A production process for high-purity high-density polyethylene plastic barrels

Abstract

The present invention relates to the technical field of production of high-purity plastic barrels, specifically to a production process of high-purity high-density polyethylene plastic barrels. The high-purity high-density polyethylene plastic barrel comprises high-purity high-density polyethylene, modified polyethylene, and glass fiber cloth, which are melt-extruded by a twin-screw extruder, blow-molded by nitrogen, and solidified by winding on the surface of the glass fiber cloth. The present invention performs branching treatment on high-density polyethylene, controls the amount of initiator and monomer olefin, and obtains modified polyethylene with good resistance to environmental stress; introduces glass fiber and modifies the glass fiber to improve the mechanical properties of the modified polyethylene; the flame retardant properties of the modified polyethylene are improved through the synergistic effect of organic phosphorus flame retardants and benzoxazine flame retardants; the amount of impurity particles dissolved in the obtained plastic barrel is low by using high-purity nitrogen blow molding treatment; and the obtained plastic barrel has high drop resistance by winding and solidifying the surface of the plastic barrel with glass fiber cloth.

Description

Technical Field

[0001] The invention relates to the technical field of production of high-purity plastic barrels, in particular to a production process of high-purity high-density polyethylene plastic barrels. Background Art

[0002] Plastic barrels are widely used for the storage and transportation of various liquids and are particularly suitable for packaging hazardous materials. They are resistant to breakage, rust, and light weight. They are also oil- and corrosion-resistant, making them ideal for packaging hazardous materials that require insulation, moisture-proofing, pressure resistance, and corrosion resistance. Plastic barrels are typically made from polyethylene, polypropylene, polyester, and other plastics through blow molding, injection molding, vacuum forming, and rotational molding.

[0003] Polyethylene (PE) is a thermoplastic resin made by polymerizing ethylene. Industrially, it also includes copolymers of ethylene with small amounts of α-olefins. Polyethylene is classified into high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE), depending on the polymerization method, molecular weight, and chain structure. High-density polyethylene (HDPE), commonly known as low-pressure polyethylene, has higher resistance to heat, oil, vapor permeation, and environmental stress cracking than LDPE and LLDPE. It also offers excellent electrical insulation, impact resistance, and cold weather resistance, making it commonly used in blow molding and injection molding.

[0004] While HDPE's simple linear molecular chain structure offers high density, high strength, and high modulus, it also suffers from unsatisfactory toughness. This is particularly true in packaging applications involving corrosive media such as lubricants and detergents, or when subjected to long-term internal pressure. Cracks can easily form, leading to product failure. Its low resistance to environmental stress reduces the material's service life.

[0005] Patent 201910991881.0 reports a high-density polyethylene resin composition for floating photovoltaic barrels and its preparation method. By introducing a combination of multiple light stabilizers such as light stabilizer M535 and light stabilizer 944, a polyethylene composite material with good aging resistance is obtained. However, these added ultraviolet absorbers are easy to migrate in the matrix, and the effect is not significant when used in low dosages. Increasing the dosage ratio will cause the polyethylene material's resistance to environmental stress to decrease, thereby reducing its service life.

[0006] High-density polyethylene has a limiting oxygen index of 17.4%, making it a flammable material. HDPE burns quickly, generates a large amount of heat and smoke, and is prone to melting and dripping during combustion, posing a great threat to life and property safety, limiting the use and development of polyethylene. Patent CN202210103784.5 reports a heat-resistant degradable plastic and a preparation method thereof. The plastic is prepared by mixing, extruding and granulating modified starch, polylactic acid, protein polyamide, sorbitol, diethylene glycol ether, glycerol monothioglycolate, triethylhexanoin, and functional fillers. The degradable plastic has good heat resistance and impact resistance. However, the addition of combustible additives does not take into account the flame retardant grade and safety of the material.

[0007] In the production process of existing plastic barrels, whether it is blow molding, injection molding, vacuum forming, or rotational molding, after the plastic barrel is formed, its drop resistance depends solely on its own structural design and material strength. It is difficult to enhance the drop resistance of the plastic barrel through subsequent processes, making the plastic barrel easy to break during use. At the same time, the plastic barrel also has the disadvantages of low notch impact strength and tensile strength, insufficient rigidity, easy aging, brittleness, easy deformation, and easy breakage.

[0008] Plastic barrels are used to hold various solvents, including chemical reagents, medical sterile reagents, and high-purity solvents used in various industries. These solvents need to be kept in a high-purity state to prevent impurity particles from seeping out of the composition or additives of the polyethylene plastic barrels and destroying the purity of the contained solvents. Therefore, high-density polyethylene plastic barrels are also required to have high cleanliness and low impurity particle dissolution to expand the application range of plastic barrels.

[0009] In summary, in order to meet the needs of different application scenarios of plastic barrels, high-density polyethylene plastic barrels need to have high mechanical strength while maintaining excellent temperature resistance and oil resistance, and at the same time have anti-drop performance to increase service life; due to the low limiting oxygen index of high-density polyethylene materials, it is necessary to improve the flame retardant properties of plastic barrels; improve the environmental stress resistance of plastic barrels and reduce environmental damage to plastic barrels; high-cleanliness high-density polyethylene plastic barrels can maintain extremely low impurity particle dissolution and can be used for the storage and transportation of high-purity solvents.

