Method for forming a surface coating layer and method for manufacturing a gasket

Abstract

To provide a surface coating layer formation method and a method for manufacturing a gasket which can reduce falling of insoluble fine particles into a chemical liquid while maintaining stable slidability while preventing leakage of a liquid agent.SOLUTION: A surface coating layer formation method has: a coating step of coating a material on a surface layer having such a composition that silicon-based rubber particles are contained in a silicon-based solution (Investigation number 1 (blending 1)) onto the surface of a base material with a predetermined coating film thickness; a drying step of drying a sliding member after coating at a first temperature for first time; a baking step of baking the sliding member after drying at a second temperature for second time; and a cleaning step of extracting and cleaning the sliding member after baking at a third temperature for third time.SELECTED DRAWING: Figure 4

Description

Technical Field

[0004] , , , ,

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[0001] The present invention relates to a method for forming a surface coating layer and a method for manufacturing a gasket.

Background Art

[0002] Conventionally, prefilled syringes filled with a chemical solution in advance have been used. A prefilled syringe (hereinafter referred to as a syringe) includes an outer cylinder, a gasket, a plunger, and a cap. The gasket prevents leakage of the chemical solution (hereinafter referred to as leakage). In order to improve the slidability of the gasket, for example, a film composed of a composition of a flexibility-imparting component (for example, urethane resin) and a sliding component (for example, fluororesin) is coated on the surface of the gasket to improve the slidability (that is, reduce the sliding resistance) of the gasket in the outer cylinder of the syringe (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the surface of the gasket is coated with solid fine particles or the like in order to improve the slidability as in the prior art, there is a problem that the solid fine particles held in the film are detached and insoluble fine particles are mixed into the chemical solution. For this reason, there is a demand for a method for forming a surface coating layer and a method for manufacturing a gasket that reduce the dropout of insoluble fine particles into the chemical solution while preventing leakage of the liquid agent and maintaining stable slidability.

[0005] The present invention has been made in view of the above circumstances, and its exemplary objective is to provide a method for forming a surface coating layer and a method for manufacturing a gasket that can reduce the shedding of insoluble fine particles into the chemical solution while maintaining stable sliding properties and preventing leakage of the liquid agent. [Means for solving the problem]

[0006] To solve the above-mentioned problems, the present invention has the following configuration.

[0007] (1) A method for forming a surface coating layer to improve the sliding properties of a sliding member made of rubber, The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the substrate to a predetermined coating thickness, A drying step in which the sliding member after coating is dried at a first temperature for a first time, A firing step in which the sliding member after drying is fired at a second temperature for a second time, A method for forming a surface coating layer, comprising a cleaning step of extracting and cleaning the sliding member after firing at a third temperature for a third period of time.

[0008] (2) A method for forming a surface coating layer to improve the sliding properties of a gasket that is placed at the tip of a plunger used in a syringe and slides against the inner wall of the syringe, The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the gasket to a predetermined coating thickness, A drying step in which the gasket after coating is dried at a first temperature for a first time, A firing step in which the gasket after drying is fired at a second temperature for a second time, A method for forming a surface coating layer, comprising a cleaning step of extracting and cleaning the gasket after firing at a third temperature for a third period of time.

[0009] (3) A method for manufacturing a gasket that is placed at the tip of a plunger used in a syringe and slides against the inner wall of the syringe, The gasket has a surface coating layer on the surface of the rubber base material to improve sliding properties. The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the substrate to a predetermined coating thickness, A drying step in which the gasket after coating is dried at a first temperature for a first time, A firing step in which the gasket after drying is fired at a second temperature for a second time, A method for manufacturing a gasket, comprising a washing step of extracting and washing the gasket after firing at a third temperature for a third period of time.

[0010] Further objects or other features of the present invention will be revealed by preferred embodiments described below with reference to the accompanying drawings. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for forming a surface coating layer and a method for manufacturing a gasket that can reduce the shedding of insoluble fine particles into the chemical solution while maintaining stable sliding properties and preventing leakage of the liquid. [Brief explanation of the drawing]

[0012] [Figure 1] (a) A schematic side view showing the configuration of the syringe in the embodiment, (b) A schematic side view showing the configuration of the gasket [Figure 2] (a) Enlarged view of the gasket before the coating process, (b) Enlarged view of the surface layer formed on the gasket after the coating process, (c) Perspective view showing the planar portion of the gasket, (d) Enlarged view of the cross-section of the gasket and surface layer, (e) Cross-sectional view of the gasket. [Figure 3]Front view showing the state of the experiment for measuring sliding resistance in the embodiment (a), and top view showing the state of the leak test (b) [Figure 4] A diagram showing the results of Evaluation 1 in the embodiment, (a) a table showing the results of Evaluation 1, and (b) a graph showing the number of insoluble fine particles in Evaluation 1 [Figure 5] A diagram showing the results of Evaluation 2 in the embodiment, (a) a table showing the results of Evaluation 2, and (b) a graph showing the number of insoluble fine particles in Evaluation 2 [Figure 6] A diagram showing the results of Evaluation 3 in the embodiment, (a) a table showing the results of Evaluation 3, and (b) a graph showing the number of insoluble fine particles in Evaluation 3

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described with reference to the drawings. Here, the longitudinal direction of the syringe is the direction in which the plunger is pushed, which is the X direction. Also, the direction in which the plunger is pushed and the chemical solution is discharged from the tip of the cylinder is the plus (+) direction of the X direction.

