Syringe gasket

Abstract

[Problem] To provide: a syringe gasket of which the surface has a reduced friction coefficient and adhesiveness; and a method for manufacturing the same. [Solution] A syringe gasket according to the present invention is characterized: by being formed from a rubber composition that contains (a) a base polymer containing a halogenated butyl rubber and (b) resin particles; and in that, in relation to an image analysis result obtained when the surface roughness is measured by using a laser microscope, at least a portion of the surface satisfies P = (Vmp / V) ≥ 0.25 where Vmp (mL / m2) is the volume of a protruding ridge section at which the load area ratio by which a core section and the protruding ridge section are separated is 40%, and V (mass%) is the amount of (a) the base polymer contained in the rubber composition.

Description

Syringe Gasket

[0001] The present invention relates to a gasket for a syringe, and more particularly to a technique for improving the sliding properties of a gasket for a syringe.

[0002] Conventionally, pre-filled syringes pre-filled with drugs have been used for reasons such as preventing drug mix-ups, preventing hospital infections, ease of disposal, and efficiency of hospital operations. Regardless of whether they are pre-filled syringes or not, syringes generally consist of a barrel, a gasket that can slide airtight and liquid-tightly within the barrel, and a plunger that moves and operates this gasket. The gasket used in syringes is required to have not only sealing properties (airtightness and liquid-tightness), but also high sliding properties (for example, low initial sliding resistance and low sliding resistance over time) in order to smoothly administer drugs.

[0003] Patent Document 1 discloses a prefilled syringe comprising an outer cylinder having a nozzle portion at the tip and an opening at the base end, a gasket that slides inside the outer cylinder, a plunger that passes through the opening and is connected to the gasket, and a medicinal solution that is contained within the outer cylinder and sealed by the gasket, wherein the periphery of the opening has a flange that extends outward from the outer cylinder, and a movable stopper is provided on the flange, and a locking portion is provided on the portion of the plunger that extends from the opening to the outside of the outer cylinder, and the gasket is moved toward the tip via the plunger, and the locking portion locks with the stopper at a position where air bubbles present in the medicinal solution and an excess amount of the medicinal solution have been discharged from the nozzle, thereby stopping the gasket.

[0004] Patent Document 2 discloses a gasket for a syringe that is formed to be in liquid-tight slidable contact with the inside of the outer cylinder of a syringe, the gasket comprising a gasket body made of an elastic body and a coating layer provided on at least the portion that contacts the syringe, the coating layer being made of a composition that is made of a condensate of reactive silicone having terminal silanol groups and that contains a silicone-based resin that has siloxane bonds derived from the silanol groups, and that is free of solid fine particles.

[0005] Patent Document 3 discloses a rubber product suitable for use as a piston rubber for syringes, which is a highly permeable liquid-sealing rubber product whose constituent parts are a rubber composition containing 10 to 80 parts by weight of fluororesin fine powder having an average particle size of 1 to 5 μm per 100 parts by weight of butyl rubber, and whose surface is laminated with a fluororesin film formed by a casting method.

[0006] Japanese Patent Application Laid-Open No. 2007-014619 Republished No. 2009-084646 Japanese Patent Application Laid-Open No. 2007-054621

[0007] Silicone oil is applied to the surface of syringe gaskets to improve sliding properties. However, when a syringe gasket coated with silicone oil comes into contact with a biopharmaceutical, protein aggregation due to silicone particles may occur. Therefore, silicone oil-coated syringe gaskets cannot be used for medical supplies that use biopharmaceuticals. In particular, there is a growing demand for silicone oil-free (SOF) syringe gaskets for prefilled syringes.

[0008] Furthermore, to prevent components of the syringe gasket from mixing with the liquid medicine inside the syringe barrel and contaminating or deteriorating the liquid medicine, the syringe gasket is laminated with a fluororesin film. Syringe gaskets laminated with a fluororesin film such as polytetrafluoroethylene (PTFE) film tend to have poor sealing properties because the elastic modulus of the PTFE film is 100 times higher than that of rubber.

[0009] Under these circumstances, in order to comply with silicone oil-free (SOF) regulations, a method is required to reduce the friction coefficient and adhesion of syringe gaskets without using silicone oil.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel syringe gasket having a reduced surface friction coefficient and reduced adhesion, and a method for producing the same.

[0011] The syringe gasket of the present invention is a syringe gasket formed from a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles, and the syringe gasket is characterized in that, in the image analysis results obtained when the surface roughness of at least a part of the surface of the syringe gasket is measured with a laser microscope, the volume Vmp (mL / m) of the protruding peaks when the areal load ratio separating the core portion and the protruding peaks is 40% is obtained. ２ ) and a content V (mass %) of the base polymer (a) in the rubber composition satisfies P = (Vmp / V) ≥ 0.25.

[0012] The volume Vmp of the protruding peaks indicates the volume of the protruding convex portions on the gasket surface. Furthermore, V is the content (mass%) of (a) base polymer in the rubber composition. (a) Base polymer is the main component constituting the gasket body. Therefore, P = (Vmp / V) indicates the volume of the protruding convex portions on the surface per unit base polymer. The larger the P, the larger the volume of the protruding convex portions per unit base polymer, which results in a rougher surface for the syringe gasket and a reduced contact area between the syringe gasket and the syringe barrel. As a result, the coefficient of friction decreases, improving sliding properties.

[0013] The method for manufacturing a syringe gasket of the present invention is characterized by including the steps of: molding a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles into a syringe gasket; and irradiating ultraviolet light onto at least a portion of the surface of the syringe gasket.

[0014] According to the manufacturing method of the present invention, by irradiating the surface of a syringe gasket formed from a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles with ultraviolet light, low-molecular-weight components that cause stickiness on the surface of the syringe gasket are decomposed and evaporated, thereby achieving low stickiness. Furthermore, the evaporation of the low-molecular-weight components exposes the resin particles (b) on the surface of the syringe gasket, roughening the surface and further reducing the coefficient of friction.

[0015] According to the present invention, a gasket for a syringe having a reduced surface coefficient of friction and reduced stickiness can be obtained.

[0016] 1 is a graph showing the results of image analysis of the surface of a syringe gasket measured with a laser microscope. FIG. 2 is a diagram of a prefillable syringe. FIG. 3 is a diagram of a syringe gasket. FIG. 4 is a diagram of a method for measuring the coefficient of friction of a medical rubber article. FIG. 5 is a photograph (substitute for drawing) of a cured product of rubber composition No. 1 observed with a laser microscope. FIG. 6 is a photograph (substitute for drawing) of a cured product of rubber composition No. 2 observed with a laser microscope. FIG. 7 is a photograph (substitute for drawing) of a cured product of rubber composition No. 5 observed with a laser microscope. FIG. 8 is a photograph (substitute for drawing) of a cured product of rubber composition No. 6 observed with a laser microscope. FIG. 9 is a photograph (substitute for drawing) of a cured product of rubber composition No. 7 observed with a laser microscope.

[0017] The syringe gasket of the present invention is a syringe gasket formed from a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles, and the syringe gasket is characterized in that, in the image analysis results obtained when the surface roughness of at least a part of the surface of the syringe gasket is measured with a laser microscope, the volume Vmp (mL / m) of the protruding peaks when the areal load ratio separating the core portion and the protruding peaks is 40% is obtained. ２ ) and a content V (mass %) of the base polymer (a) in the rubber composition satisfies P = (Vmp / V) ≥ 0.25.

