JP2012121945A - Solid natural rubber, and method and apparatus for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus which produce a high-quality solid natural rubber efficiently and at a low cost; and to provide a solid natural rubber excellent in crosslinking characteristics.SOLUTION: The apparatus 1 for producing a solid natural rubber is constituted of: a rotation member 40 having a heated endless annular surface; a spray nozzle 26 to spray a natural rubber latex to the endless annular surface; and a scraper 72 arranged downstream of the spray nozzle 26 so as to slidably contact with the endless annular surface. A coating liquid of the natural rubber latex adhered on the endless annular surface dries along with the rotation of the endless annular surface and becomes a solid natural rubber G2, and the solid natural rubber G2 is exfoliated from the endless annular surface by the scraper 72.

Description

  The present invention relates to a solid natural rubber that is a raw material for producing rubber products. The invention also relates to a method and apparatus for producing solid natural rubber from natural rubber latex.

  Natural rubber has excellent properties such as high tensile strength and low heat generation due to vibration. For this reason, it has been conventionally used as a raw material for various rubber products such as tires, anti-vibration rubber, belts and rubber gloves. Solid natural rubber distributed as a raw material for producing rubber products is roughly classified into visual rating rubber (VGR) and technical rating rubber (TSR). A representative example of VGR is a smoke sheet (RSS) based on a rating based on “International Quality Packaging Standard for Natural Rubber Grades (commonly called Green Book)”. For example, RSS is manufactured as follows. First, after adding acid such as formic acid or acetic acid to the field latex and coagulating it, it is placed on a work table and stretched with a stick to adjust the thickness. Subsequently, water is squeezed while being stretched by a corrugated (rib-shaped) roll, and formed into a sheet shape. Next, the molded sheet is hung for several days and dried. Then, the dried smokeless sheet (USS) is washed with water, smoked and dried for several days. TSR is produced by pulverizing raw materials such as cup lamps (field latex naturally coagulated in a collection cup), pulverizing, washing with water, and then drying with hot air.

  All the manufacturing methods require a lot of manpower and time, and are inferior in productivity. In addition, foreign substances are easily mixed in the manufacturing process. For this reason, it is necessary to remove foreign matters in a subsequent process. In addition, the degree of drying varies depending on the manufacturing environment such as the weather. For this reason, in the obtained rubber, quality such as viscosity tends to vary.

  In view of such problems, for example, Patent Documents 1 to 3 disclose, as a new method for producing solid natural rubber, a method in which collected natural rubber latex is sprayed into a shock wave atmosphere by pulse combustion and dried. Yes.

JP 2005-194503 A JP 2006-348065 A JP 2007-330942 A

  According to the methods disclosed in Patent Documents 1 to 3, the dried rubber particles diffuse into the airflow. Further, the rubber particles have adhesiveness. For this reason, the diffused rubber particles are likely to adhere to the inner wall of the drying chamber. Therefore, the loss of rubber particles is large and the recovery rate is low. In addition, since an expensive pulse shock wave dryer is used, the manufacturing cost is high.

  On the other hand, as a method for producing solid natural rubber, a method in which natural rubber latex is directly applied to the surface of a rotating drum (so-called “solid coating”) and dried is also conceivable. However, when the coating solution of natural rubber latex is heated, a film is formed on the surface. Therefore, it takes time to dry the solid coating liquid to the inside of the film. Further, when heated for a long time, the natural rubber may be thermally deteriorated.

  This invention is made | formed in view of such a situation, and makes it a subject to provide the method and apparatus which manufacture a high quality solid natural rubber from natural rubber latex efficiently at low cost. It is another object of the present invention to provide a solid natural rubber excellent in cross-linking characteristics using the method.

  (1) In order to solve the above-mentioned problems, the solid natural rubber production apparatus of the present invention includes a rotating member having a heated endless annular surface, a spray nozzle for spraying natural rubber latex onto the endless annular surface, and the spray nozzle And a scraper disposed so as to be in sliding contact with the endless annular surface, and the coating solution of the natural rubber latex adhering to the endless annular surface is dried and solidified with the rotation of the endless annular surface. Natural rubber is formed, and the solid natural rubber is peeled off from the endless annular surface by the scraper.

  According to the solid natural rubber production apparatus of the present invention (hereinafter referred to as “the production apparatus of the present invention” as appropriate), the natural rubber latex is dried using a rotating member. For this reason, it is possible to reduce the number of processes and personnel, and to shorten the time, as compared with the conventional methods that require a lot of manpower and time. Further, it is possible to automate a series of processes of spraying natural rubber latex → drying → peeling solid natural rubber. Therefore, productivity is greatly improved. In addition, it is difficult for foreign matters to enter during drying. For this reason, it is possible to omit the foreign matter removing step that has been conventionally required. In addition, the drying process is not easily affected by the manufacturing environment such as the weather. Therefore, there is little variation in quality such as viscosity in the obtained solid natural rubber.

  In the conventional method, the coagulated natural rubber latex is stretched with a roll to squeeze out moisture. At this time, some proteins also flow with the water. In addition, some proteins flow even during washing with USS or the like. On the other hand, according to the manufacturing apparatus of the present invention, it is not necessary to squeeze out water or perform water washing. Therefore, protein outflow can be suppressed. That is, the natural rubber latex can be dried while the protein remains. Therefore, as will be shown in the following examples, a solid natural rubber having excellent crosslinking characteristics can be obtained.

  The natural rubber latex sprayed by the spray nozzle adheres to the endless annular surface in the form of dots. Therefore, the specific surface area becomes large and it is easy to dry compared with the case where the natural rubber latex is solid-coated. That is, natural rubber latex can be dried in a short time. For this reason, the thermal deterioration of the solid natural rubber obtained can be suppressed. Further, when heat is applied to natural rubber, the molecular chain is broken. When the end of the cleaved molecular chain is oxidized, an aldehyde group, a hydroxyl group or the like is generated. Aldehyde groups are easily recombined by aldol condensation. That is, when an aldehyde group is generated, the cleaved molecular chain is likely to recombine. For this reason, it is known that when the solid natural rubber after drying is stored, the viscosity increases. In this respect, according to the manufacturing apparatus of the present invention, the drying time, that is, the heating time can be shortened. Therefore, it is difficult to generate an aldehyde group by cleavage of the molecular chain. As a result, an increase in viscosity during storage of the obtained solid natural rubber can be suppressed.

