Production Paperboard

1 production

1.1 raw materials
1.2 pulping

1.2.1 bleaching


1.3 plies
1.4 coating

production

fibrous material turned pulp (paper)/pulp , bleaching of wood bleached, create 1 or more layers of board, can optionally coated better surface and/or improved visual appearance. pulp board produced on pulping machines can handle higher grammage , several plies.

raw materials

the above-mentioned fibrous material can either come fresh (virgin) sources (e.g. wood) or recycled waste paper. around 90% of virgin paper made wood pulp. today paperboard packaging in general, , products certified sustainable sources, receiving new attention, manufacturers dealing environmental, health, , regulatory issues renewable resources meet increasing demand. mandatory in many countries paper-based packaging manufactured wholly or partially recycled material.

raw materials include:

hardwood: c. 0.05 inches (1.3 mm) in length e.g. birch has short fibres. more difficult work with; however, provide higher tensile strength, lower tear , other strength properties. although fibres not long , strong in softwood, make stiffer product defined stifness tests. hardwood fibres fill sheet better , therefore make smoother paper more opaque , better printing. hardwood makes excellent corrugating medium.
softwood: c. 0.13 inches (3.3 mm) in length e.g. pine , spruce have typically long fibres , make superior paperboard in services strength important. softwood makes excellent linerboard.
recycled: used paper collected , sorted , mixed virgin fibres in order make new material. necessary recycled fibre loses strength when reused; added virgin fibres enhance strength. mixed waste paper not deinked (skipping deinking stage) paperboard manufacture , hence pulp may contain traces of inks, adhesives, , other residues give grey colour. products made of recycled board have less predictable composition , poorer functional properties virgin fibre-based boards. health risks have been associated using recycled material in direct food contact. swiss studies have shown recycled material can contain significant portions of mineral oil, may migrate packed foods. mineral oil levels of 19.4 mg/kg found in rice packed in recycled board.


others: possible use fibres of sugarcane bagasse, straw, hemp, cotton, flax, kenaf, abaca , other plant products

pulping

two principal methods extracting fibres sources are:

chemical pulping uses chemical solutions convert wood pulp, yielding around 30% less mechanical pulping; however, pulp made kraft process has superior strength
thermo mechanical pulp two-stage process results in high yield of wood fibres @ expense of strength.

bleaching

pulp used in manufacture of paperboard can bleached decrease colour , increase purity. virgin fibre pulp naturally brown in colour, because of presence of lignin. recycled paperboard may contain traces of inks, bonding agents , other residue colors grey. although bleaching not necessary end-uses, vital many graphical , packaging purposes. there various methods of bleaching, used according number of factors example, degree of colour change required, chemicals chosen , method of treatment. there 3 categories of bleaching methods:

bleaching delignification using chlorine gas, method has been largely replaced procedures gentler environment such use of oxygen replacement chlorine gas.
bleaching oxidation using chemicals such chlorine dioxide, hydrogen peroxide or sodium hypochlorite.
bleaching reduction using chemicals such sodium bisulphite.

plies

(1) single-ply vs. (2) multi-ply

multi-ply paperboard has higher creasing , folding performance single-ply result of layering different types of pulp single product. in cases same kind of pulp being used in several layers, each separate layer treated , shaped individually in order create highest possible quality.

coating

in order improve whiteness, smoothness , gloss of paperboard, 1 or more layers of coating applied. coated paper made of:

a pigment, china clay, calcium carbonate or titanium dioxide, combination of two
an adhesive or binder styrene-butadiene emulsions or starches , water.

additional components oba (optical brightening agents).