[0018] The syringe gasket of the present invention has a surface roughness of at least a part of the surface of the gasket measured with a laser microscope, and the image analysis results obtained show that the volume Vmp (mL / m) of the protruding peaks when the area load ratio separating the core and the protruding peaks is 40%. ２ ) and a content V (mass %) of the (a) base polymer in the rubber composition satisfies P=(Vmp / V)≧0.25.

[0019] The surface roughness of the syringe gasket is measured using a laser microscope VK-X3000 manufactured by Keyence Corporation, in a scan mode: laser confocal, with an objective lens magnification of 50 times.

[0020] The images obtained by observation with the laser microscope are subjected to image processing (reference plane setting → surface correction (waviness removal: strength 5)) using the VK-X3000 multi-file analysis application. This image processing results in a graph such as that shown in Figure 1. In Figure 1, the horizontal axis represents the areal load ratio and the vertical axis represents height. In Figure 1, Vmp is the volume of the protruding peak, Vmc is the volume of the core, and Vvc is the volume of the space in the core.

[0021] In the present invention, the area bearing ratio separating the core portion from the protruding peak portion is set to 40% as a parameter for image analysis.

[0022] In the present invention, the volume of the protruding peak Vmp (mL / m ２ ) and the content V (mass%) of the rubber component in the rubber composition satisfy P = (Vmp / V) ≥ 0.25. P is more preferably 0.28 or more, even more preferably 0.30 or more, and is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less. This is because, when P is in the above-mentioned range, it is possible to achieve both sliding properties and airtight properties.

[0023] The syringe gasket of the present invention is preferably substantially cylindrical. The syringe gasket has a tip end that is inserted into the syringe barrel and a rear end that is connected to the plunger. The tip end may be referred to as the distal end, and the rear end may be referred to as the proximal end. The syringe gasket has a top surface that comes into contact with the drug solution when inserted into the syringe barrel, and a sliding surface that faces the inner surface of the syringe barrel.

[0024] The syringe gasket of the present invention preferably has one or more annular ribs on the sliding surface portion, and more preferably has multiple annular ribs. The annular rib is in sliding contact with the inner surface of the syringe barrel. The multiple annular ribs are arranged in the axial direction of the syringe gasket from the front end surface (top surface) of the syringe gasket to the rear end surface. The number of annular ribs is not particularly limited as long as it is one or more, but is preferably two or more, more preferably three or more, and preferably six or less, more preferably five or less, and even more preferably four or less.

[0025] In the syringe gasket of the present invention, it is preferable that at least a portion of the top surface is coated with an inactive resin layer, and it is more preferable that the entire top surface is coated with an inactive resin layer. By coating the top surface with an inactive resin layer, it is possible to prevent components constituting the syringe gasket from mixing with the drug in the syringe barrel and contaminating or deteriorating the drug solution.

[0026] The syringe gasket of the present invention has a top surface that comes into contact with the drug solution when inserted into a syringe barrel, and a sliding surface that faces the inner surface of the syringe barrel, and at least a portion of the sliding surface preferably satisfies P = (Vmp / V) ≥ 0.25, and more preferably the entire sliding surface satisfies P = (Vmp / V) ≥ 0.25. When at least a portion of the sliding surface satisfies P = (Vmp / V) ≥ 0.25, the syringe gasket exhibits good sliding properties.

[0027] In a preferred embodiment of the present invention, a portion of the top surface of the syringe gasket is coated with an inactive resin layer, and at least a portion of the sliding surface satisfies P = (Vmp / V) ≥ 0.25. In a more preferred embodiment of the present invention, only the top surface of the syringe gasket is coated with an inactive resin layer, and the entire sliding surface satisfies P = (Vmp / V) ≥ 0.25. In this embodiment, the inactive resin layer exhibits good chemical resistance, and the sliding surface exhibits excellent slidability.

[0028] The inactive resin layer may be a layer made of a fluororesin or a layer made of a non-fluororesin.

[0029] The material of the syringe gasket of the present invention will be described below. The syringe gasket of the present invention is molded from a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles.

[0030] (a) The base polymer contains a halogenated butyl rubber as a rubber component. The halogenated butyl rubber has excellent gas barrier properties.

[0031] (a) Examples of the halogenated butyl rubber contained in the base polymer include chlorinated butyl rubber, brominated butyl rubber, and brominated copolymers of isobutylene and p-methylstyrene. These halogenated butyl rubbers may be used alone or in combination of two or more. The halogenated butyl rubber is preferably chlorinated butyl rubber or brominated butyl rubber. The chlorinated butyl rubber or brominated butyl rubber is, for example, obtained by adding or substituting chlorine or bromine to the isoprene structure of butyl rubber, specifically to the double bond and / or the carbon atom adjacent to the double bond. Butyl rubber is a copolymer obtained by polymerizing isobutylene and a small amount of isoprene. The halogenated butyl rubber is preferably solid at room temperature (23°C).

[0032] The halogen content in the halogenated butyl rubber is preferably 0.5% by mass or more, preferably 1% by mass or more, more preferably 1.2% by mass or more, and is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0033] Specific examples of the chlorinated butyl rubber include Exxon (registered trademark) Chlorobutyl 1066 (halogen content: 1.25 wt %, Mooney viscosity: 38 ML) manufactured by Exxon Mobil Corporation. １＋８ (125°C), specific gravity: 0.92], Exxon Chlorobutyl 5066 [halogen content: 1.50 wt%, Mooney viscosity: 40 ML １＋８ (125°C, specific gravity: 0.92); LANXESS X_BUTYL (registered trademark) CB1240 manufactured by LANXESS Corporation.

[0034] Specific examples of the brominated butyl rubber include Exxon Bromobutyl 2211 (halogen content: 2.0 wt %, Mooney viscosity: 32 ML) manufactured by Exxon Mobil Corporation. １＋８ (125°C), specific gravity: 0.93], Exxon Bromobutyl 2222 [halogen content: 2.0 wt%, Mooney viscosity: 32 ML １＋８(125°C), specific gravity: 0.93], Exxon Bromobutyl 2235 [halogen content: 2.1 wt%, Mooney viscosity: 39 ML １＋８ (125°C), specific gravity: 0.93], Exxon Bromobutyl 2244 [halogen content: 2.0 wt%, Mooney viscosity: 46 ML １＋８ (125°C), specific gravity: 0.93], Exxon Bromobutyl 2255 [halogen content: 2.1 wt%, Mooney viscosity: 46ML １＋８ (125°C), specific gravity: 0.93], Exxon Bromobutyl 6222 [halogen content: 2.4 wt%, Mooney viscosity: 32 ML １＋８ (125°C), specific gravity: 0.93], Exxon Bromobutyl 7211 [halogen content: 2.0 wt%, Mooney viscosity: 32 ML １＋８ (125°C), specific gravity: 0.93], Exxon Bromobutyl 7244 [halogen content: 2.1 wt%, Mooney viscosity: 46ML １＋８ (125°C, specific gravity: 0.93); LANXESS X_BUTYL BBX2 manufactured by LANXESS Corporation.

[0035] The halogenated butyl rubber undergoes a crosslinking reaction during the ultraviolet irradiation step described below, which increases the elastic modulus of the entire base polymer (a) at the rubber surface, making it less susceptible to deformation. As a result, the syringe gasket obtained by the manufacturing method of the present invention has a reduced true contact area at the contact surface with other articles, resulting in a lower coefficient of friction.

[0036] (a) When the base polymer contains chlorinated butyl rubber or brominated butyl rubber as the halogenated butyl rubber, a crosslinking reaction occurs at the chlorinated or brominated isoprene moiety in the ultraviolet irradiation step described below. (a) When the base polymer contains brominated isobutylene-paramethylstyrene copolymer rubber (BIMS) as the halogenated butyl rubber, a crosslinking reaction occurs at the brominated paramethylstyrene moiety in the ultraviolet irradiation step described below.