[0014] [Embodiment] <Syringe> The syringe of this embodiment will be described. FIG. 1(a) is a schematic side view showing the configuration of the syringe of this embodiment, and the X direction and +, - are also shown. The syringe 100 includes an outer cylinder 102, a gasket 104, a plunger 106, and a cylinder tip 110. A cap 108 and a chemical solution 200 may be provided.

[0015] The outer cylinder 102 has a cylindrical shape with a cross-section orthogonal to the longitudinal direction being, for example, circular. The outer cylinder 102 forms a space filled with the chemical solution 200 shown by a broken line inside together with the gasket 104. The outer cylinder 102 is made of, for example, glass, resin, etc. For example, a lubricant or the like may be applied to the inner surface of the outer cylinder 102 to enhance the slidability with the gasket 104 (that is, to reduce the sliding resistance) and obtain high flow accuracy without causing large disturbances in the discharge of the chemical solution. As the lubricant, for example, silicone oil or the like may be used.

[0016] The gasket 104 is attached to one end of the plunger 106 and slides in contact with the inner surface (inner cylinder wall) of the outer cylinder 102 when the plunger 106 is pushed in the +X direction. The connection between the gasket 104 and the plunger 106 is such that, for example, the gasket 104 side is concave and the plunger 106 side is convex, with the convex portion of the plunger 106 fitting into the concave portion of the gasket 104. The convex portion of the plunger 106 may have, for example, male screw threads, and the concave portion of the gasket 104 may have, for example, female screw grooves, and they may be configured to screw into each other. The gasket 104 will be described later.

[0017] The plunger 106 has a gasket 104 attached to one end (+ side) in the X direction, and a portion of it is inserted into the outer cylinder 102 together with the gasket 104. The plunger 106 has a flange 106a on the other end (- side) in the X direction for the user's finger to rest on. When the flange 106a is pushed towards the + side in the X direction, the entire plunger 106 moves towards the + side in the X direction. The further the plunger 106 moves towards the + side in the X direction, the greater the degree to which the plunger 106 enters the outer cylinder 102. Note that the syringe 100 is not limited to being operated directly by the user, but may also be used attached to a device such as a syringe pump.

[0018] The nozzle 110 has one end (- side) in the X direction that is continuous with the space in the outer cylinder 102 that is filled with the chemical solution 200. The other end (+ side) of the nozzle 110 in the X direction is open, and when the plunger 106 moves to the + side in the X direction, if the outer cylinder 102 is filled with the chemical solution, the chemical solution 200 is released from the opening of the nozzle 110.

[0019] In a pre-filled syringe, the cap 108 seals the tip 110 to prevent the drug solution 200 from leaking out when it is not time to release the drug solution 200 from inside the syringe 100. The cap 108 may also be placed over the tip 110 to protect it from dirt, impact, etc. Note that the cap 108 is not necessary for a non-pre-filled syringe.

[0020] Syringe 100 may be a syringe with a needle, a syringe without a needle, etc. For example, if syringe 100 is a pre-filled syringe, the drug solution 200 is pre-filled and the drug solution 200 is held in place with the cap 108 attached. Using a pre-filled syringe prevents drug mix-ups and contamination of the drug solution 200 at the location where syringe 100 is used.

[0021] Syringe 100 is required to ensure that the drug solution 200 filled in the outer barrel 102 does not leak from the gasket 104 side. Syringe 100 is also required to have smooth movement (sliding) of the plunger 106 (i.e., gasket 104) during use, so that the dispensing of the drug solution does not become greatly disturbed and high flow accuracy is achieved, and that it has high sliding properties, in other words, low sliding resistance (hereinafter also referred to as low sliding). Furthermore, syringe 100 is required to have few or no impurities originating from syringe 100 in the drug solution 200 (for example, insoluble fine particles described later).

[0022] <gasket> The sliding member, the gasket 104, will now be described. Figure 1(b) is a schematic side view showing the configuration of the gasket 104 in this embodiment. The surface layer 300, which will be described later, is shown as a cross-sectional view. The gasket 104 has a base material 104a, a tapered portion 104b, a body portion 104c, and a connecting portion 104d. The surface layer 300 shown in Figure 1(b) is formed on the gasket 104 by going through a coating process described later. In the following description, the surface layer 300 may also be included in the gasket 104 after the coating process.

[0023] The base material 104a is rubber, for example, butyl rubber. Butyl rubber is a synthetic rubber obtained by copolymerizing isobutylene with several percent isoprene in molar ratio. Butyl rubber has good electrical insulation, ozone resistance, weather resistance, aging resistance, and shock absorption. In this embodiment, butyl rubber is used as the base material 104a of the gasket 104 because it has low gas permeability and does not allow oxygen to pass through, thus not degrading the chemical solution 200. In addition to butyl rubber, natural rubber, styrene-butadiene rubber, chloroprene rubber, acrylonitrile rubber, ethylene propylene rubber, urethane rubber, silicone rubber, fluororubber, chlorosulfonated polyethylene rubber, etc. may also be used as the base material 104a. Butyl rubber, isoprene rubber, styrene-butadiene rubber, silicone rubber, etc. are preferred as rubbers to be used for the base material 104a.

[0024] The tapered portion 104b is the portion of the gasket 104 at one end (+ side) in the X direction and has a tapered shape. That is, the tapered portion 104b is conical in shape. Note that the gasket 104 does not necessarily have a tapered portion; as shown in Figure 2 later, the surface perpendicular to the X direction may be a flat plane.

