JPH0465540A - Synthetic fiber bundle for cigarette filter and preparation thereof - Google Patents

Abstract

PURPOSE:To prepare the subject filter having a specific cross-sectional shape and capable of reducing the contents of nicotine and tar contained in smoked gases by spinning acetate cellulose for cigarette filters by a dry spinning method under a condition that the temperature of a dope for the spinning is higher than the boiling point of acetone. CONSTITUTION:A spinning dope prepared by dissolving cellulose acetate in solvents containing acetone as a main solvent is spun at a temperature higher than 56.3 deg.C(under the atmosphere), the boiling point of the acetone, to prepare fibers each single filament having a cross-sectional shape having a Ferearea of <=0.42. The spun filaments are wound up with a filter-winding machine to prepare the objective filter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to cellulose acetate m-Vito for cigarette filters, which improves the performance of cigarette filters, as a fiber bundle for cigarette filters, and a method for producing the same.

[Conventional technology]

Generally, fibers made of polymeric materials such as cellulose acetate, polypropylene, and polyethylene are used as fiber bundles for cigarette filters, but cellulose acetate is particularly good in its taste and processability into filters. is used in most filters.

In addition, these wl Iito have characteristics such as single yarn fineness of 2 to 9 deniers, total fineness of 20.000 to 60.000 deniers, and cross-sectional shapes of the fibers such as Y, I, X, and R shapes. something is being used.

Furthermore, the performance of cigarette filters processed using these fiber bundles has traditionally been primarily measured by the filtration rate of nicotine and tar.

In recent years, there has been an increasing demand for lower nicotine and lower tar products due to health problems and changes in smokers' tastes, and it has become essential to improve the filtration rate of nicotine and tar components.

Among the above-mentioned single fiber cross-sectional shapes, fiber bundles composed of fibers with a Y-shaped cross section are used as M-ITO for cigarette filters because they can increase the filtration rate of nicotine and tar. Even in the case of fibers with a Y-shaped cross section, low denier fibers with small single filament fineness can achieve a high filtration rate, so the use of lower denier fibers has progressed.

[Problem to be solved by the invention]

Under these circumstances, the demand for low-tar and low-nicotine products is becoming stronger and stronger, and research into ventilation technology, research on new filters, examination of cross-sectional shapes of fibers, Consideration is being given to increasing the denier. However, in the study of reducing the denier, as the denier is further reduced, problems arise from the hardness aspect of the cigarette filter characteristics, and a limit arises. In addition, when considering the cross-sectional shape, the flower shape of the spinning nozzle has been studied, but problems with spinning stability such as thread breakage occur when spinning fibers, and solutions to these problems are desired. ing.

[Means to solve the problem]

In proceeding with the study of the cross-sectional shape, the present inventors first selected an appropriate cross-sectional shape coefficient for the canopy that quantified the relationship between the filtration rate of tar and nicotine and the cross-sectional shape, and Based on this value, we investigated a fiber bundle and a method for producing the same that can increase the filtration rate of tar and nicotine (lower tar and lower nicotine) than before, and arrived at the present invention.

That is, in the present invention, in the fiber bundle for cigarette filters,
The objective can be achieved by using cellulose acetate as the fiber material and using fibers constituting the cellulose acetate fiber bundle with a cross-sectional shape that has a cross-sectional shape factor of 0.42 or less. I found out what can be done.

The cross-sectional shape factor adopted in the present invention, “occupancy rate (F
area) J is the area of an object.
Axis, length when projected to Y axisFerediaHlFer
It is a dimensionless number divided by the area of the rectangle surrounded by ediaV.

The details of the study used to reach the above conclusion are as follows.

Focusing on the mutual relationship between the cross-sectional shape of the single fibers that make up synthetic W2 ITO for cigarette filters and the filtration efficiency of tar and nicotine, we performed image processing to quantify this cross-sectional shape. The law was used.

First, in the cross section of the above-mentioned single fiber, which is a factor that affects the filtration efficiency, the "Shape Fact 1" is determined based on the peripheral length of the cross section, as shown in Figure 1a.
) J and the "occupancy rate (Fe
coefficients related to the two shapes of J are selected from among the shape coefficients that have been proposed in the past, and the two coefficients for each fiber bundle produced as a sample are processed by an image processing device as shown in FIG. Calculated using

Here, the coefficients related to the above two shapes are expressed by the following equations.

