JPH0396981A - Cleaning blade for electrophotographic copying machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention is a cleaning product for electrophotographic copying machines which is made of polyurethane and has improved heat resistance and therefore has improved durability such as abrasion resistance and chipping resistance. Regarding blades.

According to an electrostatic electrophotographic copying machine that uses plain paper as a recording paper, an electrostatic latent image is generally created by applying an electrostatic charge to the surface of a photoconductor by discharging, and then exposing an image thereon. Then, toner with opposite polarity is attached to the electrostatic latent image and developed, the toner image is transferred to recording paper, and finally, the recording paper with the toner image transferred is heated, Copying is performed by fixing toner on recording paper. Therefore, in order to sequentially copy onto multiple sheets of recording paper, it is necessary to remove the toner remaining on the surface of the photoconductor after transferring the toner image from the photoconductor to the recording paper in the above process. As one of the methods, a blade cleaning method is known in which a blade is pressed against the surface of the photoreceptor and the photoreceptor is rubbed and cleaned. A blade made of polyurethane is preferably used as a blade for this blade cleaning method because it has particularly excellent mechanical strength such as abrasion resistance.

Conventionally, such polyurethanes are generally commercially available polyols, such as polyester polyols such as polyethylene adipate ester polyol, polyethylene butylene adipate ester polyol, cabrolactone ester polyol, and polyether polyols such as polyoxypropylene glycol. and a polyisocyanate such as 4,41-diphenylmethane diisocyanate.

However, such conventional cleaning blades
Properties such as rebound resilience are highly dependent on temperature, and in particular, long-term use in high-temperature environments can cause early wear or chipping, resulting in poor durability.

Therefore, many attempts have been made to improve the heat resistance of the polyurench obtained, mainly by selecting various types of polyols, but these efforts naturally have limitations. In particular, tolylene diisocyanate and 1,4-diphenylmethane diisocyanate, which have been commonly used as polyisocyanates, have a bent molecular structure, so the hard segments formed in the isocyanate are difficult to form. It cannot form a sufficiently agglomerated crystal structure and thus melts at a relatively low temperature of 50-60°C. Since the physical properties of polyurethane elastomers are largely dependent on this hard segment, the physical properties of conventional elastomers deteriorate significantly at relatively low temperatures of 50 to 60°C.

The present inventors have conducted intensive research to solve the above-mentioned problems with conventional cleaning blades for electrophotographic copying machines made of polyurethane. As a component, p-phenylene diisocyanate and/or trans-1,4-cyclohexane diisocyanate are used, and these are reacted with a polyol component to obtain a urethane brebolymer having terminal isocyanate groups, which is then cured with a curing agent. By this,
It is possible to improve the agglomeration and crystallinity of the hard segments in polyurethane elastomers, and thus to have a structure that does not melt even at temperatures of 50 to 60°C.In this way, heat resistance is significantly improved and wear resistance is improved. The present invention was developed based on the discovery that a cleaning blade with excellent durability such as chipping resistance and chipping resistance can be obtained.

The cleaning blade for an electrophotographic copying machine according to the present invention for cleaning p-phenylene diisocyanate and trans-1,
It is characterized in that it is made by curing a urethane prepolymer obtained by reacting 4-cyclohexane diisocyanate with a polyol such that the molar ratio of isocyanate groups/hydroxyl groups is 1.1 to 4.0 with a curing agent.

According to the present invention, the urethane prebolimer iJl contains, as a polyisocyanate, p-phenylene diisocyanate or trans-1, whose molecules are linear and rigid.
, 4-cyclohexane diisocyanate is used.

In this way, the agglomerated crystallinity of the hard segments in the resulting polyurethane elastomer is increased, and
Even at a temperature of 60° C., the hard segment is prevented from dissolving, and thus a cleaning blade with excellent heat resistance and no deterioration of physical properties can be obtained even when used at high temperatures.

The polyol may include, but is not limited to,
For example, polyester polyols such as polyethylene glycol, polycabrolactone, polybutylene glycol, polycarbonate diol, and neobentyl glycol, and polyether polyols such as polytetralamethylene glycol are preferably used.

