JP2008280448A - Polyurethane foam and electroconductive roller using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyurethane foam that permits satisfactory formation of a coating film by directly applying a solvent-based coating on the surface without causing trouble by swelling and permits formation of a surface resin layer by directly applying the solvent-based layer on the elastic layer without requiring a solvent-shielding layer. <P>SOLUTION: The polyurethane foam is manufactured by the mechanical agitation blowing of a polyurethane raw material comprising a polyol component and an isocyanate component, characterized in that the polyurethane foam comprises, as the polyol component, a polyester polyol having a hydroxy value of at least 160 mgKOH and an average functional group number of 2.5-3 and, as the isocyanate component, at least one of modified TDI, modified MDI and modified HDI having an NCO content of 1-25%, and has a volume change rate by an immersion test using methyl ethyl ketone [JIS K6258 (1993), 23°C, 72 hr] of at most 400%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polyurethane foam suitably used as a constituent material of a conductive roller used in an electrophotographic apparatus, and a conductive roller using the polyurethane foam as an elastic layer.

  Conventionally, a polyurethane foam is used as an elastic layer for conductive rollers such as a developing roller, a toner conveying roller, and a charging roller used in an electrophotographic apparatus. In this case, a polyurethane foam obtained by mechanical stirring foaming (mechanical floss method) is preferably used because a foam having relatively fine bubbles is obtained particularly in a charging roller and a developing roller. Usually, a polyurethane foam obtained from this polyurethane foam is used. A surface resin layer constituting the roller surface is coated and formed on the resulting elastic layer to form a conductive roller.

  However, usually, when an organic solvent-based paint is applied directly to the surface of the polyurethane foam, the polyurethane foam swells and wrinkles occur in the coated surface resin layer. When a conductive roller is obtained using a layer, a solvent shielding film is applied to the elastic layer surface using a water-based paint, and a surface resin layer is formed thereon using a solvent-based paint. (Patent Document 1 etc.).

  As described above, when a polyurethane foam obtained by mechanical stirring foaming is used as an elastic layer in producing a conductive roller, conventionally, a solvent-based paint is applied on the elastic layer to form a surface resin layer. At this time, it was necessary to form a solvent shielding layer in order to prevent the elastic layer from swelling. For this reason, a manufacturing process increases and it becomes complicated, and this is one of the causes which raises cost.

Japanese Patent Laid-Open No. 7-119733

  The present invention has been made in view of the above circumstances, and can form a coating film by applying a solvent-based paint directly on the surface, without causing any disadvantages due to swelling, When a polyurethane foam is used as an elastic layer of a flexible roller, a solvent-shielding layer is not required, and a surface resin layer can be formed by directly applying a solvent-based paint on the elastic layer. An object is to provide a conductive roller used as an elastic layer.

  As a result of intensive studies to achieve the above object, the present inventor has obtained a polyurethane foam by mechanical stirring foaming from a polyurethane raw material containing a polyol component and an isocyanate component, and has a hydroxyl value of 160 mgKOH or more as the polyol component. In addition, a polyester polyol having an average functional group number of 2.5 to 3 is used, and methyl ethyl ketone is used by using at least one of modified TDI, modified MDI and modified HDI having an NCO content of 1 to 25% as the isocyanate component. It was found that a polyurethane foam having a good solvent resistance with a volume change rate of 400% or less according to a conventional immersion test [JIS K6258 (1993), 23 ° C., 72 hours] was obtained.

  And if it is a polyurethane foam having such good solvent resistance, by using this as an elastic layer of a conductive roller, a solvent-based paint is applied directly on the elastic layer to form a surface resin layer. Even so, wrinkles are not generated on the roller surface, and it is possible to reliably obtain a roller having a good surface state, omitting the formation of a conventional solvent shielding layer, and good performance at low cost. The present inventors have found that a conductive roller having the following can be obtained and completed the present invention.

