A blow molding process for producing an inner bag of an IBC ton barrel

Abstract

The application discloses an IBC ton barrel production inner container blow molding process and relates to the technical field of plastic hollow product manufacturing. The IBC ton barrel production inner container blow molding process sorts, cleans, dries and classifies melt flow rate of recycled materials by taking waste IBC inner container recycled materials, waste high-density polyethylene barrel recycled materials and production edge material recycled materials as main raw materials, then adds high-molecular-weight high-density polyethylene reinforcing material, polyolefin toughening material, antioxidant compound agent, acid absorbent and odor adsorbent for metering and compounding, and then carries out low-shear plasticizing, stable pressure storage, six-zone parison thickness program extrusion, pre-blowing setting, main blowing expansion, pressure maintaining internal cooling and edge trimming detection. Through function compensation of the recycled materials, six-zone thickness distribution of the parison in the axial direction, three-stage blow molding setting and partition temperature control, the problems of insufficient melt stability, easy thinning of the four corners and the bottom valve seat area and poor product consistency of the waste plastic recycled materials used for the IBC ton barrel square inner container are solved.

Description

Technical Field

[0001] This invention relates to the field of plastic hollow product manufacturing technology, specifically a blow molding process for the inner liner of an IBC (Isolated Toilet Chamber). Background Technology

[0002] IBC containers are widely used for storing and transporting liquid chemical raw materials, food ingredients, additives, cleaning fluids, lubricants, and other fluid materials. Existing IBC containers typically consist of a metal frame, a pallet, and a plastic inner liner, with the inner liner directly handling the contents. For 1000L IBC containers, square inner liners have become the mainstream structural form due to their high space utilization, high compatibility with the external metal frame, and high loading efficiency. Existing square inner liners are usually made from high-density polyethylene (HDPE) raw materials, formed using a storage-type extrusion blow molding machine. With the development of green manufacturing and the circular economy, waste plastic recycling has become an important source of raw materials for the plastic packaging industry. In particular, waste IBC inner liners, waste HDPE packaging drums, and production line trimmings all have high recycling value. Reusing recycled waste plastic materials in the manufacture of IBC inner liners can reduce raw material costs and improve the recycling rate of waste plastics, resulting in significant economic and environmental value. However, most existing IBC square inner liner blow molding processes are based on relatively stable virgin material systems. When the raw materials are changed to recycled waste plastics from multiple sources, the existing process is prone to the following problems: The thermal history of recycled waste plastics is complex, the degree of molecular chain integrity varies, the melt flow rate distribution is wide, and the residual volatiles, trace impurities and aging degradation also fluctuate. As a result, the melt strength and sag stability after plasticization are not as stable as those of virgin materials, and the preform is more likely to experience local thinning during the axial stretching and blowing stages after extrusion.

[0003] IBC (In-Balance Container) rectangular inner tanks are large-capacity hollow products. The wall thickness distribution requirements differ for the top neck area, shoulder transition area, middle body area, lower body area, bottom transition area, and valve seat area. If the existing process directly adopts the constant blank thickness method used for ordinary tanks, it easily leads to insufficient material in the shoulder, four corners, and valve seat areas, while material accumulates in some parts of the middle body, resulting in uneven wall thickness throughout the entire tank. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides the following technical solution: a blow molding process for the inner liner of an IBC (Integrated Circuit Bottling) container, comprising the following steps: S1, pre-treating waste IBC inner liner recycled material, waste high-density polyethylene (HDPE) drum recycled material, and production edge material recycled material to obtain three types of dried recycled materials; S2, detecting the melt flow rate of the three types of dried recycled materials obtained in step S1, and grouping them according to the detection results; S3, metering and mixing each group of recycled materials obtained in step S2 with reinforcing HDPE material, polyolefin toughening material, antioxidant compounding agent, acid absorbent, and deodorizing adsorbent to obtain a recycled compound; S4, feeding the recycled compound into a storage-type extrusion blow molding equipment for molding. S5. Using the preform program control function of the storage-type extrusion blow molding equipment, the preform is divided axially into a neck area, upper shoulder area, upper barrel area, middle barrel area, lower barrel area, and bottom valve seat area, and a zoned preform thickness program extrusion is implemented; S6. After the mold is closed, pre-blown gas is input into the preform cavity for pre-blowing and shaping; S7. After pre-blowing, main-blown gas is input into the preform cavity for main-blowing expansion; S8. After main-blowing, pressure holding and shaping are performed, and cooling gas is input into the preform cavity for internal cooling; S9. Zoned temperature control is performed on different areas of the mold throughout the molding process; S10. After the product is demolded, trimming is performed, and leak detection, weight detection, and ultrasonic thickness measurement are performed in sequence.

