Anti-crack and anti-seepage polymer-based light aggregate thermal insulation material and mixed extrusion equipment thereof

Abstract

The application discloses an anti-crack and anti-seepage polymer-based light aggregate thermal insulation material and a mixed extrusion equipment thereof, and belongs to the technical field of building thermal insulation materials. The thermal insulation material is prepared from an initial mixture of light aggregate particles, a polymer emulsion, a fiber reinforced component, a coupling agent and a crosslinking agent through a three-step method: first, the light aggregate particles are immersed in an alcohol solution of the coupling agent under vacuum conditions, and are stirred at a temperature of 40-60 DEG C to obtain surface-modified light aggregate particles; then, the surface-modified light aggregate particles, the polymer emulsion, the fiber reinforced component and the crosslinking agent are mixed under the condition that the shearing rate is not lower than 1000 s ‑1 -1, to form a non-Newtonian fluid state mixed slurry; finally, the mixed slurry is injected into a closed mold, a back pressure of 0.2-0.5 MPa is applied, and the temperature is increased to 70-90 DEG C at a rate of 1-3 DEG C / min for 2-4 h of insulation curing. The thermal insulation material prepared by the application has the characteristics of high interfacial bonding strength between the light aggregate and the matrix, uniform fiber dispersion, excellent anti-crack and anti-seepage performance and the like.

Description

Technical Field

[0001] This invention relates to the field of building insulation materials technology, specifically to a crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material and its mixing and extrusion equipment. Background Technology

[0002] With increasingly stringent requirements for building energy conservation, lightweight aggregate insulation materials have been widely used in roof insulation, interior wall insulation, and floor sound insulation projects due to their advantages such as low density, low thermal conductivity, and ease of construction. Common lightweight aggregates include shale ceramsite, fly ash ceramsite, expanded perlite, and vitrified microspheres. These materials themselves have a porous structure, which effectively reduces their thermal conductivity. However, traditional lightweight aggregate insulation materials have revealed many problems in practical applications.

[0003] The interfacial bond strength between lightweight aggregate particles and inorganic cementitious materials (such as cement) or organic binders is relatively weak. A thin powdery layer or closed glaze layer typically exists on the surface of lightweight aggregates, making it difficult for the binder to penetrate into the surface micropores, easily forming weak areas at the interface. When the material is subjected to temperature changes, wet-dry cycles, or mechanical loads, microcracks easily form at the interface. These cracks gradually expand and interconnect, eventually leading to overall material cracking or even spalling. This cracking not only affects the integrity of the insulation material but also significantly reduces its insulation performance, as the cracks become thermal bridges and air penetration channels. Existing lightweight aggregate insulation materials generally have insufficient waterproofing and seepage prevention performance. Lightweight aggregates themselves have a high open porosity, easily absorbing moisture. Once moisture penetrates the material, on the one hand, the high thermal conductivity of water severely weakens the insulation effect; on the other hand, in low-temperature environments, the freezing of water generates frost heave stress, accelerating material damage. Even with polymer modification, conventional blending processes often fail to ensure that the polymer uniformly coats each lightweight aggregate particle, frequently resulting in localized agglomeration or discontinuous polymer films, leading to unsatisfactory waterproofing performance.

[0004] In traditional manufacturing processes, the mixing of lightweight aggregate particles, polymer emulsions, and fibers typically employs ordinary stirring, resulting in low mixing efficiency and uneven distribution of components. The density of lightweight aggregates is much lower than that of polymer slurries, making them prone to floating and causing material stratification. This leads to significant differences in the density and mechanical properties of the final product along its thickness. To mitigate stratification, some processes employ vibration compaction or pressure molding, but this often results in the crushing of lightweight aggregate particles, destroying their porous structure and consequently reducing their thermal insulation performance. Furthermore, fiber dispersibility remains a challenge in existing fiber-reinforced lightweight aggregate insulation materials. Short-cut fibers tend to entangle and clump during mixing, failing to distribute evenly within the matrix and significantly reducing their reinforcing effect. Even with the addition of dispersants or the use of specific feeding sequences, fiber agglomeration remains difficult to completely resolve. Simultaneously, the cross-linking and curing process of the polymer matrix often occurs under normal pressure, preventing the effective expulsion of residual air bubbles within the material, creating pore defects that act as both stress concentration points and water seepage channels.

[0005] To address the aforementioned issues, some studies have attempted surface pretreatment of lightweight aggregates, but these often involve immersion or spraying, resulting in weak chemical bonding between the treated layer and the matrix, leading to limited effectiveness. Other studies have attempted to improve crack resistance by changing the polymer type or adding toughening agents, but these approaches often compromise other aspects, failing to simultaneously meet the requirements of crack resistance, seepage prevention, thermal insulation, and process feasibility. Therefore, developing a thermal insulation material that achieves a strong bond between lightweight aggregates and the matrix, uniform fiber dispersion, dense material, and crack resistance has significant application value. Summary of the Invention

[0006] The purpose of this invention is to provide a crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material and its mixing and extrusion equipment, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides a crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material and its mixing and extrusion equipment, characterized in that the thermal insulation material is prepared from an initial mixture comprising lightweight aggregate particles, polymer emulsion, fiber reinforcement components, coupling agent and crosslinking agent through the following steps: Step 1: The lightweight aggregate particles are immersed in an alcohol solution of the coupling agent under vacuum conditions, and then the temperature is raised to 40℃-60℃ while stirring to obtain surface-modified lightweight aggregate particles. Step two, the surface-modified lightweight aggregate particles are mixed with the polymer emulsion, the fiber reinforcement component, and the crosslinking agent at a shear rate of not less than 1000 s. -1 Under the conditions of mixing, a non-Newtonian fluid-state mixed slurry is formed; Step 3: Inject the non-Newtonian fluid mixed slurry into a sealed mold and apply a back pressure of 0.2MPa-0.5MPa. At the same time, heat the mixture to 70℃-90℃ at a rate of 1℃ / min-3℃ / min and keep it heated for 2h-4h to obtain the crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material.

