Combined cover for flushing and preparation method thereof

Abstract

The invention discloses a combined cover for flushing and a preparation method thereof, and relates to the technical field of packing materials. According to the invention, firstly, by optimizing the formula design, a product with better flexibility is obtained, insoluble particles caused by too hard product can be reduced, and meanwhile, the stability requirement of injection molding in the processing process is met; and secondly, the outer cover and the inner cover are assembled through a coaxial screwing assembly process, so that visible chips and insoluble particles generated by friction in the assembly process are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, and particularly relates to a combined cap for rinsing and a preparation method thereof. Background Art

[0002] The combined cap for rinsing is mainly used for a rinsing bottle containing sterile water for injection as the content, and is used in aseptic use environments such as wound rinsing and medical device rinsing. Packaging materials used in aseptic environments have relatively high requirements for the cleanliness of the loaded substances, and need to meet the requirements that there are no visible debris in the content and the insoluble particles of the pharmaceutical packaging materials in direct contact with body fluids. Once insoluble particles are generated, rejection reactions will occur at the wound of the patient, resulting in increased pain for the patient. Even when the wound heals, they enter the human body and cannot be discharged, and the insoluble particles remain in the patient's body for life, causing pain to the patient. And this kind of visible debris and insoluble particles are generally generated by the mutual friction between components during the assembly of the packaging materials. For this reason, the "National Pharmaceutical Packaging Materials Standard" promulgated in 2015 states that no foreign matter shall be mixed into the product, and the insoluble particles shall meet the requirements.

[0003] Existing rinsing caps, such as the medicinal sealing cap disclosed in the Chinese Utility Model Patent CN219077924U, designs a sealing cap with a threaded seal; the rinsing bottle cap disclosed in the Chinese Utility Model Patent CN202620228U designs a pull-ring type rinsing cap; the Chinese Utility Model Patent CN208217386U discloses a combined cap for rinsing liquid, which designs a screwing type rinsing liquid cap. None of the above patents study how to solve problems such as visible debris and insoluble particles generated during the assembly of packaging materials. Therefore, there is an urgent need to develop a new combined cap for rinsing to solve the above problems. Summary of the Invention

[0004] The technical problems to be solved by the present invention are: overcoming the deficiencies of the prior art, providing a combined cap for rinsing and a preparation method thereof. First, through optimizing the formulation design, a product with better flexibility is obtained, and the insoluble particles caused by the product being too hard can be reduced, while meeting the stability requirements of injection molding during the processing; second, the outer cap and the inner cap are assembled by a coaxial screwing assembly process, thereby reducing the visible debris and insoluble particles generated by friction during the assembly process.

[0005] The technical solution of the present invention is as follows: On the one hand, the present invention provides a preparation method for a combined cover for rinsing. The combined cover for rinsing includes an outer cover and an inner cover. The inner cover includes a base platform, on the top of which a pull cover is provided. The base platform is provided with an external thread, and the outer cover is provided with an internal thread. The inner cover is threadedly connected to the outer cover. The surface of the pull cover is provided with an inner cutting edge and an outer cutting edge. The inner cutting edge is in a C shape, and the outer cutting edge is circular. The thicknesses of the inner cutting edge and the outer cutting edge are less than the thickness of the pull cover, and a pull ring is provided on the pull cover between the inner cutting edge and the outer cutting edge. The bottom of the pull ring is connected to the inner cutting edge and the outer cutting edge. The yield strength of the granule material used for the outer cover is greater than that of the granule material used for the inner cover. The granule material used for the outer cover is polypropylene A. The granule material used for the inner cover is modified polypropylene, which is made from the following base materials by weight: 30-40 parts of polypropylene A, 30-40 parts of polypropylene B, and 20-40 parts of toughening elastomer. The yield strength of polypropylene A is 27-39 MPa, and the melt index is 48-60 g / 10 min. The yield strength of polypropylene B is 26-28 MPa, and the melt index is 8-16 g / 10 min. The preparation method for the combined cover for rinsing is as follows: the base materials of the inner cover are compounded and granulated, and then the inner cover and the outer cover are injection molded by an electric injection molding machine. Finally, the inner cover and the outer cover are assembled to obtain the combined cover for rinsing. Among them, when the base materials of the inner cover are compounded and granulated, polypropylene B and the toughening elastomer are first mixed and granulated, and then mixed with polypropylene A to obtain the granule material used for the inner cover. The outer cover adopts a one-stage injection molding process. The inner cover adopts a two-stage injection molding process. The injection molding of the pull ring is completed in the first stage, and the injection molding of the base platform is completed in the second stage. The switching point between the two-stage injection molding is the pull cover. The injection speed in the first stage is 40-50 mm / s, and the injection speed in the second stage is 15-25 mm / s. When the inner cover and the outer cover are assembled, a coaxial screwing assembly process is adopted.

