JP5610957B2 - Method for producing polyurethane foam roller - Google Patents

Description

  The present invention relates to a method for manufacturing a polyurethane foam roller used in an electrophotographic copying machine or the like, which has a core metal and two polyurethane foam layers formed on the outer peripheral surface of the core metal.

  Conventionally, a developing roller, a charging roller, a toner supply roller, a transfer roller, a cleaning roller, and the like used in an image forming apparatus such as a copying apparatus, an image recording apparatus, a printer, and a facsimile are provided on the outer periphery of a shaft core body such as a metal. An elastic roller in which various materials having functions such as elasticity, conductivity, and air permeability are arranged is used.

  For example, in a developing device that develops an electrostatic latent image formed on a photosensitive drum, a toner having a function of supplying and scraping toner to the developing roller and supplying the toner uniformly onto the developing roller A supply roller is used. As the toner supply roller, a polyurethane foam roller is generally used because appropriate flexibility and good surface cell opening are required.

  The toner supply performance and scraping performance of the toner supply roller greatly affect the characteristics such as the surface smoothness and hardness of the elastic layer, and these characteristics are very important for obtaining a good image. For example, Patent Document 1 and Patent Document 2 control the average cell diameter and the number of cells on the surface of the foamed elastic layer, the thickness of the wall between the cells, and the like, so that the toner deteriorates or the toner remaining on the developing roller surface is insufficiently scraped. The toner supply roller which does not generate | occur | produce is proposed. Also, by controlling the density and breathability of the foamed elastic layer and reducing the entry of toner into the foamed elastic layer, it prevents the foamed elastic layer from becoming hard due to long-term use and maintains appropriate flexibility. A toner supply roller that can be used is proposed.

  In addition, the foamed elastic layer of the toner supply roller is also important for the cell structure on the surface and inside, and in order to satisfy each of them well in a balanced manner, the foam layer has a multilayer structure in which the inner layer and the outer layer have different cell structures. A toner supply roller having an elastic layer has been studied. For example, in Patent Document 3, first, a roller having an inner layer is formed on the outer periphery of a core metal using a first mold having a molding cavity large enough to give an inner layer, and then a molding cavity large enough to give an outer layer is formed. The roller with the inner layer is disposed in the molding cavity using the second molding die having the outer layer, and the outer layer is integrally formed around the inner layer by introducing a predetermined polyurethane raw material and performing foam molding. A manufacturing method is proposed. However, when the outer layer is foam-molded on the outer periphery of the roller with the inner layer, air inside the inner layer may enter the outer layer portion, leading to foaming defects such as voids and air accumulation, and further, the outer layer material enters the inner layer surface. As a result, there is a problem that the hardness between the two layers becomes high and the flexibility as the urethane foam layer is lacking.

  Patent Document 4 proposes a method of manufacturing a toner supply roller by cutting out inner layer and outer layer materials from separately prepared sponge blocks to form inner and outer layers, and bonding the layers with an adhesive. ing. However, this manufacturing method has a problem of delamination due to long-term use, in addition to the extremely troublesome formation of a two-layer structure by an adhesive.

JP 2006-292909 A JP 2001-290363 A JP 2000-104728 A Japanese Patent Laid-Open No. 7-036273

  An object of the present invention is to provide a polyurethane foam roller having two polyurethane foam layers in which the cells at the boundary between the inner layer and the outer layer of the polyurethane foam layer are formed in a continuous cell structure and have no problems such as delamination. It is in.

