CA2091365C - Composite polymeric articles - Google Patents
Composite polymeric articles Download PDFInfo
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- CA2091365C CA2091365C CA002091365A CA2091365A CA2091365C CA 2091365 C CA2091365 C CA 2091365C CA 002091365 A CA002091365 A CA 002091365A CA 2091365 A CA2091365 A CA 2091365A CA 2091365 C CA2091365 C CA 2091365C
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- Prior art keywords
- polymer
- soluble
- water
- insoluble
- layer
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
- B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
- B32B37/15—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state
- B32B37/153—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state at least one layer is extruded and immediately laminated while in semi-molten state
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/70—Other properties
- B32B2307/728—Hydrophilic
Landscapes
- Laminated Bodies (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)
- Graft Or Block Polymers (AREA)
Abstract
Composite polymeric articles, which may be in layer or film form, comprise a larger portion of a polymer which is water-soluble at 20 ° C against a smaller proportion of a polymer which is substantially water-insoluble at that temperature. For exam-ple, a layer product may have a thin layer (e.g. less than 5µm) of insoluble polymer superimposed on a thicker layer (e.g. at least 20µm) of soluble polymer. Both polymers are conveniently polyvinyl alcohol, which is non-toxic and useful in a number of dom-estic applications e.g. as a nappy backing sheet. The insoluble portion gives water resistance but negligible mechanical strength; the soluble part gives the mechanical strength. On dissolution of the soluble portion, the insoluble portion disintegrates mechani-cally. Articles may be made by co-extrusion or by moulding.
Description
2i0~136a v .
'W~ 92/01556 PL~'/Gg91 /0123 i COMPOSITE POLYPiERIC ARTICLES
FTELD OF THE INVENTION
This invention relates to articles, and in particular aspects to articles in sheet form, which are composites of two organic polymers having~different properties. Important applications of this invention concern articles and materials which can readily be ZO disposed-of when no longer required.
BACKGROUND OF THE TNVENTION
It has been known to make polymeric articles which, are purposely designed to be able to be destroyed by dissolving them, using soluble polymers such as polwinyl alcohol.
Polyvinyl acetate is a water-insoluble polymer whic'.~.
is obtained by polymerization of vinyl acetate. This polymer is used---for the production of polyvinyl alcohol by hydrolysis os alcoholysis to remove the acetyl groups from polyvinyl acetate. This removal of acetyl groups maybe carried to partial completion so as to give a product which is a copolymer or W nyl alcohol and vinyl acetate. If vinyl alcohol predomrna~es,:but-there is still a substantial quantity: of vinyl acetate present, 2~9135~ : , . ; ;.
VV~ 92/01556 ~ . ~''' ':;~ ~ PC°f/GB91 /OI23',!' ~~:
such a copolymer is soluble in cold water and is frequently referred to as "partially hydrolysed"
polyvinyl alcohol. The residual vinyl acetate content is typically about 11 wto corresponding to about 12 mol%.
If the reaction is taken further, close to completion, the crystallinity of the polyvinyl alcohol increases and the solubility in cold water decreases very markedly.
Material of this type is rererred to as "fully hydrolysed" polyvinyl alcohol., Its content of residual vinyl acetate is typically no greater than 3 mol%..
Polyvinyl alcohol can be made into film o~ sheet form. US-A-4444839 (Hoechst describes PVA labels which are soluble only in hot water, but which have an adhesive fixing layer which can dissolve in cold water enabling easy detachment cf the label. The adhesive may ba a polyvinyl alcohol.
It is also known"to make hospital laundry bags from partially hydrolysed polyvinyl alcohol sheet. The idea is that such bags can be filled :with dirty iaundr.- any 20r: the entire bag with its contents can then be put into a hospital washing mabhine where the polyvinyl alcohol will dissolve on contact with the wash water, thus releasing the laundry into the wash water.
In practice there is a difficult_r that the laundry may itself be,wet and if the wet laundry contacts the material of the bag it can dissalve it prematurely so 20~~3~~
.:;
VIrO 92/01556 ~ P(.'f/GB91/01237 that the bag falls apart. Unsuccessful attempts have been made to rectify this by modifying the solubility properties of the polyvinyl alcohol. For example, DE-A-3017246 (Melchior) describes laundry bags made primarily S of relatively insoluble PVA which will not disintegrate except in hot water. To enable the desired emptying of the bag in a cold wash, a subsidiary inner layer of the bag is made of cold-soluble PVA which can form releasable welds.
[The Invention) Broadly, this invention provides an article or material comprising a first organic polymer which is water-soluble at a given temperature, typically 20°C, and a second organic polymer located directly adjacent thereto, which second organic polymer dissolves more slowly or not at all in water at the same given temperature e.g. 20°C, with the quantity by weight of. the first (water-soluble polymer being greater Khan she quantity of the second polymer.
It will be explained.in.more detail below that the first, water-soluble,, polymer is preferably partially hydrolysed polyvinyl alcohol. The water-insoluble organic polymer may be fully hydrolysed polwinyl alcohol. Generally bath polymers will feel dry, not tacky, to the touch,.,.
In certain forms o° this invention the article or 2091365 ,:'r.'r ' :., ..
;:...
WO 92/0156 . ~ PCT/GB91/0133'~ v'~
material is laminar ~:rith adjacent layers of the two polymers. Such a form oa the invention could be polymer film or sheet to be used ~.. industrial production processes. Further forms of the invention are articles ., comprising pieces of such polymer sheet or film. In particular, the pieces of polymer sheet or film may be shaped to have curvature _:z more than one direction.
Articles and materials of this inventic: have the property that if an e::posed surface of the first polymer is brought into contact with water, it dissolves but where a first polymer surface is overlaid by the second polymer that surface is protected. The second polymer acts as a barrier and protects the first polymer against dissolution if the protected surface gets wet.
Usually, the two types of polymer will be substantially co-extensive in the article c~ material e.g. a continuous uniform multilayer laminate film, cr a body of the soluble polymer subs~antially surrounded by a coat of the insoluble.polymer.
The"second polymer can be a surprisingly thin layer, ' i so thin that' it does not remain intact after the first polymer dissolves. Thsn the first polymer is relied upon to provide mechanical strength while the second polymer i.
is relied on for a caster-barrier.
-- Such functionality has a wide range of applications.
In general the articles and materials of the invention ,;
209136 .. ' .~' 'W~ 92/Q1556 1'CT/GB91/01237 can be used where i~ can be arranged that at first the slower-dissolving second polym2r acts as a barrier protecting the water-soluble polymer from a material which .is, or might be, wet and then at a later stage an i unprotected surface ef the water-soluble polymer is allowed.to come into contact with water. The consequence I
of this is that dissolution of the soluble polymer takes , z place when desired but premature dissolution ._ prevented by the second polymer.
One possibility, mentioned here as an i?lustration, is laundry bags made from polymer film which is water-soluble with a very thin layer of water-insoluble polymer on the inside of the bags. wf the laundry happens to be wet, it will not cause the bags to dissolve prematurely because of the barrier function of the very thin insoluble layer. :when the bags are put inzac~ into a hospital washing machine the soluble layer is now contacted by the wash water cn-the outside ci 4he bags .
and dissolves. The very thin insoluble layer rapidly breaks up, releasing :,he laundry into the wash water.
