Polyurethane foamed composite insole material and method for manufacturing the same

Abstract

This invention discloses a polyurethane foam composite insole material and its preparation method, comprising a first layer and a second layer. The first layer is made of one of fabric, PU leather, microfiber leather, or genuine leather. The second layer is a polyurethane foam adhesive layer, which is formed by foaming and curing a polyurethane AB material coated on a release carrier, followed by peeling off the release carrier. During the foaming and curing process, the second layer adheres to the first layer using its own adhesiveness. By using the release carrier as a temporary carrier and controlling the polyurethane mixture to foam to a semi-cured state while retaining surface tack, no additional glue is needed. The double-layer composite structure is completed by relying on the self-adhesion of the foamed layer. This process simplifies the production process, allows for continuous assembly line operation, avoids odors and delamination caused by glue, and reduces bonding bubbles and fabric wrinkles. While ensuring the cushioning and rebound performance of the insole, it improves the interlayer bonding strength and the yield of the finished product.

Description

Technical Field

[0001] This invention relates to the field of composite insole materials technology, and in particular to a method for preparing a polyurethane foam composite insole material. Background Technology

[0002] Polyurethane foam materials have been widely used in the field of insoles in recent years due to their excellent breathability, resilience, and cushioning properties. As consumers' demands for comfort, lightweight, and durability in footwear products continue to increase, multi-layer composite insoles are gradually becoming the industry mainstream. These typically include a surface layer that contacts the foot, a middle foam layer that provides cushioning support, and a bottom layer. To achieve a strong bond between the functional layers, traditional multi-layer composite insoles mostly use adhesive bonding processes.

[0003] However, existing adhesive bonding processes have many shortcomings. First, commercially available shoe adhesives are mainly solvent-based products, which release volatile organic compounds during preparation and use. This not only pollutes the production environment, but the residual organic solvents may also cause skin allergies in some wearers, affecting human health. Second, the adhesive bonding process is lengthy and inefficient. Process parameters such as the amount of adhesive applied, drying temperature, and curing time significantly affect the bonding quality. In practice, uneven adhesive application and adhesive layer aging are common problems, leading to delamination and separation of the insoles during use due to frequent bending, moisture, or temperature changes. Furthermore, uneven adhesive application during the bonding of the surface fabric or leather to the foam layer can easily produce air bubbles and fabric wrinkles, affecting the appearance and wearing comfort of the finished product.

[0004] Therefore, there is a need for a polyurethane foam composite insole material and its preparation method. Using a release carrier as a temporary carrier, the polyurethane mixture is controlled to foam to a semi-cured state while retaining surface tackiness. No additional glue is needed. The structural composite is completed by relying on the tackiness of the foam layer itself. This avoids the odor and delamination problems caused by glue, and reduces bonding bubbles and fabric wrinkles. While ensuring the cushioning and rebound performance of the insole, it improves the interlayer bonding strength and finished product yield, and enables continuous production line operation. Summary of the Invention

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a polyurethane foam composite insole material, which includes a first layer and a second layer. The first layer is made of one of fabric, PU leather, microfiber leather or genuine leather. The second layer is a polyurethane foam adhesive layer. The polyurethane foam adhesive layer is formed by foaming and curing polyurethane AB material coated on a release carrier and then peeling off the release carrier. During the foaming and curing process, the second layer is bonded to the first layer by its own adhesiveness.

[0006] Preferably, the polyurethane AB material comprises a mixture of component A and component B, wherein component A comprises, by weight percentage of the composition, the remainder of a combined polyether polyol, 1-8 parts of a foaming agent, 0.1-0.8 parts of a catalyst, and 0.5-2 parts of a foam stabilizer.

[0007] Preferably, component B comprises, by weight of liquefied modified diphenylmethane diisocyanate, 0.5-5 parts of small molecule glycol crosslinking agent, 1-3 parts of environmentally friendly plasticizer, and 0.2-1 parts of hydrolysis-resistant stabilizer.

[0008] Preferably, the foaming agent includes one or more of free water, cyclopentane, n-pentane, and hydrofluorocarbons.

[0009] Preferably, the environmentally friendly plasticizer includes at least one of citrate ester plasticizers, vegetable oil-based plasticizers, and benzoate compounds.

[0010] This invention also provides a method for preparing a polyurethane foam composite insole material as described above, comprising the following steps:

[0011] S1: Provide a release carrier, unwind the release carrier and lay it on the conveyor line;

[0012] S2: Mix component A and component B in a certain proportion to form polyurethane AB material;

[0013] S3: The polyurethane AB material is coated on the surface of the release carrier, and foamed to a semi-cured state to form a polyurethane foam adhesive layer with surface adhesion, while the release carrier is retained as a temporary carrier.

[0014] S4: Apply one of the following materials—fabric, PU leather, microfiber leather, or genuine leather—to the side of the polyurethane foam adhesive layer away from the release carrier. Utilize the self-adhesion of the polyurethane foam adhesive layer in its semi-cured state to bond the polyurethane foam adhesive layer with one of the following materials—fabric, PU leather, microfiber leather, or genuine leather—to obtain a first composite.