  According to the production apparatus of the present invention, natural rubber particles are hardly diffused and adhered, which is a problem in a pulse shock wave dryer. That is, the loss of the raw natural rubber latex is small. Moreover, according to the manufacturing apparatus of this invention, solid natural rubber can be manufactured at low cost compared with the case where a pulse shock wave dryer is used.

  The manufactured solid natural rubber becomes a rubber product through a process of blending and kneading various additives such as carbon black. For example, according to the production apparatus of the present invention, the dried solid natural rubber can be formed into a sheet shape. Therefore, it is easy to transfer the solid natural rubber to the subsequent process.

  (2) Preferably, in the configuration of the above (1), the rotating member is a drum that is supported substantially horizontally, and the endless annular surface is an outer peripheral surface of the drum.

  According to this configuration, a single rotating shaft of the rotating member is sufficient as compared to the case of using a belt conveyor-like rotating member (of course, this case is also included in (1) above). This simplifies the configuration. Further, the endless annular surface is entirely supported from the radially inner side. For this reason, the endless annular surface is difficult to rattle. The rotating member is pivotally supported substantially horizontally. For this reason, gravity acts substantially uniformly over the entire axial direction of the endless annular surface. Therefore, unevenness (shading) hardly occurs in the coating liquid of the natural rubber latex that has adhered.

  (3) Preferably, in the configuration of the above (1) or (2), the spray nozzle may be configured to be movable in a direction intersecting with the rotation direction of the endless annular surface.

  According to this configuration, the natural rubber latex can be easily applied over a wide range of the endless annular surface. For example, solid natural rubber having a desired width and thickness can be manufactured by adjusting the moving range and moving speed of the spray nozzle.

  (4) Preferably, in the configuration according to any one of the above (1) to (3), a configuration further including a biasing force adjustment unit having a spring that elastically contacts the scraper with the endless annular surface by a biasing force. Better to do.

  In this configuration, the scraper is elastically contacted with the endless annular surface by the biasing force of the spring. Therefore, the solid natural rubber formed on the endless annular surface can be reliably peeled off. Thereby, the collection rate of solid natural rubber improves more. Further, if the solid natural rubber after drying remains on the endless annular surface without being peeled off, it is deteriorated by reheating. In this regard, according to the present configuration, there is little leftover of solid natural rubber. Accordingly, there is little possibility that the heat-degraded solid natural rubber, that is, the second-round solid natural rubber, is mixed into the first-round solid natural rubber.

  (5) Moreover, the manufacturing method of the solid natural rubber of this invention is a spray process which sprays natural rubber latex on the heated endless annular surface of a rotating member, and the coating liquid of this natural rubber latex adhering to this endless annular surface Are dried while rotating the endless annular surface to form a solid natural rubber, and a peeling step of peeling the solid natural rubber from the endless annular surface.

  According to the method for producing a solid natural rubber of the present invention (hereinafter referred to as “the production method of the present invention” as appropriate), the natural rubber latex is dried using a rotating member. Therefore, the productivity of solid natural rubber is remarkably improved as in the case of the production apparatus of the present invention. In addition, it is difficult for foreign matters to enter during drying. For this reason, it is possible to omit the foreign matter removing step that has been conventionally required. In addition, the drying process is not easily affected by the manufacturing environment such as the weather. Therefore, there is little variation in quality such as viscosity in the obtained solid natural rubber.

  Further, according to the production method of the present invention, the natural rubber latex can be dried while the protein remains. Therefore, as will be shown in the following examples, a solid natural rubber having excellent crosslinking characteristics can be obtained.

  Moreover, according to the manufacturing method of this invention, natural rubber latex can be dried in a short time. For this reason, the thermal deterioration of the solid natural rubber obtained can be suppressed. In addition, aldehyde groups are not easily generated by molecular chain cleavage. Therefore, an increase in viscosity during storage of the obtained solid natural rubber can be suppressed.

  According to the production method of the present invention, there is no problem of diffusion and adhesion of natural rubber particles in the production method using a shock wave by pulse combustion. That is, the loss of the raw natural rubber latex is small. In addition, according to the production method of the present invention, solid natural rubber can be produced at a lower cost compared to a production method using a shock wave by pulse combustion.

  According to the production method of the present invention, the dried solid natural rubber can be formed into a sheet. Therefore, it is easy to transfer the manufactured solid natural rubber to a subsequent process.

  (6) Preferably, in the configuration of (5) above, the temperature of the endless annular surface is preferably 120 ° C. or higher and 200 ° C. or lower.

  If the temperature of the endless annular surface of the rotating member is too low, the natural rubber latex cannot be sufficiently dried in a practical drying time. On the other hand, if the temperature of the endless annular surface is too high, the coated natural rubber latex may be excessively heated and deteriorated. Also, energy is wasted and not economical. In this regard, according to the present configuration, it is possible to reliably perform drying while suppressing thermal degradation in a practical drying time.

  (7) Preferably, in the configuration of the above (5) or (6), the time for the drying step is preferably from 0.1 minutes to 5 minutes.

  When the time of the drying process is too long, the coated natural rubber latex is excessively heated and may be deteriorated. Further, since the time for one rotation of the rotating member becomes longer, the productivity is lowered. On the contrary, if the time of the drying process is too short, the natural rubber latex cannot be sufficiently dried. In this regard, according to the present configuration, it is possible to reliably perform drying while suppressing thermal degradation.

  (8) Preferably, in any one of the constitutions (5) to (7), the natural rubber latex is a latex whose molecular weight is reduced by adding a radical generator, and the solid natural rubber is a molecular chain. It is better to have a structure that does not contain an aldehyde group.

  Generally, a solid natural rubber produced by a conventional method has a large molecular weight and a high viscosity. Therefore, when solid natural rubber is used as a raw material for producing rubber products, mastication is performed in advance in order to reduce viscosity and improve processability. When mastication is performed, the molecular chain of the rubber is cut and the molecular weight is lowered. Thereby, the viscosity of solid natural rubber can be reduced. However, it is difficult to uniformly knead the whole. For this reason, the viscosity tends to vary from lot to lot. In addition, the number of processes increases by the amount of mastication. For this reason, the manufacturing time of a rubber product becomes long and cost becomes high. In the mastication step, heat is applied to the solid natural rubber, and the molecular chain is cut. As described in the configuration (1) above, when the end of the broken molecular chain is oxidized, an aldehyde group, a hydroxyl group, or the like is generated. Aldehyde groups are easily recombined by aldol condensation. Therefore, it is known that the viscosity increases while the rubber after mastication is stored.

