JPS63260555A - Elastic absorbing body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an elastic absorbent material suitable for sanitary products such as disposable diapers and sanitary napkins.

[Conventional technology]

Various types of disposable diapers have been proposed in the past, but their basic structure generally consists of a liquid-permeable surface part, a liquid-impermeable back part, and an absorbent part interposed between the two. .

This liquid-permeable surface portion is usually constructed of nonwoven fabric or perforated polyethylene film.

Further, the liquid-impermeable back surface portion is usually made of a synthetic resin film. On the other hand, the absorbent part is usually composed of a pulp material called pulverized pipe or flocculent pulp and a polymer absorbent, and this fibrous phase and polymer absorbent are encapsulated in a skin material such as tissue paper. This ensures that the pulp material and polymeric absorbent are stably packed.

The diaper is constructed by including a diaper main body including the front surface portion, back surface portion, and absorbent portion, and an adhesive tape for fixing the diaper to the body.

FIGS. 2 to 4 show the cross-sectional structure of the absorbent portion of the diaper. In each figure, 1 is a net (nonwoven fabric), 2 is pulverized pulp, 3 is a polymer absorbent, 4 is thin paper, and 5 is a cover stock.

As is clear from the above, the absorbent part of conventional diapers uses pulp materials such as pulverized or dalp and polymer absorbents, but these materials have almost no strength and have a low compression recovery rate, making it difficult for users to use them. The absorbent part is deformed due to dynamic loads and other factors, resulting in a decrease in usability.

Furthermore, it has the disadvantage that it contracts when it absorbs liquid, and it also has the disadvantage that it requires a mechanism to wrap the pipe material in the skin material.

In addition, from the perspective of layer structure, diapers with a single-layer or two-layer absorbent structure have a softer feel when the compression recovery rate is increased.
The flexibility deteriorates, and if the softness and flexibility are improved, the compression recovery rate decreases, and there is a problem in that the balance between the two is unbalanced.

[Problem that the invention seeks to solve]

An object of the present invention is to overcome the above-mentioned drawbacks and provide an elastic absorbent material with a well-balanced knot feel, flexibility, and compression recovery rate by using heat-adhesive conjugate fibers.

Some of the present inventors previously published JP-A No. 61-113810
In this publication, we proposed heat-adhesive conjugate fibers made from multilayer films to replace conventional heat-adhesive conjugate fibers produced by spinning. The manufacturing method is as follows.

Multilayer films consisting of at least two layers, one of which is made of a thermoplastic resin with a different melting point, are stretched after slitting or slit after stretching, then split, and further made into short fibers. Characteristic manufacturing method.

The present inventors studied elastic absorbers used as sanitary products such as disposable diapers and sanitary napkins, and after intensively studying the use and layer structure of the above-mentioned composite fibers in the absorbers, it was found that this composite fiber is an elastic absorber. It can mix well with the pulp of the upper and lower layers that make up the material, and by placing a polymer absorbent between the upper layer mixture and the lower layer mixture and heat-treating it, a solid integrated elastic absorber can be created. This absorbent body shrinks little even when it absorbs liquid, and can be integrated into a solid body without using a skin material such as tissue paper, which simplifies the process. In addition to the use of composite fibers, the layer structure is not a single layer or two layers, but at least three layers, which gives it strength compared to conventional absorbers, and also dramatically improves the amount of compression, softness, and flexibility in a well-balanced manner. The present invention was completed based on this knowledge.

[Means and effects for solving the problems] That is, the present invention has at least a three-layer structure in which both the upper layer and the lower layer are made of a mixture of pulp and heat-adhesive composite fibers, and the middle layer is made of a polymer absorbent. , wherein the ratio of the basis weight of the upper layer to the basis weight of the lower layer is 0.1 to 1:1, the pulp content of the upper layer is 5% by weight or more and less than 60% by weight, and the pulp content of the lower layer is The present invention relates to an elastic absorber characterized in that the elastic absorber is 60% by weight or more and 95% by weight or less, and the elastic absorber is heat-treated and integrated.

