JP2005219383A - Method for producing foamed rubber roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a foamed rubber roller which can suppress the occurrence of ammonia causing a defective image when used in the member of an electrophotographic device or an electrostatic recording device. <P>SOLUTION: In the production of the foamed rubber roller, a carvone amide foaming agent and a urea-containing foaming auxiliary are used in a raw material rubber composition. The foamed rubber roller obtained by foaming/vulcanizing the rubber composition formed on the periphery of a core bar is exposed to water, heated, and dried. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a foam rubber roller, and more particularly, to production of a foam rubber roller that is suitably used as a member for an image forming apparatus such as an electrophotographic apparatus such as a copying machine, a laser printer, a facsimile, or an electrostatic recording apparatus. It is about the method.

  Rubber rollers such as charging rollers and transfer rollers used in electrophotography are required to maintain a uniform nip width by contact with a photoreceptor in order to meet the recent demand for higher speed and higher image quality. A foamed rubber roller using foamed rubber is used as an elastic body provided on the outer periphery of the cored bar.

  Conventionally, such a foam rubber roller is manufactured as follows, for example. As raw material rubber composition, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), What was kneaded by adding foaming agent, foaming aid (for example, urea), fillers such as carbon black, vulcanizing agent, vulcanization accelerator, softening agent, etc. to various raw rubbers such as chloroprene rubber (CR) Used, extruded into a predetermined shape, and then foamed and vulcanized using a foamed rubber roller or mold using foamed rubber produced by foam vulcanization using a hot blast furnace or microwave vulcanizer (UHF) A foamed rubber roller using foamed rubber produced in this manner is manufactured.

  Examples of the blowing agent used herein include a carbonamide blowing agent, p, p′-oxybisbenzenesulfonyl hydrazide (hereinafter sometimes abbreviated as “OBSH”), N, N′-dinitrosopentamethylene hydrazide. (Hereinafter, may be abbreviated as “DPT”) and the like.

  Among these, DPT is inexpensive, has a large amount of foaming gas, and is suitable for foamed rubber. However, DPT is flammable and has a risk of ignition, and forms toxic formaldehyde during foaming. It itself has been suspected of becoming mutagenic and has the disadvantage of being inferior in safety to the human body.

  In addition, OBSH is an expensive compound and has a disadvantage that it is difficult to obtain a highly foamed rubber because an acidic substance generated at the time of decomposition may cause inhibition of vulcanization because the amount of generated gas is small, and it is inferior in economy. .

  On the other hand, carbonamide-based blowing agents are widely used because they are inexpensive, have a large amount of generated gas, are self-digestible, and are excellent in safety. As carbonamide-based blowing agents, hydrazocarbonamide, azodicarbonamide (hereinafter sometimes abbreviated as “ADCA”) and the like are known. In particular, ADCA represents carbonamide-based foaming agents because it has many advantages such as lower decomposition temperature, larger amount of generated gas, and superior chemical stability compared to other carbonamide-based blowing agents. Except for special cases, carbonamide foaming agents other than ADCA are rarely used. In addition, there is a problem that ammonia generated due to the decomposition of ADCA may contaminate the photoreceptor and cause image defects.

  Furthermore, although ADCA has a low decomposition temperature, it is still relatively high at about 200 ° C., so it is rarely used alone as a foaming agent in foaming rubber. Generally, urea is used as a foaming aid in combination with a decomposition temperature. It is used with lowering. Even in this case, urea generates ammonia as it is decomposed, as with ADCA. Therefore, foamed rubber using urea generates more ammonia than when ADCA is used alone, and the photoconductor is more likely to be contaminated. There is.

  There is known a technique for avoiding the use of urea by using a metal salt of benzenesulfinic acid as a foaming aid, and simultaneously trapping ammonia generated based on decomposition of ADCA by adding zeolite (for example, Patent Document 1). ). However, compared to urea, benzenesulfinic acid metal salt is an expensive compound, so it is inferior in economic efficiency, and foamed cells (foamed cells) tend to be uneven, and inferior in quality and cost compared to products using urea. There's a problem. In addition, the trap of ammonia by adding zeolite is also premised on the avoidance of urea. When urea is contained, not only the generation of ammonia cannot be suppressed, but also the generated ammonia cannot be trapped sufficiently. There is.