According to this configuration, a latex whose molecular weight is reduced by adding a radical generator is used as the natural rubber latex. Since the molecular chain of the rubber is cleaved and reduced in molecular weight in the latex state, the viscosity of the natural rubber after solidification can be reduced. That is, a solid natural rubber having a desired viscosity can be obtained. Therefore, the obtained solid natural rubber can be used as a raw material for producing rubber products as it is without mastication. Since the mastication step can be omitted, the number of manufacturing steps can be reduced. As a result, it is possible to reduce the manufacturing time and cost of the rubber product. Furthermore, according to this structure, the solid natural rubber which does not contain an aldehyde group in a molecular chain can be obtained. Therefore, an increase in viscosity due to recombination of aldehyde groups can be suppressed during storage of the solid natural rubber. In this specification, “not containing an aldehyde group” means that a shift derived from an aldehyde group in ¹ H-NMR measurement using an NMR (nuclear magnetic resonance) apparatus “INOVA-400” manufactured by Varian is used. Means not detected.

  (9) The solid natural rubber of the present invention is manufactured by drying a coating solution of natural rubber latex sprayed on the heated endless annular surface of the rotating member while rotating the endless annular surface. Features.

  The solid natural rubber of the present invention is produced by the production method of the present invention. Therefore, it is difficult for foreign matters to be mixed in the drying process of the natural rubber latex. Moreover, there is little variation in the dry state. Therefore, in the solid natural rubber of the present invention, there is little variation in quality such as viscosity. Further, the solid natural rubber of the present invention has a large amount of residual protein as compared with the solid natural rubber produced by the conventional method. For this reason, as shown in a later Example, it is excellent in cross-linking properties. The solid natural rubber of the present invention is dried in a relatively short time. Therefore, the degree of thermal degradation is small. Moreover, it is difficult to generate an aldehyde group due to the cleavage of the molecular chain. For this reason, the viscosity hardly increases during storage.

  (10) Preferably, in the configuration of the above (9), the natural rubber latex is a latex whose molecular weight is reduced by addition of a radical generator, and the rubber does not contain an aldehyde group in the molecular chain. Is good.

  As described in the configuration (8) above, when a latex having a low molecular weight is added as a natural rubber latex by adding a radical generator, a solid natural rubber adjusted to a desired viscosity can be obtained. Therefore, the solid natural rubber of this configuration can be used as it is as a raw material for producing rubber products without performing mastication. Moreover, the solid natural rubber of this structure does not contain an aldehyde group in the molecular chain. Therefore, during storage, there is little risk of an increase in viscosity due to recombination of aldehyde groups.

It is a perspective view of the manufacturing apparatus of solid natural rubber of one embodiment of the present invention. It is the front-back direction sectional drawing seen from the right side of the manufacturing apparatus. It is a perspective view of the drum part and mount part of the manufacturing apparatus. It is an enlarged view in the frame IV of FIG. It is an enlarged view in the frame V of FIG. FIG. 6 is an enlarged view in a frame VI of FIG. 5. It is a graph of the torque change with respect to the crosslinking time of the solid natural rubber of an Example.

  Hereinafter, embodiments of the solid natural rubber, the production method thereof, and the production apparatus of the present invention will be described.

<Production equipment for solid natural rubber>
In FIG. 1, the perspective view of the manufacturing apparatus of the solid natural rubber of this embodiment is shown. The housing portion is shown in a transparent manner. FIG. 2 shows a cross-sectional view in the front-rear direction viewed from the right side of the manufacturing apparatus. FIG. 3 is a perspective view of the drum unit and the gantry unit of the manufacturing apparatus.

  As shown in FIGS. 1 to 3, a solid natural rubber production apparatus (hereinafter abbreviated as “production apparatus”) 1 of the present embodiment includes a nozzle part 2, a housing part 3, a drum part 4, and a discharge part. A hopper 5, a gantry unit 6, a scraper unit 7, and a heating unit 8 are provided.

[Mounting unit 6]
As shown mainly in FIG. 3, the gantry 6 is made of steel and includes a bottom frame 60, a pair of left and right side frames 61 </ b> L and 61 </ b> R, and a motor support 62. The bottom frame portion 60 has a rectangular frame shape. The side frame portion 61L has a C-shape that opens downward. The side frame portion 61L is erected upward from the left edge of the bottom frame portion 60. The side frame portion 61R has a C-shape that opens downward. The side frame portion 61 </ b> R is erected upward from the right edge of the bottom frame portion 60. The motor support portion 62 has a rectangular plate shape. The motor support portion 62 protrudes rightward from the right surface (outer surface) of the side frame portion 61R.

[Housing 3]
The housing part 3 includes a housing body 30, a gear case 31, a pair of left and right pulley cases 32 </ b> L and 32 </ b> R, and an exhaust cylinder 33. The housing body 30 is made of steel and has a box shape. The housing body 30 is disposed between the pair of left and right side frame portions 61L and 61R.

  The gear case 31 is made of steel and has a box shape. The gear case 31 is disposed on the right side of the housing body 30 with the side frame portion 61R interposed therebetween. The gear case 31 is supported on the upper surface of the motor support portion 62.

  The pulley case 32L is made of steel and has a box shape that opens to the right. The pulley case 32 </ b> L is laid down on the left surface of the left wall of the housing body 30. The pulley case 32R is made of steel and has a box shape that opens to the left. The pulley case 32 </ b> R is laid on the right side of the right wall of the housing body 30. The pulley case 32L and the pulley case 32R face each other in the left-right direction. The exhaust tube 33 is made of steel and has a cylindrical shape. The exhaust tube 33 protrudes upward from the top of the housing body 30.

[Drum part 4]
The drum unit 4 includes a drum 40, a pair of left and right rotating shafts 41L and 41R, a large gear 42, a small gear 43, a drum motor 44, a motor bracket 45, and a pair of left and right bearings 46L and 46R. ing.

