JP5541125B2 - Process for producing epoxidized diene rubber and rubber composition containing epoxidized diene rubber - Google Patents

Description

  The present invention relates to a method for producing an epoxidized diene rubber and a rubber composition containing the epoxidized diene rubber.

  Conventionally, in the field of development of rubber materials for the purpose of energy saving, modified rubber compositions using diene rubbers such as polybutadiene modified with epoxidation together with silica in order to improve the dispersibility of silica as a filler It has been known. Therefore, many techniques for producing an epoxidized diene rubber as a raw material have been developed and disclosed.

  For example, in Patent Document 1, in a method for producing an epoxidized copolymer, an organic peracid or carboxylic acid or an anhydride thereof and hydrogen peroxide are used as an epoxidizing agent, and an aromatic hydrocarbon or a halogenated hydrocarbon is used. The technique made to react at the temperature of -20-80 degreeC in the solvent which becomes is described, and it is described that an epoxidized copolymer is obtained with a high reaction rate. Further, for example, Patent Document 2 discloses that in the presence of 15 to 90% hydrogen peroxide and a carboxylic acid having 1 to 3 carbon atoms, phosphonic acid and / or a derivative thereof as a catalyst, and further organic compounds. A method is described in which an epoxidized polyalkenylene is obtained by reacting without adding a solvent or water.

Japanese Patent Laid-Open No. 5-214014 JP 2003-221413 A

  However, Patent Document 1 requires a step of dissolving the epoxidized rubber using an organic solvent several times as large as the copolymer to be epoxidized. Also, in a factory that polymerizes rubber from monomers, there is rubber dissolved in a solvent in the middle of the process, so it is conceivable to perform epoxidation without separating the rubber. However, there is actually a monomer remaining in the solution, and there is a problem that the monomer is epoxidized, and a plurality of steps of monomer separation and epoxidation are added, and an increase in cost cannot be ignored.

  Patent Document 2 is limited to a polyalkenylene having a small molecular weight that can be epoxidized, which is disadvantageous for obtaining low energy loss and wear resistance, and further requires a step of removing carboxylic acid. There is a problem that waste water containing carboxylic acid is generated in the process of removal, and the cost is increased in the waste water treatment facility.

  Therefore, in the production of epoxidized modified rubber, an epoxidized diene rubber that can be epoxidized more efficiently, is free from problems such as waste water, and is effective as a raw material for rubber compositions at low cost. It is desired that

  The present invention has been made in view of the above problems, and in the production of epoxidized diene rubber, has good production efficiency, does not generate waste liquid such as washing water, and is suitable as a raw material for a rubber composition at low cost. An object of the present invention is to provide a method for producing a epoxidized diene rubber and a rubber composition containing the epoxidized diene rubber.

  As a result of intensive investigations to solve the above problems, the present inventors have kneaded using a mechanical shear force without using an organic solvent when adding an organic acid and hydrogen peroxide to a diene rubber. By using the method, production efficiency is good, there is no generation of waste liquid such as washing water, a low cost and suitable epoxidized diene rubber can be obtained as a raw material of the rubber composition, and the ratio of the organic acid to be added is further limited. Specifically, by setting the unsaturated bond of the diene rubber to a ratio of one carboxyl group to 50 to 500, the viscosity increase of the epoxidized diene rubber can be suppressed and the epoxidation efficiency can be increased. And found the present invention.

  That is, the present invention provides a method for producing an epoxidized diene rubber by adding an organic acid and hydrogen peroxide as an epoxidation catalyst to a diene rubber and kneading using a mechanical shearing force. The present invention relates to a method for producing an epoxidized diene rubber, wherein the addition ratio of the organic acid is a ratio in which one unsaturated group of the diene rubber has 50 to 500 carboxyl groups. Moreover, this invention relates to the rubber composition containing the epoxidized diene rubber manufactured by the manufacturing method of the said epoxidized diene rubber.

  As described above, according to the present invention, epoxidation can be efficiently performed, there is no generation of waste liquid such as washing water, the cost is low, and the viscosity increase of the epoxidized diene rubber is suppressed. It is possible to provide a method for producing an epoxidized diene rubber with improved efficiency of conversion and a rubber composition containing the epoxidized diene rubber.

