Patent Description:
Endoscopes are medical devices for examination of a patient's body cavity. Since an endoscope is inserted and used in a body cavity, an endoscope that does not damage an organ or cause pain or discomfort to a patient is desirable. To meet this need, a spiral tube formed by spirally winding a flexible metal strip is used as a flexible tube that forms the insertion section of an endoscope. In addition, the periphery of the spiral tube is covered with a soft resin and is further covered with a topcoat layer so as not to cause stimulation or damage to the surface of a body cavity such as the esophagus or intestine.

Endoscopes are repeatedly used and therefore require cleaning and chemical disinfection after each use. Accordingly, technological development has been made to improve the chemical resistance of endoscopes. For example, <CIT> describes a flexible tube, for an endoscope, having a resin layer composed of at least two layers, including a first layer including at least one elastomer or chain-extended derivative thereof selected from the group consisting of polyester elastomers, polyurethane elastomers, and polyamide elastomers and a second layer including chain-extended derivatives of at least two elastomers selected from the group consisting of polyester elastomers, polyurethane elastomers, and polyamide elastomers. This flexible tube is reported to have high resistance to washing solutions, to exhibit less change in physical properties with temperature (temperature dependence), and to have good adhesiveness between the resin layer and the topcoat layer.

<CIT> describes a flexible tube, for an endoscope, having a resin layer including a layer containing a polyester elastomer and a hindered phenol compound or hindered amine compound. This flexible tube is reported to have the desired properties for endoscopes, including good flexibility, elasticity, and bending durability, as well as good resistance to various disinfectants.

<CIT> describes a flexible tube having a cylindrical flexible tube base that has flexibility and a resin layer that coats the flexible tube base, in which the resin layer is configured by at least two layers of a first layer that contains a specific resin and a second layer that contains a specific resin, or in which the resin layer is a single layer or multiple layers of two or more layers, and a layer A that is any of the resin layers includes polyester elastomers, and, hindered phenol compounds or hindered amine compounds.

<CIT> describes a tubular article that is obtained by molding a polyester elastomer resin composition having transmittance or transparency and a haze value (degree of cloudiness) of <<NUM>% measured with a <NUM> thick sheet. The polyester elastomer resin composition comprises (A) <NUM> parts by weight of a polyester block copolymer consisting mainly of <NUM>-<NUM> wt. % of a high melting point crystalline segment comprising crystalline aromatic polyester units and <NUM>-<NUM> wt. % of a low melting point polymer segment comprising aliphatic polyether units and/or aliphatic polyester units and (B) <NUM>-<NUM> parts by weight of an ethylenic copolymer having alkali metal carboxylate groups on side chains (preferably a copolymer obtained by neutralizing an ethylene-unsaturated carboxylic acid copolymer with sodium).

The properties of flexible tubes for endoscopes have been improved by techniques such as those described in the above patent documents. On the other hand, the requirements on the handleability, durability, and other properties of flexible tubes for endoscopes are becoming more stringent year by year. In view of the foregoing, an object of the present invention is to provide a flexible tube, for an endoscope, that contains sufficiently few defects in the resin layer after molding, that has the desired sufficient chemical resistance, and that can achieve a higher adhesiveness between the topcoat layer and the resin layer, an endoscopic medical device including such a flexible tube for an endoscope, and a set of resin compositions that are suitable for forming a resin layer of such a flexible tube for an endoscope.

The foregoing object is achieved by the following solutions:.

In the description of the present invention, a "resin component" present in a resin layer refers to an elastomer. "Resin component" may be hereinafter simply referred to as "resin".

In the description of the present invention, if there are a plurality of substituents, linking groups, or the like (hereinafter referred to as "substituent or the like") represented by a particular symbol, or if a plurality of substituents or the like are specified simultaneously or alternatively, it is meant that the individual substituents or the like may be the same or different. In addition, if a plurality of substituents or the like are adjacent to each other, it is meant that they may be linked or fused to each other to form a ring, even if not specified as such.

In the description of the present invention, if it is not explicitly specified whether a substituent (or linking group) is substituted or unsubstituted, it is meant that the group may have any substituent as long as the advantages of the present invention are not impaired. This also applies if it is not explicitly specified whether a compound is substituted or unsubstituted.

The flexible tube for an endoscope according to the present invention contains sufficiently few defects in the resin layer after molding, has the desired sufficient chemical resistance, and can achieve a higher adhesiveness between the topcoat layer and the resin layer. The endoscopic medical device according to the present invention includes the flexible tube for an endoscope with the above superior properties. The set of resin compositions for covering a flexible tube substrate for an endoscope according to the present invention is suitable for use as a material for forming the resin layer of the flexible tube for an endoscope with the above properties.

An electronic endoscope will now be described as an example of an endoscopic medical device according to a preferred embodiment of the present invention. Electronic endoscopes incorporate a flexible tube for an endoscope (a flexible tube for an endoscope may be hereinafter simply referred to as "flexible tube") and are widely used as medical devices. In the example shown in <FIG>, an electronic endoscope <NUM> includes an insertion section <NUM> for insertion into a body cavity, a main-body operating section <NUM> connected to the proximal end portion of the insertion section <NUM>, and a universal cord <NUM> for connection to a processor device and a light source device. The insertion section <NUM> is composed of a flexible tube 3a connected to the main-body operating section <NUM>, an angle portion 3b connected to the flexible tube 3a, and a tip portion 3c connected to the distal end of the angle portion 3b and having an imaging device (not shown) built thereinto for imaging a body cavity. The flexible tube 3a, which accounts for most of the length of the insertion section <NUM>, is flexible substantially over the entire length thereof. In particular, the portion to be inserted into an area such as a body cavity has a more flexible structure.

As shown in <FIG>, the flexible tube 3a (flexible tube for an endoscope) is composed of a flexible tube substrate <NUM> and a resin layer <NUM> covering the outer peripheral surface of the flexible tube substrate <NUM>. The flexible tube substrate <NUM> includes a spiral tube <NUM> disposed on the innermost side and formed by spirally winding a metal strip 11a, a tubular net <NUM> covering the spiral tube <NUM> and formed by weaving metal wires, and caps <NUM> fitted to both ends. The outer surface of the resin layer <NUM> is covered with a chemical-resistant coat layer <NUM> such as one containing fluorine. Although the spiral tube <NUM> is shown as a single layer, it may be composed of two layers coaxially stacked on top of each other. To clearly illustrate the layer structure, the resin layer <NUM> and the coat layer <NUM> are shown as being thick relative to the diameter of the flexible tube substrate <NUM>.

The resin layer <NUM> according to this embodiment covers the outer peripheral surface of the flexible tube substrate <NUM>. The resin layer <NUM> has a two-layer configuration including an inner layer <NUM> covering the entire peripheral surface of the flexible tube substrate <NUM> about the axis thereof and an outer layer <NUM> covering the entire peripheral surface of the inner layer <NUM> about the axis thereof. A soft resin is used as the material for the inner layer <NUM>, whereas a hard resin is used as the material for the outer layer <NUM>. In other preferred embodiments of the present invention, the resin layer <NUM> may be composed of one layer (a layer A) or three or more layers (including the layer A).

