RU2418113C1 - Method of making bundles of acetate fibre and acetate bundles made using said method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of making a bundle from acetate fibre involves a step for obtaining initial liquid by dissolving a starting polymer in a solvent, a spinning step on which the initial liquid is released from a draw plate, and the said solvent is evaporated in a heated medium, a moistening and corrugating step from which a primary bundle of fibres is obtained, having moisture content of 23-50 wt %, a step for primary drying at temperature equal to or higher than boiling point of the said solvent, but not higher than 85°C, and a step for secondary drying on which further drying is carried out until achieving the desired moisture content, thus obtaining the said bundle of acetate fibres. Disclosed also is an acetate bundle made using said method, in which solvent content is less than 0.10 wt %.

EFFECT: invention enables obtaining acetate bundles with very low solvent content and with high production efficiency.

4 cl, 3 dwg, 2 tbl

Description

Description

The present invention relates to a method for producing acetate fiber tows and to acetate tows obtained by this method.

Typically, in the production process of acetate tows, a dry molding process is used in which a typical molding speed is 300 m / s or more. For this reason, technological operations carried out at various stages of the production of acetate tow are often required in very short periods of time.

Acetate tows are used mainly in tobacco filters. In the manufacture of acetate tows, an initial liquid consisting of an initial polymer cellulose acetate dissolved in acetone is extruded by a gear pump and then discharged from a die into a heated shaft of a spinning machine. The solvent there quickly evaporates and a primary fiber bundle is formed. This entire process is carried out for a very short period - in a second or less.

A single fiber exiting the spinneret is combined with other single fibers to form a primary bundle with a total number of fibers of 100-1500, with a single fiber thickness of 0.8-10 dtex.

An oil emulsion is then added to the primary bundle to form a primary bundle containing about 1% by weight of the oil component and about 25% by weight of moisture. From 5 to 40 such primary bundles are combined into a bundle having a total thickness of 10,000-50000 dtex. Then, to crimp the fibers of the tow, a corrugating machine is used, after which the tow is sent to the drying step to remove moisture and solvent contained therein. The steps starting with the addition of an oil emulsion and ending with the drying process are carried out for a short period of time of less than one second.

Moisture and solvent are removed, keeping the material for several minutes at the drying stage, while achieving the desired moisture content, and acetate tows are obtained. The resulting acetate tows are sent to the packaging stage, which lasts several hours until the packaging container is full.

In the production method described above, the time required for the steps from the release of material from the die to the corrugation is no more than two seconds. In addition, from the point of view of production efficiency, the usual drying time preceding the packaging process is no more than 10 minutes, even in cases of unusually long drying.

In the production of acetate tows, in which various technological operations are continuously carried out, at the time of material release from the die, it contains acetone or another similar solvent in an amount of 200-300 wt.% (Calculated on the solid component). Therefore, reducing the amount of acetone remaining after drying in acetate tows to its content not exceeding 0.10 wt.%, Is a difficult task.

Patent Document 1 discloses a method for removing a hydrophilic organic solvent in a solid polysaccharide, wherein the solid polysaccharide is treated with moist air, the residual hydrophilic organic solvent is reduced, and dried for several hours.

In the method for producing an acetate tow described in Patent Document 2, a method for increasing the moisture of a tow by adding an oil emulsion to a fiber tow including a plurality of primary bundles is disclosed.

Background Art

[ Patent Document 1 ] Japanese Unexamined Application, First Publication No. Hei 1-318001

[ Patent Document 2 ] Japanese Patent Laid-Open No. 2006-144176

Objectives of the invention

The method disclosed in Patent Document No. 1 is difficult to apply to a production line that produces uncut acetate tows of a length of 20 to 30 thousand meters. In addition, by treating with moist air, it is difficult to further increase the content of the moisture component in the primary fiber bundles, which already contain a high level of humidity due to the addition of an oil emulsion.

In addition, in the method disclosed in Patent Document No. 2, it is difficult to stably produce acetate tows with a low solvent content without limiting the drying conditions.

Usually acetate tows are used in tobacco filters and as a result, their components can be inhaled with smoke. Therefore, given their effect on the health of the smoker, it is very important to provide acetate tows (or products in which they are used) with a very low solvent content.

The present invention was developed to solve the problems of the prior art with the aim of creating a method for producing acetate tow, which would allow the production of acetate tows with a very low solvent content with good production efficiency and would provide acetate tows produced by the above method.

The solution of tasks

A method for producing an acetate tow according to the invention comprises the following steps.

The step of obtaining the starting fluid: obtaining the starting fluid by dissolving the starting polymer in a solvent.

The stage of molding (spinning): the release of the original fluid from the die and the evaporation of the solvent in a heated medium to obtain a primary fiber bundle.

Stage of humidification and corrugation: humidification of the primary fiber bundle, followed by corrugation, to obtain a primary fiber bundle with a moisture content of 23-50 wt.%.

Stage of primary drying: drying of the primary fiber bundle obtained at the stage of moistening and corrugation at a temperature equal to or higher than the boiling point of the solvent and not higher than 85 ° C.