[0010] Therefore, a production process of high-purity high-density polyethylene plastic barrels is proposed. Summary of the Invention

[0011] The present invention aims to provide a production process for high-purity high-density polyethylene plastic barrels. The process comprises the following steps: high-density polyethylene and a monomer olefin are polymerized under the action of an initiator to form branched high-density polyethylene; modified glass fiber, a flame retardant, an antioxidant, and a toughening agent are added; and the modified polyethylene is melt-extruded through a twin-screw extruder and injection-molded by an injection molding machine. By varying the amount of initiator and the initiation reaction temperature, the environmental stress cracking time of the modified polyethylene obtained is 1356 hours, indicating significantly improved environmental stress resistance. Glass fiber is introduced and modified to increase the compatibility of the glass fiber with the high-density polyethylene matrix material. The modified polyethylene obtained has a tensile strength of 52 MPa and a notched impact strength of 10.4 kJ / m 2 , with significantly improved mechanical properties; adding benzoxazine flame retardants and organophosphorus flame retardants to synergistically form a carbon flame retardant process, the resulting high-density polyethylene modified polyethylene has a limiting oxygen index of 35%, which has significantly improved flame retardant properties; using high-purity high-density polyethylene, branched high-density polyethylene, modified glass fiber, flame retardant, antioxidant, and toughening agent to melt extrude into modified polyethylene, and blow molding under the action of nitrogen flow, the prepared high-purity high-density polyethylene plastic barrel has a 0d impurity particle dissolution amount of 8 pieces / ml; the 30d impurity particle dissolution amount is 15 pieces / ml, showing a significantly reduced impurity particle dissolution amount; glass fiber cloth is used to wrap the barrel surface to form a stable glass fiber anti-drop layer. In the 1.5m drop test of the obtained high-density polyethylene plastic barrel, both the straight drop and the angle drop showed that the barrel body had no cracks or leakage, showing significantly improved drop resistance.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] A production process for high-purity high-density polyethylene plastic barrels, characterized in that: the plastic barrels comprise high-purity high-density polyethylene, modified polyethylene, and glass fiber cloth;

[0014] The modified polyethylene comprises 80-120 parts of branched high-density polyethylene, 10-25 parts of modified glass fiber, 5-25 parts of flame retardant, 5 parts of compatibilizer, and 2 parts of antioxidant;

[0015] The branched high-density polyethylene is prepared by melt extrusion of 5-25 parts of lauroyl peroxide, high-density polyethylene, and 10-40 parts of monomer olefin;

[0016] The production process of the plastic barrel comprises the following steps:

[0017] In a clean environment, the modified polyethylene is added to a modified polyethylene raw material storage tank and stirred evenly to obtain a first mixture; the high-purity high-density polyethylene is added to a high-purity polyethylene raw material storage tank and stirred evenly to obtain a second mixture; the first mixture and the second mixture are respectively introduced into a first screw extruder and a second screw extruder to completely melt to obtain molten modified polyethylene and molten high-purity high-density polyethylene;

[0018] In a clean environment, the molten modified polyethylene and the molten high-purity high-density polyethylene are added to a mold with the barrel mouth facing downward, and the blow molding machine blows in a flow rate of 20-50m 3 / h of high-purity nitrogen for blow molding, and continuously blow to make a plastic barrel; the plastic barrel is passed through the outside of the mold with a flow rate of 5-15m 3 / h of cooling water to cool down and solidify to produce polyethylene plastic barrels;

[0019] The polyethylene plastic barrel is cleaned and polished to obtain a rough surface plastic barrel; glass fiber cloth is pasted on the rough surface plastic barrel to obtain a fiber-treated plastic barrel; the fiber-treated plastic barrel is placed in a mold for hot pressing and solidification, demolded, and cooled at room temperature to obtain a high-purity high-density polyethylene plastic barrel.

[0020] Preferably, the monomer olefin is selected from one of 1-propylene, 1-butene, 1-pentene and 1-hexene.

[0021] Preferably, the method for preparing branched high-density polyethylene comprises the following steps:

[0022] The lauroyl peroxide, the high-density polyethylene, and the monomer olefin compound are placed in a vacuum drying oven and dried at 60° C. for 2 hours to obtain a dry material; the dry material is added to a high-speed mixer and stirred at 200 r / min for 30 minutes to obtain a mixture; the mixture is added to a twin-screw extruder, subjected to a melt reaction process at a temperature range of 160° C.-200° C., a main engine speed of 80 r / min, and reacted for 2 hours to obtain a reactant; the reactant is crushed by a crusher to obtain a branched high-density polyethylene.

[0023] Preferably, the preparation of the modified glass fiber comprises the following steps:

[0024] The glass fiber was added into a muffle furnace and burned at 350° C. for 10 minutes to remove the paraffin on the surface to obtain the fired glass fiber; the fired glass fiber was added into a 10% HCl solution and soaked for 2 hours, and vacuum dried at 100° C. for 1 hour to obtain the acidic glass fiber; the silane coupling agent was dissolved in a solution of anhydrous ethanol and deionized water in a ratio of 1:1, and the mixture was uniformly mixed at 200 rpm to obtain a mixed solution; the acidic glass fiber was added into the mixed solution, ultrasonicated for 2 hours, taken out, and dried at 100° C. to obtain the modified glass fiber.

[0025] Preferably, the silane coupling agent is selected from one of 3-aminopropyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and methacryloxypropyltrimethoxysilane; and the amount of the silane coupling agent is 1-8 parts.

[0026] Preferably, the flame retardant includes flame retardant 1 and flame retardant 2; the flame retardant 1 is selected from one of benzoxazine derivatives, polyvinyl chloride, polyphenylene ether, and phenolic resin; the flame retardant 2 is selected from one of triphenyl phosphate, tricresyl phosphate, phenyl aluminum phosphinate, and dimethyl methylphosphonate; the component ratio of the flame retardant 1 to the flame retardant 2 is 1-4:1-4.

[0027] Preferably, the operating parameters of the twin-screw extruder are a screw speed of 250 r / min, a feed speed of 40 r / min, the temperatures of the first temperature zone to the eighth temperature zone are: 170°C, 175°C, 185°C, 185°C, 195°C, 200°C, 190°C, 180°C, and the head temperature is 180°C.

[0028] Preferably, the operating parameters of the twin-screw extruder 2 are a screw speed of 250 r / min, a feed speed of 40 r / min, the temperatures of the first temperature zone to the eighth temperature zone are: 120°C, 130°C, 140°C, 145°C, 150°C, 160°C, 155°C, 150°C, and the head temperature is 150°C.

[0029] Preferably, the working parameters of the injection molding machine are: the temperatures of zones 1 to 3 are 180°C, 185°C, and 200°C respectively, the nozzle temperature is 180°C; the holding time is 10s, the cooling time is 20s, the holding pressure is 120MPa, the injection temperature is 185°C, and the injection pressure is 45% of the maximum pressure.

[0030] Preferably, the temperature of the screw extruder 1 is 160-200°C, and the temperature of the screw extruder 2 is 120-160°C.

