Absorbent disposable products for taking up urine, feces or menstrual blood have developed greatly since they came into more general use during the 1960s and 1970s. As they are disposable products, it is necessary that they can be manufactured and sold at a very low price. At the same time, it is important that the products function well and reliably. Good fit and comfort are also important characteristics. The first disposable nappies included products having two parts, outer pants made of plastic, which were intended to be reused, and a rectangular absorbent insert which was disposable. The absorbent material in these inserts initially included cellulose tissue. Later, better absorption materials such as fluff pulp, which is made of cellulose, were developed. The fit and comfort of these early nappies were poor. The products were unwieldy and uncomfortable for the wearer. Towards the end of the 1970s, the first complete disposable nappies arrived, that is to say nappies in which the absorption cores were integrated with a liquidtight outer layer. The absorption materials had developed and improved, which resulted in the possibility of the absorption cores being adapted better to the anatomy of the wearer. Hourglass-shaped absorption cores with a narrower crotch portion between the two end portions are now the predominant shape in the industry. The trend has also been towards increasingly thin products, which has been made possible by the inclusion of what are known as superabsorbent materials in the absorption body. There are many reasons why thinner and even smaller absorption bodies are desirable. A thinner, smaller absorption body is more comfortable and more discreet, which is especially important for adult incontinent wearers. A reduction in volume may also be very important financially because the product then requires less storage space and is easier to transport and takes up less shelf space in shops. This is important for the financial management of the shops, and if a manufacturer can produce products requiring less space in the shops than the products of the competitors, this affords a not inconsiderable competitive advantage. Moreover, there is increased pressure from authorities, in particular as far as disposable articles are concerned, to use as little material as possible for the purpose of reducing the burden on the environment.
The smaller the absorption bodies become, the more important it becomes that the absorption bodies come to lie in the correct place directly in front of the genitals of the wearer and remain in place during use even when the wearer is very active and moves a great deal. The demands of consumers for discretion, comfort and reliable functioning are also increasingly exacting. Requirements for the absorption body to come to lie correctly when put on and then be retained in the correct place have therefore increased the need for good fixing of the product on the body and the need for very good adaptability to the body when the wearer moves, at the same time as requirements have increased for the product to always come to lie in the correct place when the article is put on the wearer. This has led to the development of what are known as nappy pants, which have elastic portions for improved fit and comfort and increased flexibility during movements of the wearer compared with conventional absorbent products.
An early patent publication relating to nappy pants of the disposable type is GB 2 112 267-A. However, this publication from 1983 discloses primitive nappy pants which did not become a commercial product. Not until the 1990s did absorbent products of pants-like shape and construction become a major commercial product. Pants-like products now exist in the form of nappies for infants and nappies for adults and to some extent sanitary towel pants for absorption of menstrual fluid. Previously commercially available nappy pants have been designed in principle like conventional nappies with a front portion and a rear portion and also an intermediate crotch portion, the front and rear portions being interconnected by a side seam between each leg opening and the waist opening of the pants. The nappy pants have been produced by plane nappy-like pieces being produced in a continuous web, the individual nappy pants being formed by nappy-like blanks being folded double and provided with said side seams to form nappy pants. These side seams project laterally from the finished product and are undesirable because they project and interfere with the fit of garments worn over the top. On account of their shape, they are visible through garments worn on top of the nappy pants and fitting closely around the body. They can also snag in clothing and even cause tears in nylon tights. Such projecting side seams can also chafe and give rise to pressure sores on wearers who spend a lot of time lying on their side.
WO 00/61049 has proposed improved nappy pants, in which the projecting sides seams have been eliminated. In this construction, the side seams have been eliminated by virtue of elastic side portions extending continuously in one piece from the front portion of the nappy pants to their rear portion on both sides of the nappy pants. However, the nappy pants according to WO 00/61049 have a number of disadvantages. The nappy pants according to said publication have what is referred to as a chassis, which extends over the entire nappy pants and forms the front portion, the crotch portion and the rear portion and is most reminiscent of a conventional nappy, and also said elastic side panels which each overlap the chassis at both the front and the rear on the nappy pants. These overlapping portions do not serve any actual purpose on the finished product and are in fact undesirable because a lot of material is wasted, that is to say they are used for no other purpose than joining together. The overlapping, joined-together portions are less of a nuisance and less uncomfortable for the wearer than the projecting side seams on previously known nappy pants. Owing to their unfavourable positioning, particularly at the rear, the overlapping portions can still give rise to a risk of chafing and back sores on wearers who spend a lot of time lying on their back. Another disadvantage of the nappy pants according to WO 00/61049 is that said chassis is relatively large and, as this portion is relatively rigid at least in comparison with the elastic side portions of the nappy pants, the nappy pants as a whole are not as adaptable to the body of the wearer but there is a risk that the nappy pants will be displaced from their optimum position in relation to the body when a wearer lies in bed and moves. In particular, the rigid rear portion of the nappy pants can be displaced and pull both the crotch portion and the front portion from their optimum positions directly in front of the genitals of the wearer because the front and crotch portion are essentially rigidly joined together in one piece with the rear portion.