Conductive polyurethane foam and method for producing same

Abstract

To provide a conductive polyurethane foam that simultaneously satisfies the requirements of suppressing bleeding of a conductive agent and the like and low hardness, and that has excellent image display properties when applied to an electrophotographic image forming apparatus. [Solution] A urethane foam obtained by curing a foamable composition obtained by foaming a composition containing a polyurethane raw material (I) by a mechanical froth method, wherein the polyurethane raw material (I) contains a urethane prepolymer (A) having an ion-conductive group and an active energy ray-polymerizable functional group, and an active energy ray-polymerizable silicone (B), and the conductive polyurethane foam has a gel fraction of 90% or more when acetone is used as the extraction solvent according to JIS K 6796.

Description

[Technical Field]

[0001] The present invention relates to a conductive polyurethane foam suitable for use in an electrophotographic image forming apparatus, and a method for producing the same. [Background technology]

[0002] Electrophotographic image forming apparatuses such as laser printers have a charging roll for charging a photosensitive drum, and the conductive roll body used in this charging roll is required to have conductivity and elasticity.

[0003] Patent Document 1 discloses a conductive elastic roller having an elastic layer made of an ultraviolet-curable urethane prepolymer containing a conductive agent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-2825 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] However, it is difficult for such a conductive roll to simultaneously suppress bleeding of the conductive agent and to provide good adhesion to the photosensitive drum, etc., and image display performance may be poor.

[0006] Therefore, an object of the present invention is to provide a conductive polyurethane foam that simultaneously suppresses bleeding of conductive agents and has low hardness, and therefore has excellent image display properties when applied to an electrophotographic image forming apparatus. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to achieve the above object and have discovered that foaming and curing a composition containing specific components to produce a foam can achieve low hardness while maintaining a high gel fraction, thereby solving the above problems and thereby completing the present invention.

[0008] The present invention provides A urethane foam obtained by curing a foamable composition obtained by foaming a composition containing a polyurethane raw material (I) by a mechanical froth method, The polyurethane raw material (I) includes a urethane prepolymer (A) having an ion-conductive group and an active energy ray-polymerizable functional group, and an active energy ray-polymerizable silicone (B), The urethane foam has a gel fraction of 90% or more when the extraction solvent is acetone according to JIS K 6796. The conductive polyurethane foam is characterized by the following:

[0009] The present invention also provides A method for producing a conductive polyurethane foam, comprising: a preparation step of preparing a polyurethane raw material (I) including a prepolymer (A) synthesized from a polyol (a-1), a polyisocyanate (a-2), a conductive agent (a-3) having an active hydrogen-containing group or a functional group reactive with active hydrogen and an ionic conductive group, and an active energy ray-polymerizable compound (a-4) having an active hydrogen-containing group or a functional group reactive with active hydrogen, and an active energy ray-polymerizable silicone (B); a foaming step of foaming a composition containing the polyurethane raw material (I) by a mechanical froth method to obtain a foamable composition; an irradiation step of irradiating the foamable composition with active energy rays; Including, The urethane foam has a gel fraction of 90% or more when the extraction solvent is acetone according to JIS K 6796. The present invention relates to a method for producing a conductive polyurethane foam. In addition, the present manufacturing method may further include, after the adjustment step, a coating step of coating the foamable composition onto a roll shaft while rotating the roll shaft, thereby producing a roll-shaped conductive polyurethane foam.

[0010] Furthermore, the present invention is a member for an image-forming apparatus, which comprises the conductive polyurethane foam.

[0011] The present invention also provides an image forming apparatus including the member for an image forming apparatus.

[0012] wherein the foamable composition further contains polythiol (III), The polythiol (III) preferably has a number of functional groups of 2.0 to 6.0.

[0013] The SH-INDEX ((content [g] of polythiol (III) × number of functional groups in polythiol (III)) / (molecular weight [g / mol] of polythiol (III) × amount [mol] of active energy ray-polymerizable functional groups in prepolymer (A)) in the foamable composition is preferably in the range of 0.5 to 1.5.

[0014] The urethane foam preferably has a 10% CLD of 200 kPa or less as measured by the following method. (10% CLD measurement method) According to JIS K 6400-2, the sample size is 50 mm x 50 mm x 5 mm thick, and after pre-compressing to 50% once, the CLD is measured at 10% compression.