[0031] Preferably, the glass fiber cloth is a strip of glass fiber cloth with a width of 12 cm; the glass fiber cloth is spirally wound on the side wall of the plastic barrel, and each circle of the glass fiber cloth overlaps each other with a width of 6 cm; when the glass fiber cloth is pasted to the bottom of the plastic barrel, the glass fiber cloth is cut into strips with a width greater than the diameter of the bottom of the plastic barrel, the center of the glass fiber cloth strip is aligned with the center of the circle of the bottom of the plastic barrel, and the two ends are extended to the side wall of the plastic barrel. The glass fiber cloth on the bottom of the plastic barrel is pasted in a cross-shaped pattern until the glass fiber cloth strip completely covers the bottom of the plastic barrel.

[0032] Preferably, the curing temperature of the hot pressing curing is 90-120° C., the curing time is 30-90 min, and the curing pressure is 40-60 MPa.

[0033] Preferably, the compatibilizer is selected from maleic anhydride grafted ethylene-octene copolymer; and the antioxidant is selected from antioxidant 1010.

[0034] A high-purity, high-density polyethylene plastic barrel, comprising the high-purity, high-density polyethylene, the modified polyethylene, and the glass fiber cloth; the high-purity, high-density polyethylene plastic barrel is prepared by any of the above production processes; the environmental stress cracking time of the modified polyethylene in the plastic barrel is 1356 hours; the tensile strength of the modified polyethylene in the plastic barrel is 52 MPa, and the notched impact strength is 10.4 kJ / m 2 ; The limiting oxygen index of the modified polyethylene of the plastic barrel is 35%; the 0d impurity particle dissolution amount of the high-density polyethylene plastic barrel is 8 pieces / ml; the 30d impurity particle dissolution amount is 15 pieces / ml; in the 1.5m drop test of the high-density polyethylene plastic barrel, there is no cracking or leakage in the barrel body when falling in a straight line or at an angle.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The present invention utilizes high-density polyethylene (HDPE) and monomer olefins to react with an initiator to obtain branched HDPE. Modified glass fiber, flame retardants, antioxidants, and toughening agents are then added. The modified polyethylene material is melt-extruded through a twin-screw extruder and then injection-molded using an injection molding machine. The degree of branching in the HDPE is altered by adjusting the type and amount of the monomer olefins and controlling the amount of initiator. Because the branched chains cannot be tightly packed into the crystal lattice during crystallization, the branched chains can be used to tighten the entanglement of the connecting molecules, thereby increasing the environmental stress resistance of the material. By varying the initiation reaction temperature, the resulting modified polyethylene exhibits an environmental stress cracking time of 1356 hours, significantly improving its environmental stress resistance.

[0037] 2. The present invention introduces glass fiber and modifies the glass fiber to increase the compatibility of the glass fiber and the high-density polyethylene matrix material, thereby improving the bonding ability between the materials. When subjected to external force, the matrix material transfers the force to the glass fiber, while the glass fiber itself has a large tensile strength and small deformation, thereby improving the mechanical properties of the modified polyethylene. By controlling the type and amount of silane coupling agent and adjusting the amount of modified glass fiber, the modified polyethylene obtained has a tensile strength of 52MPa and a notched impact strength of 10.4KJ / m 2 , with significantly improved mechanical properties.

[0038] 3. The present invention increases the limiting oxygen index of high-density polyethylene plastic by adding flame retardants. The organophosphorus flame retardant generates a glassy melt during combustion to isolate oxygen and simultaneously forms a carbon layer to isolate combustion. Benzoxazine has good carbonization properties and can cooperate with the organophosphorus flame retardant to participate in the carbonization flame retardant mode, forming a dense carbon layer on the surface of the burning object to achieve a better flame retardant effect. By controlling the type and amount of flame retardant, the limited oxygen index of the modified polyethylene obtained is 35%, which has significantly improved flame retardant properties.

[0039] 4. The present invention uses high-purity high-density polyethylene, branched high-density polyethylene, modified glass fiber, flame retardant, antioxidant, and toughening agent to melt-extrude modified polyethylene to form a high-purity high-density polyethylene plastic barrel. At the same time, high-purity nitrogen flow is used in the blow molding process to avoid particle contamination in the air, control the temperature of the screw extruder, and the flow rate of nitrogen and cooling water. The 0d impurity particle dissolution amount of the prepared high-purity high-density polyethylene plastic barrel is 8 pieces / ml; the 30d impurity particle dissolution amount is 15 pieces / ml, showing a significantly reduced impurity particle dissolution amount.

[0040] 5. The present invention uses epoxy resin adhesive to graft glass fiber cloth, and solidifies and bonds it to the surface of the plastic barrel. The glass fiber cloth is wrapped around the surface of the plastic barrel by covalent bonding to form a stable glass fiber anti-drop layer. The glass fiber has high strength and good elastic recovery rate. By controlling the curing temperature, curing time and curing pressure, the high-density polyethylene plastic barrel prepared is subjected to a 1.5m drop test. Both straight-line drop and corner drop show that the barrel body has no cracks or leakage, showing significantly improved drop resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The dissolution amount of impurities of different particle sizes (0d and 30d) in Example 46 is changed;

[0042] Figure 2 The dissolution amount of impurities of different particle sizes (0d and 30d) is shown in Comparative Example 8. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0045] The high-density polyethylene of the present invention is selected from DMDY1158, which is purchased from Sinopec Qilu Petrochemical Company.

[0046] The KH-550 described in the present invention is 3-aminopropyltriethoxysilane, CAS: 919-30-2.

[0047] The KH-560 described in the present invention is 3-(2,3-epoxypropoxy)propyltrimethoxysilane, CAS: 2530-83-8.

[0048] The KH-570 described in the present invention is methacryloxypropyltrimethoxysilane, CAS: 2530-85-0.

[0049] The KH-792 described in the present invention is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, CAS: 1760-24-3.

[0050] The BOZ described in the present invention is a benzoxazine derivative.

[0051] The TPP described in the present invention is triphenyl phosphate, CAS: 115-86-6, purchased from Anhui Zesheng Technology Co., Ltd.