In the method for producing a foam rubber roller, it is disclosed that a humidification step is incorporated in order to stabilize the resistance value of the foam rubber roller after foam vulcanization is completed (for example, Patent Document 2). However, it has been humidified to stabilize the resistance value, and no investigation has been made on what happens when it is heated and dried thereafter. In addition, no study is made on the suppression of ammonia generated from the produced foamed rubber roller.
JP 2001-151923 A, especially steps 0012 to 0015. JP-A-6-256552, especially stages 0015 to 0017.

  The present invention has been made in view of these points, and it is an object of the present invention to provide a method for producing a foamed rubber roller with less release of ammonia that causes image defects.

  In order to achieve the above-mentioned problems, the present inventors have intensively studied. As a result, in the production of a foam rubber roller using a raw material rubber composition in which the foaming agent is a carbonamide-based foaming agent and urea is contained as a foaming aid. The inventors have found that the foamed rubber roller obtained after the foam vulcanization is exposed to water and dried by heating, whereby the occurrence of defects in the electrophotographic image due to ammonia is suppressed, and the present invention has been completed.

  That is, the present invention relates to a method for producing a foam rubber roller in which a foam rubber layer is formed on the outer periphery of a core metal, wherein the raw rubber composition contains at least a carbonamide-based foaming agent and urea, and the rubber is disposed on the outer periphery of the core metal. After the composition is molded and foamed and vulcanized, the foamed rubber roller obtained is exposed to water and then dried by heating.

  In the method for producing a foamed rubber roller according to the present invention, the ammonia released from the foamed rubber roller obtained by simply heating and drying after exposure to water is reduced, so that the photoconductor is not contaminated by ammonia and image defects are caused. If it is used for a charging roller or a transfer roller used in an electrophotographic apparatus, it is possible to improve the image quality, and the industrial value is very high.

  A cross-sectional view of a foam rubber roller manufactured according to the present invention is shown in FIG.

  In FIG. 1, reference numeral 1 denotes a cored bar made of stainless steel, copper, iron or the like, which is plated if necessary. A foamed rubber layer 2 is formed on the outer periphery of the cored bar 1, and a further conductive layer or protective layer may be formed thereon. In the present invention, the foamed rubber layer is exposed to water and then dried by heating.

  The raw rubber composition used for the foam rubber roller of the present invention is not particularly limited except that a rubber composition containing at least a carbonamide foaming agent and urea is used.

  The carbonamide-based blowing agent is used in an amount of 1 to 40 parts by mass, preferably 4 to 20 parts by mass, when the raw rubber composition is 100 parts by mass.

  In the present invention, as the foaming agent, a foaming agent other than the carbonamide-based foaming agent may be used in combination. For example, OBSH or the like may be used in combination.

  Urea, which is a foaming aid, is a causative agent for the generation of ammonia, so it is desirable to avoid adding a large amount. The amount of urea added is preferably 10 parts by mass or less, more preferably 100 parts by mass when the raw rubber composition is 100 parts by mass. Is preferably 4 parts by mass or less. Urea is used in an amount of 0.1 parts by mass or more, preferably 0.5 parts by mass or more in order to reduce the decomposition temperature of the carbonamide foaming agent.

  The raw rubber for the raw rubber composition used in the present invention is not particularly limited, but ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber (NR), Various raw rubbers such as butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), chloroprene rubber (CR), and epichlorohydrin rubber (CO, ECO) can be used.

  In addition, the rubber composition used in the present invention includes conductive carbon black such as Ketjen Black (trade name), SAF, ISAF, HAF, MAF for the purposes of conductivity, reinforcement, processability, and increased filling. Fillers such as carbon black for rubber such as FEF, GPF, SRF, FT, and MT, heavy calcium carbonate, light calcium carbonate, clays, magnesium carbonate, silica, magnesium silicate, and talc can be added. The amount of the filler added is 5 to 100 parts by mass, preferably 10 to 70 parts by mass with respect to 100 parts by mass of the raw rubber.

  Various vulcanizing agents can be used, but sulfur-based vulcanizing agents are preferable because the foaming and vulcanization of the rubber composition can be easily controlled. Here, the sulfur-based vulcanizing agent refers to a combination of sulfur and a vulcanization accelerator, or a sulfur-containing organic compound. Examples of vulcanization accelerators include thiazoles, sulfenamides, thioureas, thiurams, dithiocarbamates, guanidines, aldehyde amines, and aldehyde ammonia. It can be used by mixing. Examples of the sulfur-containing organic compound include morpholine disulfide, tetraalkyl thiuram disulfide, dipentamethylene thiuram tetrasulfide, and the like. The addition amount of the vulcanizing agent is preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the raw rubber.