In this embodiment, the resin layer <NUM> is formed with substantially uniform thickness in the longitudinal direction (axial direction) of the flexible tube substrate <NUM>. The resin layer <NUM> has a thickness of, for example, <NUM> to <NUM>. The flexible tube 3a has an outer diameter D of, for example, <NUM> to <NUM>. The inner layer <NUM> and the outer layer <NUM> are formed such that the proportions of the thicknesses of the individual layers <NUM> and <NUM> relative to the total thickness of the resin layer <NUM> vary in the axial direction of the flexible tube substrate <NUM>. Specifically, the proportion of the thickness of the inner layer <NUM> relative to the total thickness of the resin layer <NUM> is larger than that of the outer layer <NUM> on one end 14a side (distal side) of the flexible tube substrate <NUM> attached to the angle portion 3b. The inner layer <NUM> gradually becomes thinner from the end 14a toward the other end 14b side (proximal side) attached to the main-body operating section <NUM>. The outer layer <NUM> is thicker than the inner layer <NUM> on the other end 14b side.

The proportion of the thickness of the inner layer <NUM> is maximum at the end 14a in this embodiment. The proportion of the thickness of the outer layer <NUM> is maximum at the other end 14b in this embodiment. The proportion of the thickness of the inner layer <NUM> to the thickness of the outer layer <NUM> is <NUM>:<NUM> at the end 14a and is <NUM>:<NUM> at the other end 14b. The proportion of the thickness of the inner layer <NUM> to the thickness of the outer layer <NUM> varies so as to be reversed between both ends 14a and 14b. Thus, there is a difference in hardness between the end 14a side and the other end 14b side of the flexible tube 3a, and the softness varies in the axial direction such that the flexible tube 3a is softer on the end 14a side and is harder on the other end 14b side. Preferably, the proportion of the thickness of the inner layer to the thickness of the outer layer is <NUM>:<NUM> to <NUM>:<NUM> (inner layer:outer layer) at one end and is <NUM>:<NUM> to <NUM>:<NUM> (inner layer:outer layer) at the other end.

As in the example above, it is preferred that the proportion of the thickness of the inner layer <NUM> to the thickness of the outer layer <NUM> be <NUM>:<NUM> to <NUM>:<NUM>. Within this range, the amount of resin extruded can be more precisely controlled for the thinner layer.

The difference in modulus at <NUM>% elongation, which is a measure of hardness after molding, between the soft resin used for the inner layer <NUM> and the hard resin used for the outer layer <NUM> is preferably <NUM> MPa or more, more preferably <NUM> MPa or more. The difference in melt viscosity at a molding temperature of <NUM> to <NUM>, which is a measure of the fluidity of a molten resin, between the soft resin used for the inner layer <NUM> and the hard resin used for the outer layer <NUM> is preferably <NUM>,<NUM> Pa·s or less. This ensures that the resin layer <NUM> composed of the inner layer <NUM> and the outer layer <NUM> has both good molding accuracy and the required hardness difference between the distal side and the proximal side.

An example method for manufacturing a flexible tube including a resin layer having a two-layer structure composed of an inner layer and an outer layer will hereinafter be described. A flexible tube including a resin layer composed of one layer or three or more layers can also be manufactured as in the method described below.

To form a resin layer composed of at least two layers including an inner layer and an outer layer, it is preferred to.

A method for manufacturing the flexible tube 3a (<FIG> and <FIG>) will now be described with reference to <FIG> and <FIG>. The resin layer <NUM> is preferably molded using a continuous molding machine. It is preferred to use a continuous molding machine <NUM> composed of known extrusion units <NUM> and <NUM> composed of parts such as hoppers and screws 21a and 22a, a head unit <NUM> for covering the outer peripheral surface of the flexible tube substrate <NUM> with the resin layer <NUM>, a cooling unit <NUM>, a transport unit <NUM> (a feed drum <NUM> and a take-up drum <NUM>) that transports a continuous flexible tube substrate <NUM> to the head unit <NUM>, and a control unit <NUM> that controls these units. The head unit <NUM> is preferably composed of a nipple <NUM>, a die <NUM>, and a support <NUM> fixedly supporting them. An example configuration of such a machine that can be used is shown in, for example, Figs. <NUM> to <NUM> of <CIT>.

The interior of the die <NUM> is preferably heated to a predetermined molding temperature. The molding temperature is preferably set within the range of <NUM> to <NUM>. A soft resin <NUM> and a hard resin <NUM> can be heated to a high temperature by the heating temperature control of a heating unit within the machine. Additionally, as the rotational speeds of the screws 21a and 22a become higher, the soft resin <NUM> and the hard resin <NUM> can be heated to a higher temperature, thereby increasing their fluidity. During this process, the molding thicknesses of the inner layer <NUM> and the outer layer <NUM> can be adjusted by changing the amounts of the molten soft resin <NUM> and hard resin <NUM> ejected while transporting the continuous flexible tube substrate <NUM> at constant speed.

The process of molding the resin layer <NUM> onto the continuous flexible tube substrate <NUM> using the continuous molding machine <NUM> will now be described. When the continuous molding machine <NUM> performs the molding step, the molten soft resin <NUM> and hard resin <NUM> are extruded from the extrusion units <NUM> and <NUM> into the head unit <NUM>. At the same time, the transport unit <NUM> operates to transport the continuous flexible tube substrate <NUM> to the head unit <NUM>. During this process, the extrusion units <NUM> and <NUM> constantly extrude and feed the soft resin <NUM> and the hard resin <NUM> to the head unit <NUM>, and the soft resin <NUM> and the hard resin <NUM> extruded from the extrusion units <NUM> and <NUM> into gates <NUM> and <NUM> merge together at an edge and, in a stacked state, are fed through a resin passage <NUM> to a molding passage <NUM>. Thus, a two-layer molded resin layer <NUM> composed of a stack of an inner layer <NUM> made of the soft resin <NUM> and an outer layer <NUM> made of the hard resin <NUM> is formed.

The continuous flexible tube substrate <NUM> is composed of a plurality of flexible tube substrates <NUM> joined together. The resin layer <NUM> is continuously molded onto the plurality of flexible tube substrates <NUM> being transported through the molding passage <NUM>. When the resin layer <NUM> is molded from the end 14a side (distal side) to the other end 14b side (proximal side) of one flexible tube substrate, the inner layer <NUM> is thick immediately after the extrusion units <NUM> and <NUM> start resin ejection. The proportion of the thickness of the outer layer <NUM> gradually increases over the middle portion toward the other end 14b side. It is preferred to control the amounts of the resins ejected in this way to achieve the above gradient in the proportion of the thickness of the resin layer <NUM>.

A joint member <NUM>, which is a connecting portion between two flexible tube substrates <NUM>, is used for switching of the amounts of the resins ejected from the extrusion units <NUM> and <NUM> by the control unit <NUM>. Specifically, the control unit <NUM> preferably switches the amounts of the resins ejected from the extrusion units <NUM> and <NUM> for transition from the proportion of the thickness on the other end 14b side (proximal side) of one flexible tube substrate <NUM> to the proportion of the thickness on the end 14a side (distal side) of the next flexible tube substrate <NUM>. When the resin layer <NUM> is molded from the end 14a side to the other end 14b side of the next flexible tube substrate <NUM>, it is preferred to similarly control the extrusion units <NUM> and <NUM> such that the outer layer gradually becomes thicker from one end side toward the other end side.

After the continuous flexible tube substrate <NUM> having the resin layer <NUM> molded to the rearmost end is detached from the continuous molding machine <NUM>, the joint members <NUM> are detached from the flexible tube substrates <NUM> to separate the continuous flexible tube substrate <NUM> into the individual flexible tube substrates <NUM>. The resin layer <NUM> on the separated flexible tube substrates <NUM> is then coated with the coat layer <NUM>. Thus, flexible tubes 3a are finished. The finished flexible tubes 3a are transported to an electronic endoscope assembly step.

Preferably, the resin layer of the flexible tube according to the present invention is composed of one or more layers, and the outermost layer of the resin layer is a layer A (a layer containing a polyester elastomer (a) (resin component), at least one of a phosphorus-containing compound (b1) or a thioether compound (b2) (a phosphorus-containing compound (b1) and/or a thioether compound (b2)), and a hindered amine compound (c)). Here, the "outermost layer" of a resin layer having a single-layer structure refers to the resin layer itself, whereas the "outermost layer" of a resin layer having a multilayer structure composed of two or more layers refers to the surface layer of the resin layer of the flexible tube. The flexible tube according to the present invention preferably has another layer (e.g., a topcoat layer) outside the resin layer.

Since the flexible tube according to the present invention has the resin layer with the above configuration, the flexible tube contains few defects due to the formation of bubbles in the resin layer after molding, can achieve the desired sufficient chemical resistance, and can achieve high adhesiveness between the topcoat layer and the resin layer. Although the mechanism is not fully understood, one possible factor is that at least one of the phosphorus-containing compound (b1) or the thioether compound (b2) inhibits the degradation reaction (oxidation) of the resin due to heat, for example, during flexible tube molding. Specifically, one possible factor is that at least one of the phosphorus-containing compound (b1) or the thioether compound (b2) quickly decomposes oxidative degradation products formed from the resin component and thus inhibits the decomposition of the resin such as the polyester elastomer (a) into oligomers and other products.

If the resin layer of the flexible tube according to the present invention is composed of a plurality of layers, the flexible tube according to the present invention provides the above advantageous effects even if the layer A is not the outermost layer, but is an inner layer or interlayer. One possible factor for this is that inhibiting the degradation reaction of the resin such as the polyester elastomer (a) in the inner layer or interlayer can inhibit the formation of degradation products or the formation of bubbles, or both, in the inner layer or interlayer and can thus inhibit the migration of degradation products into the outer layer or the deformation of the resin forming the outer layer resin due to bubbles, or both.

The polyester elastomer (a) used in the present invention may be a common polyester elastomer that is applicable to the formation of flexible tubes.

Specifically, the polyester elastomer (a) used in the present invention is a copolymer composed of hard segments of a crystalline polyester and soft segments of a polyether or a polyester.

Examples of hard segments include polybutylene terephthalate and polyethylene terephthalate.

Examples of soft segments include polyalkylene glycols such as polytetramethylene glycol and polypropylene glycol, bisphenol A ethylene oxide adducts, bisphenol A propylene oxide adducts, and polyesters such as polycaprolactone.

In the present invention, a "polyester elastomer" may have urethane bonds, amide bonds, or both. In this case, of ester bonds, urethane bonds, and amide bonds, ester bonds are present in the largest number. Preferably, a "polyester elastomer" includes no urethane bond or amide bond in the molecule thereof.

Polyester elastomers (a) may be used alone (not part of the invention) or in combination.

The phosphorus-containing compound (b1) is a compound having a structure represented by general formula (<NUM>):
<CHM>.

In general formula (<NUM>), R<NUM> and R<NUM> represent an alkyl group, an aryl group, an alkoxy group, an aryloxy group, or a halogen atom; R<NUM> represents an alkyl group or an aryl group; and at least two of R<NUM>, R<NUM>, or R<NUM> may be linked to each other via a divalent or higher-valent group or a single bond.

In the present invention, compounds having a structure represented by general formula (<NUM>) include, in addition to compounds represented by general formula (<NUM>), compounds (a) and (b) below.

That is, in the present invention, compounds having a structure represented by general formula (<NUM>) are meant to include compounds represented by general formula (<NUM>) and compounds having a structure in which a plurality of structures represented by general formula (<NUM>) are present in one molecule.

The alkyl groups represented by R<NUM>, R<NUM>, and R<NUM> in general formula (<NUM>) above are linear, branched, or cyclic substituted or unsubstituted alkyl groups. Preferably, the alkyl groups have <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, particularly preferably <NUM> to <NUM> carbon atoms. Preferred examples include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, butyl, isobutyl, t-butyl, s-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, cyclohexyl, heptyl, cyclopentyl, octyl, <NUM>-ethylhexyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, and triacontyl. More preferred are methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, t-butyl, s-butyl, pentyl, isopentyl, neopentyl, hexyl, cyclohexyl, octyl, <NUM>-ethylhexyl, dodecyl, hexadecyl, and octadecyl. Even more preferred are methyl, ethyl, n-propyl, isopropyl, butyl, t-butyl, pentyl, isopentyl, hexyl, cyclohexyl, octyl, <NUM>-ethylhexyl, dodecyl, hexadecyl, and octadecyl.

The alkyl groups represented by R<NUM>, R<NUM>, and R<NUM> may further have a substituent. Examples of substituents include halogen atoms, alkyl groups (including cycloalkyl groups), alkenyl groups (including cycloalkenyl groups and bicycloalkenyl groups), alkynyl groups, aryl groups, cyano groups, hydroxy groups, nitro groups, carboxy groups, alkoxy groups, aryloxy groups, acyloxy groups, carbamoyloxy groups, alkoxycarbonyloxy groups, aryloxycarbonyloxy groups, amino groups (including anilino groups), acylamino groups, aminocarbonylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, acyl groups, aryloxycarbonyl groups, alkoxycarbonyl groups, and carbamoyl groups.

More specifically, examples of substituents include halogen atoms (e.g., chlorine, bromine, and iodine atoms); alkyl groups (which represent linear, branched, or cyclic substituted or unsubstituted alkyl groups, including alkyl groups (preferably alkyl groups having <NUM> to <NUM> carbon atoms, e.g., methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, eicosyl, <NUM>-chloroethyl, <NUM>-cyanoethyl, and <NUM>-ethylhexyl), cycloalkyl groups (preferably substituted or unsubstituted cycloalkyl groups having <NUM> to <NUM> carbon atoms, e.g., cyclohexyl, cyclopentyl, and <NUM>-n-dodecylcyclohexyl), bicycloalkyl groups (preferably substituted or unsubstituted bicycloalkyl groups having <NUM> to <NUM> carbon atoms, i.e., monovalent groups derived by removing one hydrogen atom from bicycloalkanes having <NUM> to <NUM> carbon atoms, e.g., bicyclo[<NUM>. <NUM>]heptan-<NUM>-yl and bicyclo[<NUM>. <NUM>]octan-<NUM>-yl), and structures having larger numbers of rings, including tricyclic structures; this definition of alkyl groups also applies to the alkyl groups of the substituents described below (e.g., the alkyl groups of alkylthio groups)); alkenyl groups (including alkenyl groups (preferably substituted or unsubstituted alkenyl groups having <NUM> to <NUM> carbon atoms, e.g., vinyl, allyl, prenyl, geranyl, and oleyl), cycloalkenyl groups (preferably substituted or unsubstituted cycloalkenyl groups having <NUM> to <NUM> carbon atoms, i.e., monovalent groups derived by removing one hydrogen atom from cycloalkenes having <NUM> to <NUM> carbon atoms, e.g., <NUM>-cyclopenten-<NUM>-yl and <NUM>-cyclohexen-<NUM>-yl), and bicycloalkenyl groups (substituted or unsubstituted bicycloalkenyl groups, preferably substituted or unsubstituted bicycloalkenyl groups having <NUM> to <NUM> carbon atoms, i.e., monovalent groups derived by removing one hydrogen atom from bicycloalkenes having one double bond, e.g., bicyclo[<NUM>. <NUM>]hept-<NUM>-en-<NUM>-yl and bicyclo[<NUM>. <NUM>]oct-<NUM>-en-<NUM>-yl));.

