JP2006169292A - Method for producing natural rubber/inorganic filler masterbatch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To directly produce a natural rubber/inorganic filler masterbatch from a latex without producing deterioration of the quality with improved workability and thermal efficiency. <P>SOLUTION: The natural rubber/inorganic filler masterbatch is produced by spray-drying a mixture obtained by blending a natural rubber latex, a water slurry of inorganic fillers and a surfactant or a water-soluble polymer. The method for producing the masterbatch comprises feeding a natural rubber latex and a water slurry of inorganic fillers separately from separate raw material feed paths, converging them on a single path, and then jetting a mixture into a drying chamber to spray-dry the mixture. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to the production of a natural rubber / inorganic filler masterbatch from natural rubber latex, and more particularly, natural rubber having good productivity and thermal efficiency and suppressing deterioration of rubber quality by spray drying from natural rubber latex. The invention relates to a method for producing an inorganic filler masterbatch and a natural rubber / inorganic filler masterbatch obtained therefrom.

  At present, natural rubber is shipped in the form of a sheet (RSS) or a block (TSR) obtained by manually collecting sap from a rubber tree, filtering and coagulating the latex. Thus, even at the present time when the importance of natural rubber is increasing, the current situation is that rubber is still manufactured from rubber latex with the help of human hands. Also, processes such as latex coagulation process, water washing process, and drying process, especially the drying process, have a great influence on the viscosity of the product of the resulting rubber. There are things that are not enough. From this viewpoint, Patent Document 1 proposes a manufacturing method capable of improving productivity and quality.

  On the other hand, natural rubber (NR) inorganic filler (for example, carbon black and / or silica) master batches are difficult to mix in a slurry state due to instability of latex. Patent Document 2 discloses a method of making an NR master batch by simultaneously spraying and solidifying NR latex and carbon black slurry, and removing water while mixing. However, this method is kneaded at a high temperature as a drying step, so that although the dispersibility of carbon black is good, there remains a problem in rubber physical properties due to thermal history.

JP 2003-26704 A JP 2000-507892 A

  In the production of a natural rubber / inorganic filler masterbatch from natural rubber latex, the present invention greatly improves workability and thermal efficiency, and the resulting masterbatch may cause thermal degradation or gel of the rubber that may occur by conventional heat drying. It is an object of the present invention to provide a method for producing a natural rubber / inorganic filler masterbatch with excellent quality by suppressing the formation of a natural rubber.

  According to the present invention, an aqueous slurry of an inorganic filler containing 1 to 200 parts by weight of an inorganic filler per 100 parts by weight of the rubber solid content in a natural rubber latex, and a surfactant of 1 to 30% by weight of the inorganic filler. There is provided a method for producing a natural rubber / inorganic filler masterbatch comprising spray-drying a dispersion obtained by blending the above.

According to the present invention, the production of a natural rubber / inorganic filler masterbatch comprising spray-drying a dispersion obtained by blending a natural rubber latex with a water slurry of an inorganic filler and a water- soluble polymer. A method is provided.

  According to the present invention, the natural rubber latex / inorganic filler masterbatch is instantly dried by spray drying instead of conventional processes such as coagulation with acid or natural coagulation, so that significant improvement in productivity and thermal efficiency is achieved. Furthermore, the quality of the masterbatch can be controlled much more easily by suppressing the heat deterioration of the natural rubber and the gelation of the natural rubber caused by the conventional heat drying. Moreover, there is an advantage that the viscosity is lowered by suppressing the gelation and the rubber mastication process can be simplified as compared with the conventional method.

  According to the present invention, a natural rubber / inorganic filler masterbatch is produced by drying an aqueous slurry of natural rubber latex and inorganic filler, for example, by spray drying described in JP-A-5-309201. Spray drying (spray drying) has been put into practical use in the food industry, for example, the production of powdered cheese, seasonings, fats and oils, confectionery, instant coffee and the like. In the present invention, by such spray drying, an aqueous slurry of a natural rubber (NR) latex having a solid content concentration of 60% by weight or less and an inorganic filler of 30% by weight or less, preferably NR / inorganic filler (solid content weight). Ratio) = 100/1 to 100/200, preferably at a temperature of 140 ° C. or less, more preferably 40 to 120 ° C., by spray-drying the latex in a drying chamber.