[0005] Preferably, in step S1, the pretreatment includes removing impurities, crushing, metal separation, hot washing, friction cleaning, rinsing, dehydration, and hot air drying; the crushed particle size of the waste IBC inner liner recycled material is 18mm-25mm, the crushed particle size of the waste high-density polyethylene drum recycled material is 16mm-22mm, and the crushed particle size of the production edge material recycled material is 10mm-18mm; the hot washing temperature is 75℃-85℃, the hot washing time is 15min-25min, and the mass fraction of the alkaline cleaning agent in the washing solution is 1.5%-3.0%; the friction cleaning speed is 800rpm-1200rpm. The friction cleaning time is 5-10 minutes; the rinsing is a two- to three-stage rinsing process, with the water conductivity at the rinsing endpoint not exceeding 150 μS / cm; the hot air drying temperature is 85℃-95℃, and the hot air drying time is 40-60 minutes; the recycled material after hot air drying meets the following conditions: moisture content not exceeding 0.15%, ash content not exceeding 1.0%, metal impurities not exceeding 0.05%, total paper and label residue not exceeding 0.10%, total non-polyethylene dissimilar plastics not exceeding 1.0%, and polyvinyl chloride not exceeding 0.02%.

[0006] Preferably, in step S2, the melt flow rate is measured at 190°C and 2.16 kg, and is divided into three melt flow rate ranges: a first melt flow rate range recycled material, a second melt flow rate range recycled material, and a third melt flow rate range recycled material. The melt flow rate of the first melt flow rate range recycled material is 0.20 g / 10 min to 0.35 g / 10 min, the melt flow rate of the second melt flow rate range recycled material is 0.36 g / 10 min to 0.55 g / 10 min, and the melt flow rate of the third melt flow rate range recycled material is 0.56 g / 10 min to 0.80 g / 10 min. The main resin of the waste IBC inner liner recycled material is... The high-density polyethylene has a density of 0.945 g / cm³ to 0.955 g / cm³ and a melt flow rate of 0.20 g / 10 min to 0.60 g / 10 min; the main resin of the recycled waste high-density polyethylene drum is high-density polyethylene with a density of 0.948 g / cm³ to 0.955 g / cm³ and a melt flow rate of 0.20 g / 10 min to 0.80 g / 10 min; the recycled production edge material is the recycled material obtained by crushing the trimming residue of the square inner liner of the IBC ton container, and its main resin has a density of 0.945 g / cm³ to 0.955 g / cm³ and a melt flow rate of 0.18 g / 10 min to 0.45 g / 10 min.

[0007] Preferably, in step S3, the recycled compound comprises, by mass parts: 22-30 parts of the recycled material in the first melt flow rate range, 28-36 parts of the recycled material in the second melt flow rate range, 12-20 parts of the recycled material in the third melt flow rate range, 6-12 parts of the reinforcing high-density polyethylene material, 2-5 parts of the polyolefin toughening material, 0.3-0.8 parts of the antioxidant compound, 0.1-0.4 parts of the acid absorbent, and 0.2-0.8 parts of the deodorizing adsorbent; the metering accuracy of the metering compound is within ±0.3%, and the mixing time is 3-8 minutes.

[0008] Preferably, the reinforcing high-density polyethylene material has a density of 0.952 g / cm³ to 0.959 g / cm³, a melt flow rate of 0.04 g / 10 min to 0.12 g / 10 min, and a weight-average molecular weight of 180,000 to 320,000; the polyolefin toughening material is an ethylene-octene copolymer polyolefin elastomer with a density of 0.865 g / cm³ to 0.890 g / cm³ and a melt flow rate of 0. The antioxidant compound consists of hindered phenolic primary antioxidant and phosphite auxiliary antioxidant in a mass ratio of 1:1 to 2:1; the acid absorbent is calcium stearate with an average particle size of 3μm to 8μm; the deodorizing adsorbent is modified zeolite powder with an average particle size of 2μm to 8μm and a specific surface area of ​​300m² / g to 700m² / g.

[0009] Preferably, in step S4, the plasticizing temperature is controlled in segments according to the material's forward direction: Zone 1: 175℃~182℃, Zone 2: 183℃~190℃, Zone 3: 191℃~198℃, Zone 4: 199℃~204℃, and Storage Head Zone: 198℃~205℃; the screw speed is 28rpm~45rpm, the screw compression ratio is 2.5:1~3.2:1; the pressure stabilization and storage time is 40s~90s, the melt pressure fluctuation at the storage head is controlled within ±2.0%, and the melt temperature fluctuation is controlled within ±3℃.

[0010] Preferably, in step S5, the relative thickness coefficient of each thickness control zone is defined by normalization with the average wall thickness of the billet in the middle barrel region being 1.00; the relative thickness coefficient of the neck region is 1.18–1.25, the relative thickness coefficient of the upper shoulder region is 1.12–1.20, the relative thickness coefficient of the upper barrel region is 0.98–1.05, the relative thickness coefficient of the middle barrel region is 0.92–0.98, and the relative thickness coefficient of the lower barrel region is 1. The relative thickness coefficient of the bottom valve seat area is 1.25 to 1.38. Along the axial length direction of the blank, the neck area accounts for 6% to 10% of the total length, the upper shoulder area accounts for 12% to 18% of the total length, the upper barrel area accounts for 16% to 22% of the total length, the middle barrel area accounts for 20% to 28% of the total length, the lower barrel area accounts for 16% to 22% of the total length, and the bottom valve seat area accounts for 12% to 18% of the total length.

