JP2007090820A - Foamed rubber roll and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foamed rubber roll with open cells and a high degree of foaming and a manufacturing method of the same. <P>SOLUTION: The foamed rubber roll consists of a foamed composition obtained by vulcanizing/foaming and molding a rubber composition which is added with at least a foaming agent, a vulcanizing agent and a vulcanizing accelerator. The rubber composition is subjected to the vulcanization/foaming on the conditions that the progress of vulcanization at a time (t1) when the progress of foaming is 50% is ≤5% and that the difference, (t3-t2), of a time (t2) at which the progress of foaming becomes 80% and a time (t3) at which the progress of vulcanization becomes 80%, is ≤2.5 minutes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a foam rubber roll used for an electrophotographic copying machine and printer, or an image forming apparatus such as a toner jet copying machine and printer, and a foam rubber roll manufacturing method.

  Conventionally, foamed rubber rolls are used in image forming apparatuses such as electrophotographic copying machines and printers or toner jet copying machines and printers. In the production of such a foam rubber roll, a pyrolytic chemical foaming agent is generally used. What is important when using a chemical foaming agent is the balance between the vulcanization rate and the decomposition rate of the chemical foaming agent. If the vulcanization precedes foaming, the viscosity will increase too much and foaming will not be sufficient. Also, if vulcanization precedes foaming, the viscosity will be too low and bubbles will not be retained and the gas will escape to the outside and will not foam sufficiently.

  Therefore, in order to obtain a highly foamed material, there is a method of bringing a foaming agent decomposition peak when vulcanization proceeds about 20 to 60%. However, in this method, since the vulcanization proceeds to some extent when the foaming agent is decomposed to generate gas, the bubbles are easily retained and become an independent foam. There may be problems with stability. Therefore, an open-cell foam is desired to improve dimensional stability. However, since the structure has good air permeability in which the bubbles are connected, gas can be easily released to the outside so that a high-foam can be obtained. There was a problem that it was difficult.

  Under such circumstances, a foam (see, for example, Patent Documents 1 to 3) adjusted to have a foaming speed higher than a vulcanization speed has been proposed. However, there was no mention of the choice of closed cells or open cells.

JP 2002-250336 A JP 2004-262110 A JP 2004-69980 A

  This invention makes it a subject to provide the manufacturing method of a foaming rubber roll and foaming rubber roll which are open-celled and highly foamed in view of such a situation.

  A first aspect of the present invention for solving the above problems is a foam rubber roll comprising a foam composition formed by vulcanizing and foaming a rubber composition to which at least a foaming agent, a vulcanizing agent and a vulcanization accelerator are added. The rubber composition has a vulcanization progress of 5% or less at a time (t1) when the foaming progress is 50%, and a vulcanization progress is 80% at a time (t2) when the foaming progress is 80%. The foamed rubber roll is characterized by being vulcanized and foamed under the condition that (t3−t2), which is the difference from the time (t3), is 2.5 minutes or less.

  According to a second aspect of the present invention, in the first aspect, the foamed rubber roll is characterized in that the foamed composition has an open cell ratio of 50% or more.

According to a third aspect of the present invention, there is provided the foamed rubber roll according to the first or second aspect, wherein the rubber composition has a Mooney viscosity ML _{1 + 4} (100 ° C.) of 5 to 40.

  A fourth aspect of the present invention is the foamed rubber roll according to any one of the first to third aspects, wherein the foaming agent contains azodicarbonamide as a main component.

  According to a fifth aspect of the present invention, in the foam rubber roll according to any one of the first to fourth aspects, the vulcanization accelerator includes at least a thiuram vulcanization accelerator.