[0006] Preferably, the yield strength of the polypropylene A is 27 MPa, and the melt index is 60 g / 10 min.

[0007] Preferably, the yield strength of the polypropylene B is 26 MPa, and the melt index is 16 g / 10 min.

[0008] Preferably, the toughening elastomer is SEBS. The tensile strength of SEBS is 10-14 MPa, and the hardness is 35-45A.

[0009] Preferably, the tensile strength of the SEBS is 10 MPa, and the hardness is 40A.

[0010] Preferably, when the inner cover is injection molded, the starting position of injection molding is 58-60 mm, the switching position between the two-stage injection molding is 45-47 mm, and the ending position of injection molding is 17-19 mm.

[0011] Preferably, when the outer cover is injection molded, the starting position of injection molding is 50-52 mm, and the ending position of injection molding is 15-17 mm.

[0012] On the other hand, the present invention provides a combined cap for rinsing, which is prepared by the above-mentioned preparation method of the combined cap for rinsing.

[0013] The combined cap for rinsing of the present invention adopts a design in which the inner cap and the outer cap are separated. The inner cap plays a role in sealing connection with the body of the rinsing bottle and needs to be welded to the rinsing bottle. After the inner cap is hermetically welded to the body of the rinsing bottle, they form an integral body and can be sterilized to reach a sterile state. When in use, the pull ring on the inner cap can be pulled open for rinsing operation. The outer cap serves two purposes: one is to protect the inner cap from being damaged when the pull ring is not opened, and the other is that after the pull ring is opened, if there is unused rinsing liquid, the outer cap can be covered on the inner cap to play a sealing role and ensure that the inside of the body of the rinsing bottle is not contaminated. In order to achieve the protection and sealing functions of the inner cap and the outer cap, an external thread is designed on the inner cap and an internal thread is designed on the outer cap, and the two are matched to form a screwing structure to complete the sealing connection between the two.

[0014] In the prior art, in terms of the formulation design and assembly process of the inner cap and the outer cap, there are problems that can cause product debris. First, when the inner cap and the outer cap are assembled, there will be friction at the thread, and the friction will cause debris and insoluble particles to be generated on the inner cap and the outer cap; second, when using granular materials with better toughness to produce the inner cap and the outer cap, there will be a problem of poor sealing due to insufficient stiffness of the inner cap and the outer cap; third, when using a pressing assembly process to assemble the inner cap and the outer cap, there will be a problem of thread damage at the inner cap and the outer cap; fourth, when using a screwing assembly process, due to insufficient flexibility of the granular material, debris and insoluble particles will be generated due to friction at the thread of the inner cap and the outer cap; fifth, debris and insoluble particles are likely to appear on the stressed side during assembly.

