JP2011074217A - Polyurethane resin composition for elastic layer, and roll for image formation produced using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyurethane resin composition for an elastic layer that is excellent in water resistance, solvent resistance and compression set and to provide a roll for image formation that can achieve the reduction of variation in external shape, the prevention of wrinkle occurrence on a roll surface and the prevention of roll deformation. <P>SOLUTION: In a polyurethane resin composition for an elastic layer produced by reacting a polyester polyol (I) and a polyisocyanate (II), and optionally, a chain extender (III) for use in a roll for image formation having an elastic layer on an outer peripheral surface of a core metal and further having a surface layer formed of an electroconductive coating material on the elastic layer, the polyester polyol (I) is a polyester polyol produced by using (A) glycol containing a 4C or more side chain and (B) a 2-3C linear glycol in a molar ratio of (A)/(B) of 90/10 to 30/70 and using the glycol (A) and the glycol (B) and (C) a polyfunctional glycol having three or more hydroxyl groups in a molar ratio of [(A)+(B)/(C)] of 99/1 to 85/15. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polyurethane resin composition for an elastic layer, and an image forming roll using the same. More specifically, it has excellent properties such as water resistance, solvent resistance, compression set, and the like, and can achieve reduction of outer shape fluctuation, prevention of wrinkles, prevention of roll deformation, and high quality image forming roll. Relates to a polyurethane resin composition for an elastic layer that can be supplied, and an image forming roll using the same.

  Conventionally, the market for OA printers has been faced with demands for high-speed printing, high resolution, energy saving, and the like to support on-demand printing. In order to meet these demands, improvements such as miniaturization of toner, suitability by lowering the glass transition point of the resin for toner, and liquid toner are being promoted. Along with this, the performance required for image forming rolls such as developing rolls, charging rolls, transfer rolls, conductive rolls such as electrophotographic copying machines, facsimile machines, printers, etc. is becoming more and more severe, especially reduction of external fluctuations, Prevention of wrinkle generation on the roll surface (improvement of smoothness) and prevention of roll deformation have been strongly demanded.

  Currently, polyurethane resin image forming rolls that are generally used have been used for various applications because of their good wear resistance compared to olefin rubber and silicone rubber rolls.

  However, conventional polyurethane resin image forming rolls have (1) water absorption due to the influence of humidity and large variation in outer shape, (2) low compression set and deformation of the roll surface. 3) When the conductive layer is formed on the surface layer, it is swollen by the solvent contained in the conductive paint and wrinkles are generated, or it is swollen by the liquid toner and the outer shape is changed. There is a problem in that it tends to occur and sufficient performance cannot be exhibited.

  In order to improve such a problem, various proposals have been made so far.

  For example, in a charging roll in which a conductive elastic layer is formed on the core metal surface, the conductive elastic layer is prepared from a mixture containing at least one polyol selected from polyether polyol and polyester polyol. There is known a charging roll in which the surface of the conductive elastic layer is treated with a solution containing polyisocyanate. Such a charging roll can avoid contamination of the surface of the photoconductor and the like, and can also charge the surface of the photoconductor, and the environment in which the image forming apparatus is placed changes from low temperature and low humidity to high temperature and high humidity. However, it is possible to avoid contamination of the surface of the photoconductor and the like, and to charge the surface of the photoconductor and the like and to maintain the surface potential of the photoconductor and the like for a long time (see, for example, Patent Document 1). .

  However, in the charging roll described in Patent Document 1, a polyester polyol such as 3-methylpentanediol adipate (3MPD-AA) or diethylene glycol adipate (DEG-AA) is used for the conductive elastic layer. When these are used for the conductive elastic layer, the polyester polyol is liquid and has a low viscosity, so that the workability is good, but since the solvent resistance is poor, wrinkles are generated on the roll surface due to swelling. Since (decrease in smoothness) occurs and appearance changes due to water absorption, there are practical problems.

  In addition, the polyurethane component, which is a polycarbonate polyol having a portion containing a carbonate bond and a linear portion having 5 to 12 carbon atoms, contains a conductive filler dispersed in a polyol component that forms a polyurethane, and is formed into a thin cylindrical shape. A belt for an electrophotographic apparatus is known. Such a belt for an electrophotographic apparatus is special in the structure of the polyol component forming the polyurethane, the structure of the soft segment and the hard segment, and the structure of the chemical bond, so that the elastic modulus necessary for the belt is maintained and the curl is also reduced. In addition, the toner image is excellent in carrying ability and followability to unevenness, and can be suitably used as, for example, an intermediate transfer belt or a transfer conveyance belt (see, for example, Patent Document 2).

  However, the belt for an electrophotographic apparatus described in Patent Document 2 has a high viscosity even if the polycarbonate, which is a raw material for polyurethane, is in a liquid state. There was a problem that the defect rate increased.

