Combined cover for flushing and preparation method thereof

Abstract

The present invention discloses a flushing assembly cap and a method for preparing the same, relating to the field of packaging materials technology. Firstly, through optimized formulation design, the present invention achieves a product with improved flexibility, reduces insoluble particles caused by excessively hard products, and simultaneously meets the stability requirements of injection molding during processing. Secondly, the outer cap and inner cap are assembled using a coaxial screwing assembly process, thereby reducing visible debris and insoluble particles generated by friction during assembly.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, in particular to a combined cover for flushing and a preparation method thereof. Background Art

[0002] Irrigation combination caps are primarily used for rinse bottles containing sterile water for injection. They are used in environments requiring sterile use, such as wound irrigation and medical device flushing. Packaging materials used in sterile environments have stringent requirements for the cleanliness of the contents. They must be free of visible debris and meet the insoluble particulate requirements for pharmaceutical packaging materials that come into direct contact with body fluids. The presence of insoluble particulates can trigger a rejection reaction at the patient's wound, exacerbating pain. They can even enter the body and become unexcreted after the wound heals, remaining in the patient's body for life and causing pain. These visible debris and insoluble particulates are typically generated by friction between packaging components during assembly. For this reason, the 2015 National Pharmaceutical Packaging Material Standard stipulates that products must be free of foreign matter and meet insoluble particulate requirements.

[0003] Existing flushing caps, such as Chinese utility model patent CN219077924U, disclose a pharmaceutical sealing cap with a threaded seal; Chinese utility model patent CN202620228U discloses a flushing bottle cap with a pull-ring design; and Chinese utility model patent CN208217386U discloses a flushing liquid combination cap with a screw-type design. None of these patents address issues such as visible debris and insoluble particles generated during the packaging assembly process. Therefore, there is an urgent need to develop a new flushing combination cap to address these issues. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to overcome the shortcomings of the existing technology and provide a combined cover for flushing and a preparation method thereof. First, by optimizing the formula 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 cover and the inner cover are assembled through a coaxial screwing assembly process, thereby reducing visible debris and insoluble particles generated by friction during the assembly process.

[0005] The technical solution of the present invention is:

[0006] On the one hand, the present invention provides a preparation method of a combined cover for flushing, wherein the combined cover for flushing comprises an outer cover and an inner cover, the inner cover comprises a base, a pull cover is provided on the top of the base, the base is provided with an external thread, the outer cover is provided with an internal thread, and the inner cover is threadedly connected to the outer cover; an inner blade and an outer blade are provided on the surface of the pull cover, the inner blade is C-shaped, the outer blade is circular, the thickness of the inner blade and the outer blade is less than the thickness of the pull cover, and a pull ring is provided on the pull cover between the inner blade and the outer blade, and the bottom of the pull ring is connected to the inner blade and the outer blade; the yield strength of the granular material used for the outer cover is greater than the yield strength of the granular material used for the inner cover; the granular material used for the outer cover is polypropylene A; the granular material used for the inner cover is modified polypropylene, and is made of the following base materials in parts by weight: 30-40 parts of polypropylene A, polypropylene B 30-40 parts and toughening elastomer 20-40 parts; 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 is: the base material of the inner cover is blended and granulated, and then the inner cover and the outer cover are injection molded by an electric injection molding machine, and finally the inner cover and the outer cover are assembled to obtain the flushing composite cover; wherein the base material of the inner cover is During granulation, polypropylene B is first mixed with the toughening elastomer to form granules, and then mixed with polypropylene A to form granules to obtain the granules 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 first stage injection molding completes the injection molding of the pull ring, and the second stage injection molding completes the injection molding of the base. The switching point of the two-stage injection molding is the pull cover. The injection speed of the first stage is 40-50mm / s, and the injection speed of the second stage is 15-25mm / s; the coaxial screw assembly process is adopted when assembling the inner cover and the outer cover.

