EP2254707A2

EP2254707A2 - Method for cavity sealing

Info

Publication number: EP2254707A2
Application number: EP09711601A
Authority: EP
Inventors: Thorsten Bach; Karsten Lessmann; Lisa Herrmann
Original assignee: PFINDER KG
Current assignee: PFINDER KG
Priority date: 2008-02-21
Filing date: 2009-02-20
Publication date: 2010-12-01
Also published as: WO2009103551A3; WO2009103551A2; US20110062669A1; DE102008011489A1

Abstract

The invention relates to a method for the cavity sealing of a motor vehicle component, comprising the following steps: a.) spraying a cavity preservative agent into the motor vehicle component; b.) letting the cavity preservative agent penetrate; c.) letting excess cavity preservative agent drip out of the motor vehicle component; and d.) curing the cavity preservative agent, wherein said cavity preservative agent has a component which can be cross-linked. Step a.) is preceded by a step of admixing a cross-linking component, wherein the quantity and the type of said component which can be cross-linked and said cross-linking component are selected such that the cavity preservative agent solidifies into a gel-type consistency between step c.) and step d.).

Description

Method for cavity sealing

The present invention relates to a method for cavity sealing of a motor vehicle component, comprising the following steps:

a.) spraying a cavity preservative in the motor vehicle component;

b.) allowing the cavity preservative to penetrate;

c.) draining excess cavity preservative from the automotive component; and

d.) hardening of the cavity preservative.

The present invention further relates to a composition for producing a cavity seal, as well as a motor vehicle component having a cavity seal. In the production of motor vehicle components, in particular of load-bearing components, various structures formed from metal sheet are connected to form larger components. To protect against corrosion, these components are electrochemically coated after assembly with a paint layer. In areas where two metal parts come close to each other or in which by bending parts of a single metal part close to each other, there is the formation of a Faraday cage and therefore no or at least insufficient deposition of the paint. In order to protect these areas from corrosion by environmental influences, a cavity seal is applied there from a cavity preservative.

One method of making such a cavity seal involves spraying a cavity preservative into the automotive components to be protected, permitting the cavity preservative to penetrate, draining excess cavity preservative, and curing the cavity preservative in the motor vehicle component being protected. To ensure adequate protection, the cavity preservative should always be used to some extent in excess. To ensure that the cavity preservative can penetrate into small cracks and niches of a motor vehicle component, this must have a high flowability.

After applying the cavity seal, it is desirable for the cavity preservative to solidify quickly so that the automotive components can be processed quickly without dripping cavity preservative in later processing. Such erosion of cavity preservative leads to contamination in the further processing of the motor vehicle components as well as to a risk of workers being able to slip on it.

However, solidification of the cavity preservative must not go so far as to increase the flexibility and plasticity of the cavity seal, which is necessary to compensate for movements in the components, is impaired.

Solidification on the basis of a purely oxidative hardening of the cavity preserving agent is not meaningful here because even short curing times in the case of oxidative curing are still in the range of several hours, since this prevents rapid further processing of the motor vehicle components.

The use of cavity preservatives which are rendered flowable by the addition of volatile solvents and which solidify due to evaporation of the solvent is undesirable these days due to the associated environmental impact and OSH expenses, as well as potential exposure of the vehicle owners to subsequent solvent evaporation.

Recently, the above problem has been solved by the use of cavity preservatives in which solid so-called drop-stop additives are dispersed in the cavity preservative. These dropstop additives are particles of solid polymers or waxes with a low softening point. Such cavity preservatives with drop-stop additives can be easily sprayed into the desired motor vehicle components. After dripping the cavity sealant in a further treatment step, the vehicle components are heated to a temperature of at least 55 ⁰ C for shipping. This heating causes the dropstop additive dispersed in the void preservative to soften and disperse in the void preservative. This results in a gelation of the cavity preservative, which solidifies to a gel-like consistency. As a result of this solidification, it is no longer possible during the further processing steps to cause unwanted dripping off of the cavity preservative. The use of such a cavity preservative with heat-activated drop-stop additives, however, has the disadvantage that for heating the motor vehicle components ovens or IR emitters must be provided, which are large enough to heat even large motor vehicle components to 55 ° C and more. This significantly increases the space and energy requirements of this method of cavity sealing. Further, such heating makes use of these cavity preservatives in smaller units, such as body builders, impractical and uneconomical.

It is therefore an object of the invention to describe a method for cavity sealing of a motor vehicle component, with which a cavity seal can be achieved, which shows no unwanted dripping after a short time and thereby without expensive devices, e.g. to get out of the heating of motor vehicle components.

