GB2073096A - Method for Making Objects From Straw and Other Raw Fibrous Materials - Google Patents

Abstract

A method of making containers, container blanks or other similar objects comprising a mixing straw (as defined) with a heat curable bonding agent, compressing the resultant mixture and applying heat to commence curing of the bonding agent to form a container, container blank or other similar object.

Description

SPECIFICATION Method for Making Objects from Straw and Other Raw Fibrous Materials This invention relates to a method of an apparatus for making containers, container blanks or other similar objects.

In the fruit and vegetable industry it is normal to use wooden or corrugated cardboard crates for packaging and transport. Aithough these are nonreturnable they are nevertheless expensive to produce and it is an object of the present invention to replace crates such as these with containers made from cheaper materials such as surplus materials.

According to one aspect of the present invention a method for making containers, container blanks or other similar objects comprises mixing straw or other raw fibrous material (hereinafter referred to as straw for convenience) with a heat curable bonding agent, compressing the resultant mixture and applying heat to commence curing of the bonding agent to produce a container, container blank or other similar object.

Preferably the straw is either unchopped or it is only coarsely chopped. This arrangement allows variable lengths of straw to be used which are arranged in random directions to provide good cross bonding so that material has good flexibility and also rigidity.

The proportions of bonding agent to straw are preferably approximately 89% straw to 1 1% bonding agent, although these proportions may vary by upto 2% in either direction.

The straw and the bonding agent are conveniently mixed in a mixer, the bonding agent being supplied in liquid form to the mixer, in such a way as to apply an even coating of the straw as for example by way of a spray.

The pressure applied to the resultant mixture is in the order of 80 tonnes per square metre, and the heat is preferably applied at a temperature of it 500 centigrade and at this temperature the heat is applied for 20 seconds for each millimetre of board thickness. The temperature of 1 500 centrigrade has been found to be the optimum but lower temperatures down to 1350 centrigrade can be used, curing taking correspondingly longer, and also higher temperatures up to 1 750 centrigrade can also be used but in this case care has to be taken to avoid scorching.

Conveniently a lining material is applied to the container or container blank or other similar product, and this may be applied either during molding of subsequently. The lining material may be paper or plastics sheet.

In the case of a container blank it may be provided with marking or creases where it is to be folded, and in this case provision may also be made for stacking lugs, thickened end walls, hand grips, ventillation holes and other suitable provisions for use with containers.

According to another aspect of the present invention a container or the container blank or other similar product is made by the method as set forth.

According to a further aspect of the present invention is a container of container blank or other similar product made from straw or other raw fibrous material.

According to a further aspect of the present invention apparatus for making containers, container blanks or other similar objects from straw comprises means for mixing straw with a heat curable bonding agent, means for compressing the mixture in a mould and applying heat to commence curing of the bonding agent, and subsequently removing the formed container, container blank or other similar product from the mould.

The invention may be performed in various ways and one specific embodiment will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is an illustration of a side of a container (with the lining removed) showing how a straw is arranged in a random manner and Fig. 2 is a graph of board thickness against ingredients.

In the invention, straw, normally in bale form, is supplied to a straw chopper where it is coarsely chopped with the aid of a chaff cutter for convenient handling. It is not in fact essential to effect this chopping but it tends to assist in handling. However, it is preferable to have a considerable quantity of variable lengths of straw, for example as long as 250 millimetres down to 10 millimeters or even less so that in the finished product the individual lengths are arranged in random directions to provide good cross bonding which gives strength and resistance to bending whilst at the same time enabling a degree of flexibility. An example of the finished product is shown in figure 1.This shows the side view of a panel for a container in which straw as such is used and it can be seen from this that the straw is of very considerable variation in length and is arranged in totally random directions to give the cross-bonding effect referred to. It will be appreciated that in the finished product a lining of paper would normally be placed over the straw which wouid thus be invisible.

The straw then passes from the straw chopper to a mixer where it is mixed with a bonding agent.

This is effected by having means in a mixer for applying an even coating of resin mix on the straw as by a spray in liquid form and an automatic metering device which is preset according to the quantity required. The bonding agent is a fomaldehyde, isocyanate and a hardener possibly with water added to reduce viscosity. It has been found that the proportions of 89% straw to 1 1% bonding agent, with plus or minus 12%, the proportions being by weight, form a suitable mixture. The straw and bonding agent mixture is led from the mixer into a press.The press may be in the form of a mould being the final shape of the container to be manufactured or alternatively may be in the form of a mould only for making a flat sheet for subsequently forming container blanks, or in a shape suitable for other similar articles.

