JPH04338234A - Sheet-like adsorbent - Google Patents

Abstract

PURPOSE:To obtain the sheet-like absorbent which has a large adsorption surface area, allows the easy and inexpensive selective adsorption of materials to be adsorbed and has excellent workability to filters by forming a sheet-like material of extremely fine fibers consisting of a polymonovinyl arom. compd. having specified or lower single fiber fineness. CONSTITUTION:Three-component conjugate fibers consisting of a sea component of polyester, etc., an island-sheath component of polystyrene, etc., and an island- core component of polypropylene, etc., are crimped by a crimper. The fibers are then fabricated to felt shape after cutting. This felt is subjected to the hydrolysis of the polyester with an alkali, such as aq. sodium hydroxide soln. The sea component of the sea and island type three-component conjugate fibers is dissolved to obtain the extremely fine fibers in such a manner, by which the signal fiber fineness is reduced to <=1 denier and the sheet-like material is obtd. This sheet-like material acts affinity between the polymonovinyl arom. compd., such as polystyrene and the materials to be absorbed and has a high adsorption power.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-like adsorbent. More specifically, the present invention relates to adsorption filter media such as air filters and cigarette filters, particularly sheet-like adsorbents suitable for removing harmful substances from cigarette smoke.

0002

BACKGROUND OF THE INVENTION Recently, so-called ultrafine fibers, which have a smaller fiber diameter than conventional fibers, have been developed for various uses. In particular, by making adsorbents, filtration materials, and filter materials ultrafine, the active specific surface area increases, and the contact area with the adsorbed material increases, improving the adsorption performance of useful and waste materials. proposals have been made.

[0003] For example, ultrafine ion exchange fiber (Japanese Patent Application Laid-open No.
8239) and other filter media have been proposed, and sheet-like materials made of them have been disclosed.

On the other hand, an adsorbent made of a polymonovinyl aromatic compound (Japanese Patent Laid-Open No. 107329/1999) has been proposed due to its affinity with the adsorbed material.

However, although sheet materials made of ultrafine ion-exchange fibers have excellent adsorption performance, they are difficult to manufacture and expensive, and their strength decreases due to reaction, making it difficult to form filters. Bad,
There is a problem that high quality products cannot be obtained. Also,
When attempting to selectively remove (adsorb) a specific substance, having excellent adsorption performance may actually be undesirable.

Furthermore, when an ester plasticizer is used during filter molding, the plasticizer is hydrolyzed, producing an odor and becoming ineffective as a plasticizer.

[0007] In addition, adsorbents made of polymonovinyl aromatic compounds are insufficient as there is no description of the thickness of the fibers, and sheet-like materials made of ultrafine fibers made by fibrillating the polymonovinyl aromatic compounds are Difficult to manufacture and impractical.

[0008] In addition to these, filter media made of ultrafine fibers that have been disclosed do not use polymonovinyl aromatic compounds, and therefore, when used as cigarette filter materials, they have poor adsorption performance for alkaloid compounds such as nicotine.

Furthermore, acetate, which is commonly used as a material for commercially available cigarette filters, has no affinity for nicotine, so it not only has the disadvantage of allowing nicotine to pass through, but also has thick fibers that make it difficult to form sheets. Naturally, the adsorption performance is also inferior.

0010

[Problems to be Solved by the Invention] The object of the present invention is to provide a highly practical sheet-like adsorbent that has a large adsorption surface area, can easily and inexpensively adsorb objects to be adsorbed, and has excellent filter processability. The aim is to provide materials.

[0011]

Means for Solving the Problems The present invention has the following configuration.

(1) A sheet-like adsorbent comprising ultrafine fibers made of a polymonovinyl aromatic compound having a single fiber fineness of 1 denier or less.

(2) The sheet-like adsorbent according to item (1), wherein the ultrafine fibers are in the form of composite fibers consisting of polymonovinyl aromatic compound A and reinforcing polymer B. (3) Reinforcing polymer B is poly α-olefin (
The sheet-like adsorbent described in item 1).

