JP2011093968A - Method for producing epoxidized diene rubber, and rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing epoxidized diene rubber suitable as a raw material of a rubber composition at low cost, while ensuring good production efficiency in the production of epoxidized diene rubber, without causing wastewater such as washing water, and a rubber composition using the same. <P>SOLUTION: Provided is the method for producing epoxidized diene rubber, in which a ≥4C long-chain carboxylic acid is used as an epoxidation catalyst and the long-chain carboxylic acid and hydrogen peroxide solution are added to diene rubber, and kneaded using mechanical shear force, for epoxidizing the diene rubber. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention provides a method for producing an epoxidized diene rubber, which is suitable for production of an epoxidized diene rubber, has high production efficiency, does not generate waste liquid such as washing water, is low-cost and is suitable as a raw material for a rubber composition, and the like The present invention relates to a rubber composition.

So far, in the development of energy-saving rubber materials, a number of techniques (Patent Document 1) such as a modified rubber composition using an epoxidized modified natural rubber together with silica have been disclosed. However, although dispersibility of silica can be obtained to some extent, the low energy loss as expected is not obtained. For example, Patent Document 2 discloses that this is due to reversion of epoxidized natural rubber, and it is disclosed that an organic metal salt such as zinc stearate is added as a countermeasure.

Moreover, as seen in Patent Document 3, a rubber composition using a modified rubber obtained by epoxidizing 0.05 to 5% of polybutadiene having a molecular weight of 200,000 or more is disclosed, and it is disclosed that it has excellent rolling resistance and wear resistance. Has been.
As a method for obtaining such an epoxidized diene-based rubber, other than the method using peracetic acid or formic acid as described above, or the method of generating peracid in the system by adding acetic acid or formic acid together with hydrogen peroxide. , Perpropionic acid (patent document 4), method using peroxy acid such as permonophthalic acid (patent document 5), metal salt such as phosphotungstic acid as catalyst, epoxidation using intercalation catalyst and hydrogen peroxide (Patent Document 6) and the like.

However, all of the prior arts require a step of dissolving the epoxidized rubber using an organic solvent several times that of the diene rubber to be epoxidized. Further, in a factory that polymerizes rubber from a diene monomer, there is rubber dissolved in a solvent in the middle of the process, so it is considered that epoxidation is performed without separating the rubber. However, there is actually a monomer remaining in the solution, and there is a problem that the monomer is epoxidized. For this reason, a plurality of steps of monomer separation and epoxidation are added, and an increase in cost cannot be ignored.

Furthermore, in the method using an organic peracid, since the organic acid which became unnecessary after epoxidation is removed by washing with water (Patent Document 7), a waste liquid containing organic substances is generated, and the treatment of this waste liquid becomes a problem. The method using a metal salt catalyst and hydrogen peroxide has fewer problems with waste liquid treatment than the method using an organic acid, but the metal catalyst remains in the rubber and may deteriorate the rubber when stored and vulcanized. There was a problem in the manufacturing method. (Patent Document 8)

  In the production of epoxidized modified rubber, it is possible to epoxidize more efficiently, and there are no problems such as waste water, and it is possible to obtain an epoxidized diene rubber that is effective as a raw material for rubber composition at low cost. Was requested.

Japanese Patent Application Laid-Open No. 07-090123 JP 2008-303332 A JP 2007-284542 A JP 62-034903 A JP 51-060292 A JP 2002-249516 A JP 2000-230013 A JP 2002-275236 A

  The present invention solves the problems of the prior art, and in the production of epoxidized diene rubber, epoxidation has good production efficiency, no generation of waste liquid such as washing water, low cost and suitable as a raw material for rubber composition A method for producing a diene rubber and a rubber composition using the same are provided.

Epoxidation using a long chain carboxylic acid having 4 or more carbon atoms as an epoxidation catalyst, adding the long chain carboxylic acid and hydrogen peroxide to a diene rubber, and kneading using mechanical shearing force. The present invention relates to a method for producing a diene rubber.