[0037] (a) The base polymer may contain a rubber component other than halogenated butyl rubber. Examples of other rubber components include butyl rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, natural rubber, chloroprene rubber, nitrile rubber such as acrylonitrile-butadiene rubber, hydrogenated nitrile rubber, norbornene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, acrylic rubber, ethylene-acrylate rubber, fluororubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, silicone rubber, urethane rubber, polysulfide rubber, phosphane rubber, and 1,2-polybutadiene. These may be used alone or in combination of two or more.

[0038] When other rubber components are used, the content of the halogenated butyl rubber in the (a) base polymer is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more. In a preferred embodiment, the (a) base polymer consists solely of the halogenated butyl rubber.

[0039] [(b) Resin Particles] The volume average particle diameter of the (b) resin particles used in the present invention is preferably 200 μm or less, more preferably 160 μm or less, and even more preferably 120 μm or less. The volume average particle diameter of the (b) resin particles is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. This is because, within the above range, the resin particles are easily mixed and dispersed uniformly in the base polymer. The volume average particle diameter of the (b) resin particles can be measured, for example, by the Coulter-Counter method.

[0040] (b) Examples of resin components constituting the resin particles include polyesters such as polybutylene terephthalate (PBT) and polyethylene terephthalate (PET); polyolefins such as polyethylene (PE) and polypropylene (PP); (meth)acrylic resins; acrylonitrile-butadiene-styrene copolymers (ABS resins); acrylonitrile-styrene copolymers (AS resins); epoxy resins; polyamides (PA); polyurethanes (PU); polyimides (PI); polyphenylene ethers (PPE); polysulfones (PSF); polyethersulfones (PES); polyphenylene sulfide (PPS); polyarylates (PARs); polyamideimides (PAI); polyetherimides (PEI); polyetheretherketones (PEEK); polytetrafluoroethylene (PTFE); polyaminobismaleimides (PABM); polybisamidotriazoles; polyphenylene oxides (PPO); polyacetals; and polycarbonates (PCs).

[0041] The (b) resin particles used in the present invention are preferably polyolefin-based resin particles (resin particles made of a polyolefin-based resin).

[0042] The polyolefin resin particles hardly absorb ultraviolet light (especially ultraviolet light with a wavelength of 160 nm or more), and therefore do not react during the ultraviolet irradiation process and are exposed to the surface of the rubber constituting the syringe gasket. As a result, the true contact area of ​​the syringe gasket of the present invention at the contact surface with other parts is further reduced, thereby reducing the coefficient of friction.

[0043] The polyolefin resin is not particularly limited, but examples thereof include polyethylene resins such as linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and copolymers of ethylene and an α-olefin (for example, an α-olefin having 3 to 8 carbon atoms); polypropylene resins such as polypropylene (PP), propylene-ethylene copolymer, and copolymers of propylene and an α-olefin (for example, an α-olefin having 4 to 8 carbon atoms); and homopolymers or copolymers of olefins (for example, olefins having 4 to 8 carbon atoms) such as polybutene, polypentene, and polymethylpentene. These may be used alone or in combination of two or more. The polyethylene resin refers to a resin in which the mass proportion of repeating units derived from ethylene in the resin is greater than 50% by mass (preferably 70% by mass or more, more preferably 90% by mass or more), and the polypropylene resin refers to a resin in which the mass proportion of repeating units derived from propylene in the resin is greater than 50% by mass (preferably 70% by mass or more, more preferably 90% by mass or more). Among these, polyethylene resins are preferred in terms of achieving the effects of the present invention more favorably, with low-density polyethylene (LDPE), high-density polyethylene (HDPE), and ultra-high molecular weight polyethylene (UHMWPE) being more preferred, and ultra-high molecular weight polyethylene (UHMWPE) being even more preferred.

[0044] Density of high density polyethylene (kg / m ３ ) is 930 kg / m ３ ~960 kg / m ３ is preferred, and 930 kg / m ３ ~950 kg / m ３ The density of the low-density polyethylene (kg / m ３ ) is not particularly limited, but is preferably 910 kg / m ３ ~925 kg / m ３ is preferred, and 910 kg / m ３ ~920 kg / m ３ is more preferred.

[0045] In the present invention, it is particularly preferable to use particles made of ultra-high molecular weight polyethylene (UHMWPE) as the polyolefin resin particles. Ultra-high molecular weight polyethylene is generally polyethylene having an average molecular weight of 500,000 or more.

[0046] The viscosity average molecular weight of the ultra-high molecular weight polyethylene (UHMWPE) is not particularly limited, but is preferably 500,000 or more, more preferably 1,000,000 or more, and even more preferably 1,500,000 or more, and is preferably 8,000,000 or less, more preferably 7,000,000 or less, and even more preferably 6,000,000 or less.

[0047] The viscosity average molecular weight of the ultra-high molecular weight polyethylene (UHMWPE) was determined by measuring the intrinsic viscosity [η] in a decalin solvent at 135°C and calculating the viscosity average molecular weight using the formula: Mν = k [η] α (Mν is the viscosity average molecular weight, and k and α are constants.) The intrinsic viscosity is measured by a method in accordance with JIS K7367-3 (1999).

[0048] The density of the ultra-high molecular weight polyethylene (UHMWPE) is not particularly limited, but is preferably 930 kg / m ３ It is preferable that the saturation is 932 kg / m or more. ３ More preferably, it is 934 kg / m or more. ３ More preferably, it is 945 kg / m or more. ３ Preferably, it is 943 kg / m or less. ３ More preferably, it is 940 kg / m or less. ３ It is even more preferable that:

[0049] The melting point of the ultra-high molecular weight polyethylene is preferably 120° C. or higher, more preferably 125° C. or higher, and even more preferably 130° C. or higher. The melting point of the ultra-high molecular weight polyethylene is measured in accordance with ASSM-D3418.

[0050] Specific examples of particles made of ultra-high molecular weight polyethylene (UHMWPE) include Mipelon (registered trademark) PM-200 (viscosity average molecular weight: 1,800,000, volume average particle size (Coulter-Counter method): 10 μm, density: 938 kg / m) manufactured by Mitsui Chemicals, Inc. ３ ], XM-220 [viscosity average molecular weight: 2 million, volume average particle diameter (Coulter-Counter method): 30 μm, density: 937 kg / m ３ ], XM-221U [viscosity average molecular weight: 2 million, volume average particle diameter (Coulter-Counter method): 25 μm, density: 937 kg / m ３ ], XM-330 [viscosity average molecular weight: 2 million, volume average particle diameter (Coulter-Counter method): 65 μm, density: 937 kg / m ３ ] and others.

[0051] The content of the (b) resin particles is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, relative to 100 parts by mass of the (a) base polymer component. If the content of the (b) resin particles is 5 parts by mass or more, the effect of reducing the friction coefficient by the (b) resin particles is further improved, and if it is 100 parts by mass or less, the (b) resin particles can be more easily mixed and dispersed uniformly in the base polymer.

[0052] [Other Components] The rubber composition preferably contains (c) a crosslinking agent. The (c) crosslinking agent is blended to crosslink the rubber component contained in the (a) base polymer. The (c) crosslinking agent is not particularly limited as long as it is capable of crosslinking the rubber component. Examples of the (c) crosslinking agent include sulfur, metal oxides, resin crosslinking agents, organic peroxides, and triazine derivatives, which may be used alone or in combination of two or more.