  In addition to the above additives, the raw rubber composition according to the present invention includes vulcanization acceleration aids such as zinc white and stearic acid, softeners such as paraffinic process oil, scorch prevention agents, tackifiers, and other rubbers. Additives can be appropriately added within a range not impairing the effects of the present invention.

  The present invention is characterized in that a foamed rubber roller obtained by foaming and vulcanizing a molded rubber composition is exposed to water and then heated and dried. As described above, in the method of manufacturing a foam rubber roller, it is known that moisture is adsorbed by humidifying the foam rubber roller after heat vulcanization to stabilize the resistance value of the foam rubber roller (see Patent Document 2). . In Patent Document 2, as in the present invention, no consideration is given to the process of heating and drying after exposure to water, and no consideration is given to the problem from ammonia contained in the foam rubber roller.

  First, the production of a rubber roller before foaming in which the above-described raw rubber composition is formed on a core metal (hereinafter, also referred to as “raw rubber roller”) will be described with reference to FIG.

  In FIG. 2, reference numeral 11 denotes an extruder for extruding the raw rubber composition so as to cover the core metal 1, and an unfoamed unvulcanized rubber composition on the core metal 1 that is extruded together by the cross head 12. The raw rubber roller 13 on which the layer 2a is formed is manufactured. Note that an adhesive may be applied to the cored bar 1 as necessary. Further, the rubber composition layer may be formed to a predetermined length, or both ends of the molded product may be cut out to have a predetermined length. Both ends may be cut off not only at the time of the raw rubber roller, but also after foam vulcanization, after surface polishing, after being exposed to water, and further after heat drying. Reference numeral 14 denotes a hopper for feeding the raw rubber composition into an extruder.

  Next, as a specific example, a dipping means for dipping foamed rubber in water as a means for exposing to water will be described.

  Generation of ammonia from the foamed rubber is suppressed by immersing the foamed rubber in water as one means for exposing to water and then drying by heating. The reason for this is not clear, but it is considered that the causative substance that generates ammonia present in the foamed rubber is removed by heating after contact with water.

  The immersion time of the foamed rubber in water is not particularly limited, but it is preferable to immerse the foamed rubber for 30 seconds or more in order to facilitate water penetration into the foamed rubber. The immersion of the foam rubber in water is not particularly limited as long as it is after foam vulcanization, but it is preferably performed after grinding the surface of the foam rubber. By performing the surface of the foam rubber after grinding, the skin layer on the surface of the foam rubber is removed and the cells open on the surface of the foam rubber, so that water can easily penetrate into the foam rubber when immersed in water. It is. Further, when the foamed rubber is immersed in water, it is more preferable that water is easily penetrated into the foamed rubber by applying pressure such as crushing the foamed rubber and degassing the gas in the foamed rubber.

  It is preferable that the temperature of the water at the time of immersion is 30-100 degreeC. If the temperature of water is set lower than 30 ° C., the heating and drying process for removing water becomes longer, and if it exceeds 100 ° C., pressurization is required and the apparatus becomes large and the apparatus cost increases. More preferably, it is 40-70 degreeC.

  As inferred in the example of the means for immersing in water as described above, moisture adheres to the surface of the foamed rubber, penetrates and acts on the moisture, and a high quality foamed rubber material can be obtained by drying after a predetermined time. Therefore, as means for exposing to water, in addition to immersion means, shower means, pressurized water means, steam means, etc. can be considered, and in any case, better condition setting by adding temperature conditions and pressure conditions Can be.

  Moreover, it is preferable that the temperature of heat drying after exposing a foamed rubber roller to water is 100-300 degreeC. If the temperature is lower than 100 ° C., the drying time becomes longer, and if it exceeds 300 ° C., the rubber is liable to deteriorate and the possibility of the rubber burning increases, which is not preferable.

  Further, the heating and drying method can be carried out in a continuous hot stove or electric furnace, and the time for heating and drying is not particularly limited because it varies depending on the temperature of heating and drying, but is usually about 10 minutes to 24 hours. is there.

  Foam vulcanization is not particularly limited, but is preferably performed using a hot stove or UHF. The hot stove and UHF can be continuously produced by being connected to an extruder, which is advantageous in terms of apparatus and mold cost as compared with the case of producing using a mold or the like.

