EP0934394B1 - Cleaning re-usable plastics containers or re-usable plastics-coated glass containers - Google Patents

Abstract

The invention concerns cleaning agents for re-usable plastics containers or re-usable plastics-coated glass containers, which cleaning agents contain at least one complexing agent. The invention also concerns a method of cleaning the containers. The complexing agent helps to eliminate or prevent yellowish-brown discoloration and changes in smell caused by the washing liquor conventionally used in the foodstuffs industry.

Description

The invention relates to the cleaning of reusable plastic containers or plastic-coated reusable glass containers to avoid or retrofit Removal of stains and the smell of lye.

In the prior art, the packaging of foods has become common in recent times Plastic containers used. Especially in the beverage industry Reusable plastic packaging used as an alternative to glass or cans. Reusable bottles made of polyethylene terephthalate (PET) and polycarbonate are particularly popular (PC), so-called multilayer bottles with a layer sequence, for example made of PET-polyaryl-PET as well as conventional glass bottles coated with a plastic film. Next The all-plastic containers are in particular those with a mostly made of polyurethane Plastic film-coated glass bottles of great interest to the beverage industry, since that Packaging weight significantly reduced due to the possible lower glass wall thickness can be. In addition, such can be coated with a plastic film Glass bottles in the event of explosions or broken fragments and contents in the plastic jacket to be caught.

However, such plastic containers show in practical use as reusable containers Shortcomings that do not occur when using conventional glass containers. In particular, the polymer coating shows a different cleaning behavior than conventional ones Glass. The complete wetting of the plastic surface is compared to conventional Glass surfaces are more difficult to achieve, but can generally be added by adding special achieve surfactant-containing additives. This makes the polymer layer more uniform wetted and the subsequent labeling easier. The formation of Water hardness on the outside of the bottle by drying the water drops avoid almost completely.

In practical tests, however, the polymer layers showed further properties, the usual ones Glass containers are foreign. In particular, residues from the wash liquor are stored Bottle cleaning system in the plastic. In practice, this leads to undesirable ones changes in color and smell of the coating. In practice trials were common Bottles with a typical "lye smell" and a yellow-brown color of the polymer layer obtained, especially after using the cleaning agent mainly used Caustic soda.

The object of the present invention is therefore on the one hand the formation of Avoid colorings and the smell of lye from the outset or add them later remove.

The solution to this problem is for the global introduction of such plastic containers from extremely important, because on the other hand the areas of application of this packaging concept would be severely limited. So it would be practically impossible for those who are susceptible to foreign taste and smell Foodstuffs such as mineral, table and still water in such plastic containers to fill.

According to the teaching of the European, the above-mentioned task is solved Patent application EP-A-0 527 799 (Henkel KGaA) through the use of at least one organic solvent in application concentrations of preferably 0.001 to 1% by weight directly in the main cleaning bath of the cleaning system, whereby the height of the Application concentration reflected in the cleaning result. When using the means of EP-A-0 527 799 in a separate process step, the solvent can be mixed with Water in concentrations up to 100% can be used.

The elimination of migrated components from reusable plastic containers succeeds after Teaching of DE-A-43 22 328 also by the use of oxidizing agents, for example Chlorine dioxide in aqueous solution, organic peracids, alkaline hypochlorites, Hydrogen peroxide, perborates and alkaline percarbonates.

It has now been found that agents which contain complexing agents in suitable amounts even without the addition of solvents as claimed in EP-A-0 527 799, the Avoid the formation of colorings and the smell of lye from the outset or these later can remove.