Secondary drying step: further drying the primary fiber bundle, which has passed the primary drying step, in order to achieve the desired moisture content and thereby to produce an acetate tow.

The preferred starting polymer is cellulose diacetate and the preferred solvent is acetone.

The drying time at the primary drying stage is from 0.5 to 2.0 minutes, and it is preferable that the total time of the primary drying and secondary drying stages is not more than 5.0 minutes.

The acetate tow according to the invention is characterized in that it is obtained by the production method of the acetate tow according to the invention and in that it contains a solvent in an amount not exceeding 0.10 wt.%.

[Effects of the present invention]

Using the acetate tow production method of the invention, acetate tows containing a very low amount of solvent can be produced with good production efficiency.

In addition, the amount of solvent contained in the acetate tows of the invention is very low.

Description of drawings

Figure 1 is a schematic structural view showing one example of acetate tow equipment for use in the acetate tow production method of the invention.

Fig. 2 is a view showing an example of a second oil emulsion applying device.

FIG. 3 is a schematic view showing an example of a lubricating nipple in FIG. 2.

Preferred Embodiments of the Present Invention

In this section of the present description will be an explanation of the present invention.

Figure 1 is a schematic structural view showing one example of acetate tow equipment used in the present invention. The device 1 for the production of acetate tow in this example consists of a gear pump 11 for extruding the original liquid; a die 13 placed inside the spinning shaft 12; a feed roller 14 for drawing a single fiber or the like exiting from the outlet of the die 13; a device 16 for applying an oil emulsion to a primary fiber bundle 15, which is an aggregate of a plurality of single fibers; a second device 18 for applying the oil emulsion to the fiber bundle 17, consisting of a plurality of primary bundles of fibers 15 connected together, and dryers 20 for drying the fiber bundle 17.

The number of dies provided is not limited, but it can optionally be provided in such a way that the total thickness reaches the desired value according to the area of application of the acetate tow. In addition, the present invention is not limited to a single die 13 provided inside the spinning shaft 12 in FIG. 1. For example, all dies can be placed inside one spinning shaft.

The pump used in the equipment for the production of acetate tow can be used as a gear pump 11.

Spinning shaft 12 is designed to withstand single fibers released from the outlet of the die 13 in a heated environment.

As the die 13, a conventional die can be used. However, a die having 100-1500 outlets is preferred.

As the feed roller 14, a conventional roller may be used.

As examples of the first oil emulsion application device 16 and the second oil emulsion application device 18, a structure such as a feed oil line or a rotating roller can be indicated. The first oil emulsion application device 16 and the second oil emulsion application device 18 may have the same structure or may have a different structure.

The corrugating device 19 is provided with a pair of rolls. These rolls are not specifically limited in any way, provided that they are capable of imparting corrugation to the fiber bundle.

The drying device 20 is divided into a primary (preliminary) dryer 20a and a secondary dryer 20b. These dryers are not specifically limited. However, it is preferable that a near infrared spectrophotometer and a computer (not shown) be attached to it to facilitate temperature control in the secondary dryer 20b.

In this section of the present description, using FIG. 1, a specific explanation will be given of one example of the application of the acetate tow production method of the invention.

A method for producing an acetate tow according to the invention includes a step for producing a starting liquid, a spinning step, a wetting and crimping step, a primary drying step, and a secondary drying step.

<Stage of obtaining the original liquid>

The step of preparing the starting liquid is a step for preparing the starting liquid by dissolving the starting polymer in a solvent.

It is preferable to formulate the starting liquid so that the proportion of solvent relative to the starting polymer is in the range of 200-300 wt.%.

Examples of the starting polymer that can be mentioned in this regard include flocculated cellulose diacetate, cellulose triacetate or a mixture of cellulose diacetate and cellulose triacetate.

Examples of a solvent that can be indicated in this regard include acetone, methyl ethyl ketone, methyl formate, methyl acetate, ethyl acetate, methylene chloride, methanol, and solvents mixed therefrom. The solvent may be appropriately selected according to the type of starting polymer used. When using cellulose diacetate as the starting polymer, acetone is preferred in terms of cost and solubility.

It should be noted that in the steps explained below, cellulose diacetate is used as the starting polymer and acetone as the solvent.

<Spinning Stage>

The spinning step is a process for producing a primary fiber bundle 15 by spinning a starting fluid obtained in the preparation of the starting fluid.

The feed fluid (cellulose diacetate dissolved in acetone) is delivered to the spinneret 13 by a gear pump 11. The feed fluid delivered to the spinneret 13 is discharged into the spinning shaft 12 from the outlets of the spinneret 13 in the form of a plurality of single fibers. At the same time, the evaporation of acetone occurs in the heated space inside the spinning shaft 12.

It is preferable to maintain the interior of the spinning shaft 12 at 60-80 ° C. When the temperature inside the spinning mill is below 60 ° C, evaporation of acetone is insufficient. On the other hand, the increased evaporation of acetone, which occurs at a temperature inside the spinning mill above 80 ° C., is undesirable.

When pulled by the feed roller 14, a plurality of single fibers are joined together and converted into a primary fiber bundle 15.

