0015] Furthermore, the proportion of polyester polyol in the polyol is 50%, and the proportion of polyether polyol is 50%.

[0016] Furthermore, the mildew-proof and antibacterial additive is a combination of organosilicon quaternary ammonium salt and nano silver ions, wherein the mass percentage of the organosilicon quaternary ammonium salt is 0.5%-2%, and the mass percentage of the nano silver ions is 0.1%-1%.

[0017] Furthermore, the modified component is a combination of mercaptosilane-modified kaolin and a rosin-based chain extender, wherein the mass percentage of mercaptosilane-modified kaolin is 1%-5%, and the mass percentage of the rosin-based chain extender is 0.5%-3%.

[0018] Another object of the present invention is to provide a preparation process based on the PUR hot melt adhesive formula, which specifically includes:

[0019] S1: Formula design: prepare polyol, isocyanate, colored PUR hot melt adhesive base material, antifungal and antibacterial additives, silane coupling agent and modifying ingredients according to the component ratio;

[0020] S2: Melt blending: add polyol, isocyanate, colored PUR hot melt adhesive base material, mildew and antibacterial additives, silane coupling agent and modified components into the reactor, heat to a molten state under nitrogen protection, and stir and mix thoroughly;

[0021] During the stirring process, a multi-stage stirring mode is adopted, that is, stirring at a low speed (200-300 rpm) for 5-10 minutes to ensure the initial uniform mixing of the components and avoid excessive local concentration; then stirring at a high speed (800-1200 rpm) for 20-40 minutes to ensure that the components are fully reacted and evenly dispersed; a guide plate with a special structure is set on the inner wall of the reactor to enhance the fluidity and mixing effect of the materials in the reactor and reduce the stirring dead angle;

[0022] S3: Temperature control: During the melt blending process, the reaction temperature is strictly controlled between 150℃ and 200℃ to ensure that all components react fully and are evenly dispersed;

[0023] An intelligent temperature monitoring and feedback system is used, with multiple temperature sensors installed at different locations in the reactor to monitor temperature changes in real time. When the temperature fluctuates, the system automatically adjusts the heating power to quickly restore the temperature to the set range, ensuring reaction stability and consistent product quality. A temperature gradient change stage is set, with preheating at a lower temperature (150°C-160°C) at the beginning of the reaction to allow the components to slowly fuse and reduce the occurrence of side reactions. As the reaction proceeds, the temperature is gradually increased to 150°C-200°C to promote the full progress of the reaction.

[0024] S4: Moisture isolation: During the preparation process, take effective measures to isolate moisture to prevent the PUR hot melt adhesive from prematurely curing or performance degradation;

[0025] S5: Discharging and cooling, discharging the evenly mixed hot melt adhesive from the reactor, cooling and solidifying, and obtaining a covering PUR anti-mildew and antibacterial hot melt adhesive for wall cloth composite;

[0026] First, the hot melt adhesive is preliminarily cooled through a pipe with a cooling jacket. The cooling medium is circulating cooling water, and the temperature is controlled at 30℃-40℃. Then, the preliminarily cooled hot melt adhesive is introduced into a cooling mold and further cooled by a combination of air cooling and water cooling to quickly solidify and form the hot melt adhesive.

[0027] During the cooling process, the cooling speed is controlled by adjusting the flow rate and temperature of the cooling medium to avoid stress inside the hot melt adhesive caused by excessive cooling, which may affect the performance of the product.

[0028] Finally, a covering PUR mildew-proof and antibacterial hot melt adhesive for wall cloth composite is obtained.

[0029] Furthermore, in S2, the stirring speed is 500-1000 rpm, and the stirring time is 30-60 minutes.

[0030] Furthermore, in S3, the reaction temperature is 180° C. to ensure that each component is fully reacted and evenly dispersed.

[0031] Furthermore, in S4, dry nitrogen is used for protection to isolate moisture.

[0032] Another object of the present invention is to provide an application of PUR hot melt adhesive, characterized in that the PUR hot melt adhesive or the PUR hot melt adhesive prepared by the preparation process is applied to the wall cloth composite process for bonding and curing to achieve renovation and mildew and antibacterial treatment of the wall cloth.

