ANTISLIP, HEAT SEALABLE PLASTIC FLEXIBLE PACKAGING BAG AND METHOD AND APPARATUS FOR ITS PRODUCTION

Abstract

An antislip, heat sealable plastic packaging bag, is formed from an antislip flexible packaging material whose wall has an average surface weight of at most 500 g/m.sup.2. The packaging material includes a multiplicity of randomly distributed, separate antislip protrusions of a first substance. The protrusion height is between 50 micrometres and 10000 micrometres, with an average of top-plan-view aspect ratios of the antislip protrusions being at most 5.0. Some antislip protrusions have a hidden surface portion being a portion of a free surface of the antislip protrusion, which the antislip protrusion covers from a viewer in a top plan view of the wall. The first substance is a thermoplastic polymer, and the wall's outer surface is of a substance at least somewhat different from the first substance. It is an important feature that the first substance has a melt mass flow rate of at least 0.6 g/10 min. An apparatus, for producing the packaging material, includes a film blowing die head, a cooling air ring, and a particle dispersing unit therebetween, for dispersing polymer particles on the bubble neck at a place in, or closely under, an expanding area where the bubble has a divergent shape.

Claims

1. An antislip, heat sealable plastic packaging bag, the packaging bag comprising an antislip flexible packaging material, the packaging material comprising a heat sealable plastic flexible wall having an outer surface, the wall having an average surface weight of at most 500 g/m.sup.2, in at least a part, a roughened part, of the wall the packaging material further comprising a multiplicity of separate antislip protrusions, of a first substance, randomly distributed on the outer surface and projecting from the outer surface to a protrusion height of between 50 micrometres and 10000 micrometres, with an average of top-plan-view aspect ratios of the multiplicity of the antislip protrusions being at least 1.0 and at most 5.0, at least some of the antislip protrusions having a hidden surface portion being a portion of a free surface of the antislip protrusion which the antislip protrusion covers from a viewer in a top plan view of the wall taken from above the antislip protrusions, the multiplicity of the antislip protrusions looking toward an outside of the packaging bag, the first substance being a thermoplastic polymer, and the outer surface being of a second substance different in some property from the first substance, and the first substance has a melt mass flow rate of at least 0.6 g/10 min. determined at 190 C. under a load of 2.16 kg in accordance with ISO 1133-1 and the packaging material includes plastic woven fabric.

2. The packaging bag according to claim 1, wherein the first substance has a melt mass flow rate of at least 0.7 g/10 min, at least 0.8 g/10 min., at least 0.9 g/10 min., or at least 1.0 g/10 min, determined at 190 C. under a load of 2.16 kg in accordance with ISO 1133-1.

3. The packaging bag according to claim 1, wherein the first substance has a melt mass flow rate of at most 300 g/10 min. determined at 190 C. under a load of 2.16 kg in accordance with ISO 1133-1.

4. The packaging bag according to claim 1, wherein the antislip protrusions occupy at most 60% of an area of the antislip packaging material in a top plan view of the wall roughened part taken from above the antislip protrusions.

5. The packaging bag according to claim 1, wherein the antislip protrusions are of random top-plan-view sizes.

6. The packaging bag according to claim 1, wherein the antislip protrusions are fixed to the wall.

7. The packaging bag according to claim 6, wherein the antislip protrusions are formed of particles fixed to the wall.

8. The packaging bag according to claim 7, wherein the antislip protrusions are formed of granules fused to the wall.

9. The packaging bag according to claim 1, wherein at least some antislip protrusions each have a volume of from 0.0000335 mm.sup.3 to 524 mm.sup.3.

10. The packaging bag according to claim 1, wherein the antislip protrusions having the hidden surface portion have at least one undercut and include at least one area immediately above the undercut, the antislip protrusion being so dimensioned as to form a separation between the at least one area and the wall outer surface which is greater than 12 micrometres.

11. (canceled)

12. The packaging bag according to claim 1, wherein the packaging bag is large enough to accommodate at least 4.5 kilograms of contents in it.