The amount of acetone contained in the primary fiber bundle 15, after passing through the spinning shaft 12, varies depending on the thickness of a single fiber, but usually it is 5-20 wt.%. It should be noted that, as described above, the time during which the initial liquid and the primary fiber bundle pass through the spinning shaft 12 is very short. For this reason, even maintaining the temperature inside the spinning mill at 100 ° C, it is very difficult to reduce the amount of acetone contained to a value lower than the lower threshold indicated above.

<Stage humidification and corrugation>

At the stage of wetting and corrugation, moisture is added to the primary fiber bundle 15, after which it is corrugated. At this stage, a primary fiber bundle is obtained with a moisture content in the range of 23-50 wt.%.

To impart smoothness to the primary fiber bundle 15, an oil emulsion is added to it. In this case, moisture can be added to the primary fiber bundle 15 using an oil emulsion in which water is used as a dispersant.

Examples of the oil component of the oil emulsion that can be indicated in this regard include mineral oils such as liquid paraffin (liquid paraffin) and surfactants such as polyethylene sorbitan monococate or sorbitan monolaurate. These oil components can be used individually or in combinations of two or more.

The proportion of water in the oil emulsion (100%) is preferably 93-97%. When the proportion of water is at least 93% by weight, after adding moisture, the primary fiber bundle can be stabilized and then corrugated. When the proportion of water is not more than 97 wt.%, A sufficient amount of the oil component can be added to the primary fiber bundle to obtain an acetate tow with excellent smoothness and stable processing properties.

Hydration of the primary fiber bundle 15 can be carried out by applying an oil emulsion to the primary fiber bundle 15 in the first stage of applying the oil emulsion 16 or by applying the oil emulsion to the fiber bundle 17 containing an aggregate of a plurality of primary fiber bundles 15 in the second stage of applying the oil emulsion 18. In addition Moreover, hydration can also be carried out simultaneously in the first stage of applying the oil emulsion 16 and in the second stage of applying the oil emulsion 18.

As examples, the following methods of moistening the primary fiber bundle in the first stage of applying the oil emulsion 16 and / or in the second stage of applying the oil emulsion 18 can be mentioned.

In the case of a structure such as a supply oil line, the oil emulsion is fed from the gear pump through tubes to the oil line (lubricating grease fitting), in which the tube is connected to the gear pump. The oil emulsion is applied by bringing the delivered primary fiber bundle into contact with the oiler surface saturated with the oil emulsion.

In the case of a structure such as a rotating roller, an oil emulsion is applied by bringing the supplied primary fiber bundle into contact with the surface of the rotating roller saturated with the oil emulsion.

An example application of the method of wetting the fiber tow 17 in the second stage of applying the oil emulsion 18 will be specifically explained in this section of the present description with reference to figure 2.

FIG. 2 is a schematic view showing an example of a second oil emulsion applying device 18 having an oil-conducting nipple type structure. In this example, the second oil emulsion applicator 18 is provided with oil-conducting lubricants 18a for applying oil emulsion to the fiber tow 17, gear pumps 18b for continuously supplying a certain amount of oil emulsion to the oil-conducting greasers 18a, and tubes 18c for connecting oil-conducting grease nipples 18a with gear pumps 18b.

The second oil emulsion applying device 18, shown in FIG. 2, has one oil-conducting oiler 18a, optionally located some distance above and below the delivered fiber bundle 17.

As shown in FIG. 3, the oil-conducting grease fitting 18a has a guide main body 181 for passing a supplied fiber tow. The guide main body 181 consists of a hollow cylindrical part narrowed in that part along which a fiber bundle is passed through its peripheral surface.

A pair of funnel-shaped flanges 182, 182 expanding on the outside is mounted on each side along the axis of the guide main body 181. The surface 183 of the inner end of the flange 182, which is in contact with the main body 181, has a diameter larger than the diameter of the main body 181. Therefore, the boundary between the main body 181 and the guide 183 has the shape of a ledge. The width of the feed fiber bundle 17 may be limited within a fixed size. The distance L between the surfaces of the inner extremities 183 is usually set within 3-30 mm.

In the axial direction, a slit hole 184 for applying oil is formed on the peripheral surface of the guide main body 181 through which the oil emulsion is discharged. The length of the slit W of the hole 184 for applying oil, preferably, is greater than the total width of the fiber bundle, it is usually set in the range of 3-30 mm The width T of the oil outlet 184 is not particularly limited, but is preferably set in the range of 0.2-2.0 mm.

In addition, on one side along the axis of the conductive main body 181, a connector 185 is formed, connected to the gear pump 18b via the tube 18c shown in FIG. 2. The connector 185 consists of a cylindrical part having an internal hollow portion; it is connected to an oil outlet 184. The gear pump 18b shown in FIG. 2 is connected to a conventional source of hydraulic pressure (not shown), and thus a constant amount of oil emulsion is supplied. The oil emulsion supplied from the gear pump 18b is passed through the tube 18c and the connector 185 is discharged from the oil outlet 184 in the guide main body 181 and is applied across the width in the longitudinal direction of the fiber.