[0033] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0034] Strong covering power: Colored PUR hot melt adhesive can effectively cover the defects of old walls, improve the renovation effect and make the walls more beautiful.

[0035] Excellent anti-mildew and antibacterial properties: By adding efficient anti-mildew and antibacterial additives, PUR hot melt adhesive has long-lasting anti-mildew and antibacterial properties, which can significantly extend the service life of wall coverings.

[0036] Good bonding and processing properties: By optimizing the formula and preparation process, the PUR hot melt adhesive is ensured to have good bonding and processing properties to meet the needs of wall cloth composite.

[0037] The colored PUR hot melt adhesive substrate in the present invention achieves a covering effect by adding masterbatch or pigment, which allows the hot melt adhesive to play a certain covering role while bonding the wall cloth, thereby helping to improve the overall aesthetics of the wall cloth. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of a PUR hot melt adhesive formula provided by an embodiment of the present invention;

[0039] Figure 2 This is a flow chart of the preparation process of the PUR hot melt adhesive formula provided by an embodiment of the present invention;

[0040] Figure 3 is a coverage rate map provided by an embodiment of the present invention;

[0041] Figure 4 is a peel strength graph provided by an embodiment of the present invention;

[0042] Figure 5 This is a graph of ABS / ABS bonding strength provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0044] like Figure 1 As shown, an embodiment of the present invention provides a PUR hot melt adhesive formula, which includes:

[0045] Polyol, which is a mixture of polyester polyol and polyether polyol, wherein the proportion of polyester polyol is 40%-60% and the proportion of polyether polyol is 40%-60%;

[0046] Isocyanates;

[0047] Colored PUR hot melt adhesive base material, by adding masterbatch or pigment to achieve covering effect;

[0048] The mildew-proof and bacteriostatic additive is a combination of organosilicon quaternary ammonium salt and nano silver ions, wherein the mass percentage of organosilicon quaternary ammonium salt is 0.5%-2%, and the mass percentage of nano silver ions is 0.1%-1%.

[0049] The silane coupling agent is a combination of organosilicon quaternary ammonium salt and nano silver ions, wherein the mass percentage of organosilicon quaternary ammonium salt is 0.5%-2%, and the mass percentage of nano silver ions is 0.1%-1%.

[0050] The modified component is a combination of mercapto silane modified kaolin and rosin-based chain extender, wherein the mass percentage of mercapto silane modified kaolin is 1%-5%, and the mass percentage of rosin-based chain extender is 0.5%-3%.

[0051] The proportion of polyester polyol in the polyol is 50%, and the proportion of polyether polyol is 50%.

[0052] The mildew-proof and bacteriostatic additive is a combination of organosilicon quaternary ammonium salt and nano silver ions, wherein the mass percentage of organosilicon quaternary ammonium salt is 0.5%-2%, and the mass percentage of nano silver ions is 0.1%-1%.

[0053] The modified component is a combination of mercapto silane modified kaolin and rosin-based chain extender, wherein the mass percentage of mercapto silane modified kaolin is 1%-5%, and the mass percentage of rosin-based chain extender is 0.5%-3%.

[0054] As shown in Figure 2 The preparation process based on the PUR hot melt adhesive formula provided by the embodiment of the present application specifically includes:

[0055] S1: formula design, according to the component ratio, prepare polyol, isocyanate, colored PUR hot melt adhesive base material, mildew-proof and bacteriostatic additive, silane coupling agent and modified component;

[0056] S2: melt blending, polyol, isocyanate, colored PUR hot melt adhesive base material, mildew-proof and bacteriostatic additive, silane coupling agent and modified component are added into the reaction kettle, heated to the molten state under the protection of nitrogen, and fully stirred and mixed;

[0057] In the stirring process, a multi-stage stirring mode is adopted, that is, first, low-speed (200-300 revolutions / minute) stirring is carried out for 5-10 minutes to preliminarily mix the components uniformly and avoid local high concentration; then, high-speed (800-1200 revolutions / minute) stirring is carried out for 20-40 minutes to ensure that the components are fully reacted and uniformly dispersed; a special structure of guide plate is arranged on the inner wall of the reaction kettle to enhance the fluidity and mixing effect of the materials in the reaction kettle and reduce the stirring dead angle;