[0052] The TCP described in the present invention is tricresyl phosphate, CAS: 1330-78-5, purchased from Tianjin Chemical Reagent Factory No. 1.

[0053] The DMMAP described in the present invention is dimethyl methylphosphonate, CAS: 756-79-6.

[0054] The PADP described in the present invention is aluminum phenylphosphinate, CAS: 25070-21-7.

[0055] The PVC described in the present invention is polyvinyl chloride, which is purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0056] The PPO described in the present invention is polyphenylene ether, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0057] The PFR described in the present invention is phenolic resin purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0058] See also Figure 1-2 The present invention provides a production process for high-purity high-density polyethylene plastic barrels, and the technical solution is as follows:

[0059] Examples 1-13

[0060] Preparation of modified glass fiber:

[0061] 50 parts of glass fiber were added to a muffle furnace and burned at 350° C. for 10 minutes to remove the paraffin on the surface to obtain fired glass fiber; 50 parts of the fired glass fiber were added to 10 ml of a 10% HCl solution and soaked for 2 hours, and vacuum dried at 100° C. for 1 hour to obtain acidic glass fiber; 5 parts of KH-570 were dissolved in a solution of a 1:1 mixture of anhydrous ethanol and deionized water, and the mixture was uniformly mixed at 200 rpm to obtain a mixed solution; 50 parts of the acidic glass fiber were added to the mixed solution, ultrasonicated for 2 hours, taken out, and dried at 100° C. to obtain the modified glass fiber.

[0062] Preparation of branched high-density polyethylene:

[0063] 5-25 parts of lauroyl peroxide, 80 parts of high-density polyethylene, and 10-40 parts of a monomer olefin compound are placed in a vacuum drying oven and dried at 60°C for 2 hours to obtain a dry material; the dry material is added to a high-speed mixer and stirred at 200 r / min for 30 minutes to obtain a mixed material; the mixed material is added to a twin-screw extruder, subjected to a melt reaction process at a temperature range of 160°C-200°C, a main engine speed of 80 r / min, and reacted for 2 hours to obtain a reactant; the reactant is crushed by a crusher to obtain a branched high-density polyethylene.

[0064] The branched high-density polyethylene, 20 parts of the modified glass fiber, 15 parts of a flame retardant, 10102 parts of an antioxidant, and 5 parts of a maleic anhydride grafted ethylene-octene copolymer are placed in a vacuum drying oven and dried at 60°C for 2 hours to obtain a dried raw material; the dried raw material is added to a high-speed mixer and stirred at 500 r / min for 30 minutes to mix uniformly to obtain a mixed material; the mixed material is added to a twin-screw extruder for melt blending, extrusion, cooling, and pelletizing to obtain pellets; the pellets are vacuum dried at 85°C for 5 hours and then injection molded by an injection molding machine to obtain modified polyethylene.

[0065] The specific differences between Examples 1-13 are shown in Table 1.

[0066] Comparative Example 1 refers to the preparation method and parameter conditions of Example 1, except that the monomer olefin is not added.

[0067] Comparative Example 2 refers to the preparation method and parameter conditions of Example 1, except that no branching treatment is performed.

[0068] Comparative Example 3 refers to Example 1, except that no initiation reaction is performed and branched high-density polyethylene is directly blended to obtain the branched high-density polyethylene.

[0069] Example 14 Environmental stress resistance test

[0070] The environmental stress resistance of the modified polyethylene samples prepared in Examples 1-13 and Comparative Examples 1-3 was tested using a NYK-06 environmental stress cracking tester in accordance with GB / T 1842-2008. The test samples were 38 × 13 × 2 mm in size, with a notch length and depth of 19 mm and 0.3 mm, respectively.

[0071] Bend the scored specimen into a "U" shape, secure it to a specimen holder, and place it in a test tube. Using a 10% volume fraction of nonylphenol polyoxyethylene ether (TX-10) aqueous solution as a reagent, test the specimen in a 50°C high-grade constant temperature water bath. Observe and record the number of specimens that crack and break. The time when the probability of breakage in a certain medium is 50% is defined as the environmental stress cracking time, or F 50 , unit is h, the test results are shown in Table 1.

[0072] Table 1 Environmental stress resistance test results of Examples 1-13 and Comparative Examples 1-3

[0073]

[0074] From the results in Table 1, it can be seen that the environmental stress resistance of the sample obtained by not performing branching treatment on the high-density polyethylene in Comparative Example 2 is poor. During blow molding, the material has internal stress due to uneven cooling shrinkage. During use, it is subjected to external stress caused by stacking loads, which is easily affected by the environment, resulting in reduced material performance. Compared with Comparative Example 2, the use of branched monomers in Comparative Examples 1 and 3 significantly improves the environmental stress resistance. At the same time, the samples prepared by initiating olefin polymerization with an initiator have better environmental stress resistance. From the results of Examples 1-4, it can be seen that the environmental stress resistance of samples with different types of monomers is not much different. The introduction of olefin monomers can increase the content of the branched part. Since the branched part cannot be tightly arranged into the lattice during the crystallization process, the branched chain can be relied on to make the entanglement of the connecting molecules tighter, and at the same time, the number of ligature molecules between crystals is increased, thereby strengthening the connection between crystals and improving the environmental stress resistance. From the results of Comparative Example 1 and Examples 5-7, it can be seen that with the increase of the amount of initiator, the environmental stress cracking time first increases and then decreases. This is because the excess initiator causes the coupling point in the reaction system to The increase in the amount of monomer olefins reduces the length of the branch chain, tends to the development of the structure, is not conducive to the molecular chain running through the grains and spherulites to form tie molecules, and makes it easier for the wafers to slip crack under environmental stress. At the same time, when the torque reaches equilibrium, the branching reaction time is too long, the molecular chain degrades, and the strengthening effect of the connecting molecules between the wafers is weakened, and the environmental stress resistance is weakened. The results of Examples 1 and 8-10 show that with the increase of the amount of monomer olefins, the environmental stress cracking time shows a trend of first increasing and then decreasing. The initiator content is limited. Further increasing the amount of monomer olefins is not conducive to the distribution of the molecular chains in the crystallization area, reducing the environmental stress resistance. The results of Examples 1 and 11-13 show that with the increase of temperature, the environmental stress cracking time first increases and then decreases. Experiments show that increasing the screw temperature can ensure uniform melt plasticization, but too low a melt temperature will increase molecular orientation during mold filling and increase residual stress after cooling and setting. Increasing the mold temperature is conducive to the close stacking of grains and reducing or eliminating internal defects, but too high a temperature can easily cause insufficient cooling during demolding, resulting in deformation and warping at ambient temperature. From the results in Table 1, it can be seen that by using 1-hexene as the monomer olefin, controlling the amount of initiator and monomer olefin, and maintaining the reaction temperature within 180-190°C, the environmental stress cracking time of the prepared modified polyethylene is 1356h, which has significantly improved environmental stress resistance.