  The bearing 46L is disposed on the upper surface of the side frame portion 61L. The bearing 46R is disposed on the upper surface of the side frame portion 61R. The bearing 46L and the bearing 46R face each other in the left-right direction.

  The rotation shaft 41L extends in the left-right direction. The rotating shaft 41L is rotatably supported by the bearing 46L. The rotation shaft 41R extends in the left-right direction. The rotating shaft 41R is rotatably supported by the bearing 46R.

  The drum 40 is made of steel and has a hollow cylindrical shape that is long in the left-right direction. A rotation shaft 41L is fixed to the center of the left wall of the drum 40. A rotation shaft 41R is fixed to the center of the right wall of the drum 40. Therefore, as indicated by the white arrow in FIG. 2, the drum 40 can rotate around the rotation shafts 41 </ b> L and 41 </ b> R in the direction of “front → up → back → down → front again”. The large gear 42 is made of steel and is fixed to the right end of the rotating shaft 41R. For this reason, the large gear 42 can rotate together with the drum 40.

  The motor bracket 45 is made of steel and is disposed on the upper surface of the motor support portion 62. The drum motor 44 is attached to the motor bracket 45. The small gear 43 is fixed to the left end of the rotation shaft of the drum motor 44. For this reason, the small gear 43 can rotate together with the rotating shaft of the drum motor 44. The small gear 43 and the large gear 42 mesh with each other. The driving force of the drum motor 44 is transmitted to the drum 40 via the small gear 43, the large gear 42, and the rotating shaft 41R.

[Discharge hopper 5]
The discharge hopper 5 is made of steel and has a bottomed rectangular tube shape that is pointed downward. The discharge hopper 5 is installed between the left wall and the right wall of the housing body 30. The discharge hopper 5 is disposed below the front portion of the drum 40.

[Heating unit 8]
The heating unit 8 includes high-frequency induction heating type heating devices 80U and 80D. The heating devices 80U and 80D are arranged close to the front upper part of the outer peripheral surface of the drum 40. The heating devices 80U and 80D are continuous in the vertical direction.

  The heating device 80U includes a coil (not shown). The coil is connected to an AC power source (not shown). When the coil is energized, a high-density eddy current is generated in the upper front portion of the outer peripheral surface of the drum 40. Due to the Joule heat accompanying the eddy current, the front upper part of the outer peripheral surface of the drum 40 generates heat. In this way, the heating device 80U heats the front upper portion of the outer peripheral surface of the drum 40. The configuration of the heating device 80D is the same as the configuration of the heating device 80U.

[Nozzle part 2]
FIG. 4 shows an enlarged view in the frame IV of FIG. As shown in FIGS. 1, 2, and 4, the nozzle unit 2 includes a belt 20, a pair of left and right pulleys 21 </ b> L and 21 </ b> R, a support member 22, a nozzle motor 23, a motor bracket 24, and a nozzle bracket 25. And a spray nozzle 26.

  The motor bracket 24 is made of steel and has a rectangular plate shape. The motor bracket 24 is fixed to the rear surface of the rear wall of the pulley case 32L. The nozzle motor 23 is attached to the rear surface of the motor bracket 24. The rotating shaft 230 of the nozzle motor 23 passes through the motor bracket 24 and the rear wall of the pulley case 32L and enters the inside of the pulley case 32L. The pulley 21 </ b> L is fixed to the front end of the rotating shaft 230.

  The support member 22 is disposed on the upper surface of the bottom wall of the pulley case 32R. The pulley 21 </ b> R is rotatably supported by the support member 22. The belt 20 is wound around a pair of left and right pulleys 21L and 21R.

  The nozzle bracket 25 is made of steel and has a J-plate shape. The J-shaped tip of the nozzle bracket 25 is fixed to the upper part of the belt 20. The spray nozzle 26 is attached to the lower surface of the nozzle bracket 25.

  The driving force of the nozzle motor 23 is transmitted to the spray nozzle 26 via the pulleys 21L and 21R, the belt 20, and the nozzle bracket 25. That is, the spray nozzle 26 can move in the left-right direction (direction intersecting with the rotation direction of the drum 40) together with the upper portion of the belt 20.

  The spray nozzle 26 is disposed in the vicinity of the upper part of the outer peripheral surface of the drum 40. Further, the spray nozzle 26 is disposed on the upper side of the heating device 80U. As shown in FIG. 4, liquid natural rubber latex is supplied to the spray nozzle 26 from the outside of the housing body 30 via a pipe (not shown). From the spray nozzle 26, a droplet G1 of natural rubber latex is sprayed in the form of dots on the upper part of the outer peripheral surface of the drum 40. A coating film is formed on the outer peripheral surface of the drum 40 by spraying the droplet G1 from the spray nozzle 26 that is reciprocating in the left-right direction.

[Scraper unit 7]
FIG. 5 shows an enlarged view in the frame V of FIG. As shown in FIGS. 1, 2, and 5, the scraper portion 7 is disposed in the vicinity of the front portion of the outer peripheral surface of the drum 40. Further, the scraper portion 7 is disposed above the discharge hopper 5. The scraper portion 7 includes a swinging portion 71, a scraper 72, seven biasing force adjustment units 76, a unit holding plate 77, and a nut stopper holding rib 78.

  The swing part 71 includes a swing plate 710, a spring housing member 711, a swing shaft 712, and a pair of left and right ear parts 713. The swing shaft 712 is made of steel and is laid between the left wall and the right wall of the housing body 30. The swing plate 710 is made of steel and has a thin plate shape that is long in the left-right direction. The pair of left and right ear portions 713 are disposed at both left and right ends of the swing plate 710. The pair of ear portions 713 are rotatably mounted on the swing shaft 712.

  The spring housing member 711 is made of steel and has a prismatic shape that is long in the left-right direction. The spring accommodating member 711 is fixed to the front surface of the swing plate 710. Seven spring accommodating portions 711 a are recessed in the front surface of the spring accommodating member 711. The seven spring accommodating portions 711a are arranged in the left-right direction.

  The scraper 72 is made of steel and has a thin plate shape that is long in the left-right direction. The scraper 72 is attached to the lower end of the swing plate 710. The lower end of the scraper 72 is in contact with the front portion of the outer peripheral surface of the drum 40. The swing plate 710, the spring housing member 711, and the scraper 72 can rotate around the swing shaft 712.

