JP2009202353A - Manufacturing method of rubber roller and rubber roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to manufacture the elastic layer of the foamed rubber having an expansion ratio of ≥3 times by the changes of the manufacturing conditions in the method of manufacturing a rubber roller having an elastic layer of a foamed rubber. <P>SOLUTION: A manufacturing method of a rubber roller having an elastic layer of a foamed rubber that is manufactured by vulcanizing/foaming a rubber composition containing a foaming agent in a closed vessel introducing therein a pressurized steam and has an expansion ratio ((the rubber density before the vulcanization/foaming)/(that after the vulcanization/foaming)) of ≥3 times is provided which satisfies the following conditions. The conditions are: (1) a carbonamide foaming agent is contained by 15-25 parts by mass based on 100 parts by mass of the rubber component of the rubber composition; and (2) the method comprises the step of heating/keeping the rubber composition in the closed vessel at the temperature T1 for 1-25 minutes, wherein the T1 is a temperature where both the absolute value of the difference between the time of the 50% vulcanization progress of the rubber composition and the time of the 50% foaming progress and the absolute value of the difference of the times of each 90% satisfy ≤3 minutes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a rubber roller used in an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system. In particular, the present invention relates to a method of manufacturing a rubber roller such as a charging roller or a transfer roller used in contact with an electrophotographic photosensitive member.

  Rubber rollers such as a charging roller and a transfer roller used in electrophotography are required to maintain a uniform nip width by contact with a photosensitive member in order to respond to higher speed and higher image quality of the apparatus. Therefore, a rubber roller using a foamed rubber elastic layer is used as an elastic body on the outer periphery of the core metal. In recent years, in order to optimize the nip width to the photoreceptor for each product model, the hardness of the rubber roller is set finely. In other words, the hardness of the rubber roller needs to correspond to the pinpoint hardness setting for each model, and naturally, the hardness variation is required to be as small as possible.

  Generally, in order to adjust a rubber roller having a foamed rubber elastic layer to a desired hardness, it is widely performed by adjusting the expansion ratio of the foamed rubber elastic layer. The expansion ratio is a value of (rubber density before vulcanization foaming) / (rubber density after vulcanization foaming). As a method for adjusting the expansion ratio, there is a method for adjusting the compounding of the rubber composition. For example, a method for adjusting the type, addition amount, particle diameter, etc. of the foaming agent, a method for adjusting the addition amount of the foaming aid and adjusting the decomposition rate and the foaming amount of the foaming agent, Examples include a method for adjusting the vulcanization speed depending on the type and amount added, a method for adjusting the amount added of carbon black and fillers, a method for adjusting the type and molecular weight of the main rubber component, and the like. . However, in order to obtain a desired expansion ratio, the composition of the rubber composition must be changed every time. For this reason, in order to cope with the pinpoint hardness setting for each model, not only a lot of man-hours are required for studying the formulation, but also hardness variations may occur depending on the formulation.

  The method of adjusting the expansion ratio from the manufacturing side without adjusting the composition of the rubber composition can greatly reduce the man-hours for studying the formulation, so if the expansion ratio can be controlled, pinpoint hardness for each model It becomes easy to cope with. Examples of the response by changing the production surface include a method of changing the process of vulcanization and foaming, adjusting the temperature and time of vulcanization and foaming, and the like. However, not only is it difficult to obtain a highly foamed rubber elastic layer by the above method, but it is also difficult to achieve compatibility with the reduction in hardness variation. Here, high foaming means that the expansion ratio is 3 times or more, and so on.

Generally, the rubber density before vulcanization foaming is often in the range of 0.90 to 1.50 g / cm ³ when measured by rubber-density measurement (JIS K 6268, ISO 2781). Accordingly, the expansion ratio of 3 times or more means that when the rubber density before vulcanization foaming is 0.90 g / cm ³ , the rubber density after vulcanization foaming is 0.30 g / cm ³ or less. Further, when the rubber density before vulcanization foaming of 1.50 g / cm ^3, the rubber density after vulcanization foaming is the same as that showing a 0.50 g / cm ³ or less.

