Production process of high-density elastic environment-friendly sponge

Abstract

The application relates to the technical field of sponge production, and discloses a production process of high-density elastic environment-friendly sponge. The application realizes gradient foaming under laminar flow control by designing pH-sensitive three-layer core-shell laccase microcapsules with a particle size of 3-4 microns and an enzyme activity of 180-220 U / g, combining a bio-based polyester matrix with a water and liquid CO2 composite foaming system; the process core comprises the following steps: enzyme triggering solidification, microcapsule rupture triggered by pressure relief at 55-65 DEG C, crosslinking completed by three-stage gradient heating at 75-85 DEG C; a double-gradient structure with a surface layer bubble hole density of 150-190 cells / cm3 and a core layer bubble hole density of 75-95 cells / cm3 is formed; finally, the density is 90-110 kg / m3, the compression permanent deformation is less than or equal to 5%, VOCs is less than or equal to 0.02 mu g / m3, and the biodegradation rate is greater than 90%; the process solves the problems of poor durability and insufficient environmental protection of traditional sponges.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sponge production, and particularly relates to a production process of high-density elastic environment-friendly sponge. BACKGROUND

[0002] With the continuous enhancement of environmental awareness and the popularization of green manufacturing concept, the application of bio-based polymer materials in the field of elastic sponge preparation has attracted widespread attention. Traditional elastic sponge is mainly prepared by isocyanate crosslinking of petroleum-based chemicals such as polyurethane, which has good mechanical properties and elastic recovery, and is widely used in furniture, automobiles and medical devices industries. In addition, in recent years, bio-based sponge material technology using enzyme catalysis crosslinking has also gradually developed, which realizes high selectivity crosslinking through enzyme catalysis reaction, and improves the biocompatibility and degradation performance of the material. At the same time, combined with high-pressure foaming technology and microcapsule enzyme triggering mechanism, the functional diversity and structure gradient design of the sponge are enhanced, which has become a research hotspot at present.

[0003] However, the existing technology still has many deficiencies. The preparation process of traditional polyurethane sponge relies on toxic isocyanate, has high volatile organic compound (VOCs) emission, serious environmental pollution problem, and poor biodegradability, which is difficult to meet the demand of green and sustainable development. Although enzyme catalysis crosslinking is environmentally friendly, the activity control and triggering mechanism of the enzyme in the existing scheme are not precise enough, resulting in uneven crosslinking, single bubble structure and difficult to balance strength and elasticity of mechanical properties. At the same time, the gas distribution and flow rate control technology in the high-pressure foaming process is not mature, and the bubble gradient structure is difficult to form stably, which affects the application performance of the product. More importantly, the existing process requires complex equipment and multiple process steps, which is high in cost and restricts the large-scale popularization and application. SUMMARY

[0004] The technical problem to be solved by the present application is the shortcomings in the prior art. Therefore, we propose a production process of high-density elastic environment-friendly sponge.

[0005] In order to achieve the above purpose, the following technical scheme is adopted in the present application: a production process of high-density elastic environment-friendly sponge, comprising the following steps:

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

[0007] S2. Main material blending: mix the remaining polyester matrix, foaming agent and foam stabilizer under inert atmosphere by high-speed stirring; 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 flow mode under 1.0-2.0 MPa pressure for preheating;

[0009] S4. Gradient curing: curing in three stages with temperature and pressure control, including:

[0010] S41. Pressure relief to 0.3-0.7 MPa, maintaining at 55-65℃ for 1-1.5 h to reduce pH to 4.5-5.0 to trigger microcapsule rupture;

[0011] S42. Gradient temperature rise at 75-85℃ for 1.5-2 h to activate laccase crosslinking;

[0012] S43. Curing at 45-55℃ for 20-24 h;

[0013] S5. Post-processing: water washing after demolding, and hot air setting at 55-65℃ for 2-4 h.

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

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

[0016] Preferably, the nanocellulose has a diameter of 15-25 nm and an aspect ratio ≥ 50, and the addition 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 Re of the laminar flow compounding is ≤ 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℃ for 0.5-1 h, then maintaining at 80-82℃ for 0.5-1 h, and finally maintaining at 83-85℃ for 0.5-1 h.

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

[0021] Preferably, it further includes adding pH adjuster ethyl lactate, and the addition amount is 0.5-1.5% of the mass of the polyester matrix, with a hydrolysis pH threshold of 4.5-5.0.