[0015] In addition, the injection molding process parameters of the outer cap and the inner cap will also affect the debris and insoluble particles generated by the product. The smaller size, higher injection pressure and injection volume range at the thread are likely to make the thread injection more full, resulting in increased friction during assembly and generation of debris; smaller injection pressure and injection volume range are likely to cause shrinkage of the thread size, resulting in problems with product sealing. Therefore, after determining the formulations of the inner cap and the outer cap, it is necessary to determine the corresponding injection molding process parameters according to the product properties to assist in reducing assembly friction. At the same time, compared with the hydraulic injection molding machine, the electric injection molding machine is superior in the control of precision dimensions. Therefore, in order to ensure the stability of the thread size in the present invention, it is also limited to use an electric injection molding machine to inject and mold the inner cap and the outer cap.

[0016] At the same time, according to the properties of the granular materials used for the inner cap, the present invention determines to adopt a two-stage injection molding process to ensure that the inner cap produced by using the inner cap formulation of the present invention can have a pull ring that is easy to open and can ensure the sealing performance; while adopting a one-stage injection molding process to prepare the outer cap can ensure that the outer cap is formed in one time without shrinkage problems.

[0017] When the inner cover is injection - molded, the glue injection point is set at the center position of the pull - tab. The principle of the two - stage injection molding design of the inner cover is that during the injection molding process, the melt flows in a rolling manner. When the melt touches the inner wall of the mold, the outer melt will cool first and then gradually cool to the inner core. Therefore, based on this principle, in order to make the pull - ring easier to open, first, polypropylene resin with lower strength is selected, that is, the yield strength of polypropylene is reduced by toughening modification of polypropylene to reduce the opening force of the pull - ring. Second, during injection molding, a faster injection speed is used for injection. After the melt enters, it first fills the pull - ring at the farther end. At this time, part of the inner wall has cooled. Then, the injection speed is switched to a slower one for filling and holding pressure to fill the base completely and make the pull - cover filled completely. At this time, the melt with a slower flow rate fills the inner cutting edge and the outer cutting edge. There is a stress difference between the inside and outside of the inner cutting edge and the outer cutting edge, which plays a role in reducing the opening force at the pull - ring.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The combined cover for flushing of the present invention, by optimizing the formulation design of the inner cover and the outer cover, and making the yield strength of the pellets used for the outer cover greater than that of the pellets used for the inner cover, can effectively solve the problems of abrasion debris and insoluble microparticles generated by friction during the assembly of the outer cover and the inner cover. At the same time, the present invention optimizes the injection molding process of the inner cover and the outer cover, which can effectively ensure the dimensional stability of the threads of the inner cover and the outer cover; and can ensure good sealing while the pull - ring of the inner cover is easy to open. In addition, the present invention uses a coaxial screwing assembly process to assemble the inner cover and the outer cover, which can effectively reduce the friction during assembly, thereby reducing the generation of friction debris. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural view of the outer cover of the combined cover for flushing of the present invention.

[0020] Figure 2 is a schematic structural view of the inner cover of the combined cover for flushing of the present invention.

[0021] Figure 3 is a top view of the inner cover of the combined cover for flushing of the present invention.

[0022] In the figure, 1. outer cover; 101. internal thread; 2. inner cover; 201. base; 202. pull - cover; 203. pull - ring; 204. external thread; 205. inner cutting edge; 206. outer cutting edge. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0024] As Figures 1-3As shown in the figure, the combined cover for flushing of the present invention includes an outer cover 1 and an inner cover 2. The inner cover 2 includes a base 201. A pull cover 202 is arranged on the top of the base 201. The base 201 is provided with an external thread 204, and the outer cover 1 is provided with an internal thread 101. The inner cover 2 is threadedly connected to the outer cover 1. The surface of the pull cover 202 is provided with a C-shaped inner cutting edge 205 and a circular outer cutting edge 206. The thickness of the inner cutting edge 205 and the outer cutting edge 206 is 0.15 mm. The thickness of the pull cover 202 is 1.3 mm. A pull ring 203 is arranged on the pull cover 202 between the inner cutting edge 205 and the outer cutting edge 206. The thickness of the inner cutting edge 205 and the outer cutting edge 206 is less than the thickness of the pull cover 202, which is convenient for when pulling the pull ring 203, the pull cover 202 will be first broken at the thinner C-shaped inner cutting edge 205 and the circular outer cutting edge 206, so as to open the pull cover 202. Its specific structure can refer to the veterinary medicine cover disclosed in the design patent CN308918651S.