[0008] Preferably, the vacuum condition in step one is that the absolute pressure is controlled within the range of 5 kPa-15 kPa; The immersion time in step one is 30 min-60 min, the coupling agent is silane coupling agent KH550 or KH560, the alcohol solution is a mixed solution of ethanol and deionized water in a volume ratio of (4-6):1, and the mass fraction of the coupling agent in the alcohol solution is 1%-3%.

[0009] Preferably, the step one of heating to 40℃-60℃ and maintaining stirring specifically involves heating from room temperature to 40℃-60℃ at a heating rate of 0.5℃ / min-1℃ / min, and then stirring at a speed of 60rpm-120rpm for 20min-40min under a constant temperature of 40℃-60℃. After the surface-modified lightweight aggregate particles in step one are stirred, they are dried in an oven at 60℃-80℃ for 1-2 hours until the surface moisture content of the surface-modified lightweight aggregate particles is less than 0.5%.

[0010] Preferably, the lightweight aggregate particles in step two are shale ceramsite or fly ash ceramsite, and the particle size range of the lightweight aggregate particles is 1mm-5mm, with a bulk density of 300kg / m³. 3 -600kg / m 3 The cylinder compressive strength is not less than 1.5 MPa; The polymer emulsion in step two is an ethylene-vinyl acetate copolymer emulsion or an acrylate emulsion, wherein the solid content of the polymer emulsion is 45%-55% and the pH value is 4-6.

[0011] Preferably, the fiber reinforcement component in step two includes polypropylene fibers with a length of 3mm-6mm and glass fibers with a length of 6mm-12mm, and the mass ratio of the polypropylene fibers to the glass fibers is (1-2):(1-1.5). The crosslinking agent in step two is an isocyanate crosslinking agent or an aziridine crosslinking agent, and the amount of the crosslinking agent added accounts for 0.5%-2% of the mass of the polymer emulsion.

[0012] Preferably, in the initial mixture of step two, the mass ratio of the lightweight aggregate particles, the polymer emulsion, the fiber reinforcing component, the coupling agent, and the crosslinking agent is (40-60):(20-35):(3-8):(0.5-2):(0.2-1). The shear rate in step two is controlled at 1000 s. -1 -3000s -1 Within the specified range, the mixing time is 5-15 minutes, and the mixing temperature is controlled between 15℃ and 30℃.

[0013] Preferably, in step three, the inner wall of the sealed mold is pre-coated with a release agent, which is silicone oil or polytetrafluoroethylene emulsion; The back pressure application method in step three is as follows: while injecting the non-Newtonian fluid mixed slurry, nitrogen gas is introduced from the mold exhaust port to maintain the internal pressure of the mold at 0.2MPa-0.5MPa.

[0014] Preferably, the heating to 70℃-90℃ in step three specifically involves: first heating from room temperature to 50℃ at a rate of 1℃ / min-2℃ / min, holding the temperature for 30 minutes, and then heating from 50℃ to 70℃-90℃ at a rate of 2℃ / min-3℃ / min. After the heat preservation and curing in step three is completed, the temperature is reduced to below 30°C at a rate of 0.5°C / min-1°C / min, and then the cured product is taken out from the sealed mold.

[0015] Preferably, the crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material obtained in step three has a lightweight aggregate particle volume fraction of 40%-60%, a polymer matrix porosity of less than 5%, and the fiber reinforcement component is in a three-dimensional random distribution state in the polymer matrix. The density range of the crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material is 600 kg / m³. 3 -1000kg / m 3 The thickness ranges from 10mm to 50mm.

[0016] The present invention also includes a mixing extrusion apparatus for preparing the above-mentioned crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material, characterized in that the mixing extrusion apparatus comprises: A horizontal twin-shaft forced mixer, wherein a first stirring shaft and a second stirring shaft are provided inside the horizontal twin-shaft forced mixer, and both the first stirring shaft and the second stirring shaft are equipped with spiral stirring blades, and the speed difference between the first stirring shaft and the second stirring shaft is 1:1.2 to 1:1.5; A vacuum degassing unit is connected to the upper part of the horizontal biaxial forced mixer via a pipeline, and the absolute pressure of the vacuum degassing unit is controlled at 10kPa-20kPa. A gear pumping unit, the inlet of which is connected to the bottom outlet of the horizontal twin-shaft forced mixer via a first shut-off valve, and the outlet of which is connected to the inlet of a static mixer; The static mixer has alternating left-handed and right-handed spiral baffles arranged axially inside, with the spiral angle of both the left-handed and right-handed spiral baffles being 30°-45°. The outlet of the static mixer is connected to the inlet of a back pressure regulating valve. The outlet of the back pressure regulating valve is connected to the injection port of a sealed mold. An electric heating jacket is fitted on the outside of the sealed mold. A temperature measuring thermocouple is installed inside the electric heating jacket. The control terminal of the electric heating jacket is connected to a programmable temperature controller.

[0017] Compared with the prior art, the beneficial effects of the present invention are: First, this invention significantly improves the interfacial bonding strength between lightweight aggregate particles and the polymer matrix. Immersing the lightweight aggregate particles in an alcoholic solution of a coupling agent under vacuum effectively removes air from the open pores of the lightweight aggregate, allowing the coupling agent solution to fully penetrate the particle surface and shallow pores. One end of the coupling agent molecule chemically bonds to the silanol groups on the lightweight aggregate surface, while the other end undergoes a cross-linking reaction with the active groups of the polymer emulsion, forming a chemical "bridging" structure at the interface. This chemical bonding is far stronger than physical adsorption or mechanical interlocking; even under humid and hot environments or dynamic loads, the interface is less prone to detachment or slippage. After modification with the coupling agent, the surface of the lightweight aggregate changes from hydrophilic or inert to an active surface with good affinity for the polymer, allowing the polymer emulsion to spread evenly and adhere firmly during subsequent mixing. Compared to untreated lightweight aggregates or processes that only use physical blending, the improved interfacial bonding strength of this invention directly inhibits the initiation of microcracks at the interface. When the material is subjected to drying shrinkage, temperature change, or external force, the stress can be effectively transferred and dispersed through the interface, rather than being concentrated in the weak interfacial area and causing cracking.