13. A method for providing an antislip, heat sealable plastic packaging bag, the method including: providing particles of a first substance and of a suitable size and shape, the first substance being a thermoplastic polymer, providing a film blowing machine having an annular die gap and an external bubble-cooling unit above the die gap and a haul-off unit above the external bubble-cooling unit, providing a blown film bubble consisting of a plastic wall emerging from the die gap and proceeding toward the haul-off unit, the plastic wall having an outer surface of a second substance, the second substance different in some property from the first substance and suitable to fuse with the first substance, providing a neck of the bubble, in which the wall is suitably hot and plastic-state, between the die gap and a freezing line of the bubble, the freezing line being a part of the bubble where the wall is made to reach a final thickness of the wall, selecting an area, the landing area, of the neck between the die gap and the external bubble-cooling unit, where the outer surface is tacky, in the landing area bringing and sticking, with a random distribution, the particles to the outer surface of at least a part, the roughened part, of the wall, using a heat content of the suitably hot wall for starting a fusing process in the proceeding wall for fusing the stuck particles to the outer surface, ending the fusing process, by cooling, at a desired extent of the fusing for forming a suitably strong fixation between the outer surface and the particles fused to it, freezing the wall by cooling, for providing a heat sealable, plastic, flexible frozen wall, providing in the frozen wall an average surface weight of at most 500 g/m.sup.2, thereby forming, from the particles fused to the wall, a multiplicity of separate antislip protrusions of the first substance randomly distributed on the outer surface of the frozen wall and projecting from the outer surface to a protrusion height of between 50 micrometres and 10000 micrometres with an average of top-plan-view aspect ratios of the multiplicity of the antislip protrusions being at least 1.0 and at most 5.0, providing at least some of the antislip protrusions with a hidden surface portion being a portion of a free surface of the antislip protrusion which the antislip protrusion covers from a viewer in a top plan view of the wall taken from above the antislip protrusions, the frozen wall together with the antislip protrusions projecting from its outer surface constituting an antislip flexible packaging material, forming from the antislip flexible packaging material a packaging bag with the multiplicity of the antislip protrusions looking toward an outside of the packaging bag, and selecting the first substance to have a melt mass flow rate of at least 0.6 g/10 min. determined at 190 C. under a load of 2.16 kg in accordance with ISO 1133-1.

14. The method according to claim 13, including selecting the first substance to have a melt mass flow rate of at least 0.7 g/10 min., at least 0.8 g/10 min., at least 0.9 g/10 min., or at least 1.0 g/10 min, determined at 190 C. under a load of 2.16 kg in accordance with ISO 1133-1.

15. The method according to claim 13, including selecting the first substance to have a melt mass flow rate of at most 300 g/10 min. determined at 190 C. under a load of 2.16 kg in accordance with ISO 1133-1.

16. The method according to claim 13, including forming the antislip protrusions occupying at most 60% of an area of the antislip packaging material in a top plan view of the wall roughened part taken from above the antislip protrusions.

17. The method according to claim 13, including forming the antislip protrusions of random top-plan-view sizes.

18. The method according to claim 13, including forming at least some antislip protrusions each having a volume of from 0.0000335 mm.sup.3 to 524 mm.sup.3.

19. The method according to claim 13, including the antislip protrusions having the hidden surface portion having at least one undercut and including at least one area immediately above the undercut, the antislip protrusion being so dimensioned as to form a separation between the at least one area and the wall outer surface which is greater than 12 micrometres.

20. The method according to claim 13, including forming the packaging bag large enough to accommodate at least 4.5 kilograms of contents in it.

21. The method according to claim 13, including providing an outer diameter of the die gap, providing an expanding area of the neck in which the proceeding wall, carrying the particles stuck thereto, is exposed to a horizontal expansion, the expanding area provided with a shape in which planes tangent to the outer surface close angles, the angles of expansion, of at least 2.5 degrees with the vertical, and providing a first vertical distance, in a side view of the bubble, between the landing area and the expanding area which first vertical distance is either zero or at most equals 2.0 times the die gap outer diameter.

22. The method according to claim 13, wherein each of at least some of the multiplicity of separate antislip protrusions is formed from a single particle.