[0015] S5: Peel and remove the release carrier from the first composite. After the polyurethane foam adhesive layer has completely cured, a composite roll material is obtained.

[0016] S6: The composite roll material is punched or molded to make insoles;

[0017] The polyurethane foam adhesive layer forms an adhesive layer during the foaming and curing process, and is bonded to one of the fabric, PU leather, microfiber leather or genuine leather.

[0018] Preferably, the release carrier in S3 is one of single-sided silicone-coated release paper, PET release film, or a release film with air permeability.

[0019] Preferably, the time from when the polyurethane AB material is coated on the release carrier surface in S3 to when it is bonded to the fabric in S4 is 3 minutes.

[0020] Preferably, the foaming temperature in S3 is adjusted according to the coating speed; when the conveyor speed increases, the foaming temperature is increased simultaneously to accelerate the foaming and curing speed of the polyurethane AB material; when the conveyor speed decreases, the foaming temperature is decreased simultaneously to prevent the internal micropores of the polyurethane AB material from collapsing due to heat, and to ensure the overall uniform air permeability of the polyurethane AB material.

[0021] Preferably, the width of the composite roll in S5 is 1.35-1.80 meters.

[0022] Compared with existing technologies, the preparation method of polyurethane foam composite insole material provided by this invention has the following beneficial effects:

[0023] This invention utilizes a release carrier as a temporary carrier and precisely controls the foaming of polyurethane AB material to a semi-cured state. The initial tack of the foamed layer itself allows for simultaneous online lamination with the surface fabric and underlying leather, eliminating the separate gluing, baking, and pressing processes required in traditional methods. This significantly simplifies the production process and makes it suitable for continuous assembly line operations. Furthermore, this process eliminates the use of adhesives, removing bonding bubbles and fabric wrinkles caused by uneven adhesive application. This results in dense and uniform interlayer bonding, greatly improving the product's appearance quality and yield.

[0024] This invention fundamentally avoids the introduction of solvent-based adhesives, releasing no volatile organic compounds during the entire preparation and use process. It is environmentally friendly, leaves no residual odor, and is safe and gentle on the wearer's feet. More importantly, the second polyurethane foam adhesive layer forms a strong, integrated structure with the first layer during the curing process. This avoids quality problems such as insole delamination and separation caused by aging, moisture, or repeated bending, which are common with traditional adhesives. While maintaining the insole's excellent cushioning and rebound performance for a long time, it significantly extends the insole's lifespan. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0026] Figure 1 This is a first flowchart of the present invention;

[0027] Figure 2 This is a second flowchart of the present invention;

[0028] Figure 3 This is a first air permeability test diagram of the present invention;

[0029] Figure 4 This is a second air permeability test diagram of the present invention;

[0030] Figure 5 This is the third air permeability test diagram of the present invention. Detailed Implementation

[0031] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] like Figure 1-2 As shown in the figure, an embodiment of the present invention provides a polyurethane foam composite insole material, which includes a first layer and a second layer. The first layer is made of one of fabric, PU leather, microfiber leather or genuine leather. The second layer is a polyurethane foam adhesive layer. The polyurethane foam adhesive layer is formed by foaming and curing polyurethane AB material coated on a release carrier and then peeling off the release carrier. During the foaming and curing process, the second layer is bonded to the first layer by its own adhesiveness.

[0034] The polyurethane AB compound comprises a mixture of component A and component B. Component A, by weight percentage of the composition, includes the remainder of a combined polyether polyol, 1-8 parts of a blowing agent, 0.1-0.8 parts of a catalyst, and 0.5-2 parts of a foam stabilizer. Component B, by weight percentage of the composition, includes the remainder of liquefied modified diphenylmethane diisocyanate, 0.5-5 parts of a small molecule glycol crosslinking agent, 1-3 parts of an environmentally friendly plasticizer, and 0.2-1 parts of an anti-hydrolysis stabilizer. The blowing agent includes one or more of free water, cyclopentane, n-pentane, and hydrofluorocarbon compounds. The environmentally friendly plasticizer includes at least one of citrate plasticizers, vegetable oil-based plasticizers, and dibenzoic acid ester plasticizers.

[0035] A method for preparing a polyurethane foam composite insole material includes the following steps:

[0036] S1: Provide release carrier, unwind the release carrier and lay it on the conveyor line;

[0037] S2: Mix component A and component B in a certain proportion to form polyurethane AB material;

[0038] S3: Apply polyurethane AB material to the surface of the release carrier, and foam it to a semi-cured state to form a polyurethane foam adhesive layer with surface adhesion, while retaining the release carrier as a temporary carrier.

[0039] S4: Apply one of the following materials—fabric, PU leather, microfiber leather, or genuine leather—to the side of the polyurethane foam adhesive layer away from the release carrier. Utilize the self-adhesion of the polyurethane foam adhesive layer in its semi-cured state to bond the polyurethane foam adhesive layer with one of the following materials—fabric, PU leather, microfiber leather, or genuine leather—to obtain the first composite.

[0040] S5: Peel and remove the release carrier from the first composite. After the polyurethane foam adhesive layer has completely cured, the composite roll material is obtained.

