JPH0535110A - Manufacture of foamed body for roll - Google Patents

Abstract

PURPOSE:To obtain a foamed body for a roll which is electrostatically controlled, has a smooth thin film on a surface and is improved in film strength by taking out a cylindrical body consisting of cured foamed body from a mold and coating the surface of the foamed body to form a coating film. CONSTITUTION:At first a mixture contg. a compound containing not less than two active hydrogen, a compound having no less than two isocianate group and a catalyst is mechanically agitated to form a foamed body. For these compound, a polyol or polyisocianate used for producting general soft polyurethane foam or a urethane elastmer foam can be used. Obtained foamed body is pressed into mold 4 having an air vent opening 5 and let it cure. Thus produced roll consists of a cylindrical body 2 with the cured foamed body formed around a shaft 1 and a self film, i.e., a thin skin 2A formed on the surface, and forming of the foamed body keeping low density is easy because a coating film 3 is formed at the outermost layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive material used for electrostatically controlling an object such as a toner carrying roller, a charging roller, a transfer roller and a cleaning roller in a printer for electrophotography, electrostatic recording and the like. The present invention relates to a method for producing a foam for a roller used for a roller.

[0002]

2. Description of the Related Art Toner prepared in a conventional toner cartridge is supplied to a photosensitive member on which an electrostatic latent image is formed,
The electrophotographic process of transferring and fixing on paper is generally composed of charging, photosensing, developing, transferring, fixing, and neutralizing mechanisms, and each mechanism uses various rollers for precisely controlling static electricity. The required properties for the roller material are becoming more and more severe. In particular, the roller used in the developing mechanism including the roller for toner transportation, the charging roller, the transfer roller, and the roller used in the cleaning mechanism electrostatically control the contacted object, so that the material of the roller is not conductive. It is required that the level of non-charging is controlled within a narrow range (one digit at 5 ° C to 45 ° C, for example, 1 × 10 ⁹ Ω · cm to 1 × 10 ¹⁰ Ω · cm).
In addition, these rollers are made of a conductive elastic material for the purpose of not damaging the other party by contact with precision parts such as a photosensitive drum, or increasing the contact area of the roller for accurate gripping. In particular, the use of foam has been investigated because it can reduce the compression hardness. However,
A roller made of foam generally sets a core metal on a block-shaped foam and grinds the surface of the roller to form a shape, so the surface of the final product becomes porous, and in a micro portion like a charging roller. When it was necessary to control static electricity, there was a problem with the roughness of the cells of the foam exposed on the surface. In order to solve such a problem, Japanese Patent Laid-Open No. 61-150370 discloses a conventional technique in which a shaft is arranged at the center of a cylindrical molding die and a mixture of a polyol, an isocyanate, a foaming agent and the like is provided around the shaft. It has been proposed to use a technique of so-called integral skin foam, in which the leather-like skin and the elastic foam are simultaneously molded by injecting and then foaming. As another solution, there are proposed a method of coating a roller having a porous surface, a method of manufacturing a roller having a porous surface and then covering it with a tubular surface layer, and a method of covering with a shrink tube. .

[0003]

In the method using the integral skin foam technique, the boundary of the surface skin with the internal foam part is not clear, and it is particularly noticeable in a roller for a printer having a small roller diameter. In order to obtain the desired roller surface, the entire surface is in a high-density skin state, and the effect of decreasing the hardness described above cannot be expected. In addition, such integral skin foam technology is a production technology such as the sealing property of the mold with the shaft set, because the liquid foamable mixture is injected into the mold to foam and the skin is formed at the mold temperature and the mold pressure. However, in the case of vertical foaming in order to prevent air entrapment, there is a problem that a density difference (hardness difference) occurs between the upper side and the lower side. In addition, the method of coating on a porous surface has a drawback that the surface unevenness finally remains and the desired smoothness cannot be obtained. Furthermore, in the method of covering the tube, in addition to the complexity of creating a tube having a diameter corresponding to the roller diameter, the cost increases due to an increase in the steps of coating and bonding, and a tubular material that does not impair the hardness of the foam. Material of
There was a difficulty in selecting the thickness.

