JPH0149409B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a cleaning blade for an electrophotographic copying machine that uses plain paper as a recording paper by rubbing the surface of a photoreceptor to clean it. The present invention relates to a high-performance cleaning blade for electrophotographic copying machines, which has a shore hardness of 50 to 80, preferably 65 to 75, has high impact resilience at low temperatures, and has extremely small hole distortion. (Prior Art) According to an electrostatic electrophotographic copying machine that uses plain paper as recording paper, an electrostatic latent image is generally created by applying an electrostatic charge to the surface of a photoreceptor 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 to which the toner image has been transferred is heated, and the toner image is transferred to the recording paper. Copying is done by fixing the information on recording paper. Therefore, in order to sequentially copy onto multiple sheets of recording paper, in the above steps,
After the toner image is transferred from the photoreceptor to the recording paper, it is necessary to remove the toner remaining on the surface of the photoreceptor, and one way to remove it is to constantly press a blade against the surface of the photoreceptor at a certain angle. However, a blade cleaning method is known in which the photoreceptor is cleaned by rubbing. The blade material for this blade cleaning method has particularly good mechanical strength such as wear resistance.
Urethane rubber is preferably used. Here, since the blade is always pressed against the photoreceptor at a certain angle, it is required to have appropriate hardness.However, on the other hand, permanent deformation usually occurs during long-term use, and the pressure contact Since the force is reduced and the cleaning function is reduced, it is required that the permanent deformation is small. Generally, permanent elongation can be reduced by reducing the hardness of the resulting molded product, but if the hardness is too low,
Not suitable for use as a blade. To this end, it has been proposed to obtain low permanent set polyurethane molded articles by using special diols, such as hydroquinone bis(2-hydroxyethyl) ether, in combination with ordinary diol-based curing agents. However, compositions containing a urethane prepolymer and the above diol curing agent have a short pot life and are poor in workability. It has also been proposed to obtain low-distortion polyurethane molded products by using a trifunctional curing agent such as trimethylolpropane in combination with a normal diol-based hardening agent; It has low hardness and is not suitable for manufacturing cleaning blades. Furthermore, the permanent deformation of the molded product is still large. Furthermore, if the impact resilience at low temperatures is small, the friction between the blade and the photoreceptor is large, resulting in poor cleaning. (Object of the Invention) As a result of intensive research to solve the problems with the conventional cleaning blade for electrophotographic copying machines made of polyurethane as described above, the present inventors have found that, in particular, the cleaning blade for curing urethane prepolymer As an agent, vicinal diols and 3
By using a curing agent containing a predetermined proportion of a polyfunctional curing agent with a functional or higher functionality, it has an appropriate hardness, that is, Shore A hardness of 50 to 80, preferably 65 to 75, and has a small permanent deformation. In addition, it is possible to obtain a cleaning blade for an electrophotographic copying machine that has high rebound resilience at low temperatures, and therefore has the necessary and appropriate hardness for pressure contact with the surface of a photoreceptor, and is durable for long-term use. The present invention was based on the discovery that it has a stable and excellent cleaning function. (Structure of the Invention) The cleaning blade for an electrophotographic copying machine according to the present invention comprises 100 parts by weight of a urethane prepolymer consisting of a polyol and a polyisocyanate having a molecular weight of 1000 to 10000, and (a) a diol curing agent having no vicinal hydroxyl group.
50 to 90 mol%, (b) diol curing agent having vicinal hydroxyl group 5
It is characterized by curing a composition containing 5 to 20 parts by weight of a curing agent consisting of ~25 mol % and (c) 5 to 25 mol % of a trifunctional or higher polyfunctional curing agent. In the present invention, the polyols used in the preparation of the urethane prepolymer include glycols such as ethylene glycol, butylene glycol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, or neopentyl glycol, either alone or in mixtures. polyester polyol consisting of a divalent organic acid having 2 to 6 carbon atoms,
For example, polyethylene adipate ester polyol, polyethylene butylene adipate ester polyol, polycaprolactone ester polyol obtained by ring-opening polymerization of caprolactone, polycarbonate ester polyol, and polyether polyol, such as poly(oxytetramethylene).