23. An apparatus for roughening a blown film, the apparatus having a sub-unit for a film blowing machine, the film blowing machine for producing a blown film plastic wall for a packaging material, the apparatus including: a film blowing die head with an annular die gap, and an external cooling air ring above the die head, the die gap having an outer diameter, and the air ring having a bottom, the die gap and the air ring together suitable to define a path of an outer surface of the plastic wall, the path having a shape of a bubble extending from the die gap up through the air ring, and at least above the air ring bottom the bubble having one or more expanding areas in which the wall is exposed to a horizontal expansion and planes tangent to the path close angles, the angles of expansion, of at least 2.5 degrees with the vertical, the sub-unit further including a particle dispersing unit defining a landing area of the path by being suitable for dispersing in the landing area, with a random distribution, thermoplastic polymer particles on the outer surface between the die gap and the air ring, and at least one of: a.) a second vertical distance, in a side view of the apparatus, between the landing area and the air ring bottom being either zero or at most 2.0 times the die gap outer diameter, and b.) at least one of the one or more expanding areas including at least a part of the landing area.

24. The apparatus according to claim 23, wherein an end, proximate to the outer surface, of the particle dispersing unit is suitable to be closer to the outer surface than 1.0 mm.

25. The apparatus according to claim 24, wherein the particle dispersing unit proximate end is suitable to be cooled and to have a contact with the outer surface.

26. The apparatus according to claim 25, wherein the particle dispersing unit includes a feeder for conveying the particles toward the outer surface and the particle dispersing unit proximate end is constituted by an end, proximate to the outer surface, of the feeder.

27. The apparatus according to claim 23, wherein the air ring is either a dual-lip type air ring or an air ring having more than two cooling-air-orifices.

28. The apparatus according to claim 23, wherein the apparatus further includes a wind shield between a level of the air ring bottom and a top level of at least a part of the landing area for an at least partial protecting of the at least a part of the landing area from a wind of the air ring.

29. The apparatus according to claim 28, wherein the wind shield is an active wind shield including a wind shield chamber having a top and a bottom and an opening proximate and toward the wall outer surface, for conducting the wind at least partly through the proximate opening and through the wind shield chamber for at least partly protecting the landing area under the wind shield chamber bottom from the wind.

30. The apparatus according to claim 23, wherein a third vertical distance, in a side view of the apparatus, between the landing area and the die gap is either zero or at most 70 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0102] FIG. 1. is a schematic side view of a film blowing machine (not in scale).

[0103] FIG. 2. is a film blowing die head in top plan view.

[0104] FIG. 3a. is a schematic vertical section of an apparatus for roughening a blown film (not in scale).

[0105] FIG. 3b. is a schematic side view of an apparatus for roughening a blown film, with certain parts not shown for easier reading (not in scale).

[0106] FIG. 4. is a top plan view of a particle dispersing unit.

[0107] FIG. 5a. is a perspective view of a packaging bag.

[0108] FIG. 5b. is a perspective view of a packaging bag.

[0109] FIG. 6. is a side view of an antislip protrusion.

[0110] FIG. 7. is a top plan view of a roughened part.

[0111] FIG. 8. is a schematic side view of an apparatus for roughening a blown film, with certain portions shown in vertical section (not in scale).

DETAILED DESCRIPTION

Examples

Example 1: a Comparative Example (Welding Tests)