Therefore, the present invention has a thin film having a smooth surface, a low hardness, a close contact with a contacted part at a microscopic portion, and a long-term electrostatic control which enables electrostatic control. It is an object of the present invention to provide a method for manufacturing a foam for a roller, which has improved strength.

[0005]

In order to achieve the above object, the present invention provides a compound containing two or more active hydrogens, a compound having two or more isocyanate groups, a catalyst, a foam stabilizer and the like. A step of foaming a mixture containing a substance by mechanical stirring to form a foam body, a step of press-fitting the foam body and a cylindrical mold having no dividing line on the cylindrical inner peripheral surface to cure the foam body, and curing And removing the cylindrical body made of the foamed body from the mold and coating the surface of the cylindrical body to form a coating film.

[0006]

In the present invention, a smooth thin skin (film) can be formed on the surface while maintaining a low density, and by applying a coating film, abrasion can be prevented and film strength can be improved in long-term use. Moreover, since the coating film is applied to the surface of the smooth skin, the roller surface becomes smooth.

[0007]

EXAMPLES The present invention will be described in more detail below. First, a mixture containing two or more active hydrogen-containing compounds, two or more isocyanate group-containing compounds and a catalyst was bubbled by mechanical stirring to obtain a mixture. To form a foam. Here, the compound containing two or more active hydrogens (polyhydroxyl compound) is a polyol used in the production of general flexible polyurethane foams and urethane elastomers, that is, polyether polyols having terminal hydroxyl groups, polyester polyols and both. In addition to the polyether polyester polyol which is a copolymer of the above, general polyols such as a so-called polymer polyol obtained by polymerizing an ethylenically unsaturated monomer in the polyol can be used. Also,
As the compound having two or more isocyanate groups (polyisocyanate compound), a polyisocyanate used for the production of general flexible polyurethane foams and urethane elastomers can be used as well. That is, tolylene diisocyanate (TDI), crude TDI, 4,4-diphenylmethane diisocyanate (MDI), crude MD
I, an alicyclic polyisocyanate having 2 to 18 carbon atoms, an aromatic polyisocyanate having 8 to 15 carbon atoms, and a mixture or modified product of these polyisocyanates, for example, a prepolymer obtained by partially reacting with a polyol, etc. Used. These can be used in usual amounts.

As the catalyst used in the present invention, amine-based catalysts and organometallic catalysts generally used in the production of polyurethane foam can be used, but they are used until they are foamed by mechanical stirring and then pressed into a mold. To prevent inconvenient thickening, etc. within the working time 1,8
-Using a retarding catalyst such as an aromatic sulfonate of diazabicyclo [5.4.0] undecene-7, especially 1,8 diazabicyclo [5.4.0] undecene-7
The combined use of (DBU) aromatic sulfonate and an organometallic catalyst is recommended. Thus, by using both catalysts in combination, stabilization of pot life and rapidity of heat curing can be achieved at the same time. In this case, when the aromatic sulfonic acid salt of DBU is used alone, the heat-curing property is poor and it may not be possible to obtain a foam having good physical properties. On the other hand, when the organometallic catalyst is used alone, May have a shorter pot life.

Examples of the aromatic sulfonic acid which forms a salt with DBU are benzene sulfonic acid having a benzene nucleus such as benzene sulfonic acid, toluene sulfonic acid and xylene sulfonic acid, and naphthalene skeleton such as propylnaphthalene sulfonic acid. And a sulfonic acid having a sulfonic acid, etc., and can be used in the form of an aromatic sulfonic acid ester such as methyl toluene sulfonate.

On the other hand, as the organic metal catalyst, an organic tin compound is particularly preferably used. Preferred organotin compounds include tin (II) salts of carboxylic acids such as tin acetate (I).
I), tin (II) octoate, tin (II) ethylhexoate, tin (II) laurate, etc., and further tin (IV) compounds such as dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate. Dibutyltin dilaurate, dibutyltin maleate, dioctyltin diacetate and the like.