[0025] The raw materials used in the following examples are all commercially available products: Polypropylene, 6881, Formosa Plastics Corporation, with a yield strength of 39 MPa and a melt index of 55 g / 10 min; Polypropylene, 5600XT, Formosa Plastics Industry (Ningbo) Co., Ltd., with a yield strength of 27 MPa and a melt index of 60 g / 10 min; Polypropylene, RP375RT, LyondellBasell Industries N.V., with a yield strength of 29 MPa and a melt index of 48 g / 10 min; Polypropylene, K4912, Sinopec Beijing Yanshan Company, with a yield strength of 26 MPa and a melt index of 16 g / 10 min; Polypropylene, STM866, Formosa Plastics Corporation, with a yield strength of 27 MPa and a melt index of 8 g / 10 min; Polypropylene, 5090T, Formosa Plastics Industry (Ningbo) Co., Ltd., with a yield strength of 28 MPa and a melt index of 15 g / 10 min; Toughened elastomer SEBS, 1645, Kraton Polymers LLC, with a tensile strength of 11 MPa and a hardness of 35A; Toughened elastomer SEBS, 8245D, Taixiang (Nantong) Industrial Co., Ltd., with a tensile strength of 10 MPa and a hardness of 40A; Toughened elastomer SEBS, YH-506, Sinopec Baling Company, with a tensile strength of 14 MPa and a hardness of 45A.

[0026] Examples 1-7 The preparation method of the combined cover for flushing in Examples 1-7 includes the following steps: S1 Granulation of the base materials of the inner cover 2: The formula of the inner cover 2 is shown in Table 1. Polypropylene B and toughened elastomer SEBS are placed in a high-speed mixer for mixing to obtain a mixed material, and then the mixed material is put into an extruder for extrusion granulation; subsequently, it is placed in a high-speed mixer together with polypropylene A for mixing to obtain a mixed material, and then the mixed material is put into an extruder for extrusion granulation to obtain the pellets of the inner cover 2; S2 Injection molding of the inner cover 2 and the outer cover 1: Through an electric injection molding machine, injection molding of the inner cover 2 and the outer cover 1 is carried out according to the parameters shown in Table 1; S3 Assembly of the inner cover 2 and the outer cover 1: Assembly of the inner cover 2 and the outer cover 1 is carried out through a coaxial screwing assembly process. Use a manipulator to clamp the position of the base 201 of the inner cover 2 to fix the inner cover 2, and then another manipulator clamps the top of the outer cover 1 and places the outer cover 1 at the central axis of the inner cover 2, while applying a continuous downward pressure; when the internal thread 101 of the outer cover 1 contacts the external thread 204 of the inner cover 2, the outer cover 1 is subjected to a thread acting force, and this acting force reacts on the manipulator, causing the manipulator to rotate, so that the outer cover 1 is rotationally assembled onto the inner cover 2 to obtain a combined cover for rinsing.

[0027] Table 1 Formulation of the inner cover 2 and injection molding process parameters of the inner cover 2 and the outer cover 1 in Examples 1 - 7

[0028] In Table 1, the yield strength is determined with reference to "GB / T 1040 Plastics - Determination of tensile properties".