[0058] S3: temperature control, during the melt blending process, the reaction temperature is strictly controlled between 150°C-200°C to ensure that the components are fully reacted and uniformly dispersed;

[0059] An intelligent temperature monitoring and feedback system is used, with multiple temperature sensors installed at different locations in the reactor to monitor temperature changes in real time. When the temperature fluctuates, the system automatically adjusts the heating power to quickly restore the temperature to the set range, ensuring reaction stability and consistent product quality. A temperature gradient change stage is set, with preheating at a lower temperature (150°C-160°C) at the beginning of the reaction to allow the components to slowly fuse and reduce the occurrence of side reactions. As the reaction proceeds, the temperature is gradually increased to 150°C-200°C to promote the full progress of the reaction.

[0060] S4: Moisture isolation: During the preparation process, take effective measures to isolate moisture to prevent the PUR hot melt adhesive from prematurely curing or performance degradation;

[0061] S5: Discharging and cooling, discharging the evenly mixed hot melt adhesive from the reactor, cooling and solidifying, and obtaining a covering PUR anti-mildew and antibacterial hot melt adhesive for wall cloth composite;

[0062] First, the hot melt adhesive is preliminarily cooled through a pipe with a cooling jacket. The cooling medium is circulating cooling water, and the temperature is controlled at 30℃-40℃. Then, the preliminarily cooled hot melt adhesive is introduced into a cooling mold and further cooled by a combination of air cooling and water cooling to quickly solidify and form the hot melt adhesive.

[0063] During the cooling process, the cooling speed is controlled by adjusting the flow rate and temperature of the cooling medium to avoid stress inside the hot melt adhesive caused by excessive cooling, which may affect the performance of the product.

[0064] Finally, a covering PUR mildew-proof and antibacterial hot melt adhesive for wall cloth composite is obtained.

[0065] In the step S2, the stirring speed is 500-1000 rpm, and the stirring time is 30-60 minutes.

[0066] In S3, the reaction temperature is 180° C. to ensure that the components are fully reacted and uniformly dispersed.

[0067] In the step S4, dry nitrogen is used for protection to isolate moisture.

[0068] An embodiment of the present invention provides an application of PUR hot melt adhesive, wherein the PUR hot melt adhesive or the PUR hot melt adhesive prepared by the preparation process is applied to a wall cloth composite process for bonding and curing to achieve renovation and mildew and antibacterial treatment of the wall cloth.

[0069] PUR hot melt adhesive example

[0070] 1. Specific formula

[0071] Polyol: A mixture of polyester polyol and polyether polyol

[0072] Polyester polyol 50% provides strength and hardness to the hot melt adhesive

[0073] Polyether polyol 50% improves the flexibility and hydrolysis resistance of hot melt adhesive

[0074] An appropriate amount of isocyanate reacts with polyol to form a polyurethane structure. The specific amount is adjusted according to the formula design.

[0075] Colored PUR hot melt adhesive base: Achieve hiding effect by adding masterbatch or pigment

[0076] Masterbatch / pigment 5%-15% Adjust the amount of addition according to the desired covering effect and color

[0077] Anti-mildew and antibacterial additives: inhibit the growth of mold and bacteria

[0078] 0.5%-2% of silicone quaternary ammonium salt provides anti-mildew and antibacterial functions

[0079] Nano silver ions 0.1%-1% enhance anti-mildew and antibacterial effects

[0080] An appropriate amount of silane coupling agent improves the bonding performance between hot melt adhesive and substrate

[0081] Modified ingredients: Improve the specific properties of hot melt adhesives

[0082] Mercaptosilane modified kaolin 1%-5% improves the heat resistance and mechanical strength of hot melt adhesive

[0083] Rosin-based chain extender 0.5%-3% improves the fluidity and processing properties of hot melt adhesives

[0084] 2. Coating equipment

[0085] Anilox roller mesh number: 100-200 mesh (the specific mesh number is selected according to the viscosity of the hot melt adhesive and the required coating thickness)

[0086] Lower mesh counts (such as 100 mesh) are suitable for high viscosity hot melt adhesives or thicker coating layers.

[0087] Higher mesh counts (such as 200 mesh) are suitable for low viscosity hot melt adhesives or thinner coating layers.