It is another object of the invention to describe a composition for producing a cavity seal for use in this method, and a motor vehicle part having such a cavity seal.

According to the invention, the object is achieved by a method for cavity sealing of a motor vehicle component in which the cavity preserving agent has a crosslinkable component and in which step a.) Precedes the step of admixing a crosslinking component, wherein the amount and type of crosslinkable component and the crosslinking component are chosen so that the cavity preservative between step c.) And d.) Solidifies to a gel-like consistency.

Further, the object is achieved by a composition for producing a cavity seal having a cavity preserving agent and a solidifying agent, wherein the cavity preserving agent comprises a crosslinkable component, wherein the solidifying agent is a crosslinking component and wherein the amount and type of crosslinkable component and crosslinking component are selected such that the cavity preservative solidifies to a gelatinous consistency within a predetermined time period.

Furthermore, the object is achieved by a motor vehicle component having a cavity seal, which can be produced by the method according to the invention.

It has been found that a crosslinkable component can be admixed with a cavity preservative and this can then be crosslinked by adding a suitable amount of a crosslinking component, so that a gel-like consistency of the cavity preservative is achieved, which reliably prevents unwanted dripping. The time required for this system to gel is set so that the cavity preservative is sprayed as a liquid and penetrate into the cracks and niches to be sealed and so long desired to drip from the automotive components. After this time, solidification takes place, which reliably prevents further dripping. Furthermore, the fact that there is a period between spraying and gelation in which the cavity preserving agent remains liquid, also clogging of the spray nozzles by solidified cavity preservative can be avoided.

The addition of the crosslinking component to the cavity preservative may in this case take place directly before the injection of the cavity preservative or already during the preparation of the cavity preservative.

In the first case, the corresponding composition for producing the cavity seal is generally in the form of a 2-component system. However, it is also conceivable that the cross-linking component, eg in the form of atmospheric moisture, is present in the ambient air, so that the mixing and introduction of spraying takes place in one step and the composition is present as a one-component system.

In the second case, the composition for forming a cavity seal is in the form of a one-component system and further comprises means for suppressing the reaction between the crosslinkable component and the crosslinking component. These reaction suppression agents are selected to be eliminated from the composition shortly before or during spraying (e.g., by evaporation or reactive degradation) and thus the desired reaction occurs between the crosslinkable component and the crosslinking component.

Since the crosslinking reaction leading to the formation of the gel-like structure proceeds at about room temperature, heating of the automotive component to solidify the cavity preservative and thus to achieve the drop-stop effect is no longer necessary. Thus, no large heaters are needed for the method of the invention, and such a method can be used in any device designed to apply a cavity seal. Furthermore, the method according to the invention also works without great expenditure of energy, e.g. for heating the motor vehicle component.

According to the invention, the cavity preservative may be any commercially available cavity preservative which either contains a crosslinkable component from the beginning or to which a crosslinkable component is admixed.

Typically, such cavity preservatives include ingredients such as anti-corrosion additives such as calcium sulfonate, oxidatively crosslinking binders such as alkyd resins, flexibilizers such as mineral oils or esters, fillers such as talc, rheological additives such as inorganic thickeners such as bentonites, organic or inorganic Bases that also contribute to corrosion protection, such as triethylenediamine, catalysts for oxidativc curing of the binder, such as manganese salts and other additives, for example, to prevent the formation of a skin during standing, such as 2-butanone oxime on.

As the crosslinkable component, any compound or mixture of compounds crosslinkable by reaction with another compound is suitable insofar as they are compatible with the cavity preservative, do not hinder its anticorrosive effect, and do not interfere with the flexibility and plasticity of the final cavity seal.

The crosslinking component may comprise any compound or mixture of compounds which can undergo crosslinking reaction with the crosslinkable component and which does not interfere with the anticorrosive effect, as well as the flexibility and plasticity of the cavity seal.

The exact combination of crosslinkable component and crosslinking component and their used amounts can be determined by those skilled in the art with regard to the desired gelation time and the degree of solidification and the nature of the cavity preservative used by known methods.

In one embodiment, the crosslinkable component is selected from the group consisting of the compounds having active hydrogen atoms, the unsaturated polyesters, the epoxy resins, the moisture-curing prepolymers, and mixtures thereof.

Preferably, the crosslinkable component comprises at least one medium to long-chain organic compound which has at least one functional group selected from the group consisting of the amino groups, the carboxy groups and the hydroxy groups. Preferred examples of such compounds are alkyd resins, acrylic resins, polyesters, native and synthetic oils having OH functionality, oxidized waxes and petrolates, and hydrocarbon resins having OH functionality.