[0053] Examples of sulfur used as a crosslinking agent include insoluble sulfur, powdered sulfur, finely divided sulfur, precipitated sulfur, colloidal sulfur, and sulfur chloride.

[0054] Examples of metal oxides used as crosslinking agents include magnesium oxide, calcium oxide, zinc oxide, and copper oxide.

[0055] Examples of the resin crosslinking agent include alkylphenol formaldehyde resins such as alkylphenol formaldehyde resin, heat-reactive phenol resin, phenol dialcohol resin, bisphenol resin, and heat-reactive bromomethyl alkylated phenol resin.

[0056] Specific examples of the organic peroxides include dialkyl peroxides, peroxy esters, peroxy ketals, and hydroperoxides. Examples of dialkyl peroxides include di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxy, di-t-hexyl peroxy, di-t-butyl peroxy, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3. Examples of peroxy esters include t-butyl peroxymaleate, t-butylperoxy-3,3,5-trimethylcyclohexanoate, t-butyl peroxylaurate, t-butylperoxyisopropyl monocarbonate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxyacetate, and t-butyl peroxybenzoate. Examples of peroxyketals include 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)-2-methylcyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, n-butyl-4,4-di(t-butylperoxy)valerate, and 2,2-di(4,4-di(t-butylperoxy)cyclohexyl)propane. Examples of hydroperoxides include p-menthane hydroperoxide and diisopropylbenzene hydroperoxide. These organic peroxides may be used alone or in combination of two or more.

[0057] The triazine derivative used as the crosslinking agent includes, for example, a compound represented by the general formula (1).

[0058]

[0059] [Wherein R represents -SH, -OR １ , -SR ２ , -NHR ３ or -NR ４R ５ (R １ , R ２ , R ３ , R ４ and R ５ represents an alkyl group, an alkenyl group, an aryl group, an aralkyl group, an alkylaryl group, or a cycloalkyl group. ４ and R ５ may be the same or different. １ and M ２ is H, Na, Li, K, ½ Mg, ½ Ba, ½ Ca, an aliphatic primary amine, a secondary amine or a tertiary amine, a quaternary ammonium salt or a phosphonium salt. １ and M ２ may be the same or different.

[0060] In general formula (1), examples of the alkyl group include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl, 1,1-dimethylpropyl, octyl, isooctyl, 2-ethylhexyl, decyl, and dodecyl. Examples of the alkenyl group include alkenyl groups having 1 to 12 carbon atoms, such as vinyl, allyl, 1-propenyl, isopropenyl, 2-butenyl, 1,3-butadienyl, and 2-pentenyl. Examples of the aryl group include monocyclic or fused polycyclic aromatic hydrocarbon groups, such as aryl groups having 6 to 14 carbon atoms, such as phenyl, naphthyl, anthryl, phenanthryl, and acenaphthylenyl. Examples of aralkyl groups include aralkyl groups having 7 to 19 carbon atoms, such as benzyl, phenethyl, diphenylmethyl, 1-naphthylmethyl, 2-naphthylmethyl, 2,2-diphenylethyl, 3-phenylpropyl, 4-phenylbutyl, 5-phenylpentyl, 2-biphenylylmethyl, 3-biphenylylmethyl, and 4-biphenylylmethyl. Examples of alkylaryl groups include alkylaryl groups having 7 to 19 carbon atoms, such as tolyl, xyl, and octylphenyl. Examples of cycloalkyl groups include cycloalkyl groups having 3 to 9 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclononyl.

[0061] Specific examples of the triazine derivative represented by general formula (1) include 2,4,6-trimercapto-s-triazine, 2-methylamino-4,6-dimercapto-s-triazine, 2-(n-butylamino)-4,6-dimercapto-s-triazine, 2-octylamino-4,6-dimercapto-s-triazine, 2-propylamino-4,6-dimercapto-s-triazine, 2-diallylamino-4,6-dimercapto-s-triazine, 2-dimethylamino-4,6-dimercapto-s-triazine, 2-dibutylamino- Examples thereof include 4,6-dimercapto-s-triazine, 2-di(iso-butylamino)-4,6-dimercapto-s-triazine, 2-dipropylamino-4,6-dimercapto-s-triazine, 2-di(2-ethylhexyl)amino-4,6-dimercapto-s-triazine, 2-dioleylamino-4,6-dimercapto-s-triazine, 2-laurylamino-4,6-dimercapto-s-triazine, and 2-anilino-4,6-dimercapto-s-triazine, or sodium salts or disodium salts thereof.

[0062] Among these, 2,4,6-trimercapto-s-triazine, 2-dialkylamino-4,6-dimercapto-s-triazine, and 2-anilino-4,6-dimercapto-s-triazine are preferred, and 2-dibutylamino-4,6-dimercapto-s-triazine is particularly preferred due to its availability.

[0063] Examples of triazine derivatives include one or more of 6-[bis(2-ethylhexyl)amino]-1,3,5-triazine-2,4-dithiol, 6-diisobutylamino-1,3,5-triazine-2,4-dithiol, 6-dibutylamino-1,3,5-triazine-2,4-dithiol, 6-dibutylamino-1,3,5-triazine-2,4-dithiol monosodium, 6-anilino-1,3,5-triazine-2,4-dithiol, and 1,3,5-triazine-2,4,6-trithiol.

[0064] In the rubber composition used in the present invention, one type of triazine derivative may be used alone, or two or more types may be used in combination.

[0065] When chlorinated butyl rubber and brominated butyl rubber are used as the rubber component, it is preferable to select and use an optimal crosslinking component for crosslinking, since the chlorinated butyl rubber and the brominated butyl rubber have different crosslinking mechanisms. When the rubber composition contains chlorinated butyl rubber as the halogenated butyl rubber, it is preferable to contain a triazine derivative as the crosslinking agent (c). Furthermore, when the rubber composition contains brominated butyl rubber as the halogenated butyl rubber, it is preferable to contain a metal oxide as the crosslinking agent (c).

[0066] The content of the crosslinking agent (c) in the rubber composition is preferably 0.2 parts by mass or more, more preferably 0.4 parts by mass or more, and even more preferably 0.6 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the base polymer component (a). This is because, when the content of the crosslinking agent (c) is within the above range, a rubber having good rubber properties (hardness, tensile strength, Cset) and good processability (less discoloration) can be obtained.

[0067] When a chlorinated butyl rubber is used as the halogenated butyl rubber and a triazine derivative is used as the (c) crosslinking agent, the content of the (c) crosslinking agent in the rubber composition is preferably 0.2 parts by mass or more, more preferably 0.4 parts by mass or more, and even more preferably 0.6 parts by mass or more, and preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of the (a) base polymer component. This is because, when the content of the (c) crosslinking agent is within the above range, a rubber having good rubber properties (hardness, tensile strength, Cset) and good processability (less discoloration) can be obtained.

[0068] When a brominated butyl rubber is used as the halogenated butyl rubber and a metal oxide is used as the (c) crosslinking agent, the content of the (c) crosslinking agent in the rubber composition is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the (a) base polymer component. This is because, when the content of the (c) crosslinking agent is within the above range, a rubber having good rubber properties (hardness, tensile strength, Cset) and good processability (less discoloration) can be obtained.

[0069] The rubber composition preferably does not contain a vulcanization accelerator. This is because the vulcanization accelerator may remain in the final rubber product and dissolve into the chemical solution in a syringe, etc. Examples of the vulcanization accelerator include guanidine-based accelerators (e.g., diphenyl guanidine), thiuram-based accelerators (e.g., tetramethylthiuram disulfide, tetramethylthiuram monosulfide), dithiocarbamate-based accelerators (e.g., zinc dimethyldithiocarbamate), thiazole-based accelerators (e.g., 2-mercaptobenzothiazole, dibenzothiazyl disulfide), and sulfenamide-based accelerators (N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazole sulfenamide).

