TECHNICAL FIELD QF THE INVENTION

The invention relates to a three-dimensionally moulded fibrous pulp packaging product. More particularly, the invention relates to such packaging comprising a new class of fillers. Furthermore, the invention relates to a method of manufacturing such packaging product and the use of the new class of filers.

BACKGROUND QF THE INVENTION

Fibrous three-dimensional packaging products are used for protection and/or pres- entation of various products, such as food, e.g. eggs, ready-cooked dishes, vegetable etc. and electronic devices, e.g. mobile phones, electric shavers, etc. Such packaging products are appreciated for example due to one or more of shock absorbing behaviour, tear strength, compressive strength, affordability and/or environmental profile.

However, until now such products have been limited with respect to the weight of the goods to be protected by the packaging product. This is mainly due to relatively large bulk dimensions, which would be required to achieve acceptable protective properties for heavy goods^ Manufacturing of such packaging products with large wall thickness requires long processing times (e.g. suction time and drying time) and obviously consumption of large amounts of fibrous pulp. This is not acceptable financially or environmentally. Furthermore, when manufacturing of thicker products by the traditional method, the products tend to bend during drying, are likely to develop surface irregularities and are prone to uneven drying.

Hence, there is a need for a strong packaging product and an acceptable manufacturing method for such a packaging product.

The use of inorganic filler material for manufacturing of packaging products is known e.g. from WO 96/05254, which discloses a method of manufacturing an article comprising passive inorganic filler particles being glued together by a starch-based binder. The process involves gelating the starch-based binder at least partially prior to or during shaping the article plastically.

A traditional inorganic filler facilitates dewatering and increases the dry content matter during the moulding process, possibly by providing routes of water escape at the particle surfaces and/or by being arranged in areas not accessible by the rela- tively long fibres. Furthermore, addition of an inorganic filler tends to decrease the average cost per weight by being more affordable than fibres and binder. However, such a filler is inactive in the sense that it does not provide any strength to the structure and in fact typically decreases the strength of the article by taking up space which would otherwise have been occupied by fibres or binder

In WO 94/18384 is provided a method of plastically shaping a cellulose-containing fibre product wherein a hydrocolloid material is added to a fibrous pulp and activated by mechanical heavy mixing so that the hydrocolloid material facilitates formation of a homogeneous high-viscosity paste. This leads to a high solid content of the pulp suitable for shaping by extrusion. It is describe that the hydrocolloid material may be a native starch,

WO 01/32987 concerns a method manufacturing a moulded fibre article, wherein an additive comprises a starch, starch derivative or starch degradation product, which starch is modified chemically with at least one polymeric component. The modified starch/polymeric-additive is added in a low amount to the pulp mass prior to moulding of the moulded fibre article.

OBJECTS OF THE INVENTION

It is an object of the invention to provide an improved three-dimensionally moulded packaging product obtainable by moulding of a fibrous pulp-

DISCLOSURE OF THE INVENTION

The above and other objects of the invention are realised by a three-dimensionally moulded packaging product, which packaging product is obtainable by moulding of a fibrous puip. For the active filler to act as not just a common binder after activation, but also as a filler during moulding prior to activation, a minimum amount of active filler must be present in the product. Experimental results have shown that the packaging product should comprise at least 5% by dry weight activated active filler. If the content is too low, then the filler effect of the active filler will be insignificant and the active filler would essentially only act as a binder upon activation. Hence, higher contents, e.g about 7% by dry weight activated active filler, are more advantageous. If the content of active filler is too high, then the shock-absorbing properties is reduced, and hence the content of active filler is preferably between about 5 - 50 % by dry weight activated active filler and more preferably 7 - 25 % by dry weight activated active filler In a highly preferred embodiment, the content of the activated active filler is about 9 - 20 % by dry weight as this allows for a superior balancing of the properties with high dewatering, very high strength and fine shock- absorbing properties. In another preferred embodiment, the content of the active filler is preferably between about 8 - 50 % by dry weight activated active filler and more preferably 9 - 25 % by dry weight activated active filler. In another highly preferred embodiment, the content of the activated active filler is about 10 - 20 % by dry weight.