  The foamed rubber roller manufactured in the present invention may be provided with one or more conductive layers or protective layers on the outer periphery of the foamed rubber of the elastic layer for the purpose of further improving the surface smoothness, resistance adjustment and protection. Absent.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

  The amount of ammonia generated from the foam rubber roller was measured according to the following method.

[Method of measuring ammonia generation from foamed rubber roller]
Cut 50 mg of foam rubber from the foam rubber roller, put it in a 50 ml glass bottle with a lid together with 3 ml of distilled water and seal it in the glass bottle. This sealed glass bottle is put into a constant temperature and humidity chamber set at 40 ° C. and a humidity of 95% for 24 hours, and then the sealed glass bottle is taken out from the constant temperature and humidity chamber and left at room temperature for 30 minutes. After opening the lid of the glass bottle, a gas sampling device [trade name “GV-100S”, manufactured by Gastec Co., Ltd.] in which an ammonia detector tube [trade name “Ammonia 3L”, manufactured by Gastec Co., Ltd.] was previously set Is used to collect the gas in the glass bottle and measure the ammonia amount (ppm) in the glass bottle from the standard calibration curve.

Example 1
100 parts by mass of ethylene-propylene-nonconjugated diene copolymer rubber (EPDM) [trade name “EPT4070”, manufactured by Mitsui Chemicals, Inc.], zinc oxide [trade name “Zinc Hana 2”, manufactured by Hakusui Tec Co., Ltd.] 5 parts by mass, stearic acid [trade name “Stearic acid S” manufactured by Kao Corporation] 1 part by mass, conductive carbon [trade name “Ketjen Black EC”, manufactured by Ketjen Black International Co., Ltd.] 11 parts by mass, 30 parts by mass of FEF grade carbon black [trade name “Asahi # 60” manufactured by Asahi Carbon Co., Ltd.], paraffin oil [trade name “Diana Process Oil PW-380”, manufactured by Idemitsu Kosan Co., Ltd.] 50 parts by mass, 2- 2 parts by mass of mercaptobenzothiazole (MBT) [trade name “Noxeller M”, manufactured by Ouchi Shinko Chemical Co., Ltd.], dipentamethylene thiuram tetrasulfide (DP) T) [trade name “Noxeller TRA”, manufactured by Ouchi Shinko Chemical Co., Ltd.] 1 part by mass, zinc dibutyldithiocarbamate (ZDBC) [trade name “Noxeller BZ”, manufactured by Ouchi Shinko Chemical Co., Ltd.] 1 1 part by mass, sulfur [trade name “Sulfax PMC”, manufactured by Tsurumi Chemical Industry Co., Ltd.], carbonamide-based foaming agent (azodicarbonamide) [trade name “Vinihole AC # LQ”, Eiwa Kasei Co., Ltd. )] 8 parts by mass and 3 parts by mass of urea-based foaming aid [trade name “SELTON NP”, Sankyo Chemical Co., Ltd.] were kneaded to prepare a raw rubber composition.

  Next, the raw rubber composition is extruded using a cross head extruder 11 having a diameter of 40 mm shown in FIG. 2, and at the same time, the core metal 1 continuously coated with the hot melt adhesive is passed through the cross head die 12 of the extruder. Then, after molding the rubber composition on the outer periphery of the core metal 1 to form a roller shape, the foam is vulcanized by placing in a hot air oven at 200 ° C. for 20 minutes to form a foam rubber layer on the core metal A rubber roller was created. The obtained foamed rubber roller was set in a grinding machine equipped with a grinding wheel GC80, and the foamed rubber layer on the surface of the foamed rubber roller was ground by 0.5 mm at a rotational speed of 2000 RPM and a feed speed of 500 m / min. The foamed rubber roller having been ground was immersed in water at 50 ° C. for 3 minutes, and immediately after being taken out, it was heated and dried in an electric furnace at 150 ° C. for 20 minutes to produce a foamed rubber roller. The amount of ammonia generated in the obtained foamed rubber roller was measured as described above, and the results obtained are shown in Table 1.

Example 2
In Example 1, a foamed rubber roller was prepared in the same manner as in Example 1 except that the foamed rubber layer was ground for 3 minutes in 50 ° C. water and then heated and dried in an electric furnace at 150 ° C. for 20 minutes. . The amount of ammonia generated in the obtained foamed rubber roller was measured as described above, and the results obtained are shown in Table 1.

