JP3331221B2 - Elastic composite and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elastic composite formed by combining a sheet-like elastic body and a sheet-like base material such as a nonwoven fabric, and particularly to an elastic composite suitable for use in disposable products such as diapers, and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Daily necessities such as underwear and socks, disposable diapers waist, crotch, elastic bandages, surgical gown cuffs and the like are used to enhance and improve the adhesion to the human body. An elastic body is used. These include natural rubber,
Materials such as synthetic rubber and urethane resin are used in the form of thread, foam, film, net, and covered with woven, non-woven, or thread to avoid direct contact with the human body. Is common.

[0003] Generally, in order to use disposable products, it is extremely difficult to design products that are inexpensive, have excellent workability for mass production at high speed, and require strict safety for sensitive skin of infants. High-quality materials are required.

The following three are known as prior arts used for the above purposes.

(1) So-called Stretched Bo
This is a method called ned Laminate.
The process shown in FIG. That is, first, the elastic body is stretched, and in the stretched tension state, it is bonded to the material by heat, ultrasonic waves, an adhesive or the like to form a combined body. An elastic composite is obtained. Most elastic bodies applied to the waist and crotch parts of currently available disposable diapers and the like are manufactured by this method.

(2) A method of exerting elasticity by heat shrinkage, which comprises the steps shown in FIG. In other words, after the latent elastic body having heat shrinkability and the non-extensible material are bonded by ultrasonic waves, an adhesive, etc., the combined body is treated in a hot atmosphere in a non-tension state, so that a pleated elastic composite is obtained. This is how you get your body. This method is partially commercially available as a waist elastic body.

(3) A method proposed by Japanese Patent Application Laid-Open No. 59-59901, comprising the steps shown in FIG. That is, a net-like elastic body in a relaxed state is partially and discontinuously bonded to a non-extensible base material having relatively low extensibility, such as a PE or EVA-containing film. When stretched under high tension to the extent necessary within the allowable elongation of the substrate, the unbonded portion of the substrate portion is stretched while undergoing greater permanent deformation as compared to the bonded portion. When the tension is removed from such an elongated joint and the elastic portion is brought into a relaxed state, an elastic composite having elasticity is obtained. Although this material has begun to be applied to elastic bandages, etc., it has relatively low elasticity to obtain a uniform elastic composite, and is industrially excellent for producing a material having elasticity in the sheet length direction. It is a method.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an improvement of the above-mentioned third method, and is intended to provide an industrially inexpensive elastic body by selecting a material to be used and optimizing bonding conditions. Another object of the present invention is to provide a novel composite elastic body using such an elastic body.

[0009]

The present invention SUMMARY OF THE INVENTION, first made and the sheet-shaped elastic body relaxed state, not be extended, or fold a sheet material that does not form, the sheet
The extensibility in the longitudinal direction (MD) is in the transverse direction (CD).
And the elastic body is continuously bonded to the base material in the length direction (MD) of the sheet and has discontinuity in the cross direction (CD). An elastic composite and a method for producing the same, characterized in that they are bonded and the base material has a lateral elongation property but does not have an elongation recovery property. The present invention further comprises a sheet-like elastic body in a relaxed state and a sheet-like base material formed with elongated folds, wherein the elastic body is continuously formed on the base material in a sheet length direction (MD). The elastic composite is characterized by being bonded with discontinuity in the transverse direction (CD). Such an elastic composite cuts the elastic composite first described above into an elastic body and a substrate,
It can be manufactured by elongating to the elongation limit within a range not causing breakage, causing permanent deformation (folds) in the substrate, and then relaxing the elongation.

[0010] The components of the present invention are firstly concerned with the elastic body and the base material which are the materials constituting the elastic composite,
The second relates to the bonding state of the constituent materials, the third relates to elongation conditions for optimizing the elasticity of the elastic composite, and the fourth relates to the function and performance of the obtained elastic composite. is there. First, a sheet-like elastic body and a sheet-like base material, which are constituent materials, will be described.

