JPH0531815A - Method and device for manufacturing rubber basis foam - Google Patents

Abstract

PURPOSE:To provide the above method and device for manufacturing a sheetlike or boardlike foam where the foam has a uniform thickness and is free from a warp, further size of a cell constituting the foam is uniform and possesses a stable quality. CONSTITUTION:In the manufacturing device of a rubber basis foam, which is provided with a preheating furnace 3 preheating a rubber basis foamable sheetlike molded body including a foaming agent, a heating and foaming furnace 5 foaming a sheetlike molded body S1 by heating the same after preheating by passing through the preheating furnace 3, the preheating furnace 3 is provided with an upper surfacelike far infrared heater 31a to be arranged on the top of the sheetlike molded body and a lower surfacelike far infrared heater 31b to be arranged underneath the undersurface of the sheetlike molded body. Then a sheetlike rubber foam S2 is manufactured under the atmosphere by using this device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for manufacturing a rubber-based foam, and more specifically, it has a uniform thickness, a uniform cell size, and a small amount of deformation during foaming. The present invention relates to a method and an apparatus for manufacturing a rubber-based foam that can improve the yield during the next processing. INDUSTRIAL APPLICABILITY The present invention is applied to a rubber-based foam used for waterproofing, soundproofing and the like of civil engineering and construction, connecting points and gaps in vehicles and the like.

[0002]

2. Description of the Related Art A method for continuously or discontinuously producing a polyolefin-based rubber foam is known, and for example, a polyolefin mixed with a foaming agent, a cross-linking agent and appropriate additives is used by using an extruder. It is known that a desired foamed product is obtained by molding it into a continuous sheet or plate and heating it to cause crosslinking and foaming. As the heating method, generally, hot air, microwave, high frequency, low melting point metal salt or the like is used (JP-A-59-9028, JP-A-54-118464, and JP-A-54-54).
No. 120669, etc.). Further, as a conventional foam manufacturing apparatus, there is also known one having a preheating tank in which a sheet-shaped molded body is immersed in a liquid heating medium made of a low melting point metal (Japanese Patent Laid-Open No. 60-56535).

[0003]

However, in the former conventional manufacturing method in which the preheating is not performed among the above, the thickness of the foam obtained is not uniform, the yield is poor, or the foam is warped. There are problems that post-processing such as slicing is difficult, and that the size of cells forming the foam is different between the surface portion and the central portion side and the quality is unstable.
Furthermore, when a hot air circulation type heating and foaming furnace is used, it is extremely difficult to individually set the temperature.

Further, the latter manufacturing apparatus equipped with the latter preheating tank preheats using a low-melting metal liquid, and since it is a liquid metal, it does not cause defects such as oil, but it is a liquid preheating tank. It is complicated in itself, and it is difficult to handle because it is a metal. Further, since the whole sheet is heated, the sheet cannot be divided and heated in this case as well, so that the problem that the thickness of the foam becomes uneven and warps occur similarly.

The present invention overcomes the above-mentioned drawbacks and has a uniform thickness of the foam and no warp. Further, the cells constituting the foam have a uniform size and a sheet shape with stable quality. Alternatively, it is an object to provide a method for manufacturing a plate-shaped foam and a manufacturing apparatus for the same.

[0006]

As a result of various studies on foams having stable properties, the present inventor has found that this defect can be solved by adjusting the temperature of each heater during preheating. The invention was completed. Regardless of the presence or absence of a preheating furnace, the sheet or the like formed by the extruder is first preheated to the decomposition temperature of the foaming agent or less,
At this time, it is desirable that the temperature distribution of the sheet (for example, the central portion side and each end portion side, or the surface portion and the central portion) is heated to be constant or almost constant. Further, in the method for producing a rubber foam, it is important to perform stepwise heating, and specifically, the crosslinking rate and the viscosity increase due to the crosslinking reaction with respect to the decomposition of the foaming agent are started simultaneously or slightly sooner. It is of utmost importance to adjust the decomposition rate so that the bubble film can be easily destroyed during the communication step.