  A sixth aspect of the present invention is a method for producing a foamed rubber roll which is molded by vulcanizing and foaming a rubber composition to which at least a foaming agent, a vulcanizing agent and a vulcanization accelerator are added, and the rubber composition is At the time (t1) when the foaming progress is 50%, the vulcanization progress is 5% or less and the time (t2) when the foaming progress is 80% and the time (t3) when the vulcanization progress is 80%. In the method for producing a foamed rubber roll, vulcanization foaming is performed under the condition that the difference (t3-t2) is 2.5 minutes or less.

  FIG. 1 is a diagram showing the relationship between the degree of foaming progress and the degree of vulcanization progress of a rubber composition. The horizontal axis is time, the vertical axis of the foaming curve is pressure (MPa), and the vertical axis of the vulcanization curve is torque (dN · m).

  In the foam rubber roll of the present invention, foaming proceeds sufficiently at the initial stage of vulcanization by adjusting the type and blending ratio of the foaming agent, vulcanizing agent, vulcanization accelerator, vulcanization foaming temperature, etc. Designed to be. That is, it is designed so that the progress of foaming proceeds faster than the progress of vulcanization.

  In addition, the foaming progress and the vulcanization progress of the rubber composition when actually manufacturing the foam rubber roll can be confirmed by simulating the manufacturing conditions. For example, a rotorless rheometer RLR-3 (manufactured by Toyo Seiki Seisakusho Co., Ltd.) ) And a vulcanization foam measuring machine equipped with a foam pressure measuring device, and the foaming progress and vulcanization progress of the rubber composition may be simultaneously measured at the same composition and the same temperature as in the production of the foamed rubber roll.

The degree of foaming progress according to the present invention is determined in accordance with JIS K6300-2. As shown in FIG. 1, the difference P _E between the minimum value P _L and the maximum value P _H is 100. maximum and a ratio of the foaming pressure at each time when the, also, with such vulcanization progress in this invention are those obtained in conformity with JIS K6300-2, and the minimum value M _L of the torque the ratio of the torque at each time when the difference between M _E between the value M _H and 100. The minimum value P _L and the minimum value M _L of the torque of the pressure is the minimum value in the initial stage of pressure or torque is reduced, and the maximum value P _H and the maximum value M _H torque pressure across It is the maximum value. However, in the foaming curve and the vulcanization curve, there are those in which the maximum value of the vertical axis is flat, those having a maximum value, and those that continue to rise, and as shown in FIG. If it is not possible, the maximum value within a predetermined measurement time is set as the maximum value _MH .

  In the foamed rubber roll according to the present invention, the rubber composition is vulcanized at the time (t2) when the vulcanization progress is 5% or less and the foaming progress is 80% at the time (t1) when the foaming progress is 50%. Vulcanized and foamed under the condition that (t3−t2), which is the difference from the time (t3) when the progress is 80%, is 2.5 minutes or less. With this configuration, the foamed rubber roll is open-celled and highly foamed. When the progress of vulcanization at the time (t1) when the foaming progress is 50% is larger than 5%, it becomes a foam of closed cells instead of open cells, and (t3-t2) is 2.5 minutes or more. This is because when the size is increased, a high foam cannot be obtained.

  The time (t2) at which the degree of foaming progress is 80% is preferably 10 minutes or less, and particularly preferably 5 minutes or less. This is because if the decomposition time of the foaming agent is too long, vulcanization is inhibited and the vulcanization is greatly delayed.

  The foam composition according to the present invention preferably has an open cell ratio of 50% or more. By setting the open cell ratio to 50% or more, a foamed rubber roll having elasticity is obtained. The open cell ratio is the ratio of open cells to the total bubbles, and is obtained from the following equation.

In the present invention, it is preferable to use a rubber composition having a Mooney viscosity of ML _{1 + 4} (100 ° C.) of 5 to 40. If the Mooney viscosity is less than 5, the viscosity is too low, so the rubber will sag when vulcanized and foamed in a hot air oven or the like, resulting in a non-uniform molded product. It is because it becomes difficult to obtain a high foam since it does not grow in size.

