JPS6284761A - Absorbable article - 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 disposable absorbent articles with excellent absorbency, particularly absorbent articles such as sanitary napkins and paper diapers.

[Conventional technology and problems]

Conventional absorbent articles, such as sanitary napkins or disposable diapers, basically consist of an absorbent layer made of a cotton-like bulb, absorbent paper, etc., a leak-proof layer placed on the bottom and sides if necessary, and a layer on the surface. It consists of a non-woven fabric on which it is placed.

The nonwoven fabric that forms the surface layer of such absorbent articles is required to have various performances, but one of the most important is to suppress the flow of liquid on the surface that can lead to leakage, and to prevent the discharge of urine and menstrual blood. The nonwoven fabric itself does not retain water or become sticky, and it also reduces the amount of liquid retained in the absorbent layer that returns to the skin. The good thing is the performance.

In conventional nonwoven fabrics used in absorbent articles, for example, in order to suppress liquid flow on the surface, it has been common to use hydrophilic natural fibers such as rayon. This method can certainly increase the water absorption rate on the surface of the nonwoven fabric and reduce the flow of liquid on the surface, but on the other hand, the hydrophilic natural fiber itself absorbs water deep into its interior and has a strong water retention capacity. Bulky when wet
As a result, in applications such as sanitary napkins and disposable diapers, the surface that comes in contact with the skin becomes sticky and liquid returns to the skin from the absorbent layer, resulting in problems such as a decrease in the feeling of use and the occurrence of rashes. occurred.

In recent years, dry non-woven fabrics made mainly of synthetic fibers have rapidly become popular as surface materials for absorbent articles, and as mentioned above, non-woven fabrics made mainly of hydrophilic natural fibers have high stickiness and liquid return. These problems are gradually being improved. However, conventional dry nonwoven fabrics made of hydrophobic fibers often have water-repellent surfaces, which causes large liquid flow and leakage. In addition, there are some devices in which hydrophobic fibers are treated with a surfactant to make the surface of the nonwoven fabric hydrophilic and to suppress liquid flow on the surface, but in the case of surfactant treatment, the durability against moisture is low, Once menstrual blood or urine passes through, the hydrophilicity of that area decreases significantly, and the second time menstrual blood or urine is discharged into the same area of the nonwoven fabric, the liquid will flow more easily and the leakage prevention effect will be reduced. It was insufficient. In particular, polyolefin fibers with a low melting point and excellent flexibility are often selected as materials for heat-adhesive nonwoven fabrics, which have excellent texture and are becoming increasingly popular even when dry-processed. It was very difficult to make the surface hydrophilic and impart absorbency.

As described above, it cannot be said that currently commercially available absorbent articles do not provide nonwoven fabrics with the desired properties listed at the beginning.

[Means for solving problems]

The method of treating hydrophobic fibers with a surfactant, as described at the end of the previous section, maintains the advantages of dry nonwoven fabrics mainly made of synthetic fibers, such as low stickiness and liquid return, and no loss of bulkiness when wet. This also suggests that a method of imparting hydrophilicity to the surface of hydrophobic fibers in some way is very effective in enhancing the water guiding effect to the absorbent layer.

As mentioned in the previous section, surfactant treatment is one example, but the water resistance is low and it is difficult to maintain the initial performance while using the absorbent article.

By the way, the method of making the surface of hydrophobic fibers hydrophilic is not limited to surfactant treatment. Many inventions have been made regarding hydrophilic treatment methods or hydrophilic treated fibers that provide sufficient water resistance. However, these fibers are considered for use in sports clothing and bedding, and because of the preconceived notion that disposable rainforests are used for a much shorter time than clothing, it is difficult to use these special fibers for disposable rainforests. There was no idea of using it, and there are almost no examples of it being used in sanitary napkins or disposable diapers. Among them, hydrophilization using plasma is one of the few methods that can be expected to be effective for making the surface of polyolefin fibers hydrophilic. I have yet to see any examples of applied processing.

Therefore, in order to improve the drawbacks of nonwoven fabrics used as surface materials for conventional absorbent articles, the present inventors conducted a water-resistant surface hydrophilic treatment as described above, in particular a surface hydrophilic treatment for polyolefin fibers. We focused on hydrophilic processing using plasma, which is effective for
As a result of intensive research to find a nonwoven fabric that satisfies these contradictory properties at the same time, the present invention was completed.

