JP3033337B2 - Method of manufacturing surface materials for sanitary materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a surface material of a sanitary material, such as a disposable diaper or a sanitary napkin, which is mainly used for absorbing body fluids by directly contacting the body.

[0002]

2. Description of the Related Art Conventionally, a sanitary material is composed of a liquid absorbing material such as pulp for absorbing and retaining body fluid, and a surface material for enclosing the liquid absorbing material. The surface material is
It is used to prevent liquid-absorbing pulp and the like from adhering to the body, and as the material, a fiber product excellent in body fluid permeability and touch is used. As a method for producing the surface material, attention has begun to be paid to using a method for producing a so-called spunbonded nonwoven fabric. This spunbonded nonwoven fabric manufacturing method melts and spins a thermoplastic resin to obtain a bundled long fiber group, imparts the same charge to the long fiber group, and opens the fiber by repulsion between the long fibers. Subsequently, the opened filaments are accumulated on a collecting conveyor to obtain a fiber web, and thereafter, the filaments are fixed to each other by a certain means. This method has an advantage in terms of production cost since the process from fiber formation to surface material production can be performed continuously. Therefore,
Since it is disposable, it is attracting attention as a method for manufacturing surface materials of sanitary materials that are required to be inexpensive.

[0003] In a method for producing a surface material of a sanitary material, a hot embossing method has been proposed as a means for fixing between long fibers. In the hot embossing method, a fibrous web is introduced between a heated uneven roll and a smooth roll to fix the long fibers to each other. That is, in the area of the fibrous web heated and pressed by the projections of the uneven roll, the thermoplastic long fibers are softened or melted, and the area is formed into a film. It is to integrate them.

However, the surface material obtained in this manner is inferior in bulkiness and flexibility due to the presence of a film-formed area, and further has a large flexural rigidity in the film-formed area. Was bad.
If the hand feeling is poor, the skin contact of the surface material will be poor, and the wearing feeling of the sanitary material will be poor. In addition, the presence of a film-formed area also has a disadvantage that the permeability of bodily fluids such as urine deteriorates.

[0005] For this reason, an attempt is made to reduce the proportion of protrusions on the surface of the uneven roll, to reduce the area of the surface material formed into a film, to improve bulkiness and flexibility, and to further reduce bending rigidity. Has also been made. However, since the film-formed area in the surface material is for fixing the long fibers to each other, if this area is reduced, the tensile strength of the surface material is reduced or fluffing is likely to occur. It causes serious drawbacks. When the tensile strength is reduced, the surface material is easily broken, and the pulp or the like of the liquid absorption may adhere to the skin, and when it is easily fluffed, the fluff adheres to the skin and the feeling of use of the sanitary material is poor. It becomes. For this reason, the area of each individual projection is reduced, that is, the number of projections is increased, while the ratio of the projections occupying the uneven roll surface is kept as it is, to increase the area of each individual film formation. Attempts have been made to reduce the area and improve the overall feel. But,
There is a limit in minimizing the area of each individual protrusion, and it has been difficult to obtain a desired texture. Therefore, when a surface material of a sanitary material is obtained by using a so-called spunbond method and a hot embossing method, there is a disadvantage that a surface material having excellent feeling, high tensile strength, and less fuzzy is not easily obtained. It was.

[0006]

From the above, the present inventors have studied to obtain a surface material of a sanitary material by another method without using the hot embossing method. As a result, it was concluded that the method of fixing the long fibers under no pressure was optimal. However, in this method as well, it is common that when a sufficient tensile strength is applied, the feeling decreases, and conversely, when the feeling is improved, the tensile strength decreases. For this reason, as a result of further studies by the present inventors, as long fibers constituting the fibrous web, contributing to the bonding between the long fibers, a low melting point component as an adhesive component,
It was found that the use of a side-by-side type composite long fiber formed of a high melting point component that does not contribute to the bonding between long fibers can provide a surface material having a relatively good feel and sufficient tensile strength. . The reason is that the low melting point component, which is the adhesive component, is exposed only at a part of the surface of the long fiber, so that it bonds only at a part of the contact point between the long fibers, and the contact point does not bond at other places. Because. That is,
Since the low-melting point components are in contact with each other, and the low-melting-point component and the high-melting-point component are joined at the point of contact, and the high-melting-point components are not joined at the point of contact, and therefore not joined at all of the contact points. The feeling can be prevented from lowering, and since the number of bonding points per unit area is relatively large, sufficient tensile strength can be obtained.