[0007] Preferably, the polypropylene A has a yield strength of 27 MPa and a melt index of 60 g / 10 min.

[0008] Preferably, the polypropylene B has a yield strength of 26 MPa and a melt index of 16 g / 10 min.

[0009] Preferably, the toughening elastomer is SEBS, and the tensile strength of SEBS is 10-14 MPa and the hardness is 35-45A.

[0010] Preferably, the SEBS has a tensile strength of 10 MPa and a hardness of 40A.

[0011] Preferably, when the inner cover 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.

[0012] Preferably, when the outer cover is injection molded, the injection start position is 50-52 mm, and the injection end position is 15-17 mm.

[0013] In another aspect, the present invention provides a flushing composite cover, which is prepared by the above-mentioned method for preparing the flushing composite cover.

[0014] The combined cover for flushing of the present invention adopts a design in which the inner cover and the outer cover are separated. The inner cover plays the role of sealing and connecting with the body of the flushing bottle, and needs to be welded with the flushing bottle. After the inner cover and the body of the flushing bottle are sealed and welded, they form a whole, which can be sterilized to achieve a sterile state. When in use, the pull ring on the inner cover can be pulled open to perform the flushing operation. The outer cover plays two roles: one is to protect the inner cover 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 flushing liquid, the outer cover can be covered on the inner cover to play a sealing role, thereby ensuring that the inside of the flushing bottle body is not contaminated. In order to achieve the protection and sealing effects of the inner cover and the outer cover, an external thread is designed on the inner cover and an internal thread is designed on the outer cover. The two are matched to form a screwing structure to complete the sealing connection between the two.

[0015] In the existing technology, both the inner and outer caps have issues with their formulation design and assembly processes that can lead to debris in the product. First, during assembly, friction occurs at the threads, which can cause debris and insoluble particles to form on the inner and outer caps. Second, using tough granular materials to produce the inner and outer caps can lead to insufficient stiffness, resulting in poor sealing. Third, using a press-type assembly process can damage the threads of the inner and outer caps. Fourth, using a screw-type assembly process can cause friction on the threads of the inner and outer caps due to the lack of flexibility of the granular materials, resulting in debris and insoluble particles. Fifth, during assembly, debris and insoluble particles are likely to appear on the side receiving the force.

[0016] In addition, the injection molding process parameters of the outer cover and the inner cover will also affect the debris and insoluble particles generated by the product. The smaller size of the thread, the higher injection pressure and the injection range will easily make the thread injection molded more full, resulting in increased friction during assembly and the generation of debris; smaller injection pressure and injection range will easily cause the thread size to shrink, resulting in problems with the sealing of the product. Therefore, after determining the formula of the inner cover and the outer cover, it is necessary to determine the corresponding injection molding process parameters according to the properties of the product to assist in reducing assembly friction. At the same time, compared with hydraulic injection molding machines, electric injection molding machines are better at controlling precise dimensions. Therefore, in order to ensure the stability of the thread size, the present invention also limits the need to use electric injection molding machines to injection mold the inner cover and the outer cover.

[0017] At the same time, the present invention adopts a two-stage injection molding process based on the properties of the granular material used for the inner cap to ensure that the inner cap formula of the present invention can produce an inner cap with a pull ring that is easy to open and can ensure sealing; and the outer cap is prepared by a one-stage injection molding process, which can ensure that the outer cap is molded in one step and does not cause shrinkage problems.