[0011] Preferably, in step S6, the pre-blowing gas pressure is 0.08MPa to 0.14MPa, the pre-blowing time is 1.5s to 3.0s, and the dew point of the pre-blowing gas is not higher than -20℃; in step S7, the main blowing gas pressure is 0.38MPa to 0.55MPa, the main blowing time is 8s to 15s, and the dew point of the main blowing gas is not higher than -20℃; in step S8, the holding pressure is 0.22MPa to 0.32MPa, the holding time is 8s to 16s, the cooling gas temperature is 8℃ to 15℃, the internal cooling time is 8s to 18s, and the cooling gas dew point is not higher than -20℃; at the end of the holding and shaping process, the inner surface temperature of the product is 35℃ to 55℃, the outer surface temperature of the product when demolding is 40℃ to 60℃, and the molding cycle of a single IBC ton square inner liner is 55s to 85s.

[0012] Preferably, in step S9, the mold temperature for the neck area is 18℃~24℃, the mold temperature for the upper shoulder area is 16℃~22℃, the mold temperature for the upper barrel area is 15℃~18℃, the mold temperature for the middle barrel area is 14℃~17℃, the mold temperature for the lower barrel area is 14℃~18℃, and the mold temperature for the bottom valve seat area is 12℃~16℃; in step S10, the leak detection medium is air, the leak detection pressure is 30kPa, the pressure holding time is 60s, and the pressure drop judgment value is not greater than 0.8kPa; the weight detection corresponds to a square inner liner of an IBC ton container with a nominal volume of 1000L, and the standard weight of the finished product is 12.4kg~13.2kg, with allowable weight deviation. The thickness is ±0.20 kg; ultrasonic thickness measurement includes 16 measuring points on the four main surfaces, 8 measuring points on the four corners, and 4 measuring points on the bottom valve seat area. The 16 measuring points on the four main surfaces are set at 20%, 40%, 60%, and 80% heights of the vertical line at the center of each main surface, respectively. The 8 measuring points on the four corners are set at 35% and 70% heights of the vertical line at each corner, respectively. The 4 measuring points on the bottom valve seat area are distributed at equal angles along the outer periphery of the valve seat center. The minimum wall thickness on the main surfaces is not less than 2.7 mm, the minimum wall thickness at the corners is not less than 3.4 mm, and the minimum wall thickness in the bottom valve seat area is not less than 4.0 mm.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention classifies the melt flow rate of the recycled material and adds high molecular weight high density polyethylene reinforcing material, polyolefin toughening material, antioxidant compounding agent, acid absorbent and deodorizing adsorbent to form a functional compensation type recycled material suitable for the square inner liner of IBC ton, which improves melt strength, thermo-oxidative stability, toughness and processing stability; (2) The present invention does not use a single constant blank thickness, but establishes a six-zone thickness program for the neck area, upper shoulder area, upper barrel body area, middle barrel body area, lower barrel body area and bottom valve seat area according to the stress and deformation requirements of different parts of the square inner liner of IBC ton, so that the material is allocated according to the part requirements before molding, which significantly improves the thinning problem of the shoulder, four corners and bottom valve seat area; (3) The present invention The three-stage blow molding method of pre-blowing shaping, main blow expansion and pressure holding internal cooling is adopted. Compared with the traditional one-time rapid blowing method, it can reduce the risk of local thinning caused by the excessive stretching of recycled material in the square mold cavity and improve the molding stability of the four corners, shoulders and bottom transition areas; (4) The present invention uses mold temperature control to implement differentiated mold temperature control for the neck area, shoulder area, barrel area and bottom valve seat area, so that different areas can be shaped according to their molding requirements and shrinkage characteristics, which improves the dimensional stability, surface quality and wall thickness uniformity of the square inner liner; (5) The present invention forms an online quality judgment method for waste plastic recycled material by leak detection, weighing and fixed point ultrasonic thickness measurement, which can timely identify wall thickness abnormalities and weight abnormalities caused by the fluctuation of recycled material, and improve product consistency and traceability. Attached Figure Description

[0014] Figure 1 This is a flowchart of the overall process of the present invention. Detailed Implementation

[0015] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0016] This invention provides a blow molding process for the inner liner of an IBC (Iron Chamber) container, comprising the following steps: Sorting and pretreatment of recycled materials: Waste IBC inner liner recycled material, waste high-density polyethylene drum recycled material, and production edge material recycled material are respectively subjected to debriding, crushing, metal separation, hot washing, friction cleaning, rinsing, dehydration, and hot air drying to obtain three types of dried recycled materials. Specifically: the crushed particle size of the waste IBC inner liner recycled material is 18mm–25mm; the crushed particle size of the waste high-density polyethylene drum recycled material is 16mm–22mm; and the crushed particle size of the production edge material is 10mm–18mm; the moisture content after drying is no higher than 0.15%.