  Accordingly, the present invention provides a polyurethane foam obtained by mechanical stirring foaming from a polyurethane raw material containing a polyol component and an isocyanate component, and a polyester polyol having a hydroxyl value of 160 mgKOH or more and an average functional group number of 2.5 to 3 as the polyol component. In addition, the isocyanate component contains at least one of modified TDI, modified MDI, and modified HDI having an NCO content of 1 to 25%, and a soaking test using methyl ethyl ketone [JIS K6258 (1993), 23 ° C., The polyurethane foam is characterized in that the volume change rate by 72 hours] is 400% or less.

  The present invention also provides a conductive roller having a surface resin layer formed on an elastic layer made of a foamed elastic body, wherein the elastic layer is formed of the polyurethane foam of the present invention, and a solvent system is directly formed on the elastic layer. A conductive roller is characterized in that a surface resin layer is formed by applying a paint.

  Since the polyurethane foam of the present invention is excellent in solvent resistance, when this polyurethane foam is used as an elastic layer and a conductive roller such as a developing roller, a toner conveying roller or a charging roller is produced, It is possible to form a surface resin layer by directly applying a solvent-based paint on the elastic layer without providing a solvent shielding layer, and to obtain a conductive roller having good performance at low cost. is there.

Hereinafter, the present invention will be described in more detail.
As described above, the polyurethane foam of the present invention is obtained by mechanical stirring foaming from a polyurethane raw material containing a polyol component and an isocyanate component.

  In this case, a polyester polyol is used as the polyol component. The polyester polyol used in the present invention has a hydroxyl value of 160 mgKOH or more, preferably 300 to 350 mgKOH, and an average functional group number of 2.5 to 3. In this case, if the hydroxyl value of the polyester polyol is less than 160 mgKOH, the solvent resistance and compression set are deteriorated, wrinkles on the roller surface, and the pressure contact portion with other parts are easily adhered, and the object of the present invention Cannot be achieved. Further, when the average functional group number of the polyester polyol deviates from the above range, the same inconvenience tends to occur, and in this case, the object of the present invention cannot be achieved.

  The polyester polyol is not particularly limited as long as the polyester polyol has the hydroxyl value and the average number of functional groups, and is appropriately selected according to the use and form of the obtained foam and required characteristics. In particular, a polyester polyol containing a branched methyl group in the molecular chain obtained by polymerizing terephthalic acid or adipic acid and a diol having a methyl branch is particularly preferably used.

  In other words, polyester polyols are often pasty or solid at room temperature, so that they are poor in handleability when mixed with isocyanate and subjected to mechanical stirring foaming, and polyurethanes obtained from polyester polyols are hard. However, by using the above-mentioned branched methyl group-containing polyester polyol, it is possible to solve these problems and to perform a mechanical stirring foaming operation with good handleability and to obtain a soft polyurethane.

  Specific examples of such a branched methyl group-containing polyester polyol include 3-methylpentane terephthalate polyol, 3-methylpentane adipate polyol, 3 methylpentane isophthalate, and 3-methylpentane sebacate polyol. it can.

  In addition, as a polyol component, the polyester polyol which has the said hydroxyl value and the average number of functional groups should just be included, and these and other polyol components can also be used together. In this case, examples of other polyol components include polyether polyols, polycarbonate diols, polybutadiene polyols, and polyester polyols whose hydroxyl value and average functional group number deviate from the above ranges.

  Next, as the isocyanate component, one or more selected from modified tolylene diisocyanate (TDI), modified diphenylmethane diisocyanate (MDI), and modified hexamethylene diisocyanate (HDI) are used. In this case, the type of the modified product is not particularly limited, and examples thereof include a polyol-modified product, a nurate-modified product, and a carbodiimide-modified product. Particularly, a polyol-modified product is preferable, and polyol-modified TDI, polyol-modified MDI and One or more isocyanates selected from polyol-modified HDI are preferably used.

  Here, in the present invention, the modified TDI, modified MDI, and modified HDI used as the isocyanate component are all those having an NCO content of 1 to 25%, preferably 4 to 10%. In this case, if the NCO content is less than 1%, there may be a decrease in compression set and poor curing when there are few reaction points. On the other hand, if it exceeds 25%, the reaction becomes very fast and molding is performed by the mechanical floss method. Can be difficult.

