JPS6325085B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing fibrous activated carbon, and more specifically, to producing high-yield, high-performance fibrous activated carbon by oxidizing and activating acrylonitrile fibers to which a water-soluble basic aluminum composite salt is attached. Regarding how to. Fibrous activated carbon (ACF) is a cellulosic fiber,
It is produced by carbonizing and then activating phenolic resin fibers or acrylonitrile fibers as raw materials, and is used in the form of tow, woven fabric, or felt as an adsorbent or filter in, for example, solvent recovery equipment. It has been increasing in recent years. In particular, those made from acrylonitrile fibers
ACF is expected to have a variety of uses due to its unique adsorption performance due to the nitrogen atoms it contains and its excellent mechanical strength. Generally made from acrylonitrile fibers
ACF is manufactured as follows. That is, in the first oxidation process, acrylonitrile fibers are heated in an oxidizing atmosphere such as oxygen at 200%
Oxidation is carried out by treatment at ~300°C, and then, in the second activation step, the oxidized fibers are activated at 700~1000°C in an atmosphere of water vapor, carbon dioxide, or the like. Normally, in order to form felt, woven fabric, yarn, etc., the oxidized fiber bundle after the first stage is processed or
Alternatively, either method is used to process the ACF after the second stage is completed. When processing ACF, particularly sufficient strength and crimpability are required, and the processability of such ACF depends on the performance of the oxidized fiber in the first stage. Therefore, at any stage of processing, the oxidized fiber must have high strength and excellent crimpability necessary for processing. However, conventionally, this oxidized fiber has been difficult to crimp, and as a result, yarn breakage has occurred frequently when it is made into yarn, which has tended to significantly reduce work efficiency. Furthermore, when it is made into felt, there are problems such as a large amount of falling cotton, resulting in a decrease in yield, deterioration in workability, and a decrease in the strength of the felt. In order to improve the processability of such oxidized fibers, in the conventional method, the first oxidation step suppresses the rapid heat generation of the acrylonitrile fiber bundle, maintains good fiber opening properties, and prevents a decrease in fiber strength. For this purpose, it is necessary to carry out heat treatment at a low temperature for a considerable period of time, but there are still problems in terms of processability. Furthermore, approximately 80% of the total time required for manufacturing ACF is spent on the oxidation step, which requires such a long heat treatment, which is a factor in high costs. As a result of studying these problems, the present inventors discovered that by attaching a water-soluble basic aluminum composite salt to an acrylonitrile fiber bundle,
The inventors have discovered that oxidized fibers free from the above-mentioned problems can be obtained with high efficiency, and that ACF with high yield and high performance can be obtained, leading to the present invention. That is, in the present invention, acrylonitrile fibers to which a water-soluble basic aluminum composite salt represented by the general formula below is attached in an amount of 0.01 to 5% by weight as aluminum based on the weight of the fibers are oxidized in an oxidizing atmosphere, and then treated with an activating gas. This is an ACF production method characterized by processing at medium temperature of 700℃. Al _{2 (} OH) It can be shortened to about 1/2 or less,
Yet ACF with good adsorption performance and mechanical performance can be produced in high yield. The present invention will be explained in further detail. In the present invention, acrylonitrile fibers are fibers made of polyacrylenitrile containing at least 85% by weight or more preferably 90 to 98% by weight of acrylonitrile, or fibers made of polyacrylonitrile containing two or more types of unsaturated compounds copolymerizable with acrylonitrile. It refers to fibers made from a combination of fibers or fibers made from a polymer made by mixing these copolymers. Water-soluble basic aluminum composite salts to be attached to the fibers are disclosed in, for example, JP-A-49-130387 and JP-A-50.
- It is produced according to the method known in Publication No. 153799 and is represented by the above general formula. When aluminum hydroxide, aluminum sulfate, aluminum phosphate, etc. are used instead, there is no effect at all, and on the contrary, it becomes difficult to crimp the fibers. Since the complex salt used in the present invention is a water-soluble complex salt that contains a hydroxyl group, it can not only be applied uniformly to the fibers, but also moderately absorb heat generated during the process of oxidizing acrylonitrile fibers. Since it is possible to prevent excessive heat accumulation and temperature rise, it is effective in making homogeneous oxidized fibers and making it easier to crimp the fibers. In order to attach the composite salt used in the present invention to the acrylonitrile fiber bundle, a commonly used attachment method is used, such as preparing an aqueous solution of the composite salt and immersing the fiber bundle in this solution, or spraying the aqueous solution. . As is clear from Tables 2 and 3 below, the amount of these composite salts deposited on acrylonitrile fiber bundles is 0.01 to 5% as aluminum based on the fiber weight.
It is necessary that the amount is within the range of % by weight. If it is less than this range, the effect of the present invention will not be exhibited, and if it exceeds this range, a decrease in fiber strength and activation yield will occur during oxidation treatment. The acrylonitrile fiber to which water-soluble basic aluminum is attached is oxidized in an oxidizing atmosphere such as oxygen. In this case, the treatment temperature varies depending on the amount of comonomer in the raw fiber, and the optimum conditions are selected as appropriate. However, the fiber to which the water-soluble basic aluminum composite salt of the present invention is attached has a higher temperature than the conventional acrylonitrile fiber. Oxidation treatment can be performed at high temperature and in a short time. A major advantage of the present invention is that the following effects are produced by attaching a water-soluble basic aluminum composite salt to conventional acrylonitrile fibers. That is, (1) even if the oxidation treatment temperature is higher than that of the conventional method, the fiber bundle does not burn, and therefore the oxidation time can be significantly shortened. (2) Even at the same oxidation temperature as the conventional method, the oxidation rate is faster and the treatment time is shorter than the conventional method. (3) Oxidized fibers with higher strength and better crimpability than conventional methods can be obtained. (4) Activation time is shortened and activation yield is improved compared to conventional methods. (5) ACF with higher strength and workability than conventional methods can be obtained. As described above, according to the method of the present invention, productivity and quality are significantly improved, especially in the oxidation step. For example, _Al2
A water-soluble basic aluminum complex salt with a composition of (OH) ₃ Cl _1.7 (PO ₄ ) _0.3 is 0.05 as aluminum.
Table 1 shows a comparison of the case where aluminum is deposited in a weight percent and subjected to two-stage oxidation treatment with the conventional method which does not contain aluminum.

