CA1190465A

CA1190465A - Packaging film and packaging of detergent compositions therewith

Info

Publication number: CA1190465A
Application number: CA000414775A
Authority: CA
Inventors: Zia Haq
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1981-11-11
Filing date: 1982-11-03
Publication date: 1985-07-16
Also published as: ES8900250A1; EP0079248A2; DE3278073D1; JPH0124066B2; AU9022682A; US4416791A; BR8206490A; EP0079248B1; GB2109706B; ATE32327T1; ZA828235B; EP0079248A3; AU549230B2; PT75821A; GB2109706A; PT75821B; JPS5887050A; ES517260A0

Abstract

ABSTRACT
A packaging film comprises a base film of at least partially water-soluble plastics film, for example, polyvinyl alcohol, carrying on one side a protective layer of particulate inert plastics material, for example, polytetrafluoroethylene powder, having a high water repellency. The film is thus vulnerable to attack by aqueous media on one side and protected against such attack on the other. It may be used, with the protected side innermost, for unit packaging of detergent compositions, especially liquids containing bleach. In use in the washing machine, the unprotected surface is attacked by the wash liquor to release the contents; the protective layer prevents attack of the package by the contents during storage.

Description

o~

C.1317 PACKAGING FILM AND PACKAGING OF DETERGENT
COMPOSITIONS THEREWITH

The present invention relates to a packaging film and its use in the packaging of prod~cts at least partially in liquid form, especially liquid detergents.

The unit packaging of detergents in sachets for d1rect dosing lnto washing machines has already been proposed in the literature, but in practice bulk packaging of both powdered and liquid detergents in cartons, drums, bottles and the like is generally employed, although this imposes restraints both on formulations and on methods of production. In particular, products must be designed so that ingredients do not segregate on storage, and this presents par~icular problems in ~he case of liquid products with insoluble ingredlents. Wastage or underdosage also tends to occur when the consumer is left to judge the correct amount of a product to use.

Unit packaging alleviates these problems and also avoids skin contact of the detergent composition, so that more highly alkaline compositions can be used. The danger of accidental ingestion by children is also lessened.

Sachets for unit packaging of detergent powders are disclosed in US 4 188 304 (Lever Bros. Co.) and

- 2 - C.1317 EP 0 011 500, EP 0 011 501, EP 0 011 502 and EP 0 011 968 (Unilever). These documents disclose sachets of water-insoluble, water-permeable material, which are clearly unsui~able for the packaging of llquids, and sachets 5 designed to open in use. The latter type of sachet requires seals that are sensitive to the wash water, and they would accordingly be unsuitable, in general, for the packaging of liquids.

US 3 277 009 (GAF Corp) discloses packages made of water-soluble film and their use for the packaging of, inter alia, solid detergent compositions and non-aqueous liquids such as petrol and carbon tetrachloride. Such packages are clearly unsuitable for packaging liquids 5 having an appreciable water content since such liquids would attack the package walls.

CA 1 112 534 (Procter & Gamble) discloses a package made of water-soluble film containing a detergent suitable for use in an automatic dishwasher, but the package contents must be in the form of a paste which will not dissol~e the filrn.

US 3 186 869, US 3 322 674 and GB 954 602 (Friedman) 25 dlsclose a package for bleach-containing detergents in the form of a bag of water-soluble film material. The problem of attack of the bag walls by the contents is here alleviated by providing the inner surfaces of the bag walls with a barrier coating of waxy or oleaginous material,

3 especially paraffin wax.

US 3 790 067 (Scheier) discloses a disposable container having an innex layer of wa~er-insoluble polymeric film material and an outer layer of water-soluble polymeric material. The outer layer is relatively trong, and the inner layer is 6ufficiently ~hin to be shredded under normal atmospheric forces, or the weight of material in the container, once the outer layer has dissolved away.
US 3 7~7 382 (General Electric Co.) discloses a process for the production of powdery polytetrafluoro-ethylene and its use for coating various substrates, for example, metals, glass, quartz, mical carbon, boron, cotton and other textiles.
US 3 860 117 (Possis Corp.) discloses a method of skin packaging in which a thin blanket of powdered material is interposed between the contiguous surfaces of the packa~ed article and the transparent thermoplastic packaging film. The powdered material preerably has a particle size less than 15 micrometres and may consist of polytetrafluoroethylene or polypropylene.
In a first aspect, the present invention provides a packaging film comprising a base film of at least partially water-soluble plastics material carrying on one surface only a protective layer, in particulate form, of an inert plastics material having a contact angle to water of at least 80, said layer being effective to protect ~he base film sur~ace from attack by aqueous media.
The packaging film has the advantage that, on its unprotected side, it can be dissolved away, or partly dissolved and partly dispersed, by water, whereas on the side carrying the protective layer it is protected from attack by aqueous systems and other aggressive media. It is essential that the inert protective layer be in the form of substantially uncoalesced discrete particles attached firmly to the base film but only loosely or not at all to each other, so that if the base film is dissolved away the protective layer has little or no integrity and is rapidly ~i o/~ g _ ~ _ C.1317 dispersed.