The object is achieved by the following present inventions [1] to [3] .
[1] A roller molding die formed of a cylindrical member, an upper piece member having a cored bar holding part, a lower bar member having a cored bar holding part and a foaming material injection hole, In a method for manufacturing a polyurethane foam roller, in which a polyurethane foam layer is formed on the outer peripheral surface of a core metal by using a foam molding apparatus having a foam material receiving portion that can be attached to and detached from the piece member, the core metal includes an upper piece member and a lower piece. In the state of being held by the member, the step of separating the two types of polyurethane foam materials into the lower layer and the upper layer in the foam material receiving portion and then bonding the foam material receiving portion to the lower piece member, and the upper layer polyurethane foam material as a roller Forming a polyurethane foam layer on the inner wall surface of the cylindrical member by foam injection into the molding die, and then injecting the lower polyurethane foam material into the roller molding die by foam injection; Forming an inner layer of polyurethane foam layer between the gold and the outer layer, the cell boundary of the outer layer and the inner layer, in the manufacturing method of the polyurethane foam rollers having a continuous cell structure toward the outer from the inner layer A method for producing a polyurethane foam roller, wherein the cream time A of the polyurethane foam material of the upper layer and the cream time B of the polyurethane foam material of the lower layer satisfy the relationship of A ≦ B.
[2] The method for producing a polyurethane foam roller according to [1], wherein the polyurethane foam material of the upper layer has a cream time A of 5 to 20 seconds.
[3] The cream time A of the polyurethane foam material of the upper layer and the cream time B of the polyurethane foam material of the lower layer satisfy the relationship of 0 <BA−10 (seconds) [1] Or the manufacturing method of the polyurethane foam roller as described in [2] .

  According to the present invention, it is possible to obtain a polyurethane foam roller having a two-layer polyurethane foam layer in which cells at the boundary between the inner layer and the outer layer of the polyurethane foam layer are formed in a continuous cell structure and have no problems such as delamination. it can.

It is the schematic of the conventional metal mold | die for roller molding. It is a figure which shows the manufacture procedure of this invention. It is a figure explaining the material foaming state of this invention

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.
The present invention comprises a roller molding die formed of a cylindrical member, an upper piece member having a cored bar holding part, a cored bar holding part and a lower piece member having a foaming material injection hole, In a method for manufacturing a polyurethane foam roller in which a polyurethane foam layer is formed on the outer peripheral surface of a core metal by using a foam molding apparatus having a foam material receiving part that can be attached to and detached from the lower piece member, the core metal is attached to the upper piece member and the lower piece member. A process of joining the foam material receiving portion to the lower piece member after separating and arranging two types of polyurethane foam materials into the lower layer and the upper layer in the foam material receiving portion while being held by the piece member, Forming a polyurethane foam layer on the inner wall surface of the cylindrical member by injecting foam into the roller mold, and then injecting and injecting the lower polyurethane foam material into the roller mold The step of forming an inner layer of a polyurethane foam layer between the core metal and the outer layer has a cell structure in which cells at the boundary between the inner layer and the outer layer have a continuous cell structure from the inner layer toward the outer layer. It is a manufacturing method of a polyurethane foam roller.

(Roller mold)
As shown in FIG. 1, a foam molding apparatus according to the present invention includes a roller molding die formed of an upper piece member 3 and a lower piece member 4 each having a holding portion for a cylindrical member 1 and a core metal 2, and casting. The foam material receiving portion 5 for receiving the foam material discharged from the machine is fitted and connected to the lower piece member, and the foam material is injected from the injection hole 6 of the lower piece member.

  Each member of the roller molding die is not particularly limited. In addition to a metal member obtained by plating a steel material such as iron with nickel or chromium, a metal member such as iron, copper, aluminum, stainless steel, polycarbonate, Synthetic resins such as polyamide and ceramics can be used as appropriate.

  The inner diameter of the cylindrical member requires higher precision when the molded product is extracted from the mold and does not require surface polishing / grinding. It is not always necessary to have high accuracy.

(Foam material)
The raw material for forming the polyurethane foam layer is a polyurethane raw material containing polyol, polyisocyanate, catalyst, foam stabilizer and the like.

  There is no restriction | limiting in particular as a polyol, It can select and use suitably from conventionally well-known various polyols as a raw material of a polyurethane foam. For example, it can be appropriately selected from known polyols such as polyether polyols, polyester polyols, polymer polyols, etc., which are generally used for the production of flexible polyurethane foams, and can be used alone or in combination of two or more. Can be used.

  Of the above polyols, polyether polyols are suitable for producing soft, highly elastic polyurethane foams having excellent heat and heat resistance. Further, a prepolymer polymerized with polyisocyanate in advance may be used as a polyol.