[0070] The rubber composition may further contain (d) an acid acceptor. The acid acceptor (d) functions to absorb chlorine-based gases and bromine-based gases generated during crosslinking of the halogenated butyl rubber and to prevent the occurrence of crosslinking inhibition due to these gases. The acid acceptor (d) also functions as a scorch inhibitor during crosslinking of the halogenated butyl rubber and to prevent the compression set of the syringe gasket from increasing.

[0071] (d) Examples of the acid acceptor include hydrotalcite, metal oxides, and metal hydroxides.

[0072] Examples of hydrotalcite include Mg ４．５ Al ２ (OH)１３ CO ３ ・3.5H ２ O, Mg ４．５ Al ２ (OH) １３ CO ３ , Mg ４ Al ２ (OH) １２ CO ３ ・3.5H ２ O, Mg ６ Al ２ (OH) １６ CO ３ ・4H ２ O, Mg ５ Al ２ (OH) １４ CO ３ ・4H ２ O, Mg ３ Al ２ (OH) １０ CO ３ ・1.7H ２ Examples of the metal oxide include magnesium oxide, calcium oxide, and zinc oxide. Examples of the metal hydroxide include calcium hydroxide. These acid acceptors may be used alone or in combination of two or more. The metal oxides used as the crosslinking agents described above can also function as acid acceptors.

[0073] The content of (d) the acid acceptor is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, relative to 100 parts by mass of the (a) base polymer component, because the content of the acid acceptor within the above range can suppress rust formation on a mold or the like and reduce the problem of the raw material itself becoming white spots.

[0074] The rubber composition may further contain a filler. Examples of the filler include inorganic fillers such as clay and talc. Among these, inorganic fillers are preferred, and clay or talc is more preferred. The filler functions to adjust the rubber hardness of the syringe gasket and also functions as an extender to reduce the production cost of the syringe gasket.

[0075] Examples of the clay include calcined clay and kaolin clay. Specific examples of the clay include SILLITIN (registered trademark) Z manufactured by HOFFMANN MINERAL, SATINTONE (registered trademark) W manufactured by ENGELHARD, NN kaolin clay manufactured by Tsuchiya Kaolin Kogyo Co., Ltd., and PoleStar 200R manufactured by Imerys Specialties Japan.

[0076] Specific examples of the talc include Hitron A manufactured by Takehara Chemical Industry Co., Ltd., MICRO ACE (registered trademark) K-1 manufactured by Nippon Talc Co., Ltd., and Mistron (registered trademark) Vapor manufactured by Imerys Specialties Japan.

[0077] The content of the filler in the rubber composition is preferably set appropriately depending on the rubber hardness of the intended gasket for syringe. The content of the filler in the rubber composition is, for example, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less, per 100 parts by mass of the (a) base polymer component.

[0078] The rubber composition may further contain, in an appropriate ratio, colorants such as titanium oxide and carbon black, lubricants such as stearic acid, processing aids, polyethylene glycol as a crosslinking activator, process oil, etc.

[0079] At least a portion of the surface of the syringe gasket of the present invention may be coated with an inactive resin layer.

[0080] The resin constituting the inactive resin layer is not particularly limited, but examples thereof include at least one fluororesin selected from the group consisting of tetrafluoroethylene-ethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), and polychlorotetrafluoroethylene (PCTFE), or a non-fluororesin, in terms of obtaining good chemical resistance.

[0081] Tetrafluoroethylene-ethylene copolymer (ETFE) is a copolymer of ethylene and tetrafluoroethylene in a molar ratio of 30 / 70 to 70 / 30, and there is also modified ETFE in which other components are further copolymerized for the purpose of modification. Examples of other components include fluorine-containing olefins and hydrocarbon olefins. Specifically, α-olefins such as propylene and butene, fluorine-containing olefins such as hexafluoropropylene, vinylidene fluoride, perfluorobutylethylene, and trifluorochloroethylene, vinyl ethers such as ethylene vinyl ether, perfluoromethyl vinyl ether, and perfluoropropyl vinyl ether, and fluorine-containing acrylates are copolymerized at about 2 to 10 mol% to modify ETFE.

[0082] As the modified ETFE, ETFE having a functional group that imparts adhesiveness can be suitably used, and examples of the functional group include a carboxyl group, a carboxyl anhydride group, an epoxy group, a hydroxyl group, an isocyanate group, an ester group, an amide group, an aldehyde group, an amino group, a cyano group, a carbon-carbon double bond, a sulfonic acid group, an ether group, etc. Furthermore, an example of a commercially available modified ETFE is Fluon AH-2000 manufactured by Asahi Glass Co., Ltd.

[0083] Examples of non-fluorine-containing resins include olefin-based resins. Examples of the olefin-based resins include polyethylene-based resins such as polyethylene, ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-ethyl acrylate copolymer, and chlorinated polyethylene; polypropylene-based resins such as polypropylene, propylene-ethylene random copolymer, propylene-ethylene block copolymer, and chlorinated polypropylene; polybutene, polyisobutylene, polymethylpentene, and cyclic olefin copolymers; and polyethylene (particularly ultra-high molecular weight polyethylene (UHMWPE)). The olefin-based resin may contain fluorine.

[0084] [Method for manufacturing a syringe gasket] The present invention includes a method for manufacturing a syringe gasket, comprising: a step of molding a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles into a syringe gasket; and a step of irradiating ultraviolet light onto at least a portion of the surface of the syringe gasket.

[0085] In the manufacturing method of the present invention, by irradiating with ultraviolet light the surface of a syringe gasket obtained by molding (a) a base polymer containing a halogenated butyl as a rubber component and (b) a rubber composition containing resin particles, the surface of the syringe gasket after ultraviolet light irradiation satisfies the above-mentioned P = (Vmp / V) ≧ 0.25.

[0086] [Molding of Syringe Gasket] The rubber composition used in the present invention is obtained by kneading (a) a base polymer, (b) resin particles, and other compounding materials added as necessary. Kneading can be performed using, for example, an open roll or an internal kneader. The kneaded product is preferably molded into a ribbon, sheet, pellet, or the like, and more preferably molded into a sheet.

[0087] The kneading of the (a) base polymer and the (b) resin particles is preferably carried out at a temperature equal to or lower than the melting point of the (b) resin particles.

[0088] Next, the obtained kneaded product is molded into a syringe gasket. The kneaded product in ribbon, sheet, or pellet form is press-molded into a desired shape. Vulcanization (crosslinking reaction) of the rubber composition progresses during pressing. The molding temperature is, for example, preferably 130°C or higher, more preferably 140°C or higher, and preferably 200°C or lower, more preferably 190°C or lower. The molding time is preferably 2 minutes or longer, more preferably 3 minutes or longer, preferably 60 minutes or shorter, more preferably 30 minutes or shorter. The molding pressure is preferably 0.1 MPa or higher, more preferably 0.2 MPa or higher, and preferably 10 MPa or lower, more preferably 8 MPa or lower.

[0089] When at least a portion of the surface of the syringe gasket of the present invention is coated with an inactive resin layer, at least a portion of the surface of the syringe gasket is coated with the inactive resin layer by press-molding an inactive resin film overlaid on a sheet made of a rubber composition.

[0090] The thickness of the inactive resin film used may be adjusted appropriately depending on the shape and size of the syringe gasket, but is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and is preferably 150 μm or less, more preferably 130 μm or less, and even more preferably 110 μm or less, because if the thickness of the inactive resin film is within the above range, the film will not break during product molding, and wrinkles or floating defects will not occur on the film surface of the product after molding, and both moldability and product properties can be achieved.

