CA1240231A - Borate solution soluble polyvinyl alcohol films - Google Patents

Abstract

Abstract Conventional polyvinyl alcohol envelopes will not readily dissolve in wash water which has a significant borate concentration and a pH frequently encountered in wash liquors. Herein, such films are rendered sufficient-ly soluble in such solutions. In the preferred embodiment this is done by utilizing a polyvinyl alcohol film having an acid having an acid dissociation constant of 10-9M or larger or a polyvinyl alcohol film containing mixtures thereof with a polyvinyl alcohol having a number average molecular weight below about 50,000.

Description

~4C~231 orate solution soluble polyvinyl alcohol films The present application has been divided out of Canadian Patent Application Serial No. 414,399 filed October 28, 1982.
The invention relates to polyvinyl alcohol films which are soluble in borate containing solutions and more particularly to such films in the form of envelopes con-twining laundry additives such as detergents and the like.
Several film materials are available which are water soluble and which can be formed into envelopes in which remeasured amounts of laundry additives can be sealed. Methyl cellulose, polyethylene oxide and polyp vinyl alcohol are particularly useful film materials of this nature. Methyl cellulose films generally do not have sufficient volubility at higher water temperatures.
polyethylene oxide films tend to absorb moisture too readily and become tacky.
Polyvinyl alcohol films do not have the problems of methyl cellulose or polyethylene oxide films. However, when these films are placed in solutions containing borate at levels and pus frequently encountered in laundry apply-cations, the rate of volubility of such films is severely reduced. Yet, borate is often present in clothes washing liquors and the like, since one of the most widely used ~Z~2~1 leaching compositions is principally sodium perorate, which forms borate ions in solution. Other borate sources such as borax, are also often used as laundry additives.
The present invention is directed to overcoming 5 the problem of slow dissolution rates of polyvinyl alcohol films in borate containing solutions as set forth above.

SUMMARY OF THE INVENTION
In accordance with an embodiment of the present invention, there is provided a laundry additive combine-Zion, comprising: a laundry additive; and a sealed water soluble envelope adapted to syllables in an aqueous laundry solution containing borate at levels as high as 3.4 x 10 EM, said envelope being formed of a plasticized film of a polymer consisting essentially of polyvinyl alcohol, the volubility rate of said plasticized film in a laundry solution having a borate concentration of about 1.7 x 10 EM and a pi of about 10.7 being increased by the presence therein, in addition to a plasticizing amount of plasticizer, of a volubility rate increasing amount of an acid having an acid disco-elation constant, in water at 25C, greater than about 10 EM and the compound used as plasticizer being different from the acid compound used as solubilizer.
lrhe above polyvinyl alcohol may also be used mixed with a polyvinyl alcohol having a number average molecular weight below about 50,000.
In accordance with another embodiment of the resonate invention there is provided a method of intro-during a laundry additive to an aqueous laundry solution containing borate at levels as high as 3.4 x 10 EM, comprising: enclosing said additive in a sealed water soluble envelope, said envelope being formed of a pies-ticized film of a polymer consisting essentially of polyvinyl alcohol, the volubility rate of said pies-us ticized film in a laundry solution having a borate concentration of about 1.7 x 10 EM and a pi of about 10.7 being increased by the presence thereon, in Addition

2 I Z 3 t. a plasticizing amount of plasticizer, of a Sealab-lily rate increasing amount of an acid having an acid dissociation constant, in water at 25C, greater than about 10 EM and the compound used as plasticizer being different from the acid compound used as solubilizer;
and contacting said envelope with an aqueous laundry solution containing borate at levels as high as 3.4 x 10 EM for a sufficient time for said envelope to dissolve sufficiently to allow said additive to contact said aqueous laundry solution.
The present invention thus solves the problem of providing polyvinyl alcohol films which will rapidly dissolve in solutions which contain borate at levels and pus normally encountered in laundry applications.