  Further, in Patent Document 2, a polyester polyol of diethylene glycol (DEG) / trimethylolpropane (TMP) / adipic acid (AA) is used, but the polyurethane obtained using the polyester polyol has high water absorption and rolls. As a result, the outer diameter fluctuates greatly and the hydrolysis resistance is inferior, resulting in inferior durability in long-term use.

  As described above, it has low water absorption (water resistance), excellent solvent resistance and compression set, reduction of external variation, prevention of wrinkles on the roll surface (improvement of smoothness), prevention of roll deformation Therefore, development of an elastic layer polyurethane resin composition that can supply a high-quality image-forming roll and an image-forming roll using the same has been desired.

JP-A-5-281830 Published Japanese Patent Application Laid-Open No. 2006-22227

  An object of the present invention is to provide a polyurethane resin composition for an elastic layer that has low water absorption (water resistance) and is excellent in solvent resistance and compression set.

  In addition, by using the polyurethane resin composition for an elastic layer, an image forming roll that can achieve reduction in outer shape variation, prevention of wrinkles on the roll surface (improvement of smoothness), and prevention of roll deformation is provided. It is to be.

  As a result of intensive research to solve the above problems, the present inventor has an elastic layer on the outer peripheral surface of the cored bar, and further has an image layer having a surface layer formed by applying a conductive paint thereon. In a polyurethane resin composition for an elastic layer obtained by reacting a polyester polyol and a polyisocyanate used for a roll for a roller, and a chain extender as necessary, the polyester polyol contains a specific glycol containing a side chain, and a specific glycol A polyester polyol that uses a linear glycol and a polyfunctional glycol having 3 or more hydroxyl groups in a specific molar ratio, resulting in low water absorption (water resistance), solvent resistance, and compression set. An excellent polyurethane resin composition for an elastic layer is obtained, and by using the polyurethane resin composition for an elastic layer, the outer shape fluctuation is reduced, and wrinkles are generated on the roll surface. Prevention (improvement of smoothness), found that it is possible to obtain an image forming roll achievable to prevent roll deformation, and have completed the present invention.

  That is, the present invention provides a polyester polyol (I) and a polyisocyanate (II) used for an image forming roll having an elastic layer on the outer peripheral surface of a core metal and further having a surface layer made of a conductive paint. ), And if necessary, in the polyurethane resin composition for an elastic layer obtained by reacting the chain extender (III), the polyester polyol (I) is a glycol (A) containing a side chain having 4 or more carbon atoms. The linear glycol (B) having 2 to 3 carbon atoms is used in a molar ratio of (A) / (B) = 90/10 to 30/70, and 3 or more of the (A), the (B), and the hydroxyl group. A polyurethane resin composition for an elastic layer, which is a polyester polyol using the polyfunctional glycol (C) having [(A) + (B)] / (C) = 99/1 to 85/15 molar ratio It is about things.

  The present invention also relates to an image forming roll comprising the polyurethane resin composition for an elastic layer.

The polyurethane resin composition for an elastic layer of the present invention has low water absorption (water resistance) and is excellent in solvent resistance and compression set.
In addition, the image forming roll of the present invention is formed by using the polyurethane resin composition for an elastic layer, thereby reducing external variation, preventing wrinkles on the roll surface (improving smoothness), and preventing roll deformation. For example, various OA such as a conductive roll for powder toner, a conductive roll for liquid toner, a toner supply roll, a developing roll, a charging roll, a transfer roll, etc. for electrophotographic copying machines, facsimiles, printers, etc. Useful for rolls for members.

  First, the polyurethane resin composition for an elastic layer of the present invention will be described.

  The polyurethane resin composition for an elastic layer of the present invention is used for an image forming roll having an elastic layer on the outer peripheral surface of a cored bar, and further having a surface layer formed by applying a conductive paint thereon. The elastic layer is made of a polyurethane resin composition obtained by reacting polyester polyol (I), polyisocyanate (II), and, if necessary, chain extender (III).

  The polyester polyol (I) includes a glycol (A) containing a side chain having 4 or more carbon atoms, a linear glycol (B) having 2 to 3 carbon atoms, and a polyfunctional glycol (C) having 3 or more hydroxyl groups. As an essential component.

  The polyurethane resin composition for an elastic layer of the present invention comprises a glycol (A) containing a side chain having 4 or more carbon atoms, a linear glycol (B) having 2 to 3 carbon atoms, and a polyfunctional glycol having 3 or more hydroxyl groups ( By using polyester polyol (I) using C) in a specific molar ratio range and polyisocyanate (II) as essential, [1] control of water absorption and [2] solvent resistance as follows: The three effects of control and [3] reduction of compression set can be obtained together.