  Patent Document 1 proposes to obtain a highly foamed rubber elastic layer having an expansion ratio of 3 times or more by the following method. A foamed rubber roll comprising a foamed composition produced by vulcanizing and foaming a rubber composition to which at least a foaming agent, a vulcanizing agent, and a vulcanization accelerator are added, wherein the rubber composition has a foaming progress of 50%. Vulcanization and foaming are performed under the condition that the degree of progress of vulcanization at time (t1) is 5% or less. Further, vulcanization foaming is performed under the condition that (t3−t2), which is the difference between the time (t2) when the foaming progress is 80% and the time (t3) when the vulcanization progress is 80%, is 2.5 minutes or less. . This indicates that a highly foamed rubber elastic layer having a foaming ratio of 4.1 times to 5.0 times can be obtained.

  In Patent Document 2, in a method for producing a conductive roller having a vulcanized and foamed cylindrical rubber composition on a conductive core, the vulcanization and foaming step of vulcanizing and foaming the cylindrical rubber composition is performed by the cylindrical rubber. It has the process of heating up to vulcanization foaming temperature by the heat retention and holding means which encloses a composition. The temperature raising step has (i) at least a first temperature raising step and (ii) a low temperature raising step having a lower temperature raising rate than the temperature raising step of (i) in this order, and the vulcanization Let the foaming temperature reach. Thus, a method for producing a conductive rubber roller that reduces the variation in the shape of the vulcanized and foamed cylindrical rubber composition, has an excellent inner diameter accuracy, and has less hardness unevenness is described.

JP 2007-90820 A ([0052], [0053]) JP 2006-21379 A ([Summary], [0050] to [0057])

  In Patent Document 1, vulcanization hardly progresses in a state where the foaming has progressed halfway. In the state where both foaming and vulcanization are progressing 80%, a high foamed rubber elastic layer is obtained because the speed of firing and vulcanization is relatively close (the speed of foaming and vulcanization is synchronized). It is shown that. However, the rubber composition part at the time (t1) at which the degree of foaming progress is 50% and the degree of vulcanization progress is 5% or less can hardly suppress the foaming gas escape due to cross-linking. May occur. When the foaming gas escapes, the individual foamed cells are connected, so the size of the foamed cells (hereinafter sometimes referred to as the foamed cell diameter) increases, and if the foamed cell diameter is large, hardness variation may occur. It is not preferable. In addition, in patent document 1, since the result of a hardness measurement is not shown, it is unknown about hardness variation.

  Moreover, in patent document 2, it is possible to suppress hardness variation by adjusting the temperature rise at the time of vulcanization foaming. However, when producing a highly foamed rubber elastic layer having a foaming ratio of 3 times or more, it has not been confirmed whether hardness variation can be satisfied, and a highly foamed rubber elastic layer having a uniform hardness required for electrophotographic applications. The manufacturing method is desired.

  That is, the object of the present invention is to prepare a rubber roller having a foamed rubber elastic layer, and to adjust the composition of the rubber composition for the production of the foamed rubber elastic layer having a desired foaming ratio even at a foaming ratio of 3 times or more. Without changing the manufacturing conditions, this is possible. It is another object of the present invention to provide a method for manufacturing a rubber roller which can freely adjust the hardness of the rubber roller having the foamed rubber elastic layer and has a small hardness variation.

Foaming ratio indicated by (Rubber density before vulcanization foaming) / (Rubber density after vulcanization foaming) produced by vulcanizing and foaming a rubber composition containing a foaming agent in a closed container into which pressurized steam is introduced. In the method of manufacturing a rubber roller having a foamed rubber elastic layer of 3 times or more, the following method (1) and (2) are satisfied:
(1) When the rubber component of the rubber composition is 100 parts by mass, the carbonamide foaming agent is contained in an amount of 15 parts by mass or more and 25 parts by mass or less.
(2) The absolute value of the difference (tc50−tp50) between the time (tp50) when the vulcanization progress of the rubber composition is 50% and the time (tp50) when the foaming progress is 50%, and the rubber composition When the absolute value of the difference (tc90-tp90) between the time when the vulcanization progress is 90% (tc90) and the time when the foaming progress is 90% (tp90) is 3 minutes or less is T1, A heating and holding step of heating and holding the rubber composition in the sealed container at the temperature T1 for 1 minute or more and 25 minutes or less.

  According to the present invention, in the method for producing a rubber roller having a foamed rubber elastic layer, the production of the foamed rubber elastic layer having a desired foaming ratio can be adjusted even when the foaming ratio is 3 times or more. However, it can be performed by changing the manufacturing conditions. Further, it is possible to freely adjust the hardness of the rubber roller having the foamed rubber elastic layer, and to obtain a rubber roller having a small hardness variation.