That is, the present invention provides an absorbent article having an absorbent layer and a nonwoven fabric covering at least one surface of the absorbent layer, in which the nonwoven fabric has a hydrophobic fiber whose surface is made hydrophilic by plasma polymerization with a hydrophilic group-containing compound. This relates to an absorbent article characterized in that the content is 100% by weight.

In order for the nonwoven fabric of an absorbent article to quickly guide liquids such as body fluids to the absorbent layer, the surface of the fibers constituting the nonwoven fabric is required to be hydrophilic at least at the time the absorbent article is composed of the nonwoven fabric. However, the interior of these fibers must be hydrophobic because the nonwoven fabric must maintain sufficient bulk when wet to reduce stickiness and liquid backflow from the absorbent layer.

Such fibers have a hydrophilic surface and a hydrophobic interior, for example, hydrophobic synthetic fibers such as polyolefin fibers such as polyethylene and polypropylene, polyester fibers, polyamide fibers, and polyacrylonitrile fibers. It can be obtained by sex. Among these fibers, polyolefin fibers, which have relatively low melting points, are excellent materials for dry heat-adhesive nonwoven fabrics that are rapidly becoming popular for use in sanitary napkins and disposable diapers.
Polyester fibers that can be subjected to various surface treatments, have excellent bulkiness, and are inexpensive are most desirable.

To perform durable hydrophilic treatment on the surface of hydrophobic fibers by plasma processing, there are two methods: direct plasma treatment of the fibers to add hydrophilic groups, and plasma treatment to add hydrophilic groups to the fiber surface or hydrophilic agent monomer (hydrophilic agent monomer). There are two methods of activating a hydrophilic agent (group-containing compound) to graft-polymerize the hydrophilic agent and fix it near the fiber surface, but the latter method must be used to achieve the object of the present invention. In the case of the former, the effect is smaller than in the latter, and it is good when the amount that must be absorbed at one time is small, such as sweat, but when the amount that must be absorbed at one time is large, such as menstrual blood and urine. In addition, in the case of polyolefin fibers, the modification effect caused by plasma treatment deteriorates in a short period of time. On the other hand, the latter method has the advantage of being able to control the degree of hydrophilicity by appropriately selecting the hydrophilizing agent monomer, and hardly causing any regression of the modification effect.

The hydrophilic agent used in the present invention is preferably one having two or more highly reactive double bonds, particularly vinyl bonds. Hydrophilic groups include hydroxyethyl groups, polyoxyethylene glycol chains, amines or quaternary ammonium salts, alkyl phosphates, sulfonates, sulfate salts,
Examples include carboxylic acid salts, N-methylolamide, and the like.

By constructing a nonwoven fabric using hydrophobic fibers with a hydrophilic surface, the nonwoven fabric has the following properties: less stickiness and liquid return, no loss of bulkiness when wet, and a high water conduction effect to the absorbent layer. can be expressed.

Another great advantage of hydrophilic processing using plasma is that
The hydrophilic treatment of hydrophobic fibers as described above can also be performed on nonwoven fabrics. That is, a nonwoven fabric is manufactured once using fibers that have not been subjected to hydrophilic treatment, and in a subsequent process, the nonwoven fabric is subjected to plasma treatment to impart hydrophilicity. According to this method, sufficient hydrophilicity can be obtained even for nonwoven fabrics whose manufacturing process is such that the hydrophilic treatment applied to the fibers during the process significantly deteriorates, making it difficult to ultimately impart hydrophilicity to the nonwoven fabric. can give.

In this case as well, as mentioned above, the method of activating the fiber surface or the hydrophilic agent monomer by the above-mentioned plasma treatment, graft polymerizing the hydrophilic agent, and fixing it near the fiber surface is excellent.

In order for the nonwoven fabric of the absorbent article to have a high water conduction effect and low liquid return from the absorbent layer, the nonwoven fabric should be made of fibers with a hydrophilic surface and a hydrophobic interior as described above. Although it is necessary to configure the
The composition of such fibers does not need to be 100% by weight - it is sufficient that the composition is at least 40% by weight.

