Production process of high-density elastic environment-friendly sponge

Abstract

The invention relates to the technical field of sponge production, and discloses a production process of high-density elastic environment-friendly sponge. The pH-sensitive three-layer core-shell laccase microcapsule is designed, the particle size is 3-4 microns, the enzyme activity is 180-220 U / g, and gradient foaming is achieved under laminar flow control by combining a bio-based polyester matrix, water and a liquid-state COC composite foaming system; the core of the process comprises the following steps: enzyme-triggered curing, pressure relief at 55-65 DEG C to trigger microcapsule breakage, and three-section gradient heating at 75-85 DEG C to complete crosslinking; the surface layer cell density of the double-gradient structure is 150-190 cells / cm, and the core layer of the double-gradient structure is 75-95 cells / cm; finally, when the density is 90-110 kg / m, the compression set is smaller than or equal to 5%, VOCs is smaller than or equal to 0.02 mu g / m, the biodegradation rate is larger than 90%, and the process solves the problems that traditional sponge is poor in durability and insufficient in environmental protection property.

Description

Technical Field

[0001] The present invention relates to the technical field of sponge production, in particular to a production process of a high-density elastic environmentally friendly sponge. Background Art

[0002] With the increasing awareness of environmental protection and the popularization of green manufacturing concepts, the application of bio-based polymer materials in the preparation of elastic sponges has received widespread attention. Traditional elastic sponges mainly rely on petroleum-based chemicals such as polyurethane to be prepared through isocyanate cross-linking. They have good mechanical properties and elastic recovery and are widely used in industries such as furniture, automobiles, and medical equipment. In addition, in recent years, the technology of bio-based sponge materials using enzyme-catalyzed cross-linking has gradually developed. Through enzymatic reactions, highly selective cross-linking is achieved, improving the biocompatibility and degradation performance of the material. At the same time, combining high-pressure foaming technology with microencapsulated enzyme triggering mechanism to enhance the functional diversity and structural gradient design of sponges has become a current research hotspot.

[0003] However, the existing technology still has many shortcomings. The traditional polyurethane sponge preparation process relies on toxic isocyanates, resulting in high emissions of volatile organic compounds (VOCs), serious environmental pollution problems, and poor biodegradability, making it difficult to meet the needs of green and sustainable development. Although enzyme-catalyzed cross-linking is environmentally friendly, the enzyme activity control and triggering mechanism in the existing scheme are not precise enough, resulting in uneven cross-linking, a single pore structure, and mechanical properties that are difficult to balance strength and elasticity. At the same time, the gas distribution and flow rate control technology in the high-pressure foaming process is not yet mature, and the pore gradient structure is difficult to form stably, affecting the application performance of the product. More importantly, the existing processes often require complex equipment and multiple process steps, which are costly and restrict large-scale promotion and application. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: the shortcomings of the existing technology. For this purpose, we propose a production process for high-density elastic environmentally friendly sponge.

[0005] In order to achieve the above objectives, the present application adopts the following technical solution: a production process of a high-density elastic environmentally friendly sponge, comprising the following steps:

[0006] S1. Pre-dispersion: Mix pH-sensitive laccase microcapsules, nanocellulose, and a portion of the polyester matrix at 30-40°C to form a homogeneous colloid;

[0007] S2 main ingredient blending: the remaining polyester matrix, foaming agent, foam stabilizer in an inert atmosphere, high-speed stirring mixed, the foaming agent is a composite foaming agent of water and liquid CO2;

[0008] S3 high-pressure composite foaming: The premixed colloid in S1 and the main material in S2 are injected into the mold in a laminar composite manner and preheated at a pressure of 1.0-2.0MPa;

[0009] S4. Gradient curing: Curing is performed in three stages with controlled temperature and pressure, including:

[0010] S41. Release the pressure to 0.3-0.7 MPa and maintain at 55-65°C for 1-1.5 hours to reduce the pH to 4.5-5.0, triggering microcapsule rupture.

[0011] S42. Activate laccase crosslinking by increasing the temperature gradually from 75 to 85°C for 1.5 to 2 h;

[0012] S43. Mature at 45-55°C for 20-24 hours;

[0013] S5. Post-processing: After demoulding, wash with water and set with hot air at 55-65℃ for 2-4h.

[0014] Preferably, the pH-sensitive laccase microcapsules in step S1 are of a core-shell structure, comprising a laccase solution core, a calcium alginate gel middle layer and a polylysine membrane outer layer. The particle size of the microcapsules is 3-4 μm, the embedding efficiency is ≥95%, and the enzyme activity is 180-220 U / g.

