Mark J. Kirwan Paper and Paperboard Packaging Technology

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FIBRE DRUMS

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7.6 Waste management

Fibre drums can either be reused, the component materials recovered and recycled,

or disposed of in energy-to-waste systems. Internationally agreed identification

code data and a recyling logo can be applied to drum sidewalls and bases which

indicate their composition (SEFFI, 2004). This information is used as a guide to

recycling. Fibre drum manufacturers can provide information and support on all

environmental and waste management issues. This can include advice with respect

to drum recycling companies and equipment to assist recycling.

7.7 Summary of the advantages of fibre drums

•

Bespoke designed pack, matching customers’ specific requirements

•

Cost effective compared with metal alternatives

•

Available globally in a wide range of diameters, heights and styles

•

The fibre is naturally renewable and both the fibre and the other components

are easily recoverable and recyclable

•

Fibre drums can incorporate linings and barriers, increasing their performance

and range of applications

•

Approved for the packing and transportation of hazardous solids

•

Used predominantly by the chemical, pharmaceutical and food industries.

7.8 Specifications and standards

A British Standard for fibreboard drums, BS 1596:1992, provides a minimum

specification, a series of definitions and the normal size/capacity range. BS 1133-7.4:

1989 Packaging Code describing paper and board wrappers and containers

including fibreboard drums is also a current standard.

European standard BS EN 12710:2000 covers the construction requirements of

fibre drums in the 15–250l range.

Hazardous products which are allowed to be packed in fibre drums are listed in

the UN Orange Book, with its proper title being, Recommendations on the Transport

of Dangerous Goods: Model Regulations.

Reference

Hanlon, J.F., Kelsey, R.J. & Forcino, H.E., Handbook of Package Engineering, Third edition, p. 201.

SEFFI, 2004, Identification codes for drum sidewall and base materials and components (Website).

Websites

SEFFI (European Fibre Drum Association), www.seffi.org.

Industrial Packaging Association at www.theipa.co.uk.

Fibrestar Drums, www.fibrestar.co.uk.

8 Multiwall paper sacks

The Environmental and Technical Association for the Paper Sack

Industry

8.1 Introduction

Multiwall paper sacks are concentric tubes of 2–6 layers (or plies) of paper with

a choice in the type of end closure. Many different designs of paper sack will be

described in this chapter. The designs differ mainly in respect of whether the sack

is to be filled through an open mouth or a valve, which in turn depends on the

product and the volume to be handled. Valve designs are closed automatically as

a consequence of their design and there are various methods, including sewing and

tying with wire, for closing the open mouth paper sack.

Other key features of the specification are the number of plies and the types of

paper and other materials used by way of paper coatings, impregnations, laminations

or whether separate liners are incorporated depending on the product, protection and

performance required.

Paper sacks were developed in the late 1800s and became a major type of

packaging from the 1920s. Their traditional uses from the early days were building

materials, chiefly cement, foods such as flour, dried milk, sugar and potatoes,

animal feed, chemicals and fertilisers. Today, it is claimed that over 2000 different

products are packed in paper sacks in the USA. Advantages for paper sacks

include easy bulk palletisation, stacking and handling and the fact that plain paper

sacks, as for instance are used for cement, are permeable to air allowing the products

to ‘breathe’.

Paper sacks have been used to pack up to 50 kg of products but this weight has

been reduced to ease handling and meet health and safety requirements. Furthermore

with a wide use of paper sacks in the retail sector today, where there are customer

convenience needs, the weights range from 25 down to 10 and 5 kg. Products

packed for the retail trade include cement and similar materials in DIY, together

with gardening products, pet food and pet litter. The retail trade also requires

a higher quality of printing and features such as carrying handles.

Over four billion paper sacks are used per annum (pa) in Europe and over three

billion pa in the USA. The typical end-use range is shown in Table 8.1.

