JP2007303029A - Heat treatment furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat treatment furnace that increases a temperature difference between zones and reduces wrinkles, undulation, etc., without reducing a contact pressure application function. <P>SOLUTION: The heat treatment furnace 2 for producing a product sheet 40 by heat-treating a raw material sheet 4 has an upstream furnace part 16 that forms a raw material sheet inlet part 8 and has contact pressure rollers 22a and 22b inside, a downstream furnace part 18 that form a product sheet outlet part 12 and has contact pressure rollers 22d and 22e inside, a partition wall 14 that divides the furnace 2 into the upstream furnace part 16 and the downstream furnace part 18 and forms a sheet conveying window 20, a heat insulating roller 22c attached to the sheet conveying window 20 and heating means 32a, 32b, .., 36d installed in the furnace. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat treatment furnace used for producing a product sheet by heat-treating a raw material sheet, such as when producing a carbon fiber sheet from a sheet made of flame-resistant fiber that performs heat treatment of the sheet. The present invention relates to a heat treatment furnace capable of reliably forming a temperature difference between an upstream furnace part and a downstream furnace part and applying sufficient contact pressure to a raw material sheet to improve the quality of a product sheet to be obtained.

  The carbon fiber sheet has uses such as a reinforcing material, a heat insulating material, and a refractory material. Furthermore, since it has good conductivity and air permeability, it is expected to be used as a conductive material or an electrode material. In particular, the use as a battery electrode material is important.

  When a carbon fiber sheet is used as an electrode material, it is required to reduce the thickness of the carbon fiber sheet itself so as to cope with the recent reduction in size and weight of batteries.

  As a conventional method for producing a thin-layer carbon fiber sheet, there is a method in which raw fibers such as carbon fiber and flame-resistant fiber are processed into a thin-layer sheet such as paper, nonwoven fabric, felt, and woven fabric, and this is continuously heat-treated. Are known.

  In the conventional method for producing a thin-layer carbon fiber sheet using a flame-resistant fiber sheet as a raw material, heat treatment at a low temperature in the temperature range of 800 ° C. or less (first carbonization treatment) and heat treatment at a high temperature in the temperature range of 1500 to 2500 ° C. A method of performing a two-stage heat treatment (second carbonization treatment) is the mainstream. In this two-stage heat treatment, the low-temperature heat treatment of the flame resistant fiber is often performed without tension. The high-temperature treatment of the thin-layer sheet subjected to the low-temperature heat treatment is usually performed under no tension, under tension, or in a state where the surface of the sheet is pressed by contacting with a heating body.

  However, in the conventional method for producing a carbon fiber sheet, when heat-treating a flame resistant fiber sheet at a low temperature, the sheet undergoing heat treatment has a large thermal shrinkage, and when subjected to heat treatment under no tension, wrinkles and undulations occur in the sheet. There is a problem that the surface quality (wrinkles, undulation) of the obtained carbon fiber sheet is lowered.

  There has been proposed a manufacturing apparatus for the purpose of improving surface quality degradation caused by thermal shrinkage that occurs during the manufacture of the carbon fiber sheet (see, for example, Patent Documents 1 and 2).

  In Patent Document 1, in a carbon fiber sheet manufacturing apparatus having a low-temperature heat treatment furnace and a high-temperature heat treatment furnace as basic components, by providing a flame heating straightening furnace downstream of the high-temperature heat treatment furnace, It is disclosed to improve surface quality.

  Patent Document 2 discloses that the surface quality of a sheet after low-temperature treatment is improved by continuously heating and pressing the flame-resistant fiber sheet before low-temperature treatment with a hot plate or a mold.

  However, both of the manufacturing apparatuses disclosed in Patent Documents 1 and 2 require an additional facility for improving the sheet surface quality in addition to the heat treatment furnace having the basic configuration, which increases the size of the entire manufacturing apparatus and increases the cost. There's a problem.

  In the production of the carbon fiber sheet, two heat treatments, a low temperature heat treatment (first carbonization treatment) in a temperature range of 500 to 1000 ° C. and a high temperature heat treatment (second carbonization treatment) in a temperature range of 1500 to 2300 ° C., may be performed. preferable.