[0025] The body portion 104c is the side surface of the gasket 104 and has multiple ribs. The multiple ribs of the body portion 104c are in contact with the inner surface of the outer cylinder 102. Note that the body portion 104c does not necessarily have multiple ribs, and the entire surface of the body portion 104c may be in contact with the inner surface of the outer cylinder 102. The connecting portion 104d is the other end (-side) of the gasket 104 in the X direction and is the connecting portion to the plunger 106. The manner in which the connecting portion 104d is connected to the plunger 106 is not particularly limited, but as described above, it is sufficient that it has a shape corresponding to the connecting portion on the plunger 106 side.

[0026] A surface layer 300 is formed on the gasket 104 during the coating process. The surface layer 300 enhances the airtightness to prevent leakage of the chemical solution 200 and also improves the sliding properties of the plunger 106. The material forming the surface layer 300 is required to not detach into the chemical solution 200 and generate insoluble fine particles, or to generate only a small amount (hereinafter referred to as low insoluble fine particle property).

[0027] <Surface layer and coating liquid> A material for forming a surface layer 300 (hereinafter referred to as the coating liquid) is applied to the gasket 104. Note that in addition to the term "application," the terms "coating" or "covering" may also be used, and the surface layer 300 may be described as a film. The surface layer 300 is formed when the outer surface of the gasket 104 is coated with the coating liquid.

[0028] The coating liquid of this embodiment contains a flexibility-imparting component and a sliding-resistance-imparting component. Here, the flexibility-imparting component is a component that imparts elasticity to the surface layer 300. The surface layer 300 can deform in accordance with the substrate 104a when the substrate 104a is compressed by the flexibility-imparting component. The sliding-resistance-imparting component is a component that enhances the sliding properties between the gasket 104 and the inner wall of the outer cylinder 102. Furthermore, by using materials with similar compositions for the flexibility-imparting component and the sliding-resistance-imparting component, a highly compatible coating can be achieved. By improving compatibility, the shedding of insoluble fine particles from the surface layer 300 of the gasket 104 into the chemical solution 200 (hereinafter referred to as the generation of insoluble fine particles) can be reduced. For example, when a silicon-based material is used for the flexibility-imparting component, a silicon-based material is also used for the sliding-resistance-imparting component. In this embodiment, for example, an aqueous silicon-based solution is used as the flexibility-imparting component in the coating liquid, and silicon-based rubber particles are used as the sliding-resistance-imparting component. In other words, the coating solution of this embodiment has a composition containing silicon-based rubber particles in an aqueous silicon-based solution.

[0029] The coating solution is, for example, a silicon-based solution to which silicon-based rubber fine particles are added. The silicon-based solution (silicone-based liquid) may be, for example, a silicone (reactive silicone) having silanol groups and a polysiloxane as its basic structure. The silicon-based rubber fine particles may be, for example, silicone rubber with a polysiloxane as its basic structure.

[0030] The particle size of the silicon-based rubber microparticles is between 1 μm and 50 μm in average size. If the particle size of the silicon-based rubber microparticles is less than 1 μm in average size, aggregation may occur easily, potentially making it difficult to prepare the coating solution. Also, if the particle size of the silicon-based rubber microparticles is greater than 50 μm in average size, the sealing performance may decrease.

[0031] The gasket 104 is formed by a kneading process in which the raw material rubber is kneaded, and a molding process in which the kneaded rubber is vulcanized and molded. The surface layer 300 of the gasket 104 is formed by applying a coating liquid by spraying, drying it, then baking it, and washing it.

[0032] <Gasket manufacturing method> This invention describes a method for forming a surface coating layer on a gasket 104 that achieves low friction and low insoluble particulate matter (a method for manufacturing a gasket 104). The surface coating layer formation method of this embodiment includes a coating step, a drying step, a firing step, and a cleaning step. The finishing step for completing the gasket 104 may be performed before the coating step or before the cleaning step. Furthermore, a sterilization step may be performed after the cleaning step to sterilize the gasket 104 on which the surface layer 300 has been formed.

[0033] (Coating process) In the coating process, the predetermined film thickness of the coating liquid to be applied is, for example, 5 μm. However, the predetermined film thickness is not limited to 5 μm; for example, it may be within the range of 1 μm or more and 50 μm or less, and the suitable film thickness depends on the size of the silicon-based rubber fine particles. If the film thickness is less than 1 μm, the sliding resistance may increase. Also, if the film thickness is more than 50 μm, the sealing performance will decrease, and the possibility of cracking of the coating will increase.

[0034] Known methods can be used for coating, such as spin coating, slit coating, dip coating, spray coating, and direct coating by hand (e.g., with a brush), but in this embodiment, spray coating is used. Hereafter, the gasket 104 on which the surface layer 300 has been formed by the coating process will also be simply referred to as gasket 104.

[0035] (drying process) In the drying process, the gasket 104, to which the coating liquid has been applied and the surface layer 300 has been formed, is dried at a first temperature, for example, room temperature to 100°C, for a first time, for example, 1 hour to 24 hours. If the first temperature is lower than room temperature, the surface layer 300 will not dry easily, and it may take a long time to complete the drying process. Also, a temperature lower than room temperature requires a cooled liquid (for example, water), which is burdensome to the process. If the first temperature is high, in the case of a solvent-based coating liquid, there are safety concerns such as ignition, and in the case of a water-based coating liquid, the drying time is shorter, but a smooth surface layer may not be formed. Also, if the first time is shorter than 1 hour, drying will be insufficient, and a smooth surface layer may not be formed after firing. Furthermore, if the first time is longer than 24 hours at a high temperature of 100°C, the deterioration of the base material 104a may progress. Also, excessively long times are undesirable from a process perspective.