  In addition to the polyol component and the isocyanate component, an appropriate amount of known additives such as a foam stabilizer, a conductive agent, a crosslinking agent, a surfactant, and a catalyst are added to the polyurethane foam of the present invention as necessary. be able to.

  Examples of the foam stabilizer include polydimethylsiloxane-polyethylene oxide copolymer, polydimethylsiloxane-polypropylene oxide copolymer, polydimethylsiloxane-polyethylene adipate copolymer, and the like.

  As the conductive agent, a known ionic conductive agent or electronic conductive agent can be used. Examples of ionic conductive agents include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (eg, lauryltrimethylammonium), hexadecyltrimethylammonium, octadecyltrimethylammonium (eg, stearyltrimethylammonium), benzyltrimethylammonium, and modified fatty acid dimethylethylammonium. Perchlorate, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, ethyl sulfate, carboxylate, sulfonate, ammonium salt, lithium, sodium, Perchlorates, chlorates, hydrochlorides, bromates, iodates, borofluorides, trifluoromethyl sulfates of alkali metals and alkaline earth metals such as potassium, calcium and magnesium Salts, sulfonates, and the like.

  In addition, as the electronic conductive agent, conductive carbon such as ketjen black and acetylene black; rubber carbon such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT; carbon for ink subjected to oxidation treatment, Examples include pyrolytic carbon, natural graphite, and artificial graphite; conductive metal oxides such as tin oxide, titanium oxide, and zinc oxide; metals such as nickel, copper, silver, and germanium.

  Examples of the catalyst include dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, dibutyltin marker tide, dibutyltin thiocarboxylate, dibutyltin dimalenate, dioctyltin marker peptide, dioctyltin thiocarboxylate as organometallic catalysts. , Phenylmercury, silver propionate, tin octenoate, amine catalyst triethylamine, N, N, N ′, N′-tetramethylethylenediamine, triethylenediamine, N-methylmorpholine, dimethylaminoethanol, bis (2-dimethylaminoethyl) ) Ether, 1,8-diazabicyclo (5,4,0) -undecene-7 and the like are preferably used. These catalysts may be used alone or in combination of two or more.

  In the polyurethane foam of the present invention, the isocyanate component, the polyol component, and the additive that is added as necessary are mixed, foamed with mechanical stirring, cast into a mold, and foamed into a desired form. It is obtained by this. In this case, the mixing of the above components is not particularly limited, but the catalyst, foam stabilizer and ionic conductive agent are preferably premixed with the polyol component and then mixed with the isocyanate component. When using, it is preferable to mix carbon black with an isocyanate component before mixing with a polyol component. Further, various conditions for foam molding may be employed as appropriate according to the type of each component used and the density, use, form, etc. of the foam to be obtained.

  As described above, the polyurethane foam of the present invention is obtained by mechanically foaming a polyurethane raw material containing a specific polyol component and an isocyanate component (mechanical flossing method), and thereby using a methyl ethyl ketone immersion test [JIS]. K6258 (1993), 23 ° C., 72 hours] has a volume change rate of 400% or less, preferably 200 to 300%. In this case, when the volume change rate exceeds 400%, when a coating film is formed by applying a solvent-based paint on the polyurethane foam, wrinkles are likely to occur in the coating film due to swelling of the foam, The object of the present invention cannot be achieved. In this immersion test, an elastomer that is molded without foaming from the polyurethane raw material having the composition of the present invention can be used as a test piece.

  As described above, the polyurethane foam of the present invention is suitably used as an elastic layer for conductive rollers such as a developing roller, a toner conveying roller, and a charging roller used in an electrophotographic apparatus. In this case, the polyurethane foam of the present invention is formed as an elastic layer around the core metal, and a surface resin layer is formed thereon to form a conductive roller. In this case, as described above, the present invention By using this polyurethane foam as an elastic layer, a surface resin layer can be formed by directly applying a solvent-based paint on the elastic layer without forming a solvent shielding layer on the elastic layer surface. . Although not particularly limited, when the elastic layer of the conductive roller is used as described above, the polyurethane foam of the present invention preferably has closed cells.