[0015] The viscosity of the prepolymer (A) at 80° C. according to JIS K 7117-2 is preferably 1 to 20 Pa·s. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a conductive roll body which simultaneously satisfies the requirements of suppressing bleeding of conductive agents and the like and low hardness, and therefore has excellent image display properties. DETAILED DESCRIPTION OF THE INVENTION

[0017] In the present invention, the functional group containing active hydrogen is preferably a hydroxyl group, an amino group, a thiol group, a carboxyl group, etc. The functional group containing active hydrogen may be one type or a combination of two or more types.

[0018] In the present invention, the functional group capable of reacting with active hydrogen preferably includes an alkoxy group, an isocyanate group, an epoxy group, etc. The functional group capable of reacting with active hydrogen may be one type or a combination of two or more types.

[0019] The ionic conductive group in the present invention refers to a functional group having cationic or anionic properties. The ionic conductive group is preferably a cationic group derived from a salt such as a quaternary ammonium salt, a phosphonium salt, a sulfonium salt, a pyridinium salt, or an imidazolium salt. An anionic ionic conductive group may be, for example, a sulfonic acid group.

[0020] In the present invention, the active energy rays refer to X-rays, electron beams, ultraviolet rays, visible light rays, infrared rays, etc. Furthermore, ultraviolet rays, visible light rays, and infrared rays may be collectively referred to as "light".

[0021] In the present invention, the term "active energy ray polymerizable" refers to the presence of an active energy ray reactive group (preferably a photoreactive functional group), more preferably a functional group containing an ethylenic or acetylenic (preferably ethylenic) unsaturated carbon bond. Examples of the functional group containing an unsaturated carbon bond include an alkenyl group (vinyl group, allyl group, butenyl group, petenyl group, hexenyl group, etc.) and a (meth)acryloyl group. The active energy ray reactive group may also be referred to as an active energy ray polymerizable functional group.

[0022] In the present invention, the solid content means the components constituting the composition other than the solvent (particularly the organic solvent), or the mass or volume thereof.

[0023] The conductive agent in the present invention is an agent that can improve the conductivity of a urethane foam when added to the foam, and refers to, for example, an additive that can make the resistance value 11 (Log Ω) or less (preferably 9 (Log Ω) or less). The resistance value can be measured according to the following method. A sample formed on an A4 size, 2mm thick roller is placed flat and a load of 500gf is applied to each end. The terminals of an R8340a (the name of the measuring device) are connected and the average resistance value is measured when 100V is applied for 10 seconds. The measurement conditions are as follows: Measuring instrument: ADVANTEST R8340a Applied voltage 100V Application time 10sec Measurement environment: 22°C, 55% RH Load 500gf (load on each end) Measurement method Flat plate measurement method

[0024] The foamable composition for obtaining the conductive polyurethane foam, the method for producing the conductive polyurethane foam, the structure of the conductive polyurethane foam, and the image display device will be described below. Note that the conductive polyurethane foam may also be referred to simply as urethane foam.

[0025] <<<<<Foamable Composition>>>> The conductive polyurethane foam is obtained by curing a foamable composition containing a polyurethane raw material (I). The foamable composition is obtained by foaming a composition containing the polyurethane raw material (I) by a mechanical froth method. The foamable composition preferably contains a polythiol (III) and may further contain another component (IV). The mechanical froth method is usually carried out in the presence of a foam-forming gas (II), and the foamable composition also contains this foam-forming gas (II). However, the conductive polyurethane foam itself that is finally obtained may or may not contain the foam-forming gas (II) within its structure (within the cells of the foam). Each of the components (I) to (IV) is described below.

[0026] <<<Polyurethane Raw Materials (I)>>> The polyurethane raw material (I) contains a prepolymer (A) and an active energy ray-polymerizable silicone (B).

[0027] <<Prepolymer (A)>> The prepolymer (A) has an ion-conductive group and an active energy ray-polymerizable functional group incorporated in the skeleton.

[0028] Although the urethane prepolymer (A) is usually obtained from raw materials containing a polyol and a polyisocyanate, the ion-conductive group and the active energy ray-polymerizable functional group may be introduced into the urethane prepolymer (A) in any form. The urethane prepolymer (A) can be obtained, for example, by synthesizing a polyol (a-1), a polyisocyanate (a-2), a conductive agent (a-3) having an active hydrogen-containing group or a functional group reactive with active hydrogen, and an active energy ray-polymerizable compound (a-4) having an active hydrogen-containing group or a functional group reactive with active hydrogen.

[0029] These (a-1) to (a-4) may be different components from each other, but when the conductive agent (a-3) or the active energy ray-polymerizable compound (a-4) has two or more alcoholic hydroxyl groups, they may be treated as the polyol (a-1), and when the conductive agent (a-3) or the active energy ray-polymerizable compound (a-4) has two or more isocyanate groups, they may be treated as the polyisocyanate (a-2).

