WO2014068110A1

WO2014068110A1 - Delayed-release shaped bodies

Info

Publication number: WO2014068110A1
Application number: PCT/EP2013/072933
Authority: WO
Inventors: Peter Iwan Stuut; Jan Van Krieken
Original assignee: Purac Biochem Bv
Priority date: 2012-11-05
Filing date: 2013-11-04
Publication date: 2014-05-08
Also published as: EP2727992A1

Abstract

The invention pertains to a shaped body suitable for use as acid-releasing body in aqueous media, which comprises 5-100% of a lactic acid oligomer with an average degree of polymerization between 10 and 30. The use of lactic acid oligomers of this type results in the controlled release of lactic acid, which serves to reduce or prevent to the formation of hard deposits. The shaped bodies may be used in deposit stones, for toilet cleaning or for automatic machine cleaning.

Description

DELAYSD-RELEASE SHAPED BODIES

The present invention pertains to shaped bodies which show a delayed release of lactic acid.

More in particular the invention relates to water degradable compositions of lactic acid oligomers that dissolve over time in aqueous media and prevents deposit formation such as limestone formation or calcification of drainage systems and scale,, soap scum and bacteria in toilets and automatic washing machines .

The risk of scale formation in aqueous systems can be

calculated using the Langelier Saturation Index (LSI) . This index is based on the study of the carbonate equilibrium in water. The elements that are important for the carbonate equilibrium are gaseous carbon dioxide CO2, aqueous carbon dioxide (CO2) _aq, carbonic acid H2CO3, bicarbonate HCO3- ,

carbonate CO3^2" and solids containing carbonate like calcium carbonate CaCOs or magnesium carbonate MgCC . The assumption implicit in the calculations is that if the calcium carbonate content exceeds the level that can be maintained in solution, scale will occur.

The LSI is expressed as the difference between the actual system pH and the pH at which water is saturated with

carbonate .

Scale formation problems are common at pH value above 7.5. The risk of scale formation is increased by increasing the water temperature, increasing the pH and increasing the calcium concentration in water, which will occur when part the water is evaporated. Scale formation problems can be reduced or even eliminated by reducing the water pH or by adding chelants. Chelants are chemicals that form soluble, complex molecules with certain metal ions, inactivating the ions so that they cannot normally react with other elements or ions to produce precipitates or scale.

Scale formation and scale prevention is relevant for a large number of home care and industrial applications, like toilet care applications, laundry applications, auto dish

applications, bathroom cleaners, but also for the

construction industry. Products that can deliver a gradual and long lasting pH drop or a long lasting release of

che l a n ts can be used to avoid scale formation for these application areas.

Shaped bodies showing a delayed release of a their

composition are known for instance for use in toilets.

Commercial tablets often generate a neutral to alkaline environment. 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 .

US 5,110,868 describes a molded solid water-degradable composition comprising a copolymer of hydroxyacetic acid and lactic acid with a molecular weight of 800-4000 and a ratio between hydroxyacetic acid and lactic acid of the order of 1:1. It is indicated that the release of hydroxyacetic acid due to polymer degradation prevents the formation of calcium and magnesium carbonates from hard water.

WO2010/097398 describes the use of low molecular weight lactic acid oligomers in toilet care compositions. This reference describes blocks with lactic acid oligomers with an average degree of polymerization between 1.8 and 4. These compositions preferably also comprise lactides. These

oligomers dissolve in water thereby generating a lower pH. There is need for a slow acid releasing product with an increased product life that prevent deposit formation. A delayed release will further improve the product life.

The present invention provides such a product. According to the present invention tablets are provided with a further increase of the delayed release properties .

The present invention pertains to a shaped body suitable for use as acid-releasing body, which comprises 5-100% of a lactic acid oligomer with an average degree of polymerization between 10 and 30. It has been found that the use of a lactic acid oligomer with a degree of polymerization in this range provides the release of lactic acid at a speed and a

concentration which is active against the formation of alkaline earth metal deposits, more in particular calcium and magnesium deposits.