Best Mode For Carrying Out The Invention When the term polyvinyl alcohol is used here-in this term is meant to include the polyvinyl alcohol itself, derivatives thereof, and its water soluble copolymers. The polyvinyl alcohol resins described herein ace generally produced by the hydrolysis of polyvinyl acetate and generally have a degree of hydrolysis between about 70% and about 98~.
It is well known that envelopes made of polyvinyl alcohol films can be used to enclose remeasured amounts of laundry additives such as detergents, bleaches, brighteners, builders, fabric 23~

softeners, and the like. Such polyvinyl alcohol films are generally formed from polyvinyl alcohol resins of a desired degree of hydrolysis. In practice, the polyvinyl alcohol is dissolved in water, with heating, and one or another conventional plasticizers, such as, for example, polyethylene glycol having a molecular weight of 200 to 600, release agents, and an anti-blocking agent, if desired, are also dissolved in the same solution.
Lo Thereafter, the solution is simply cast and the water evaporated to produce a film with the desired physical properties, The conventional polyvinyl alcohol films of the prior art have very adequate volubility in lo water. However, when there is a significant borate concentration in the water and when the pi is that frequently encountered in washing liquors, such polyvinyl alcohol films will not dissolve sufficiently readily to deliver a laundry additive to the solution early in the wash cycle.
An objective test, which simulates results found for top loading automatic washing machines, has been developed for determining when a polyvinyl alcohol film will have sufficient volubility in borate containing solutions so as to be readily soluble under normal laundry conditions. Acceptable volubility rate is demonstrated when at least 50% by volume of a l.Scm x 1.5cm x 0.0038cm sample of the film substantially dissolves or disperses within 300 seconds, as determined by visual evaluation, in a ~z~23~

wildly agitated aqueous solution having a borate concern-traction of 1.7 x 10 EM and having a pi of about 10.7 a- a temperature of 37.5C. Mild agitation is defined, for the purposes of the test, as agitation in a volume of 750cc of the solution in a cylindrical container 9.5cm in diameter using an oblong magnetic stirring rod about tam x Sam at a speed sufficient to cause a vortex to extend about 20% of the way downwardly from the surface of the solution.
It has been discovered that when the film is any one of three compositions, or any mixture of such compositions in sufficient quantities, a film results kick satisfies the above-set-out test and is acceptable for laundry use.
Canadian Patent Application Serial No. 414,399 from which the present application was divided discloses a first composition which satisfies the test. A polyp vinyl alcohol film produced from polyvinyl alcohol resins characterized by having a number average mole-cuter weight below about 50,000, more preferably below about 25,000~ and still more preferably of about 10,000.
When this first composition is utilized without any of the second or third compositions set out below, at least about 50~ of the polyvinyl alcohol resin on which the film is based must consist of a polyvinyl alcohol of such an average molecular weight, more preferably at least about 80% and still more preferably about 100~. Somewhat unexpectedly, such low molecular weight polyvinyl alcohol resins produce films of sufficient strength, stability in humid weather, and integrity ~2~323~L