  Moreover, there is no restriction | limiting in particular as polyisocyanate, It can select suitably from conventionally well-known various polyisocyanate as a raw material of a polyurethane foam, and can use it. For example, the following compounds can be used alone or in combination of two or more. 2,4- and 2,6-tolylene diisocyanate (TDI), tolidine diisocyanate (TODI), naphthylene diisocyanate (NDI), xylylene diisocyanate (XDI), 4,4'-diphenylmethane diisocyanate (MDI), and carbodiimide modification MDI, polymethylene polyphenyl polyisocyanate, polymeric polyisocyanate, etc. In addition, the isocyanate group terminal prepolymer obtained by making polyisocyanate react with 1 type, or 2 or more types of a well-known active hydrogen compound can also be used as polyisocyanate.

  Examples of other raw materials for polyurethane foam that can be appropriately used as necessary include the following.

  There is no restriction | limiting in particular as a catalyst, It can select from the conventionally well-known various catalysts suitably, and can be used. Conventionally known catalysts in the field of polyurethane foam production such as triethylenediamine, dimethylethanolamine, bis (dimethylamino) ethyl ether can be used.

  There is no restriction | limiting in particular as a foam stabilizer, It can select from the conventionally well-known various foam stabilizer in the field | area of polyurethane foam manufacture, and can use it. For example, silicone surfactants such as SRX-274C, L-5309, L-520, etc. (all trade names) manufactured by Toray Dow Corning Silicone may be used.

  Moreover, a crosslinking agent, a foaming agent (water, low boiling point, gas body, etc.), a foam breaker, etc. are added to the polyurethane raw material in which these polyol component and polyisocyanate component are blended in the same manner as in the past. Can do. At this time, the structure of the polyurethane foam layer after foam molding, that is, a known foaming composition that is easy to produce either an open-cell type or a closed-cell type is added, and a reactive foam raw material is added. Is done. In addition, known materials such as a conductivity-imparting agent and an antistatic agent for imparting desired conductivity are added to such raw materials as necessary. As the conductivity-imparting agent, known materials can be used. For example, conductive metal oxides such as carbon black, graphite, titanium oxide and tin oxide, metals such as Cu and Ag, and conductive materials such as these can be used on the particle surface. And particles made conductive by coating. These conductivity-imparting agents can be used alone or in combination.

  In particular, carbon black is preferable in that desired conductivity can be imparted by adding a relatively small amount (mass ratio). As other additives, flame retardants, thickeners, pigments, stabilizers, colorants, anti-aging agents, ultraviolet absorbers, antioxidants, antioxidants and the like can be blended as necessary. Examples of the crosslinking agent include conventionally known ones such as triethanolamine and diethanolamine.

  In the present invention, first, a polyurethane foam material is prepared by mixing homogeneously polyurethane raw materials such as polyol, polyisocyanate, catalyst, foam stabilizer, water, and other auxiliary agents used as required. There are no particular restrictions on the temperature and time for mixing the raw materials. The mixing temperature is usually in the range of 10 to 90 ° C., preferably 20 to 60 ° C., and the mixing time is usually 1 second to 10 minutes, depending on the structure of the mixing unit normally used, the rotation conditions, etc. Preferably, it is about 3 seconds to 5 minutes.

(Separate arrangement of upper and lower layers)
The prepared polyurethane foam material is discharged from the casting machine and filled into the foam material receiving portion. There are two types of polyurethane foam materials, one for the outer layer and one for the inner layer, and each polyurethane foam material is arranged separately in a two-layer state of a lower layer and an upper layer in the foam material receiving part. For example, as shown in FIG. 2, the separation arrangement is performed by first filling the polyurethane foam material 7 for the inner layer into the lower layer of the foam material liquid receiving portion 5 and then filling the polyurethane foam material 8 for the outer layer. Each polyurethane foam material can be disposed separately in upper and lower layers in the foam material receiving portion.