In the present invention, the urethane polymer made of polyisocyanate and polyolefin/polymer has an isocyanate group/hydroxyl group molar ratio of 1.1 to 4.0, preferably,
It is carried out in the range of 1.5 to 3.5. However, the reaction itself between the polyisocyanate and the polyol may be carried out by a conventional method, and usually the polyol and polyisocyanate are reacted at a temperature of 60 to 120°C to obtain a brevolimer having terminal isocyanate groups.

Cast crosslinking of such a prepolymer may also be carried out by a conventional method.
A curing agent and, if necessary, a catalyst may be added to the liquid prebolymer, poured into a mold, and reacted and crosslinked at a temperature of 100 to 180°C. Therefore, conventionally known curing agents can be used as appropriate; for example, 1,4-
Bifunctional curing of butanediol, ethanediol, neobentyl glycol, hydroquinone bis(2-hydroxyethyl) ether, 3,3-dichloro-4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, etc. agents, 1.1.1- }limethylolpropane, glycerin, L2,6-hexanetriol, L
2,4-butanetriol, trimethylolethane, L
LI-tris(hydroxyethoxymethyl)propane,
Trihydric and higher polyhydric alcohols such as diglycerin and pentaerythritol, aminopolyhydric alcohols such as triethanolamine, triisopropanolamine, and diisopropanolamine, and alkylene oxides with these polyfunctional compounds, e.g. ethylene oxide,
An amino polyhydric alcohol obtained by ring-opening polymerization of propylene oxide or a mixture thereof is used.

In the present invention, dihydric alcohol and trihydric alcohol are preferably used together as the curing agent. However, 3
When using too much alcohol, it lowers the impact resilience of the resulting elastomer at low temperatures, so it is usually
It is used in an amount of 40 mol% or less based on the total amount of dihydric alcohol and trihydric alcohol.

These curing agents, for the urethane prepolymer,
Usually, the ratio of the active hydrogen of the hydroxyl group or 72 group of the polyol and curing agent to the isocyanate group of the urethane prepolymer and the number of equivalents, that is, the active hydrogen/isocyanate group equivalent ratio is 0.8 to 0.95. It is blended as follows.

After the primary crosslinking as described above, secondary crosslinking is performed according to a conventional method,
After ripening, it is cut to meet the specifications of the electrophotographic copying machine used and used as cleaning blades.

According to the present invention, p-phenylene diisocyanate and/or trans-1.4 cyclohexane diisocyanate having a linear and rigid molecular structure are used as the polyisocyanate component, and these are reacted with a polyol component. By curing the urethane prepolymer with a terminal isocyanate group and then curing it with a curing agent containing active hydrogen, it is possible to obtain a polyurethane elastomer with no deterioration in physical properties even at high temperatures. A cleaning blade made of elastomer has sufficient durability and practicality even in a high temperature range.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Polycaprolactone ester as polyol (Plaxel 220N manufactured by Daicel Chemical Industries, Ltd., hydroxyl value 5 6
．． 0) was dried under reduced pressure at 70°C for 3 hours. 100 parts by weight of this polyol was charged into a four-eye glass flask, and heated to 90° C. while stirring under a nitrogen atmosphere.

Next, 16 parts by weight of p-phenylene diisocyanate in flake form was charged into a flask so that the isocyanate group/hydroxyl group molar ratio was approximately 2.0, and the mixture was heated at a temperature of 90 to 100°C while stirring under a nitrogen stream. After reacting for 3 hours, a transparent and viscous prebolimer was obtained. After the reaction, the amount of residual isocyanate groups in the system was determined by back titration with hydrochloric acid using a dibutylamine-toluene solution using a conventional method, and it was found to be 3.65.
%Met.

A mixture of 1,4-butanediol/trimethylolpropane (80/20 molar ratio) was added as a curing agent to the prebolimer thus obtained so that the molar ratio of hydroxyl groups/isocyanate groups was 0.90. After reacting for a minute, the mixture was poured into a centrifugal molding machine and cured at 140°C for 1 hour to obtain a polyurethane plate. This shaped object was subjected to secondary crosslinking at 110° C. for 24 hours, and then aged for two weeks at room temperature. After that, it was cut to a predetermined size to produce a cleaning blade for an electrophotographic copying machine. .

