JP2024027230A - Foamed rubber roller manufacturing method and foamed rubber roller - Google Patents

Abstract

An object of the present invention is to provide a foamed rubber roller that is less likely to cause unevenness in a skin layer on the surface of a foamed rubber layer, and has stable performance by suppressing variations in the diameter of bubbles in the foamed rubber layer. A method for manufacturing a foamed rubber roller in which the outer periphery of a shaft core 2 is coated with a foam rubber layer 6 includes a molding step of molding an uncured rubber compound layer 3a on the shaft core 2; a rubber tube covering step in which the rubber tube 5 is covered, a vulcanization step in which the rubber compound layer 3a is heated, foamed and cured while the rubber tube 5 is covered to form a foamed rubber layer 6, and the rubber tube 5 is foamed. and a step of removing a rubber tube from the outer periphery of the rubber layer 6, and a foamed rubber roller manufactured by these manufacturing steps is provided. [Selection diagram] Figure 4

Description

The present invention relates to a method for manufacturing a foamed rubber roller and a foamed rubber roller used in OA equipment such as electronic copying machines and printers.

The manufacturing method for foamed rubber rollers used in OA equipment such as electronic copiers and printers involves coating the shaft core with an uncured rubber compound containing a foaming agent using a crosshead extruder, and then heating the rubber compound. There are some products in which a foamed rubber layer is formed by foaming and curing the foamed rubber layer.

A method of manufacturing a foamed rubber roller using such a crosshead extruder has conventionally existed. For example, a crosshead extruder 10 shown in FIG. 8 (FIG. 2 of Patent Document 1) includes a cylinder 11, a screw 12, a head portion 13, a mouthpiece 14, and an inner cylinder 15.
The cylinder 11 is filled with an uncured rubber compound 3 containing a foaming agent. The rubber compound 3 advances forward (to the right in FIG. 8) by the rotation of the screw 12, and after reaching the head portion 13, the rubber compound 3 changes its direction of travel downward at the head portion 13, and is released from the base 14 into a cylindrical shape. is pushed out. On the other hand, the shaft core 2 is inserted through the insertion port 18 of the inner cylinder 15. This shaft core 2 passes through the inner cylinder 15, is discharged from the base 14, and advances downward. As a result, in the vicinity of the base 14, the outer peripheral surface of the shaft core 2 is coated with uncured (unvulcanized, unfoamed) rubber compound 3 in a cylindrical shape.

Next, regarding the process of heating the rubber compound 3 to foam and harden it to form a foamed rubber layer, for example, in Patent Document 2, a method for manufacturing a foamed rubber roller is described as a molding process of forming a cylindrical foamed rubber layer (patent document 2). (Refer to Document 1), a primary vulcanization step in which the molded cylindrical foam rubber layer is vulcanized and hardened to the extent that it can maintain its shape, and a grinding step in which the surface of the cylindrical foam rubber layer after the primary vulcanization is ground. and a secondary vulcanization step of vulcanizing and hardening the cylindrical foamed rubber layer after the grinding to the final degree of vulcanization.

Japanese Patent Application Publication No. 2001-310362 Japanese Patent Application Publication No. 2008-145979

Foamed rubber rollers that are molded using such normal manufacturing methods have a skin layer (surface coating) formed on the surface of the foamed rubber layer when the heated and foamed rubber hardens, but this skin layer has irregularities. There were some problems that could easily occur. As the unevenness of the skin layer increases, the variation in the diameter of cells in the foamed rubber layer also increases.
Further, as in the invention described in Patent Document 2, the unevenness of the skin layer can be smoothed by grinding, but if there is large variation in the diameter of the bubbles in the foamed rubber layer, this will have a negative effect on the performance of the roller. There was an issue.

Therefore, the present invention has been made to solve these problems, and it is possible to prevent unevenness from occurring in the skin layer on the surface of the foam rubber layer, and to suppress variations in the diameter of the bubbles in the foam rubber layer. The purpose is to provide a foam rubber roller with stable performance.