The pieces of the insoluble layer are washed'into the sewage system with-the wash water at the end of the washing procedure.
The presence c~ insoluble polymer in the sewage system need not be'a problem.because the preferred _.
material, namely fully hydrolysed polyvinyl alcohol, is ~ ~r ,~ 1 t, ti .,.. .
Vd~ 92/01956 .. , , . ~ PCT/G~91/0123'i bio-degradable.
Another possibility is to have a piece or layer of the first polymer surrounded by the second polymer, so that the article can maintain its integrity in the S presence of water unless broken or ruptured, allowing water to attack the first polymer.
The. preferred soluble polymer is partially hydrolysed polyvinyl alcohol. As already mentioned above this is a copolymer of polyvinyl alcohol with vinyl acetate. Generally these copolymers are hydrolysed to an extent between 75 and 95 mol%, more.commonly '~etween 80 and 90 mal%. Thus, the mol ratio of vinyl alcohol to vinyl acetate lies between 75:25 and 95:5, more preferably 80:20 and 90:10. Partially hydrolysed polwinyl alcohol is fully bio-degradable. This has the considerable benefit that ~_ the polymer is allowed to dissolve in water which is ;:hen run to waste, the polymer which enters_the sewage system. will degrade into ecologically acceptable produce s. For this reason i~,. may be desirable that the soluble polymer does not' incorporate any other monomer although the possibility of incorporating a further comonomer is not excluded by this , invention.
The speed with which the more rapidly soluble first polymer dissolves. can be altered by selection of the:
polymer and also by selection of processing condiwi.ons, dV0 ~2/a1556 fCT/GF391/41237 as will be mentioned below. The length oz time for this polymer to dissolve can be chosen according to the use envisaged for the article or material and can range from a matter of seconds to several hours.
The speed with which partially hydrolysed polyvinyl alcohol dissolves decreases somewhat with increasing molecular weight of the polymer. Higher degrees of hydrolysis (so long as the material remains only partially hydrolysed) tend to decrease speed of solution.
Subjecting the polymer to heat during processing also ' retards the speed with which the eventual processed polymer will dissolve.
The mare rapidly soluble polymer used in the present invention will generally have a speed of solution such that when a sheet of the polymer with at least one side face of the 'sheet exposed is placed in distilled water at 20°C, the sheet dissolves sufficiently to break up wzthin a period of time not longer than 24 hours, usually not longer than 8 hours and possibly very much shorter than ~ this e.g. less than 10 sees for a test sheet 50um thick.
r..
The relatively less soluble polymer should of course dissolve more slowly than the more soluble polymer. For many applications it will be desirable that the polymer is essentially insoluble, to the extent that if a test r ~~heet~of the.material-with.sufficient._;thickness to be handled, e.g. 50um, is placed in .sterile_distilled water 209~39a.... , . . . . ~-:~. , ~'~ 92/01555 PCT/G1191/012"s .:
at 20°C, the sheet remains undissolved and intact for a period exceeding-,8~hours and perhaps more than 24 hours.
It is however possible that a soluble polymer which dissolves slowly will provide adequate barrier protection for a faster dissolving polymer in certain applications.
The relatively slowly dissolving polymer is preferably fully hydrolysed polyvinyl alcohol or a suitably insoluble pol:rvinyl alcohol copolymer. Fully-hydrolysed PVAs are over 96 mola hydrolysed; commonly over 98 mol%. They are in fact appreciably water-soluble at raised temperatures, e.g. over about 50°C, and.
usually highly soluble over about 80°C, although some special 'types can withstand such temperatures for some time without dissolving. At about room temperature, however, solubility is sparing and particularly so for the more highly polymerised PVAs.
It will frequentJ.y be preferred that both polymers are biodegradable, meaning that ;when discarded into sewage or otherwise exposed to water and natural bacteria, they decompose to naturally occurring chemical species within a few months at most. Using polyvinyl alcohol for both layers achieves this result.
The articles of the invention will usually have the "insoluble" polymer exposed to the exterior. The soluble polymer may.also be exposed, or may be enclosed by the insoluble polymer. However t:ne insoluble layer will W~ 92101555 ' 2 fl 913 6 ~ PCT/GB91/01237 usually contact only the ex~eerior and the more soluble polymer; not any adhesive or other type of layer.
In the article or material, the weight ratio of the more soluble to the less soluble polymer will preferably be at least 2:1, more preferably at least 3:1, still more preferably at least 5:1 and perhaps above 10:1 up to even 100:1, particularly for thick or three-dimensional articles.
In an alternative preferred aspect, the less soluble polymer covers the more soluble polymer with a general thickness which is preferably not more than 20um, more preferably not more than l0um, most preferably not more than Sum. It may be as thin as 2um or thinner.
In a film product, the total film thickness may f5 range typically from Sum to lmm, more typically from l0um to 200um.
Each polymer may be used in admixture with other , substances. In particular,~a phasticiser is usuall,~
desirable to achieve a pliable film product. Glycerol, trimethylol propane, and glycols are suitable plasticisers. Colours and/or fillers may also be used if desired, in one or both layers. These may be conventional. v Articles mav.take various forms, for example, a film - may comprise justw two layers, one of each kind of -polymer. -Or, the film may be a.sandwiGh.of more soluble ~~91365 iVVO 92/01556 .~ ; ' ~ ~. "1: ' ~ ~. P~'f/GB91 /0123 , ' polymer between layers of less soluble polymer.
Non-film articles may comprise a "core" of the soluble polymer substantially or entirely covered by the ' Y.
less soluble polymer.W,.Such an article can resist attack 5 by water, but when it is broken water can dissolve the exposed core and hence the entire article may be disintegrated.
In another aspect, the invention provides processes for preparing composite articles and materials as 10 described above.
There are a number of ways of forming respective portions e.g. layers of the two polymers superimposed and bonded together as a composite article e.g. film or sheet. Broadly 'these are various (a) casting/moulding and (b) extrusion processes.
A cast/mould process for film or shee'c involves forming a first of the layers - the less soluble one if PVA - on a flat or shaped surface and subseauently applying the second layer on 'top of it. Application may , be e.g. by spraying or by a dripped feed. PVA~can be applied with water e.g. as an aqueous solution or dispersion optionally containing plasticisers, thickeners etc. as appropriate, from which water is evaporated in forming the two layers of polymer.
Extrusion preferably involves co-extrusion of the two layers. Hlown film co-extrusion is pbeferred. ' I
~C~9~.~~~~;: :_ , 1~V0 92/01556 PCf/G B91 /01237 The process can be an adaptaticn of the known process for forming a blown film from a single PVA
polymer. The conventional production of PVA film by extrusion entails feeding a plasticised volume e.g. an i aqueous solution or dispersion of the PVA, to a die with an annular extrusion orifice surrounding an air inlet.
I
As the plasticised polyvinyl alcohol is extruded from the orifice it forms a tube which is blown out into a larger diameter tube by the pressure of air introduced through the air inlet. The blown tube is drawn off between a pear of nip rollers which close off the air space.