[0017] Melt flow rate classification: The melt flow rate of the three types of dried recycled materials was tested and classified according to the melt flow rate to form recycled materials in the first melt flow rate range (melt flow rate from 0.20 g / 10 min to 0.35 g / 10 min), the second melt flow rate range (melt flow rate from 0.36 g / 10 min to 0.55 g / 10 min), and the third melt flow rate range (melt flow rate from 0.56 g / 10 min to 0.80 g / 10 min).

[0018] Functional compensating recycled compound: The recycled materials in the first melt flow rate range, the second melt flow rate range, and the third melt flow rate range are metered and mixed with high molecular weight high density polyethylene reinforcing material, polyolefin toughening material, antioxidant compounding agent, acid absorbent and deodorizing adsorbent to obtain recycled compound.

[0019] The recycled compound, by weight, includes: 22-30 parts of recycled material in the first melt flow rate range, 28-36 parts of recycled material in the second melt flow rate range, 12-20 parts of recycled material in the third melt flow rate range, 6-12 parts of reinforcing high-density polyethylene material, 2-5 parts of polyolefin toughening material, 0.3-0.8 parts of antioxidant compounding agent, 0.1-0.4 parts of acid absorbent, and 0.2-0.8 parts of deodorizing adsorbent; the metering accuracy of the compounding is within ±0.3%, and the mixing time is 3-8 minutes.

[0020] Among them: high molecular weight high-density polyethylene reinforcing material is used to improve the strength and stress cracking performance of recycled melt (density of 0.952 g / cm³ to 0.959 g / cm³, melt flow rate of 0.04 g / 10 min to 0.12 g / 10 min, weight-average molecular weight of 180,000 to 320,000); polyolefin toughening material is used to improve low-temperature impact toughness and anti-brittle fracture performance (density of 0.865 g / cm³ to 0.890 g / cm³, melt flow rate of 0.5 g / 10 min to 5.0 g / 10 min, Shore A hardness of 70 to 9). 0); Antioxidant compound is used to compensate for the decrease in oxidative stability caused by the thermal history of recycled materials (the antioxidant compound consists of hindered phenolic primary antioxidant and phosphite auxiliary antioxidant, with a mass ratio of 1:1 to 2:1); Acid absorbent is used to suppress the influence of acidic residues in recycled materials on processing stability (the acid absorbent is calcium stearate, with an average particle size of 3μm to 8μm); Odor remover is used to reduce the influence of residual odor and trace volatiles from recycled materials on the finished product (the odor remover is modified zeolite powder, with an average particle size of 2μm to 8μm and a specific surface area of ​​300m² / g to 700m² / g). By combining recycled materials with different melt flow rate ranges, the melt viscosity distribution tends to be continuous, thereby improving the extrusion stability and blowing uniformity of the preform.

[0021] Shear plasticizing and pressure stabilization storage: The recycled compound is fed into the plasticizing system of the storage-type extrusion blow molding equipment for low-shear plasticizing, and pressure stabilization storage is completed in the storage head.

[0022] The plasticizing temperature is controlled in segments according to the material's direction of travel: Zone 1: 175℃ to 182℃; Zone 2: 183℃ to 190℃; Zone 3: 191℃ to 198℃; Zone 4: 199℃ to 204℃; Storage head zone: 198℃ to 205℃. During plasticizing, the screw speed is controlled at 28 rpm to 45 rpm, the melt pressure fluctuation at the storage head is controlled within ±2.0%, and the melt temperature fluctuation is controlled within ±3℃.

[0023] Six-zone preform thickness programmed extrusion: Utilizing the preform program control function built into the storage-type extrusion blow molding equipment, the preform is divided into six thickness control zones along its axial length, and six-zone preform thickness programmed extrusion is implemented. The six thickness control zones are, in order: neck zone; upper shoulder zone; upper barrel zone; middle barrel zone; lower barrel zone; and bottom valve seat zone.

[0024] The relative thickness coefficients for the six thickness control zones are set as follows: neck zone: 1.18 to 1.25; upper shoulder zone: 1.12 to 1.20; upper barrel zone: 0.98 to 1.05; middle barrel zone: 0.92 to 0.98; lower barrel zone: 1.00 to 1.08; bottom valve seat zone: 1.25 to 1.38. This ensures higher material distribution in the shoulder and bottom valve seat zones, and a relatively moderate material distribution in the middle barrel zone, thereby improving the overall wall thickness uniformity of the square inner liner. Along the axial length of the blank, the neck zone accounts for 6% to 10% of the total length, the upper shoulder zone accounts for 12% to 18%, the upper barrel zone accounts for 16% to 22%, the middle barrel zone accounts for 20% to 28%, the lower barrel zone accounts for 16% to 22%, and the bottom valve seat zone accounts for 12% to 18%. By increasing the blank thickness coefficient in the corner region, the material can preferentially compensate for the stretching and thinning at the corner during the blowing process, thereby ensuring the minimum wall thickness at the corner.