8.2 Sack designs

There is a wide range of sack designs from which users may choose to meet

their requirements. When making the choice, account will need to be taken of the

Paper and Paperboard Packaging Technology

Edited by Mark J. Kirwan

MULTIWALL PAPER SACKS

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properties of the product to be packaged, the requirement of the filling, closing

and distribution systems and the needs of the final user.

8.2.1 Types of sacks

The first basic division of paper sack types is open mouth and valved designs.

Each of these may be subdivided into pasted or sewn closure types and into further

subdivisions by the sack body being either gusseted or flat. Further minor variations

can also arise from the inclusion of certain other design features.

Not all the possible combinations of design features are practicable due to the

restrictions in manufacturing machinery or sack design geometry.

A schematic range of multiwall sack designs are shown in Figures 8.1 and 8.2.

Each design will now be discussed briefly outlining the important features, advantages

and limitations, etc.

8.2.1.1 Open mouth sacks

There are four basic open-mouth sack designs depending on the type of closure

types, namely sewn, pasted, pinched and double-folded closures (Fig. 8.1).

Open mouth, sewn, flat sack

This is the simplest form of multiwall paper sack (Fig. 8.1a). It may be directly

compared with the traditional jute and cotton sacks that have been used for centuries

to pack granular and powdered products. The name ‘pillow sack’ is sometimes

used to describe this design, which has an inherent disadvantage in that, when filled,

corners tend to jut out. These can give rise to difficulties after palletising, by snagging

against objects to cause tearing and leakage.

There are certain considerations that may dictate the use of these sacks. For

instance, it is possible to include a layflat seamless polyethylene film tube as the

Table 8.1 End-uses of paper sacks (in Euro)

Source: Eurosac.

European end-uses for 2001

Product end-use Quantity used in 2001

(in million units)

Building materials 2204 50.1

Mineral products 158 3.6

Food products 704 16.0

Animal feed 496 11.3

Chemicals and fertilisers 448 10.2

Refuse sacks 88 2.0

Seeds 104 2.4

Miscellaneous 195 4.4

Total 4397 100.0

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innermost ply. Such a sack may be heat-sealed within the line of the sewing to

give an hermetic closure. These layflat film tubes may also be made longer than the

paper plies by including a Z-fold section in the tube length. This enables it to be

pulled out, filled and closed as a separate operation prior to the closure of the

paper plies.

(a) (b) (c)

(d) (e)

(g)

(f)

Figure 8.1 A schematic range of open mouth multiwall sack designs: (a) sewn, flat; (b) sewn,

gusseted; (c) pasted, flat; (d) pinch closed, flat; (e) pinch closed, gusseted; (f) pasted, double-folded,

flat; and (g) pasted, double-folded, gusseted.

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Open mouth, sewn, gusseted sack

By having gussets inserted at the sides of the sack, the user is ensured of a rectangular

block shape after filling (Fig. 8.1b). The choice of face width, gusset depth and

sack length will be governed by factors mainly associated with the volume of contents

and palletising requirements.

Because of the gusset folds, it is not possible to include an internal polyethylene

layflat film liner contiguous with the paper plies. In certain circumstances, it

is feasible to include an edge-folded layflat tube of polyethylene film, which is

inserted into one sidefold of each gusset. A Z-fold may also be included in this

construction, as with the open mouth, sewn, flat sack.

The most popular gusset sizes are 75mm, 100mm, 125 mm and 200mm. Larger

gussets than these are possible but the filled shape of the sack becomes less

rectangular.

Open mouth, pasted, flat sack

The pasted bottom closure (Fig. 8.1c) will automatically give filled sacks a rectangular

end, and a sewn closure at the top will allow them to be either butted or overlapped

when stacked onto pallets. A layflat polyethylene film liner can be incorporated

into this sack during manufacture, which may be made longer than the sack plies

by the inclusion of a Z-fold.

The open mouth, pasted, flat sack may be designed as a baler bag. Here the sack

is a preformed wrapper for packing single items, quantities of small containers, trays

of eggs, etc. Baler bags can be made with bottom widths up to approximately 350mm.

The top of a baler bag is generally folded down and sealed by either tape or adhesive.