In order to achieve such an object, a first invention provides a method for manufacturing a foamed rubber roller in which the outer periphery of a shaft core is coated with a foamed rubber layer.
a molding step of coating the shaft core with an uncured rubber compound and molding a rubber compound layer;
a rubber tube covering step of covering the outer periphery of the rubber compound layer with a rubber tube;
a vulcanization step of heating, foaming and curing the rubber compound layer while covering the rubber tube to form a foamed rubber layer;
a rubber tube removal step of removing the rubber tube from the outer periphery of the foamed rubber layer;
It is characterized by including.
A second invention is characterized in that, in the first invention, after the rubber tube removing step, a cutting step is included in which both end surfaces of the foamed rubber layer protruding from the end surfaces of the shaft core are cut.
A third invention is characterized in that, in the first invention or the second invention, after the rubber tube removal step, a polishing step of polishing the outer peripheral surface of the foamed rubber layer is included.
A fourth invention is characterized in that, in the first invention or the second invention, the rubber compound and the rubber tube use the same kind of raw rubber.
A fifth invention is characterized in that, in the third invention, the rubber compound and the rubber tube use the same kind of raw rubber.
A sixth invention is a foamed rubber roller manufactured by the method for manufacturing a foamed rubber roller according to the first invention or the second invention.
A seventh invention is a foamed rubber roller manufactured by the method for manufacturing a foamed rubber roller according to the third invention.

According to the present invention, it is possible to provide a foamed rubber roller that is less likely to have unevenness in the skin layer on the surface of the foamed rubber layer, and that has stable performance by suppressing variations in the diameter of the bubbles in the foamed rubber layer.

1 is a schematic sectional view schematically showing an axial cross section of a roller whose shaft core is coated with an unvulcanized rubber compound according to an embodiment of the present invention. 1 is a schematic cross-sectional view schematically showing an axial cross section of a core mold for explaining a method for manufacturing a rubber tube according to an embodiment of the present invention. 1 is a schematic sectional view schematically showing an axial cross section of a roller in which a rubber tube is coated with a rubber compound according to an embodiment of the present invention. 1 is a schematic cross-sectional view schematically showing an axial cross section of a roller formed by heating and foaming a compound according to an embodiment of the present invention. 1 is a schematic sectional view schematically showing an axial cross section of a roller from which a rubber tube is removed according to an embodiment of the present invention. 1 is a schematic cross-sectional view schematically showing an axial cross section of a roller obtained by cutting an end face of a foamed rubber layer according to an embodiment of the present invention. 1 is a schematic sectional view schematically showing an axial cross section of a roller with a polished surface of a foamed rubber layer according to an embodiment of the present invention. FIG. 1 is a cross-sectional view of a main part of a conventional crosshead extruder.

The present invention is a method of manufacturing a foamed rubber roller in which the outer periphery of a shaft core is coated with a foamed rubber layer, and the manufacturing process of one embodiment thereof will be explained with reference to FIGS. 1 to 7. Note that the sizes of the rubber rollers 1a to 1f shown in each step in the drawings are not actual sizes but are shown for convenience of explanation, and are not limited to these.

First, there is a molding process in which the shaft core is coated with an uncured (unvulcanized, unfoamed) rubber compound to form a rubber compound layer. FIG. 1 shows a rubber roller 1a molded in this molding process, in which a shaft core 2 is coated with a rubber compound 3 to form a rubber compound layer 3a.

Such a rubber roller 1a is molded using, for example, a crosshead extruder 10 as shown in FIG.
In the crosshead extruder 10 shown in FIG. 8, a cylinder 11 is filled with an uncured (unvulcanized, unfoamed) rubber compound 3 containing a foaming agent, and this rubber compound 3 is passed through a screw 12. It moves forward (to the right in FIG. 8) due to the rotation of , and after reaching the head part 13, the direction of movement is changed downward by the head part 13, and it is extruded from the base 14 in a cylindrical shape. On the other hand, the shaft core 2 is inserted through the insertion opening 18 of the inner cylinder 15, passes through the inner cylinder 15, is discharged from the base 14, and advances downward. As a result, in the vicinity of the base 14, the outer peripheral surface of the shaft core 2 is coated with uncured rubber compound 3 in a cylindrical shape.