In the second oil emulsion application device 18 shown in FIG. 2, the conductive grease nipples 18a are installed above and below the delivered fiber bundle 17. As a result, the oil emulsion can be applied to both the front and rear surfaces of the fiber bundle 17.

It should be noted that it is permissible to place oil conduits 18a both above and below the fiber bundle 17. However, to uniformly apply the oil emulsion to the fiber bundle 17, it is preferable to install the oil conduits 18a both above and below the fiber bundle 17, as shown in FIG. 2.

As the tube 18c, elastic plastic tubes, tubes, and the like can be used.

Using the tube 18c, the oiler 18a can be placed in a place separate from the gear pump 18b. Accordingly, the degree of freedom for accommodating the oiler 18a and the gear pump 18b is increased.

In the second oil emulsion application device 18 shown in FIG. 2, the following arrangement is effective when the oil emulsion is discharged from the oil application hole in the oiler 18a and when a certain amount of oil emulsion is continuously applied to the fiber bundle 17.

Namely, the fiber bundle 17 is placed in close proximity to the outlet of the lubricator so that the oil emulsion does not drip from the opening of the lubricator. In addition, the translational movement of the fiber bundle is carried out in contact with an oil film formed on the contact surface of the oiler 18a with the fiber bundle 17.

When the fiber bundle 17 continuously moves in close proximity to the outlet of the lubricator, a certain amount of oil emulsion, due to the action of the gear pump 18b, is continuously released from the outlet of the lubricator 18a and applied to the fiber bundle 17. As a result, the amount of applied oil emulsion can be stabilized, which can significantly improve the uniformity and effectiveness of the adhesion of the oil emulsion.

In order to continuously and uniformly apply the oil emulsion to the fiber bundle while maintaining its quantitative characteristics, it is preferable to install the oiler 18a at a position above the position of the gear pump 18b. As a result, the tube 18c, which connects the grease fitting 18a and the gear pump 18b, is installed with an upward slope. As a result of this, it becomes possible to create internal pressure in the tube 18c, which is determined by the difference in the heights of the positions of the oiler 18a and the gear pump 18b. As a result of this, a relatively viscous oil emulsion, which, compared to water, has a noticeable surface tension, can be quantitatively delivered to the oiler 18a.

It should be noted that even when the primary bundle of fibers 15 is wetted in the first stage of applying the oil emulsion 16, this can be done in the same way as the wetting method in the second device for applying the oil emulsion 18, described above.

A moistened primary fiber bundle, onto which the oil emulsion was applied as described above, is then corrugated in a corrugating device 19.

Specifically, a fiber bundle 17 on which an oil emulsion was applied on a second oil emulsion applicator 18 is passed between a pair of rolls in a corrugating device 19. As a result, the primary fiber bundle becomes corrugated.

The degree of corrugation attached is not particularly limited in any way, but it can be set accordingly to the field of application of the obtained acetate tows.

As described above, in the wetting and crimping steps, the primary fiber bundle is moistened and then crimped to produce a primary fiber bundle with a moisture content in the range of 23-50 wt.%. By wetting the primary fiber bundle in the preliminary drying step discussed below, it is possible to evaporate a sufficient amount of acetone remaining in the primary fiber bundle, and thereby significantly reduce the amount of acetone contained. It is believed that the effect of reducing the amount of acetone contained has the following nature.

On single fibers formed from the starting liquid, there is a surface layer (“skin layer”) with a relatively high density that is formed when the fiber is spun. Acetone, penetrating deep beneath the skin layer, is difficult to remove back through this layer to the surface of the fiber by heating alone in the drying step. Therefore, this acetone is not amenable to easy evaporation. When moisture is added to the primary fiber bundle 15, this moisture becomes a dispersing medium for acetone, contributing to its dispersion to the surface of the fiber. Due to this, acetone is sufficiently volatilized at the drying stage, which allows to reduce the amount of acetone contained.

The adjustable parameters of the first device for applying the oil emulsion 16 and the second device for applying the oil emulsion 18 can be adjusted so that the moisture content in the primary fiber bundle is in the range of 23-50 wt.% At the stage of wetting and crimping. For example, when the nipples in the first oil emulsion applicator 16 and the second oil emulsion applicator 18 are in the form of the oil type structure shown in FIG. 2, the moisture content can be adjusted by adjusting the rotation speed of the gear pump 18b. Specifically, the moisture content increases when the rotation speed of the gear pump 18b is increased. When the nipples in the first oil emulsion applicator 16 and the second oil emulsion applicator 18 are in the form of a rotating roller type structure, the moisture content can be adjusted by adjusting the rotation speed of this roller. Specifically, the moisture content increases when the rotation speed of the roller is increased.

The moisture content in the primary fiber bundle can be adjusted by adjusting the rotation speed of the gear pump or roller in accordance with the moisture content measurements obtained by the methods described below.

The moisture content in the primary fiber bundle obtained from the stage of wetting and corrugation is 23-50 wt.%. If the moisture content is at least 23 wt.%, A sufficient effect of reducing the acetone content can be obtained. In contrast, even with a moisture content exceeding 50 wt.%, It is difficult to obtain a more noticeable effect of reducing the acetone content.