[0018] During the injection molding of the inner cap, the injection point is located at the center of the pull-tab. The principle behind the two-stage injection molding design for the inner cap is that during the injection molding process, the melt flows in a rolling pattern. When the melt contacts the inner mold wall, the outer melt cools first, then gradually cools to the inner core. Therefore, based on this principle, to make the pull tab easier to open, a lower-strength polypropylene resin is first selected. Specifically, toughening the polypropylene to reduce its yield strength and the pull-tab opening force is performed. Secondly, a faster injection speed is used during molding. Upon injection, the melt first fills the pull tab farther away, allowing the inner wall to partially cool. The injection speed is then switched to a slower speed to maintain pressure, filling the base and ensuring the full filling of the pull tab. The slower melt now fills both the inner and outer cutting edges. This creates a stress differential between the inner and outer cutting edges, which reduces the opening force at the pull tab.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The flushing combination cap of the present invention effectively addresses the problem of wear debris and insoluble particles generated by friction during assembly of the outer and inner caps by optimizing the formulation design of the inner and outer caps and ensuring that the yield strength of the granular material used in the outer cap is greater than that of the granular material used in the inner cap. Furthermore, by optimizing the injection molding process for the inner and outer caps, the present invention effectively ensures the dimensional stability of the threads of the inner and outer caps, and ensures that the inner cap pull ring is easy to open while maintaining good sealing. Furthermore, the present invention utilizes a coaxial screw assembly process to assemble the inner and outer caps, effectively reducing friction during assembly and thereby reducing the generation of friction debris. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the outer cover of the flushing composite cover of the present invention.

[0022] Figure 2 It is a structural schematic diagram of the inner cover of the flushing composite cover of the present invention.

[0023] Figure 3 It is a top view of the inner cover of the flushing combination cover of the present invention.

[0024] In the figure, 1, outer cover; 101, internal thread; 2, inner cover; 201, base; 202, pull cover; 203, pull ring; 204, external thread; 205, internal blade; 206, external blade. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solutions of 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.

[0026] like Figure 1-3 As shown, the flushing combination cover 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 provided on the top of the base 201, the base 201 is provided with an external thread 204, the outer cover 1 is provided with an internal thread 101, and 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 blade 205 and a circular outer blade 206, the thickness of the inner blade 205 and the outer blade 206 is 0.15mm, and the thickness of the pull cover 202 is 1.3mm. A pull ring 203 is provided on the pull cover 202 between the inner blade 205 and the outer blade 206. The thickness of the inner blade 205 and the outer blade 206 is less than the thickness of the pull cover 202, so that when the pull ring 203 is pulled, the pull cover 202 will first be broken at the thinner C-shaped inner blade 205 and the circular outer blade 206, thereby opening the pull cover 202. Its specific structure can refer to the veterinary medicine cover disclosed in the design patent CN308918651S.

[0027] The raw materials used in the following examples are all commercially available products:

[0028] Polypropylene, 6881, Lee Chang Jung Chemical Co., Ltd., yield strength 39 MPa, melt index 55 g / 10 min;

[0029] Polypropylene, 5600XT, Formosa Plastics (Ningbo) Co., Ltd., yield strength 27 MPa, melt index 60 g / 10 min;

[0030] Polypropylene, RP375RT, LyondellBasell Industries, Ltd., with a yield strength of 29 MPa and a melt index of 48 g / 10 min;

[0031] Polypropylene, K4912, from Sinopec Beijing Yanshan Branch, with a yield strength of 26 MPa and a melt index of 16 g / 10 min;

[0032] Polypropylene, STM866, manufactured by Lee Chang Jung Chemical Co., Ltd., with a yield strength of 27 MPa and a melt index of 8 g / 10 min;

[0033] Polypropylene, 5090T, Formosa Plastics (Ningbo) Co., Ltd., yield strength 28 MPa, melt index 15 g / 10 min;

[0034] Toughened elastomer SEBS, 1645, Kraton Polymers Co., Ltd., with a tensile strength of 11 MPa and a hardness of 35A;

[0035] Toughened elastomer SEBS, 8245D, TSRC (Nantong) Industrial Co., Ltd., with a tensile strength of 10 MPa and a hardness of 40A;

[0036] Toughened elastomer SEBS, YH-506, produced by Baling Petrochemical Company, China Petrochemical Corporation Asset Management Co., Ltd., has a tensile strength of 14 MPa and a hardness of 45A.