[0018] Secondly, this invention achieves ultra-uniform dispersion of the fiber reinforcement component in the slurry, fully leveraging the bridging and crack-resistant properties of the fibers. This is achieved at a shear rate of not less than 1000 s⁻¹. -1In a high-shear field, the polymer emulsion, surface-modified lightweight aggregate particles, and fiber-reinforced components undergo a high-intensity dispersion and mixing process. This shear rate is far higher than the shear capacity of conventional mixing equipment, forcibly breaking up agglomerated fiber bundles into monofilaments while ensuring each fiber surface is fully wetted and coated by the polymer emulsion. The non-Newtonian fluid-like slurry exhibits significant shear-thinning characteristics; the viscosity reduction under high shear facilitates the relative movement of fibers and particles, and the viscosity rapidly recovers after shearing ceases, thus maintaining the uniformity of component distribution. Polypropylene fibers and glass fibers are blended in a specific ratio. Short fibers primarily act as anti-crack agents during the microcrack initiation stage, while long fibers provide bridging stress during crack propagation, working synergistically. Because the fibers are uniformly distributed in a three-dimensional random orientation within the matrix, a micron-scale spatial reinforcement network is formed. When the material is under tension or bending, the fibers can cross the crack surface to transfer loads, preventing further crack opening and propagation. This uniform dispersion avoids localized stress concentrations or reinforcement blind spots caused by fiber agglomeration, resulting in a systematic improvement in the overall crack resistance of the material.

[0019] Third, the thermal insulation material prepared by this invention exhibits excellent seepage and water resistance. Through coupling agent modification and the introduction of crosslinking agents, the polymer emulsion forms a three-dimensional crosslinked network structure during the curing process. The crosslinking agent reacts with active functional groups such as carboxyl and hydroxyl groups on the polymer molecular chains, connecting linear or branched macromolecules into a three-dimensional network, significantly improving the compactness, water resistance, and chemical stability of the polymer film. Curing is carried out under back pressure, with a positive pressure environment of 0.2MPa-0.5MPa maintained inside the mold. This pressure can suppress the volatilization and escape of residual gases and low-boiling-point components in the slurry, forming bubbles, while promoting the close packing of polymer molecular chains. The heating process uses programmed temperature control to ensure a smooth crosslinking reaction, avoiding bubble formation or uneven crosslinking caused by local overheating. The final polymer matrix continuous phase tightly encapsulates each lightweight aggregate particle and completely fills the gaps between particles, resulting in a high closed-pore ratio and very few interconnected pores. Water molecules have difficulty penetrating into the interior of the material, and even when in a humid environment for a long time or in direct contact with liquid water, the water absorption rate of the material remains at a very low level. Since moisture cannot penetrate, the material will not increase its thermal conductivity due to water absorption, nor will it suffer damage from freeze-thaw cycles, thus ensuring the material's insulation performance and service life. Attached Figure Description

[0020] Figure 1 This is a diagram illustrating the working steps for preparing a crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to the present invention. Figure 2 This is a schematic diagram of the overall structure of a mixing extrusion device for preparing crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material according to the present invention. Detailed Implementation

[0021] This invention discloses a crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material. This insulation material uses lightweight aggregate particles as the skeleton, polymer emulsion as the matrix, and composite fibers as the reinforcing phase. It is prepared through a process of surface modification with a coupling agent and crosslinking curing with a crosslinking agent, via vacuum impregnation modification, high-shear homogeneous mixing, and pressure gradient temperature curing. It possesses excellent crack resistance, seepage prevention, and thermal insulation properties, while also exhibiting strong structural stability and a long service life. All raw materials used in the embodiments and comparative examples of this invention are commercially available industrial-grade raw materials. The equipment used in the preparation process includes a vacuum impregnation kettle, a high-speed shear mixer, a sealed pressure curing mold, a constant temperature drying oven, a pressure monitoring system, and a gradient temperature control system. All raw material parameters and process parameters strictly match the core technical solution of this invention. The basic raw material parameters uniformly used in the embodiments and comparative examples of this invention are as follows: Lightweight aggregate particles: fly ash ceramsite is selected, with a particle size of 1mm-5mm and a bulk density of 450kg / m³. 3 Compressive strength: 1.8 MPa; Polymer emulsion: Acrylic emulsion, solid content 50%, pH 5.0; Fiber reinforcement components: 3mm-6mm polypropylene fiber, 6mm-12mm glass fiber; Coupling agent: silane coupling agent KH560; Crosslinking agent: aziridine crosslinking agent; Alcohol solution: ethanol and deionized water mixed solution in a volume ratio of 5:1; Release agent: polytetrafluoroethylene emulsion. Example 1

[0022] See appendix Figure 1 This embodiment provides a crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material. The mass ratio of each raw material in the initial mixture is as follows: 50 parts lightweight aggregate particles, 28 parts polymer emulsion, 5 parts fiber reinforcement component, 1.2 parts coupling agent, and 0.6 parts crosslinking agent; wherein the mass ratio of polypropylene fiber to glass fiber is 1.5:1.2, and the amount of crosslinking agent added is 1.0% of the mass of polymer emulsion.

[0023] The specific preparation steps are as follows: Step 1: Vacuum surface modification treatment of lightweight aggregate particles. Silane coupling agent KH560 is added to an ethanol-deionized water mixture and stirred until homogeneous to prepare a modified solution with a coupling agent mass fraction of 2%. Fly ash ceramsite lightweight aggregate particles are placed in a vacuum impregnation reactor. The reactor valve is closed, and a vacuum is drawn to an absolute pressure of 10 kPa. The reactor is maintained under vacuum for 45 minutes to ensure the modified solution fully penetrates and coats the surface pores of the lightweight aggregate particles. After impregnation, the reactor heating system is activated, and the temperature is increased from room temperature to 50°C at a rate of 0.8°C / min. The mixture is then stirred at 90 rpm for 30 minutes under constant temperature conditions to achieve uniform surface modification of the lightweight aggregate particles. After stirring, the modified lightweight aggregate particles are removed and placed in a 70°C constant temperature oven for drying for 1.5 hours. The surface moisture content is checked and found to be 0.42%, below the 0.5% standard, yielding dried surface-modified lightweight aggregate particles for later use.