[0091] The arithmetic mean roughness Ra of the inactive resin film ranges from 0.01 to 0.03 μm for cast films and extruded films to 0.10 μm for skived films, but by setting the surface roughness of the mold to 0.03 μm or less, medical rubber articles with excellent liquid adhesion and airtightness can be obtained. There is no particular lower limit for the Ra of the inactive film itself.

[0092] The inactive resin film is preferably subjected to a treatment to enhance its adhesiveness to rubber, etc. Examples of treatments to enhance adhesiveness include chemical treatments, treatments for roughening the surface of the film, and combinations of these, and specific examples include sodium treatment, glow discharge treatment, plasma treatment (discharge treatment) under atmospheric pressure or in a vacuum, excimer laser treatment (discharge treatment), and ion beam treatment.

[0093] <Ultraviolet Ray Irradiation Step> The method for producing a medical rubber article of the present invention includes a step of irradiating at least a portion of the surface of the syringe gasket with ultraviolet rays. The syringe gasket to be irradiated with ultraviolet rays may be one that has been molded into the final shape of the syringe gasket, or may be a preform that has not yet been molded into the final shape of the syringe gasket.

[0094] The method for irradiating the syringe gasket with ultraviolet light is not particularly limited, but for example, a method for irradiating the surface of the syringe gasket with ultraviolet light using a light source that emits ultraviolet light can be mentioned.

[0095] The wavelength of the ultraviolet light is preferably 160 nm or more, more preferably 165 nm or more, and even more preferably 170 nm or more. When the wavelength of the ultraviolet light is 160 nm or more, the (b) polyolefin resin particles hardly absorb ultraviolet light of this wavelength, and therefore do not react even when irradiated with ultraviolet light, and are scattered on the gasket surface. Furthermore, the upper limit of the wavelength of the ultraviolet light is not particularly limited, but is preferably 380 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less. When the wavelength of the ultraviolet light is 380 nm or less, the energy of the ultraviolet light is high, which increases the crosslinking efficiency of the halogenated butyl rubber and makes it less likely to deform. Furthermore, the high-energy ultraviolet light decomposes and evaporates low-molecular-weight components that cause stickiness on the gasket surface, thereby achieving low stickiness. Furthermore, the evaporation of the low-molecular-weight components exposes the (b) polyolefin resin particles on the surface of the syringe gasket. As a result, a sea-island structure having island portions (b) where polyolefin resin particles are exposed and a sea portion made of rubber is formed on the surface of the syringe gasket after ultraviolet irradiation. According to the manufacturing method of the present invention, the surface of the syringe gasket becomes rough by ultraviolet irradiation, and the gasket surface after ultraviolet irradiation satisfies the above-mentioned P = (Vmp / V) ≥ 0.25.

[0096] Among these, vacuum ultraviolet light having a wavelength of 200 nm or less is particularly preferred, as it allows the effects of the present invention to be obtained more effectively.

[0097] The light source for emitting the ultraviolet rays is not particularly limited as long as it can emit ultraviolet rays in the above wavelength range. For example, a low-pressure mercury lamp, a high-pressure mercury lamp, an excimer lamp, etc. are used. In particular, an excimer lamp is preferable because it has high energy and can modify the surface in a relatively short time. The excimer lamp emits ultraviolet rays with different wavelengths depending on the type of discharge gas used. For example, xenon (Xe ２When xenon chloride (XeCl) is used, ultraviolet light having a center wavelength of 172 nm is emitted, when xenon bromide (XeBr) is used, 308 nm is emitted, when xenon iodide (XeI) is used, 283 nm is emitted, when xenon iodide (XeI) is used, 193 nm is emitted, when argon fluoride (ArF), 165 nm is emitted, when argon bromide (ArBr), 222 nm is emitted, and when krypton chloride (KrCl) is used, 207 nm is emitted (also called "excimer UV light"). In the present invention, an excimer lamp that emits vacuum ultraviolet light having a center wavelength of 200 nm or less is preferred, and an excimer lamp using xenon (center wavelength: 172 nm) is particularly preferred.

[0098] In the ultraviolet irradiation step, the integrated illuminance on the surface of the syringe gasket is 1000 mJ / cm ２ It is preferable that the concentration is 3000 mJ / cm or more. ２ More preferably, 5000 mJ / cm or more. ２ It is more preferable that the integrated illuminance on the surface of the syringe gasket is 1000 mJ / cm or more. ２ If the irradiance is above this level, the crosslinking of the halogenated butyl rubber is sufficiently carried out and the low molecular weight components that cause the stickiness of the gasket surface are more easily decomposed. The upper limit of the integrated irradiance on the gasket surface is not particularly limited, but is preferably 50,000 mJ / cm. ２ Preferably, it is 45,000 mJ / cm or less. ２ More preferably, it is 40,000 mJ / cm or less. ２ It is more preferable that the integrated illuminance on the surface of the syringe gasket is 50,000 mJ / cm or less. ２ This is because a balance between the life of the irradiation equipment and the efficiency of surface modification can be achieved if the cumulative irradiance on the surface of the syringe gasket is the total irradiance (arrival irradiance) of ultraviolet light that reaches the surface of the syringe gasket, and can be calculated by multiplying the intensity (arrival intensity) of ultraviolet light that reaches the surface of the syringe gasket by the irradiation time of ultraviolet light.

[0099] The ultraviolet light reaching intensity and irradiation time may be adjusted appropriately so that the integrated illuminance falls within the range described above. Usually, the ultraviolet light reaching intensity is 10 mW / cm ２ / sec~100mW / cm ２ It is preferable that the irradiation time is 10 to 5000 seconds, because by setting the ultraviolet light reaching intensity and irradiation time within these ranges, it is easy to achieve an integrated illuminance within the above range.

[0100] The distance between the surface of the syringe gasket and the light source (lamp) that emits ultraviolet light is not particularly limited, but is preferably 1 mm to 20 mm in order to improve the uniformity of ultraviolet light irradiation.

[0101] In the present invention, by irradiating at least a portion of the surface of a syringe gasket with ultraviolet light, the gasket surface can be significantly modified to have a low coefficient of friction and low adhesion.

[0102] In the manufacturing method of the present invention, when at least a portion of the surface of the syringe gasket is coated with an inactive resin layer, the entire syringe gasket including the inactive resin layer may be irradiated with ultraviolet light, or the exposed rubber surface that is not coated with the inactive resin layer may be irradiated with ultraviolet light. When irradiating the exposed rubber surface with ultraviolet light, only a portion of the exposed rubber surface may be irradiated with ultraviolet light, or the entire exposed rubber surface may be irradiated with ultraviolet light.

[0103] For example, when only the top surface of the syringe gasket is covered with an inactive resin layer, it is preferable to irradiate only the sliding surface with ultraviolet light.

[0104] The method for manufacturing a syringe gasket of the present invention may include the steps of processing a cured product of the rubber composition into a predetermined shape, washing, sterilizing, and drying. For example, the syringe gasket is manufactured by cutting and removing unnecessary portions from the cured product of the rubber composition after ultraviolet irradiation to form a predetermined shape, and then washing, sterilizing, drying, and packaging. Note that cutting and removing unnecessary portions to form a predetermined shape may be performed before irradiating the cured product of the rubber composition with ultraviolet light.

[0105] In view of SOF regulations, it is preferable that the syringe gasket of the present invention is not coated with silicone oil. Examples of silicone oil include dimethylpolysiloxane, methylphenylpolysiloxane, and modified versions thereof. The syringe gasket of the present invention can achieve a low coefficient of friction and low adhesion without using silicone oil.