[0041] S6: Composite roll material is punched or molded to make insoles;

[0042] Among them, the polyurethane foam adhesive layer forms an intermediate adhesive layer during the foaming and curing process, which is bonded to one of the fabrics, PU leather, microfiber leather or genuine leather.

[0043] In S3, the release carrier is either single-sided silicone-coated release paper or PET release film, which are breathable release films. The time from when the polyurethane AB material in S3 is coated onto the surface of the release carrier to when it is bonded to one of the following in S4: fabric, PU leather, microfiber leather, or genuine leather. The foaming temperature in S3 is adjusted according to the coating speed. When the conveyor speed increases, the foaming temperature increases simultaneously to accelerate the foaming and curing speed of the breathable material. When the conveyor speed decreases, the foaming temperature decreases simultaneously to prevent the internal micropores of the breathable material from collapsing due to heat, ensuring the overall uniform breathability of the breathable material. The width of the composite roll in S5 is 1.35-1.80 meters.

[0044] The above technical solution involves first unwinding one of the following: single-sided silicone-coated release paper, PET release film, or a breathable release film, and then laying it on a conveyor line. Simultaneously, component A and component B are mixed in a specific ratio to form a polyurethane AB material. This mixed polyurethane AB material is then coated onto the surface of the release paper, followed by a foaming process. The foaming temperature is dynamically adjusted according to the coating speed. When the conveyor speed increases, the foaming temperature is increased to accelerate the foaming and curing process; when the conveyor speed decreases, the foaming temperature is decreased to prevent the internal micropores from collapsing due to heat. After foaming to a semi-cured state, a polyurethane foam with surface tack is formed. The polyurethane foam adhesive layer is formed by retaining the release paper as a temporary carrier. Three minutes after coating is completed, the first layer is attached to the side of the polyurethane foam adhesive layer away from the release carrier. The self-adhesion of the semi-cured layer allows it to bond with the fabric, forming the first composite. The release carrier is then peeled off and removed from the first composite. After the polyurethane foam adhesive layer is fully cured, a composite roll is obtained. Finally, the composite roll is die-cut or molded to make an insole. Throughout the process, the polyurethane foam adhesive layer forms an intermediate adhesive layer during the foaming and curing stage, bonding the fabric with PU leather or genuine leather.

[0045] Example 2

[0046] like Figure 1-2 As shown in the embodiment of the present invention, a polyurethane foam composite insole material is provided. The first layer is selected from any one of fabric, PU leather, microfiber leather, or genuine leather, specifically as follows: When the first layer is fabric, the fabric is selected from any one of knitted fabric, woven fabric, or non-woven fabric, preferably a polyester fiber knitted fabric with a weight of 80-200 g / m². The fabric is in direct contact with the human foot, providing good breathability, moisture absorption, and tactile comfort. Before use, the fabric can be corona-treated or plasma-treated to improve its surface polarity and enhance the interfacial bonding force between it and the subsequent polyurethane foam layer.

[0047] When PU leather is selected as the first layer, it consists of a base fabric layer and a polyurethane surface layer. The base fabric layer is a knitted or napped fabric, and the surface layer is a dry or wet polyurethane coating. The thickness of the PU leather is preferably 0.6-1.2mm. PU leather has a leather-like texture and good abrasion resistance and weather resistance, making it suitable for mid-to-high-end insole products. Before use, it is preferable to sand or solvent-wipe the back of the PU leather to remove any residue of release agent or surface treatment agent, thus improving bonding reliability.

[0048] When the first layer is made of microfiber leather, it consists of a microfiber nonwoven fabric substrate and a polyurethane impregnation coating, with a fiber fineness between 0.01 and 0.001 denier. Microfiber leather has a similar feel and appearance to genuine leather, while also possessing superior abrasion resistance, flexural strength, and colorfastness, making it suitable for high-end insoles and luxury footwear accessories. The preferred thickness of the microfiber leather is 0.8-1.5 mm. Because the microfiber leather substrate itself contains polyurethane components, it has good chemical affinity with the polyurethane foam adhesive layer of this invention. During the foaming reaction, the two can form an interface fusion, resulting in a bonding strength superior to other surface materials. Before lamination, the back of the microfiber leather is lightly sanded or roughened to expose the microfiber fibers and increase mechanical anchoring points.

[0049] When the first layer is made of genuine leather, selected from any one of top-grain cowhide, split cowhide, or sheepskin, the preferred thickness is 0.8-1.8mm. Genuine leather possesses natural breathability, moisture absorption and wicking properties, and an excellent feel, making it the preferred surface material for high-end insoles. Before use, genuine leather undergoes conventional retanning, fatliquoring, and dyeing processes. Before bonding, the flesh side of the leather is sanded and napped to remove residual grease and smooth collagen fibers, creating a slightly rough nap that increases the physical bonding area with the polyurethane foam adhesive layer. Simultaneously, the moisture content of the genuine leather should be controlled between 8% and 14%. Too low a moisture content will affect the degree of cross-linking in the foaming reaction, while too high a moisture content will lead to excessive carbon dioxide bubbles during foaming, affecting the interfacial bonding quality. Before bonding, a small amount of isocyanate-based primer can be applied to the flesh side of the genuine leather as needed to further enhance bonding durability.

[0050] Furthermore, the second layer is set as a polyurethane foam adhesive layer. The polyurethane foam adhesive layer is processed by coating polyurethane AB material onto the surface of the release paper, and after on-site foaming and gradient curing, the surface release paper is peeled off and directly formed, which can have self-adhesive properties without additional glue.

[0051] The second layer relies on its own inherent adhesiveness generated during the foaming and curing process to directly and synchronously bond with the first layer, achieving a glue-free, integrated molding of the double-layer structure. This eliminates the need for additional glue application and drying curing processes in traditional insole composite processes, simplifying the production process and avoiding defects such as odor, environmental non-compliance, and later delamination caused by external glue.

[0052] Example 3

[0053] Based on Example 2, this invention further defines the composition of the polyurethane AB material. The polyurethane AB material is prepared by uniformly mixing and reacting component A and component B in a specified ratio. Both components are measured by mass parts, and the specific raw material composition is as follows:

[0054] Component A uses a combination of polyether polyols as the remaining base material, with the following proportions of functional additives: foaming agent: 1-8 parts, catalyst 5: 0.1-0.8 parts, and foam stabilizer 6: 0.5-2 parts. The foaming agent is not used alone, but is a combination of one or more of free water, cyclopentane, n-pentane, and hydrofluorocarbons to adapt to the rapid foaming reaction characteristics of polyurethane raw materials on site. The compounded foaming system can precisely match the exothermic polymerization rate of polyurethane, control the foaming initiation speed and cell growth size, and promote the formation of a large number of uniform and interconnected open-cell microporous structures inside the intermediate polyurethane foam adhesive layer. From the microstructure level of the material, it gives the insole continuous and stable breathability, sweat wicking, and moisture-wicking properties, solving the problems of uneven cell size, excessive closed-cell rate, and poor breathability of insoles that are easily caused by single foaming agents.

[0055] Component B, by weight percentage of the composition, includes the remainder of liquefied modified diphenylmethane diisocyanate, 0.5-5 parts of small molecule glycol crosslinking agent, 1-3 parts of environmentally friendly plasticizer, and 0.2-1 parts of hydrolysis-resistant stabilizer. The environmentally friendly plasticizer is limited to at least one of the following categories: citrate ester, vegetable oil-based, or dibenzoate ester without phthalates. This can prevent the risks of VOC exceeding standards and environmental non-compliance caused by traditional phthalate plasticizers. The hydrolysis-resistant stabilizer can inhibit the breakage and degradation of polyurethane foam molecular chains in humid and sweat-eroded environments, effectively improving the structural integrity of the insole during long-term use and avoiding problems such as foam layer powdering, collapse, and delamination failure.

[0056] Example 4

[0057] A method for preparing a polyurethane foam composite insole material includes the following steps:

[0058] S1: Provide a release carrier, which is continuously unwound and laid flat on the conveyor line of the automated production line. In this step, the release carrier is selected from one of the following: single-sided silicone-coated release paper, PET release film, or a breathable release film. All three types of substrates have excellent surface release properties and structural support. On the one hand, the release carrier provides a flat and impermeable bearing surface for the liquid polyurethane AB material, effectively preventing the liquid raw material from penetrating or leaking during the coating process. On the other hand, before the polyurethane foam adhesive layer is fully set, the release carrier supports and sets the foam layer, preventing the foam layer from stretching and deforming or experiencing thickness deviations due to its own weight or conveyor line vibration, ensuring the uniformity of the foam layer's thickness and dimensional stability. At the same time, the release carrier can be cleanly peeled off in the subsequent peeling process without any polyurethane raw material residue, thus completely preserving the original adhesive interface after the foam adhesive layer is peeled off, ensuring the bonding strength when bonded to the first layer.

[0059] Preferably, a breathable release film can be used as the release carrier. Compared to ordinary release paper or PET release film, the breathable release film allows the gas and water vapor generated by the foaming reaction to escape through the film surface during the foaming and curing process, avoiding the accumulation of gas at the interface between the foam layer and the release carrier, which can form bubbles or bulges. This helps to form a uniform and interconnected open-cell structure on the bottom surface of the foam layer, further improving the overall breathability and wearing comfort of the finished insole.

[0060] S2: Weigh components A and B according to the predetermined mass ratio, and feed the weighed raw materials of both components into the mixing equipment for thorough mixing and homogenization to form a uniformly mixed polyurethane AB material with consistent reactivity. Thorough mixing ensures that the polymerization reaction of the two components proceeds simultaneously, avoiding localized under-foaming or over-foaming issues caused by imbalances in the raw material ratio. This ensures that the foaming ratio, cell structure, and interfacial adhesion remain consistent throughout the entire production line, improving the performance consistency of different batches of insoles.

[0061] S3: The mixed polyurethane AB material is evenly coated onto the surface of the release carrier. Then, the coated material is foamed. The foaming reaction process is precisely controlled to a semi-cured state to form a polyurethane foam adhesive layer with native adhesiveness on the surface. The release carrier is retained as a temporary carrier throughout this process and is not peeled off prematurely.