[0007] However, when the side-by-side type composite filament is used, there is a case where the fiber cannot be sufficiently opened while the filament is collected on the collecting conveyor after the filament is obtained. That is, there was a regret that it was not possible to impart the same charge to the group of the bundled long fibers by the charging device and to open the fibers by the repulsive force of the long fibers. This is considered to be because the surface of the long fiber is not formed of the same polymer, so that the amount of charge applied is not uniform. Thus, if the spreadability is poor,
In some cases, the texture of the obtained surface material became non-uniform, resulting in a decrease in hand feeling and a decrease in tensile strength.

Therefore, the present invention provides a low-melting point component and a high-melting point component constituting a side-by-side type composite filament.
By adopting a specific polymer, the side-by-side type composite long fiber group can be favorably opened by the charging device, and a fiber web formed by accumulating the well-opened side-by-side type composite long fibers, Under non-pressing, it is intended to provide a surface material of a sanitary material which has a sufficient tensile strength, is hardly fluffed and has an excellent feeling by heating the fibers by a specific heating means and fixing the long fibers to each other. Things.

[0009]

That is, the present invention uses a crystalline polypropylene as a high melting point component, a high density polyethylene having a density of 0.94 g / cm ³ or more as a low melting point component, and a fineness of 1%. 0.5 to 5 denier side-by-side type composite filaments were obtained, the same charge was given to a group of filaments obtained by bundling a plurality of the filaments, and the filaments were opened by repulsion between the filaments. Thereafter, the filaments are accumulated on a collection conveyor to obtain a fibrous web, and then the fibrous web is introduced into a heated gas under non-pressing, thereby melting and solidifying the low melting point component. The present invention relates to a method for producing a surface material of a sanitary material, which comprises fixing long fibers to each other.

First, the side-by-side type composite long fiber used in the present invention will be described. The side-by-side type composite long fiber is obtained by laminating a low melting point component and a high melting point component having a substantially half-moon cross section in a state where both chords are in contact with each other. In the present invention, crystalline polypropylene is used as the high melting point component. Here, the crystalline polypropylene is composed mainly of stereotactic isotactic polypropylene as a main component, and has relatively high crystallinity and a high melting point. In the present invention, the reason why the crystalline polypropylene is used is to increase the melting point and to make it difficult to soften or melt at a temperature at which the high-density polyethylene used as the low melting point component melts. Further, it is for improving the chargeability and the opening property. As specific examples of crystalline polypropylene,
Melt flow rate (measured under JIS K 7210, Table 1, Condition 14)
Is preferably in the range of 10 to 80. When the melt flow rate is out of this range, there is a tendency that it becomes difficult to obtain side-by-side type composite continuous fibers by melt spinning.

In the present invention, a high-density polyethylene having a density of 0.94 g / cm ³ or more is used as the low melting point component. In particular, it is preferable to use one having a density of 0.945 to 0.965 g / cm ³ . It is not preferable to use polyethylene having a density of less than 0.94 g / cm ^{3, because the} amount of electric charge provided by the charging device is reduced, and the opening property due to repulsion between the long fibers becomes poor. As described above, it is considered that the reason why it is difficult to be charged when the density is low is that the dielectric constant also decreases as the density decreases. As a specific example of such a high-density polyethylene, it is preferable to use one having a melt flow rate (measured by JIS K6760) of 10 to 50. When the melt flow rate is out of this range, there is a tendency that it becomes difficult to obtain side-by-side type composite continuous fibers by melt spinning.

