JPH02284191A - Cleaning blade for electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To obtain a cleaning blade having proper impact resilience even in the range of low temperatures by hardening a urethane polymer obtained by reacting plyester-polyol produced by opening a lactone ring with polyisocyanate. CONSTITUTION:The material of the cleaning blade is obtained by using as a polyol component, the polyester-polyol produced by opening the lactone ring and substituted by lower alkyl groups, and as the isocyanate component, phenylenediisocyanate and the like having linear rigid molecular structure, reacting them, and hardening the obtained reaction product with a hardener, thus permitting the obtained resin to have a hardness of 65 - 80, an impact resilience of 25 - 70%, and a glass transition point of <=-10 deg.C, and a accordingly, the obtained cleaning blade to be superior in cleaning performance even at low temperatures.

Description

[Detailed description of the invention] ■■Ribun on the peel! The present invention relates to a cleaning blade for electrophotographic copying machines that is made of polyurethane and has a small rate of change in impact resilience with respect to temperature. Repulsion elasticity is 25
Cleaning for electrophotographic copying machines in the range of ~70%
Regarding blades.

According to an electrostatic electrophotographic copying machine that uses distorted plain paper as recording paper, an electrostatic latent image is generally formed by applying an electrostatic charge to the surface of a photoconductor by discharging and then exposing an image thereon. Next, toner with opposite polarity is attached to the electrostatic latent image and developed, and the toner image is transferred to recording paper.Finally, the recording paper with the toner image transferred is heated to remove the toner. A copy is made by fixing it 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 molded product made of polyurethane is preferably used as a blade for this blade cleaning method because it has particularly excellent mechanical strength such as wear resistance.

Traditionally, such polyurethanes have generally been made from commercially available polyols, such as polyester polyols such as polyethylene adipate ester polyol, polyethylene butylene adipate ester polyol, caprolactone ester polyol, or polyether polyols such as polyoxypropylene glycol, and 414'-diphenylmethane. It is produced by reaction with polyisocyanates such as diisocyanates.

Such conventional cleaning blades have a large rate of change in repulsion resiliency with respect to temperature, and typically the repulsion resiliency changes over a range of 10 to 85% in a temperature range of 0 to 60°C. For example, a blade obtained from polyethylene adipate and 4.4"-diphenylmethane diisocyanate has poor low-temperature properties, whereas a braid obtained from polycaprolactone ester polyol and 4.4"-diphenylmethane diisocyanate has poor low-temperature properties. However, in the temperature range of 40 to 50°C, the impact resilience is 75% or more.Normally, if the impact resilience is less than 20%, the cleaning performance will be significantly reduced, whereas if it is 70% or more, the cleaning performance will decrease significantly. When the blade presses against the surface of the photoreceptor, an abnormal noise, so-called squeal, is produced.

Therefore, in order to improve impact resilience at low temperatures, a method has been proposed, for example, by reducing the polyisocyanate content and using a difunctional low molecular weight curing agent. The impact resilience at the blade becomes extremely high, and the blade easily becomes stale. On the other hand, in order to reduce the impact resilience at high temperatures, a method has also been proposed in which the amount of polyisocyanate used is increased and a large amount of a trifunctional or higher polyfunctional curing agent is used. According to this method, the rebound resilience at high temperatures can be reduced to some extent, but the glass transition point of the resulting elastomer increases significantly and the elastomer becomes glassy at low temperatures, making cleaning at low temperatures difficult. Characteristics deteriorate significantly.

As described above, there has been no known cleaning blade that has appropriate repulsion resiliency from a low temperature range to a high temperature range. It has also been proposed to use polycarbonate polyol in order to reduce impact resilience at high temperatures, but this significantly increases the glass transition point of the resulting Meiko lastomer.

Therefore, in order to solve this problem in cleaning blades, for example, Japanese Patent Application Laid-open No. 145274/1983 discloses that a polyol obtained by copolymerizing polyoxytetramethylene glycol and polycaprolactone ester and a polyisocyanate are used. A cleaning blade using polyurethane obtained by reaction as a material has been proposed.