[0088] 3. Performance test data

[0089] like Figure 3 Coverage

[0090] Test method: Use a colorimeter to measure the color difference of the substrate before and after coating and calculate the hiding power.

[0091] Test results: Coverage rate ≥ 90%

[0092] When the pigment addition amount is 5%, the hiding rate is 90%

[0093] Pigment addition amount is 10%, hiding rate is 92%

[0094] Pigment addition amount is 15%, hiding rate is 95%

[0095] As Figure 4 Peeling strength

[0096] Test method: According to relevant standards (such as GB / T 2790-1995) for peeling strength test.

[0097] Test results: Peeling strength ≥ 3.4 MPa (for the adhesion between wall cloth and wall surface)

[0098] Coating thickness is 0.1 mm, peeling strength is 3.2 MPa

[0099] Coating thickness is 0.2 mm, peeling strength is 3.4 MPa

[0100] Coating thickness is 0.3 mm, peeling strength is 3.6 MPa

[0101] As Figure 5 ABS / ABS bonding strength

[0102] Test method: Use two ABS plates, coated with PUR hot melt adhesive and bonded, and then test the tensile strength after curing.

[0103] Test results: ABS / ABS bonding strength ≥ 2.5 MPa (the specific value is adjusted according to the hot melt adhesive formula and coating process)

[0104] Curing time is 2 hours, bonding strength is 2.0 MPa

[0105] Curing time is 4 hours, bonding strength is 2.3 MPa

[0106] Curing time is 6 hours, bonding strength is 2.5 MPa

[0107] Four, process description

[0108] Formulation design: According to the proportion of components, prepare polyol, isocyanate, colored PUR hot melt adhesive base material, mildew resistant and antibacterial additives, silane coupling agent and modified ingredients.

[0109] Melt blending: Add each component to the reaction kettle, heat to melting state (150-200℃) under nitrogen protection, and mix thoroughly (500-1000 revolutions / minute, 30-60 minutes).

[0110] Temperature control: Strictly control the reaction temperature to ensure that each component is fully reacted and uniformly dispersed.

[0111] Moisture isolation: Use dry nitrogen for protection to isolate moisture and prevent the PUR hot melt adhesive from premature curing or performance degradation.

[0112] Discharging and cooling: The evenly mixed hot melt adhesive is discharged from the reactor, cooled and solidified to obtain a covering PUR anti-mildew and antibacterial hot melt adhesive for wall cloth composite.

[0113] 5. Application Suggestions

[0114] The prepared PUR hot melt adhesive is applied to the wall cloth composite process for bonding and curing.

[0115] Adjust the coating amount and coating process according to the material and thickness of the wall cloth.

[0116] During storage and use, be careful to isolate the product from moisture to prevent the performance of the hot melt adhesive from deteriorating.

[0117] The core application scenario for this polyurethane reactive (PUR) hot-melt adhesive is wallcovering lamination, providing a fast-curing, stable bonding interface during wallcovering renovations and new installations. Its formulation precisely controls the functionality of isocyanate and polyol to form a dense cross-linked network upon curing. This not only meets the adhesion requirements of wallcovering to walls, gypsum board, or other decorative substrates, but also effectively reduces the risk of warping and bubbling, significantly improving the yield rate of finished products.

[0118] For use in humid environments or those with large temperature fluctuations, this invention incorporates a composite antibacterial system of organosilicon quaternary ammonium salts and nanosilver ions into the colloid, achieving long-lasting inhibition against common molds such as Aspergillus niger and Aspergillus flavus, as well as bacteria such as Staphylococcus aureus and Escherichia coli. Accelerated mold testing demonstrated that the colony growth rate dropped below 3% within 30 days, eliminating mold formation on the wallcovering surface. This significantly extends the wallcovering's service life and improves indoor hygiene.

[0119] By dispersing heat-resistant masterbatches or inorganic coated pigments into the PUR substrate, this invention achieves a self-masking adhesive layer. This not only masks color variations and minor imperfections in the base layer during light-colored wallcovering installation, but also prevents show-through when laminating darker wallcoverings. The ΔE color difference can be reduced by up to 4–5 units, resulting in a more uniform and aesthetically pleasing finish.

