DE4004468C1 - - Google Patents

Description

The invention relates to SiO₂ matting agent, a method its manufacture and its use for the manufacture of thixotropic, based on polyamide-modified alkyd resins Paints and varnishes.

Thixotropic, polyamide-modified alkyd resins are described in US Pat 26 63 649. A polyalkyd molecule is combined with a Polyamine (up to 10%) reacted. The emerging Molecule is particularly suitable via hydrogen bonds to build a three-dimensional networked structure. By These bonds are easily sheared, so that the Lacquer becomes low viscosity and the right one for processing Has consistency. As soon as the mechanical stress ends, the viscosity builds up again within minutes. This z. B. a run-off of the color of vertical surfaces prevented.

A disadvantage of such coating systems is that the thixotropy of the additional components present in the paint are negative can be influenced. Hydroxyl groups have a particularly drastic effect  containing solvents such as. B. alcohols, glycols and some organic color pigments such as phthalocyanine blue, Hansa yellow and Bordeaux red. SiO₂ matting agents also have a similar influence.

In addition to the thixotropic polyamide-modified alkyd resins, there are also thixotropic polyurethane-modified alkyd resins. At in contrast to the former, the latter is the viscosity build-up through from solvents, pigments or matting agents originating hydroxyl groups are not disturbed.

In view of the difficulties outlined above, the invention was accomplished based on the task of a matting agent based on SiO₂ create the least possible negative or no negative Influence on the thixotropic behavior of unmatted, thixotropic, colors based on polyamide modified alkyd resins and Has paint.

To solve this problem, an SiO₂ matting agent is proposed which is characterized in that it consists of SiO₂ and 1 up to 25 wt .-% polyol.

The invention further relates to a method for the production an SiO₂ matting agent, which is characterized in that that you bring SiO₂ together with such an amount of polyol that the polyol content of the finished matting agent is 1 to 25% by weight is.

The invention also relates to the use of the invention SiO₂ matting agent for the production of thixotropic, based on polyamide-modified alkyd resins Paints and varnishes.

Preferred embodiments and advantages of the invention are Subclaims and the following description can be found.

It was surprisingly found that the negative effects of Matting agents based on SiO₂ on the thixotropy of paints based on thixotropic polyamide-modified alkyd resins  and varnishes through the use of polyhydric alcohols can be reduced or canceled. The affinity between the SiO₂ surface and the polyol is so large that even separate addition of the SiO₂ and the polyol to thixotropic colors and paints based on alkyd resin the polyol molecules from the SiO₂- Surface are adsorbed. In other words, it is in the inventive modification of SiO₂ matting agents an impregnation or coating of the SiO₂ surface with polyols. The realization is that polyols are the negative Cancel the effect of the hydroxyl groups on the SiO₂ surface, Particularly surprising since alcohols and glycols in particular Substances are known that severely impair thixotropy. For example, a manufacturer of thixotropic polyamide-modified alkyd resins expressly suggest that Hydroxyl groups, such as those found in alcohols and glycols are completely destroy the thixotropic structure.

For the treatment of the SiO₂ surface are suitable according to the invention higher alcohols, especially two to hexavalent alcohols with e.g. B. 2 to 100 carbon atoms, wherein the carbon chains are linear or branched and by any many oxygen atoms can be interrupted (C-O-C groups = Ether). The OH groups can be in any position are located. Mixtures of the above can of course also be used Polyols are used.

Examples of polyols suitable according to the invention are given in other glycerin, ethylene glycol, diethylene glycol, polyethylene glycols, Sorbitol, trimethylolpropane, di-trimethylolpropane, ethoxylated trimethylolpropanes, pentaerythritol and ethoxylated  Pentaerythrite.

SiO₂ matting agents are mostly silica gels or precipitated silicas. Pyrogenic silicas in the usual form are not used as matting agents; however, there is one made by post-agglomeration Form that is also used as a matting agent. Particle size and particle size distribution of the SiO₂ matting agent lie in the usual, familiar to the expert Areas.

The matting agent according to the invention can be prepared in done situ by SiO₂ and polyol in the paint or varnish be introduced. Alternatively, SiO₂ and polyol can be used Incorporation into the paint or varnish can be brought together. This can be done by using the SiO₂ in a jet mill micronized and simultaneously with the SiO₂ the polyol added. Another option is to have a Spray dried suspension of SiO₂ in an aqueous polyol solution and the obtained polyol impregnated SiO₂ by sighting or jet grinding to the appropriate grain size distribution sets. You can even the SiO₂ before drying impregnate by washing (e.g. the hydrogel in the In the case of silica gel), add polyol to the wash water or to one even earlier point in time polyol into the one surrounding the hydrogel introduces liquid phase. According to one of these procedures obtained with polyol treated SiO₂ is then in the paint or the color incorporated.