[0024] Step 2: Preparation of a non-Newtonian fluid-state mixed slurry under high shear conditions. The surface-modified lightweight aggregate particles, acrylate emulsion, composite fiber reinforcement components, and aziridine crosslinking agent prepared in Step 1 are sequentially added to a high-speed shear mixer. The mixing environment temperature is controlled at 22°C, the mixer is started, and the shear rate is set to 2000 s. -1 The mixture is continuously sheared and mixed for 10 minutes to ensure thorough dispersion and fusion of all components, forming a uniform, stable, and non-agglomerated non-Newtonian fluid slurry. This shear rate effectively breaks up fiber agglomeration, ensuring uniform dispersion of polypropylene and glass fibers in the slurry system, while simultaneously promoting interfacial bonding between the polymer emulsion and the modified lightweight aggregate particles.

[0025] Step 3: Pressurized gradient temperature-sealed curing. Beforehand, evenly coat the inner wall of the sealed mold with a polytetrafluoroethylene (PTFE) emulsion release agent and allow it to dry for 10 minutes. Inject the mixed slurry prepared in Step 2 into the sealed mold at a uniform rate, seal the mold inlet and conventional vent, and introduce high-purity nitrogen through the mold's dedicated pressure port to maintain a stable back pressure of 0.35 MPa inside the mold. Start the gradient temperature-curing system, first raising the temperature from room temperature to 50°C at a rate of 1.5°C / min, and holding it at this temperature for 30 minutes to complete the initial evaporation of moisture from the slurry and pre-forming of the system. Then, raise the temperature from 50°C to 80°C at a rate of 2.5°C / min and hold it at this temperature for 3 hours to ensure full cross-linking of the polymer emulsion, tight bonding between the fibers and the matrix, and the formation of an integrated structure between the lightweight aggregate skeleton and the polymer matrix. After curing, the temperature is slowly reduced to 28℃ at a rate of 0.8℃ / min to release the internal pressure of the mold, open the mold to remove the cured product, and trim any excess waste material at the edges to obtain the finished crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material.

[0026] The thermal insulation material prepared in this embodiment has a lightweight aggregate particle volume fraction of 52%, a polymer matrix porosity of 3.8%, and fiber reinforcement components exhibiting a complete three-dimensional random distribution within the matrix. The overall density of the material is 820 kg / m³. 3 Thickness 30mm. Example 2

[0027] This embodiment provides a crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material. The mass ratio of each raw material in the initial mixture is as follows: 45 parts lightweight aggregate particles, 32 parts polymer emulsion, 6 parts fiber reinforcement component, 1.5 parts coupling agent, and 0.8 parts crosslinking agent; wherein the mass ratio of polypropylene fiber to glass fiber is 2:1.5, and the amount of crosslinking agent added is 1.5% of the mass of polymer emulsion.

[0028] The specific preparation steps are as follows: Step 1: Vacuum surface modification treatment of lightweight aggregate particles. Silane coupling agent KH560 was added to an ethanol-deionized water mixed solution to prepare a modification solution with a coupling agent mass fraction of 2.5%. The fly ash ceramsite lightweight aggregate particles were placed in a vacuum impregnation kettle, and a vacuum was drawn to an absolute pressure of 12 kPa. Impregnation was carried out for 50 minutes to ensure the modification solution fully wetted the inner and outer surfaces of the lightweight aggregate particles. After impregnation, the temperature was increased from room temperature to 55℃ at a rate of 1.0℃ / min, and then stirred at 100 rpm for 35 minutes under constant temperature conditions at 55℃ to ensure uniform surface modification of the lightweight aggregate particles. After stirring, the modified lightweight aggregate particles were placed in a 75℃ oven to dry for 2 hours. The surface moisture content was measured to be 0.38%, meeting the moisture content requirements, and the particles were ready for use.

[0029] Step 2: Preparation of non-Newtonian fluid-state mixed slurry under high shear conditions. Pretreated modified lightweight aggregate particles, acrylic emulsion, composite fibers, and crosslinking agent are sequentially added to a high-speed shear mixer. The ambient temperature is controlled at 25°C, and the shear rate is set to 2500 s⁻¹. -1 Shear mixing for 12 minutes fully disperses the components, eliminates fiber agglomeration and slurry stratification, and forms a non-Newtonian fluid mixture with uniform flowability and system stability. Higher shear rates can further improve fiber dispersion and enhance the uniformity of the slurry system.

[0030] Step 3: Pressurized gradient heating and sealed curing. The inner wall of the sealed mold is coated with PTFE release agent and dried for later use. After injecting the mixed slurry into the mold, nitrogen gas is introduced to maintain a back pressure of 0.4 MPa inside the mold. The gradient heating program is started, first heating to 50°C at a rate of 2.0°C / min and holding at that temperature for 30 minutes to complete the pre-forming of the slurry; then heating to 85°C at a rate of 3.0°C / min and holding at that temperature for 3.5 hours to ensure full cross-linking and curing of the polymer, building a dense matrix structure. After curing, the temperature is lowered to 25°C at a rate of 1.0°C / min, the pressure is released, the mold is opened, the product is removed and trimmed, and the finished thermal insulation material is obtained.

[0031] The thermal insulation material prepared in this embodiment has an internal lightweight aggregate particle volume fraction of 48%, a polymer matrix porosity of 3.2%, excellent three-dimensional fiber uniformity, and an overall material density of 880 kg / m³. 3 Thickness 30mm. Example 3

[0032] This embodiment provides a crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material. The mass ratio of each raw material in the initial mixture is as follows: 55 parts lightweight aggregate particles, 22 parts polymer emulsion, 4 parts fiber reinforcement component, 0.8 parts coupling agent, and 0.4 parts crosslinking agent; wherein the mass ratio of polypropylene fiber to glass fiber is 1:1, and the amount of crosslinking agent added is 0.8% of the mass of polymer emulsion.

