Method for the blow molding of hollow bodies by means of ultraviolet light in-line crosslinking

Abstract

This invention relates to a method for online crosslinking of hollow bodies using ultraviolet light through blow molding. The molding method includes the following steps: 1) Two preforms are cut into blanks, which are then positioned between two molds and an intermediate mold; an ultraviolet light emitting device is installed on the intermediate mold; 2) The molds are closed, and air is blown into the intermediate mold to preform the preforms; 3) After preforming, ultraviolet light irradiation and fixing of the internal components are performed; 4) The molds are closed, and blown needles on the molds begin blowing air, fusing the two preformed half-shells together along the parting line to form a hollow body, which is then cooled and solidified; 5) The molds are opened, and the product is removed. This method addresses the problems of low strength in plastic fuel tanks, which, in the field of high-pressure fuel tanks, cannot withstand the high fuel vapor pressure generated by temperature differences and prolonged engine inactivity, leading to large deformation of the fuel tank, as well as the high cost of existing plastic high-pressure fuel tank solutions.

Description

Technical Field

[0001] This invention relates to a method for forming hollow blow-molded bodies, particularly a method for forming hollow blow-molded bodies using ultraviolet light online crosslinking, which is especially applicable to the field of fuel tank blow molding manufacturing. Background Technology

[0002] Passenger vehicle fuel tanks can be divided into atmospheric pressure tanks and high pressure tanks according to their working pressure. Generally, traditional fuel vehicles can use atmospheric pressure tanks, but new energy hybrid vehicles must use high pressure tanks due to environmental protection requirements.

[0003] Passenger vehicle fuel tanks can be categorized into metal and plastic tanks based on their material. Plastic tanks, with their advantages of lightweight design and greater design flexibility compared to metal tanks, have largely replaced metal tanks in the atmospheric pressure fuel tank market. However, in the high-pressure fuel tank market, plastic tanks, due to their lower structural strength, cannot withstand the higher fuel vapor pressures caused by temperature differences and prolonged engine inactivity. To improve the strength of plastic tanks and meet high-pressure tank standards, the main solutions currently offered by plastic fuel tank manufacturers include:

[0004] 1) By inserting reinforcing internal rods inside the fuel tank, the internal pressure resistance of the fuel tank can be improved. However, this method has a significant impact on the drop / sliding impact test of the fuel tank, which will greatly increase the debugging cost of new products. In addition, the unit price of reinforcing internal rods is relatively high, and a large number of them are needed for a single plastic fuel tank, which will greatly increase the unit cost of plastic fuel tanks and reduce their advantages over metal fuel tanks.

[0005] 2) Improving the rigidity and insulation properties of fuel tanks by manufacturing multi-walled fuel tanks. For example: (a) TI's patent CN102770298B describes a fuel tank with inner and outer walls connected to provide a gap between them. The outer and inner walls are formed sequentially from cylindrical preforms. This method has a long production cycle and requires more raw materials, leading to a significant increase in the unit cost and weight of the plastic fuel tank. (b) KAUTEX's patent CN103813895B describes a fuel tank with a pre-formed protective sleeve. This sleeve must contain an outer layer (fiber reinforcement layer) and a rigid foam layer. The protective sleeve is placed into the mold half by a robot before the preform is cut. This method increases the manufacturing cost of the fuel tank body and also significantly increases the weight of the fuel tank. In addition, since the protective sleeve is pre-prepared, it cannot guarantee good interlayer adhesion when bonded to the fuel tank shell. When the protective sleeve is placed in the mold half, it will block the vent hole on the mold half, making it difficult for gas to escape between the protective sleeve and the blank. A large number of air bubbles are left at the bonding point between the protective sleeve and the fuel tank shell. After pressure alternation, they will gradually separate from this point. Summary of the Invention

[0006] This invention addresses the technical problems existing in the prior art by providing a simple, easy-to-operate, and low-cost ultraviolet light online crosslinking hollow blow molding method. This method solves the problems of low strength of plastic fuel tanks, which cannot withstand the high fuel vapor pressure generated by temperature differences and long-term engine inactivity in the field of high-pressure fuel tanks, resulting in large deformation of the fuel tank, as well as the high cost of existing plastic high-pressure fuel tank solutions.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: a method for blow molding hollow bodies using ultraviolet light online crosslinking, the molding method comprising the following steps.

[0008] 1) Two blanks are cut, and the two blanks are respectively located between the two molds and the intermediate mold; the intermediate mold is equipped with an ultraviolet light emitting device.