  As a result of intensive studies, the present inventors have found that the vulcanization speed and foaming speed from the state where the vulcanization and foaming of the rubber composition have progressed about half progressed until the vulcanization and foaming are almost completed proceed at a relatively close speed. Let T1 be the temperature that satisfies this condition. At this time, it was found that when the rubber composition was heated and held at the temperature T1, the expansion ratio increased in proportion to the length of the heating and holding time.

  The speed at which the vulcanization speed and the foaming speed are relatively close is, in other words, that the vulcanization speed and the foaming speed are synchronized. Can efficiently avoid the phenomenon that the foaming gas escapes and the foaming ratio decreases. Therefore, if the rubber composition is heated and held at a temperature at which the vulcanization speed and the foaming speed are relatively close to each other, a foamed rubber elastic layer having a desired foaming ratio and a small hardness variation can be obtained even under conditions with a high foaming ratio. Can do. For example, if the heating and holding time at the temperature is increased, the foaming progresses in proportion to the length, so that the foaming ratio increases. If the heating and holding time is shortened, the foaming does not proceed and the foaming ratio is increased. Becomes lower. At that time, it is necessary that the vulcanization speed and the foaming speed until the vulcanization and foaming are almost completed after the vulcanization and foaming of the rubber composition have progressed about half are synchronized.

  More specifically, the absolute value of the difference (tc50-tp50) between the time (tp50) when the vulcanization progress of the rubber composition is 50% and the time (tp50) when the foaming progress is 50%, and the rubber Vulcanization foaming temperature at which the absolute value of the difference (tc90-tp90) between the time (tc90) when the vulcanization progress of the composition is 90% and the time (tp90) when the foaming progress is 90% satisfies 3 minutes or less. Is set to T1, a heating and holding step of heating and holding the rubber composition in a sealed container at the temperature T1 is performed. Thereby, it can be changed to a desired foaming ratio in proportion to the heating and holding time, and a foamed rubber elastic layer having a small hardness variation can be obtained even at a foaming ratio of 3 times or more.

  The time (tc50) at which the degree of vulcanization of the rubber composition is 50% and the time (tc90) at 90% are 50% and 90% of vulcanization of the rubber composition, respectively, by measuring the vulcanization rate described later. Indicates the vulcanization time as it progresses. Further, the time when the degree of foaming of the rubber composition is 50% (tp50) and the time of 90% (tp90) indicate that the foaming of the rubber composition proceeds by 50% and 90%, respectively, by measuring the foaming rate described later. The foaming time is shown.

  If the absolute value of the time difference (tc50-tp50) between the vulcanization progress and the foam progress of the rubber composition is not more than 3 minutes, the vulcanization speed and the foaming speed are not sufficiently synchronized, and the heating Holding time and expansion ratio are not proportional. For this reason, a foamed rubber elastic layer having a desired foaming ratio and a foaming ratio with a small hardness variation of 3 times or more cannot be obtained, which is not preferable.

  The difference between the time when the vulcanization progress and the foam progress of the rubber composition are 50% (tc50-tp50) is judged at less than 50% because both foaming and vulcanization are not sufficiently advanced. The vulcanization rate and the foaming rate do not need to be synchronized. However, this is because the effect becomes large when it is 50% or more.

  Further, if the absolute value of the time difference (tc90-tp90) between the vulcanization progressing degree and the foaming progressing degree of the rubber composition is 90% or less, the vulcanization speed and the foaming speed are synchronized near the end of the vulcanization foaming. Is not sufficient, and the heating and holding time and the expansion ratio are not proportional, as described above, which is not preferable.

  The difference between the time when the vulcanization progress and the foaming progress are 90% (tc90-tp90) is determined because the vulcanization speed and the foaming speed are synchronized until the vulcanization and foaming are almost completed. Otherwise, the contribution of the heating and holding time to the expansion ratio is reduced, which is not preferable. Further, if the progress of vulcanization and the progress of foaming are not synchronized up to 90%, the hardness variation is undesirably increased. Originally, it is preferable that the degree of vulcanization and the degree of foaming are synchronized until the vulcanization and foaming is completed, but in order to balance the foaming ratio and hardness variation, the degree of vulcanization and the degree of foaming The degree should be synchronized to 90%.

