JP2005246754A - Manufacturing method of foamed rubber sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foamed rubber sheet manufacturing method capable of manufacturing a closed cell type long foamed rubber sheet good in surface smoothness, mechanical characteristics and thickness uniformity, provided with cells having a homogenous size and capable of easily controlling the expansion ratio and thickness of the foamed rubber sheet without adjusting the kind and/or compounding amount of a foaming agent. <P>SOLUTION: A long sheet comprising a rubber composition compounded with heat expansible microcapsules is continuously heated and pressed using a drum type press not only to vulcanize a rubber but also to expand the heat expansible microcapsules to be foamed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a foamed rubber sheet, and more particularly, to a method for producing a closed cell type long foamed rubber sheet excellent in surface smoothness, mechanical properties, thickness uniformity and the like.

The long foamed rubber sheet is used in various fields as it is or after being punched and cut.
The expansion ratio of the foamed rubber sheet (specific gravity of the rubber composition before foaming / specific gravity of the foamed rubber) needs to be 1.05 or more from the viewpoint of sufficiently expressing the properties as a foam. Here, the expansion ratio is usually controlled by adjusting the type and / or blending amount of the foaming agent to be blended with the rubber.
Moreover, the foamed rubber sheet used as a sealing material (various packings, gaskets) or the like is required to be a closed cell type foam (closed cell ratio is 95% or more).

Conventionally, it is known to produce a long foamed rubber sheet by a continuous vulcanization method.
For example, Patent Document 1 discloses a production method in which an extruded rubber sheet containing a pyrolytic foaming agent is vulcanized by a hot air heating device and / or a microwave heating device.

However, in the production method disclosed in Patent Document 1, a rubber sheet containing a pyrolytic foaming agent is vulcanized under no pressure by a hot air heating device and / or a microwave heating device. There are the following problems.
(1) The surface of the obtained foamed rubber sheet becomes uneven and crater-like, and a smooth surface state cannot be formed. In addition, wrinkles are likely to occur on the sheet surface.
(2) The bubble diameter becomes excessive, resulting in a decrease in mechanical properties and a thinning of the surface layer.
(3) The resulting foamed rubber sheet tends to vary in thickness.
(4) A closed-cell foam cannot be obtained and cannot be used as a sealing material or the like.

  On the other hand, in Patent Document 2 relating to “Manufacturing method and manufacturing apparatus for long foamed rubber flooring”, as a conventional technique, a rubber sheet containing a foaming agent (a pyrolytic foaming agent that is vaporized by heating) is funneled. A method of continuously vulcanizing by a drum type press called a cure method has been introduced (see paragraphs 0002 to 0004 of Patent Document 2).

However, in this method (rotor cure method using a pyrolytic foaming agent), when the foaming agent is vaporized inside the rubber sheet, the expansion is suppressed by the pressure applied to the rubber sheet. In addition, the foaming agent comes off from the rubber sheet before contributing to foaming, and there is a problem that a foamed rubber sheet having an expected foaming ratio (for example, 1.05 or more) cannot be obtained (Patent Document 1). Paragraph number 0011).
JP 2003-335883 A JP 2002-103366 A

The present invention has been made based on the above situation.
The object of the present invention is to foam a closed cell type long foamed rubber sheet having good surface smoothness, mechanical properties and thickness uniformity, and having suitable and uniform size bubbles. It is providing the manufacturing method of a rubber sheet.
Another object of the present invention is to provide a method for producing a foamed rubber sheet that can easily control the foaming ratio and thickness of the foamed rubber sheet without adjusting the type and / or blending amount of the foaming agent. is there.
Still another object of the present invention is to provide a closed cell type long foamed rubber sheet having good surface smoothness, mechanical properties and thickness uniformity, and having suitable and uniform size bubbles. It is in.

  The production method of the present invention vulcanizes rubber by continuously heating and pressurizing a long sheet made of a rubber composition containing thermally expandable microcapsules using a drum press, The sheet is foamed by expanding the thermally expandable microcapsule.

  The production method of the present invention comprises a long sheet made of a rubber composition in which 1 to 10 parts by mass of thermally expandable microcapsules having an expansion start temperature of 100 to 200 ° C. are blended with 100 parts by mass of unvulcanized rubber. Using a drum press, the rubber is vulcanized and the thermally expandable microcapsules are expanded by continuously heating and pressing under conditions of a temperature of 120 to 220 ° C. and a pressure of 0.05 to 0.3 MPa. The sheet is foamed by causing the sheet to foam.

  In the production method of the present invention, it is preferable to foam the sheet so that the expansion ratio is 1.05 to 2.0.

  In the production method of the present invention, when the long sheet (unvulcanized rubber composition containing thermally expandable microcapsules) is continuously heated and pressurized using a drum press, 1) Foaming ratio required for foamed rubber sheet to be manufactured; (2) Heating and pressing conditions by a drum press for the same composition as the rubber composition constituting the long sheet, and the conditions It is preferable to set the heating and pressing conditions based on the data (heating and pressing conditions-the calibration curve of the foaming ratio) measured in advance for the relationship with the foaming ratio of the foamed rubber sheet obtained in (1).

  In the manufacturing method of this invention, the uneven | corrugated pattern for transferring to the surface of a foamed rubber sheet may be formed in the surface of the heating drum and / or metal band which comprise the said drum type press.

The foamed rubber sheet of the present invention is obtained by the production method of the present invention.
Moreover, it is preferable that the expansion ratio is 1.05-2.0.

(1) According to the production method of the present invention, it is possible to produce a long foamed rubber sheet that is excellent in all of surface smoothness, mechanical properties and thickness uniformity and has closed cells of suitable and uniform size. it can.
(2) According to the production method of the present invention, the expansion ratio and thickness of the long foamed rubber sheet are adjusted to the heating and pressing conditions in the drum press without adjusting the type and / or blending amount of the foaming agent. Can be easily controlled. Accordingly, various long foamed rubber sheets having different foaming ratios can be produced from a long sheet (unvulcanized sheet) made of the rubber composition having the same composition.
(3) According to the production method of the present invention, a long foamed rubber sheet having a uniform bubble size and dispersed state (dispersed state in the sheet) and extremely small variation in the foaming ratio and characteristics depending on the part is produced. Can do.
(4) According to the production method of the present invention, a skin layer having a certain thickness (for example, 10 to 20 μm) can be formed as the surface layer of the obtained foamed rubber sheet.
(5) The foamed rubber sheet of the present invention is excellent in all of surface smoothness, mechanical properties and thickness uniformity, and is a closed cell having a suitable and uniform size (for example, 15 to 120 μm) derived from a thermally expandable microcapsule. have.

  The production method of the present invention is characterized in that a long sheet made of a rubber composition containing thermally expandable microcapsules is continuously heated and pressed using a drum press. Thereby, the rubber in the rubber composition is vulcanized, and the thermally expandable microcapsules are thermally expanded to foam the sheet, thereby obtaining a foamed rubber sheet.

<Rubber composition>
The raw rubber constituting the “rubber composition” used in the production method of the present invention is not particularly limited. For example, natural rubber (NR), styrene butadiene rubber (SBR), chloroprene rubber (CR), ethylene Examples include propylene rubber (EPM, EPDM), silicone rubber (Q), fluorine rubber (FKM), and nitrile rubber (NBR).

  Further, as a compounding agent constituting the rubber composition, a vulcanizing agent, a vulcanization accelerator, a vulcanization acceleration aid, an anti-aging agent, a reinforcing agent, a filler, a softening agent, a plasticizer, a lubricant, a coloring agent, and the like, Known rubber compounding agents can be used. Moreover, in order to improve the dispersibility of a thermally expansible microcapsule, it is preferable to mix | blend a dispersing agent.

<Thermal expandable microcapsules>
“Thermal expandable microcapsules” blended in a rubber composition are microcapsules in which a thermoplastic resin having a gas barrier property is used as a shell, and a low boiling point material (thermal expander) is included in the shell. is there. By heating the heat-expandable microcapsules, the thermoplastic resin in the shell is softened, and expands with the vaporization of the low-boiling substance to form microballoons (hollow spherical particles).

  Examples of the thermoplastic resin constituting the shell of the thermally expandable microcapsule include vinylidene chloride and acrylonitrile. Due to the gas barrier properties of the thermoplastic resin, the gas resulting from the vaporization of the low boiling point substance is retained in the expanded particles (microballoons). As a result, even if the sheet containing the thermally expandable microcapsule is continuously heated and pressurized using a drum press, the vaporized gas (as in the case where a pyrolytic foaming agent is blended) is still in the sheet. The foamed rubber sheet is ensured to have closed cells, and a foamed rubber sheet having a desired foaming ratio (for example, 1.05 to 2.0) can be reliably produced.

Examples of the low boiling point substance contained in the shell include a low boiling point liquid hydrocarbon.
The particle size of the thermally expandable microcapsule (particle size p before expansion) is preferably 5 to 40 μm, more preferably 10 to 30 μm.
Moreover, it is preferable that the particle diameter P of the microballoon after expansion is 15 to 120 μm, and more preferably 30 to 90 μm.

The expansion start temperature of the thermally expandable microcapsule is preferably 100 to 200 ° C, more preferably 120 to 190 ° C.
The maximum expansion temperature of the thermally expandable microcapsule is preferably 130 to 220 ° C, more preferably 160 to 200 ° C.

The expansion coefficient (P / p) of the thermally expandable microcapsule is preferably 3 times or more [volume expansion coefficient (P / p) ³ is 27 times or more], more preferably 3 to 5 times (volume expansion). 27 to 125 times).
Examples of commercially available thermally expandable microcapsules include “Expansel” (manufactured by Nippon Philite Co., Ltd.), “Matsumoto Microsphere” (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), and the like.

The compounding amount of the thermally expandable microcapsule is 1 to 10 parts by mass, preferably 2 to 6 parts by mass with respect to 100 parts by mass of the raw rubber.
When the blending amount is too small, it is not possible to ensure the foaming ratio necessary for expressing the properties as a foam. On the other hand, when the blending amount is excessive, the surface smoothness of the foam rubber sheet finally obtained is impaired, or the mechanical strength is lowered.

<Composition example of rubber composition>
Hereafter, the compounding prescription of the rubber composition used suitably for the manufacturing method of this invention is shown.
-Raw rubber (SBR, NR): 100.0 parts-Sulfur: 1-3 parts-Accelerator: 1-3 parts-Zinc oxide: 2-5 parts-Stearic acid: 0.5-2 parts-Dispersant: 1-3 parts-White filler: 10-50 parts-Carbon black: 10-50 parts-Oil: 5-50 parts-Thermally expandable microcapsules: 1-10 parts

Raw material rubber (silicone rubber): 100.0 parts Vulcanizing agent: 0.8 to 2.5 parts Thermal expansion microcapsules: 1 to 10 parts

Raw material rubber (EPM / EPDM): 100.0 parts Vulcanizing agent (organic peroxide) 1-10 parts Zinc oxide 2-5 parts TAIC 1-5 parts Dispersant 1-3 parts White filling Agent: 10-50 parts Carbon black: 10-50 parts Oil: 10-50 parts Thermally expandable microcapsules: 1-10 parts

<Long sheet>
The method for producing a long sheet made of the rubber composition is not particularly limited, and a known sheet forming method using an extruder or a calendar can be employed.
As the size of the sheet, for example, a sheet having a width of 0.5 to 1.2 m, a length of 1 m or more (for example, 1 to 100 m), and a thickness of 1 to 10 mm can be suitably used.

<Drum type press>
In the production method of the present invention, the above-described long sheet (unvulcanized rubber sheet in which thermally expandable microcapsules are blended) is continuously heated and pressurized using a drum press.
And the foaming (expansion) of a sheet | seat by expansion | swelling of a thermally expansible microcapsule can be controlled by adjusting the heating-pressing conditions to a sheet | seat, As a result, a foaming magnification is controlled.

That is, when the heating temperature is set high, the foaming pressure (expansion pressure) of the sheet is also increased, so that a foamed rubber sheet having a high foaming ratio is obtained.
Also, if the pressure applied to the sheet is set high, foaming (expansion) of the sheet can be suppressed low, and a foamed rubber sheet having a low expansion ratio can be obtained.
In this way, by adjusting the heating and pressing conditions (heating temperature and pressure applied to the sheet), a closed-cell foamed rubber sheet having a desired foaming ratio can be obtained.

  The control of the expansion ratio by such a method can be achieved only when a thermally expandable microcapsule is blended in the rubber composition, and when a pyrolytic foaming agent is blended. In this case, the gas generated by the foaming agent escapes from the sheet by heating and pressurization with a drum press, and the foaming (expansion) of the sheet cannot be controlled, and as a result, the foaming ratio cannot be controlled.

  In the production method of the present invention, when a long sheet is continuously heated and pressed using a drum press, the one having the same composition as the rubber composition constituting the sheet is heated by a drum press. Measure the pressure condition and the expansion ratio of the foamed rubber sheet obtained under that condition (heating pressure condition-calibration curve for expansion ratio) in advance, and set the heating and pressure condition using this calibration curve It is preferable from the viewpoint of manufacturing efficiency and the like.

According to the manufacturing method of the present invention, the smooth surface state of the heating drum and the metal band constituting the drum press is transferred. As a result, the surface smoothness equivalent to that of solid rubber is obtained, and the thickness is uniform. An excellent long foamed rubber sheet can be produced.
Moreover, the said pattern can also be transcribe | transferred on the surface of the foamed rubber sheet obtained by forming an uneven | corrugated pattern in the surface of a heating drum and / or a metal band.

FIG. 1 is an explanatory view showing an example of a drum-type press (continuous heating and pressurizing device) called “roto-cure”.
In FIG. 1, 11 is a heating drum, 12 is a heating device, 13 and 14 are pressure rolls, 15 is a tension roll, 16 is a drive roll, 17 is an endless steel band, 18 and 19 are guide rolls, respectively. 21 is a long sheet (unvulcanized / unfoamed rubber sheet), and 22 is a foamed rubber sheet (vulcanized sheet).

The heating drum 11 is configured to be heated by a heating device 12, and a pressure roll 13, a pressure roll 14, a tension roll 15, and a drive roll 16 are disposed around the heating drum 11.
The steel band 17 is wound around the outer periphery of each of the heating drum 11, the pressure roll 13, the pressure roll 14, the tension roll 15, and the drive roll 16.

  When the drive roll 16 is rotated in the clockwise direction and the tension roll 15 is moved in the direction indicated by the arrow T, each of the pressure roll 13, the pressure roll 14, and the tension roll 15 is rotated in the clockwise direction by the transmission force of the steel band 17. The heating drum 11 rotates counterclockwise. Further, a pressing force is applied to the outer peripheral surface of the heating drum 11 by the tension of the steel band 17 (the pressing force of the pressure rolls 13 and 16). The magnitude of this pressure can be adjusted by the amount of movement of the tension roll 15.

  When a long sheet 21 is supplied through the guide roll 18 to the gap between the pressure roll 13 around which the steel band 17 is wound and the heating drum 11, the sheet 21 is formed between the steel band 17 and the heating drum 11. Heated and pressurized continuously. As a result, the rubber constituting the sheet 21 is vulcanized, and the thermally expandable microcapsule expands to foam the sheet 21 to form a foamed rubber sheet 22. The foamed rubber sheet 22 is collected through the outer periphery of the drive roll 16 and the guide roll 19.

  Here, as the heating and pressing conditions of the sheet 21, when the expansion start temperature of the thermally expandable microcapsule blended in the sheet 21 is 100 to 200 ° C, for example, the temperature is 120 to 220 ° C, the pressure is 0 0.05 to 0.3 MPa, preferably a temperature of 140 to 200 ° C. and a pressure of 0.08 to 0.2 MPa.

  When the heating temperature of the sheet 21 is less than 120 ° C., the vulcanization reaction of the rubber composition constituting the sheet 21 is not sufficiently accelerated. On the other hand, if it exceeds 220 ° C., it will greatly exceed the maximum expansion temperature of the thermally expandable microcapsules, and the desired expansion rate (and expansion ratio) may not be obtained.

In addition, when the pressure applied to the sheet 21 is less than 0.05 MPa, the foaming ratio of the resulting foamed rubber sheet is excessive (for example, a ratio exceeding 2.00), and good surface smoothness and mechanical characteristics are obtained. Further, the uniformity of the sheet thickness is impaired.
On the other hand, when the pressure applied to the sheet 21 exceeds 0.3 MPa, the foaming ratio of the foamed rubber sheet obtained is too low (for example, less than 1.05), and the characteristics as a foam can be sufficiently expressed. Can not.

  The heating and pressing time under the above conditions (temperature 120 to 200 ° C., pressure 0.05 to 0.3 MPa) is, for example, 30 seconds to 10 minutes.

<Foamed rubber sheet>
The foamed rubber sheet (foamed rubber sheet of the present invention) obtained by the production method of the present invention has closed cells of suitable and uniform size derived from thermally expandable microcapsules, and has surface smoothness, mechanical properties and thickness. Excellent in all of the uniformity.
In addition, the state of dispersion of bubbles (microballoons) derived from the thermally expandable microcapsules is uniform, and therefore, the variation in the foamed state (foaming ratio) and properties (for example, mechanical properties) are extremely small.
Furthermore, since a skin layer having a certain thickness (for example, 10 to 20 μm) is formed as the surface layer, the surface layer has an excellent surface state, that is, a surface state similar to that of solid rubber, and has a high mechanical property. Strength is secured.

The foamed rubber sheet of the present invention is a closed-cell foamed rubber sheet having a closed cell ratio of theoretically 100%.
In the foamed rubber sheet of the present invention, the bubble size is preferably 15 to 120 μm, more preferably 30 to 90 μm.
Here, the size of the bubble derived from the thermally expandable microcapsule substantially matches the particle diameter P of the microballoon (hollow spherical particle) after expansion. This particle diameter P is determined by the heating and pressing conditions applied to the long sheet by the drum press, and is uniform in the foamed rubber sheet manufactured under the same conditions.

As the size of the foamed rubber sheet of the present invention, its width and length are the same as those of the above-mentioned long sheet (unvulcanized / unfoamed rubber sheet), and its thickness is 1 of that of the long sheet. 0.05 to 2.0 times.
If the suitable range of the size of the foamed rubber sheet of the present invention is shown, the width is 0.5 to 1.2 m, the length is 1 m or more (for example, 1 to 100 m), and the thickness is 1 to 10 mm.
And in the foam rubber sheet of the same lot manufactured continuously on the same conditions, the thickness variation is small (for example, within ± 7.5%), and the thickness uniformity is excellent.

In the foamed rubber sheet of the present invention, the surface form (smooth surface or concavo-convex pattern) of the heating drum and metal band constituting the drum press is faithfully transferred.
When the heating drum and the metal band constituting the drum-type press have a smooth surface, a skin layer having a thickness of about 10 to 20 μm is formed on the surface of the obtained foam rubber sheet. Excellent surface condition and high mechanical strength are ensured.

The foaming ratio of the foamed rubber sheet of the present invention is preferably 1.05 to 2.0, and more preferably 1.1 to 1.5.
Here, the “foaming ratio” is obtained by (D ₀ / D) where D is the specific gravity of the foamed rubber sheet and D ₀ is the specific gravity of the rubber composition before foaming.
When the expansion ratio is less than 1.05, the properties as a foam cannot be sufficiently exhibited. On the other hand, a foam having an expansion ratio exceeding 2.0 is inferior in surface smoothness and mechanical properties.

  The specific gravity of the foamed rubber sheet of the present invention is preferably 1.0 or less, more preferably 0.5 to 0.9.

  Examples of the present invention will be described below, but the present invention is not limited thereto. In addition, the evaluation or measuring method about the foamed rubber sheet obtained by the following example and the comparative example is as follows.

(Surface smoothness)
The surface of the foamed rubber sheet is visually observed. “○” indicates that the surface has good smoothness equivalent to that of solid rubber, “S” indicates that some irregularities are observed, and “△” indicates that the smoothness is inferior, And and / or a crater shape was designated as “x”.

(Mechanical properties)
Tensile strength (T _B ) and elongation (E _B ) were measured according to JIS K 6251, and hardness (Shore-A) was measured according to JIS K 6253.

(Thickness uniformity)
At 6 or more sites per 1 m ² , the sheet thickness was measured, and the average thickness and variation were determined.

[Adjustment Example 1]
Styrene butadiene rubber oil exhibition "SBR-1778" (manufactured by JSR Corporation, oil content = 27.3 mass%) 71.5 parts by mass, styrene butadiene rubber "SBR-1502" (manufactured by JSR Corporation) 22. 0 parts by mass, natural rubber (RSS-3) 26.0 parts by mass, vulcanization accelerator (TMTS) 0.2 parts by mass, vulcanization accelerator (CZ) 1.5 parts by mass, sulfur 1 0.5 parts by mass, 5.0 parts by mass of zinc oxide, 1.0 part by mass of stearic acid, 2.0 parts by mass of the dispersant “Neocoat 60XP” (manufactured by Sanchemtech), and the dispersant “Neocoat 100F” [Manufactured by Sanchemtech Co., Ltd.] 1.0 part by mass, 30.0 parts by mass of magnesium hydroxide, 15.0 parts by mass of carbon black (FEF), 5.0 parts by mass of naphthenic oil, thermal expansion micro Capsule "Expansel 092) DU80 "(manufactured by Nippon Philite Co., Ltd., particle size p = 18-24 μm, expansion start temperature = 122-132 ° C., maximum expansion temperature = 176-186 ° C.) By mixing, kneading, extruding with a T-die extruder, and calendering, a long sheet made of a rubber composition (width = 1.05 m, length = 40 m, thickness = 2.5-2.6 mm) ) Was prepared.

[Preparation Example 2]
Silicone rubber “KE-951U” (manufactured by Shin-Etsu Chemical Co., Ltd.) 100.0 parts by mass, vulcanizing agent “C-15” (manufactured by Shin-Etsu Chemical Co., Ltd.) 1.5 parts by mass, and thermal expansibility By blending 3.5 parts by mass of microcapsule “Expansel (092) DU80” (manufactured by Nippon Philite Co., Ltd.) according to a conventional method, extruding with a T-die extruder, and calendering, A long sheet (width = 1.05 m, length = 20 m, thickness = 2.00-2.10 mm) made of a rubber composition was prepared.

[Preparation Example 3]
A rubber composition was prepared in the same manner as in Preparation Example 1, except that 3.5 parts by mass of a pyrolytic foaming agent [p, p′-oxybis (benzenesulfonylhydrazide)] was blended in place of the thermally expandable microcapsules. A long sheet (width = 1.05 m, length = 40 m, thickness = 2.5-2.6 mm) was prepared.

<Example 1>
Using the long sheet (thickness = 2.5 to 2.6 mm) obtained in Preparation Example 1 using a drum-type press (continuous heating and pressurizing device called a rotocure) as shown in FIG. Then, by heating and pressurizing continuously for 150 seconds under a heating temperature of 190 ° C. and the respective pressurization conditions shown in Table 1 below, the rubber constituting the sheet is vulcanized and the sheet is foamed and foamed. A rubber sheet (width = 1.05 m, length = 40 m) was produced.
Here, as the heating drum constituting the drum type press, one having a smooth surface form was used. Thereby, formation of the skin layer about 10-20 micrometers thick was recognized by the obtained foamed rubber sheet.
For the foamed rubber sheet obtained as described above, specific gravity and foaming ratio were measured for each pressurizing condition during production, and surface smoothness, mechanical properties and thickness uniformity were evaluated. The results are also shown in Table 1.

<Example 2>
Using the long sheet (thickness = 2.5 to 2.6 mm) obtained in Preparation Example 1 using a drum-type press (continuous heating and pressurizing device called a rotocure) as shown in FIG. Then, by heating and pressurizing continuously for 150 seconds under the respective heating conditions shown in the following Table 2 at a heating temperature of 190 ° C., the rubber constituting the sheet is vulcanized and the sheet is foamed. A rubber sheet (width = 1.05 m, length = 40 m) was produced.
Here, as the heating drum constituting the drum-type press, one having a concavo-convex pattern having a cross-sectional shape shown in FIG. 2 (a convex portion extending in the circumferential direction of the drum) was used. Note that the unit of numerical values in FIG. 2 is “mm”. Thereby, the uneven | corrugated pattern (groove extended in the longitudinal direction of a sheet | seat) of a heating drum was faithfully transferred on the surface of the obtained foamed rubber sheet.
For the foamed rubber sheet obtained as described above, the specific gravity and the foaming ratio were measured for each pressing condition during production, and the surface smoothness and mechanical properties were evaluated. The results are also shown in Table 2.

<Example 3>
The long sheet (thickness = 2.00 to 2.10 mm) obtained in Preparation Example 2 is used with a drum-type press (continuous heating and pressing device called a rotocure) as shown in FIG. Then, by heating and pressurizing continuously for 120 seconds under the respective heating conditions of heating temperature 190 ° C. and Table 3 below, the silicone rubber constituting the sheet is vulcanized and the sheet is foamed. A foamed rubber sheet (width = 1.05 m, length = 20 m) was produced.
Here, as the heating drum constituting the drum type press, one having a smooth surface form was used. Thereby, formation of the skin layer about 10-20 micrometers thick was recognized by the obtained foamed rubber sheet.
For the foamed rubber sheet obtained as described above, specific gravity and foaming ratio were measured for each pressurizing condition during production, and surface smoothness, mechanical properties and thickness uniformity were evaluated. The results are also shown in Table 3.

<Comparative Example 1 (combination of pyrolytic foaming agent and hot air heating device)>
By heating the long sheet (thickness = 2.5 to 2.6 mm) obtained in Preparation Example 3 using a hot air heating device at a temperature of 190 ° C. for 450 seconds under no pressure, the sheet is obtained. A rubber sheet (width = 1.05 m, length = 40 m) was produced by vulcanizing the rubber constituting the rubber and foaming the sheet.
The foamed rubber sheet thus obtained was measured for specific gravity and expansion ratio to evaluate surface smoothness, mechanical properties and thickness uniformity. The results are shown in Table 4 below.

<Comparative Example 2 (combination of pyrolytic foaming agent and drum type press)>
The long sheet (thickness = 2.5 to 2.6 mm) obtained in Preparation Example 3 is used with a drum-type press (continuous heating and pressurizing device called rotocure) as shown in FIG. Then, by continuously heating and pressurizing for 150 seconds under the conditions of a heating temperature of 190 ° C. and a pressing force of 0.12 MPa, the rubber constituting the sheet is vulcanized and the sheet is foamed. Width = 1.05 m, length = 40 m).
Here, as the heating drum constituting the drum type press, one having a smooth surface form was used.
In addition, a part of rubber composition which comprises a long sheet | seat flowed in the width direction with the pressurization force by a drum type press.
The foamed rubber sheet thus obtained was measured for specific gravity and expansion ratio to evaluate surface smoothness, mechanical properties and thickness uniformity. The results are also shown in Table 4.

<Comparative Example 3 (combination of thermally expandable microcapsule and hot air heating device)>
The long sheet (thickness = 2.5 to 2.6 mm) obtained in Preparation Example 1 is heated under a non-pressurized condition at a temperature of 190 ° C. for 450 seconds using a hot air heating apparatus, thereby the sheet. A rubber sheet (width = 1.05 m, length = 40 m) was produced by vulcanizing the rubber constituting the rubber and foaming the sheet.
The foamed rubber sheet thus obtained was measured for specific gravity and expansion ratio to evaluate surface smoothness, mechanical properties and thickness uniformity. The results are shown in Table 4 below.

  The foamed rubber sheet obtained by the production method of the present invention can be suitably used for applications such as various rugs (mats), various cushioning materials (for example, packings and gaskets).

It is explanatory drawing which shows an example of the drum type press used for the manufacturing method of this invention. It is sectional drawing which shows the uneven | corrugated pattern formed in the heating drum surface which comprises the drum type press used in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Heating drum 12 Heating device 13 Pressure roll 14 Pressure roll 15 Tension roll 16 Driving roll 17 Endless steel band 18 Guide roll 19 Guide roll 21 Long sheet 22 Foam rubber sheet

Claims (7)

  A rubber sheet is vulcanized by continuously heating and pressing a long sheet made of a rubber composition containing a thermally expandable microcapsule using a drum press, and the thermally expandable microcapsule is A method for producing a foamed rubber sheet, wherein the sheet is foamed by being expanded.   Using a drum-type press, a long sheet made of a rubber composition in which 1 to 10 parts by mass of thermal expansion microcapsules having an expansion start temperature of 100 to 200 ° C. are blended with 100 parts by mass of unvulcanized rubber The rubber is vulcanized by continuously heating and pressing under conditions of a temperature of 120 to 220 ° C. and a pressure of 0.05 to 0.3 MPa, and the thermally expandable microcapsule is expanded to foam the sheet. A method for producing a foam rubber sheet, characterized by comprising:   The method for producing a foamed rubber sheet according to claim 2, wherein the sheet is foamed so that a foaming ratio is 1.05 to 2.0. When the long sheet is continuously heated and pressed using a drum press,
(1) the expansion ratio required for the foamed rubber sheet to be manufactured;
(2) Preliminarily measured the relationship between the heating and pressing conditions by a drum press and the expansion ratio of the foamed rubber sheet obtained under the same conditions for the same composition as the rubber composition constituting the long sheet. The method for producing a foamed rubber sheet according to any one of claims 1 to 3, wherein heating and pressurizing conditions are set based on the obtained data.   5. A concavo-convex pattern for transferring onto a surface of a foamed rubber sheet is formed on the surface of a heating drum and / or metal band constituting the drum type press. A method for producing a foamed rubber sheet as described in 1.   A foamed rubber sheet obtained by the method according to any one of claims 1 to 5. The foamed rubber sheet according to claim 6, wherein the foaming ratio is 1.05 to 2.0.

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