[0009] 2) The mold is closed, and air is blown into the intermediate mold to pre-form the parison;

[0010] 3) After preforming is completed, ultraviolet irradiation and fixing of built-in components are carried out;

[0011] 4) The mold closes, the blow needles on the mold begin to blow air, and the two pre-formed half shells are fused together along the parting line to form a hollow body, which is then cooled and solidified.

[0012] 5) Open the mold and remove the product.

[0013] The specific process in step 3) is as follows:

[0014] 3-11) After preforming is completed, the ultraviolet emitting device irradiates a predetermined area on the inner surface of the preformed half shell to cause cross-linking of the material in the predetermined area;

[0015] 3-12) The mold opens, the intermediate mold exits, and the robotic arm drives the built-in component fixture to weld the built-in component to the guide area on the inner surface of the preformed half shell;

[0016] In this scheme, crosslinking enables the formation of a three-dimensional network structure between the molecules of the inner layer material, effectively improving its mechanical properties, such as resistance to deformation under pressure. This reduces the number of internal pillar components needed, lowering their development costs and the manufacturing cost of the hollow product. Compared to existing hollow product crosslinking schemes, this scheme achieves online crosslinking for the first time. During the hollow product molding process, ultraviolet light irradiation is applied directly to the inner surface of the hollow material for crosslinking. Since the inner surface is still in a molten state, the crosslinking efficiency is extremely high, completing the crosslinking of a 2-3 mm thick material on the inner surface within 10 seconds. The process is simple.

[0017] Low investment in tooling and low manufacturing costs.

[0018] or

[0019] 3-21) After the preforming is completed, the mold is opened, the intermediate mold is removed, and then the ultraviolet light emitting device starts to irradiate. 3-22) The ultraviolet light emitting device irradiates the predetermined area on the inner surface of the preformed half shell, causing the material in the predetermined area to cross-link. Then the robotic arm drives the built-in component fixture to weld the built-in component to the guided area on the inner surface of the preformed half shell.

[0020] In this scheme, crosslinking enables the molecules of the inner layer material to form a three-dimensional network connection structure, which can effectively improve the mechanical strength of the inner layer material, such as its resistance to deformation under pressure. This reduces the number of built-in pillar parts used, lowers the development cost of built-in pillar parts, and reduces the manufacturing cost of hollow products. Compared with existing hollow crosslinking schemes, this scheme achieves online crosslinking for the first time. Ultraviolet light crosslinking is performed directly on the inner surface of the hollow body during the hollow body molding process. At this time, the inner surface of the hollow body is still in a molten state, and the crosslinking efficiency is extremely high. It can complete the crosslinking of materials with a thickness of 2-3 mm on the inner surface in about 10 seconds. The process is simple, the tooling investment is low, and the manufacturing cost is low.

[0021] In step 3), the pre-ultraviolet irradiation time is 0-10 min, preferably 1s-15s.

[0022] The ultraviolet light irradiation area is the entire inner surface of the hollow body, or a local area of ​​the inner surface. It is preferable to irradiate only the area with large deformation after being compressed.

[0023] Before the pre-formed semi-shell is cross-linked by ultraviolet light and before the hollow material enters the screw for plasticization, 0% to 5% of a mixture is added, and the mixture is added to the inner layer of the hollow material. Preferably, the mixture is 0.5% to 2%.

[0024] The mixture is one or more of the following: crosslinking agent, photoinitiator, stabilizer, and co-crosslinking agent;

[0025] The crosslinking agent is triallyl isocyanurate (TAIC) or triallyl cyanurate (TAC); the photoinitiator is benzoyl ether, benzoyl acetal, benzophenone, anthraquinone, etc.; the stabilizer is benzotriazole, phenol, phenyltriazine; and the co-crosslinking agent is triethylene glycol diacrylate (TEGDA) or ethylene glycol dimethacrylate (EGDMA).

[0026] The inner layer material is transparent or translucent in the molten state, preferably polypropylene or polyethylene; the thickness of the inner layer is 0-5 mm, preferably 2 mm-4 mm.

[0027] The ultraviolet light emitting device can be one or more sets, depending on the size of the hollow body irradiation area and the molding cycle requirements.