  A rubber composition for obtaining a foamed composition according to the present invention comprises a foaming agent, a foaming aid, a vulcanizing agent, a vulcanization accelerator, and a filler in an unvulcanized rubber material so as to be vulcanized and foamed under the conditions described above. Etc. are mixed as necessary.

  The rubber member is not particularly limited. For example, natural rubber, styrene / butadiene / styrene rubber, butadiene rubber, butyl rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, chloroprene rubber, nitrile rubber, urethane rubber, acrylic rubber, epichlorohydrin. Examples thereof include rubber, silicone rubber, fluorine rubber, and hydrogenated nitrile rubber.

  Examples of the foaming agent include azodicarbonamide (ADCA), p, p′-oxy (benzenesulfonylhydrazide) (OBSH), N, N′-dinitrosopentamethylenetetramine (DPT), hydrazodicarbonamide, barium azodicarbonoxy. Examples thereof include foaming agents such as rate, sodium hydrogen carbonate, and azobisisobutyronitrile, and ADCA foaming agents or combined use of ADCA foaming agents and other foaming agents are particularly preferred. When the ADCA foaming agent is used, the rubber composition is preferably vulcanized and foamed at 130 ° C. or higher, and more preferably vulcanized and foamed in the range of 150 to 200 ° C. This is because if the temperature is too low, the vulcanization foaming time becomes long, and if the temperature is too high, the plasticizer volatilizes when a relatively low decomposition plasticizer is used, which may affect the rubber properties.

  The addition amount of the foaming agent is preferably 1 to 12 parts by weight, more preferably 3 to 8 parts by weight with respect to 100 parts by weight of the rubber component. This is because if the amount of the foaming agent added is less than the above range, the gas pressure is too small to swell, and if the number of added parts is too large, the rubber elasticity of vulcanized foam deteriorates. In addition, what is necessary is just to use what is used generally as a foaming adjuvant, for example, urea can be mentioned.

  Examples of the vulcanizing agent include sulfur, peroxide, resin crosslinking agent, inorganic vulcanizing agent, etc., and examples of the vulcanization accelerator include guanidine, aldehyde-amine, aldehyde-ammonia, thiazole, Examples thereof include organic vulcanization accelerators such as sulfenamide-based, thiourea-based, thyrium-based, dithiocarbamate-based, and xanthate-based salts, and inorganic vulcanization accelerators such as zinc oxide. When sulfur vulcanization is performed, thiuram vulcanization accelerator or a combination of thiuram vulcanization accelerator and another vulcanization accelerator is preferable. By using the vulcanization accelerator described above, it is relatively elastic. A flexible foam is obtained.

  On the other hand, as filler, carbon black, white carbon, calcium carbonate, high styrene resin, clay, talc, magnesium silicate, wollastonite, zelite, potassium titanate, diatomaceous earth, silica sand, pumice powder, aluminum white , Barium sulfate, calcium sulfate, molybdenum disulfide, eponite, silicone resin powder and the like.

  The expansion ratio varies depending on the type and blending of the rubber, but can be increased to about 8 times by vulcanizing and foaming under the conditions according to the present invention. However, in the case of a foam rubber roll used for a transport roll or the like, a foaming ratio of 3 to 6 times is preferable. This is because if the expansion ratio is too high, the cell diameter is enlarged and the roll surface becomes poor.

  In the method for producing a foamed rubber roll of the present invention, the rubber composition has a vulcanization progress of 5% or less at a time (t1) when the foaming progress is 50% and a time (t2) when the foaming progress is 80%. And vulcanization foaming may be performed under the condition that (t3−t2), which is the difference between the time (t3) when the vulcanization progress is 80%, and 2.5 minutes or less.

  In the method for producing a foamed rubber roll of the present invention, the apparatus for vulcanization and foaming is not particularly limited. For example, free foaming that performs vulcanization foaming by an electric furnace can be employed. An open-cell foamed rubber roll can be produced. Of course, vulcanization foaming may be performed by pressure foaming using a steam vulcanizing can or mold foaming.