  Here, the surface resin layer can be formed using a known resin selected according to the application of the roller, such as urethane resin, acrylic resin, acrylic urethane resin, fluorine resin, silicone resin, and the like. Illustrated.

  In this surface resin layer, an appropriate additive can be blended according to the use of the roller, for example, an appropriate amount of a conductive agent or a resin curing agent similar to those exemplified for the elastic layer as necessary. Can be added.

Further, resin particles and the like can be mixed and dispersed in the surface resin layer in order to adjust the surface roughness of the roller. In this case, the resin particles can be appropriately selected according to the type of resin forming the surface resin layer, the thickness of the surface resin layer, and the like. Specific examples include urethane resin particles, acrylic resin particles, silicone resin particles, silica particles, polyamide resin particles, nylon resin particles, and the like, and one or more of these can be used. Further, the shape, size, particle size distribution, etc. of the particles are appropriately selected and are not particularly limited. Usually, spherical, square and needle-shaped particles are preferably used, and the particle size is D ⁵⁰ = 1. ˜50 μm, in particular D ⁵⁰ = 5-20 is preferred.

  This surface resin layer is formed by coating a paint obtained by blending and dispersing each of the above components in an organic solvent on the elastic layer of the roller. In this case, as a solvent for the paint, methyl ethyl ketone (MEK), methyl isobutyl is used. An appropriate organic solvent can be used depending on the type of resin used, such as ketone, toluene, ethyl acetate, and methylcyclohexane, but it is particularly preferable to use a paint using MEK as a solvent.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not restrict | limited to the following Example.

[Examples 1 to 3 and Comparative Examples 1 to 5]
Polyurethane foams having the composition shown in the following Tables 1 to 3 were subjected to foam molding, and an elastic layer (thickness 3 mm) made of polyurethane foam was formed on the outer periphery of the core metal (6 mmφ). At this time, A liquid in which polyol, foam stabilizer, ionic conductive agent, and catalyst are mixed and B liquid in which isocyanate and carbon black are mixed are prepared in advance, and these A liquid and B liquid are mechanically stirred and mixed. The polyurethane foam elastic layer having a density of 0.64 g / cm ³ was formed on the outer periphery of the core metal by foaming together and casting into a metal mold in which the core metal was set. In addition, an unfoamed test piece (20 × 50 × 2 mm) having the same composition was molded and subjected to the following immersion test. In addition, all the mixing | blending parts in Tables 1-3 are a mass part, and the unit of the hydroxyl value in each table | surface is (mgKOH). Moreover, the detail of the isocyanate component in Tables 1-3 and a polyol component is as follows.

Polyol-modified tolylene diisocyanate (* 1)
Asahi Glass Urethane Co., Ltd. prototype “BS 008”

Diphenylmethane diisocyanate (* 2)
"MP102" made of BASF INOAC polyurethane

Polyester polyol (* 3)
"Kuraray polyol F-510" manufactured by Kuraray Co., Ltd.

Polyester polyol (* 4)
"Kuraray polyol F-750" manufactured by Kuraray Co., Ltd.

Polyester polyol (* 5)
"Kuraray polyol F-1010" manufactured by Kuraray Co., Ltd.

Polyether polyol (* 6)
“EXCENOL 420” manufactured by Asahi Glass Urethane Co., Ltd.

Polyether polyol (* 7)
SANYO KASEI KOGYO Co., Ltd. “SANNICS FA951”

Polyether polyol (* 8)
Produced by Asahi Glass Urethane Co., Ltd. “Excenol 430”

Polyether polyol (* 9)
Produced by Asahi Glass Urethane Co., Ltd. “Excenol 828”

Polymer polyol (* 10)
Mitsui Chemicals Polyurethane Co., Ltd. “Accor POP-34 / 28”

Polyester polyol (* 11)
Mitsui Chemicals Polyurethane Co., Ltd. “U-2410T”

  Using the obtained test piece, a volume change rate was calculated by performing an immersion test on methyl ethyl ketone under the following conditions in accordance with JIS K6258 (1993). Moreover, the Asker C hardness of the roller elastic layer surface was measured. These results are shown in Tables 1-3.