The present inventors have conducted extensive research to solve the above-mentioned problems with conventional cleaning blades for electrophotographic copying machines made of polyurethane. Using a lactone ring-opened polyester polyol having an alkyl group as a substituent, using phenylene diisocyanate, naphthalene diisocyanate and/or cyclohexane diisocyanate as the polyisocyanate component, and curing the urethane prepolymer obtained by reacting these with a curing agent. By doing so, the hardness (JIS A) is in the range of 65 to 80, and the rebound resilience is in the range of 25 to 70 in the temperature range of 0 to 60°C.
% range, and furthermore, it was possible to obtain a cleaning blade having a glass transition point of 110° C. or less, leading to the present invention.

The cleaning blade for an electrophotographic copying machine according to the present invention is obtained by reacting a lactone ring-opened polyester polyol having a lower alkyl group as a substituent with phenylene diisocyanate, naphthalene diisocyanate and/or cyclohexane diisocyanate. It is characterized by being made by curing urethane prepolymer with a curing agent.

The lactone ring-opened polyester polyol having a lower alkyl group as a substituent used in the present invention includes:
For example, α-methyl-ε-caprolactone, β-methyl-ε-caprolactone, ε-methyl-ε-caprolactone, α-methyl-δ-valerolactone, β-methyl-δ
- Mention may be made of ring-opened polyester polyols such as valerolactone. These can be used alone or as a mixture of two or more.

The rebound resilience of polyurethane elastomers is related to the ease of micro-Brownian motion of soft segment chains.
The reason why rebound resilience increases in the high temperature range of 50 to 60°C is that in addition to the micro-Brownian motion of the soft segment chains, hydrogen bonding between the hard segment chains and soft segment chains and the This is because secondary bonds such as weak hydrogen bonds between the soft segment chains are broken, increasing the mobility of the soft segment chains. Therefore, in the present invention, in order to suppress the mobility of the soft segment chains as described above, a ring-opened polyester polyol of a lactone having a lower alkyl group such as a sterically hindered side chain methyl group or ethyl group is used as a polyol component. It is used.

However, for the polyol component as mentioned above, 4.4
When polyisocyanates having a bent structure such as diphenylmethane diisocyanate and tolylene diisocyanate are used as the polyisocyanate component, the resulting polyurethane elastomer does not have sufficient hardness to be used as a cleaning blade, and at high temperatures, In addition, it has high rebound resilience. Therefore, in order to increase the hardness, if the amount of polyisocyanate used is increased, the glass transition point of the resulting elastomer will be significantly lower.
At around 20°C, impact resilience decreases.

According to the present invention, by using phenylene diisocyanate, naphthalene diisocyanate, or cyclohexane diisocyanate whose molecules are linear and rigid as the polyisocyanate component constituting the hard segment, the hardness of the hard segment is increased to a hardness of 65 to 80.
and increase the cohesive force of the hard segments.
Molecular movement of the soft segment chains can be suppressed, thus making it possible to reduce the rate of change in impact resilience of polyurethane with respect to temperature. Furthermore, according to the present invention, since the polyisocyanate used has a linear and rigid structure, even if a small amount is used, the obtained elastomer has high hardness and a structure with many soft segment chains, and the elastomer has a structure with a large number of soft segment chains. The glass transition point can be kept in a sufficiently low temperature range.

From this point of view, particularly in the present invention, as the polyisocyanate, 4,4'-phenylene diisocyanate, 1,5-naphthalene diisocyanate and/or
Or 1,4-cyclohexane diisocyanate is preferably used.

The urethane prepolymer may be prepared by a conventional method, and usually the above polyol and polyisocyanate are mixed in a ratio of 60 to 1
The reaction is carried out at a temperature of 00° C. to obtain a prepolymer 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 prepolymer, poured into a mold, and crosslinked by reaction at a temperature of 100 to 180°C. Therefore, the curing agent used can be any conventionally known curing agent, for example, 1.4
-Butanediol, ethanediol, neopentyl glycol, hydroquinone -bis(2-hydroxyethyl)
Difunctional curing agents such as ether, 3.3"-dichloro-4+4"-diaminodiphenylmethane, 4,4"-diaminodiphenylmethane, 1,1.1-)limethylolpropane, glycerin, 1.2.6- Trivalent and higher polyhydric alcohols such as hexanetriol, 1,2.4-butanetriol, trimethylolethane, 1,1.1-tris(hydroxyethoxymethyl)propane, diglycerin, pentaerythritol, triethanolamine , triisopropaturamine, diisopropaturamine, etc., and amino polyhydric alcohols such as diisopropaturamine, and alkylene oxides, such as ethylene oxide, propylene oxide, or mixtures thereof, are ring-opening polymerized with these polyfunctional compounds. Polyhydric alcohols are 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 isocyanate group to the number of equivalents of active hydrogen in the hydroxyl group or amino group of the polyol and curing agent is 1.
00 to 1.50.