Furthermore, the present invention will be explained in detail in comparison with the prior art. Conventional composite fibers are produced by simultaneously spinning two types of spinning dope from two partitioned spinnerets and laminating both fibers together into a single fiber (Conduit 3 & Dart fiber). It is being

On the other hand, conventionally, as thermoadhesive composite fibers that take advantage of the difference in melting point, for example, crystalline polypropylene (m-p 165°C) is used as a high-melting point thermoplastic resin, and polyethylene (m-p 125°C) is used as a low-melting thermoplastic resin. ) and are formed by melt composite spinning using these as composite components.

Examples of cross-sectional models of these thermoadhesive composite fibers are shown in FIGS. 7 and 8. In the heat-adhesive composite fibers shown in both figures, the inside is made of a thermoplastic resin 6 with a high melting point, and the outside is made of a thermoplastic resin 7 with a low melting point.

Such heat-adhesive composite fibers are usually formed into a web and then heat-treated at a temperature that melts the thermoplastic resin with a low melting point but does not melt the thermoplastic resin with a high melting point. can be fused to form a nonwoven fabric.

However, in the above-mentioned melt composite spinning, dies are used.

Due to the complicated nozzle structure, it is generally almost impossible to manufacture composite fibers with three or more components.

Furthermore, even in the case of two-component composite fibers, it is generally impossible to color the raw materials because color quality is difficult to achieve.

For this reason, despite the excellent performance of thermally adhesive webs, their range of use has been severely limited.

Furthermore, it is difficult to make a blend of this thermoadhesive conjugate fiber with pulp, and even if a blend is made, the elastic recovery rate is low.

The inventors of the present invention were able to overcome the above-mentioned drawbacks by obtaining heat-adhesive conjugate fibers using a method different from the conventional conjugate spinning as described above.

In other words, this composite fiber is easy to color and can be produced in a wide variety of colors, and it is also possible to manufacture not only two-layer but also multi-layer structures with three or more layers, and the fiber structure is made of non-adhesive thermoplastic resins. It is also possible to realize Moreover, problems with dies and nozzles that are common in conventional melt composite spinning (
There is no disassembly and cleaning required. And the texture changes due to changes in die shape, etc. It is possible to produce a wide variety of webs with a sense of volume, and it is also sanitary and safe since it does not use a binder, and has the advantage of being cheaper than conventional methods.

Furthermore, unlike those produced by conventional spinning, this thermoadhesive conjugate fiber is a machine fiber with non-uniform thickness and length) and has a branched structure.

Since the fibers used in the absorbent portion generally have a non-uniform and branched structure, they can be well mixed with the thermoadhesive collated fibers of the present invention.

Such thermoadhesive composite fibers are made from multilayer film frames.

First, to explain the manufacturing method for multilayer films, taking multilayer films as an example, this is the calendar method.

It can be manufactured from thermoplastic resin by various known molding methods such as extrusion and casting.

Among these, extrusion methods using an inflation method and a T-die method are preferable.Specifically, there are various methods such as inflation, coextrusion using a II/die or T-die, and lamination.

For example, a method is employed in which a multilayer ink film is formed by simultaneously extruding different plastic resins from two or more extruders, thereby obtaining a multilayer film similar to a laminate product.

Examples of thermoplastic resins include d? It is preferable to use a material that can be formed into a film, such as an olefin polymer such as polyethylene polypropylene, polyamide, or polyester.

Such a resin may be a copolymer with a different type of monomer, and may also contain an antioxidant and a lubricant as necessary.

It may also contain ultraviolet absorbers, matting agents, stabilizers, flame retardants, etc.

In the present invention, as mentioned above, it is preferable to use a thermoplastic resin that can be formed into a film, but even if one thermoplastic resin cannot be formed into a multilayer film, this non-formable thermoplastic resin It is possible to form a multilayer film by first forming a single film, and then combining this with a material that can be formed into a single film, and it is also possible to manufacture composite fibers.

A multilayer film consists of at least two layers.

Among the thermoplastic resins constituting the multilayer film, the thermoplastic resin constituting at least one layer and the thermoplastic resin constituting the other layer have different melting points.

