JPH04344226A - Manufacture of sponge roll - Google Patents

Abstract

PURPOSE:To unify foam and easily obtain a sponge roll being uniform in its outer diameter and having a skin layer in its surface by constituting with a material wherein the heat conductivity in the core mold receiving part of a mold is smaller than that of a mold material and the load deflection temperature at the time of being specific in bending stresses is higher than the heating temperature of the mold. CONSTITUTION:The construction is such that two upper and lower sheets of molds are superimposed which comprise engraving parts and a core metal receiving part 2 for regulating the core metal 1 to the mold central part. The engraving part used herein is made by a material similar to the conventional one. However, the core metal receiving part 2 uses different material in its all part or only adjacent part to the core metal is the material changing part 3 of different material. In comparison with the conventional material one, this is composed of material in which the heat conductivity is smaller than the heat conductivity of the mold material and when the bending stress is 18.6kg f/cm<2>, the load deflection temperature is higher than the heat temperature of the mold.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing sponge rolls, and more particularly to a method for manufacturing sponge rolls used in copying machines and the like.

0002

[Prior Art] Conventionally, sponge rolls with a skin layer on the surface have been manufactured by extruding unfoamed rubber material to a uniform diameter along with a core material made of metal such as aluminum, iron, or stainless steel, and then bonding the upper and lower two sheets together. This is done by heating and foaming using a mold. However, in this conventional method, when charging the mold with unfoamed rubber extruded together with the core material, there is a difference in the amount of heat received by the unfoamed rubber from the mold and the amount of heat received from the core metal. Foaming of the rubber starts from the end of the core metal that is in direct contact with the mold, and the gas generated during foaming accumulates in the longitudinal center of the product, and the center of the product is heated and foamed due to the influence of this gas. There is a disadvantage that the diameter of the roll is extremely small compared to the diameter of the end portion.

0003

[Problem to be Solved by the Invention] For this reason, this heating foaming process usually involves raising the mold temperature from a relatively low temperature of 50 to 80°C to a high temperature of 120 to 200°C to improve heat conduction to the unfoamed rubber. This is done under the condition of minimizing variations in temperature, but if this temperature increase is done too quickly, a difference in heat conduction will occur, so it is necessary to raise the temperature slowly over time, and once the temperature is raised, The mold temperature must then be cooled down to a low temperature.
This has the disadvantage of increasing cycle time;
Separate heating and cooling stages have been used to shorten the cycle time, but this method has the drawbacks of very expensive equipment, difficult temperature control, and unstable product quality. .

0004

[Means for Solving the Problems] The present invention relates to a method for manufacturing a sponge roll that solves the above-mentioned disadvantages. The thermal conductivity of the material is smaller and the bending stress is 1
A mold made of a material whose deflection temperature under load of 8.6 kgf/cm2 is higher than the heating temperature of the mold is used to carry out heating and foaming.

That is, as a result of various studies conducted by the present inventors on methods for efficiently and uniformly foaming unfoamed rubber,
The molds used here are two upper and lower molds, and the core receiving part of the two upper and lower molds has a thermal conductivity smaller than that of the mold material, and the bending stress is 18.
If the material is made of a material whose deflection temperature under load is higher than the heating temperature of the mold at 6 kgf/cm2, heat can be transferred to the unfoamed rubber only from the entire mold. can prevent foaming of the rubber in the
As a result, the unfoamed rubber can be foamed uniformly, and the gas generated during foaming does not accumulate in the longitudinal center of the product, so it is advantageous to obtain a sponge roll with a uniform outer diameter and a skin layer on the surface. The present invention was completed by discovering that this can be done. This will be explained in further detail below.

[0006]

[Function] The present invention relates to a method of manufacturing sponge rolls, in which the metal molds used in foam molding are made of two upper and lower molds, and the core metal receiving part of the mold is made of a mold material whose thermal conductivity is the same as that of the mold material. The bending stress shall be smaller than 18.
The gist is that the mold is made of a material whose deflection temperature under load is higher than the heating temperature of the mold at 6 kgf/cm2.

[0007] The sponge roll in the present invention is said to be made of a foam made of synthetic rubber such as natural rubber, silicone rubber, butyl rubber, etc., but this is silicone rubber that has excellent heat resistance, weather resistance, and electrical properties. It is better to use the one that was created.

