MOISTURE-PERMEABLE, MICROPOROUS LUXURY FOOD PACKAGING MATERIAL MADE OF NONWOVEN FABRIC

Abstract

The invention relates to moisture-permeable, microporous luxury food packaging material made of nonwoven fabric, consisting of a carded web of staple fibres and at least one thermoplastic binder. According to the invention the nonwoven fabric has a uniformly distributed perforation in the form of a plurality of holes, the fluctuation around the median value of the diameter of the holes being in the region of +/- 30%. In the method according to the invention the perforation is formed by creating holes by means of piercing the pre-bonded nonwoven fabric.

Claims

1. A moisture-permeable, microporous luxury food packaging material made of non-woven fabric, consisting of a carded web of staple fibres and at least one thermoplastic binder, characterized in that the non-woven fabric has a uniformly distributed perforation in the form of a plurality of holes, wherein the fluctuation around the median value of the diameter of the holes is in the range of +/- 30%.

2. The moisture-permeable, microporous luxury food packaging material according to claim 1, characterized in that the non-woven fabric is chemically strengthened, in particular by means of a polymer dispersion.

3. The moisture-permeable, microporous luxury food packaging material according to claim 1, characterized in that at least 99% of the equivalent diameters of the holes are in the range of +/- 30% of the median value.

4. The moisture-permeable, microporous luxury food packaging material according to claim 1, characterized in that the median of the equivalent diameter of the holes is in the range from 250 to 1000 .Math.m, preferably from 500 to 750 .Math.m.

5. The moisture-permeable, microporous luxury food packaging material according to claim 1, characterized in that the position of the fibres in the region of the holes has a reorientation.

6. The moisture-permeable, microporous luxury food packaging material according to claim 5, characterized in that the fibres have an orientation at the edge of the holes resulting in a funnel-shape to be formed.

7. The moisture-permeable, microporous luxury food packaging material according to claim 6, characterized in that the funnel-shape protrudes beyond the non-woven fabric surface.

8. The moisture-permeable, microporous luxury food packaging material according to claim 1, characterized in that the holes have a circular up to oval structure or the shape of a polygon.

9. The moisture-permeable, microporous luxury food packaging material according to claim 1, characterized in that the holes have a sharp contour that is essentially free from fibre ends or fibre tips.

10. The moisture-permeable, microporous luxury food packaging material according to claim 1, characterized in that the median of the equivalent diameters of the holes is adapted to the respective luxury food to be enclosed.

11. A method for producing a moisture-permeable, microporous luxury food packaging material made of non-woven fabric, the latter consisting of a carded web of staple fibres and at least one thermoplastic binder, according to claim 1, characterized in that the non-woven fabric strengthened in a manner known per se is subjected to a perforation treatment by means of piercing.

12. The method according to claim 11, characterized in that needles are used for the piercing process which displace the non-woven fabric fibres for forming the holes.

13. The method according to claim 12, characterized in that the needles are heated at least during the piercing process such that the thermoplastic binder at least partially softens at the contact points to the needle and adopts a deformable state, resulting in a hole formation having a sharp and reproducible contour during cooling down.

14. The method according to claim 13, characterized in that with the needles penetrating into the non-woven fabric, parts of the fibres are displaced along the direction of movement of the needles and reoriented.

15. The method according to claim 14, characterized in that the needles cause the fibres to be reorientated while forming a funnel-like structure, wherein the funnel forms from the exit point of the respective needle from the non-woven fabric to the surface side there.

16. The method according to claim 11, characterized in that the penetration density of the needles and thus the number of holes is selectable in the range from between 4 to 50 holes per cm.sup.2.

Description

[0052] Shown are in:

[0053] FIG. 1 an exemplary embodiment in the form of a view onto a non-woven fabric with holes created by needles, as a microscopically made enlarged image;

[0054] FIG. 2 an identified and quantitatively evaluated hole arrangement in analogy to the image section according to FIG. 1; and

[0055] FIG. 3 an exemplary frequency distribution of the equivalent diameter of the perforations.

[0056] In the exemplary embodiment, a parallel-laid carded web of 100% viscose fibres in a fineness of 1.7 dtex is chemically strengthened in a first step by means of a dispersion of a thermoplastic polyacrylate having a softening point of 115° C. The thus created binder non-woven fabric has a surface weight of 26 g/m.sup.2.

[0057] In the second step, the non-woven fabric is pierced and perforated by means of hot needles.

[0058] The needles have a temperature of ≥130° C. so that the thermoplastic polyacrylate at the piercing points becomes deformable.

[0059] The selected exemplary piercing density is at 4.65 per cm.sup.2. The mechanical properties such as, for example, the maximum tensile force and maximum tensile force elongation surprisingly remain unchanged relative to the initial material.

[0060] For determining the hole size, microscopic images with a 100-fold enlargement were made at several points.

[0061] A subsequent evaluation by means of an image processing software firstly converts the image into grey scales. By means of a threshold value, the automatic recognition of the position and size of the holes, as well as the calculation of the surface area thereof is performed subsequently by the software used.

[0062] From the thus obtained surface area, the equivalent diameter is in each case calculated. The evaluation of the measured values resulted in a median of the equivalent diameter of 536 .Math.m.

[0063] 99% of the measured values are in a range of +/- 30% around the median, thus in the range from 375 to 697 .Math.m, as is illustrated by FIG. 3.

[0064] 96% of the measured values are in a range of +/- 20% around the median, thus in the range from 429 to 643 .Math.m.

[0065] The frequency distribution of the equivalent diameters illustrated in FIG. 3 comprises the evaluation of several areas as illustrated in FIGS. 1 and 2.