[0015] Preferably, the polyester matrix is ​​lignin sulfonate grafted polycaprolactone, with a grafting rate of 15-25% and a bio-based content of ≥70%.

[0016] Preferably, the diameter of the nanocellulose is 15-25 nm, the aspect ratio is ≥50, and the added amount is 3-7% of the mass of the polyester matrix.

[0017] Preferably, the mass ratio of water to polyester matrix in the foaming agent is 4-6:100, and the injection pressure of liquid CO2 is 0.8-1.2 MPa.

[0018] Preferably, the Reynolds number of the laminar compound is Re≤500, and the flow rate ratio of the premixed colloid to the main material is 1:1.8-2.2.

[0019] Preferably, the gradient curing step S42 includes first maintaining at 75-78° C. for 0.5-1 h, then maintaining at 80-82° C. for 0.5-1 h, and finally maintaining at 83-85° C. for 0.5-1 h.

[0020] Preferably, the foam stabilizer is a silicone compound with an HLB value of 13-15, and the added amount is 1-1.5% of the mass of the polyester matrix.

[0021] Preferably, the method further comprises adding ethyl lactate as a pH regulator, with the addition amount being 0.5-1.5% of the mass of the polyester matrix, and the hydrolysis pH threshold being 4.5-5.0.

[0022] The present invention proposes another technical solution: a high-density elastic environmentally friendly sponge: with a gradient pore structure, the surface pore density is 150-190 cells / cm³, and the pore diameter is 160-200μm; the core layer pore density is 75-95 cells / cm³, and the pore diameter is 300-350μm; when the density is 90-110kg / m³, the compression permanent deformation is ≤5%, and the VOCs release is ≤0.02μg / m³.

[0023] The technical effects and advantages of the present invention are as follows:

[0024] In the present invention, the technical bottleneck of traditional sponge materials is broken through. By adopting all-biobased raw materials and enzyme-triggered cross-linking technology, toxic substances such as isocyanate are completely eliminated, so that the sponge can be completely degraded into harmless substances in the natural environment. VOCs release is close to zero, solving the white pollution problem from the source. Through the precise controlled release of microcapsules and gradient foaming process, the product improves the anti-collapse performance while maintaining a high rebound rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The disclosure of the present invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. In the drawings, the same reference numerals are used to refer to the same components:

[0026] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0027] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solution of the present invention and should not be regarded as the entire invention or as a limitation or restriction of the technical solution of the present invention.

[0028] Example 1:

[0029] Reference Figure 1 As shown, the present invention provides a technical solution: a production process for a high-density elastic environmentally friendly sponge, comprising a pre-dispersion step 1, a main material blending step 2, a high-pressure composite foaming step 3, a gradient curing step 4 and a post-processing step 5.

[0030] Among them, the pre-dispersion step 1 is used to prepare a homogeneous colloid containing pH-sensitive laccase microcapsules; the main material blending step 2 is used to prepare the foaming main material; the high-pressure composite foaming step 3 is to inject the premixed colloid and the main material into the mold in a laminar flow manner; the gradient curing step 4 realizes the microcapsule triggering and cross-linking reaction by controlling temperature and pressure in stages; and the post-processing step 5 completes demoulding and shaping.

[0031] In this embodiment, the process is suitable for industrial continuous production equipment and can also be implemented in a batch reactor. Each step is described in detail below.

[0032] The pre-dispersion step is specifically used to prepare a homogeneous colloidal system containing laccase microcapsules and nanocellulose.

[0033] In a specific implementation, this step includes the following operations:

[0034] 1. Raw material preparation: Lignin sulfonate grafted polycaprolactone was selected as the polyester matrix, with a grafting rate of 20±2% and a biobased content of 75%. The laccase microcapsules had a core-shell structure, consisting of a laccase solution core 10, a calcium alginate gel middle layer 11, and a polylysine membrane outer layer 12. The microcapsules had a particle size of 3.5 μm, an encapsulation efficiency of 97%, and an enzyme activity of 200 U / g. The nanocellulose had a diameter of 20 nm and an aspect ratio of ≥50.

[0035] 2. Low-temperature mixing: Add 8% laccase microcapsules (based on the weight of the polyester matrix) and 30% polyester matrix into a double planetary mixer at a constant temperature of 30°C and mix at 200 rpm for 10 minutes. The viscosity of the mixture is controlled within the range of 2500 ± 200 cP to ensure that the microcapsules are evenly dispersed without breaking.

