Special receptacle or package – With specified material for container or content
Reexamination Certificate
2000-11-22
2004-08-17
Sergent, Rabon (Department: 1711)
Special receptacle or package
With specified material for container or content
C206S484000, C206S524200, C428S423100, C524S591000, C524S839000, C524S840000, C528S059000, C528S061000, C528S071000, C528S076000
Reexamination Certificate
active
06776287
ABSTRACT:
The present invention relates to water-soluble films suitable for the preparation of water-soluble packaging, e.g. sachets, capsules and bags, and to water-soluble packaging made from such films and to the production of aqueous polymer solutions which may be used for making such films.
Water-dissolvable packaging, particularly of the type provided by sachets, capsules and bags, have utility for packaging and delivering a range of materials, usually formulated compositions, and particularly formulated compositions which are hazardous (or at any rate unpleasant) to individuals with whom they come into contact or are hazardous or harmful to the environment. Examples include agrochemicals compositions (e.g. insecticides, herbicides, pesticides and fungicides), pharmaceutical compositions, laundry care products (e.g. detergents, fabric softeners and bleaches), dyestuffs, biocides, industrial or home cleaners, and public health products. The use of water-soluble packaging for packaging certain formulated compositions also provides a convenient way of adding a measured dosage of the formulation for subsequent dilution with water in order to provide the desired final concentration of the diluted formulation.
Polyvinyl alcohol (PVA) has been widely utilised for the preparation of water dissolvable film for the production of sachets for packaging hazardous materials such as agrochemicals; methyl cellulose is also widely utilised (see e.g. WO 93/22215). Such polymers however have limitations. For example, it is necessary to incorporate plasticisers to achieve the desired level of flexibility; also such films have poor heat seal characteristics in the absence of plasticisers; however plasticisers can migrate out of the film to render it brittle. Still further, the presence of reactable hydroxyl groups in such films restricts their use for packaging hydroxyl-reactive compounds. Yet still further such films are insolubilised by borates (used in laundry care).
It has also been proposed to employ carboxylated acrylic polymers for making water-dissolvable films for the production of water-soluble packaging (sachets, and the like). Such films, however, tend to have poor mechanical properties.
We have now discovered certain polyurethane films which are water-soluble and are suitable for the provision of water-dissolvable packaging (sachets, capsules, bags etc) for packaging. Such films, can e.g, have improved solubility in cold water compared to conventional PVA films; also unlike the PVA films, there is no need for externally added plasticiser (although plasticiser can be added if desired). Such films also have good mechanical properties and good heat seal characteristics without the need for added plasticisers.
According to the present invention there is provided a water-soluble film comprising a polyurethane polymer(s), which polyurethane polymer(s) has:
0 to 35 weight %, based on the weight of polyurethane polymer, of poly(ethylene oxide) groups which have a chain length(s) corresponding to a number average molecular weight within the range of from 200 to 5000 Daltons;
15 to 150 milliequivalents, per 100 g of polyurethane polymer, of acid-functional groups, and wherein
at least 50% of the acid-functional groups are neutralised, such neutralisation being with a base(s) at least part of which is a non-volatile base(s); and said polyurethane polymer(s) is a chain extended product formed using:
(A) a prepolymer component comprising an isocyanate-terminated polyurethane prepolymer, said component being formed from reactants which comprise:
(i) at least one organic polyisocyanate;
(ii) if poly(ethylene oxide) groups are present, at least one isocyanate-reactive compound providing said poly(ethylene oxide) groups in the resulting polyurethane polymer; and
(iii) at least one isocyanate-reactive compound providing said acid-functional groups in the resulting polyurethane polymer, and
(B) an active hydrogen component comprising an active hydrogen chain-extending compound(s).
The polyurethane films of the invention are normally made from an aqueous solution of the polyurethane, e.g. by casting. Alternatively dry polymer may be recovered from an aqueous solution (e.g. by spray drying or freeze drying, whereby any cosolvent used in its synthesis can be removed) and the film then formed by a) redissolving the polymer in water and applying (casting, spraying or doctor blading) to a substrate or b) melt processing (e.g. slit extension or blown film formation).
Therefore there is further provided according to the invention an aqueous solution of a polyurethane polymer as defined supra.
There is further provided according to the invention water-soluble packaging, particularly a sachet, capsule or bag, in which the enveloping film of the packaging comprises a polyurethane polymer film as defined supra.
There is further provided according to the invention the use of packaging as defined supra for packaging a material.
There is further provided according to the invention the combination of a water-soluble packaging as defined supra and a material packaged therein.
It has been proposed in JP-A-2102225 to use certain polyurethane polymers containing poly(ethylene oxide) groups and optionally (inter alia) acid-functional groups for the provision of water-soluble films for packaging. Such polyurethanes, however, have poly(ethylene oxide) groups with molecular weight of 6000 or more, and may contain acid-functional groups which if present are preferably at a very low level. Moreover the minimum amount of poly(ethylene oxide) in the polyurethane is about 69 weight % based on the weight of the polyurethane. Such a compositional make-up conspires to make the resulting films inferior to those of the present invention, particularly with regard to inferior mechanical properties and film softness-the high amount of poly(ethylene oxide) causing excessive moisture uptake, particularly in high humidity conditions.
Water-soluble films formed from certain polyurethane polymers have also been disclosed in JP-A-6032976, where such polymers are derived from polyoxyethylerie polyols and polyisocyanates. The. poly(ethylene oxide) group content in such polyurethanes is at least 50 weight %, and there is no disclosure or suggestion that acid groups should also be present. The resulting films are inferior to those of the present invention, e.g. having inferior mechanical properties due to the very high amount of poly(ethylene oxide) groups.
It is preferred that the polyurethane film is cold water-soluble since it may be difficult in some applications (e.g. large scale outdoor use as might be encountered when dispensing agrochemical materials) to provide hot water for dissolving the packaging. Cold water-soluble means herein soluble in water at temperatures ≦35° C., and generally between 5 and 35° C. (Note that if the film is cold water-soluble it will usually be hot water soluble as well, i.e. soluble at water temperatures >35° C.—e.g. up to 70° C. or above).
The poly(ethylene oxide) (hereinafter PEO) groups are preferably present in the polyurethane polymer in an amount within the range 2 to 35 weight % based on the weight (dry) of the polyurethane polymer, more preferably 2 to 20 weight %, and especially 2 to 15 weight %. Other preferred ranges are 5 to 35 weight % based on the dry weight of the polyurethane polymer, more preferably 5 to 20 weight % and especially 5 to 15 weight %. Above a level of 35 weight %, the resulting film tends to be unacceptably soft and of extremely inferior mechanical strength.
The PEO chains may be in-chain in the polyurethane polymer, or may be chain-pendant to the urethane backbone, or some may be in-chain and some may be chain-pendant. Also some of the PEO groups may be chain-terminal, e.g. at the end of a urethane chain. Usually, the PEO units are at least in-chain. The PEO groups, if present, contribute to the water-solubility and flexibility of the film.
The number average molecular weight of the PEO groups should be within the range of 200 to 5000 Daltons, preferably 300 to 3000 Daltons, and
Cheshire Phillip
Hinde David Charles
Overbeek Gerardus Cornelis
Padget John Christopher
Smak Yvonne Wilhelmina
Aquasol Limited
Pillsbury & Winthrop LLP
Sergent Rabon
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