[1] Control of water absorption Among glycols containing a side chain, a glycol having a long chain alkyl group, a glycol containing a side chain having 4 or more carbon atoms (A) [hereinafter, a side chain containing glycol (A) That's it. ], The hydrophobicity of the polyester polyol (I) is enhanced, so that the water absorption and hydrolysis resistance of the polyurethane resin composition can be controlled.

[2] Control of solvent resistance Since the solvent resistance decreases only with the side chain-containing glycol (A), linear glycol (B) having 2 to 3 carbon atoms [hereinafter, linear glycol (B) That's it. ] In combination with the above (A) at a molar ratio within a specific range, the ester group concentration can be controlled to prevent a decrease in solvent resistance.

[3] Reduction of compression set Furthermore, polyfunctional glycol (C) having three or more hydroxyl groups as a polyfunctional component [hereinafter referred to as polyfunctional glycol (C). ] In combination at a molar ratio within a specific range, a crosslinking point can be introduced into the molecule and the occurrence of a shift (distortion) between the hard segment and the soft segment can be prevented.

  The side chain-containing glycol (A) is a glycol containing a side chain having 4 or more carbon atoms, preferably a side chain-containing glycol having 4 to 9 carbon atoms. When the side chain-containing glycol (A) has less than 4 carbon atoms, the viscosity of the polyester may increase rapidly, and the water absorption of the polyester becomes too high, so that the size variation due to swelling of the polyurethane resin is large. For reasons such as, it is not preferable.

  Examples of the side chain-containing glycol (A) include 2-methylpropanediol, 3-methylpentanediol (abbreviation 3MPD), 2,2-dimethyl-1,3-propanediol, 2-methyl-2-butyl- 1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 2,4-diethyl- 1,5-pentanediol and the like are mentioned, and among these, 2-methylpropanediol and 3-methylpentanediol are more preferable in terms of better solvent resistance and handling properties. These may be used alone or in combination of two or more.

  As the side chain-containing glycol (A), a lactone ring-opening polymerization polyester polyol can also be used. For example, a pentano-4-lactone compound, a γ-valerolactone compound, etc., 4,4-dimethyltetrahydro A lactone ring-opening polymerization polyester polyol obtained by ring-opening polymerization of a cyclic ester compound (that is, a lactone) containing a side chain such as a -2H-pyran-2-one compound can be given.

  Examples of the linear glycol (B) include ethylene glycol (abbreviation EG), 1,3-propylene glycol (1,3PD), and the like, and a polyurethane obtained by using these linear glycols (B). The solvent resistance and compression set of the resin are improved. These may be used alone or in combination of two or more. When the linear glycol (B) has more than 3 carbon atoms, the resulting polyurethane resin has poor solvent resistance and compression set, which is not preferable.

  Further, the polyester polyol (I) is reacted with a polyfunctional glycol (C) within a range not impairing the object of the present invention. The polyfunctional glycol (C) is a trifunctional or higher functional polyol having three or more hydroxyl groups in the molecule.

  Examples of the polyfunctional glycol (C) include trifunctional compounds such as trimethylolpropane (abbreviated as TMP), glycerin, pentaerythritol, and hexanetriol, dimers such as trimethylolpropane and pentaerythritol, and sugars such as sorbitol. Among these compounds, trimethylolpropane and glycerin are preferable, and trimethylolpropane is more preferable. These may be used alone or in combination of two or more.

  By using the polyfunctional glycol (C) in combination, it is possible to prevent the occurrence of displacement (distortion) between the hard segment and the soft segment, and to improve the solvent resistance and compression set. Specifically, by using a polyfunctional glycol (C) in combination, a crosslinking group is introduced into the soft segment to prevent swelling of the polyurethane layer by the solvent and to prevent the occurrence of displacement (distortion) when the polyurethane is compressed. And compression set can be reduced.

  Polyfunctional having 4 or more carbon atoms glycol (A) containing a side chain, straight chain glycol (B) having 2 to 3 carbon atoms, and 3 or more hydroxyl groups, which are essential components of the polyester polyol (I). The composition ratio of glycol (C) is as follows.

  In the polyester polyol (I), the use ratio of the side chain-containing glycol (A) and the linear glycol (B) is the above-mentioned (A) / (B) = 90 / 10-30 / 70 molar ratio, preferably The molar ratio is 80/20 to 50/50. When the range (A) / (B) is within such a range, it is possible to obtain a polyurethane resin having an excellent balance between solvent resistance and water absorption and little dimensional variation with respect to environmental conditions during use. When (A) / (B) exceeds 90/10 molar ratio, the solvent resistance is poor. For example, swelling occurs due to the conductive paint for forming the conductive layer of the image forming roll. It is not preferable.