A high pressure, short screw extruder is'suitable.
This usually has a smooth bush, and e.g, a vibrating trickle feeder to avoid overloading the screw, which can .
be a problem with PVA.
A film-blowing process which is one aspect of this invention comprises supplying an appropriate extrudable form e.g. solution or dispersion of the polymers to respective extrusion orifices of a die, the orifices being annular and one within the other, so as to extrude j tubes of the polymers from the orifices, while also ' s . .
supplying gas pressure to the interior of the inner tube thereby expanding both pubes and. uniting the inner tube i with the outer tube to form a single tube made up fram -25 : - layers of the two palymers . .. .
The-extrusion machinery can resemble conventional 2~913fi~~ ;:,;~;~:.
W~ 92/01556 PCf/GB91 /012:; :'::
machinery for forming blown films of polyvinyl alcohol except however that its extrusion die has two annular orifices instead of the usual single orifice and a feed screw for each orifice with associated means for supply to each feed screw.,. ~~° ' The gas which is blown in is suitably hot air, via an inlet~within the inner annular slit. The heated air .
can also evaporate water From the PVA so that the film bubble dries and can be passed through e.g. nip rollers above the die.
Extrusion of PVA, including blown film extrusion, is known technology and the skilled man will be~able to select suitable conditions, for example a die temperature in the region of 150°C, etc.
The relative rates of feed to the die arifices and concentrations of the polymers can be adjusted to achieve the desired ratio of thickness of the two layers.
Processing aids such as antifoamers and lubricants may be used if desired.
In a third aspect, the invention provides a co-extrusion apparatus adapted for producing bubble-blown film as described above.
Particular uses envisaged for the laminar. articles include disposable packaging material and barrier layers in sanitary products e.g. nappies and bed-pan liners.
These need to be able to withstand wetness on one side;
2~9136~~~
~~ W~ 92/01556 PCT/GB9a/01237 by using film embodying the present invention they can after use be dropped, with their, contents, into a WC bowl to disintegrate. The whole can then~be flushed away.
The advantage in terms of convenience is apparent, while from the environmental point of view. PVA is not only biodegradable to harmless C02 and water, but also has no known toxicity and hence does not present.a risk before chemical degradation.
Embodiments of the invention are now described by way of example, with reference to the accompanying drawings in,which:
Fig 1 is a schematic side view of a blown film co-extrusion apparatus;
Fig 2 is a schematic top view of the apparatus;
Fig 3 is a schematic cross-section of the co-extrusion die of the apparatus;
Fig 4 shows steps in making a baby's potty liner;
Fig 5 shows a disposable nappy.
Fig 6 shows a two layer film; ' , Fig 7 shows a three-layer laminar article, and Fig 8 shows a three-dimensional moulded article.
Materials Used Tn the following embodiments, both the insoluble and soluble layers- were made from PVP: . The PVAs used were "Mowiol" (Registered Trade Mark) obtainable from Hoechst . '., ~~ 9x/01556 PGT/~ B91 /012 : v AC.. The soluble layers were made using Mowiol 26-88, a partially-hydrolysed PVA having a mean molecular weight of 103000, an 8~3 molo degree of hydrolysis and whose viscosity, measured..as~a 4% aqueous solution, is 26 mPa.s2. The insoluble layers were made using (i) Mowiol 20-98, a fully-hydrolysed grade in which the mean ' molecular weight, viscosity and hydrolysis values are 70,000, 20 mPa.s2 and 98.4 mol% respectively, and (ii) a 50:50 blend of Mowiol 56/98 and Mowiol 28/99 which are fully-hydrolysed grades having viscosities and hydrolysis values substantially as indicated by their respective specification numbers, as before.
For the cast processes, each of these was made up in a respective aqueous composition containing,. by weight, Z5 15~ PVA granules 5~ glycerine (plasticiser) 80~ water.
The PVA granules were added.;:o the water and glycerine and then heated at 93°C for °ifteen to twenty minutes to form a solution.
For the coextrusion process, the make-up~pf the individual PVA compositions can be selected in accordance with known criteria.
Co-extrusion Apparatus 25' An experimental apparatus caas set up as shown v schematically in Figs l to 3. A pair of heated s~.pply - i 2~9~.36~w- ;
i~VO 92/01956 ' PC'f/GB91/01237 tanks 1 were provided, one for each PVA type, and connected to respective intakes of a pair of 10 cm-long feed screws 2. A variable electric drive 3 was connected to drive the feed screws at predetermined proportional 5 rates. Outputs from the feed screws 2 passed in conventional manner to respective extrusion inputs of an upwardly opening co-extrusion die 5. This had two circular and concentric extrusion slit openings 10,~.~.
In the experimental apparatus the outer slit 10 had a 10 diameter of 35 mm and the inner slit a diameter of 25 mm.
The width of the outer slit 10 was approximately 0.5 mm and this was approximately four times the width of the inner slit 11. A centrally-opening hole 15 was provided in the die for blowing warm air up through the extrusion 15 rings in conventional manner.
Vertically above the die, a.pair of nip rollers 16 were mounted with a take off to a collecting point snot shown) for the film produced.
Co-extrusion Process .Aqueous extrudable PVA compositions are prepared as described above e.g. from Mowiol 26-88 and Mowiol 20-98, and each put in a respective heated tank 1 of the apparatus. The tank of Mowiol 26-88 (soluble, partially hydrolysed) composition communicates via its feed screw 2 -with thewouter, wider extrusion slit 10. ..The Mowiol 20-98 (insoluble, fully hydrolysed) compositiow communicates 209136~;~ ~ : . . .
wo 9z/oms6 Pcz'icB9mo~z~.=;~
~,16 via its feed screca ,2,~,;~it!~ the inner , narrower extrusion slit 11.
The die is heated to 1~0°C and the heated PVA
compositions then fed to the die by their respective scxews 2 at rates of~e.g. .,:1 (soluble:insoluble). At the same.time, warm air is blown to the air inlet 17 and out through the hole in the centre of the die ~. A blown .
film bubble 20 can thereby be formed above the die, with the thin insoluble.PVA layer on the inside. Cooling air is blown, again in conventional manner, over the outside of the bubble above the die. The two extruded layers , emerging from their respective slits 10,11 coalesce to . form the composite film within a few millimeters of exiting the die. ' The blown air dries the bubble rapidly to a non-tacky state such that it can be flattened between the nip rollers 16 and collected folded flat, to be cut open into single sheet form subsequentl:;.
The process was repeated using the blend of Mowiol 56/98 and 28/99 in place of the Mowiol 20/98, to produce a still less soluble protective thin layer in the film.: ' Mould Process This process was used to make a liner for a child's potty: - A conve.x~. mould surface 2~ ( see Fig 4a i was i v prepared, made from.a, shaped metal sheet.., This had a hat ...-. -.shape, with an upwardly-projecting central portion 26 and ~fl913fi5 ~'~ 92/01556 PCT/G1391/01237 a surrounding bottom rim 27 for forming the rim of the liner. ' An insoluble PVA layer was formed by spraying a solutian of Mowiol 20-98 onto the outer, convex mould surface. The solution was as described previously under '°Materials Used", but with the substitution of 10~
cellulose ether thickener ("Tylose" (Registered Trade Mark)) for 10~ of the water to improve adhesion of the.