[0029] Performance testing is carried out on the combined covers for rinsing prepared in Examples 1 - 7: 1) Thread dimensions of the outer cover 1 and the inner cover 2: Test is carried out with reference to the method in "GB / T40742.1 Geometrical Product Specifications (GPS) - Inspection and verification of geometrical accuracy", and check whether it meets the requirements that the internal thread diameter of the outer cover 1 is 22 ± 0.3 mm and the external thread diameter of the inner cover 2 is 22.8 ± 0.3 mm. If it meets the requirements, it is judged as qualified; otherwise, it is judged as unqualified; 2) Processing stability of the inner cover 2: After each injection molding by an electric injection molding machine, the control panel displays the injection pressure of that time. When the injection pressure is within the range of 55 ± 2 MPa, it indicates that the injection amount each time is relatively uniform. At the same time, observe the appearance of the product after each injection, and confirm that there is no incomplete injection or overflow. Then it can be judged as stable injection molding; 3) Opening force at the pull ring 203 of the inner cover 2: Test is carried out with reference to the pull ring opening force in "YBB00242004 - 2015 Polypropylene combined caps (pull ring type) for plastic infusion containers"; 4) Sealing performance of the inner cap 2: Test the sealing performance at the pull-ring cut mark with reference to "YBB00242004-2015 Polypropylene Composite Caps for Plastic Infusion Containers (Pull-ring Type)". 5) Insoluble particles in the composite cap for rinsing: Test with reference to "YBB00272004-2015 Test Method for Insoluble Particles in Packaging Materials". If the number of insoluble particles with a size of more than 5μm per 1 mL does not exceed 100; the number of insoluble particles with a size of more than 10μm per 1 mL does not exceed 20; and the number of insoluble particles with a size of more than 25μm per 1 mL does not exceed 2, it is determined to be qualified.

[0030] The performance test results of the composite caps for rinsing prepared in Examples 1-7 are shown in Table 2: Table 2 Performance Test Results of the Composite Caps for Rinsing Prepared in Examples 1-7

[0031] Comparative Example 1 The difference from Example 2 is that in step S2, when the inner cap 2 and the outer cap 1 are injection-molded, an oil hydraulic injection molding machine is used, and the injection molding parameters of the oil hydraulic injection molding machine are the same as those in Example 2.

[0032] When using an oil hydraulic injection molding machine, the control precision of the injection start position, two-stage injection switching position, injection end position of the inner cap 2, and the injection start position and injection end position of the outer cap 1 is weaker than that of an electric injection molding machine, and the position deviation is ±2 mm, which cannot reach the injection molding parameters of Example 2, resulting in poor dimensional stability at the thread of the inner cap 2 and the outer cap 1, and it is easy to have dimensional deviation at the thread. During assembly, the friction contact area between the inner cap 2 and the outer cap 1 is too large, which will generate abrasive debris and insoluble particles.

[0033] Comparative Example 2 The difference from Example 2 is that in step S1, the base material of the inner cap 2 is compounded and pelletized: Polypropylene B, toughening elastomer SEBS and Polypropylene A are placed in a high-speed mixer for mixing to obtain a mixed material, and then the mixed material is put into an extruder for extrusion pelletization to obtain the inner cap 2 pellets.

[0034] When using the pellets of Comparative Example 2 to injection-mold the inner cap 2, due to the different flow rates of each base material, it cannot ensure the flow stability of each part when the melt is injected by an electric injection molding machine, resulting in the problem of incomplete injection during the processing; and there will be a sealing problem of leakage caused by incomplete injection of the inner cap 2.

[0035] Comparative Example 3 The difference from Example 2 lies in that in step S3, the inner cover 2 and the outer cover 1 are assembled: the inner cover 2 and the outer cover 1 are assembled through a pressing assembly process. A manipulator is used to grip the base 201 position of the inner cover 2 to fix the inner cover 2, and then another manipulator grips the top of the outer cover 1 and places the outer cover 1 at the central axis of the inner cover 2 while applying a continuously downward pressure; when the internal thread 101 of the outer cover 1 contacts the external thread 204 of the inner cover 2, the outer cover 1 is subjected to a thread acting force, and the manipulator does not rotate. The outer cover 1 is vertically pressed and assembled onto the inner cover 2 by mechanical pressing to obtain a combined cover for rinsing.

[0036] Adopting the pressing assembly process will cause friction between the threads of the inner cover 2 and the outer cover 1 in the vertical direction during assembly, resulting in thread wear and generating abrasive debris.

