WO2014118113A1

WO2014118113A1 - Slow release gelled lactic acid bodies

Info

Publication number: WO2014118113A1
Application number: PCT/EP2014/051483
Authority: WO
Inventors: Chris François Hubert SCHAEKENS; Wilhelmus Jacobus Adrianus Honcoop; Peter Iwan Stuut; Rick Jeffrey VAN STRIEN
Original assignee: Purac Biochem Bv
Priority date: 2013-01-31
Filing date: 2014-01-27
Publication date: 2014-08-07

Abstract

The invention pertains to a soft solid body suitable for use as carboxylic acid-releasing body in aqueous media, which comprises 10-30% thickener chosen from the group of hydroxypropyl cellulose, hydroxyethyl cellulose and xanthan or a mixture thereof. The use thickeners of this type in combination with carboxylic acids results in the controlled release of carboxylic acid. The soft solid bodies may be used in home care products.

Description

Slow release gelled lactic acid bodies

This invention relates to cleaning compositions for use in home care products for example fabric washing, machine dish washing or toilet cleaning.

Such a composition should show a delayed release of its contents. Their main action is to remove or prevent the formation of scale via sequestering / chelating of mineral deposits. This is often accompanied by the use of

environmentally unfriendly sequestering agents such as EDTA and phosphates.

Commercial liquid cleaning formulations are typically acidic in nature, to remove scale, soap scum, and bacteria. It is believed that acidic compositions show a higher

effectiveness .

The use of lactic acid oligomers in slow release bodies has been described in EP2228427. These bodies comprise lactic acid oligomers with an average degree of polymerization between 1.8 and 4. Such a lactic acid oligomer is water- insoluble. If it is contacted with water, the water attacks the ester bond to give carboxylic acid and alcohol, thus ensuring a controlled release of lactic acid.

It would be an advantage if bodies could be prepared with a high content of lactic acid. Lactic acid, however, exists as a liquid at room temperature. In the present invention this problem was solved by the addition of thickeners to the lactic acid thereby converting the lactic acid to a soft solid .

Thickeners have been described in literature.

Patent US 5,707,952 describes sprayable thickened

compositions with a low percentage of mono or dicarboxylic acids. The composition is used for removing lime scale and soap scum. As thickener polyurethane/polyol is used. Other thickeners are reported to be unstable.

US 4,614,545 describes the use of hydroxypropyl cellulose ethers for thickening an organic liquid or a mixture of an organic liquid with water. Preparations with a high

carboxylic acid content, however, have not been described. As described in EP2228427 for use in toilets, usually

additives such as dyes, surfactants and flavours are added to the tablets. One of the disadvantages is that these

ingredients can only be mixed by prior heating and cooling down of the mixture in order to obtain a tablet with

homogeneously divided ingredients.

By preparing soft solids such an additional preparation step is not needed anymore.

It is an object of the present invention to provide soft solids compositions comprising a high amount of carboxylic acids. Such compositions can be prepared by making use of thickening agents.

Thus, the present invention pertains to slow acid releasing bodies in a semi-solid phase. More in particular the

invention relates to a soft solid composition of organic carboxylic acids that dissolve in aqueous media and can be applied in home care products.

A further advantage of using such soft solid is that this form may contain highly concentrated organic acids. The soft solid forms are found to be gradually soluble in water and can easily be mixed with other liquid ingredients. The high concentration of organic acids not only guarantees a higher product effectiveness, but also allows less and more sustainable packaging which from an environmental point of view is of great advantage.

The presence of low amounts of water further prevents

migration of other ingredients. As a consequence ingredients tend to oxidize to a lesser extent at the surface of the body thereby increasing the shelve life of the body.

In a first aspect the invention the invention relates to a slow acid-releasing body which comprises by weight a) more than 60% of a C1-C9 monocarboxylic acid with a melting point below a temperature of 25 ^°C, or a mixture of these acids, b) 10-30% thickener chosen from the group of hydroxypropyl cellulose, hydroxyethyl cellulose and xanthan or a mixture thereof and c) optionally water up to a maximum of 20%.

As used herein the percentage is indicated by weight based on the final weight of the body.

With the term C1-C9 monocarboxylic acid is meant a carboxylic acid having 1 to 9 carbon atoms group. The carboxylic acid has only one carboxylic group which is attached to a C0-C8 alkyl group. As used herein the carbon atoms in the aikyl chain, having 0-8 carbon atoms, might be substituted if appropriate, with one or more hydroxyl groups. The alkyl chain may be saturated or unsaturated. Examples of such acids are formic acid, acetic acid, propionic acid, 3- hydroxypropionic acid, lactic acid, acrylic acid, butanoic acid, methacrylic acid, isobutiric acid, pentanoic acid, hexanoic acid, heptanoic acid, caprilyc acid and nonanoic acid .