In addition, at the stages of wetting and corrugation, the preferred moisture content in the primary fiber bundle is 23-32 wt.%. If the moisture content is less than 32 wt.%, The load on the first device for applying oil emulsion 16 and the second device for applying oil emulsion 18 is limited. Specifically, in the case of the oil-conducting type structure shown in FIG. 2, the rotation speed of the gear pump 18b can be set within such limits that it is difficult to apply excessive load. In addition, in the case of a structure such as a rotating roller, the rotation speed of this roller can be set within such limits that it is difficult to apply excessive load.

Using a fiber tow 17 before feeding it to the primary drying step and measuring the content of the volatile component and the content of acetone, as described below, it is possible to obtain the moisture content in the primary fiber bundle obtained in the wetting and crimping step according to the following Formula (1).

Moisture content (wt.%) = Volatile component content - acetone content ... (1)

(Measurement of volatile component content)

The corrugated fiber tow is cut off before being fed to the primary drying step, and a 10 m length is quickly placed in a 300 ml test bottle. After filling the bottle with a fiber bundle, it is closed with a lid and sealed. The content of the volatile component is measured according to the following Formula (2).

The content of the volatile component (wt.%) = 100 × (A - B - C) / C, (2)

where A (g) is the mass of a test bottle filled with a fiber bundle; C (g) represents the mass of the empty test bottle and C (g) represents the mass determined after the fiber tow that fills the test bottle was dried for 45 minutes at 110 ° C. using an air dryer.

(Measurement of acetone content)

The fiber tow is placed in a test bottle, closed with a lid and sealed in the same way as for measuring the content of a volatile component. Then, 3-4 g of fiber bundle filling the bottle is taken and placed in an Erlenmeyer flask equipped with a cork, to which 200 ml of distilled water is added. The flask is closed with a stopper. An ultrasonic treatment is carried out for 30 minutes at 24 ° C. using an ultrasonic cleaning system so that the acetone contained in the fiber tow is extracted into distilled water. This distilled water is collected and the acetone content is determined by gas chromatography.

<Drying Stage>

The primary fiber bundle obtained in the wetting and crimping step is sent to the drying compartment 20 in the form of a fiber tow and dried in the following stages of primary (preliminary) drying and secondary drying to obtain an acetate tow 21.

In the primary drying step, the fiber tow 17 is dried in the primary dryer 20a of the drying compartment 20, in which the specific drying temperature is set.

In the secondary drying step, the fiber tow 17 is further dried in the secondary dryer 20b of the drying compartment 20, in which the specific drying temperature is set.

(Stage of primary drying)

The primary drying stage is the stage of drying the primary fiber bundle obtained at the stage of moistening and corrugation at a temperature equal to or higher than the boiling point of acetone (solvent) and not higher than 85 ° C. It should be noted that when acetone is used as the solvent, the lower drying temperature threshold (i.e., the boiling point of acetone) is at 56.6 ° C.

When the drying temperature is lower than the boiling point of acetone, it is difficult to evaporate the acetone sufficiently and it is difficult to reduce the acetone content in the acetate tow. On the other hand, when the drying temperature exceeds 85 ° C, the aqueous component is easily volatilized, and the effect of reducing the amount of remaining acetone becomes difficult to achieve. In other words, moisture added to the primary fiber bundle acts as a dispersing medium for acetone. Accordingly, acetone penetrated into the skin layer of a single fiber is dispersed to the surface of this fiber. If the aqueous component evaporates during the primary drying stage, the dispersion of acetone is not sufficiently stimulated. As a result of this, a sufficient degree of evaporation of acetone is not achieved and it becomes difficult to reduce the amount of acetone remaining in the obtained acetate tow.

In the primary drying step, the fiber tow is dried under conditions in which acetone in the fiber tow is easily volatilized and the aqueous component does not evaporate. As a result, acetone can be selectively evaporated in a fiber bundle (i.e., in a primary fiber bundle).

Provided that the drying temperature remains within the above range, at the stage of primary drying it can be kept constant at any level or a temperature gradient can be created.

The duration of the primary drying step is preferably 0.5-2.0 minutes. With a drying time in the indicated range, a sufficient degree of evaporation of acetone can be achieved and good performance can be achieved.

(Stage of secondary drying)

The secondary drying step is intended to further dry the primary fiber bundle that has passed the primary drying step until a certain moisture content is reached.

The temperature of the secondary drying is not particularly limited in any way, provided that it is a temperature capable of evaporating the moisture component until a certain moisture content is reached. For example, this temperature can be set at 80-120 ° C.

Provided that the drying temperature remains within the above range, at the stage of secondary drying it can be kept constant at any level or a temperature gradient can be created.

From the point of view of productivity, it is preferable to set the duration of the secondary drying stage so that the total drying time at the stages of primary drying and secondary drying is not more than 5.0 minutes.