  As described above, in the present invention, the rubber composition has a vulcanization progress of 5% or less at a time (t1) when the foaming progress is 50% and a time (t2) when the foaming progress is 80%. And vulcanization foaming under the condition that (t3−t2) is 2.5 minutes or less, which is the difference between the time (t3) when the vulcanization progress is 80%, and a foamed rubber roll with open cells and high foaming Can be provided.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, these Examples do not limit the scope of the present invention at all.

Example 1
100 parts by weight of acrylonitrile butadiene rubber (NBR), 5 parts by weight of zinc oxide, 1 part by weight of stearic acid, 1 part by weight of anti-aging agent, 25 parts by weight of filler, 40 parts by weight of oil, 2 parts by weight of thiuram vulcanization accelerator, A rubber composition was obtained by kneading 1 part by weight of sulfur, 7 parts by weight of azodicarbonamide (ADCA), and 7 parts by weight of a foaming aid with a 10-inch roll. Next, this rubber composition was extruded using a core metal having a diameter of 6 mm with a cross-head extruder to form a roll-shaped product having an inner diameter of 6 mm and an outer diameter of 12 mm. After molding, the roll-shaped product was put into an electric furnace at 150 ° C. and vulcanized and foamed for 40 minutes to obtain a foamed rubber roll.

(Example 2)
0.5 parts by weight of thiuram vulcanization accelerator, 1 part by weight of sulfenamide vulcanization accelerator, 1.5 parts by weight of thiazole vulcanization accelerator, dithiocarbamate vulcanization accelerator A foamed rubber roll was obtained in the same manner as in Example 1 except that 0.5 part by weight was used.

(Example 3)
A foam rubber roll was prepared in the same manner as in Example 1 except that 1 part by weight of the thiuram vulcanization accelerator, 1 part by weight of the sulfenamide vulcanization accelerator, and 1 part by weight of the thiazole vulcanization accelerator were used. Obtained.

Example 4
A foamed rubber roll was obtained in the same manner as in Example 1 except that the foaming aid was changed to 5 parts by weight.

(Example 5)
A foamed rubber roll was obtained in the same manner as in Example 1 except that the foaming aid was changed to 3 parts by weight.

(Comparative Example 1)
A foam rubber roll was obtained in the same manner as in Example 1 except that 1 part by weight of the thiuram vulcanization accelerator, 1 part by weight of the sulfenamide vulcanization accelerator, and 0.5 part by weight of sulfur were used.

(Comparative Example 2)
A foamed rubber roll was obtained in the same manner as in Example 1 except that 2 parts by weight of the sulfenamide vulcanization accelerator and 1 part by weight of the thiazole vulcanization accelerator were used instead of the thiuram vulcanization accelerator.

(Comparative Example 3)
A foamed rubber roll was obtained in the same manner as in Example 1 except that 0.3 parts by weight of the thiuram vulcanization accelerator and 1 part by weight of the sulfenamide vulcanization accelerator were used.

(Comparative Example 4)
A foamed rubber roll was obtained in the same manner as in Example 1 except that 1 part by weight of a sulfenamide vulcanization accelerator and 2 parts by weight of a thiazole vulcanization accelerator were used instead of the thiuram vulcanization accelerator.

(Comparative Example 5)
A foam rubber roll was obtained in the same manner as in Example 1 except that the thiuram vulcanization accelerator was changed to 0.5 part by weight.

(Comparative Example 6)
Foaming as in Example 1 except that 0.5 parts by weight of thiuram vulcanization accelerator, 1 part by weight of thiazole vulcanization accelerator, and 1.5 parts by weight of dithiocarbamate vulcanization accelerator were used. A rubber roll was obtained.

