JP2007131664A - Method for producing crosslinked rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely produce a crosslinked rubber having low hardness, small compression set and excellent processability in high efficiency. <P>SOLUTION: The method for producing a crosslinked rubber comprises the kneading of a liquid rubber with a crosslinking agent and other ingredients, defoaming the mixture, forming to a desired form and curing the product by crosslinking, wherein the kneading operation is carried out by using a planetary mixer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a crosslinked rubber product that can efficiently and reliably obtain a crosslinked rubber product having a low hardness and a small compression set.

  In general, when manufacturing rubber products, first, a rubber composition is prepared by blending raw materials rubber with compounding agents such as reinforcing agents, fillers, softeners, anti-aging agents and the like, and then kneading the rubber composition. A non-crosslinked rubber composition is prepared by adding a crosslinking (vulcanization) agent, a crosslinking (vulcanization) accelerator, etc. to the product, and after this is molded into a desired shape, it is subjected to crosslinking curing or simultaneously with molding. A method of obtaining a crosslinked rubber product by performing crosslinking and curing is employed.

  In this case, the reinforcing agent and filler are often in the form of powder and are likely to be scattered during kneading with the raw rubber. Therefore, in order to complete kneading in a short time, it is necessary to use a closed kneader to prevent scattering of these compounding agents, and kneading work is performed using a closed kneader such as a Banbury or a kneader. (For example, refer to Patent Documents 1 and 2 below).

  On the other hand, a large amount of liquid rubber is blended with raw rubber for the purpose of reducing the hardness of the resulting rubber product (reducing the hardness) or improving processability during production (for example, the following patents). Reference 2). At this time, in order to knead the liquid rubber and other compounding agents in the raw rubber, these materials are put into the above-mentioned closed kneader and kneaded. In this case, the liquid rubber is sealed in the closed kneader. There is a problem that the other compounding agent adheres to the surface of the rotor and becomes difficult to disperse in the liquid rubber, and the kneading efficiency decreases.

  Therefore, in order to cope with this problem, a method of suppressing the adhesion of the liquid rubber to the rotor surface by introducing the liquid rubber into the closed kneader little by little and dispersing it in the liquid rubber has been adopted. This method takes too much time for kneading and lowers productivity, and also in this method, the amount of liquid rubber adhering to the rotor surface gradually increases, and other kneading operations are repeated as the kneading operation is repeated. There are many cases where the dispersion of the compounding agent becomes insufficient.

JP 2000-129037 A JP 2005-154545 A

  The present invention has been made in view of the above circumstances, and can efficiently and reliably obtain a rubber cross-linked product having good performance with low hardness and small compression set, without reducing productivity or product quality. It is an object of the present invention to provide a method for producing a crosslinked rubber product.

  As a result of intensive studies to achieve the above object, the present inventor blended a rubber with a cross-linking agent and other desired compounding agents as required, kneaded, molded into a desired shape, and cross-linked and cured. Thus, in the case of producing a rubber cross-linked product, the above kneading operation is carried out by a planetary mixing device, particularly a planetary mixing / desorbing device that revolves while the container containing the object rotates and defoams while kneading the object. By using a foaming device, even if liquid rubber such as low molecular weight butadiene rubber or isoprene rubber is used as a rubber raw material, crosslinking agents and other compounding agents are sufficiently and well dispersed in these liquid rubbers, and bubbles are also generated. A very few good uncrosslinked rubber compositions can be efficiently prepared without causing inconvenience due to adhesion of liquid rubber, etc., and by molding and crosslinking and curing this uncrosslinked rubber composition, Excellent processability, moreover a rubber cross-linked product having excellent performance in low compression set, found that it is possible to efficiently manufactured without variation in performance, and completed the present invention.

  Accordingly, the present invention provides a method for producing a crosslinked rubber product in which a compounding agent is blended in a liquid rubber, kneaded, defoamed, and then molded into a desired shape and crosslinked and cured. Provided is a method for producing a crosslinked rubber product characterized by performing an operation.

  According to the method for producing a crosslinked rubber product of the present invention, a crosslinked rubber product having low hardness, small compression set and excellent workability can be produced efficiently and reliably.

Hereinafter, the present invention will be described in more detail.
As described above, the present invention is to produce a crosslinked rubber product by blending a liquid rubber with a compounding agent, kneading, defoaming, molding into a desired shape and crosslinking and curing.