  In the polyester polyol (I), the use ratio of the (A), the (B) and the polyfunctional glycol (C) is [(A) + (B)] / (C) = 99/1. It is -85/15 molar ratio, Preferably it is 97/3-90/10 molar ratio. When [(A) + (B)] / (C) is in such a range, it is excellent in solvent resistance and compression set, and is effective in improving the dimensional stability of polyurethane resin and suppressing distortion. When the above [(A) + (B)] / (C) exceeds 99/1 molar ratio, the crosslinking density is too low, and therefore the effect of improving the solvent resistance and compression set is inferior. On the other hand, when the molar ratio is less than 85/15, the crosslink density becomes too high, so that it is difficult to reduce the hardness of the polyurethane resin, and the resin becomes brittle and the mechanical strength is lowered. .

  The polyester polyol (I) used in the present invention may have a hydrophilic group represented by a carboxyl group, a carboxylate group, a sulfonic acid group, a sulfonate group, a phosphonic acid group, a phosphonate group, and the like.

  The polyurethane resin composition for an elastic layer of the present invention comprises the polyester polyol (I) as an essential component. For example, a polyol other than a polyester polyol such as a polyether polyol and a polycarbonate polyol can be used as long as the object of the present invention is not impaired. Can be used.

  The number average molecular weight (hereinafter also referred to as “Mn”) of the polyester polyol (I) is preferably in the range of 500 to 10,000, and more preferably in the range of 1000 to 4000. When Mn of the polyester polyol (I) is less than 500, the hardness of the polyurethane resin becomes too high, and rubber elasticity and mechanical strength tend to decrease, which is not preferable. Moreover, when Mn of said (I) exceeds 10,000, there exists a tendency for handling property to fall and it is unpreferable.

  Next, polyisocyanate (II) to be reacted with the polyester polyol (I) in the polyurethane resin composition for an elastic layer of the present invention will be described below.

  The polyisocyanate (II) is not particularly limited, and conventionally known ones can be used. For example, diphenylmethane diisocyanate (abbreviation MDI: 4,4′-form, 2,4′-form or 2,2′-form) Or a mixture thereof), polymethylene polyphenyl polyisocyanate, carbodiimidized diphenylmethane polyisocyanate, tolylene diisocyanate (TDI: 2,4 or 2,6, or a mixture thereof), xylylene diene Aromatic diisocyanates such as isocyanate (XDI), 1,5-naphthalene diisocyanate (NDI), tetramethylxylene diisocyanate, or isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate ( Alicyclic diisocyanate hydrogenated XDI), etc., hexamethylene diisocyanate (HDI), dimer acid diisocyanate, aliphatic diisocyanates such as norbornene diisocyanate and the like, may be used in combination of two or more kinds of these alone. Among these, since it is possible to obtain moderate reactivity, excellent mechanical strength, solvent resistance, etc., diphenylmethane diisocyanate, tolylene diisocyanate, polymethylene polyphenyl polyisocyanate, carbodiimidized diphenylmethane poly Isocyanates are preferred.

  In the polyurethane resin composition for an elastic layer of the present invention, when the number of moles of isocyanate group of the polyisocyanate (II) is represented by [NCO] and the number of moles of hydroxyl group of the polyester polyol (I) is represented by [OH], The equivalent ratio ([NCO] / [OH]) of the polyisocyanate (II) and the polyester polyol (I) is preferably in the range of 0.70 to 1.20, more preferably 0.80 to 1. The range is 05. When the equivalent ratio of (II) and (I) is within such a range, the hardness, elasticity, and mechanical properties of the polyurethane resin suitable for the elastic layer can be obtained.

  When adjusting the polyurethane resin composition for an elastic layer, the chain extender (III) can be reacted in an optional step as necessary.

  Examples of the chain extender (III) include ethylene glycol, 1,2-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,3- Butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 3,3′-dimethylol heptane, 1,4-cyclohexanedi Bifunctional components such as methanol, 3,3-bis (hydroxymethyl) heptane, diethylene glycol, dipropylene glycol, triethylene glycol and the like can be mentioned. Among these, ethylene glycol, 1 in terms of solvent resistance and handling properties 1,4-butanediol and diethylene glycol are preferred, and ethylene glycol is more preferred. Examples of the chain extender (III) include trifunctional compounds such as trimethylolpropane, glycerin, pentaerythritol, and hexanetriol, dimers such as trimethylolpropane and pentaerythritol, and sugars such as sorbitol. Among these compounds, trimethylolpropane and glycerin are preferable, and trimethylolpropane is more preferable. These chain extenders may be used alone or in combination of two or more.

  The amount of the chain extender (III) used is preferably in the range of 1 to 10 parts by mass, more preferably in the range of 3 to 5 parts by mass with respect to 100 parts by mass of the polyester polyol (I). If the amount of the chain extender (III) used is within such a range, it is excellent in solvent resistance, mechanical properties, compression set, and rebound resilience, for example, suppression of swelling of urethane elastomer by solvent, improvement in tear properties, Effects such as prevention of deformation during compression can be obtained.