The amount of DBU to be used with the aromatic sulfonate and the organometallic catalyst is appropriately selected, but to 100 parts of the compound containing 2 or more active hydrogens (parts by weight, the same applies to the above), the amount of DBU 0.01 to 5 parts of aromatic sulfonate,
It is particularly preferably 0.1 to 1 part, and the organometallic catalyst is preferably 0.0001 to 1 part, and particularly preferably 0.001 to 0.2 part. The combined ratio of the aromatic sulfonate of DBU and the organic metal catalyst is 1: 100 to 50000:
It is preferably set to 1, particularly 1: 2 to 1000: 1.

Further, in the present invention, if necessary, silicone type foam stabilizers, flame retardants, organic fillers, inorganic fillers, pigments, plasticizers, and auxiliary foaming such as chlorofluorocarbon and methylene chloride, which are used in ordinary polyurethane foams. Agents and the like can be added.

The invention provides a foam obtained by bubbling a mixture containing a compound containing two or more active hydrogens as described above, a compound having two or more isocyanate groups, a catalyst and other additives by mechanical stirring. Forming a body, this foam can be formed by uniformly dispersing an inert gas in the mixture by a known method. The inert gas used here is air, C
Examples thereof include O ₂ gas and N ₂ gas.

In the present invention, the foam thus obtained is press-fitted into a mold having an air vent to cure the foam in the mold. In this case, the method of the present invention can be suitably used for molding a long and slender tubular body, and in particular, has a length of about 100 to 300 mm and an outer diameter of 5 to 30 mm.
It can be molded by preventing defects such as voids.

Here, the pressure for pressing the foam into the mold is not less than atmospheric pressure, preferably 2 to 5 atm.
If the pressure is less than atmospheric pressure, a void-like defect will occur when a slender tubular body is molded. In addition, the method of press-fitting is not particularly limited, but it is possible to press-fit into the mold with a hose or the like by utilizing the pressure of a pump or the discharge pressure of a stirrer.

As shown in FIG. 1, the mold has an air vent 6, and the air vent 6 allows the foam to smoothly replace air in the cylindrical portion 4 of the mold. It is possible to prevent the occurrence of defects such as voids in the product. The position, size, number, shape, etc. of the air bleeding port 6 are not particularly limited, but it is generally preferable that the air bleeding port 6 is provided on the opposite side of the cavity from the foam body introduction port 5, that is, at the position where the foam body is finally filled. The shape of the hole of the air vent port 6 on the surface may be circular, square, or any other suitable shape.
Generally, the area of each hole is preferably in the range of 0.5 to ² mm ² . Further, since the cylindrical portion 4 having no dividing line on the cylindrical surface is integrally molded with the shaft 1 and then pulled out and removed from the mold, the cylindrical portion 4 can be separated from the portion holding the cylindrical portion 4 as shown in FIG.

Further, the heat curing can be carried out under the usual conditions, for example, the condition of heating at a temperature of 50 to 120 ° C. for 5 to 20 minutes can be adopted.

The foam thus obtained can have foams of various densities by selecting the amount of foam during foam formation. In particular, the method of the present invention is 0.2 to 0.8 g / cm ^3.
It is suitably adopted when obtaining a foam having a density of. When coating after demolding, the paint should have a JIS A hardness of 70 ° or less and a thickness of 300 μm or less, preferably 50 to 100 μm so as not to increase the surface hardness of the roller. Polyurethane is suitable for the material of the paint in terms of hardness and strength, but the material is not limited to this. The roller thus manufactured is shown in FIG. A cylindrical body 2 made of a cured foam is formed around the shaft 1, a self-coating film, that is, a thin skin 2A is formed on the surface thereof, and a coating film 3 is formed on the outermost layer.