It should be noted that the drying temperature in the secondary drying stage can be easily controlled by attaching a near infrared spectrophotometer and a computer (not shown) to the secondary dryer. Specifically, the near-infrared rays are emitted by the near-infrared spectrophotometer to the acetate tow 21 passing through the drying compartment 20, and the moisture content of the acetate tow is measured. The computer is used to calculate the amount of heat from the measured value and the temperature of the dryer is automatically controlled by this amount of heat. Using this control method, it is possible to stably produce acetate tow 21 having a certain moisture content, even with a change in production speed or product variety.

The moisture content in the acetate tow 21 is determined based on the requirements of the particular application of the acetate tow 21 and products that use the acetate tow 21. Accordingly, without making generalizations, it can be indicated that the fiber tow 17 is usually dried in the secondary drying stage so that the content moisture was in the range of 4.5-7.5 wt.% or 5.0-8.0 wt.%.

It should be noted that the moisture content in the acetate tow 21 can be measured by the emission of rays in the near infrared region, as described above.

The acetate tow 21 thus obtained has a very low solvent content. Specifically, the amount of solvent contained can be reduced below 0.10 wt.%.

The amount of solvent contained in the acetate tow 21 can be determined as follows.

Namely, the fiber tow (acetate tow), dried in the secondary drying step, is cut off and about 10 m quickly packed into a 300 ml test bottle. After filling the test bottle with an acetate tow, the test bottle is closed with a lid and sealed. Then, 3-4 g of acetate tow packed in this bottle is taken and placed in an Erlenmeyer flask equipped with a cork, into which 200 ml of distilled water is introduced. Then the flask is closed with a stopper. An ultrasonic treatment is carried out for 30 minutes at 24 ° C. using an ultrasonic cleaning system so that the acetone contained in the acetate tow is extracted into distilled water. Distilled water is then collected and the acetone content is determined by gas chromatography.

It should be noted that the obtained acetate tow 21 is sent to the packaging process, where it is placed in a packaging container (not shown); the duration of this operation before filling the container can be several hours.

As indicated in the above explanation, in the present invention, the moisture content in the primary fiber bundle in the primary drying step is 23-50 wt.%. As a result of this, the added moisture component acts as a dispersing medium for the solvent. In other words, the solvent penetrated into a single fiber can be easily dispersed to the surface of the fiber and can be sufficiently evaporated at the stage of primary drying. Accordingly, it is possible to produce an acetate tow containing a very low amount of solvent. It should be noted that at the stage of primary drying, the added moisture component does not volatilize also easily, and therefore the solvent dispersion effect produced by the moisture component is not disturbed.

Since the above steps can be carried out continuously, the production of the acetate tow according to the invention is characterized by excellent production efficiency.

It should be noted that the production method of the acetate tow according to the invention is not limited to the method described above. For example, as a method of wetting a primary fiber bundle, it is permissible to use a method in which water or distilled water is added directly.

In the case where water is added directly, the method of addition is not particularly limited. For example, you can specify the method in which water is added by bringing the incoming primary fiber bundle into contact with the water-saturated surface of the rotating roller. In addition, instead of the lubricating nipple 18a shown in FIG. 2, it is possible to provide a plumbing humidifier having a similar structure. Using a device in which the gear pump and the tube are connected to the humidifier, it is possible to deliver water through the tube from the gear pump to the humidifier. Water can be added by bringing the incoming primary fiber bundle into contact with the water-saturated surface of this humidifier.

When directly distilled water is added, the method of addition is not particularly limited. For example, you can specify a method in which a device having a nozzle spraying distilled water is used, and this distilled water can be sprayed onto the incoming primary fiber bundle.

When water or distilled water is added directly to the primary fiber bundle, the time for this addition is not particularly limited, provided that it is carried out before the corrugation of the primary fiber bundle is carried out. For example, when applying the oil emulsion to the primary fiber bundle 15 in the oil emulsion applying device 16 shown in FIG. 1, water or distilled water can be added before or after applying the oil emulsion. In addition, when the oil emulsion is applied to the fiber tow 17 in the second oil emulsion applicator 18, water or distilled water can be added before or after the oil emulsion is applied. It is also permissible to directly add water or distilled water to the primary bundle of fibers 15 and the fiber bundle 17.

However, from the point of view of simplifying the equipment for the production of acetate tow and reducing its size, a method is preferred in which the moisture component is added to the primary fiber bundle using an oil emulsion in which water is used as a dispersant.

[Examples]

This section of this document will provide a specific explanation of the present invention using examples. However, they do not limit the present invention.

Methods for measuring the moisture content and solvent measured in Examples and Comparative Examples are as follows.

<Measurement of moisture content in the primary fiber bundle obtained at the stage of wetting and corrugation>

Using a fiber tow before feeding it to the stage of primary drying and measuring the content of the volatile component and the content of acetone, as described below, according to Formula (1), the moisture content in the primary fiber bundle obtained at the stage of wetting and corrugation was determined.

Moisture content (wt.%) = Volatile component content - acetone content ... (1)

(Measurement of volatile component content)

At the stage of production of acetate tow, a fiber tow was cut off, which was corrugated at the stage of moistening and corrugation, and quickly packed from the surface of the cut end into a polyethylene test bottle (300 ml capacity). After filling this test bottle with a fiber bundle (approximately 10 m of fiber bundle) cut off at the wetting and crimping step, the bottle was lidded and sealed. Then measured the content of the volatile component according to the following Formula (2).

