JP2587337B2 - Method of manufacturing cleaning blade for electrophotographic copying machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cleaning blade for an electrophotographic copying machine, and more particularly to a method for manufacturing a cleaning blade for an electrophotographic copying machine.
The present invention relates to a method for manufacturing a cleaning blade for an electrophotographic copying machine, which is made of a polyurethane elastomer having an SA hardness of about 60 to 70, reduces the occurrence of defects in edges even after long-term use, and thus has excellent durability.

[0002]

2. Description of the Related Art According to an electrostatic electrophotographic copying machine using plain paper as recording paper, an electrostatic charge is generally applied to the surface of a photoreceptor by discharging, and an image is exposed thereon to form an electrostatic latent image. Forming, then applying toner of opposite polarity to the electrostatic latent image and developing, transferring the toner image to recording paper, and finally,
Copying is performed by heating and pressing the recording paper on which the toner image has been transferred and fixing the toner on the recording paper.

Therefore, in order to sequentially perform copying on a plurality of recording papers, it is necessary to remove the toner remaining on the surface of the photoreceptor after transferring the toner image from the photoreceptor to the recording paper in the above process. There is a known blade cleaning method in which a blade is pressed against the surface of a photoreceptor and the photoreceptor is rubbed and cleaned as one of the removal methods.
For the blade for this blade cleaning method, a molded article made of polyurethane elastomer is preferably used because of its excellent mechanical strength such as abrasion resistance.

[0004] This polyurethane elastomer is usually
Prepare a prepolymer using polyethylene adipate ester or polycaprolactone ester as the polyol component, and 4,4'-diphenylmethane diisocyanate as the polyisocyanate component, add a curing agent and a catalyst as needed, In a mold, post-crosslinking in a furnace, and aging at room temperature. As the curing agent, a dihydric alcohol such as 1,4-butanediol and a trihydric or higher polyhydric alcohol such as trimethylolpropane and pentaerythritol are usually used in combination.

[0005] However, it is generally known that a conventionally known cleaning blade made of a polyurethane elastomer is damaged in an edge due to its long-term use. Therefore, conventionally, as countermeasures, the friction coefficient of the polyurethane elastomer constituting the cleaning blade has been reduced, the friction coefficient of the photoconductor has been reduced, a lubricant has been mixed in the toner, and the cleaning blade has been applied to the surface of the photoconductor. Various measures have been proposed, such as reducing the pressing force. However, these methods have a bad effect on the quality of the obtained image and the like, and at present, they do not exhibit sufficient effects.

In particular, for a photosensitive member having a soft surface layer that is easily worn or scratched by rubbing with a cleaning blade, the rubber hardness of the cleaning blade is generally 60 to JIS A hardness. It must be made of a relatively soft elastic body of about 70. However, when the cleaning blade is made of such a soft elastic material, the physical properties of rubber are inevitably reduced, and the edge is likely to be damaged. Defects in the edge portion of the cleaning blade cause filming of the toner on the photoreceptor, and further, toner slip-through, leading to image defects.

[0007]

SUMMARY OF THE INVENTION The present invention relates to JIS A
A cleaning blade for an electrophotographic copying machine comprising a relatively soft polyurethane elastomer having a hardness of 60 to 70, which has been made in order to solve the above-mentioned problem. Thus, an object of the present invention is to provide a method for producing a cleaning blade for an electrophotographic copying machine which is less likely to cause filming or the like and has excellent durability.

[0008]

According to the present invention, there is provided a method for producing a cleaning blade for an electrophotographic copying machine, comprising the steps of: preparing an isocyanate group content of 8 to 20% from a polyisocyanate and a high molecular weight polyol having a molecular weight of 1,000 to 3,000;
Urethane pseudo-prepolymer having a molecular weight of 1,000 to 3,000
After mixing and stirring a curing agent consisting of a high molecular weight polyol and a low molecular weight polyol having a molecular weight of 60 to 250 at a hydroxyl / isocyanate equivalent ratio of 0.8 to 0.9, or in a preheated mold while mixing and stirring. By injecting, the obtained elastic body is given a JIS A hardness of 60 to 70,
It is characterized by having a 300% modulus of 30 to 250 kg / cm ² .

According to the method of the present invention, first, a urethane pseudoprepolymer having an isocyanate group content of 8 to 20% is prepared from a polyisocyanate and a high molecular weight polyol having a molecular weight of 1,000 to 3,000 by a conventional method. In the preparation of the pseudo prepolymer, as the polyisocyanate, for example, tolylene diisocyanate, 3,3′-dimethyldiphenyl diisocyanate, 4,4′-diphenylmethane diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene A diisocyanate such as diisocyanate is used, and 4,4′-diphenylmethane diisocyanate is preferably used.