for storage and laundry use.
A second composition which will satisfy the above test, either by itself or in combination with the first constituent or the third constituent which will be set out below, or with both the first and third constituents, it a polyvinyl alcohol film which contains a polyhydroxy compound (PHI) which has a binding constant with borate in aqueous solutions (K2) as defined by the equation K = (Complex) , that is greater than (borate) (PHI) about 800 to 2 at 25C; the constituents concentrations being in moles per liter.
Particularly useful polyhydroxy compounds are lovelies (fructose), minutely, catcall, sorbitol, sorbs, pentaerythritol and meso-erythritol. In general, the higher the binding constant, the more effective the polyhydroxy compound in providing the desired volubility characteristics. It is somewhat surprising that significant quantities of the polyhydroxy compound can be incorporated into the polyvinyl alcohol without rendering envelopes made from 'he 'I
laundry use.
If the polyhydroxy compound is utilized by itself to syllables the polyvinyl alcohol film, it is preferably present in an amount of at least about 10%, by weight, of the polyvinyl alcohol film, the effective amount depending on the identity of the polyhydroxy compound. On the other hand, lesser 12~Z31 amounts of the polyhydroxy compound can be utilized if the film includes a polyvinyl alcohol having a relatively lower molecular weight, for example, a number average molecular weight below about 50,000, or if the film includes an acid as will be set out below.
A third polyvinyl alcohol film having the desired characteristics is one which contains an organic, inorganic or polymeric acid having an acid dissociation constant, in water at 25C, greater than about 10 EM and preferably greater than about 10 EM. Polyacrylic acids with average molecular weights in the range from about 3000 to about 150,000 are very useful acids for such purposes.
Other acids are also useful, for example, citric acid, succinic acid, tartaric acid, potassium hydrogen phthalate, sodium dihydrogen phosphate, adipic acid, Sistine, glutamic acid, benzoic acid and oxalic acid. It should be noted that when the acid is utilized by itself, it is preferred that it be in a concentration of at least about 103, by weight, based on the weight of the polyvinyl alcohol film. The amount of acid can be reduced if some polyhydroxy compound, as set out above, is present and/or if the film includes polyvinyl alcohol having a number average molecular weight below about 50,000 and more preferably below about 25,000.
It is essential, in any case, that the polyvinyl alcohol film, in accordance with the present invention, be capable of satisfying the - a -objective test of volubility in a borate containing solution and at a pi as set out above.
When envelopes are made from the films, such films will generally be about 1.5 miss thick.
This provides an envelope of sufficient strength which will dissolve sufficiently quickly in normal laundry use. However, film thicknesses of from about 1.0 to about 3.5 miss are practical for the application described herein.
It should be noted that not only may detergents be enclosed in envelopes in accordance with the present invention, but also builders, bleaches, brighteners, fabric softeners, anti-soiling polymers and other laundry additives may be so enclosed, provided they do not dissolve or otherwise interact deleteriously with the film material.
The invention will be better understood by reference to the following examples:
Examples 1-5 20.1g of polyvinyl alcohol (number average molecular weight 10,000. 88% hydrolyzed) was added slowly with mixing to 8.6g of polyethylene glycol (average molecular weight = 200) and 86.4g of distilled water. After the polyvinyl alcohol was dispersed, the dispersion was heated for approximately two hours at 60C to completely dissolve the polyvinyl alcohol. the solution was cooled to 23C, stirred slowly to remove air bubbles and cast on a glass plate using a film applicator with an 0.051cm clearance.

lZ~UZ31 g The resulting film was dried at room temperature for 1-2 hours, dried further at 37.5C
for 2 hours and allowed to equilibrate to room temperature conditions (- 23C, 50% relative humidity) before being removed from the glass plate for testing. This procedure yielded a film 0.0038cm thick containing approximately 66% polyvinyl alcohol, pa% polyethylene glycol and I water.
Using the evaluation procedure as set out above, >95% of the film dissolved in lS0 seconds. In this procedure borax was added as the source of borate and sodium carbonate and sodium bicarbonate were used to maintain the pi at 10.7. Using a similar procedure, additional films 0.0038cm in thickness with different number average molecular weight polyvinyl alcohol resins were prepared and evaluated and the results are summarized in Table I.
These examples demonstrated that a polyvinyl alcohol resin of a number average 20 molecular weight of about 50,000 or less is necessary to provide a film that meets desired volubility criteria in the absence of any polyhydroxy compound or acid. The 603 dissolved/dispersed result at 300 second for 50,000 molecular weight polyvinyl alcohol is somewhat low but is quite sufficient for normal laundry use.
examples 6-15 12.9g of polyvinyl alcohol (average molecular weight 96,000, 88~ hydrolyzed) was added slowly with mixing to 0.49 of polyethylene glycol ~z4~23~

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3Z4~:1231 (average molecular weight - 200) and 81.6g of distilled water. After the polyvinyl alcohol was dispersed, the dispersion was heated for approximately two hours at 60C to completely dissolve the polyvinyl alcohol. The solution was cooled to approximately 30C and a slurry of ~.19 of fructose in 159 of distilled water was added with mixing. The viscous mixture was stirred for 16 hours at 23C to insure complete mixing and to remove any air bubbles. It was then cast on a glass plate using a film applicator with an 0.051cm clearance.
The resulting film was dried at room temperature for 1-2 hours, dried further at 37.5C
for 2 hours and allowed to equilibrate to room temperature conditions ( ~23C, 50% relative humidity) before being removed from the glass plate for testing. This procedure yielded a film 0.0038cm thick containing approximately 66% polyvinyl alcohol 20 (number average molecular weight - 96,000, 88~
hydrolyzed), 2% polyethylene glycol (number average molecular weight - 200), 26% fructose and I water.
Using the evaluation procedure as set out above, 70%
of the film dissolved in 300 seconds.
Using a similar procedure, additional films of a thickness of approximately 0.0038cm with different polyhydroxy compounds at levels of approximately 26% by weight were prepared and evaluated. The polyvinyl alcohol used in these examples was 88% hydrolyzed and had a number average molecular weight of approximately 96,000. Table II
presents the results of testing such films.