[0106] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings.

[0107] 2 is a diagram showing an exploded view of a medical syringe in which the syringe gasket of the present invention is used, a syringe known as a prefillable syringe 30. In FIG. 2, half of the syringe barrel 31 and syringe gasket 33 are shown in cross section. The prefillable syringe 30 includes a cylindrical syringe barrel 31, a plunger 32 that is combined with the syringe barrel 31 and can reciprocate within the syringe barrel 31, and a syringe gasket 33 that is attached to the tip of the plunger 32.

[0108] The plunger 32 is formed, for example, from a resin plate piece having a cross-shaped cross section, and is provided at its tip with a head portion 38 to which the syringe gasket 33 is attached. The head portion 38 is made of resin and formed integrally with the plunger 32, and is machined into a male thread shape. The syringe gasket 33 is approximately cylindrical with a short axis, and its tip surface has, for example, an obtuse angled chevron shape with the central axis protruding. A female thread-shaped mating recess 35 is formed axially from the rear end surface. The head portion 38 of the plunger 32 is screwed into the mating recess 35 of the syringe gasket 33, thereby attaching the syringe gasket 33 to the tip of the plunger 32.

[0109] 3 is a half-sectional front view of an example of a syringe gasket. Syringe gasket 40 includes a main body 41 made of a cured rubber composition and an inactive resin layer 42 that covers a portion of the surface of the main body. Syringe gasket 40 has a top surface 47 that comes into contact with the drug solution and a sliding surface 46 that faces the inner surface of the syringe barrel.

[0110] 3, when syringe gasket 40 is inserted into a syringe barrel, only mountain-shaped top surface 47 that comes into contact with the drug solution is coated with inactive resin layer 42. As inactive resin layer 42, for example, a polytetrafluoroethylene film is preferable.

[0111] The sliding surface (outer peripheral surface) 46 of the syringe gasket 40, which comes into contact with the inner surface of the syringe barrel, is not provided with the inactive resin layer 42 and is irradiated with ultraviolet light. The sliding surface (outer peripheral surface) 46 has high slidability.

[0112] The syringe gasket 40 has a short cylindrical shape and includes a plurality of annular ribs 43, 44, and 45 on a sliding surface portion (outer peripheral surface) 46 of the cylindrical shape. The annular ribs are in sliding contact with the inner peripheral surface of the syringe barrel. The plurality of annular ribs are arranged in the axial direction from a leading end surface (top surface) 47 of the syringe gasket toward a rear end surface 48. The number of annular ribs is not particularly limited as long as it is one or more, but is preferably two or more, more preferably three or more, and preferably six or less, more preferably five or less, and even more preferably four or less.

[0113] The syringe gasket 40 in Fig. 3 has, from the tip side, a first annular rib 43, a second annular rib 44, and a third annular rib 45. The radial compression rate of the first annular rib 43 at the tip is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less. The compression rate is calculated from the outer diameter D1 of the annular rib in an uncompressed state and the inner diameter R of the syringe barrel using the following formula: Compression rate (%) = 100 x (D1 - R) / D1

[0114] The linear length H1 (the axial length) of the sliding contact portion of the annular rib 43 at the tip is preferably 1% or more, more preferably 3% or more, and even more preferably 6% or more, of the linear length Ho (the axial length of the outer peripheral surface) of the cylindrical sliding surface portion (outer peripheral surface), and is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less.

[0115] The linear length H2 (axial length) of the sliding contact portion of the second annular rib 44 and the linear length H3 (axial length) of the sliding contact portion of the third annular rib 45 are each preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more, of the linear length Ho (axial length of the outer peripheral surface) of the cylindrical outer peripheral surface, and are preferably 15% or less, more preferably 14% or less, and even more preferably 13% or less.

[0116] The syringe gasket is sometimes called a stopper or a plunger stopper.

[0117] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples, and all modifications and embodiments that do not deviate from the spirit of the present invention are included within the scope of the present invention.

[0118] [Preparation of Rubber Composition and UV Irradiation] The materials shown in Table 1 were kneaded using an open roll at 60°C for 20 minutes to prepare a rubber composition. The obtained rubber composition was crosslinked under molding conditions of 170°C for 15 minutes, and then punched out into a circular slab with a diameter of 28 mm and a thickness of 2 mm to prepare a test specimen for UV irradiation (cured product of rubber composition). The test specimen for UV irradiation was irradiated with vacuum UV light (wavelength: 172 nm) to achieve the cumulative illuminance shown in Table 1. UV irradiation conditions: Irradiation device: Electrodeless excimer 172 nm irradiation device (manufactured by MD.com Co., Ltd.); Distance between the surface of the cured product and the lamp: 7 mm; UV light intensity: 57.9 mW / cm ２ / sec

[0119]

[0120] Details of the compounding materials used are as follows: Chlorinated butyl rubber: Exxon (registered trademark) Chlorobutyl 1066 (chlorine content: 1.25 wt%) manufactured by ExxonMobil Corporation General-purpose butyl rubber: Exxon (registered trademark) Butyl 268 (unsaturation: 2.30 mol%) manufactured by ExxonMobil Corporation Ultra-high molecular weight polyethylene: Mipelon (registered trademark) XM-220 (volume average particle size: 30 μm, viscosity average molecular weight: 2 million, melting point 136°C) manufactured by Mitsui Chemicals, Inc. Triazine derivative: Jisnet DB manufactured by Sankyo Kasei Co., Ltd. Sulfur: Insoluble sulfur (Seimi OT) manufactured by Nippon Kanritsu Kogyo Co., Ltd. Zinc oxide: Activated zinc oxide AZO manufactured by Seido Chemical Industry Co., Ltd. Magnesium oxide: Magsarat 150s manufactured by Kyowa Chemical Industry Co., Ltd. Dithiocarbamate: Noccela (registered trademark) ZTC manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0121] [Evaluation method] (1) Analysis of surface roughness Measuring device: Laser microscope VK-X3000 manufactured by Keyence Corporation Scan mode: Laser confocal Objective lens magnification: 50x Image analysis software: VK-X3000 multi-file analysis application Image processing: Reference surface setting → Surface correction (Waviness removal: Strength 5) Surface area ratio: 40%

[0122] (2) Friction Coefficient <Measurement of Static and Dynamic Friction Coefficients> Figure 4 is an explanatory diagram showing the method for measuring the friction coefficient of a measurement sample (a circular slab with a thickness of 2 mm and a diameter of 28 mm after UV irradiation) using a static and dynamic friction coefficient measuring instrument TL201 (manufactured by TAILAB). The measurement sample 63 was fixed to a lower stage 64, and a 10-g weight 61 was placed on a dedicated probe equipped with a 10-mm-diameter SUS ball 62, bringing the surface of the measurement sample 63 into contact with the SUS ball 62. The stage 64 was then moved 20 mm in the direction indicated by the arrow at a speed of 10 mm / s. The friction coefficient μ was calculated by dividing the friction force F generated during this process by the load (normal force) N. (μ = F / N) The coefficient of kinetic friction was calculated by dividing the coefficient by the average normal force N1 over a 20-mm travel distance, and the coefficient of static friction was calculated by dividing the coefficient by the maximum average normal force N2 over a 20-mm travel distance. <Evaluation of Static Friction Coefficient> The static friction coefficient was evaluated according to the following evaluation criteria. ◯: The static friction coefficient is less than 1.50. ×: The static friction coefficient is 1.50 or more. <Evaluation of Dynamic Friction Coefficient> The dynamic friction coefficient was evaluated according to the following evaluation criteria. ◯: The dynamic friction coefficient is less than 1.30. ×: The dynamic friction coefficient is 1.30 or more.