(a) Polycarbonsäuren oder Monocarbonsäuren, bei denen die Summe der Carboxylund gegebenenfalls Hydroxylgruppen mindestens 5 beträgt,

(b) stickstoffhaltigen Mono- oder Polycarbonsäuren,

(c) geminalen Diphosphonsäuren,

(d) Aminophosphonsäuren,

(e) Phosphonopolycarbonsäuren,

(f) Cyclodextrinen,

(g) Tripolyphosphat, Hexametaphosphat, Pyrophosphat,

in einer Anwendungslösung, deren Gehalt an Komplexbildner 0,2 bis 10 Gew.-% beträgt, bei der Reinigung von Kunststoff-Mehrweggebinden oder kunststoffbeschichteten Mehrwegglasgebinden zur Vermeidung oder nächträglicher Entfernung von Färbungen und des Laugeruchs.The invention accordingly relates to the use of at least one complexing agent, selected from:

(a) polycarboxylic acids or monocarboxylic acids in which the sum of the carboxyl and optionally hydroxyl groups is at least 5,

(b) nitrogen-containing mono- or polycarboxylic acids,

(c) geminal diphosphonic acids,

(d) aminophosphonic acids,

(e) phosphonopolycarboxylic acids,

(f) cyclodextrins,

(g) tripolyphosphate, hexametaphosphate, pyrophosphate,

in an application solution with a complexing agent content of 0.2 to 10 wt.

To investigate and find the cause of the problem of discoloration and the Lye smell was used to analytically identify new and discolored plastic bottles semi-quantitative energy dispersive X-ray microanalysis examined and thereby found that the in the

Coating stored impurities is a typical alkali composition of a Practice lye included. So sodium from the caustic soda, magnesium and calcium from the Water hardness, silicon from glass abrasion, chrome and iron from printing inks from labels, Potassium etc. from labels as well as sulfur, possibly from melamine resins of the coating be determined. A significant influence of iron or other machine and procedural parameters could not be determined.

a) Polycarbonsäuren oder Monocarbonsäuren, bei denen die Summe der Carboxyl- und gegebenenfalls Hydroxylgruppen mindestens 5 beträgt wie Gluconsäure,

b) stickstoffhaltige Mono- oder Polycarbonsäuren wie Ethylendiamintetraessigsäure (EDTA), N-Hydroxyethylethylendiamintriessigsäure, Diethylentriaminpentaessigsäure, Hydroxyethyliminodiessigsäure, Nitridodiessigsäure-3-propionsäure, Isoserindiessigsäure, N,N-Di-(β-hydroxyethyl)-glycin, N-(1,2-Dicarboxy-2-hydroxyethyl)-glycin, N-(1,2-Dicarboxy-2-hydroxyethyl)-asparaginsäure oder Nitrilotriessigsäure (NTA),

c) geminale Diphosphonsäuren wie l-Hydroxyethan-1,1-diphosphonsäure (HEDP), deren höhere Homologe mit bis zu 8 Kohlenstoffatomen sowie Hydroxy- oder Aminogruppen-haltige Derivate hiervon und 1-Aminoethan-1,1-diphosphonsäure, deren höhere Homologe mit bis zu 8 Kohlenstoffatomen sowie Hydroxy- oder Aminogruppen-haltige Derivate hiervon,

d) Aminophosphonsäuren wie Ethylendiamintetra(methylenphosphonsäure), Diethylentriaminpenta(methylenphosphonsäure) oder Nitrilotri(methylenphosphonsäure),

e) Phosphonopolycarbonsäuren wie 2-Phosphonobutan-1,2,4-tricarbonsäure,

f) Cyclodextrine sowie

g) Tripolyplosphat, Hexametaphosphat, Pyrophosphat.
Als Polycarbonsäuren a) werden im Rahmen dieser Patentanmeldung Carbonsäuren -auch Monocarbonsäuren- verstanden, bei denen die Summe aus Carboxyl- und den im Molekül enthaltenen Hydroxylgruppen mindestens 5 beträgt. Komplexbildner aus der Gruppe der stickstoffhaltigen Polycarbonsäuren, insbesondere EDTA, sind bevorzugt. Bei den erfindungsgemäß erforderlichen alkalischen pH-Werten der Behandlungslösungen liegen diese Komplexbilner zumindest teilweise als Anionen vor. Es ist unwesentlich, ob sie in Form der Säuren oder in Form von Salzen eingebracht werden. Im Falle des Einsatzes als Salze sind Alkali-, Ammonium- oder Alkylammoniumsalze, insbesondere Natriumsalze, bevorzugt.