[0036] (Firing process) In the firing process, the dried gasket is fired at a second temperature, for example, room temperature to 200°C, for a second time, for example, 5 minutes to 2 hours. If the second temperature is lower than room temperature, the curing of the surface layer 300 may take longer. Also, the strength of the formed surface layer 300 may be reduced. If the second temperature is higher than 200°C, the deterioration of the base material 104a may progress, and the surface layer 300 may also deteriorate. If the second time is shorter than 5 minutes, the curing reaction of the surface layer 300 may not be completed, and the strength of the surface layer 300 may also be reduced. Furthermore, if the second time is longer than 2 hours, the deterioration of the base material 104a may progress.

[0037] Figure 2(a) is an enlarged view of the gasket 104 before the coating process. Note that the gasket 104 shown in Figure 2 does not have a tapered shape like the tapered portion 104b, but rather a gasket 104 with a flat portion 104e (see Figure 2(c)). Figure 2(b) is an enlarged view of the surface layer 300 formed on the gasket 104 after the coating process. Figure 2(c) is a perspective view showing the flat portion 104e of the gasket 104, and Figures 2(a) and (b) show the flat portion 104e before and after the coating process. As shown in Figure 2(a), the coating liquid is applied to the surface of the rubber gasket 104, and as shown in Figure 2(b), a surface layer 300 is formed on the gasket 104, and it can be seen that silicone rubber particles 302 in the coating liquid are dispersed. Note that although only one silicone rubber particle 302 is labeled in Figure 2(b), the other round structures in the figure are also silicone rubber particles 302.

[0038] Figure 2(d) is an enlarged cross-sectional view of the base material 104a and the surface layer 300, and is a cross-sectional view parallel to the X direction of the gasket 104. Figure 2(e) is a cross-sectional view of the gasket 104, and Figure 2(d) shows an enlarged portion of the right side of this cross-section, where a surface layer 300 of a predetermined thickness is formed on the surface of the gasket 104. In Figure 2(d), only one silicone rubber particle 302 is labeled, but the other round structures in the figure are also silicone rubber particles 302.

[0039] (Washing process) In this embodiment, by cleaning the coated gasket 104 by extraction washing, fine particles adhering to the surface of the surface layer 300 of the gasket 104 are removed, thereby achieving a further reduction in insoluble fine particles.

[0040] In the washing process, the fired gasket 104 is extracted and washed at a third temperature, for example, room temperature to 200°C, for a third time, for example, 5 minutes to 135 minutes. If the third temperature is lower than room temperature, a cooled liquid (e.g., water) is required, which is burdensome to the process. If the third temperature is higher than 200°C, the deterioration of the base material 104a may progress. If the third time is shorter than 5 minutes, the washing may be insufficient, and the generation of insoluble fine particles may not be reduced. Furthermore, if the third time is longer than 135 minutes, the deterioration of the base material 104a may progress. In addition, excessively long times are undesirable from a process perspective.

[0041] By the surface coating layer formation method described above, a coating of a predetermined thickness, for example, about 5 μm to 10 μm, is formed on the gasket 104 of this embodiment.

[0042] <Coating liquid formulation> Below, we will describe formulation 1 of this embodiment and formulations 2 to 6 of comparative examples as coating solutions. Formulations 1 to 6 correspond to formulations 1 to 6 in the "Coating Formulation" table in Figures 4 to 6, which will be described later.

[0043] [Formulation 1] In this embodiment, the coating liquid is formulated using a silicon-based material for the flexibility-imparting component and a silicon-based material for the sliding-imparting component. In other words, the flexibility-imparting component and the sliding-imparting component are materials with similar compositions.

[0044] [Formulation 2] This formulation is for comparison with this embodiment, and uses a silicon-based material as the flexibility-imparting component, without including a sliding-imparting component. In other words, formulation 2 is a formulation that does not generate insoluble fine particles caused by the sliding-imparting component, and can be considered a standard formulation for formulations 1 to 3.

[0045] [Formulation 3] This formulation is for comparison with the embodiment, using a silicon-based material for the flexibility-imparting component and a fluorine-based material for the sliding-imparting component. In other words, the flexibility-imparting component and the sliding-imparting component are materials with different (distant) compositions.

[0046] [Formulation 4] This formulation is for comparison with this embodiment, and uses a urethane-based material as the flexibility-imparting component, without incorporating a sliding-imparting component. In other words, formulation 4 is a condition under which insoluble fine particles caused by the sliding-imparting component do not occur, and can be considered a standard formulation for formulations 4 through 6.

[0047] [Formulation 5] This formulation is for comparison with the embodiment, using a urethane-based material for the flexibility-imparting component and a silicon-based material for the sliding-imparting component. In other words, the flexibility-imparting component and the sliding-imparting component are made of materials with different compositions.

[0048] [Formulation 6] This formulation is for comparison with the embodiment, using a urethane-based material for the flexibility-imparting component and a fluorine-based material for the sliding-imparting component. In other words, the flexibility-imparting component and the sliding-imparting component are made of materials with different compositions.

[0049] <Rating 1> In Evaluation 1, to clarify the effects of the coating solution formulation on sliding properties, leakage, and insoluble fine particles, sliding resistance measurements, leakage tests, and insoluble fine particle tests were performed on gaskets 104 with surface layers formed using the coating solutions formulations 1 to 6 described above.

[0050] Furthermore, the relationship between the coating step and the cleaning step in the surface coating layer formation method of this embodiment was also evaluated. Specifically, a silicon-based material was used as the flexibility-imparting component, and formulation 1 using a silicon-based material and formulation 3 using a fluorine-based material were used as the sliding-impeding component. The evaluation was conducted by comparing the case in which the cleaning step was performed with the case in which the cleaning step was not performed.