First, as the sheet-like elastic material used in the present invention, a thin sheet of natural rubber, synthetic rubber or the like, a polyurethane film, a polyurethane melt blown nonwoven fabric,
A sheet-like elastic body such as a styrene-butadiene-block polymer film and a polyolefin-based elastomer film can be used. However, from the viewpoint of the adhesion to a cost base material, EVA, ultra-low density LLDPE, ethylene-propylene elastomer, ethylene-propylene elastomer, etc. Polyolefin elastomers such as methyl acrylate elastomers alone or their synthetic rubbers, styrene ethylene butadiene
A blend of a styrene block polymer (SEBS) or a coextruded film of a polyurethane elastomer and a polyolefin elastomer is desirable. These polyolefin elastomers are characterized by low resin costs, easy melt-extrusion molding, and industrially very low cost materials. The bonding with the base material described later is also extremely good in bonding by thermocompression bonding, ultrasonic bonding or the like.
Importantly, these polyolefin-based elastomers are extremely difficult to use in a single film. That is, the melting point is low, so-called self-adhesion easily occurs due to the properties of the elastomer. Even if a single film is formed and a roll-shaped film is obtained, self-adhesion easily occurs at room temperature and stable unwinding is performed. It is extremely difficult. If this is possible, forming the sheet,
When winding, it is necessary to store, transport, and store the product at a low temperature of 30 ° C or less, and it is extremely difficult to use a single film, so it is considered difficult to use it for consumer products. I have been.

However, it has been found that by using a composite with a nonwoven fabric as in the present invention, these handling problems can be solved and an elastic composite with extremely excellent performance can be obtained. It is. The elastic body used in the present invention does not need elasticity in the sheet direction in which the polymer is easily oriented, but only has to have elasticity in the lateral direction. In this sense, the merits in production are further emphasized.

The performance of the substrate used in the present invention is as follows.
First, the material must have a high elongation in the CD direction. So-called anisotropy in MD and CD directions, ie, MD
A nonwoven fabric having a small elongation in the direction and excellent in directional stability, and a large elongation in the CD direction and easy to deform is desirable.

FIG. 1 shows the relationship between the elongation direction of the nonwoven fabric substrate and the C
The state extended in the D direction is shown. FIG. 2 is a model diagram showing a strength and elongation curve of a substrate which is desirable in the present invention.

Table 1 shows typical examples of the nonwoven fabric.

[0016]

[Table 1]

In Table 1, those indicated by numbers C and D are as follows:
It is a nonwoven fabric relatively oriented in the MD direction. A non-woven fabric formed by joining parallel card webs with a high-pressure water flow,
The nonwoven fabric obtained by weaving filaments and tows has the above-mentioned properties and can be used as the base material of the present invention. On the other hand, nonwoven fabrics having high randomness with little difference in MD and CD directions, for example, nonwoven fabrics such as spunbonded nonwoven fabrics to be melt-spun and nonwoven fabrics formed by cross-wrapper webs, have a stable CD direction. Not fit.

In particular, among the nonwoven fabrics described above, a nonwoven fabric obtained by a hydroentanglement method, which is a nonwoven fabric having high elongation and high strength and having high toughness, is suitable. In particular, the required elongation of the CD is at least 100% or more (2 times), preferably 150% (2.5 times) or more. As raw material fibers of the nonwoven fabric, PE, PP, PE which are preferably hydrophobic fibers having low wettability and low irritation to the skin and having safety.
A 1.5d to 3d synthetic fiber staple such as T is desirable.

The state of connection between the base material and the elastic body, which is the second important requirement, will be described in detail. Figure 3 shows the base material and the elastic body
As shown in the perspective view of FIG. 4 and the cross-sectional view of FIG. 4, the elastic body and the base material are continuously connected (A portion) in the MD direction of the sheet, and discontinuity is caused in the CD direction of the sheet. It is necessary to be combined (B). The connecting portion A is a joint between the base material and the elastic body. This portion is a fixing portion between the base material and the elastic body, and at the same time, the strength of the elastic body is reinforced by the base material. In the non-bonded portion B, it is necessary that the base material and the elastic body are not bonded, or that the B portion is in a weaker bonding state than the A portion even if the bonding is performed. Part B is a part that is extended by an extension operation described later, and part A needs to be in a stable binding state so as not to be separated by extension, but part B must be in a state that does not hinder extensibility as much as possible. is necessary.

As for the joining method, it is also possible to carry out the joining treatment in the form of a strand with an adhesive having excellent binding properties between the base material and the elastic body. Is advantageous. The most preferable method is a method of completing the bonding with the nonwoven fabric during the manufacturing process of the elastic body. The method is, for example, as shown in the flowchart of FIG. At the time of film formation, a nonwoven fabric as a base material is united, and then passed through a grid roll. At that time, it is also effective to make the grid roll in a heated state. Next, the abundance ratio of A and B, and a desirable state, which will be wound into a product, will be described later. FIG. 6 is a conceptual diagram of this manufacturing apparatus.