  The unit holding plate 77 is made of steel and has a thin plate shape that is long in the left-right direction. The unit holding plate 77 is installed between the left wall and the right wall of the housing body 30. The unit holding plate 77 is disposed in front of the swing plate 710.

  FIG. 6 shows an enlarged view in the frame VI of FIG. As shown in FIG. 6, the nut stopper holding rib 78 includes a pair of left and right ear portions 780, a swing shaft 781, seven spring accommodating portions 782, and a rib body 783. The rib main body 783 is made of steel and has a thin plate shape that is long in the left-right direction. The rib body 783 protrudes forward from the front surface of the unit holding plate 77. The pair of left and right ears 780 are made of steel and project downward from the left and right edges of the rib body 783. The swing shaft 781 is provided between the pair of ear portions 780. The swing shaft 781 is disposed below the rib main body 783. The seven spring accommodating portions 782 are recessed in the lower surface of the rib main body 783 side by side in the left-right direction.

  Returning to FIG. 5, the seven urging force adjustment units 76 are attached to the unit holding plate 77 side by side in the left-right direction. The biasing force adjustment unit 76 includes a shaft portion 760, a nut 761, a holder 762, a nut stopper 763, and a spring 765.

  The shaft portion 760 includes a handle 760a, a shaft 760b, a ring 760c, and a bearing 760d. The shaft 760b is made of steel and penetrates the unit holding plate 77 in the front-rear direction. The shaft 760 b is screwed to the unit holding plate 77. The handle 760a is fixed to the front end of the shaft 760b. The ring 760c and the bearing 760d are attached to the rear end 760b1 of the shaft 760b in order from the front to the rear. The nut 761 is mounted on the shaft 760b. The nut 761 is screwed into the shaft 760b. The nut 761 is in contact with the front surface of the unit holding plate 77.

  The holder 762 is made of steel and has a long cylindrical shape in the front-rear direction. The holder 762 covers the rear end 760b1 of the shaft 760b. The holder 762 includes a bearing housing portion 762a, a spring housing portion 762b, and a partition wall 762c. The bearing housing portion 762 a is recessed in the front surface of the holder 762. A bearing 760d is accommodated in the bearing accommodating portion 762a. The spring accommodating portion 762 b is recessed on the rear surface of the holder 762. The spring accommodating portion 762b and the spring accommodating portion 711a of the spring accommodating member 711 are opposed to each other in the front-rear direction. The partition wall 762c partitions the bearing housing portion 762a and the spring housing portion 762b. The rear end 760b1 of the shaft 760b reaches the spring accommodating portion 762b via the bearing accommodating portion 762a and the partition wall 762c from the front to the rear.

  The spring 765 is a so-called coil spring. The front end of the spring 765 is accommodated in the spring accommodating portion 762b. The rear end of the spring 765 is accommodated in the spring accommodating portion 711a. The spring 765 biases the spring housing member 711 backward. The scraper 72 is in elastic contact with the front portion of the outer peripheral surface of the drum 40 by the biasing force.

  As shown in FIG. 6, the nut stopper 763 includes an engaging claw 763a, a spring 763d, and a bolt 763e. The engaging claw 763a is made of steel and has a prismatic shape. The engaging claw 763a is rotatably mounted on the swing shaft 781. A spring accommodating portion 763a1 is recessed in the upper surface of the engaging claw 763a. The spring accommodating portion 763a1 and the spring accommodating portion 782 of the nut stopper holding rib 78 face each other in the vertical direction. The spring 763d is a so-called coil spring. The upper end of the spring 763d is accommodated in the spring accommodating portion 782. The lower end of the spring 763d is accommodated in the spring accommodating portion 763a1. The spring 763d biases the engaging claw 763a downward. With the urging force, the front end of the engaging claw 763 a is engaged with the front edge of the nut 761. The engaging claw 763a prevents the nut 761 from being loosened (separated from the unit holding plate 77). The bolt 763e is screwed to the rib main body 783. The bolt 763e penetrates the rib main body 783 in the vertical direction. The front end (lower end) of the bolt 763e is in contact with the rear end of the engagement claw 763a. The bolt 763e regulates the rotation of the engagement claw 763a.

  Hereinafter, a method for adjusting the elastic contact force of the scraper 72 with respect to the drum 40 will be briefly described. In order to increase the elastic contact force of the scraper 72 with respect to the drum 40, first, as shown in FIG. 6, by increasing the immersion amount of the bolt 763e with respect to the rib main body 783, the front end of the bolt 763e can be Push the end down. The engagement claw 763a swings around the swing shaft 781 in the clockwise direction in FIG. 6 against the urging force of the spring 763d. For this reason, the front end of the engaging claw 763a is disengaged from the front edge of the nut 761, as shown by a one-dot chain line in FIG.

  Next, as shown in FIG. 5, the shaft 760b is moved backward by turning the handle 760a. When the shaft 760b moves backward, the holder 762 also moves backward. For this reason, the spring 765 is compressed. Therefore, the elastic contact force of the scraper 72 with respect to the drum 40 is increased.

  Finally, as shown in FIG. 6, the immersion amount of the bolt 763 e with respect to the rib main body 783 is reduced. The engagement claw 763a swings about the swing shaft 781 counterclockwise in FIG. 6 by the biasing force of the spring 763d. For this reason, the front end of the engaging claw 763a engages with the front edge of the nut 761, as shown by the solid line in FIG.

  In order to reduce the elastic contact force of the scraper 72, the shaft 760b and the holder 762 are moved forward by turning the handle 760a in the direction opposite to the above direction. Then, the spring 765 is extended. That is, the elastic compressive force of the spring 765 is released.

<Method for producing solid natural rubber>
Hereinafter, the rotation direction of the drum 40 is defined with reference to the starting edge A where the droplet G1 adheres to the drum 40, as shown in FIG. That is, the clockwise direction from the starting edge A in FIG. 2 is defined as the “rotation direction”. As shown in FIG. 2, on the radially outer side of the drum 40, the spray nozzle 26, the scraper 72, the heating device 80D, and the heating device 80U are arranged in order from the upstream side in the rotational direction to the downstream side in the rotational direction. . Further, by operating the seven biasing force adjusting units 76 in advance, the elastic contact force of the scraper 72 with respect to the drum 40 is adjusted.