[0025] Pre-blowing and shaping: After the mold closes, pre-blowing gas is introduced into the cavity of the preform for pre-blowing and shaping. Pre-blowing parameters are: pre-blowing pressure: 0.08MPa to 0.14MPa; pre-blowing time: 1.5 seconds to 3.0 seconds; gas dew point not higher than -20℃. The purpose of the pre-blowing stage is to allow the preform to expand to near the mold cavity contour, reducing the localized instantaneous stretching amplitude during the subsequent main blowing stage and minimizing the rapid thinning of recycled material at the shoulders and corners.

[0026] Main blowing expansion: After pre-blowing, main blowing gas is introduced into the inner cavity of the preform to ensure the preform fully conforms to the mold cavity. Main blowing parameters are: main blowing pressure: 0.38MPa to 0.55MPa; main blowing time: 8 seconds to 15 seconds; gas dew point not higher than -20℃. The main blowing stage focuses on completing the overall forming of the main surface of the barrel, the four corner areas, and the bottom contour.

[0027] Pressure holding and internal cooling: After the main blowing process, pressure holding and internal cooling are performed, and cooling gas is introduced into the inner cavity for internal cooling. The pressure holding and internal cooling parameters are as follows: pressure holding: 0.22MPa to 0.32MPa; pressure holding time: 8 seconds to 16 seconds; internal cooling gas temperature: 8℃ to 15℃; internal cooling time: 8 seconds to 18 seconds; gas dew point not higher than -20℃. Through pressure holding and internal cooling, the square inner liner made of recycled material achieves more stable dimensions and a more uniform crystallization state before demolding. At the end of pressure holding and internal cooling, the inner surface temperature of the product is 35℃ to 55℃, and the outer surface temperature of the product at demolding is 40℃ to 60℃. The molding cycle of a single IBC ton square inner liner is 55s to 85s.

[0028] Zoned mold temperature control: Throughout the molding process, mold temperature control equipment is used to regulate the temperature of different areas of the mold. The mold temperature is set by region as follows: neck area 18℃~24℃, upper shoulder area 16℃~22℃, upper barrel area 15℃~18℃, middle barrel area 14℃~17℃, lower barrel area 14℃~18℃, and bottom valve seat area 12℃~16℃. By differentially controlling the mold temperature of different areas, the neck area maintains good dimensional integrity, the shoulder and bottom valve seat areas are shaped more quickly, and the barrel area achieves more stable surface quality and thickness distribution.

[0029] Trimming and Online Inspection: After demolding, the product is trimmed, followed by leak detection, weight inspection, and ultrasonic thickness measurement. Online inspection parameters are: leak detection pressure: 30 kPa; leak detection holding time: 60 seconds; pressure drop threshold: not greater than 0.8 kPa; standard finished product weight: 12.4 kg to 13.2 kg; allowable weight deviation: ±0.20 kg.

[0030] The ultrasonic thickness measurement points are set as follows: 16 measuring points on the four main surfaces (these 16 measuring points are set at 20%, 40%, 60%, and 80% heights of the vertical line at the center of each main surface); 8 measuring points on the four corners (these 8 measuring points are set at 35% and 70% heights of the vertical line at each corner); and 4 measuring points in the bottom valve seat area (these 4 measuring points are evenly distributed along the outer perimeter of the valve seat center). The wall thickness qualification standards are: minimum wall thickness on the main surfaces not less than 2.7 mm; minimum wall thickness at the corners not less than 3.4 mm; and minimum wall thickness in the bottom valve seat area not less than 4.0 mm.

[0031] Example 1: Raw materials include: recycled waste IBC inner liner material; recycled waste high-density polyethylene drum material; recycled production edge material; high molecular weight high-density polyethylene reinforcing material; polyolefin toughening material; antioxidant compound; acid absorbent; deodorizing adsorbent.

[0032] Among them: the recycled material of waste IBC inner liner comes from the recycled ton drum inner liner; the recycled material of waste high-density polyethylene drum comes from waste chemical packaging drums; and the recycled material of production edge material comes from the trimming scraps of products made in this process.

[0033] Pre-treatment process: First, remove valves, seals, labels, and metal accessories from the recycled waste IBC liners; remove lids, handles, seals, and labels from the recycled waste high-density polyethylene drums; remove any foreign matter mixed in with the recycled production edge materials. Then, each material is pulverized, with the following particle size controls: recycled waste IBC liners: 20mm to 24mm; recycled waste high-density polyethylene drums: 18mm to 22mm; recycled production edge materials: 12mm to 16mm. After pulverization, the material undergoes sequential metal separation, 80℃ hot washing, friction cleaning, rinsing, centrifugal dehydration, and 90℃ hot air drying for 45 minutes. The moisture content after drying is controlled below 0.12%.

[0034] Melt flow rate classification: The melt flow rate of the three types of recycled materials was tested separately and classified according to the following standards: 0.20 g / 10 min to 0.35 g / 10 min: recycled material in the first melt flow rate range; 0.36 g / 10 min to 0.55 g / 10 min: recycled material in the second melt flow rate range; 0.56 g / 10 min to 0.80 g / 10 min: recycled material in the third melt flow rate range. The three grades of material were then loaded into separate silos for batching.