The above compounds have the advantage that they are easily modifiable and can be optimized for use in cavity preservation. They are already widely used today. They give the formed film a resistance to heat and mechanical stress. Furthermore, they hold the film together and prevent cracking in case of contamination etc.

In one embodiment of the abovementioned measure, the crosslinkable component comprises castor oil.

Castor oil is a plant-based oil containing hydroxy groups which is biodegradable and thus advantageous in terms of environmental protection. Furthermore, castor oil is also available in large quantities at reasonable prices, so that its use is also advantageous from an economic point of view.

In a further embodiment, the crosslinking component is selected from the group consisting of the amines, the peroxides, the diisocyanates and mixtures thereof and is preferably selected from the group consisting of diphenylmethane diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, their tri- or polymers and biuret.

It has been found that these crosslinking components in combination with the above-mentioned crosslinkable components lead to a safe and easily controllable gelation of the cavity preservative.

In a further embodiment, a catalyst is further added, which is preferably selected from the group consisting of the amines, the acids Tin compounds, the bismuth compounds, the mercury compounds and mixtures thereof.

By adding a catalyst, the period of time during which the cavity preservative solidifies to a gel-like consistency can be set particularly precisely.

The catalyst may be present in a composition in the form of a 2-component system either in the void preservative or the solidifying agent or in both components. But it is also possible to mix the catalyst as a separate component.

In one embodiment of the invention, the crosslinkable component is present in an amount of 5 to 15 parts by weight.

In the present invention, amounts in parts by weight each refer to 100 parts by weight of the ready-to-use cavity preservative, i. the cavity preservative, to which the crosslinking component has already been added.

It has been found that through the use of the above amounts, secure gelation can be achieved without over curing the cavity preservative which would adversely affect the physical properties of the cavity seal, such as its elasticity and plasticity.

In a further embodiment of the invention, the crosslinking component is present in an amount of 0.1 to 10 parts by weight.

It has been shown that when using these amounts of the crosslinking component, a secure gelation can be achieved without the later physical properties of the cavity seal, such as their flexibility and plasticity would be adversely affected. Furthermore, it has been found that the use of these amounts of crosslinking component lead to a period of time until the formation of the gelatinous consistency, which is long enough to achieve a trouble-free spraying and a safe penetration of the cavity preservative, but at the same time a rapid further processing of the motor vehicle component allows.

In a further embodiment of the invention, the mixture from the cavity preservatives and the crosslinking component before being sprayed has a viscosity of less than 500 mPa-s and especially of less than 200 mPa-s in each case at a shear rate of 760 s ¹ and 23 ° C ,

The above-mentioned viscosities are measured according to DIN 53018. It has been found that mixtures with the stated viscosities can be sprayed well in motor vehicle components and have sufficient flowability to penetrate small cracks and niches in a short time.

In another embodiment, the composition is such that the period of time within which the void preservative solidifies to a gel-like consistency is from 15 to 45 minutes.

By choosing such a period, on the one hand, there is sufficient time available for the cavity preservative to be easily sprayed into a motor vehicle component and to penetrate into the desired cavities and, secondly, for a quick subsequent further processing of the motor vehicle component.

It is understood that the features mentioned above and those yet to be explained not only in the combination specified, but can also be used in other combinations or in isolation, without departing from the scope of the present invention.

The invention will now be explained in more detail by means of examples and the accompanying drawings. It shows:

Fig. 1 is a graph showing the evolution of the viscosity of a composition according to Example 1 over time, and

Fig. 2 shows a motor vehicle component which is provided with a cavity seal, at three different times of the cavity seal, namely ti = 0, t ₂ = 5 and t3 = 20 minutes.

example 1

A first composition for producing a cavity seal has, as a first component, a cavity preservative according to the formulation shown in Table 1. The constituent referred to as base mixture is a cavity preservative which is commercially available from Art. No. 0090 0500 from Pfinder Chemie, Boeblingen, Germany.

In this first component, the castor oil forms the crosslinkable component. The triethylenediamine acts as a catalyst for the reaction of the crosslinkable component with the crosslinking component.

The quantities are in parts by weight based on 100 parts of the finished cavity preservative, ie including the crosslinking component. Table 1

The second component comprising the crosslinking component, that is to say the solidifying agent of the composition, has diphenylmethane diisocyanate or its polymer in an amount which, after mixing with the cavity preservative, corresponds to five parts by weight.

The mixture of the first component and the second component has a viscosity of 150 + 20 mPa-s at a shear rate of 760 S ¹ and 23 ° C measured according to DIN 53018 directly after mixing. 30 minutes after mixing, the composition is a Pa-s at a shear stress of 1 Pa and 23 ° C measured according to DIN 53018 frozen gel with a viscosity of approximately 35 x 10. ³

Thus, from the first and second components of Example 1, a void sealant can be prepared which is initially easy to spray and can also penetrate into small scratches and niches and which, after a defined period of time, solidifies into a gel which no longer shows leakage.

Example 2

A second composition for producing a cavity seal has, as a first component, a cavity preservative according to the formulation shown in Table 2. The constituent referred to as the base mixture is a cavity preservative which is commercially available under the item number 0090 0600 from the company Pfinder Chemie, Böblingen, Germany. In this first component, the castor oil in turn forms the crosslinkable component. The triethyldiamine acts as a catalyst for the reaction of the crosslinkable component of the crosslinked component.

The quantities are again in parts by weight based on 100 parts of the finished cavity preservative, ie including the crosslinking component.

Table 2

The second component comprising the crosslinking component, that is to say the solidifying agent of the composition, has the composition shown in Table 3.

Table 3

In this second component, the diphenylmethane diisocyanate polymer forms the crosslinking component. The paraffinic mineral oil is a commercially available paraffinic mineral oil having a viscosity at 40 ⁰ C 12.5 to 15.5 mm ² per second (measured according to DIN 51562-1), which acts as a diluent for the crosslinking component , The pentaerythritol tetrastearate serves as Stabilizer to stabilize the suspension of the diphenylmethane diisocyanate polymer in the mineral oil.

The mixture of the first component and the second component has a viscosity of 150 ± 30 mPa-s at a shear rate of 760 s ¹ and 23 ° C, measured according to DIN 53018 directly after mixing. 30 minutes after mixing, the composition is too a gel having a viscosity of about 35 x 10 ³ Pa-s at a shear stress of 1 Pa and 23 ° C, measured in accordance with DIN 53018 solidifies.

Thus, from the first and second components of Example 2, a void sealant can be prepared that is initially easy to spray and can also penetrate small crevices and niches, and which, after a defined period of time, solidifies into a gel that no longer shows leakage.

In the method for producing a cavity seal, as shown in Fig. 2, in a first step, a cavity preserving agent is mixed with the composition shown in Table 1 in a suitable mixing chamber with the solidifying agent of Example 1. The resulting mixture is applied by means of a spray gun 22 known to those skilled in the art for applying cavity preservatives, e.g. sprayed by hand or using robots or a nozzle frame in a vehicle component 10, the sprayed mixture is used to some extent in slight excess. The illustrated vehicle component 10 is a door spar consisting of two molded components 12 and 14, e.g. is composed by spot welding.

In the next step, the sprayed mixture is now allowed to penetrate into cracks and niches of the motor vehicle component, wherein, if appropriate, the motor vehicle component is moved in order to ensure complete penetration of the cavity preserving agent. Such a crack exists between the two connecting parts 18 and 20. In this case, wax 24 drops out of the motor vehicle component 10 in the form of drops 26. From the time the two components are mixed, a crosslinking reaction between the diphenylmethane diisocyanate of the solidifying agent and the castor oil present in the cavity preservative commences in the composition according to Reaction Scheme 1 below. This process results in gelation of the cavity preservative which causes subsequent unwanted dripping of the cavity Cavity sealing wax prevented. In the interior 16, a layer 25 of cavity-preserving agent 24 forms.

Reaction Scheme 1

+

+ Catalyst

Next networking

The development of the viscosity of a composition according to Example 1 is shown in FIG. 1 here. The reaction profile between the crosslinkable component (castor oil) and the crosslinking component (diphenylmethane diisocyanate) is such that for the first 15 minutes, the formulation has a flowability that is only slightly different from that of known cavity preservative formulations. Thereafter, a rapidly developing gelation of the cavity preservative begins, so that after about 30 minutes, a consistency is achieved in which no more dripping can occur. The complete curing the cavity seal 28 is then carried out by an oxidative curing during the further processing of the motor vehicle component 10 over the next few hours,

Claims

claims

A method of cavity sealing a motor vehicle component, comprising the steps of: a.) Spraying a cavity preservative into the motor vehicle component; b.) allowing the cavity preservative to penetrate; c.) draining excess cavity preservative from the automotive component; and d.) curing the cavity preservative; characterized in that the void preserving agent comprises a crosslinkable component and in that step a.) precedes the step of admixing a crosslinking component, wherein the amount and type of crosslinkable component and crosslinking component are chosen such that the void preserving agent between step c. ) and d.) solidified to a gel-like consistency.