  The solid content concentration of the mixture of the natural rubber latex and inorganic filler slurry to be dried according to the present invention is preferably 60% by weight or less, and more preferably 20 to 50% by weight. If the solid content is too high, the viscosity of the natural rubber latex will increase and the stability will decrease, so there will be problems such as coagulation inside the transport pipe and poor spraying when thrown into the spray dryer. May occur. If the solid content concentration is too low, there is no problem with the drying itself, but it is not practical because the amount of treatment that can be dried per unit time is reduced.

  The inventors of the present invention mix a slurry of natural rubber latex and an inorganic filler in water to form a slurry or sol, and then spray dry to remove the solvent (water, organic solvent) and dry instantaneously. Thus, it has been found that a masterbatch can be produced in a short time and at a low cost without deteriorating or gelling the polymer. The method for injecting the natural rubber latex and the aqueous slurry liquid of the inorganic filler is not particularly limited. For example, the natural rubber latex and the inorganic filler slurry may be simultaneously injected from different nozzles, or each may be supplied separately. However, it may be allowed to meet at a certain ratio immediately before injection, and this may be injected from one nozzle, or a natural rubber latex and an inorganic filler water slurry may be mixed in advance and then supplied and injected from the nozzle. Good. There is no limitation in particular in the inorganic filler to be used, For example, arbitrary carbon black, a silica, etc. can be used. The viscosity at 25 ° C. of the mixed solution before drying thus treated is preferably 3000 mPa · s or less, more preferably 2000 mPa · s or less, and particularly preferably 1000 mPa · s or less. It is possible to effectively prevent clogging and poor drying.

  As described above, according to the method of the present invention, since the drying of the wet masterbatch containing the inorganic filler, which has been very time-consuming in the past, becomes instantaneous, the natural rubber / inorganic filler masterbatch can be processed with industrially sufficient processing capacity. It can be manufactured.

  If necessary, the liquid mixture to be spray-dried is mixed with rubber compounding agents that are generally blended in rubber compositions such as vulcanizing agents, vulcanization accelerators, anti-aging agents, metal oxides, fatty acids, resins, and oils. By drying by the method of the present invention, the compounding step of the compounding agent into the rubber, which has been conventionally performed by a Banbury mixer, a kneader or the like, can be largely omitted, and the compound is immediately added to a subsequent process such as extrusion or rolling. It becomes possible to supply.

  In the first aspect of the present invention, the natural rubber latex and / or the inorganic filler slurry has an interface of 1 to 30% by weight, preferably 3 to 20% by weight, based on the weight of the inorganic filler in advance, before spray drying. The desired master batch can be obtained by uniformly mixing the active agent and drying. By using a surfactant, it is possible to improve the stability of a mixed liquid of NR latex and inorganic filler that is unstable and easily gelled, and to make a master batch that achieves uniform dispersion. Also, by spray drying, you can dry with less molecular cutting and heat history, you can get a masterbatch with very good physical properties, you can also mix other rubber compounding agents together and dry Thus, the compounding in the subsequent process of these compounding agents can be omitted, and a significant improvement in productivity can be achieved.

The surfactant that can be used in the present invention is not particularly limited, and nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and the like can be used. In particular, the use of a nonionic surfactant or an anionic surfactant is preferred.
Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, sugar fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyhydric alcohol fatty acid ester, polyoxyethylene fatty acid ester. , Polyoxyethylene alkylamine, alkylalkanolamide, and the like.
Examples of the anionic surfactant include alkyl sulfate ester salt, polyoxyethylene alkyl ether sulfate ester salt, alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, naphthalene sulfonate, alkyl sulfosuccinate, Examples thereof include alkyl diphenyl ether disulfonate, fatty acid salt, polyvalent carboxylate, alkyl sulfate triethanolamine, alkenyl succinate, alkyl phosphate ester salt, polyoxyalkylene phosphate ester salt and the like.

  According to the second aspect of the present invention, a desired master batch is obtained by blending the natural rubber latex and / or inorganic filler slurry with a water-soluble polymer in advance and uniformly mixing and drying before drying. Can be obtained. The amount of the water-soluble polymer used is preferably 1 to 30% by weight, more preferably 3 to 20% by weight, based on the weight of the inorganic filler. It is possible to create a master batch that improves the stability of the liquid and achieves uniform dispersion. Moreover, by spray drying, drying with little molecular cutting and heat history can be performed, and very good physical properties can be exhibited.