In the side-by-side type composite filament according to the present invention, the composite ratio of the low melting point component and the high melting point component is preferably 1: 1 to 3 (weight ratio). When the composite ratio of the high melting point component is smaller than this range, the amount of the low melting point component as the adhesive component relatively increases. Then, the proportion of the low melting point component exposed on the fiber surface increases, the bonding at the contact points between the long fibers increases, and the feeling of the obtained surface material tends to decrease. Conversely, when the composite ratio of the high melting point component is larger than this range, the amount of the low melting point component, which is the adhesive component, relatively decreases. Then, the proportion of the low-melting-point component exposed on the fiber surface decreases, and the bonding at the contact points between the long fibers decreases, and the tensile strength of the obtained surface material tends to decrease.

The fineness of the side-by-side type composite filament according to the present invention is 1.5 to 5 denier. 1.5 fineness
Making it less than denier is difficult in the production of long fibers.
Conversely, if the fineness exceeds 5 denier, the bending stiffness of the long fiber itself increases, and the feeling of the surface material obtained decreases.

[0014] The side-by-side type composite long fiber used in the present invention can be produced by a conventionally known composite melt spinning method. The spinning temperature is a matter which can be appropriately determined depending on the melting points of the low-melting point component and the high-melting point component to be employed, but in general, it is preferable to perform composite melt spinning in the range of 200 to 260 ° C. Less than 200 ° C or 260
If the temperature exceeds ℃, there is a tendency that stable spinning becomes difficult.

After obtaining a side-by-side type composite filament by a conventionally known composite melt spinning method, the plurality of filaments are bundled and introduced into air soccer. After the long fiber is drawn and pulled by air soccer to have a predetermined fineness, a charge is provided by a charging device installed at an outlet of the air soccer. Then, since the same charge is given to each filament, the filament is opened by the repulsive force between the filaments, and then the filaments are accumulated on the collecting conveyor. In this way, a fibrous web in which the side-by-side type composite long fibers are accumulated can be obtained.

The fiber web obtained as described above is
Under no pressure, it is introduced into the heated gas. Here, introducing the fibrous web into the heated gas under no pressing means that the fibrous web is passed through the heated gas without substantially compressing and pressurizing the fibrous web with a pressure roll or the like. Therefore, before the fibrous web passes through the heated gas,
Alternatively, it is needless to say that the fibrous web may be introduced into a pressure roll or the like after passing. In order to introduce the fibrous web into the heated gas, the fibrous web may be introduced into a rotary dryer such as a hot air circulation type or a hot air transmission type, or an infrared heating furnace. The temperature of the heating gas may be a temperature at which the low-melting component in the side-by-side type conjugate long fibers in the fiber web is melted, and the temperature at which the high-melting component is not melted or softened.

By introducing the fiber web into a heated gas at a constant temperature, the low-melting-point component in the side-by-side type conjugate long fibers constituting the fiber web is melted. And
After the fibrous web passes through the heated gas, it is allowed to cool and the low melting point component is solidified. As a result, the low melting point component adheres to the long fibers that are in contact. As described above, the long fibers are fixed to each other, and a surface material of a sanitary material having excellent shape stability can be obtained.

The basis weight of the surface material obtained as described above is a matter which can be arbitrarily determined, but is generally 10 to 50 g.
/ M ² . When the basis weight of the surface material is less than 10 g / m ² , the surface material is too thin to be easily handled and tends to be difficult to produce a sanitary material. Conversely, if the basis weight of the surface material exceeds 50 g / m ² , the surface material becomes too thick,
Bending stiffness and the like increase, and the feeling of the surface material tends to decrease.

[0019]

EXAMPLES Various physical properties and measurement methods of surface materials of sanitary materials used in the examples are as follows. (1) the surface material of sanitary materials basis weight: expressed in weight per surface material 1 m ² (g). (2) Tensile strength of surface material of sanitary material: Tensile tensile strength in the longitudinal and transverse directions was measured by a Tensilon tensile test in accordance with JIS L 1096, and the average value was defined as the tensile strength. (3) Fluff on the surface material of the sanitary material: The presence or absence of fluff on the surface of the surface material was visually evaluated according to the following criteria. ○…
Fuzz is scarcely seen, △ ... A little fluff is seen. (4) Hand feeling of the surface material of the sanitary material: Measured by the handle ometer method of the JIS L 1096 E method, and the average value of the hand feeling in the vertical and horizontal directions was shown. In addition, the size of the sample is 20 cm × 20 cm,
The slot width was 6.35 mm.