[0008] Furthermore, this rubber composition is foam-molded by adding a vulcanizing agent and a foaming agent to it and heating it. ,5-dimethyl-2
, 5-di-t-butylperoxyhexane, cyclohexanone peroxide, lauroyl peroxide, etc. are used as the blowing agent.
-dimethyl-N,N'-dinitrosoterephthalamide,
Dinitrosopentamethylenetetramine, azobisisobutyronitrile, azodicarboxylic acid amide, para-toluenesulfonyl hydrazide, etc. may be used.

[0009] In addition, to manufacture a sponge rubber roll from the unfoamed rubber composition thus produced, the composition is extruded to a uniform diameter using an extruder or the like, and then vulcanized and foamed under appropriate conditions. This can be done by secondary vulcanization.

The manufacture of the sponge roll according to the present invention relates to the structure of the mold used therein, and this is carried out using two mating molds, upper and lower, as shown in FIG. FIG. 1(a) is a plan view of the same, and FIG. 1(b) is a vertical cross-sectional view of the same. It has a structure in which two molds each consisting of a core metal receiving part 2 are placed one above the other.

[0011] However, in the conventional method, the recessed part 1 and the core metal receiving part 2 are made of the same material, and they are made of aluminum, iron, etc., which have good thermal conductivity. In the product used in the present invention, the digging part 1 is made of the same material as the conventional product, but the core metal receiving part 2 is entirely different from the conventional product, or As shown in FIG. 2, only the portion in contact with the metal core is a material-changed portion 3 that is different from the conventional product. Compared to conventional materials, this material has a thermal conductivity lower than that of the mold material, and a bending stress of 18.6 kg.
The deflection temperature under load at f/cm2 is assumed to be higher than the heating temperature of the mold.

[0012] That is, in the conventionally known two-piece upper and lower mating mold, the digging part 1 and the core metal receiving part are made of the same material, which has a thermal conductivity of, for example, 9.2 x 102 W.
/m・k, which was considered to be an aluminum alloy, etc.
In the present invention, the core metal receiving part in this mating mold has a thermal conductivity lower than that of the mold material, for example, the thermal conductivity is extremely lower than that of the mold material, 1 W/m・k or less. glass fiber, which is a thermoplastic resin, whose deflection temperature under load is higher than the mold heating temperature of 200°C when the bending stress is 18.6 kgf/cm2, for example, the deflection temperature under load is 215 to 225°C; /or car
It is made of a thermosetting resin such as cresol resin containing carbon fiber or melamine resin. At this time, if the material has a deflection temperature under load at a bending stress of 18.6 kgf/cm2 that is lower than the mold temperature, this will soften during heating, making it difficult to hold the core metal.

[0013] The sponge roll according to the present invention is produced by foam molding using the above-mentioned two upper and lower molds. The unfoamed rubber composition is brought into close contact with the core metal in a crosshead and extruded to the desired outer diameter. It is preferable to set the outer diameter smaller than the outer diameter and extrude.

The unfoamed rubber extruded in this way is then treated with unnecessary rubber parts at both ends to make it into a product length.
The extruded product is placed in the above-mentioned upper and lower molds of the present invention and is vulcanized and foamed. According to the method, the vulcanization and foaming time after injection into the mold can be shortened.

[0015] In this case, the mold is heated to the vulcanization and foaming temperature, but if this temperature is less than 120°C, it takes a long time for the unfoamed rubber to rise to the temperature at which it starts foaming. However, if the temperature is higher than 200°C, there will be a difference in the amount of heat received by the unfoamed rubber between the ends of the core metal and the center part, and the effect of changing the material of the metal core receiving part 2 will not be produced.
This needs to be set at a constant temperature of 120 to 200°C, and if the mold is set at this temperature, the extruded product introduced therein will be vulcanized and foamed to form a sponge roll.

[0016] According to this, heat transfer to the unfoamed rubber is carried out only by heat transfer from the entire mold, regardless of the amount of heat from the core metal, so foaming in the rubber portion at the end of the core metal is prevented. This prevents the unfoamed rubber from foaming uniformly, and the gas generated during foaming does not accumulate in the longitudinal center of the product, making it easy to produce sponge rolls with a uniform outer diameter and a skin layer on the surface. In this case, there is no need to cool the mold or slowly raise the temperature of the mold, giving the advantage that the sponge roll can be obtained in a short time with high productivity.