Open mouth, pinch closed, flat sack

The pinch closed sack (Fig. 8.1d) is one with an envelope-type closure, as the

design uses an extended flap at each end, which is folded over and glued down.

This allows a fully sealed barrier sack to be made using a thermoplastic-coated

aluminium foil to paper laminate as the innermost ply. This may be sealed at the

side seam and at each closure to encapsulate the contents.

Pre-applied hotmelt adhesive may be employed on the open mouth flap of the

sack for the user to close by re-activating with hot air.

Performance figures for pinch closed sacks compared with the same size of

sewn sacks show the design makes a stronger sack, which effectively means that

they may be of lighter construction to give equal performance.

If a barrier ply is present next to the sack contents, it is generally important for

the sack closure to include an effective seal of the barrier ply. With pinch closed

sacks, a heat seal may be included above the fold line of the flap so that, after

closure, no stress is put on the heat seal by the contents. By using a layflat tube of

polyethylene film for the innermost ply, which is heat sealed at both closures, the

product can be very effectively encapsulated.

There is a variation to this design in which the open mouth flap is trimmed

away during the final stage of manufacture to allow the user to make a normal sewn

closure. A tear string may be incorporated into the closed flap, during manufacture,

as an easy-opening device.

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Open mouth, pinch closed, gusseted sack

The inclusion of gussets overcomes the problem of sharp corners and the filled sack

can assume an almost perfect rectangular block shape (Fig. 8.1e). As with sewn

sacks, the gussets prevent the incorporation of a contiguous polyethylene film tube

but a side-folded layflat film tube inserted into one side of each gusset is possible.

The design variation, in which the top flap is trimmed off to allow closure by sewing,

is also available, as is the easy-opening tear string.

Open mouth, pasted, double folded, flat sack

A pasted bottom closure may be achieved on a flush-cut multiwall paper tube by

simply folding the bottom edge over twice and gluing (Fig. 8.1f). To ensure a strong

closure, and to resist any tendency for the bottom to unfold, the outer ply is slit on

the edges to form a flap which is adhered to the body of the sack above the folding.

These sacks are also known as ‘double fold’ and ‘roll bottom’ sacks. The user closure

is normally made by sewing. A layflat polyethylene film may be incorporated as the

innermost ply at the tubing stage of manufacture.

Open mouth, pasted, double folded, gusseted sack

The presence of gussets results in a rectangular shape after filling, and the packer/

filler closure is normally made by sewing (Fig. 8.1g). A contiguous layflat tube cannot

be incorporated into the construction but it is possible to include an edge-folded

layflat polyethylene film tube into one side of each gusset.

8.2.1.2 Valved sacks

A valved sack is closed at both ends during manufacture and includes an opening

for filling purposes in one corner. Valved sack designs may be divided in a similar

manner to open mouth sacks; first into sewn and pasted types and then into the

gusseted and flat varieties (Fig. 8.2). There is a further subdivision of the valved,

pasted, flat sacks into those made from either stepped-end or flush-cut multiwall

tubes.

Valved, sewn, flat sack

The valve of this sack can be inserted only by a complex manual operation during

manufacture and the filled sack has the disadvantage of protruding corners (Fig. 8.2a).

The valved, pasted, flat sack has superseded it almost totally.

Valved, sewn, gusseted sack

This design of sack also requires complex manual corner folding for the valve

insertion stage of manufacture (Fig. 8.2b). Although the presence of the gussets

overcomes the protruding corners problem, the demand for this type of sack is

negligible and it has largely been replaced by valved, pasted sack designs.

Valved, pasted, flush-cut, flat sack

In the manufacture of paper sacks, the paper is drawn from the reels and formed

into a flattened tube which is then separated into the required length needed for the

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sacks. With flush-cut sacks, the preformed tube is cut into lengths with a guillotine

or chop knife (Fig. 8.2c).

The use of a flush-cut tube is the simplest way to achieve a folded and pasted

closure. Sacks made in this way are usually given an additional paper-capping strip

on each end to strengthen the closure and resist sifting. Alternatively, longitudinal

slits may be made in the ends, down to the diagonal fold, to form rectangular flaps

for pasting down.