[0030] A composition for synthesizing a prepolymer containing these (a-1) to (a-4) may be referred to as a prepolymer composition (a).

[0031] The prepolymer (A) may contain, within the range that does not impair the effects of the present invention, a monool, a monoisocyanate, a conductive agent that does not have an active hydrogen-containing group or a functional group that can react with active hydrogen, an active energy ray-polymerizable compound that does not have an active hydrogen-containing group or a functional group that can react with active hydrogen, and the like.

[0032] The viscosity of the prepolymer (A) according to JIS K 7117-2 at 80°C is preferably 1 to 20 Pa·s, more preferably 1 to 10 Pa·s, and even more preferably 1.5 to 7.5 Pa·s. This viscosity can be changed by adjusting the content of each component, etc.

[0033] Each of the components (a-1) to (a-4) will be described below. Note that the components (a-1) to (a-4) shown below are only examples and can be changed as appropriate within the scope that does not impair the effects of the present invention.

[0034] <Polyol (a-1)> The polyol (a-1) is a compound having two or more hydroxyl groups in one molecule, and is not particularly limited as long as it does not impair the effects of the present invention.

[0035] Examples of the polyol compound include polyester polyol, polycarbonate polyol, polyether polyol, polyester ether polyol, polydiene polyol, and hydrogenated polydiene polyol.

[0036] Examples of polyester polyols include polyester polyols obtained by a dehydration condensation reaction between a polyol and a polycarboxylic acid, and polyester polyols obtained by ring-opening polymerization of lactone monomers such as ε-caprolactone and methylvalerolactone.

[0037] The polyol forming the polyester polyol is not particularly limited as long as it does not impair the effects of the present invention.

[0038] Examples of polyols include: Aliphatic polyols such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, 1,4-tetracosanediol, 1,6-tetracosanediol, 1,4-hexacosanediol, 1,6-octacosanediol, glycerin, trimethylolpropane, trimethylolethane, hexanetriol, pentaerythritol, sorbitol, mannitol, sorbitan, diglycerin, and dipentaerythritol; alicyclic polyols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, cyclohexanedimethanol, tricyclodecane dimethanol, cyclopentadiene dimethanol, 2,5-norbornanediol, 1,3-adamantanediol, and dimer diol; Aromatic polyols such as bisphenol A, bisphenol F, phenol novolac, and cresol novolac; These can be used alone or in combination of two or more.

[0039] The polycarboxylic acid is a substance having a plurality of carboxyl groups in its molecular structure, and is not particularly limited as long as it does not impair the effects of the present invention.

[0040] Examples of polycarboxylic acids include: Aliphatic polycarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid; aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid; Alicyclic polycarboxylic acids such as hexahydrophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid; acid esters of these polycarboxylic acids; The following can be mentioned:

[0041] Examples of polycarbonate polyols include: at least one polyhydric alcohol such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, or diethylene glycol; Diethylene carbonate, dimethyl carbonate, diethyl carbonate, etc. Examples include those obtained by reacting

[0042] Examples of polyether polyols include: Examples include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc., which are obtained by polymerizing cyclic ethers such as ethylene oxide, propylene oxide, tetrahydrofuran, etc., and copolyethers thereof.

[0043] Alternatively, the cyclic ether can be polymerized using a polyhydric alcohol such as glycerin or trimethylolethane.

[0044] Examples of polyester ether polyols include those obtained by a dehydration condensation reaction between a polycarboxylic acid and a glycol such as diethylene glycol or a propylene oxide adduct.

[0045] Examples of polycarboxylic acids include: Aliphatic polycarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid; aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid; Alicyclic polycarboxylic acids such as hexahydrophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid; acid esters of these polycarboxylic acids; The following can be mentioned:

[0046] The polyol compounds may be used alone or in combination of two or more.

[0047] <Polyisocyanate (a-2)> The polyisocyanate (a-2) is a compound having two or more isocyanate groups in one molecule, and is not particularly limited as long as it does not impair the effects of the present invention.