While the research group to which the inventor belongs is studying a method for producing a carbon fiber sheet that does not cause shape changes such as wrinkles and swells during heat treatment, the temperature distribution in the furnace in the first carbonization furnace is made appropriate. Furthermore, the present inventors have conceived a method in which a roller is disposed in the first carbonization furnace and a heat treatment is performed while applying a contact pressure with the roller in a state where tension is applied to the raw flame-resistant fiber sheet. According to this method, it was learned that carbon fiber sheets can be continuously produced without causing problems such as wrinkles and undulations caused by thermal shrinkage occurring in the sheets, and an application was made earlier (Patent Document 3).
JP 2004-256959 A (Claims, paragraph numbers [0008] to [0010], [0017] to [0020], [0040], FIGS. 1 to 3) JP 2004-308098 A (claims, paragraph numbers [0006], [0029] to [0044], [0062] to [0069], FIGS. 1-2) JP 2005-344246 A (Claims, paragraph number [0019])

  In the first carbonization furnace that further performs low-temperature heat treatment in a temperature range of 500 to 1000 ° C., the present inventor uses a contact pressure applying means such as a contact pressure roller, a nip roller, and a press to apply a contact pressure of 150 Pa or more to the flame resistant fiber sheet. Attempts were made to heat-treat. By adopting this method of applying contact pressure, an intermediate sheet having a high surface quality was obtained without causing shape deterioration such as wrinkles and undulations during the heat treatment. By heat-treating this intermediate sheet in a second carbonization furnace that performs high-temperature heat treatment in a temperature range of 1500 to 2300 ° C., a high surface quality carbon fiber sheet that does not cause shape changes such as wrinkles and swells during the heat treatment is obtained. I understood that.

  Of the contact pressure applying means, the press is normally a batch operation. In consideration of continuous production, heat treatment is performed by applying a contact pressure with a roller while applying tension to the raw flame-resistant fiber sheet using a heat treatment furnace having a contact pressure roller, a nip roller, or the like as a contact pressure applying means. The method is efficient. In this case, the contact area with the flame resistant fiber sheet is increased by arranging a large number in the furnace with a sufficiently small distance between the contact pressure rollers, and stretching the flame resistant fiber sheet zigzag between the contact pressure rollers. As a result, it was found that the contact pressure imparting function is effectively exhibited.

  Compared to a normal heat treatment furnace that does not have a contact pressure roller or the like in the furnace, a heat treatment furnace that has a contact pressure roller in the furnace inevitably has a cross-sectional area in the furnace opening or a furnace perpendicular to the conveyance direction of the flame resistant fiber sheet. The inner height increases. When the furnace opening cross-sectional area is large, even if the heating means is installed on the downstream side in the furnace, the amount of radiation from the heating means passing through the opening cross-section is increased, so the temperature in the furnace becomes uniform, The temperature at the entrance of the furnace cannot be kept low. As a result, the temperature rise from the outside of the furnace to the inside of the furnace at the furnace inlet becomes abrupt, and the flame resistant fiber sheet is heated rapidly when passing through the furnace inlet, and shrinks at the furnace inlet and generates soot. End up.

  In order to lower the temperature of the inlet portion in the furnace, as described in the above-mentioned prior patent (Patent Document 3), a partition wall is provided along the longitudinal direction of the furnace, and the temperature rise zone temperature zone, the high temperature zone temperature zone It is conceivable to increase the temperature difference between the zones by providing such zones. However, when the partition between the zones is provided between the contact pressure rollers, the distance between the contact pressure rollers is increased at that location, and as a result, the non-contact portion between the roller and the sheet is increased at the partition installation location. Therefore, as a whole in the furnace, there is a problem that the contact area between the roller and the sheet is reduced, and the contact pressure application function is lowered.

  While further studying the improvement of the surface quality of the sheet, the inventor does not provide a partition wall between the contact pressure rollers, but a sheet conveyance window formed in the partition wall that partitions the upstream portion and the downstream portion in the furnace. By arranging a heat insulating roller, the temperature difference between zones can be increased without reducing the contact pressure imparting function, and as a result, wrinkles and undulations due to thermal contraction of the sheet during heat treatment are reduced. I learned that I can do it. Furthermore, it has been found that the heat treatment furnace can be applied to heat treatment other than carbonization treatment. The present invention has been completed based on the above findings, and an object of the present invention is to provide a heat treatment furnace that solves the above problems.

  The present invention for achieving the above object is described below.

  [1] A heat treatment furnace for heat-treating a raw material sheet, wherein an upstream furnace portion having a raw material sheet inlet portion on the upstream side of the furnace and having one or more rollers therein, and a product sheet outlet on the downstream side of the furnace A downstream furnace having one or more rollers in the interior, a partition partitioning the interior of the furnace into an upstream furnace and a downstream furnace and forming a sheet conveyance window, and heat insulation attached to the sheet conveyance window A heat treatment furnace having a roller and heating means provided in the upstream furnace part and the downstream furnace part, wherein the heating means in the downstream furnace part has a higher calorific value than the heating means in the upstream furnace part.

  According to the heat treatment furnace of the present invention, the partition is provided in the furnace, and the heat insulating roller is attached to the sheet conveyance window of the partition, so that the temperature difference between the zones is increased without deteriorating the contact pressure imparting function. Can do. As a result, it is possible to continuously produce product sheets such as carbon fiber sheets in which wrinkles and swells due to heat shrinkage are suppressed.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic side view showing an example of a heat treatment furnace of the present invention. Reference numeral 2 denotes an internal hollow rectangular parallelepiped heat treatment furnace in which a heat insulating material is laminated in a furnace wall 5 constituting the furnace to form a heat insulating material layer 6.