In one embodiment of the invention, water is present up to a maximum of 10%. In another embodiments water is present up to an amount of 1%. In yet another embodiment no water is present.

In another embodiment of the invention, the monocarboxylic acid in the slow acid-releasing body is a C1-C4

monocarboxylic acid. In yet another embodiment of the invention, the

monocarboxylic acid in the slow acid-releasing body is a C2- C3 monocarboxylic acid.

In another embodiment of the invention, the monocarboxylic acid in the slow acid-releasing body is a member of the group lactic acid, propionic acid and acetic acid, or a mixture thereof .

In yet another embodiment, the monocarboxylic acid in the slow acid-releasing body is lactic acid.

In one embodiment of the invention the thickener is present in an amount of 10-20% by weight based upon the final contents of the soft solid body. In another embodiment of the invention the thickener is present in an amount of 10%. It will be understood by the skilled person that small

deviations of this value are allowable without any effect on the solid property of the final body.

In still another embodiment the amount of monocarboxylic acid is at least 80% by weight based upon the final contents of the soft solid body.

It is to be understood that the percentages mentioned in the embodiments of the invention are by weight based upon the final contents of the soft solid body and ranges of

concentrations have to be considered as a minimum

concentration in such a way as to make a total of 100% for the whole body. Thus, within the limitations of the range, the percentage of a certain component might add up to the 100% weight of the body.

The thickener used in the present invention preferably is hydroxypropylcellulose .

In another aspect the invention relates to a process for manufacturing a slow acid-releasing body as described

hereabove by mixing the carboxylic acid and the thickener and other additional components wherein the mixture is subjected to a shaping step to form shaped bodies. The slow acid-releasing bodies according to the invention can be used in the preparation of home care products including machine cleaners, rinse aids and fabric conditioners.

Thus in one embodiment the slow acid-releasing body is used for fabric washing, machine dish washing or toilet cleaning.

The slow carboxylic acid-releasing bodies according to the invention are not solid as the lactic acid oligomer bodies described in EP2228427. On the other hand, they are also not in a liquid state. The bodies according to the invention can be considered soft solid. For the purpose of this invention the term "soft solid" refers to compositions which are on the one hand solid enough to retain their shape at ambient temperature and on the other hand smooth in appearance. Smooth textures are generally of low or no porosity and have at normal viewing distance, the appearance of a continuous phase for example as opposed to porous and particulate appearance of a compacted particulate material. Preferably the soft solid is transparent or translucent.

Soft solid compositions are on the one hand solid enough to retain their shape at ambient temperature but they are not completely solid. A suitable test to check if the composition can be considered as a soft solid is, for example, described in EP 1,375636.

The soft solid bodies according to the invention each generally have a weight of from 15 to 100 grams,

preferably from 15 to 70 grams, more preferably from 20 to about 65 grams.

The soft solid body according to the invention may comprise various additional components.

In one embodiment the soft solid body comprises one or more fragrances. The term fragrance is intended to refer to any compound which gives of an appropriate odour, generally of freshness, when the toilet is flushed. The fragrance may be in solid form or liquid form suitably present in an amount of 0.1 to 7 wt.%, more rticular in an amount of 0.5 to 4 wt.%.

If so desired, the soft solid body may also

comprise fillers, which do not provide additional cleaning activity to the body.

Filler materials may be used in the compositions of the invention so that it can be formed into solid objects of desired sizes, shapes and designs without using excessive amounts of active ingredients.

The amount of filler will depend on the desired weight of th final block and on the desired amount of active component. Preferably, the filler is water-soluble, to allow complete dissolution of the shaped body according to the invention. Suitable fillers include water-soluble inert salts such as sodium chloride, sodium or calcium sulfate, sodium carbonate starch, etc. The solid body may also contain a dye, to impart colour to the water when the toilet is flushed. Suitable dyes are released from the shaped object when the toilet is flushed.

The dye, if present, may be used in a concentration of, generally, from 0.01 to 5 wt.%. For in-cistern bodies, a general range of 1 to 5 wt.%. may be mentioned. For in-bowl bodies, a general range of 0.01 to 0.5 wt.% may be mentioned. Suitable dyes are known in the art. Examples of suitable dyes are Acid Blue No. 9, Carta Blue V (C.I.24401) , Acid Green 2G (C. I . 2085) , Astragon Green D (C. I .42040) , Maxilon Blue

3RL (C.I. Basic Blue 80), Drimarine Blue Z-RL (C . I . Reactive Blue 18), other Acid Blue 9 type dyes, and Sanolin-Blau EHRL, material No. 154640 of Clariant. If so desired, the composition may comprise a surfactant, in particular an anionic or non-ionic surfactant, or a

quaternary surfactant with a low water content. An example of such a surfactant is LAS.