Shape Factor 1 (Shape Factl) Area Occupancy Rate of Object (Ferearea) Next, a method for calculating the above two coefficients will be shown below.

A fiber bundle for a cigarette filter is embedded so as to be wrapped in paraffin, and formed into a pencil shape so that the fiber bundle is placed at the 8th minute, which corresponds to the lead of a pencil.Then, the thickness is reduced to 1-10-1 using a microtome. Cut into slices. By observing this sliced section with an optical microscope and importing the image obtained from the observation into an image processing device, the above two
Calculate two coefficients.

It should be noted that the above-mentioned coefficients for about 100 single fibers can be measured on one screen displayed on the display of the image processing device, and the average value of each of the above-mentioned coefficients is used as the measured value. Therefore, when calculating the value of Ferearea J, since each single fiber does not have a fixed directionality,
The axis setting method can be arbitrary.

Furthermore, the relationship between each value of the section modulus of the fibers measured by the above method and the ventilation resistance of a cigarette filter made of a fiber bundle composed of the above-mentioned fibers was investigated.

The results of the study are shown in Figures 3a and 3b of Figure 3.

Here, ventilation resistance refers to the pressure loss of the filter that occurs when a certain amount of air flows through the cigarette filter, and refers to the pressure of the water column (mm water column, 1710,000 kg/cn).
f), and it is said in the tobacco industry that there is a good correlation between the filtration rate of nicotine and tar components and the ventilation resistance.

From the examination results in FIG. 3b, it can be seen that there is a good correlation between the occupancy and the ventilation resistance, and the smaller the occupancy, the higher the ventilation resistance. Furthermore, from the definition of the occupancy rate in equation (2) above, it can be seen that the degree of obstruction of the fibers to the air flow has a large influence on the magnitude of ventilation resistance.

From the above study results, it is clear that there is a relationship between the change in cross-sectional shape and the filtration rate of nicotine and tar components, and that the occupancy rate is effective as an index of the cross-sectional shape that indicates the relationship between the two.

Next, the results of measuring the occupancy in the cross section of fiber bundles currently used in cigarette filters using an image processing device are summarized in a frequency distribution diagram, which is shown in FIG. As shown in FIG. 4, the occupancy ratio exceeds 0.42 in most cases, and in particular, in the Y-section fiber bundles, the occupancy ratio is in the range of over 0.42 and 0.48 or less.

Therefore, by developing fiber bundles composed of fibers with a occupancy ratio of 0.42 or less, which is an index showing the cross-sectional shape of a single fiber, it is possible to achieve lower nicotine and tar levels than currently possible. It was found that it is possible.

Note that the above conditions regarding fiber bundles can be applied to single fibers having a cross section other than Y-shape.

Furthermore, in order for the above-mentioned occupancy to be 0.42 or less, cellulose acetate is optimal as a material for synthetic fibers, and the following method is optimal as a method for manufacturing fiber bundles made of cellulose acetate. I found out something.

Conventionally, the temperature when spinning a dope obtained by dissolving cellulose acetate in a solution containing acetone as the main solvent was below 56.3°C (under atmospheric pressure), which is the boiling point of acetone. It has been found that by spinning the dope above the boiling point of , the occupancy, which is an index indicating the cross-sectional shape of a single fiber, becomes 0.42 or less.

The fiber bundle produced by the above method was processed into a filter using a cigarette filter winding machine, and the ventilation resistance was measured. Table 1 shows the results.

The fibers of the fiber bundle for cigarette filters used in the measurement had a single fiber fineness of 3 denier and a total fineness of 36.0.
00 denier was used.

From the results in Table 1, it can be seen that compared to the conventional fiber bundle in which the spinning dope temperature is 54°C, the temperature is 56°C, which is the boiling point of acetone.
It was found that when the temperature was 3°C (under atmospheric pressure) or higher, the ventilation resistance was high and the removal rate of nicotine and tar was high.

[For production]

In the synthetic fiber bundle for cigarette filters, cellulose acetate is used as the fiber material, and the cross section of the single fibers constituting the synthetic fiber bundle is shaped such that the occupancy rate, which is an index of the cross-sectional shape, is 0.42 or less. Furthermore, the dope temperature when spinning cellulose acetate using the dry spinning method (
The spinning stock solution temperature) was adjusted to 56.3°C (the boiling point of acetone).
By setting the temperature to exceed atmospheric pressure (atmospheric pressure), the ventilation resistance of a portion of the filter increases, so the removal rate of nicotine and tar components improves, and it becomes possible to reduce nicotine and tar.