The other 60% or less may be ordinary hydrophobic fibers or hydrophilic fibers such as rayon. Further, the nonwoven fabric according to the present invention can have a single layer structure as long as it contains 40% by weight or more of the above-mentioned fibers whose surface is hydrophilic and the inside is hydrophobic, and if the thickness is appropriate, i.e. , a multilayer structure may be used as long as the thickness is as described below.

Next, conditions for most effectively exhibiting the above-mentioned properties of the nonwoven fabric according to the present invention will be described in detail below.

The thickness of the nonwoven fabric is one of the major factors in liquid return from the absorbent layer to the outside of the nonwoven fabric. That is, if the thickness of the nonwoven fabric is too small, the distance between the skin and the absorbent layer becomes very close under the pressure of wearing the absorbent article when it is wet, resulting in large liquid return and a marked decrease in the feeling of use. On the other hand, as the thickness of the nonwoven fabric increases, liquid return certainly decreases, but if it is larger than necessary, the entire absorbent article becomes a prototype, which increases the user's discomfort and increases manufacturing costs. arise.

As described above, the thickness of the nonwoven fabric needs to be within the most appropriate range, taking into consideration liquid return performance, usability, and manufacturing cost. The appropriate thickness range varies depending on the application, but for example, when the nonwoven fabric is used for sanitary napkins, the total thickness is 0.3u to 0.8U under a load of 2.5 g/cffl. When used for paper diapers, it is desirable that the value be in the range of 0.6 sn to 2.51.

In order to provide the above-mentioned thickness to the nonwoven fabric of an absorbent article, it is necessary to appropriately select the fibers that constitute the nonwoven fabric and to provide the nonwoven fabric with an appropriate basis weight. first,
As already mentioned, it is necessary to use a hydrophobic synthetic fiber whose surface has been made hydrophilic so that its bulkiness does not decrease significantly even when wet. The thickness of the fiber is 1
．． The denier may be in the range of 5 to 6 denier.

This is because if the denier is less than 1.5, it is difficult to increase the bulkiness of the entire nonwoven fabric, and if the denier exceeds 6 denier, the entire nonwoven fabric becomes stiff and deteriorating in feel. Furthermore, in order to impart bulkiness to a nonwoven fabric, it is generally sufficient to increase the basis weight, but in consideration of manufacturing costs, it is desirable to keep the basis weight as low as possible. Therefore, it is best to make the fibers as highly elastic as possible, and ways to do this include not using very thin fibers as mentioned above, and choosing hollow fibers or fibers with three-dimensional crimp. It will be done. In this way, considering the ease of controlling moisture resistance of surface hydrophilic treatment, low price, ease of imparting high elasticity, and ease of processing into nonwoven fabrics,
The most suitable fibers for the nonwoven fabric are polyester and polyolefin fibers.

As for the basis weight of a nonwoven fabric, in general, the lower the basis weight, the smaller the thickness, and the higher the basis weight, the greater the thickness, so there is an appropriate range depending on the use. When using the above-mentioned fibers, for example, when used for sanitary napkins, the total amount is in the range of 10 to 30 g/m, and when used for disposable diapers, the total amount is in the range of 20 to 50 g/n ( This is desirable.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 27, Comparative Examples 1 to 8 The performance of nonwoven fabrics constructed using the various hydrophilized fibers shown in Table 1 and absorbent articles constructed from these nonwoven fabrics was tested by the methods shown below. The results are shown in Table 2.

The plasma processing conditions are as follows.

An untreated base material (fiber or nonwoven fabric) was placed in a glass Pel jar, and the inside of the Pel jar was evacuated to 10 Torr or less, and then the exhaust pulp was closed and air was supplied to a volume of 0.1 mm and 11 g. Next, a dilute amount of the hydrophilic monomer shown in Table 1 was supplied to the fiber to a concentration of 0.5% based on the weight of the fiber, and a voltage was applied to the electrode from a high frequency type ia (13.56 Mllz) for about 3 minutes. In the case of J in Table 1, voltage was applied without supplying the hydrophilizing agent monomer.

The nonwoven fabrics except for Comparative Examples 7 and 8 had a HL layer or a two-layer structure and were manufactured by a dry heat bonding method using heat-melting fibers as a binder. Furthermore, the nonwoven fabric of Comparative Example 7 was manufactured using a wet method, and the nonwoven fabric of Comparative Example 8 was a commercially available product manufactured using a spunbond method.

