JPS5991473A - Cleaning blade for electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To obtain a cleaning blade scarcely varying due to temperature of a physical property and having durability by using polyurethane which uses 1, 6- hexanediole and neopentyl glycol in the ratio within a specified range as a polyole raw material of polyurethane rubber. CONSTITUTION:A blade is prepared with urethane rubber being a reaction formation product of polyester of 1,000-4,000 mean molecular weight consisting of glycol having 9/1-5/5 mol ratio of 1, 6-hexanediole and neopentyl glycol and adipic acid, and a polyisocyanate. As for polyurethane rubber which uses 1, 6 hexanediole and neopentyl glycol within a range of 9/1-5/5 in the mol ratio, repulsive elasticity and a varition of Young's modulus due to a temperature are pretty small, and an almost satisfactory result is obtained within a range of 0-50 deg.C. When only 1, 6-hexanediol is used, the crystalizing tendency is strong, therefore, the low temperature characteristic is deteriorated although the mechanical strength is large enough.

Description

DETAILED DESCRIPTION OF THE INVENTION A number of toners are applied to the electrostatic latent image formed on the surface of the photoconductor after transfer to a sheet such as an IE (the residual toner is rubbed with the surface of the photoconductor). The first properties required of a cleaning blade are high mechanical strength, small change in strength, Hydrolysis resistance G is reduced by 1/1 and has excellent meson resistance.

Currently, polyethylene adipate ester is used as the polyol raw material for polyurethane currently used in cleaning blades, and polyurethane using this polyol does not fully satisfy the above-mentioned properties. In particular, the large temperature dependence and poor added hydrohydration IQγ properties cause many problems.

Inside an electrophotographic copying machine, a large amount of heat is emitted from the exposure lamp, fuser, etc., and the temperature is usually S~λθC higher than the environmental temperature, and the environmental humidity ranges from low humidity and low temperature in winter to summer. Since the temperature changes from θ to J left C left position up to the high humidity and high temperature of the period, it is a practical problem if the characteristics of the blade change greatly due to such changes in temperature and humidity.

Polyurethane rubber is significantly different from other general rubbers in that it depends primarily on mechanical and physical properties, or intermolecular cohesive force, and its h properties change greatly when the temperature changes. In particular, temperature dependence is largely controlled by the type of polyol forming the soft segment.

The present invention uses polyol raw materials for polyurethane rubber/
The above problem can be solved by using a polyurethane containing hexanediol and neopentyl glycol in a molar ratio of 9/I to 515.

The polyurethane rubber used in the following tests was made mainly of polyethylene adipate, adipate of O-hexanediol and neopendel glycol, and diphenylmethane-tac-diisocyanate as incyanate, and as a curing agent, coubutanediol and tritriol. Methylolpropane was also used.

Clarification of Specification (No change in content) As shown in the table above, polyurethane rubber based on polyethylene adipate has a large change in repulsion tensile strength and Young's modulus depending on temperature. Ot,' has extremely low elasticity and adhesion with the photoreceptor becomes a problem, and the Young's modulus is much higher than at normal humidity, so the pressure when pressing the plate becomes high and the contact angle becomes larger than the crotch d1 value. This may result in abnormal noises or poor cleaning. In 30C, the repulsion elasticity becomes (6), which causes bounce phenomenon and abnormal noise, and a decrease in Young's modulus causes the contact pressure between the cleaning blade and the photoreceptor to decrease, which reduces the force of the cleaning blade and reduces the toner's ability to clean. The bales become easier after passing through Play F and the photoreceptor.

On the other hand, in the polyurethane rubber of the present invention using hexanediol and neopentyl glycol in a molar ratio of 9/1 to 515, the impact resilience and Young's modulus change with humidity compared to polyethylene adipate-based polyurethane rubber. It is considerably smaller than that, and almost satisfactory results can be obtained in the range of θ to SOC. However, in the case where O-hexanediol and neopentyl glycol were used in a molar ratio of 3=7, the rebound resilience of the SOC increased and abnormal noise was generated. Furthermore, due to the increased number of methyl groups, the physical properties are poor and it is unsuitable for blades.

/, Otsu - When only hexanediol is used, there is a strong tendency to crystallize, so the mechanical strength is sufficiently high, but the low temperature properties deteriorate ○/, Otsu - Neopentyl glycol is used in common with hexanediol. By doing so, the effect of hindering crystallization of the methyl group is produced, the low temperature properties are improved, and changes in properties due to temperature can be reduced.

Another disadvantage of polyurethane rubber is that it has poor water resistance. For urethane rubber based on polyethylene adipate basetel, it has been observed that if 2 to 9 years have passed since the cleaning blade was manufactured, hydrolysis (W) has progressed, although this varies depending on the usage conditions. be done. This is molecular cleavage of the ester bond to -1-,
This is because the process progresses gradually at first, but once it has progressed to a certain extent, the organic acid produced by hydrolysis becomes an accelerator and rapidly deteriorates. If the hydrolysis has progressed, it becomes soft in the summer and lacks strength, making it impossible to obtain a sufficient cleaning effect, and in the winter, the elasticity decreases due to crystallization, resulting in insufficient cleaning.

In order to compare the hydrolysis resistance, a small amount of water was placed at the bottom of a sealed container, the sample was hung on top of the container so as not to come into direct contact with water, and the result was kept at 70C for 3S. Changes in physical properties are shown in the table below.

As shown in the table above, hexanediol and neopentyl glycol 9:/ is highly hydrolyzed resistant to polyurethane rubber based on polyethylene glycol adivate ester. The reason for this is thought to be that the degree of ester bond a'p is lower in the present invention and steric hindrance is caused by the neopentyl glycolzmethyl group.

Conventionally, injection molding is a common processing method for manufacturing cleaning blades.
It is obtained by adding a curing agent to a prepolymer obtained by reacting a polyisocyanate with a polyester treated with IBM® in a process of crosslinking.At this time, if the molecular fi of polynisder is less than 10θθ, a curing agent is added to the prepolymer and a curing agent is added. There is a drawback that the reaction rate is too fast and injection molding cannot be completed completely.
If it is more than that, the viscosity of the polyester will be too high, and the crosslinking reaction will occur, resulting in slow curing, and the defoaming will be insufficient, resulting in lack of bubbles on the blade surface.

As described above, according to the present invention, it is possible to provide a durable cleaning blade whose physical properties change little due to turbidity.

Applicant: Hokushin Kogyo Co., Ltd. Agent, Patent attorney's patent application amendment (method): 1982 Special Edition Application No. λθ Cog No. 07 No. 2, Title of invention: Cleaning blade for electrophotographic copying machine 3, Case of person making an amendment Applicant 4, Agent 5, Date of amendment order 1 February 2, 1950 6, Number of inventions increased by amendment 7, Subject of amendment

Claims (1)

[Claims] (11/, Otsu-hekinanediol and nemepentyl)
The 6-sensitized gel is composed of a polyester with an average molecular weight of 1,000 to tioθO, which has a recall molar ratio of 9/1 to 515, and has an average molecular weight of 1000 to tioθO, and a urethane coat that is the reaction product of polyynocyanate. Clean the surface by rubbing it. Cleaning blade for photocopiers.