  If the polyurethane foam material placed in the upper layer has a higher density than the polyurethane foam material placed in the lower layer, foaming is performed before filling the foam material receiving portion, such as by increasing the mixing time of the polyurethane foam material in the upper layer. It can arrange | position to an upper layer by advancing reaction and making a density small. When the density of the polyurethane foam material disposed in the lower layer is large, even if two types of polyurethane foam materials are filled in the foam material receiving portion at the same time, the higher density is quickly disposed below, so Separate arrangement is possible.

  Typical foaming conditions of the polyurethane foam material for each layer are as follows. The upper polyurethane foam material is one that has been previously prepared to foam, and the lower polyurethane foam material is one that has been prepared to subsequently foam.

(Formation of outer layer)
When two types of polyurethane foam materials are separated and arranged in the upper and lower layers in the foam material receiving portion, and the foam material receiving portion is joined to the lower piece member of the roller molding die, the polyurethane foam material arranged in the upper layer precedes, Foam is injected into the roller mold from the injection hole. Here, the foam injection means that the polyurethane foam material starts to foam in the foam material receiving portion, and the foam is injected into the roller molding die. The state where the foaming of the material continues is also included.

  In the roller molding die, as shown in FIG. 3, the polyurethane foam material 7 disposed in the upper layer of the foam material receiving portion 5 is filled into the cylindrical member 1. The polyurethane foam material 7 in the vicinity of the inner wall surface of the cylindrical member has a low flow rate due to the resistance of the wall surface, and is further stagnated on the wall surface side by being heated from the mold side and proceeding with the curing reaction. Form.

(Formation of inner layer)
The polyurethane foam material 8 disposed in the lower layer of the foam material receiving portion 5 is foamed between the core metal 2 and the outer layer because the outer layer is formed in the vicinity of the inner wall surface when the foam is injected into the mold. Then, the inner layer of the polyurethane foam roller is formed.

  In the polyurethane foam roller manufactured by the foam injection process, two types of polyurethane foam materials are mixed at the boundary between the inner layer and the outer layer during the foam curing reaction (gel state). As a result, the cells at the boundary between the inner layer and the outer layer can have a continuous cell structure from the inner layer toward the outer layer.

(Cream time)
In forming the polyurethane foam layer in the present invention, if the lower polyurethane foam material starts the foaming reaction before the upper polyurethane foam material in the foam material receiving portion, the following problems may occur. That is, the polyurethane foam material arranged in the lower layer may involve the polyurethane foam material arranged in the upper layer, and in particular, when a material such as a conductivity imparting agent is used, desired conductivity may not be obtained. is there.

  Therefore, the reaction rate of each polyurethane foam material, particularly the cream time, which is the time from mixing the polyol component, polyisocyanate component, and catalyst to the start of foaming (rise), is an indicator of the reaction rate. In the present invention, it is preferable that the cream time A of the polyurethane foam material in the upper layer portion and the cream time B of the polyurethane foam material in the lower layer portion satisfy the relationship of A ≦ B. The polyurethane foam material disposed in the upper layer is foam-injected into the cylindrical member in advance, thereby forming a two-layer polyurethane foam layer that does not cause the above problem.

  The cream time A of the upper polyurethane foam material is preferably 5 to 20 seconds. If it is less than 5 seconds, the foaming reaction starts after filling the foamed material receiving portion with the polyurethane foam material and before the foamed material receiving portion is joined to the lower piece member, and the polyurethane foamed material from within the foamed material receiving portion. May overflow. Further, if the time is longer than 20 seconds, the reactivity is slowed down, so that the foam may be broken due to insufficient strength when removed from the roller molding die.

  Furthermore, it is desirable that the cream time A of the upper polyurethane foam material and the cream time B of the lower polyurethane foam material satisfy the relationship of 0 <B−A ≦ 10 (seconds). If it is longer than 10 seconds, the lower layer polyurethane foam material is not subsequently foam-infused with respect to the upper layer polyurethane foam material previously foam-injected into the cylindrical member. An overpack rate may fall and a desired material density may not be obtained. In some cases, foaming failure such as cell roughening occurs. The cream time can be adjusted to the above range by adjusting the reaction temperature, raw material temperature, stirring conditions, catalyst type, and the like.