Examples include glycol, polyoxypropylene glycol, and the like. The above polyol needs to have a molecular weight in the range of 1,000 to 10,000. If the molecular weight of the polyol is less than 1,000, the resulting cleaning blade for an electrophotographic copying machine will have poor low-temperature properties, while if it exceeds 10,000, permanent deformation will increase. The polyisocyanate to be reacted with the above polyol is not particularly limited, but typical examples include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, naphthalene-1,5-diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. can. A composition for a cleaning blade for an electrophotographic copying machine according to the present invention contains the above-mentioned urethane prepolymer and a curing agent as main components, and includes:
The curing agent is (a) a diol-based curing agent that does not have vicinal hydroxyl groups;
50 to 90 mol% (b) Diol curing agent having vicinal hydroxyl group 5
25 mol % and (c) 5 to 25 mol % of a trifunctional or higher polyfunctional curing agent. First, a diol-based curing agent that does not have a vicinal hydroxyl group is a curing agent that has been commonly used in the past for manufacturing various polyurethane molded products. 3-butanediol, 1,4-
Butanediol, diethylene glycol, 1,5
-Pentanediol, 1,6-hexanediol, neopentyl glycol, etc. are used. In the present invention, this curing agent is blended in the curing agent mixture in an amount of 50 to 90 mol%. If the amount is less than 50 mol%, the final cleaning blade for an electrophotographic copying machine will have poor low-temperature properties, and if it is more than 90 mol%, the permanent deformation will be large. Next, the diol curing agent having a vicinal hydroxyl group is an aliphatic diol having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and preferably ethanediol, 1,2-propanediol, 2,3-butanediol. Diols and the like are used. The curing agent comprises 5% of the curing agent mixture.
It is used in a range of ~25 mol%. This curing agent is
By shortening the distance between the carbon chains between the crosslinking points of the urethane prepolymer and increasing the crosslinking density,
The permanent deformation of the obtained molded product can be reduced, and the hardness can be adjusted to a Shore hardness of 50 to 80, preferably 65 to 75, which is appropriate for cleaning blades. Therefore, when the amount of the curing agent is less than 5 mol %, the resulting cleaning blade for an electrophotographic copying machine has a large permanent deformation and a low hardness. On the other hand, if it is added in a large amount exceeding 25 mol%, the permanent elongation can be reduced, but the low temperature properties deteriorate and the hardness falls below the above range, making it difficult to manufacture cleaning blades. It's inappropriate. In addition, examples of trifunctional or higher polyfunctional curing agents include 1,1,1-trimethylolpropane, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, and trimethylolethane. , 1,1,1-tris(hydroxyethoxymethyl)propane, diglycerin, pentaerythritol, ring-opened polymer of caprolactam with trimethylolpropane (for example, commercially available as Plaxel 308AL from Daicel Chemical Industries, Ltd.). trihydric and higher polyhydric alcohols such as trihydric and higher polyhydric alcohols, aminopolyhydric alcohols such as triethanolamine, triisopropanolamine, diisopropanolamine, etc., and alkylene oxides such as ethylene oxide, propylene oxide, or polyfunctional compounds thereof. Examples include amino polyhydric alcohols obtained by ring-opening polymerization of mixtures of these. These polyfunctional curing agents are used in a range of 5 to 25 mol%. This curing agent is used to improve the mold releasability when molding the composition described above, and is used in an amount of 5 mol%.
If the amount is less than 25% by mole, the mold releasability will not be good, while if the amount is more than 25 mol %, the resulting molded product will have low impact resilience at low temperatures. Further, in the present invention, the curing agent made of the above mixture is blended in an amount of 5 to 20 parts by weight per 100 parts by weight of the urethane prepolymer. When the amount is less than 5 parts by weight, the hardness is too low, while when it is more than 20 parts by weight, the hardness is too high, making it particularly unsuitable for manufacturing cleaning blades for electrophotographic copying machines. The cleaning blade for an electrophotographic copying machine according to the present invention is prepared by mixing the dehydrated polyol and polyisocyanate and cleaning the mixture at a temperature of 70 to 150°C.