(Comparative Example 7)
A foam rubber roll was obtained in the same manner as in Example 1 except that 1 part by weight of the thiuram vulcanization accelerator was used, 2 parts by weight of a thiazole vulcanization accelerator, and 1 part by weight of a dithiocarbamate vulcanization accelerator were used.

(Test Example 1)
In each example and each comparative example, when vulcanizing and foaming a roll-shaped product in an electric furnace at 150 ° C., simultaneous measurement of foaming progress and vulcanization progress for 25 minutes from the start of vulcanization foaming using a testing machine Went. The tester is a vulcanized foam measuring machine equipped with a foaming pressure measuring device in a rotorless rheometer RLR-3 (manufactured by Toyo Seiki Seisakusho Co., Ltd.). The progress of foaming and the progress of vulcanization were determined according to JIS K6300-2.

(Test Example 2)
The Mooney viscosity (100 ° C.) ML _{1 + 4} , the open cell ratio, and the expansion ratio of the foamed rubber rolls molded in each Example and each Comparative Example were determined.

The Mooney viscosity (100 ° C.) ML _{1 + 4} was measured using a Mooney viscometer SMV-202 (manufactured by Shimadzu Corporation).

  The open cell ratio was obtained from the above-described formula. The expansion ratio was determined from expansion ratio = (material specific gravity / specific gravity after foaming).

  The results of Test Examples 1 and 2 are shown in Tables 1 and 2.

(Summary of results)
The foamed rubber rolls of Examples 1 to 5 have a vulcanization progress of 5% or less at a time (t1) when the foaming progress is 50% and a time (t2) when the vulcanization progress is 80% and the foam progress. Is obtained by vulcanization foaming under the condition that (t3−t2) is 2.5 minutes or less, which is the difference from the time (t3) of 80%, both of which have a foaming ratio of 4.1 times or more. It was highly foamed. Furthermore, the open cell ratio was as high as 70% or more. On the other hand, in Comparative Examples 1 to 5, the value of (t3−t2) was larger than 2.5, and the expansion ratio was low. Since Comparative Example 6 and Comparative Example 7 had a foaming progress of 50% and a vulcanization progress of 8%, both had an open cell ratio of 10% or less. In addition, it was found that the bubbles were retained because of particularly fast vulcanization and became closed cells.

  From the above, the time (t2) when the vulcanization progress is 5% or less at the time (t1) when the foaming progress is 50% and the time (t3) when the vulcanization progress is 80% and the foaming progress is 80%. It was found that a foamed rubber roll vulcanized and foamed under a condition that (t3-t2) is 2.5 minutes or less, which is a difference from), is a foamed rubber roll having a high expansion ratio and a high open cell ratio.

It is a figure which shows the relationship between foaming progress and vulcanization progress.

Claims (6)

A foamed rubber roll comprising a foamed composition formed 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%. This is the difference between the time (t2) when the vulcanization progress at time (t1) is 5% or less and the foaming progress is 80% and the time (t3) when the vulcanization progress is 80% (t3-t2). ) Is a foamed rubber roll characterized by being vulcanized and foamed under conditions of 2.5 minutes or less. The foamed rubber roll according to claim 1, wherein the foam composition has an open cell ratio of 50% or more. The foamed rubber roll according to claim 1 or 2, wherein the rubber composition has a Mooney viscosity ML _{1 + 4} (100 ° C) of 5 to 40. 4. The foamed rubber roll according to claim 1, wherein the foaming agent contains azodicarbonamide as a main component. The foamed rubber roll according to any one of claims 1 to 4, wherein the vulcanization accelerator includes at least a thiuram vulcanization accelerator. A method for producing a foamed rubber roll, which is obtained 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% ( (t3−t2), which is the difference between the time (t2) when the vulcanization progress in t1) is 5% or less and the foaming progress is 80% and the time (t3) when the vulcanization progress is 80%. A method for producing a foamed rubber roll, characterized by vulcanizing and foaming under conditions of 2.5 minutes or less.

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