Plastic model for producing polyurethane balloon and production process of plastic model

Abstract

The invention relates to a plastic model for producing a polyurethane balloon and a production process thereof. The invention discloses a polyurethane balloon forming mold and a preparation method thereof in order to solve the problems that a ceramic mold used for a waterborne polyurethane balloon is difficult to demold, and a common plastic mold is easy to deform, low in precision and the like. The preparation method comprises the steps of injection molding, precise cutting (150-80 microns), gradient rough polishing (325 #-800 # abrasive paper) and gradient fine polishing (10-5 microns particle size treatment). The obtained mold is easy to demold, the temperature resistance reaches 130 DEG C or above, the thermal deformation rate is smaller than 0.1%, and the surface roughness Ra is smaller than or equal to 30 microns. The mold produced through the process is particularly suitable for the continuous production process of the waterborne polyurethane balloons.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing heat-resistant plastic molds, and specifically to a plastic mold for producing polyurethane balloons and its production process. Background Art

[0002] Traditional balloon products are mainly prepared by an impregnation mold forming process using natural latex materials. The industry generally selects rigid materials such as ceramics, glass, and stainless steel as the mold substrates. Such materials have high surface energy (70 mN / m for glass and 75 mN / m for stainless steel) and high-temperature resistance characteristics, which can meet the low-adhesion demolding requirements of latex materials (modulus 0.7 MPa).

[0003] Waterborne polyurethane is regarded as an ideal material to replace latex due to its non-toxic, environmentally friendly, dense film-forming, and excellent airtightness characteristics. Although waterborne polyurethane has superior performance, its industrial application faces the problem of difficult demolding. The surface energy of waterborne polyurethane is 45 mN / m, the modulus is ≥1.5 MPa, the surface energy of natural materials is 30 mN / m, the modulus is 0.7 MPa, and the cohesive force after film formation is more than twice that of natural latex. The increase in cohesive force results in the interfacial adhesion force between waterborne polyurethane and traditional molds reaching 12.5 J / ㎡, which is 3.8 times higher than that of the latex system, and it is difficult to separate by conventional demolding processes.

[0004] Poor mold structure adaptability: Except for the long balloon mold, other balloon molds adopt an integrated design of the balloon and the balloon handle. Usually, the diameter of the balloon is more than twice the diameter of the balloon handle, and the diameter ratio of the balloon handle to the balloon of some models reaches 1:15 times. The roughness of the mold directly affects the quality of the product and the demolding effect.

[0005] Insufficient heat-resistant stability; The impregnation process needs to undergo a stepped temperature treatment of 80 - 130 °C, while ordinary plastic mold materials soften and deform in an environment above 80 °C, and need to be replaced and processed in a timely manner, increasing the production cost of enterprises.

[0006] In view of the above problems, developing a balloon mold suitable for waterborne polyurethane materials has become an urgent problem to be solved in this industry. Summary of the Invention

[0007] Provide a plastic mold with excellent high-temperature resistance and dimensional stability and its production process, and solve the technical defects of difficult demolding of traditional waterborne polyurethane balloons, easy deformation of plastic molds, and residual mold parting lines.

[0008] Technical Solution The present invention uses high-density polyethylene and heat-resistant polypropylene materials as the base materials, and is prepared by injection molding, precision cutting (150 - 100 μm), gradient rough polishing (#325 - #800 sandpaper), and gradient fine polishing (gradually processing with particle sizes of 10 - 5 μm). The obtained mold is easy to demold, has a heat resistance performance of over 130 °C, a thermal deformation rate of < 0.1%, and a surface roughness Ra ≤ 30 μm. The mold produced by the process of the present invention is particularly suitable for the continuous production process of waterborne polyurethane balloons.

[0009] Further described: The matrix materials are high-density polyethylene (HDPE, melt index 5 - 20 g / 10 min, ASTM D1238) and heat-resistant polypropylene (Vicat softening point ≥ 135 °C, ISO 306).

[0010] Further described: Precision cutting adopts laser cutting technology, and the mold joint line is controlled within 150 - 100 μm.