[0022] The application provides another technical scheme: a high-density elastic environment-friendly sponge, which has a gradient cell structure, the cell density of a surface layer is 150-190 cells / cm3, and the cell diameter is 160-200 mu m; the cell density of a core layer is 75-95 cells / cm3, and the cell diameter is 300-350 mu m; the compression permanent deformation is less than or equal to 5% when the density is 90-110 kg / m3, and the VOCs release amount is less than or equal to 0.02 mu g / m3.

[0023] The application has the following technical effects and advantages:

[0024] In the application, the technical bottleneck of a traditional sponge material is broken through, full-biological-based raw materials and enzyme-triggered cross-linking technology are used, toxic substances such as isocyanate are completely eliminated, the sponge can be completely degraded into harmless substances in a natural environment, the VOCs release tends to be zero, the white pollution problem is solved from the source, through microcapsule precise controlled release and gradient foaming process, the product maintains high resilience while improving the anti-collapse performance. BRIEF DESCRIPTION OF DRAWINGS

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

[0026] Figure 1 The application is a flowchart. DETAILED DESCRIPTION

[0027] It is easy to understand that, according to the technical scheme of the application, a person skilled in the art can propose a plurality of structure modes and implementation modes which can be replaced with each other without changing the essential spirit of the application. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical scheme of the application, and should not be regarded as the whole or as a limitation or restriction on the technical scheme of the application.

[0028] Example one:

[0029] Referring to Figure 1 The application provides a technical scheme: a production process of a high-density elastic environment-friendly sponge, which comprises 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-treatment step 5.

[0030] The pre-dispersion step 1 is used for preparing a homogeneous colloid containing pH-sensitive laccase microcapsules; the main material blending step 2 is used for preparing foaming main materials; the high-pressure composite foaming step 3 composites and injects the premixed colloid and the main materials into a mold in a laminar flow mode; the gradient curing step 4 realizes microcapsule triggering and cross-linking reaction by controlling temperature and pressure in stages; and the post-treatment step 5 completes demolding and shaping.

[0031] In the present embodiment, the process is suitable for industrial continuous production equipment, and can also be implemented in a batch reaction kettle. The following will be described in detail.

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

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

[0034] 1. Raw material preparation: lignin sulfonate grafted polycaprolactone with a grafting rate of 20±2% and a bio-based content of 75% is selected as the polyester matrix; the laccase microcapsules are of a core-shell structure, composed of a laccase solution core, a calcium alginate gel intermediate layer, and a polylysine membrane outer layer, with a particle size of 3.5 μm, an embedding rate of 97%, and an enzyme activity of 200 U / g; the nanocellulose has a diameter of 20 nm and an aspect ratio of ≥50;

[0035] 2. Low-temperature mixing: under constant temperature conditions at 30°C, 8% of the laccase microcapsules and 30% of the polyester matrix are added to a double-planetary mixer at a speed of 200 rpm for 10 minutes; at this time, the viscosity of the mixture is controlled within the range of 2500±200 cP, ensuring uniform dispersion of the microcapsules without rupture;

[0036] 3. Nanocellulose dispersion: after adding 5% of the nanocellulose based on the mass of the polyester matrix, a 40 kHz ultrasonic disperser is turned on for 15 minutes; the ultrasonic power is set to 300 W, and the material temperature is controlled below 35°C through a circulating water bath during the process; this process forms a three-dimensional network structure of nanocellulose in the polyester matrix, and scanning electron microscopy observation shows that the fibers are uniformly dispersed without aggregation.

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

[0038] 1. Inert gas establishment: the remaining 70% of the polyester matrix is added to a high-pressure stirred tank, and nitrogen gas with a purity of ≥99.99% is introduced to replace it three times, so that the oxygen content is reduced to below 50 ppm;

[0039] 2. Additive mixing: 1.2% of a siloxane foam stabilizer and 1.0% of an ethyl lactate pH adjuster based on the mass of the polyester matrix are sequentially added, and the siloxane foam stabilizer has an HLB value of 14, and is stirred at a speed of 1500 rpm for 5 minutes; at this time, the viscosity of the system is 1800±150 cP, and the surface tension is reduced to 28±2 mN / m;

[0040] 3. Foaming agent injection: while keeping stirring, first inject 4.5% of the mass of the polyester matrix of deionized water, 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 is complete, the system presents a milky white uniform emulsion state, and bubble size distribution detection shows that D50 is 15 ± 3 pm.