  The water-soluble polymer used in the present invention is not particularly limited as long as it is water-soluble. For example, starch such as corn starch, natural polysaccharides such as mannan and pectin, seaweed such as agar and alginic acid, various gums, dextran and pullulan. Polysaccharides derived from microorganisms such as proteins such as glue and gelatin, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, synthetic polymers such as polyacrylic acid, polyacrylamide, polyvinyl alcohol, polyethyleneimine, polyethylene oxide, and polyvinylpyrrolidone Particularly preferred water-soluble polymers are polyvinyl alcohol (PVA) or water-soluble cellulose derivatives or salts thereof.

  Among the polyvinyl alcohols, sulfonic acid-modified polyvinyl alcohol is more preferable, and a mixed liquid having further excellent emulsion stability can be obtained. Of the water-soluble cellulose derivatives, carboxymethyl cellulose (CMC) or a salt thereof is particularly preferable, and those having a degree of etherification of 0.5 to 1.6, more preferably 0.6 to 1.5 are more preferable. This is because carboxymethyl cellulose (CMC) is superior in emulsification stability to ordinary emulsifiers and can provide a stable mixture, and CMC is cellulose, so the burden on the environment is very low and the stability is high. is there.

  According to the third aspect of the present invention, as shown in FIG. 1, for example, a spray drying apparatus comprising a spray nozzle and a drying chamber is provided with a raw material liquid (in FIG. Each of the rubber latex and the inorganic filler slurry) is pumped and mixed, and then sprayed from a spray nozzle and spray dried. At this time, by controlling the supply ratio of each pump, at least two kinds of raw material liquids can be supplied at any desired ratio. After converging at least two raw material liquid supply paths and the at least two raw material liquid supply paths into one path, and spraying them into a drying chamber from a spray nozzle, natural rubber latex and inorganic filler slurry, and optionally In the conventional method, a dispersion obtained by adding a surfactant or a water-soluble polymer to one or both of these is introduced from a separate raw material supply path and spray-dried to mix the latex and the inorganic filler slurry, followed by drying. The method is batch processing, which is suitable for mass production but not suitable for low-volume, multi-product production. On the other hand, each raw material is supplied separately and a master batch with an arbitrary blending ratio is controlled by controlling this supply ratio. Alternatively, the composition can be freely set and dried. The spray-dried master batch can be obtained, for example, by collecting it with a cyclone and separating it from a gas.

  In particular, the method of the present invention is very effective for preparing a master batch of a mixed liquid of NR latex and inorganic filler that is unstable and easily gelled after mixing. By spray drying, molecular cutting and thermal history can be prevented. Less drying is possible. In addition, you may add emulsifiers, such as surfactant, sulfonic acid modification PVA, or carboxymethylcellulose, to either as needed.

According to the present invention, when producing a master batch by mixing a natural rubber latex and an aqueous slurry of an inorganic filler and spray drying, the natural rubber latex and the inorganic filler slurry are separated from at least two raw material supply paths. , And after converging it into a single path, it is sprayed into a drying chamber and spray-dried to produce a masterbatch. The time from when this raw material supply path is converged to one before it is injected into the drying chamber is preferably 0.1 to 10 seconds, more preferably 1 to 5 seconds. If this time is too long, it may be solidified in the nozzle, which is not preferable.
The viscosity of the dispersion of the raw material latex and the inorganic filler slurry at 25 ° C. is preferably 3000 [mPa · s] or less, more preferably 100 to 2000 [mPa · s].

  The temperature of the drying chamber for spray drying is preferably 140 ° C. or lower, more preferably 40 to 120 ° C. According to the present invention, although not specifically shown in FIG. 1, two or more kinds of control mechanisms for automatically controlling the supply ratio of each pump for supplying the raw material liquid are provided. Raw materials can be supplied at an arbitrary ratio, and after converging at least two raw material supply paths into one, a desired master batch can be obtained by spraying and spraying from a spray nozzle. .

  Examples of the present invention will be described below, but it goes without saying that the scope of the present invention is not limited to these examples.

Examples 1-2 and comparative example 1 (conventional example)
As Comparative Example 1, from a mixed solution of 5 kg of natural rubber latex (Thai solid content concentration 35% by weight) and 0.7 kg of silica (inorganic filler) (Nippal VN3 manufactured by Tosoh Silica Co., Ltd.) by a conventional acid coagulation method. The manufacturing method of the natural rubber masterbatch by spray drying (spray drying) is shown. After collecting the natural rubber latex, remove foreign matter, mix silica slurry with water, solidify by adding formic acid to the mixture, stir and dry under reduced pressure at 80 ° C to remove moisture, roll mixing Thus, a desired rubber composition was obtained. The required time during this period was about 7 days as shown in Table I.