〔Example〕

The present invention will be explained below with reference to Examples, but the present invention is not limited by the Examples.

Example 1 Cellulose diacetate manufactured by Daicel Chemical Industries, Ltd. with an acetylation degree of 55.2% was prepared, and the cellulose diacetate was added to a solution containing acetone as the main solvent so that the acetate concentration was 25%. A dope solution (spinning stock solution) obtained by dissolving the above was prepared.

Further, the dope solution was filtered in two stages using a filter material made of a combination of a piece of filter paper Na 6 B and a nonwoven fabric to remove foreign substances in the dope solution. Next, the dope solution was discharged from a nozzle with 500 holes, and the single yarn fineness was 3.0 denier and the total fineness was 36. ．． A fiber bundle of 0 (if) denier (3Y -36,000>
Spinning was performed at 0°C. Furthermore, the above 3 Y -36,00
As a result of measuring the value of the coefficient occupancy rate, which is an index indicating the cross-sectional shape of the fibers, with an image processing device for the fiber bundle of 0.0, the occupancy rate was 0.4032. Also, using the above fibers,
The circumference is 24.8mm, the length is 120mm, and the fiber weight is 0.
After winding up a 626g filter plug with a filter winding machine, it was kept in an air-conditioned room at a temperature of 20°C and a humidity of 65% for 24 hours, and the ventilation resistance was measured.The ventilation resistance was 346mm water column. Met.

Example 2 The conditions other than the dope temperature were the same as in Example 1, the dope temperature was set to 70°C, and a fiber bundle of 3 Y -36,000 was spun. As a result of measuring the airflow resistance of the filter plug that was wound up with the filter winding machine under the same conditions as in Example 1, the occupancy rate was 0.3752 and the airflow resistance was 3.
The water column was 62 mm.

Comparative Example 1 The conditions other than the dope temperature were the same as in Example 1, the dope temperature was set to 54 °C below 56.3 °C, which is the boiling point of acetone (under atmospheric pressure), and a fiber bundle of 3 Y -36,000 was produced. After spinning, the coefficient occupancy rate, which is an index indicating the cross-sectional shape of the fiber, and the ventilation resistance of the filter plug wound up by the filter winding machine under the same conditions as in Example 1 were measured. As a result, the occupancy rate was 0.4235. , the ventilation resistance was 329 mm water column.

The above measurement results are summarized in Table 1 above, and Figure 5 shows the relationship between doping temperature and occupancy rate. These results show that fiber bundles produced under the conditions of the examples are better for cigarette use. It is possible to obtain a fiber bundle for a cigarette filter that has a high filter ventilation resistance and a high removal rate of nicotine and tar components.

〔Effect of the invention〕

A cigarette filter composed of a fiber bundle produced according to the present invention can be produced as a high-performance cigarette filter that can contain less nicotine and less tar than conventional cigarette filters.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a Y-shaped cross section of a single fiber;
The figure shows the shape factor 1, Figure 1b shows the occupancy rate, and Figure 2 shows the Y-shaped cross section displayed on the screen of the image processing device.
Figure 2a shows various cross-sectional tows, Figure 2b shows a Y-section tow, Figure 3 is a graph showing the relationship between the cross-sectional shape factor and ventilation resistance, and Figure 3a shows the relationship between ventilation resistance and shape factor 1. Figure 3b shows the relationship between ventilation resistance and occupancy rate, Figure 4 shows the frequency distribution diagram of occupancy rate for current cigarette filters, and Figure 5 shows the relationship between dope temperature and occupancy rate. FIG. Figure a b Figure a b Figure shape factor 1 (dimensionless) a Dimension v * tm dimension) b

Claims (1)

[Scope of Claims] 1. In a cellulose acetate fiber bundle for cigarette filters, the fibers constituting the fiber bundle have a cross-sectional shape such that the value of Ferearea, which is a cross-sectional shape coefficient, is 0.42 or less. Characteristic fiber bundles for cigarette filters. 2. The cigarette according to claim 1, wherein the cellulose acetate fiber bundle for cigarette filters is spun by a dry spinning method at a spinning dope temperature exceeding 56.3° C. (under atmospheric pressure), which is the boiling point of acetone. A method for producing fiber bundles for filters.