Of the above substituents, those having hydrogen atoms may have their hydrogen atoms replaced by the above substituents. Examples of such substituents include alkylcarbonylaminosulfonyl groups, arylcarbonylaminosulfonyl groups, alkylsulfonylaminocarbonyl groups, arylsulfonylaminocarbonyl groups, methylsulfonylaminocarbonyl groups, p-methylphenylsulfonylaminocarbonyl groups, acetylaminosulfonyl groups, and benzoylaminosulfonyl groups.

The aryl groups represented by R<NUM>, R<NUM>, and R<NUM> represent substituted or unsubstituted aryl groups. Preferably, the aryl groups have <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, particularly preferably <NUM> to <NUM> carbon atoms. Preferred examples include phenyl, <NUM>-methylphenyl, <NUM>-methylphenyl, <NUM>-methylphenyl, <NUM>-ethylphenyl, <NUM>-ethylphenyl, <NUM>,<NUM>-dimethylphenyl, <NUM>,<NUM>-dimethylphenyl, <NUM>,<NUM>,<NUM>-trimethylphenyl, <NUM>-naphthyl, <NUM>-naphthyl, <NUM>-chlorophenyl, <NUM>-chlorophenyl, <NUM>-chlorophenyl, <NUM>-methoxyphenyl, <NUM>-methoxyphenyl, <NUM>-methoxyphenyl, <NUM>-benzylphenyl, <NUM>-benzylphenyl, <NUM>-methylcarbonylphenyl, and <NUM>-methylcarbonylphenyl.

More preferably, the aryl groups represented by R<NUM>, R<NUM>, and R<NUM> are phenyl, <NUM>-methylphenyl, <NUM>-methylphenyl, <NUM>-ethylphenyl, <NUM>-ethylphenyl, <NUM>,<NUM>-dimethylphenyl, <NUM>,<NUM>-dimethylphenyl, <NUM>,<NUM>,<NUM>-trimethylphenyl, <NUM>-naphthyl, <NUM>-naphthyl, <NUM>-chlorophenyl, <NUM>-chlorophenyl, <NUM>-methoxyphenyl, <NUM>-methoxyphenyl, <NUM>-methoxyphenyl, <NUM>-benzylphenyl, or <NUM>-benzylphenyl, particularly preferably phenyl.

The above aryl groups represented by R<NUM>, R<NUM>, and R<NUM> may further have a substituent. Examples of substituents include the substituents listed above that the alkyl groups represented by R<NUM>, R<NUM>, and R<NUM> may have.

The alkoxy groups represented by R<NUM> and R<NUM> represent linear, branched, or cyclic substituted or unsubstituted alkoxy groups. Preferably, the alkoxy groups have <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, particularly preferably <NUM> to <NUM> carbon atoms. Preferred examples include methoxy, ethoxy, n-propoxy, isopropoxy, cyclopropoxy, butoxy, isobutoxy, t-butoxy, s-butoxy, pentyloxy, isopentyloxy, neopentyloxy, t-pentyloxy, hexyloxy, cyclohexyloxy, heptyloxy, cyclopentyloxy, octyloxy, <NUM>-ethylhexyloxy, nonyloxy, decyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy, octadecyloxy, eicosyloxy, docosyloxy, and triacontyloxy, more preferably methoxy, ethoxy, n-propoxy, isopropoxy, butoxy, isobutoxy, t-butoxy, s-butoxy, pentyloxy, isopentyloxy, neopentyloxy, hexyloxy, cyclohexyloxy, octyloxy, <NUM>-ethylhexyloxy, dodecyloxy, hexadecyloxy, and octadecyloxy, particularly preferably methoxy, ethoxy, n-propoxy, isopropoxy, t-butoxy, pentyloxy, isopentyloxy, hexyloxy, cyclohexyloxy, octyloxy, <NUM>-ethylhexyloxy, dodecyloxy, hexadecyloxy, and octadecyloxy.

The above alkoxy groups represented by R<NUM> and R<NUM> may further have a substituent. Examples of substituents include the substituents listed above that the alkyl groups represented by R<NUM>, R<NUM>, and R<NUM> may have.

The aryloxy groups represented by R<NUM> and R<NUM> represent substituted or unsubstituted aryloxy groups. Preferably, the aryloxy groups have <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, particularly preferably <NUM> to <NUM> carbon atoms. Preferred examples include phenoxy, <NUM>-methylphenoxy, <NUM>-methylphenoxy, <NUM>-methylphenoxy, <NUM>-ethylphenoxy, <NUM>-ethylphenoxy, <NUM>,<NUM>-dimethylphenoxy, <NUM>,<NUM>-di-t-butylphenoxy, <NUM>,<NUM>-di-t-butylphenoxy, <NUM>,<NUM>-dimethylphenoxy, <NUM>,<NUM>-di-t-butyl-<NUM>-methylphenoxy, <NUM>,<NUM>,<NUM>-trimethylphenoxy, <NUM>,<NUM>,<NUM>-tri-t-butylphenoxy, <NUM>-naphthyloxy, <NUM>-naphthyloxy, <NUM>-chlorophenoxy, <NUM>-chlorophenoxy, <NUM>-chlorophenoxy, <NUM>-methoxyphenoxy, <NUM>-methoxyphenoxy, <NUM>-methoxyphenoxy, <NUM>-benzylphenoxy, <NUM>-benzylphenoxy, <NUM>-methylcarbonylphenoxy, and <NUM>-methylcarbonylphenoxy.

More preferred examples include phenyl, <NUM>,<NUM>-di-t-butylphenoxy, and <NUM>,<NUM>,<NUM>-tri-t-butylphenoxy.

The above aryloxy groups represented by R<NUM> and R<NUM> may further have a substituent. Examples of substituents include the substituents listed above that the alkyl groups represented by R<NUM>, R<NUM>, and R<NUM> may have.

From the viewpoint of the compatibility between the resin and the phosphorus-containing compound (b1), it is preferred that, in general formula (<NUM>), R<NUM> and R<NUM> be alkoxy groups or aryloxy groups, and R<NUM> be an alkyl group or an aryl group.

Examples of divalent or higher-valent groups that serve as a linking group in the compound having a structure represented by general formula (<NUM>) include divalent or higher-valent groups derived by removing one or more hydrogen atoms from the substituents listed above for the alkyl groups represented by R<NUM>, R<NUM>, and R<NUM> (divalent groups if one hydrogen atom is removed from the substituents, or trivalent groups if two hydrogen atoms are removed from the substituents) and combinations thereof. These divalent or higher-valent groups are preferably divalent to hexavalent, more preferably divalent to tetravalent. The above divalent or higher-valent groups are preferably organic groups.

The above divalent or higher-valent groups may further have a substituent. Examples of substituents include the substituents listed above that the alkyl groups represented by R<NUM>, R<NUM>, and R<NUM> may have.

The above divalent or higher-valent groups preferably have a molecular weight of <NUM> to <NUM>,<NUM>.

Preferred of the above divalent or higher-valent groups and single bonds are single bonds and divalent or higher-valent groups derived by removing one or more hydrogen atoms from amino groups, alkyl groups, aryl groups, bis-aryl groups (arylaryl groups), arylalkylaryl groups, aryloxyaryl groups, alkoxyalkyl groups, alkoxyaryl groups, and alkylaryl groups.

If the compound having a structure represented by general formula (<NUM>) is a compound in which a plurality of structures represented by general formula (<NUM>) are present in one molecule, it preferably has, in one molecule, <NUM> to <NUM> phosphorus atoms, more preferably <NUM> to <NUM> phosphorus atoms, even more preferably <NUM> to <NUM> phosphorus atoms.