[0028] Compared to existing technologies, the advantages of this invention are as follows: After the pre-forming step in the blow molding process of a plastic fuel tank, this invention uses an ultraviolet light emitting device fixed on an intermediate mold to irradiate a predetermined area on the inner surface of the molten pre-formed semi-shell. This causes the molecular chains of the fuel tank material to generate a three-dimensional network cross-linked structure under the combined action of a cross-linking agent and a photoinitiator, thereby improving the material strength of the predetermined area and reducing the deformation of the predetermined area under pressure. This invention solves the problem of low inherent strength in plastic fuel tanks, which, in the field of high-pressure fuel tanks, cannot withstand the high fuel vapor pressure generated by temperature differences and prolonged engine inactivity, leading to large deformation of the fuel tank. Ultraviolet light irradiation and cross-linking modification of polyethylene significantly improves its performance, not only significantly enhancing its mechanical properties but also improving its overall performance, including resistance to environmental stress cracking, chemical corrosion, creep resistance, electrical properties, and temperature resistance. Furthermore, this solution is lower in cost and has less impact on volume compared to existing plastic high-pressure fuel tank solutions, giving it high market competitiveness. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the preform extrusion state in step 1.

[0030] Figure 2 This is a schematic diagram illustrating the preforming of the parison during step 2, where the mold is closed and air is blown into the intermediate mold.

[0031] Figure 3 This is a schematic diagram of the irradiation status of the ultraviolet emitting device in step 3.

[0032] Figure 4 This is a schematic diagram of the fixed state of the built-in components in step 3.

[0033] Figure 5 This is a schematic diagram of the state in step 4.

[0034] Figure 6 This is a schematic diagram of the state in step 5.

[0035] In the diagram: 1. Mold, 2. Intermediate mold, 3. Ultraviolet light emitting device, 4. Blank, 5. Preformed half shell, 6. Blow needle one, 7. Blow needle two, 8. Blow needle three, 9. Robotic arm, 10. Internal component fixture, 11. Material oil tank product. Detailed Implementation

[0036] To enhance understanding of the present invention, the invention will be further described and explained below in conjunction with the accompanying drawings and specific embodiments.

[0037] Example 1: See Figures 1-6 A method for blow molding hollow bodies using ultraviolet light online crosslinking, the molding method comprising the following steps:

[0038] 1) Two blanks are cut, and the two blanks are respectively located between the two molds and the intermediate mold; the intermediate mold is equipped with an ultraviolet light emitting device, see details. Figure 1 ,

[0039] 2) The mold is closed, air is blown into the intermediate mold to pre-form the parison. See [link / reference] Figure 2 ,

[0040] 3) After preforming, ultraviolet irradiation and fixing of the internal components are performed; specifically as follows: 3-11) After preforming, the ultraviolet irradiation device irradiates a predetermined area on the inner surface of the preformed semi-shell, causing cross-linking of the material in that predetermined area; see [link to relevant documentation]. Figure 3 ,

[0041] 3-12) The mold opens, the intermediate mold retracts, and the robotic arm drives the internal component fixture to weld the internal component to the guide area on the inner surface of the pre-formed semi-shell; see also Figure 4 ,

[0042] 4) The mold closes, and the blower pins on the mold begin blowing air. The two pre-formed half-shells are fused together along the parting line to form a hollow body, which then cools and solidifies. See [link to documentation]. Figure 5 ,

[0043] 5) Open the mold, remove the product, see below. Figure 6 .

[0044] Example 2: A method for blow molding hollow bodies using ultraviolet light online crosslinking, which differs from Example 1 in that...

[0045] The specific process in step 3) is as follows:

[0046] 3-21) After the preforming is completed, the mold is opened, the intermediate mold is removed, and then the ultraviolet light emitting device starts to irradiate. 3-22) The ultraviolet light emitting device irradiates the predetermined area on the inner surface of the preformed half shell, causing the material in the predetermined area to cross-link. Then the robotic arm drives the built-in component fixture to weld the built-in component to the guided area on the inner surface of the preformed half shell.

[0047] The remaining steps are exactly the same as in the example.

[0048] Example 3: A method for blow molding hollow bodies using ultraviolet light online crosslinking, wherein the pre-ultraviolet light irradiation time in step 3) is 0-10 min, preferably 1 s-15 s. The remaining steps are exactly the same as in Example 1 or 2.

[0049] Example 4: A method for blow molding hollow bodies using ultraviolet light online crosslinking. The ultraviolet light irradiation area is the entire inner surface of the hollow body, or a local area of ​​the inner surface, preferably only the area with large deformation under pressure. The remaining steps are exactly the same as in Example 1 or 2.