[0075] Examples 15-27

[0076] Preparation of modified glass fiber:

[0077] 50 parts of glass fiber were added to a muffle furnace and burned at 350° C. for 10 minutes to remove the paraffin on the surface to obtain a fired glass fiber; the fired glass fiber was added to 10 ml of a 10% HCl solution and soaked for 2 hours, and vacuum-dried at 100° C. for 1 hour to obtain an acidified glass fiber; a silane coupling agent was dissolved in a solution of anhydrous ethanol and deionized water in a ratio of 1:1, and the mixture was uniformly mixed at 200 rpm to obtain a mixed solution; the alkaline glass fiber was added to the mixed solution, ultrasonicated for 2 hours, taken out, and dried at 100° C. to obtain the modified glass fiber.

[0078] The preparation method of the modified polyethylene refers to the preparation method parameter conditions of Example 1.

[0079] Examples 16-27 refer to the preparation method and parameter conditions of Example 15, with the differences as shown in Table 2.

[0080] Table 2 Relationship between the dosage of components in Examples 15-27

[0081]

[0082]

[0083] Comparative Example 4 refers to the preparation method and parameter conditions of Example 15, except that no silane coupling agent is added to modify the glass fiber.

[0084] Comparative Example 5 refers to the preparation method and parameter conditions of Example 15, except that no modified glass fiber is added.

[0085] Example 29 Mechanical Properties Test

[0086] Tensile strength test: The modified polyethylene samples prepared in Examples 15-27 and Comparative Examples 4-5 were prepared into dumbbell-shaped specimens with the shape and size of the national standard 1A type. The test was performed using a WDW universal testing machine at a tensile rate of 50 mm / min. The test results are shown in Table 3.

[0087] Notched impact strength test: The modified polyethylene samples prepared in Examples 15-27 and Comparative Examples 4-5 were prepared into strips with perpendicular surfaces and no edge defects using a ZHY-W universal prototyping machine. Then, a QYJ1251 notched prototyping machine was used to process an A-type notch with a notch angle of 45°±1°. The notched cantilever beam impact strength of the samples was measured using an XJJD-5J electronic impact testing machine in accordance with the national standard GB / T1843-2008, in kJ / m2. The test results are shown in Table 3.

[0088] Table 3 Test results of Examples 15-27 and Comparative Examples 4-5

[0089]

[0090]

[0091] From the results in Table 3, it can be seen that the tensile strength of Comparative Example 4 is slightly increased relative to that of Comparative Example 5. Since the glass fiber is not modified, there are a large number of polar groups on the surface of the glass fiber, which has poor binding with the polyethylene material. The tensile strength of the glass fiber itself is very high, so the tensile strength of the composite material does not increase much; while the notched impact strength is relatively reduced. Since the glass fiber is an inorganic filler, it will play a role of heterogeneous nucleation when the high-density polyethylene crystallizes. The number of crystal nuclei increases, the grains become smaller, the crystallinity increases, the rigidity of the material is greatly improved, and the deformation of the material is poor. In addition, with the addition of glass fiber, the interface strength between the high-density polyethylene and the glass fiber is relatively strong. The material is poor, when the material is subjected to impact, the cracks cannot extend on the surface of polyethylene and glass fiber, the spline cannot fully absorb energy, and the notched impact strength will decrease; the results of Examples 15-18 show that due to the use of methacryloxypropyltrimethoxysilane, siloxane is hydrolyzed into silanol under acidic conditions, and covalently bonds with the hydroxyl group on the surface of glass fiber. The free alkenyl group increases the compatibility of glass fiber and high-density polyethylene, thereby improving the mechanical properties of the material; the results of Examples 15 and 19-24 show that with the increase in the amount of modified glass fiber, the tensile strength of the material gradually increases, which is only because when subjected to external force, the matrix material transmits the force to the substrate. The tensile strength of the glass fiber is improved, and the glass fiber itself has a large tensile strength and a small deformation, so the tensile strength will be improved. The glass fiber plays a role in enhancing the load-bearing capacity in the composite material. In addition, the high-density polyethylene reacts with the free olefin bonds in the modified glass fiber, which reduces the surface energy of the fiber, improves the bonding ability of the high-density polyethylene and the glass fiber, and improves the tensile strength. However, with the increase in the amount of modified glass fiber, the notched impact strength slowly decreases. Due to the weak interfacial bonding strength between the matrix and the glass fiber, the cracks caused by the fiber breakage can change direction and expand along the interface, and the ability to absorb impact energy is improved. However, due to the high brittleness of the glass fiber, , which reduces the notched impact strength; the results of Examples 15 and 25-27 show that with the increase in the amount of silane coupling agent, the notched impact strength and tensile strength of the material show a trend of first increasing and then decreasing. The main reason is that the introduction of olefinic bonds increases the compatibility of glass fiber and high-density polyethylene and improves the bonding ability between the materials. However, when too much silane coupling agent is added, it is in an oversaturated state, and the excess coupling agent has a negative impact on the material. From the results of Table 3, it can be seen that the tensile strength of the modified polyethylene prepared by adding KH-570 modified glass fiber is 52MPa and the notched impact strength is 10.4KJ / m 2 , with significantly improved mechanical properties, the resulting high-density plastic barrel has good mechanical properties.