Due to the presence of a so-called chirai carbon atom, lactic acid (2-hydroxy propanoic acid) can exist in two enantiomeric forms . These enantiomers are usually referred to as L-l ctic acid (corresponding to (S) -lactic acid, also referred to as (+) -lactic acid) and D-lactic acid (corresponding to (R) - lactic acid, also referred to as {-) -lactic acid) . In the present invention with lactic acid is meant a stereochemical purified lactic acid as well as a mixture of the enantiomeric forms . The use of a lactic acid oligomer has been found to have a number of further advantages. One advantage is that lactic acid is produced by fermentation, and therewith qualifies as a renewable material .

In the composition of the present invention, the lactic acid oligomer is water-insoluble and is biodegradable. The oligomer is a polyester which reacts with water, i.e., the water attacks the ester bond to give carboxylic acid and alcohol, thus ensuring the controlled release of lactic acid. Lactic acid is soluble in water, and its presence reduces or prevents the formation of calcium and magnesium.

Further, lactic acid has a sanitizing and disinfecting effect due to its antibacterial activity. It also contributes to soap scum removal if present.

For some applications it might be desirable to add certain additives. The solubility of e.g. fragrances in lactic acid oligomers is better than the solubility of fragrances in the hydroxyacetic acid-lactic acid polymer used in US 5,110,868.

The shaped acid-releasing bodies according to the present invention are particularly useful as deposit stones.

With the term deposit stones is meant products that are being used in the construction industry to avoid lime scale build up in tunnels, drainage systems, reservoirs, tubes and pipes. The products are positioned in the drainage system where they come in direct contact with water. At contact with water they slowly dissolve, resulting in a gradual release of calcium binding agents (certain cheiants) and/or pH lowering agents. The result is prevention of deposits on the subsequent water flow path. As product forms several shaped bodies are

suitable, like blocks, slabs and also tablets.

The invention will be described in more detail below.

The shaped body according to the invention comprises 5-100 wt.% of a lactic acid oligomer with an average degree of polymerization of at least 10. A preferred polymerization grade is between 10 and 30. Another preferred range is between 10 and 20. Again another preferred range is between 10 and 18. The amount of lactic acid oligomer is in the range of 2 to 500 grams, a more specific range may be given of 5 to 150 grams . The amount generally is determined by cost

considerations and activity considerations. In general, the amount of lactic acid oligomer in the shaped body according to the invention depends on its use.

For deposit stones the amount is in the range of 2 to 500 grams, more specifically of 5 to 150 grams, more in

particular of 10 to 100 grams.

In addition to the choice of polymerization grade of the lactic acid oligomer, selection of the amount of lactic acid oligomer within this range ensures that the shaped body has an adequate lifetime, e.g., a life-time in the range of one week to 40 weeks, in particular in the range of 2 weeks to 20 weeks . The life-time of the shaped body is defined as the time between the provision of the body in the water stream (for deposit stones) and the moment that the body has

completely dissolved.

The shaped body according to the invention comprises 5-100 wt . % of lactic acid oligomer. A more specific range may be given of 5-95 wt.%, more in particular of 10-95 wt . % even more in particular 25-95 wt.%.

In one embodiment, the shaped body comprises at least 20 wt.% of lactic acid oligomer, in particular at least 25%, more in particular at least 30 wt.% of lactic acid oligomer.

The shaped bodies according to the invention each generally have a weight of from 2-500 grams, preferably 10-250 grams. Deposit stones may also have a weight of from 20-150 grams. Alternative weights are from 50-150 grams and from 20-100 grams. Also clusters of more blocks in one net or water permeable container such as a bag or a box may be used for these purposes, resulting in an overall weight of 1000 to 5000 grams. Copolymers of lactic acid and hydroxyacetic acid with a molecular weight of 800-4000, as describes in US5, 110, 868 are believed not to contribute to obtaining the effects

associated with the present invention, their presence in the tablets according to the invention is not required.