  On the other hand, in Example 1, 3 kg of the same natural rubber latex as in Comparative Example 1 was filtered and centrifuged, and then added with water to a solid content concentration of 20%, and the mixed solution mixed with 0.42 kg of silica was discharged to the outlet. Spray drying was performed using a spray dryer (spray dryer ADL310 manufactured by Yamato Kagaku) at a temperature of 80 ° C. In Example 2, natural rubber latex from which impurities were filtered without centrifugation was spray-dried under the same conditions. The drying times of the latexes of Examples 1-2 and Comparative Example 1 were compared in Table I. As is apparent from the results in Table I, in Examples 1 and 2 according to the present invention, the drying time for treating about 5 liters of latex was reduced to about 3 hours. The drying time is the processing capacity of the spray dryer, and the time required for the actual removal of moisture is 1 second or less. The amount of latex that can be dried per unit time is determined by the scale of the dryer. The throughput of the dryer used in Examples 1 and 2 according to the present invention was about 1.3 kg / hour.

Examples 3 to 4 and Comparative Example 2
The rubber properties of the natural rubber and silica masterbatch obtained in Examples 1-2 and Comparative Example 1 were compared. That is, in the formulation shown in Table II, the components other than the vulcanization accelerator and sulfur were kneaded with a 1.7 liter Banbury mixer for 5 minutes and released when the temperature reached 140 ° C. to obtain a master batch. A vulcanization accelerator and sulfur were kneaded with this master batch with an 8-inch open roll to obtain a rubber composition. The Mooney viscosity (100 ° C.) of the obtained unvulcanized rubber composition was measured according to JIS K6300, and the results are shown in Table II. Next, this composition was vulcanized in a 15 × 15 × 0.2 cm mold at 150 ° C. for 30 minutes to obtain a vulcanized rubber sheet, and rubber physical properties were measured by the following test methods. The results are shown in Table II.

300% modulus (MPa): Measured according to JIS K-6251 (JIS No. 3 dumbbell) Breaking strength: Measured according to JIS K-6251 (JIS No. 3 dumbbell) Break elongation: JIS K-6251 (JIS No. 3 dumbbell) Measured according to

  As is apparent from the results in Table II, in Examples 3 and 4 according to the present invention, the silica was improved in dispersibility, the Mooney viscosity was lowered, and the breaking property was improved by instantaneously drying the latex. Has been.

Examples 5 to 8 and Comparative Example 3
According to the formulation shown in Table III, spray drying was performed and a stabilization test was performed. Spray drying was performed by adding a surfactant or a water-soluble polymer to the carbon slurry at a outlet temperature of 80 ° C. using a spray dryer ADL310 manufactured by Yamato Scientific. The results are shown in Table III. In Comparative Example 3, gelation occurred immediately after mixing the NR latex and the carbon slurry, and spray drying could not be performed.

Stabilization test: Immediately after the production of the produced master batch and after standing at room temperature for 24 hours, the following criteria were observed and evaluated.
A: Maintains a uniform liquid state and does not show thickening or gelation.
○ ... Although it thickens slightly, it remains liquid.

Example 9
Using the spray drying apparatus shown in FIG. 1, according to the blending amounts of A and B shown in Table IV, using Yamato Scientific spray dryer ADL310, at an outlet temperature of 80 ° C., supplying NR latex and carbon black slurry, A masterbatch was produced. Normally, NR latex and carbon black slurry coagulate in a few tens of seconds when mixed, but in this method, both were mixed immediately before spraying, so that they could be spray dried without coagulation.

Examples 10-14
Next, rubber physical properties were evaluated by the formulations shown in Table V using the master batches of Examples 5 to 9 obtained above. That is, in the formulation shown in Table V, the components other than the vulcanization accelerator and sulfur were kneaded for 3 minutes with a 1.7 liter Banbury mixer and released when the temperature reached 120 ° C. to obtain a master batch. A vulcanization accelerator and sulfur were kneaded with this master batch with an 8-inch open roll to obtain a rubber composition. The obtained unvulcanized rubber composition was vulcanized in a 15 × 15 × 0.2 cm mold at 150 ° C. for 30 minutes to obtain a vulcanized rubber sheet, and the physical properties of the rubber were measured by the following test methods. The results are shown in Table V. The weight average molecular weight was measured and the results are shown in Table V.