[0037] Comparative Example 4-5 The difference between Comparative Example 4-5 and Example 2 is that the formulation of the inner cover 2 in Comparative Example 4-5 is different from that in Example 2, as shown in Table 3 specifically: Table 3 Formulation of the inner cover 2 and injection molding process parameters of the inner cover 2 and the outer cover 1 in Example 2 and Comparative Example 4-5

[0038] The performance test results of the combined covers for rinsing prepared in Example 2 and Comparative Example 4-5 are shown in Table 4: Table 4 Performance test results of the combined covers for rinsing prepared in Example 2 and Comparative Example 4-5

[0039] As can be seen from Tables 3-4, too much polypropylene is added to the formulation of the inner cover 2 in Comparative Example 4, resulting in the inner cover 2 being too hard, causing wear at the thread during demolding, and generating abrasive debris easily after being assembled with the outer cover 1. Also, the opening force of the pull ring 203 is relatively large, affecting the use. In the formulation of the inner cover 2 in Comparative Example 5, too much SEBS is added, resulting in the inner cover 2 being too soft, the pull ring 203 being prone to deformation and unable to be used; moreover, the cover body is too soft and has poor stiffness, resulting in liquid leakage after being assembled with the outer cover 1.

[0040] Comparative Example 6-7 The difference between Comparative Example 6-7 and Example 2 is that the injection molding process parameters of the inner cover 2 in Comparative Example 6-7 are different from those in Example 2, as shown in Table 5 specifically: Table 5 Formulation of the inner cover 2 and injection molding process parameters of the inner cover 2 and the outer cover 1 in Example 2 and Comparative Example 6-7

[0041] The performance test results of the combined covers for rinsing prepared in Example 2 and Comparative Example 6-7 are shown in Table 6: Table 6 Performance test results of the combined caps for rinsing prepared in Example 2 and Comparative Examples 6-7

[0042] As can be seen from Tables 5-6, in Comparative Example 6, when injection molding the inner cap 2, the range from the injection starting position to the injection end position was shortened, resulting in the problem of incomplete injection during the injection molding process of the inner cap 2. As a result, the dimensions at the thread of the inner cap 2 could not be formed normally, and there would be incomplete injection at the pull ring 203, causing liquid leakage. At the same time, there would also be problems with the normal assembly of the inner cap 2 and the outer cap 1.

[0043] In contrast, in Comparative Example 7, the range from the injection starting position to the injection end position was enlarged, resulting in the problem of injection overflow during the injection molding process of the inner cap 2. As a result, the thread dimensions at the inner cap 2 were too large, and there would be abrasion debris when assembling with the outer cap 1. And due to the large range, there was too much injection plastic, causing overflow at the pull ring 203 of the inner cap 2 and the opening force at the pull ring 203 of the inner cap 2 was too large.

[0044] Comparative Examples 8-9 The differences between Comparative Examples 8-9 and Example 2 are that the injection molding process parameters of the outer cap 1 in Comparative Examples 8-9 are different from those in Example 2, as shown in Table 7 specifically: Table 7 Formulation of the outer cap 1 and injection molding process parameters of the inner cap 2 and the outer cap 1 in Example 2 and Comparative Examples 8-9

[0045] The performance test results of the combined caps for rinsing prepared in Example 2 and Comparative Examples 8-9 are shown in Table 8: Table 8 Performance test results of the combined caps for rinsing prepared in Example 2 and Comparative Examples 8-9

[0046] As can be seen from Tables 7-8, in Comparative Example 8, when injection molding the outer cap 1, the range from the injection starting position to the injection end position was shortened, resulting in the problem of incomplete injection during the injection molding process of the outer cap 1. As a result, the dimensions at the thread of the outer cap 1 could not be formed normally, and there were problems with the normal assembly of the inner cap 2 and the outer cap 1.

[0047] In Comparative Example 9, when injection molding the outer cap 1, the range from the injection starting position to the injection end position was enlarged, resulting in the problem of injection overflow during the injection molding process of the outer cap 1. As a result, the thread dimensions at the outer cap 1 were too large, and there would be abrasion debris when assembling with the inner cap 2.

