JPH06248174A - Polymer composition and roll with layer of the composition - Google Patents

Abstract

PURPOSE:To prevent the bleeding of a conducting agent comprising an alkali metal salt into dew by incorporating the conducting agent into a specific polyurethane. CONSTITUTION:100 pts.wt. polyurethane elastomer obtained by reacting a polyol comprising a polyether polyol or polyester polyol with a polyisocyanate in such a proportion that the NCO to OH ratio is 0.7-1 is mixed with 0.1-1.0 pt.wt. alkali metal salt as a conducting agent to obtain the objective composition. A conductive elastomer layer made of the composition and having a hardness of 15-50 deg. is formed on the surface of a metal core, thereby giving a roll having a volume resistivity of 8X10<4> to 5X10<7>OMEGA.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer composition comprising a polyol containing a polyether polyol or a polyester polyol and a polyisocyanate and containing a conductive agent. It also relates to a roll having a layer of the composition formed on the surface of a cored bar, and particularly to a roll used in an electrophotographic copying machine.

[0002]

2. Description of the Related Art A material obtained by blending a polymer compound with a conductive compound, which has an electric resistance value of about 5 × 10 ⁵ to 5 × 10 ⁷ Ω, is a conductive or semi-conductive material (hereinafter referred to as “ The term “conductive” is sometimes used instead of “conductive or semi-conductive”) has been widely known before the filing of the present application. As the polymer compound, a resin such as a thermoplastic resin or a thermosetting resin or an elastomer is used, and by making good use of the characteristics of each resin, an article having a useful conductive molded body or conductive layer is used. Is manufactured. Among them, polyurethane, in particular, a polyurethane polymer composed of a polyol including a polyether polyol or a polyester polyol and a polyisocyanate has characteristics, handleability,
It is advantageous in terms of price, etc., and it is especially widely used.

Conventionally, conductive particles such as copper powder and carbon black have been widely used as a conductive agent to be mixed with the polymer compound constituting the conductive material.
However, when the conductive agent is blended with a polymer compound, the electrical resistance of the composition varies greatly, which is not practical.

It has been attempted to use various antistatic agents or highly dielectric liquids as conductive agents, but the conductive materials obtained by blending these conductive agents have electric resistance values. In addition to being unstable, there are still problems such as surface contamination due to seepage of the conductive agent.

Alkali metal salts have been proposed as a new conductive agent that solves these problems. Among them, lithium perchlorate is excellent in that it has a small variation in conductivity, provides a stable electric resistance value, and avoids the problem of contamination due to seepage of the conductive agent.

However, the Applicant has found that the conductive agent, particularly lithium perchlorate, is a high molecular compound such as polyurethane prepared from a mixture of a polyol and polyisocyanate having an NCO / OH of 1 or more. It has been found that the alkali metal salt is likely to be deposited on the surface of the polymer compound especially when dew condensation is caused when it is blended with.

[0007]

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a polyurethane composition which solves the above-mentioned drawbacks and can prevent the deposition of a conductive agent even when dew condensation occurs.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been proposed to achieve the above-mentioned object, and is a polyurethane produced from an excess of a polyol and a polyisocyanate, particularly, as the polyol, a polyether polyol. Or, when the alkali metal salt is blended in the polyurethane obtained by using the polyester polyol,
It is based on the finding that the precipitation of the metal salt is prevented.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in more detail below. One feature of the present invention is that a polyol containing a polyether polyol or a polyester polyol is used as a polyol for producing polyurethane. In addition, a polyol containing a cyclic polyether is used. The cyclic polyether means a cyclic compound containing an oxygen atom. Among these cyclic polyethers, for example, hydrophobic cyclic polyethers having a solubility in water of about 0.5% or less are more preferable. An example of this cyclic polyether is a cyclic polyether in which tetrahydrofuran and propylene oxide are alternately bonded.

Examples of the polyether polyol include polyalkylene glycol, polytetramethylene ether glycol, which is known as polyethylene glycol, polypropylene glycol, polypropylene glycol-ethylene glycol or a blend thereof, and a copolymer of tetrahydrofuran and alkylene oxide. Examples thereof include polymerized polyols, various modified products thereof, and blends thereof.

Examples of the polyester polyols include condensed polyester polyols obtained by condensing dicarboxylic acids such as adipic acid and glycols such as ethylene glycol, lactone polyester polyols, polycarbonate polyols, and blends thereof. In the present invention, known polyols other than the above-mentioned polyols may coexist as long as the initial purpose is not impaired.

Another compound used in the formation of polyurethane is polyisocyanate. The polyisocyanate may be any polyisocyanate as long as it is commonly used in the preparation of polyurethane.

In the present invention, in the reaction of the polyisocyanate and the polyol, it is important to adjust the polyol so as to be in excess with respect to the polyisocyanate. That is, the NCO / OH is adjusted to be 0.7 or more and less than 1 and further 0.75 to 0.95. If the NCO / OH is out of the above range, the blended alkali metal salt is likely to be deposited, which causes problems such as contamination.

A known auxiliary agent may be present during the reaction of the polyol and the polyisocyanate. Examples of these auxiliaries include chain extenders and crosslinking agents. Specific examples include glycols, hexanetriol, trimethylolpropane, and amines.

One feature is that an alkali metal salt is used as the compound that imparts conductivity. As the alkali metal salt, lithium, sodium and potassium salts are known, and the lithium salt is particularly preferable. Also,
Halogen oxyacid salts, perhalogen oxyacid salts, thiocyanates, phosphates and the like are used, but lithium perchlorate is particularly preferable. The amount of the alkali metal salt added is usually in the range of 0.1 to 1.0 part by weight based on 100 parts by weight of the urethane elastic body.