[0112] We made comparative welding tests with antislip flexible packaging materials. In each welding sample, two identical specimens of a selected roughened (or, in the reference case: plane, not roughened) polyethylene film type were overlapped, both of them looking upwards with their roughened sides, and were welded together with an impulse sealer. The impulse sealer was of a type Unifol 32 (made by company Unifol kft, Hungary) and included two similar flat heating wires (of a width of 2.4 mm) facing each other, providing a double-sided welding of the samples, simulating a package forming welding operation. In each sample, the welding was made starting with a uniformly cold welding apparatus, applying uniform pressures and uniform heating currents in each case. To each film type we found out, by trial and error, the shortest welding time necessary for a good-quality welding of the given film type. That way, each film type we characterised with a time value, the time found necessary for suitably welding the film type. The polyethylene base film wall was identical in all of the cases, the roughened films were roughened with high density polyethylene (HDPE) powder particles welded to one side of the base film, the roughening particles were approximately of the same sizes and used in approximately the same quantity (g/m.sup.2) in each case and only the polymer of the roughening particles differed essentially, from case to case, in the melt mass flow rate (MFR). The film types we prepared and used were as follows: [0113] Film type 1.: Base film, without roughening: monoextruded, 100 micrometres thick, LDPE+LLDPE blend. [0114] Film type 2.: Base film+roughening. Data of the roughening particles: Abifor's Abifor 1300/20 HDPE powder, size: 80-200 micrometres, melting range (Kofler method): 126-130 C., melt mass flow rate: 20 g/10 min (2.16 kg, 190 C.). [0115] Film type 3.: Base film+roughening. Data of the roughening particles: Rowak's Rowalit N100-3 HDPE powder, size: 100-220 micrometres, melting range (DSC): 130-135 C., melt mass flow rate: 4 g/10 min (2.16 kg, 190 C.). [0116] Film type 4.: Base film+roughening. Data of the roughening particles: Solvay's Eltex B 4002 HDPE powder, size: 100-200 micrometres, main melting point: 132 C., melt mass flow rate: 0.25 g/10 min (2.16 kg, 190 C.).

[0117] The test results:

TABLE-US-00001 Welding Welding time time in % Film type 1. (Base film) 2.0 sec 100% Film type 2. (Roughening MFR: 20 g/10 min) 2.2 sec 110% Film type 3. (Roughening MFR: 4 g/10 min) 2.4 sec 120% Film type 4. (Roughening MFR: 0.25 g/10 min) 3.2 sec 160%

[0118] This provides an exact illustration to our general experience that low fractional-melt-mass-flow-rate (-MFR) powders change the welding operating point to the greatest extent relative to that of the non-roughened film, and the higher the melt mass flow rate of the roughening particles is, the nearer the welding operating point, to that of the non-roughened film, is.

Example 2: Apparatus, Method and Product

[0119] See the Figures, especially FIGS. 1-5a, 6-7. Note that in FIG. 3b the wind shield 49 and the air ring 1 are not shown, for an easier understanding of the figure. This example is based on real life test runs. The film blowing machine 31 that we use is monoextrusion-type, with a single extruder 27 and internal bubble cooling (not shown), for producing a blown film plastic wall 45 for a packaging material 35. The invention apparatus, constituting a sub-unit in the film blowing machine 31, includes a film blowing die head 24 with an annular die gap 22, of an outer diameter 23 of 90 mm, and above the die head 24, as an external bubble cooling unit 26, an external cooling air ring 1 of an inner diameter 5 of 125 mm. The air ring 1 is of a dual-lip type, i.e., it has two cooling-air-orifices 62. The die gap 22 and the air ring 1 together define a path 39 of an outer surface 46 of the plastic wall 45, the path 39 having a shape of a bubble 19 extending from the die gap 22 up through the central opening 4 of the air ring 1. The bubble 19 has an expanding area 25 both under and above the air ring bottom 2. In the most divergent part of the path 39 under the air ring bottom 2 the planes 40 tangent to the path 39 close an angle of expansion 6 of about 12 degrees with the vertical. The greatest angle of expansion 6 which is believed to be about 25 mm above the air ring bottom 2 is estimated to be about 35 degrees, closed with the vertical. The sub-unit further includes two, uniform, oppositely placed and uniformly operated particle-dispersing units 38 each of which is a linear vibrational feeder 28, having a hopper 56 for storing the particles 36 and having a floor 29, for conveying the particles 36 on its floor 29 toward the outer surface 46 and the particle dispersing unit-proximate end 37 is constituted by the internally water-cooled feeder-proximate end 30 and its shape, in a top plan view, matches the arched surface of the outer surface 46. The cooled, arched feeder-proximate end 30 is suitable to have a constant contact, of a positive but very low force, with the hot outer surface 46. The particle-dispersing unit 38 defines the landing area 34 of the path 39 by being suitable for dispersing in the landing area 34, with a random distribution, thermoplastic polymer particles 36 on the outer surface 46 between the die gap 22 and the air ring 1. Essentially, in this example, the landing area 34 is the line of the outer surface 46 where the outer surface 46 contacts the floor 29 of the feeder 28. The landing area 34 is in the mentioned expanding area 25 under the air ring bottom 2. The second vertical distance 41, in a side view of the apparatus, between the landing area 34 and the air ring bottom 2 is 30 mm. The third vertical distance 43, in a side view of the apparatus, between the landing area 34 and the die gap 22 is 15 mm. The apparatus further includes a wind shield 49 between the air ring bottom level 3 and the top level 44 of the landing area 34/feeder floor 29 for protecting the landing area 34 from a wind 48 of the air ring 1. The wind shield 49 is an active wind shield 49 including a wind shield chamber 50 having a top 54 and a bottom 51 and a height of about 16 mm. It is built up from two similar though not fully uniform flat metal plates, one above the other, with circular holes, for the bubble 19, in them, whose diameters are 108 mm (in the wind shield chamber top 54) and 101 mm (in the wind shield chamber bottom 51), respectively. The wind shield chamber 50 thus has an annular opening 53 proximate and toward the wall outer surface 46, for conducting the wind 48 at least partly through the proximate opening 53 and through the wind shield chamber 50 for at least partly protecting the landing area 34 under the wind shield chamber bottom 51 from the wind 48. A suction unit (not shown) is attached to the wind shield chamber outer perimeter 52 for conducting wind 48 through the proximate opening 53 and through the wind shield chamber 50, between its top 54 and bottom 51, away from the bubble 19. The film blowing machine 31 further includes a haul-off unit 33, and could include an in-line bag making unit 17 at the end of the line.