The difference in melting point between a low-melting point thermoplastic resin and a high-melting point thermoplastic resin is determined by considering the heat treatment conditions, multilayer film extrusion conditions, and post-process stretching conditions described below.If the former's melting point is Mp℃, the latter's melting point is It is preferable that M is +10°C or higher.

A specific example of a multilayer film with a two-layer structure is one in which polyethylene is used as a low melting point thermoplastic resin and crystalline polypropylene is used as a high melting point thermoplastic resin. An example of a multilayer film with a three-layer structure is one in which a thermoplastic resin with a similar low melting point is further laminated on the back side of a thermoplastic resin with a high melting point in the two-layer structure described above.

In addition, if these resins do not have adhesive properties, such as when linear low-density polyethylene is used as a low-melting thermoplastic resin and polyamide is used as a high-melting thermoplastic resin, there may be a gap between these resins. By interposing an adhesive resin, it is also possible to form a thermoadhesive composite fiber made of thermoplastic resins that do not have adhesive properties to each other.

As an example of this adhesive resin, a resin composition obtained by modifying polyethylene, polypropylene, etc. with an acid anhydride such as maleic anhydride or an acid can be used. Mention may be made of low density polyethylene.

In the present invention, the structure is not limited to these two-layer and three-layer structures, but it goes without saying that four or more layers may be used. Considering heat treatment conditions at a temperature that does not melt,
A multilayer film is constructed.

When forming the multilayer film according to the present invention by a T-die method or the like, the die lip structure may be flat, but it is preferable to use a lined die.

As a result, texture and volume can be imparted to the heat-adhesive conjugate fiber according to the present invention.

Fig. 5 shows an example of a cross-sectional model of heat-adhesive conjugate fiber when using a flat die, and Fig. 6 shows an example of a sectional model of heat-adhesive conjugate fiber when using a striated die. . In both figures, 8 and 10 each indicate a low melting point thermoplastic resin layer, and 9 indicates a high melting point thermoplastic resin layer.

The multilayer film according to the invention is then slit and stretched. A multilayer film, ie, a tape, which has already been slit may be stretched. therefore,
The multilayer films referred to in the present invention include those in the form of tapes, and may also be in the form of sheets.

Furthermore, the multilayer film may be slit after being stretched, or if the multilayer film has already been stretched, it can be directly sent to the slitting process. The thickness of the multilayer film is not particularly limited, but is generally preferably 30 to 100 microns.

The multilayer film may be stretched using any stretching method such as a hot plate, a hot roll, or an oven. There are no particular restrictions on the stretching temperature and stretching ratio, and the composition of the multilayer film,
The optimum conditions may be set depending on the shape. However, the strength, texture, volume, etc. of webs and nonwoven fabrics obtained through post-processing greatly depend on the physical properties of the raw fibers.

Preferred examples of stretching temperature and stretching ratio are -
When stretching a multilayer film made of polyethylene and crystalline polypropylene in the longitudinal direction using hot rolls, the stretching temperature is preferably 100 to 130°C and the stretching ratio is preferably 4 to 10 times. .

After this step, splitting is performed.

For example, a slitted stretched film (tape-like material) is brought into contact with a split roll having needles on its surface.
This process involves turning the film into fibers by rotating the rolls in the same direction as the film's traveling direction, and the final fiber diameter is determined by the lead and pitch of the needles of the split rolls. be done.

The average fineness of the obtained defibrated yarn (sugerit yarn) is 10, considering mixing with pulp in the subsequent process and web formation.
It is suitable that the fibers are fibrillated to 0d or less.

The bonding strength of the elastic absorber after heat fusion is 100dl.
- If it exceeds this, not only will it decrease, but the compression recovery rate will also be around 60 inches, which is not much different from that of conventional disposable diaper absorbers.

Once the sterit yarn is formed, the continuous fibers are then shortened using a cutter or the like, or the continuous fibers are formed into a web using a combing roll with a number of needles erected on its surface.

Simultaneously with this short fiber formation or web formation, for example, the sheet notarde is crushed and mixed with the above short fibers or web to obtain a blended cotton.

