GB2370224A

GB2370224A - Protection of fibres from attack by insects

Info

Publication number: GB2370224A
Application number: GB0125237A
Authority: GB
Inventors: Christine Jillian Armstrong
Original assignee: Second Nature UK Ltd
Current assignee: Second Nature UK Ltd
Priority date: 2000-11-03
Filing date: 2001-10-22
Publication date: 2002-06-26
Anticipated expiration: 2021-10-22
Also published as: GB2370224B; GB0125237D0; GB0410187D0

Abstract

A method of protecting natural or other fibres from attack by insects in any form, e.g. moth, larva, etc., is disclosed. A substance, which insects find objectionable, is added to the fibre mass and intimately mixed with and associated with the fibres. The substance is preferably diatomaceous earth, either on its own, or mixed with silica, silicate(s), and is added as a finely divided powder to the fibres, ideally, at an opening stage in a cleaning, pre-treatment or manufacturing process. An example of the scouring (cleaning) of wool is taught. In the opening stage, metal combs separate the individual fibres, probably generating static electricity in the fibres. It is believed that electrostatic forces cause the fine diatomaceous earth powder to be attracted to and held to the fibres. The use of the protected fibres as a wadding for thermal insulation, acoustic insulation, cushioning and vibration damping is taught. Because the powder is uniformly distributed throughout the bulk of the wadding, the whole is protected from insect attack and cut edges are not vulnerable, as would be the case if only the un-cut wadding surfaces had been sprayed with a protective compound. The application teaches numerous environmental benefits. A substance for protecting fibres from insect attack comprises diatomaceous earth and optionally silicon dioxide.

Description

PROTECTION OF NATURAL FIBRES FROM ATTACK BY INSECTS

This specification relates to the application of substances to natural fibres to protect them against attack by insects, irrespective of the form of that insect, e. g. larva, imago, etc.

Moths are commonly blamed for damage to natural fibres, e. g. in woollen clothing. This is not quite true as moths lay eggs which turn into larvae and it is the larvae which eat the fibres. However,'mothproofing'is a commonly used term and, in this description, means protecting natural, and other fibres, against attack by insects in any, or all, of their biological forms.

It is known to apply mothproofing to natural fibres after they have been made up into finished items, e. g. spraying proprietary products (for example, Polybore) onto carpets, or placing crystals (for example, naphtalene) in drawers containing woollen garments, etc. Mothproofing substances can be expensive and may also have a vapour pressure so that the active ingredient sublimes and thus provides an odour, adjacent to the fibres, which deters moths, insects and the like, as they have very sensitive senses of smell. A disadvantage of substances which sublime, is that they have to be replaced at regular intervals.

Another method of mothproofing is to incorporate an active insect repellent compound, e. g. permethrin, into an inert carrier particle. The particles are sprinkled onto, say, a carpet, brushed in and heat-treated. Despite this, vacuuming and shampooing gradually removes the particles, even before all of the active agent has evaporated If these substances were applied to the raw material, e. g. during the manufacturing process, much of the effectiveness is likely to be lost before the finished product is put into use.

It is thus normal to add mothproofing substances to finished items. A disadvantage of this is that only the exposed surfaces can be treated and, if any insects do get into the substrate of the material, e. g. deep into the pile of a carpet, they will be able to attack the fibres without hindrance. This is a particular problem where wool wadding is used as thermal insulation in buildings as the cut edges will be unprotected and provide easy access to the substrate. One solution is to use synthetic insulating materials, such as glass fibres, but many people strongly prefer natural products, like wool, as taught in co-pending UK patent application No. 00 17670.1.

There is thus a need to be able to apply an insect repellent substance (s) to natural fibres preferably during a cleaning, pre-treatment or manufacturing process, ideally to proof both the surface and the whole of the fibre bulk for an indefinite lifetime.

According to a first aspect of the invention, there is provided a method of protecting natural and other fibres from insect attack by adding a substance, which insects find objectionable, at an appropriate point in a fibre cleaning, pre-treatment or manufacturing process (es) so that the substance becomes intimately associated with the fibres.

According to a first variation of the method of the invention, the fibres are wool and the process is scouring.