[0120] To provide the particles 36, we provide a ground powder from company Rowak, of type Rowalit N100-6 of a particle size of 160-300 micrometres. The material of the powder, i.e., the first substance, is high density polyethylene of a density between 940 and 970 kg/m.sup.3, melting range (DSC): 128-130 C., vicat softening point (ISO 306): 126 C., melt mass flow rate (ISO 1133-1, 190 C./2.16 kg): 6 g/10 minutes. The shape of the particles 36 is random and roughly spherical, as is known to the skilled person in respect of a good-quality polymer powder, having good flow properties, made with pellet-grinding for scatter coater application. We feed the extruder 27 with a polymer, the second substance, a blend of 40% linear low density polyethylene, 20% medium density polyethylene and 40% low density polyethylene. The second substance has a density of 922 kg/m.sup.3 and a melt mass flow rate (ISO 1133-1, 190 C./2.16 kg) of 0.73 g/10 minutes. The first substance and the second substance are suitable to fuse with each other. The heated extruder 27 is operated to press the melt out through the heated die gap 22 and that is how a plastic wall 45 emerging from the die gap 22 is provided. The haul-off unit 33 is operated, without alternation, to pull up the wall 45 and a blown film bubble 19, consisting of the proceeding wall 45, is formed, whose volume is adjusted with blowing a suitable quantity of inflating air into the bubble 19. As the wall 45 proceeds toward the haul-off unit 33, it is exposed to a cooling and a forming. With adjusting the extruder 27 speed and the haul-off unit 33 speed a final bubble 19 perimeter of 980 mm is set and in the frozen wall 45 a surface weight of 92.2 g/m.sup.2, is provided. The outer surface 46 of the wall 45 consists of the second substance. The air ring 1 is fed with cooling air from a fan (not shown). For example by adjusting the volume and temperature of the cooling air and the air ring 1 lip settings, it is possible to adjust the shape of the bubble 19 thus mutually defined by the die gap 22 and the air ring 1. The part of the bubble 19 between the die gap 22 and the bubble freezing line 20, where the wall 45 reaches its final thickness, i.e., the bubble neck 21, is kept so hot, from the heat of the extruder 27 and of the die head 24, as keeps the wall 45 in it in a plastic state. The top of the neck 21 is configured to be above the air ring 1 in this example. We adjust a suitable airflow from the lower cooling-air-orifice 62 of the air ring 1 and thereby use a venturi force to keep the neck 21 close to the air ring 1 in the air ring central opening 4. Simultaneously, we keep the air ring bottom 2 at a distance of about 45 mm from the die gap 22, i.e., relatively near to the die gap 22, as compared to the background art. By combining it with the fact that the air ring inner diameter 5 is selected significantly greater than the die gap outer diameter 23, we provide a shape of the neck 21 having a single expanding area 25 from the die gap 22 to above the air ring 1, in which expanding area 25 the neck 21 is made to expand to its final perimeter. The feeder 28 is operated and is used for bringing and sticking, with a random distribution, the particles 36 to the hot outer surface 46 in the landing area 34, where the outer surface 46 is tacky. The landing area 34 is selected in the expanding area 25 and therefore the first vertical distance 32, in a side view of the bubble 19, between the landing area 34 and the expanding area 25 is provided to be zero. The internal water-cooling (not shown) of the feeder proximate end 30 is operated and thereby the feeder 28 is prevented from getting as hot as to possibly soften or stick the particles 36 carried, despite the fact that it is kept in constant contact with the hot and tacky outer surface 46. A cooling water temperature of about 25 C. is suitable. Warmer water could lead to a blocking of the particle 