PVA layer to the sloping sides of the mould 25. This first layer was then dried to tackiness by blowing it with warm air, and a second layer of a corresponding thickened aqueous solution of Mowiol 2588 was sprayed over it to a considerably greater thickness. In particular, a pronouncedly thick layer was formed on the .
brim 27 of the former, to strengthen the rim oø the liner.
After drying the water from this second coat using warm air blowers, the basic composite PVA liner 30 was lifted from the mould 25. An absorbent pad 31 of cellulose wadding was placed in its base, and the flat upper surface of the rim was given a coating of PVA
adhesive 32 which was then covered by a ring of siliconised release paper 33.
' In use, the insoluble inner layer of the liner was ~ able to contain the potty contents for an extended period without leaking. -To dispose of both liner and contents ~U~fl3~~ . , .
'W~ 92/01556 PCf/GB91 /0123-: - ' the release paper 33 was lifted off and two opposing sides of the rim stuck together face-to-face using the PVA adhesive coat 32, so as to form a sealed bag completely enclosing the contents. The whole was then taken to a WC and dropped into the water where after about ten seconds it had already broken up so much as to be fully flushable.
Again, the process.was repeated using instead the 56/98 and 28/99 blend to form the insoluble layer.
Improved resistance to water was noted.
Disposable Nappy A backing sheet 40 for a disposable nappy was made by sequential spraying and drying of two different PVA
layers as described above for the liner, but~this time on a flat steel surface and without the Tylose thickener.
The thicker, soluble layer formed the outside of the nappy and the thin, insoluble layer the inside (uppermost in Fig 5). ~In the cast sheet; the more soluble layer may_ be about 0.1 mm thick and the less soluble layer about 0...02 mm, but these can be adjusted according ~o the required strength. A conventional cellulosic absorbent pad 41 was affixed to the thin insoluble layer using a aommercial PVA adhesive.
In an experiment,- aqueous liquid was poured onto the :- 25 padding and the nappy was then ralled up. After being left for eight hours, the nappy. was still intact and ~U~l~b;~-~ v : . ..
'NVO 92/01556 PCT/GB91/01237 there was no leakage. However, on putting the rolled-up nappy into a bowl of water, it broke up in seconds and dispersed.
Figures 6 to 8 illustrate schematically various forms of article embodying the invention.
Figure 6 shows a two-layer flexible film comprising a layer.50 of fully-hydrolysed PVA, 3~am thick, superimposed on a layer~~l of partially-hydrolysed (soluble) PVA 25~am thick.
Figure 7 shows a disposable drinking cup.made from a three layer laminar product. This has a thick intermediate layer 61 of partially-hydrolysed PVA, perhaps 0.5mm thick, giving mechanical strength to the cup. The inner and outer surfaces of the cup have a thin, Sum coating 60 of fully-hydrolysed PVA which prevents outside moisture, and liquid in the cup, from attacking the intermediate layer 61. To render the cup disposable it need only be torn up, whereupon the intermediate layer is exposed and can be dissolved.
20. Fig. 8 shows a moulded golf tee having a central core 7l of partially-hydrolysed PVA forming the basic shape of the tee. Sum coating 70 of insoluble PVA covers the tea. The coating may be applied to the moulded "soluble" tee by conventional methods. The tee can a withstand normal use. If it is lost, any natural wear or damage will allow natural moisture to destroy it quickly ~U~1~~~~~ ~. .
WO 92/01556 PCd'/GB91/0123 ~
and hence avoid a litter problem.
'W~ 92/01556 PL~'/Gg91 /0123 i COMPOSITE POLYPiERIC ARTICLES
FTELD OF THE INVENTION
This invention relates to articles, and in particular aspects to articles in sheet form, which are composites of two organic polymers having~different properties. Important applications of this invention concern articles and materials which can readily be ZO disposed-of when no longer required.
BACKGROUND OF THE TNVENTION
It has been known to make polymeric articles which, are purposely designed to be able to be destroyed by dissolving them, using soluble polymers such as polwinyl alcohol.
Polyvinyl acetate is a water-insoluble polymer whic'.~.
is obtained by polymerization of vinyl acetate. This polymer is used---for the production of polyvinyl alcohol by hydrolysis os alcoholysis to remove the acetyl groups from polyvinyl acetate. This removal of acetyl groups maybe carried to partial completion so as to give a product which is a copolymer or W nyl alcohol and vinyl acetate. If vinyl alcohol predomrna~es,:but-there is still a substantial quantity: of vinyl acetate present, 2~9135~ : , . ; ;.
VV~ 92/01556 ~ . ~''' ':;~ ~ PC°f/GB91 /OI23',!' ~~:
such a copolymer is soluble in cold water and is frequently referred to as "partially hydrolysed"
polyvinyl alcohol. The residual vinyl acetate content is typically about 11 wto corresponding to about 12 mol%.
If the reaction is taken further, close to completion, the crystallinity of the polyvinyl alcohol increases and the solubility in cold water decreases very markedly.
Material of this type is rererred to as "fully hydrolysed" polyvinyl alcohol., Its content of residual vinyl acetate is typically no greater than 3 mol%..
Polyvinyl alcohol can be made into film o~ sheet form. US-A-4444839 (Hoechst describes PVA labels which are soluble only in hot water, but which have an adhesive fixing layer which can dissolve in cold water enabling easy detachment cf the label. The adhesive may ba a polyvinyl alcohol.
It is also known"to make hospital laundry bags from partially hydrolysed polyvinyl alcohol sheet. The idea is that such bags can be filled :with dirty iaundr.- any 20r: the entire bag with its contents can then be put into a hospital washing mabhine where the polyvinyl alcohol will dissolve on contact with the wash water, thus releasing the laundry into the wash water.
In practice there is a difficult_r that the laundry may itself be,wet and if the wet laundry contacts the material of the bag it can dissalve it prematurely so 20~~3~~
.:;
VIrO 92/01556 ~ P(.'f/GB91/01237 that the bag falls apart. Unsuccessful attempts have been made to rectify this by modifying the solubility properties of the polyvinyl alcohol. For example, DE-A-3017246 (Melchior) describes laundry bags made primarily S of relatively insoluble PVA which will not disintegrate except in hot water. To enable the desired emptying of the bag in a cold wash, a subsidiary inner layer of the bag is made of cold-soluble PVA which can form releasable welds.
[The Invention) Broadly, this invention provides an article or material comprising a first organic polymer which is water-soluble at a given temperature, typically 20°C, and a second organic polymer located directly adjacent thereto, which second organic polymer dissolves more slowly or not at all in water at the same given temperature e.g. 20°C, with the quantity by weight of. the first (water-soluble polymer being greater Khan she quantity of the second polymer.
It will be explained.in.more detail below that the first, water-soluble,, polymer is preferably partially hydrolysed polyvinyl alcohol. The water-insoluble organic polymer may be fully hydrolysed polwinyl alcohol. Generally bath polymers will feel dry, not tacky, to the touch,.,.