  The polyurethane resin composition for an elastic layer of the present invention can contain various known additives used as an ordinary polyurethane raw material as optional components as long as the object of the present invention is not impaired.

  Examples of such optional components include, but are not limited to, catalysts, plasticizers, antioxidants, defoaming agents, antifoaming agents, ultraviolet absorbers, reaction modifiers, reinforcing agents, fillers, colorants (dyes or pigments). ), Mold release agents, stabilizers, light stabilizers, conductivity enhancers, fungicides, organic acid metal salts, waxes (amides, etc.), metal oxides, metal hydroxides and other extenders Additives can be mentioned.

  The method for preparing the polyurethane resin composition for an elastic layer of the present invention is not particularly limited. For example, a polyol containing polyester polyol (I) as an essential component, polyisocyanate (II), and optionally a chain. It can be prepared by the so-called “one-shot method”, which is a one-step reaction in which the extender (III) is stirred and mixed and reacted. In addition, a so-called “two-stage reaction” in which a polyol having polyester polyol (I) as an essential component and polyisocyanate (II) are reacted to form a prepolymer and then the prepolymer and a chain extender are reacted. It can be prepared by the “prepolymer method”.

  At the time of adjusting the polyurethane resin composition for the elastic layer, it can be prepared by stirring and mixing various additives as necessary, and performing vacuum defoaming treatment as necessary.

  The image forming roll of the present invention is a roll having an elastic layer on the outer peripheral surface of a core metal, and further having a surface layer formed by applying a conductive paint thereon, and the elastic layer is a polyester polyol. It comprises the polyurethane resin composition for an elastic layer obtained by reacting (I), polyisocyanate (II), and, if necessary, a chain extender (III).

  The “image forming roll” as used in the present invention refers to, for example, a conductive roll for powder toner, a conductive roll for liquid toner, a toner supply roll, a developing roll, a charging roll, used for electrophotographic copying machines, facsimiles, printers, etc. It is a roll for various OA members such as a transfer roll, and is intended to supply toner as a uniform layer by being pressed against a photosensitive drum.

  The polyurethane resin composition for an elastic layer constituting the image forming roll of the present invention is not particularly limited, but can be formed by a conventionally known method such as a one-shot method or a prepolymer method. If an example is given, as a one-shot method, it can shape | mold by a series of processes (1)-(3) as shown below, for example.

Step (1): Polyester polyol (I), polyisocyanate (II), and if necessary, chain extender (III) and other optional components are mixed with stirring by an appropriate method such as a manual or a mixer. Then, the polyurethane resin composition for an elastic layer of the present invention is obtained by vacuum defoaming treatment.
Step (2): The polyurethane resin composition for the elastic layer is poured into a preheated mold in which a core metal is set in advance, and subjected to a curing treatment under specific temperature conditions, and polyester polyol (I) and polyisocyanate (II ).
Step (3): The molded product after the curing treatment is taken out from the mold, the surface is cut or polished, and a conductive paint is applied and cured, whereby a desired image forming roll can be obtained.

  Examples of the mixing method include manual mixing and mechanical mixing, and are not particularly limited, and conventionally known methods can be employed.

  The mold to be used is preferably preheated, and the preheating temperature is not particularly limited, but is usually preferably 60 to 150 ° C.

  The curing conditions (temperature, time, etc.) for the curing treatment are not particularly limited, but are usually preferably 1 to 24 hours at 60 to 150 ° C, and more preferably 2 to 16 hours at 80 to 120 ° C.

  In the image forming roll of the present invention, when the polyurethane resin composition for an elastic layer is an elastic layer covering a cored bar, the same operation as the molding method described above except that the cored bar is incorporated into a mold, The image forming roll of the present invention is obtained. Even if the molded polyurethane resin composition for an elastic layer is mounted on a metal core to form an image forming roll, the effect of the present invention is not impaired.

  Since the polyurethane resin composition constituting the elastic layer of the image forming roll of the present invention has low water absorption, excellent solvent resistance, and balanced performance, it is a conductive paint that forms a surface layer. It has excellent stability due to its extremely small change in swelling due to the solvent and the change in roll shape due to environmental conditions (humidity, temperature, etc.) during use.

  Therefore, when the image forming roll of the present invention is used, a beautiful image can be continuously printed stably over a long period of time regardless of whether powder toner or liquid toner is used.