36 flow due to heat and much colder water could lead to moisture condensation possibly leading to a blocking of the particle 36 flow due to wet particles 36. A width of the feeder floor 29, used for the bringing and sticking of the particles 36, is selected to be 90 mm and thereby a strip-shaped roughened part 47, of a width of 320 mm, of the wall 45 is defined. When the particle 36 reaches the hot outer surface 46 in the landing area 34, the heat content of the hot wall 45 is used for starting the fusing process in which the particle 36 is fused to the wall 45. As the wall 45 is kept proceeding by the haul-off unit 33, the particle 36 is given time, spent on the hot wall 45, for the fusing. The fusing process is brought to an end by cooling, at a desired extent of the fusing for forming a suitably strong fixation between the outer surface 46 and the particle 36 fused to it. It is essentially the air ring 1 that is used to provide the mentioned cooling. The configuration detailed above provides a good fixation for the mentioned particles 36. We can further adjust, or fine-tune, the fixation for example with adjusting the die head 24 temperature or melt temperature and/or the extruder 27 throughput. The given arrangement can be used to produce the wall 45, without regard to the roughening, at melt temperatures of between about 170 C. and about 220 C. With regard to the roughening, we got the best result with a melt temperature of about 215 C. and an extruder 27 throughput of about 60 kg/h. Further useful rules that we found are that if a given powder grade is welded too weakly (or too strongly) then using a smaller (or larger) powder size, of the same powder polymer, can in itself solve the problem and further that if a given configuration results in a too weak (or too strong) particle 36-welding then adjusting the air ring 1 to provide from the upper cooling-air-orifice 62 a thinner (or thicker) cooling air layer (with the same orientation, air speed and air temperature) can in itself solve the problem. All these measures proved for us suitable for effectively controlling the fusing process (with powder polymers of a melt mass flow rate from 0.25 to 20 g/10 minutes and with wall 45 surface weights of from 23 g/m.sup.2 to 140 g/m.sup.2) without essentially compromising the film blowing process. Further, in the example process, the suction unit (not shown), is used for providing a suitably constant pressure value at the wind shield chamber outer perimeter 52. Such a pressure value is selected (empirically) for the purpose, at which the wind 48, blown back from the air ring central opening 4 beside the bubble 19 does not reach the landing area 34, but enters the wind shield chamber proximate opening 53, instead. After the wall 45 proceeds up from the air ring 1, it gains its final dimensions and the fixation of the particles 36 is also finalised. Thereby, from the particles 36 fused to the wall 45, we form a multiplicity of separate antislip protrusions 7 of the first substance randomly distributed on the outer surface 46 of the frozen wall 45 and projecting from the outer surface 46 to a typical protrusion height 11 of between about 130 micrometres and 270 micrometres with an average of top-plan-view aspect ratios of the multiplicity of the antislip protrusions 7 being at most 1.5. Each separate antislip protrusion 7 (except very few) is formed from a single powder particle 36. The tube-form frozen wall 45 together with the antislip protrusions 7 projecting from its outer surface 46 constitutes an antislip flexible packaging material 35, as it is forwarded downstream the haul-off unit 33. The tube-form packaging material 35 could be lead into the in-line bag making unit 17 at the end of the line for forming from the antislip flexible packaging material 35 packaging bags 16 with the multiplicity of the antislip protrusions 7 looking to an outside 18 of the packaging bag 16.