Selected complexing agents of the prior art can be used in the context of the present invention. These can belong to different chemical groups. The following are preferably used individually or in a mixture:

a) polycarboxylic acids or monocarboxylic acids in which the sum of the carboxyl and optionally hydroxyl groups is at least 5, such as gluconic acid,

b) nitrogen-containing mono- or polycarboxylic acids such as ethylenediaminetetraacetic acid (EDTA), N-hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, hydroxyethyliminodiacetic acid, nitridodiacetic acid-3-propionic acid, isoserinediacetic acid, N, N-di- (β-hydroxyethyl) -glycine Dicarboxy-2-hydroxyethyl) glycine, N- (1,2-dicarboxy-2-hydroxyethyl) aspartic acid or nitrilotriacetic acid (NTA),

c) Geminal diphosphonic acids such as l-hydroxyethane-1,1-diphosphonic acid (HEDP), their higher homologues with up to 8 carbon atoms, and derivatives thereof containing hydroxyl or amino groups, and 1-aminoethane-1,1-diphosphonic acid, their higher homologues with up to 8 carbon atoms as well as derivatives thereof containing hydroxyl or amino groups,

d) aminophosphonic acids such as ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) or nitrilotri (methylenephosphonic acid),

e) phosphonopolycarboxylic acids such as 2-phosphonobutane-1,2,4-tricarboxylic acid,

f) cyclodextrins and

g) tripolyplosphate, hexametaphosphate, pyrophosphate.
In the context of this patent application, polycarboxylic acids a) are understood to mean carboxylic acids, including monocarboxylic acids, in which the sum of carboxyl groups and the hydroxyl groups contained in the molecule is at least 5. Complexing agents from the group of nitrogen-containing polycarboxylic acids, in particular EDTA, are preferred. At the alkaline pH values of the treatment solutions required according to the invention, these complexing agents are at least partially present as anions. It is immaterial whether they are introduced in the form of acids or in the form of salts. In the case of use as salts, alkali metal, ammonium or alkylammonium salts, in particular sodium salts, are preferred.

In a preferred embodiment of the present invention, the application solutions additionally known components of cleaning agents in the food industry contain. These are components of cleaning agents in the food industry which are selected from Alkali metal hydroxide, organic solvents, surface-active substances, Anti-corrosion agents, anti-foaming agents, anti-dust agents, fragrances, Control agents, indicators and enzymes. These are, for example, from Ullmann's Encyklopedia of technical chemistry, 4th edition, volume 20, pages 153 to 155 known. Reusable glass bottles are usually used in the food industry in a bottle cleaning system cleaned with a dilute sodium hydroxide solution, which in addition to 1.5 to 2.5% by weight Sodium hydroxide as dirt-disrupting component, in particular 0.2% by weight of the rest Contains components.

(a) geradkettigen, verzweigten oder cyclischen, gesättigten oder ungesättigten einwertigen oder mehrwertigen Alkoholen mit 1 bis 10 C-Atomen,

(b) geradkettigen, verzweigten oder cyclischen, gesättigten oder ungesättigten Ketonen und Aldehyden mit 2 bis 10 C-Atomen,

(c) Alkylenalkylether der allgemeinen Formel (I)

wobei
X für eine Einfachbindung oder eine Methylengruppe,
Y für Wasserstoff oder eine Methylgruppe,
R¹ und R² jeweils unabhängig voneinander für Wasserstoff oder einen geradkettigen oder verzweigten Alkylrest mit 1 bis 4 C-Atomen und
n für eine ganze Zahl im Bereich von 1 bis 6
steht,

(d) geradkettigen, verzweigten oder cyclischen, gesättigten oder ungesättigten Estern mit 2 bis 10 C-Atomen im Carbonsäurerest und 1 bis 10 C-Atomen im Alkoholrest,

(e) symmetrischen oder unsymmetrischen Dialkylether mit jeweils geradkettigen oder verzweigten Alkylresten mit 1 bis 8 C-Atomen je Alkylrest sowie

(f) Dimethylacetal, Dimethylformamid, Dimethylacetamid, Dimethylsulfoxid Tetramethylsulfon, N-Methylpyrrolidon und Hexamethylphosphorsäuretriamid eingesetzt.