According to a second variation of the method of the invention, the fibres are cotton.

According to a third variation of the method of the invention, the substance includes diatomaceous earth.

According to a fourth variation of the method of the invention, the substance includes silica and/or silicon compounds and/or other compounds.

According to a fifth variation of the method of the invention, the substance is added as a finely divided powder.

According to a sixth variation of the method of the invention, the substance is added during a fibre opening stage of a cleaning process.

According to a seventh variation of the method of the invention, the substance is added during a fibre opening stage of a pre-treatment or manufacturing process.

According to an eighth variation of the method of the invention, the substance is attracted to the fibres by an external influence.

According to a further aspect of the invention, there is provided a substance for protecting natural and other fibres from insect attack consisting of diatomaceous earth or a mixture of 85-92.5% diatomaceous earth and 15-7.5% silicon dioxide by weight.

According to a first variation of the further aspect of the invention, the silicon dioxide is in the form of silica gel.

According to a second variation of the further aspect of the invention, the substance may contain up to 1% of sodium sulphate by weight.

In a preferred application of the invention, a finely divided powder, or dust, of 90% diatomaceous earth and 10% silica gel is added to new wool fibres at the end of the scouring (i. e. cleaning) process, that is after the fleeces have been washed, the lanolin removed and during final drying or opening stages. 'Opening'is the process of separating the individual fibres with (usually) metal toothed combs and is known to generate static electrical charges in the fibres. By adding the moth-repellent dust at this stage, the particles are attracted to individual fibres, adhere to the surfaces and are likely to become'caught'in the natural surface roughnesses of the fibres by air movement and/or the'jostling'action of the fibre mass.

At the end of the scouring process, the wool is baled, so that no dust should be lost. In the manufacturing process, the first stage is usually opening, so that the electrostatic charges are re-established, to reinforce and maintain the particle-fibre bond during the subsequent stages, te. g. formation into wadding. This invention is ideally suited to the mothproofing of wadding-like products where the wadding, once manufactured, is left essentially undisturbed afterwards. Such products include thermal insulating blankets in the roofs and walls of build, thermal insulation or padding in furniture, etc.

For a clearer understanding of the invention and to show how it may be put into effect, reference will now be made, by way of example only, to the accompanying drawings in which :- Figure 1 is a diagrammatic representation of an experiment to determine the affinity, or otherwise, of moth larvae for wool wadding; Figure 2 is a diagrammatic representation of the experiment shown in Fig. 1 with un-treated wool wadding ; Figure 3 is a diagrammatic representation of the experiment shown in Fig. 1 with treated wool wadding; Figure 4 is a block diagram of the wool scouring process; and Figure 5 is a part sectional elevation of a mothproofing substance on the surface of a woollen fibre, shown at the microscopic level.

In the following description, the same reference numeral is used for the same component, or for different components fulfilling an identical function.

The principle of the invention is shown in Figs. 1-3, which are diagrammatic representations of a British Standard laboratory test to determine the affinity of insect larvae to materials. As explained previously, it is the larvae which attack the fibres not the moths but the moths have highly developed olfactory organs and are extremely sensitive to substances which the larvae will find objectionable and thus avoid materials which contain them.

Figs. 1-3 show a plan views of a shallow Petrie-type dish 1 with a ring 3 marked on the base. A piece of material 2, e. g. wool wadding, is placed in the centre 3A of dish 1, inside ring 3, and insect larvae 4 are placed in the annular space 3B outside ring 3. When un-treated wadding 2A is used, the larvae 4 quickly cross ring 3 (as shown by arrow 5) and enter the wadding (Fig. 2) and the annular space 3B outside ring 3 is soon completely free of larvae. When the wadding is treated with a substance consisting of a diatomaceous earth-silica (silicon dioxide) dust mixture, e. g. 2B (Fig. 3), most larvae 4A move radially away 5A from the wadding towards the side of the dish 1. Some larvae 4B do not appear to move in any direction and a very, very few enter the wadding 2B.