[0051] (Sliding resistance measurement) Figure 3(a) is a front view showing the experiment during sliding resistance measurement, and the vertical direction is also shown. As shown in Figure 3(a), a syringe 100 equipped with a gasket 104 having been coated with the coating liquids of formulations 1 to 6 described above, and then subjected to appropriate drying and firing processes to form the cleaned surface layers of study numbers 1 to 17 described later, was set in the measuring instrument 400, and the plunger 106 was slid downward (white arrow in the figure) from above at a speed of 100 mm / min (millimeters per minute) (hereinafter also called sliding speed) for a distance of 20 mm (hereinafter also called sliding distance), and the maximum resistance value (N) was measured (hereinafter referred to as sliding measurement). Note that sliding properties refer to the ease of sliding, and the unit of measurement is "N (Newton)". The larger the value, the higher the sliding and the less slippery it is, and the smaller the value, the lower the sliding and the easier it is to slide.

[0052] (Leak test) Figure 3(b) is a side view showing the leak test, and the X direction corresponding to Figure 1 is also shown. Here, coating solutions of formulations 1 to 6 were applied, and after appropriate drying and firing processes, the gasket 104, which had a cleaned surface layer according to study numbers 1 to 17 described later, was inserted into the outer cylinder 102. A colored surfactant solution 200a corresponding to the chemical solution 200 (simulated chemical solution) was filled from the tip of the cylinder 110, and the cap 108 was attached to seal it. After that, it was left in an environment at a temperature of 40°C for 24 hours, then moved to room temperature and left for another hour, and the presence or absence of leaks was checked.

[0053] (Insoluble particulate matter test) After applying the coating solutions of formulations 1 to 6 described above, and following appropriate drying and firing processes, the gasket 104, which had the cleaned surface layers of study numbers 1 to 17 described later, was connected to the plunger 106. 2.25 ml of pure water was injected into the outer cylinder 102, and the gasket 104 and plunger 106 were inserted into the outer cylinder 102 and sealed. The tip 110 was then sealed with a cap 108. This sealed the pure water inside the syringe 100. After sealing the pure water inside the syringe 100, a sterilization process, such as autoclave sterilization, was performed, and then the syringe 100 was attached to a shaker and shaken to measure the amount of insoluble fine particles in the pure water.

[0054] (Result of evaluation 1) Figure 4 shows the results of Evaluation 1, with (a) being a table showing the results of Evaluation 1 and (b) being a graph showing the number of insoluble particles in Evaluation 1. Figure 4(a) shows the sample preparation conditions, coating components, and test details. The test details show the results of the sliding resistance value (N), leak test (no leak, -), and insoluble particle test (particles / 3ml) as described above. The sample preparation conditions show the study number, the coating liquid formulation (coating formulation) as described above, and the cleaning process. The coating components show the materials used for the flexibility-imparting component (silicon-based, urethane-based, etc.) and the materials used for the sliding-imparting component (silicon-based, fluorine-based, etc.). The cleaning process is extraction cleaning, especially high-pressure extraction cleaning, and the conditions (temperature × time) when high-pressure extraction cleaning was performed are also shown. A "〇" next to the implemented process (or condition) indicates that that process (or condition) was adopted. The insoluble particulate matter test shows the particle size of insoluble particulate matter (5 μm or larger, 10 μm or larger, etc.) and the number of particles of that size (particles / 3 ml). In Evaluation 1, in all cases, high-pressure extraction washing was performed in the washing process, with a third temperature of 121°C and a third time of 45 minutes. The circled numbers in the top row of the table represent the study number, and hereafter, "circled number 1," etc., will be referred to as "study number 1," etc. Figure 4(b) shows the study number on the horizontal axis and the number of insoluble particulate matter [particles / 3 ml] on the vertical axis. In Figure 4(b), the black bar graph shows the number of insoluble particulate matter with a particle size of 5 μm or larger, the diagonal pattern bar graph shows the number of insoluble particulate matter with a particle size of 10 μm or larger, and the grid pattern bar graph shows the number of insoluble particulate matter with a particle size of 25 μm or larger.

[0055] Furthermore, Figure 4 also shows the results for formulations 1 and 3 when no cleaning process was performed (study numbers 7 and 8). Although Figure 4 also shows columns for sliding resistance and leak tests, studies 7 and 8 are evaluated based on the results of the insoluble particulate matter test.

[0056] [Consideration Number 1 (Formulation 1)] In formulation 1 using the surface coating layer formation method of this embodiment, the sliding resistance value was 3.9 N and there was no leakage. For insoluble fine particles, there were 0 particles / 3 ml for particles 25 μm or larger, 5 particles / 3 ml for particles 10 μm or larger, and 7 particles / 3 ml for particles 5 μm or larger.

[0057] [Consideration Number 2 (Formulation 2)] In formulation 2, the sliding resistance value was 6.0 N and there was no leakage. Regarding insoluble fine particles, there were 0 particles / 3 ml for particles 25 μm or larger, 5 particles / 3 ml for particles 10 μm or larger, and 8 particles / 3 ml for particles 5 μm or larger. In other words, since it was equivalent to formulation 1, it was shown that the sliding-impregnating component in formulation 1 does not increase the amount of insoluble fine particles. Furthermore, even if no insoluble fine particles are generated due to the sliding-impregnating component, there are still 8 insoluble fine particles / 3 ml of 5 μm or larger mixed in the chemical solution 200. These are thought to be insoluble fine particles caused by, for example, dust floating in the air or particles that were originally attached to the container and could not be removed in the cleaning process.