As a result, a roller 1a having an uncured rubber compound layer 3a around the shaft core 2 as shown in FIG. 1 is formed. Here, the outer peripheral surface 2a of the shaft core 2 and the inner peripheral surface 3b of the rubber compound layer 3a are bonded to each other, and the shaft core 2 and the rubber compound layer 3a are integrated. The shaft core 2 consists of a shaft core main body 2b covered with a rubber compound layer 3a, and a shaft core end portion 2c not covered with the rubber compound layer 3a. The shaft end portion 2c protrudes from both end surfaces of the shaft main body 2b, and is formed to have a smaller diameter than the shaft main body 2b.

The shaft core 2 is generally made of a metal material, and a free-cutting steel SUM23, for example, is preferably used as the metal material. Other materials such as metals such as stainless steel and plastics can also be used.
Further, the surface of the shaft core 2 is preferably plated with electroless nickel for purposes such as rust prevention.
Furthermore, an adhesive is applied to the surface (outer peripheral surface) of the shaft core 2 before the rubber compound 3 is coated. As this adhesive, for example, DY39-051A/B manufactured by Dow Toray Industries, Inc. is preferably used, and the baking conditions are preferably about 170° C. for 1 hour. This adhesive application is performed before inserting the shaft core 2 into the crosshead extruder 10.

As the raw material rubber for the rubber compound 3, for example, silicone rubber is suitably used. In addition, chloroprene rubber, ethylene propylene rubber, epichlorohydrin rubber, acrylic rubber, urethane rubber, isoprene rubber, nitrile rubber, butadiene rubber, natural rubber, etc. can be used.

A blending example of Rubber Compound 3 is shown below.
Silicone rubber: Shin-Etsu Chemical Co., Ltd. NT-522-U 100.0 parts by mass Foaming agent: Shin-Etsu Chemical Co., Ltd. KE-P-26 4.0 parts by mass Curing agent: Shin-Etsu Chemical Co., Ltd. C-25A 0.3 parts by mass
Curing agent: Shin-Etsu Chemical Co., Ltd. C-25B 2.0 parts by mass Coloring agent: Shin-Etsu Chemical Co., Ltd. KE-COLOR-BR 0.5 parts by mass

The rubber compound 3 having such a composition is uniformly kneaded using a known kneading machine such as a Banbury mixer or a kneader, and then introduced into the cylinder 11 of the crosshead extruder 10 shown in FIG. Thus, a roller 1a having an uncured rubber compound layer 3a around a shaft core 2 as shown in FIG. 1 is formed.
Here, in the roller 1a of the example, the outer diameter of the shaft core body 2b is 12 mm, the length of the shaft core body 2b and the rubber compound layer 3a is 225 mm, and the outer diameter of the rubber compound layer 3a is 22 mm.

Next, a rubber tube covering step of covering the outer periphery of the rubber compound layer 3a with the rubber tube 5 will be explained.
Here, the rubber tube must be prepared in advance, and a method for producing this rubber tube is shown in FIG. That is, in this example, uncured liquid rubber is applied to the outer periphery of the roller-shaped core mold 4, heated and cured by vulcanization to form the rubber tube 5, and then the core mold 4 is pulled out.
In this case, the core mold 4 is made of a material such as metal or plastic, and the free-cutting steel material SUM23, like the shaft core 2, is suitably used as the metal material. It is preferable to apply electroless nickel plating to the circumferential surface of the core mold 4 in order to improve slipperiness, and due to the slipperiness, the core mold 4 can be smoothly removed after molding the rubber tube 5. Alternatively, after forming the rubber tube 5, the rubber tube 5 may be peeled off from the core mold 4 by winding the entire circumference from one end to the other end.

As the liquid rubber that is the material of the rubber tube 5, for example, liquid silicone rubber is preferably used, and in addition, liquid chloroprene rubber, liquid urethane rubber, liquid isoprene rubber, liquid nitrile rubber, liquid butadiene rubber, etc. can be used. .