[Table] As is clear from the results in Table 1, acrylonitrile fibers coated with water-soluble basic aluminum complex salts do not cause yarn combustion even at high initial temperatures, and their oxidation rate is fast. Therefore, the time required for the oxidation process can be reduced to less than half of the conventional method.
However, oxidized fibers with excellent processability can be obtained. In the present invention, the acrylonitrile fibers to which a water-soluble basic aluminum composite salt is attached are treated until the average moisture content of the oxidized fibers reaches a range of 10 to 13%, which increases the activation yield of the resulting ACF. Desirable because of its high fiber strength. The oxidized fibers that have undergone the above oxidation treatment are then subjected to activation treatment. Activation can be carried out by a known method, and is carried out by heating at a temperature of 700° C. or higher, preferably 800 to 950° C., for several seconds to 2 hours in an atmosphere of steam, carbon dioxide, ammonia, or the like. In this step, the aluminum and phosphorus compounds remaining in the oxidized fibers promote the activation reaction, shortening the activation time and improving the activation yield compared to conventional methods. The feature of the present invention is that by using acrylonitrile fibers to which a water-soluble basic aluminum composite is attached, the oxidation process and activation process are simultaneously improved, which significantly reduces ACF production costs compared to conventional methods. It's all about what you can do. EXAMPLES The present invention will be explained below using Examples, but the present invention is not limited thereto. Example 1 Hydrochloric acid, phosphoric acid, and an appropriate amount of water are added to aluminum hydroxide fine powder, and the mixture is heated at 110°C in an autoclave to change the composition to Al ₂ (OH) _2.1 Cl _2.4 (PO ₄ ).
An aqueous solution of basic aluminum complex salt consisting of _0.5 was prepared. This aqueous solution was appropriately diluted to produce 94.7% by weight of acrylonitrile and 5.3% by weight of methyl acrylate.
A copolymer fiber tow with a single fiber fineness of 3 denier and a total denier of 540,000 denier was prepared by soaking at room temperature so that 0.01 to 6.5% by weight of aluminum was attached to the weight of the fiber. However, cases where it exceeds 5% by weight are comparative examples. These fiber bundles were incubated in air at an initial temperature of 250°C for 1 hour.
Next, oxidation treatment was performed in two stages at 270°C for 1.5 hours. For comparison, the same treatment was performed on the same fibers as above but without aluminum attached.
The results are shown in Table 2. The above oxidized fibers were then activated in superheated steam at 910° C. to obtain ACF with a specific surface area of 900 m ² /g, and the activation yield and performance are summarized in Table 3.