Example 2 In Example 1, 1,4 as a curing agent was used so that the hydroxyl group/isocyanate group 9 10 molar ratio was 0.90.
-butanediol/trimethylolpropane (molar ratio 6
A cleaning blade was obtained in the same manner as in Example 1, except that 0/40) was used.

Example 3 Polycaprolactone ester as a polyol (Plaxel 22ON manufactured by Daicel Chemical Industries, Ltd., hydroxyl value 5 6
．． 0) was dried under reduced pressure at 70°C for 3 hours. 100 parts by weight of this polyol was charged into a four-eye glass flask, and heated to 90°C while stirring under a nitrogen atmosphere.

Next, dibutyltin dilaure-1-0.0 was added to the polyol in the flask as a catalyst. 0.1 part by weight was added and stirred. After that, 14 parts by weight of trans-14-cyclohexane diisocyanate was charged into the flask so that the molar ratio of isocyanate groups/hydroxyl groups was about 1.7.
The reaction was carried out at a temperature of 90 to 100° C. for 3 hours while stirring under a nitrogen stream to obtain a transparent and viscous prebolimer. The amount of residual isocyanato groups in the system was 2.55%.

L4-butanediol/trimethylolpropane (
A mixture (molar ratio 80/20) was added and reacted for 2 minutes.

Thereafter, in the same manner as in Example 1, a cleaning blade for an electrophotographic copying machine was manufactured.

Example 4 In Example 3, 1,4-butanediol/trimethylolpropane (molar ratio 60/4) was used as a curing agent so that the hydroxyl group/isocyanate group molar ratio was 0.90.
A cleaning blade was obtained in the same manner as in Example 3, except that 0) was used.

Comparative Example 1 Polycaprolactone ester as a polyol (Plaxel 220N manufactured by Daicel Chemical Industries, Ltd., hydroxyl value 5 6
．． 0> was dried under reduced pressure at 70°C for 3 hours. 100 parts by weight of this polyol was charged into a four-eye glass flask and maintained at 70°C.

Next, 42 parts by weight of 4,4'-diphenylmethane diisocyanate was put into the flask so that the molar ratio of isocyanate groups/hydroxyl groups was approximately If 12 3.4, and the mixture was heated at 70 to 80°C while stirring under a nitrogen stream. The reaction was carried out at a temperature of 3 hours to obtain a transparent and viscous prebolimer.

The amount of residual isocyanate groups in the system was 7.1%.

A compound of 1,4-butanediol/trimethylolpropane (molar ratio 80/20) 11 was added as a curing agent so that the hydroxyl group/isocyanate group molar ratio was 0.90 in the thus obtained prebolimer. In addition,
The reaction was allowed to proceed for 2 minutes.

Thereafter, in the same manner as in Example 1, a cleaning blade for an electrophotographic copying machine was manufactured.

Comparative Example 2 In Comparative Example 1, 1,4-butanediol/trimethylolpropane (molar ratio 60/4) was used as a curing agent so that the hydroxyl group/isocyanate group molar ratio was 0.90.
A cleaning blade was obtained in the same manner as in Comparative Example 1 except that Comparative Example 1 was used.

Physical properties of each of the cleaning blades obtained as described above at initial temperature and at 50°C, and at 120°C.
Table 1 shows the physical properties after holding for 10 days.

Physical properties at 50°C were measured in an atmosphere at 50°C after the sample was left in an atmosphere at 50°C for 2 hours or more. 120℃
The physical properties were measured after the sample was left in an atmosphere at 120° C. for IO days and then left at room temperature for 2 hours or more.

In addition, a continuous copying test using an actual machine was conducted to determine the number of continuous copies until a defective image appeared and the amount of wear on the cleaning blade. The results are shown in Table 1. In addition, Example 1,
3 and Comparative Example 1, Examples 2 and 4, and Comparative Example 2 are values measured using different copying machines.

Claims (1)

[Claims] (1) p-phenylene diisocyanate and trans-1
, 4-cyclohexane diisocyanate and a polyol at an isocyanate group/hydroxyl group molar ratio of 1.1 to 4.0. An electrophotographic product characterized in that the urethane prepolymer obtained by reacting 4-cyclohexane diisocyanate with a polyol is cured with a curing agent. Cleaning blade for copying machines.