[0048] Comparative Example 10 The difference from Example 2 is that in Comparative Example 10, the pellets of the inner cap 2 and the outer cap 1 in Example 2 were interchanged.

[0049] The performance test results of the combined caps for rinsing prepared in Example 2 and Comparative Example 10 are shown in Table 9 as follows: Table 9 Performance Test Results of the Combined Caps for Rinsing Prepared in Example 2 and Comparative Example 10

[0050] In Comparative Example 10, after the pellets of the inner cap 2 and the outer cap 1 were interchanged, that is, the pellets with better plasticity of the outer cap 1 were switched to the pellets with better toughness, the injection-molded outer cap 1 was too soft, which was prone to burrs, resulting in too large dimensions at the thread; and after the pellets with better toughness of the inner cap 2 were switched to the pellets with better plasticity, the injection-molded inner cap 2 was too hard, resulting in difficult flow at the thin-walled part and incomplete injection molding. Moreover, because the yield strength of the pellets was relatively large, the opening force at the pull ring 203 was also relatively large. And affected by the burrs of the outer cap 1, friction occurred during the assembly of the inner cap 2 and the outer cap 1, thus generating insoluble particles.

[0051] Comparative Examples 11 - 12 Differing from Example 2, the formulation of the inner cap 2 in Comparative Examples 11 - 12 was different from that in Example 2, as specifically shown in Table 10: Table 10 Formulation of the Inner Cap 2 and Injection Molding Process Parameters of the Inner Cap 2 and the Outer Cap 1 in Example 2 and Comparative Examples 11 - 12

[0052] The performance test results of the combined caps for rinsing prepared in Example 2 and Comparative Examples 11 - 12 are shown in Table 11 as follows: Table 11 Performance Test Results of the Combined Caps for Rinsing Prepared in Example 2 and Comparative Examples 11 - 12

[0053] As can be seen from Tables 10 - 11, since the inner cap 2 in Comparative Example 11 was not toughened and modified with a toughening elastomer, and the pellets were only obtained by blending polypropylene A and polypropylene B, the yield strength of the pellets was relatively large, resulting in a relatively large opening force at the pull ring 203. The yield strengths of the pellets of the inner cap 2 and the outer cap 1 were similar. Therefore, the inner cap 2 and the outer cap 1 made of two relatively hard pellets would generate relatively large friction during assembly, and insoluble particles were likely to be generated. In addition, since Comparative Example 11 did not use a toughening elastomer for modification, it would also lead to poor melt fluidity during the injection molding process, resulting in incomplete injection molding.

[0054] Since the function of polypropylene B in the inner cap 2 is a compatibilizer, which can make polypropylene A and the toughening elastomer have good compatibility, Comparative Example 12 did not use polypropylene B, resulting in the injection of incompatible components during the injection molding process, manifested as poor sealing of the inner cap 2 and occasional leakage.

[0055] Comparative Example 13 The difference from Example 2 is that in step S2, when the inner cover 2 is injection-molded, the injection speeds of the first-stage injection molding and the second-stage injection molding are the same, both being 45 mm / s.

[0056] The performance test results of the combined caps for rinsing prepared in Example 2 and Comparative Example 13 are shown in Table 12: Table 12 Performance test results of the combined caps for rinsing prepared in Example 2 and Comparative Example 13

[0057] As can be seen from Table 12, the injection speed of the second stage in Comparative Example 13 is the same as that of the first stage, resulting in excessive opening force at the injection molding flash and the pull ring 203. First, because during the second-stage injection molding process, a too-fast injection speed is adopted, so that the cavities at the inner cutting edge 205 and the outer cutting edge 206 are filled relatively quickly, and the internal stress generated by the two-stage injection molding cannot be formed. As a result, when the pull ring 203 is opened, the inner cutting edge 205 and the outer cutting edge 206 are uniformly stressed as a whole, leading to a large opening force at the pull ring 203. Second, because the too-fast injection speed causes the resin that should be filled at a low speed during the second-stage injection molding to be quickly injected into the cavity, resulting in the entry of the rubber material after the cavity is filled, so injection molding flash is generated, resulting in a larger size, and further leading to greater friction during the assembly of the inner cover 2 and the outer cover 1, generating insoluble particles.