By active filler is herein meant a filler material that acts as a traditional filler during moulding and - upon activation during drying - acts as a binder. Furthermore, by terms like "activated active filler comprising unmodified starch" should be understood that the active filler originates at least partially from unmodified starch and that the active filler has been activated for example by heating In other words, in such connections the term unmodified starch does not relate to the actual condition of the starch but to the state of the starch when introduced into the pulp for making the moulded packaging product.

By three-dimensional is herein meant that the variation in height of the member is more than 2.5 mm, typically and preferably, as this allows for more safe securing of members held by a product according to the invention; the variation in height is more than 5 mm, such as more than 10 mm.

By packaging product is herein meant a board having cavities or compartments for receiving one or more members to be held, for example gripped by or contained in the product,

It is preferred that the active filler comprises starch, as starch sources are activated above temperatures typically utilised during preparation of the fibrous pulp used for the manufacturing of the moulded packaging products. The starch is mostly or completely unmodified.

In a particularly preferred embodiment of the invention, the active filler comprises unmodified starch. By unmodified starch is herein meant that the starch has not been chemically modified. Unmodified starch is favoured by a lower price, as less treatment of the starch source is required. Furthermore, it has surprisingly been found that unmodified starch, and in particularly unmodified starch based on wheat flour, exhibits superior properties as compared to wheat flour with added ascorbic acid and wheat flour that has been treated to facilitate suspension in aqueous solutions.

The packaging products according to the invention may comprise some modified starch. In a preferred embodiment, the packaging product comprises smaller amounts of modified starch, such as less than 2% modified starch by dry weight. However, it is preferred to have less than about 1% modified starch by dry weight or even more preferred less than 0.1 % modified starch by dry weight. The lower con- tents of modified starch are favoured by the cost of modified starch compared to unmodified starch and - when the starch has been modified by addition of e.g. ascorbic acid - by the lower content of nutrients, which potentially may lead to unde- sired biological growth (see discussion below). Such smaller amounts of modified

starch will not act as an active filler in the sense of the present invention but rather will act purely as a binder or as a modifier, such as a surfactant.

The active filler is preferably activable by heating. By activation of the active filler is meant that the active filler changes physically (e.g. structurally) or chemically (e.g. by curing or reaction) from being a passive filler to being a binder. The activation temperature should preferably be substantially above the temperature of the processing of the pulp prior to the moulding process, such as at least 1O ⁰ C above the pulp processing temperature, as this ensures that the activation of the active filler is delayed until after the moulding. It is hence preferred that the active filler is activable at a temperature above about 60 ⁰ C. Since, particularly with regards to starch-based active fillers, water appears to play a significant role in the activation process, it is more preferred that the active filler is selected from a starch source, which starch is activable at a temperature between about 70°C - 110 ⁰ C. The most advantageous temperature range for the active filler to be activated has been found to be at a temperature between about 75 ⁰ C - 9O ⁰ C as this allows for a safety margin to the pulp processing temperature and fast activation upon drying in the oven and hence rapid complete activation of the active filler.

Particularly, it is advantageous that the active filler is activated during the passage of the packaging product through the oven, as this allows for a through control of the activation process and typically ensures complete activation of the active filler.

Alternatively, the active filler may be activabie by other means than heat, such as radiation (UV-radiation, X-ray or another short-waved electromagnetic radiation source) or chemically (via a retarder, a catalyst or a second part of a multi-component system).

Experimental work has shown that suitable results may be obtained for active fillers comprising starch selected from the group consisting of potato starch, tapioca starch, rice starch, sago starch, corn starch and grain starch, such as enriched or native flour including e.g. wholemeal, bolted rye flour, rye flour, wheat flour low grade, wheat starch or high gluten wheat. In other words, the starch source may

preferably be selected from that group or other native starch sources. These starch sources are readily available, affordable and result in a pulp and packaging product having adequate properties.