[0121] The example antislip, heat sealable plastic packaging bag 16, made with the apparatus and method described above, has the following characteristics. The packaging bag 16 is formed from an antislip flexible packaging material 35. The packaging material 35 comprises a heat sealable polyethylene flexible wall 45 having an outer surface 46, the wall 45 having an average surface weight of 92.2 g/m.sup.2. The wall 45, including its outer surface 46, is of the second substance, a blend of 40% linear low density polyethylene, 20% medium density polyethylene and 40% low density polyethylene. The second substance has a density of 922 kg/m.sup.3 and a melt mass flow rate (ISO 1133-1, 190 C./2.16 kg) of 0.73 g/10 minutes. The bag 16 is a pillow bag 16 formed of a seamless tube extending from a bag bottom 57 to a bag mouth 58. The bag 16 has a cross welded bottom 57. The bag 16 has a bag height 59, from bottom 57 to mouth 58, of 900 mm. The bag 16 has a layflat bag width 60 of 490 mm. The bag 16 is large enough to accommodate 25 kilograms of individually-quick-frozen vegetables in it. The bag's 16 wall 45 has a roughened part 47 in the middle of the bag's 16 front side, in the form of a roughened strip, from the bag bottom 57 to the bag mouth 58, with a strip width 61 of 320 mm. Further, the bag's 16 wall 45 has a similar roughened part 47 in the middle of the bag's 16 back side. In the wall's roughened parts 47 the packaging material 35 comprises a multiplicity of separate antislip protrusions 7 of a first substance. The antislip protrusions 7 are formed of particles 36 fixed, namely fused, to the wall 45. The multiplicity of the antislip protrusions 7 look to the outside 18 of the packaging bag 16. The first substance is high density polyethylene of a density between 940 and 970 kg/m.sup.3, melting range (DSC): 128-130 C., vicat softening point (ISO 306): 126 C., melt mass flow rate (ISO 1133-1, 190 C./2.16 kg): 6 g/10 minutes. The antislip protrusions 7 are randomly distributed on the wall outer surface 46 and projecting from the outer surface 46 to a typical protrusion height 11 of between about 130 micrometres and 270 micrometres with an average of top-plan-view aspect ratios of the multiplicity of the antislip protrusions 7 being at most 1.5. The top-plan-view aspect ratio of an antislip protrusion 7 means a ratio of the antislip protrusion greatest extent 10 to antislip protrusion smallest extent 13 of the antislip protrusion 7 in a top plan view of the wall roughened part 47 taken from above the antislip protrusions 7 (see FIG. 7.). The antislip protrusions 7 are of random top-plan-view sizes 14 typically of between 160 and 300 micrometres. The antislip protrusions 7 have a typical volume of from about 0.0021447 mm.sup.3 to about 0.0141372 mm.sup.3 per antislip protrusion 7. There are about 60 antislip protrusions 7 per cm.sup.2 within the roughened parts 47. The multiplicity of the antislip protrusions 7 occupy about 2.5% of the area of the antislip packaging material 35 in a top plan view of the wall roughened part 47 taken from above the antislip protrusions 7. As concerning a shape of the antislip protrusions 7, a vast majority of them typically have a hidden surface portion 12 being a portion of the free surface of the antislip protrusion 7 which the antislip protrusion 7 covers from a viewer in a top plan view of the wall 45 taken from above the antislip protrusions 7. A vast majority of the antislip protrusions 7 typically have at least one undercut 15 and include at least one area 8 immediately above the undercut 15, the antislip protrusion 7 being so dimensioned as to form a separation 42 between the at least one area 8 and the wall outer surface 46 which, in average, is at least about 50 to 100 micrometres.