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

[0042] 1. Flow channel design: a 316L stainless steel static mixer with an inner diameter of 8 mm is used, the length to diameter ratio (L / D) of the flow channel is 120:1, and 60 groups of helical units are arranged in the mixer;

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

[0044] 3. Mold injection: the composite material is injected into an aluminum alloy mold preheated to 45°C, and the surface of the mold is treated with a Teflon coating; a pressure of 1.8 MPa is applied for 2 minutes, at which 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 curing step is precisely controlled in three stages:

[0046] 1. First stage microcapsule triggering: depressurize to 0.5 MPa at a rate of 0.1 MPa / min, and keep at 60°C for 1.2 hours; in this stage, the hydrolysis of ethyl lactate produces lactic acid, which reduces the pH of the system from the initial 6.2 to 4.8; through fluorescence labeling observation, when the pH is less than or equal to 5.0, the outer layer 12 of polylysine membrane protonates and dissolves, the calcium alginate gel layer 11 dissociates, and the laccase solution core 10 is released;

[0047] 2. Second stage enzyme activation crosslinking: a three-stage gradient temperature program is used: keep at 75°C for 0.5 hours: the laccase activity reaches 65% of the maximum value, which initiates the oxidative coupling of the phenolic hydroxyl groups of lignosulfonate; keep at 82°C for 1 hour: the enzyme activity is increased to 85%, and the crosslinking network construction of the polycaprolactone segment is completed; keep at 85°C for 0.5 hours: the residual monomers are further crosslinked, and the crosslinking degree reaches 92 ± 3%;

[0048] 3. Third stage maturation: cool down to 50°C and keep for 24 hours to make the cell wall fully crystallize; differential scanning calorimetry shows that the crystallinity at this time reaches 45 ± 2%, and the storage modulus E' is increased to 1.8 ± 0.2 MPa.

[0049] The post-processing step comprises:

[0050] 1. Demolding water washing: demolding after the mold is cooled to 30°C, ultrasonic cleaning in 40°C deionized water for 2 times, 10 minutes each time; VOCs residue detection after cleaning shows that the benzene series content is ≤0.005 μg / m³;

[0051] 2. Hot air setting: placed in a 60°C hot air circulating oven for 3 hours, the wind speed is controlled at 2.5±0.5 m / s; the dimensional stability of the product after setting reaches 99.3% (ASTM D3574 standard test).

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

[0053] 1. Raw material pretreatment: the lignin sulfonate grafted polycaprolactone is vacuum dried at 50°C for 4 hours to a water content of ≤0.1%; the laccase microcapsules are stored in a 4°C environment in the dark, and are balanced to room temperature before use;

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

[0055] 3. Main material preparation: the foaming main material is prepared according to Example 1, and 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 through a two-component metering pump at a mass ratio of 1:2, and the mold pressure curve shows that the bubble nucleation density reaches a maximum value when the pressure is kept at 1.8 MPa for 2 minutes;

[0057] 5. Gradient curing: real-time monitoring shows that the pH drops to 5.0 after 60 minutes to trigger the release of the microcapsules; the storage modulus G' of the 82°C stage increases from the initial 500 Pa to 8500 Pa; the volume shrinkage rate in the curing stage is stably at 2.1±0.3%;

[0058] 6. Post-processing and detection: the finished product is observed by laser confocal microscope, showing that the surface layer bubble 20 has a density of 172±8 cells / cm³ and a pore size of 182±15 μm; the core layer bubble 21 has a density of 92±6 cells / cm³ and a pore size of 318±22 μm; the compression permanent deformation test shows that the deformation amount after 50% compression is 4.2%, and the recovery rate after 72 hours is 98.5%.

[0059] In summary, the examples of the present application achieve:

[0060] pH-sensitive microcapsule design: realizes the precise release of laccase at pH=4.8±0.2, and the enzyme activity retention rate is ≥95%.

[0061] Laminar flow composite foaming: Flow conditions with Re≤500 enable the formation of a cell gradient, with a cell density ratio of 1.86:1 between the surface layer and the core layer;

[0062] Segmented curing control: Gradual temperature increase from 75 to 85℃ increases the crosslinking reaction rate constant k from 0.15 min⁻¹ to 0.38 min⁻¹;

[0063] The final product achieves a compression set of ≤4.5% at a density of 98 kg / m³, and its VOC emissions are only 1 / 100 of those of the traditional process.