A detailed description will be given of a third important requirement, that is, how a good elastic composite is developed by elongating the combined body of the elastic and the base material. The elastic performance of the elastic composite according to the present invention is determined by the degree of elongation of the elastic body and the base material. This principle will be described with reference to FIGS.
Here, if the extension limit point is defined as the extension just before reaching the elongation at break, if the extension limit of the elastic body is 200% and the extension limit of the nonwoven fabric as the base material is 100%, the elasticity is as shown in FIG. The composite cannot elongate more than 100% and the resulting elastic composite will have a stretch elasticity in the range of 100% or less.

If the stretch limit of the elastic body is 200% and the stretch limit of the nonwoven fabric as the base material is 250%, the elastic composite has 200% stretch elasticity as shown in FIG. Therefore, in order to obtain a more desirable elastic composite, it is clear how important the optimal selection of the elastic body and the base material and the elongation conditions are. FIG. 9 shows a model of the relationship between the physical properties of the elastic body, the physical properties of the base material, and the physical properties of the bonded composite and the extension limit point.

The degree of elongation generally used as an elastic body is in the range of 50% to 200% (1.5 to 3 times).
If it is less than 0%, the elongation is insufficient. On the other hand, there are many elastic bodies having a breaking elongation of 500% or more.
%, More preferably 250% or less.

The extension limit point of the elastic composite is determined by comparing the extension limit point of the base material and the extension limit point of the elastic body with the extension limit point having a lower numerical value. Therefore, in order to increase the elasticity of the elastic body as much as possible, it is necessary to take full advantage of the performance of the elastic body, and this is the reason why the extensibility of the substrate in the CD direction is increased. In the example of FIG.
5% is the limit capability of the elastic composite. However, if the degree of elongation is reduced, as shown in FIG. 10, if the elongation degree is low, the elongation elasticity is within 100% if the elongation is only 100%. If it can be stretched by 225%, it will have elasticity of 225% or less.

Fourth, in order to use the elastic composite according to the present invention obtained as described above more effectively with a waist elastic body, a crotch elastic body, etc. of a disposable diaper, what considerations are necessary? Will be described. In order to exhibit the expected effects, the effects of the elastic body and the base material must be synergistically enhanced by the compounding.

One of the important effects is the covering effect of the elastic body by the base material. The soft touch and safety of the nonwoven fabric can reduce chemical and physical irritation to the skin surface of the human body. The expected effect is that the elastic body is strengthened and stabilized by the presence of the joint due to the composite. However, as the number of joints (A) increases, the strength of the composite increases, but the elasticity of elasticity decreases. Therefore, as shown in FIG. 11, the numerical value of the connection portion (A) and the ratio of the connection portion (A) and the non-connection portion (B), that is, A / (A
+ B) × 100 (%) needs to be set appropriately. A needs a width of 0.5 m / m or more, preferably 1 m / m.
m to 10 m / m, and more preferably 2 m / m to 5 m / m. If it is 0.5 m / m or less, it is easy to cause cutting and separation. Further, the ratio represented by A / (A + B) × 100 (%) needs to be 50% or less, and if it exceeds 40% to 50%, the elasticity of the composite elastic body is remarkably reduced. Will do. It is also expected to be an effect that contributes to stabilization in processing.
The elastic body is easily affected by the tension in the process, and is very difficult to handle such as winding and unwinding. In particular, in the case of a polyolefin elastomer having a low melting point, self-adhesion tends to occur, and industrial handling is extremely difficult. However, all of these problems can be easily solved by forming a composite with a nonwoven fabric.

FIGS. 12 and 1 show the shape of the elastic composite.
3 is also possible, in which a base material is bonded to both sides, and a sandwich type is also possible. FIG. 12 shows a single film-like elastic member having base materials bonded to both sides, and FIG. The composite is obtained by overlapping the elastic member on the surface. These sandwich-like elastic composites also exhibit very good stretch elasticity.

This will be described below with reference to embodiments.

[0029]

【Example】

Example 1 As an elastic body, a polyolefin elastomer (a copolymer of EVA and synthetic rubber) PFB-75 manufactured by Nippon Yunika was used.
0 m / min. To obtain an elastic film of 40 g / m ² . This film had a breaking elongation MD at 25 ° C. of 180% and a CD of 580%. According to the results of the cycle test performed five times, when the content was within 250% in the CD direction, good elastic recovery was exhibited although there was application relaxation.
This film is connected to a take-up roll 2 of 1000 m
Created a book. Both winding rolls could be unwound immediately after winding. One was left overnight at room temperature of 35 ° C. The other was left overnight in a cold room at 20 ° C. 20 ° C
The film at room temperature could be unwound, but the film left at room temperature of 35 ° C. caused self-adhesion between the films, making unwinding impossible.

On the other hand, as a nonwoven fabric substrate, a.
Spunbond, b. Thermal bond, c. Water flow coupling,
d. We prepared four types of tow weaving. The physical properties of each nonwoven fabric are as shown in Table 1.