(Application of roller)
The polyurethane foam roller having the polyurethane foam layer formed by the production method of the present invention can be used as an elastic roller such as a charging roller, a developing roller, a transfer roller, or a cleaning roller. Preferably, the toner supply roller is optimally used. The toner supply roller is a developing device that develops an electrostatic latent image formed on the photosensitive drum, and is required to have a function of supplying the toner to the developing roller and scraping the toner to uniformly supply the toner onto the developing roller. It is done. For this reason, characteristics such as the average cell diameter and the number of cells on the outer surface of the polyurethane foam layer, which is in contact with the developing roller, are important. Affects takeability. Therefore, when the polyurethane foam layer is divided into two layers, the above-mentioned required characteristics are shared between the outer layer and the inner layer, so that the characteristics of the entire urethane foam layer can be more satisfied when compared with a single layer structure.

  Hereinafter, the present invention will be described specifically by way of examples.

(Examples 1-7 and Reference Example 1 )
Formed by holding an iron cylindrical member with an inner diameter of 14.5 mm and a length of 260 mm and a stainless steel core (outer diameter of 5 mm and length of 270 mm) held by an upper piece member and a lower piece member. A roller molding die (shape shown in FIG. 3) was prepared. The lower piece member is provided with an injection hole for injecting a foam material into the cylindrical member.

  On the other hand, the premix polyol which mix | blended the polyol component of the mass part shown in Table 1 as a polyurethane foam material for outer layers, and was stirred and mixed for 5 to 30 minutes was prepared. Similarly, a premix polyol for the inner layer was prepared using the polyol component in parts by mass shown in Table 2, and each premix polyol and polyisocyanate were placed in a casting machine tank. Next, the inner layer premix polyol and polyisocyanate weighed so as to have an NCO index of 80 are stirred and mixed in the casting machine head with the stirring time shown in Table 3 to prepare the polyurethane foam material B for the inner layer. Then, the foamed material receiving portion was filled in 3 seconds or less. At almost the same time, a polyurethane foam material A for the outer layer having an NCO index of 100 is prepared and filled in the foam material receiving portion in 3 seconds or less. The polyurethane foam materials A and B are placed in each 3 g foam material receiving portion as a lower layer. Separated into the upper layer. Moreover, the cream time shown in Table 3 was adjusted by the stirring and mixing time of the premix polyol and polyisocyanate.

  The foam material receiving part was joined to the lower piece member, and the temperature of the mold was adjusted to 70 ° C. The foamed material was cured for 10 minutes in this mold for molding to produce a polyurethane foam roller. The thickness of each layer was 2.0 mm for the inner layer and 2.5 mm for the outer layer.

(Image evaluation)
The obtained polyurethane foam roller was subjected to image evaluation (ghost, solid density uniformity). The image evaluation was performed as follows. That is, the toner supply roller was incorporated in a toner cartridge of a commercially available copying machine (manufactured by Canon, LBP-2510), stored at 15 ° C. and 10% RH for 1 day, and then set in the copying machine. After printing 6000 sheets of 4% printed images at 15 ° C. and 10% RH, the images were printed using ordinary ordinary copier paper, and the ghost and density uniformity were examined visually. The image was evaluated according to the criteria. The results are summarized in Table 3.
(Double-circle): A ghost or density nonuniformity is hardly observed and is favorable.
○: There is no problem in using a ghost or a substance with slightly uneven density.
(Triangle | delta): A ghost or density unevenness is seen a little, and it is a grade which is worrisome to use.
X: Ghost or density unevenness is observed and cannot be used.

  As is clear from the results in Table 3, in any of the examples, the ghost or density unevenness was a good result, and the supply and scraping of the toner to the developing roller functioned stably.

  In Example 6, since the cream time (reactivity) of the material forming the outer layer of the polyurethane foam is delayed, there is a portion where the foam is partially broken due to insufficient strength when removed from the roller mold. It was. In addition, slight density unevenness was observed in the image area corresponding to the portion. Moreover, about Example 7, the cell roughening phenomenon was partially seen, and as a result, the density unevenness was somewhat seen.