The present invention relates to a method for producing the epoxidized diene rubber, wherein the long-chain carboxylic acid having 4 or more carbon atoms used as the epoxidation catalyst is a higher fatty acid.

The long-chain carboxylic acid having 4 or more carbon atoms used as the epoxidation catalyst is stearic acid, and relates to a method for producing the epoxidized diene rubber.

  The method for producing an epoxidized diene rubber is characterized in that the kneading method using the mechanical shearing force is carried out using any one of a roll kneader, a continuous extruder, and a batch kneader.

  The present invention relates to a rubber composition used as a part of a vulcanization accelerator by adding zinc oxide to the epoxidized diene rubber.

  The present invention relates to the rubber composition described above, wherein zinc oxide is added and used as a part of the vulcanization accelerator without removing the long chain carboxylic acid used as the epoxidation catalyst from the epoxidized diene rubber.

In the present invention, it is possible to obtain an epoxidized diene rubber that can be efficiently epoxidized, is free from problems such as waste water, and is advantageous as a raw material for a rubber composition that is low in production cost.

In the present invention, the diene rubber used as a raw material before modification is not particularly limited, and any known rubber can be used. Examples thereof include natural rubber, butadiene rubber (BR), syndiotactic-1.2-polybutadiene-containing butadiene rubber (VCR), isoprene rubber, butyl rubber, and chloroprene rubber.
Of these, butadiene rubber is preferred. These can be used alone or in combination of two or more.

Further, the rubber preferably has a weight average molecular weight (Mw) by GPC (gel permeation method) of 50,000 to 2,000,000, 200,000 to 1,000,000, particularly 400,000 to 800,000. When the weight average molecular weight (Mw) is less than 50,000, the mechanical strength is lowered, and when it exceeds 2 million, the workability is deteriorated.

The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) is preferably 1.2 to 10, more preferably 1.5 to 6, and particularly preferably 2.0 to 2.5. . When the molecular weight distribution is lower than 1.2, there is a problem in that it is disadvantageous for the dispersion of the stearic acid particles before dissolution. On the other hand, when the molecular weight distribution is higher than 10, the oligomer is increased and the mechanical properties are deteriorated.

Furthermore, it is preferable that Mooney viscosity (ML1 _{+ 4} , 100 degreeC) is 5-200, and 40-60 are more preferable. When the Mooney viscosity is lower than 5, no shearing force is applied during kneading, which causes a problem in dispersion of stearic acid particles before dissolution. Conversely, if the Mooney viscosity is 200 or more, processing by kneading becomes difficult.

  The epoxidation catalyst used in the present invention is preferably a long-chain carboxylic acid having 4 or more carbon atoms. More preferred are higher fatty acids having 12 or more carbon atoms. Specific examples include butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, mytilic acid, palmitic acid, palmitoyl acid, margaric acid, stearic acid, oleic acid, vaccenic acid , Linoleic acid, (9,12,15) -linolenic acid, (6,9,12) -linolenic acid, eleostearic acid, tuberculostearic acid, arachidic acid, 8,11-icosadienoic acid, 5,8, Examples thereof include 11-icosatrienoic acid, arachidonic acid, behenic acid, lignoceric acid, nervonic acid, nervonic acid, serotic acid, montanic acid, melicic acid and the like. These acid anhydrides may be used. Of these, saturated fatty acids having 12 or more carbon atoms are preferable, and stearic acid is particularly preferable. These catalysts are generally used alone, but two or more kinds can also be used in combination.

  In the present invention, a desired epoxidized diene rubber can be obtained by the following three steps. The apparatus to be used is not particularly limited as long as it can apply a mechanical shearing force to knead the molten resin. A roll kneader, a Banbury mixer, a pressure kneader, a single screw extruder, a twin screw extruder, a twin screw taper extruder, etc. A general kneading machine used for resin processing can be used. In addition, this step can be performed in three steps step by step with a roll kneader, a pressure kneader, or the like, or apparently using a continuous extruder having a plurality of raw material inlets and a large L / D ratio. It can also be performed in one step. Moreover, you may carry out in steps using 2 or 3 types of apparatuses. From the viewpoint of productivity and the low volatilization of hydrogen peroxide, which is an epoxidizing agent, it is particularly preferable to use a continuous extruder and apparently one step. In the following description, it will be simply referred to as a kneader.