  In the heating and holding step, the heating and holding time for heating and holding at the temperature T1 is set to 1 minute or more and 25 minutes or less. If the heating and holding time is less than 1 minute, the heating and holding time is too short, and it becomes difficult to adjust the expansion ratio. Moreover, when the heating and holding time exceeds 25 minutes, the decomposition reaction of the foaming agent is almost completed, so that the expansion ratio is not changed even if the heating and holding is continued. The heating and holding time for heating and holding at the temperature T1 is preferably 5.0 minutes or more and 10.0 minutes or less.

  For the vulcanization rate measurement and the foaming rate measurement in the present invention, a vulcanization tester “MDR-200P” (trade name, manufactured by Alpha Technologies) with a foaming pressure measuring function is used. The said measurement is based on JIS K6300-2 (Unvulcanized rubber Physical property How to obtain vulcanization property by vibration type vulcanization tester) and measured for 60 minutes at each temperature. The measuring instrument is not particularly limited as long as it is a measuring instrument conforming to JIS K6300-2.

  The time (tc50) of the vulcanization progress rate 50% indicating the vulcanization rate is measured for 60 minutes at a predetermined temperature using the vulcanization tester with a foam pressure measurement function according to JIS-K6300-2. At this time, when ME which is the difference between the maximum vulcanization pressure (maximum vulcanization torque) MH and the minimum vulcanization pressure (minimum vulcanization torque) ML is 100, the vulcanization time when the ME value is 50% is shown. Is. Similarly, the time of 90% vulcanization progress (tc90) indicates the vulcanization time when the ME value is 90%.

  Similarly to the vulcanization rate, the time (tp50) at which the foaming progress rate indicating the foaming rate is 50% (tp50) is 60 minutes at a predetermined temperature using the vulcanization tester with the foaming pressure measuring function according to JIS-K6300-2. taking measurement. At this time, when PE which is the difference between the foaming maximum pressure (foaming maximum torque) PH and the foaming minimum pressure (foaming minimum torque) PL is 100, the foaming time when the PE value is 50% is shown. Similarly, the time (tp90) when the foaming progress rate is 90% indicates the foaming time when the PE value is 90%.

  The method of vulcanizing and foaming the foamed rubber elastic layer is classified into a method of vulcanizing and foaming under no pressure and a method of vulcanizing and foaming under pressure. Examples of the method of vulcanizing and foaming under no pressure include a hot air tank, UHF (microwave continuous vulcanizer) using a microwave, and the like. However, in the vulcanization foaming method under no pressure, since the expansion of the foamed cell is not suppressed, the foamed cell diameter tends to vary. If the foamed cell diameter is not uniform, it causes a variation in hardness, which is not preferable.

  On the other hand, the method of vulcanizing and foaming under pressure can be preferably used because the expansion of the foamed cells can be suppressed by appropriate pressure, and the foamed cell diameter becomes uniform and the hardness variation is reduced.

  As a vulcanization method under pressure, a method using a mold and a method using a sealed container into which pressurized steam is introduced are generally used. However, when a mold is used, a large amount of mold is required in the case of mass production, which is disadvantageous in terms of operation cost and has a disadvantage of being inferior in continuous productivity.

  In the present invention, vulcanization foaming is performed in a closed container into which pressurized steam is introduced. The method of performing vulcanization and foaming in a closed vessel into which pressurized steam is introduced not only adjusts the production volume depending on the size of the closed vessel, but also includes various impurities produced by decomposition during vulcanization and foaming as an effect of using steam. Can be efficiently removed by moisture. In particular, the rubber composition used in the present invention contains a carbonamide foaming agent. Carboxamide-based foaming agents generate ammonia during foaming, and if any amount of ammonia remains, image defects may occur. Therefore, vulcanization foaming is performed in a sealed container into which pressurized steam is introduced. A preferable range of the pressure of the pressurized steam to be introduced is not particularly limited as long as vulcanization and foaming proceeds and ammonia can be sufficiently removed, but it is preferably 0.3 MPa or more and 0.8 MPa or less.

  As the closed container, a vulcanized can is preferable from the viewpoint of pressure resistance and heat resistance. The pressure of the pressurized steam introduced into the sealed container is not particularly limited as long as vulcanization and foaming proceeds and ammonia can be sufficiently removed, but it is preferably 0.2 MPa or more and 0.80 MPa or less.

  The rubber composition used in the present invention contains 15 parts by mass or more and 25 parts by mass or less of a carbonamide-based foaming agent when the rubber component in the rubber composition is 100 parts by mass, and (tc50-tp50) As long as both the absolute value of and the absolute value of (tc90-tp90) can satisfy 3 minutes or less, they are not particularly limited.