  The polyurethane resin composition for an elastic layer of the present invention has low water absorption (water resistance) and is excellent in solvent resistance and compression set. In addition, the image forming roll of the present invention is formed by using the polyurethane resin composition for an elastic layer, thereby reducing external variation, preventing wrinkles on the roll surface (improving smoothness), and preventing roll deformation. For example, various OA such as a conductive roll for powder toner, a conductive roll for liquid toner, a toner supply roll, a developing roll, a charging roll, a transfer roll, etc. for electrophotographic copying machines, facsimiles, printers, etc. Useful for rolls for members.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited only to these examples.
Further, in the present invention, unless otherwise specified, “part” is “part by mass” and “%” is “mass%”.
The measurement method and evaluation method used in the present invention are as follows.

[Measurement method of melt viscosity of polyester polyol (I)]
The melt viscosity (mPa · s) at a temperature of 25 ° C. or 75 ° C. of each polyester polyol (I) was measured under the following conditions.
Measuring instrument: BM viscometer (manufactured by Tokyo Keiki Co., Ltd.)
Rotor: No. 3
Number of revolutions: 6 RPM

[Measuring method of melting point of polyester polyol (I)]
About 10 mg of each polyester polyol (I) is weighed into a measuring container, and nitrogen gas is measured using a differential scanning calorimeter (model: DSC 220C, manufactured by Seiko Electronics Co., Ltd.) (hereinafter abbreviated as “DSC”). The temperature was raised from 20 ° C. to 210 ° C. at a flow rate of 50 ml / min and a heating rate of 10 ° C./min, then held at 210 ° C. for 3 minutes, then cooled to −100 ° C. at a cooling rate of 50 ° C./min. The next temperature increase was performed up to 200 ° C., and the melting point (° C.) was determined from the DSC curve drawn on the chart.

[Molding method]
Coronate T-80 (trademark, manufactured by Mitsui Chemicals, Tolylene Diisocyanate), which is polyisocyanate (II), and each polyester polyol (I) obtained in Synthesis Examples 1 to 9 have a hardness of a molded product of JIS-A35 ±. The [NCO] / [OH] equivalent ratio was adjusted to 1 and the resin was blended at this blending ratio and stirred and mixed. It is poured into a mold, left to stand in a 120 ° C. dryer for 2 hours for primary curing, and then left to stand in a 110 ° C. dryer for 16 hours for secondary curing to obtain a target polyurethane resin composition for elastic layer (urethane elastomer composition). ).

[Measurement method of JIS-A hardness]
JIS-A hardness is measured according to the durometer hardness test prescribed | regulated to Japanese Industrial Standard JIS-K-6253, using the cylinder created as mentioned above as a test body.

[Water resistance test method]
(1) Water resistance test method The sheet of 2 mm thickness prepared as described above is punched out to 5.0 cm × 2.5 cm, and the mass change rate after the test body is immersed in ion-exchanged water at 40 ° C. for 3 days is expressed by the following equation: taking measurement.
(2) Calculation method of mass change rate Mass change rate (%) = W ₁ / W ₀ × 100
In the formula, W ₀ and W ₁ mean the following.
W ₀ : Mass of sheet before immersion W ₁ : Mass of sheet after immersion for 3 days at 40 ° C. in ion-exchanged water (3) Evaluation of water resistance test results Evaluation of the water resistance test results was performed according to the following criteria.
Evaluation criteria for water resistance test A: Less than 102.5% and excellent in water resistance.
○: 102.5% or more and less than 103.0%, and water resistance is good.
Δ: 103.0% or more and less than 103.5%, slightly inferior in water resistance.
X: 103.5% or more, extremely inferior in water resistance.

[Moisture and heat resistance test method]
(1) Moisture and heat resistance test method The 2 mm thick sheet prepared as described above was punched out to 5.0 cm × 2.5 cm, and left in a constant temperature and humidity chamber set at 75 ° C. in an atmosphere with a relative humidity of 95%. The mass after the day is measured, the mass change rate (%) is calculated by the following formula, and the heat and humidity resistance is evaluated.
(2) Mass change rate calculation method Mass change rate after 3 days (%) = X ₁ / X ₀ × 100
In the formula, X ₀ and X ₁ mean the following.
X ₀ : Mass of the cylinder before the test X ₁ : Mass of the cylinder after curing for 3 days in an atmosphere of 75 ° C. × 95% (3) Evaluation of the moist heat resistance test result The evaluation of the moist heat resistance test result is according to the following criteria: went.
Evaluation Criteria for Moisture and Heat Resistance Test A: Less than 106.0%, excellent in moisture and heat resistance.
○: 106.0% or more and less than 106.5%, and the heat and moisture resistance is good.
Δ: 106.5% or more and less than 107.0%, slightly inferior in heat and moisture resistance.
X: 107.0% or more, extremely inferior in heat and moisture resistance.