Production Example 1 Propylene oxide and ethylene oxide were added to glycerin as a compound containing two or more active hydrogens, and a molecular weight of 5000 was obtained. Polyether polyol (Exenol 828 manufactured by Asahi Glass Co., Ltd.) 100 parts, 1,4- Butanediol (manufactured by Toyo Soda Co., Ltd.) 7.5 parts, urethane-modified MD as a compound having two or more isocyanate groups
50 parts (Sumijour PF, manufactured by Sumitomo Bayern),
Silicon-based surfactant (manufactured by Nippon Unicar, SZ161
8) 1.5 parts, as a catalyst, 0.5 parts of toluenesulfonate of 1.8-diazabicyclo [5.4.0] undecene-7 and 0.0015 parts of dibutyltin dilaurate, and an average particle size of 2. Natural graphite with a fixed carbon content of 99% of 5 μm (high-purity graphite AOP manufactured by Nippon Graphite Co., Ltd.) 5
0 part was frothed with a frothing and pouring machine manufactured by MONDOMIX Co., and a cylindrical roller was molded from this froth using the mold shown in FIG. The inner diameter of the cylindrical portion 4 in FIG. 1 is 16 mm,
The length was 23 cm, the shaft 1 had a diameter of 8 mm and a length of 25 cm. By press-fitting the foam into the mold, the air in the mold is smoothly replaced with the foam, and after the foam is filled in the mold, the foam is filled with 80
By curing at 10 ° C. for 10 minutes, an elongated cylindrical body having void-free fine cells could be molded with a smooth skin 2A on the surface. Since this smooth skin 2A is thin and has no strength, when a flexible urethane coating is applied,
Self-forming skin 2A with almost no penetration into the interior
It was possible to form a smooth coating film 3 that was integrated with, and the strength was also improved. The coating film 3 was prepared by reacting 100 g of Sannix PP-2000 manufactured by Sanyo Kasei Co., Ltd. and 53 g of pure MDI manufactured by Nippon Polyurethane Co., Ltd. at 80 ° C. for 5 hours to prepare a prepolymer having an NCO% of 9%. 1.) A mixture of 40 parts of graphite-made AOP was added to 1.
14.6 g of 4-butadiol was further mixed and applied to the above roller, and cured at 80 ° C. for 1 hour to form a coating film 3.
The thickness of the coating film 3 was 50 μm. Further, in order to further improve the surface smoothness in the post-coating and to prevent defects such as pinholes on the surface, a cylindrical portion 4 having a Teflon finish on the inner surface is used. After dip coating, dry, assemble the mold in the same way, press in the foamed material,
After heating at 80 ° C. for 10 minutes, the upper lid having the air vent port 6 is removed, and the cured foam is pulled out together with the shaft 1, and the burr at the air vent port 6 and the burr at the foam port 5 are cut to obtain a surface roughness. A product of 5 μm was obtained. This product has a coating 3 with a smooth surface as the outermost layer, and a self-forming skin 2 on the inside.
A is a sponge roller with a skin having a surface layer (coating 3) that is integrated and flexible (Asker C hardness 40 °) and is most suitable for a transfer roller or the like.

[0019]

As described above, according to the present invention, a coating film is formed on the surface of a cured foam which is not a porous surface on which a smooth thin skin which is self-formed is formed. A foam having a low density can be easily molded, the surface is smooth, the strength of the surface layer is improved, and abrasion during long-term use is prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one step of a manufacturing process.

FIG. 2 is a sectional view of the manufactured roller.

[Explanation of symbols]

2 cylindrical body 2A skin 3 paint film

Claims (3)

[Claims] 1. A foam is formed by mechanically agitating a mixture containing a compound containing two or more active hydrogens, a compound having two or more isocyanate groups, and an additive such as a catalyst and a foam stabilizer. The steps, the step of press-fitting the foam and the cylindrical mold having no dividing line on the inner peripheral surface of the cylinder to cure the foam, and the step of removing the cylinder made of the cured foam from the mold and A method for producing a foam for a roller, which comprises a step of coating the surface to form a coating film. 2. The method for producing a foam for a roller according to claim 1, wherein a conductive powder such as conductive carbon or graphite is mixed in the foam. 3. The method for producing a foam for a roller according to claim 1, wherein a conductive powder such as conductive carbon or graphite is mixed in the coating material.