Of course, it is also possible to combine the application solutions to be used according to the invention, which contain complexing agents, with solvents, as are described as the sole active component in European application EP-A-0 527 799. According to a preferred embodiment of the present invention, at least one organic solvent is therefore additionally selected from:

(a) straight-chain, branched or cyclic, saturated or unsaturated monohydric or polyhydric alcohols with 1 to 10 C atoms,

(b) straight-chain, branched or cyclic, saturated or unsaturated ketones and aldehydes with 2 to 10 carbon atoms,

(c) alkylene alkyl ethers of the general formula (I)

in which
X represents a single bond or a methylene group,
Y represents hydrogen or a methyl group,
R ¹ and R ^{2 are} each independently of one another hydrogen or a straight-chain or branched alkyl radical having 1 to 4 carbon atoms and
n for an integer ranging from 1 to 6
stands,

(d) straight-chain, branched or cyclic, saturated or unsaturated esters with 2 to 10 C atoms in the carboxylic acid residue and 1 to 10 C atoms in the alcohol residue,

(e) symmetrical or asymmetrical dialkyl ethers, each with straight-chain or branched alkyl radicals having 1 to 8 carbon atoms per alkyl radical and

(f) Dimethylacetal, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, tetramethyl sulfone, N-methylpyrrolidone and hexamethylphosphoric triamide are used.

The decisive factor here, however, is that the concentration of the complexing agents is used within the limits of 0.2 to 10% by weight, preferably from 0.2 to 2% by weight. The concentration of the solution titles is moving preferably from 0.001 to 1% by weight, in particular from 0.001 to 0.5% by weight, related to the application solution.

When cleaning plastic-coated glass bottles, a temperature of 70 to 95 ° C aimed for. The temperature of the cleaning bath to be selected depends primarily on this cleaning plastic material.

The concentration of the detergents in the main cleaning bath as well as in one downstream cleaning step is less critical because the concentration is too low can be read directly from the cleaning result. Accordingly, the concentration is Complexing agents, based on the application solution, in the range from 0.2 to 10% by weight, in particular from 0.2 to 2% by weight, application solution in this case means that Detergent in the main cleaning bath of the bottle washer.

Preferred plastic containers in the sense of the present invention are plastic reusable bottles or plastic-coated reusable glass bottles.

An embodiment of the present invention is that the Containers with a combination of known components from Detergents in the food industry and complexing agents in the Main cleaning bath of the bottle washer at a temperature that is in Depending on the plastic material to be cleaned is selected in contact brings. In principle, this is the use of the above mentioned complexing agent as a cleaning additive to known Detergents in the food industry. According to another Embodiment of the present invention becomes the complexing agent afterwards used for the main cleaning.

Practical tests have shown that with increasing organic stress the Wash liquor increases the problem of discoloration. It seems to be to act a purely physical adsorptive problem.

An increasing load of the wash liquor with organic compounds lowers the Surface tension and thus facilitates penetration into the polymer. Through the Property, in particular the polyurethane layer, about 2% by weight of its own weight If liquid is absorbed, the organic contaminants can get into the polymer but are not sufficiently rinsed out and remain with the slow evaporation of the Water back.

According to initial knowledge, surface polarities do not appear to have any significant influence to have this problem.