In certain forms o° this invention the article or 2091365 ,:'r.'r ' :., ..
;:...
WO 92/0156 . ~ PCT/GB91/0133'~ v'~
material is laminar ~:rith adjacent layers of the two polymers. Such a form oa the invention could be polymer film or sheet to be used ~.. industrial production processes. Further forms of the invention are articles ., comprising pieces of such polymer sheet or film. In particular, the pieces of polymer sheet or film may be shaped to have curvature _:z more than one direction.
Articles and materials of this inventic: have the property that if an e::posed surface of the first polymer is brought into contact with water, it dissolves but where a first polymer surface is overlaid by the second polymer that surface is protected. The second polymer acts as a barrier and protects the first polymer against dissolution if the protected surface gets wet.
Usually, the two types of polymer will be substantially co-extensive in the article c~ material e.g. a continuous uniform multilayer laminate film, cr a body of the soluble polymer subs~antially surrounded by a coat of the insoluble.polymer.
The"second polymer can be a surprisingly thin layer, ' i so thin that' it does not remain intact after the first polymer dissolves. Thsn the first polymer is relied upon to provide mechanical strength while the second polymer i.
is relied on for a caster-barrier.
-- Such functionality has a wide range of applications.
In general the articles and materials of the invention ,;
209136 .. ' .~' 'W~ 92/Q1556 1'CT/GB91/01237 can be used where i~ can be arranged that at first the slower-dissolving second polym2r acts as a barrier protecting the water-soluble polymer from a material which .is, or might be, wet and then at a later stage an i unprotected surface ef the water-soluble polymer is allowed.to come into contact with water. The consequence I
of this is that dissolution of the soluble polymer takes , z place when desired but premature dissolution ._ prevented by the second polymer.
One possibility, mentioned here as an i?lustration, is laundry bags made from polymer film which is water-soluble with a very thin layer of water-insoluble polymer on the inside of the bags. wf the laundry happens to be wet, it will not cause the bags to dissolve prematurely because of the barrier function of the very thin insoluble layer. :when the bags are put inzac~ into a hospital washing machine the soluble layer is now contacted by the wash water cn-the outside ci 4he bags .
and dissolves. The very thin insoluble layer rapidly breaks up, releasing :,he laundry into the wash water.
The pieces of the insoluble layer are washed'into the sewage system with-the wash water at the end of the washing procedure.
The presence c~ insoluble polymer in the sewage system need not be'a problem.because the preferred _.
material, namely fully hydrolysed polyvinyl alcohol, is ~ ~r ,~ 1 t, ti .,.. .
Vd~ 92/01956 .. , , . ~ PCT/G~91/0123'i bio-degradable.
Another possibility is to have a piece or layer of the first polymer surrounded by the second polymer, so that the article can maintain its integrity in the S presence of water unless broken or ruptured, allowing water to attack the first polymer.
The. preferred soluble polymer is partially hydrolysed polyvinyl alcohol. As already mentioned above this is a copolymer of polyvinyl alcohol with vinyl acetate. Generally these copolymers are hydrolysed to an extent between 75 and 95 mol%, more.commonly '~etween 80 and 90 mal%. Thus, the mol ratio of vinyl alcohol to vinyl acetate lies between 75:25 and 95:5, more preferably 80:20 and 90:10. Partially hydrolysed polwinyl alcohol is fully bio-degradable. This has the considerable benefit that ~_ the polymer is allowed to dissolve in water which is ;:hen run to waste, the polymer which enters_the sewage system. will degrade into ecologically acceptable produce s. For this reason i~,. may be desirable that the soluble polymer does not' incorporate any other monomer although the possibility of incorporating a further comonomer is not excluded by this , invention.
The speed with which the more rapidly soluble first polymer dissolves. can be altered by selection of the:
polymer and also by selection of processing condiwi.ons, dV0 ~2/a1556 fCT/GF391/41237 as will be mentioned below. The length oz time for this polymer to dissolve can be chosen according to the use envisaged for the article or material and can range from a matter of seconds to several hours.
The speed with which partially hydrolysed polyvinyl alcohol dissolves decreases somewhat with increasing molecular weight of the polymer. Higher degrees of hydrolysis (so long as the material remains only partially hydrolysed) tend to decrease speed of solution.
Subjecting the polymer to heat during processing also ' retards the speed with which the eventual processed polymer will dissolve.
The mare rapidly soluble polymer used in the present invention will generally have a speed of solution such that when a sheet of the polymer with at least one side face of the 'sheet exposed is placed in distilled water at 20°C, the sheet dissolves sufficiently to break up wzthin a period of time not longer than 24 hours, usually not longer than 8 hours and possibly very much shorter than ~ this e.g. less than 10 sees for a test sheet 50um thick.
r..
The relatively less soluble polymer should of course dissolve more slowly than the more soluble polymer. For many applications it will be desirable that the polymer is essentially insoluble, to the extent that if a test r ~~heet~of the.material-with.sufficient._;thickness to be handled, e.g. 50um, is placed in .sterile_distilled water 209~39a.... , . . . . ~-:~. , ~'~ 92/01555 PCT/G1191/012"s .:
at 20°C, the sheet remains undissolved and intact for a period exceeding-,8~hours and perhaps more than 24 hours.
It is however possible that a soluble polymer which dissolves slowly will provide adequate barrier protection for a faster dissolving polymer in certain applications.
The relatively slowly dissolving polymer is preferably fully hydrolysed polyvinyl alcohol or a suitably insoluble pol:rvinyl alcohol copolymer. Fully-hydrolysed PVAs are over 96 mola hydrolysed; commonly over 98 mol%. They are in fact appreciably water-soluble at raised temperatures, e.g. over about 50°C, and.
usually highly soluble over about 80°C, although some special 'types can withstand such temperatures for some time without dissolving. At about room temperature, however, solubility is sparing and particularly so for the more highly polymerised PVAs.
It will frequentJ.y be preferred that both polymers are biodegradable, meaning that ;when discarded into sewage or otherwise exposed to water and natural bacteria, they decompose to naturally occurring chemical species within a few months at most. Using polyvinyl alcohol for both layers achieves this result.
The articles of the invention will usually have the "insoluble" polymer exposed to the exterior. The soluble polymer may.also be exposed, or may be enclosed by the insoluble polymer. However t:ne insoluble layer will W~ 92101555 ' 2 fl 913 6 ~ PCT/GB91/01237 usually contact only the ex~eerior and the more soluble polymer; not any adhesive or other type of layer.
In the article or material, the weight ratio of the more soluble to the less soluble polymer will preferably be at least 2:1, more preferably at least 3:1, still more preferably at least 5:1 and perhaps above 10:1 up to even 100:1, particularly for thick or three-dimensional articles.
In an alternative preferred aspect, the less soluble polymer covers the more soluble polymer with a general thickness which is preferably not more than 20um, more preferably not more than l0um, most preferably not more than Sum. It may be as thin as 2um or thinner.