Subsequent inspection of wadding 2B shows that those larvae, which did enter, will be dead. Diatomaceous earth and silica are naturally occurring substances and the process by which they kill insect larvae is a purely physical one, Le. as opposed to a chemical poison. Microscopic examinations show that, larvae moving through the wadding, pick up dust particles on their cuticle, i. e. the outer waxy layer of the epidermis found on insects. The dust acts against insects by adsorption onto and abrasion of the cuticle, leading to loss of body fluids and eventual death through desiccation. Silica gel is a well-known desiccant and is included in the formulation to enhance its efficacy further.

Tests have shown that a diatomaceous earth-silica gel mixture, containing 7.5-15% silica gel provides an effective moth deterrent.

The performance of diatomaceous earth as a control agent against insect pests in bulk grain stores is well documented and research shows it to be equally effective for mothproofing wool insulation. There are very few environmental objections to either the substances themselves or the method of killing and the desiccated remains do not cause any unpleasant smells. These are very significant benefits of this invention, particularly for environmentally sensitive applications.

Diatomaceous earth occurs in two forms, viz. amorphous and crystalline. Of the two, the amorphous form is preferred, as the crystalline form has been associated with silicosis, a lung condition resulting from inhalation. In contrast, amorphous silica presents much less of a health hazard ; it is of negligible toxicity to mammals,

non-carcinogenic, with no evidence of mutagenic or teratogenic effects. However, like all inert dusts, prolonged exposure should be avoided as this may impair lung function.

Diatomaceous earth can be obtained from freshwater sources, which tend to be amorphous silica, or from marine sources, which tend to be cryatalline in nature ; thus, amorphous, freshwater diatomaceous earth is strongly preferred.

The exact mechanism by which the mixture acts as a mothproofing is not known but it may be that the diatomaceous earth acts as a long range (for insects) deterrent and the silica gel desiccates the larvae from close range or actual contact. This is supported by the fact that, when lower levels of silica gel are present, it takes rather longer to kill (desiccate) the larvae than at higher levels. Tests have shown that 10% silica gel is about an optimum level. Sodium sulphate is often associated with diatomaceous earths and may have a beneficial effect.

Fig. 4 shows the principle of the wool cleaning process, known as scouring. Fleeces 6, straight from shearing, are placed in a blender 7. It is normal to mix fleeces 6 from different types of sheep, e. g. Herdwick, Swaledale, Texel, etc. , to achieve particular properties and three arrows 6 are shown to indicate this. From blender 7, the fleece mixture passes to an opener 8, where a light machining occurs, to separate the individual fibres from each other. Further blending takes place here. The fibres then pass into a first washer 9 where a wash liquor 22 is added. The fibre mass is agitated and, after a period of time, the liquor is run off 22A. The wool mass passes through squeeze rollers 10, where further wash liquor 22A is extracted, and thence into a second washer 9. The washing process is repeated, perhaps with a different wash liquor 23 which is subsequently removed 23A.

Dashed line 11 indicates a plurality of further washing 9 and squeezing 10 stages. In one process, a total of eight stages is used. The washing process is to remove both dirt, e. g. soil, etc. , and natural oils, such as lanolin, and the wash liquors are selected accordingly.

The lanolin is recovered as a valuable by-product and the dirty wash liquors 22A and 23A are cleaned for re-use or discharge to the environment (not shown).

After the final squeeze roller 10 stage, the wool mass passes 11 into a drum dryer 12 and, when sufficiently dry, to an opening machine 13, known as a'Fearnought'. The diatomaceous earth-silica gel dust mixture 24 is added here and the highly efficient opening action distributes the dust evenly throughout the mass of wool. Any appropriate method of adding dust mixture 24 to Fearnought 13 may be used, e. g. a vibratory feeder (not shown) or venturi (not shown), etc. The method chosen will ideally add dust 24 progressively as the wool enters Fearnought 13 and allow for the movement of the air locally.

Fearnought 13 is provided with a great many metal teeth (not shown) which tease the individual fibres apart. In so doing, there is considerable relative motion between the teeth and the wool fibres. The teeth are metal and indirectly connected to the frame of Fearnought 13, which is earthed via its mounting (not shown).