Specific examples of compounds represented by general formula (<NUM>) above are given below, although these examples are not intended to limit the present invention. <CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

Other compounds suitable for use as the compound having a structure represented by general formula (<NUM>) include phosphorous acid ester compounds described in <CIT>.

The thioether compound (b2) is a compound having a structure represented by general formula (<NUM>):
<CHM>.

In general formula (<NUM>), R<NUM> and R<NUM> represent an alkyl group and may be linked to each other via a divalent or higher-valent group or a single bond.

In the present invention, compounds having a structure represented by general formula (<NUM>) includes, in addition to compounds represented by general formula (<NUM>), compounds (c) and (d) below.

The alkyl groups represented by R<NUM> and R<NUM> represent linear, branched, or cyclic substituted or unsubstituted alkyl groups. Preferably, the alkyl groups have <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, particularly preferably <NUM> to <NUM> carbon atoms. Preferred examples include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, butyl, isobutyl, t-butyl, s-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, cyclohexyl, heptyl, cyclopentyl, octyl, <NUM>-ethylhexyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, and triacontyl. More preferred are methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, t-butyl, s-butyl, pentyl, isopentyl, neopentyl, hexyl, cyclohexyl, octyl, <NUM>-ethylhexyl, dodecyl, hexadecyl, and octadecyl. Particularly preferred are methyl, ethyl, n-propyl, isopropyl, butyl, t-butyl, pentyl, isopentyl, hexyl, cyclohexyl, octyl, <NUM>-ethylhexyl, dodecyl, hexadecyl, and octadecyl.

Examples of substituents for the substituted alkyl groups represented by R<NUM> and R<NUM> include the substituents listed above that the alkyl groups represented by R<NUM>, R<NUM>, and R<NUM> in general formula (<NUM>) may have.

Of the substituted alkyl groups represented by R<NUM> and R<NUM>, alkoxycarbonylalkyl groups are preferred. The alkoxycarbonyl groups of the alkoxycarbonylalkyl groups preferably have <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, particularly preferably <NUM> to <NUM> carbon atoms.

The divalent or higher-valent group serving as a linking group in the compound having a structure represented by general formula (<NUM>) is similar to the divalent or higher-valent group described as a linking group in general formula (<NUM>) above, and a preferred range is also similar.

Specific examples of compounds represented by general formula (<NUM>) above are given below, although these examples are not intended to limit the present invention. <CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

Thioether compounds (b2) may be used alone (not part of the invention) or in combination.

The hindered amine compound (c) is a compound having a structural moiety represented by general formula (<NUM>) below.

In general formula (<NUM>), R<NUM> to R<NUM> represent a hydrogen atom or an alkyl group having <NUM> to <NUM> carbon atoms (preferably <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms). Specific examples of alkyl groups represented by R<NUM> to R<NUM> include methyl, ethyl, n-butyl, isopropyl, s-butyl, t-butyl, t-pentyl, t-hexyl, and t-octyl. Preferably, R<NUM> to R<NUM> are primary (linear) alkyl groups. More preferably, all of R<NUM> to R<NUM> are primary (linear) alkyl groups (particularly preferably methyl groups).

In general formula (<NUM>), R<NUM> represents a hydrogen atom, an alkyl group having <NUM> to <NUM> carbon atoms (preferably <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, even more preferably <NUM> to <NUM> carbon atoms, further preferably <NUM> or <NUM> carbon atoms), or -OR<NUM>, where R<NUM> represents a hydrogen atom or a linear, branched, or cyclic alkyl group having <NUM> to <NUM> carbon atoms (preferably <NUM> to <NUM> carbon atoms). In particular, R<NUM> is preferably a hydrogen atom, which results in a higher chemical resistance.

In general formula (<NUM>), * represents a point of attachment.

The compound having a structural moiety represented by general formula (<NUM>) is preferably a compound represented by general formula (<NUM>-<NUM>) below or a compound having a component (preferably a repeating unit) represented by general formula (<NUM>-<NUM>) below.

In the formulae, R<NUM> to R<NUM> have the same meanings as R<NUM> to R<NUM>, respectively, in general formula (<NUM>) above, and preferred ranges are also the same; q represents an integer of <NUM> or more; D<NUM> represents a q-valent linking group; s represents <NUM> or <NUM>; r represents a positive integer, preferably within the range of degrees of polymerization described later; and Q represents an s+<NUM>-valent linking group such as a group including an aromatic hydrocarbon group, a group including an imino group (NRN), or a group including a triazine linking group. Specific examples of RN include hydrogen atoms, alkyl groups having <NUM> to <NUM> carbon atoms, and piperidyl-containing groups represented by general formula (<NUM>).

The linking group represented by D<NUM> preferably has a molecular weight of <NUM> to <NUM>,<NUM>, more preferably <NUM> to <NUM>. The linking group represented by Q preferably has a molecular weight of <NUM> to <NUM>,<NUM>, more preferably <NUM> to <NUM>.

More preferably, the compound having a structural moiety represented by general formula (<NUM>) is a compound represented by any of formulae (<NUM>-A) to (<NUM>-C), (<NUM>-E), (<NUM>-G), and (<NUM>-H) below, a polymer or oligomer having a repeating unit represented by formula (<NUM>-D) below (preferably a polymer or oligomer having a repeating unit represented by any of formulae (3D1) to (3D3)), or a polymer or oligomer having a repeating unit represented by formula (<NUM>-F) below. <CHM>
<CHM>
<CHM>
<CHM>.

In the formulae, R<NUM> has the same meaning as R<NUM> in general formula (<NUM>), and preferred forms are also the same.

R<NUM> represents a hydrogen atom or an alkyl group having <NUM> to <NUM> carbon atoms (preferably <NUM> to <NUM> carbon atoms, more preferably <NUM> to <NUM> carbon atoms, even more preferably <NUM> to <NUM> carbon atoms). L<NUM> represents a single bond or an alkylene group having <NUM> to <NUM> carbon atoms (preferably <NUM> to <NUM> carbon atoms). RN has the same meaning as RN in general formula (<NUM>-<NUM>). n represents an integer of <NUM> to <NUM> (preferably <NUM> to <NUM>) (in formula (3D3), n represents an integer of <NUM> to <NUM> (preferably <NUM> to <NUM>)).

In formula (<NUM>-G), at least one R is not H, but a group including triazine. In formula (<NUM>-H), the wavy lines represent a point of attachment.

If the compound having a structural moiety represented by general formula (<NUM>) is a polymer or oligomer, the number of repeating units (degree of polymerization) is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, even more preferably <NUM> to <NUM>. The terminal structures of the polymer or oligomer may each be, for example, but not limited to, a hydrogen atom, a substituted or unsubstituted amino group, or a substituted or unsubstituted triazyl group.

Hindered amine compounds (c) may be used alone (not part of the invention) or in combination.

The amount of the polyester elastomer (a) is preferably <NUM>% by mass or more, more preferably <NUM>% by mass or more, even more preferably <NUM>% by mass or more, further preferably <NUM>% by mass or more, of the resin component forming the layer A (preferably the outermost layer) of the resin layer.

Although the amount of the polyester elastomer (a) may be <NUM>% by mass of the resin component forming the layer A, the amount of the polyester elastomer (a) is preferably <NUM>% by mass or less, more preferably <NUM>% by mass or less, even more preferably <NUM>% by mass or less. If the amount of the polyester elastomer (a) in the layer A falls within the above preferred range, and a soft resin is blended as the remainder, better flexibility can be achieved.