  A raw material sheet inlet portion 8 is provided through the furnace wall 5 and the heat insulating material layer 6 on the uppermost stream side of the furnace 2 along the conveying direction of the raw material sheet 4 to be heat-treated in the heat treatment furnace 2. A product sheet outlet portion 12 is provided in the furnace wall 5 and the heat insulating material layer 6 on the most downstream side of the furnace 2 so as to pass through them. The product sheet 40 is carried out from the product sheet outlet 12.

  The raw material sheet inlet portion 8 and the product sheet outlet portion 12 are gas-sealed using an inert gas such as nitrogen gas by a sealing means (not shown) so that air is not mixed into the furnace 2. It is configured.

  The furnace 2 is partitioned into an upstream furnace section 16 and a downstream furnace section 18 by a partition wall 14 provided perpendicular to the sheet conveyance direction. A sheet conveying window 20 is formed in the partition wall 14.

  In the furnace 2, a plurality (five in this figure) of rollers 22a, 22b, 22c, 22d, and 22e are sequentially arranged from the upstream side to the downstream side. More specifically, contact pressure rollers 22a and 22b that contact the sheet and press the sheet surface are disposed in the upstream furnace section 16, and a heat insulating roller 22c is attached to the sheet conveyance window 20, and the downstream furnace section 18 is provided. Inside, pressure roller 22d, 22e is arrange | positioned.

  The heat insulating roller 22c also functions as a contact pressure roller.

  FIG. 2 is a partially enlarged front sectional view taken along line AA in the apparatus of FIG. 1, and shows the partition 14, the sheet conveyance window 20, the heat insulating roller 22 c and the vicinity thereof.

  As shown in FIG. 2, the heat insulating roller 22 c includes a cylindrical casing 24 that is hollow inside and closed at both ends in the axial direction, and a rotary shaft 26 that is inserted into the casing 24 with the casing 24 aligned with the axial center. It consists of. The hollow portion 28 between the casing 24 and the rotating shaft 26 is filled with a heat insulating material.

  As a material of the casing 24 of the heat insulating roller 22c, a material (metal, ceramic, carbon, or the like) appropriately selected according to the use temperature can be applied.

  As the heat insulating material filled in the hollow portion 28, a heat insulating material (such as glass, ceramic, carbon web, paper, felt, non-woven fabric, etc.) appropriately selected according to the operating temperature can be applied.

  In the heat treatment furnace 2 of FIG. 1, reference numerals 30a and 30b denote upper heating means storage boxes. The upper heating means storage box 30a sequentially stores the upper heating means 32a and 32b from the upstream side to the downstream side, and the upper heating means storage. The box 30b accommodates similar upper heating means 32c and 32d sequentially from the upstream side toward the downstream side.

  Reference numerals 34a and 34b denote lower heating means storage boxes. Similarly to the upper heating means storage box 30a, the lower heating means storage box 34a stores lower heating means 36a and 36b, and the lower heating means storage box 34b stores lower heating means. 36c and 36d are accommodated.

  Examples of the heating means include an electric heater, a steam heater, and an infrared heater. The amount of heat generated by the heating means 32c, 32d, 36c, 36d of the downstream furnace section 18 is designed to be greater than the amount of heat generated by the heating means 32a, 32b, 36a, 36b of the upstream furnace section 16. Thereby, the in-furnace temperature of the downstream furnace part 18 becomes higher than the upstream furnace part 16.

  Reference numeral 38 denotes an exhaust gas treatment chamber attached to the upstream furnace unit 16, which combusts exhaust gas generated in the furnace 2.

  The heat treatment furnace 2 is appropriately determined in dimensions and the like according to the purpose, such as a target raw material sheet and product sheet.

  The furnace length, furnace height, and residence time vary depending on the basis weight of the raw material sheet 4 and heat treatment conditions. For example, when firing a sheet that is hard and has low bending strength, it is necessary to increase the diameters of the contact pressure rollers 22d and 22e installed in the downstream furnace 18 so that the sheet does not break. These are determined as appropriate.

  The raw material sheet 4 targeted in the heat treatment furnace 2 of FIG. 1 includes a resin film, a ceramic sheet, a paper made of flame-resistant short fibers, a spun yarn or filament bundle fabric, a staple nonwoven fabric, a web needle-punched felt, or the like. Applicable.

  In addition, although the heat insulating material was put in the inside as the said heat insulation roller, it is not necessary to put a heat insulating material, and you may use it with a hollow. Further, the roller itself may be made of a heat insulating material without making the inside hollow.