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 a cleaning blade.

According to the present invention, a lactone ring-opened polyester polyol having a lower alkyl group as a substituent is used as a polyol component, and phenylene diisocyanate and naphthalene having a linear and rigid molecular structure are used as a polyisocyanate component. By curing the urethane prepolymer obtained by reacting diisocyanate and/or cyclohexane diisocyanate with a curing agent, the hardness is in the range of 65 to 80, and the hardness is in the range of 0 to 80.
It is possible to obtain a cleaning blade that has rebound resilience in the range of 25 to 70% in the temperature range of 60°C, has a glass transition point of -lO°C or lower, and has excellent cleaning performance even at low temperatures. can.

Therefore, such a cleaning blade is practical in a wide temperature range, and on the other hand, there is no need to install large cooling equipment in the electrophotographic copying machine, making the electrophotographic copying machine compact and reducing its manufacturing cost. can be reduced.

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 1 100 parts by weight of polymethylvalerolactone polyol (Kuraball 2010 manufactured by Kuraray ■, hydroxyl value 56.4) was weighed into a glass flask, heated to 100°C, and p-phenylene was added to it. 16 parts by weight of diisocyanate (hydroxyl group/isocyanate group molar ratio 0.5) was added in the form of flakes at a time, and reacted while being dissolved. A urethane prepolymer was obtained by reacting at 100°C for 4 hours. The isocyanate content in this urethane prepolymer was determined to be 3.63% by a conventional diptylamine method.

The prepolymer thus obtained was heated at 100°C for 3
After defoaming under reduced pressure for 0 minutes, a mixture of 1,4-butanediol and trimethylolpropane (molar ratio 85/
15) as shown in Table 1, add 3.5 parts by weight, and add 2.
After stirring vigorously for a minute, pour into a centrifugal molding machine and
Crosslinking was carried out at 60 rpm+ for 1 hour. Thereafter, the elastomer was taken out of the mold, subjected to secondary crosslinking at 110°C for 24 hours, further aged at room temperature for 2 weeks, and cut into a predetermined size to obtain a cleaning blade.

Example 2 In Example 1, a mixture of 1,4-butanediol and trimethylolpropane (mole ratio 72
/2B) A cleaning blade was obtained in the same manner as in Example 1 except that 3.5 parts by weight was used.

Example 3 In Example 1, as a curing agent, a mixture of 1,4-butanediol and trimethylolpropane (molar ratio 60
/40) A cleaning blade was obtained in the same manner as in Example 1 except that 3.5 parts by weight was used.

Example 4 Polymethylvalerolactone polyol 1 same as Example 1
Weigh out 00 parts by weight into a glass flask and add 10 parts by weight.
After raising the temperature to 0°C, 17 parts by weight of cyclohexane diisocyanate (hydroxyl group/isocyanate group molar ratio 0.5) and 0% dibutyltin dilaurate as a catalyst were added.
．． Add 03 parts by weight and react at 100°C for 4 hours,
A urethane prepolymer was obtained. The isocyanate content in this urethane prepolymer was 3.51%.

The prepolymer thus obtained was heated at 100°C for 3
After defoaming under reduced pressure for 0 minutes, a mixture of 134-butanediol and trimethylolpropane (molar ratio 85/
15) After adding 3.5 parts by weight and stirring vigorously for 2 minutes,
In the same manner as in Example 1, centrifugal molding was performed at 150°C for 1 hour. After this, the resulting elastomer was heated at 110'C for 2
The mixture was subjected to secondary crosslinking for 0 hours, further aged for 2 weeks at room temperature, and cut into a predetermined size to obtain a cleaning blade.

Example 5 In Example 4, a mixture of 1,4-butanediol and trimethylolpropane (mole ratio 60
/40) A cleaning blade was obtained in the same manner as in Example 4, except that 3.5 parts by weight was used.