In a second aspect, the present invention provides a package comprised of the packaging film defined above, having the protective layer on its internal surface(s), so that the layer protects the package rom attack by any water present inside the package.

In a third aspect, the present invention provides a package as defined in the previous paragraph containing an a~ least partially liquid composition that would be capable of attacking the unprotected base film.
Advantageously the composition is a detergent composition, in particular one containing a bleach. Such a product is useful for dosing into domestic or commercial washing machines. The contents are released in use by dissolution of the base film by the wash water.

Suitable materials for the base film include polyvinyl alcohol and partially hydrolysed polyvinyl acetate, alginates, carboxymethylcellulose, and methylcellulose. Films of polyvinyl alcohol and polyvinyl acetate/polyvinyl alcohol mixtures are especially suitable.
The inven~ion encompasses the use of materials having water-solubilities ranging from partial solubility in hot water to complete solubility in cold water; in the case of a package containing detergent or other washing products intended for washing machine use it is suficient that water at ~ash temperatures will cause enough disintegration 3 of the film to allow release of the contents from the package into the wash water. It may be advantageous for the base film to be of thermoplastic material, as explained in more detail below.

The protective layer consists of a solid pulverulen~
material having a high degree of water-repellency, r~

- 5 - C.1317 expressed as a contac~ angle to water of at least 80.
Examples of materials that may be used are polystyrene (contact angle ~6), polyvinyl chloride, polyethylene, and pol~propylene. The contact angle is advantageously at least ~0~, and materials having a contact angle to water of at least 100 are especially effective. An especially preferred material is polytetrafluoroethylene (PTFE), which has a contact angle to water of 106, and other solid polyfluorocarbons are also suitable. The protec~ive material is, as stated above, in the form of discrete particles.

The particles may be adhered to the base film by means of an adhesive. In a preferred embodiment of the 1~ invention, however, they are pressed onto the base film when the latter is in a slightly tacky state. The tackiness may be achieved, for example, by heating the film to a temperature slightly above its glass transition temperature; in this method, it is essential that the base film is of thermoplastic material that softens at a substantially lower temperature than does the particulate material of the pro~ective layer. During the pressing process, coalescence of the particles must be minimised by choice of a suitable temperature at which the particles are not softened while the base film is. For example, PTFE
particles are not softened at temperatures below 500C, so that a very wide range of thermoplastic films can be coated with them using this method. Polystyrene, however, has a glass transition temperature of 101C, and thus polystyrene particles can only be used on conjunction with base films having glass transition temperatures below about 75C if this coating method is used.

In an alternative procedure, ~he tackiness of the base film may be achieved by spraying with a finely-divided jet o~ water. This method ~voids the necessity o~

C`,~.i - ~ - C.1317 ~emperature matching as described in the previous paragraph.

The thickness of the protective layer will of necessity be low since adhesion between the particles is minimal. Sufficient particula~e material must, however, be present to form a layer sufficiently coherent to prevent contact of ~he package contents with the base film. 100%
CQVerage of the surace area of the base film is not in general necessary in order to provide protection.

It is an essential feature of the packaging film of the invention that one side is protec~ed from attack by aqueous media, by means of the protective particulate layer, while the other side is vulnerable to such attack.
The vulnerable side of the film may, if desired, be completely uncoated. Advantageously, however, it may be lightly coated with an inert water-repellent particulate material, but to a lesser extent than the protected side.
This measure helps to reduce tackiness in handling. The degree of coating must no~, of course, be such that attack of ~he base film by aqueous media is prevented. The coating material may advantageously be the same as that used for the protective layer.
The thickness of the base film itself should be sufficient to give it the required mechanical strength.
Typically the thickness of ~he film will lie within the range of from 0.002 to 0.01 cm. The film also desirably has a tensile strength of at least 2 ~o 3 x 103 p.s.i.
(1.4 to 2.1 x 106 kg/m2) and an initial tear s~rength of at least 40 to 60 lb/in (700 ~o 1100 kg/m~. High bursting strength is also desirable.

~5 As mentioned above, the base film i5 advantageously thermoplastic for ease of attachment of the protective C.1317 layer. It is also advantageously of high heat-sealability, since heat-sealing represents a convenient and inexpensive method of maklng packages according to the invention.

Advantageously, the packaging film of the invention has uncoated edge or border areas on the side bearing the protective layer, to facilitate heat-sealing.