[0033] The specific preparation steps are as follows: Step 1: Vacuum surface modification treatment of lightweight aggregate particles. Silane coupling agent KH560 was added to an ethanol-deionized water mixed solution to prepare a modified solution with a coupling agent mass fraction of 1.5%. The fly ash ceramsite lightweight aggregate particles were then placed in a vacuum impregnation kettle, and a vacuum was drawn to an absolute pressure of 8 kPa. Impregnation was carried out for 35 minutes to achieve preliminary surface modification and wetting of the lightweight aggregate particles. After impregnation, the temperature was increased from room temperature to 45℃ at a rate of 0.5℃ / min, and the particles were stirred at 70 rpm for 25 minutes under constant temperature conditions at 45℃ to complete the uniform modification treatment. After stirring, the modified lightweight aggregate particles were placed in a 65℃ oven for drying for 1 hour. The surface moisture content was measured to be 0.45%, meeting the process requirements, and the particles were ready for use.

[0034] Step 2: Preparation of a non-Newtonian fluid-state mixed slurry under high shear conditions. Modified lightweight aggregate particles, acrylic emulsion, composite fibers, and crosslinking agent are sequentially added to a high-speed shear mixer. The ambient temperature is controlled at 18°C, and the shear rate is set to 1500 s. -1 Shear mixing for 8 minutes allows all components to fully blend and form a stable non-Newtonian fluid slurry, ensuring that the slurry has both good flowability and molding stability.

[0035] Step 3: Pressurized gradient heating and sealed curing. The inner wall of the sealed mold is pre-treated with a release agent. After injecting the mixed slurry into the mold, nitrogen gas is introduced to maintain a back pressure of 0.25 MPa inside the mold. The gradient heating program is started, first heating to 50°C at a rate of 1.0°C / min and holding at that temperature for 30 minutes for pre-forming; then heating to 75°C at a rate of 2.0°C / min and holding at that temperature for 2.5 hours to complete polymer crosslinking and overall material curing. After curing, the temperature is lowered to 26°C at a rate of 0.6°C / min, the pressure is released, the mold is opened, and after finishing, the finished insulation material is obtained.

[0036] The thermal insulation material prepared in this embodiment has a lightweight aggregate particle volume fraction of 58%, a polymer matrix porosity of 4.5%, and fibers that are uniformly and randomly distributed in three dimensions. The overall density of the material is 750 kg / m³. 3 Thickness 30mm.

[0037] To verify the superiority of the core processes and component ratios of vacuum surface modification, high shear mixing, and pressure gradient curing of this invention, three comparative examples were set up, one without the core modification process, the other without high shear mixing, and the other without closed back pressure curing. The other raw materials and basic parameters remained the same as in Example 1.

[0038] Comparative Example 1 (vacuum modification process without coupling agent) The raw material ratio of this comparative example is exactly the same as that of Example 1. The difference is that the vacuum impregnation surface modification process of the coupling agent in step one is omitted. Unmodified fly ash ceramsite lightweight aggregate particles are used directly for preparation. The other process parameters and steps are exactly the same.

[0039] The specific preparation steps are as follows: Step 1: Lightweight aggregate pretreatment. Select aggregates with a particle size of 1mm-5mm and a bulk density of 450kg / m³. 3 The fly ash ceramsite lightweight aggregate particles were directly placed in a 70℃ oven and dried for 1.5 hours to remove surface free moisture. They were then set aside for use without any coupling agent vacuum impregnation or heating and stirring modification treatment.

[0040] Step 2: High-shear preparation of the mixed slurry. Unmodified lightweight aggregate particles, acrylate emulsion, fiber reinforcement components, and crosslinking agent are mixed according to the proportions in Example 1, with the ambient temperature controlled at 22°C and the shear rate at 2000 s. -1 Shear and mix for 10 minutes to prepare a mixed slurry.

[0041] Step 3: Pressurized gradient heating and curing. Using the same mold pretreatment, nitrogen back pressure, gradient heating and cooling process as in Example 1, the finished insulation material is cured and formed.

[0042] The thermal insulation material prepared in this comparative example has a lightweight aggregate particle volume fraction of 52%, a polymer matrix porosity of 9.6%, obvious gaps at the interface between the lightweight aggregate particles and the polymer matrix, and localized agglomeration of the fiber distribution.

[0043] Comparative Example 2 (without high-shear mixing process, using ordinary stirring) The raw material ratios, pretreatment processes, and curing processes in this comparative example are completely identical to those in Example 1. The difference is that the 1000s step in step two is omitted. -1 The above high-shear mixing process uses ordinary low-speed stirring at a stirring rate of 300 rpm and a mixing time of 10 min, with other parameters remaining unchanged.

[0044] The specific preparation steps are as follows: Step 1: Vacuum surface modification treatment of lightweight aggregate particles. The vacuum impregnation, heating and stirring, and drying process of Example 1 is completely replicated to prepare modified lightweight aggregate particles for later use.

[0045] Step 2: Preparation of mixed slurry by ordinary stirring. Modified lightweight aggregate particles, polymer emulsion, fiber reinforcement components, and crosslinking agent are added to ordinary stirring equipment and stirred at a low speed of 300 rpm for 10 minutes at 22°C to prepare mixed slurry. The slurry shows obvious fiber agglomeration and component stratification.

[0046] Step 3: Pressurized gradient heating and curing. Using the same curing process as in Example 1, the finished insulation material was prepared.

[0047] The polymer matrix of the thermal insulation material prepared in this comparative example has a porosity of 7.8%, and the fibers exhibit severe irregular agglomeration, failing to form a complete three-dimensional distribution structure.

[0048] Comparative Example 3 (curing process without sealed back pressure, curing at normal pressure) The raw material ratio, pretreatment process, and slurry mixing process of this comparative example are completely consistent with those of Example 1. The difference is that the nitrogen back pressure application process in the closed mold is cancelled in step three, and the curing is carried out in an open mold under normal pressure. The other gradient heating, heat preservation, and cooling parameters remain unchanged.

[0049] The specific preparation steps are as follows: Step 1: Vacuum surface modification treatment of lightweight aggregate particles. The pretreatment process of Example 1 is completely replicated to prepare modified lightweight aggregate particles.

[0050] Step 2: High-shear mixing process to prepare a homogeneous non-Newtonian fluid slurry. The high-shear mixing process of Example 1 is completely replicated.