【table】

【table】

[Table] As is clear from the above results, the oxidation process and quality were significantly improved by attaching a water-soluble basic aluminum complex salt, and a high yield was obtained.
ACF can be obtained. Example 2 A copolymer fiber tow with a single fiber of 3 denier and a total denier of 560,000 denier consisting of 91% by weight of acrylonitrile and 9% by weight of methyl acrylate was immersed in the same basic aluminum composite salt aqueous solution as in Example 1. After drying, a fiber having 0.03% by weight of aluminum deposited was obtained. This fiber was oxidized in air under the conditions listed in Table 4. The obtained oxidized fiber tow was applied to a crimper at a nip pressure of 2 Kg/cm ² and a stuffing pressure of 1 Kg/cm ² .
The material was crimped by feeding at a feed rate of 80 m/hr, and then cut with a cutter to a length of 102 mm. Next, this oxidized fiber staple was supplied to a nonwoven fabric manufacturing apparatus and processed into an oxidized fiber felt having a basis weight of 500 g/m ² . For comparison, the same treatment was carried out on a case having the same composition as above but without aluminum attached. Table 4 summarizes the results regarding the characteristics of the oxidized fibers and their felts. Furthermore, these oxidized fiber felts were activated in steam at 930°C. Table 5 shows the yield and performance of the obtained ACF felt.

【table】

[Table] Shows the values.
(2): No. 20 and 21 show comparative examples (no aluminum adhesion). As described above, in the examples of the present invention, since the oxidation temperature can be increased, the oxidation time can be shortened and the oxidation rate can also be increased, and the crimped state of the obtained oxidized fibers is excellent, thus improving the quality of the final product. It can be seen that the strength of ACF is also high. Example 3 Copolymer fiber tow (single fiber fineness 2 denier, number of constituent fibers 280,000) consisting of 92% by weight of acrylonitrile and 8% by weight of vinyl acetate was coated with Al ₂ (OH) _2.8 Cl _1.7
A water-soluble basic aluminum composite salt having a composition of (PO ₄ ) _0.5 was deposited as aluminum in an amount of 0.2% by weight. This tow was oxidized in air at 245° C. for 1.5 hours and then at 265° C. for 2 hours, and then passed through a crimper to be crimped. The number of crimps of the obtained oxidized fiber was 13.8, and the tensile strength was 26.3 kg/
mm ² , elongation of 15.6%, and equilibrium moisture content of 11.3%, it had good crimp properties and excellent fiber performance. Furthermore, this oxidized fiber was treated in steam at 900°C for 10 minutes to obtain an activation yield of 25% and a specific surface area of 1000 m ² /g.
Tensile strength 25.8Kg/mm ² , number of crimps 6.3 Good
Got ACF. For comparison, a fiber tow having the same composition as above was subjected to the same oxidation treatment by attaching aluminum sulfate in the same amount as aluminum instead of the aluminum composite salt. The performance of the obtained oxidized fiber is as follows: number of crimps is 4.1, tensile strength is 10.2 kg/
mm ² , elongation of 8.2%, and equilibrium moisture content of 10.1%, and no effect was observed on processability or shortening of oxidation time. Furthermore, ACF obtained by activation under the same conditions had an activation yield of 23%, a specific surface area of 900 m ² /g, and a tensile strength of 15.1 kg/g.
mm ² and number of crimps of 3.8, both performances were inferior to those of the present invention.

Claims (1)

[Claims] 1 _A water-soluble compound represented by the following general formula Al ₂ (OH) A fibrous material characterized by oxidizing acrylonitrile fibers to which a basic aluminum composite salt is attached in an amount of 0.01 to 5% by weight of aluminum based on the weight of the fibers in an oxidizing atmosphere, and then treating the fibers at 700°C or higher in an activating gas. Method of manufacturing activated carbon.