Examples of the high molecular weight polyol having a molecular weight of 1,000 to 3,000 include polyester polyols which are condensates of alkylene glycol and aliphatic dibasic acid, such as ethylene adipate ester polyol, butylene adipate ester polyol,
Polyester polyols such as hexylene adipate ester polyols, ethylene propylene adipate ester polyols, ethylene butylene adipate ester polyols, polyester polyols of alkylene glycol and adipic acid such as ethylene neopentylene adipate ester polyol, and caprolactone obtained by ring-opening polymerization. Polycaprolactone-based polyols such as polycaprolactone ester polyols, poly (oxytetramethylene) glycol, poly (oxypropylene)
A polyether polyol such as glycol is used. Particularly, in the present invention, adipic acid-based polyester polyol and polycaprolactone-based polyol are preferably used. In addition to the above, for example, polycarbonate diol is also used.

Conventionally, a cleaning blade for an electrophotographic copying machine usually has a isocyanate group / hydroxyl group equivalent ratio in the range of 1.1 to 4.0, and a predetermined amount of a total amount of polyisocyanate and a predetermined amount of a total amount of polyol. And 60 to 90
Preparing a prepolymer by reacting all at once at a temperature of ℃
Then, the prepolymer is produced by adding a low molecular weight curing agent and curing the prepolymer. Such a method is called a complete prepolymer method because a prepolymer is prepared by using all required amounts of a polyisocyanate and a polyol all at once.

However, according to the process of the present invention, a pseudo-prepolymer is prepared by reacting a required amount of a polyisocyanate with a portion of a required amount of a high-molecular-weight polyol in a complete prepolymer method. A low molecular weight polyol is added to the remainder of the high molecular weight polyol to form a curing agent, which is added to the prepolymer and cured to obtain a cleaning blade for an electrophotographic copying machine. Hereinafter, such a method is referred to as a pseudo-prepolymer method.

Here, the high molecular weight polyol used as the curing agent component may be the same as or different from the high molecular weight polyol used for preparing the pseudo-prepolymer. Further, as described above, according to the present invention, the amount of the high molecular weight polyol used as the curing agent component is preferably 30 mol% or more of the required amount of the high molecular weight polyol in the complete prepolymer method.

On the other hand, the low molecular weight polyol used as another curing agent component in the present invention has a molecular weight of 60 to 250.
As long as it is within the range, any conventionally known one can be appropriately used. Accordingly, examples of such low molecular weight polyols include 1,4-butanediol, ethylene glycol, neopentyl glycol,
Dihydric alcohols such as hydroquinone-bis (2-hydroxyethyl) ether, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, and 1,1,1- Trimethylolpropane, glycerin,
Trivalent and higher trivalent compounds such as 1,2,6-hexanetriol, 1,2,4-butanetriol, trimethylolethane, 1,1,1-tris (hydroxyethoxymethyl) propane, diglycerin and pentaerythritol. Valent alcohols can be mentioned.

In particular, in the present invention, a mixture of a dihydric alcohol and a trihydric alcohol is preferably used as the low molecular weight polyol as the curing agent component. For example, 1,4
A mixture of -butanediol and 1,1,1-trimethylolpropane in a 1,4-butanediol / 1,1,1-trimethylolpropane molar ratio in the range of 60/40 to 90/10 is preferably used.

Further, in the present invention, the curing agent is a mixture of the low-molecular-weight polyol in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the high-molecular-weight polyol. The ratio of the number of equivalents of the hydroxyl group of the curing agent to the isocyanate group of the prepolymer, that is, the equivalent ratio of the hydroxyl group / isocyanate group is used in the range of 0.8 to 0.9. Most preferably, the hydroxyl / isocyanate group equivalent ratio ranges from 0.82 to 0.88.

According to the method of the present invention, a curing catalyst is preferably used together with the curing agent. Specific examples of such curing catalysts include, for example, 2-methylimidazole and 1,2-
Dimethylimidazole can be mentioned, but in particular,
1,2-dimethylimidazole is preferably used. Such a catalyst is usually used in an amount of 0.
It is used in the range of 0.01 to 0.5 part by weight, preferably 0.05 to 0.3 part by weight.

According to the method of the present invention, the above-mentioned pseudo-prepolymer is mixed and stirred with the above-mentioned curing catalyst, and then the mixture is poured into a mold at a predetermined temperature into which a connector which has been subjected to an adhesive treatment is inserted. Thus, a cleaning blade can be obtained. The present inventors have produced urethane elastomers in the pseudo-prepolymer method while varying the hydroxyl / isocyanate group equivalent ratio in various ways, and conducted extensive research on their physical properties. Has been found to behave differently from urethane elastomers obtained by the conventionally known conventional complete prepolymer method.