It can be obtained by reacting for ~180 minutes to obtain a urethane prepolymer, then adding the above-mentioned curing agent to this urethane prepolymer and curing it according to a conventional method. Incidentally, the composition consisting of the above-mentioned urethane prepolymer and curing agent is usually
It is liquid. More specifically, the cleaning blade according to the present invention is capable of applying a liquid composition comprising the urethane prepolymer and a curing agent to a desired mold using, for example, an injection molding method, an extrusion molding method, a centrifugal casting method, or a desired mold. After molding into a plate shape by casting, it is heat treated and aged to produce rubber for cleaning blades. The plate-shaped cleaning blade rubber thus obtained is cut to meet the specifications of the electrophotographic copying machine used, and is used as a cleaning blade for the electrophotographic copying machine. (Effects of the Invention) As described above, the cleaning blade for an electrophotographic copying machine according to the present invention comprises a urethane prepolymer composed of a polyol and a polyisocyanate having a molecular weight of 1,000 to 10,000, and a diol-based curing agent having a vicinal hydroxyl group as a curing agent. Since it is obtained by curing a composition containing as main components a curing agent and a curing agent including a trifunctional or higher polyfunctional curing agent, it has a high crosslinking density and Shore A hardness of 50 to 80, preferably 65 to 75.
It has high impact resilience at low temperatures and extremely low permanent deformation. Therefore, such a cleaning blade has appropriate hardness and high rebound resilience at low temperatures, and
Since the permanent deformation is extremely small, it stably maintains an excellent cleaning function even if it is pressed against the surface of a photoreceptor at a certain angle for a long period of time. (Example) Examples of the present invention are shown below together with comparative examples. Example 1 (1) Preparation of urethane prepolymer As shown in the table, polyol (molecular weight 2000) and diisocyanate were mixed and heated at 80°C.
A urethane prepolymer was obtained by reacting for 120 minutes. (2) Preparation of urethane rubber and production of cleaning blade A predetermined amount of curing agent was added to each of the above urethane prepolymers as shown in the table, and the mixture was mixed and reacted at 110° C. for 2 minutes. The obtained liquid rubber composition is pre-applied.
Injected into a mold heated to 150℃, 2 hours later

【table】

[Table] The solidified rubber plate was taken out from the mold, heat treated in a heating furnace at a temperature of 120°C for 8 hours, and then aged at room temperature for 7 days to obtain a urethane rubber plate with a thickness of 3.0 mm. The pot life of the mixture of urethane prepolymer and curing agent obtained as described above and the physical properties of the urethane rubber plate are shown in the table. Comparative Examples 1 and 2 contain hydroquinone bis(2-hydroxyethyl) ether as a curing agent,
The hardness of the molded product obtained is within an appropriate range, but
The permanent elongation at 200% elongation (the same applies hereinafter) is also large, and the pot life of the composition is also short. Comparative Examples 3 and 4 contain a trifunctional curing agent as a curing agent, and although the permanent elongation is somewhat improved, the hardness of the resulting molded product is significantly reduced. Furthermore, the pot life of the composition is short. In contrast, according to the present invention, the composition used has a long pot life and excellent workability, and the molded product obtained has extremely low permanent elongation.
Moreover, the hardness is also appropriate. Furthermore, it has high impact resilience at low temperatures. Therefore, the cleaning blade according to the present invention made of such polyurethane stably maintains an excellent cleaning blade function even if it is pressed against the surface of the photoreceptor at a certain angle for a long period of time.

Claims (1)

[Claims] 1. Urethane prepolymer 100 consisting of polyol and polyisocyanate having a molecular weight of 1,000 to 10,000
Part by weight and (a) Diol curing agent without vicinal hydroxyl group
50 to 90 mol%, (b) diol curing agent having vicinal hydroxyl group 5
A cleaning blade for an electrophotographic copying machine obtained by curing a composition containing 5 to 20 parts by weight of a curing agent consisting of ~25 mol% and (c) a trifunctional or higher polyfunctional curing agent.