[0048] Examples of polyisocyanates include: Difunctional polyisocyanates include 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 2,2'-diphenylmethane diisocyanate (2,2'- Aromatics such as MDI), hydrogenated MDI, xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, polymethylene polyphenyl polyisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, tetramethylxylene diisocyanate (TMXDI), etc.; Alicyclic ones such as cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and methylcyclohexane diisocyanate; Alkylene-based isocyanates such as butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, and lysine diisocyanate; As difunctional or higher polyisocyanates, polymeric MDI; Tri- or higher functional polyisocyanates include 1-methylbenzene-2,4,6-triisocyanate, 1,3,5-trimethylbenzene-2,4,6-triisocyanate, biphenyl-2,4,4'-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'tetraisocyanate, triphenylmethane-4,4',4"-triisocyanate, lysine ester triisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecane triisocyanate, bicycloheptane triisocyanate, and 1,8-diisocyanatomethyloctane; Modified products and derivatives of these polyisocyanates; etc.

[0049] The polyisocyanate (a-2) may be used singly or in combination of two or more kinds.

[0050] The content of polyisocyanate is not particularly limited, but it can be blended so that the isocyanate index is, for example, 50 to 200 or 70 to 150. The isocyanate index is a numerical value that represents the equivalent ratio of isocyanate groups in polyisocyanate (a-2) to hydroxyl groups in prepolymer composition (a) that can react with polyisocyanate (a-2), expressed as a percentage.

[0051] <Conductive agent (a-3)> The conductive agent (a-3) is not particularly limited as long as it is a conductive agent having an active hydrogen-containing group or a functional group capable of reacting with active hydrogen.

[0052] Examples of the conductive agent (a-3) include those containing a quaternary ammonium salt, a phosphonium salt, a sulfonium salt, a pyridinium salt, an imidazolium salt, or the like in the skeleton.

[0053] The conductive agent (a-3) preferably contains a quaternary ammonium salt in the skeleton.

[0054] The conductive agent (a-3) may be used alone or in combination of two or more.

[0055] The content of the conductive agent (a-3) is not particularly limited, but is preferably 0.01 to 5% by mass in the prepolymer composition (a).

[0056] <Active energy ray polymerizable compound (a-4)> The active energy ray-polymerizable compound (a-4) is not particularly limited as long as it is an active energy ray-polymerizable compound having an active hydrogen-containing group or a functional group capable of reacting with active hydrogen. The active energy ray-polymerizable compound (a-4) may contain a plurality of such functional groups in one molecule.

[0057] Examples of the active energy ray-polymerizable compound (a-4) having a hydroxyl group as the active hydrogen-containing group include monools having an allyl ether group, such as allyl ether glycol and hydroxyethyl allyl ether; monools having a vinyl ether group, such as 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether and 4-hydroxybutyl vinyl ether; and monools having a (meth)acrylic group, such as hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate and 2-hydroxypropyl methacrylate.

[0058] The active energy ray polymerizable compound (a-4) may be used alone or in combination of two or more.

[0059] The content of the active energy ray-polymerizable compound (a-4) is not particularly limited, but is preferably 1 to 25% by mass in the prepolymer composition (a).

[0060] <<Active energy ray polymerizable silicone (B)>> The active energy ray-polymerizable silicone (B) is not particularly limited as long as it is a silicone having a functional group containing an unsaturated carbon bond in the molecule. The active energy ray-polymerizable silicone (B) may contain a plurality of functional groups containing unsaturated carbon bonds in one molecule (preferably 2 to 3 in one molecule).

[0061] Examples of the active energy ray-polymerizable silicone (B) include compounds ((meth)acrylic-modified silicones) in which a (meth)acryloyl group is attached to at least one of the terminals of the main chain and the side chain of a nonionic surfactant having a siloxane structure (e.g., dimethylsiloxane-polyoxyalkylene copolymer, etc.). More specific examples of the active energy ray-polymerizable silicone (B) include those obtained by subjecting a siloxane polymer having silanol ends, such as polydimethylsiloxane having silanol ends at both ends, polydiphenylsiloxane-dimethylsiloxane copolymer, or polydimethyldiphenylsiloxane having silanol ends at both ends, to a dehydration condensation reaction and a dealcoholization reaction between a trialkylalkoxysilane such as trimethylethoxysilane and an ethylenically unsaturated bond-containing silane compound such as (3-acryloxypropyl)methyldimethoxysilane, in the presence of a catalyst (e.g., tin 2-ethylhexanoate).

[0062] The active energy ray-polymerizable silicone (B) may be used alone or in combination of two or more kinds.

[0063] The weight average molecular weight of the active energy ray-polymerizable silicone (B) is not particularly limited, but is preferably 500 to 50,000, and more preferably 1,000 to 10,000.

[0064] The content of the active energy ray-polymerizable silicone (B) is not particularly limited, but is preferably 0.01 to 5% by mass in the foamable composition.