Example 3
In Example 1, before being immersed in water at 50 ° C. for 3 minutes, the metal plate was brought into contact with the surface of the foamed rubber roller and the foamed rubber was degassed by applying pressure while rolling the foamed rubber roller. A foamed rubber roller was prepared in the same manner as in Example 1 except that the pressure was continuously applied while being pressed against the roller. The amount of ammonia generated in the obtained foamed rubber roller was measured as described above, and the results obtained are shown in Table 1.

Comparative Example 1
In Example 1, a foamed rubber roller was prepared in the same manner as in Example 1 except that immersion in 50 ° C. water and heating and drying for 20 minutes in an electric furnace at 150 ° C. were not performed. The amount of ammonia generated in the obtained foamed rubber roller was measured as described above, and the results obtained are shown in Table 1.

Comparative Example 2
In Example 1, a foamed rubber roller was produced in the same manner as in Example 1 except that the immersion in 50 ° C. water was not performed. The amount of ammonia generated in the obtained foamed rubber roller was measured as described above, and the results obtained are shown in Table 1.

Comparative Example 3
In Example 1, a foamed rubber roller was prepared in the same manner as in Example 1 except that immersion in water at 50 ° C. was not performed and heating and drying in an electric furnace at 150 ° C. was performed for 12 hours. The amount of ammonia generated in the obtained foamed rubber roller was measured as described above, and the results obtained are shown in Table 1.

Comparative Example 4
The amount of ammonia generated was measured when the foamed rubber roller obtained in Comparative Example 1 was allowed to stand for 24 hours at 30 ° C. and 85% humidity. The results are shown in Table 1.

Using the foamed rubber roller obtained in these examples and comparative examples, a conductive roller provided with a resistance adjusting layer on its surface is incorporated as a charging roller in an image forming apparatus of an electrophotographic printer, and is 40 ° C. and 95%. After storing in a humidity environment for one month, a black and white standard pattern was output, image output was confirmed, and the following criteria were evaluated. The results are shown in Table 1.
○: No image defect was observed at all.
X: An image defect that appears to be a photoconductor contamination by ammonia was observed.

  It can be seen that Examples 1 to 3 have a significantly smaller amount of ammonia generated from the foam rubber roller than the comparative example. In addition, when stored for one month at 40 ° C. and 95% humidity, the foamed rubber roller of the present invention had no problem when incorporated into an electrophotographic apparatus due to the influence of ammonia generated. A defect occurred. That is, in a method for producing a foamed rubber roller comprising a foamed rubber obtained using a rubber composition containing at least a carbonamide-based foaming agent and urea on the outer periphery of the core metal, the foamed rubber is exposed to water and then heated. By drying, generation of ammonia from the obtained foamed rubber roller is suppressed.

It is sectional drawing of the foamed rubber roller of this invention. It is explanatory drawing which shows the example of the extruder used when manufacturing the foamed rubber roller of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core metal 2 Foam rubber layer 2a Unfoamed unvulcanized rubber layer 11 Extruder 12 Crosshead 13 Raw material rubber roller 14 Hopper

Claims (6)

  In a method for manufacturing a foam rubber roller in which a foam rubber layer is formed on the outer periphery of a core metal, the raw rubber composition contains at least a carbonamide-based foaming agent and urea, and the rubber composition is molded and foamed on the outer periphery of the core metal. A method for producing a foam rubber roller, characterized in that after vulcanization, the obtained foam rubber roller is exposed to water and then heated and dried.   The method for producing a foamed rubber roller according to claim 1, wherein the foamed rubber roller is exposed to water after the surface of the foamed rubber is ground.   3. The method for producing a foam rubber roller according to claim 1, wherein when the foam rubber roller is exposed to water, air contained in the foam rubber is degassed.   The method for producing a foamed rubber roller according to any one of claims 1 to 3, wherein the temperature of the water when the foamed rubber roller is exposed to water is 30 to 100 ° C.   The method for producing a foam rubber roller according to any one of claims 1 to 4, wherein the heat drying after the foam rubber roller is exposed to water is performed at 100 to 350 ° C.   2. The foam vulcanization when foaming vulcanizing a rubber composition formed on a metal core to form a foamed rubber is performed using a hot air oven or a microwave vulcanizer (UHF). The manufacturing method of the foamed rubber roller in any one of -5.

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