[0035] Composition of recycled compound: The recycled compound comprises, by mass, the following: 26 parts of recycled material in the first melt flow rate range; 32 parts of recycled material in the second melt flow rate range; 16 parts of recycled material in the third melt flow rate range; 8 parts of high molecular weight high density polyethylene reinforcing material; 3 parts of polyolefin toughening material; 0.5 parts of antioxidant compounding agent; 0.2 parts of acid absorbent; and 0.3 parts of odor-removing adsorbent.

[0036] Among them: the high molecular weight high density polyethylene reinforcing material is blow-molded high molecular weight high density polyethylene; the polyolefin toughening material is ethylene-octene polyolefin elastomer; the antioxidant compound is composed of hindered phenolic antioxidant and phosphite antioxidant; the acid absorbent is calcium stearate; and the odor-removing adsorbent is modified zeolite powder.

[0037] Plasticizing and Storage: The above-mentioned recycled compound is fed into a storage-type extrusion blow molding equipment. The plasticizing temperature is set in sections as follows: Zone 1: 178℃; Zone 2: 186℃; Zone 3: 194℃; Zone 4: 201℃; Storage head zone: 202℃. The screw speed is set to 36 rpm, and the melt pressure fluctuation at the storage head is controlled within ±1.5%.

[0038] Six-zone preform thickness program: Utilizing the equipment's preform program control function, the preform thickness is distributed across six zones along the axial direction, set as follows: Neck zone: 1.22; Upper shoulder zone: 1.16; Upper barrel zone: 1.02; Middle barrel zone: 0.95; Lower barrel zone: 1.05; Bottom valve seat zone: 1.32. This ensures that the neck, shoulder, and bottom valve seat zones receive more material, while the middle barrel zone maintains a moderate thickness, thus laying the foundation for the wall thickness distribution after the square inner liner is formed.

[0039] Blow Molding and Shaping Procedure: The blow molding and shaping procedure begins immediately after the mold closes, specifically as follows: Pre-blow shaping stage: Pre-blow pressure: 0.10 MPa; Pre-blow time: 2.2 seconds. Main blow expansion stage: Main blow pressure: 0.46 MPa; Main blow time: 11 seconds. Holding pressure shaping stage: Holding pressure: 0.28 MPa; Holding time: 12 seconds. Internal cooling stage: Internal cooling gas temperature: 10℃; Internal cooling time: 12 seconds.

[0040] Mold temperature control: Using mold temperature control equipment, the following temperature control is implemented for each area of ​​the mold: neck area mold temperature: 22℃; upper shoulder area mold temperature: 18℃; barrel body area mold temperature: 16℃; bottom valve seat area mold temperature: 14℃.

[0041] Demolding and Inspection: After molding, the inner liner is demolded and proceeds to the trimming process to remove burrs at the top, excess material at the bottom, and excess material in the valve seat area. The trimmed square inner liner undergoes the following tests in sequence: Leakage test: 30 kPa, pressure held for 60 seconds, pressure drop 0.6 kPa; Weight test: standard weight 12.8 kg, allowable deviation ±0.20 kg; Ultrasonic thickness test: 16 measuring points on the four main surfaces, 8 measuring points on the four corners, and 4 measuring points in the bottom valve seat area.

[0042] Test results: Minimum wall thickness of main surface: 2.9mm; Minimum wall thickness of corner: 3.6mm; Minimum wall thickness of bottom valve seat area: 4.2mm.

[0043] Products that pass inspection will proceed to the next assembly process; defective products will be recycled, crushed, and re-enter the recycling system.

[0044] Example 2: Based on Example 1, to increase the thickness of the bottom valve seat area and the lower barrel area, the thickness program of the six-zone preform is adjusted as follows: Neck area: 1.20; Upper shoulder area: 1.15; Upper barrel area: 1.00; Middle barrel area: 0.94; Lower barrel area: 1.08; Bottom valve seat area: 1.35. Simultaneously, the high molecular weight high-density polyethylene reinforcing material is increased to 10 parts, the polyolefin toughening material is increased to 4 parts, the main blowing time is extended to 12 seconds, and the pressure holding time is extended to 14 seconds. This is suitable for IBC ton tank liners with high requirements for bottom pressure bearing and valve seat strength.

[0045] The working principle is as follows: First, the waste plastic recycling material is classified according to the melt flow rate, so that the flow properties of the raw materials are changed from discrete to controllable; high molecular weight high density polyethylene reinforcing material and polyolefin toughening material are used to compensate for the function of the recycled material, thereby improving the melt strength and toughness; antioxidant compounding agent, acid absorbent and deodorizing adsorbent are used to improve the processing stability and use stability of the recycled material; through a six-zone preform thickness program, the material is preferentially distributed to the neck area, shoulder and bottom valve seat area before molding; through a staged blow molding method of pre-blowing, main blowing, holding pressure and internal cooling, the preform gradually fits the mold, reducing the thinning caused by sudden local stretching; through differentiated mold temperature control and online detection closed loop, the stable manufacturing of large volume square IBC inner liner is achieved.