As shown in FIG. 1, the elastic absorber of the present invention has an upper layer and a lower layer consisting of crushed pulp 7'll and heat-adhesive composite fiber 1.
2, the middle layer of which is a sandwich structure consisting of a polymer absorbent 13, is basically heat-treated. As long as at least pulp and thermoadhesive composite resin are mixed, a layer structure of three or more layers can be adopted in combination with a polymer absorbent.

In the elastic absorber of the present invention, the basis weight ratio of the upper layer and the lower layer is
The ratio is 0.1 to 1:1, preferably 0.3 to 1:1, more preferably 1:1. This is because the upper layer has a texture and a thirium feel, and even when water is dripped from the upper layer, it has good drainage properties and flows immediately to the lower layer, so that the upper layer is always kept dry. If the basis weight of the upper layer is smaller than 041, the upper layer will be extremely sticky, and if the basis weight of the upper layer is greater than 1, the water pulling property will be poor.

In the present invention, it is necessary that the pulp content in the upper layer be lower than that in the lower layer. When the Noyalp content in the upper layer of Seven Nine is higher than that in the lower layer, even if water is dripped from the upper layer, the upper layer absorbs water and the water is stored in the upper layer, making it difficult to flow to the lower layer and making it impossible to increase the number of water absorptions. It is from.

The upper layer has a lug content of 5% by weight or more and less than 60% by weight, preferably 8% by weight or more and less than 40% by weight, more preferably 10% by weight or more and less than 30% by weight. The pulp content of the lower layer is from 60% by weight to 95% by weight, preferably from 65% by weight to 85% by weight, and more preferably from 70% by weight to 80.74% by weight.

If the pulp content in the upper layer is less than 5% by weight and the pulp content in the lower layer is less than 60% by weight, the surface water drawing properties will be poor; If the pulp content is more than 95% by weight, the joint strength and compression recovery rate will be poor. The total ratio of pulp/thermoadhesive conjugate fiber of the elastic absorber according to the present invention is 40 to 60% by weight of pulp/40% by weight of thermoadhesive conjugate fiber to 6% by weight.
Preferably it is 0% by weight. In addition, the ratio of pulp/thermal adhesive composite fiber/polymer absorbent is:
-% ~ 50 heavy poverty: Chi/thermal adhesive composite fiber 30% by weight ~ 5
A range of 0% by weight/20% by weight of polymer absorbent to 30i is suitable.

The polymer absorbent used in the present invention has an absorption capacity [
Those with a water absorption amount (me/absorbent) of 500 to 1000 are preferred. Typical examples include sodium polyacrylate, saponified product of acrylic acid-vinyl acetate copolymer, potassium I-lyacrylate, and Denzone-acrylic acid. Examples include powders of glatt polymer and inbutylene-maleic anhydride copolymer.The particle size of the polymer absorbent is usually 10 to 1,000.
μ, particularly those of 100 to 500 μ are preferable in terms of availability and handling.

Moreover, the type of seaweed used in the present invention is not limited as long as it is made of natural fibers. Representative examples include mechanical pulp,
Chemical mechanical pulp, semi-chemical pulp, chemical no! Examples include wood pulp such as rug.

It is preferable to use these /4'rugs after crushing them.

After forming a sandwich structure in which the upper and lower layers are made of a mixture of pulp and heat-adhesive conjugate fibers and the middle layer is made of a polymeric absorbent, this sandwich structure is heat-treated.

The heat treatment is carried out using, for example, a hot air circulating oven at a temperature that melts the low melting point thermoplastic resin constituting the thermoadhesive conjugate fibers, but does not melt the high melting point thermoplastic resin. By this heat treatment, the bonding portions between the heat-adhesive conjugate fibers are fused, and a solid, integrated elastic absorber is obtained.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In addition, prior to that, the physical property evaluation method applied to Examples and Comparative Examples will be explained.