From Fearnought 13, the fibres pass to an automatic collector bin 14 and thence to a baler 15, where they are pressed and wrapped, leaving as bales 16 for delivery to the manufacturer. A product particularly suited to the mothproofing process of the invention is wool wadding, e. g. for use as thermal insulation for buildings (roofs, walls, etc. ); as thermal insulation in duvets, eiderdowns, jackets, etc.; as cushioning in bedsteads, mattresses, carpet underlay. etc.; as acoustic insulation and/or vibration damping in buildings, cars, trains, etc.

A further point to note is that none of the substances taught in this disclosure is flammable ; they do, in fact, act as flame-retardants. This is a further environmental advantage of the insect protection of the invention. The use of amorphous diatomaceous earth is specified as a precaution in case some of the dust in inhaled by workers, e. g. those laying insulation blankets in lofts or people cutting wadding for duvets, etc. This is a further environmental aspect of the invention.

Tests (e. g. Figs. 1-3) have shown that diatomaceous earth is the most effective of this type of insect deterrent/killer.. It may be used pure or mixed with other suitable powders, e. g. silica, silicates, etc. Preferably, the powders should be very finely divided, ideally in the 5-l01 m (micrometres) or smaller size range, i. e. as a dust. A rate of

application of one percent by weight of dust to fibres (1% wt.) has been shown to be effective but, as some of the dust is usually lost in stages 13, 14 and 16 of the scouring process and also in the subsequent manufacturing process (es), the addition of, for example, two percent by weight (2% wt. ) is preferred. Tests have shown that this, level of addition results in at least 1% wt. in the final wadding and hence effective mothproofing.

Diatomaceous earth does not sublime over a period of time. However, insects can certainly detect its presence from a distance and shun it. Because of this keen ability to detect diatomaceous earth dust and diatomaceous earth dust mixtures from (for an insect) a considerable distance, it is not necessary to coat every fibre and a 1 % wt. addition, evenly distributed, provides full effective insect proofing (mothproofing).

The mechanism by which the powders'adhere'to the fibre surfaces is unclear but there are several possibilities, viz: * electrostatic attraction; * Vander Waals'forces ;

e h ionic attraction between polar molecules (e. g. like the hydrogen bonds in water) ; and/or * surface roughness, etc.

The size range of 5-1 um, or less, diameter powders on 30-35um diameter fibres is that where inter-molecular and electrostatic forces become significant and such forces are sufficient to keep the powder particles in intimate contact with the wool fibres.

Electrostatic bonding is one probable mechanism and will be described. It is known that valency electrons can be stripped from the outer layers of atoms by relative movement against another surface. The best known example of this is the party trick in which a balloon is rubbed against a woollen jumper and electrons are transferred, e. g. from the wool to the balloon, giving a net static negative charge to the balloon. The balloon may then be offered up to a ceiling where its net negative charge will displace electrons in the ceiling leaving a residual positive charge in the plaster so that the balloon will be

attracted to, and held against, the ceiling. It will remain there for a period of time until the residual charge leaks away.

In Fearnought 13, the vigorous'opening'action of the metal teeth (not shown), Le. separating individual fibres one from another, causes relative motion between the teeth and the wool fibres. Such a process could generate static electricity, stripping electrons from the fibres. As the teeth are metal and indirectly earthed, the electrical charges generated on the teeth are discharged to earth. The fibres are not so earthed and are thus likely to retain their charge, especially in the warm, dry, non-conducting atmosphere inside the plant. When dust particles 24 are added, they are immediately attracted to the nearest fibre by this static electricity. The absence of water in this ultra dry environment would promote electrostatic processes.

There is evidence for this mechan ! sm as, when workers are actually handling the cleaned wool fibres in stages 14 or 15 of the scouring process (Fig. 4), their hair is sometimes observed'standing on end', indicating the presence of static electrical charges.