The method for producing a rubber-based foam of the present invention is a rubber-based foamable sheet-shaped molded product or a rubber-based foamable plate-shaped molded product (hereinafter referred to as “rubber-based foamable sheet-shaped molded product, etc.”). Or a "sheet-shaped molded article") is preheated and then heat-foamed to produce a rubber-based foamed body. It is characterized in that it is preheated below the decomposition temperature of the foaming agent by an infrared heater.

Here, the "sheet-shaped molded product" may be a continuous product, or may be molded and cut to a predetermined length, and the "plate-shaped product" is the above-mentioned sheet-shaped product. Means thicker than. In the present production method, a continuous foaming method can be used in which the rubber-based foamable sheet-shaped molded product or the like is continuously conveyed, and preheating and heat foaming of the molded product are continuously performed. In this case, it can be carried out by continuously transporting the molded body by a belt conveyor, a roll conveyor or the like and passing it through each furnace. Further, the temperature for preheating the upper surface of the rubber-based foamable sheet-shaped molded product or the like is preferably 20 to 40 ° C. lower than the temperature for preheating the lower surface of the sheet-shaped molded product or the like. This is because it is possible to uniformly preheat both the surface portion and the central portion, so that uniform foaming is possible. Further, in the width direction of the rubber-based foamable sheet-shaped molded product, the heating temperature on each end side is 15 to 25 higher than the heating temperature on the central part side.
It is preferable that the temperature is lower by ° C. This is because in this case, uniform preheating can be performed on both the center side and each end side, and thus uniform foaming can be performed.

An apparatus for producing a rubber-based foam of the present invention comprises a preheating furnace for preheating a rubber-based foamable sheet-shaped molded product containing a foaming agent, and a preheated sheet-shaped molded product which has passed through the preheating furnace. And a foaming heating furnace for foaming, wherein the preheating furnace comprises an upper side surface far infrared heater arranged on the upper surface of a rubber-based foamable sheet-shaped molded product, and the rubber-based foamable sheet-shaped molding. And a lower side surface far-infrared heater disposed below the lower surface of the body or the like.

In the present manufacturing apparatus, the rubber-based foamable sheet-like molded article is continuously transported, and the molded article transporting means is capable of continuously preheating and foaming the molded article continuously. It can be a manufacturing apparatus. A belt conveyor, a roll conveyor, or the like can be used as the molded body conveying means. Further, in the manufacturing apparatus, the upper side surface far infrared heater and the lower side surface far infrared heater are divided into at least a central portion and three end portions thereof in the width direction of the sheet-shaped molded body or the like. Therefore, it is preferable that the temperature of each of them can be controlled independently. By setting an appropriate heating temperature,
This is because the whole can be preheated uniformly and therefore uniform foaming can be performed. The number of divisions can be divided into three on the center side and each end side, or can be four or five. Further, the heaters in this case may have a configuration in which separate sheet heaters (for example, three) are juxtaposed, or heating means capable of heating to different temperatures at predetermined locations on one heater surface are independently provided. It may be configured.

Further, in the above, the exhaust gas generated by heating and foaming may be re-combusted to save energy by reusing the combustion gas and prevent air pollution by cleaning the exhaust gas.

As a raw material for the rubber-based foamable sheet-shaped molded product or the like, one which can be foam-molded, for example, an olefin terpolymer composed of ethylene, α-olefin and polyene having a non-conjugated double bond as a main material. It is possible to use a synthetic rubber raw material or the like. Here, as the α-olefin, propylene, butene-1 or the like can be used. As the polyene having a non-conjugated double bond,
Norbornenes, cyclic dienes, aliphatic dienes and the like can be used, and particularly 5-ethylidene-2-norbornene, dicyclopentadiene, and 1,4-hexadiene can be mentioned as typical ones.

[0013]

In the present invention, the foaming agent is preheated to a temperature below the decomposition temperature of the foaming agent to be used by the far infrared heater, and then heated to a temperature above the decomposition temperature of the foaming agent for foaming. Cross-linking reaction precedes,
Next, since it can be foamed and further heated by far infrared rays, the heat permeates quickly into the inside of the sheet-shaped molded product, and the surface portion and the inside thereof can be preheated at a uniform temperature. Moreover, the temperature for heating the upper surface of the sheet-shaped molded product is lower than the temperature for heating the lower surface of the sheet-shaped molded product by 20 to 40 ° C., and each end of the sheet-shaped molded product in the width direction is reduced. When the heating temperature on the part side is lower by 15 to 25 ° C. than the heating temperature on the central part side,
The temperatures of the front surface and the back surface, the temperatures of the central portion side and the end portions side, and the temperatures of the surface portion and the central portion can be made substantially uniform.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. (1) Outline of the device The device used in this example is shown in FIGS. 1, 2 (overall schematic view), FIG. 3, FIG. 4 (explanatory view of preheating tank and foaming heating tank), and FIG. 5 (heater panel, etc.). (Explanatory drawing of the front side), an extruder 1, a powdered roller 2, a preheating furnace 3, a heating adjustment furnace 4, a heating and foaming furnace 5, a conveyor 6, a cooling roll 7, a take-up conveyor 8 and a crushing. A roll 9, a cutter 10, and a conveyor 11 are provided in sequence. And the preheating furnace 3,
A releasable conveyor 6a, belt conveyors 6b, 6c, and roller conveyors 6d, 6e for transporting a predetermined sheet-shaped compact (hereinafter, simply referred to as a sheet) S ₀ in the heating adjustment furnace 4 and the heating and foaming furnace 5. Is provided. Extruder 1
As a T-die of 120 mm, with vent, discharge amount;
A roller head with a width of 320 kg / hour and a width of 1400 mm was used.

The preheating furnace 3 has 1800 (width) × 400.
The size is 0 (length) × 1750 (height), and as shown in FIG. 3, upper and lower electric far infrared panel heaters (width;
(500 mm, length: 1000 mm, thickness: 20 mm, maximum surface temperature: 400 ° C.)) 31a, 31b are arranged above and below the sheet S. In addition, this upper panel heater 31a
And the lower panel heater 31b is about 1 each from the seat S.
50 mm and about 50 mm apart. The upper and lower panel heaters 31a and 31b are the same as those shown in FIG.
As shown in FIG. 5, the upper panel heater 31a is divided into three sections A (left side portion), B (center side portion), and C (right side portion) in the widthwise direction of the sheet-shaped molded body S ₀ substantially equally. Split,
Lower panel heater 31b is D (left side), E (center side)
And F (right side) are similarly divided into three sections, each of which is capable of independent temperature control.

Further, as shown in FIG. 1, after the preheating furnace 3, a heating adjustment furnace 4 and a foaming heating furnace 5 are connected. This heating adjustment furnace 4 is also the same size as the preheating furnace 3, and the heating and foaming furnace 5 is a furnace having the same size as the heating adjustment furnace 4 connected to each other.
a, 5b, 5c, 5d. As the adjusting furnace 4 and the foaming heating furnace 5, LPG [liquefied propane (petroleum) gas] is used.
Using the hot air circulation method, hot air outlets (13a, 13a
b, 13c, etc.) are installed above and below, and hot air is blown out through the gas burners (14a, 14b, etc.) (13a).
-C etc.) is blown out to heat the sheet. The total length of the entire furnace is 22 m, and the temperature in the heating and foaming furnace is about 200 ° C (maximum 250 ° C). Also,
Only the heating and foaming furnaces (second foaming regions) 5c and 5d are driven by the roller conveyors 6d and 6e. As the belt used, a glass fiber reinforced mesh belt (width: 1300 mm, plain weave 20 to 30 mesh, with meandering correction device) was used. The transport speed is 0.5 to 5 m / min (using an ES motor). Further, the exhaust gas is introduced into the hot air generator by a circulation fan to form a closed circuit for reburning. In addition, a part is exhausted.