[0065] <<<Foam-forming gas (II)>>> The foam-forming gas is not particularly limited, but is preferably a gas that does not adversely affect the reaction of polyols, isocyanates, etc., and more preferably dry air or an inert gas (e.g., nitrogen, carbon dioxide, helium, argon, etc.).

[0066] The content of the foaming gas (II) in the foamable composition can be appropriately changed depending on the foam density and other factors.

[0067] The foam-forming gas (II) may be used alone or in combination of two or more.

[0068] <<<Polythiol (III)>>> The polythiol (III) can undergo an enethiol reaction with the active energy ray-polymerizable functional group (unsaturated carbon bond) contained in the polyurethane raw material (I). By curing via such an enethiol reaction, oxygen inhibition can be prevented and the desired cured product can be obtained.

[0069] Examples of polythiols include esters of mercaptocarboxylic acids and polyhydric alcohols, aliphatic polythiols, and aromatic polythiols.

[0070] In the esters of mercaptocarboxylic acids and polyhydric alcohols, examples of the mercaptocarboxylic acids include thioglycolic acid and mercaptopropionic acid, and examples of the polyhydric alcohols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerin, trimethylolpropane, pentaerythritol, and sorbitol. Among these, esters of mercaptocarboxylic acids and polyhydric alcohols are preferred because they have little odor, and specific examples include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), tetraethylene glycol bis(3-mercaptopropionate), and dipentaerythritol hexa(3-mercaptopropionate).

[0071] Examples of the aliphatic polythiol and aromatic polythiol include ethanedithiol, propanedithiol, hexamethylenedithiol, decamethylenedithiol, tolylene-2,4-dithiol, and xylenedithiol.

[0072] The polythiol (III) may be used singly or in combination of two or more kinds.

[0073] The number of functional groups of the polythiol (III) is preferably 2.0 to 6.0. When a plurality of polythiols (III) are contained, the number of functional groups is the average number of the polythiols.

[0074] When the foamable composition contains polythiol (III), the SH-INDEX of the foamable composition is preferably in the range of 0.5 to 1.5. The SH-INDEX is calculated by (content of polythiol (III) [g] × number of functional groups in polythiol (III)) / (molecular weight of polythiol (III) [g / mol] × amount of active energy ray-polymerizable functional groups in prepolymer (A) [mol]).

[0075] <<<Other Ingredients (IV)>>> The foamable composition may contain other components as long as they do not impair the effects of the present invention. Examples of other components include known additives such as solvents, dispersion media, catalysts, foam stabilizers, blowing agents, foaming agents, polymerization initiators, light stabilizers, crosslinking agents, surfactants, thickeners, bubble nucleating agents, plasticizers, lubricants, colorants, antioxidants, oxygen scavengers, fillers, reinforcing agents, flame retardants, and surface treatment agents.

[0076] <<<<Conductive polyurethane foam>>>> The structure of the conductive polyurethane foam is not particularly limited, and may be any structure appropriate for the intended use.

[0077] When the conductive polyurethane foam is incorporated into an image forming apparatus, it is preferable to form the conductive polyurethane foam into a roll-shaped conductive foam roll. When the conductive polyurethane foam is used as the conductive foam roll, the inner diameter, outer diameter, thickness, length, etc. of the conductive foam roll can be appropriately changed depending on the shape, size, etc. of the image forming apparatus in which the conductive foam roll is incorporated.

[0078] The density of conductive polyurethane foam is 30 to 800 kg / m 3 is preferably 50 to 500 kg / m 3 It is more preferable that the cell diameter of the urethane foam is 1 to 300 μm.

[0079] The conductive polyurethane foam has a gel fraction according to JIS K 6796 using acetone as the extraction solvent of 90% or more, preferably 91.5% or more, more preferably 93% or more, and particularly preferably 95% or more.

[0080] According to the present invention, by blending specific components, it is possible to obtain a conductive polyurethane foam that has the above-mentioned high gel fraction while maintaining hardness. Note that such gel fraction can be appropriately adjusted by changing the amount of functional groups of each active energy ray-polymerizable compound in the foamable composition and various production conditions (e.g., reaction time, etc.).

[0081] The conductive polyurethane foam preferably has a 10% CLD measured by the following method of measurement of 200 kPa or less. (10% CLD measurement method) According to JIS K 6400-2, the sample size is 50 mm x 50 mm x 5 mm thick, and after pre-compressing to 50% once, the CLD is measured at 10% compression.

[0082] The conductive polyurethane foam may be a closed-cell foam or an open-cell foam.

[0083] When a conductive polyurethane foam is used as a conductive foam roll, the entire roll may be made of urethane foam, or only a portion of the roll may be made of urethane foam. However, it is preferable that at least the entire outer surface of the roll is made of urethane foam.