That is, according to a conventionally known ordinary complete prepolymer method, a urethane elastomer is produced with a hydroxyl group / isocyanate group equivalent ratio in the range of 0.9 to 1.0. The physical properties of the elastomer thus obtained tend to increase with a gentle gradient in hardness, 200-300% modulus, permanent elongation, etc. as the hydroxyl / isocyanate group equivalent ratio approaches 1.0.

On the other hand, the present inventors show that the pseudo prepolymer method shows the opposite tendency to the above,
It has been found that 0-300% modulus changes significantly. Although the reason is not always clear, a part of the high molecular weight polyol in the complete prepolymer method is used as a curing agent together with a low molecular weight polyol to act on the pseudo prepolymer and crosslink the pseudo prepolymer to obtain the obtained product. A change may have occurred in the internal structure of the resulting elastomer, particularly in the form of chemical bonds.

More specifically, with respect to the obtained rubber properties, according to the complete prepolymer method, the amount of the hard segment is dominant, while according to the pseudo prepolymer method, the crosslink density acts dominantly. It seems to be something. Therefore, by setting the equivalent ratio of hydroxyl group / isocyanate group to the range of 0.8 to 0.9 by the pseudo-prepolymer method, the hardness (JIS A hardness) of the obtained urethane elastomer is 60 to 60.
At the same time as 70, the modulus in the large deformation region can be increased, so that the edge loss can be effectively prevented.

Thus, according to the present invention, a pseudo-prepolymer is prepared by a pseudo-prepolymer method, and a curing agent composed of a high-molecular-weight polyol and a low-molecular-weight polyol is added to a hydroxyl group / isocyanate group equivalent ratio. By acting in the range of 0.8 to 0.9, the resulting polyurethane elastomer has a hardness (JIS A hardness) of 60 to 70, and has a hardness of 130 to 250 kg / cm ² , preferably 150 to 200 kg / cm ² . ⁽² ) 300% modulus. Thus, according to the present invention, it is possible to obtain a cleaning blade made of a polyurethane elastomer which does not cause a defect in an edge even after long-term use.

In particular, according to a preferred embodiment of the method of the present invention, using a casting device with a mixing head,
The cleaning blade is made by so-called reaction-injection molding (RIM molding) in which the main agent and the curing agent component are immediately mixed into the mold while being colliding and mixed at a low temperature, for example, a temperature of 50 to 70 ° C., by a mixing head. Obtainable. Therefore, according to the method of the present invention, after curing in the mold, the product can be removed from the mold and made into a product without being subjected to secondary curing.

[0024]

In general, the cleaning of the photosensitive member by the cleaning blade is performed by pressing the edge against the surface of the rotating photosensitive member. In such a cleaning operation, the edge elastically deforms following the surface of the photoreceptor and then resiliently recovers, at which time the toner particles are repelled from the surface of the photoreceptor, thereby causing the toner to repel. The toner particles are removed from the surface.

That is, the edge is caught while being bent in the rotational direction of the photoconductor by the frictional force between the edge and the surface of the photoconductor, and then changes at a short interval by the elastic force. In this way, the surface of the photoreceptor is cleaned, and on the other hand, it is considered that the edge is damaged due to the repetitive fatigue, and the amount of entanglement plays an important role in the edge loss. It seems to be. If the entanglement amount is too large, the cleaning effect is deteriorated, and the edge is subjected to repeated concentrated stress in the large deformation region. Also, due to the lack of such an edge,
Filming of the toner on the surface of the photoreceptor and so-called slip-through of the toner particles occur, thereby deteriorating the quality of the copied image.

The defect of the edge of the cleaning blade made of the urethane elastomer increases the modulus in the large deformation region, reduces the amount of entrainment caused by the frictional force with the surface of the photoreceptor, and preferably reduces 1
By suppressing the thickness to about 0 to 20 μm, the occurrence can be effectively prevented. According to the method of the present invention, a pseudo-prepolymer is prepared as described above and then the hydroxyl / isocyanate equivalent ratio of this pseudo-prepolymer is
The hardness (JIS A) of the resulting urethane elastomer is obtained by allowing a curing agent composed of a high molecular weight polyol and a low molecular weight polyol to act so as to be 0.8 to 0.9.
Hardness) is set to 60 to 70, and the modulus (300% modulus) in the large deformation region is set to 130 to 250.
Since the cleaning blade has been increased to Kg / cm ² , it is possible to obtain a cleaning blade that effectively prevents the edge from being damaged. Thus, such a cleaning blade may cause the edge to be damaged even after long-term use. There is no.

