JP5236150B2 - Blade for image forming apparatus and method for manufacturing the same - Google Patents

Description

  The present invention relates to residual toner on the surface of a member that carries a toner such as a photoreceptor or a transfer belt or contacts a toner carrying surface in an electrostatic image forming apparatus such as a plain paper copier, a plain paper facsimile, or a laser beam printer. The present invention relates to an elastic blade for an image forming apparatus such as a cleaning blade to be removed, a toner regulating blade used in a developing device for supplying toner to a photoreceptor, and a method for manufacturing the same.

  As the elastic blade used in the image forming apparatus, a cleaning blade using a polyurethane elastomer and a toner regulating blade are known (for example, Patent Documents 1 and 2).

  In Patent Document 1, as a cleaning blade that achieves both low temperature characteristics, permanent distortion and prevention of chatter noise at high temperature, polyethylene adipate is used as a polyol component, 1,4-butanediol is used as a chain extender, and trimethylolpropane is used as a cleaning blade. A cleaning blade made of a polyurethane elastomer as a crosslinking agent is disclosed.

  Patent Document 2 discloses that a cleaning blade having ultra-low rebound resilience and excellent mechanical strength, polycarbonate diol as a polyol component, and short-chain diols such as 1,3-butanediol and 1,4-butanediol. Has disclosed a cleaning blade made of a polyurethane elastomer using as a chain extender and another functional alcohol such as trimethylolpropane as a crosslinking agent.

JP-A-8-179669 Japanese Patent Laid-Open No. 2004-220018

  In recent years, image forming apparatuses such as copiers are required to reduce the number of parts replacement, and members such as cleaning blades are also required to have a longer durability.

However, a cleaning blade made of a polyurethane elastomer using a chain extender and a cross-linking agent represented by Patent Documents 1 and 2 has a tendency to reduce the pressure contact force with a contact object such as a photoreceptor due to permanent distortion when used over a long period of time. This phenomenon causes a problem that a cleaning failure occurs in the cleaning blade due to such settling. Therefore, improvement is demanded.
In order to obtain a cleaning blade made of a polyurethane elastomer having a small permanent set, it is conceivable to increase the ratio of the crosslinking agent such as trimethylolpropane used in Patent Documents 1 and 2, but the ratio of the crosslinking agent is increased. Then, problems such as curing of the polyurethane elastomer do not occur.

  An object of the present invention is to provide an elastic blade for an image forming apparatus and a method for manufacturing the same, which have a smaller permanent set than conventional ones and are less likely to cause settling over a long period of use.

  The blade for an image forming apparatus of the present invention is characterized by comprising a polyurethane elastomer having a polyol compound, an aromatic diisocyanate, a crosslinking agent, and an aliphatic diol having a side chain as a chain extender as constituent components.

  The blade for an image forming apparatus having such a configuration is an elastic blade for an image forming apparatus that has a smaller permanent distortion than conventional ones and is less likely to cause settling over a long period of use.

  In the above-described blade for an image forming apparatus, it is preferable that the polyol compound contains polyester glycol as a main component.

  A blade formed of a polyurethane elastomer having such a configuration has a particularly small permanent set and is less likely to cause settling over a long period of use.

  The method for producing a blade for an image forming apparatus according to the present invention comprises a prepolymer production step of producing an NCO group-terminated prepolymer by reacting at least a part of a polyol compound with an aromatic diisocyanate in excess of an NCO group. And a crosslinking step and a chain extender containing an aliphatic diol having at least a side chain to be mixed into a reaction stock solution composition, and a molding step for casting and curing the reaction stock solution composition. To do.

  With the manufacturing method having such a configuration, it is possible to manufacture an elastic blade for an image forming apparatus that has a smaller permanent set than conventional ones and is less likely to cause settling over a long period of use.

  As the polyol compound constituting the polyurethane elastomer elastic blade for the image forming apparatus of the present invention, a polyol compound for polyurethane elastomer having an average molecular weight of 1000 to 3000 can be used without limitation, polyether polyol, polyester polyol. , Polycarbonate polyol, polyether-polyester copolymer polyol and the like.

  As the polyether polyol, polytetramethylene glycol (PTMG) is preferably used. Examples of polyether-polyester copolymer polyols include copolymer polyols obtained by ring-opening addition of ε-caprolactone to PTMG.

  Among the above polyols, it is preferable to use polyester glycol. Examples of the polyester glycol include one or more of low molecular weight glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, pentanediol, hexanediol, and cyclohexanedimethanol. Condensation weight of glutaric acid, adipic acid, pimelic acid, speric acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, hydrogenated dimer acid or other low molecular dicarboxylic acid or oligomeric acid Examples thereof include polyols such as ring-opening polymers of ring-opening esters such as coalescence, propiolactone, caprolactone and valerolactone.