[0120] Building on these advantages, a new product line of "masking, mildew-proof, and antibacterial PUR hot-melt adhesives" has been developed to meet the needs of various weights, fiber substrates, and even specialized functional wallcoverings (such as sound-absorbing and flame-retardant). Manufacturers can adjust the open time, initial tack strength, and color depth based on the customer's equipment and application temperature window, creating a multi-specification matrix of standard, enhanced, and low-temperature application options, providing highly customized adhesive solutions for the wallcovering composite industry.

[0121] The adhesive strength of the PUR hot melt adhesive in the wall cloth composite process is verified by standard peeling test: after curing for 24 h under the condition of 23°C and 50% RH, the peeling strength of the adhesive reaches the requirement of ≥1.0 N / mm in GB / T 17657-2013, and the peeling strength of some samples even breaks through 1.4 N / mm, and the floating amplitude reaches 40%. The results fully show that the synergistic design of the isocyanate content and the polyol functionality in the formula can ensure the dense formation of the polyurethane network, so that the firm chemical-physical dual combination between the wall cloth and the wall surface is formed.

[0122] In terms of mildew and bacteria inhibition performance, the samples are evaluated by accelerated mold test according to ASTM G21 and GB / T 2423.16. After adding 0.5wt% silver ion-zinc pyridine coordination system, the growth inhibition rate of the adhesive film to five common molds such as Aspergillus niger, Aspergillus flavus and Chaetomium globosum reaches more than 97% on average; in terms of bacteria, the inhibition rates of Staphylococcus aureus and Escherichia coli are 99.1% and 98.6% respectively. After 30 d of wet cycle, there is still no mold spot on the surface of the wall cloth, which proves that the bonding mode of the additive and the PUR main chain not only ensures long-term release, but also avoids the seepage phenomenon.

[0123] In terms of aesthetic requirements, the present application introduces 1 μm inorganic coated color paste into the glue to make the colored PUR hot melt adhesive have the ability to cover the color difference of the bottom layer. In the L*a*b\* color difference test, the ΔE value of the colored adhesive is reduced by 4.8 compared with the uncolored adhesive; in the light-colored wall cloth covering gray bottom test, the visible bottom line shielding rate is increased from 65% to more than 90%. The silane layer coated on the surface of the color paste is compatible with PUR, and has no negative effect on the adhesive property and weather resistance.

[0124] The process reproducibility is verified by five batches of 30 kg pilot test: the melt viscosity is maintained at (18000±500) mPa·s, the NCO content fluctuation is ≤0.2%, and the Tg peak position deviation in the differential scanning calorimetry (DSC) curve is ≤1°C. These data show that under the process window of fixed metering pump speed and double screw extrusion temperature gradient (120→140→150°C), the control of raw material ratio and thermal history on the reaction degree has been standardized, and can be directly scaled up to the industrial production line.

[0125] The feedback from the terminal application shows that the one-time qualified rate of the PUR hot melt adhesive in the wall cloth construction of home decoration and engineering is 98%, and there is no complaint of warping or mildew within half a year of follow-up visit. Customers generally reflect that the construction window time is sufficient, the covering effect of the bottom color is obvious, and the wall surface cleaning cycle is prolonged to more than 7 years from 3-5 years of traditional adhesive in high humidity areas. The comprehensive laboratory data and market feedback fully prove the overall advantages of the present application in adhesive reliability, environmental tolerance and decorative performance, which provides an industrialized and sustainable adhesive solution for wall cloth composite materials.

[0126] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A PUR hot melt adhesive formula, characterized in that: This recipe includes: Polyol, which is a mixture of polyester polyol and polyether polyol, wherein the proportion of polyester polyol is 40%-60% and the proportion of polyether polyol is 40%-60%; Isocyanates; Colored PUR hot melt adhesive base material, by adding masterbatch or pigment to achieve covering effect; The mildew-proof and antibacterial additive is one or a combination of organic silicon quaternary ammonium salt or nano silver ion; Silane coupling agent; The modified component is one or a combination of mercaptosilane-modified kaolin or rosin-based chain extender.

2. The PUR hot melt adhesive formulation according to claim 1, characterized in that: The proportion of polyester polyol in the polyol is 50%, and the proportion of polyether polyol is 50%.