(4) The sheet-like adsorbent according to item (1), which has a basis weight of 5 to 150 g/m2.

The present invention will be explained in detail below.

[0016] The sheet-like adsorbent of the present invention must be an ultrafine fiber having a single fiber fineness of 1 denier or less of the fibers made of a polymonovinyl aromatic compound constituting the sheet. That is, the adsorption effect of the sheet-like adsorbent is due to the affinity that acts between the polymonovinyl aromatic compound and the adsorbed substance, and when the denier exceeds 1 denier, the active specific surface area becomes small and the adsorption effect becomes significantly small. Moreover, if it is thicker than 1 denier, it becomes too thick when processed into a sheet, which is not preferred in practice. For this reason, it is preferably 0.7 denier or less, particularly 0.5 denier or less.

[0017] The polymonovinyl aromatic compound as used in the present invention includes, for example, homopolymers, copolymers, and blends of styrene, α-methylstyrene, vinyltoluene, halogenated styrene, vinylnaphthalene, vinylthiophene, and other compounds. They are copolymers with copolymerizable compounds and blends with these polymers. Among these, polystyrene is particularly preferred because it is easily available at low cost and has excellent fiber-forming and adsorption properties.

These polymonovinyl aromatic compounds have excellent adsorption performance for harmful substances in tobacco smoke, particularly mutagens and alkaloid compounds, especially nicotine. This is thought to be due to the adsorption effect due to the affinity with the adsorbed material, as described above, and it is naturally preferable that the polymonovinyl aromatic compound be used alone in the form of fibers.

However, when the polymonovinyl aromatic compound is made into fibers, spinnability and fiber strength are important. In consideration of moldability, it is more preferable to form a composite fiber consisting of the polymonovinyl aromatic compound A and the reinforcing polymer B.

For example, it can be produced by spinning a three-component composite consisting of an island component, which is a composite of polymers A and B, surrounded by a sea component polymer C, as a sea-island composite fiber. By adopting this spinning method, even polymer A, which has strength problems and is difficult to make into fibers, can be spun extremely well using reinforcing polymer B, and by having the C component surrounding the A component, fibers can be made to the maximum extent possible. can be made thinner.

Component C may be any material as long as it has excellent spinning stability and can be easily dissolved, but it is selected so that the solvent during the dissolution treatment will not dissolve component A. For example, polyester-based polymers are preferably used.

The thus obtained three-component sea-island composite fiber becomes an ultrafine composite fiber composed of polymers A and B by removing the sea component C. To dissolve the sea component, for example, in the case of a polyester polymer, the polyester is hydrolyzed with an alkaline substance before or after processing the three-component sea-island composite fiber into a sheet shape by a known method. There is a way to do it. Hydrolysis can be carried out by treating in a hot aqueous solution containing an alkaline substance such as caustic soda for 30 to 120 minutes, or by applying an alkaline substance and then treating with saturated steam at about 100°C for 1 to 5 minutes, There is a method of leaving it at 60° C. for 10 to 30 hours, but any method is acceptable as long as it can be treated stably.

Island component (A+B) that becomes the ultrafine fiber of the present invention
The proportion of sea component C is usually about 10 to 90%, but preferably about 20 to 80% taking spinning stability into consideration. Although the number is not particularly limited, it is usually 5 or more, preferably 10 or more, and from the viewpoint of economy and efficiency, a larger number is preferable, and in particular, 50 or more is preferable when the fineness is reduced to 0.1 denier or less. preferable.

Composite fiber (A+B) can be a simple mixed fiber of A and B, a core-sheath type composite fiber with A as a sheath and B as a core, or a multicore sea-island composite fiber with A as a sea and B as an island. Preferably, it takes the form of fibers. In this case, the proportion of reinforcing polymer B is preferably in the range of 10 to 90% from a functional standpoint.