[0036] 3. Nanocellulose dispersion: After adding 5% nanocellulose by weight to the polyester matrix, a 40kHz ultrasonic disperser was used for 15 minutes. The ultrasonic power was set to 300W, and the material temperature was controlled below 35°C using a circulating water bath. This process allowed the nanocellulose to form a three-dimensional network structure in the polyester matrix. Scanning electron microscopy showed that the fibers were evenly dispersed without agglomeration.

[0037] The main material blending step is used to prepare the foaming main material system, which specifically includes:

[0038] 1. Establish inert atmosphere: Add the remaining 70% of the polyester matrix into the high-pressure stirred autoclave, introduce nitrogen with a purity of ≥99.99% and replace it three times to reduce the oxygen content to below 50ppm;

[0039] 2. Additive mixing: Add 1.2% of the polyester matrix weight of a silicone foam stabilizer and 1.0% of an ethyl lactate pH regulator. The silicone foam stabilizer has an HLB value of 14 and stir at 1500 rpm for 5 minutes. At this point, the system viscosity is 1800 ± 150 cP and the surface tension is reduced to 28 ± 2 mN / m.

[0040] 3. Foaming agent injection: While maintaining stirring, first inject deionized water (4.5% of the polyester matrix mass), and then inject liquid CO2 at a pressure of 0.8 MPa; the CO2 injection rate is 0.5 L / min, which is precisely controlled by a mass flow meter; after mixing, the system presents a milky white uniform emulsion state, and the bubble size distribution test shows that D50 is 15±3 μm.

[0041] The high-pressure composite foaming step realizes the laminar composite of the premixed colloid and the main material. The specific process is as follows:

[0042] 1. Flow channel design: A 316L stainless steel static mixer with an inner diameter of 8mm is used, with a flow channel length to diameter ratio (L / D) of 120:1 and 60 sets of staggered spiral units;

[0043] 2. Laminar flow control: The premixed colloid is pumped into the mixer inlet at a flow rate of 0.5 m / s and the main material is pumped into the mixer inlet at a flow rate of 1.0 m / s. The Reynolds number is calculated to be 480, and the calculation formula is: , where ρ = 1.05 g / cm³, v = 0.75 m / s, D = 8 mm, μ = 1.8 Pa·s, satisfying laminar flow conditions;

[0044] 3. Mold injection: The composite material is injected into an aluminum alloy mold preheated to 45°C. The mold surface is treated with Teflon coating. A pressure of 1.8 MPa is applied and maintained for 2 minutes. At this time, the apparent density of the system decreases from 1.12 g / cm³ to 0.45 g / cm³, and the expansion ratio is 2.5:1.

[0045] The gradient solidification step is precisely controlled in three stages:

[0046] 1. First stage: Microcapsule triggering: The pressure was released at a rate of 0.1 MPa / min to 0.5 MPa and maintained at 60°C for 1.2 hours. During this stage, ethyl lactate was hydrolyzed to produce lactic acid, causing the system pH to drop from an initial pH of 6.2 to 4.8. Fluorescence labeling revealed that when the pH was ≤ 5.0, the outer layer 12 of the polylysine membrane was protonated and dissolved, and the calcium alginate gel layer 11 dissociated, releasing the laccase solution core 10.

[0047] 2. The second stage of enzyme-activated cross-linking: a three-stage gradient temperature program was used: 75°C for 0.5 hours: the laccase activity reached 65% of the maximum value, initiating the oxidative coupling of the phenolic hydroxyl groups of lignin sulfonate; 82°C for 1 hour: the enzyme activity increased to 85%, completing the construction of the cross-linked network of polycaprolactone segments; 85°C for 0.5 hours: the residual monomers were further cross-linked, and the cross-linking degree reached 92±3%;

[0048] 3. The third stage of aging: cooling to 50 ° C and maintaining for 24 hours to allow the cell walls to fully crystallize; differential scanning calorimetry shows that the crystallinity reaches 45 ± 2% at this time, and the storage modulus E' increases to 1.8 ± 0.2 MPa.

[0049] Post-processing steps include:

[0050] 1. Demolding and water washing: After the mold cools to 30°C, demold it and ultrasonically clean it twice in deionized water at 40°C, each time for 10 minutes. After cleaning, the VOCs residual test shows that the benzene content is ≤0.005μg / m³;

[0051] 2. Hot air setting: Place in a hot air circulation oven at 60℃ for 3 hours with the wind speed controlled at 2.5±0.5m / s; after setting, the product dimensional stability reaches 99.3% (ASTMD3574 standard test).