Claims

1. A method for preparing a flushing combined cover, the flushing combined cover comprising an outer cover (1) and an inner cover (2), the inner cover (2) comprising a base (201), a pull cover (202) being provided on the top of the base (201), the base (201) being provided with an external thread (204), the outer cover (1) being provided with an internal thread (101), the inner cover (2) being threadedly connected to the outer cover (1); characterized in that: An inner blade (205) and an outer blade (206) are provided on the surface of the pull cover (202); the inner blade (205) is C-shaped, and the outer blade (206) is circular; the thickness of the inner blade (205) and the outer blade (206) are less than the thickness of the pull cover (202); a pull ring (203) is provided on the pull cover (202) between the inner blade (205) and the outer blade (206); and the bottom of the pull ring (203) is connected to the inner blade (205) and the outer blade (206); The yield strength of the granular material used for the outer cover (1) is greater than the yield strength of the granular material used for the inner cover (2); The granular material used for the outer cover (1) is polypropylene A; The granular material used for the inner cover (2) is modified polypropylene, which is made of the following base materials in parts by weight: 30-40 parts of polypropylene A, 30-40 parts of polypropylene B and 20-40 parts of toughening elastomer; The yield strength of polypropylene A is 27-39MPa, and the melt index is 48-60g / 10min; the yield strength of polypropylene B is 26-28MPa, and the melt index is 8-16g / 10min; The preparation method of the flushing composite cover comprises: blending and granulating the base material of the inner cover (2), then injection molding the inner cover (2) and the outer cover (1) by an electric injection molding machine, and finally assembling the inner cover (2) and the outer cover (1) to obtain the flushing composite cover; When the base material of the inner cover (2) is blended and granulated, the polypropylene B is firstly mixed with the toughening elastomer and granulated, and then mixed with the polypropylene A and granulated to obtain the granulated material used for the inner cover (2); The outer cover (1) adopts a one-stage injection molding process; the inner cover (2) adopts a two-stage injection molding process, wherein the first stage injection molding completes the injection molding of the pull ring (203), and the second stage injection molding completes the injection molding of the base (201), the switching point of the two-stage injection molding is the pull cover (202), the first stage injection speed is 40-50 mm / s, and the second stage injection speed is 15-25 mm / s; The inner cover (2) and the outer cover (1) are assembled using a coaxial screwing assembly process.

2. The method for preparing the flushing assembly cover according to claim 1, characterized in that: The yield strength of the polypropylene A is 27 MPa and the melt index is 60 g / 10 min.

3. The method for preparing the flushing assembly cover according to claim 1, characterized in that: The yield strength of the polypropylene B is 26 MPa and the melt index is 16 g / 10 min.

4. The method for preparing the flushing assembly cover according to claim 1, characterized in that: The toughening elastomer is SEBS, and the tensile strength of SEBS is 10-14MPa and the hardness is 35-45A.

5. The method for preparing the flushing assembly cover according to claim 4, characterized in that: The SEBS has a tensile strength of 10 MPa and a hardness of 40A.

6. The method for preparing the flushing assembly cover according to claim 1, characterized in that: When the inner cover (2) is injection molded, the injection start position is 58-60 mm, the switching position of the two-stage injection molding is 45-47 mm, and the injection end position is 17-19 mm.

7. The method for preparing the flushing assembly cover according to claim 1, characterized in that: When the outer cover (1) is injection molded, the injection start position is 50-52 mm, and the injection end position is 15-17 mm.

8. A flushing combined cover, characterized in that: The flushing composite cover is prepared by the preparation method of any one of claims 1 to 7.

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