Thus, according to one embodiment the slow acid-releasing body comprises a surfactant.

Addition of a surfactant, like for instance LAS, results in a faster weight decrease of the blocks and a larger pH drop of the water phase in time. For some applications, like toilet care applications this faster dissolution rate of the full block and larger pH drop can be beneficial. By varying the surfactant amount this weight loss rate and pH drop can be adjusted to meet specific pH drop or dissolution rate

requirements. These requirements can depend from case to case and application area to application area.

If so desired, the composition may also contain additional components like oxidizing agents, chelants , algicides, quaternary ammonium salt, and bleaching agents like (solid) peroxides, such as sodium percarbonate or perborate. It is within the scope of the skilled person to select appropriate further components for the shaped body according to the invention. The soft solid bodies of the present invention may be manufactured by an easy process i.e. by just mixing all the components. As the carboxylic acid is already in a liquid phase melting of the acid, blending in other

components, and allowing the composition to solidify, is not needed. The soft solid carboxylic acid / thickener mixture can be subjected to a shaping step to form shaped bodies, e.g., by pouring it in a mold, or by cutting shaped bodies of appropriate size and shape from a solidified block or plate. Usually, after mixture of the ingredients, it takes it takes a few minutes before the materials start to set and a few hours before the final strength has been obtained. The bodies may also be shaped using an extrusion process.

Thus, gel blocks can easily be prepared by mixing the right amount of organic acid with liquid additives like perfume oil and surfactant and adding the thickener. The mixture can then firmly be stirred till a homogeneous material is formed. At this time the final material is still well pourable and can be poured into e.g. silicon moulds. After some time the semi solid materials can be taken out of their moulds.

In one embodiment, the composition is cast into polymer molds, or molds coated with a polymer foil wherein the polymer mold or foil is subsequently used in the

packaging of the product. In this case, it is preferred for the foil to be impermeable for water under storage conditions of the shaped bodies .

The soft solid body may have any desirable shape, e.g., rectangular (block), in the shape of pucks, stars, bails, shells, cylinders or any other suitable shape. The shape of the product, more in particular its surface to volume ratio is of influence on the dissolution rate of the body. It is within the scope of the skilled person to optimize the shape of the body.

The soft solid bodies according to the invention are suitable for use as tablets for cleaning machines, for use in dish washing machines and fabric machines and for toilet cleaning as in-cistern agent to effect the delayed release of lactic acid. Accordingly, the present invention also pertains to the use of these compositions in these applications.

The present invention is elucidated by the following examples, without being limited thereto or thereby. Examples

Example 1. Screening thickeners

Different types of (bio based) thickeners were screened for their geilating effect/properties on lactic acid in order to find an effective thickener for turning lactic acid into solid blocks, preferably transparent.

Therefore, gel formulations were made by adding a certain amount of thickener to PURAC HS100 100% pure lactic acid at room temperature in a glass beaker. Two formulations were made: 80 grams of lactic acid with addition of 20 grams thickener and 90 grams of lactic acid with addition of 10 grams thickener. The various tested thickeners are reflected in the table below (table 1) . The thickeners were added while vigorously stirring the lactic acid for 5 minutes. After mixing at room temperature the samples were stored for 2 hours. After storage, the samples were put out of the beaker and put on a table top, followed by a visual check on

solidity, stickiness and transparency.

The thickeners tested were hydroxypropyl cellulose (Klucel m- cs and Klucel HF, Ashland Inc.), hydroxyethyl cellulose

(Cellosize PCG-10, Dow) , polysaccharide (Keltrol (Xanthan) , CP Kelco) , heteropolysaccharide (Pectine, Acros organics ) , mixture of peptides and proteins (Gelatine type B , Across Organics), mixture of glucoproteins and polysaccharides (Gum Arabic, Across organics, mixture of agarose and agaropectin

(agar-agar, Oxoid) and carboxy methyl cellulose (Across

Organics) . Table 1 Properties thickener types combined with lactic acid

From the results of table 1, it can be concluded that that the following thickeners in combination with lactic acid give good solidifying results: Xanthan gum, hydroxypropyl

cellulose and hydroxyethyl cellulose.

