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/m2. 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.