The package of the invention is conveniently in the form of a ~ag or sachet. Such a bag may be formed from one or more sheets of the packaging film of the invention or from a tubular section of such film, but it is most conveniently formed from a single folded sheet or from two sheets, sealed together at the edge regions either by means of an adhesive or, preferably, by heat-sealing. A
preferred form of sachet according to the inven~ion is a rectangular one formed from a single folded sheet sealed on three sldes.

As previously indicated, the film and package of the present invention are especially suitable for the packaging of detergents and other treatment compositions for home laundr~ use, especially such compositions in liquid form~

Like the sachets disclosed in the previously mentioned US 4,1~8,304, EP 0 011 500, EP 0 011 501, EP 0 011 502 and EP 0 011 968, the films and packages of the present invention can be used for the packaging of particulate detergent compositions, with similar advantages over bulk packaging: the detergent is available in precisely metered quantities, and wastage and under-dosing are both avoided; since s~in contact is avoided more highly alkaline powders can be used than would be advisable in bulk packaging; the powders can be of higher density than usual, which decreases packaging, transport and 8 - C.1317 storage costs and simplifies powder processing techniques;
appearance of the powder is less important, 50 that acceptable powders can be produced entirely by simple admixture or by granula~ion, and flowability of the powder is less important, also leading to process simplification.

The ~ilm and package of the invention also possess the additional advantage that they can be used for the packaging of detergents in liquid or paste form. The packing of detergent powders into sachets involves certain diEficulties because of their flow and compressibility characteris~ics; these impose limitations on the rate at which sachets can be filled by machines. Liquids, on the other hand, are subs~antially incompressible and packing speed is in principle limited only by their viscosity.
High-speed packing of liquids into sachets is a well-known and convenient technique.

Unit pacXaging in sachets or the like is of particular advantage for liquid products containing insoluble ingredients, since the correct proportion of insoluble ingredlents in every dose is ensured. In bul};
packaging a suspending system is required to achieve this, otherwise the consumer has to shake the container eYery time the product is used.

Any detergent composition in liquid form may with advantage be packaged using the film and package of the invention. Such detergent compositions are amply described in the literature, for example, in "Surface Active Agents ~nd Detergents", Volumes I and II, by Schwart~, Perry Berch.

Detergent compositions generally contain a6 major in~rPdients one or more detergent active compounds and one or more detergency builder~. Since detergent-active ~Q~

- 9 - C.1317 materials are frequently supplied by manufacturers in the form of fairly concentrated aqueous solutions, it is a simple matter to mix the other ingredients in to form liquids, slurries or pastes.

Advantageously the free water content of the final product does not exceed 20~ by weight, and more preferably does no~ exceed 10% by weight; this limitation applies not just to detergent compositions but to any material that can be packaged according to the invention. The term "free wa~er" is used in order to exclude water derived from water of crystallisation in solid ingredients.

The film and package of the invention are especially useful for the packaging of detergent compositions containing reactive or aggressive ingredients, especially bleaching agents. The protective layer prevents or substantially reduces interaction between bleaching agents such as inorganic persalts and the base film.
Although ~he film and package of the invention have been described with reference principally to the packagi.ng of detergent compositions, -they are useful for the packaging of o~her materials, especially liquids of limited or zero water content, as will be appreciated by the worker ~killed in the art.

The invention will now be described in more detail, by way of example only, with reference to ~he accompanying drawings, in which Figure 1 represents a cross-sec~ion through a packaging film according to the invention, Figure 2 represents a plan view of a sache~ constructed ~5 from the film of Figure 1, and Figure 3 represents a sectional view, in the direc~ion of - 10 - C.1317 the arrows, on the line III-III of Figure 2.

Referring now to Figure 1 of the accompanying drawings, a packaging film consists of a base film 1 of ~ra~sparent water-soluble plastics material, for example, polyvinyl alcohol/polyvinyl acetate. Pressed into one surface of the film 1 are discrete particles 2 of an inert pulverulent plastics material, for example, polytetra-fluoroethylene. Edge regions 3 of the base film 1 are free of particles so that they can be used for heat-sealing.

Figures 2 and 3 show a rectangular sachet for~ed from a single sheet of the film shown in Figure 1. The sachet has one folded edge 4 and three heat-sealed edges 5, and contains a liquid detergent composition 6. The particulate layer 2 is on the inner side of the sachet to protect the base film 1 from the liquid detergent 6.

The invention is further illustrated by the following non-limiting Examples.