[0062] During the foaming process, a linkage control method between the production line speed and the foaming temperature is adopted to eliminate product quality defects caused by fluctuations in production speed: when the coating speed of the conveyor line increases, the foaming temperature is increased simultaneously to accelerate the foaming crosslinking reaction rate of the polyurethane system, match the high-speed production cycle, and ensure that the foaming reaction process remains unchanged; when the coating speed of the conveyor line decreases, the foaming temperature is decreased simultaneously to prevent the internal micropores of the polyurethane from being baked at high temperatures for a long time, resulting in pore wall collapse and closed-cell defects, stabilize the microporous structure of the intermediate layer, and ensure constant breathability of the insole.

[0063] S4: After the fabric, PU leather, microfiber leather or genuine leather is bonded to the side of the polyurethane foam adhesive layer away from the release carrier, wait for 3 minutes. This time is the optimal adhesive window period for the semi-curing of the polyurethane foam system. At this time, the cross-linking reaction of the foam layer has not been completely completed, and the original adhesive force of the interface reaches its peak. No additional glue or other adhesive additives are needed. The fabric and the polyurethane foam adhesive layer can be tightly bonded and composited by the adhesiveness of the foam layer itself. There are no voids or bubbles at the interface, and finally a first composite with a stable structure is obtained.

[0064] S5: Completely peel off and remove the temporary release carrier from the surface of the first composite, fully exposing the adhesive surface on the other side of the polyurethane foam adhesive layer, and cure it under the conditions of temperature 20-35℃ and relative humidity 40%-70%. After the polyurethane foam adhesive layer is completely cured, the composite roll material is obtained. In the composite roll material, the surface of the polyurethane foam adhesive layer exposed after peeling off the release carrier forms a self-skinning layer during the curing process. The self-skinning layer is directly used as the bottom surface of the insole.

[0065] The materials are then left to stand until the polyurethane foam adhesive layer completes all cross-linking reactions and reaches a fully cured state, resulting in a composite roll material with two layers integrated into one. During the preparation process, the width of the composite roll material is uniformly controlled at 1.35m-1.80m to match the processing specifications of commonly used shoe insole punching and molding equipment on the market, reducing waste of scrap materials, improving raw material utilization, and adapting to large-scale continuous production;

[0066] S6: The fully cross-linked and cured double-layer composite roll is conveyed to the subsequent forming station. According to the actual insole pattern requirements, either punching or molding is selected to shape and cut the composite roll, and finally a polyurethane foam composite insole with standard size, strong interlayer adhesion and complete cell structure is obtained.

[0067] In the entire preparation process described above, the polyurethane foam adhesive layer continuously provides adhesive force throughout its foaming and curing process, simultaneously serving as both a buffer foam layer and an intermediate adhesive layer, directly bonding to the first layer as a whole. This process eliminates the need for external adhesives at the source, avoiding defects such as odors, environmental non-compliance, and interlayer delamination under humid and hot conditions caused by glues. It also simplifies production processes and reduces energy consumption and overall production costs.

[0068] Example 5

[0069] Based on Example 3, the core structural parameters and process compatibility of the single-sided silicone-coated release paper and PET release film used in step S3 of Example 3 are compared in the table below:

[0070] Substrate type Release paper (glassine paper, white kraft paper, or CCK paper) Biaxially oriented polyester film (BOPET) substrate weight / thickness 60-160 g / m2 25-125μm Release coating Silicone release agent (solvent-based: 0.30-0.80 g / m², solvent-free: 0.80-1.30 g / m²) Silicone release agent (coating thickness 0.2-0.9μm) Peeling force 15-60 g / 25mm 5-20g / 25mm Heat shrinkage rate The applicable temperature is generally not more than 120°C. The heat shrinkage rate is ≤3.0% under 150°C × 30 min conditions, and ≤1.5% for high-quality products. Residual adhesion rate ≥90% ≥90% Width adaptation The material should be adapted to the width of the composite roll (1.35-1.80 meters) and not smaller than this size. The material should be adapted to the width of the composite roll (1.35-1.80 meters) and not smaller than this size. Surface flatness good Excellent

[0071] Regarding the impact of the aforementioned parameters on process implementation, the two types of carriers exhibit different emphases in the two core stages of coating support and peeling / removal. The type of substrate determines its physical stiffness and thermal dimensional stability. Release paper, due to its fiber substrate, has good tensile stiffness and is less prone to edge wrinkling during conventional width conveying. Although PET film is thinner, its biaxial stretching process gives it higher dimensional stability. Under heating conditions, its thermal shrinkage rate in both length and width directions is significantly lower than that of release paper. Therefore, within the dynamic adjustment range of foaming temperature (68 to 100°C), PET film can maintain more precise coating width consistency, avoiding edge polyurethane AB material accumulation or release layer curling due to shrinkage.