[0058] [Consideration Number 3 (Formulation 3)] In formulation 3, the sliding resistance value was 5.8 N and there was no leakage. Regarding insoluble fine particles, there were 0 particles / 3 ml for particles 25 μm or larger, 8 particles / 3 ml for particles 10 μm or larger, and 20 particles / 3 ml for particles 5 μm or larger. In other words, even when the same silicon-based material is used for the flexibility-imparting component, using a fluorine-based material for the sliding material resulted in the generation of more insoluble fine particles 5 μm or larger than in formulation 1.

[0059] [Consideration Number 5 (Formulation 5)] In formulation 5, the lubricity-improving component did not mix with the flexibility-improving component, so a surface layer could not be formed (dispersion was not possible; the same applies below). Therefore, it was not possible to obtain the three evaluation results.

[0060] [Consideration Number 6 (Formulation 6)] In formulation 6, the sliding resistance value was 21.1 N. Regarding insoluble fine particles, there were 0 particles / 3 ml for particles 25 μm or larger, 21 particles / 3 ml for particles 10 μm or larger, and 27 particles / 3 ml for particles 5 μm or larger. Formulation 6 exhibited both a high sliding resistance value and a large number of insoluble fine particles.

[0061] [Consideration Number 7 (Formulation 1)] Study No. 7 is formulation 1 using the surface coating layer formation method of this embodiment, but without high-pressure extraction washing. In Study No. 7, for insoluble fine particles, there were 15 particles / 3ml for particles 25μm or larger, 50 particles / 3ml for particles 10μm or larger, and 63 particles / 3ml for particles 5μm or larger.

[0062] [Consideration Number 8 (Formulation 3)] Study No. 8 was formulation 3, but high-pressure extraction washing was not performed. In Study No. 8, for insoluble fine particles, there were 21 particles / 3ml for particles 25μm or larger, 65 particles / 3ml for particles 10μm or larger, and 80 particles / 3ml for particles 5μm or larger.

[0063] From the above, it was found that when a surface layer is formed on the gasket 104 using the surface coating layer formation method of this embodiment, friction is reduced, there is no leakage, and the generation of insoluble fine particles is also reduced.

[0064] Furthermore, when the washing process was not performed in both formulation 1 and formulation 3, a large number of insoluble fine particles were observed. However, formulation 1 showed that the generation of insoluble fine particles was suppressed compared to formulation 3.

[0065] On the other hand, comparing formulation 1 (formulation 1) and formulation 7 (formulation 1) in Figure 4, and comparing formulation 3 (formulation 3) and formulation 8 (formulation 3) in Figure 4, it was found that in all cases, insoluble fine particles can be reduced by performing a washing process. However, formulation 1 using the surface coating layer formation method of this embodiment showed a greater reduction in insoluble fine particles compared to formulation 3. In other words, the degree of reduction in the number of insoluble fine particles in formulation 1 compared to formulation 7 (89% reduction) was greater than the degree of reduction in the number of insoluble fine particles in formulation 3 compared to formulation 8 (70% reduction).

[0066] As described above, from Evaluation 1, by using the surface coating layer formation method of this embodiment, which has a coating step and a cleaning step, using a silicon-based material for the flexibility-imparting component and a silicon-based material with a similar composition for the sliding-imparting component, it was possible to form a surface layer 300 on the gasket 104, thereby achieving both low sliding and low insoluble particulate matter properties.

[0067] <Rating 2> Figure 5 shows the results of Evaluation 2, with (a) being a table showing the results of Evaluation 2 and (b) being a graph showing the number of insoluble microparticles in Evaluation 2. Figure 5(a) shows the sample preparation conditions, coating components, and test details. The test details show the results of the insoluble microparticle test (particles / 3ml). The sample preparation conditions show the study number, coating formulation, and washing process (extraction, high-pressure extraction). The coating components show the materials used for the flexibility-imparting component (silicon-based, urethane-based, etc.) and the materials used for the sliding-imparting component (silicon-based, fluorine-based, etc.). The washing process (extraction, high-pressure extraction) also shows the conditions (temperature × time) when washing was performed. A "〇" next to an implemented process (or condition) indicates that that process (or condition) was adopted. The insoluble microparticle test shows the particle size of the insoluble microparticles (5μm or larger, 10μm or larger, etc.) and the number of particles of that size (particles / 3ml). The conditions for the cleaning process when forming a surface layer 300 on a gasket 104 using the surface coating layer formation method of this embodiment were evaluated. Figure 5(a) is a table showing the results when the cleaning process was performed on the surface layer 300 of formulation 1 at different temperatures and times, and Figure 5(b) is a graph based on the table in Figure 5(a). Evaluation 2 is evaluated based on the results of the insoluble fine particle test. In addition, extraction cleaning and high-pressure extraction cleaning were performed as cleaning processes.

[0068] (Consideration number 7) The results for study number 7 in Figure 4 are shown, and the explanation is omitted.

[0069] (Consideration number 9 (when extraction and washing is performed at a temperature of 60°C for 45 minutes)) For insoluble fine particles, there were 0 particles / 3ml for particles 25μm or larger, 5 particles / 3ml for particles 10μm or larger, and 7 particles / 3ml for particles 5μm or larger.

[0070] (Consideration number 10 (when extraction and washing is performed at a temperature of 80°C for 45 minutes)) Regarding insoluble microparticles, there were 0 particles / 3ml for those 25μm or larger, 4 particles / 3ml for those 10μm or larger, and 8 particles / 3ml for those 5μm or larger.