As the reinforcing polymer component B, homopolymers such as polyester, polyamide, poly-α-olefin, or copolymers and blends thereof are used. Among these, poly-α-olefins having excellent chemical resistance are preferably used. As the poly-α-olefin, polypropylene, polyethylene, poly-3-methylbutene-1, poly-4-methylpentene-1, etc. are preferably used, and polypropylene is particularly preferred.

The adsorbent of the present invention must be in the form of a sheet. That is, when ultrafine fibers are used in the form of long fibers or cut fibers, for example, when used in cigarette filters, the filter processability and shape retention are inferior, which is not preferable.

Any known method may be used to obtain the sheet material of the present invention, but for example, the above-mentioned three-component sea-island composite fiber is crimped by applying it to a crimper.
Then, after cutting, it is processed into a felt shape using a known method to make it ultra-fine, or the sea component of the three-component sea-island type composite fiber is dissolved and made ultra-fine, and then it is made into a sheet, or a composite melt blow spinning method is used. There is a method of making sheets and ultra-fine fibers all at once by spinning.

The sheet-like material of the present invention is subjected to press processing using an embossing roll, calendar roll, etc., heat treatment using a suction drum dryer, or water jet treatment before or after ultrafine treatment under heating for the purpose of improving strength and shape retention. It's okay to punch.

Examples of the sheet-like material of the present invention include any known sheet-like forms such as woven fabrics, knitted fabrics, felts, non-woven fabrics, and paper, as well as aggregates and cut products thereof.

[0030] The basis weight of the sheet-like material of the present invention is 5 to 15.
It is good that it is 0g/m2. If it is smaller than this, it is not only difficult to manufacture, but it is also not strong enough to cause problems in handling, and when used as a cigarette filter, the suction resistance becomes too large, which is not preferable. On the other hand, if it is too large, the sheet becomes thick, which is also undesirable because it increases handling and pressure loss during use. For this reason, preferably 10
-130g/m2, particularly preferably 20-100g/m2 for cigarette filters.

The sheet-like adsorbent of the present invention can be combined with, for example, activated carbon fibers, electret fibers, glass fibers, ion-exchange fibers, other inert fibers, and molded products thereof, as well as reinforcement or improved durability, as well as other functions. For the purpose of application, it may be used by mixing, interweaving, or laminating. Furthermore, adsorption/sterilization/deodorizing agents, plasticizers, adhesives, etc. may be mixed or attached. However, even in this case, the amount of the sheet-like adsorbent needs to be 10% by weight or more, and if it is less than this, the effects of the present invention cannot be fully exhibited. Therefore, preferably 30% by weight or more, more preferably 50% by weight or more.
It is preferable that the content is at least % by weight.

The sheet-like adsorbent of the present invention can be widely used as a cigarette filter material, a tobacco pipe filling material, other filter materials, and a material for adsorbing useful and unnecessary materials that are compatible with the sheet-like adsorbent.

Examples will be shown below, but the present invention is not limited thereto.

[0034]

[Example] Example 1, Comparative Example 1 Polyester (43 parts) as the sea component, polystyrene (28.5 parts) as the island sheath component, polypropylene (28.5 parts) as the core component
．． 5 parts) of 3-component composite fibers stretched 1.5 times (number of islands: 13)
, single yarn fineness of 4.6 denier, total fineness of 60,000 denier), and then crimped using a crimper. Then 51
The fibers were cut into mm pieces, opened with an opener, and passed through a roller card to form a web. This web was needle punched to produce felt of 70 g/m2.

[0035] The obtained felt was immersed in 30% sodium hydroxide, squeezed with a nip roller so that it contained about twice the amount required to dissolve (hydrolyze) the sea component polyester, and heated at 40°C. Hold for 9 hours. Next, it was washed with hot water until it became neutral and then dried to obtain a sheet with a basis weight of 40 g/m2 made of ultrafine fibers (single fineness 0.2 denier).