  For example, the rubber component includes ethylene-propylene-diene copolymer rubber (EPDM), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), epichlorohydrin rubber (CO, ECO). , GECO) and the like. These may be used alone or in combination of two or more.

  The reason why the carbonamide foaming agent is used as the foaming agent in the present invention is that the vulcanization speed and the foaming speed can be easily adjusted by the particle diameter and the addition amount of the carbonamide foaming agent. When a foaming agent other than the carbonamide-based foaming agent is used, it is difficult to satisfy the condition that the absolute value of (tc50-tp50) and the absolute value of (tc90-tp90) are both 3 minutes or less. .

  Examples of the carbonamide-based blowing agent include azodicarbonamide (hereinafter sometimes referred to as ADCA), hydrazodicarbonamide (HDCA), and the like. Among them, ADCA is preferable because it is inexpensive, has a large amount of generated gas, and can easily be highly foamed.

  When the rubber component in the rubber composition is 100 parts by mass, when the content of the carbonamide foaming agent is less than 15 parts by mass, when the rubber composition is heated and held at a temperature T1, the heating and holding time is And the expansion ratio is not proportional. For this reason, a foamed rubber elastic layer having a desired foaming ratio and a foaming ratio with a small hardness variation of 3 times or more cannot be obtained, which is not preferable.

  Further, when the content of the carbonamide-based foaming agent exceeds 25 parts by mass, when the rubber composition is heated and held at the temperature T1, foaming is rapidly promoted when the predetermined heating and holding time is exceeded, and the expansion ratio Tends to be unstable, which is not preferable. Preferably, when the rubber component in the rubber composition is 100 parts by mass, the carbonamide foaming agent is contained in an amount of 17 parts by mass to 23 parts by mass.

  Further, since the decomposition temperature of the carbonamide-based foaming agent is as high as 200 ° C. or higher, it is preferable to use urea as a foaming auxiliary agent with the decomposition temperature lowered.

  The amount of urea added is preferably 0.3 parts by mass or more and 2 parts by mass or less when the rubber component in the rubber composition is 100 parts by mass. Within the above range, the decomposition temperature of the carbonamide-based blowing agent can be sufficiently lowered, and there is no problem due to ammonia generated by the decomposition of urea, which is preferable. More preferably, they are 0.5 mass part or more and 1.8 mass parts or less.

  The rubber composition includes conductive carbon black such as ketjen black, various carbon blacks for rubber classified into SAF, ISAF, HAF, MAF, FEF, GPF, SRF, FT, MT, etc., clays, carbonic acid Various fillers such as magnesium, silica, magnesium silicate and talc, vulcanization accelerators such as zinc white and stearic acid, scorch inhibitors, tackifiers, vulcanizers, and other rubber additives may be included.

  A feature of the present invention is that when the rubber composition is heated and held in the sealed container at the temperature T1 for 1 minute or more and 25 minutes or less, the expansion ratio can be adjusted by the heating and holding time.

  The heating and holding temperature needs to be the temperature T1, but is preferably in a temperature range in which the foaming agent is sufficiently decomposed and the rubber composition can be foamed at an appropriate rate. Specifically, it is preferably 130 ° C. or higher and 150 ° C. or lower. In the temperature range, the absolute value of (tc50-tp50) and the absolute value of (tc90-tp90) can both satisfy the condition of 3 minutes or less. More preferably, it is 135 degreeC or more and 150 degrees C or less.

  After passing through the heating and holding step of heating and holding the rubber composition in the sealed container at the temperature T1 for 1 minute or more and 25 minutes or less as the first step, the rubber composition is further vulcanized and foamed at a temperature higher than the temperature T1. It is preferable to perform a foaming process. The temperature higher than the temperature T1 is not particularly limited as long as the temperature is higher than the temperature T1, but it is preferable that the foaming agent is rapidly decomposed at a temperature at which the foaming agent is rapidly decomposed to terminate the foaming reaction. . The reason is that the foaming cell diameter becomes small and uniform by decomposing the foaming agent at once and terminating the foaming reaction. A preferable temperature of the high temperature vulcanization foaming step is 155 ° C. or more and 170 ° C. or less. If it is 155 ° C. or higher, the temperature is sufficient for the decomposition of the foaming agent to proceed rapidly, and if it is 170 ° C. or lower, even when a rubber component having low heat resistance is used, the rubber deteriorates. This is preferable because it does not occur.