  The liquid rubber as the main component of the rubber cross-linked product is not particularly limited as long as it is liquid at normal temperature and exhibits elasticity by cross-linking, and can be appropriately selected according to the use of the cross-linked product, for example, liquid Examples include butadiene rubber, liquid isoprene rubber, liquid chloroprene rubber, liquid acrylonitrile butadiene rubber, liquid ethylene propylene diene rubber, and liquid epichlorohydrin rubber. Among these, liquid butadiene rubber and liquid isoprene rubber are preferably used in the present invention. Further, these liquid rubbers preferably have a number average molecular weight of 2000 to 50000.

  Here, depending on the case, two or more liquid rubbers may be mixed and used. Moreover, although about 5-20 mass parts solid rubber can also be mix | blended with respect to 100 mass parts of liquid rubbers as needed, in this invention, it is liquid as a raw material rubber component, without mix | blending solid rubber at all. It is preferable to use only rubber, whereby a rubber cross-linked product with low hardness and small compression set can be obtained more reliably. Examples of the solid rubber in the case of blending the solid rubber include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, chloroprene rubber, nitrile rubber, epichlorohydrin rubber, and the like.

  In the present invention, an appropriate compounding agent can be blended with the liquid rubber as necessary. For example, a crosslinking agent can be blended in order to favorably cure and cure the liquid rubber by thermal crosslinking. In this case, as the crosslinking agent, known crosslinking agents such as organic peroxides, sulfur, organic sulfur compounds, and metal oxides can be used depending on the type of liquid rubber and the use of the obtained crosslinked product. In particular, organic peroxides are preferably used. Specifically, 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-amylperoxy) -3,3,5-trimethylcyclohexane, 1,1 -Di (t-butylperoxy) cyclohexane, 1,1-di (t-hexylperoxy) cyclohexane, 2,2-di (t-butylperoxy) cyclohexane, n-butyl 4,4-di (t-butylperoxy) Peroxides such as valerate and di (2-t-butylperoxyisopropyl) benzene are preferably used.

  The cross-linking method is not limited to thermal cross-linking using the cross-linking agent. For example, a method in which a photopolymerization initiator is blended with the liquid rubber and cross-linked and cured by ultraviolet irradiation or the like may be employed. . In this case, there is no restriction | limiting in particular as a photoinitiator, A well-known thing can be used. For example, 4-dimethylaminobenzoic acid, 4-dimethylaminobenzoic acid ester, 2,2-dimethoxy-2-phenylacetophenone, acetophenone diethyl ketal, alkoxyacetophenone, benzyldimethyl ketal, benzophenone and 3,3-dimethyl-4-methoxy Benzophenone, benzophenone derivatives such as 4,4-diaminobenzophenone, benzoyl alkylbenzoate, bis (4-dialkylaminophenyl) ketone, benzyl derivatives such as benzyl and benzylmethyl ketal, benzoin derivatives such as benzoin and benzoin isobutyl ether, benzoin isopropyl Ether, 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, xanthone, thioxanthone Thioxanthone derivatives, fluorene, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -Phenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1, 2-benzyl-2-dimethylamino-1- (morpholinophenyl) -butanone-1, etc. These may be used alone or in combination of two or more.

  The crosslinking agent or photopolymerization initiator is added to the liquid rubber and kneaded to prepare an uncrosslinked rubber composition. The uncrosslinked rubber composition includes a filler, a conductive agent, and crosslinking acceleration as necessary. Known compounding agents such as an agent, a reinforcing agent, a softening agent and an anti-aging agent can be added and compounded.

  Examples of the filler include carbon black, calcium carbonate, silica, clay, magnesium carbonate, magnesium silicate and the like.

  As the conductive agent, carbon black such as gas black such as ketjen black and acetylene black, oil furnace black including ink black, thermal black, channel black and lamp black is preferably used. In some cases, an ionic conductive agent can be used, for example, tetradecammonium, tetrabutylammonium, dodecyltrimethylammonium such as lauryltrimethylammonium, octadecyltrimethylammonium such as stearyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, modified Ammonium such as perchlorate such as aliphatic dimethylethylammonium, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, alkyl sulfate, carboxylate, sulfonate Salt: lithium, sodium, calcium, magnesium or other alkali metal or alkaline earth metal perchlorate, chlorate, hydrochloride, bromate, iodate, borofluoride, Fluoromethyl sulfate, may be formulated and sulfonate.