[0036] The obtained sheet has a length of 20 mm and a width of 25 m.
A filter chip was made by stacking 3 pieces cut into 1.5 m squares and inserting them into a cylinder made of thin paper with a circumference of 24.7 mm. This was used to create a test cigarette in which the filter of a commercially available cigarette (highlight) was inserted in place of the filter (resistance during smoking was the same as that of a commercially available cigarette).

The amounts of tar and nicotine in the produced test cigarettes were measured (Example 1).

[0038] Furthermore, the amounts of tar and nicotine were similarly measured for a commercially available cigarette (Highlight) (Comparative Example 1). The results of each measurement are shown in Table 1.

[0039] The measurements were carried out in the following manner.

The test cigarette was connected to an automatic smoking device and smoked under the following standard conditions, and mainstream smoke was collected using a smoke collector equipped with glass fiber filter paper. Smoking capacity: 35ml/time Smoking time: 2 seconds/time Smoking cycle: 1 time/minute Smoking length: 30mm Number of cigarettes smoked: 5/glass fiber filter paper [tar, nicotine amount] A. Amount of tar (mg/piece) = {Weight of smoke collector after smoking (mg) - Weight of smoke collector before smoking (
mg)}/5 (books) B. Nicotine amount (mg/bottle) The glass fiber filter paper that has collected tar and the glass fiber filter paper that has been wiped off the inside of the smoke collector are extracted with an extraction solvent (isopropanol/ethanol/anethole = 4974/25/1) 1
0ml into a container, shake it to prepare the sample solution, and then apply it to a gas chromatograph (Shimadzu Gas Chromatograph GC).
-8A hydrogen flame ionization type detector), and the amount of nicotine was calculated from a calibration curve prepared in advance.

Comparative Example 2 Polypropylene was spun using a melt blow spinning method to obtain a sheet having a basis weight of 39 g/m 2 and consisting of fibers having an average fineness of 0.17 denier.

A test cigarette was prepared in the same manner as in Example 1 using the obtained sheet.

The tar and nicotine removal performance of the produced test cigarettes was investigated in the same manner as in Example 1 and is shown in Table 1.

[0044]

[Table 1]

As can be seen from Table 1, the tobacco of the present invention has a lower amount of tar and nicotine than commercially available cigarettes, indicating that it has excellent adsorption performance. Furthermore, when the commercially available cigarette (Comparative Example 1) is used as a blank, the product of the present invention has a tar removal rate of 16.7% and a nicotine removal rate of 22.5%, and can selectively adsorb and remove nicotine. On the other hand, in the sheet made of polypropylene ultrafine fibers (Comparative Example 2), the tar removal rate was 9.1% and the nicotine removal rate was 8.4%, which is just inferior to the sheet of the present invention. It can be seen that nicotine cannot be selectively adsorbed and removed. Furthermore, the taste of the products of the present invention did not change at all.

[0046]

[Effect of the invention] The sheet-like adsorbent made of ultrafine fibers of the present invention has a large specific surface area, so it has good filtration performance, and has high performance, good quality, and excellent filter processability, so it can be widely applied as a filter material. .

[0047] Also, it is possible to selectively adsorb waste materials, and when used as a cigarette filter, harmful materials can be removed without impairing the taste. It is particularly effective as a cigarette filter material for low nicotine and low tar applications.

Claims (4)

[Claims] 1. A sheet-like adsorbent comprising ultrafine fibers made of a polymonovinyl aromatic compound with a single fiber fineness of 1 denier or less. 2. The sheet-like adsorbent according to claim 1, wherein the ultrafine fibers are in the form of a composite fiber composed of a polymonovinyl aromatic compound A and a reinforcing polymer B. 3. The sheet-like adsorbent according to claim 2, wherein the reinforcing polymer B is a polyα-olefin. 4. The sheet-like adsorbent according to claim 1, having a basis weight of 5 to 150 g/m2.