[0072] The peel force parameter directly affects the separation quality in the semi-cured state. The peel force of release paper is set at 15 to 60 g / 25 mm, which is higher than that of PET film (5 to 20 g / 25 mm). This difference stems from the difference in surface energy and silicone oil curing method between the two. Release paper requires a larger release force to overcome the physical anchoring effect due to the roughness of the original paper surface, while PET film has a dense and smooth surface, and a lower release force can achieve clean peeling. However, both require a residual adhesion rate of not less than 90% to ensure that the release performance does not degrade after multiple or long-term storage. This indicator is crucial for controlling the amount of silicone oil transferred to the surface of the polyurethane foam adhesive layer. If the residual adhesion rate is too low, it means that the silicone oil is not fully cured. During peeling, some silicone oil will migrate to the surface of the foam layer, reducing the adhesion strength between the polyurethane foam adhesive layer and the subsequent bottom layer PU leather or genuine leather. If the peel force is too high, the tearing stress may damage the open-cell microstructure in the semi-cured state, causing the cell walls near the surface to be torn and forming macroscopic defects, which in turn reduces the uniformity of air permeability.

[0073] In terms of surface smoothness, the smooth surface of the PET film gives the polyurethane AB material a more uniform initial coating thickness distribution, and the relative deviation of the coating thickness can be controlled within ±3%. However, the release paper has a coating thickness deviation of about ±5% to ±8% due to the slight fiber texture and thickness fluctuation of the base paper itself. But in the insole application scenario of the present invention, this deviation will not affect the cushioning and breathability of the final product.

[0074] In summary, when the foaming temperature is set low (below 85℃) and cost control is required, single-sided silicone-coated release paper has an economic advantage due to its lower raw material cost. When the foaming temperature is high (above 85℃) or the production line speed is high, resulting in increased heat radiation intensity, PET release film can ensure width stability and coating uniformity due to its better heat shrinkage resistance. Both carriers meet the process requirements of peeling and removing the release paper or release film from the first composite in step S5, and neither will cause substantial damage to the three-dimensional interconnected microporous structure inside the polyurethane foam adhesive layer.

[0075] Example 6

[0076] Based on Example 3, this invention sets the time from when the polyurethane AB material is coated onto the release paper surface to when it adheres to the fabric to be 3 minutes. To verify the necessity and rationality of this time parameter, comparative tests were conducted with different standing times under fixed formulation and fixed foaming temperature (85℃). The results are shown in the figure below:

[0077] 0.5 Highly fluid and sticky 15-20 The cells did not grow sufficiently, and a large amount of liquid resin continuous phase remained. 0.8 0.4 The fabric was soaked and penetrated by liquid resin, causing the surface to harden. 1.5 It has high viscosity and produces noticeable stringiness. 40-50 During cell growth, the pores are small and dense, and open pores have not yet formed. 1.6 0.7 The fabric adheres well, but a small amount of resin has seeped into the surface. 3.0 Moderate viscosity, does not string. 60-75 The bubbles have grown fully, and the open-cell structure has initially formed but not yet closed. 2.8 1.6 The fabric is firmly bonded and the surface is dry with no resin penetration. 4.5 The viscosity decreased, and it became slightly sticky. 80-90 The bubble walls have basically taken shape, and the pore opening is becoming stable. 2.1 1.5 The fit is acceptable, but the localized separation force is low. 6.0 Slightly sticky, almost surface dry ≥95 The bubbles are fully set, and a thin, cured skin forms on the surface. 1.2 1.1 The fabric can be bonded but the adhesion is insufficient. 8.0 Non-sticky, completely surface dry 100 The foam cells are fully cured, and the surface is smooth and non-sticky. 0.5 0.8 The fabric either cannot be glued or only has a weak adhesion.

[0078] The data above indicate that the settling time has a decisive impact on the surface condition and bonding quality of the polyurethane foam adhesive layer. When the settling time is only 0.5 minutes, the polyurethane AB material has just been coated, and the foaming reaction is still in its early stages. A large amount of unreacted liquid polyol and isocyanate components remain in the composite material, and the foaming completion rate is less than 20%. If the fabric is bonded at this time, the liquid resin will penetrate into the fiber gaps of the fabric through capillary action. After curing, the fabric is anchored and wrapped by the resin. Although the peel strength can reach a certain value, the fabric feels stiff and loses its softness. Simultaneously, the large amount of resin clogging the fabric pores leads to a severe decrease in air permeability (only 0.4 mL / cm²·s).

[0079] When the settling time is extended to 1.5 minutes, the foaming reaction has progressed to about halfway. Gas in the system begins to nucleate and grow, but the cell size is small and mainly closed-cell, and a through channel has not yet been formed. At this time, there is still a slight risk of resin penetration into the laminated fabric, and the air permeability is only 0.7. When the settling time reaches exactly 3 minutes, the foaming completion rate is about 60% to 75%, and the system is in a semi-cured critical state. That is, the foaming reaction has released enough gas to allow the cells to grow fully. The cell walls have been thinned to an appropriate degree under the action of the foam stabilizer and have begun to break down and connect to form a preliminary open-cell network. However, the cross-linking and curing reaction has not yet entered the rapid gelation stage. Therefore, the surface still maintains uniform wet tackiness and no longer runs or drips. At this time, the laminated fabric will not be contaminated by liquid resin penetration, and the fabric can be firmly bonded by the adhesive layer itself. The peel strength reaches a peak of 2.8 N / cm, and the air permeability recovers to 1.6.