  The method for producing a rubber roller in the present invention is not particularly limited as long as the requirements of the present invention are satisfied, and can be appropriately selected from known methods. For example, it can be produced as follows. First, a metal core with an adhesive applied to the surface is prepared. On the other hand, the rubber composition is extruded into a tube shape with an extruder and vulcanized and foamed under the conditions of the present invention. As a result, a tube having a hole in the center is produced. Thereafter, the tube is covered on a metal core having an adhesive applied to the surface, and the tube and the metal core are bonded by heating. A rubber roller having a foamed rubber elastic layer having a predetermined diameter can be obtained by cutting and removing unnecessary tube ends and polishing.

  Further, the rubber roller in the present invention may have a surface layer composed of one layer or a plurality of layers on the foamed rubber elastic layer as necessary in order to change the surface characteristics.

  The rubber roller of the present invention can be used for a rubber roller used in an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system. In particular, it can be used for a charging roller, a developing roller, a transfer roller, a developer regulating roller, and the like in an electrophotographic apparatus.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The properties of the rubber roller obtained in each example were measured according to the following method.

[Vulcanization speed, foaming speed]
Using a vulcanization tester “MDR-200P” (trade name, manufactured by Alpha Technologies) with a foam pressure measurement function for both vulcanization speed and foaming speed, using JIS K6300-2 (unvulcanized rubber, physical properties, vibration vulcanization tester) Measurement was performed at 140 ° C. for 60 minutes according to the method for obtaining vulcanization characteristics.

[Density of foam rubber elastic layer]
The density of the foamed rubber elastic layer was measured according to JIS K 6268 (rubber-density measurement) and ISO 2781.

[Foaming ratio]
The value calculated by (rubber density before vulcanization foaming) / (rubber density after vulcanization foaming) was taken as the expansion ratio. Each rubber density was measured according to JIS K 6268 (rubber-density measurement) and ISO 2781.

〔hardness〕
The hardness of the rubber roller was measured using a spring type hardness tester for sponge according to JIS S 6050 (trade name: “ASKER C-type hardness meter”, manufactured by Kobunshi Keiki Co., Ltd., measurement load 500 g). The measurement is performed at three locations at 60 mm intervals in the longitudinal direction from the end of the foamed rubber elastic layer, and the average value is calculated. The above measurement was performed on five rubber rollers, and the average value of the five was defined as the hardness of the rubber roller.

[Hardness variation]
The hardness variation was measured using a spring type hardness tester for sponges according to JIS S 6050 (trade name: “Asker C-type hardness meter”, manufactured by Kobunshi Keiki Co., Ltd., measurement load 500 g). The hardness of one rubber roller was measured at an interval of 40 mm in the longitudinal direction from the end of the foamed rubber elastic layer, and the total measured value (maximum value−minimum value) was regarded as hardness variation.

[Example 1]
[A raw material for kneading]
-100 parts by mass of ethylene-propylene-nonconjugated diene copolymer rubber (EPDM) (trade name: “EPT4070”, manufactured by Mitsui Chemicals, Inc.)
・ Zinc oxide 5 parts by mass (trade name: “Zinc Hana 2”, manufactured by Hakusui Tec Co., Ltd.)
-1 part by mass of stearic acid (trade name: “Lunac S-20”, manufactured by Kao Corporation)
FT grade carbon black 10 parts by mass (trade name: “Asahi # 15”, manufactured by Asahi Carbon Co., Ltd.)
・ 10 parts by mass of conductive carbon black (trade name: “Ketjen Black 600JD”, manufactured by Ketjen Black International Co., Ltd.)
Paraffin oil 60 parts by mass (trade name: “Diana Process Oil PW-380”, manufactured by Idemitsu Kosan Co., Ltd.).

[B materials for kneading]
-Morpholinodithio compound (MDB) 2 parts by mass (trade name: “Noxeller MDB”, manufactured by Ouchi Shinko Chemical Co., Ltd.)
2 parts by mass of 2-mercaptobenzothiazole (MBT) (trade name: “Noxeller M”, manufactured by Ouchi Shinko Chemical Co., Ltd.)
Dipentamethylene thiuram tetrasulfide (DPTT) 2 parts by mass (trade name: “Noxeller TRA”, manufactured by Ouchi Shinko Chemical Co., Ltd.)
・ Sulfur 2 parts by mass ・ Azodicarbonamide (ADCA) 15 parts by mass (trade name: “Vinole AC # R”, manufactured by Eiwa Chemical Industry Co., Ltd.)
Urea 1 part by mass (trade name: “Cell Paste 101”, manufactured by Eiwa Kasei Kogyo Co., Ltd.).