[0092] Example 29

[0093] Preparation of benzoxazine derivatives:

[0094] 3 mol of aniline, 3.0 mol of 1,2-diphenyl-1,2-bis(4-hydroxyphenyl)ethylene (phenolic hydroxyl group), and 6 mol of paraformaldehyde were stirred and mixed uniformly in a beaker at room temperature to prepare a mixed solution; 1 / 10 of the mixed solution was added to a 1000 ml flask, the temperature was raised to 70° C., and the reaction was carried out for 10 minutes to prepare a reaction solution 1; 1 / 10 of the second batch of the mixed solution was added to the reaction solution 1, and the reaction was carried out for 10 minutes to prepare a reaction solution 2; the remaining mixed solutions were added in sequence, and after the raw materials were added, the reaction temperature was maintained at 110° C. and the reaction was carried out under reflux for 20 minutes to prepare a reaction system; the reaction system was heated to 130° C., stirred and refluxed for 30 minutes to evaporate water, centrifuged, and vacuum dried at 80° C. for 2 hours to prepare a benzoxazine derivative.

[0095] The preparation of modified polyethylene refers to the preparation method and parameter conditions of Example 17.

[0096] Examples 30-43 refer to the preparation method and parameter conditions of Example 29, with the differences as shown in Table 4.

[0097] Comparative Example 6 refers to the preparation method and parameter conditions of Example 29, except that no benzoxazine flame retardant is added.

[0098] Comparative Example 7 refers to the preparation method and parameter conditions of Example 29, except that triphenyl phosphate is not added.

[0099] Example 44 Flame retardant performance test

[0100] The modified polyethylene prepared in Examples 29-43 and Comparative Examples 6-7 was sampled with a sample size of 150 mm × 6.5 mm × 3 mm. Referring to GB / T 2406.2-2009, an oxygen index meter (model JF-3, Nanjing Jiangning District Analytical Instrument Factory) was used to perform limiting oxygen index testing. The test results are shown in Table 4.

[0101] Table 4 Flame retardant performance test of samples of Examples 29-43 and Comparative Examples 6-7

[0102]

[0103]

[0104] The results in Table 4 show that the limiting oxygen index of the polyethylene obtained by using a single flame retardant in Comparative Examples 6 and 7 is significantly lower than that of Examples 29-43. When BOZ is added alone, the heat resistance of the modified polyethylene can be increased, but the crosslinking density is too low to achieve the desired flame retardant effect. Since high-density polyethylene has a low limiting oxygen index and is difficult to form carbon by itself, when DMMAP is added alone, it is difficult to form a carbon layer due to the lack of a carbon source, which plays a role in stopping combustion. At the same time, the organophosphorus flame retardant easily volatilizes at low temperatures, further affecting the flame retardant effect. Comparative Examples 29-35 The results show that the flame retardant properties of modified polyethylene can be effectively improved by combining organophosphorus flame retardants with other flame retardants. Since the polymetaphosphoric acid generated by the organophosphorus flame retardant under combustion conditions is a glassy melt, it can form a protective film on the surface of the flame-retardant material to isolate oxygen. At the same time, the generated phosphoric acid and polymetaphosphoric acid are both strong acids with strong dehydration properties, which can dehydrate and carbonize the polymer, forming a carbon layer on the polymer surface, thereby isolating oxygen and preventing combustion. In addition, the PO· free radicals generated by the organophosphorus flame retardant when heated can absorb a large amount of HO· and H· free radicals. The combustion reaction can be interrupted by the formation of a base. Comparing the results of Examples 29 and 36-39, it can be seen that with the increase in the amount of BOZ, the limiting oxygen index shows a trend of first increasing and then decreasing. Due to the good carbonization property of BOZ, it can participate in the carbonization flame retardant mode with the organophosphorus flame retardant. During the ring-opening curing, BOZ forms a cross-linked network, thereby inhibiting the volatilization of DMMAP. At the same time, the phenolic hydroxyl groups formed during the ring-opening curing process react with the phosphoric acid and polymetaphosphoric acid generated by the decomposition of DMMAP at high temperature to undergo an esterification reaction, thereby increasing the cross-linking density of the benzoxazine resin and forming a dense carbon layer on the surface of the burning object. And achieve a better flame retardant effect; compared with the results of Example 29 and Examples 40-43, it can be seen that with the increase of the total amount of flame retardant, the flame retardant properties of the modified polyethylene gradually increase. However, excessive BOZ leads to a decrease in compatibility with the system, thereby reducing the mechanical properties of the modified polyethylene and affecting the comprehensive performance of the high-purity high-density polyethylene plastic barrel; Comprehensive results in Table 4 show that when BOZ / DMMAP is used as a flame retardant compound and the amount of flame retardant and the ratio of components are controlled, the modified polyethylene obtained has a limiting oxygen index of 35%, which has significantly improved flame retardant properties.

[0105] Examples 45-55

[0106] The high-purity high-density polyethylene plastic barrel includes high-purity high-density polyethylene and modified polyethylene;

[0107] In a 10,000-class clean environment, 100 parts of branched high-density polyethylene, 5 parts of maleic anhydride grafted ethylene-octene copolymer, 15 parts of flame retardant, 20 parts of modified glass fiber, and 2 parts of antioxidant 1010 are poured into the corresponding raw material storage tank and stirred evenly to obtain a mixture 1; the high-purity high-density polyethylene is poured into the corresponding raw material storage tank and stirred and mixed evenly to obtain a mixture 2; the mixture 1 and the mixture 2 are vacuum dried at 100° C. for 2 hours to obtain a dry material; the dry materials are respectively introduced into two different screw extruders of a blow molding machine, the temperature of screw extruder 1 is set to 160-200° C., and the temperature of screw extruder 2 is set to 120-160° C., and the materials are completely melted to obtain melt-modified polyethylene and melt-modified high-purity high-density polyethylene;

[0108] In a 10,000-class clean environment, 60 parts of the molten modified polyethylene and 40 parts of the molten high-purity high-density polyethylene are added to a mold with the barrel mouth facing downwards, and the blow molding machine blows in a flow rate of 20-50m 3 / h of high-purity nitrogen gas for blow molding, and continue blowing for 20 minutes to make a plastic barrel; the plastic is introduced into the outside of the mold at a flow rate of 5-15m 3 / h of cooling water for cooling and solidification for 10 minutes to obtain high-purity high-density polyethylene plastic barrels.