[0037] Examples 1-7

[0038] The preparation method of the flushing assembly cover of Examples 1-7 comprises the following steps:

[0039] S1 Inner cover 2 base material blending and granulation: The inner cover 2 formula is shown in Table 1. Polypropylene B and toughening elastomer SEBS are placed in a high-speed mixer to mix to obtain a mixture, and then the mixture is put into an extruder for extrusion granulation; then the mixture is placed in a high-speed mixer together with polypropylene A to obtain a mixture, and then the mixture is put into an extruder for extrusion granulation to obtain inner cover 2 pellets;

[0040] S2 Injection molding of inner cover 2 and outer cover 1: Injection molding of inner cover 2 and outer cover 1 is performed using an electric injection molding machine according to the parameters shown in Table 1;

[0041] S3 Inner cover 2 and outer cover 1 are assembled: The inner cover 2 and outer cover 1 are assembled through a coaxial screwing assembly process. A robot is used to clamp the base 201 position of the inner cover 2 and fix the inner cover 2. Then another robot clamps the top of the outer cover 1 and places the outer cover 1 on the central axis of the inner cover 2 while applying continuous downward pressure. When the inner thread 101 of the outer cover 1 contacts the outer thread 204 of the inner cover 2, the outer cover 1 is subjected to the thread force, and this force reacts to the robot, causing the robot to rotate, thereby rotating the outer cover 1 and assembling it to the inner cover 2 to obtain a combined cover for flushing.

[0042] Table 1 Inner cover 2 formulations and injection molding process parameters of inner cover 2 and outer cover 1 in Examples 1-7

[0043]

[0044] In Table 1, the yield strength was measured with reference to GB / T 1040 Plastics - Determination of Tensile Properties.

[0045] The performance tests of the flushing combination covers prepared in Examples 1-7 were carried out:

[0046] 1) Thread dimensions of outer cover 1 and inner cover 2: Test according to the method of GB / T40742.1 Geometrical Technical Specification for Products (GPS) - Testing and Verification of Geometric Accuracy, and check whether they meet the requirements of 22±0.3mm for the inner thread diameter of outer cover 1 and 22.8±0.3mm for the outer thread diameter of inner cover 2. If they meet the requirements, they are qualified; otherwise, they are unqualified.

[0047] 2) Processing stability of the inner cover 2: After each injection molding is completed by the electric injection molding machine, the control panel displays the injection pressure of that time. When the injection pressure is within the range of 55±2MPa, it indicates that the injection volume of each time is relatively uniform. At the same time, observe the appearance of the product after each injection to confirm that there is no incomplete injection or overflow. This can be judged as stable injection.

[0048] 3) Opening force of the inner cover 2 pull ring 203: refer to the pull ring opening force in "YBB00242004-2015 Polypropylene combination cover for plastic infusion container (pull ring type)" for testing;

[0049] 4) Sealing performance of inner cap 2: Test the sealing performance of the pull ring cut in accordance with the requirements of "YBB00242004-2015 Polypropylene Composite Caps for Plastic Infusion Containers (Pull Ring Type)";

[0050] 5) Insoluble particles in the combined lid for rinsing: Test according to "YBB00272004-2015 Determination of Insoluble Particles in Packaging Materials". The liquid is considered qualified if the number of insoluble particles larger than 5μm per mL does not exceed 100; the number of insoluble particles larger than 10μm per mL does not exceed 20; the number of insoluble particles larger than 25μm per mL does not exceed 2.

[0051] The performance test results of the flushing combination covers prepared in Examples 1-7 are shown in Table 2:

[0052] Table 2 Performance test results of the flushing combination covers prepared in Examples 1-7

[0053]

[0054] Comparative Example 1

[0055] The difference from Example 2 is that in step S2 , a hydraulic injection molding machine is used for injection molding of the inner cover 2 and the outer cover 1 , and the injection molding parameters of the hydraulic injection molding machine are the same as those of Example 2.