As a sample for measurement, the nonwoven fabric of a commercially available sanitary napkin (trade name Laurier, manufactured by Kao Soap Takiku) was removed, and the nonwoven fabrics listed in Examples 1 to 21 and Comparative Examples 1 to 8 in Table 2 were placed instead. The product was made into an absorbent article assuming a sanitary napkin, and the nonwoven fabric of a commercially available disposable diaper (trade name: Mary's, manufactured by Kao Soap ■) was removed and replaced with the nonwoven fabric listed in Examples 22 to 27 in Table 2. The absorbent article was used as an absorbent article intended for disposable diapers.

<Test method> (1) Surface liquid flow Drop the test liquid from 1 cm above the sample surface inclined at 245 degrees and measure the distance it flows on the nonwoven fabric surface from the dropping point to the point where it is absorbed into the sample. This was defined as the first surface liquid flow. next,
One minute after dropping the test liquid, drop the test liquid again on the part where it was dropped earlier, observe how it flows on the surface of the nonwoven fabric, and evaluate it based on the following ranks. The surface liquid flow of

○: There was almost no change in the surface liquid flow from the first time, and it was immediately absorbed as soon as it fell.

Δ: It flows within the area wetted the first time, but is absorbed within that area.

×: The water flowed outside the area that was wetted the first time, and was absorbed by the not-yet-wetted area of the nonwoven fabric.

If the first surface liquid flow is short and the second surface liquid flow is ○ or , it means that there is no major lateral leakage and the durability of the surface hydrophilic treatment is high.

The dropping conditions were as follows: Hypothetical sanitary napkin samples (Example 1 to
21, Comparative Examples 1 to 8), 0 and 1 g/sec, and disposable diaper assumed samples (Examples 22 to 27), 0
．． The rate was set at 5 g/sec.

(2) Amount of liquid returned: 10 cc of the test liquid was absorbed into a sanitary napkin sample and 150 cc was absorbed into a disposable diaper sample, and after a certain period of time, pressure was applied and the amount of test liquid returned from the inside through the nonwoven fabric was measured.

The smaller the amount of return, the less sticky it will be on the surface.
Easy to use and has excellent wiping effect.

(3) Thickness: The thickness of the nonwoven fabric (dry and wet) was measured using a thickness meter under a load of 2.5 g/cal.

〔Effect of the invention〕

As can be seen from Examples 1 to 27, in absorbent articles using the nonwoven fabric according to the present invention, the flow of liquid on the surface is small both in the first and second times, and the return of liquid from the inside to the surface is small.

On the other hand, Comparative Examples 1 to 8 are the results of manufacturing absorbent articles in the same manner as in Examples using nonwoven fabrics outside the scope of the present invention, and measuring the surface liquid flow and liquid return. 2.8
is made of 100% hydrophobic fibers treated with only the spinning oil and without any surface hydrophilic treatment, and the test liquid flows completely on the surface.

In Comparative Example 1, the blend ratio of fibers whose surfaces were made hydrophilic by plasma polymerization treatment was less than 40% by weight, so the durability against moisture was weak, and the surface liquid flow upon dropping the test liquid for the second time was greatly deteriorated.

In Comparative Examples 5 and 6, only the plasma treatment was performed directly on the fiber surface. Since the degree of hydrophilicity is insufficient compared to non-woven fabrics using fibers plasma-polymerized with a hydrophilic agent, surface liquid flow is significantly higher.

Comparative Example 7 was made of 100% by weight rayon, had a significant amount of liquid return, and was highly sticky. Furthermore, the thickness of the nonwoven fabric when wet is smaller than that of other examples, and it lacks a sense of volume.

In Comparative Example 4, the blend ratio of fibers whose surfaces were made hydrophilic by plasma polymerization treatment was less than 40% by weight, but because rayon was used, although the second surface liquid flow was good, the liquid return was extremely large.

In Comparative Example 3, the surface was treated only with a surfactant, so the affinity with the fibers was small, and the flow of the surface liquid upon the second drop of the test liquid was deteriorated.

Claims (1)

[Claims] 1. In an absorbent article having an absorbent layer and a nonwoven fabric covering at least one surface of the absorbent layer, the nonwoven fabric contains 40 to 100% by weight of hydrophobic fibers whose surfaces have been made hydrophilic by plasma polymerization with a hydrophilic group-containing compound. An absorbent article characterized by containing: