Description

The present application pertains to process for determining a mixing ratio of organic, miscible components in a mixture of these components, wherein inorganic markers are use an in indicator about the mixing ratio and where a known amount of the markers in respective components, into which the markers are incorporated, is used to calculate the amount of the respective component in the mixture. In the inventive process, at least one of the inorganic markers is molybdenum sulphide (M0S2). The present invention further pertains to a kit comprising at least one component of a water curable- mixture and a further component comprising molybdenum sulphide, the use of molybdenum sulphide for the determination of mixing ratios in multicomponent mixtures and processes for bonding battery boxes or directly bonding automotive windows.

State of the art

Commercially available multicomponent mixtures, for example mousses, foams, sealants and adhesives, once prepared or applied, frequently make it impossible to determine the original mixing ratios between the components. This compromises the qualitative policing of the manufacturing operation for multicomponent mixtures and hinders any attempt to reconstruct the causes of process discrepancies. As a result, mixtures manufactured are incapable of meeting the functional expectations.

As a means to obviate this problem, WO2017/055066 A1 describes a process for the determination a mixing ratio of a plurality of organic, miscible components in a given mixture of these components, wherein in a first step an inorganic marker is incorporated into each of the components or each of the components except one in defined mixing ratios and after mixing the components, the content of the inorganic marker is determined in the mixture. From the respective content of the inorganic marker (or markers) the mixing ratio is then determined in a next step.

As inorganic markers, WO2017/055066 A1 suggests the use of oxides or sulfides of the elements copper (Cu), zinc (Zn), iron (Fe), nickel (Ni) and manganese (Mn) and in particular of zinc sulfide, as this is sufficiently available in an industrial context and is not toxic or harmful to health.

Unfortunately, a disadvantage of zinc based markers is that zinc is often used e.g., in adhesives and in particular in polyurethane adhesives as a catalyst, filler material or for other purposes. Accordingly, in such materials it is not possible to fully attribute a given content of zinc only to a zinc sulfide marker, which provides a source or error for the determination of the mixing ratio of the components in the mixture. Accordingly, there is a need for a reliable marker material, which is based on an element which is not used in adhesives and which can accurately be quantified in even a cured mixture of components such as in a cured adhesive.

The present application addresses these needs.

Description of the invention

In the investigations, which are underlying the present invention, various potential marker materials have been tested, which include sulfates such as barium sulfate, other sulfides and oxides such as chromium oxide. In these tests, it has unexpectedly been found, that molybdenum sulphide provides a highly reliable and accurate marker system for respective more component mixtures, as the respective content of Mo can e.g., be accurately quantified by microwave assisted acidic digestion and ICP/OES. In addition, molybdenum sulphide is non-reactive towards most constituents of conventional adhesives, so that it can be incorporated in respective components and mixtures without detrimentally affecting the performance thereof.

Accordingly, the present invention in a first aspect relates to a process for determining a mixing ratio A of n organic, miscible components (1 , 4) in a mixture (5) of these components, which comprises the steps:

- Providing n components (1 , 4) in predefined quantities, where n is an integer > 2,

- Mixing at least one inorganic marker (2) with at least one of the components (1 ) in a predefined mixing ratio of respective inorganic marker (2) to respective component (1 ) to provide respective mixtures (3), wherein at least one component (1 ) is mixed with an inorganic marker (2), and wherein, where more than one inorganic markers (2) is use, the markers are of different chemical nature,

- Preparing a mixture (5) of the components,

- Performing an analysis for the quantitative determination of the amount(s) of the inorganic marker(s) (2) in the mixture, and

- Determining the mixing ratio A of the n components (1 , 4) from the determined amount(s) of the inorganic marker(s) (2) via the respective predefined mixing ratios of the respective inorganic marker (2) to the respective component (1 ), wherein at least one of the inorganic markers is present as in the form of molybdenum sulphide.

The term “component” in the above is intended to be understood in the seance that the Components are to be kept separate before the mixture (5) is formed. Nonetheless the components by themselves be a mixture of different constituents, which are mixed to provide the respective component. As is apparent for the above, n is an integer > 2, where n is preferably 2, 3 or 4 and in a particularly preferred embodiment n is 2. In this case, molybdenum sulphide may be used in one of the components, whereas the other component does not contain an inorganic marker, or molybdenum sulphide may be used in one of the components, whereas the other component comprises another marker, e.g. in the form of zinc sulfide. In a particularly preferred embodiment, n is 2 and one of the components contains sulphide while the other component does not comprise an inorganic marker.