Example 3: Apparatus and Method

[0122] See the Figures, especially FIG. 8. (not in scale!). This example apparatus differs from the apparatus of Example 2 in that here the landing area 34 is not in an expanding area 25 but in a non-divergent, cylindrical part of the bubble 19. The second vertical distance 41, in a side view of the apparatus, between the (top of the) landing area 34 and the air ring bottom 2 is 0.3 times the die gap outer diameter 23. Further, the particle dispersing unit 38 includes a blowing feeder 28 and a contacting unit 63. The feeder 28 is suitable for carrying particles 36 to the path 19 of the wall outer surface 46 and for filling particles 36 onto a top surface 64 of the contacting unit 63. The contacting unit 63 has an internal fluid cooling and has an end proximate to the outer surface 46 which constitutes the particle dispersing unit proximate end 37 and is suitable to be in a constant contact with the outer surface 46 of the proceeding wall 45 and has a top surface 64 slanting toward the path 39, the top surface 64 suitable to deliver the particles 36, filled onto the top surface 64, to the wall outer surface 46.

[0123] In operation, the bubble 19 is adjusted to have a cylindrical shape and a tacky hot wall outer surface 46 adjacent the contacting unit 63. The feeder 28 is operated and thereby particles 36 are sprayed from the feeder 28 to the outer surface 46 and other particles 36 are filled onto the slanting top surface 64 of the contacting unit 63, which is used to conduct, like a chute, the particles 36 to the hot and tacky outer surface 46. These particles 36 gathering on the top surface 64 adjacently the tacky outer surface 46 are stuck to the outer surface 46 and made to proceed therewith further. From that moment on, they are exposed to the fusing process as explained above.

Example 4: Packaging Bag 16

[0124] See the Figures, especially FIG. 5b. An antislip, heat sealable plastic packaging bag 16 can be made with providing a polyolefin woven fabric 55 tube, e.g., of a fabric surface weight of 100 g/m.sup.2, and laminating both main sides of the layflat tube with roughened film strips corresponding to the roughened part 47 of the wall 45 of the packaging material 35 of Example 2. The laminating could happen e.g., with a PUR reactive adhesive or extrusion lamination or with any other suitable means. The multiplicity of the antislip protrusions 7 look to the outside 18 of the packaging bag 16.

Example 5: Method for Producing a Packaging Bag 16

[0125] An antislip, heat sealable plastic packaging bag 16 can be made with providing particles 36 of a powder of high density polyethylene of a melt mass flow rate (ISO 1133-1, 190 C./2.16 kg) of 20 g/10 minutes in a size of 125 to 180 micrometres and with providing a polypropylene woven fabric 55 tube (either coated or non-coated type) and with fixing the particles 36 onto the outer surface 46 of the wall 45 of woven fabric 55 with an adhesive glue. Technical details of such a coating of a polyolefin wall outer surface 46 with such particles 36 we worked out in a test series in which we used a polyethylene film wall outer surface 46 instead of a polypropylene woven fabric 55 wall outer surface 46 but we think our results are also valid for this example case. We used a plastic wall outer surface 46 corona treated once, having a treatment of at least 42 dyn/cm (measured with a 42-dyn test ink). For roughening the outer surface 46, we used high density polyethylene powder screened to a size-fraction of 125 to 180 micrometres. We applied about 160 roughening particles 36 per cm.sup.2. We adhered the particles 36 to the outer surface 46. Namely, we applied a lacquer to the outer surface 46 and sprayed the powder particles 36 into the tacky lacquer then crosslinked the lacquer with ultraviolet light irradiation. The particles 36 were blown through a corona discharge treating station while they were sprayed onto the outer surface 46 in order to provide a good bond between the particles 36 and the lacquer. We recorded the following manufacturing data. Lacquer type used: SunChemical IU 10050 screen-printing UV lacquer (Spanish make). Lacquer viscosity we measured to be 73 seconds at 20 C. with DIN cup 4 (much thicker than water). Lacquer quantity applied to the outer surface (cured): 9.57 g/m.sup.2, corresponding to 8.7 micrometres lacquer thickness (without powder in it). The result was that in many antislip protrusions 7 the antislip protrusion has a hidden surface portion 12 covered by the antislip protrusion 7 from a viewer in a top plan view.