[0052] The following is an example of a standard production batch to illustrate the complete process flow:

[0053] 1. Raw material pretreatment: vacuum dry the lignin sulfonate grafted polycaprolactone at 50°C for 4 hours until the moisture content is ≤0.1%. Store the laccase microcapsules in a dark place at 4°C and equilibrate to room temperature before use.

[0054] 2. Pre-dispersion stage: a homogeneous colloid containing microcapsules was prepared according to the method of Example 1. Sampling and testing showed that the particle size distribution index PDI = 0.21, meeting the uniformity requirement;

[0055] 3. Preparation of main ingredients: Prepare the main ingredients for foaming according to Example 1. The bubble stability test shows that the volume change is ≤3% within 30 minutes.

[0056] 4. Composite foaming: The premixed colloid and the main material are injected into the mold at a mass ratio of 1:2 through a two-component metering pump. The mold pressure curve shows that the cell nucleation density reaches the maximum value when the pressure is maintained at 1.8 MPa for 2 minutes;

[0057] 5. Gradient curing: Real-time monitoring showed that the pH dropped to 5.0 after 60 minutes, triggering the release of microcapsules; the storage modulus G' increased from the initial 500Pa to 8500Pa at 82°C; and the volume shrinkage rate during the curing stage was stable at 2.1±0.3%;

[0058] 6. Post-processing and testing: Laser confocal microscopy observation of the finished product showed that the surface cell density (20) was 172±8 cells / cm³, and the pore diameter was 182±15μm. The core cell density (21) was 92±6 cells / cm³, and the pore diameter was 318±22μm. Compression set testing showed that the deformation after 50% compression was 4.2%, and the 72-hour recovery rate reached 98.5%.

[0059] In summary, the embodiments of the present invention are as follows:

[0060] pH-sensitive microcapsule design: achieves precise release of laccase at pH = 4.8 ± 0.2, with enzyme activity retention rate ≥ 95%;

[0061] Laminar composite foaming: The flow condition of Re≤500 forms a cell gradient, and the cell density ratio of the surface layer to the core layer reaches 1.86:1;

[0062] Staged curing control: 75→85℃ gradient temperature increase to increase the crosslinking reaction rate constant k from 0.15min-1 to 0.38min-1;

[0063] The final product achieves a compression permanent deformation of ≤4.5% at a density of 98kg / m³, and the VOCs emission is only 1 / 100 of that of traditional processes.

[0064] Example 2:

[0065] This embodiment provides another specific implementation of the production process of a high-density elastic environmentally friendly sponge of the present invention.

[0066] This embodiment will be described in detail below. The parts that are the same as those in the first embodiment will not be repeated. The main adjustments of this embodiment are reflected in the two aspects of raw material specifications and process parameter control. Specific features include:

[0067] Polyester matrix adjustment: lignin sulfonate grafted polycaprolactone is still used, but the grafting rate is reduced to 18±0.5%, the bio-based content is 72%, and the intrinsic viscosity is reduced from 1.6dL / g to 1.4dL / g.

[0068] Laccase microcapsule performance: enzyme activity was 185U / g, the embedding efficiency was reduced to 95%, and the microcapsule release kinetics test showed that at pH = 4.8, the release rate was 90±3% within 30 minutes.

[0069] Comparison of process parameters:

[0070] Process stage Example 1 Parameters Example 2 Parameters Reason for adjustment Laminar composite Re=480 Re=520 Reduced pump speed control accuracy Gradient solidification stage S42 75→82→85℃ precise gradient 80℃ constant temperature for 2h Cancel the staged heating and simplify the equipment Curing time 24h 20h Production efficiency optimization

[0071] When implementing:

[0072] The pre-dispersion step was adjusted as follows: the nanocellulose addition amount was 4.5%, the ultrasonic power was adjusted to 280 W, and the dispersion time was 12 minutes. After dispersion, the colloidal viscosity increased to 2700 ± 300 cP. Electron microscopy showed that the fiber dispersion uniformity decreased and the number of agglomerated particles increased.

[0073] Gradient curing step adjustment:

[0074] The first stage: the temperature was still maintained at 60°C for 1.2 hours, but the microcapsules were not fully released until the pH dropped to 4.9, which was 0.1 pH unit later than that in Example 1.