[0084] When a part of the conductive foam roll is made of urethane foam, the other materials used are not particularly limited, and may be combined with metal, glass, ceramics, resin, rubber, etc.

[0085] <<<<<Preferred Example of the Method for Producing Conductive Polyurethane Foam>>>> The method for producing the conductive polyurethane foam preferably includes the following steps: (Step 1: Preparation step) This is a process for preparing a polyurethane raw material (I) including a prepolymer (A) synthesized from a polyol (a-1), a polyisocyanate (a-2), a conductive agent (a-3) having an active hydrogen-containing group or a functional group capable of reacting with active hydrogen, and an active energy ray-polymerizable compound (a-4) having an active hydrogen-containing group or a functional group capable of reacting with active hydrogen, and an active energy ray-polymerizable silicone (B). (Process 2: Foaming process) This is a process in which polyurethane raw material (I) and foam-forming gas (II) are mechanically stirred under a nitrogen atmosphere to foam, thereby obtaining a foamable composition. (Process 3: Coating process (optional process)) This is a step that can be carried out when the conductive polyurethane foam is a conductive foam roll, and is a step of applying the foamable composition onto the roll shaft while rotating the roll shaft. (Process 4: Irradiation process) This is a step of irradiating the foamable composition with active energy rays.

[0086] Furthermore, a processing step may be provided in which the urethane foam obtained in the irradiation step is processed (cutting, polishing, etc.).

[0087] In addition, the method for producing a conductive polyurethane foam includes not only a form in which each step is performed in order, but also a form in which the order of some steps and other steps is reversed, a form in which some steps and other steps (e.g., a preparation step and a foaming step) are performed simultaneously, and a form in which some steps are performed repeatedly, as long as the effects of the present invention are not impaired.

[0088] Each step (preparation step, foaming step, coating step, and irradiation step) will be described below. Note that the description of each raw material may be omitted as it has been described above.

[0089] <<<Preparation process>>> The preparation step can be carried out by a known method. For example, the polyurethane raw material (I) can be prepared by adding a predetermined amount of the active energy ray-polymerizable silicone (B) to the prepolymer (A) while stirring it.

[0090] The preparation step may include a synthesis step of synthesizing the prepolymer (A). The synthesis step can be carried out according to a known method, for example, according to the following method.

[0091] An appropriate amount of polyisocyanate (a-2) is placed in a container and stirred under a nitrogen atmosphere. Polyol (a-1), conductive agent (a-3), and active energy ray polymerizable compound (a-4) are added dropwise to prepare prepolymer composition (a). Prepolymer composition (a) is stirred for a predetermined time to complete the reaction, thereby obtaining prepolymer (I).

[0092] In the synthesis step, a catalyst may be added as needed to promote the reaction.

[0093] The catalyst is not particularly limited, and examples thereof include known catalysts such as metal catalysts, for example, tin-based catalysts, lead-based catalysts, other metal catalysts, amine-based catalysts, other acidic catalysts, basic catalysts, etc. One or more of these catalysts can be used.

[0094] The amount of catalyst added is not particularly limited, but can be, for example, 0.001 to 5% by mass in the prepolymer composition (a).

[0095] Furthermore, when the polythiol (III) is added, it may be added simultaneously with the preparation of the polyurethane raw material (I), or may be added after the preparation of the polyurethane raw material (I).

[0096] <<<Foaming process>>> In the foaming process, the so-called mechanical frothing method can be used.

[0097] The mechanical froth method is a method in which the composition is usually stirred with a stirring blade or the like to mix gas in the atmosphere into the composition and foam it, and therefore the foaming step is usually carried out in an atmosphere of foam-forming gas (II).

[0098] As the stirring device, any stirring device generally used in the mechanical froth method can be used without any particular limitation, such as a homogenizer, a dissolver, a mechanical froth foaming machine, etc.

[0099] The foam-forming gas (II) forms bubbles (cells) in the urethane foam, and the amount of foam-forming gas (II) to be mixed may be determined depending on the desired density of the urethane foam, etc.

[0100] As the type of foam-forming gas (II), dry air or an inert gas (e.g., nitrogen, carbon dioxide, helium, argon, etc.) can be used, as described above. Only one type of foam-forming gas (II) may be used alone, or two or more types may be used.

[0101] In order to prevent unwanted reactions of each composition, steps other than the foaming step may also be carried out in an atmosphere of dry air or an inert gas.