It was, however, found that the best mode of operation and packaging products were obtained when the main starch source was unmodified wheat flour Particularly good results were obtained when the activated active filler was unmodified or native wheat flour, as the strength reduction realised due to the filler-effect was more than compensated for by the binder-effect of the activated active filler.

Another aspect of the invention relates to a fibrous pulp for manufacturing a packaging product according to the invention. The pulp comprises 5 to 50% by dry weight of non-activated active filler, 50 to 95% by dry weight of fibrous material and 0 to 20% by dry weight of additives, In preferred embodiments, the pulp comprises 7 - 25 % by dry weight non-activated active filler, more preferably 9 - 20 % by dry weight non-activated active filler. In general, most of the active filler is retained in the moulded packaging product and only a small amount of the active filler follows the water into recycling. Therefore, the content of active filler in the moulded packaging product corresponds substantially to the content of active filler in the pulp.

The fibrous material may e.g. be cellulose-based fibres, such as virgin or recycled fibres. Advantageously, the fibrous material is a combination of various fibres, including natural fibres of various sources such as recycled paper and chemically and/or mechanically treated cellulosic fibres. The additives may e.g. be passive fill- ers, surfactants, binders, fungicides or other biologically active substances, lubricants, pigment or dye, etc.

The pulp according to this aspect of the invention should advantageously be ready for moulding and hence have a fibrous content of about 0.3 to 3% by weight of the total pulp. Experimental work has shown that fibrous contents of between about 0.5 to 2% by weight of the total pulp are advantageous, since the pulp according to the invention and having this fibrous content may be substituted for at traditional pulp utilised for moulding of three-dimensionally moulded packaging products by the

traditional wet process, for example as described in WO 00/46447 without material changes to the apparatus or processing parameters of the manufacturing process being required. The use of active filler is particularly advantageous for the traditional wet process, as a relatively large amount of water needs to be transported through the moulded packaging product during the moulding process.

The active filler is advantageously selected according to the same criteria as discussed herein above with regard to the activated filler in the packaging product according to the invention. In other words, in a preferred embodiment, the active filler is activable at a temperature above 60 ^α C. More advantageously, the active filler is activable at a temperature of between about 70 ⁰ C - 110 ⁰ C, and more preferably the active filler is activable between about 75 ⁰ C - 90 ⁰ C. However, it is material that the active filler in the pulp according to the invention is substantially non-activated until after the moulding of the packaging product

Furthermore, the active filler may advantageously comprise starch which is selected from the group consisting of potato starch, tapioca starch, rice starch, sago starch, corn starch and grain starch, such as enriched or native flour including wholemeal, bolted rye flour, rye flour, wheat flour low grade, wheat starch or high gluten wheat.

Particularly, it has been found that a pulp wherein the active filler substantially consists of wheat flour, and particularly unmodified wheat flour is highly advantageous for the properties of the packaging product to be moulded from the pulp according to the invention.

Yet another aspect of the invention relates to a method of manufacturing a three- dimensionally moulded packaging product, the method comprising the steps of providing a pulp, such as a pulp according to another aspect of the present invention, inserting a moulding surface of a moulding screen into the pulp and providing a vac- uum on a suction surface of the moulding screen so that a packaging product is formed on the moulding surface. The moulding is typically prepared on a rotational moulding apparatus, such as the one described in WO 00/46447. Thereafter, the packaging product is transferred to a conveyer system and the packaging product is

passed on the conveyer system through an oven for drying the packaging product To achieve the desired effect of the active filler, the pulp must comprise sufficient active filler for the active filler to act as a filler material during the moulding. Finally, the method according to the invention further comprises the step of activating the active filler after the moulding.