[Test method for solvent resistance]
(1) Solvent resistance test method Calculate the mass change rate (%) after immersing the specimens used for the above hardness measurement in toluene and methyl ethyl ketone (MEK) at 25 ° C. for 6 hours according to the following formula. Evaluate solvent resistance.
(2) Mass change rate calculation method Mass change rate after 3 days (%) = Y ₁ / Y ₀ × 100
In the formula, Y ₀ and Y ₁ mean the following.
Y ₀ : Mass of the cylinder before the test Y ₁ : Mass of the cylinder after being immersed in each solvent at 25 ° C. for 6 hours (3) Evaluation of the solvent resistance test result The evaluation of the solvent resistance test result is according to the following criteria: went.
Evaluation criteria for solvent resistance test Test solvent: Toluene
A: Less than 30% and excellent in solvent resistance.
○: 30% or more and less than 40%, and the solvent resistance is good.
Δ: 40% or more and less than 60%, slightly inferior in solvent resistance
X: 60% or more, extremely poor in solvent resistance.
Test solvent: MEK
A: Less than 45% and excellent in solvent resistance.
A: 45% or more and less than 55%, solvent resistance is good.
Δ: 55% or more and less than 75%, slightly inferior in solvent resistance
X: 75% or more, extremely poor in solvent resistance.

  Polyester polyols (I-1) to (I-9) were synthesized according to the operations of Synthesis Examples 1 to 9 described below.

[Synthesis Example 1]
In a 5-liter four-necked flask, 2201 parts of 3-methylpropanediol (hereinafter abbreviated as “3MPD”) as a glycol component (A) having 4 or more carbon atoms containing a side chain, a linear glycol having 2 to 3 carbon atoms (B) 128 parts of ethylene glycol (hereinafter abbreviated as “EG”), 325 parts of trimethylolpropane (hereinafter abbreviated as “TMP”) as polyfunctional glycol (C) having 3 or more hydroxyl groups, adipic acid (hereinafter referred to as “B”) (Abbreviated as “AA”) 2968 parts and 0.06 part of tetrabutyl titanate were charged and reacted at 220 ° C. for 24 hours under a nitrogen stream from a nitrogen introduction tube.
After completion of the reaction, the obtained polyester polyol (I-1) is a pale yellow liquid at room temperature, has an acid value of 0.15 (unit: mgKOH / g, hereinafter abbreviated), and a hydroxyl value of 83.2 (unit: mgKOH). / G, hereinafter abbreviated).

[Synthesis Example 2]
A 5-liter four-necked flask was charged with 1802 parts of 3MPD, 406 parts of EG, 325 parts of TMP, 3126 parts of AA, and 0.06 part of tetrabutyl titanate, and reacted at 220 ° C. for 24 hours in a nitrogen stream from a nitrogen introduction tube. .
After completion of the reaction, the obtained polyester polyol (I-2) was a pale yellow liquid at room temperature, and had an acid value of 0.15 and a hydroxyl value of 84.9.

[Synthesis Example 3]
A 5-liter four-necked flask was charged with 1361 parts of 3MPD, 715 parts of EG, 325 parts of TMP, 3300 parts of AA, and 0.06 part of tetrabutyl titanate, and reacted at 220 ° C. for 24 hours under a nitrogen stream from a nitrogen introduction tube. .
After completion of the reaction, the obtained polyester polyol (I-3) was a pale yellow liquid at room temperature, and had an acid value of 0.60 and a hydroxyl value of 84.3.

[Synthesis Example 4]
A 5 liter four-necked flask was charged with 1518 parts of 3MPD, 797 parts of EG, 33 parts of TMP, 3371 parts of AA, 0.06 part of tetrabutyl titanate, and reacted at 220 ° C. for 24 hours in a nitrogen stream from a nitrogen inlet tube. .
After completion of the reaction, the obtained polyester polyol (I-4) was a pale yellow liquid at room temperature, having an acid value of 0.37 and a hydroxyl value of 70.7.

[Synthesis Example 5]
A 5 liter four-necked flask was charged with 3MPD 1316 parts, 1,3PD 845 parts, TMP 325 parts, AA 3189 parts, and tetrabutyl titanate 0.06 parts, and reacted at 220 ° C. for 24 hours in a nitrogen stream from a nitrogen inlet tube. I let you.
After completion of the reaction, the obtained polyester polyol (I-5) was a pale yellow liquid at room temperature, and had an acid value of 0.29 and a hydroxyl value of 84.2.

[Synthesis Example 6]
A 5-liter 4-necked flask was charged with 1116 parts of 2MPD, 769 parts of EG, 325 parts of TMP, 3550 parts of AA, 0.06 part of tetrabutyl titanate, and reacted at 220 ° C. for 24 hours in a nitrogen stream from a nitrogen inlet tube.
After completion of the reaction, the obtained polyester polyol (I-6) was a pale yellow liquid at room temperature, and had an acid value of 0.41 and a hydroxyl value of 83.5.