  The raw material for kneading A was kneaded using a kneader (7 L) of a closed rubber kneader until the temperature reached 130 ° C. to obtain an A kneaded rubber. After the A kneaded rubber was cooled to 60 ° C., the raw material for kneading B was kneaded with the A kneaded rubber with an open roll for 10 minutes to prepare a rubber composition.

  The rubber composition was extruded into a hollow tube shape using an extruder having a diameter of 60 mm to produce an unvulcanized rubber tube. The unvulcanized rubber tube is put into a vulcanizing can into which pressurized steam (0.40 MPa) is introduced, heated and maintained at 140 ° C. for 5 minutes, and then continuously vulcanized and foamed at 160 ° C. for 30 minutes to form a tube. A foamed rubber elastic layer was prepared.

  A SUS cored bar having a diameter of 6 mm and a length of 250 mm coated with a hot melt adhesive (trade name: “ThreeBond 3315E”, manufactured by ThreeBond Co., Ltd.) was press-fitted into the foamed rubber elastic layer. Then, it was put into an electric furnace at 160 ° C. for 30 minutes, and the foamed rubber elastic layer and the core metal were adhered to produce an unground rubber roller. Then, both end portions were cut so that the length of the foamed rubber elastic layer was 240 mm. This unground rubber roller is set in a grinding machine equipped with a grinding wheel “GC80” (trade name, manufactured by Tsugami Co., Ltd.) and the outer surface of the foam rubber elastic layer is rotated at a rotational speed of 2000 rpm and a feed speed of 10 mm / min. Grinding was performed so that the diameter was 10 mm. Thus, a rubber roller having the foamed rubber elastic layer was produced. The results are shown in Table 1.

[Example 2]
A rubber roller was produced in the same manner as in Example 1 except that the amount of azodicarbonamide added to the rubber composition was changed to 20 parts by mass with respect to Example 1. The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 3
A rubber roller was produced in the same manner as in Example 1 except that the amount of azodicarbonamide added to the rubber composition was changed to 25 parts by mass with respect to Example 1. The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 4
A rubber roller was produced in the same manner as in Example 1 except that the heating and holding time at 140 ° C. in the vulcanizing can was changed to 1 minute. The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 5
A rubber roller was produced in the same manner as in Example 1 except that the heating and holding time at 140 ° C. in the vulcanizing can was changed to 7 minutes. The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 6
A rubber roller was produced in the same manner as in Example 1 except that the heating and holding time at 140 ° C. in the vulcanizing can was changed to 10 minutes. The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 7
A rubber roller was produced in the same manner as in Example 1 except that the heating and holding time at 140 ° C. in the vulcanizing can was changed to 20 minutes. The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 8
For Example 2, the EPDM of the rubber composition was changed to acrylonitrile butadiene rubber (NBR) (trade name: “Nipol DN401LL”, manufactured by Nippon Zeon Co., Ltd.). Further, a rubber roller was produced in the same manner as in Example 1 except that the amount of conductive carbon black added was changed to 5 parts by mass and no paraffin oil was added. The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 9
A rubber roller was produced in the same manner as in Example 2, except that the heating and holding time at 140 ° C. in the vulcanizing can was changed to 25 minutes. The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 10
A rubber roller was produced in the same manner as in Example 2 except that the measurement temperature of the vulcanization rate and the foaming rate was changed to 135 ° C. and the heating and holding temperature in the vulcanization can was changed to 135 ° C. . The production conditions and evaluation results of the rubber roller are shown in Table 1.

Example 11
A rubber roller was produced in the same manner as in Example 2, except that the measurement temperature of the vulcanization speed and the foaming speed was changed to 150 ° C. and the heating and holding temperature in the vulcanization can was changed to 150 ° C. . The production conditions and evaluation results of the rubber roller are shown in Table 1.

  Regarding Examples 1 to 11, a highly foamed rubber elastic layer having a foaming ratio of 3 times or more was obtained, and the hardness variation of the rubber roller obtained despite high foaming was small. For Example 2, Examples 4 to 7 and Example 9, the foaming ratio can be controlled only by changing the heating and holding time at 140 ° C., and a rubber roller having a desired hardness can be obtained without changing the formulation. Met.