[0051] Step 3: Gradient heating and curing at ambient pressure. A release agent is applied to the inner wall of the mold. After injecting the mixed slurry, the mold is not sealed, and no nitrogen back pressure is applied. Under ambient pressure, the process of gradient heating, constant temperature curing, and cooling as described in Example 1 is carried out to obtain the final thermal insulation material.

[0052] The polymer matrix of the thermal insulation material prepared in this comparative example has a porosity of 11.2%, and there are a large number of air bubbles and voids inside the material, resulting in extremely poor structural density.

[0053] To accurately test the comprehensive performance of the materials in each embodiment and comparative example, the following national standards were uniformly adopted for testing: Bulk density was tested according to GB / T 5486-2008 "Test Methods for Inorganic Rigid Thermal Insulation Products"; compressive strength was tested according to GB / T13480-2014 "Determination of Compressive Properties of Thermal Insulation Products for Buildings"; water permeability pressure was tested according to GB / T 1732-1993 "Determination of Washability of Coatings" to assess impermeability; crack resistance was tested according to JGJ / T 253-2011 "Technical Specification for Inorganic Lightweight Aggregate Mortar Insulation System"; thermal conductivity was tested according to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method". All samples were 30 mm thick, and five parallel samples were tested for each group of samples. The average value was taken as the final test result.

[0054] Table 1: Comparison of Basic Physical Structure Performance of Each Embodiment and Comparative Example

[0055]

[0056] As shown in Table 1, the three sets of examples prepared using the core process of this invention all had polymer matrix porosity controlled below 5%, far lower than the three comparative examples, and their structural density was significantly better than the comparative examples. Among them, Example 2 had a higher proportion of polymer emulsion and the optimal amount of crosslinking agent, combined with the highest shear rate and suitable curing back pressure, resulting in a matrix porosity as low as 3.2% and the best structural density. Example 3 had the highest proportion of lightweight aggregate, and its porosity was slightly higher than the other two examples, but it still met the core standard of being below 5%.

[0057] Comparative Example 1, by omitting the vacuum modification process with coupling agent, failed to form an active modified layer on the surface of the lightweight aggregate particles, resulting in poor interfacial bonding with the polymer emulsion and the generation of numerous micro-gaps at the interface. This led to a significant increase in matrix porosity and extremely poor interfacial stability. Comparative Example 2, using ordinary low-speed stirring, could not break up the fiber agglomeration structure, resulting in uneven fiber dispersion, low component integration in the slurry system, and numerous pore defects inside the matrix after molding. Comparative Example 3, by omitting closed back pressure curing, resulted in internal air bubbles being unable to escape in time during the slurry curing process. These bubbles remained inside the matrix, forming macropores with a porosity of 11.2%, which is 2.95 times that of Example 1, indicating significant structural looseness and defects.

[0058] Table 2: Comparison of Mechanical, Crack-Resistant, and Waterproofing Performance of Each Example and Comparative Example

[0059]

[0060] Compressive strength, permeability pressure, crack resistance grade, and crack elongation are the core indicators for evaluating the crack resistance, seepage prevention performance, and structural stability of materials. The higher the crack elongation, the better the toughness of the material and the stronger its crack resistance; the higher the permeability pressure, the better the seepage prevention and seepage prevention performance of the material; Crack resistance grade I is the best grade, representing that no cracks will form under thermal cycling and load.

[0061] All three sets of examples showed significantly better performance than the comparative examples. Example 2 exhibited the best overall performance, with a compressive strength of 4.68 MPa, a permeability pressure of 0.52 MPa, a crack elongation of 3.95%, and no cracks formed throughout the process. This is because Example 2 had a high polymer emulsion content and an optimal crosslinking agent ratio. Combined with a highly dense matrix structure and a uniform three-dimensional composite fiber network, it effectively dispersed stress and blocked seepage channels. Simultaneously, the fiber's binding effect significantly improved the material's toughness and resistance to deformation. Example 1 showed moderate performance across the board, with balanced and stable overall performance. Example 3, due to its higher proportion of lightweight aggregate and lower proportion of polymer matrix, experienced a slight decrease in matrix bonding strength, resulting in slightly lower performance than the first two sets of examples, but still possessed excellent crack resistance and seepage prevention capabilities.

[0062] Comparative Example 1, due to the lack of coupling agent modification on the lightweight aggregate, suffered from interface bonding failure and numerous interface defects. Under stress, the interface was prone to cracking, allowing rapid water penetration through the interface gaps. Consequently, compressive strength and permeability pressure decreased significantly, and fine network cracks appeared. Comparative Example 2 exhibited severe fiber agglomeration and significant local stress concentration, easily generating strip cracks under stress. The fiber reinforcement effect could not be fully utilized, resulting in significantly weakened impermeability. Comparative Example 3 had extremely high matrix porosity, numerous internal voids and defects, extremely poor structural integrity, the lowest compressive strength, dense water seepage channels, and the worst impermeability. It was also highly susceptible to large-area cracking, resulting in the lowest crack resistance grade. This demonstrates that the three core processes of coupling agent vacuum modification, high-shear dispersion, and closed-back-pressure curing are crucial for ensuring the crack resistance and impermeability of materials, and none can be omitted.

[0063] Table 3: Comparison of thermal insulation durability performance between each embodiment and the comparative example

[0064]

[0065] Thermal conductivity is a core indicator for measuring the thermal insulation performance of insulation materials. The lower the thermal conductivity, the better the thermal insulation effect. The rate of change of thermal conductivity and the rate of mass loss after freeze-thaw cycles can directly reflect the durability and environmental adaptability of the material. The lower the rate of change and loss, the stronger the structural stability and weather resistance of the material.

[0066] As shown in Table 3, the initial thermal conductivity of all three examples is below 0.07 W / (m·K), indicating excellent thermal insulation performance. Example 2 has the densest matrix and the best overall structural integrity, with an initial thermal conductivity as low as 0.059 W / (m·K). It exhibits the smallest performance degradation after freeze-thaw cycles, with a thermal conductivity change rate of only 3.39% and a mass loss rate of 0.25%, demonstrating the best durability. The thermal insulation and durability performance of Examples 1 and 3 decrease sequentially, but are still significantly better than the comparative examples. Example 3, due to its high proportion of lightweight aggregate and relatively more internal pores, has a slightly higher thermal conductivity and a slightly larger performance degradation, but still maintains a stable thermal insulation effect.