  The method for producing an epoxidized diene rubber according to the present invention includes, for example, a first step of kneading an organic acid into a raw diene rubber using a preheated kneader, and a diene in which the organic acid is kneaded. It is preferable to include a second step of kneading hydrogen peroxide into the rubber, and further including a third step of kneading and homogenizing the diene rubber kneaded with the organic acid and hydrogen peroxide. It is preferable.

  Unlike the method of epoxidizing using an organic solvent, by producing the epoxidized diene rubber in the process as described above, epoxidation can be performed efficiently, and there is no waste liquid generation such as washing water, Low cost epoxidized diene rubber can be produced.

  The kneading machine used in the first to third steps is not particularly limited as long as it is an apparatus capable of kneading the molten resin by applying a mechanical shearing force, and is a roll kneader, a Banbury mixer, a pressure kneader, a single screw extruder. A general kneading machine used for resin processing, such as a twin screw extruder or a twin screw taper extruder, can be used. Also, the above process can be performed in three steps step by step with a roll kneader, a pressure kneader, etc., or it is apparent using a continuous extruder having a plurality of raw material inlets and a large L / D ratio. It can also be carried out in one step. Moreover, you may carry out in steps using 2 or 3 types of apparatuses. From the viewpoint of productivity and low volatilization of the hydrogen peroxide to be added, it is particularly preferable to carry out in one step apparently using a continuous extruder.

  In the first step of kneading the organic acid into the raw diene rubber using a preheated kneader, the temperature of the heated kneader before epoxidation of the diene rubber is preferably 0 to 200 ° C., 40 -150 degreeC is more preferable. When the temperature is lower than 0 ° C., there is a problem that the organic acid which is an epoxidation catalyst does not melt, and when the temperature is higher than 200 ° C., there is a problem that the diene rubber molecules as a raw material are thermally deteriorated and cut.

  Moreover, there is no restriction | limiting in particular as diene type rubber | gum used as a raw material in said 1st process, A well-known thing can be used. For example, natural rubber, butadiene rubber (BR), syndiotactic-1,2-polybutadiene-containing butadiene rubber (VCR), isoprene rubber, butyl rubber, chloroprene rubber and the like. Among these, butadiene rubber is preferable. These can be used alone or in combination of two or more.

  The diene rubber preferably has a number average molecular weight (Mn) of 100,000 to 1,000,000, further 150,000 to 300,000, particularly 200,000 to 250,000. When the number average molecular weight (Mn) is less than 100,000, low energy loss and wear resistance are lowered, and when it exceeds 1,000,000, workability is lowered, which is not preferable.

  The diene rubber preferably has a weight average molecular weight (Mw) by GPC (gel permeation chromatography) of 50,000 to 2,000,000, more preferably 200,000 to 1,000,000, particularly 400,000 to 900,000. . 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 diene rubber preferably has a molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of 1.2 to 10, more preferably 1.5 to 6, and preferably 2.0 to 2.5 is particularly preferred. When the molecular weight distribution is lower than 1.2, there is a problem in that it is disadvantageous for the dispersion of the organic acid 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, the diene rubber preferably has a Mooney viscosity (ML1 + 4, 100 ° C.) of 5 to 200, more preferably 40 to 60. When the Mooney viscosity is lower than 5, no shearing force is applied during kneading, which causes a problem in dispersion of the organic acid before dissolution. Conversely, if the Mooney viscosity exceeds 200, processing by kneading becomes difficult.

  In the first step, the organic acid used as the epoxidation catalyst preferably has a molecular weight of 88 to 600, and more preferably 200 to 400. If the molecular weight is less than 88, odor and toxicity become strong and handling in the process becomes difficult. Furthermore, if it remains in the product, it becomes a bad odor and is not preferable because it needs to be removed by high purification. On the other hand, if the molecular weight exceeds 600, the unsaturated bond that can be epoxidized per added amount decreases, which is not preferable. 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, serotic acid, montanic acid, and melicic acid. These acid anhydrides may be used. Of these, stearic acid is particularly preferred because it has a low odor and toxicity and is generally used as a part of the composition of the rubber compound, and therefore does not necessarily need to be removed. These catalysts are generally used alone, but two or more kinds can also be used in combination.

  The ratio of the organic acid added as the epoxidation catalyst is a ratio in which the number of unsaturated bonds of the unmodified raw diene rubber is 50 to 500 and one carboxyl group is present, and the number of unsaturated bonds is 70 to 200. A ratio in which one carboxyl group is present is particularly preferable. If the ratio of the organic acid is less than the ratio of one carboxyl group to the number of unsaturated bonds of the unmodified raw diene rubber, the viscosity of the epoxidized diene rubber increases and the epoxidation efficiency decreases, Since productivity falls, it is not preferable. Further, if the proportion of the organic acid is more than the proportion of one carboxyl group with respect to the number of unsaturated bonds of the unmodified raw diene rubber, the mechanical properties when blended into the rubber composition to obtain a vulcanized product This is not preferable because it causes a decrease in the temperature.

  In the first step, after the epoxidation catalyst is kneaded, it is desirable that the catalyst is kneaded for a period of time so that the catalyst is sufficiently adapted to the diene rubber.

  In the second step of kneading hydrogen peroxide into a diene rubber kneaded with an organic acid, it is necessary to add the hydrogen peroxide after kneading the epoxidation catalyst. That is not preferable. If it is added first, problems such as decomposition and scattering of hydrogen peroxide occur.

  The amount of hydrogen peroxide to be added is preferably 0.001 to 0.5 equivalent, particularly preferably 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.

  After the second step, it is desirable to provide a third step of kneading and homogenizing the diene rubber kneaded with an organic acid and hydrogen peroxide. The kneading time depends on the type of the kneader, but if it is too short, the epoxidation becomes non-uniform and a 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.

  In the method for producing an epoxidized diene rubber according to the present invention, it is desirable that the obtained epoxidized diene rubber is 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 obtained by the method for producing an epoxidized diene rubber according to the present invention will be described.

  In the rubber composition according to the present invention, a vulcanizing agent and a vulcanization accelerator can be added to the epoxidized diene rubber.

  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.

  In the method for producing an epoxidized diene rubber according to the present invention, when stearic acid is used as an epoxidation catalyst, zinc oxide is vulcanized in order to utilize the stearic acid in the obtained epoxidized diene rubber. It is preferably used as an accelerator. 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.

  Other typical vulcanization accelerators include, for example, 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- Examples include mercaptobenzothiazole (MBT), zinc di-n-butyldithiocarbide (ZnBDC), zinc dimethyldithiocarbide (ZnMDC), and the like.

  In addition, the rubber composition according to the present invention may be added to the epoxidized diene rubber with known additives commonly used in rubber compositions, such as anti-aging agents, fillers, and process oils, as necessary. can do.

  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.

  Furthermore, in the rubber composition according to the present invention, a silane coupling agent may be added to 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 amount of the silane coupling agent added 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.

  Further, the rubber composition according to the present invention can be used as a rubber composition by adding other rubbers in addition to the above. There is no restriction | limiting in particular as rubber added, A well-known thing can be used. For example, polymers of diene monomers such as natural rubber, butadiene rubber (BR), syndiotactic-1,2-polybutadiene-containing butadiene rubber (VCR), isoprene rubber, butyl rubber, chloroprene rubber; acrylonitrile butadiene rubber ( NBR), acrylonitrile-diene copolymer rubber such as nitrile chloroprene rubber and nitrile isoprene rubber; styrene-diene copolymer rubber such as styrene butadiene rubber (SBR), styrene chloroprene rubber and styrene isoprene rubber; ethylene propylene diene rubber (EPDM) 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.

  Furthermore, a rubber reinforcing agent can be added to the rubber composition according to the present invention. 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 dibutyl phthalate (DBP) oil absorption of 70 ml / 100 g or more, and for example, FEF, FF, GPF, SAF, ISAF, SRF, HAF, etc. are used, and particularly preferred. Is an 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 exceeds 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 the 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.