When manufacturing the carbon fiber sheet for electrode materials as a product sheet, the flame resistant fiber sheet of the raw material sheet to be processed preferably has a thickness of 0.1 to ² mm and a basis weight of 50 to 400 g / m ² . When the thickness is less than 0.1 mm, the strength of the sheet is insufficient. If the thickness exceeds 2 mm, the final product becomes too large. When the basis weight is less than 50 g / m ² , the strength of the sheet is insufficient. When the basis weight exceeds 400 g / m ² or more, the sheet lacks flexibility.

  When baking the said raw material sheet 4, the partition 14 is provided in the position where 30 to 60% of the thermal contraction of the raw material sheet 4 is completed. Usually, this position is a position of 40% or more and 60% or less of the furnace length from the most downstream heat insulating material layer 6 of the furnace 2.

  Furthermore, heat transfer such as radiant heat from the upper heating means 32c, 32d and the lower heating means 36c, 36d, and the upstream furnace section 16 as it goes from upstream to downstream by the upper heating means 32a, 32b, lower heating means 36a, 36b. A temperature rising region having a temperature gradient that becomes high temperature may be formed.

  In the above description, the heat insulating roller is provided in one sheet conveyance window 20 formed on the partition wall. However, the present invention is not limited to this, and by forming a plurality of partition walls and attaching the heat insulating roller to each partition wall, more precise. The furnace temperature may be set. Other modifications may be made as appropriate unless the gist of the present invention is changed.

  A product sheet 40 (carbon fiber sheet in this example) was manufactured using the heat treatment furnace 2 shown in FIG.

  The length in the furnace in the sheet conveying direction was 2 m in the upstream furnace section 16, 2 m in the downstream furnace section 18, the furnace width was 1.2 m, and the furnace height was 0.8 m. The position of the partition wall 14 was 50% of the furnace length from the most downstream side heat insulating material layer 6 of the furnace 2. The diameters of the contact pressure rollers 22a, 22b, 22d, 22e and the heat insulating roller 22c were all 0.5 m.

  The material of the casing 24 of the heat insulating roller 22c was carbon, and the heat insulating material filled in the hollow portion 28 was a nonwoven fabric made of carbon.

  The inside of the furnace 2 is heated in a nitrogen atmosphere, the temperature in the furnace portion of the raw material sheet inlet portion 8 is 50 ° C., the temperature in the vicinity of the partition wall 14 in the upstream furnace portion 16 is 550 ° C., and the temperature in the vicinity of the partition wall 14 in the downstream furnace portion 18. Was adjusted to 650 ° C., and the temperature in the furnace portion of the carbon fiber sheet outlet portion 12 was adjusted to 700 ° C.

In the heat treatment furnace 2, a flame resistant fiber sheet having a thickness of 0.4 mm, a width of 1000 mm, and a basis weight of 200 g / m ² is applied to a contact pressure roller 22a, 22b, 22d, 22e, a contact pressure of 150 Pa in a heat insulating roller 22c, and a conveyance speed of 50 m / m. It was conveyed by hr.

The obtained carbon fiber sheet had a thickness of 0.38 mm and a basis weight of 154 g / m ² , and had a high quality without wrinkles or undulations.

It is a schematic side view which shows an example of the heat processing furnace of this invention. It is front sectional drawing along the AA line in the heat processing furnace of FIG. 1, and is an enlarged view which shows a partition, a sheet conveyance window, a heat insulation roller, and its vicinity.

Explanation of symbols

2 Heat treatment furnace 4 Raw material sheet 5 Furnace wall 6 Heat insulation material layer 8 Raw material sheet inlet part 12 Product sheet outlet part 14 Bulkhead 16 Upstream furnace part 18 Downstream furnace part 20 Sheet conveying window 22a, 22b, 22d, 22e Contact pressure roller 22c Thermal insulation roller 24 Casing 26 Rotating shaft of heat insulating roller 28 Hollow portion of heat insulating roller 30a, 30b Upper heating means storage box 32a, 32b, 32c, 32d Upper heating means 34a, 34b Lower heating means storage box 36a, 36b, 36c, 36d Lower heating means 38 Exhaust gas treatment chamber 40 Product sheet

Claims (1)

A heat treatment furnace for heat-treating a raw material sheet, in which a raw material sheet inlet portion is formed on the upstream side of the furnace, an upstream furnace portion having one or more rollers therein, and a product sheet outlet portion on the downstream side of the furnace And a downstream furnace part having one or more rollers therein, a partition partitioning the inside of the furnace into an upstream furnace part and a downstream furnace part and forming a sheet conveyance window, a heat insulating roller attached to the sheet conveyance window, A heat treatment furnace comprising heating means provided in an upstream furnace part and a downstream furnace part, wherein the heating means in the downstream furnace part has a higher calorific value than the heating means in the upstream furnace part.

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