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These examples demonstrate that polyhydroxy compounds should have R2 values greater than about 800M 2 to provide a film that meets desired volubility criteria. Furthermore, a polyvinyl alcohol film of number average molecular weight greater than 50,000 has been shown to be rapidly soluble due to the inclusion of these polyhydroxy compounds having K2 greater than 800. Thus, polyvinyl alcohol resins of as much as 200,000 number average molecular weight are expected to be rendered rapidly soluble by the correct choice of polyhydroxy compounds and its level in the film.
Examples 16-27 12.9g of polyvinyl alcohol number average 15 molecular weight 96,000, 88% hydrolyzed) was added slowly with mixing to 0.99 of polyethylene glycol (average molecular weight - 200), 4.6g of polyacrylic acid (average molecular weight - 5,000) and 96.69 of deionized water. After the polyvinyl alcohol was dispersed, the dispersion was heated for approximately two hours at 60C to dissolve the polyvinyl alcohol. The solution was cooled at 23C, stirred slowly to remove air bubbles and cast on a glass plate using a film applicator with an 0.051cm clearance. The resulting film was dried at room temperature for 1-2 hours, dried further at 37.5C
for 2 hours and allowed to equilibrate at room temperature conditions (z 23C, 50% relative humidity) before being removed from the glass plate 30 for testing. This procedure yielded a film 0.0038cm lZ9~023~

thick containing approximately 66% polyvinyl alcohol, 24~ polyacrylic acid, 5% polyethylene glycol and 5%
water. Using the evaluation procedure as set out above, >95~ of the film dissolved in lS0 seconds.
r' using a similar procedure additional films, approximately 0.0038cm thick, containing other acids at levels of approximately 24% by weight were prepared and evaluated. These films contained polyvinyl alcohol, 88% hydrolyzed, and with a number average molecular weight of approximately 96,000.
The results are summarized in Table III.
These examples demonstrate that acids must have Kay values greater than 10 EM to provide a film that meets desired volubility criteria. Furthermore, a polyvinyl alcohol film of number average molecular weight greater than 50,000 has been shown to be rendered rapidly soluble due to the inclusion of these acidic components having Kay >10 . Thus films based on polyvinyl alcohol resins of as much as 200,000 number average molecular weight are expected to be rapidly soluble by the correct choice of acidic compound and its level in the film.
Example 28 using procedures similar to those described in the previous examples, a film combining two of the embodiments presented previously herein was made and evaluated. The procedure yielded a film approximately 0.0038cm thick with a composition of approximately 81% polyvinyl alcohol (88% hydrolyzed, number average molecular weight approximately ~-~ 25!000)~ 14% minutely and 5% water. This film .

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lZ9~231 combines the use of a polyvinyl alcohol resin with a number average molecular weight less than S0,000 and a polyhydroxy compound with a binding constant with borate that is greater than 800M 2. The film was evaluated using the procedures set forth previously and it was found that >95% of the film by volume, dissolved or dispersed, as determined by visual examination, in 30 seconds under the test conditions set forth previously. This represents an improvement I over either embodiment alone (examples 2 and 7) and although both previous examples set forth films that met volubility criteria, this example indicates that combinations of the embodiments yield films with still better volubility characteristics.
Better volubility characteristics can become important when the laundry additive combination comprising a laundry additive and an envelope made from a film as set forth herein is used in extreme or misuse conditions. For example, it is not uncommon for the consumer to use more than the recommended amount of bleaching compositions containing sodium perorate when laundering a heavily soiled load or in small volumes of washing liquor.
Such would result in a concentration ox orate as high as 3.4 x 10 EM or even higher in the laundry liquor. Also, it is not uncommon for the consumer to launder delicate items at temperatures significantly less than 37.5C. Both conditions can have the effect of reducing the volubility rate of films that meet the criteria set forth previously herein.