According to the process shown in the first step of FIG. 14, an elastomer film is first melt-extruded as an elastic member under exactly the same conditions as described above. Pressurization was performed at 0.5 kg / cm. The press roll was a Teflon / surface processing roll on the film side, and the chrome plating roll was on the nonwoven fabric side. After compression, a take-up roll was made. Immediately after winding, unwinding was possible. The roll was left overnight at room temperature of 35 ° C. In this case, although the unwinding load was slightly increased, stable unwinding was possible. The obtained pressed sheet shows a temporary bonding state between the nonwoven fabric and the elastic film, does not separate under normal conditions, and is joined to such an extent that it can be handled as an integrated sheet. It was about.

Table 2 shows the performance of the united product in the temporarily bonded state obtained by passing the four types of nonwoven fabric and the elastic member through the first step shown in FIG. 14 under the above conditions. That is, the union of the nonwoven fabric a and the nonwoven fabric b showed almost no elasticity.
Before the nonwoven fabric c and the nonwoven fabric d were broken, phase separation occurred in the two layers of the nonwoven fabric and the film from the elongation of about 100%.

[0033]

[Table 2]

On the other hand, as an experiment, in the case of nonwoven fabric c, a heating roll at 100 ° C. was prepared as a pressure roll, and the nonwoven fabric and the film were completely adhered when passed through while applying heat from the nonwoven fabric side, and phase separation was performed until breakage. Did not happen,
The elasticity of the elastic body has almost been lost.

Next, of the union obtained from the process of the first step, the nonwoven fabric c and the nonwoven fabric d are shown in FIG.
5 step 2 process. That is, FIG.
A roll (grid roll) cut fully in the circumferential direction as shown in (1) is heated to 100 ° C., a silicon rubber roll is combined with a lower portion, and a linear pressure is 0.5 kg / cm so that the nonwoven fabric is in contact with the heating roll side. At 30 m / min. As a result, a composite elastic body was obtained in which the groove portions were completely joined and the other portions were in a pseudo-adhesion state. The characteristics are shown on the right of Table 2. As can be seen from the results, the elastic composite obtained by grit processing the elastic film and the nonwoven fabrics c and d exhibited good stretch elasticity.

Example 2 A non-woven fabric C shown in Table 1 was prepared as a non-woven fabric substrate, and a lavaze resin manufactured by Tonen Chemical was used as an elastic member (EVAS).
The process shown in FIG. 5 is incorporated into the manufacturing process of the RR copolymer, and a rubbed film having a size of 35 μm is melt-extruded and combined with the nonwoven fabric and compressed. 2m / m width, 10m / m spacing between grit valleys, 1m / m deep diameter 20
A non-woven fabric and a crimped elastic member were passed at a rate of 30 ° C./min at 100 ° C. between a combination press of a chrome-plated grooved roll of 0 m / m and silicone rubber. The nonwoven fabric surface was brought into contact with the surface of the grid roll. The groove of the elastic composite thus obtained was completely adhered.
After the elastic composite was stretched 200% in the groove direction and the tension was relaxed, the film and nonwoven fabric remained bonded in the grit portion, but the film and nonwoven fabric were separated in the other portions, and the nonwoven fabric was pleated. An elastic composite having good stretchability was obtained. After the elastic composite was stretched to about 180% again, the film portion was bonded to the nonwoven fabric surface of the waist portion of a commercially available disposable diaper as shown in FIG. 17 to obtain a disposable diaper having an excellent elastic waist gather. Was.

FIG. 18 shows the cross-sectional structure of the joint.

[0038]

The present invention is an elastic composite which is particularly suitable for the waist and the crotch of a disposable diaper or the like, and has a high degree of expansion and stability and is gentle on the skin. , Can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory view of elongation of a nonwoven fabric suitable for a substrate of the present invention.

FIG. 2 is a model curve showing the relationship between strength and elongation of the substrate of the present invention.

FIG. 3 is a perspective view showing a bonded state between a base material and an elastic body in the present invention.

FIG. 4 is a cross-sectional view showing a bonded state between a base material and an elastic body according to the present invention.

FIG. 5 is a process chart showing the concept of the manufacturing process of the present invention.

FIG. 6 is a conceptual diagram of an apparatus suitable for the production method of the present invention.

FIG. 7 is an explanatory view showing that the elastic composite of the present invention exerts elasticity by elongation.

FIG. 8 is an explanatory view showing that the elastic composite of the present invention exerts elasticity by elongation.

FIG. 9 is a graph of physical properties and elongation limit points of the base material, the elastic body, and the composite material of the present invention.