[0109] The specific parameters of Examples 45-55 are shown in Table 5.

[0110] Comparative Example 8 refers to the preparation method and parameter conditions of Example 45, except that air blow molding is used.

[0111] Comparative Example 9 refers to the preparation method and parameter conditions of Example 45, except that conventional high-density polyethylene is used instead of high-purity high-density polyethylene.

[0112] Example 56 Microparticle Measurement

[0113] The impurity particle dissolution amount (number / ml) of the high-purity high-density polyethylene plastic barrels produced in Examples 45-55 and Comparative Examples 8-9 at 0 day and 30 days was measured using a particle analyzer (Liquid Sampler LS-60, produced by LIGHTHOUSE, USA). The impurity particle (particle) determination method is as follows:

[0114] In a Class 100 clean environment, a molded plastic barrel is filled with ultrapure water, and immediately after extraction and after storage for 30 days and then extracted again at 25°C, the barrel is left standing for 20 minutes, and a test sample is taken from the container as a test specimen. The microparticle counter is cleaned with ultrapure water before measurement; after cleaning, 10 ml of ultrapure water is injected into the microparticle counter to measure the number of particles A (pieces / mL) in the ultrapure water; 25 ml of the test specimen is used to clean the test device twice, and after cleaning, 10 ml of ultrapure water of the test specimen is taken out from Examples 45-55 and Comparative Examples 8-9, and injected into the microparticle counter to measure the number of particles B (pieces / mL) in the pure water in the container. The particle value P in 1 ml is calculated from the measured value: P = (BA) / 10; the test results of the total amount of 0d and 30d impurity particles are shown in Table 5; the changes in the dissolution amount of 0d and 30d impurities of different particle sizes in Example 46 are shown in Table 5. Figure 1 Comparative Example 8: Changes in the dissolution amount of impurities of different particle sizes 0d, 30d particles Figure 2 shown.

[0115] Table 5: Dissolution amount of impurity particles in Examples 45-55 and Comparative Examples 8-9

[0116]

[0117]

[0118] Depend on Figure 1 、 Figure 2 The results of the comparative examples 8-9 in Table 5 show that the amount of impurity particles dissolved in the high-density polyethylene plastic barrels prepared by using air as the blowing gas or using high-density polyethylene is significantly improved compared with Examples 45-55. The impurity particles increase under long-term storage conditions, affecting the performance of the plastic barrels. The results of comparative examples 45-50 show that the initial impurity particle dissolution amount of the plastic barrels prepared by using different screw extruder temperatures is low. Due to the use of high-temperature melting, nitrogen blowing reduces the impurity content of high-purity high-density polyethylene and modified polyethylene, and reduces the impurity particles. However, as time goes on, the polyethylene material under the melting condition of lowering the temperature decreases. Due to insufficient melting of the material, the molecules between the materials are not uniform. The introduction of bubbles during the blow molding process causes pores in the material. Under long-term storage conditions, the material's adsorption capacity for impurities increases, and the amount of impurity particles dissolved increases. Comparing the results of Example 45 and Examples 51-53, it can be seen that the size of the nitrogen flow rate has little effect on the amount of impurity particles dissolved. The results of Examples 45 and Examples 54-55 show that if the cooling water flow rate is too large, the plastic barrel will cool down quickly, releasing a large amount of gas. Bubbles are formed between the molecules of the plastic barrel and fill the pores. Long-term storage increases the content of impurity particles and affects the overall performance. If the cooling water flow rate is too low, the cooling and solidification time will be prolonged. Comprehensive Table 5, Figure 1-2The results show that the high-density polyethylene plastic barrels prepared by nitrogen blow molding, and the screw temperature, nitrogen flow rate and cooling water flow rate are controlled. The 0d impurity particle dissolution amount of the prepared high-density polyethylene plastic barrels is 8 pieces / ml; the 30d impurity particle dissolution amount is 15 pieces / ml, showing a significantly reduced impurity particle dissolution amount.

[0119] Examples 57-64

[0120] The plastic barrel prepared in Example 46 was cleaned and sanded into a rough surface to prepare a rough-surface plastic barrel; the rough-surface plastic barrel was coated with epoxy resin adhesive and adhered with glass fiber cloth to prepare a fiber-treated plastic barrel; the fiber-treated plastic barrel was placed in a mold for hot pressing and curing at a curing temperature of 90-120°C, a curing time of 30-90min, and a curing pressure of 40-60MPa to prepare a cured plastic barrel; the cured plastic barrel was demolded and cooled at room temperature to prepare a high-density polyethylene plastic barrel.

[0121] The specific parameters are shown in Table 6.

[0122] Comparative Example 10 refers to the preparation method and parameter conditions of Example 57, except that glass fiber cloth is not added for curing.

[0123] Example 65: Drop resistance test

[0124] The plastic barrels produced in Examples 57-64 and Comparative Example 10 were subjected to a drop resistance test. The volume of each plastic barrel was 100 L. The drop test was conducted at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 2%. The steps are as follows:

[0125] The plastic bucket was filled with clean water, filled to a capacity of 100L, and dropped from a height of 1.5m. The drop test consisted of an angled drop and a straight-line drop. In the angled drop, the centerline of the bucket formed an angle of 10° with the vertical, and the bucket was dropped freely onto a concrete floor. After each drop, the bucket was inspected for damage. In the straight-line drop, the bottom of the bucket was dropped vertically onto the concrete floor. After each drop, the bucket was inspected for damage. The test results are shown in Table 6.