Accordingly, in one embodiment, the oligomers in the shaped body according to the invention contain more than 90 wt.%, more in particular more than 95 wt.%, even more in particular more than 98 wt.% of lactic acid. In another embodiment no copolymer of lactic acid and hydroxyacetic acid is present. In this embodiment the oligomer is a homooligomer of lactic acid .

If so desired, the shaped body may also comprise fillers, which do not provide additional activity to the shaped 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.

Fillers may be used in an amount of, for example, 0-90 wt.%, more in particular 10-50 wt.%. The amount of filler will depend on the desired weight of the 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. If so desired, the composition may comprise a surfactant, in particular an an-ionic surfactant, or a quaternary surfactant with a low water content. 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.

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. The shaped bodies according to the present invention are particularly useful as deposit stones . The preferred

application of the deposit stones are water drains in new construction projects. At contact with cementitious

materials, the pH of the water increases. This results in less calcium solubility and calcium deposition onto the drainage systems walls.

The shaped bodies according to the invention can also be used for toilet care and in washing machines .

For use in toilets, two embodiments may be distinguished, namely shaped bodies that are applied in as in-cis tern agents, and shaped bodies that are applied as in-bowl agents. For use in toilet blocks the amount of lactic oligomer is in the range of 5 to 60 grams. For in-cistern bodies in toilets a more specific range may be given of 5-50, in particular 12 to 50 grams, more in particular of 24 to 50 grams. For toilet in-bowl bodies, a more specific range may be given of 10 to 50 grams. For washing machine blocks the amount of lactic acid oligomer more particularly is in the range of 10 to 40 grams. The shaped bodies according to the invention for use in toilets or automatic cleaning machines 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 shaped body according to the invention may comprise various additional components .

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

The composition may also contain a dye, to impart color to the water e.g. 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.1.42085) , Astragon Green D (C.1.42040) , 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.

An additional advantage of the shaped bodies according to the invention is that moving to a higher degree of polymerization results in transparent glass like products. These products are more appealing to customers . The shaped bodies of the present invention may be

manufactured by a process comprising the steps of melting the lactic acid oligomer, blending in other components, and allowing the composition to solidify, wherein the composition is subjected to a shaping step to form shaped bodies before the solidification step, e.g., by pouring it in a moid, or after the solidification step, e.g., by cutting shaped bodies of appropriate size and shape from a solidified block or plate. The bodies may also be shaped using an extrusion process.

It will be clear to those skilled in the art that the

dissolution and hydro l. ysa t. i on speed, in addition to the oligomer chain length, can also be influenced amongst others by varying e.g. the free lactic acid content or by providing mixtures of lactic acids with different polymerization grades, by varying the surface to volume ratio and by the addition of fillers and highly soluble salts. In one embodiment, the molten 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 shaped body may have any desirable shape, e.g.,

rectangular (block), in the shape of pucks, stars, balls, 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 shaped bodies according to the invention can be used to prevent the formation of deposits in e.g. drainage systems of underground buildings. Accordingly, the present invention also pertains to the use of these compositions in these applications .

The present invention also pertains to a process for ensuring a delayed release of lactic acid in a drainage system, wherein a shaped body or a number of shaped bodies of the present invention is placed in a water stream.

Release tablets comprising the lactic acid oligomer according to the invention can be prepared and placed in drainage systems were they come into contact with water. The slowly released lactic acid prevents the formation of deposits on the subsequent flow path. The active lactic acid has the advantage that is environmentally friendly and is

biologically degradabie. The size and the form of the block can be easily adapted to the need in the drainage system. It is within the scope of the skilled person to determine and adapt the optimal size of the body for this particular use.

The shaped bodies according to the invention are also

suitable for use in toilets as in-cistern or in-bowi agents, in particular for use as in cistern agent, to effect the delayed release of lactic acid. The present invention also pertains to the use of these compositions in these

applications .

The in-bowl toilet bodies will in use generally be affixed to the rim of the toilet bowl using a removable holder. The in- cistern bodies may be placed in the cistern of the toilet, e.g., on the bottom, or connected by some means to the edge of the cistern.