[0056] When using a hydraulic injection molding machine, the control accuracy of the injection starting position, two-stage injection switching position, injection end position of the inner cover 2, and the injection starting position and injection end position of the outer cover 1 is weaker than that of an electric injection molding machine. The position deviation is ±2mm, which does not meet the injection molding parameters of Example 2, resulting in poor dimensional stability at the threads of the inner cover 2 and the outer cover 1, and dimensional deviations are prone to occur at the threads. During assembly, the friction contact area between the inner cover 2 and the outer cover 1 is too large, which will produce wear debris and insoluble particles.

[0057] Comparative Example 2

[0058] The difference from Example 2 is that in step S1, the base material of the inner cover 2 is blended and granulated: polypropylene B, toughening elastomer SEBS and polypropylene A are placed together in a high-speed mixer and mixed to obtain a mixture, which is then put into an extruder for extrusion and granulation to obtain inner cover 2 pellets.

[0059] When the pellets of comparative example 2 are used to injection mold the inner cover 2, due to the different flow rates of the base materials, the flow stability of each part cannot be guaranteed when the melt is injected from the electric injection molding machine, resulting in incomplete injection molding during the processing; and the inner cover 2 will have a sealing problem caused by leakage due to incomplete injection molding.

[0060] Comparative Example 3

[0061] The difference from Example 2 is 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 by a press-type assembly process, a robot is used to clamp the base 201 of the inner cover 2, the inner cover 2 is fixed, and then another robot clamps the top of the outer cover 1 and places the outer cover 1 on the central axis of the inner cover 2, while applying continuous downward pressure; when the inner thread 101 of the outer cover 1 contacts the outer thread 204 of the inner cover 2, the outer cover 1 is subjected to the force of the thread, the robot does not rotate, and the outer cover 1 is vertically pressed and assembled onto the inner cover 2 by mechanical pressing to obtain a combined cover for flushing.

[0062] The use of a press-type assembly process will cause friction between the threads of the inner cover 2 and the outer cover 1 in the vertical direction during assembly, thereby causing thread wear and generating wear debris.

[0063] Comparative Examples 4-5

[0064] The difference between Comparative Example 4-5 and Example 2 is that the formula of the inner cover 2 of Comparative Example 4-5 is different from that of Example 2, as shown in Table 3:

[0065] Table 3 Inner cover 2 formulations and injection molding process parameters of inner cover 2 and outer cover 1 in Example 2 and Comparative Examples 4-5

[0066]

[0067] The performance test results of the flushing assembly covers prepared in Example 2 and Comparative Examples 4-5 are shown in Table 4:

[0068] Table 4 Performance test results of the flushing assembly covers prepared in Example 2 and Comparative Examples 4-5

[0069]

[0070] As can be seen from Tables 3-4, the inner cap 2 of Comparative Example 4 contains too much polypropylene, making the inner cap 2 too hard. This causes wear on the threads during demolding and easily generates wear debris after assembly with the outer cap 1. The pull ring 203 also has a large opening force, which affects its usability. The inner cap 2 of Comparative Example 5 contains too much SEBS, making it too soft. The pull ring 203 easily deforms and becomes unusable. The cap body is also too soft and has poor stiffness, resulting in leakage after assembly with the outer cap 1.

[0071] Comparative Examples 6-7

[0072] The difference between Comparative Examples 6-7 and Example 2 is that the injection molding process parameters of the inner cover 2 of Comparative Examples 6-7 are different from those of Example 2, as shown in Table 5:

[0073] Table 5 Inner cover 2 formulations and injection molding process parameters of inner cover 2 and outer cover 1 in Example 2 and Comparative Examples 6-7

[0074]

[0075] The performance test results of the flushing assembly covers prepared in Example 2 and Comparative Examples 6-7 are shown in Table 6:

[0076] Table 6 Performance test results of the flushing assembly covers prepared in Example 2 and Comparative Examples 6-7

[0077]

[0078] It can be seen from Tables 5-6 that when injection molding the inner cover 2, the range from the injection start position to the injection end position is shortened in Comparative Example 6, resulting in incomplete injection molding of the inner cover 2 during the injection molding process, which in turn causes the size of the thread of the inner cover 2 to not be formed normally, and causes incomplete injection molding at the pull ring 203, resulting in leakage, and also causes the inner cover 2 and the outer cover 1 to be unable to be assembled normally.