In a film product, the total film thickness may f5 range typically from Sum to lmm, more typically from l0um to 200um.
Each polymer may be used in admixture with other , substances. In particular,~a phasticiser is usuall,~
desirable to achieve a pliable film product. Glycerol, trimethylol propane, and glycols are suitable plasticisers. Colours and/or fillers may also be used if desired, in one or both layers. These may be conventional. v Articles mav.take various forms, for example, a film - may comprise justw two layers, one of each kind of -polymer. -Or, the film may be a.sandwiGh.of more soluble ~~91365 iVVO 92/01556 .~ ; ' ~ ~. "1: ' ~ ~. P~'f/GB91 /0123 , ' polymer between layers of less soluble polymer.
Non-film articles may comprise a "core" of the soluble polymer substantially or entirely covered by the ' Y.
less soluble polymer.W,.Such an article can resist attack 5 by water, but when it is broken water can dissolve the exposed core and hence the entire article may be disintegrated.
In another aspect, the invention provides processes for preparing composite articles and materials as 10 described above.
There are a number of ways of forming respective portions e.g. layers of the two polymers superimposed and bonded together as a composite article e.g. film or sheet. Broadly 'these are various (a) casting/moulding and (b) extrusion processes.
A cast/mould process for film or shee'c involves forming a first of the layers - the less soluble one if PVA - on a flat or shaped surface and subseauently applying the second layer on 'top of it. Application may , be e.g. by spraying or by a dripped feed. PVA~can be applied with water e.g. as an aqueous solution or dispersion optionally containing plasticisers, thickeners etc. as appropriate, from which water is evaporated in forming the two layers of polymer.
Extrusion preferably involves co-extrusion of the two layers. Hlown film co-extrusion is pbeferred. ' I
~C~9~.~~~~;: :_ , 1~V0 92/01556 PCf/G B91 /01237 The process can be an adaptaticn of the known process for forming a blown film from a single PVA
polymer. The conventional production of PVA film by extrusion entails feeding a plasticised volume e.g. an i aqueous solution or dispersion of the PVA, to a die with an annular extrusion orifice surrounding an air inlet.
I
As the plasticised polyvinyl alcohol is extruded from the orifice it forms a tube which is blown out into a larger diameter tube by the pressure of air introduced through the air inlet. The blown tube is drawn off between a pear of nip rollers which close off the air space.
A high pressure, short screw extruder is'suitable.
This usually has a smooth bush, and e.g, a vibrating trickle feeder to avoid overloading the screw, which can .
be a problem with PVA.
A film-blowing process which is one aspect of this invention comprises supplying an appropriate extrudable form e.g. solution or dispersion of the polymers to respective extrusion orifices of a die, the orifices being annular and one within the other, so as to extrude j tubes of the polymers from the orifices, while also ' s . .
supplying gas pressure to the interior of the inner tube thereby expanding both pubes and. uniting the inner tube i with the outer tube to form a single tube made up fram -25 : - layers of the two palymers . .. .
The-extrusion machinery can resemble conventional 2~913fi~~ ;:,;~;~:.
W~ 92/01556 PCf/GB91 /012:; :'::
machinery for forming blown films of polyvinyl alcohol except however that its extrusion die has two annular orifices instead of the usual single orifice and a feed screw for each orifice with associated means for supply to each feed screw.,. ~~° ' The gas which is blown in is suitably hot air, via an inlet~within the inner annular slit. The heated air .
can also evaporate water From the PVA so that the film bubble dries and can be passed through e.g. nip rollers above the die.
Extrusion of PVA, including blown film extrusion, is known technology and the skilled man will be~able to select suitable conditions, for example a die temperature in the region of 150°C, etc.
The relative rates of feed to the die arifices and concentrations of the polymers can be adjusted to achieve the desired ratio of thickness of the two layers.
Processing aids such as antifoamers and lubricants may be used if desired.
In a third aspect, the invention provides a co-extrusion apparatus adapted for producing bubble-blown film as described above.
Particular uses envisaged for the laminar. articles include disposable packaging material and barrier layers in sanitary products e.g. nappies and bed-pan liners.
These need to be able to withstand wetness on one side;
2~9136~~~
~~ W~ 92/01556 PCT/GB9a/01237 by using film embodying the present invention they can after use be dropped, with their, contents, into a WC bowl to disintegrate. The whole can then~be flushed away.
The advantage in terms of convenience is apparent, while from the environmental point of view. PVA is not only biodegradable to harmless C02 and water, but also has no known toxicity and hence does not present.a risk before chemical degradation.
Embodiments of the invention are now described by way of example, with reference to the accompanying drawings in,which:
Fig 1 is a schematic side view of a blown film co-extrusion apparatus;
Fig 2 is a schematic top view of the apparatus;
Fig 3 is a schematic cross-section of the co-extrusion die of the apparatus;
Fig 4 shows steps in making a baby's potty liner;
Fig 5 shows a disposable nappy.
Fig 6 shows a two layer film; ' , Fig 7 shows a three-layer laminar article, and Fig 8 shows a three-dimensional moulded article.
Materials Used Tn the following embodiments, both the insoluble and soluble layers- were made from PVP: . The PVAs used were "Mowiol" (Registered Trade Mark) obtainable from Hoechst . '., ~~ 9x/01556 PGT/~ B91 /012 : v AC.. The soluble layers were made using Mowiol 26-88, a partially-hydrolysed PVA having a mean molecular weight of 103000, an 8~3 molo degree of hydrolysis and whose viscosity, measured..as~a 4% aqueous solution, is 26 mPa.s2. The insoluble layers were made using (i) Mowiol 20-98, a fully-hydrolysed grade in which the mean ' molecular weight, viscosity and hydrolysis values are 70,000, 20 mPa.s2 and 98.4 mol% respectively, and (ii) a 50:50 blend of Mowiol 56/98 and Mowiol 28/99 which are fully-hydrolysed grades having viscosities and hydrolysis values substantially as indicated by their respective specification numbers, as before.
For the cast processes, each of these was made up in a respective aqueous composition containing,. by weight, Z5 15~ PVA granules 5~ glycerine (plasticiser) 80~ water.
The PVA granules were added.;:o the water and glycerine and then heated at 93°C for °ifteen to twenty minutes to form a solution.
For the coextrusion process, the make-up~pf the individual PVA compositions can be selected in accordance with known criteria.
Co-extrusion Apparatus 25' An experimental apparatus caas set up as shown v schematically in Figs l to 3. A pair of heated s~.pply - i 2~9~.36~w- ;
i~VO 92/01956 ' PC'f/GB91/01237 tanks 1 were provided, one for each PVA type, and connected to respective intakes of a pair of 10 cm-long feed screws 2. A variable electric drive 3 was connected to drive the feed screws at predetermined proportional 5 rates. Outputs from the feed screws 2 passed in conventional manner to respective extrusion inputs of an upwardly opening co-extrusion die 5. This had two circular and concentric extrusion slit openings 10,~.~.
In the experimental apparatus the outer slit 10 had a 10 diameter of 35 mm and the inner slit a diameter of 25 mm.