Fig. 5 illustrates the electrostatic attraction of a diatomaceous earth particle 18 on to the surface 17A of a wool fibre 17, by showing a part microsection of a single fibre 17. As shown, the surface 17A of fibre 17 is electrostatically charged. For the purposes of explanation only, it is assumed that (negatively charged) electrons have been stripped from the fibres 17 in Fearnought 13, leaving them with a net positive charge. The electrostatic attraction causes dust particles 18 to be attracted to the fibres 17 and to adhere to surface 17A. As shown on the left of Fig. 5, the valency electrons in particle 18 are drawn towards surface 17A, to balance the net positive charges in fibre 17, leaving the non-contact side with a positive charge.

Under static conditions, particle 18 would remain fixed, as shown. However, in an air flow 19, the drag effect may cause the particle 18A to roll 21, or skid, over the surface 17A until it reaches a roughness 20. The same effect may occur when adjacent fibres are

jostled together. For diagrammatic simplicity, particle 18 is shown as a sphere and the surface of fibre 17 as mostly flat with a rectangular pit 20, to represent surface

r ss.

As shown, particle 18B has rolled 21 or slid into pit 20, under the influence of air flow 19. Here, only about a third of the projected area of particle 18B is exposed to airflow 19 and so it would be unlikely to be move further. It must be borne in mind that, though the surfaces of particles 18 and fibre 17,20 are shown as'smooth', they are, in fact, very 'rough'on the molecular scale and particles can easily'snag'onto, or into, surface roughnesses 20 and become tightly attached.

Over time, the wool will gradually lose its electrostatic charge as stray electrons leak in but, in the dry compact centre of a bale 16, this process should be slow. Despite this, residual charges and particles 18B in/on surface roughnesses will retain the bulk of the powder, even during further processing, e. g. to form insulating wadding. As most manufacturing processes usually start with an'opening'stage on the baled wool, this is likely to re-establish, or generate more electrostatic charges and so strengthen the dust-fibre bonding.

When making wool insulation, new wool is sometimes mixed with re-claimed wool and a thermoplastic, e. g. polyester, bonding agent may also be added. Though the new wool may be a minority of the total mixture, and though only a minority of the new fibres may actually carry particles 18, the effect of diatomaceous earth on insects is so strong that it will still act as an effective mothproofing treatment. It will be understood that a sufficient quantity of diatomaceous earth dust 24 is added to allow for the dilution of new wool by re-claimed wool and bonding agent and yet provide adequate mothproofing. Thus, the effect of the invention is to add a whole new dimension to the practice of protection of natural fibres from insect attack.

Because it is the mere presence of diatomaceous earth which provides the mothproofing to the fibres, this is a very effective insect deterrent (mothproofing) and the protection provided, will last as long as the powder is present, i. e. providing permanent protection under static conditions, such as with roof insulation, carpet nuderlay, etc. Also, as both surface and substrate are protected, there will be no risk of attack via cut surfaces of the wadding. Various uses of the wadding have been taught and many others will be apparent to the skilled man, all falling within the scope of the invention.

The method of insect proofing of the invention uses naturally occurring substances which are not poisonous to human beings nor do they have any (detectable) smell or other environmentally objectionable property. The action of the substances is to deter moths from laying their eggs in or near protected fibres. In the event that insect larvae do enter the fibre mass, they will be killed by a purely physical process, i. e. without chemical poisons. After death, the desiccated bodies will not cause objectionable smells.

The addition of these substances to the fibre mass can be done by unskilled personnel with, probably, only a face mask to avoid ingestion/inhalation of dust which, in the case of the amorphous form of diatomaceous earth taught herein, is harmless. The presence of the substances also acts as a fire retardant.

The above advantages should be contrasted with current mothproofing techniques, where (usually) volatile, possibly flammable, compounds are sprayed on by trained personnel, wearing protective clothing, working to strict procedures, in carefully controlled environments. Surface sprays may have to be repeated at regular intervals and the protection is limited to the immediate surface, allowing any larvae, which can penetrate the deep fibre, to live unhindered.

This invention adds greatly to mothproofing technology, especially where environmental benefits are required.