The advantageous effect of the modification of the invention SiO₂ matting agents with polyols are probably based insist that a masking of the OH groups of the SiO₂ surface through attachment and bonding via hydrogen bonds he follows. It is crucial that several OH groups per Molecule are present to meet the required liability other polar molecules, e.g. B. water. Across from  the known esterification of OH groups on SiO₂ surfaces with According to the invention there is the difference that alcohols Modifying SiO₂ matting agents with polyols none Energy must be supplied. Accordingly, the Production of the SiO₂ matting agent according to the invention or the modification with polyol basically below the Temperature at which esterification would occur, i.e. H. in the generally below 150 ° C, preferably below 100 ° C and especially at room temperature or only slightly higher Temperature.

In general, for the modification of SiO₂ matting agents 1 to 25 wt .-% polyol, based on that Weight of the SiO₂ matting agent, required. Are preferred Amounts from 3 to 15% by weight.

example 1

An SiO₂ matting agent with a particle size of 5 µm (measured with the Coulter Counter), a BET surface area of 400 m² / g and a pore volume (both by nitrogen adsorption of 1.75 ml / g was determined using a so-called dissolver (in high-speed used in the paint and coatings industry High shear mixer for dispersing Pigments and fillers) dispersed in a thixotropic lacquer, the main component is a polyamide modified contained thixotropic alkyd resin. The paint composition is in reproduced in the following table. The concentration of the Matting agent, based on the solids content of the paint, was 9% by weight. The matt paint was at 24 ° C for 24 hours stored and then the viscosity was measured with the Haake viscometer (Haake RV3 Rotovisko, measuring head 500, spindle MV1). The Measurement took place at 20 ° C. A flow curve was determined by 0 to 32 rpm with a change in rotational frequency of 25 rpm. The viscosity was read from the curve at 8 rpm with increasing rotational frequency. The results obtained are in  Table 1 reproduced.

Example 2

The paint used in Example 1 was the same as in Example 1 treated without adding a matting agent. It the corresponding tests were carried out with this paint and the results are also shown in Table 1 reproduced.

Example 3

The SiO₂ matting agent used in Example 1 was already impregnated with glycerine during micronization in the jet mill, by glycerin simultaneously with the SiO₂ in the Jet mill was dosed. The glycerol concentration in the Matting agent was 11% by weight. The matting agent impregnated in this way  was in the same paint as in Example 1 incorporated and checked as described there. The results are again shown in Table 1.

Example 4

The procedure was as in Example 3, with the difference that a Polyol with 4 OH groups and a molecular weight of 270 the micronization was metered in the jet mill. The Polyol concentration in the matting agent was 12.5% by weight. Training in the paint and testing then took place as in Example 1. The results are shown in Table 1.

Example 5

The procedure was as in Example 1, with the difference that simultaneously with 7.9 wt .-% SiO₂ a polyol with 4 OH groups and a molecular weight of 270 in a concentration of 1.1 % By weight was dispersed. The test results are again reproduced in Table 1.

Example 6

The procedure was as in Example 5, with the difference that instead of the polyol with 4 OH groups, a polyethylene glycol (Molecular weight 400) was used. The concentration of the Matting agent, based on the solids content of the paint, was 9 wt .-% (8.3 wt .-% SiO₂ + 0.7 wt .-% polyethylene glycol). The test results are also shown in Table 1.  

Table 1

The thorough testing of the paints according to Examples 1 to 6 gave no adverse results in terms of drying delay, State of dispersion of the matting agent and Transparency.

Claims (12)

1. SiO₂ matting agent, characterized in that it consists of SiO₂ and 1 to 25 wt .-% polyol. 2. matting agent according to claim 1, characterized in that the polyol content is 3 to 15 wt .-%. 3. matting agent according to claim 1 or 2, characterized in that that the SiO₂ silica gel or precipitated silica is. 4. Process for the preparation of an SiO₂ matting agent, characterized in that SiO₂ with such an amount Polyol matches that of the finished polyol Matting agent is 1 to 25 wt .-%. 5. The method according to claim 3, characterized in that one SiO₂ brings together with such an amount of polyol that the Polyol content of the finished matting agent 3 to 15% by weight is. 6. The method according to claim 4 or 5, characterized in that used as SiO₂ silica gel or precipitated silica. 7. The method according to any one of claims 4 to 6, characterized in that that the micronized SiO₂ in a jet mill and metered in simultaneously with the SiO₂ polyol. 8. The method according to any one of claims 4 to 6, characterized in that a suspension of SiO₂ in an aqueous Sprayed polyol solution and the obtained, with polyol  impregnated SiO₂ by sighting or jet grinding on the sets a suitable grain size distribution. 9. The method according to any one of claims 4 to 6, characterized in that the SiO₂ already with the wash Polyol impregnated by adding the polyol to the wash water adds. 10. The method according to any one of claims 4 to 6, characterized in that that one with the SiO₂ in the hydrogel state Polyol impregnated by removing the polyol from the hydrogel surrounding liquid phase is added. 11. Use of the SiO₂ matting agent according to one of the Claims 1 to 3 or produced by the method according to one of claims 4 to 10 for the production of thixotropic, colors based on polyamide-modified alkyd resins and Paints. 12. Use according to claim 11, characterized in that one SiO₂ and polyol as separate components in the color or introduces the paint or first brings SiO₂ and polyol together and then color the resulting product or incorporated the paint.