Claims

1. A blow molding process for the inner liner of an IBC (Iron Chamber Container) tank, characterized in that, Includes the following steps: S1. The waste IBC inner liner recycled material, the waste high-density polyethylene drum recycled material and the production edge material recycled material are pretreated to obtain three types of dry recycled materials; S2. The melt flow rate of the three types of dried recycled materials obtained in step S1 is tested respectively, and they are grouped according to the test results; S3. The recycled materials obtained in step S2 are metered and mixed with reinforcing high-density polyethylene material, polyolefin toughening material, antioxidant compound, acid absorbent and deodorizing adsorbent to obtain recycled compound material. S4. The recycled compound is fed into a storage-type extrusion blow molding equipment for plasticization and pressure stabilization storage; S5. Using the preform program control function of the storage-type extrusion blow molding equipment, the preform is divided into the neck area, upper shoulder area, upper barrel area, middle barrel area, lower barrel area and bottom valve seat area along the axial direction, and the preform thickness program extrusion is implemented in the zone. S6. After the mold is closed, pre-blown gas is introduced into the cavity of the parison for pre-blowing and shaping; S7. After pre-blowing, main blowing gas is introduced into the inner cavity of the preform for main blowing expansion; S8. After the main blowing is completed, pressure holding and shaping are carried out, and cooling gas is introduced into the inner cavity of the blank for internal cooling; S9. Implement zoned temperature control for different areas of the mold throughout the molding process; S10. After the product is demolded, trim the edges and then perform leak detection, weight detection and ultrasonic thickness measurement in sequence.

2. The blow molding process for the inner liner of an IBC (Iron Chamber) container as described in claim 1, characterized in that: In step S1, the pretreatment includes impurity removal, crushing, metal separation, hot washing, friction cleaning, rinsing, dehydration and hot air drying; The particle size of the recycled waste IBC inner liner is 18mm to 25mm, the particle size of the recycled waste high-density polyethylene drum is 16mm to 22mm, and the particle size of the recycled production edge material is 10mm to 18mm. The hot washing temperature is 75℃~85℃, the hot washing time is 15min~25min, and the mass fraction of the alkaline cleaning agent in the washing solution is 1.5%~3.0%. The friction cleaning speed is 800 rpm to 1200 rpm, and the friction cleaning time is 5 min to 10 min; The rinsing is a two- to three-stage rinsing process, and the water conductivity at the end of the rinsing process is not higher than 150 μS / cm. The hot air drying temperature is 85℃~95℃, and the hot air drying time is 40min~60min; The recycled material after hot air drying must meet the following conditions: moisture content not exceeding 0.15%, ash content not exceeding 1.0%, metal impurities not exceeding 0.05%, total paper and label residue not exceeding 0.10%, total non-polyethylene dissimilar plastics not exceeding 1.0%, and polyvinyl chloride not exceeding 0.02%.

3. The blow molding process for the inner liner of an IBC (Iron Chamber) container as described in claim 1, characterized in that: In step S2, the melt flow rate is measured at 190°C and 2.16 kg, and is divided into three melt flow rate ranges: the first melt flow rate range, the second melt flow rate range, and the third melt flow rate range. The melt flow rate of the recycled material in the first melt flow rate range is 0.20 g / 10 min to 0.35 g / 10 min, the melt flow rate of the recycled material in the second melt flow rate range is 0.36 g / 10 min to 0.55 g / 10 min, and the melt flow rate of the recycled material in the third melt flow rate range is 0.56 g / 10 min to 0.80 g / 10 min. The main resin of the recycled waste IBC inner liner is high-density polyethylene, with a density of 0.945 g / cm³ to 0.955 g / cm³ and a melt flow rate of 0.20 g / 10 min to 0.60 g / 10 min. The main resin of the recycled waste high-density polyethylene drum is high-density polyethylene, with a density of 0.948 g / cm³ to 0.955 g / cm³ and a melt flow rate of 0.20 g / 10 min to 0.80 g / 10 min; The recycled material from the production edge is the recycled material obtained by crushing the trimming residue of the square inner liner of the IBC ton. Its main resin density is 0.945g / cm³~0.955g / cm³, and its melt flow rate is 0.18g / 10min~0.45g / 10min.

4. The blow molding process for the inner liner of an IBC (Iron Chamber) container as described in claim 1, characterized in that: In step S3, the recycled compound comprises, by weight, 22 to 30 parts of the recycled material in the first melt flow rate range, 28 to 36 parts of the recycled material in the second melt flow rate range, 12 to 20 parts of the recycled material in the third melt flow rate range, 6 to 12 parts of the reinforcing high-density polyethylene material, 2 to 5 parts of the polyolefin toughening material, 0.3 to 0.8 parts of the antioxidant compound, 0.1 to 0.4 parts of the acid absorbent, and 0.2 to 0.8 parts of the deodorizing adsorbent. The metering accuracy of the mixing is within ±0.3%, and the mixing time is 3 min to 8 min.