FIG. 10 is an explanatory diagram of the extension limit of the elastic composite of the present invention.

FIG. 11 is an explanatory diagram of a relationship between a bonded portion and a non-bonded portion between the elastic body and the base material in the present invention.

FIG. 12 is an explanatory diagram of an example of the composite elastic body of the present invention.

FIG. 13 is an explanatory view of another example of the composite elastic body of the present invention.

FIG. 14 is an explanatory diagram of a first step in the embodiment of the present invention.

FIG. 15 is an explanatory diagram of a second step in the embodiment of the present invention.

FIG. 16 is an explanatory diagram of a heating roll used in the production method of the present invention.

FIG. 17 is an explanatory diagram of a diaper used in another embodiment of the present invention.

FIG. 18 is an explanatory diagram of a cross-sectional structure according to a second embodiment.

FIG. 19 is an explanatory diagram of an example of a conventional example.

FIG. 20 is an explanatory diagram of another example of the conventional example.

FIG. 21 is an explanatory diagram of another example of the conventional example.

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Claims (14)

(57) [Claims] 1. A sheet-like elastic body in a relaxed state and a sheet-like base material that is not stretched or has no folds, wherein the sheet-like base material is arranged in a longitudinal direction (MD).
From non-woven fabric with less extensibility than cross direction (CD)
And the elastic body is continuously bonded to the base material in the length direction (MD) of the sheet, and in the transverse direction (CD)
An elastic composite, wherein the elastic composite is bonded with a discontinuity, and the substrate has elongation in the CD direction but does not have elongation recovery. 2. The elastic composite according to claim 1, wherein the elastic body is a polyolefin elastomer having thermocompression bonding properties. 3. The elastic composite according to claim 1, wherein the base material is a nonwoven fabric mainly composed of synthetic fibers having thermocompression bonding properties. 4. The elastic composite according to claim 1, wherein the elastic body has a small extensibility in the longitudinal direction (MD) of the sheet, and a relative extensibility in the transverse direction (CD) is twice or more. 5. The elastic composite according to claim 1, wherein the base material has low extensibility in the longitudinal direction (MD) of the sheet, and has relatively twice or more extensibility in the transverse direction (CD). 6. The elastic composite according to claim 4, wherein the elongation in the CD direction is 100% or more. 7. The bonding state of the elastic body and the base material according to claim 1, wherein the bonding part A and the non-bonding part B in the MD direction have a strand shape, and A / (A + B) × 100 (%). An elastic composite that is between 5 and 40%. 8. The elastic composite according to claim 3, wherein the substrate is obtained by a hydroentanglement method. 9. A sheet-like elastic body relaxed state, it has the extensibility of the order of equivalent elastic bodies, it was lifting elongation recovery
Sheet-like base material, and has excellent lateral (MD) extensibility.
A sheet-shaped substrate made of a nonwoven fabric having less elongation in the direction (CD) is continuously bonded in the sheet length direction (MD) and discontinuously in the sheet transverse direction (CD). A method for producing an elastic composite, comprising: 10. A polyolefin elastomer having thermocompression bonding as a sheet-like elastic body is extruded in a molten state,
The method for producing an elastic composite according to claim 9, wherein after cooling, the elastic composite is pressure-bonded to the sheet-shaped substrate made of a nonwoven fabric, and further passed between rolls having grooves to form a strand-shaped strong pressure-bonded portion. 11. A sheet-like base material having a relaxed sheet-like elastic body and elongated folds , wherein
Length (MD) extensibility is less than lateral (CD) extensibility
The elastic body is continuously bonded to the sheet-like substrate in the sheet length direction (MD), and has a discontinuity in the transverse direction (CD). An elastic composite characterized by being bonded. 12. The elastic composite according to claim 11, wherein the relationship between the length (P) of the elastic member and the total length (Q) of the base material including the fold is Q / P ≧ 1.5. 13. The method of claim 12, before having pleats
An elastic composite in which the sheet-like base material is formed on both sides of an elastic body as a core material. 14. A sheet-like elastic body in a relaxed state, and a sheet-like base material having the same extensibility as the elastic body but having no elongation-recovery property, and having an elongation in the machine direction (MD). Is sideways
An elastic composite is formed by bonding a sheet-like substrate made of nonwoven fabric with less elongation in the direction (CD) continuously in the machine direction (MD) and discontinuous in the cross direction (CD). Formed, and then stretches the elastic composite to an elastic body up to the stretching limit within a range that does not cause cutting or breaking of the base material, causing permanent deformation to the base material, and then relaxing the stretching. A method for producing an elastic composite.