(2) Examination of Proper Temperature Setting of Panel Heater When setting the temperature of the panel heater, the following test was conducted to determine the proper temperature. First, in the above apparatus, the temperatures of the upper panel heater and the lower panel heater shown in Table 1 below were set, and the surface temperature and back surface temperature of the sheet at that time were measured and evaluated. The foamed sheet was also evaluated for variations in wall thickness, presence or absence of warpage, and variations in cell size between the surface portion and the central portion, and the results are shown in Table 2.

[0018]

[Table 1]

[0019]                                 Table 1   −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−     Test No Upper panel heater Lower panel heater Upper and lower heaters Seat front and back               Temperature difference (℃) Temperature difference (℃) Temperature difference ℃                                               (Top-bottom) (front-back)   −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−       1 200 220 -20 +10       2 200 230 -30 + 5       3 200 240 -40 -5       4 220 200 +20 +15   −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0020]

[Table 2]

[0021]                                 Table 2   −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−     Test No Presence / absence of wall thickness variation Surface / center cell                 (Mm) size variation   −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−       1 10 No Somewhat large       25 less       3 5 Yes Somewhat high       4 10 Yes Many   ---------------

From the above, the test No. In the case of the difference of −30 ° C. of 2, the temperature difference between the front surface and the back surface of the sheet was the smallest, and as a result, a foamed sheet with less variation in wall thickness could be obtained, and the most appropriate temperature was shown. Furthermore, in the device,
The center side temperature and each end side temperature of each heater shown in Table 2 below were set, and the center side temperature and each end side temperature of the sheet at that time were measured and evaluated. The sheet after foaming was also evaluated for variations in wall thickness, presence or absence of warpage, and variations in cell size between the surface portion and the central portion.

[0023]

[Table 3]

[0024]                                 Table 3   −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−   Test Bottom heater Bottom heater Bottom heater seat temperature ℃ Seat   No Each end side Central part temperature difference (℃) Both ends / Center part temperature difference ℃         Temperature ℃ Temperature ℃ (edge-center) (each center) (edge-center)   −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−     5 210 220-10 95 / 100-5     6 210 230-20 100 / 110-10     7 210 240-30 100 / 115-15     8 220 200 +20 105/95 +10   −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0025]

[Table 4]

[0026]                                 Table 4   ---------------     Test No Presence / absence of wall thickness variation Surface / center cell                 (Mm) size variation   ---------------       5 5 None       6 5 None       7 5 Yes Somewhat high       8 10 Yes Many   ---------------

From the above, the test No. In the case of the difference of −20 ° C. of 6, the temperature difference between the central portion of the central portion of the sheet and the central portion of each end portion is the smallest, and therefore the temperature difference between the central portion side and each end portion side is small. As a result, a foamed sheet with less variation in wall thickness could be obtained, and the most suitable temperature was exhibited.
Therefore, in the manufacturing method described below, the temperature of the upper panel heater 31a of the preheating furnace 3 is set to the lower panel heater 31a.
Set about 30 ° C. lower than the temperature of b. This is because the heat from the lower panel heater 31b is absorbed by the conveyor 6a. Further, regarding the adjustment of the preheating temperature in the width direction, as shown in FIG. 5, the heater temperature on each end side A, C, D, F is lowered by about 20 ° C. from the heater temperature on the central side B, E. To set. From the above, the temperature of the front surface and the back surface of the sheet, the temperature of the central portion and each end portion, and the temperature of the surface portion and the central portion become substantially uniform.

(3) Method for Manufacturing Foamed Sheet Using the above apparatus, a foamed sheet was manufactured as follows. The upper panel heater 31a and the lower panel heater 3
1b is the most appropriate test number. The temperature is set to the same temperature as that of No. 2, and the temperatures of the central portion side temperature and the respective end portion side temperatures are the most appropriate test No. The same temperature as 2 was set. First, a predetermined rubber-like composition is kneaded and plasticized in the extruder 1, and a continuous sheet-shaped molded body (simply referred to as a sheet) S ₀ is extruded and molded. This rubber composition has 100 parts of EPDM and 6 parts of polybutene.
0 parts, heavy calcium carbonate 80 parts, carbon black 30 parts, aluminum hydroxide 40 parts, sulfur (sulfax) 2 parts, zinc white 10 parts, vulcanization accelerator (dithiocarbamate) 2 Parts, 1 part of stearic acid, 1 part of polyethylene glycol, 10 parts of factice, 12 parts of foaming agent, 10 parts of foaming aid, 2 parts of anti-aging agent, 3 parts of processing aid. The sheet S ₀ before preheating has a width of 1100 mm and a thickness of 25 mm, and its weight is 12 kg / m.

Next, the sheet S ₀ is smoothed by the calender rolls 2 and then continuously conveyed into the preheating furnace 3 through the roller 12 with powder (talc). Then, it is conveyed by the releasable conveyor 6a between the upper and lower far infrared panel heaters 31a and 31b arranged in the preheating furnace 3 and simultaneously preheated. Then, the preheated sheet S ₁ is fed to the belt conveyor 6a and the belt conveyor 6a.
b, 6c and roller conveyors 6d, 6e convey the heating adjustment furnace 4 and the heating foaming furnace 5. Then, hot air obtained by the hot air generator is sent into the furnaces 4 and 5 through the jet ports 13a, 13b, 13c, etc., and the hot air heats the pre-heated sheet S ₁ . Is foamed. The foaming was started from the middle of the heating and foaming furnaces 5a and 5b arranged in the first foaming region. This can be visually confirmed. And the second
Foaming was completed in the foaming region (heating foaming furnaces 5c and 5d).

Thereafter, the foamed sheet S ₂ is cooled by the cooling roll 7, then taken by the take-up conveyor 8, and the bubbles are made to communicate by the crushing roll 9, and then cut by the cutting device 10 to an arbitrary length. Then, the final product was obtained as a foamed sheet S ₃ .
The foamed sheet S ₃ has a length of 2000 mm and a width of 2000 mm.
1100 mm, thickness; 40 mm, weight; about 5 kg / m.

As a comparative example, a foamed sheet was produced by directly foaming and heating without providing a preheating tank. With respect to the foamed sheet of the present example and the foamed sheet of the comparative example, the variation of the wall thickness and the variation of the constituent cells were measured by a dial sheet gauge and a 10-fold projector, respectively. The thickness was as large as 15 to 20 mm, and the warpage occurred, but in the present example, the thickness variation was as small as 5 to 10 mm and warpage did not occur. Regarding the variation in the size of the constituent cells, the variation in the comparative example was as large as 0.2 to 1.0 mm, but in the present example, the variation was as small as 0.3 to 0.8 mm.

Further, in the far infrared rays, heat is quickly permeated into the rubber due to the proper selection of the wavelength, which results in obtaining a uniform cell foam. Furthermore, for adjusting the preheating temperature in the width direction, both ends A, C, D, F
By lowering the heater temperature of about 20 ° C. to the center side B and E, the rubber internal temperature could be made uniform,
It was possible to produce a foam having a uniform wall thickness and a regular cell size. Regarding the method for producing a rubber-based foam, as the temperature of the sheet formed by the extruder rises due to heating, first the crosslinking reaction is preceded without decomposing the foaming agent, and then it is heated above the decomposition temperature of the foaming agent. Therefore, foaming becomes important. According to the present production method, it was possible to give priority to the crosslinking reaction and then to foam, so that a high-quality foam could be obtained. The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application.