The rubber tube 5 thus formed is then placed over the outer periphery of the rubber compound layer 3a of the rubber roller 1a shown in FIG.
FIG. 3 shows a rubber roller 1b in which a rubber tube 5 is coated on the outer periphery of a rubber compound layer 3a.
Here, the thickness W1 of the rubber tube 5 is formed to be sufficiently thinner than the thickness W2 of the rubber compound rubber layer 3a, resulting in a thin film-like coating. That is, the rubber tube 5 has a thickness that does not impair the expansion flexibility of the rubber compound layer 3a during vulcanization and foaming. In the example, the film thickness W1 of the rubber tube 5 is 100 μm.

Further, the rubber tube 5 is formed to have an inner diameter slightly larger than the outer diameter of the rubber compound layer 3a. In the embodiment, the outer diameter of the rubber compound layer 3a is 22 mm, and the inner diameter of the rubber tube 5 is 22.5 mm, so that the rubber tube 5 can be smoothly placed over the outer periphery of the rubber compound layer 3a.
Further, the rubber tube 5 has a length that sufficiently covers the rubber compound layer 3a, and in the example, the length of the rubber tube 5 is 250 mm while the length of the rubber compound layer 3a is 225 mm.
Further, the properties of the rubber tube 5 of the example after curing include a hardness of durometer A: 50 degrees (preferably 10 to 60 degrees) and a 100% modulus of 1.1 MPa (preferably 1.0 to 5.0 MPa). ), tensile strength is 12.4 Mpa (preferably 10 to 20 Mpa), and elongation at break is 680% (preferably 300% or more).

In the step of covering the rubber tube 5, the rubber tube 5 may be rolled up in advance from one end to the other end, and then unwound to cover the rubber compound layer 3a.

Next is a vulcanization step in which the rubber compound layer 3a is heated and foamed while the rubber tube 5 is covered to form a foamed rubber layer 6. FIG. 4 shows a foamed rubber roller 1c in which the rubber compound 3 coated with the rubber tube 5 has been vulcanized to such an extent that it can maintain its shape.

The vulcanization process includes a primary vulcanization process and a secondary vulcanization process. In the primary vulcanization step, vulcanization and foaming is performed by heating at a heating temperature of 230°C (preferably 130 to 250°C) and a heating time of 30 minutes (preferably 10 to 40 minutes) (vulcanization and foaming step). ). As a result, a rubber foam having a closed cell structure is obtained.

After the foaming in the primary vulcanization, a secondary vulcanization is further performed to vulcanize and harden the foamed rubber layer 6 to the final degree of vulcanization. This secondary vulcanization is performed at a heating temperature of 200° C. (preferably 130 to 250° C.) and a heating time of 4 hours (preferably 1 to 5 hours).
As a heating method in these vulcanization steps, in addition to a general constant temperature bath, heating means such as a hot air vulcanization tank, an electric furnace, a microwave vulcanization device (UHF), and steam can be used.

In this vulcanization step, the rubber compound 3 expands by foaming and becomes a foamed rubber layer 6 after curing. In the example, this foamed rubber layer 6 expands and expands to an outer diameter of 30 mm. As the rubber compound 3 foams and expands, the rubber tube 5 also expands and expands in diameter along with the foamed rubber layer 6.
Note that here, as the rubber compound expands and extends longer than the end surface 2d of the shaft main body 2b, a protruding burr portion 8 is generated on the foamed rubber layer 6, but this burr portion 8 is removed in the cutting process described later. Ru.

Further, in this vulcanization process, a skin layer (surface coating) 7 is formed on the surface of the foamed rubber layer 6 at the stage where the heated and foamed rubber compound 3 is cured into foamed rubber. In the past, when the unevenness of the skin layer 7 increased, the variation in the diameter of the bubbles (cells) in the foamed rubber layer 6 also increased, which had a negative effect on the performance of the roller, but the present invention solves the problem. At this time, the skin layer 7 is formed into a smooth surface without irregularities due to the presence of the rubber tube 5.

In addition, according to the present invention, the reaction force caused by the expansion of the rubber tube 5 uniformly applies an appropriate internal pressure to the foaming rubber, so that the bubbles in the foamed rubber layer 6 are stable and fine with a uniform diameter. Becomes a cell. Such effects cannot be achieved by conventional manufacturing methods.