With other plastic materials such as polyethylene terephthalate and polycarbonate, which have a significantly lower moisture absorption, the phenomenon of yellow-brown discoloration only appeared in a weakened form. In principle, however, this phenomenon is also identical for these plastics and supports the thesis that it is a physical diffusion problem. The reason for the discoloration therefore appears to be neither oxidation nor acid-base reactions, but rather an accumulation of organic and inorganic materials via the moisture absorption in the polymer layer. Additively contribute to the observed effect:
Glue, labels, active ingredients, beverage residues, impurities, increased layer thicknesses of the polymer and elevated temperatures, both during the treatment and during the annealing of the polymer layer during the manufacturing process.

The following test results show that the observed phenomenon of Brown color and the absorption of odors by oxidation of the organic impurities only partially and by using the complexing and if necessary, can completely compensate for solvent.

The odor absorption of the plastic-coated surfaces was olfactory by 5 independent evaluating test persons determined that the odor absorption in the criteria "none Odor absorption "," barely perceptible odor absorption "," low odor absorption ", "clearly perceptible odor absorption" and "strong odor absorption" rated. The Results were averaged from the values given by the test subjects. For Assessment of odor reduction through the use of comparative agents and The same scoring scale was used according to the invention.

Examples: Comparative Example 1 (Cleaning Solution Not According to the Invention)

Standardized sample strips of a polyurethane coating of a commercial one Reusable glass bottles were made and these among the following Test conditions examined. When exposed to deionized water Temperature of 80 ° C in the course of 24 h, the following results were obtained. Commercial, plastic-coated glass bottles were also subjected to the test, these were also completely immersed in the test solution in question.

Comparative Example 1.1

According to Comparative Example 1, no discoloration of the Coating and no odor absorption observed.

Comparative Example 1.2

Corresponding to Comparative Example 1, a 2% by weight sodium hydroxide solution was used received a light yellow-colorless coating and no odor absorption was observed.

Comparative Example 1.3

According to Comparative Example 1, 2% by weight was used Sodium hydroxide solution, the 0.2 wt .-% of a common detergent additive based on Contained phosphoric acid, phosphonic acids and alkoxylated fatty alcohols, a light yellow-yellow Get coating, with a low odor absorption was observed.

Comparative Example 1.4

According to Comparative Example 1, using the solution according to Comparative Example 1.3 with the additional use of 0.5% casein glue a yellow-yellow-brown Received coating and found a strong odor absorption.

Comparative Example 1.5

According to Comparative Example 1, using a practical liquor from a Brewery that contained aluminum salts, got a brown coating and also one strong smell absorption found.

It was found that the discoloration of Comparative Examples 1.2 to 1.5 increased with increasing Fade standing time in the air a little. The strength of the lye smell also decreased in the course of time.

The yellow-brown discolored polymer platelets became in the course subjected to the subsequent treatment of 60 h, taking a blank sample in air Room temperature gave a light brown coating.

Comparative Example 2.1 (UV radiation not according to the invention)

Even after exposure to UV light in water at room temperature, it became a light yellow-yellow Coating observed. The smell was only reduced to a very small extent.

Comparative Example 2.2 (Oxidation with H ₂ O ₂ not According to the Invention)

Chemical oxidation with an approximately 10% hydrogen peroxide solution Room temperature only led to a slight lightening of the coating. there has been a preserved light yellow coating. The reduction in odor from the treatment was clear recognizable.

Comparative Example 2.3 (heat treatment not according to the invention)

Thermal treatment of the polymer platelet at a temperature of 90 ° C gave only a light yellow-yellow coating with a low odor reduction.

Comparative Example 2.4 (Acid Treatment Not According to the Invention)

Using 5.0% citric acid only brightened the coating detected. The coating was rated as yellow-brown and no discernible Odor reduction found.

In the following examples, a solution was prepared in accordance with Comparative Example 1.4, those additionally indicated in the examples with those to be used according to the invention, Complexing agent was added. The smell absorption became olfactory as before described determined.

Example 2

Using 2.0% by weight of EDTA, no discoloration and none Odor absorption determined.

Example 3

Using 1.5% by weight of NTA, no discoloration of the coating and no odor absorption is found.