Volatile component content (wt.%) = 100 × (A - B - C) / C ..., (2)

where A (g) is the mass of a test bottle filled with a fiber bundle; B (g) represents the mass of an empty test bottle; and C (g) is the mass determined after the fiber tow that fills the test bottle was dried for 45 minutes at 110 ° C using an air dryer.

(Measurement of acetone content)

The fiber tow was packaged in a test bottle and then closed with a cap and sealed in the same manner as for measuring the content of the volatile component. Then 3-4 g of a fiber bundle packed in this bottle was taken and placed in an Erlenmeyer flask equipped with a cork, to which 200 ml of distilled water was added. Then the flask was closed with a stopper. An ultrasonic treatment was carried out for 30 minutes at 24 ° C. using an ultrasonic cleaning system so that the acetone contained in the fiber tow was extracted into distilled water. 2 μl of distilled water was collected and introduced into a gas chromatograph (flame ionization detector manufactured by Hitachi, Ltd.) and the acetone content was measured. Measurement conditions on a gas chromatograph are shown below.

Detector: Flame Ionization Detector (FID)

Column: A stainless steel column (inner diameter: 3 mmϕ × 2 m) using Chromosorb 102 (particle diameter: 60-80 mesh) as a filler

Thermostat temperature: 150 ° C

Inlet temperature: 150 ° C

<Measurement of solvent content in acetate tow>

At the stage of production of acetate tow, a fiber tow (acetate tow) was cut off, sent to drying at the secondary drying stage and to the packaging stage, and quickly packed from the surface of the cut end into a polyethylene test bottle (300 ml capacity). After filling the test bottle with an acetate tow (approximately 10 m of acetate tow) cut off at the secondary drying stage, the test bottle was closed with a lid and sealed.

Then, 3-4 g of acetate tow packed in this bottle was taken. The solvent (acetone) included in the acetate tow was extracted into distilled water in the same way as when measuring the acetone content in the procedure for measuring the moisture content in the primary fiber bundle obtained in the humidification and corrugation step. The extracted liquid was collected and the solvent content was measured by gas chromatography.

<Example 1-1>

Acetate tows were produced as follows, using the equipment 1 for the production of acetate tow, shown in figure 1.

Cellulose diacetate having an average degree of acetylation of 55.5% was dissolved in acetone to prepare an initial liquid having a density (concentration) of cellulose diacetate of 29.3 wt.%. This starting fluid was then used to form the primary fiber bundle 15 by spinning using a die 13 having 250 outlets. After that, using the first device for applying oil emulsion 16, an oil emulsion having the following composition (indicated below) in an amount of 15 wt.% Was applied to the primary fiber bundle 15. Then, a feed roller 14 was used to connect the eleven primary bundles of fibers 15 at a traction speed of 450 m / min to form a fiber bundle 17 having a total thickness of 17300 dtex and a thickness of a single fiber of 2750. Then, using a second device for applying oil emulsion 18 to the fiber bundle 17, an oil emulsion of the following composition (as indicated below) was applied at a rate of 20 ml / min. After that, a corrugating device 19 was used to impart corrugation to the fiber bundle. After corrugation, the moisture content in the fiber bundle was 23.4 wt.%.

Then, dryers 20 were used to dry the corrugated fiber bundle 17 at the primary drying stage and at the secondary drying stage to obtain acetate tow 21. At the primary drying stage, the drying temperature was set at 59 ° C and the drying time was set to 1.5 minutes. At the secondary drying stage, the drying time was set to 1.5 minutes. In addition, the drying temperature at the secondary drying stage was automatically controlled using a spectrophotometer for the near infrared region (not shown), so that the moisture content in the fiber tow (acetate tow 21) after the secondary drying step was in the range of 4.5-7.5 the weight.%.

In the acetate tow thus obtained, the solvent content (acetone content) was measured. These results are shown in Table 1.

(Composition of the emulsion)

- Mixed oil containing mineral oil (liquid paraffin) and a surfactant (polyoxyethylene sorbitan monococate): 4.5 wt.%

- Water: 95.5 wt.%

<Examples 1-2 - 1-6>

With the exception of changes in the drying temperature in the primary drying stage, illustrated in Table 1, acetate tows were produced in the same manner as in Example 1-1, and the acetone content of the obtained acetate tows was measured. These results are shown in Table 1.

<Comparative Examples 1-1 to 1-5>

With the exception of changes in the drying temperature in the primary drying stage, illustrated in Table 1, acetate tows were produced in the same manner as in Example 1-1, and the acetone content of the obtained acetate tows was measured. These results are shown in Table 1.