First, there is a first stage process in which a long chain carboxylic acid having 4 or more carbon atoms is kneaded as a catalyst in a kneader heated before epoxidation of the diene rubber as a raw material. After the first step, a two-step process for kneading hydrogen peroxide is performed.
Finally, there is a third stage process in which the diene rubber charged with the epoxy agent is further kneaded and homogenized.

The temperature of the heated kneader before the first step is preferably 0 to 200 ° C, more preferably 40 to 150 ° C. When the temperature is lower than 0 ° C., there is a problem that the long-chain carboxylic acid that is an epoxidation catalyst does not melt, and when the temperature is higher than 200 ° C., there is a problem that the raw rubber molecules are thermally deteriorated and cut.

  After kneading the epoxidation catalyst in the first stage process, it is desirable to knead for a time such that the catalyst is sufficiently adapted to the diene rubber.

  The mixing of hydrogen peroxide in the second stage process must be carried out after kneading the epoxidation catalyst, and should not be mixed at the same time or previously. If mixed first, hydrogen peroxide decomposes and scatters.

After the second stage process, it is desirable to provide a third stage process for homogenization. The kneading time depends on the type of the kneader, but if it is too short, the epoxidation becomes non-uniform and part of the kneading may solidify. On the other hand, if the length is too long, there is a problem that the molecular weight is lowered or gelled due to thermal degradation.

  The amount of the long-chain carboxylic acid added as the epoxidation catalyst is preferably 0.001 to 0.5 equivalent, and 0.01 to 0.1 equivalent relative to the total number of unsaturated bonds of the unmodified raw diene rubber. Particularly preferred. If the amount of the long-chain carboxylic acid is too small, the progress of the epoxidation reaction is delayed and the productivity is lowered. On the other hand, if it is too much, it will cause a decrease in mechanical properties when blended with a rubber composition to obtain a vulcanized product.

Similarly, the hydrogen peroxide solution is preferably from 0.001 to 0.5 equivalent, particularly preferably from 0.01 to 0.1 equivalent, based on the total number of unsaturated bonds of the unmodified raw diene rubber. When the amount is too small, epoxidation is not sufficiently performed. If the amount is too large, the mixed water reacts with the epoxy group to cause a part of the epoxy group to be hydroxylated, and further reacts with another epoxy group to gel the rubber.

  The epoxidized diene rubber of the present invention is desirably stored for a certain period of time after completion of kneading. The storage time is preferably 3 hours or more and 1 year or less, more preferably 1 week or more and 6 months or less. The hydrogen peroxide remaining during the storage time is further converted into an epoxy group and disappears, and there is no possibility of becoming a hindrance when a rubber composition is obtained. If the storage time is too long, the permeated moisture reacts with the epoxy group to become a hydroxyl group, and further reacts with another epoxy group to gel the rubber.

Next, a rubber composition using the epoxidized diene rubber of the present invention will be described.
A vulcanizing agent and a vulcanization accelerator can be added to the rubber composition of the present invention.
Examples of the vulcanizing agent include sulfur, a compound that generates sulfur by heating, a metal oxide such as an organic peroxide and magnesium oxide, a polyfunctional monomer, and a silanol compound. Examples of the compound that generates sulfur by heating include tetramethyl thiuram disulfide and tetraethyl thiuram disulfide.

  Moreover, in order to utilize the stearic acid in the epoxidized rubber of the present invention, it is preferable to use zinc oxide as a vulcanization accelerator.