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An additional demonstration of the advantage of combining the embodiments in one film is set forth in the next examples.
Examples 29 and 30 Using procedures similar to those described to the previous examples, two additional films were produced at a thickness of approximately 0.0079cm.
The volubility rates of the two films were evaluated under conditions identical to those set forth previously herein with the exceptions that the borate concentration was maintained at I x 10 EM and that the temperature was maintained at 23C. The results appear in Table IV.
Thus, although the film presented in Example 29, in which one of the embodiments of-this invention is used slow molecular weight), has an acceptable volubility rate under the conditions set forth in this example, the volubility rate is relatively low. However, by combining the embodiments which teach the use of polyvinyl alcohol rosins with number average molecular weight of about 50,000 or lest, end the use of a polyhydroxy compound which has a binding constant with borate above Ahab 800M 2, a film is produced with a volubility rate considerably higher and more acceptable than that of Example 29. Thus, the combinations of the embodiments presented herein offers significant advantages over separate use of the individual embodiments. It can be expected that combinations of any two of the particular embodiments presented ~Z~231 o) t, R. V
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Industrial Applicability The present invention is directed to and discloses both a polyvinyl alcohol film and a laundry additive-envelope combination with the film being of proper volubility rate in borate containing solutions under normal laundry conditions so as to deliver the lo contents of an envelope made of the film early during a wash cycle, even when borate is present.

Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A laundry additive combination, comprising:
a laundry additive; and a sealed water soluble envelope adapted to solubilize in an aqueous laundry solution containing borate at levels as high as 3.4 x 10-3M, said envelope being formed of a plasticized film of a polymer consisting essentially of polyvinyl alcohol, the solubility rate of said plasticized film in a laundry solution having a borate concentration of about 1.7 x 10-3M and a pH of about 10.7 being increased by the presence therein, in addition to a plasticizing amount of plasticizer, of a solubility rate increasing amount of an acid having an acid disso-ciative constant, in water at 25°C, greater than about 10-9M and the compound used as plasticizer being different from the acid compound used as solubilizer.

2. A laundry additive combination as set forth in claim 1, wherein said acid is selected from the group consisting of polyacrylic acid, citric acid, succinic acid, tartaric acid, potassium hydrogen phthalate, sodium dihydrogen phosphate, adipic acid, cysteine, glutamic acid, benzoic acid and oxalic acid.

3. A laundry additive as set forth in claim 1, wherein polymer has a molecular weight of no more than about 25,000.

4. A laundry additive as set forth in claim 1, wherein polymer has a molecular weight of about 10,000.

5. A laundry additive as set forth in claim 1, wherein said film is formed of a mixture of (a) said polyvinyl alcohol containing an acid having an acid dissociative constant greater than 10-9M
and (b) a polyvinyl alcohol having a number average molecular weight of no more than about 50,000.

6. A method of introducing a laundry additive to an aqueous laundry solution containing borate at levels as high as 3.4 x 10-3M, comprising:
enclosing said additive in a sealed water soluble envelope, said envelope being formed of a plasticized film of a polymer consisting essentially of polyvinyl alcohol, the solubility rate of said plasticized film in a laundry solution having a borate concentration of about 1.7 x 10-3M and a pH of about 10.7 being increased by the presence therein, in addition to a plasticizing amount of plasticizer, of a solubility rate increasing amount of an acid having an acid dissociation constant, in water at 25°C, greater than about 10-9M and the compound used as plasticizer being different from the acid compound used as solubilizer; and contacting said envelope with an aqueous laundry solution containing bor-ate at levels as high as 3.4 x 10-3M for a sufficient time for said envelope to dissolve sufficiently to allow said additive to contact said aqueous laundry solution.

7. A method as set forth in claim 6, wherein said acid is selected from the group consisting of polyacrylic acid, citric acid, succinic acid, tartaric acid, potassium hydrogen phthalate, sodium dihydrogen phosphate, adipic acid, cysteine, glutamic acid, benzoic acid and oxalic acid.

8. A method as set forth in claim 6, wherein said polymer has a molecular weight of no more than about 25,000.

9. A method as set forth in claim 6, wherein said polymer has a molecular weight of about 10,000.

10. A method as set forth in claim 6, wherein said film is formed of a mixture of (a) said polyvinyl alcohol containing an acid having an acid dissociative constant greater than 10-9M
and (b) a polyvinyl alcohol having a number average molecular weight of no more than about 50,000.