Furthermore, according to the present invention, the presence of the rubber tube 5 makes it possible to suppress foaming air from escaping to the outside during foaming of the rubber compound 3, thereby enabling efficient foaming. Thereby, the amount of foaming agent added can be suppressed.

Furthermore, in the present invention, it is preferable to use the same kind of raw rubber for the rubber tube 5 and the rubber compound 3. For example, if the rubber compound 3 is a silicone rubber compound (silicone rubber + foaming agent + curing agent, etc.), the rubber tube 5 is made of liquid silicone rubber. If the same type of raw material rubber is used in this way, it can be expected that problems during heat foaming and curing (vulcanization failure) will be reduced due to the affinity of the rubber.

Next is a rubber tube removal step in which the rubber tube 5 is removed from the outer periphery of the foamed rubber layer 6. FIG. 5 shows the foamed rubber roller 1d from which the rubber tube 5 has been removed. The rubber tube 5 can be easily removed from the foam rubber layer 6 by, for example, rolling the entire circumference of the rubber tube 5 from one end to the other end to peel it off from the foam rubber layer 6. Can be removed.

The rubber tube 5 extracted in such a process can be reused. Further, if the rubber tube is not to be reused, the rubber tube may be removed by polishing using a polishing means. Since the rubber tube 5 is a thin film with a thickness of 100 μm, it can be easily removed by polishing.

Next is a cutting step in which the protruding portion (burr portion) 8 of the foamed rubber layer 6 protruding from the end surface 2d of the shaft core 2 (the shaft main body 2b) is cut at the position of the end surface 2d. FIG. 6 shows a foamed rubber roller 1e in which the protruding portion (burr portion) 8 is cut at the end face 2d (in the figure, the “end face cut” of the protruding portion (burr portion) 8 indicated by a dotted line is indicated by an arrow). reference).
As a method for cutting this end face, a so-called scalpel cut method is suitably used, in which the end face is cut with a scalpel while rotating a roller.

Furthermore, the outer peripheral surface (circumferential surface) of the foamed rubber layer 6 is polished as needed (polishing step). FIG. 7 shows a foamed rubber roller 1f in which the outer peripheral surface of the foamed rubber layer 6 of the foamed rubber roller 1e of FIG. 6 has been polished (see "surface polishing" and the arrow mark in the figure). In the example, when the outer diameter of the foamed rubber layer 6 after the rubber tube is removed is 30 mm, the outer diameter is adjusted to the specified size of 25 mm by polishing. By polishing the outer circumferential surface (circumferential surface) of the foamed rubber layer 6 in this manner, it is possible to obtain foamed rubber rollers 1f with further different variations.

As the polishing means, although not specified, known techniques such as polishing with a rotary grindstone and peeling with a blade can be mentioned. Among these, polishing using a rotating whetstone includes traverse polishing, which uses a whetstone whose width is narrower than the length of the roller, and plunge polishing, which uses a whetstone whose width is approximately equal to the length of the roller.

According to the present invention, a foamed rubber roller having required dimensions and physical properties is produced through the steps described above. In the foamed rubber roller 1 of the example, the outer diameter of the shaft main body 2b is 12 mm, the length of the shaft main body 2b and the foam rubber layer 6 is 225 mm, and the outer diameter of the foam rubber layer 6 is 25 mm. The physical properties of the foamed rubber layer 6 are as follows: hardness is Asker C: 28 degrees, density is 0.35 g/cm ³ , and average cell diameter is 250 μm.

As explained above, the present invention adopts different manufacturing processes before and after the normal vulcanization process from the viewpoint of improving the manufacturing process of foamed rubber rollers. In other words, the conventional manufacturing method for foamed rubber rollers involves coating the shaft core with an uncured rubber compound containing a foaming agent using a crosshead extruder, followed by a vulcanization process in which the rubber compound is heated to foam and harden. By carrying out this process, a foamed rubber layer was formed.