The indication that at least one inorganic marker (2) is mixed with at least one of the components (1 , 4) in a predefined mixing ratio of respective inorganic marker (2) to respective component (1 ) is intended to mean, that in case there are more than two components, an inorganic marker is incorporated either into all of the components (1 , 4) or at least into all of the components (1 , 4) except one (i.e. n-1 components are mixed with one organic marker each). In this manner, respective contents of the components can be calculated from the contents of the inorganic markers in the mixture. The content of the component, into which no inorganic marker has been incorporated, can be calculated from the full amount of the mixture and the content of the component(s), which contain(s an) inorganic marker(s), which can be calculated from the respective contents of the inorganic markers. The case where n-1 components are mixed with one organic marker (2) each is preferred for the inventive process.

If more than one component in the inventive process is modified with a marker, the inorganic markers which are used in addition to molybdenum sulphide, are preferably selected from metal oxides and/or metal sulphides. Particular preferred additional inorganic markers are selected from the group of copper (Cu), zinc (Zn), iron (Fe), nickel (Ni) and manganese (Mn) sulfides. The content of the molybdenum sulphide inorganic marker in the organic, miscible component, into which it is incorporated is not subject to any relevant restrictions, except that the content should be high enough to allow for accurate dosing of the inorganic marker and should be sufficiently low to provide a “dilution” in the component which facilitates homogeneous distribution of the inorganic additive in the mixture. As a suitable amount to meet these requirements, an amount in terms of a total weight of the inorganic marker (2) in the component (1 ) into which it is incorporated of less than 5% by weight, preferably of at least 0.05% by weight to 4% by weight and more preferably 0.5 to 3% by weight can be mentioned.

The content of the molybdenum sulphide inorganic marker in the mixture, which is prepared in the process, is regularly adjusted thus that the content can still be accurately detected (in terms of a signal to noise ratio in the measurement) but is as low as possible from a cost perspective. In a preferred embodiment of the inventive method, the proportion of the molybdenum sulphide inorganic marker (2) relative to the total mixture of the n components is set in the range from 0.01 to 0.1 % by weight, preferably from 0.02 to 0.075% by weight and more preferably in the range from 0.03 to 0.05% by weight.

For detecting the molybdenum sulphide inorganic marker is a cured mixture, non-destructive and destructive methods (i.e. methods, where the cured mixture or a test sample thereof is degraded) are available. In a destructive method, the mixture provided by the degradation is then analysed. A suitable destructive method to quantify an amount of molybdenum sulphide in a cured mixture is e.g. an acidic digestion of the mixture, which is particularly effective if a mixture of HCI and HNOs (aqua regia) is used for the digestion. This mixture is highly oxidative and can usually bring the molybdenum sulphide into solution for further analysis in a quantitative manner. The acidic digestion may suitably be assisted by microwave irradiation. Another suitable means to quantify the content of molybdenum sulphide in a cured mixture is a determination of the ignition residue of the mixture according to DIN EN ISO 1 172: 1998-12. An ignition residue determination takes place at temperatures at which the functional, active or reactive compounds of the organic components which are based essentially on hydrocarbon compounds burn and only inorganic products remain as incineration residue. It is annealed to constant mass, so that it can be concluded directly from the residue on the mixing ratio of the components.

If the content of the molybdenum sulphide inorganic marker is determined by acidic digestion, the quantitative analysis of the marker can be carried out by suitable spectroscopic methods. When additional markers have been incorporated into the mixture, the spectroscopic method also qualitatively differentiates the markers from one another. Thus, even in multi-component systems with more than 2 components and more than one marker, an accurate qualitative analysis of each marker can be performed.

In a particularly preferred embodiment, the quantitative analysis of molybdenum sulphide and other inorganic markers, which may be present is performed by means of inductively coupled plasma optical emission spectrometry (ICP-OES), atomic absorption spectroscopy (AAS) or atomic emission spectroscopy (OES). ICP-OES, also known as ICP-AES or ICP plasma spectroscopy, is an optical emission spectroscopy with inductively coupled plasma (ICP) as an excitation source, which offers easy handling, high sensitivity and precision, and relative freedom from interference. It also allows a qualitative and quantitative analysis of the marker (M0S2 and others), so that each component can be assigned a corresponding amount of marker.

In the inventive method it is further preferred that the organic, miscible component, into which the molybdenum sulphide is incorporated and/or an organic, miscible component, which is mixed with the organic, miscible component having the molybdenum sulphide incorporated therein, is selected from thermoplastics, thermosets, elastomers and their starting materials, such as the monomers used. These organic compounds are widely used in multicomponent systems and functional products, so that the determination of the mixing ratio of their starting components is highly relevant. Preferably, these organic components are in the form of polyurethanes, epoxides, polyacrylates, polyamides, polyolefins (and their monomeric or oligomeric precursors, respectively) and mixtures thereof.