[0033]

As described above, by using the manufacturing method and the manufacturing apparatus of the present invention, a rubber-based foam having a uniform thickness and a uniform cell size can be obtained, and deformation such as warpage during foaming can be obtained. It is possible to suppress the above and improve the yield at the time of secondary processing and the quality of products.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing apparatus from extrusion to foaming used in Examples.

FIG. 2 is a schematic view of a manufacturing apparatus used in Examples until a final product is obtained after foaming.

FIG. 3 is an explanatory view seen from the front of the preheating furnace, the heating adjustment furnace, and some of the heating and foaming furnaces used in the examples.

FIG. 4 is a plan view of a preheating furnace, a heating adjusting furnace, and a part of a heating and foaming furnace used in Examples.

FIG. 5 is a cross-sectional explanatory view showing a state in which the heater panel heats the sheet in the preheating furnace used in the examples.

[Explanation of symbols]

1 Extruder 2 Calender Roll 3 Preheating Furnace 31 Far Infrared Panel Heater 4 Heating Adjustment Furnace 5 Heating Foaming Furnace 6 Conveyor 7 Cooling Roll 9 Crushing Roll 10 Cutting Device 13 Hot Air Jet A, C, D, F Far Infrared Panel Heater End side B, E Far-infrared panel heater center side S ₀ Pre-heated sheet S ₁ Pre-heated sheet S ₂ Foamed sheet S ₃ Foamed sheet of final product

Claims (7)

[Claims] 1. A method for producing a rubber-based foam, which comprises preheating a rubber-based foamable sheet-shaped molded product or a rubber-based foamable plate-shaped molded product containing a foaming agent, and then heat-foaming the rubber-based foamable molded product. A method for producing a rubber-based foam, which comprises heating the upper surface and the lower surface of a sheet-shaped molded product or a rubber-based foamable plate-shaped molded product with a far-infrared heater in the atmosphere at a temperature not higher than the decomposition temperature of the foaming agent. 2. The rubber-based foamable sheet-shaped molded product or the rubber-based foamable plate-shaped molded product is continuously conveyed to preheat and heat-foam the molded product continuously. Method for producing rubber-based foam. 3. The temperature for heating the upper surface of the rubber-based foamable sheet-shaped molded product or the rubber-based foamable plate-shaped molded product is 20 to 40 than the temperature for heating the lower surface of the sheet-shaped molded product.
The method for producing a rubber-based foam according to claim 1 or 2, which has a low temperature of ℃. 4. The heating temperature on each end side in the width direction of the rubber-based foamable sheet-shaped molded product or the rubber-based foamable plate-shaped molded product is 15 higher than the heating temperature on the central part side thereof.
The method for producing a rubber-based foam according to claim 1, wherein the temperature is lower by -25 ° C. 5. A preheating furnace for preheating a rubber-based foamable sheet-shaped molded product or a rubber-based foamable plate-shaped molded product containing a foaming agent, and a preheated sheet-shaped molded product or preheated plate-shaped product which has passed through the preheating furnace. A heating foaming furnace that heats and foams the molded body,
In the apparatus for manufacturing a rubber-based foamed body, the preheating furnace includes an upper side surface far infrared heater disposed on an upper surface of the rubber-based foamable sheet-shaped molded body, and a lower surface of the rubber-based foamable sheet-shaped molded body. An apparatus for manufacturing a rubber-based foam, comprising: a lower side surface far infrared heater disposed below. 6. A molded product capable of continuously conveying the rubber-based foamable sheet-shaped molded product or the rubber-based foamable plate-shaped molded product, and continuously performing preheating and heat foaming of the molded product. The rubber-based foam manufacturing apparatus according to claim 5, further comprising a conveying unit. 7. The far-infrared heater on the upper side and the far-infrared heater on the lower side are divided into at least a central portion and both end portions thereof in the width direction of the sheet-shaped molded body or the plate-shaped molded body. 7. The apparatus for producing a rubber-based foam according to claim 5, wherein the temperature control is possible for each of them.