[0080] Extend the settling time to 4.5 minutes. The foaming completion rate exceeds 80%. The cross-linking density of the cell walls increases, causing the surface tackiness to begin to decrease. Although it can still bond to the fabric, the peel strength has dropped to 2.1. At 6 minutes, the foaming is close to complete (≥95%). An extremely thin cured skin layer forms on the surface, resulting in a significant decrease in tackiness. The peel strength is only 1.2, and the air permeability is also reduced to 1.1 due to the partial closure of the open channels by the surface skin layer. By 8 minutes, the composite material is completely cured, the surface loses all tackiness, and the fabric can no longer bond with it.

[0081] Further analysis of the technological value of the 3-minute critical point reveals that this time point precisely corresponds to the inflection point of the reaction rate under the synergistic effect of the foaming agent, catalyst, and foam stabilizer in the formulation of this invention. At this time point, the gas escape rate generated by the foaming reaction and the viscosity increase rate brought about by the gelation reaction reach a dynamic balance, so that the cell wall has sufficient strength to support the open-cell structure without complete collapse, while retaining enough active isocyanate groups to wet the surface of the fabric fibers and form chemical bonds. This dual state of "both open-cell and adhesive" is a necessary condition for the foam adhesive layer to achieve interlayer bonding and breathability. In continuous industrial production, the 3-minute settling time also corresponds to the length of the conveyor line and the speed of the machine. With a conventional machine speed of 10 to 15 m / min, the coating section length corresponding to 3 minutes is 30 to 45 meters, which is sufficient to accommodate the foaming drying tunnel without causing excessive equipment footprint.

[0082] Example 7

[0083] Based on Example 3, the foaming temperature in S3 is adjusted according to the coating speed. The foaming and gelation reaction of polyurethane AB material follows the temperature dependence law described by the Arrhenius equation. The reaction rate constant increases exponentially with increasing temperature. The change in coating speed directly determines the residence time of polyurethane AB material coated on the release paper surface in the heating tunnel. The residence time T=L / V (L is the effective heating length of the tunnel, and V is the coating speed). Therefore, there is a definite and inseparable compensatory coupling relationship between speed and temperature.

[0084] When the conveyor speed increases, the heating time of polyurethane AB material in the drying tunnel is shortened. If the foaming temperature is not increased accordingly, the activation energy supply for the reaction will be insufficient, and the foaming and gelation processes will lag behind the pace of the production line. When the material reaches the subsequent fabric bonding station, the foaming completion rate will be low, and a large amount of unreacted liquid components will still exist in the system. At this time, the bonded fabric will suffer from resin penetration and contamination of the fabric fibers. At the same time, due to insufficient gas nucleation and cell growth, the cells are small, dense, and mostly closed-cell structures, unable to form through channels, resulting in severely degraded air permeability. Therefore, it is necessary to simultaneously increase the foaming temperature to compensate for the shortened reaction time by increasing the heat input, accelerating the collision frequency and reaction rate of isocyanate groups and polyol hydroxyl groups, and speeding up the vaporization of the foaming agent and the gas diffusion rate. This ensures that the foaming and curing process can still reach the semi-cured bonding window of 60% to 75% foaming completion within the shortened residence time.

[0085] Conversely, when the conveyor speed decreases, the residence time of polyurethane AB material in the drying tunnel increases. If the foaming temperature is not reduced accordingly, the foaming reaction will cross the semi-curing window and enter the highly cross-linked curing stage before reaching the bonding station. The surface will be completely dry and lose its adhesiveness, making it impossible for the fabric to be bonded. At the same time, the already formed open-cell micropore walls will undergo viscoelastic relaxation and secondary shrinkage due to prolonged exposure to high temperatures. The through channels will be fused and closed, and the open-cell structure will suffer irreversible damage, resulting in a significant decrease in air permeability. Therefore, it is necessary to reduce the foaming temperature simultaneously to slow down the reaction rate, reduce the intensity of thermal motion of molecular chain segments, and prevent the cell walls from collapsing under excessive heating conditions. This will ensure the integrity of the three-dimensional interconnected network structure inside the polyurethane foam adhesive layer and the uniformity of the overall air permeability.

[0086] This dynamic adjustment mechanism is not a simple empirical operation, but a necessary requirement based on the principles of reaction kinetics and the formation mechanism of cell structure. The matching relationship between the two can be quantitatively described by the Arrhenius equation—the acceleration factor of temperature change on the reaction rate and the change factor of residence time caused by speed change must satisfy a compensatory balance. That is, when the speed changes from v1 to v2, the temperature T should be adjusted accordingly according to the relationship ln(v2 / v1) to keep the reaction progress constant when reaching the bonding station. In specific implementation, a speed of 8 to 15 m / min combined with a synchronous temperature adjustment range of 68 to 95℃ constitutes the preferred process operation window. When the speed is 10 m / min, the foaming temperature is set at 80℃ as the benchmark. For every 1 m / min increase in speed, the temperature increases by about 2 to 3℃, and for every 1 m / min decrease in speed, the temperature decreases by about 2 to 3℃. This proportional relationship has been experimentally verified on a continuous production line with a drying tunnel length of 25 to 35 meters, which can stably control the foaming completion within the target range.