[Synthesis Example 7]
Into a 5 liter four-necked flask, 1592 parts of EG, 3408 parts of AA, 0.06 part of tetrabutyl titanate were charged, and reacted at 220 ° C. for 24 hours under a nitrogen stream from a nitrogen introduction tube.
After completion of the reaction, the obtained polyester polyol (I-7) was a white solid and had an acid value of 0.23 and a hydroxyl value of 56.4.

[Synthesis Example 8]
A 5 liter four-necked flask was charged with 2390 parts of 3MPD as side chain-containing glycol (A), 2610 parts of AA, and 0.06 part of tetrabutyl titanate, and reacted at 220 ° C. for 24 hours in a nitrogen stream from a nitrogen inlet tube. It was.
In Synthesis Example 8, the reaction was carried out without using linear glycol (B) and polyfunctional glycol (C).
After completion of the reaction, the obtained polyester polyol (I-8) was a pale yellow liquid at room temperature, having an acid value of 0.30 and a hydroxyl value of 55.6.

[Synthesis Example 9]
A 5-liter four-necked flask was charged with 2510 parts of diethylene glycol (hereinafter abbreviated as “DEG”), 161 parts of TMP, 3239 parts of AA, 0.06 part of tetrabutyl titanate, and at 220 ° C. under a nitrogen stream from a nitrogen inlet tube. The reaction was performed for 24 hours.
After completion of the reaction, the obtained polyester polyol (I-9) was a pale yellow liquid, having an acid value of 0.23 and a hydroxyl value of 60.1.

[Examples 1-6] and [Comparative Examples 1-3]
<Adjustment of polyurethane resin composition for elastic layer and molding by one-shot method>
As the polyisocyanate (II), Cosmonate T-80 (product number: TDI-80, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) and polyester polyols (I-1) to (I-9) obtained in Synthesis Examples 1 to 9, NCO] / [OH] = 0.80 to 1.05 The mixing ratio was 0.85 to 1.05 equivalent ratio, and a polyurethane resin composition for an elastic layer (a urethane elastomer composition for an image forming roll) was prepared as a mixed solution.
The polyurethane resin composition for an elastic layer was poured into a 2 mm thick sheet mold and a cylindrical mold having a diameter of 4.0 cm and a thickness of 1.2 cm by the one-shot method.
These molds were heated in a hot air dryer at 120 ° C. for 2 hours for primary curing, and further heated at 110 ° C. for 16 hours for secondary curing to produce a molded product using the polyurethane resin composition for the elastic layer. . This molded article is subjected to the above test.
The results of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Tables 1 and 2.

The abbreviations listed in Tables 1 and 2 mean the following.
EG; ethylene glycol 1,3PD; 1,3-propanediol DEG; diethylene glycol 2MPD; 2-methylpropanediol 3MPD; 3-methylpentanediol TMP; trimethylolpropane AA; adipic acid MEK; methyl ethyl ketone

  The polyurethane resin composition for an elastic layer of the present invention has low water absorption (water resistance) and is excellent in solvent resistance and compression set. In addition, the image forming roll of the present invention is formed by using the polyurethane resin composition for an elastic layer, thereby reducing external variation, preventing wrinkles on the roll surface (improving smoothness), and preventing roll deformation. For example, various OA such as a conductive roll for powder toner, a conductive roll for liquid toner, a toner supply roll, a developing roll, a charging roll, a transfer roll, etc. for electrophotographic copying machines, facsimiles, printers, etc. Useful for rolls for members.

Claims (5)

  Polyester polyol (I) and polyisocyanate (II) used for an image forming roll having an elastic layer on the outer peripheral surface of the cored bar and further having a surface layer made of a conductive paint thereon, if necessary In the polyurethane resin composition for an elastic layer obtained by reacting the chain extender (III), the polyester polyol (I) is a glycol (A) containing a side chain having 4 or more carbon atoms and a C2 to 3 carbon atoms. Polyfunctional glycol (C) using linear glycol (B) at (A) / (B) = 90 / 10-30 / 70 molar ratio and having (A), (B) and three or more hydroxyl groups ) Is a polyester polyol using [(A) + (B)] / (C) = 99/1 to 85/15 molar ratio, a polyurethane resin composition for an elastic layer.   The polyurethane resin composition for an elastic layer according to claim 1, wherein the glycol (A) containing a side chain having 4 or more carbon atoms is 2-methylpropanediol and / or 3-methylpentanediol.   The polyurethane resin composition for an elastic layer according to claim 1, wherein the linear glycol (B) having 2 to 3 carbon atoms is ethylene glycol and / or 1,3-propylene glycol.   The polyurethane resin composition for an elastic layer according to claim 1, wherein the polyfunctional glycol (C) having three or more hydroxyl groups is trimethylolpropane.   An image forming roll comprising the polyurethane resin composition for an elastic layer according to any one of claims 1 to 4.