[0071] (Study number 11 (When high-pressure extraction washing is performed at a temperature of 121°C for 5 minutes)) Regarding insoluble microparticles, there were 0 particles / 3ml for particles 25μm or larger, 4 particles / 3ml for particles 10μm or larger, and 7 particles / 3ml for particles 5μm or larger.

[0072] (Consideration number 1 (When high-pressure extraction washing is performed at a temperature of 121°C for 45 minutes)) The results for evaluation 1, study number 1 (formulation 1) in Figure 4 are shown, and the explanation is omitted.

[0073] (Consideration number 12 (When high-pressure extraction washing is performed at a temperature of 121°C for 90 minutes)) Regarding insoluble microparticles, there were 0 particles / 3ml for those 25μm or larger, 2 particles / 3ml for those 10μm or larger, and 9 particles / 3ml for those 5μm or larger.

[0074] (Consideration number 13 (When high-pressure extraction washing is performed at a temperature of 170°C for 45 minutes)) For insoluble microparticles, there were 0 particles / 3ml for those 25μm or larger, 2 particles / 3ml for those 10μm or larger, and 6 particles / 3ml for those 5μm or larger.

[0075] Based on the above, studies 9-13, which included a cleaning process, all yielded better results compared to study 7, which did not include a cleaning process.

[0076] <Rating 3> Figure 6 shows the results of Evaluation 3, where (a) is a table showing the results of Evaluation 3 and (b) is a graph showing the number of insoluble particles in Evaluation 3. Note that Figure 6 is the same table and graph as Figure 4. Regarding the cleaning process of the surface coating layer formation method of this embodiment, the cases of using a shaker, ultrasonic cleaning, and a shaker were evaluated for the surface layer 300 of formulation 1, and compared with the case of using high-pressure extraction cleaning of study number 1 (Evaluation 1). Figure 6(a) is a table showing the results when the above-described cleaning processes were performed on the surface layer 300 of formulation 1, and Figure 6(b) is a graph based on the table in Figure 6(a).

[0077] (Consideration number 1 (when using high-pressure extraction washing)) This is evaluation number 1 (composition 1) in Figure 4, and the explanation is omitted.

[0078] (Consideration number 14 (when using a shaker)) When a shaker was used in the washing process, the sliding resistance value was 4.4 N and there was no leakage. Regarding insoluble particles, there were 4 particles / 3 ml for particles 25 μm or larger, 11 particles / 3 ml for particles 10 μm or larger, and 25 particles / 3 ml for particles 5 μm or larger. A large number of insoluble particles 25 μm or larger were observed when a shaker was used.

[0079] (Consideration number 15 (when using ultrasonic cleaning)) When ultrasonic cleaning was used in the cleaning process, the sliding resistance value was 4.8 N and there was no leakage. Regarding insoluble fine particles, there was 1 particle / 3 ml for particles 25 μm or larger, 6 particles / 3 ml for particles 10 μm or larger, and 14 particles / 3 ml for particles 5 μm or larger. When ultrasonic cleaning was used, insoluble fine particles 25 μm or larger were observed.

[0080] (Consideration number 16 (when using an orbital shaker)) When a shaker was used in the washing process, the sliding resistance value was 4.2 N and there was no leakage. Regarding insoluble fine particles, there were 0 particles / 3 ml for particles 25 μm or larger, 11 particles / 3 ml for particles 10 μm or larger, and 24 particles / 3 ml for particles 5 μm or larger. When a shaker was used, a large number of insoluble fine particles 5 μm or larger were observed.

[0081] (Study number 17 (Ultrasonic cleaning after high-pressure extraction cleaning)) When ultrasonic cleaning was used in addition to high-pressure extraction cleaning during the cleaning process, the sliding resistance value was 3.7 N and there was no leakage. For insoluble fine particles, there were 0 particles / 3 ml for particles 25 μm or larger, 5 particles / 3 ml for particles 10 μm or larger, and 8 particles / 3 ml for particles 5 μm or larger. No significant difference was observed when ultrasonic cleaning was used after high-pressure extraction cleaning compared to when high-pressure extraction cleaning was used alone.

[0082] From the above results, it was found that for gaskets 104 with a surface layer 300 formed by formulation 1, it is preferable to perform high-pressure extraction cleaning in the cleaning process. Furthermore, it was found that insoluble fine particles can be sufficiently removed by high-pressure extraction cleaning alone, without combining it with other cleaning methods.

[0083] <Summary> The following summarizes the case studies, from study number 1 of this embodiment to comparative examples studies 2, 3, and 5-17, which were explained using Figures 4 to 6. • Study number 1 was able to reduce the sliding resistance value to approximately 1 / 20 to 2 / 3 compared to studies 2-3 and 6. Study No. 1 was able to achieve a low number of insoluble particles, comparable to Study No. 2, and compared to Studies No. 3 and 6, the number of insoluble particles was reduced to approximately 1 / 2 to 1 / 7. Based on the results of studies 1, 9-17, it was possible to reduce the number of insoluble particles by using high-pressure extraction washing in the washing process and by setting the temperature to 60°C or higher. Comparing study number 1 and study number 17, no change in the number of insoluble particles was observed even when ultrasonic cleaning was performed after high-pressure extraction cleaning. A comparison between study number 7 and study number 8 showed that study number 8 had approximately 1.3 times more insoluble particles than study number 7. A comparison between study number 1 and study number 7 showed that high-pressure extraction washing reduced the number of insoluble particles by approximately 1 / 9 to 1 / 10. On the other hand, a comparison between study number 3 and study number 8 showed that the effect of high-pressure extraction washing on reducing the number of insoluble particles was reduced to approximately 1 / 4 to 1 / 7.