Examples of other general vulcanization accelerators include aldehydes, ammonia, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, xanthates, and the like. Tetramethylthiuram disulfide (TMTD) N-oxydiethylene-2-benzothiazolylsulfenamide (OBS), N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), dibenzothiazyl disulfide (MBTS), 2-mercapto Examples thereof include benzothiazole (MBT), zinc di-n-butyldithiocarbide (ZnBDC), zinc dimethyldithiocarbide (ZnMDC) and the like.
When using zinc oxide as a vulcanization accelerator, it is preferable to use it together with a general vulcanization accelerator rather than using it alone.

In addition, known additives that are usually used in rubber compositions, such as anti-aging agents, fillers, and process oils, can be blended as necessary.
Anti-aging agents include amine / ketone-based, imidazole-based, amine-based, phenol-based, sulfur-based and phosphorus-based anti-aging agents. More specifically, as an anti-aging agent, phenol-based 2,6-di-tert-butyl-p-cresol (BHT), phosphorus-based trinonylphenyl phosphite (TNP), sulfur-based 4.6-bis (Octylthiomethyl) -o-cresol, dilauryl-3,3′-thiodipropionate (TPL) and the like.
Examples of fillers include inorganic fillers such as calcium carbonate, basic magnesium carbonate, clay, Lissajous, diatomaceous earth, and other fillers such as recycled rubber and powder rubber. Process oils include aromatic and naphthenic fillers. And paraffinic process oil.

Further, a silane coupling agent may be used for the epoxidized diene rubber. As the silane coupling agent, a silane coupling agent having a functional group capable of reacting with an epoxy group is particularly preferable.

Examples of commercially available silane coupling agents having a functional group capable of reacting with an epoxy group include, but are not limited to, the following. 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, 3 -Aminopropyltriethoxysilane, 3-aminopropyldimethylbutoxysilane, 3-aminopropylmethyldibutoxysilane, 3- (2-aminoethylaminopropyl) dimethoxymethylsilane, 3- (2-aminoethylaminopropyl) dimethoxyethyl Silane, 3- (2-aminoethylaminopropyl) dimethoxypropylsilane, 3- (2-aminoethylaminopropyl) dimethoxybutylsilane, 3- (2-aminoethylaminopropyl) diethoxy Methylsilane, 3- (2-aminoethylaminopropyl) trimethoxysilane, 3- (2-aminoethylaminopropyl) triethoxysilane, 3- (2-aminoethylaminopropyl) tributoxysilane, 2- (3,4 -Epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyldimethoxymethylsilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, (3-mercaptopropyl) triethoxysilane, (3-mercaptopropyl) trimethoxysilane, (3-mercaptopropyl) methyldimethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 11- Mercaptoethyloleates undecyl trimethoxysilane, and the like 11 mercaptoundecyl triethoxysilane.
Among these, (3-mercaptopropyl) triethoxysilane is particularly preferable.

  The addition amount of the silane coupling agent having a functional group capable of reacting with an epoxy group is preferably 0.1 to 1 molar equivalent with respect to the number of epoxy groups of the epoxidized diene rubber. When the addition amount of the silane coupling agent is less than 0.1 molar equivalent, the effect of improving tan δ and wear resistance tends to be reduced. Moreover, when the addition amount of the said silane coupling agent exceeds 1 molar equivalent, there exists a tendency which is not economically preferable.

In the present invention, other rubbers can be added and used as a rubber composition. The rubber that can be added is not particularly limited, and any known rubber can be used. For example, polymers of diene monomers such as natural rubber, butadiene rubber (BR), butadiene rubber (VCR) containing syndiotactic-1.2-polybutadiene, isoprene rubber, butyl rubber, chloroprene rubber; acrylonitrile butadiene rubber ( NBR), acrylonitrile-diene copolymer rubber such as nitrile chloroprene rubber, nitrile isoprene rubber; styrene-diene copolymer rubber such as styrene butadiene rubber (SBR), styrene chloroprene rubber, styrene isoprene rubber, ethylene propylene diene rubber (EPDM), etc. Is mentioned. Of these, butadiene rubber, syndiotactic-1.2-polybutadiene-containing butadiene rubber, acrylonitrile butadiene rubber, styrene butadiene rubber, natural rubber, and isoprene rubber are preferable. These can be used alone or in combination of two or more.