[0017]

[Examples] Next, examples of the present invention and comparative examples will be given. Examples 1-4, Comparative Examples 1-2 Silicone rubber KE-951U [Shin-Etsu Chemical Co., Ltd.
Product name] 20 parts by weight and silicone rubber KE-151
Mix 80 parts by weight of U [trade name manufactured by Shin-Etsu Chemical Co., Ltd.] with C-2 [trade name manufactured by Shin-Etsu Chemical Co., Ltd.] as a vulcanizing agent.
Product name] 1.0 parts by weight and KEP-13 as a blowing agent
[trade name manufactured by Shin-Etsu Chemical Co., Ltd.] 4.0 parts by weight were added thereto, and these were uniformly kneaded using a kneader to prepare a foamable, unfoamed silicone rubber composition.

Next, using an extruder, this unfoamed silicone rubber composition was combined with an aluminum core metal into a diameter of 2 mm.
Extrude it with a uniform diameter of 3 mm, and insert this into the dug part 1.
As shown in Figure 2, the core metal receiving part of a mold using 50C (carbon steel for mechanical structures) has a thermal conductivity of 0.21 W/m・
Polyphenylene sulfide resin Rayon PPSR-4 [Philips Petroleum (
Upper and lower parts 2 with material-changed parts made by Co., Ltd. (product name)
When the temperature of this mold was set to 120 to 200°C as shown in Table 1, vulcanization and foaming was performed for 20 to 35 minutes, and secondary vulcanization was performed at 200°C. Since the unfoamed rubber composition was uniformly foamed and a sponge roll with a skin layer was obtained, the outer diameter of this roll was measured and the difference between the maximum and minimum values (outer diameter difference) was determined. As a result, the results shown in Table 1 were obtained. In addition, in Example 4, the extrudate was preheated at 90° C. for 15 minutes.

However, for comparison, the core metal receiving part of the upper and lower two mating molds used here was made of S50C (thermal conductivity 2.4 x 102 W/m), which is the same material as the dug part.
・Use the product made in step k) and vulcanize and foam at 160°C for 20 minutes (Comparative Example 1), or heat the mold from 100°C to 160°C.
It was heated slowly to ℃ and vulcanized and foamed for 40 minutes (
Comparative Example 2) A sponge roll was made in the same manner as above, and the difference in outer diameter of the roll was examined, and the results shown in Table 1 were obtained.

That is, in the comparative example, it took a long time for vulcanization and foaming, and it was necessary to cool down the heated mold to 100°C, but according to the present invention, the vulcanization and foaming time was shortened. A sponge roll with a skin layer on the surface with little difference in diameter could be easily obtained.

[0021]

[Table 1]

[0022]

Effects of the Invention The present invention relates to a method of manufacturing a sponge roll, which is characterized in that the core receiving portion of two upper and lower molds is made of a material having a thermal conductivity lower than that of the material of the mold, and is free from bending stress. This method uses a mold structure made of a material whose deflection temperature under load is higher than the heating temperature of the mold at 18.6 kgf/cm2, and is characterized by heating and foaming. The heat transferred to the composition is only from the entire mold, and foaming from the edge of the core metal is prevented, so the unfoamed rubber composition can be foamed uniformly, and the foaming Since the gas generated during this process does not accumulate in the longitudinal center of the product, it is advantageous that a sponge roll having a uniform outer diameter and a skin layer on the surface can be easily obtained.

[Brief explanation of drawings]

FIG. 1 shows two upper and lower mating molds used in the present invention, in which (a) is a plan view thereof, and (b) is a longitudinal sectional view thereof.

FIG. 2 is a perspective view showing a core metal receiving part in two upper and lower mating molds used in the present invention.

[Explanation of symbols]

1 Core metal 2 Core metal receiving part 3 Material change part of core metal receiving part

Claims (1)

[Claims] Claim 1: The core mold receiving part of the upper and lower molds has a thermal conductivity lower than that of the mold material, and the deflection temperature under load when the bending stress is 18.6 kgf/cm2 is that of the mold. Using a mold made of a material higher than the heating temperature,
A method for producing a sponge roll characterized by heating and foaming it.