5. The blow molding process for the inner liner of an IBC (Iron Chamber) container as described in claim 4, characterized in that: The density of the reinforcing high-density polyethylene material is 0.952 g / cm³ to 0.959 g / cm³, the melt flow rate is 0.04 g / 10 min to 0.12 g / 10 min, and the weight-average molecular weight is 180,000 to 320,000. The polyolefin toughening material is an ethylene-octene copolymer polyolefin elastomer with a density of 0.865 g / cm³ to 0.890 g / cm³, a melt flow rate of 0.5 g / 10 min to 5.0 g / 10 min, and a Shore A hardness of 70 to 90. The antioxidant compound is composed of hindered phenolic primary antioxidant and phosphite auxiliary antioxidant, with a mass ratio of 1:1 to 2:

1. The acid absorbent is calcium stearate with an average particle size of 3μm to 8μm. The deodorizing adsorbent is modified zeolite powder with an average particle size of 2μm to 8μm and a specific surface area of ​​300m² / g to 700m² / g.

6. The blow molding process for the inner liner of an IBC (Iron Chamber) container as described in claim 1, characterized in that: In step S4, the plasticizing temperature is controlled in segments according to the material's direction of movement: Zone 1: 175℃~182℃, Zone 2: 183℃~190℃, Zone 3: 191℃~198℃, Zone 4: 199℃~204℃, and Storage Head Zone: 198℃~205℃. The screw speed is 28 rpm to 45 rpm, and the screw compression ratio is 2.5:1 to 3.2:1; The pressure stabilization and storage time is 40s to 90s, the melt pressure fluctuation at the storage head is controlled within ±2.0%, and the melt temperature fluctuation is controlled within ±3℃.

7. The blow molding process for the inner liner of an IBC (Iron Chamber) container as described in claim 1, characterized in that: In step S5, the relative thickness coefficient of each thickness control zone is defined with the average wall thickness of the billet in the middle barrel area being 1.00; The relative thickness coefficient of the neck area is 1.18 to 1.25, the relative thickness coefficient of the upper shoulder area is 1.12 to 1.20, the relative thickness coefficient of the upper barrel area is 0.98 to 1.05, the relative thickness coefficient of the middle barrel area is 0.92 to 0.98, the relative thickness coefficient of the lower barrel area is 1.00 to 1.08, and the relative thickness coefficient of the bottom valve seat area is 1.25 to 1.

38. Along the axial length of the blank, the neck area accounts for 6% to 10% of the total length, the upper shoulder area accounts for 12% to 18% of the total length, the upper barrel area accounts for 16% to 22% of the total length, the middle barrel area accounts for 20% to 28% of the total length, the lower barrel area accounts for 16% to 22% of the total length, and the bottom valve seat area accounts for 12% to 18% of the total length.

8. The blow molding process for the inner liner of an IBC (Iron Chamber) container as described in claim 1, characterized in that: In step S6, the pre-blowing gas pressure is 0.08MPa to 0.14MPa, the pre-blowing time is 1.5s to 3.0s, and the dew point of the pre-blowing gas is not higher than -20℃. In step S7, the main blowing gas pressure is 0.38MPa to 0.55MPa, the main blowing time is 8s to 15s, and the dew point of the main blowing gas is not higher than -20℃. In step S8, the holding pressure is 0.22MPa to 0.32MPa, the holding time is 8s to 16s, the cooling gas temperature is 8℃ to 15℃, the internal cooling time is 8s to 18s, and the cooling gas dew point is not higher than -20℃. When the pressure holding and shaping is completed, the inner surface temperature of the product is 35℃~55℃, and the outer surface temperature of the product is 40℃~60℃ when it is demolded. The molding cycle of a single IBC ton square inner liner is 55s~85s.

9. The blow molding process for the inner liner of an IBC (Iron Chamber) container as described in claim 1, characterized in that: In step S9, the mold temperature of the neck area is 18℃~24℃, the mold temperature of the upper shoulder area is 16℃~22℃, the mold temperature of the upper barrel area is 15℃~18℃, the mold temperature of the middle barrel area is 14℃~17℃, the mold temperature of the lower barrel area is 14℃~18℃, and the mold temperature of the bottom valve seat area is 12℃~16℃. In step S10, the leak detection medium is air, the leak detection pressure is 30 kPa, the pressure holding time is 60 s, and the pressure drop judgment value is no greater than 0.8 kPa. The weight test corresponds to the square inner liner of the IBC ton container with a nominal volume of 1000L. The standard weight of the finished product is 12.4kg to 13.2kg, and the allowable weight deviation is ±0.20kg. The ultrasonic thickness measurement includes 16 measuring points on the four main surfaces, 8 measuring points on the four corners, and 4 measuring points on the bottom valve seat area. The 16 measuring points on the four main surfaces are set at 20%, 40%, 60%, and 80% heights of the vertical line at the center of each main surface, respectively. The 8 measuring points on the four corners are set at 35% and 70% heights of the vertical line at each corner, respectively. The 4 measuring points on the bottom valve seat area are evenly distributed along the outer periphery of the valve seat center. The minimum wall thickness of the main surface shall not be less than 2.7 mm, the minimum wall thickness of the corner shall not be less than 3.4 mm, and the minimum wall thickness of the bottom valve seat area shall not be less than 4.0 mm.

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