  First, the drum motor 44 is driven to rotate the small gear 43 and the large gear 42, whereby the drum 40 is moved in the direction of “front → up → back → down → front again” about the rotation shafts 41 </ b> L and 41 </ b> R. Rotate. The rotation speed is about 1 rpm (about 1 rotation per minute). Next, the coils of the heating devices 80U and 80D are energized to heat the front upper part of the outer peripheral surface of the drum 40. By rotating the drum 40 in this state, the entire outer peripheral surface of the drum 40 is heated. When the outer peripheral surface of the drum 40 reaches about 180 ° C., a droplet G1 of natural rubber latex (rubber concentration 10 to 60% by mass) is sprayed from the spray nozzle 26 onto the outer peripheral surface of the drum 40 (spraying process). . At this time, the nozzle motor 23 is driven to rotate the pulleys 21L and 21R, so that the spray nozzle 26 attached to the belt 20 is repeatedly reciprocated in the left-right direction. The spray nozzle 26 sprays droplets G1 of natural rubber latex in a dot shape while repeatedly reciprocating in the left-right direction. The natural rubber latex droplets G1 overlap and adhere to the outer peripheral surface of the drum 40, whereby a coating film is formed.

  Thereafter, the natural rubber latex droplets G1 are bonded together while being dried along with the rotation of the drum 40, and become a natural rubber sheet G2 (drying step). The natural rubber sheet G2 is included in the solid natural rubber of the present invention. During this time, the steam generated with the drying is discharged through the exhaust pipe 33.

  When the drum 40 rotates about ¾, the formed natural rubber sheet G2 is peeled off from the outer peripheral surface of the drum 40 by the scraper 72 (peeling step). The peeled natural rubber sheet G2 falls due to its own weight and is accommodated in the discharge hopper 5. Thereafter, the outer peripheral surface of the drum 40 is again heated to a predetermined temperature by the heating devices 80D and 80U. In this way, a series of steps of spraying the natural rubber latex droplet G1 → drying → peeling the natural rubber sheet G2 is repeated.

<Natural rubber sheet G2 (solid natural rubber)>
The thickness of the obtained natural rubber sheet G2 is about 0.1 to 1 mm. Further, a relatively large amount of protein remains in the natural rubber sheet G2. Further, since the heating time is as short as 1 minute, the degree of thermal deterioration in the natural rubber sheet G2 is small.

<Effect>
The effects of the solid natural rubber, the manufacturing method and the manufacturing apparatus of the present embodiment will be described. According to this embodiment, it is possible to automate a series of steps of spraying the natural rubber latex droplet G1, drying, and peeling the natural rubber sheet G2. Therefore, the process and personnel can be reduced and the time can be shortened as compared with the conventional methods that require a lot of manpower and time. Thereby, productivity of solid natural rubber improves markedly. In addition, it is difficult for foreign matters to be mixed in when the natural rubber latex is dried. Therefore, the step of removing foreign matter, which has been necessary conventionally, can be omitted. Also, the drying process is not easily affected by the manufacturing environment such as the weather. Therefore, the manufactured solid natural rubber (natural rubber sheet G2) has little variation in quality such as viscosity.

  According to the present embodiment, the water is not squeezed out and washed with the natural rubber latex coagulum. Therefore, protein outflow from natural rubber can be suppressed. That is, a relatively large amount of protein remains in the manufactured solid natural rubber. Therefore, the produced solid natural rubber is excellent in cross-linking properties.

  According to this embodiment, the natural rubber latex droplet G1 sprayed by the spray nozzle 26 adheres to the outer peripheral surface of the drum 40 in the form of fine dots. Therefore, the specific surface area becomes large and it is easy to dry compared with the case where the natural rubber latex is solid-coated. That is, natural rubber latex can be dried in a short time of less than 1 minute. For this reason, the thermal deterioration of natural rubber can be suppressed. Moreover, the production | generation of the aldehyde group by cutting | disconnection of the molecular chain of rubber | gum can also be suppressed. Therefore, according to the solid natural rubber of this embodiment, the viscosity hardly increases during storage.

  According to this embodiment, the problem of diffusion and adhesion of natural rubber particles does not occur in the manufacturing method using shock waves by pulse combustion. That is, the loss of the raw natural rubber latex is small. Moreover, solid natural rubber can be manufactured at low cost compared with the case where a pulse shock wave dryer is used. Furthermore, the natural rubber latex is recovered as a natural rubber sheet G2 after drying. For this reason, it is easy to transfer the manufactured solid natural rubber to a subsequent process.

  According to the manufacturing apparatus 1 of the present embodiment, the drum 40 is employed as the rotating member. For this reason, a manufacturing apparatus can be comprised easily. Further, by rotating the drum 40, the outer peripheral surface to which the natural rubber latex is adhered can be stably rotated. Moreover, gravity acts substantially uniformly over the entire axial direction of the outer peripheral surface. Therefore, unevenness (shading) hardly occurs in the coating liquid of the natural rubber latex that has adhered.

  Further, the front upper portion of the outer peripheral surface of the drum 40 is heated by the high frequency induction heating type heating devices 80U and 80D. Thereby, the outer peripheral surface of the drum 40 can be efficiently heated. Further, as shown in FIG. 2, on the radially outer side of the drum 40, the spray nozzle 26, the scraper 72, the heating device 80D, and the heating device 80U are arranged in order from the upstream side in the rotational direction to the downstream side in the rotational direction. It is out. In other words, the heating device 80U and the heating device 80D are arranged in the vicinity of the starting edge A where the droplet G1 of natural rubber latex adheres to the drum 40. For this reason, as shown in FIG. 4, the temperature of the portion where the droplet G1 adheres on the outer peripheral surface of the drum 40 is unlikely to decrease. Therefore, the natural rubber latex can be dried at the set temperature.

  Further, the spray nozzle 26 is movable in the left-right direction via the belt 20. Thereby, the droplet G1 of natural rubber latex can be easily applied to the entire outer peripheral surface of the drum 40.