The width of the outer slit 10 was approximately 0.5 mm and this was approximately four times the width of the inner slit 11. A centrally-opening hole 15 was provided in the die for blowing warm air up through the extrusion 15 rings in conventional manner.
Vertically above the die, a.pair of nip rollers 16 were mounted with a take off to a collecting point snot shown) for the film produced.
Co-extrusion Process .Aqueous extrudable PVA compositions are prepared as described above e.g. from Mowiol 26-88 and Mowiol 20-98, and each put in a respective heated tank 1 of the apparatus. The tank of Mowiol 26-88 (soluble, partially hydrolysed) composition communicates via its feed screw 2 -with thewouter, wider extrusion slit 10. ..The Mowiol 20-98 (insoluble, fully hydrolysed) compositiow communicates 209136~;~ ~ : . . .
wo 9z/oms6 Pcz'icB9mo~z~.=;~
~,16 via its feed screca ,2,~,;~it!~ the inner , narrower extrusion slit 11.
The die is heated to 1~0°C and the heated PVA
compositions then fed to the die by their respective scxews 2 at rates of~e.g. .,:1 (soluble:insoluble). At the same.time, warm air is blown to the air inlet 17 and out through the hole in the centre of the die ~. A blown .
film bubble 20 can thereby be formed above the die, with the thin insoluble.PVA layer on the inside. Cooling air is blown, again in conventional manner, over the outside of the bubble above the die. The two extruded layers , emerging from their respective slits 10,11 coalesce to . form the composite film within a few millimeters of exiting the die. ' The blown air dries the bubble rapidly to a non-tacky state such that it can be flattened between the nip rollers 16 and collected folded flat, to be cut open into single sheet form subsequentl:;.
The process was repeated using the blend of Mowiol 56/98 and 28/99 in place of the Mowiol 20/98, to produce a still less soluble protective thin layer in the film.: ' Mould Process This process was used to make a liner for a child's potty: - A conve.x~. mould surface 2~ ( see Fig 4a i was i v prepared, made from.a, shaped metal sheet.., This had a hat ...-. -.shape, with an upwardly-projecting central portion 26 and ~fl913fi5 ~'~ 92/01556 PCT/G1391/01237 a surrounding bottom rim 27 for forming the rim of the liner. ' An insoluble PVA layer was formed by spraying a solutian of Mowiol 20-98 onto the outer, convex mould surface. The solution was as described previously under '°Materials Used", but with the substitution of 10~
cellulose ether thickener ("Tylose" (Registered Trade Mark)) for 10~ of the water to improve adhesion of the.
PVA layer to the sloping sides of the mould 25. This first layer was then dried to tackiness by blowing it with warm air, and a second layer of a corresponding thickened aqueous solution of Mowiol 2588 was sprayed over it to a considerably greater thickness. In particular, a pronouncedly thick layer was formed on the .
brim 27 of the former, to strengthen the rim oø the liner.
After drying the water from this second coat using warm air blowers, the basic composite PVA liner 30 was lifted from the mould 25. An absorbent pad 31 of cellulose wadding was placed in its base, and the flat upper surface of the rim was given a coating of PVA
adhesive 32 which was then covered by a ring of siliconised release paper 33.
' In use, the insoluble inner layer of the liner was ~ able to contain the potty contents for an extended period without leaking. -To dispose of both liner and contents ~U~fl3~~ . , .
'W~ 92/01556 PCf/GB91 /0123-: - ' the release paper 33 was lifted off and two opposing sides of the rim stuck together face-to-face using the PVA adhesive coat 32, so as to form a sealed bag completely enclosing the contents. The whole was then taken to a WC and dropped into the water where after about ten seconds it had already broken up so much as to be fully flushable.
Again, the process.was repeated using instead the 56/98 and 28/99 blend to form the insoluble layer.
Improved resistance to water was noted.
Disposable Nappy A backing sheet 40 for a disposable nappy was made by sequential spraying and drying of two different PVA
layers as described above for the liner, but~this time on a flat steel surface and without the Tylose thickener.
The thicker, soluble layer formed the outside of the nappy and the thin, insoluble layer the inside (uppermost in Fig 5). ~In the cast sheet; the more soluble layer may_ be about 0.1 mm thick and the less soluble layer about 0...02 mm, but these can be adjusted according ~o the required strength. A conventional cellulosic absorbent pad 41 was affixed to the thin insoluble layer using a aommercial PVA adhesive.
In an experiment,- aqueous liquid was poured onto the :- 25 padding and the nappy was then ralled up. After being left for eight hours, the nappy. was still intact and ~U~l~b;~-~ v : . ..
'NVO 92/01556 PCT/GB91/01237 there was no leakage. However, on putting the rolled-up nappy into a bowl of water, it broke up in seconds and dispersed.
Figures 6 to 8 illustrate schematically various forms of article embodying the invention.
Figure 6 shows a two-layer flexible film comprising a layer.50 of fully-hydrolysed PVA, 3~am thick, superimposed on a layer~~l of partially-hydrolysed (soluble) PVA 25~am thick.
Figure 7 shows a disposable drinking cup.made from a three layer laminar product. This has a thick intermediate layer 61 of partially-hydrolysed PVA, perhaps 0.5mm thick, giving mechanical strength to the cup. The inner and outer surfaces of the cup have a thin, Sum coating 60 of fully-hydrolysed PVA which prevents outside moisture, and liquid in the cup, from attacking the intermediate layer 61. To render the cup disposable it need only be torn up, whereupon the intermediate layer is exposed and can be dissolved.
20. Fig. 8 shows a moulded golf tee having a central core 7l of partially-hydrolysed PVA forming the basic shape of the tee. Sum coating 70 of insoluble PVA covers the tea. The coating may be applied to the moulded "soluble" tee by conventional methods. The tee can a withstand normal use. If it is lost, any natural wear or damage will allow natural moisture to destroy it quickly ~U~1~~~~~ ~. .
WO 92/01556 PCd'/GB91/0123 ~
and hence avoid a litter problem.
Claims (14)
1. A polymeric composite comprising a first organic polymer of partially hydrolyzed polyvinyl alcohol which is from 75 to 95 mole percent hydrolyzed and is water soluble at 20°C and a second organic polymer of fully hydrolyzed polyvinyl alcohol located adjacent to the first polymer, the second polymer being substantially less soluble than the first polymer, or insoluble, in water at 20°C, the quantity of the first polymer in the composite being substantially greater than the quantity of the second polymer and wherein the second polymer acts as a barrier to protect the first polymer from becoming wet.
2. A polymeric composite according to claim 1 in which the second polymer forms a layer less than 20µm thick on the first polymer.
3. A polymeric composite according to claim 2 in which the second polymer forms a layer less than 5µm thick on the first polymer.
4. A polymer composite according to any one of claims 1 to 3 in which the weight proportion of the first polymer to the second polymer is at least 3:1.
5. A polymeric composite according to claim 4 in which said weight proportion is at least 5:1.
6. A polymeric composite according to any one of claims 1 to 5 which is laminar, comprising adjacent layers (50,51;60,61) of the polymers.