[0075] The second stage: the temperature was kept constant at 80°C for 2 hours instead of the stepwise heating, which resulted in the laccase activity peak reaching only 80% and the cross-linking degree dropping to 88±3%;

[0076] The third stage: the aging time is shortened to 20 hours and the crystallinity is reduced to 42±2%.

[0077] Performance test comparison under standard production batches:

[0078] Performance indicators Example 1 This embodiment Difference rate Surface cell density (cells / cm³) 172±8 165±10 ↓4% Core layer pore size (μm) 318±22 335±25 ↑5% Compression set (50%) 4.2% 5.7% ↑36% VOCs emission (μg / m³) 0.005 0.018 ↑260% Biodegradation rate (180 days) 93% 89% ↓4%

[0079] Analysis of causes of performance degradation:

[0080] Compression set exceeds the standard: the cross-linking degree decreases, resulting in increased molecular chain slippage;

[0081] Increased VOCs: The shortened aging time causes incomplete reaction of residual monomers;

[0082] The cell uniformity decreases: Re exceeding the limit triggers turbulence, destroying the laminar composite effect, and the cell density gradient ratio drops to 1.6:1.

[0083] This embodiment reduces the production cost by 8% by lowering the raw material specifications and relaxing the process control, but the key performance of the product fails to fully meet the requirements, which proves the irreplaceability of the patented parameters of Example 1.

[0084] The technical scope of the present invention is not limited to the contents of the above description. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of ​​the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A production process for high-density elastic environmentally friendly sponge, characterized in that: The following steps are involved: S1. Pre-dispersion: Mix pH-sensitive laccase microcapsules, nanocellulose, and a portion of the polyester matrix at 30-40°C to form a homogeneous colloid; S2 main ingredient blending: the remaining polyester matrix, foaming agent, foam stabilizer under an inert atmosphere, high-speed stirring mixed, the foaming agent is a composite foaming agent of water and liquid CO2; S3 high-pressure composite foaming: The premixed colloid in S1 and the main material in S2 are injected into the mold in a laminar composite manner and preheated at a pressure of 1.0-2.0MPa; S4. Gradient curing: Curing is performed in three stages with controlled temperature and pressure, including: S41. Release the pressure to 0.3-0.7 MPa and maintain at 55-65°C for 1-1.5 hours to reduce the pH to 4.5-5.0, triggering microcapsule rupture. S42. Activate laccase crosslinking by increasing the temperature gradually from 75 to 85°C for 1.5 to 2 h; S43. Mature at 45-55°C for 20-24 hours; S5. Post-processing: After demoulding, wash with water and set with hot air at 55-65℃ for 2-4h.

2. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: The pH-sensitive laccase microcapsules in step S1 are of a core-shell structure, comprising a laccase solution core, a calcium alginate gel middle layer, and a polylysine membrane outer layer. The particle size of the microcapsules is 3-4 μm, the embedding rate is ≥95%, and the enzyme activity is 180-220 U / g.

3. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: The polyester matrix is ​​lignin sulfonate grafted polycaprolactone, with a grafting rate of 15-25% and a bio-based content of ≥70%.

4. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: The diameter of the nanocellulose is 15-25 nm, the aspect ratio is ≥50, and the added amount is 3-7% of the mass of the polyester matrix.

5. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: The mass ratio of water to polyester matrix in the foaming agent is 4-6:100, and the injection pressure of liquid CO2 is 0.8-1.2 MPa.

6. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: The Reynolds number of the laminar compounding is Re≤500, and the flow rate ratio of the premixed colloid to the main material is 1:1.8-2.

2.

7. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: The gradient curing step S42 includes first maintaining the temperature at 75-78° C. for 0.5-1 hour, then maintaining the temperature at 80-82° C. for 0.5-1 hour, and finally maintaining the temperature at 83-85° C. for 0.5-1 hour.

8. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: The foam stabilizer is a silicone compound with an HLB value of 13-15, and the added amount is 1-1.5% of the mass of the polyester matrix.

9. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: The method also includes adding ethyl lactate as a pH regulator, with the added amount being 0.5-1.5% of the mass of the polyester matrix and the hydrolysis pH threshold being 4.5-5.

0.

10. A high-density elastic environmentally friendly sponge, produced by the production process according to any one of claims 1 to 9, characterized in that: It has a gradient pore structure, with a surface pore density of 150-190 cells / cm³ and a pore diameter of 160-200μm; a core pore density of 75-95 cells / cm³ and a pore diameter of 300-350μm; when the density is 90-110kg / m³, the compression permanent deformation is ≤5%, and the VOCs release is ≤0.02μg / m³.

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