300% modulus (MPa): Measured according to JIS K-6251 (JIS No. 3 dumbbell) Breaking strength: Measured according to JIS K-6251 (JIS No. 3 dumbbell) Break elongation: JIS K-6251 (JIS No. 3 dumbbell) Measured according to

  According to the method for producing a master batch from the natural rubber latex and the inorganic filler slurry according to the present invention, the solvent is removed by spray drying and the natural rubber latex and the inorganic filler slurry are instantaneously dried. The workability and thermal efficiency of batch production can be improved, and the quality of the obtained master batch is also free from the risk of thermal degradation and gelation as in the past, and the master batch production can be greatly simplified. At the same time, the rubber mixing time and energy by a Banbury mixer can be reduced, which is useful as a method for producing a new masterbatch.

It is explanatory drawing which shows an example of the spray-drying apparatus used by this invention.

Claims (22)

  It is obtained by blending a natural rubber latex with an aqueous slurry of an inorganic filler containing 1 to 200 parts by weight of an inorganic filler per 100 parts by weight of the rubber solid content and a surfactant of 1 to 30% by weight of the weight of the inorganic filler. A method for producing a natural rubber / inorganic filler masterbatch, characterized in that the resulting mixed liquid is spray-dried.   The manufacturing method of the masterbatch of Claim 1 which mix | blends the said surfactant with at least one of the water slurry of a natural rubber latex or an inorganic filler previously, and then stirs and mixes a natural rubber latex and an inorganic filler slurry.   The masterbatch manufacturing method according to claim 2, wherein the inorganic filler is carbon black.   The method for producing a masterbatch according to claim 1, wherein the surfactant is a nonionic surfactant or an anionic surfactant.   The master batch according to any one of claims 1 to 4, wherein the mixed solution before drying has a viscosity at 25 ° C of 3000 (mPa · s) or less.   The temperature of a spray-drying chamber is 140 degrees C or less, The manufacturing method of the masterbatch of any one of Claims 1-5.   The master batch according to any one of claims 1 to 6, wherein the dispersion further contains at least one compounding agent of a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a metal oxide, a fatty acid, a resin and an oil. Manufacturing method.   The masterbatch manufactured with the method of any one of Claims 1-7.   A method for producing a natural rubber / inorganic filler masterbatch, characterized in that a mixed liquid obtained by blending a natural rubber latex with a water slurry of an inorganic filler and a water-soluble polymer is spray-dried.   The manufacturing method of the masterbatch of Claim 9 which mix | blends the said water-soluble polymer beforehand with at least one of the natural rubber latex and the water slurry of an inorganic filler, and then stirs and mixes a latex and an inorganic filler slurry.   The method for producing a masterbatch according to claim 9 or 10, wherein the water-soluble polymer is polyvinyl alcohol (PVA), a water-soluble cellulose derivative or a salt thereof.   The method for producing a master batch according to claim 11, wherein the polyvinyl alcohol is sulfonic acid-modified polyvinyl alcohol.   The method for producing a master batch according to claim 11, wherein the water-soluble cellulose derivative has a degree of etherification of 0.5 to 1.6.   The method for producing a masterbatch according to any one of claims 11 to 13, wherein the viscosity of the mixed liquid at 25 ° C is 3000 (mPa · s) or less.   The method for producing a masterbatch according to any one of claims 9 to 14, wherein the temperature of the drying chamber for spray drying is 140 ° C or lower.   The master according to any one of claims 9 to 15, wherein the dispersion further contains at least one rubber compounding agent of vulcanizing agent, vulcanization accelerator, anti-aging agent, metal oxide, fatty acid, resin and oil. Batch manufacturing method.   The masterbatch manufactured by the method of any one of Claims 9-16.   In a method for producing a natural rubber / inorganic filler master batch by mixing and drying natural rubber latex and water slurry of 1 to 200 parts by weight of inorganic filler with respect to 100 parts by weight of natural rubber, from at least two raw material supply paths A method for producing a masterbatch, characterized in that a natural rubber latex and an inorganic filler slurry are separately supplied, converged in one path, and then sprayed and dried.   The method for producing a masterbatch according to claim 18, wherein the time from when the raw material supply paths are converged to one after being converged is 0.1 to 10 seconds.   The method for producing a masterbatch according to claim 18 or 19, wherein the natural rubber latex and the inorganic filler slurry each have a viscosity at 25 ° C of 3000 [mPa · s] or less.   The temperature of the drying chamber which injects latex is 140 degrees C or less, The manufacturing method of the masterbatch of any one of Claims 18-20.   The masterbatch manufactured by the method of any one of Claims 18-21.

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