[0102] <<<Coating process>>> The coating step is a step that can be carried out when the conductive polyurethane foam is a conductive foam roll, and is a step of coating the foamable composition onto the roll shaft while rotating the roll shaft.

[0103] In the coating step, the material of the roll shaft, the shape of the roll shaft, the rotation speed of the roll shaft, etc. are not particularly limited, and may be any known condition.

[0104] In the coating step, the means for supplying the foamable composition onto the roll shaft is not particularly limited, and the coating may be carried out by discharging the foamable composition onto the roll shaft, or by bringing the roll shaft into contact with a layer containing the foamable composition. The supply speed of the foamable composition can also be changed appropriately.

[0105] The coating step may be carried out multiple times to adjust the thickness of the foamable composition.

[0106] <<<Irradiation process>>> The irradiation step is a step of irradiating the foamable composition with active energy rays.

[0107] In the irradiation step, crosslinking is performed by irradiating with active energy rays (preferably light) of a specific wavelength to which an active energy ray reactive group (preferably a photoreactive functional group) reacts. When a photopolymerization initiator or the like is used in combination, the wavelength can be set to be such that the photopolymerization initiator reacts.

[0108] The amount of irradiation of the active energy rays may be determined depending on the formulation and thickness of the foamable composition.

[0109] When carrying out the coating process, the thickness of the urethane foam can be adjusted by changing the coating speed, etc., in the coating process described above, but it is also possible to increase the thickness of the roll by repeating the coating process and the irradiation process multiple times.

[0110] When the coating step is performed, a roll-shaped urethane foam can be obtained by pulling out the roll shaft from the urethane foam obtained through the irradiation step. Note that the roll shaft and the urethane foam may be supplied to the image forming apparatus as an integrated part without pulling out the roll shaft from the urethane foam.

[0111] Furthermore, the aforementioned other component (IV) may be added at any step before the irradiation step.

[0112] In addition, in the coating step or the irradiation step, heating may be performed for the purpose of reducing the viscosity of the raw material or promoting curing. The heating temperature and heating time are not particularly limited and may be appropriately changed depending on the purpose of heating and the raw material used.

[0113] <<<<Image forming devices>>>> The electrophotographic image-forming device in which the conductive polyurethane foam of the present invention can be incorporated is not particularly limited, but is preferably a laser printer. The conductive polyurethane foam of the present invention has low hardness and is prevented from bleeding of the conductive agent, so it can be preferably used as a charging roll (a roll body that charges a photosensitive drum) of a laser printer. [Example]

[0114] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples and can be practiced in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

[0115] <<<Raw materials>>> The raw materials used are as follows: <<Polyol (a-1)>> PPG1000: Polypropylene glycol, molecular weight 1000 PPG2000: Polypropylene glycol, molecular weight 2000 PPG3000: Polypropylene glycol, molecular weight 3000 BEPG: butyl ethyl propanediol <<Polyisocyanate (a-2)>> TDI: Toluene diisocyanate <<Conductive agent (a-3)>> Cation IN: Hydroxyl group-containing quaternary ammonium salt type cationic conductive agent, NOF Corporation <<Active energy ray polymerizable compound (a-4)>> HEMA: 2-hydroxyethyl methacrylate <<Active energy ray polymerizable silicone (B)>> Foam stabilizer A: TEGORAD 2100, manufactured by Evonik The TEGORAD 2100 has the following structure: TIFF0007820319000001.tif46169<<Polythiol(III)>> Thiol 3F: Lecad803 SC Organic Chemical Thiol 4F: Lecad804 SC Organic Chemicals Thiol 6F: Lecad806 SC Organic Chemicals The thiol 4F has the structure shown below. TIFF0007820319000002.tif20168<<Other ingredients>> Conductive agent A: 1SX-1090, polymeric ionic conductive agent, manufactured by Taisei Fine Chemical Co., Ltd.