[Comparative Example 1]
A rubber roller was produced in the same manner as in Example 1 except that the amount of azodicarbonamide added to the rubber composition was changed to 13 parts by mass with respect to Example 1. Table 2 shows the production conditions and evaluation results of the rubber roller. However, since the amount of azodicarbonamide added is small, it was not possible to obtain a highly foamed rubber elastic layer having a foaming ratio of 3 times or more.

[Comparative Example 2]
A rubber roller was produced in the same manner as in Example 1, except that the amount of azodicarbonamide added to the rubber composition was changed to 13 parts by mass and the heating and holding time at 140 ° C. was changed to 20 minutes. . Table 2 shows the production conditions and evaluation results of the rubber roller. However, since the amount of azodicarbonamide added is small, there is no change in the foaming ratio of the foamed rubber elastic layer even if the heating and holding time at 140 ° C. is increased, and a highly foamed rubber elastic layer having a foaming ratio of 3 times or more is obtained. I couldn't.

[Comparative Example 3]
A rubber roller was produced in the same manner as in Example 1 except that the amount of azodicarbonamide added to the rubber composition was changed to 28 parts by mass with respect to Example 1. Table 2 shows the production conditions and evaluation results of the rubber roller. However, since the amount of azodicarbonamide added is large, decomposition of the foaming agent abruptly causes variation in the foam cell diameter, and only a rubber roller having hardness variations could be obtained.

[Comparative Example 4]
A rubber roller was produced in the same manner as in Example 1 except that the amount of urea added to the rubber composition was changed to 5 parts by mass with respect to Example 2. Table 2 shows the production conditions and evaluation results of the rubber roller. However, at 140 ° C., both the absolute value of (tc50-tp50) and the absolute value of (tc90-tp90) cannot satisfy the condition of 3 minutes or less, and as a result, the high foamed rubber elasticity with a foaming ratio of 3 times or more is obtained. Could not get a layer. In addition, since the absolute value of (tc50−tp50) was as large as 3.9 minutes, a rubber roller with hardness variation that was considered to be caused by variation in the foamed cell diameter due to foaming gas loss was obtained.

[Comparative Example 5]
A foamed rubber roller was produced in the same manner as in Example 1 except that DPTT as a rubber composition was not added to Example 2. Table 2 shows the production conditions and evaluation results of the rubber roller. However, the absolute value of (tc90-tp90) could not satisfy the condition of 3 minutes or less, and as a result, a rubber roller having a highly foamed rubber elastic layer having a foaming ratio of 3 times or more could not be obtained.

Claims (5)

Foaming ratio indicated by (Rubber density before vulcanization foaming) / (Rubber density after vulcanization foaming) produced by vulcanizing and foaming a rubber composition containing a foaming agent in a closed container into which pressurized steam is introduced. In the method for producing a rubber roller having a foamed rubber elastic layer of 3 times or more,
A rubber roller manufacturing method characterized by satisfying the following conditions (1) and (2):
(1) When the rubber component of the rubber composition is 100 parts by mass, it contains 15 to 25 parts by mass of a carbonamide foaming agent.
(2) The absolute value of the difference (tc50−tp50) between the time (tp50) when the vulcanization progress of the rubber composition is 50% and the time (tp50) when the foaming progress is 50%, and the rubber composition The temperature at which the absolute value of the difference (tc90-tp90) between the time (tc90) when the vulcanization progress of 90% is 90% and the time (tp90) when the foaming progress is 90% is less than 3 minutes is defined as T1. A heating and holding step of heating and holding the rubber composition in the sealed container at the temperature T1 for 1 minute or more and 25 minutes or less.   2. The method for producing a rubber roller according to claim 1, wherein a temperature T <b> 1 in the heating and holding step is 130 ° C. or higher and 150 ° C. or lower.   The method for producing a rubber roller according to claim 1, wherein the rubber composition contains urea.   The tube-shaped rubber composition is subjected to the heating and holding step, and then subjected to a high-temperature vulcanization and foaming step in which vulcanization and foaming is performed at a temperature higher than the temperature T1, and the tube shape after the vulcanization and foaming on the core The method for producing a rubber roller according to any one of claims 1 to 3, wherein the rubber composition is coated and adhered.   The rubber roller manufactured by the manufacturing method of the rubber roller of any one of Claim 1 to 4.