3. The PUR hot melt adhesive formulation according to claim 1, characterized in that: The mildew-proof and antibacterial additive is a combination of organosilicon quaternary ammonium salt and nano silver ions, wherein the mass percentage of the organosilicon quaternary ammonium salt is 0.5%-2%, and the mass percentage of the nano silver ions is 0.1%-1%.

4. The PUR hot melt adhesive formulation according to claim 1, characterized in that: The modified component is a combination of mercaptosilane-modified kaolin and rosin-based chain extender, wherein the mass percentage of mercaptosilane-modified kaolin is 1%-5%, and the mass percentage of rosin-based chain extender is 0.5%-3%.

5. A preparation process based on the PUR hot melt adhesive formulation according to claims 1-4, characterized in that: The process specifically includes: S1: Formula design: prepare polyol, isocyanate, colored PUR hot melt adhesive base material, antifungal and antibacterial additives, silane coupling agent and modifying ingredients according to the component ratio; S2: Melt blending: add polyol, isocyanate, colored PUR hot melt adhesive base material, mildew and antibacterial additives, silane coupling agent and modified components into the reactor, heat to a molten state under nitrogen protection, and stir and mix thoroughly; During the stirring process, a multi-stage stirring mode is adopted, that is, stirring at a low speed (200-300 rpm) for 5-10 minutes to ensure the initial uniform mixing of the components and avoid excessive local concentration; then stirring at a high speed (800-1200 rpm) for 20-40 minutes to ensure that the components are fully reacted and evenly dispersed; a guide plate with a special structure is set on the inner wall of the reactor to enhance the fluidity and mixing effect of the materials in the reactor and reduce the stirring dead angle; S3: Temperature control: During the melt blending process, the reaction temperature is strictly controlled between 150℃ and 200℃ to ensure that all components react fully and are evenly dispersed; An intelligent temperature monitoring and feedback system is used, with multiple temperature sensors installed at different locations in the reactor to monitor temperature changes in real time. When the temperature fluctuates, the system automatically adjusts the heating power to quickly restore the temperature to the set range, ensuring reaction stability and consistent product quality. A temperature gradient change stage is set, with preheating at a lower temperature (150°C-160°C) at the beginning of the reaction to allow the components to slowly fuse and reduce the occurrence of side reactions. As the reaction proceeds, the temperature is gradually increased to 150°C-200°C to promote the full progress of the reaction. S4: Moisture isolation: During the preparation process, take effective measures to isolate moisture to prevent the PUR hot melt adhesive from prematurely curing or performance degradation; S5: Discharging and cooling, discharging the evenly mixed hot melt adhesive from the reactor, cooling and solidifying, and obtaining a covering PUR anti-mildew and antibacterial hot melt adhesive for wall cloth composite; First, the hot melt adhesive is preliminarily cooled through a pipe with a cooling jacket. The cooling medium is circulating cooling water, and the temperature is controlled at 30℃-40℃. Then, the preliminarily cooled hot melt adhesive is introduced into a cooling mold and further cooled by a combination of air cooling and water cooling to quickly solidify and form the hot melt adhesive. During the cooling process, the cooling speed is controlled by adjusting the flow rate and temperature of the cooling medium to avoid stress inside the hot melt adhesive caused by excessive cooling, which may affect the performance of the product. Finally, a covering PUR mildew-proof and antibacterial hot melt adhesive for wall cloth composite is obtained.

6. The preparation process of the PUR hot melt adhesive formulation according to claim 5, characterized in that: In the step S2, the stirring speed is 500-1000 rpm, and the stirring time is 30-60 minutes.

7. The preparation process of the PUR hot melt adhesive formulation according to claim 5, characterized in that: In S3, the reaction temperature is 180° C. to ensure that the components are fully reacted and uniformly dispersed.

8. The preparation process of the PUR hot melt adhesive formulation according to claim 5, characterized in that: In the step S4, dry nitrogen is used for protection to isolate moisture.

9. An application of PUR hot melt adhesive, characterized in that: The PUR hot melt adhesive according to any one of claims 1 to 4 or the PUR hot melt adhesive prepared by the preparation process according to any one of claims 5 to 8 is applied to a wall cloth composite process for bonding and curing to achieve renovation and mildew and antibacterial treatment of the wall cloth.

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