[0079] Comparative Example 7 is the opposite of Comparative Example 6. It expands the measuring range from the starting position of injection molding to the end position of injection molding, resulting in the problem of injection overflow of the inner cover 2 during the injection molding process, which causes the thread size of the inner cover 2 to be too large, and generates grinding chips when assembled with the outer cover 1; and due to the large measuring range, the amount of injected plastic is too much, resulting in overflow at the pull ring 203, and the opening force at the pull ring 203 of the inner cover 2 is too large.

[0080] Comparative Examples 8-9

[0081] The difference between Comparative Examples 8-9 and Example 2 is that the injection molding process parameters of the outer cover 1 of Comparative Examples 8-9 are different from those of Example 2, as shown in Table 7:

[0082] Table 7 Formulations of the outer cover 1 of Example 2 and Comparative Examples 8-9 and injection molding process parameters of the inner cover 2 and the outer cover 1

[0083]

[0084] The performance test results of the flushing assembly covers prepared in Example 2 and Comparative Examples 8-9 are shown in Table 8:

[0085] Table 8 Performance test results of the flushing assembly covers prepared in Example 2 and Comparative Examples 8-9

[0086]

[0087] It can be seen from Tables 7-8 that when injection molding the outer cover 1, the range from the injection start position to the injection end position is shortened in Comparative Example 8, resulting in incomplete injection molding of the outer cover 1 during the injection molding process, which in turn results in the size of the thread of the outer cover 1 not being formed normally, and the inner cover 2 and the outer cover 1 cannot be assembled normally.

[0088] In comparative example 9, when injection molding the outer cover 1, the range from the injection starting position to the injection ending position is expanded, resulting in the problem of injection overflow during the injection molding process of the outer cover 1, which causes the thread size of the outer cover 1 to be too large, and generates wear debris when assembled with the inner cover 2.

[0089] Comparative Example 10

[0090] The difference from Example 2 is that, in Comparative Example 10, the pellets of the inner cover 2 and the outer cover 1 of Example 2 are interchanged.

[0091] The performance test results of the flushing assembly covers prepared in Example 2 and Comparative Example 10 are shown in Table 9:

[0092] Table 9 Performance test results of the flushing combination cover prepared in Example 2 and Comparative Example 10

[0093]

[0094] In Comparative Example 10, after the pellets of inner cap 2 and outer cap 1 were interchanged, that is, the pellets with better plasticity of outer cap 1 were replaced with pellets with better toughness, the molded outer cap 1 was relatively soft, easily causing burrs and resulting in oversized threads. Meanwhile, after the pellets with better toughness of inner cap 2 were replaced with pellets with better plasticity, the molded inner cap 2 was relatively hard, resulting in poor flow in thin-walled areas and incomplete injection molding. Furthermore, due to the high yield strength of the pellets, the opening force at the pull ring 203 was also high. Furthermore, due to the influence of the burrs of outer cap 1, friction occurred during assembly of inner cap 2 and outer cap 1, resulting in the generation of insoluble particles.

[0095] Comparative Examples 11-12

[0096] The difference from Example 2 is that the formula of the inner cover 2 of Comparative Examples 11-12 is different from that of Example 2, as shown in Table 10:

[0097] Table 10 Inner cover 2 formulations and injection molding process parameters of inner cover 2 and outer cover 1 in Example 2 and Comparative Examples 11-12

[0098]

[0099] The performance test results of the flushing assembly covers prepared in Example 2 and Comparative Examples 11-12 are shown in Table 11:

[0100] Table 11 Performance test results of the flushing assembly covers prepared in Example 2 and Comparative Examples 11-12