Example 1 First, crystalline polypropylene (melt flow rate 40, melting point 163 ° C.) was prepared as a high melting point component, and high density polyethylene (melt flow rate 20, melting point
135 ° C., density 0.94 g / cm ³ ). Then, the polypropylene is extruded from the first extruder while being heated and melted at 230 ° C, while the high-density polyethylene is extruded from the second extruder while being heated and melted at 230 ° C, and is provided with a side-by-side composite spinning hole. Introduced to several bases. At this time, the spinneret was heated to 230 ° C., and the number of spinning holes in the spinneret was 120 holes. Then, both components were discharged from the spinning hole such that the total discharge amount of both components was 1 g / min, and a discharge fiber group was obtained. The ejected fiber group was pulled and drawn by air soccer to obtain a side-by-side type composite long fiber having a fineness of about 2.0 denier. The composite ratio of both components in this composite continuous fiber was 1: 1.

After the group of side-by-side type composite filaments is discharged from the air football, the same charge is applied to each composite filament by a charging device provided below the air football, and the composite filaments are opened by mutual repulsion. Was. afterwards,
The composite long fibers were accumulated on a collecting conveyor made of a wire mesh to obtain a fiber web having a basis weight of 23 g / m ² . Then, the fiber web is introduced into a hot air circulation type rotary dryer filled with a heated gas flow. At this time, the temperature of the heated gas is 150 ° C
The heated gas passed in the thickness direction of the fibrous web. As a result, the low-melting-point component made of high-density polyethylene melted, and was fixed at the point where the low-melting-point component was in contact with the long fibers, and the long fibers were firmly bonded to each other. As described above, a surface material of a sanitary material having a basis weight of 23 g / m ² was obtained.

Example 2 Same as Example 1 except that the composite ratio of crystalline polypropylene (high melting point component) and high density polyethylene (low melting point component) was 2: 1 high melting point component: low melting point component. The surface material of the sanitary material was obtained.

Example 3 Same as Example 1 except that the composite ratio of crystalline polypropylene (high melting point component) and high density polyethylene (low melting point component) was 1: 2 for high melting point component: low melting point component. The surface material of the sanitary material was obtained.

Comparative Example 1 Crystalline polypropylene (melt flow rate 40, melting point 16
3 ° C) alone. Then, the crystalline polypropylene was extruded from an extruder while being heated and melted at 230 ° C., and introduced into several spinnerets having a circular spinning hole. At this time, the spinneret was heated to 230 ° C., and the number of spinning holes in the spinneret was 120 holes. Then, from the spinning hole, the discharge rate is set to 1 g / min,
The crystalline polypropylene was discharged to obtain a discharge fiber group. The ejected fiber group was pulled and drawn by air soccer to obtain a crystalline polypropylene long fiber having a fineness of about 2.0 denier.

After the group of crystalline polypropylene filaments was discharged from the air football, the same charge was applied to each filament by a charging device provided below the air football, and the filaments were opened by mutual repulsion. . After that, the long fibers are accumulated on a wire mesh collection conveyor, and the basis weight is 23 g / m.
^Two fiber webs were obtained. Then, this fiber web was introduced between a pair of rolls in which the upper stage was an uneven roll and the lower stage was a smooth roll. The uneven roll had a large number of convex portions, and the distal ends of the convex portions were round and had a diameter of 0.6 mm. Further, the temperature of the uneven roll was 145 ° C., and the temperature of the smooth roll was 140 ° C. By introducing the fibrous web between the rolls, heating and pressurizing are applied to the area of the fibrous web where the convex portion of the uneven roll abuts,
The area turned into a film. In the area where the film was formed, the long fibers were melted and solidified, thereby obtaining a surface material of a sanitary material in which the long fibers were fixedly bonded to each other. The total area of the filmed area is 5% of the surface area of the surface material.
% Area.