[0116] <<<Production of rolled urethane foam>>> <<Example 1>> <Preparation process> Prepolymer (A) was synthesized by mixing (a-1) to (a-4) in the amounts shown in Table 1. The synthesis was carried out under the following conditions. 1. (a-1) and (a-2) were mixed and heated to 80°C in a nitrogen atmosphere and reacted for 3 hours. 2. After the temperature of the mixture was raised to 60°C, component (a-3) was added and the mixture was allowed to react for 1 hour. 3. Component (a-4) was added to the mixture and reacted for 1 hour. 4. The temperature of the mixture was raised to 80°C, and additives such as photopolymerization initiator, antioxidant, and light stabilizer were added in a total amount of 1 to 1.5 g per 100 g of prepolymer. Next, polyurethane raw material (I) was prepared by mixing prepolymer (A), silicone (B), and polythiol (III) in the amounts shown in Table 1. If the mixture had a high viscosity, it was heated to about 80°C. <Foaming process, coating process, irradiation process> A foamable composition was prepared by mechanical foaming. Mechanical foaming was carried out in air using an in-line homomixer to mix carbon dioxide. Both ends of a Φ5 metal shaft were chucked with a rotating jig, and while the shaft was rotated at a speed of 50 rpm, the foamed raw material was applied from one end of the shaft to the required length (L dimension, 250 mm). The coating thickness was 1.5 mm. After coating was completed, the raw material was irradiated with UV light using an irradiator (high-pressure mercury lamp) to harden it. The irradiation conditions were 100 mW / cm 2 Over 10,000mJ / cm 2 It was deemed appropriate. <Processing process> Both ends of the cured product were cut to leave the required dimensions, and the surface of the cured product was polished using a cylindrical grinder to form a roller.

[0117] <<Examples 2 to 13, Comparative Examples 1 to 4>> Roll-shaped urethane foams according to Examples 2 to 13 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the raw materials used were changed to those shown in Table 1.

[0118] The resulting roll-shaped urethane foam had sufficient electrical conductivity.

[0119] <<<Physical property measurement>>> The following physical property measurements were carried out, and the measurement results are shown in Table 1.

[0120] <<Viscosity>> The viscosity of the prepolymer (A) at 80°C was measured in accordance with JIS K 7117-2.

[0121] <<Gel fraction>> For each roll-shaped urethane foam, the gel fraction was measured using acetone as the extraction solvent in JIS K 6796.

[0122] <<10%CLD>> According to JIS K 6400-2, each roll of urethane foam was cut into a sample size of 50 mm x 50 mm x 5 mm thick, and after pre-compressing once by 50%, the CLD at 10% compression was measured.

[0123] <<<Evaluation Test>>> <<Image evaluation>> Each roll of urethane foam was used to carry out an image evaluation test, which was carried out according to the following methods. <Evaluation method> To evaluate bleeding, a 500g load was applied to both ends of each roller after it had been conditioned in an environment of 22°C and 55% RH, and a continuous current test was conducted for 6 hours at an applied voltage of 1000V. The conductive rollers that had undergone this bleeding evaluation were then set in an image forming device and image evaluation was carried out. If bleeding occurs in the conductive roller, the bleed material will adhere to other rollers and bleed into the image, resulting in phenomena such as white spots and black spots. Furthermore, if the hardness of the conductive roller is high, adhesion will decrease, similarly deteriorating the image evaluation. Based on the state of this image, the bleeding suppression effect of the roll-shaped urethane foam and the achievement of low hardness were evaluated. <Evaluation criteria> ◯: No bleeding, white spots, black spots, etc. due to the bleeding substance were observed. ×: Blurring, white spots, black spots, etc. due to the bleed-out substance were observed.

[0124] [Table 1]

[0125] [Table 2]

Claims

1. The gel fraction in JIS K 6796 using acetone as the extraction solvent is 90% or more, The 10% CLD measured by the following measurement method is 200 kPa or less, A conductive polyurethane foam characterized by being obtained by irradiating with active energy rays a composition containing a polyurethane raw material (I) including a prepolymer (A) having an ion-conductive group and an active energy ray-polymerizable functional group, and an active energy ray-polymerizable silicone (B), and curing the composition. (Measurement method) According to JIS K 6400-2, the sample size is 50 mm x 50 mm x 5 mm thick, and after 50% pre-compression is performed once, the CLD at 10% compression is measured.

2. the composition is cured by irradiating with active energy rays a composition comprising a polyurethane raw material (I) including a prepolymer (A) synthesized from a polyol (a-1), a polyisocyanate (a-2), a conductive agent (a-3) having an active hydrogen-containing group or a functional group reactive with active hydrogen and an ionic conductive group, and an active energy ray-polymerizable compound (a-4) having an active hydrogen-containing group or a functional group reactive with active hydrogen, and an active energy ray-polymerizable silicone (B); The gel fraction in JIS K 6796 using acetone as the extraction solvent is 90% or more, A conductive polyurethane foam having a 10% CLD of 200 kPa or less as measured by the following measurement method: (Measurement method) According to JIS K 6400-2, the sample size is 50 mm x 50 mm x 5 mm thick, and after 50% pre-compression is performed once, the CLD at 10% compression is measured.

3. 3. A member for an image-forming apparatus, comprising the conductive polyurethane foam according to claim 1.

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