[0027]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples. Example 1 As shown in Table 1, a predetermined amount of polyol (molecular weight 200
0 polycaprolactone diol) at 70 ° C. for 3 hours,
After stirring and heating under reduced pressure (5 mmHg) and dehydration, this was charged into a glass reaction vessel. Subsequently , 4,4'-diphenylmethane diisocyanate was added to the reaction vessel, and the mixture was heated at 70 ° C. under a nitrogen gas atmosphere at 70 ° C. Stir for ~ 2 hours to prepare a pseudo-prepolymer. The amount of isocyanate groups was measured by the dibutylamine method, and the reaction was terminated when the reaction rate reached about 100%. Table 1 shows the isocyanate group content of the obtained pseudo-prepolymer.

Separately, a curing agent (1,4-butanediol, trimethylolpropane, and the above polyol) was added in 1 part each.
After stirring and heating at 00 ° C. for 1 hour under reduced pressure (5 mmHg) and dehydration, a predetermined amount was charged into a glass reaction vessel as shown in Table 1, and the mixture was colorless and transparent under a nitrogen atmosphere until the mixture became colorless and transparent. The mixture was stirred and mixed at 100 ° C. Further, a predetermined amount of a catalyst was further added to obtain a curing agent component.

Next, the pseudo-prepolymer and the curing agent component were heated to the temperatures shown in Table 1, respectively, supplied to the mixing head at the ratio shown in Table 1, and mixed and agitated beforehand.
It was poured into a mold heated to 45 ° C. to form a cleaning blade. Next, the molded product is removed from the mold,
Secondary curing was performed by heating at 110 ° C. for 24 hours. Table 2 shows the physical properties of the obtained cleaning blade.

Further, the obtained cleaning blade was mounted on a plain paper copying machine manufactured by Canon Inc., and a black / white 7% character chart was used as an image to be copied at room temperature and normal humidity at a rate of 25 sheets per minute. After 20,000 images were continuously copied on A4 paper, the state of occurrence of edge damage of the cleaning blade was examined. Table 2 shows the results. Example 2 As shown in Table 1, a polyol having a molecular weight of 2,000 was used.
A cleaning blade was formed in the same manner as in Example 1 except that polyethylene adipate diol was used.

With respect to this cleaning blade, the physical properties evaluated in the same manner as in Example 1 and the state of occurrence of edge damage during image copying were examined. Table 2 shows the results. As shown in Comparative Example 1 in Table 1 for 3 hours at 70 ° C. a predetermined amount of polyol, heated with stirring under reduced pressure (5 mmHg), was dehydrated, it was charged into a glass reaction vessel, subsequently, 4,4 '-Jifu
Enylmethane diisocyanate was added to the reaction vessel, and stirred at 70 ° C. for 1 to 2 hours under a nitrogen gas atmosphere to prepare a prepolymer by a complete prepolymer method. The isocyanate group content was measured by the dibutylamine method, and the reaction rate was about 1
The reaction was terminated when it reached 00%. Table 1 shows the isocyanate group content of the obtained prepolymer.

Separately, each of the curing agents was stirred and heated at 100 ° C. for 1 hour under reduced pressure (5 mmHg) and dehydrated.
As shown in Table 2, a predetermined amount was charged into a glass reaction vessel, and stirred and mixed at 100 ° C under a nitrogen atmosphere until the mixture became colorless and transparent. Further, a predetermined amount of a catalyst was further added to obtain a curing agent component. The prepolymer and the curing agent component were each heated to the temperature shown in Table 1, mixed, and then 145 in advance.
The cleaning blade was molded by pouring into a mold heated to ° C. Next, the molded product is removed from the mold, and 11
Secondary curing was performed by heating at 0 ° C. for 24 hours. Table 2 shows the physical properties of the obtained cleaning blade.

In the same manner as in Example 1, the obtained cleaning blade was mounted on a plain paper copier, and an image was copied. Then, the occurrence state of the edge of the cleaning blade was examined. Table 2 shows the results. Comparative Example 2 A cleaning blade was formed in the same manner as in Example 1 except that the equivalent ratio of hydroxyl group / isocyanate group was 0.95. With respect to this cleaning blade, the physical properties evaluated in the same manner as in Example 1 and the state of occurrence of edge damage during image copying were examined. Table 2 shows the results.

[0034]

[Table 1]

[0035]

[Table 2]

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Atsushi Higashi 3-2-15 Meiwadori, Hyogo-ku, Kobe City Inside Bando Chemical Co., Ltd.

Claims (1)

(57) [Claims] 1. A polyisocyanate having a molecular weight of 1,000 to 3,
And a high molecular weight polyol having an isocyanate group content of 8 to 20%.
High molecular weight polyol of 0 to 3000 and molecular weight of 60 to 25
After mixing and stirring a curing agent consisting of a low molecular weight polyol having a hydroxyl group / isocyanate group equivalent ratio of 0.8 to 0.9, or while mixing and stirring, the mixture is poured into a pre-heated mold to obtain an elastic body. A JIS A hardness of 60 to 70 and a 300% modulus of 130 to 250 kg / cm < ² >.