Valved, pasted, stepped-end, flat sack

The multi-ply tubes for stepped-end sacks are made in similar manner to those for

flush-cut sacks, but the individual plies are perforated before the tube is formed

(Fig. 8.2d). The tube is separated into sack lengths by pulling apart the perforations.

By this means the ply ends may be stepped relative to each other, and by perforating

in a different pattern for each ply, it is possible to substantially increase the area

that is available for folding in and pasting. The stepping also allows the individual

ends of the plies to be pasted and incorporated directly into the closure. Stepped-end

(a) (b) (c)

(d) (e)

Figure 8.2 A schematic range of valved multiwall sack designs: (a) sewn, flat; (b) sewn, gusseted;

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sacks do not generally require caps and may be made from multiwall tubes of two

to six plies.

Valved, pasted and sewn, flat sack

This design of sack enables a pasted valve to be used for filling and allows the

final customer easier access to contents through the sewing line (Fig. 8.2e). Carrying

handles may also be included with the sewing line.

8.2.2 Valve design

Valves used in paper sacks are held closed after filling, either by the pressure

of the contents of the sack or by the folding down of an external sleeve. These

are termed ‘internal’ and ‘external’ valves respectively and either design may be

incorporated into sewn or pasted types of sacks. There are many possible combin-

ations of the various valve design features, especially with pasted valves, and it is

not possible to illustrate all of these in this guide. (Users are advised to consult

paper sack suppliers for more specific information.)

8.2.2.1 Valve designs for sewn sacks

Sewn sack valves are made by folding in one corner of the sack prior to sewing the

closure. An extended corner or ‘notch’ may be employed in the multi-ply tube to

allow a greater length of paper to be folded in to form the valve.

The simplest valve is made without the use of any additional paper, but generally

a folded paper patch is inserted and sewn in as the internal or external component.

Figure 8.3 shows the three basic sewn valves.

8.2.2.2 Valve designs for pasted sacks

The simplest type of filling valve is for one corner of a capped flush-cut pasted

sack to be left unglued. Such a design is weak and a strengthening patch of paper

is usually included under the corner fold.

(a) (b) (c)

Figure 8.3 Valve designs for sewn sacks: (a) plain sewn valve; (b) internal sewn valve; and

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An improved type of valve is achieved by the inclusion of a flattened tube of

paper or plastic film into one corner to form either an internal or an external valve.

In addition to the tubular component of the valve, it is possible to insert other

paper or plastic components to produce a whole variety of designs to improve the

efficiency of the valve or to tailor the valve design to the filling requirements.

It is not possible to illustrate all the combinations of design features, but Figure 8.4

shows the six basic types of valve design used in pasted sacks.

(a) (b)

(c)

(d)

Figure 8.4 Valve designs for pasted sacks: (a) patch valve; (b) internal sleeve valve; (c) external

sleeve valve; (d) small valve in larger bottom; (e) polyethylene film valve; and (f) polyethylene tubular

sleeve valve.

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Patch valve

A single ply of folded paper is positioned in the valve opening to give strength and

rigidity (Fig. 8.4a).

Internal sleeve valve

A tubular paper sleeve is positioned in the valve opening and protruding into the

sack (Fig. 8.4b).

External sleeve valve

This type comprises a tubular sleeve extending out of the valve opening, often

with an internal pocket formed by a folded paper patch (Fig. 8.4c). This sleeve can

be supplied with a thumb notch to facilitate easy opening.

Small valve in larger bottom

This is similar in formation to the external sleeve valve but includes a preformed

valve sleeve smaller than the bottom width (Fig. 8.4d).

Polyethylene film valve

This valve is comprised of two sheets, one paper and one polyethylene, generally

slightly offset from each other (Fig. 8.4e). They are inserted together, folded and

positioned in the sack aperture to form an internal valve.

(e)

(f)

Figure 8.4 (Continued).