Further preferably, the inventive process is applied to a mixture which is an adhesive, sealant or foam. These homogeneous mixtures have a high functionality, whose quality by determining the mixing ratio A is essential. In an especially preferred embodiment, the mixture (5) is an adhesive.

In a further aspect, the present invention pertains to a kit, which comprises a first component and a second component, the first component being a moisture-curing mixture and the second component being an accelerator for the moisture-curing mixture of the first component, wherein the second component contains molybdenum sulphide in a defined proportion, preferably in the range from 0.1 to 5% by weight and more preferably in the range from 0.5 to 3% by weight. As is apparent, this kit is specifically adapted for use in the above described process, where the first two steps (providing the components and mixing one or more inorganic makers into the component) have been implemented. In a preferred embodiment of this aspect, the first component of the kit is a moisture-curing adhesive. In this case, it is further preferred that the second component, which contains the molybdenum sulphide, is a booster for the moisture curing adhesive (i.e., a composition which comprises compounds to accelerate the curing of the moisture curing adhesive).

In a particularly preferred embodiment, the first component of the kit is a polyurethane adhesive with reactive isocyanate groups and the second component contains one or more components with groups reactive towards isocyanate, preferably in the form of OH and/or NH2 groups and/or water.

In a further aspect, the present invention pertains to a use of molybdenum sulphide as an inorganic marker (2) for determining a mixing ratio of organic, miscible components (1 , 4) in multicomponent mixtures (5). The multicomponent mixtures can in particular have the form of a foam, adhesive or sealant.

The inventive kit is particular suitable in an adhesive application, where the observance of an exact mixing ratio may have an impact on the strength and durability of the cured adhesive. This is important especially in automotive applications, where e.g., battery boxes have to be securely bonded or where automotive windows as directly attached via an adhesive (direct glazing). Thus, in a yet further aspect, the present invention is directed to a process of bonding battery boxes or directly bonding automotive windows comprising the steps of preparing an adhesive by mixing the components of a kit as defined above (where one of the components alone or in admixture with the second component provides an adhesive), optionally, determining the mixing ratio of the components of the kit by the content of molybdenum sulphide in the adhesive mixture, and then bonding a battery box or an automotive window. In this method, the step of bonding a battery box or an automotive window is a mandatory step. In addition, the indication that the mixing ratio of the components of the kit is optionally determined via the content of molybdenum sulphide in the adhesive mixture is intended to encompass processes, where the determination is carried out on a spot check basis. In one embodiment, the step of determining the mixing ratio of the components of the kit by the content of molybdenum sulphide in the adhesive mixture is mandatory.

In the following, the present invention will be further illustrated by means of Examples, which should however not be understood as limiting to the scope of the invention by any means. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

Example 1

2 wt.-% of molybdenum sulfide (M0S2) were incorporated into a curing booster paste, which is constituted from about 6 wt.-% of a PPG diol, about 2 wt.-% of an anionic surfactant, about 10 wt.-% of a 2-ethylhexylbenzoate, about 25.5 wt.-% of a PPG diamine, 36 wt.-% water, 1 1 .5 wt.-% of fumed silica and about

3 wt.-% of CaCOs. In the curing booster paste, the amount of Mo (derived from M0S2) was determined as 18’050 mg/kg via ICP/OES.

In the following, the booster paste was mixed in ratios of 1.8%, 2.1 % and 2.4% with Sikaflex-250 DB-11 as a one component polyurethane adhesive. A respective comparative test series was prepared with 2 wt.-% ZnS instead of M0S2. In the comparative ZnS containing curing booster paste, the amount of Zn was determined as 11 ’100 mg/kg via ICP/OES

In the following table 1 , the identified amounts of ZnS in the cured samples after acidic digestion with HCI/HNO3 as analysed by ICP/OES is given:

Table 1

SD = standard deviation; 1 = given as content of pure metal (Zn or Mo)

As is apparent for the table above, M0S2 provides for about the level of accuracy (in terms of the SD) as ZnS. However, the measurement precision (i.e. , the quantification of the detected marker) is significantly higher in the case of M0S2 compared to ZnS, meaning that the detected and quantified content of marker is closer to the actual content in the case of M0S2. This shows that M0S2 is a better marker than ZnS for quantitative analysis. Furthermore, M0S2 is substantially not detected in the uncured adhesive, whereas this adhesive contains 15 mg/kg ZnS. This shows that ZnS will produce false positive results in samples that should not contain the marker, whereas M0S2 does not. The accurate content of the booster paste in the adhesive booster mixture (in wt.-%) can be calculated from the content of Mo and Zn in the booster paste (see above) and the content of Mo/Zn in the final adhesive mixture.