1. Apparent thickness [ν] Tsuru 2. Weight
[M] 117m23, Seat joint strength
[St'3kp /25Dry & Wein St: 25mm width, 10 holes between chucks, tensile speed 200
Average strength of mV' ml n Dry & Wet, V3: 1 min + 311/cm2 Initial height when loaded, v4o: 1 m1n 1401/an Height after holding load 2v3:, After v4o measurement, leave for 5 min Afterwards, the final height at the time of 3 min load AR-1: Immersed in artificial urine for 10 minutes → drained for 5 minutes (1 c
WL (lay flat on square wire mesh) → Measurement AR-2: After AR-1 measurement → Drain at 45° tilt for 5 minutes → Measurement 6, Surface water absorption rate When l ec of artificial urine was dropped onto the sample surface, absorption was complete. time until.

Example 1 Linear low density on both sides of crystalline polypropylene (PP)? Liethylene (LLDPE) (density 0.92, MF
R1, 2) were arranged and coextruded by the T-die method, and then -axially stretched to a thickness of LLDPE (30 μ)/PP (9
A multilayer film of 0μ)/LLDPE (30μ) was molded.

In addition, by the same method as above, the thickness of LLDPE (10
A multilayer film of μ)/PP (30 μ)/LLDPE (10 μ) was molded.

Next, each film was defibrated using a conventional method, and the single fiber fineness of the former was 604. The latter yielded a 20d split yarn. This split yarn was cut into short fibers using a cutter, and the short fibers and previously crushed pulp were simultaneously blended to obtain a blended cotton web.

Next, an elastic absorbent body as shown in FIG. 1 was manufactured using this mixed cotton web and a polymer absorbent in the following manner.

First, a split yarn with a single fiber fineness of 60 d was used as the upper layer mixed cotton web, and a sedgerit yarn with a single fiber fineness of 20 d was used as the lower layer mixed cotton web, and a polymer absorbent was added between these two layers. Potassium lyacrylate powder (average particle size 200μ) was dispersed. At that time, the ratio of /4'/177'/thermoadhesive composite fiber was 13.8 / 86.2 (weight ratio) in the upper layer and 73 in the lower layer.
．． 2/26.8 (weight ratio), T of the upper layer and lower layer
otal ratio was set to 58.4741°6 (weight ratio).

The ratio of pulp/thermal adhesive composite fiber/polymer absorbent including the polymer absorbent in the middle layer is 45.1/32.2/22.
．． 7 (weight ratio), and the upper layer/lower layer basis weight ratio was 0.33/1. The resulting three-layer sandwich structure was heat-treated at 140° C. for 5 minutes while it was open, to obtain an elastic absorber. The obtained elastic absorbent material had a soft feel, had good flexibility, had good water drainage in the upper layer, was smooth and had good elasticity overall. The results are shown in Table 1.

Example 2 In Example 1, the weight ratio of armpit/thermoadhesive composite fiber was 13.8786.2 in the upper layer and 60.373 in the lower layer.
9.7, the total ratio of upper and lower layers is 47.9 /
52.1, ratio of pulp/thermal adhesive composite fiber/polymer absorbent including the polymer absorbent in the intermediate layer t37.6/39.
An elastic absorber was obtained in the same manner as in Example 1 except that the sample was 7/22.7. The resulting elastic absorber has a soft feel.

It was flexible, had good water drainage in the upper layer, and was smooth and elastic overall. The results are shown in Table 1.

Example 3 M ratio of pulp/thermoadhesive composite fiber is 13.9 in upper layer
/86.1. The lower layer is 73.1/26.9, the total ratio of the upper and lower layers is 43.5/56.5, and the ratio of pulp/thermal adhesive composite fiber/polymer absorbent including the polymer absorbent in the middle layer is 73.1/26.9. An elastic absorber was obtained in the same manner as in Example 1, except that the weight ratio was 33.5/43.5/23 and the upper layer/lower layer basis weight ratio was 171. The obtained elastic absorbent material had a soft feel, was flexible, had good water drainage in the upper layer, was smooth and had good elasticity overall.

The results are shown in Table 1.