[0101]

[0102] Tables 10-11 show that because the inner cap 2 of Comparative Example 11 was not toughened with a toughening elastomer and was produced solely by blending polypropylene A and polypropylene B into pellets, the pellets exhibited a high yield strength, resulting in a high opening force at the pull ring 203. The pellets of the inner cap 2 and outer cap 1 have similar yield strengths. Therefore, the assembly of the inner cap 2 and outer cap 1, made from these two relatively hard pellets, results in significant friction and the generation of insoluble particles. Furthermore, the lack of a toughening elastomer in Comparative Example 11 also results in poor melt flowability during the injection molding process, leading to incomplete injection molding.

[0103] Since the role of polypropylene B in the inner cover 2 is a compatibilizer, which can make polypropylene A more compatible with the toughening elastomer, comparative example 12 does not use polypropylene B, resulting in incompatible components being injected during the injection molding process, which manifests as poor sealing of the inner cover 2 and occasional leakage.

[0104] Comparative Example 13

[0105] The difference from Example 2 is that in step S2, when the inner cover 2 is injection molded, the injection speed of the first-stage injection molding and the second-stage injection molding are the same, both of which are 45 mm / s.

[0106] The performance test results of the flushing assembly covers prepared in Example 2 and Comparative Example 13 are shown in Table 12:

[0107] Table 12 Performance test results of the flushing assembly covers prepared in Example 2 and Comparative Example 13

[0108]

[0109] As can be seen from Table 12, the second-stage injection speed in Comparative Example 13 is the same as the first-stage injection speed, resulting in injection burrs and excessive opening force at the pull ring 203. This is because, during the two-stage injection molding process, the injection speed is too fast, causing the cavity at the inner blade 205 and the outer blade 206 to fill quickly, failing to form the internal stress generated by the two-stage injection molding. As a result, the inner blade 205 and the outer blade 206 are uniformly stressed when the pull ring 203 is opened, resulting in a large opening force at the pull ring 203. Secondly, the excessive injection speed causes the resin, which should have been filled at a lower speed during the two-stage injection molding, to be injected into the cavity quickly. As a result, some resin still enters the cavity after the cavity is filled, resulting in injection burrs and an oversized shape. This, in turn, causes greater friction during the assembly of the inner cover 2 and the outer cover 1, and produces insoluble particles.

Claims

1. A method for preparing a flushing combined cover, wherein the flushing combined cover comprises an outer cover (1) and an inner cover (2), wherein the inner cover (2) comprises a base (201), a pull cover (202) is provided on the top of the base (201), the base (201) is provided with an external thread (204), the outer cover (1) is provided with an internal thread (101), and the inner cover (2) is threadedly connected to the outer cover (1); characterized in that, The surface of the pull cover (202) is provided with an inner blade (205) and an outer blade (206), the inner blade (205) is C-shaped, the outer blade (206) is circular, the thickness of the inner blade (205) and the outer blade (206) is less than the thickness of the pull cover (202), and 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 27-39 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 of the flushing composite cover is as follows: the base material of the inner cover (2) is blended and granulated, the inner cover (2) and the outer cover (1) are then injection-molded by an electric injection molding machine, and finally the inner cover (2) and the outer cover (1) are assembled to obtain the flushing composite cover; When the base material of the inner cover (2) is blended and granulated, polypropylene B is first mixed with the toughening elastomer and granulated, and then mixed with polypropylene A and granulated to obtain the granules 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), and the switching point of the two-stage injection molding is the pull cover (202). The injection speed of the first stage is 40-50 mm / s, and the injection speed of the second stage 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, wherein: The polypropylene A has a yield strength of 27 MPa and a melt index of 60 g / 10 min.

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

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

5. The method for preparing the flushing assembly cover according to claim 4, wherein: 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, wherein: 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, wherein: 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 combination cover, characterized in that: The flushing composite cover is prepared by the preparation method according to any one of claims 1 to 7.

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