  Examples of the crosslinking accelerator include ethylene dimethacrylate, trimethylolpropane trimethacrylate, triallyl isocyanurate, triallyl cyanurate, and the softening agent includes paraffinic oil, naphthenic oil, aromatic oil, Adipic acid ester, sebacic acid ester and the like are exemplified, and examples of the antiaging agent include phenolic antiaging agent, imidazole antiaging agent and amine antiaging agent.

  In the production method of the present invention, first, the crosslinking agent and the compounding agent are blended in the liquid rubber, kneaded, and defoamed to prepare an uncrosslinked rubber composition. In this case, in the present invention, the kneading operation is performed using a planetary mixer instead of a Banbury mixer or a kneader. As the planetary mixing device to be used, a general planetary mixing device such as a so-called planetary mixer in which a paddle, a stirring arm, a stirring blade and the like revolve while rotating (planetary motion) can also be used. A planetary mixing / defoaming apparatus that defoams while revolving while the container containing the object rotates and kneads the object is particularly preferably used. By using such a planetary mixing / defoaming device, the above compounding agent can be uniformly and efficiently dispersed in the liquid rubber without causing any inconvenience related to the adhesion of the liquid rubber, and kneading and mixing operations can be performed. At the same time, by performing defoaming, it is possible to efficiently obtain a very high quality uncrosslinked rubber composition having almost no bubbles. In addition, as such a planetary mixing and defoaming device, AR-100, ARV-200, AR-250, AR-500, ARV-1000, ARV-300 and Kurashiki Boseki Co., Ltd. Commercially available devices such as Mazerustar KK-50S, KK-100, KK-300, KK-10000 can be used.

  The mixing and kneading conditions (stirring speed, stirring temperature, stirring time, etc.) are not particularly limited, and may be set as appropriate according to the type of liquid rubber, compounding agent, compounding amount of the compounding agent, and the like.

  The uncrosslinked rubber composition prepared by the kneading operation is molded into a desired shape and cured by a crosslinking reaction to obtain a target rubber crosslinked product. In this case, the molding of the rubber composition is not particularly limited, but a LIM molding machine is preferably used. In this case, crosslinking can be performed simultaneously with injection molding.

  The use of the rubber cross-linked product obtained by the production method of the present invention is not particularly limited, and is molded into a desired shape according to the use by the above molding operation, and subjected to processing such as polishing and cutting as necessary. , Used in various applications. In this case, according to the production method of the present invention, a rubber cross-linked product having a high uniformity of compounding agents such as a filler and a conductive agent dispersed and compounded, a low hardness and a small compression set can be obtained. Examples of applications in which the properties and performances of the rubber cross-linked product obtained by the production method of the present invention are effectively exhibited include toner conveying rollers used in electrophotographic devices such as printers and copying machines, and electrostatic recording devices, Examples thereof include rollers such as a developing roller, a charging roller, a transfer roller, and a paper feed roller, and blades such as a developing blade (toner layering blade) and a cleaning blade. These rollers and blades are required to have low hardness, sufficient durability, and more uniform conductivity. According to the present invention, a roller or blade made of a crosslinked rubber having such characteristics and performance is provided. It can be manufactured efficiently.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
[Examples and comparative examples]
The compounding agent is blended into the liquid rubber in the proportions shown in Table 1 below, kneaded using a planetary mixing / defoaming device (Kurashiki Boseki Co., Ltd. Mazerustar KK-100) or a normal four-blade mixer, and then removed. Foaming was performed to prepare an uncrosslinked liquid rubber composition. The formulation in Table 1 below is parts by weight.

When the planetary mixing / defoaming apparatus is used (Examples 1 and 2), defoaming is performed simultaneously with the kneading operation using the same apparatus, and when a four-blade mixing machine is used (Comparative Example 1). In 2), after the kneading operation was completed, the mixture was left to stand overnight in a vacuum oven at 50 ° C. to perform a defoaming operation. The kneading conditions were as follows.
Examples 1 and 2
Equipment: Planetary mixing and defoaming device Autorotation speed: 400rpm
Revolution speed: 800rpm
Kneading time: 5 minutes
Comparative Examples 1 and 2
Equipment: 4-blade mixer Stirring speed of blade: 570 rpm
Kneading time: 10 minutes

  Next, the obtained uncrosslinked liquid rubber composition was injected into a mold in which a shaft was previously arranged using a LIM molding machine, and then crosslinked by heating in an oven heated to 170 ° C. for 30 minutes. A roller having a rubber cross-linked layer formed around the shaft was molded. Next, the roller was taken out of the mold, cooled, and then polished to a predetermined outer diameter using a polishing machine manufactured by Mizuguchi Seisakusho to obtain a conductive roller.