The layer A of the resin layer may have the polyester elastomer (a) alone as the resin component or may further include a component other than the polyester elastomer (a) as the resin component. If the layer A of the resin layer further includes a component other than the polyester elastomer (a) as the resin component, the remainder of the resin component excluding the polyester elastomer (a) preferably includes, as a softer resin, at least one of a polyurethane elastomer (d) or a polyamide elastomer (e).

The polyurethane elastomer (d) may be a common polyurethane elastomer that is applicable to the formation of flexible tubes. The polyamide elastomer (e) may be a common polyamide elastomer that is applicable to the formation of flexible tubes. In the present invention, the polyurethane elastomer (d) preferably has no amide bond, and the polyamide elastomer (e) preferably has no urethane bond.

The inclusion of at least one of the polyurethane elastomer (d) or the polyamide elastomer (e) can improve the adhesiveness between the resin layer including the layer A and the topcoat layer. If the resin component in the layer A of the resin layer includes at least one of the polyurethane elastomer (d) or the polyamide elastomer (e), the total amount of at least one of the polyurethane elastomer (d) or the polyamide elastomer (e) is preferably <NUM>% by mass or more, more preferably <NUM>% by mass or more, even more preferably <NUM>% by mass or more. On the other hand, the total amount of at least one of the polyurethane elastomer (d) or the polyamide elastomer (e) is preferably <NUM>% by mass or less, more preferably <NUM>% by mass or less, even more preferably <NUM>% by mass or less, of the resin component in the layer A of the resin layer. The inclusion of at least one of the polyurethane elastomer (d) or the polyamide elastomer (e) in the above amount can improve the adhesiveness while maintaining desirable elasticity and flexibility and maintaining sufficient chemical resistance.

Polyurethane elastomers (d) may be used alone or in combination. Polyamide elastomers (e) may be used alone or in combination.

In a preferred form of the layer A of the resin layer, at least one of the phosphorus-containing compound (b1) or the thioether compound (b2) (the phosphorus-containing compound (b1) and/or the thioether compound (b2)) is preferably present in a total amount of <NUM> parts by mass or more, more preferably <NUM> parts by mass or more, based on <NUM> parts by mass of the resin component. On the other hand, the total amount of at least one of the phosphorus-containing compound (b1) or the thioether compound (b2) is preferably <NUM> parts by mass or less, more preferably <NUM> parts by mass or less, based on <NUM> parts by mass of the resin component. If the total amount of at least one of the phosphorus-containing compound (b1) or the thioether compound (b2) falls within the above range, a layer A that provides the desired effect while allowing less of this compound to migrate from the resin can be obtained.

In a preferred form of the layer A of the resin layer, the hindered amine compound (c) is preferably present in an amount of <NUM> parts by mass or more, more preferably <NUM> parts by mass or more, even more preferably <NUM> parts by mass or more, based on <NUM> parts by mass of the resin component. The upper limit is preferably <NUM> parts by mass or less, more preferably <NUM> parts by mass or less. If the amount of the hindered amine compound (c) falls within the above range, a layer A that provides the desired effect while allowing less of this compound to migrate from the resin can be obtained.

In a preferred form of the layer A of the resin layer, the ratio of the total amount of at least one of the phosphorus-containing compound (b1) or the thioether compound (b2) (the amount of the phosphorus-containing compound (b1) and/or the amount of the thioether compound (b2) to the amount of the hindered amine compound (c) is preferably, by mass, <NUM>:<NUM> to <NUM>:<NUM>, more preferably <NUM>:<NUM> to <NUM>:<NUM>, particularly preferably <NUM>:<NUM> to <NUM>:<NUM>. If the ratio of the amounts of these additives falls within the above range by mass, the antagonism between the additives can be inhibited, thus further improving the properties such as chemical resistance.

If the resin layer is composed of a plurality of layers, at least one layer other than the layer A (preferably the outermost layer) preferably contains at least one of the polyester elastomer (a), the polyurethane elastomer (d), or the polyamide elastomer (e) (the polyester elastomer (a), the polyurethane elastomer (d), and/or the polyamide elastomer (e)) (this layer is hereinafter referred to as "layer B"). More preferably, the layer B contains at least the polyurethane elastomer (d), which can improve the adhesiveness between the resin layer including the layer A and the topcoat layer. The layer B preferably contains the polyurethane elastomer (d) as the main component. In this case, the amount of the polyurethane elastomer (d) is preferably <NUM>% by mass or more, more preferably <NUM>% by mass or more, even more preferably <NUM>% by mass or more, further preferably <NUM>% by mass or more, of the resin component in the layer B. It is preferred that all resin component in the layer B be the polyurethane elastomer (d); otherwise, the remainder is preferably at least one of the polyamide elastomer (e) and/or the polyester elastomer (a) (the polyamide elastomer (e) and/or the polyester elastomer (a)).

Alternatively, the layer B may contain the polyamide elastomer (e) as the main component. For example, if the layer B contains the polyamide elastomer (e), the amount of the polyamide elastomer (e) may be <NUM>% by mass or more, or <NUM>% by mass or more, of the resin component. All resin component in the layer B may be the polyamide elastomer (e); otherwise, the remainder is preferably at least one of the polyurethane elastomer (d) or the polyester elastomer (a) (the polyurethane elastomer (d) and/or the polyester elastomer (a)), more preferably the polyurethane elastomer (d).

If the layer B is used as the outermost layer, the layer B preferably includes at least one of the phosphorus-containing compound (b1) or the thioether compound (b2) and the hindered amine compound (c). This can further improve the chemical resistance of the flexible tube. If the layer B is used as an inner layer or interlayer, it may be preferred not to include these compounds, for example, by taking into account adhesiveness to the outer layer, rather than chemical resistance. If the layer B is used as the outermost layer, preferred amounts of the phosphorus-containing compound (b1), the thioether compound (b2), and the hindered amine compound (c), for example, are similar to those of the layer A.

The flexible tube according to the present invention is preferably produced using a resin composition for covering a flexible tube substrate for an endoscope. The resin composition for covering a flexible tube substrate for an endoscope includes a polyester elastomer (a), at least one of a phosphorus-containing compound (b1) or a thioether compound (b2), and a hindered amine compound (c) as a mixture thereof,
wherein the phosphorus-containing compound (b1) is a compound having a structure in which only one structure represented by general formula (<NUM>) is present in one molecule
<CHM>
in general formula (<NUM>), R<NUM> and R<NUM> represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, or a halogen atom; R<NUM> represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group; and at least two of R<NUM>, R<NUM>, or R<NUM> may be linked to each other via a divalent or higher-valent group or a single bond.

A flexible tube according to the present invention in which the resin layer is composed of a plurality of layers is preferably produced using a set of resin compositions for covering a flexible tube substrate for an endoscope according to the present invention (a set of resin compositions for covering a flexible tube substrate for an endoscope is hereinafter also simply referred to as "set of resin compositions"). The set of resin compositions according to the present invention includes a resin composition (A) according to the present invention that includes a polyester elastomer (a), at least one of a phosphorus-containing compound (b1) or a thioether compound (b2), and a hindered amine compound (c) and a resin composition (B) that includes at least one of a polyester elastomer (a1), a polyurethane elastomer (d), or a polyamide elastomer (e) (a polyester elastomer (a1), a polyurethane elastomer (d), and/or a polyamide elastomer (e)), wherein the resin composition (A) is for forming an outer layer covering the flexible tube substrate for an endoscope and the resin composition (B) is for forming an inner layer covering the flexible tube substrate for an endoscope. The resin compositions (A) and (B) are separately included in the set of resin compositions.

In the set of resin compositions according to the present invention, the polyester elastomer (a) and the polyester elastomer (a1) may be the same or different.