In contrast, the inventor proposed a manufacturing process in which the rubber tube 5 is placed on the outer circumferential surface (circumferential surface) of the rubber compound layer 3a before the vulcanization process, and the rubber tube 5 is removed after the vulcanization process is carried out in this state. It was discovered that by using this method, unique effects not seen before can be obtained. According to this manufacturing method, the rubber compound 3 is heated and foamed with the rubber tube 5 covered to form the foamed rubber layer 6, so that the skin layer 7 formed on the surface of the foamed rubber layer 6 is heated and foamed. Since unevenness is less likely to occur and variations in the diameter of the bubbles in the foamed rubber layer 6 can be suppressed, it is possible to provide the foamed rubber roller 1 with stable performance.

Applicants have compared the foamed rubber roller of the present invention with a foamed rubber roller according to the prior art, which does not involve steps related to covering and removing rubber tubes. The conditions for comparison are exactly the same except for whether or not a rubber tube is used. That is, the manufacturing method according to the present invention is performed under the same conditions for all of the dimensions of the rubber roller, the rubber compound, the shaft core, the crosshead extruder, the dimensions of the roller after extrusion, the vulcanization conditions, and the dimensions of the roller after vulcanization. A foamed rubber roller was manufactured using a conventional manufacturing method that does not use a rubber tube (does not include the steps shown in FIGS. 2, 3, and 4) and was compared.

The comparison method was to visually check the skin layer (surface layer coating) of the foamed rubber layer of the foamed rubber roller manufactured using the conventional manufacturing method and the skin layer (surface layer coating) of the foamed rubber layer of the foamed rubber roller using the rubber tube according to the present invention. The degree of unevenness was compared. Furthermore, both foamed rubber layers were cut and the cut surfaces were checked under a microscope to compare the diameters of the bubbles (cell diameters).

As a result of the comparison, it was found that the foamed rubber roller manufactured by the conventional manufacturing method had irregularities on the surface skin layer, whereas the foamed rubber roller manufactured by the manufacturing method of the present invention had almost no irregularities in the surface skin layer and was smooth. This was recognized. In addition, while foamed rubber rollers manufactured using the conventional manufacturing method had large variations in the diameter of the bubbles, in the foamed rubber roller manufactured using the manufacturing method of the present invention, the diameter of the bubbles was uniform throughout, indicating that the foaming was well-balanced. was recognized.

1 Rubber roller 2 Axial core 3 Rubber compound 3a Rubber compound layer 4 Core mold 5 Rubber tube 6 Foamed rubber layer 7 Skin layer 8 Extrusion part (burr part)
10 crosshead extruder 11 cylinder 12 screw 13 head part 14 mouthpiece 14
15 Inner cylinder 15

Claims (7)

In a method for manufacturing a foam rubber roller in which the outer periphery of a shaft core is coated with a foam rubber layer,
a molding step of coating the shaft core with an uncured rubber compound and molding a rubber compound layer;
a rubber tube covering step of covering the outer periphery of the rubber compound layer with a rubber tube;
a vulcanization step of heating, foaming and curing the rubber compound layer while covering the rubber tube to form a foamed rubber layer;
a rubber tube removal step of removing the rubber tube from the outer periphery of the foamed rubber layer;
A method of manufacturing a foam rubber roller, the method comprising: 2. The method of manufacturing a foamed rubber roller according to claim 1, further comprising a cutting step of cutting both end surfaces of the foamed rubber layer protruding from the end surface of the shaft core after the rubber tube removal step. 3. The method of manufacturing a foam rubber roller according to claim 1, further comprising a polishing step of polishing the outer peripheral surface of the foam rubber layer after the rubber tube removal step. 3. The method for manufacturing a foamed rubber roller according to claim 1, wherein the rubber compound and the rubber tube use the same kind of raw rubber. 4. The method of manufacturing a foamed rubber roller according to claim 3, wherein the rubber compound and the rubber tube use the same kind of raw rubber. A foamed rubber roller manufactured by the foamed rubber roller manufacturing method according to claim 1 or 2. A foamed rubber roller manufactured by the foamed rubber roller manufacturing method according to claim 3.

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