In the present invention, a rubber reinforcing agent can be used. Examples of the rubber reinforcing agent include various carbon blacks, white carbon, silica, activated calcium carbonate, and ultrafine magnesium silicate. Among these, at least one of carbon black and silica is preferable. Particularly preferred is carbon black having a particle size of 90 nm or less and a dibutyl phthalate (DBP) oil absorption of 70 ml / 100 g or more. For example, FEF, FF, GPF, SAF, ISAF, SRF, HAF and the like are used.
Particularly preferred is ISAF having a small particle size from the viewpoint of low heat build-up and low fuel consumption.

When carbon black and silica used for the rubber reinforcing agent are mixed, it becomes possible to achieve both workability, low energy loss and wear. In particular, the weight ratio of carbon black / silica is preferably 90/10 to 10/90, more preferably 80/20 to 20/80, and particularly preferably 70/30 to 30/70.
If the amount of silica is less than 10%, energy loss increases, and if it is more than 90%, there is a drawback that workability and wear resistance are deteriorated.

  A rubber composition using a silane coupling agent functions to improve the dispersibility of the rubber reinforcing agent in the rubber matrix by mixing with a rubber reinforcing agent such as silica. As a result, it also leads to effects such as low fuel consumption.

  In the rubber composition according to the present invention, the maximum temperature during kneading using the banbury, open roll kneader, kneader, biaxial kneader, etc., in which each of the above components is usually performed, is the silane coupling agent and epoxy group It can be obtained by kneading under conditions that are equal to or higher than the reaction temperature.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, these do not limit the objective of this invention. First, various chemicals used in the following examples and comparative examples will be described below.

(Description of various chemicals)
Diene rubber: UBEPOL BR150L manufactured by Ube Industries, Ltd.
Stearic acid: Adeka fatty acid SA-300 manufactured by Asahi Denka Co., Ltd.
Hydrogen peroxide solution: Wako Pure Chemical Industries, Ltd. reagent grade roll: Yasuda Seiki 6 inch roll kneader Acetic anhydride: Wako Pure Chemical Industries, Ltd. reagent grade silane coupling agent: 3-mercaptopropyltriethoxysilane, Tokyo Kasei Kogyo Co., Ltd. Reagents

  In the following examples and comparative examples, the Mooney viscosity and the epoxidation rate of the epoxidized diene rubber were measured by the following methods.

Mooney viscosity after epoxidation (ML _{1 + 4} , 100 ° C.) According to JIS K6300, after preheating at 100 ° C. for 1 minute, it was measured for 4 minutes.

The epoxidation rate was measured according to JIS K7236 after storing for 3 hours or more after the completion of the sample process.
The difference from JIS K7236 is that the amount of epoxidized rubber is 0.6 g to 0.9 g. The amount of chloroform used when dissolving the epoxidized rubber was 30 ml. In JIS K7236, 20 ml of acetic acid is added immediately before the measurement, but this is reduced to 5 ml. When a standard amount of acetic acid was added, a rubber having a low epoxidation rate precipitated in a lump and could not be titrated. When the amount of acetic acid was reduced, the equivalence point became difficult to understand, but the precipitated sample spread on the measurement liquid in the form of an oil film, and titration became possible if time was taken. Other reagent adjustments are as described in JIS K7236.
Moreover, the epoxidation rate was calculated using the following formula here. The epoxy equivalent is the mass (g) of the epoxidized resin corresponding to 1 mol of the epoxy group, and is determined by the method described in JIS K7236. In the case of 100% epoxidized polybutadiene, it is butadiene molecular weight + oxygen 1 atomic weight.
Epoxidation rate = 5409 / (epoxy equivalent-16)