Example 4

No discoloration was observed using 1.5% by weight of N, N-di (β-hydroxyethyl) glycine the coating can be determined. A smell of lye was hardly noticeable.

Example 5

No discoloration was observed using 3.0% by weight of gluconic acid Plastic showed no odor absorption.

Example 6

Using 2.0% by weight of a cyclodextrin, no discoloration and only one could very low, barely perceptible odor absorption can be observed.

Example 7

Using 2.0% tripolyphosphate, no discoloration and only a very great deal low odor absorption can be observed.

Example 8

With the use of 2.0% by weight of hexametaphosphate, no discoloration and only a barely perceptible odor absorption can be observed.

Example 9

Even when using 2.0% by weight of pyrophosphate, no discoloration and only one could very low, barely perceptible odor absorption can be observed.

Comparative Example 3

Using 20% by weight of a commercially available defoamer in the food industry based on an alkoxylated fatty alcohol, the quaternary Contains ammonium compounds, there was a discolouration of the coating to lemon yellow observed. The coating became completely cloudy. The material lost its shape and is therefore unusable in practice. In addition, there was a strong smell of lye.

Claims (8)

1. The use of at least one complexing agent selected from

   (a) polycarboxylic acids or monocarboxylic acids in which the sum total of carboxyl and optionally hydroxyl groups is at least 5,

   (b) nitrogen-containing mono- or polycarboxylic acids,

   (c) geminal diphosphonic acids,

   (d) aminophosphonic acids,

   (e) phosphonopolycarboxylic acids,

   (f) cyclodextrins,

   (g) tripolyphosphate, hexametaphosphate, pyrophosphate,

   in an in-use solution containing from 0.2 to 10% by weight of complexing agent(s), in the cleaning of returnable plastic containers or returnable plastic-coated glass containers for avoiding or subsequently removing colorations and the lye odour.
2. The use claimed in claim 1, characterized in that known components of cleaning compositions used in the food industry selected from alkali metal hydroxide, organic solvents, surfactants, corrosion inhibitors, antifoam agents, antidust agents, fragrances, fillers, indicators and enzymes are additionally used.
3. The use claimed in claim 1 or 2, characterized in that at least one organic solvent selected from

   (a) linear, branched or cyclic, saturated or unsaturated monohydric or polyhydric alcohols containing 1 to 10 carbon atoms,

   (b) linear, branched or cyclic, saturated or unsaturated ketones and aldehydes containing 2 to 10 carbon atoms,

   (c) alkylene alkyl ethers corresponding to general formula (I):

   

   where
   X is a single bond or a methylene group
   Y is hydrogen or a methyl group,
   R¹ and R² independently of one another represent hydrogen or a linear or branched alkyl chain containing 1 to 4 carbon atoms and n is an integer of 1 to 6,

   (d) linear, branched or cyclic, saturated or unsaturated esters containing 2 to 10 carbon atoms in the carboxylic acid molecule and 1 to 10 carbon atoms in the alcohol molecule,

   (e) symmetrical or asymmetrical dialkyl ethers containing linear or branched alkyl chains with 1 to 8 carbon atoms per alkyl chain and

   (f) dimethyl acetal, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, tetramethyl sulfone, N-methyl pyrrolidone and hexamethyl phosphoric acid triamide,
   is additionally used.
4. The use claimed in claim 3, characterized in that the concentration of solvents is from 0.001 to 1% by weight and preferably from 0.001 to 0.5% by weight, based on the in-use solution.
5. The use claimed in one or more of claims 1 to 4, characterized in that the concentration of complexing agent(s) is from 0.2 to 2% by weight, based on the in-use solution.
6. The use claimed in one or more of claims 1 to 5, characterized in that the complexing agent is used in the main cleaning bath of a bottle washing machine.
7. The use claimed in one or more of claims 1 to 5, characterized in that the complexing agent is used after the main cleaning cycle.
8. The use claimed in one or more of claims 1 to 7, characterized in that the returnable containers are returnable plastic bottles or returnable plastic-coated glass bottles.