The resin composition (A) is used to form the layer A of the resin layer of the flexible tube according to the present invention. The resin composition (B), on the other hand, is used to form a layer other than the layer A of the resin layer. The resin composition (B) may include any component present in the resin composition (A) as long as the advantages of the present invention are not impaired.

Preferred ratios of the amount of the polyester elastomer (a), the amount of at least one of the phosphorus-containing compound (b1) or the thioether compound (b2), and the amount of the hindered amine compound (c) in the resin composition (A), for example, are the same as those of the layer A.

The flexible tube according to the present invention preferably includes a resin layer having a two-layer structure composed of one inner layer and one outer layer. In this case, the inner layer is composed of the layer B of the resin layer, whereas the outer layer is composed of the layer A of the resin layer. Preferred formulations for the resin layer are as follows.

· If the adhesiveness between the inner layer and the outer layer is prioritized.

· If the chemical resistance is prioritized.

The constituents in parentheses are optional.

To improve the chemical resistance, the molecular weights of the elastomers applied are preferably, but not limited to, <NUM>,<NUM> to <NUM>,<NUM>,<NUM>, more preferably <NUM>,<NUM> to <NUM>,<NUM>, particularly preferably <NUM>,<NUM> to <NUM>,<NUM>.

In the present invention, the molecular weight of an elastomer refers to the weight average molecular weight unless otherwise specified. The weight average molecular weight can be determined by GPC as the molecular weight based on polystyrene. An HLC-<NUM> GPC apparatus (trade name, available from Tosoh Corporation) is used. The eluants used are chloroform for polyester elastomers, N-methyl-<NUM>-pyrrolidone (NMP) for polyurethane elastomers, and m-cresol/chloroform (available from Shonan Wako Pure Chemical Co. ) for polyamide elastomers. The columns used are G3000HXL and G2000HXL (trade names, available from Tosoh Corporation). The temperature is <NUM>. The flow rate is <NUM>/min. RI detection is employed.

It is preferred to suitably set the physical properties of the layer B (preferably the inner layer). For example, the layer B preferably has an A hardness (JIS-K7215) of <NUM> or more, more preferably <NUM> or more, particularly preferably <NUM> or more. The upper limit is preferably <NUM> or less, more preferably <NUM> or less, particularly preferably <NUM> or less.

The layer B preferably has a storage modulus E' of <NUM> MPa or more, more preferably <NUM> MPa or more, particularly preferably <NUM> MPa or more. The upper limit is preferably <NUM> MPa or less, more preferably <NUM> MPa or less, particularly preferably <NUM> MPa or less. The layer B preferably has a loss modulus E" of <NUM> MPa or more, more preferably <NUM> MPa or more, particularly preferably <NUM> MPa or more. The upper limit is preferably <NUM> MPa or less, more preferably <NUM> MPa or less, particularly preferably <NUM> MPa or less. The layer B preferably has a loss tangent of <NUM> or more, more preferably <NUM> or more, particularly preferably <NUM> or more. The upper limit is preferably <NUM> or less, more preferably <NUM> or less, particularly preferably <NUM> or less.

As used herein, the viscoelasticity parameters are measured at <NUM> unless otherwise specified. The measurement procedure follows JIS-K7244-<NUM>.

It is preferred to suitably set the physical properties of the layer A of the resin layer. For example, the layer A preferably has a D hardness (JIS-K7215) of <NUM> or more, more preferably <NUM> or more, particularly preferably <NUM> or more. The upper limit is preferably <NUM> or less, particularly preferably <NUM> or less.

The layer A of the resin layer preferably has a storage modulus E' of <NUM> MPa or more, more preferably <NUM> MPa or more, particularly preferably <NUM> MPa or more. The upper limit is preferably <NUM> GPa or less, more preferably <NUM> MPa or less, particularly preferably <NUM> MPa or less. The layer A of the resin layer preferably has a loss modulus E" of <NUM> MPa or more, more preferably <NUM> MPa or more, particularly preferably <NUM> MPa or more. The upper limit is preferably <NUM> MPa or less, more preferably <NUM> MPa or less, particularly preferably <NUM> MPa or less. The layer A of the resin layer preferably has a loss tangent of <NUM> or more, more preferably <NUM> or more, particularly preferably <NUM> or more. The upper limit is preferably <NUM> or less, more preferably <NUM> or less, particularly preferably <NUM> or less.

The layer B preferably has a modulus at <NUM>% elongation of <NUM> MPa or more, more preferably <NUM> MPa or more, particularly preferably <NUM> MPa or more. The upper limit is preferably <NUM> MPa or less, more preferably <NUM> MPa or less, particularly preferably <NUM> MPa or less.

The layer A of the resin layer preferably has a modulus at <NUM>% elongation of <NUM> MPa or more, more preferably <NUM> MPa or more, particularly preferably <NUM> MPa or more. The upper limit is preferably <NUM> MPa or less, more preferably <NUM> MPa or less, particularly preferably <NUM> MPa or less.

As used herein, the modulus is measured at <NUM> unless otherwise specified. The measurement procedure follows JIS-K7311.

The resin layer is preferably soluble in <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-hexafluoro-<NUM>-propanol (specific solvent). "Soluble in the specific solvent" means that the resin layer exhibits a degree of solubility of <NUM>% by mass at <NUM>. Thus, the technical significance of "soluble in the specific solvent" is that the resin has no three-dimensional (crosslinked) structure, which is preferred because the use of such a resin layer provides good flexibility for a flexible tube for an endoscopic medical device.

The elastomer forming the resin layer is preferably not substantially crosslinked. Here, "not substantially crosslinked" not only means that the resin is not crosslinked, but also means that the resin has no branched structure within the detection limit of, for example, NMR.

It is preferred that the elastomer forming the resin layer (particularly the second layer or the outer layer) according to this embodiment be not substantially crosslinked because the use of such a resin layer provides good flexibility and bending durability for a flexible tube for an endoscopic medical device.

The topcoat layer (coat layer) <NUM> is applied to the flexible tube according to this embodiment. Examples of materials the can be applied to the topcoat layer include, but not limited to, urethane coatings, acrylic coatings, fluorinated coatings, silicone coatings, epoxy coatings, and polyester coatings. To achieve high adhesiveness between the resin layer and the topcoat layer and good chemical resistance, which are advantages of this embodiment, urethane coatings, acrylic coatings, and fluorinated coatings are preferred. The topcoat layer may be formed by common processes. One example process involves dissolving the coating component in a predetermined solvent, optionally adding a curing agent to the solution, and hardening the solution. The hardening treatment may be performed, for example, by heating to <NUM> to <NUM>.

In this embodiment, the topcoat layer is primarily used to protect and add a gloss to the surface of the flexible tube and to impart smoothness and chemical resistance. Thus, a topcoat layer with high elasticity, high surface smoothness, and good chemical resistance is preferred. The topcoat layer alone preferably has a storage modulus E' of <NUM> MPa or more, more preferably <NUM> MPa or more, particularly preferably <NUM> MPa or more. The upper limit is preferably <NUM> GPa or less, more preferably <NUM> MPa or less, particularly preferably <NUM> MPa or less. If the storage modulus E' is higher than or equal to the lower limit, the topcoat layer can provide a surface protection function. If the storage modulus E' is lower than or equal to the upper limit, the resulting flexible tube can maintain its flexibility.

Although a two-layer molded resin layer composed of a soft resin layer (layer B) as an inner layer and a hard resin layer (layer A) as an outer layer is formed in the foregoing embodiment, the hard resin layer may be disposed as the inner layer, and the soft resin layer may be disposed as the outer layer. Although a resin layer having a two-layer configuration has been described by way of example in the foregoing embodiment, the resin layer, in another embodiment, may have a multilayer configuration including two or more layers. The two layers need not be in contact with each other, but may be separated by another functional layer.