2. The method according to claim 1, characterized in that the crosslinkable component is selected from the group consisting of the compounds having active hydrogen atoms, the unsaturated polyesters, the epoxy resins, the moisture-curing prepolymers and mixtures thereof.

3. The method according to claim 2, characterized in that the crosslinkable component comprises at least one medium to long-chain organic compound having at least one functional group selected from the group consisting of the amino groups, the carboxy groups and the hydroxy groups.

4. The method according to claim 3, characterized in that the crosslinkable component comprises castor oil.

5. The method according to any one of claims 1 to 4, characterized in that the crosslinking component is selected from the group consisting of the amines, the peroxides, the isocyanates and mixtures thereof.

6. The method according to claim 5, characterized in that the crosslinking component is selected from the group consisting of diphenylmethane diisoeyanat, hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, their tri- or polymers and biuret.

7. The method according to any one of claims 1 to 6, characterized in that it further comprises the addition of a catalyst.

8. The method according to claim 7, characterized in that the catalyst is selected from the group consisting of the amines, the acids, the tin compounds, the bismuth compounds, the mercury compounds and mixtures thereof.

9. The method according to any one of claims 1 to 8, characterized in that the crosslinkable component is present in an amount of 5 to 15 parts by weight.

10. The method according to any one of claims 1 to 9, characterized in that the crosslinking component is present in an amount of 0.1 to 10 parts by weight.

11. The method according to any one of claims 1 to 10, characterized in that the mixture of the cavity preservative and the crosslinking component prior to spraying in step a.) Has a viscosity of less than 500 mPa-s at a shear rate of 760 s ¹ and 23 ° C.

12. The method according to claim 11, characterized in that the mixture of the cavity sealant and the crosslinking component before spraying in step a.) A viscosity of less than 200 mPa-s at a shear rate of 760 s ¹ and 23 ° C.

A composition for making a cavity seal (28) having a void preservative and a solidifying agent, said void preservative having a crosslinkable component, said solidifying agent having a crosslinking component, and wherein the amount and type of crosslinkable component and crosslinking component are as follows are chosen so that the cavity preservative solidifies to a gel-like consistency within a predetermined period of time.

14. A composition according to claim 13, characterized in that the crosslinkable component is selected from the group consisting of the compounds having active hydrogen atoms, the unsaturated polyesters, the epoxy resins, the moisture-curing prepolymers and mixtures thereof.

15. The composition according to claim 14, characterized in that the crosslinkable component comprises at least one medium to long-chain organic compound having at least one functional group selected from the group consisting of the amino groups, the Carbboxy groups and the hydroxy groups.

16. The composition according to claim 15, characterized in that the crosslinkable component comprises castor oil.

17. The composition according to any one of claims 13 to 16, characterized in that the crosslinking component is selected from the group from the amines, the peroxides, the isocyanates and mixtures thereof.

18. The composition according to claim 17, characterized in that the crosslinking component is selected from the group consisting of diphenylmethane diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanates, their tri- or polymers and biuret.

19. The composition according to any one of claims 13 to 18, characterized in that it further comprises a catalyst.

20. The composition according to claim 19, characterized in that the catalyst is selected from the group consisting of the amines, the acids, the tin compounds, the bismuth compounds, the mercury compounds and mixtures thereof.

21. The composition according to any one of claims 13 to 20, characterized in that the crosslinkable component is present in an amount of 5 to 15 parts by weight.

22. The composition according to any one of claims 13 to 21, characterized in that the crosslinking component is present in an amount of 0.1 to 10 parts by weight.

23. A composition according to any one of claims 13 to 22, characterized in that the mixture of the cavity preservative and the crosslinking component before solidification has a viscosity of less than 500 mPa · s at a shear rate of 760 s ¹ and 23 ° C.

24. The composition according to claim 23, characterized in that the mixture of the cavity preservative and the cross-linking Component before solidification has a viscosity of less than 200 mPa-s at a shear rate of 760 S ^"1 and 23 ° C.

Composition according to any one of Claims 13 to 24, characterized in that the period of time within which the cavity preservative solidifies to a gel-like consistency is between 15 and 45 minutes.

26. Motor vehicle component having a cavity seal (28) which can be produced by the method according to one of claims 1 to 12.