Table 1 Drying temperature at the stage of primary drying (° C) Acetate content in acetate tow
(the weight.%) Examples 1-1 59 0,068 1-2 60 0,076 1-3 62 0,050 1-4 65 0,061 1-5 70 0,061 1-6 75 0,082 Comparative
Examples 1-1 56 0.108 1-2 86 0.114 1-3 90 0.121 1-4 one hundred 0.213 1-5 110 0.252

As is clear from Table 1, the acetate tows obtained in each of the Examples had an acetone content of less than 0.10 wt.%. According to this, it was possible to sufficiently reduce the acetone content.

In contrast, acetate tows obtained in each of the Comparative Examples had an acetone content in excess of 0.10 wt.%. Accordingly, the residual amount of acetone was significant compared to Examples.

<Examples 2-1 to 2-7>

For the production of acetate tows under various conditions, modified as shown in Table 2, the production equipment 1 shown in FIG. 1 and the initial liquid prepared according to Example 1-1 were used.

The primary fiber bundle 15 was formed by dry spinning using a die 13 having 250-1075 outlets. Then, an oil emulsion identical to the emulsion of Example 1-1 was applied to the primary fiber bundle 15 in an amount of 15% by weight using the first oil emulsion applicator 16. After that, a feed roller 14 was used to connect the primary fiber bundles 15 at a speed of 430-470 m / min, forming a fiber bundle 17 with the number of single fibers 2750-23652, with a single fiber thickness of 1.8-7.3 dtex and a total thickness of 17300-44000 dtex. Then, an oil emulsion identical to the emulsion according to Example 1-1 was applied to the fiber tow 17 at the feed rate shown in Table 2 using the second oil emulsion applicator 18. Thereafter, a corrugating device 19 was used to impart corrugation to the fiber tow. The moisture content of this fiber tow after corrugation is shown in Table 2.

Then, dryers 20 were used to dry the corrugated fiber tow 17 at the stage of primary drying and at the stage of secondary drying, obtaining acetate tow 21. At the stage of primary drying, the drying temperature was set at the level indicated in Table 2, and the drying time was set at 1.5 min . At the secondary drying stage, the drying time was set to 1.5 minutes. In addition, the drying temperature in the secondary drying stage was controlled using a near infrared spectrophotometer (not shown), so that the moisture content in the fiber tow (acetate tow) after the secondary drying step was in the range of 4.5-7.5 weight. %

In the acetate tow thus obtained, the solvent content (acetone content) was measured. These results are shown in Table 2.

table 2 Single fiber thickness (dtex) Total Thickness (dtex) The number of single fibers Number of dies The number of outlets in the die Oil emulsion feed rate (ml / min) The moisture content in the fiber bundle after corrugation (wt.%) Drying temperature at the stage of primary drying (° C) The acetone content in the acetate tow (wt.%) P 2-1 7.3 34000 5160 12 430 60 28.8 60 0,077 R 2-2 6.0 17300 2750 eleven 250 60 29.2 65 0,042 AND 2-3 5,0 34400 7021 17 413 60 29.4 60 0,036 M 2-4 3.3 33600 10750 10 1075 40 26.9 68 0,035 E 2-5 3.0 34100 11825 eleven 1075 40 27.3 60 0,025 R 2-6 2,8 34600 10750 10 1075 twenty 25.0 78 0,021 S 2-7 1.9 44000 23652 27 876 twenty 25.1 84 0,022

As is clear from Table 2, the acetate tows obtained in each of the Examples had an acetone content of less than 0.10 wt.%. According to this, it was possible to sufficiently reduce the acetone content.

[Applicability in the production environment]

The present invention allows to obtain acetate tows containing less than 0.10 wt.% Solvent, with good production efficiency. These low-solvent acetate tows are highly beneficial as a material optimally used in the tobacco industry

[Description of symbols]

one Equipment for the production of acetate tow eleven Gear pump 12 Spinning mine 13 Die fourteen Feed roller fifteen Primary fiber bundle 16 The first device for applying oil emulsion 17 Fiber harness eighteen The second device for applying oil emulsion 19 Corrugating device twenty Dryers 21 Acetate tourniquet

Claims (4)

1. A method of producing a bundle of acetate fibers, comprising the following stages:
a step for producing a starting liquid, wherein the starting liquid is obtained by dissolving the starting polymer in a solvent;
a spinning step in which the starting liquid is discharged from the die and said solvent is evaporated in a heated medium to obtain a primary fiber bundle;
a moistening and corrugating step, in which moisture is added to the primary fiber bundle, followed by corrugation to obtain a primary fiber bundle having a moisture content of 23-50 wt.%;
a primary drying step in which said fiber tow obtained in a wetting and crimping step is dried at a temperature equal to or higher than the boiling point of said solvent, but not higher than 85 ° C; and
a secondary drying step, wherein said primary fiber bundle passed through said primary drying step is further dried to achieve a desired moisture content, obtaining said bundle of acetate fibers. 2. The method according to claim 1, wherein said source polymer is cellulose diacetate and said solvent is acetone. 3. The method according to claim 1 or 2, in which the drying time during the specified stage of primary drying is 0.5-2.0 minutes, and the total drying time at the indicated stages of primary drying and secondary drying does not exceed 5.0 minutes 4. An acetate tow obtained by the method according to any one of claims 1 to 3, in which the solvent content is less than 0.10 wt.%.

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