[0067] The initial thermal conductivity of the three comparative examples was significantly higher than that of the control examples. The core reason is that the comparative examples had more internal pores, gaps, and voids, which intensified air convection, accelerated heat transfer, and significantly reduced thermal insulation performance. After 50 freeze-thaw cycles, the micro-defects inside the comparative examples continued to expand and enlarge, the structure became more porous, and the thermal conductivity increased significantly, with a change rate exceeding 15%. At the same time, the loose structure on the surface and inside of the material suffered severe detachment, and the mass loss rate increased significantly. Among them, Comparative Example 3, which was cured under normal pressure, had the most internal voids and defects, suffered the most severe structural damage after freeze-thaw cycles, and had the worst durability. Comparative Example 1 showed interface bonding failure, with repeated cracking and peeling of the interface under freeze-thaw cycles, resulting in a significant performance degradation. The data from the three sets of tables fully verify that the present invention, through the synergistic process of vacuum coupling agent modification of lightweight aggregates, high-shear homogeneous mixing, and closed back pressure gradient temperature curing, combined with a scientific component ratio, can effectively reduce the porosity of the material matrix, optimize the fiber distribution structure, and strengthen the interfacial bonding strength, so that the prepared thermal insulation material has excellent crack resistance, seepage prevention, thermal insulation performance, and weather resistance and durability.

[0068] This invention also includes a mixing extrusion apparatus for preparing crack-resistant and seepage-proof polymer-based lightweight aggregate insulation materials, such as... Figure 2 As shown, it includes a horizontal twin-shaft forced mixer 100, a vacuum degassing unit 108, a gear pumping unit 112, a static mixer, a back pressure regulating valve, and a sealed mold.

[0069] The horizontal biaxial forced mixer 100 adopts a horizontal biaxial shell structure, with a first stirring shaft and a second stirring shaft 106 arranged horizontally and parallel inside. The two ends of the first and second stirring shafts 106 are mounted on the left and right side walls of the horizontal biaxial forced mixer 100 via bearings and sealing assemblies 102. Spiral stirring blades extending axially are fixedly mounted on the shafts of both the first and second stirring shafts 106, and one end of each stirring shaft extends out of the shell and connects to a drive device interface 104. An external drive motor drives the two stirring shafts to rotate at different speeds in the same or opposite directions through the drive device interface 104. In this embodiment, the speed difference between the first and second stirring shafts 106 is controlled between 1:1.2 and 1:1.5. This asymmetric, different-speed biaxial forced mixing generates strong shearing, convection, and three-dimensional diffusion effects on the materials inside the mixer, enabling the polymer matrix and lightweight aggregates to achieve a highly uniform mixing state in a very short time, effectively avoiding agglomeration and stratification of the lightweight aggregates during the mixing process.

[0070] The vacuum degassing unit 108 is connected to the top of the upper shell of the horizontal biaxial forced mixer 100 via a connecting pipe 110. During the forced mixing of materials by the stirring shaft 106, the vacuum degassing unit 108 is activated to strictly control the absolute pressure inside the horizontal biaxial forced mixer 100 to 10kPa-20kPa. By maintaining this low-pressure vacuum environment, the tiny bubbles carried and generated during the forced mixing process, as well as trace gases volatilized from the polymer components, can be efficiently extracted, fundamentally eliminating the micropore defects that may form inside the cured material, thereby significantly improving the overall density, crack resistance, and impermeability of the final lightweight aggregate insulation material.

[0071] The horizontal twin-shaft forced mixer 100 has a discharge port at its bottom, which is connected to the inlet of the gear pumping unit 112 via a first shut-off valve 114. The first shut-off valve 114 controls the opening and closing of the material conveying path from the bottom of the mixer to the subsequent stage. The gear pumping unit 112 uses internal high-precision gear meshing to forcefully pump the degassed mixture in a metered, high-pressure manner. This not only provides stable and sufficient extrusion power but also ensures the continuity and uniformity of the material conveying process, preventing material pulsation from adversely affecting subsequent molding.

[0072] The outlet of the gear pumping unit 112 is connected to the inlet of the static mixer. The static mixer contains several alternating left-handed and right-handed spiral baffles arranged axially, with the helix angle of both baffles designed to be 30°-45°. When high-pressure material flows through the static mixer, due to the blocking and guiding effect of the alternating spiral baffles, the material flow is continuously split, sheared, displaced, overlapped, and merged during its forward movement. This achieves secondary deep micro-mixing of the material without moving parts, further ensuring the absolute uniform distribution of polymer components and aggregates at the microscale.

[0073] The outlet of the static mixer is connected to the inlet of the back pressure regulating valve. The back pressure regulating valve is used to dynamically adjust and maintain the reference back pressure at the front end of the extrusion system, so that the material maintains a constant pressure state when flowing through the static mixer and gear pumping unit 112, preventing fluctuations in material density caused by changes in downstream flow resistance.

[0074] The outlet of the back pressure regulating valve is connected to the injection port of the sealed mold. The insulation material mixture, after secondary micro-mixing and with stable pressure, is continuously and stably injected into the sealed mold for molding. An electrically heated jacket is tightly fitted around the outside of the sealed mold to provide a precise heat and temperature environment for the material's curing reaction. A thermocouple is strategically embedded inside the electrically heated jacket to monitor the actual temperature of the mold wall and the material inside in real time. The control terminal of the electrically heated jacket is electrically connected to a programmable temperature controller. Based on a preset curing temperature process curve for the insulation material, the programmable temperature controller receives the temperature signal from the thermocouple in real time and precisely adjusts the output power of the electrically heated jacket using an internal control algorithm. This achieves precise temperature control throughout the entire curing process of the material within the sealed mold, ultimately resulting in a crack-resistant and leak-proof polymer-based lightweight aggregate insulation material molded body with stable structure, excellent quality, and regular specifications.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material, characterized in that, The thermal insulation material is prepared from an initial mixture comprising lightweight aggregate particles, polymer emulsion, fiber reinforcement components, coupling agents, and crosslinking agents through the following steps: Step 1: The lightweight aggregate particles are immersed in an alcohol solution of the coupling agent under vacuum conditions, and then the temperature is raised to 40℃-60℃ while stirring to obtain surface-modified lightweight aggregate particles. Step two, the surface-modified lightweight aggregate particles are mixed with the polymer emulsion, the fiber reinforcement component, and the crosslinking agent at a shear rate of not less than 1000 s. -1 Under the conditions of mixing, a non-Newtonian fluid-state mixed slurry is formed; Step 3: Inject the non-Newtonian fluid mixed slurry into a sealed mold and apply a back pressure of 0.2MPa-0.5MPa. At the same time, heat the mixture to 70℃-90℃ at a rate of 1℃ / min-3℃ / min and keep it heated for 2h-4h to obtain the crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material.