As discussed herein above, the activation may involve heating or other means for activation. If the activation involves heating, it is preferred that the activation takes place during the passing of the packaging product through the oven

In preferred embodiments, the active filler is selected as discussed herein above with regard to the sort of material, the concentration and the activation temperature In other words, it is preferred that the active filier comprises starch, which starch is selected from the group consisting of potato starch, tapioca starch, rice starch, sago starch, corn starch and grain starch, such as enriched or native flour including wholemeal, bolted rye flour, rye flour, wheat flour low grade, wheat starch or high gluten wheat. Preferably the starch comprises unmodified flour, and more preferably the starch comprises unmodified wheat flour. Furthermore, it has been found to be advantageous that the pulp comprises at least 5% by dry weight active filler; pref- erably the pulp comprises 5 to 50% by dry weight of active filler; more preferably the pulp comprises 7 to 25% by dry weight of active filler, and most preferably the pulp comprises 9 to 20% by dry weight of active filier. In another embodiment, the pulp comprises 7 to 50% by dry weight of active filler; more preferably the pulp comprises 8 to 25% by dry weight of active filler. Finally, if the active filler is activable by heating, it is advantageous that the active filler is activated above about 6O ⁰ C, preferably the active filler is activated between about 70 ⁰ C - 110 ⁰ C, and more preferably the active filler is activated between about 75°C - 90 ⁰ C.

In a particularly advantageous embodiment, the pulp - and hence the packaging product - before the drying comprises substantially no activated active filler when the packaging product enters into the oven, and substantially only activated active filler when the packaging product exits the oven. This provides for a maximised filler

effect of the active filler during the moulding and maximised binder effect of the active filler in the completed product.

The use of active filler in a moulding of a three-dimensionally moulded packaging product form a fibrous pulp is highly advantageous, as de-watering or retention during moulding is a significant processing parameter in the traditional wet process of manufacturing of moulded pulp members such as the packaging products according to the present invention. The water, which has not been removed during the moulding, must be removed by evaporation in an oven, which consumes substantial amounts of energy. The increased de-watering is therefore a significant environmental and financial improvement. However, the use of an active filler is particularly advantageous for moulded three-dimensionally moulded packaging products for packaging of heavy goods, as the expected reduction of strength due to the filler effect is more than compensated for by the binder effect when the active filler is activated.

It was found that the use of a starch source as an active filler in moulding of a three- dimensionally moulded packaging product was particularly advantageous. Particularly for an active filler comprising flour, and more preferably when the active filler is an unmodified flour, such as unmodified wheat flour.

DISCUSSION

A number of particularly advantageous aspects and unexpected aspects will be discussed in the following.

After-press

After-pressing of three-dimensionally moulded packaging products is often required to improve the surface properties, i.e. roughness and/or appearance, of the product, However, after-pressing reduces the strength of the product, and in particularly the tear strength and compressive strength. Surprisingly, it was found that by replacing a small amount of the fibrous content of the pulp, such as about 10%, by an active

filler, and in particularly unmodified wheat fiour, the after-pressed product exhibits an increase in strength of about 20% as compared to a reference three- dimensionally moulded fibrous pulp packaging product without flour. More important, the relative increase in strength did not degrade by after-pressing of the packaging products.

Humidity

Starch is known to have a very high affinity towards water and humidity and hence the skilled person wouid expect that it would be more difficult to dry the packaging products according to the invention as water is expected to more tightly bond to an activated active filler containing starch. However, this was not observed. In fact, the required oven temperature and drying airflow rates are not larger than for traditional compositions, whereas less water had to be removed due to the filler effect and hence the higher solid matter content of the packaging product right off the mould.

Furthermore, the skilled person would expect activated active filler containing starch to be more sensitive towards humidity than a packaging product with a traditional composition. Surprisingly, it was found that the increased relative strength observed at 50% relative humidity was maintained at 85% relative humidity.

In other words, the prejudice in the art against the use of starch-based fillers was proven to be wrong.

Application of active filler Moulded packaging products comprising active filler may be utilised either to manufacture stronger packaging product or to reduce the amount of material in the product, since the active filler provides improved strength without substantially changing the shock-absorbing properties of the moulded packaging product. Reduction of the amount of material will lead to a dramatic reduction in the expense for raw material as well as a reduction in the transportation cost of the product, both of which are highly desirable from an economical and environmental point of view.