The above compounds can be mixed by a known method to prepare the polymer composition of the present invention. Then, an electrically conductive molded article or an article having an electrically conductive coating layer can be produced from the polymer composition of the present invention by a known method. Examples of the molded article or the article having the coating layer include an antistatic film, a conductive belt, an antistatic housing, a cord having an antistatic layer, and a conductive roll.

The polymer composition of the present invention is particularly useful for producing a conductive roll. Hereinafter, the conductive roll will be described in detail. The conductive roll is usually
It is composed of a core shaft and a conductive layer formed on the shaft, particularly a conductive elastic layer.

The conductive roll is formed on an arbitrary core metal surface,
It can be produced by forming a conductive layer obtained from the polymer composition. For example, in the present invention, it is preferable to form the conductive layer by adopting a known one-shot method or a prepolymer method. The conductivity hardness is preferably 15 to 50 ° (JIS A), more preferably 25 to 45 ° (JIS A). Hardness
If it exceeds 50 ° (JIS A), there is a defect that a sufficient nip width cannot be secured, and the hardness is 15 ° (JIS A
) It is not preferable because the mechanical strength is reduced if it is below.

A surface layer containing polyamide or polyurethane may be formed on the surface of the elastic body formed on the surface of the cored bar.

The electroconductive roll thus obtained has a volume resistance of 8 × 10 ⁴ to 5 × 10 ⁷ Ω at all from low temperature and low humidity (25% at 5 ° C.) to high temperature and high humidity (80% at 30 ° C.).
It is preferable to set it so that it falls within the range.

The conductive roll thus obtained is suitably used, for example, as a charging roll, a transfer roll, a developing roll, a cleaning roll and the like in an electrophotographic copying machine.

[0022]

Since the polymer composition of the present invention uses an alkali metal salt as a conductive agent, it is possible to provide a conductive material having a uniform electric resistance value.
Moreover, the alkali metal salt blended in the composition is not deposited even in an environment where a large amount of water is present, such as when dew condensation occurs. Therefore, the polymer composition of the present invention makes it possible to produce an article having a conductive molded body or a conductive coating layer which has a stable electric resistance value and does not contaminate a contacted partner. Became. In particular, the polymer composition of the present invention is useful as a conductive roll, and more particularly as a charging roll. By using an electrophotographic copying machine using the roll, it has become possible to obtain a high-quality printed image with no black streaks even in a high temperature and high humidity atmosphere.

[0023]

The present invention will be described in more detail with reference to the following examples, but it goes without saying that the present invention is not limited to these examples. Example 1 0.5 parts by weight of lithium perchlorate was added to 100 parts by weight of polyether polyol (trade name: PPTG2000, Hodogaya Chemical Co., Ltd.), and the mixture was stirred and dissolved, then the temperature was adjusted to 100 ° C., and then polyisocyanate (product Name: Coronate-HX, manufactured by Nippon Polyurethane Co., Ltd.) 15 parts by weight are added and stirred, and NCO / OH = 0.
A mixture of 75 was obtained. This mixture was poured into a mold preheated to 120 ° C where the shaft (φ: 6 mm, l: 240 mm) was placed in advance, and heated at 120 ° C for 90 minutes, and the surface of the shaft excluding both ends was A roll on which the conductive polyurethane elastic layer was formed was obtained.

This roll was allowed to stand for 2 weeks in an atmosphere of 50 ° C. and 90% RH, but no deposition of lithium perchlorate was observed on the roll surface. Using this roll as a charging roll for the surface of the photoreceptor, a printed image was obtained by a conventional electrophotographic method. The measurement results are shown in Table 1.

Example 2 Polyester polyol (trade name: Clapol P-2010,
(Kuraray Co., Ltd.) 0.5 part by weight of lithium perchlorate was added to 100 parts by weight of the mixture, and the mixture was stirred and dissolved, then the temperature was adjusted to 90 ° C., and then 15.5 parts by weight of polyisocyanate (trade name: Coronate-HX) was added and stirred to obtain NCO / A mixture of OH = 0.78 was obtained. This mixture was poured into a mold preheated to 130 ° C, where a shaft (φ: 6 mm, l: 240 mm) was placed in advance, and the mixture was heated to 130 ° C.
Was heated for 60 minutes to obtain a roll having a conductive polyurethane layer formed on the shaft surface excluding both ends.

When this roll was left in an atmosphere of 50 ° C. and 90% RH for 2 weeks, no deposition of lithium perchlorate was observed on the roll surface. This roll was used as a charging roll for the surface of the photoconductor in the same manner as in Example 1, and a printed image was obtained by a conventional electrophotographic method. The measurement results are shown in Table 1.

Comparative Example 1 Polyisocyanate (trade name: Coronate-HX) 20
A roll was obtained by performing the same operation as in Example 2 except that a part by weight was used and a mixture of NCO / OH = 1.00 was obtained. When this roll was left in an atmosphere of 50 ° C. and 90% RH for only 30 minutes, precipitation of lithium perchlorate was observed from the roll surface. Using a roll different from this left roll as a charging roll, the same operation as in Example 1 was carried out to obtain a printed image. The results are shown in Table 1.

[0028] * In the column of the surface condition of the roll, "○" indicates a state in which precipitation of the alkali metal salt was not found, and "x" indicates a state in which precipitation of the alkali metal salt was observed. * "○" in the image column indicates that the image of the copy is good, and "X" indicates that black lines are observed in the image of the copy.

Claims (2)

[Claims] 1. A polymer composition comprising a polyol containing a polyether polyol or a polyester polyol and a polyisocyanate, and containing a conductive agent,
A polymer composition, wherein the conductive agent comprises an alkali metal salt, and the polymer composition has an OH / NCO ratio of 0.7 or more and less than 1. 2. A roll having a core bar on which a layer comprising the composition of claim 1 is formed.