  An aromatic diisocyanate compound is preferably used as the polyisocyanate component constituting the polyurethane elastomer elastic blade for the image forming apparatus of the present invention. Examples of the aromatic diisocyanate compound include 4,4'-diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), and p-phenylene diisocyanate. There are 2,4-TDI and 2,6-TDI in TDI, either of which may be used, or in combination. 100% 2,4-TDI (TDI-100), 2,4-TDI / 2,6-TDI = 95/5 (TDI-95), 80/20 (TDI-80), 60/40 ( TDI-60) and the like are commercially available, and any of them can be used.

  As the aliphatic diol having a side chain used as a chain extender, known compounds can be used without limitation, and specifically, 1,2-propylene glycol, 1,3-butanediol, and neopentyl glycol are preferable. Examples of such compounds.

  As the chain extender, known linear glycols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol and the like may be used in combination as necessary.

  As the crosslinking agent, a tri- or tetrafunctional polyhydric alcohol is used. Specific examples include aliphatic polyhydric alcohols such as trimethylolpropane, glycerin and pentaerythritol, and amino group-containing polyhydric alcohols such as triethanolamine and N, N, N ′, N′-tetrahydroxyethylethylenediamine. be able to. Two or more kinds of these crosslinking agents may be used in combination, and when a trifunctional polyhydric alcohol and a tetrafunctional polyhydric alcohol are used in combination, the average number of functional groups is 3-4.

  The ratio between the chain extender and the cross-linking agent is preferably a chain extender / cross-linking agent = 95/5 to 60/40 in molar ratio. When the ratio of the chain extender / crosslinker exceeds 95/5 and the ratio of the chain extender increases, the permanent set of the obtained elastic blade increases, and when the ratio of the crosslinker exceeds 60/40, the elasticity obtained The mechanical properties of the body blade are lowered, and chipping resistance is lowered. It is more preferable that chain extender / crosslinker = 90/10 to 70/30.

As a method for forming a polyurethane elastomer using the above-mentioned polyurethane elastomer raw material, a one-shot method in which a predetermined amount of each component is mixed (mixing step) and the reaction stock solution composition is reacted and cured as a reaction stock solution composition, a polyol At least a part of the compound is preliminarily reacted with an isocyanate component to prepare a prepolymer (prepolymer production step), and the prepolymer, at least a chain extender and a crosslinking agent are mixed (mixing step) to obtain a reaction stock solution composition. There is a prepolymer method in which the reaction stock solution composition is reacted and cured, and any method may be used. However, since a polyurethane elastomer having more excellent physical properties can be obtained, the prepolymer method is preferable as described above. The NCO / H ^* equivalent ratio (NCO index) in the curing reaction is preferably 1.05 to 1.30.

  In the prepolymer method, a total amount of a polyol compound and an isocyanate component are reacted to form a prepolymer, and the prepolymer is reacted with a chain extender and a crosslinking agent. There is a pseudo prepolymer method in which a prepolymer is reacted to react with a mixture of the prepolymer, the remaining polyol compound, a chain extender, and a crosslinking agent, and any method can be used. In the case of using a low molecular weight glycol in addition to the polyol compound, it is preferable to use a prepolymer method and use the low molecular weight glycol as a prepolymer constituent.

The blade for an image forming apparatus can be manufactured, for example, by a manufacturing method having the following molding process.
<1> Sheet Forming Method 1) The reaction stock solution composition is cast into a sheet shape and reacted and cured to form a raw sheet, and the raw sheet is cut (cutting step) into a blade. In sheet forming, a centrifugal forming method is generally used.
2) A blade is mounted on a base material (metal fitting) for mounting the blade on the image forming apparatus by bonding or the like.
<2> Direct molding method A base material (metal fittings, etc.) for mounting the blade on the image forming apparatus is arranged in the mold having the cavity of the shape of the blade to be molded as required, and reacts to the molding cavity. The stock solution composition is cast to form a blade or blade unit.

<Example of polyurethane elastomer sheet production>
Example 1
A pseudo prepolymer was prepared by reacting 56.9 parts by weight of 4,4′-diphenylmethane diisocyanate (MDI) with 43.1 parts by weight of Plaxel 220N (polycaprolactone glycol; Daicel Chemical Industries), which is a polyester glycol.
100 parts by weight of the obtained pseudo prepolymer was heated to 80 ° C., 55.4 parts by weight of Plaxel 220N, 6.0 parts by weight of propylene glycol which is an aliphatic diol having a side chain, and trimethylolpropane as a crosslinking agent. A total of 63.6 parts by weight of a curing agent component comprising 2.2 parts by weight (chain extender / crosslinking agent molar ratio = 83/17) was added, and a polyurethane elastomer sheet for blade production having a thickness of 2 mm was prepared by centrifugal molding. Produced. Physical properties were evaluated after post-cure and aging.