[0087] Beyond the aforementioned speed range, even with temperature compensation, it's impossible to simultaneously guarantee foaming quality and adhesive performance. Excessive speed leads to insufficient heat transfer due to short dwell time, and the rapid vaporization of the surface physical foaming agent at high temperatures forms a micro-cured skin layer that hinders internal heat transfer, resulting in uneven surface and internal reactions. Conversely, at excessively low speeds, even with temperature reduction, the long dwell time fails to completely suppress the slow thermal shrinkage of the cell walls, causing the open-cell ratio to continue to decrease. Therefore, those skilled in the art, based on the quantitative matching relationship and operating window between speed and temperature, can determine the appropriate foaming temperature for different speed conditions in specific production processes, thereby ensuring that polyurethane foam composite insole materials with uniform open-cell structure and stable breathability can be obtained at various production speeds.

[0088] Example 8

[0089] Based on Example 7, the present invention includes an air permeability test on insoles made from composite rolls through punching or molding, as shown in the figure below:

[0090] This polyurethane foam composite insole, thanks to its glue-free composite process, fully preserves the microporous structure of the foam, successfully achieving the special properties of being breathable and waterproof: it can quickly wick away sweat and moisture from the soles of the feet, solving the problem of stuffy and sweaty feet when wearing shoes, while also preventing external liquid water stains from penetrating to the bottom of the insole; compared to traditional insoles that use glue to seal the pores, its breathability and heat dissipation performance are greatly improved, while also having basic water-repellent capabilities, resulting in better dryness and comfort when worn, and meeting the actual needs of daily insole use.

[0091] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0092] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the spirit and scope of the technical solution of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A polyurethane foam composite insole material, characterized in that, include: The first layer is made of one of the following materials: fabric, PU leather, microfiber leather, or genuine leather. The second layer is a polyurethane foam adhesive layer. The polyurethane foam adhesive layer is formed by foaming and curing polyurethane AB material coated on a release carrier and then peeling off the release carrier. During the foaming and curing process, the second layer is bonded to the first layer by its own adhesiveness.

2. The polyurethane foam composite insole material according to claim 1, characterized in that, The polyurethane AB material comprises a mixture of component A and component B. Component A, by weight percentage of the composition, includes the remainder of a combined polyether polyol, 1-8 parts of a foaming agent, 0.1-0.8 parts of a catalyst, and 0.5-2 parts of a foam stabilizer.

3. The polyurethane foamed composite shoe mat material according to claim 2, wherein, Component B, by weight percentage of the composition, includes the remainder of liquefied modified diphenylmethane diisocyanate, 0.5-5 parts of small molecule glycol crosslinking agent, 1-3 parts of environmentally friendly plasticizer, and 0.2-1 parts of hydrolysis-resistant stabilizer.

4. The polyurethane foam composite insole material according to claim 2, characterized in that, The foaming agent includes one or more of free water, cyclopentane, n-pentane, and hydrofluorocarbons.

5. The polyurethane foam composite insole material according to claim 3, characterized in that, The environmentally friendly plasticizer includes at least one of citrate plasticizers, vegetable oil-based plasticizers, and dibenzoic acid ester plasticizers.

6. A method for preparing a polyurethane foam composite insole material according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Provide a release carrier, unwind the release carrier and lay it on the conveyor line; S2: Mix component A and component B in a certain proportion to form polyurethane AB material; S3: The polyurethane AB material is coated on the surface of the release carrier, and foamed to a semi-cured state to form a polyurethane foam adhesive layer with surface adhesion, while the release carrier is retained as a temporary carrier. S4: Apply one of the following materials—fabric, PU leather, microfiber leather, or genuine leather—to the side of the polyurethane foam adhesive layer away from the release carrier. Utilize the self-adhesion of the polyurethane foam adhesive layer in its semi-cured state to bond the polyurethane foam adhesive layer with one of the following materials—fabric, PU leather, microfiber leather, or genuine leather—to obtain a first composite. S5: Peel and remove the release carrier from the first composite. After the polyurethane foam adhesive layer has completely cured, a composite roll material is obtained. S6: The composite roll material is punched or molded to make insoles; The polyurethane foam adhesive layer forms an adhesive layer during the foaming and curing process, and is bonded to one of the fabric, PU leather, microfiber leather or genuine leather.

7. The method for preparing a polyurethane foam composite insole material according to claim 6, characterized in that, The release carrier in S3 is one of single-sided silicone-coated release paper, PET release film, or a breathable release film.

8. The method for preparing a polyurethane foam composite insole material according to claim 6, characterized in that, The time from when the polyurethane AB material is coated on the release carrier surface in S3 to when it is bonded to the fabric in S4 is 3 minutes.

9. The method for preparing a polyurethane foam composite insole material according to claim 6, characterized in that, The temperature of the foaming process in S3 is adjusted according to the speed of the coating vehicle; when the conveying speed is increased, the foaming temperature is increased simultaneously to accelerate the foaming and curing speed of the polyurethane AB material; when the conveying speed is decreased, the foaming temperature is decreased simultaneously to prevent the internal micropores of the polyurethane AB material from collapsing due to heat, and to ensure the overall uniform air permeability of the polyurethane AB material.

10. The method for preparing a polyurethane foam composite insole material according to claim 6, characterized in that, The width of the composite roll in S5 is 1.35-1.80 meters.

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