  Further, the scraper unit 7 of the manufacturing apparatus 1 includes an urging force adjustment unit 76. The scraper 72 is elastically contacted with the outer peripheral surface of the drum 40 by the biasing force of the spring 765. Therefore, the formed natural rubber sheet G2 can be reliably peeled off by the scraper 72. Thereby, the collection rate of solid natural rubber improves more. Moreover, since there is little leftover of the natural rubber sheet G2, there is little possibility that the heat-degraded solid natural rubber, that is, the solid rubber of the second rotation is mixed into the natural rubber sheet G2 formed in the first rotation.

<Others>
The embodiment of the solid natural rubber, the production method and the production apparatus of the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

[Manufacturing equipment]
For example, in the above embodiment, a hollow cylindrical drum is used as the rotating member. However, the rotating member only needs to have an endless annular surface, and the material, shape, and hollow or solid are not particularly limited. For example, a rotating member such as a tapered shape or a barrel shape may be used. Further, a belt conveyor-like rotating member may be used. In this case, the outer peripheral surface of the belt is an endless annular surface.

  In the said embodiment, the drum (rotary member) was heated with the heating apparatus of the high frequency induction heating system. However, the type of the heating device is not particularly limited. For example, a heating device such as an electric heating type or a microwave heating type may be used. Further, when the rotating member is solid, not only the outer peripheral surface but also the whole may be heated. Moreover, when the rotating member is hollow, a heating device may be arranged on the radially inner side of the rotating member. This increases the space efficiency. Furthermore, when the rotating member is hollow, it may be heated by steam. In addition, about a heating apparatus, you may use 2 or more types together.

  In the said embodiment, one spray nozzle was arrange | positioned so that a movement in the left-right direction was possible. However, the number and type of spray nozzles are not particularly limited. For example, the orifice diameter of the spray nozzle may be appropriately determined in consideration of the temperature of the endless annular surface of the rotating member, the rotational speed, etc. so that the natural rubber latex can be reliably dried. Note that the spray nozzle need not move. A plurality of spray nozzles may be juxtaposed in the axial direction of the rotating member.

  Further, the material, shape, attachment mechanism and the like of the scraper are not particularly limited. For example, as long as the scraper can be disposed in sliding contact with the endless annular surface of the rotating member, the urging force adjusting unit may be omitted. In addition to the spring, an elastic member such as rubber may be used to adjust the elastic contact force of the scraper with respect to the rotating member.

  In the above embodiment, the housing portion is installed, and the drum is arranged inside the housing body. However, the housing portion may not be provided. Moreover, in the said embodiment, the peeled natural rubber sheet was accommodated in the discharge hopper. The peeled natural rubber sheet may be cut into a predetermined length and stored. Moreover, you may comprise the manufacturing apparatus of this invention further with the winding roller which winds up and accommodates the natural rubber sheet peeled with the scraper. According to this structure, the peeled natural rubber sheet can be accommodated in a roll shape on the spot. Therefore, it is easy to convey to a post process.

[Production method]
The conditions of the drying process, that is, the temperature of the outer peripheral surface (endless annular surface) of the drum and the drying time (time from the spraying of the natural rubber latex to the peeling of the natural rubber sheet) are not limited to the above embodiment. What is necessary is just to determine suitably in consideration of the orifice diameter of a spray nozzle, the amount of spraying, etc.

  As the raw natural rubber latex, a field latex collected by tapping or a latex (high ammonia latex) treated with ammonia added thereto may be used. The rubber content (dry rubber mass, hereinafter the same) concentration of natural rubber latex is not particularly limited. If the rubber concentration is too low, the amount of solid natural rubber obtained is small, which is not economical. On the other hand, if the rubber concentration is too high, the rubber component in the latex becomes unstable and the rubber particles agglomerate and the spray nozzle is easily clogged. For example, the rubber concentration is desirably 10% by mass or more and 60% by mass or less.

Further, as the natural rubber latex, a latex having a low molecular weight by adding a radical generator may be used. In this case, the radical generator to be added may be one or more selected from a peroxide radical generator, a redox radical generator, and an azo radical generator. Peroxide radical generators include potassium persulfate (KPS), ammonium persulfate (APS), benzoyl peroxide (BPO), hydrogen peroxide, cumene hydroperoxide, tert-butyl hydroperoxide (TBHPO), di- -Tert-butyl peroxide, 2,2-azobisisobutyronitrile and the like. Examples of the reducing agent combined with the peroxide as the redox radical generator include tetraethylenepentamine (TEPA), mercaptans, acidic sodium sulfite, reducing metal ions, ascorbic acid and the like. Examples of suitable combinations include TBHPO and TEPA, hydrogen peroxide and Fe ²⁺ salt, KPS and sodium acid sulfite, and the like. Examples of the azo radical generator include azobisisobutyronitrile, methyl azobisisobutyrate, azobiscyclohexanecarbonitrile, azobisisobutylamidine hydrochloride, 4,4′-azobis-4-cyanovaleric acid, and the like. Of these, potassium persulfate (KPS), ammonium persulfate (APS), and benzoyl peroxide (BPO) are effective because the effect of reaction temperature is small and the viscosity can be stably adjusted in addition to the large effect. It is desirable to use at least one of

  What is necessary is just to determine the addition amount of a radical generator suitably according to the kind of radical generator so that the solid natural rubber obtained may be adjusted to desired viscosity. The viscosity of the solid natural rubber can be adjusted by increasing or decreasing the amount of radical generator added. For example, if the amount of radical generator added is too small, it is difficult to adjust the viscosity to a low level because the molecular chain scission and the oxidation reaction do not proceed easily. Conversely, the addition of excess radical generator is not economical. For example, the addition amount of the radical generator is desirably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the rubber content in the natural rubber latex.

  Moreover, it is desirable to stir the latex at room temperature after adding the radical generator. The stirring time is adjusted depending on the required viscosity, but may be about several minutes to several hours.

[Solid natural rubber]
When a latex whose molecular weight is reduced by adding a radical generator is used as the natural rubber latex, a solid natural rubber having a relatively low viscosity and containing no aldehyde group in the rubber molecular chain can be obtained. . For example, in order to omit mastication, the Mooney viscosity [ML (1 + 3) 121 ° C.] of the solid natural rubber is preferably 80 or less. The Mooney viscosity [ML (1 + 3) 121 ° C.] is more preferably 30 or more and 70 or less. In this specification, the Mooney viscosity adopts a value measured according to JIS K6300-1 (2001).