Comparative Example 2 A fibrous web was obtained in the same manner as in Example 1;
The long fibers were fixedly bonded to each other by the same hot embossing method as in Example 1 to obtain a surface material of a sanitary material.

The physical properties and evaluation of the surface materials of the sanitary materials obtained in Examples 1 to 3 and Comparative Examples 1 and 2 are as shown in Table 1.

[Table 1] As apparent from Table 1, Comparative Examples 1 and 2
The surface material of the sanitary material according to the above has a film forming area formed by heating and pressing by the convex portion of the concave and convex roll,
In the film-formed portion, the long fibers are connected to each other. Therefore, the long fibers in the areas other than the film-forming area were not fixedly bonded to each other at all, and were more likely to fluff than the surface material of the sanitary material according to the example. Furthermore, the surface material of the sanitary material according to Comparative Example 1 is:
The morphology of long fibers is lost in the filming area,
Since the long fibers were integrated into a plate shape, the feeling was inferior to the surface material of the sanitary material according to the example and the surface material according to Comparative Example 2. Therefore, the surface material of the sanitary material according to the example has a good balance of tensile strength, fluffiness and feeling, and is improved.

[0028]

The side-by-side conjugate long fiber used in the present invention comprises crystalline polypropylene as a high melting point component and high density polyethylene as a low melting point component having a density of 0.94 g / cm ³ or more. Therefore, the side-by-side type conjugate long fibers have better chargeability than the side-by-side type conjugate long fibers composed of a combination of other polymers. It is considered that the reason is that both the crystalline polypropylene and the high-density polyethylene have a high dielectric constant and a large charge amount. Therefore, after bundling this side-by-side type conjugate long fiber, applying a charge and opening the fiber, accumulating on a collection conveyor to obtain a fiber web, since the spreadability is good, uniform formation is possible. A fibrous web can be obtained. Then, when this fiber web is passed through a heated gas under no pressing, the low melting point component is melted and solidified to bond the long fibers with each other, and the pressing reduces the bulkiness and greatly increases the number of contact points. Can be prevented and the feeling can be improved.

[0029]

As described above, when the side-by-side type bicomponent filament according to the present invention is used, the fibrous web is obtained by opening with a charging device, and is introduced into a heated gas under no pressing, the formation is reduced. Uniform, rich in bulk, low in bending stiffness, soft and excellent in feel, and long fibers are fixed at many contact points between long fibers, making it hard to fluff and have high tensile strength. The surface material of the material can be easily obtained. Therefore, a sanitary material using this surface material has an excellent feeling of the surface material, so that it has a good feeling of wearing, and since the surface material has a high tensile strength and the surface material is not easily fluffed, the pulp is applied to the body during wearing. It is advantageous in that it is less likely to adhere to the hair and fluff and has an excellent feeling in use. In addition, since the production method according to the present invention does not employ the hot embossing method, there is no film forming area,
It also has the effect of providing a surface material having good body fluid permeability.

Continuation of the front page (51) Int.Cl. ⁷ identification code FI A61F 13/511 13/54 (58) Field surveyed (Int.Cl. ⁷ , DB name) D04H 3/00-3/16

Claims (1)

(57) [Claims] 1. A crystalline polypropylene is used as a high melting point component, and a density is 0.94 g / cm ³ as a low melting point component.
Using the above high-density polyethylene , fineness 1.5 to 5
After obtaining a denier side-by-side type composite filament, the same charge is given to a group of filaments obtained by bundling a plurality of filaments, and the filaments are opened by repulsion between the filaments. By accumulating the fibers to obtain a fibrous web, and then by introducing the fibrous web into a heated gas under no pressure, the low melting point component is melted and solidified to fix the long fibers to each other. A method for producing a surface material for a sanitary material.