The shaped bodies according to the invention are also

suitable for use in automatic washing machines. During the cleaning cycle in an automatic washing machine the

substrates, e.g. dishes or laundry, are cleaned by circulating a detergent solution over the substrates. This detergent solution is obtained by mixing a detergent in water, which detergent can contain builders, bleaches, enzymes surfactants for defoaming or cleaning, polymers, corrosion inhibitors etc. The detergent solution can be obtained by contacting a detergent composition comprising one or more of the above identified elements and the lactic acid oligomer composition according to the present invention in water .

The present invention is elucidated by the following

examples, without being limited thereto or thereby.

EXAMPLE 1: Lactic acid based blocks

The lactic based blocks were manufactured as follows:

The ingredients except for the dye and the fragrances were combined and the mixture was heated until a homogenous liquid mixture was obtained. Then, the dye and the fragrances were added and mixed through the mixture. The hot transparent and homogenous liquid mixture was poured into a cylinder-shaped mold, with a diameter of ± 2.5 cm, and cooled down to room temperature. The obtained blocks had a weight of about 35 grams, a diameter of about 5 cm, and a height of about 5 cm. All prepared formulations have a typical melting point of above 60 °C.

The following physical properties were observed:

Table 1

EXAMPLE 2: Dissolution rate

10L buckets were filled with 51 water. In each bucket a block was placed on a holding device which made it possible to stir the solution without stirring the block. The water was stirred at a constant stirring speed of ± 400 rpm.

Dissolution of the blocks was measured for at least 3 hours. Every hour the block was removed, dried in the oven at 40 °C and the weight was measured. Thereafter the block was

replaced at the same position with fresh water and stirring was proceeded for another hour.

Measurements were performed with two blocks: Block A which consists for 100% out of Dp20 lactic acid based oligomers and Block B which consists of 70% Dp20 lactic acid based

oligomers with the addition of LAS (Alpha-step PC-40) up to 30%.

The results are shown in Figures 1 and 2.

It can be seen that the weight of the blocks slightly

decreases in time. EXAMPLE 3: pH development The pH of the water with the samples A and B as described in Example 2 was monitored at set time intervals for each hour of water refreshment.

The pH change is indicated in Figures 3 and 4 for blocks A and B , respectively.

Both samples show a continuous acid release. The pure

oligomer block resulted in a slight pH drop of the water over time when a 40 gr block was immersed in 5L water of 20 °C for 1 hour. The LAS containing oligomer block had a faster dissolution rate and a larger pH drop effect than the pure oligomer containing block. This indicates that addition of non oligomer ingredients like surfactants and fillers could be used to adapt the dissolution rate.

Claims

1. A shaped acid-releasing body, which comprises 5-100% of an oligomer which is composed of at least more than 90% by weight of lactic acid and has an average degree of

polymerization between 10 and 30.

2. The shaped body according to claim 1 wherein the

oligome r has an average degree of polymerization between 10 and 20.

3. The shaped body according to claim 2 wherein the

oligomer has an average degree of polymerization between 10 and 18.

4. The shaped body according to claims 1-3, which has a weight of from 2 to 500 grams , preferably from 10 to 250 grams .

5. The shaped body according to claims 1-3 which comprises an oligomer in an amount of from 2 to 500 grams, preferably from 5 to 150 grams, more preferably from 10 to 100 grams.

6. The shaped body according to any one of the preceding claims which comprises at least 20 wt . % of oligomer, in particular at least 25 wt . % of oligomer.

7. The shaped body according to an one of the preceeding claims which comprises a lactic acid homo oligomer.

8. A process for manufacturing a shaped body according to any one of the preceding claims, comprising the steps of melting the lactic acid oligomer, blending in any other components, and allowing the composition to solidify, wherein the composition is subjected to a shaping step to form shaped bodies before the solidification step or after the

solidification step.

9. Use of the acid releasing body according to claims 1-7 for the preparation of deposit stones.

10. Use of the acid releasing body according to claims 1-7 for cleaning toilets .

11. Use of the acid releasing body according to claims 1-7 for preparation of a detergent composition for automatic washing machines .