Next, a coating material having the following composition was applied onto the elastic layer to form a surface resin layer having a thickness of 10 μm, thereby obtaining a conductive roller.
Coating compositions <br/> urethane resin (manufactured by Nippon Polyurethane Co., Ltd. "N5196") 100 parts by weight Carbon black 35 parts by weight urethane particles (manufactured by Dainippon Ink and Chemicals, "Burnock", spherical, D ⁵⁰ = 10 [mu] m) 10 parts by weight Methyl ethyl ketone 350 parts by mass Part isocyanate curing agent ("Coronate HX" manufactured by Nippon Polyurethane Co., Ltd.) 20 parts by mass

For each of the obtained rollers, the arithmetic average height (Ra) of the contour curve was measured according to JIS B 0601 (2001), and the surface roughness was examined. In addition, each roller is mounted on a printer cartridge as a developing roller, and this cartridge is set in a laser beam printer “Laser Jet 4050” manufactured by Hewlett-Packard Co. Evaluation was made in three stages, Δ and ×. The results are shown in Tables 1-3.

  As shown in Table 1 above, Examples 1 to 3 adjusted to a volume change rate of 400% or less (276 to 340%) by the immersion test specified in JIS B 0601 (2001) using the isocyanate and polyol specified in the present invention. Even when a polyurethane resin foam is used as an elastic layer and a surface-based resin layer is formed by directly applying a solvent-based paint thereon, the surface roughness of the roller is Ra = 1.1 to 1.4 μm. It was confirmed that a high-performance developing roller capable of being controlled in a good state and capable of obtaining a good image was obtained.

  On the other hand, as shown in Tables 2 and 3, the polyurethane foams of Comparative Examples 1 to 5 using isocyanates and polyols that deviate from the provisions of the present invention are immersed in the JIS B 0601 (2001). The volume change rate by a test is 410-546%, and the volume change by swelling is large. For this reason, a conductive roller using these polyurethane foams as an elastic layer and directly applying a solvent-based paint thereon to form a surface resin layer has a roller surface roughness of Ra = 2 to 2.8 μm. It becomes rough and it is difficult to obtain a good image.

Claims (8)

In a polyurethane foam obtained by mechanical stirring foaming from a polyurethane raw material containing a polyol component and an isocyanate component,
The polyol component contains a polyester polyol having a hydroxyl value of 160 mgKOH or more and an average functional group number of 2.5 to 3, and the isocyanate component is at least one of modified TDI, modified MDI and modified HDI having an NCO content of 1 to 25%. Including seeds,
And the polyurethane foam characterized by the volume change rate by the immersion test [JIS K6258 (1993), 23 degreeC, 72 hours] using methyl ethyl ketone being 400% or less.   The polyurethane foam according to claim 1, wherein the polyester polyol has a branched methyl group in the molecular chain.   The polyurethane foam according to claim 1, wherein the isocyanate component contains at least one of polyol-modified TDI, polyol-modified MDI and polyol-modified HDI.   The polyurethane foam according to any one of claims 1 to 3, obtained by mixing the polyol component with a catalyst, a foam stabilizer, and an ionic conductive agent and reacting with the isocyanate component.   The polyurethane foam of any one of Claims 1-4 obtained by mixing carbon isocyanate as a electrically conductive material with the said isocyanate component, and making it react with a polyol component. The polyurethane foam according to any one of claims 1 to 5, wherein the foam density is 0.5 to 0.8 g / cm ³ .   The polyurethane foam according to any one of claims 1 to 6, which is a foam composed of closed cells.   In the conductive roller formed by forming a surface resin layer on an elastic layer made of a foamed elastic body, the elastic layer is formed of the polyurethane foam according to any one of claims 1 to 7, and the elastic layer is formed on the elastic layer. A conductive roller characterized in that a solvent-based paint is directly applied to form a surface resin layer.