2. The crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to claim 1, characterized in that, The vacuum condition in step one is that the absolute pressure is controlled within the range of 5 kPa-15 kPa. The immersion time in step one is 30 min-60 min, the coupling agent is silane coupling agent KH550 or KH560, the alcohol solution is a mixed solution of ethanol and deionized water in a volume ratio of (4-6):1, and the mass fraction of the coupling agent in the alcohol solution is 1%-3%.

3. The crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to claim 2, characterized in that, The step one, heating to 40℃-60℃ and stirring, specifically involves heating from room temperature to 40℃-60℃ at a heating rate of 0.5℃ / min-1℃ / min, and then stirring at a speed of 60rpm-120rpm for 20min-40min under a constant temperature of 40℃-60℃. After the surface-modified lightweight aggregate particles in step one are stirred, they are dried in an oven at 60℃-80℃ for 1-2 hours until the surface moisture content of the surface-modified lightweight aggregate particles is less than 0.5%.

4. The crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to claim 1, characterized in that, The lightweight aggregate particles in step two are shale ceramsite or fly ash ceramsite, with a particle size range of 1mm-5mm and a bulk density of 300kg / m³. 3 -600kg / m 3 The cylinder compressive strength is not less than 1.5 MPa; The polymer emulsion in step two is an ethylene-vinyl acetate copolymer emulsion or an acrylate emulsion, wherein the solid content of the polymer emulsion is 45%-55% and the pH value is 4-6.

5. The crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to claim 4, characterized in that, The fiber reinforcement component in step two includes polypropylene fibers with a length of 3mm-6mm and glass fibers with a length of 6mm-12mm, and the mass ratio of the polypropylene fibers to the glass fibers is (1-2):(1-1.5). The crosslinking agent in step two is an isocyanate crosslinking agent or an aziridine crosslinking agent, and the amount of the crosslinking agent added accounts for 0.5%-2% of the mass of the polymer emulsion.

6. The crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to claim 5, characterized in that, In the initial mixture of step two, the mass ratio of the lightweight aggregate particles, the polymer emulsion, the fiber reinforcing component, the coupling agent, and the crosslinking agent is (40-60):(20-35):(3-8):(0.5-2):(0.2-1). The shear rate in step two is controlled at 1000 s. -1 -3000s -1 Within the specified range, the mixing time is 5-15 minutes, and the mixing temperature is controlled between 15℃ and 30℃.

7. The crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to claim 1, characterized in that, In step three, the inner wall of the sealed mold is pre-coated with a release agent, which is silicone oil or polytetrafluoroethylene emulsion. The back pressure application method in step three is as follows: while injecting the non-Newtonian fluid mixed slurry, nitrogen gas is introduced from the mold exhaust port to maintain the internal pressure of the mold at 0.2MPa-0.5MPa.

8. The crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to claim 7, characterized in that, The heating to 70℃-90℃ in step three is specifically as follows: first, the temperature is raised from room temperature to 50℃ at a rate of 1℃ / min-2℃ / min, held at that temperature for 30 minutes, and then raised from 50℃ to 70℃-90℃ at a rate of 2℃ / min-3℃ / min. After the heat preservation and curing in step three is completed, the temperature is reduced to below 30°C at a rate of 0.5°C / min-1°C / min, and then the cured product is taken out from the sealed mold.

9. The crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to claim 1, characterized in that, The crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material obtained in step three has a lightweight aggregate particle volume fraction of 40%-60%, a polymer matrix porosity of less than 5%, and the fiber reinforcement component is in a three-dimensional random distribution state in the polymer matrix. The density range of the crack-resistant and seepage-proof polymer-based lightweight aggregate insulation material is 600 kg / m³. 3 -1000kg / m 3 The thickness ranges from 10mm to 50mm.

10. A mixing extrusion apparatus for preparing the crack-resistant and seepage-proof polymer-based lightweight aggregate thermal insulation material according to any one of claims 1 to 9, characterized in that, The mixing extrusion equipment includes: A horizontal twin-shaft forced mixer, wherein a first stirring shaft and a second stirring shaft are provided inside the horizontal twin-shaft forced mixer, and both the first stirring shaft and the second stirring shaft are equipped with spiral stirring blades, and the speed difference between the first stirring shaft and the second stirring shaft is 1:1.2 to 1:1.5; A vacuum degassing unit is connected to the upper part of the horizontal biaxial forced mixer via a pipeline, and the absolute pressure of the vacuum degassing unit is controlled at 10kPa-20kPa. A gear pumping unit, the inlet of which is connected to the bottom outlet of the horizontal twin-shaft forced mixer via a first shut-off valve, and the outlet of which is connected to the inlet of a static mixer; The static mixer has alternating left-handed and right-handed spiral baffles arranged axially inside, with the spiral angle of both the left-handed and right-handed spiral baffles being 30°-45°. The outlet of the static mixer is connected to the inlet of a back pressure regulating valve. The outlet of the back pressure regulating valve is connected to the injection port of a sealed mold. An electric heating jacket is fitted on the outside of the sealed mold. A temperature measuring thermocouple is installed inside the electric heating jacket. The control terminal of the electric heating jacket is connected to a programmable temperature controller.

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