Example 2. Effect of dilution lactic acid with water

A series of further tests were carried out determining the effect of partial replacement of lactic acid by water and their effects on soft solid properties. The preparation and evaluation of the mixtures was as described in example 1. The experiment was carried out at room temperature. Two

thickeners were tested i.e. polysaccharide (Keltrol (Xanthan, CP Kelco) and hydroxypropyl cellulose (Klucel m-cs , Ashland Inc . ) The results, presented in table 2, show that by lowering the lactic acid concentration the soft solids are becoming very soft and at 60% acid (40% water) become even liquid. Lowering the acid concentration also negatively influences the

preparation of the mixtures because at concentrations less than 60% gelling almost instantly occurs making it hard to homogenously mix the thickener into the acid.

It can be concluded that the minimal concentration of lactic acid required for a solid gel block is >60% acid. The amount of water should be less than 20%.

Table 2. Effect of dilution with water

Example 3. Properties thickener types combined with

carboxylic acids

The effect of different thickeners combined with carboxylic acids other than lactic acid was studied as described in Example 1. The mixtures were prepared with 15% thickener. The acids were added as water mixtures in the concentrations 99% propionic acid and 99% acetic acid (final amounts 84.15% and 84.15%, respectively). The results show that hydroxypropyl cellulose is perfectly well suited to form solid gels with propionic acid and acetic acid. Table 3. Effect of thickener on other carboxylic acids

Example 4. Effect of other ingredients

A series of further tests were carried out determining the effect of partial replacement of lactic acid by other

ingredients like Fragrance (E-2747 Lemon Lime fragrance, Arylessence, Inc } and LAS (Linear alkylbenzene sulfonate, Alpha-Step PC48, Stefan S) . As a source of lactic acid HS100 Lactic acid (Purac) was used. The end concentration of the thickener was 10%. The end concentrations of the other ingredients in the final mixture is indicated in Table 4. Further preparation and evaluation of the mixtures was as described in example 1. Table 4. Effect of other ingredients on the gel structure.

It can be concluded that there is a negligible effect if fragrance is added. The addition of LAS tends to make the blocks more yellow and somewhat softer, though still sufficiently solid.

Example 5. Dissolution profile in water

A soft solid body was prepared as described with 10%

hydroxyethyl cellulose (Cellosize PCG-10, Dow) and 90% HS100

Lactic acid (Purac) . 10L buckets were filled with 51 water. In the bucket the slow acid-releasing bodies were placed on a holding device which made it possible to stir the solution without stirring the body. The water was stirred at a

constant stirring speed of ± 400 rpm. Dissolution of the body was measured for at least 3 hours. Every hour the body from a bucket was removed and dried in the oven at 40 °C and

weighed. Results are shown in Figure 1.

Claims

1. A slow acid-releasing body which comprises by weight a) more than 60% of a C1-C9 monocarboxylic acid with a melting point below a temperature of 25 ^"C, or a mixture of these acids, b) 10-30% thickener chosen from the group of hydroxypropyi cellulose, hydroxyethyl cellulose and xanthan or a mixture thereof and c) optionally water up to a maximum of 20%.

2. The slow acid-releasing body according to claims 1

wherein the thickener is present in an amount of 10- 20%.

3. The slow-acid releasing body according to claims 1-2 wherein water is added up to a maximum of 10%.

4. The slow-releasing body according to claims 1-2 wherein essentially no water is added.

5. The slow acid-releasing body according to claims 1-4 wherein the monocarboxylic acid is C1-C4 monocarboxylic acid .

6. The slow-acid releasing body according to claim 5

wherein the monocarboxylic acid is a C2-C3

monocarboxylic acid.

7. The slow-acid releasing body according to claim 6

wherein the monocarboxylic acid is a member of the group of lactic acid, propionic acid and acetic acid, or a mixture thereof.

8. The slow-acid releasing body according to claim 7

wherein the monocarboxylic acid is lactic acid.

9. The slow acid-releasing body according to claims 1-8 wherein the thickener is present in an amount of 10%.

10. The slow acid-releasing body according to claims 1-9 wherein the monocarboxylic acid is present in a more than 80% weight concentration.

11. The slow acid-releasing body according to claims 1-10 wherein the thickener is hydroxypropylcellulose .

12. he slow acid-releasing body according to claims 1-11 wherein a surfactant is added.

13. A process for manufacturing a slow acid-releasing body according to any one of the preceding claims comprising mixing the carboxylic acid and the thickener and other additional components and subjecting the mixture to a shaping step to form shaped bodies.

14. Use of the slow acid-releasing body according to claims 1-12 in home care products.