[0084] As described above, according to this embodiment, it is possible to provide a method for forming a surface coating layer and a method for manufacturing a gasket that can reduce the shedding of insoluble fine particles into the chemical solution while maintaining stable sliding properties and preventing leakage of the liquid agent.

[0085] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes are possible within the scope of its essence.

[0086] Furthermore, for example, the present invention shall include the following aspects.

[0087] [Purpose 1] The present invention's method for forming a surface coating layer is: A method for forming a surface coating layer to improve the sliding properties of a sliding member made of rubber, The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the substrate to a predetermined coating thickness, A drying step in which the sliding member after coating is dried at a first temperature for a first time, A firing step in which the sliding member after drying is fired at a second temperature for a second time, The process includes a cleaning step of extracting and cleaning the sliding member after firing at a third temperature for a third period of time.

[0088] [Purpose 2] The particle size of the silicon-based rubber particles may be 1 μm or more and 50 μm or less in average particle size.

[0089] [Purpose 3] The predetermined coating thickness may be 1 μm or more and 50 μm or less.

[0090] [Purpose 4] The third temperature may be above room temperature and 200°C or less, and the third time may be 5 minutes or more and 135 minutes or less.

[0091] [Purpose 5] The present invention's method for forming a surface coating layer is: A method for forming a surface coating layer to improve the sliding properties of a gasket that is placed at the tip of a plunger used in a syringe and slides against the inner wall of the syringe, The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the gasket to a predetermined coating thickness, A drying step in which the gasket after coating is dried at a first temperature for a first time, A firing step in which the gasket after drying is fired at a second temperature for a second time, The process includes a washing step of extracting and washing the gasket after firing at a third temperature for a third period of time.

[0092] [Purpose 6] The method for manufacturing a gasket according to the present invention is: A method for manufacturing a gasket that is placed at the tip of a plunger used in a syringe and slides against the inner wall of the syringe, The gasket has a surface coating layer on the surface of the rubber base material to improve sliding properties. The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the substrate to a predetermined coating thickness, A drying step in which the gasket after coating is dried at a first temperature for a first time, A firing step in which the gasket after drying is fired at a second temperature for a second time, The process includes a washing step of extracting and washing the gasket after firing at a third temperature for a third period of time. [Explanation of symbols]

[0093] 100 syringes 102 Outer cylinder 104 Gasket 104a Base material 104b Tapered section 104c Torso 104d Connection part 104e Flat part 106 Plunger 106a Flange 108 Cap 110 Tube tip 200 chemical solution 200a Surfactant solution 300 surface layer 302 Silicone rubber particles 400 Measuring equipment

Claims

1. A method for forming a surface coating layer to improve the sliding properties of a sliding member made of rubber, The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the substrate to a predetermined coating thickness, A drying step in which the sliding member after coating is dried at a first temperature for a first time, A firing step in which the dried sliding member is fired at a second temperature for a second time, The process includes a cleaning step of extracting and washing fine particles adhering to the surface of the sliding member after firing at a third temperature for a third period of time, The predetermined coating thickness is 1 μm or more and 50 μm or less. The first temperature is above room temperature and 100°C or less, and the first time is 1 hour or more and 24 hours or less. The second temperature is above room temperature and 200°C or less, and the second time is 5 minutes or more and 2 hours or less. The third temperature is above room temperature and 200°C or less, and the third time is 5 minutes or more and 135 minutes or less. Surface coating layer forming method.

2. The method for forming a surface coating layer according to claim 1, wherein the particle size of the silicon-based rubber particles is 1 μm or more and 50 μm or less in average particle size.

3. A method for forming a surface coating layer on the surface of a rubber-based gasket, which is a gasket placed at the tip of a plunger used in a syringe and slides against the inner wall of the syringe, in order to improve its sliding properties. The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the gasket to a predetermined coating thickness, A drying step in which the gasket after coating is dried at a first temperature for a first time, A firing step in which the gasket after drying is fired at a second temperature for a second time, The process includes a washing step of extracting and washing fine particles adhering to the surface of the gasket after firing at a third temperature for a third period of time, The predetermined coating thickness is 1 μm or more and 50 μm or less. The first temperature is above room temperature and 100°C or less, and the first time is 1 hour or more and 24 hours or less. The second temperature is above room temperature and 200°C or less, and the second time is 5 minutes or more and 2 hours or less. The third temperature is above room temperature and 200°C or less, and the third time is 5 minutes or more and 135 minutes or less. Surface coating layer forming method.

4. A method for manufacturing a gasket that is placed at the tip of a plunger used in a syringe and slides against the inner wall of the syringe, The gasket has a surface coating layer on the surface of the rubber base material to improve sliding properties. The material of the surface coating layer has a composition containing silicon-based rubber particles in a silicon-based solution. A coating step of applying the material to the surface of the substrate to a predetermined coating thickness, A drying step in which the gasket after coating is dried at a first temperature for a first time, A firing step in which the gasket after drying is fired at a second temperature for a second time, The process includes a washing step of extracting and washing fine particles adhering to the surface of the gasket after firing at a third temperature for a third period of time, The predetermined coating thickness is 1 μm or more and 50 μm or less. The first temperature is above room temperature and 100°C or less, and the first time is 1 hour or more and 24 hours or less. The second temperature is above room temperature and 200°C or less, and the second time is 5 minutes or more and 2 hours or less. The third temperature is above room temperature and 200°C or less, and the third time is 5 minutes or more and 135 minutes or less. A method for manufacturing gaskets.

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