[0011] Further described: The rough polishing process adopts a stepped polishing process with #325 - #800 sandpaper for 10 minutes in each stage.

[0012] Further described: The fine polishing process adopts alumina abrasive with a particle size of 10 - 5 μm and a time of 30 minutes.

[0013] Further described: Injection molding process: Melting temperature 135 - 210 °C, injection pressure 80 - 120 MPa, and the mold is kept at a constant temperature of 65 - 75 °C.

[0014] Further described: The model consists of a ball handle part and a balloon part, and the diameter ratio of the two is 1:2 - 1:10, and the axial length ratio is 1:1 - 20:1 ( Figure 1 )

[0015] Further described: Special-shaped model: Ball handle - balloon integration ( Figure 2 )

[0016] Further described: Special-shaped cylinder ( Figure 3 )

[0017] Beneficial effects It solves the problem of difficult demolding of waterborne polyurethane balloons; the heat resistance of the mold is improved, the material can withstand a temperature of ≥ 130 °C, and through precision cutting and gradient polishing technologies, the residual mold joint line is < 30 μm, and the surface finish reaches the medical grade standard; the stability of the model is improved, supporting continuous and stable production, and significantly reducing the production cost of enterprises. Description of the drawings

[0018] Figure 1 : Schematic structural diagram of the ball handle - balloon integrated mold.

[0019] Figure 2:Schematic diagram of the structure of a special-shaped balloon mold.

[0020] Figure 3 :Schematic diagram of the structure of a cylindrical mold. Specific implementation mode

[0021] It should be understood that the terms described in the present invention are only for describing specific implementation modes to facilitate the understanding of those skilled in the art, and are not used to limit the present invention. This process is adopted for other heterogeneous model shapes; and the numerical ranges in the present invention should be understood as specifically disclosing that each numerical value between the upper and lower limits of the range is also included in the present invention.

[0022] Example 1 Step 1: Mold opening: A ball handle-balloon integrated mold, the ratio of the ball handle to the balloon is 1:3, the diameter of the circular ball handle is 17.2 mm, the diameter of the circular balloon is 52.5 mm, and there is a threaded interface and a fixed buckle at one end of the circular ball handle (as shown in the attachment Figure 1 ) Step 2: Material preparation: HDPE (melt index 15 g / 10 min), model Daehan Oil & Chemical - HJ4006, equipment: twin-screw extruder, melting and blending temperature is 190 °C; Step 3: Injection molding: The mold temperature is set at 65 °C, the injection pressure is 80 MPa, the holding pressure time is 15 s, and demolding is carried out after cooling; Step 4: Laser cut the demolded plastic model, with a power of 50 W and a speed of 10 mm / s, and remove the mold joint line to 100 μm; Step 5: Move the plastic model with the mold joint line removed into an automatic polishing machine equipped with 325# sandpaper, polish the whole body for 10 minutes, then move it into an automatic polishing machine equipped with 625# sandpaper, polish the whole body for 10 minutes, move it into an ultrasonic cleaning tank for ultrasonic water washing for 10 minutes, then move it into a precision polishing machine with 10 μm alumina abrasive, polish the whole body precisely for 30 minutes, and finally move it into an ultrasonic cleaning tank for ultrasonic water washing for 10 minutes to obtain a smooth plastic model with a surface Ra = 30 μm.

[0023] Test results: The mold works continuously at 110 °C for 12 hours, and the thermal deformation is 0.08%; the molded polyurethane spherical balloon has a smooth surface and no mold joint line marks on the balloon surface.