The following items were evaluated for the uncrosslinked liquid rubber composition, the crosslinked rubber obtained from the uncrosslinked liquid rubber composition, and the conductive roller. The results are shown in Table 1.
[State of uncrosslinked liquid rubber composition]
The uncrosslinked liquid rubber composition prepared by the kneading and defoaming operation was observed with the naked eye to confirm the generation of bubbles and the dispersion of the compounding agent.
[Compression set]
Measurement was performed in accordance with a vulcanized rubber compression set test method defined in JIS K6262.
[Asker C hardness]
Measurement was performed according to a vulcanized rubber hardness test method defined in JIS K6253 with the obtained conductive roller.
[Roller resistance]
A resistance of R10340A (manufactured by Advantest Co., Ltd.) was applied to the both ends of the roller under test by applying a load of 500 g to the copper plate, and a resistance value was measured by applying a voltage of 10V. The measurement was performed at room temperature (23 ° C.).
[Variation of roller resistance]
Using a rotary roller resistance measuring machine, a cylindrical metal electrode was pressed against the roller under test with a load of 1000 g, and 72 points on the outer periphery of the roller were measured with a resistivity meter R8340A (manufactured by Advantest). The difference in value was regarded as resistance variation. The measurement was performed at room temperature (23 ° C.).

ＬＩＲ−３０：クラレ社製液状イソプレンゴム
ＬＩＲ−３００：クラレ社製液状ブタジエンゴム
パーヘキサＴＭＨ：１，１−ジ（ｔ−ヘキシルペルオキシ）−３，３，５−トリメチルシクロヘキサン
ケッチェンブラックＥＣ：ケッチェンブラックインターナショナル社製
ケッチェンブラックＥＣ−６００ＪＤ：ケッチェンブラックインターナショナル社製

LIR-30: Kuraray liquid isoprene rubber LIR-300: Kuraray liquid butadiene rubber Perhexa TMH: 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane ketjen black EC: Ket Ketjen Black EC-600JD made by Chain Black International: Ketjen Black International

  As shown in Table 1, according to the production method of the present invention, a rubber cross-linked product having a low hardness and a small compression set is obtained, and the rubber cross-linked product has few bubbles and the conductive agent blended is uniformly dispersed. Therefore, a low-resistance, extremely small variation in hardness and resistance value, and a high-quality conductive rubber roller can be obtained.

Claims (10)

  In a method for producing a crosslinked rubber product in which a compounding agent is mixed and kneaded in a liquid rubber, defoamed, and then molded into a desired shape and crosslinked and cured, the kneading operation is performed using a planetary mixer. A method for producing a crosslinked rubber product.   The method for producing a crosslinked rubber according to claim 1, wherein the rubber component is only liquid rubber.   The method for producing a crosslinked rubber product according to claim 1 or 2, wherein a crosslinking agent is blended as one of the blending agents to be crosslinked and cured.   The planetary mixing device is a planetary mixing / defoaming device that defoams while revolving while a container containing an object rotates to knead the object. A method for producing a rubber cross-linked product.   The rubber crosslinking according to any one of claims 1 to 4, wherein the liquid rubber is a liquid butadiene rubber, a liquid isoprene rubber, a liquid butadiene / isoprene copolymer rubber, or a mixed rubber of two or more selected from these. Manufacturing method.   The method for producing a crosslinked rubber product according to any one of claims 1 to 5, wherein the liquid rubber has a number average molecular weight of 2,000 to 50,000.   The manufacturing method of the rubber crosslinked material of any one of Claims 1-6 which mix | blended carbon black as one of the said compounding agents.   The method for producing a crosslinked rubber product according to any one of claims 3 to 7, wherein the crosslinking agent is thermally crosslinked using peroxide.   The crosslinking agent is 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-amylperoxy) -3,3,5-trimethylcyclohexane, n-butyl. The method for producing a crosslinked rubber product according to claim 8, which is one or more peroxides selected from 4,4-di (t-peroxy) valerate and di (2-t-butylperoxyisopropyl) benzene.   The method for producing a crosslinked rubber product according to any one of claims 1 to 9, wherein, after kneading and defoaming, the uncrosslinked rubber composition is injection-molded using a LIM molding machine and simultaneously crosslinked.