(Example 2)
57.6 parts by weight of Plaxel 220N as a curing agent component, 6.9 parts by weight of 1,3-butanediol which is an aliphatic diol having a side chain, and 2.2 parts by weight of trimethylolpropane as a crosslinking agent (chain extension) A polyurethane elastomer sheet was prepared in the same manner as in Example 1 except that a total of 66.7 parts by weight of the curing agent component consisting of the agent / crosslinking agent molar ratio = 83/17) was added.

(Example 3)
59.8 parts by weight of Plaxel 220N as a curing agent component, 7.9 parts by weight of neopentyl glycol, an aliphatic diol having a side chain, and 2.3 parts by weight of trimethylolpropane as a crosslinking agent (chain extender / crosslinking) A polyurethane elastomer sheet was prepared in the same manner as in Example 1 except that a total of 70.0 parts by weight of the curing agent component consisting of the agent molar ratio = 82/18) was added.

(Comparative Example 1)
A total of 60 hardener components comprising 53.1 parts by weight of Plaxel 220N as a hardener component, 5.0 parts by weight of ethylene glycol which is a linear aliphatic diol, and 2.2 parts by weight of trimethylolpropane as a crosslinking agent. A polyurethane elastomer sheet was prepared in the same manner as in Example 1 except that 3 parts by weight was added.

(Comparative Example 2)
It consists of 57.6 parts by weight of Plaxel 220N as a curing agent component, 6.9 parts by weight of a linear aliphatic diol 1,4- and butanediol, and 2.2 parts by weight of trimethylolpropane as a crosslinking agent. A polyurethane elastomer sheet was produced in the same manner as in Example 1 except that a total of 66.7 parts by weight of the curing agent components were added.

<Evaluation>
(hardness)
The hardness was measured using an ASKER A hardness meter according to JIS K 6253. The measurement was performed on a sample having a thickness of 12 mm by stacking six polyurethane elastomer sheets having a thickness of 2 mm obtained in Examples and Comparative Examples.

(Rebound resilience)
The rebound resilience at 23 degrees was measured according to JIS K 6255 (Lupke type). The measurement was performed on a sample having a thickness of 12 mm by stacking six polyurethane elastomer sheets having a thickness of 2 mm obtained in Examples and Comparative Examples.

(Permanent elongation)
Two strip-shaped test samples having a width of 10 mm were made by punching from the polyurethane elastic sheet obtained in the production example, the distance between marked lines was 100 mm (measured value Lo), the measurement temperature was 20 ± 3 ° C., and the tensile speed was 500 mm / Elongate to 100% at min, leave in that state for 10 minutes, then open and measure the distance between marked lines (L). Permanent elongation is represented by the following formula: Permanent elongation = 100 (L-Lo) / Lo (%)
Calculate with Let the average value of the measurement result of two test samples be permanent elongation.

<Evaluation results>
The evaluation results are shown in the lower part of Table 1. As a result, the cleaning blade made of the polyurethane elastomer using the aliphatic diol having a side chain of the present invention as a chain extender has a low resilience compared to the cleaning blade made of the polyurethane elastomer using the conventional linear diol. It can be seen that it is elastic and has a small permanent set, and is not prone to settling even after long-term use.

Claims (3)

  It consists of a polyurethane elastomer comprising a polyol compound, an aromatic diisocyanate, a crosslinking agent and an aliphatic diol having a side chain as a chain extender (except for a vicinal diol in which both adjacent carbon atoms have a hydroxyl group). A blade for an image forming apparatus.   The blade for an image forming apparatus according to claim 1, wherein the aliphatic diol having a side chain comprises only 1,3-butanediol or neopentyl glycol. A prepolymer production step of producing an NCO group-terminated prepolymer by reacting at least a part of the polyol compound with an aromatic diisocyanate in excess of NCO groups, an aliphatic diol having the prepolymer and a crosslinking agent and at least a side chain ( However, a mixing step of mixing with a chain extender containing a vicinal diol in which adjacent carbon atoms both have a hydroxyl group (excluding a vicinal diol) to form a reaction stock solution composition, molding for casting and curing the reaction stock solution composition A method of manufacturing a blade for an image forming apparatus, comprising a step.