Although an electronic endoscope for observation of an image of the condition of a subject captured using an imaging device has been described by way of example in the foregoing embodiment, the present invention is not limited thereto, but may also be applied to an endoscope for observation of the condition of a subject using an optical image guide.

The flexible tube according to the present invention is not limited to endoscope applications, but can also be applied to a wide variety of endoscopic medical devices. For example, the flexible tube according to the present invention can be applied to an endoscope equipped with a clip or wire at the distal end thereof or to a device equipped with a basket or brush and provides its superior effect. Endoscopic medical devices are meant to include a wide variety of flexible medical and diagnostic devices for introduction and use in a body, including medical devices having an endoscope as a basic structure, as described above, and remotely operated medical devices.

The present invention will now be described in more detail with reference to the following examples, although these examples should not be construed as limiting the invention.

Resin compositions (resin mixtures for outer and inner layers) having the formulations shown in Table <NUM> below (in parts by mass) were prepared and were melt-kneaded in a twin-screw kneader available from Technovel Corporation (product name: KZW15-<NUM>) at a barrel set temperature of <NUM> and a screw rotational speed of <NUM> rpm. The ejected molten resin strand was cooled in a water bath and was pelletized with a pelletizer to form pelletized samples.

The resulting pelletized samples were introduced into the continuous molding machine shown in <FIG> and <FIG> to produce flexible tubes for endoscopes. Specifically, flexible tube substrates having a diameter of <NUM> and a length of <NUM> were covered with the resin mixtures (compositions) for the inner layer and then with the resin mixtures (compositions) for the outer layer in Table <NUM> below. The resin layer had a thickness of <NUM>. The inner-to-outer-layer ratios at the distal and proximal ends were as shown in Table <NUM> below. For flexible tubes having no inner layer, the inner-to-outer-layer ratio is shown as inner layer:outer layer = <NUM>:<NUM>. The resulting flexible tubes were subjected to the following tests. The results are summarized in Table <NUM>.

The resin was removed from each flexible tube and was cut to a size of <NUM> × <NUM> to obtain a test specimen. The test specimen was immersed in a <NUM>% aqueous peracetic acid solution at <NUM> for <NUM> hours. After the surface of the test specimen was thoroughly washed with water and was then dried at <NUM> and <NUM>% RH (relative humidity) for <NUM> hours, the test specimen was subjected to a tensile test at elongations of <NUM>%, <NUM>%, and <NUM>% (an elongation of <NUM>% means stretching to twice the original length) with a TENSILON RTF-<NUM> universal material testing machine (trade name, available from A&D Company, Limited). The test specimen was rated on the following scale, where "B" or higher is satisfactory. The results are summarized in Table <NUM>.

The outer layers of the manufactured flexible tubes were visually observed and were rated on the following scale, where "B" or higher is satisfactory. The results are summarized in Table <NUM>.

The resulting resin mixtures were used to form sheet-shaped articles. The results are summarized in Table <NUM>.

Each resin composition for the outer layer was heated to <NUM> and was pressed at <NUM> MPa for <NUM> seconds using a MINI TEST PRESS (available from Toyo Seiki Seisaku-sho, Ltd. ) to form a <NUM> thick, <NUM> square sheet.

The resulting sheet was coated with a topcoat layer under the following conditions.

The material used for the topcoat layer was Obbligato SS0068 (trade name, available from AGC COAT-TECH Co. ), serving as a base, with a curing agent (available from AGC COAT-TECH Co. This material was applied to the sheet formed as above with a <NUM> thick doctor blade. The coated sample was dried at room temperature (<NUM>) and was further dried at <NUM> for <NUM> hours to form a resin sheet with a topcoat layer. The topcoat layer had a thickness of <NUM>.

The resulting resin sheet with a topcoat was immersed in a <NUM>% aqueous peracetic acid solution at <NUM> for <NUM> hours. After the surface was washed with water and was then dried at <NUM> and <NUM>% RH for <NUM> hours, the following adhesiveness evaluation was performed.

A polyester tape (available from <NUM> Company, model No. <NUM>, length: <NUM>, width: <NUM>) was attached to the topcoat layer side of the resulting resin sheet with a topcoat layer that had been subjected to the peracetic acid immersion test. The polyester tape was then removed to determine whether the topcoat peeled from the resin sheet. On the following rating scale, "B" or higher is satisfactory.

HA-<NUM>: ADK STAB LA-63P (trade name), available from Adeka Corporation
<CHM>
where the wavy lines represent a point of attachment, which also applies to the following formulae; and n represents <NUM> or <NUM>.

HA-<NUM>: Chimassorb 944FDL (trade name), available from BASF SE
<CHM>
where n represents an integer of <NUM> to <NUM>.

HA-<NUM>: Tinuvin <NUM> (trade name), available from BASF SE
<CHM>.

HA-<NUM>: Flamestab NOR <NUM> (trade name), available from BASF SE
<CHM>.

HA-<NUM>: Chimassorb 2020FDL (trade name), available from BASF SE
<CHM>
where t represents an integer of <NUM> to <NUM>, and nBu represents a n-butyl group.

P-<NUM>: ADK STAB PEP-<NUM> (trade name), available from Adeka Corporation
<CHM>.

P-<NUM>: ADK STAB HP-<NUM> (trade name), available from Adeka Corporation
<CHM>.

S-<NUM>: ADK STAB AO-<NUM> (trade name), available from Adeka Corporation
<CHM>.

As can be seen from Table <NUM>, the flexible tubes having resin layers that did not meet the requirements of the present invention were unsatisfactory in terms of at least one of the evaluations items. In contrast, it was found that the flexible tubes according to the present invention contained sufficiently few defects in the resin layer after molding, had the desired sufficient chemical resistance, and achieved a higher adhesiveness between the topcoat layer and the resin layer.

While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention in any detail of the description unless otherwise specified.

Claim 1:
A flexible tube for an endoscope, comprising a flexible tube substrate, for an endoscope, that is flexible and tubular and a resin layer covering the flexible tube substrate for an endoscope,
wherein the resin layer includes one or more layers, the layers including a layer A including a polyester elastomer (a) as a resin component, at least one of a phosphorus-containing compound (b1) or a thioether compound (b2), and a hindered amine compound (c),
the phosphorus-containing compound (b1) is a compound having a structure represented by general formula (<NUM>),
the thioether compound (b2) is a compound having a structure represented by general formula (<NUM>), and
the hindered amine compound (c) is a compound having a structural moiety represented by general formula (<NUM>):
<CHM>
wherein
in general formula (<NUM>), R<NUM> and R<NUM> represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, or a halogen atom; R<NUM> represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group; and at least two of R<NUM>, R<NUM>, or R<NUM> may be linked to each other via a divalent or higher-valent group or a single bond,
in general formula (<NUM>), R<NUM> and R<NUM> represent a substituted or unsubstituted alkyl group and may be linked to each other via a divalent or higher-valent group or a single bond, and
in general formula (<NUM>), R<NUM> to R<NUM> represent a hydrogen atom or an alkyl group having <NUM> to <NUM> carbon atoms; R<NUM> represents a hydrogen atom, an alkyl group having <NUM> to <NUM> carbon atoms, or -OR<NUM>, wherein R<NUM> represents a hydrogen atom or an alkyl group having <NUM> to <NUM> carbon atoms; and * represents a point of attachment;
the recited alkyl and alkoxy groups are linear, branched or cyclic groups.