Comparative Example 1 The weight ratio of pulp/thermoadhesive composite fiber was 4.0 in the upper layer.
/ 96.0, 50.0150.0 in the lower layer. The total ratio of the upper layer and lower layer is 38.5 / 61.5, including the polymer absorbent in the middle layer.
The ratio of polymer absorbent was 29.8/47.5/22.
An elastic absorber was obtained in the same manner as in Example 1 except that the elastic absorbent material was changed to No. 7. The obtained elastic absorber had a slow surface water absorption rate and poor water pulling properties.

Comparative Example 2 - The weight ratio of 9 Luso/thermoadhesive composite fiber was 70.
0 / 30.0, 40.0 / 60.0 in the lower layer, total ratio of upper and lower layers 62.5 / 37.5, pulp including polymer absorbent in the middle layer / thermoadhesive composite fiber /
An elastic and absorbent body was obtained in the same manner as in Example 1, except that the ratio of the polymer absorbent was 48.3/29.0/22.7 and the basis weight ratio of upper layer/lower layer was 3/1. . The obtained elastic absorber had low bonding strength and poor surface water resistance.

〔Effect of the invention〕

1) In the elastic absorber of the present invention, the thermoadhesive composite fiber, which is one of the constituent components, can be well mixed with the crushed pulp, and the polymer absorbent can also be intercalated at the same time. It has a soft feel, is highly flexible, has a surface that does not easily get wet, has overall elasticity, and has a good water retention effect.

2) According to the present invention, by heat-treating the above mixture, a solidified sheet-like material (mat) can be obtained, and the crushing valve and polymer absorbent can be completely fixed. Therefore, the process of wrapping the pulp with a skin material such as tissue paper, which was required in the past, is no longer necessary, and the process of manufacturing the elastic absorbent body can be significantly simplified.

3) The elastic absorber of the present invention has high strength and a compression recovery rate of D
It is good even in dry and wet conditions, and the feeling of use as a disposable diaper is comfortable both before and after urination, and there is almost no deformation due to shrinkage or the like.

4) In the elastic absorber of the present invention, the swelling free space of the crushed nonlupe and polymer absorbent is expanded, so the absorption capacity per unit weight is increased, and it is possible to reduce the weight of paper diapers, for example. Significant cost reductions can be achieved.

5) Therefore, the elastic absorber of the present invention can exhibit high commercial value not only as disposable diapers but also as sanitary napkins and other sanitary products.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of an elastic absorber showing an embodiment of the present invention, Figs. 2 to 4 are cross-sectional views of the water absorption part of a conventional disposable diaper, and Fig. 5 is a thermal adhesive composite according to the present invention. A cross-sectional view showing an example of a #1im model, Fig. 6 is a cross-sectional view showing another example of the same fiber model, Fig. 7 is a cross-sectional view showing an example of a conventional composite fiber, and Fig. 8 is a cross-sectional view showing an example of a conventional composite fiber. It is a sectional view showing other examples of fibers. 1... Net, 2... Crushed Noyalp, 3... Polymer absorbent, 4... Thin paper, 5... Cover stock, 6
...High melting point thermoplastic resin layer, 7...Low melting point thermoplastic resin layer, 8...Low melting point thermoplastic resin layer, 9.High melting point thermoplastic resin layer, 10...Low Melting point thermoplastic resin layer, 11...Crushed pulp, 12...Thermoadhesive composite fiber, 13...Polymer absorbent. Figure 1 Figure 2IXJ Figure 3 Figure 4 Figure 5 Figure 6 Figure 7- Figure 8

Claims (2)

[Claims] (1) An elastic absorbent body having at least three layers, in which both the upper layer and the lower layer are made of a mixture of pulp and heat-adhesive composite fibers, and the middle layer is made of a polymer absorbent, and the basis weight of the upper layer and the lower layer are The basis weight ratio is 0.1 to 1:1, the pulp content of the upper layer is 5% by weight or more and less than 60% by weight, the pulp content of the lower layer is 60% by weight or more and 95% by weight or less, and an elastic absorbent material. is an elastic absorber characterized by being heat-treated and integrated. (2) A multilayer film consisting of at least two layers of the thermoadhesive composite fiber, one layer and the other layer consisting of thermoplastic resins having different melting points, is stretched after slitting or stretched and then slit, and then Claim no.
Elastic absorber as described in section.