7. A method of forming a polymeric composite comprising providing a first organic polymer of partially hydrolyzed polyvinyl alcohol which is from 75 to 95 mole percent hydrolyzed and is water soluble at 20°C and providing a second organic polymer of fully hydrolyzed polyvinyl alcohol located adjacent to and bonded to the first polymer, the second polymer being substantially less soluble than the first polymer, or insoluble, in water at 20°C, the quantity of the first polymer in the composite being substantially greater than the quantity of the second polymer and wherein the second polymer acts as a barrier to protect the first polymer from becoming wet.
8. A method according to claim 7 in which the second polymer forms a layer less than 20µm thick on the first polymer.
9. A method according to claim 8 in which the second polymer forms a layer less than 5µm thick on the first polymer.
10. A method according to any one of claims 7 to 9 in which the weight proportion of the first polymer to the second polymer is at least 3:1.
11. A method according to claim 10 in which said weight proportion is at least 5:1.
12. A method according to any one of claims 7 to 11 in which the composite is laminar, comprising adjacent layers (50,51;60,61) of the two polymers.
13. A method according to claim 7 in which the polymers are co-extruded.
14. A method according to claim 13 in which the polymers are blown-film co-extruded.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9016151.4 | 1990-07-24 | ||
| GB909016151A GB9016151D0 (en) | 1990-07-24 | 1990-07-24 | Composite polymeric articles |
| PCT/GB1991/001237 WO1992001556A1 (en) | 1990-07-24 | 1991-07-24 | Composite polymeric articles |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2091365A1 CA2091365A1 (en) | 1992-01-25 |
| CA2091365C true CA2091365C (en) | 2003-05-13 |
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ID=10679521
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002091365A Expired - Fee Related CA2091365C (en) | 1990-07-24 | 1991-07-24 | Composite polymeric articles |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0540593A1 (en) |
| JP (1) | JPH05509045A (en) |
| AU (1) | AU656731B2 (en) |
| BR (1) | BR9106667A (en) |
| CA (1) | CA2091365C (en) |
| GB (1) | GB9016151D0 (en) |
| WO (1) | WO1992001556A1 (en) |
| ZA (1) | ZA915792B (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IE64670B1 (en) * | 1990-05-02 | 1995-08-23 | Rhone Poulenc Agriculture | Soluble sachets |
| US5280835A (en) * | 1990-05-02 | 1994-01-25 | Rhone-Poulenc Inc. | Laminated bags for containerization of toxic and hazardous materials |
| EP0644823A1 (en) * | 1992-04-23 | 1995-03-29 | British Technology Group Inter-Corporate Licensing Limited | Polymeric articles and materials |
| CA2113151A1 (en) * | 1993-01-25 | 1994-07-26 | Stacy W. Byrd | Multi-layer waterproofing articles including a layer of water-soluble polymer and method |
| US5472518A (en) * | 1994-12-30 | 1995-12-05 | Minnesota Mining And Manufacturing Company | Method of disposal for dispersible compositions and articles |
| EP0800455B1 (en) * | 1994-12-30 | 2002-02-27 | Kimberly-Clark Worldwide, Inc. | A water-flushable film |
| US6579814B1 (en) | 1994-12-30 | 2003-06-17 | 3M Innovative Properties Company | Dispersible compositions and articles of sheath-core microfibers and method of disposal for such compositions and articles |
| WO1997009379A1 (en) * | 1995-09-08 | 1997-03-13 | Solplax Limited | Biodegradable plastic material and a method for its manufacture |
| GB2320456B (en) | 1996-12-18 | 2001-09-05 | Fip Holdings Ltd | Polymer processing method |
| AU7447198A (en) * | 1997-05-08 | 1998-11-27 | Polyval Research Limited | Biodegradable materials and products and methods for their manufacture |
| US6838504B1 (en) | 1998-05-06 | 2005-01-04 | Solucorp Industries Ltd. | Integrated fixation systems |
| GB2340835B (en) | 1998-08-26 | 2003-01-15 | Pvax Ploymers Ltd | PVA-containing compositions |
| GB0005016D0 (en) | 2000-03-01 | 2000-04-26 | Jumik Technologies Limited | PVA-Containing compositions |
| GB2376680A (en) * | 2001-06-19 | 2002-12-24 | Procter & Gamble | Laundry bag with water soluble features |
| US7049272B2 (en) | 2002-07-16 | 2006-05-23 | Santrol, Inc. | Downhole chemical delivery system for oil and gas wells |
| GB0228618D0 (en) * | 2002-12-07 | 2003-01-15 | Grt Ltd | Method & apparatus for packing powdered or granular material |
| DE102008063520A1 (en) * | 2008-12-18 | 2010-07-01 | Huhtamaki Forchheim Zweigniederlassung Der Huhtamaki Deutschland Gmbh & Co. Kg | Rinsable multilayer film |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3546716A (en) * | 1968-06-19 | 1970-12-15 | David H E Laumann | Disposable bedpan liner |
| US3790067A (en) * | 1970-12-04 | 1974-02-05 | S Scheier | Container |
| EP0010171B1 (en) * | 1978-09-21 | 1981-08-26 | Intermedicat GmbH | Multilayer sheet disintegratable in an aqueous medium, and vessel and bag made from this sheet |
| MX151028A (en) * | 1978-11-17 | 1984-09-11 | Unilever Nv | IMPROVEMENTS IN INSOLUBLE BAG BUT PERMEABLE TO WATER THAT HAS A DISPERSIBLE PROTECTIVE LAYER OR SOLUBLE IN WATER, WHICH CONTAINS A PARTICULATE DETERGENT COMPOSITION |
| US4372311A (en) * | 1980-09-12 | 1983-02-08 | Union Carbide Corporation | Disposable articles coated with degradable water insoluble polymers |
| GB2193925B (en) * | 1986-08-18 | 1990-07-04 | Enak Ltd | Improvements relating to wc-disposable sheet material |
-
1990
- 1990-07-24 GB GB909016151A patent/GB9016151D0/en active Pending
-
1991
- 1991-07-24 JP JP3512569A patent/JPH05509045A/en active Pending
- 1991-07-24 EP EP91913355A patent/EP0540593A1/en not_active Ceased
- 1991-07-24 ZA ZA915792A patent/ZA915792B/en unknown
- 1991-07-24 WO PCT/GB1991/001237 patent/WO1992001556A1/en not_active Application Discontinuation
- 1991-07-24 CA CA002091365A patent/CA2091365C/en not_active Expired - Fee Related
- 1991-07-24 BR BR919106667A patent/BR9106667A/en not_active Application Discontinuation
- 1991-07-24 AU AU82281/91A patent/AU656731B2/en not_active Ceased
Also Published As
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|---|---|
| BR9106667A (en) | 1993-06-08 |
| AU656731B2 (en) | 1995-02-16 |
| ZA915792B (en) | 1992-04-29 |
| CA2091365A1 (en) | 1992-01-25 |
| GB9016151D0 (en) | 1990-09-05 |
| EP0540593A1 (en) | 1993-05-12 |
| AU8228191A (en) | 1992-02-18 |
| JPH05509045A (en) | 1993-12-16 |
| WO1992001556A1 (en) | 1992-02-06 |
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