Stickiness

Starch is rather sticky when activated and hence the use of starch as a main binder in three-dimensionaily moulded packaging products is typically expected to involve substantial problems related to keeping the production facility tidy. However, no iπ- creased sticking to the production facility was observed for the preferred embodiment, where the activation solely takes place in the oven. It could be theorised that this is due to a combination of the beiow facts, viz. that i) the starch is not activated until after the moulding and handling prior to the oven, and that ii) the starch has been completely cured upon exit from the oven.

Contrary to the prejudice in the art, this allows for the use of substantial amounts of active filler comprising starch for the manufacturing of packaging products by moulding of fibrous pulp and not just plastically shaping as discussed above in the background section.

An individual feature or a combination of features from an embodiment of the invention described herein, as well as obvious variations thereof, are combinable with or exchangeable for features of the other embodiments described herein, unless the person skilled in the art would immediately realise that the resulting embodiment is not physically feasible.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below with reference to exemplary experimental results presented in diagrams, in which

Fig. 1 shows the dry matter content of just moulded packaging products,

Fig 2 shows the compressive strength as a function of the deformation for various concentrations of active filler, and

Fig. 3 shows the compressive strength as a function of the deformation for 50 and 85% relative humidity.

EXAMPLES

Basis pulp

To emphasise the effect of the active filler, a very basic pulp consisting of recycled paper and water was utilised. Unmodified wheat flour was used as active filler

The recycled paper was suspended by mechanical means in a concentration of about 1 % (200 g newspaper in 20 I of tap water^ The wheat flour was mixed into the suspension by mechanical means, leading to a homogeneous suspension. The moulding was conducted by suction from a stirred pulp vat. Reference products and test products are prepared to similar total dry material content.

Filler effect

The filler effect of the active filler was investigated by comparing the dry matter content of just moulded packaging products. The weight of just moulded packaging products for pulp without addition of wheat flour (reference pulp) and with added wheat flour was established and compared to the weight of the same packaging products after drying,

In Fig. 1 are shown the results for the reference pulp and a pulp with an addition of 60 g wheat flour to a pulp of 200 g recycled paper, Le. 23 % by dry weight of wheat flour or about 20 % by dry weight of wheat starch.

It is observed that the packaging products manufactured from the pulp with wheat starch have significantly higher solid matter contents than the packaging products manufactured from the reference pulp. In other words, addition of the active filler to the pulp results in a reduction of the water content of the just moulded packaging product and hence a reduction of the energy consumption related to evaporation of water during the drying stage. The reduction in required evaporation of water is highly advantageous, not only from an environmental point of view, but also since

the process time may be reduced and the cost of the apparatus may be reduced as the size of the equipment may be reduced correspondingly.

Binder effect Upon activation of the active filler, the active filler substantially acts as a binder and hence increases the strength of the packaging product In Fig. 2, this is illustrated by showing the compressive strength as a function of deformation for a range of concentrations of the active filler. 'Reference' in Fig. 2 refers to a packaging product with no active filler. The pulp with optional active filler additions of wheat flour as the active filler is prepared as discussed herein above.

In Fig, 2, it is observed that the compressive strength increases by a huge jump upon addition of the first 10% by dry weight of the active filler (here wheat flour), whereas further additions have a reduced, yet significantly positive, effect on the compressive strength. Addition of about 10% of wheat flour is hence particularly advantageous when it comes to increasing the compressive strength. The increased compressive strength may be "converted" into an ability to handle more heavy members and/or a reduction in the amount of material required to realise the same compressive strength as the reference product

Effect of humidity

As discussed herein above, it is the general conception in the art that packaging products comprising substantial amounts of starch, such as more than about 7% by dry weight of starch, are highly prone to degradation in humid environments.

In Fig, 3, this has been investigated by comparing the compressive strength of a reference packaging product made from the basic pulp described above with the compressive strength of a packaging product comprising 8% by dry weight of wheat flour. As shown in Fig. 2, the addition of wheat flour increases the strength in rela- tively low humidity (50 % relative humidity). However, it was surprisingly found that in a more humid environment (here exemplified by 85% relative humidity), even though the compressive strength decreases as the humidity is increased, the com-

pressive strength of the packaging product with active filler remains substantially above the compressive strength of the reference packaging product.