Comparative Example 1 Polymethylvalerolactone polyol 1 same as Example 1
Weigh out 00 parts by weight into a glass flask, and add 70 parts by weight.
The temperature was raised to °C. To this was added 45 parts by weight of 4.4''-diphenylmethane diisocyanate (hydroxyl group/isocyanate group molar ratio 0.2 B), and the reaction was carried out at 70°C for 3 hours to obtain a urethane prepolymer.Isocyanate in this urethane prepolymer The content is 7.34%
Met.

The prepolymer thus obtained was heated at 100°C for 3
After defoaming under reduced pressure for 0 minutes, a mixture of 1,4-butanediol and trimethylolpropane (molar ratio 85/
15) After adding 3.5 parts by weight and stirring vigorously for 2 minutes,
In the same manner as in Example 1, centrifugal molding was performed at 150°C for 1 hour. After this, the obtained elastomer was heated at 110°C for 20
The mixture was subjected to secondary crosslinking for a period of time, then aged for two weeks at room temperature, and cut into a predetermined size to obtain a cleaning blade.

Comparative Example 2 100 parts by weight of polycaprolactone polyol (Plaxel 2ON manufactured by Daicel Aji, hydroxyl value 56.0) was weighed into a glass flask, and the temperature was raised to 100°C.

To this, 4,4゛-diphenylmethane diisocyanate 1
6 parts by weight (hydroxyl group/isocyanate group molar ratio 0.5) was added and reacted at 100° C. for 4 hours to obtain a urethane prepolymer. The isocyanate content in this urethane prepolymer was 3.63%.

The prepolymer thus obtained was heated at 100°C for 3
After defoaming under reduced pressure for 0 minutes, a mixture of 1□4-butanediol and trimethylolpropane (molar ratio 85/
15) After adding 3.5 parts by weight and stirring vigorously for 2 minutes,
In the same manner as in Example 1, centrifugal molding was performed at 150°C for 1 hour. After this, the obtained elastomer was heated at 110°C for 20
The mixture was subjected to secondary crosslinking for a period of time, then aged for two weeks at room temperature, and cut into a predetermined size to obtain a cleaning blade.

Comparative Example 3 100 parts by weight of polyethylene adipate (Sannistar 2620 manufactured by Sanyo Chemical Industries, Ltd., hydroxyl value 53.1) was weighed into a glass flask, heated to 100°C, and then 17 parts by weight of cyclohexane diisocyanate was added thereto. % (hydroxyl group/isocyanate group molar ratio 0.5) and 0.03 parts by weight of dibutyltin dilaurate as a catalyst were added and reacted at 100°C for 4 hours to obtain a urethane prepolymer.

The isocyanate content in this urethane prepolymer was 3.40%.

The prepolymer thus obtained was heated at 100°C for 3
After defoaming under reduced pressure for 0 minutes, a mixture of 1,4-butanediol and trimethylolpropane (molar ratio 60/
40) After adding 3.5 parts by weight and stirring vigorously for 2 minutes,
In the same manner as in Example 1, centrifugal molding was performed at 150° C. for 1 hour. Thereafter, the obtained elastomer was subjected to secondary crosslinking at 110° C. for 20 hours, further aged at room temperature for 2 weeks, and cut into a predetermined size to obtain a cleaning blade.

Table 1 shows the hardness, impact resilience at 0 to 60''C, and glass transition point of each of the cleaning blades obtained as described above.

Note that the impact resilience was measured according to JIS K 6301.

Further, the glass transition point was determined from the peak temperature of tan δ of dynamic viscoelasticity under the conditions of 5% elongation and 10 Hz.

The cleaning blade according to Comparative Example 1 has a low impact resilience at low temperatures and a high glass transition point.

Although the blades according to Comparative Examples 2 and 3 have improved impact resilience at low temperatures, their impact resilience at high temperatures is significantly high.

On the other hand, the blade according to the present invention has the following characteristics:
It has high impact resilience at low temperatures while suppressing impact resilience at high temperatures, and its glass transition point is also well within the low temperature range.

Patent applicant Band-Kagaku Co., Ltd. Agent Patent Attorney Makino Ittobu

Claims (1)

[Claims] (1) A urethane prepolymer obtained by reacting a lactone ring-opened polyester polyol having a lower alkyl group as a substituent with phenylene diisocyanate, naphthalene diisocyanate and/or cyclohexane diisocyanate, and curing it with a curing agent. A cleaning blade for electrophotographic copying machines.