[0064] Example 2:

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

[0066] The following will describe this embodiment in detail. The parts that are the same as in Embodiment 1 will not be repeated. The main adjustments in this embodiment are in two aspects: raw material specifications and process parameter control. Specific features include:

[0067] Polyester matrix adjustment: Lignosulfonate 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 1.6 dL / g to 1.4 dL / g.

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

[0069] Comparison of process parameters:

[0070] Process stage Example one parameter Example two parameter Adjustment reason Laminar flow compounding Re = 480 Re = 520 Pump speed control precision reduction Gradient solidification stage S42 75→82→85℃ precision gradient 80℃ constant temperature 2h Cancel segmented temperature rise to simplify equipment Curing time 24h 20h Production efficiency optimization

[0071] In practice:

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

[0073] Gradient curing steps adjusted:

[0074] Phase 1: Maintain 60°C for 1.2 hours, but the microcapsules are fully released only when the pH drops to 4.9, which is 0.1 pH unit later than in Example 1;

[0075] The second stage: the segmented heating was cancelled and replaced with a constant temperature of 80℃ for 2 hours, which resulted in the peak laccase activity reaching only 80% and the degree of cross-linking decreasing to 88±3%;

[0076] Third stage: the maturation time is shortened to 20 hours, and the crystallinity is reduced to 42±2%.

[0077] Performance test comparison under standard production batch:

[0078] Performance index Example one This example Difference rate Surface layer 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 release amount (μg / m³) 0.005 0.018 ↑260% Biodegradation rate (180 days) 93% 89% ↓4%

[0079] Performance degradation cause analysis:

[0080] Compression permanent deformation exceeds the standard: reduced crosslinking degree leads to increased molecular chain slip;

[0081] VOCs increase: shortened maturation time causes incomplete reaction of residual monomers;

[0082] Bubble uniformity decreases: Re exceeds the limit, causing turbulent flow, destroying laminar flow composite effect, and bubble density gradient ratio decreases to 1.6:1.

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

[0084] The technical scope of the present application is not limited to the content in the above description, and those skilled in the art can make various modifications and changes to the above embodiments without departing from the technical idea of the present application, and these modifications and changes should all belong to the protection scope of the present application.

Claims

1. A production process for a high-density, elastic, and environmentally friendly sponge, characterized in that, Includes the following steps: S1. Pre-dispersion: pH-sensitive laccase microcapsules, nanocellulose, and a portion of the polyester matrix are mixed at 30-40°C to form a homogeneous colloid; the pH-sensitive laccase microcapsules have a core-shell structure, comprising a laccase solution core, a calcium alginate gel intermediate layer, and a polylysine membrane outer layer; the microcapsules have a particle size of 3-4 μm, an encapsulation efficiency of ≥95%, and an enzyme activity of 180-220 U / g; the polyester matrix is ​​lignin sulfonate grafted with polycaprolactone. S2. Main material blending: The remaining polyester matrix, foaming agent and foam stabilizer are mixed at high speed under an inert atmosphere. 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 flow manner and preheated under a pressure of 1.0-2.0MPa; S4. Gradient Curing: Curing is carried out in three stages with controlled temperature and pressure, including: S41. Depressurize to 0.3-0.7 MPa and maintain at 55-65℃ for 1-1.5 h to allow the pH to drop to 4.5-5.0, triggering microcapsule rupture; S42. Activate laccase cross-linking by gradually increasing the temperature at 75-85℃ for 1.5-2 hours; S43. Grind at 45-55℃ for 20-24 hours; S5. Post-treatment: After demolding, wash with water and set with hot air at 55-65℃ for 2-4 hours.

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

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

4. 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.

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

2.

6. 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℃ for 0.5-1h, then maintaining the temperature at 80-82℃ for 0.5-1h, and finally maintaining the temperature at 83-85℃ for 0.5-1h.

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

8. The production process of a high-density elastic environmentally friendly sponge according to claim 1, characterized in that: It also includes the addition of ethyl lactate, a pH adjuster, at an amount of 0.5-1.5% of the polyester matrix mass, with a hydrolysis pH threshold of 4.5-5.

0.

9. A high-density elastic environmentally friendly sponge, produced by the manufacturing process described in any one of claims 1-8, characterized in that: It has a gradient pore structure, with a surface pore density of 150-190 cells / cm³ and a pore size of 160-200μm; a core pore density of 75-95 cells / cm³ and a pore size of 300-350μm; and a compression set of ≤5% and VOCs emission of ≤0.02μg / m³ when the density is 90-110kg / m³.

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