Example 1
200 g of diene rubber (Ube Industries, Ltd. 150L) was taken and passed through a roll (temperature: 50 ° C., roll interval: 2 mm) to obtain a sheet. 8 g of stearic acid was spread on impervious paper and adhered to one side of the sheet. This sheet was wound up and passed again through a roll to obtain a sheet. This operation was repeated 20 times, and 8 g of stearic acid was all kneaded into the diene rubber.
Next, 6.5 g of hydrogen peroxide (30%) was spread on the impervious paper and adhered by wiping on one side of a rubber sheet. This sheet was wound up and passed again through a roll to obtain a sheet. This operation was repeated 30 times, and all the hydrogen peroxide solution was kneaded into the diene rubber.
Further, the diene rubber was wound around a roll and kneaded for 3 minutes to obtain a sample to be Example 1.
When this sample was stored at room temperature for 17 hours and the epoxy group was titrated by the method described above, the epoxy group conversion rate was 0.8%, but no insoluble matter was detected. The Mooney viscosity (ML _{1 + 4} , 100 ° C.) was 33.2.

(Example 2)
The same procedure as in Example 1 was carried out except that the amount of hydrogen peroxide was 11 g in Production Example 1 and the time until titration of the epoxy group was 3 hours at room temperature. The epoxy group conversion rate was 1.1%, but no insoluble matter was detected at this time. The Mooney viscosity (ML _{1 + 4} , 100 ° C.) was 32.0.

(Comparative Example 1)
200 g of diene rubber (Ube Industries, Ltd., 150 L) was taken, put into 1300 cc of cyclohexane in a separable flask, stirred, and dissolved overnight (about 8 hours).
The temperature of the separable flask was set to 70 ° C. in a water bath, 7 g of acetic anhydride was added and stirred, and then 12.6 g of hydrogen peroxide (30%) was added and stirring was continued for 3 hours. Thereafter, the heating was stopped, and ice was poured into the water bath to lower the temperature to room temperature. At the same time, 1000 cc of 2% sodium hydrogen carbonate was added and stirring was continued for 5 minutes. Thereafter, the mixture was allowed to stand to separate the reaction solution and the aqueous layer, and the aqueous layer was removed using a siphon.
Add 500 cc of water and stir for 5 minutes. Thereafter, the reaction solution and the aqueous layer were separated by allowing to stand, and the aqueous layer was removed. This was done again.
Thereafter, the reaction solution was taken out into a Teflon (registered trademark) -coated vat and placed in a vacuum dryer at 100 ° C. for 1:30 to remove cyclohexane.
Further, it was wound around a roll at 100 ° C., kneaded for about 10 minutes, and dried while extruding water remaining in the epoxidized rubber.
After drying, it was stored for about 50 hours, and the epoxidation rate and Mooney viscosity were measured. The epoxidation rate was 1.2%, and the Mooney viscosity (ML _{1 + 4} , 100 ° C.) was 14.0.

The epoxidized modified diene rubber of the present invention can be used for industrial rubber, particularly conveyor belts, rubber crawlers and golf balls.

Claims (6)

Epoxidation using a long chain carboxylic acid having 4 or more carbon atoms as an epoxidation catalyst, adding the long chain carboxylic acid and hydrogen peroxide to a diene rubber, and kneading using mechanical shearing force. Method for producing diene rubber. The method for producing an epoxidized diene rubber according to claim 1, wherein the long-chain carboxylic acid having 4 or more carbon atoms used as the epoxidation catalyst is a higher fatty acid. The method for producing an epoxidized diene rubber according to any one of claims 1 and 2, wherein the long-chain carboxylic acid having 4 or more carbon atoms used as the epoxidation catalyst is stearic acid.   The epoxy according to any one of claims 1 to 3, wherein the kneading method using the mechanical shearing force is performed using any one of a roll kneader, a batch kneader, and a continuous extruder. Process for producing diene rubber.   A rubber composition used as a part of a vulcanization accelerator by adding zinc oxide to the epoxidized diene rubber.   6. The rubber composition according to claim 5, wherein zinc oxide is added and used as a part of the vulcanization accelerator without removing the long chain carboxylic acid used as the epoxidation catalyst from the epoxidized diene rubber.