[0050] Example 5: A method for online crosslinking of hollow materials using ultraviolet light in blow molding. Before the pre-formed semi-shell is crosslinked by ultraviolet light and before the hollow material enters the screw for plasticization, 0% to 5% of a mixture is added. The mixture is added to the inner layer of the hollow material. Preferably, the mixture is 0.5% to 2%. The mixture is one or more of a crosslinking agent, a photoinitiator, a stabilizer, and a co-crosslinking agent; the crosslinking agent is triallyl isocyanurate (TAIC) or triallyl cyanurate (TAC); the photoinitiator is benzoyl ether, benzoylacetyl acetal, benzophenone, anthraquinone, etc.; the stabilizer is benzotriazole, phenol, or phenyltriazine; the co-crosslinking agent is triethylene glycol diacrylate (TEGDA) or ethylene glycol dimethacrylate (EGDMA); the inner layer material is transparent or translucent in the molten state, preferably polypropylene or polyethylene; the inner layer thickness is 0-5 mm, preferably 2 mm-4 mm; and the ultraviolet light emitting device can be one or more sets depending on the size of the hollow body irradiation area and the molding cycle requirements.

[0051] It should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or alternatives made on the basis of the above shall all fall within the scope of protection of the present invention, and the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for on-line ultraviolet light crosslinking of blow molded hollow bodies, characterized in that, The molding method includes the following steps: 1) Two blanks are cut, and after cutting, the two blanks are located between the two molds and the intermediate mold; the intermediate mold is equipped with an ultraviolet light emitting device. 2) The mold is closed, air is blown into the intermediate mold to pre-form the parison. 3) After preforming is completed, ultraviolet irradiation and fixing of the built-in components are performed. 4) The mold closes, and the blower pins on the mold begin blowing air. The two pre-formed half-shells are fused together along the parting line to form a hollow body, which then cools and solidifies. 5) Open the mold and remove the product.

2. The ultraviolet light on-line crosslinking process for blow molding hollow bodies according to claim 1, characterized in that, The specific process in step 3) is as follows: 3-11) After preforming is completed, the ultraviolet emitting device irradiates a predetermined area on the inner surface of the preformed semi-shell to cause cross-linking of the material in that predetermined area. 3-12) The mold opens, the intermediate mold exits, and the robotic arm drives the built-in component fixture to weld the built-in component to the guide area on the inner surface of the preformed half shell; or 3-21) After preforming is completed, the mold is opened, the intermediate mold is removed, and then the ultraviolet light emitting device begins irradiation. 3-22) The ultraviolet emitting device irradiates a predetermined area on the inner surface of the preformed half shell, causing the material in the predetermined area to cross-link. Then, the robotic arm drives the built-in component fixture to weld the built-in component to the guided area on the inner surface of the preformed half shell.

3. The ultraviolet light on-line crosslinking process for blow molding hollow bodies according to claim 2, characterized in that, The pre-ultraviolet irradiation time in step 3) is 0-10 min.

4. The ultraviolet light on-line crosslinking process for blow molding hollow bodies according to claim 1, characterized in that, The area irradiated by ultraviolet light is the entire inner surface of the hollow body, or a local area of ​​the inner surface.

5. The method according to claim 4, wherein Before the pre-formed semi-shell is cross-linked by ultraviolet light and before the hollow material enters the screw for plasticization, 0% to 5% of a mixture is added, and the mixture is added to the inner layer of the hollow material.

6. The method according to claim 5, wherein The mixture is one or more of the following: crosslinking agent, photoinitiator, stabilizer, and co-crosslinking agent; Wherein, the crosslinking agent is one or more of triallyl isocyanurate (TAIC) and triallyl cyanurate (TAC); the photoinitiator is one or more of benzoyl ether, benzoyl acetal, benzophenone, and anthraquinone; the stabilizer is one or more of benzotriazole, phenol, and phenyltriazine; and the co-crosslinking agent is one or more of triethylene glycol diacrylate (TEGDA) and ethylene glycol dimethacrylate (EGDMA).

7. The ultraviolet light on-line crosslinking process for blow molding hollow bodies according to claim 5, characterized in that, The inner layer material is transparent or semi-transparent in the molten state, and is made of polypropylene or polyethylene; the thickness of the inner layer is 0-5mm.

8. The ultraviolet light on-line crosslinking process for blow molding hollow bodies according to claim 5, characterized in that, The ultraviolet light emitting device is configured as one or more sets, depending on the size of the hollow body irradiation area and the molding cycle requirements.

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