Heat is then supplied to the press to start the curring process and in this heating period approximately 90% of the curing takes place, the remaining 10% ocurring during the subsequent cooling.

In the case of the blank, creases or marking lines or other indentations are provided during the moulding where the blank is to be folded. In this form the blank can be stored until required for use. A blank may be made up into a carton at any time. This is effected by taking the blank, bending the sides at the appropriate creases and securing the sides together as by stapling or gluing.

Alternatively a carton can be produced by securing together sheets of preformed material which may be for example in the shape as shown in figure 1 and these sheets can be secured similarly by stapling or gluing.

Also during the moulding process features such as stacking lugs, thickened end walls, hand grips, ventillation holes and the like can be formed.

With the present invention it is thus possible to utilise either on site or in a factory supplied locally a surplus product such as straw for making into a container or container blanks and for example on a farm which produces ceral and fruit crops surplus from the cereal crop can easily be converted into blanks, but the methods set forth above, the blanks stored until such time as the containers are needed and the blanks then made into containers for packing the crops. As the raw material is in abundant supply the expenses are thus kept down to a minimum particularly by using local farm labour when it is not required for other purposes.

It has been founa for example that a convenienent pressure for use in the press is 240 tonnes for a three square metre sheet i.e. a pressure of 80 tonnes per metre for a board of 254 mm thick.

Reference is now made to figure 2 which is a graph and where it will be seen that the X coordinate represents board thickness in millimetres and the Y co-ordinate grammes of straw (x 100) per resin mix and the resin mix itself and which has been found to provide the best results is made from fomaldehyde in the quantity of 90.225 grammes, isocyanate 40 grammes, hardener 8 grammes, water 12.5 grammes (the water being optional but being used to reduce viscisity). As can be seen from the graph it is possible to obtain soft lightweight board, good standard board, or hard dense board according to the quantity of straw per resin mix. In fact in the example the quantities are based on a board having an area of 5,000 sq centimetres. Thus for example it will be seen from the graph that if a lightweight board is required at 14 millimetres thickness, then only 2,800 grammes of straw and resin mix are required for a unit of 5,000 quare centimetres.

However, if a hard dense board is required then 3,880 grammes of the straw resin mix are required for the same thickness of 14 mm board.

Claims (14)

Claims

1. A method of making containers, container blanks or other similar objects comprising mixing straw (as defined) with a heat curable bonding agent, compressing the resultant mixture and applying heat to commence curing of the bonding agent to form a container, container blank or other similar object.

2. A method as claimed in claim 1 in which the straw is either unchopped or is only coarsely chopped.

3. A method as claimed in claim 1 or claim 2 in which there is a proportion of approximately 89% straw to 1 1% bonding agent

4. A method as claimed in claim 3 in which the proportions may vary by plus or minus 2%.

5. A method as claimed in any one of the preceding claims in which the straw and the bonding agent are mixed in a mixer, the bonding agent being supplied in liquid form to a spray in the mixer.

6. A method as claimed in any one of the preceding claims in which the pressures applied to the resultant mixtures is in the order of 80 tonnes per square metre.

7. A method as claimed in any one of the preceding claims in which the heat is supplied at a temperature of approximately 1 500C.

8. A method as claimed in claim 7 in which the said temperature is maintained for 20 seconds for each millimetre of board.

9. A method as claimed in any one of the preceding claims in which the resin mix comprises 90.225 grammes fomaldehyde, 40 grammes isocyanate, and 8 grammes hardener.

10. A method as claimed in claim 9 including

12.5 grammes of water.

11. A method as claimed in any one of the preceding claims in which a lining material is applied to the surface of the finished product.

12. A method as claimed in claim 10 in which the lining material is paper or plastics sheet.

13. A method as claimed in any one of the preceding claims in which in the case of a blank it is provided with markings or creases where it is to be folded.

14. A method as claimed in any one of the preceding claims in which in the case of a blank provision is also made for stacking lugs, thickended end walls, hand grips, ventillation holes and other suitable provisions for use with containers.

1 5. A method of making containers, container blanks or other similar products substantial as described herein with reference to and as shown in the accompanying drawings.

1 6. A container or container blank or other similar product made by the method claimed in any one of the preceding claims.

1 7. A method of making a container, container blank or other similar product substantially as described herein with reference to and as shown in the accompanying drawings.

1 8. A container or container blank or other similar product made from straw (as defined).

1 9. Apparatus for making containers, container blanks or other similar products from straw comprising means for mixing straw with a heat curable bonding agent, means for compressing the mixture and applying heat to commence curing of the bonding agent to form a container, container blank or similar product.