  In addition, additives such as cross-linking agents, cross-linking accelerators, processing aids, plasticizers, anti-aging agents, reinforcing agents, and coloring agents are blended with solid natural rubber as necessary, and kneaded with a roll or a kneader. Thus, a rubber composition may be prepared. Then, the prepared rubber composition is molded into a predetermined shape and crosslinked. By doing so, various rubber products can be produced.

  The solid natural rubber produced by the production apparatus 1 of the above embodiment was crosslinked to evaluate the crosslinking characteristics. First, 100 parts by mass of solid natural rubber, 2.5 parts by mass of sulfur, and N-cyclohexyl-2-benzothiazolylsulfenamide (“Noxeller (registered trademark) CZ-G” manufactured by Ouchi Shinsei Chemical Co., Ltd.) ) 1 part by mass, 5 parts by mass of zinc oxide type 2 and 1 part by mass of stearic acid were kneaded using a 6 inch open roll to prepare a rubber composition. As the solid natural rubber, two types of rubber compositions were prepared using two types having different production lots (Example 1 and Example 2). Next, the prepared two types of rubber compositions were crosslinked at 150 ° C., and the crosslinking rate and the like were measured. The measurement was performed according to JIS K6300-2 (2001) using a rotorless rheometer tester manufactured by Toyo Seiki Seisakusho. Further, for comparison, a smoke composition (RSS1) manufactured by a conventional method was similarly prepared and crosslinked at 150 ° C. to measure the crosslinking rate (Comparative Example 1). ). FIG. 7 shows a graph of torque change versus crosslinking time.

  As can be seen from the cross-linking curve shown in FIG. 7, in Examples 1 and 2, the torque increase was faster than in Comparative Example 1. That is, the crosslinking rate in Examples 1 and 2 was higher than the crosslinking rate in Comparative Example 1. In Examples 1 and 2, the maximum torque value was larger than that in Comparative Example 1. That is, the crosslinking density of Examples 1 and 2 was larger than the crosslinking density of Comparative Example 1. The rubber properties after crosslinking in Examples 1 and 2 were the same as those in Comparative Example 1. As described above, according to the production method and production apparatus of the present invention, it was confirmed that a solid natural rubber having a high crosslinking speed and a high crosslinking density and excellent crosslinking characteristics can be produced.

  According to the method and apparatus for producing solid natural rubber of the present invention, high-quality solid natural rubber can be produced from natural rubber latex with a small number of people, in a short time, and at low cost. Further, the obtained solid natural rubber is excellent in cross-linking properties and has a relatively small increase in viscosity during storage. Therefore, the solid natural rubber of the present invention is useful as a raw material for producing rubber products.

1: Manufacturing device 2: Nozzle part 20: Belt 21L, 21R: Pulley 22: Support member 23: Nozzle motor 24: Motor bracket 25: Nozzle bracket 26: Spray nozzle 230: Rotating shaft 3: Housing part 30: Housing body 31: Gear case 32L, 32R: Pulley case 33: Exhaust cylinder 4: Drum section 40: Drum 41L, 41R: Rotating shaft 42: Large gear 43: Small gear 44: Drum motor 45: Motor bracket 46L, 46R: Bearing 5: Discharge hopper 6: frame part 60: bottom frame part 61L, 61R: side frame part 62: motor support part 7: scraper part 71: swinging part 72: scraper 76: urging force adjustment unit 77: unit holding plate 78: nut stopper holding rib 710: Oscillating plate 711: Spring accommodating member 711a: Spring accommodating portion 71 2: Oscillating shaft 713: Ear portion 760: Shaft portion 760a: Handle 760b: Shaft 760b1: Rear end 760c: Ring 760d: Bearing 761: Nut 762: Holder 762a: Bearing housing portion 762b: Spring housing portion 762c: Bulkhead 763: Nut stopper 763a: engaging claw 763a1: spring accommodating portion 763d: spring 763e: bolt 765: spring 780: ear portion 781: swinging shaft 782: spring accommodating portion 783: rib main body 8: heating unit 80D, 80U: heating device G1 : Droplet G2: Natural rubber sheet (solid natural rubber)

Claims (10)

A rotating member having a heated endless annular surface;
A spray nozzle for spraying natural rubber latex onto the endless annular surface;
A scraper disposed on the downstream side of the spray nozzle so as to be in sliding contact with the endless annular surface;
The coating solution of the natural rubber latex adhering to the endless annular surface is dried with rotation of the endless annular surface to become solid natural rubber, and the solid natural rubber is peeled off from the endless annular surface by the scraper. Production equipment for solid natural rubber. The rotating member is a drum pivotally supported substantially horizontally,
The solid natural rubber manufacturing apparatus according to claim 1, wherein the endless annular surface is an outer peripheral surface of the drum.   3. The solid natural rubber manufacturing apparatus according to claim 1, wherein the spray nozzle is movable in a direction intersecting a rotation direction of the endless annular surface.   The solid natural rubber production apparatus according to any one of claims 1 to 3, further comprising a biasing force adjusting unit having a spring that elastically contacts the scraper with the endless annular surface by a biasing force. Spraying natural rubber latex onto the heated endless annular surface of the rotating member;
A drying step of drying the natural rubber latex coating solution adhering to the endless annular surface into a solid natural rubber by rotating the endless annular surface;
A peeling step of peeling the solid natural rubber from the endless annular surface;
A method for producing solid natural rubber, characterized by comprising:   The method for producing a solid natural rubber according to claim 5, wherein the temperature of the endless annular surface is 120 ° C or higher and 200 ° C or lower.   The method for producing a solid natural rubber according to claim 5 or 6, wherein a time of the drying step is from 0.1 minutes to 5 minutes. The natural rubber latex is a latex whose molecular weight is reduced by adding a radical generator,
The method for producing a solid natural rubber according to any one of claims 5 to 7, wherein the solid natural rubber does not contain an aldehyde group in a molecular chain.   A solid natural rubber produced by drying a coating solution of natural rubber latex sprayed on a heated endless annular surface of a rotating member while rotating the endless annular surface. The natural rubber latex is a latex whose molecular weight is reduced by adding a radical generator,
The solid natural rubber according to claim 9, wherein the molecular chain of the rubber does not contain an aldehyde group.

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