[0126] Table 6 Anti-drop performance test of Examples 57-64 and Comparative Example 10

[0127]

[0128] The results in Table 6 show that in Comparative Example 10, no glass fiber cloth is used to wrap around the outside of the barrel to form a stable glass fiber anti-drop layer. The barrel body will crack and leak when the plastic barrel falls from an angle or falls in a straight line. The results in Examples 57-59 show that when the curing temperature is high, the barrel body will crack when the plastic barrel falls in a straight line. Due to the addition of epoxy resin adhesive, a cross-linking reaction can occur with the high-density polyethylene plastic barrel during the curing process, forming a stable covalent bonding effect between the glass fiber cloth and the plastic barrel. As the temperature rises, the cross-linking effect becomes stronger, the force offset weakens, and the plastic barrel material becomes brittle and easily cracked. Comparative Example 57 and Example From the results of Example 60-62, it can be seen that a too short curing time is not conducive to the cross-linking between the glass fiber cloth and the plastic barrel, thereby reducing the drop resistance of the plastic barrel. If the curing time is too long, the cross-linking points increase, the brittleness increases, and the barrel is easy to break. From the results of Example 57 and Examples 63-64, it can be seen that the change in curing pressure has little effect on the drop resistance, and the change in pressure does not affect the generation of cross-linking points. From the results of Table 6, it can be seen that by wrapping glass fiber cloth around the surface of the plastic barrel and controlling the curing time and curing temperature, the high-density polyethylene plastic barrel prepared was subjected to a 1.5m drop test. Both the straight-line drop and the corner drop showed that the barrel body had no cracks or leakage, showing significantly improved drop resistance.

[0129] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A production process for high-purity high-density polyethylene plastic barrels, characterized by: The plastic barrel includes high-purity high-density polyethylene, modified polyethylene, and glass fiber cloth; The modified polyethylene comprises 80-120 parts of branched high-density polyethylene, 10-25 parts of modified glass fiber, 5-25 parts of flame retardant, 5 parts of maleic anhydride grafted ethylene-octene copolymer, and 2 parts of antioxidant 1010; The branched high-density polyethylene, 20 parts of the modified glass fiber, 15 parts of a flame retardant, 2 parts of an antioxidant 1010, and 5 parts of a maleic anhydride grafted ethylene-octene copolymer were placed in a vacuum drying oven and dried at 60° C. for 2 hours to obtain a dried raw material; the dried raw material was added to a high-speed mixer and stirred at 500 r / min for 30 minutes to obtain a mixed material; the mixed material was added to a twin-screw extruder for melt blending and extrusion, cooled, and pelletized to obtain pellets; the pellets were vacuum dried at 85° C. for 5 hours and then injection molded by an injection molding machine to obtain modified polyethylene; The flame retardant comprises a flame retardant 1 and a flame retardant 2; the flame retardant 1 is a benzoxazine derivative; the flame retardant 2 is dimethyl methylphosphonate; the amount ratio of the flame retardant 1 to the flame retardant 2 is 1-4:1-4; The branched high-density polyethylene is prepared by melt extrusion of 15 parts of lauroyl peroxide, 80 parts of high-density polyethylene, and 20 parts of 1-hexene; 15 parts of the lauroyl peroxide, 80 parts of the high-density polyethylene, and 20 parts of the 1-hexene were placed in a vacuum drying oven at 60° C. and dried for 2 hours to obtain a dry material; the dry material was added to a high-speed mixer and stirred at 200 r / min for 30 minutes to obtain a mixed material; the mixed material was added to a twin-screw extruder, subjected to a melt reaction process at 180° C. and a main engine speed of 80 r / min, and reacted for 2 hours to obtain a reactant; the reactant was crushed by a crusher to obtain the branched high-density polyethylene; The glass fiber was placed in a muffle furnace and burned at 350° C. for 10 minutes to remove the paraffin on the surface to obtain a fired glass fiber; the fired glass fiber was added to a 10% HCl solution for immersion for 2 hours, and vacuum dried at 100° C. for 1 hour to obtain an acidic glass fiber; a silane coupling agent was dissolved in a solution of anhydrous ethanol and deionized water in a volume ratio of 1:1, and the mixture was uniformly mixed at 200 rpm to obtain a mixed solution; the acidic glass fiber was added to the mixed solution, ultrasonicated for 2 hours, and then dried at 100° C. to obtain the modified glass fiber; The silane coupling agent is methacryloxypropyltrimethoxysilane; the amount of the silane coupling agent is 1-8 parts; The production process of the plastic barrel comprises the following steps: In a clean environment, the modified polyethylene is added to a modified polyethylene raw material storage tank and stirred evenly to obtain a first mixture; the high-purity high-density polyethylene is added to a high-purity polyethylene raw material storage tank and stirred evenly to obtain a second mixture; the first mixture and the second mixture are respectively introduced into a first screw extruder and a second screw extruder to completely melt to obtain molten modified polyethylene and molten high-purity high-density polyethylene; The temperature of the screw extruder 1 is 160-200°C, and the temperature of the screw extruder 2 is 120-160°C; In a clean environment, add 60 parts of the molten modified polyethylene and 40 parts of the molten high-purity high-density polyethylene into a mold with the barrel mouth facing downward, and blow the flow rate of the blow molding machine at 20-50m 3 / h of high-purity nitrogen for blow molding, and continuously blow to make a plastic barrel; the plastic barrel is passed through the outside of the mold with a flow rate of 5-15m 3 / h of cooling water to cool down and solidify to produce polyethylene plastic barrels; The polyethylene plastic barrel is cleaned and polished to obtain a rough surface plastic barrel; the rough surface plastic barrel is pasted with glass fiber cloth to obtain a fiber-treated plastic barrel; the fiber-treated plastic barrel is placed in a mold for hot pressing and solidification, demolded, and cooled at room temperature to obtain a high-purity high-density polyethylene plastic barrel; The curing temperature of the hot pressing curing is 90-120° C., the curing time is 30-90 min, and the curing pressure is 40-60 MPa.

2. A high-purity, high-density polyethylene plastic barrel, characterized by: The high-purity high-density polyethylene plastic barrel includes high-purity high-density polyethylene, modified polyethylene, and glass fiber cloth; the environmental stress cracking time of the modified polyethylene in the plastic barrel is 1356h; the tensile strength of the modified polyethylene in the plastic barrel is 52MPa, and the notched impact strength is 10.4KJ / m 2 ; The limiting oxygen index of the modified polyethylene in the plastic barrel is 35%; the 0d impurity particle dissolution amount of the high-density polyethylene plastic barrel is 8 pieces / ml; the 30d impurity particle dissolution amount is 15 pieces / ml; in the 1.5m drop test of the high-density polyethylene plastic barrel, there is no cracking or leakage in the barrel body when falling in a straight line or at an angle; the high-purity high-density polyethylene plastic barrel is prepared by the production process described in claim 1.

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