(Comparative Examples 1 and 2)
In Comparative Example 1, only the polyurethane foam material for the outer layer of Example 1 was used, and in Comparative Example 2, only the polyurethane foam material for the inner layer of Example 1 was used. A polyurethane foam roller was created. Other molding conditions were the same as in Example 1. Table 3 shows the image evaluation results performed in the same manner as in Example 1.

  In Comparative Example 1, the hardness of the entire foam was higher than that of the two-layer structure, the rubbing force with the developing roller was increased, toner deterioration was promoted, and the density was lowered. In Comparative Example 2, the scraping property of the toner was lowered due to the large cell diameter of the outermost surface of the urethane foam layer and the low hardness of the entire foam, and as a result, ghost defects were observed.

(Comparative Example 3)
A polyurethane foam layer prepared under the same conditions as in Comparative Example 2 was polished to a diameter of 9 mm. This was placed in the same roller molding die as in Comparative Example 2, and the foamed polyurethane foam material forming the outer layer was foamed and molded to form the outer layer integrally around the inner layer 2 A layered polyurethane foam roller was prepared. Table 3 shows the image evaluation results performed in the same manner as in Example 1.

  When the outer layer was foam-molded on the roller with the inner layer, the air inside the inner layer entered the outer layer portion, and foam defects in the air pool were confirmed. Further, the outer layer material enters the inner layer surface, thereby increasing the hardness between the layers and increasing the hardness of the entire foam. As a result, in the image evaluation, ghosts and uneven density were remarkably observed.

(Comparative Example 4)
A polyurethane foam layer prepared under the same conditions as in Comparative Example 2 was polished to a diameter of 9 mm. Further, the polyurethane foam material forming the outer layer was cut into a cylindrical shape having an inner diameter of 8.5 mm and an outer diameter of 14 mm, and this was covered with the polyurethane foam layer to prepare a polyurethane foam roller having a two-layer structure. Table 3 shows the image evaluation results performed in the same manner as in Example 1.

  When the urethane foam roller after image evaluation was observed, delamination was partially observed, and the partial increase in the hardness of the foam due to the stagnation of the toner in the gap resulted in density unevenness.

DESCRIPTION OF SYMBOLS 1 ... Cylindrical member 2 ... Core metal 3 ... Upper piece member 4 ... Lower piece member 5 ... Polyurethane foam material receiving part 6 ... Injection hole 7 ... Lower layer polyurethane foam material 8 ... Upper layer polyurethane foam material

Claims (3)

A roller molding die formed of a cylindrical member, an upper piece member having a cored bar holding part, a lower bar member having a cored bar holding part and a foaming material injection hole, and the lower piece member In a method for producing a polyurethane foam roller, a polyurethane foam layer is formed on the outer peripheral surface of the core metal using a foam molding apparatus having a removable foam material receiving portion.
In a state where the core metal is held by the upper piece member and the lower piece member, two kinds of polyurethane foam materials are separately arranged in the lower layer and the upper layer in the foam material receiving portion, and then the foam material receiving portion is coupled to the lower piece member. Process,
Forming an outer layer of a polyurethane foam layer on the inner wall surface of the cylindrical member by foam-injecting an upper layer polyurethane foam material into a roller molding die;
Next, foaming and injecting a lower polyurethane foam material into the roller molding die to form an inner layer of a polyurethane foam layer between the core metal and the outer layer,
The cell of the boundary portion between the inner layer and the outer layer is a method for producing a polyurethane foam roller having a continuous cell structure from the inner layer toward the outer layer ,
A process for producing a polyurethane foam roller, wherein the cream time A of the upper polyurethane foam material and the cream time B of the lower polyurethane foam material satisfy the relationship of A ≦ B. The method for producing a polyurethane foam roller according to claim 1 , wherein the cream time A of the polyurethane foam material of the upper layer is 5 to 20 seconds. And cream time A of the upper layer of polyurethane foam, cream time B of the lower layer of polyurethane foam material, 0 <according to claim 1 or 2, characterized by satisfying the relationship of B-A ≦ 10 (sec) Manufacturing method of polyurethane foam roller.

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