[0123] (3) Adhesion Test <Measurement of Tack Value> Using a testing machine EZ-SX (manufactured by Shimadzu Corporation), the measurement sample prepared above (a circular slab with a thickness of 2 mm and a diameter of 28 mm after UV irradiation) was fixed to a dedicated jig on the lower side, and the upper metal Φ10 mm SUS probe was pressed against the surface of the measurement sample. After reaching the set pressure (10 N), the pressure was held for 10 seconds and then raised at a rate of 10 mm / s. The peak value of the adhesion force generated between the probe and the measurement sample was defined as the tack value. Five measurements were taken, and the average value of three measurements, excluding the maximum and minimum values, was taken as the tack value. <Evaluation of Adhesion> Adhesion was evaluated according to the following evaluation criteria. ◯: The tack value (N) was 0.50 N or less. ×: The tack value (N) was greater than 0.50 N.

[0124] (4) Overall Evaluation ◯: The evaluation results of the friction coefficient and the adhesiveness are both ◯. ×: Both the evaluation results of the friction coefficient and the adhesiveness are ×.

[0125] The measurement and evaluation results of the friction coefficient and adhesion are shown in Table 1. From Table 1, it can be seen that the syringe gasket of the present invention has a reduced surface friction coefficient and adhesion.

[0126] 5 to 8 are photographs, taken with a laser microscope, of the surfaces of cured rubber compositions No. 1 to No. 3, and No. 5, which were molded from a rubber composition containing (a) a base polymer containing a rubber component and (b) resin particles, irradiated with ultraviolet light. It can be seen that a sea-island structure is formed on the surface of the cured rubber, comprising islands where the (b) resin particles are exposed and a sea made of rubber.

[0127] 9 is a laser microscope photograph of the surface of a cured product of Rubber Composition No. 6, which was molded from a rubber composition containing (a) a base polymer containing a rubber component but (b) no resin particles, after UV irradiation. It can be seen that minute irregularities were formed on the surface of the cured rubber after UV irradiation. This is thought to be due to the UV irradiation decomposing and evaporating low-molecular-weight components, while the crosslinked portions formed remain, forming minute irregularities on the surface.

[0128] Figure 10 is a laser microscope photograph of the surface (without UV irradiation) of a cured rubber composition molded from Rubber Composition No. 7, which contains (a) a base polymer containing a rubber component and (b) resin particles. Comparing this to Figures 5 to 8 reveals that the (b) resin particles are not exposed on the surface of the cured rubber. Furthermore, because no UV irradiation was performed, the surface of the cured rubber is smooth.

[0129] According to the present invention, it is possible to provide a gasket for a syringe having a reduced surface friction coefficient and reduced adhesion.

[0130] 30: Prefillable syringe, 31: Syringe barrel, 33: Syringe gasket, 40: Syringe gasket, 43, 44, 45: Annular rib, 47: Top surface portion, 46: Sliding surface portion 46

[0131] A preferred embodiment (1) of the present invention is a gasket for a syringe formed from a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles, wherein the gasket for a syringe is formed from a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles, and the gasket ... ２ and a content V (mass%) of the base polymer (a) in the rubber composition satisfies P=(Vmp / V)≧0.25.

[0132] A preferred aspect (2) of the present invention is the syringe gasket of aspect (1), wherein the syringe gasket has a top surface that comes into contact with the medicinal solution when inserted into the syringe barrel and a sliding surface that faces the inner surface of the syringe barrel, and at least a portion of the sliding surface satisfies P = (Vmp / V) ≥ 0.25.

[0133] A preferred embodiment (3) of the present invention is the syringe gasket of embodiment (1) or (2), wherein at least a part of the top surface is covered with an inactive resin layer.

[0134] A preferred embodiment (4) of the present invention is the syringe gasket of embodiment (3), wherein the inactive resin layer is a layer made of a fluororesin.

[0135] A preferred embodiment (5) of the present invention is the syringe gasket of embodiment (3), wherein the inactive resin layer is a layer made of a non-fluorine-containing resin.

[0136] A preferred embodiment (6) of the present invention is the syringe gasket according to any one of embodiments (1) to (5), wherein (b) the resin particles have a volume average particle size of 200 μm or less.

[0137] A preferred aspect (7) of the present invention is the syringe gasket according to any one of aspects (1) to (6), wherein (b) the content of the resin particles is 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the (a) base polymer.

[0138] A preferred aspect (8) of the present invention is the syringe gasket according to any one of aspects (1) to (7), wherein the halogenated butyl rubber is at least one selected from the group consisting of chlorinated butyl rubber, brominated butyl rubber, and a brominated copolymer of isobutylene and p-methylstyrene.

[0139] A preferred embodiment (9) of the present invention is the syringe gasket according to any one of embodiments (1) to (8), wherein (b) the resin particles are polyolefin-based resin particles.

[0140] A preferred embodiment (10) of the present invention is the syringe gasket according to embodiment (9), wherein the polyolefin resin particles are at least one selected from the group consisting of ultra-high molecular weight polyethylene, high density polyethylene, and low density polyethylene.

[0141] A preferred aspect (11) of the present invention is a method for producing a gasket for a syringe, comprising: a step of molding a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles into a gasket for a syringe; and a step of irradiating ultraviolet light onto at least a part of the surface of the gasket for a syringe.

Claims

1. A syringe gasket formed from a rubber composition containing (a) a base polymer containing a butyl halide rubber and (b) resin particles, wherein at least a part of the surface of the syringe gasket has a load area ratio of 40% for separating the core part and the protruding mountain part with respect to the image analysis result obtained when measuring the surface roughness with a laser microscope, and the volume Vmp (mL / m ２ ), and the content V (mass%) of the (a) base polymer in the rubber composition satisfy P = (Vmp / V) ≧ 0.

25. The syringe gasket is characterized by this.

2. The syringe gasket has a top surface portion that contacts the chemical solution and a sliding surface portion that faces the inner surface of the syringe barrel when inserted into the syringe barrel, and at least a part of the sliding surface portion satisfies P = (Vmp / V) ≧ 0.

25. The syringe gasket according to claim 1.

3. The syringe gasket according to claim 2, wherein at least a part of the top surface portion is coated with an inert resin layer.

4. The syringe gasket according to claim 3, wherein the inert resin layer is a layer made of a fluororesin.

5. The syringe gasket according to claim 3, wherein the inert resin layer is a layer made of a non-fluororesin.

6. (b) The syringe gasket according to claim 1, wherein the volume average particle diameter of the resin particles is 200 μm or less.

7. (b) The syringe gasket according to claim 1, wherein the content of the resin particles is 5 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the base polymer (a).

8. The syringe gasket according to claim 1, wherein the halogenated butyl rubber is at least one selected from the group consisting of chlorinated butyl rubber, brominated butyl rubber, and brominated products of copolymers of isobutylene and p-methylstyrene.

9. (b) The syringe gasket according to claim 1, wherein the resin particles are polyolefin-based resin particles.

10. The syringe gasket according to claim 9, wherein the polyolefin-based resin particles are at least one selected from the group consisting of ultra-high molecular weight polyethylene, high density polyethylene, and low density polyethylene.

11. A method for manufacturing a syringe gasket, comprising: a step of molding a rubber composition containing (a) a base polymer containing a halogenated butyl rubber and (b) resin particles into a syringe gasket; and a step of irradiating at least a part of the surface of the syringe gasket with ultraviolet light.

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