  In this example, UBEPOL BR150L manufactured by Ube Industries, Ltd. is used as the diene rubber, Adeka Fatty Acid SA-300 manufactured by Asahi Denka Co., Ltd. is used as stearic acid, and Wako Pure Chemical Industries, Ltd. A special reagent grade was used, Wako Pure Chemical Industries special grade was used as acetic anhydride, and 3-mercaptopropyltriethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the silane coupling agent. Moreover, the 6-inch roll kneader by Yasuda Seiki was used as a roll as a kneader.

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

  The Mooney viscosity (ML1 + 4, 100 ° C.) after epoxidation was measured for 4 minutes after preheating at 100 ° C. for 1 minute in accordance with JIS K6300.

  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 was 0.6 g to 0.9 g, and the amount of chloroform used when dissolving the epoxidized rubber was 20 ml. According to JIS K7236, 20 ml of acetic acid is added immediately before the measurement, but no acetic acid other than acetic acid contained in the tetraethylammonium bromide acetic acid solution is added. 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 1. 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.

Example 1
First, 99 g of diene rubber (manufactured by Ube Industries, Ltd .: BR150L) was taken and passed through a roll (temperature: 60 ° C., roll interval: 2 mm) to obtain a sheet. 1 g of stearic acid was spread on impervious paper and adhered to one side of the sheet. The number of unsaturated bonds in (A) / the number of carboxyl groups in (B) was 454.8. This sheet was wound up and passed again through a roll to obtain a sheet. This operation was repeated 20 times, and 1 g of stearic acid was all kneaded into the diene rubber.

  Next, 10.5 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. Furthermore, the work which winds said sheet | seat and makes it a sheet | seat again through a roll is continued for 15 minutes, The sample used as Example 1 was obtained.

  When this sample was stored at room temperature for 17 hours and the epoxy group was titrated by the method described above, the epoxidation rate was 2.62%, but no insoluble matter was detected. The Mooney viscosity (ML1 + 4, 100 ° C.) was 61.2. The results are shown in Table 1.

(Example 2)
In Example 1, the amount of diene rubber was 97.5 g, the amount of stearic acid was 2.5 g, and the number of unsaturated bonds in (A) / the number of carboxyl groups in (B) was 179.2. This was carried out in the same manner as in Example 1. The epoxidation rate was 4.78%, but no insoluble matter was detected at this time. The Mooney viscosity (ML1 + 4, 100 ° C.) was 39.3.

(Example 3)
Example 1 except that the amount of diene rubber in Example 1 was 95 g, the amount of stearic acid was 5 g, and the number of unsaturated bonds in (A) / the number of carboxyl groups in (B) was 87.3. And performed in the same manner. The epoxidation rate was 3.84%, but no insoluble matter was detected at this time. The Mooney viscosity (ML1 + 4, 100 ° C.) was 33.8.

(Comparative Example 1)
The same procedure as in Example 1 was carried out except that the amount of diene rubber in Example 1 was 100 g and stearic acid was not added. The epoxidation rate was 1.26%, but no insoluble matter was detected at this time. The Mooney viscosity (ML1 + 4, 100 ° C.) was 142.6.

  As described above, if one carboxyl group of stearic acid is present for 50 to 500 unsaturated bonds of diene rubber, epoxidation is performed at a high epoxidation rate, and an increase in viscosity is suppressed. As a result, it is understood that an epoxidized diene rubber having excellent processability can be obtained.

Claims (5)

  A method for producing an epoxidized diene rubber wherein an organic acid and hydrogen peroxide as an epoxidation catalyst are added to a diene rubber and epoxidized by kneading using a mechanical shearing force. A method for producing an epoxidized diene rubber, characterized in that the addition ratio is a ratio in which one carboxyl group is present for 50 to 500 unsaturated bonds of the diene rubber.   2. The method for producing an epoxidized diene rubber according to claim 1, wherein the diene rubber has a number average molecular weight of 100,000 to 1,000,000.   The method for producing an epoxidized diene rubber according to claim 1 or 2, wherein the organic acid has a molecular weight of 88 to 600. A first step of kneading an organic acid into the diene rubber;
The method for producing an epoxidized diene rubber according to any one of claims 1 to 3, further comprising a second step of kneading hydrogen peroxide into the diene rubber kneaded with the organic acid.   A rubber composition comprising an epoxidized diene rubber produced by the method for producing an epoxidized diene rubber according to any one of claims 1 to 4.