[0024] Example 2 Step 1: Mold opening: A special-shaped ball handle-balloon integrated mold, the ratio of the ball handle to the balloon is 1:4, the diameter of the circular ball handle is 30 mm, the diameter of the circular balloon is 120 mm, and there is a threaded interface at one end of the circular ball handle (as shown in Figure 2 ) Step 2: Material preparation: Heat-resistant polypropylene (Vicat softening point ≥ 135°C, ISO 306), grade: Fushow - PF7251; Equipment: Twin-screw extruder for melt blending (temperature 200°C); Step 3: Injection molding: Mold temperature is set at 70°C, injection pressure is 85 MPa, holding pressure time is 15 s, demolding after cooling; Step 4: Laser cut the demolded plastic model with a power of 50 W and a speed of 10 mm / s to remove the mold joint line to 90 μm; Step 5: Transfer the plastic model with the mold joint line removed to an automatic polishing machine equipped with 400# sandpaper, polish the whole body for 10 minutes, then transfer it to an automatic polishing machine equipped with 625# sandpaper, polish the whole body for 10 minutes, transfer it to an ultrasonic cleaning tank for ultrasonic water washing for 10 minutes, then transfer it to a precision polishing machine with 6.5 μm alumina abrasive, polish the whole body precisely for 30 minutes, and then transfer it to an ultrasonic cleaning tank for ultrasonic water washing for 10 minutes to obtain a smooth plastic model with a surface Ra of 28 μm.

[0025] Test results: The mold works continuously at 120°C for 12 hours, and the thermal deformation is 0.07%; The molded polyurethane special-shaped balloon has a smooth surface and no mold joint line marks on the balloon surface.

[0026] Example 3 Step 1: The diameter of the circular handle of the cylindrical balloon model is 6.2 mm, and one end of the circular handle has a threaded interface and a fixed buckle (as shown in the attachment Figure 3 ) Step 2: Material preparation: Heat-resistant polypropylene (Vicat softening point ≥ 135°C, ISO 306), grade: Fushow - PF7251; Equipment: Twin-screw extruder for melt blending, temperature 205°C; Step 3: Injection molding: Mold temperature is set at 75°C, injection pressure is 80 MPa, holding pressure time is 15 s, demolding after cooling; Step 4: Laser cut the demolded plastic model with a power of 50 W and a speed of 10 mm / s to remove the mold joint line to 80 μm; Step 5: Transfer the plastic model with the mold joint line removed to an automatic polishing machine equipped with 400# sandpaper, polish the whole body for 10 minutes, then transfer it to an automatic polishing machine equipped with 625# sandpaper, polish the whole body for 10 minutes, transfer it to an ultrasonic cleaning tank for ultrasonic water washing for 10 minutes, then transfer it to a precision polishing machine with 5 μm alumina abrasive, polish the whole body precisely for 30 minutes, and then transfer it to an ultrasonic cleaning tank for ultrasonic water washing for 10 minutes to obtain a smooth plastic model with a surface Ra of 25 μm.

[0027] Test results: The mold works continuously at 130 °C for 12 hours, and the thermal deformation is 0.07%; the forming hardness is good, without jitter. The formed polyurethane straight balloon has a smooth surface and no mold joint line marks on the balloon surface.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A plastic mold for producing polyurethane balloons and its production process, characterized in that: The plastic mold is made of high-density polyethylene (HDPE) and heat-resistant polypropylene (pp) materials through an injection molding process. The preparation method includes the following steps: (a) Melting high-density polyethylene particles or heat-resistant polypropylene particles at 165 - 250 °C; (b) Injecting the molten material into the mold cavity, maintaining the injection pressure at 80 - 140 MPa, and controlling the mold temperature at 40 - 70 °C; (c) Demolding after cooling and setting, and removing the mold joint line in the range of 150 - 80 μm by a cutting process; (d) Rough polishing (325# - 800# sandpaper), ultrasonic water washing and fine polishing treatment are carried out on the product in sequence. The fine polishing uses abrasives with a particle size of 13 - 5 μm.

2. The plastic model according to claim 1, characterized in that: The mold cavity includes a circular ball handle part and a balloon part that are interconnected. The ratio of the diameter of the ball handle part to the diameter of the balloon part is 1:2 - 1:10, and the ratio of the axial length is 1:1 - 20:

1. One end of the ball handle has a threaded structure and a fixed card slot.

3. The plastic model according to claim 1, characterized in that: The mold cavity is constructed as one of a cylindrical structure, a ball handle - balloon integrated structure or a special-shaped balloon structure.

4. The production process according to claim 1, characterized in that: The rough polishing steps use 325# - 800# sandpaper; in the fine polishing process, the particle size of the abrasive is set to 13 - 5 μm, and the final surface roughness Ra ≤ 30 μm.

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