5 Preparation of a water-soluble packaging film with a protective layer of polytetrafluoroethylene Method (i) A cold-water~soluble polyvinyl alcohol/polyvinyl acetate film supplied by Enak Ltd, UK having a thickness of 0.0038 cm wa~ heated to a temperature just above i~s glass ~ransition temperature (70-80C), to render it slightly ~acky. Polytetrafluoroethylene powder having an av~rage particle size of 5 fum, supplied by British Drug Houees ~5 Ltd, was sprinkled onto the upper surface of the h~ated film. The film was then paes2d between rollers heated to o~

~ C.1317 about 150C, then allowed to cool.

Method (ii) A polyvinyl alcohol/polyvinyl acetate film as described above was subjected at room temperature to a fine spray of water on one surface only, until that surface became tacky. Polytetrafluoroethylene particles were sprinkled onto the tackified surface, excess particles being brushed off.
The coated film prepared by both methods retained its solubility in water.

Preparation of detergent sachets 10 cm x 10 cm sachets were prepared from the coated films prepared in Example 1. Each sachet was made from a single folded sheet of the film, wlth one folded edge and two heat sealed edges, the fourth edge being left unsealed for filling purposes. For comparison, similar sachets of uncoated film were prepared.

A detergent slurry was prepared from the following 25 ingredients:
%

(weight) Nonionic detergent (C15 alcohol 40 condensed with an average of 9 moles of ethylene oxide per mole) Sodium tripolyphosphate hexahydrate 37 Sodium perborate tetrahydrate 20 Sodium carboxymethylcellulose Silicone oil 35 P~rfume ~ fluorescer - 12 - C.1317 Each sachet was filled with 75 g of detergent slurry and closed by heat-sealing along the fourth edge.

A filled sachet was placed in a Hoover (Trade Mark) Electronic 1100 front-loading automatic washing machine together with a 7 lb soiled fabric load together with detergency monitors. The 40C wash cycle was selected.

It was found that the sachet released its contents in less than two minutes from the beginning of the wash cycle and good detergency results were obtained.

Storage tests Sachets prepared as described in Example 2 were subjected to storaye in cartons for periods of 4, 24 and 28 weeks under conditions of 20C/90% relative humidity and 37C/70~ relative humidity. The contents of the sachets were then analysed, by titration of available oxygen, to determine the percentage decomposition of the sodium perborate initially present. The solubilities of the sachets were also tested. The results were as shown in the following Tables.

TABLE 1 - Storage tests at 20C/90% RH
Solubility~ after Sachet Storage time % bleach storage material (weeks) decomposed at 20C at 60C

Uncoated 4 15 VP G
film 24 90 VP G

35 Coated 4 5 ~ G
film 28 40 & &

o~

- 13 - C.1317 TABLE 2 - Storage testæ at 37C/70~ RH
Solubility* ater Sachet Storage time % bleach storage material (weeks) decomposed at 20C at 60C

Uncoated 4 20 VP G
film 24 93 VP G

Coated 4 10 G G
10 film 28 45 P G

*Solubility ratings:

VP - Sachet released its contents when immersed in water 15 but sachet film was not soluble.

P - Sachet released its contents but film was not completely soluble.
0 G - Sachet released its contents and film was soluble.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A packaging film comprising a base film of at least partially water-soluble plastics material carrying on one surface a protective layer, in particulate form, of an inert plastics material having a contact angle to water of at least 80°, said layer being effective to protect the base film surface from attack by aqueous media.

2. A film as claimed in claim 1, wherein the base film is of thermoplastic material.

3. A film as claimed in claim 2, wherein the base film is of polyvinyl alcohol or partially hydrolysed polyvinyl acetate.

4. A film as claimed in claim 1, wherein the material of the protective layer has a contact angle to water of at least 90°.

5. A film as claimed in claim 4, wherein the material of the protective layer has a contact angle to water of at least 100°.

6. A film as claimed in claim 1, wherein the pro-tective layer comprises particles of a material selected from the group consisting of polyfluorocarbon, poly-styrene, polyvinyl chloride, polyethylene and polyprop-ylene.

7. A film as claimed in claim 6, wherein the pro-tective layer comprises particles of polytetrafluoro-ethylene.

8. A film as claimed in claim 1, 2 or 3, wherein that surface of the base film not carrying the protective layer is provided with a light coating of an inert water-repellent plastics material in an amount insufficient to protect that surface from attack by aqueous media.

9. A package comprised of the packaging film claimed in claim 1, wherein the protective layer is on the inside surface of the base film, said layer being effective to protect the base film from attack by any water present inside the package.

10. A package as claimed in claim 10, which comprises a sachet formed from one or more sheets of said packaging film.

11. A package as claimed in claim 11, wherein the sheet(s) is or are thermoplastic and joined together by heat-sealing.

12. A package as claimed in claim 10, containing a detergent composition.

13. A package as claimed in claim 10, containing an at least partially liquid composition capable of attacking the material of the base film.

14. A package as claimed in claim 13 or claim 14, containing a bleaching agent.