Claims

What we claim is :1 A method of protecting natural and other fibres from insect attack by adding a substance, which insects find objectionable, at an appropriate point in a fibre cleaning, pre-treatment or manufacturing process (es) so that the substance becomes intimately associated with the fibres.
2 A method of protecting natural fibres, as claimed in claim 1, wherein the fibres are wool.
3 A method of protecting natural fibres, as claimed in claim 1, wherein the fibres are cotton.
4 A method of protecting natural fibres, as claimed in claims 2 or 3, wherein the substance contains diatomaceous earth.
5 A method of protecting natural fibres, as claimed in claims 2 or 3, wherein the substance contains silica, silicates or other compounds of silicon.
6 A method of protecting natural fibres, as claimed in claims 2 or 3, wherein the substance contains sodium, or other, sulphates.
7 A method of protecting natural fibres, as claimed in claims 4 to 6, wherein the substance is a finely divided powder or dust.
8 A method of protecting natural fibres, as claimed in any preceding claim, wherein the substance is added during a fibre cleaning process.
9 A method of protecting natural fibres, as claimed in any preceding claim, wherein the substance is added during a pre-treatment process prior to the manufacture of the fibres into products.
10 A method of protecting natural fibres, as claimed in any preceding claim, wherein the substance is added during a process for manufacturing the fibres into products.
11 A method of protecting natural fibres, as claimed in claims 8, 9 or 10, wherein the substance is added at an opening stage in either the fibre cleaning, pre-treatment or manufacturing process.
12 A method of protecting natural fibres, as claimed in claims 8,9, or 10, wherein the substance is added at a drying stage in either the fibre cleaning, pre-treatment or manufacturing process.
13 A method of protecting natural fibres, as claimed in any preceding claim, wherein the particles of the finely divided substance are attracted to and/or held to the fibres by an external influence.
14 A method of protecting natural fibres, as claimed in claim 13, wherein the external influence is an electrostatic attraction.
15 A method of protecting natural fibres, as claimed in claim 13, wherein the external influence is mutual contact between the surface roughness (es) of substance and fibre.
16 A method of protecting natural fibres, as claimed in any preceding claim, wherein the substance is uniformly distributed among the natural fibres so that a small quantity of the substance effectively protects a large volume of fibres.
17 A method of protecting natural fibres, as claimed in claim 16, wherein the natural fibres to which the substance has been added are mixed with other natural fibres so that the natural fibres with added substance effectively protect the other natural fibres without.
18 A method of protecting natural fibres, as claimed in claim 16, wherein the natural fibres to which the substance has been added are mixed with other synthetic fibres so that the natural fibres with added substance effectively protect the whole fibre bulk
19 A method of protecting natural fibres, as claimed in claims 16 to 18, wherein the mixture of protected natural fibres, unprotected natural fibres and/or synthetic fibres contains a thermoplastic bonding agent.
20 A method of protecting natural fibres, as claimed in claims 16 to 19, wherein the substance is added at a rate sufficient to give approximately one percent by weight of finished product.
21 A method of protecting natural fibres, as claimed in any preceding claim, wherein the protected natural fibres with, or without unprotected natural fibres and/or synthetic fibres, are used to produce wadding.
22 A method of protecting natural fibres, as claimed in claim 21, wherein the wadding is used for thermal insulation.
23 A method of protecting natural fibres, as claimed in claim 21, wherein the wadding is used for cushioning.
24 A method of protecting natural fibres, as claimed in claim 21, wherein the wadding is used for acoustic insulation.
25 A method of protecting natural fibres, as claimed in claim 21, wherein the wadding is used for vibration deadening of panels, or other members.
26 A substance for protecting natural and other fibres from insect attack consisting of diatomaceous earth.
27 A substance for protecting natural and other fibres from insect attack, as claimed in claim 26, consisting of a mixture of 85-92.5% diatomaceous earth and 15-7.5% silicon dioxide by weight.
28 A substance for protecting natural fibres from insect attack, as claimed in claim 27, wherein the silicon dioxide is in the form of silica gel.
29 A substance for protecting natural fibres from insect attack, as claimed in claim 28, wherein the substance contains up to 1% of sodium sulphate by weight.
30 A substance for protecting natural fibres from insect attack, as claimed in claims 26 and tel7, wherein the diatomaceous earth is of the amorphous form.
31 A method of protecting natural fibres as described in and by the above statement with reference to the accompanying drawings.