CS395591A3 - Silanized pigments and their use for pigmented plastic yellowinginhibition - Google Patents

Description

Silanized pigments and their use for inhibiting yellowing of pigmented plastics

TJ x:

Technical Field c. '' Xx! 5 -ii

The present invention relates to silanized pigments, methods for their production and their use for inhibiting yellowing of pigmented plastics. Further, the invention relates to plastic systems comprising silane-pigments.

Usually, industrially applicable plastics contain numerous additives, such as plasticizers, fillers, stabilizers, anti-aging agents, lubricants, mold release agents, antistatic agents, coloring agents and other additives, which is to improve their properties.

Often, there is undesirable interaction between these additives. This is particularly the case with coloring agents on the one hand and stabilizers and antioxidants on the other. This phenomenon is likely to occur because the stabilizer and / or antioxidant molecules diffuse onto the surface of the pigment particles where they cause a reaction-associated yellowing, which often occurs in the dark. This yellowing is undesirable, especially in the case of pigments of light colored shade and often exacerbates the aesthetic impression produced by the plastic system. SUMMARY OF THE INVENTION It is an object of the present invention to provide silanized pigments which, when used in plastic systems, do not cause yellowing reaction reactions, even over long periods of time. It is another object of the invention to provide stable coloring plastic systems.

SUMMARY OF THE INVENTION It has now been found in the present invention that this object can be solved by means of the pigments of the invention which are 2

of the formula I

SiRXR2R3R4 (I) 12-3 wherein at least one of R, R, R or R is halo or an alkoxy group having 1 to 20 carbon atoms, wherein one or two non-adjacent groups are optionally substituted by at least one other radical of the radicals R, R, R and R represents an alkyl group containing from 1 to 30 carbon atoms, with one or more of the radicals R, R, R and R being one or more radicals. two non-adjacent -C 1 - 4 groups are respectively. replaced by -HC = CH- and / or -O-, and the remaining two radicals independently of one another are halogen or C 1 -C 30 alkyl or C 1 -C 30 alkoxy, wherein 1 or 2 non-adjacent -CE 3 groups they are optionally replaced by groups of the formula -CH = CH-, -O-, -CO-, -COO- or -OCO-. Accordingly, the present invention provides pigments coated with a general formula (I). In addition, the present invention provides the use of those pigments for inhibiting yellowing of plastics. Finally, the invention relates to color-fastening plastic systems comprising a pigment according to the invention and a novel process for producing such pigments.

Apparently, the diffusion of the stabilizer molecules and / or the antioxidant is effectively prevented by coating the silane pigments of formula (I). Plastic systems which are color fast and yellow resistant for a long time can be obtained with the pigments of the present invention modified on the surface.

The silanes of formula (I) can be coated with both organic and organic pigments, with inorganic pigments being preferred. Various types of pigments can be used, such as white pigments, color pigments, black pigments, so-called glosses and also fluorescent pigments.

The yellowing reaction is particularly unfavorable in white pigments such as titanium dioxide, zinc oxide, zinc sulfide, lithopones, aluminum silicate, barium sulfate or calcium carbonate, and also in silver-white pearlescent pigments such as mica platelets. coated with a thin layer (40 nm or less) of titanium dioxide. A similar situation occurs with other white pearlescent pigments, as well as with white pigments of metallic type or spiral pigments. Particular preference is given to the white pigments coated with the silanes of the general formula I.

Color pigments with a light color shade, such as, for example, orange, red, pale green, pale blue or pale brown pigments are also preferably coated with the silanes of the formula I, in which yellowing also causes a substantial deterioration of color and clarity. colors.

Also in the case of non-white pearlescent pigments and metallurgical pigments, the coating with the silane of the formula I is very advantageous, since in these pigments yellowing leads to a deterioration of the coloring effect or of the auxiliary coloring effect (interference effect or non-flicker effect) and thus a substantial deterioration of the overall coloring effect. action that is required.

In many instances, stabilizer and / or antioxidant molecules have been found to bind reactively to the pigment surface, often altering their molecular structure so that they no longer satisfactorily fulfill their true function, which usually involves increasing stability to atmospheric oxygen, heat and light . In contrast, the interaction of many aantioxidant stabilizers with the silane of formula I is considerably weaker and is often only purely steric in nature, so that the stabilizer and antioxidant action is only slightly diminished or not at all. Therefore, it is preferred to coat the silanes according to the invention also with black pigments or other dark color pigments, since it is possible to improve the long-term stability of the plastic systems which are dyed with these pigments. In the silanes of the formula I, at least one of R @ 4, R @ 2, R @ 2 and R @ 4 is preferably halogen or alkoxy of from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms. replaced by groups of formula -CH = CH-, -O-, -CO-, -COO- or -OCO-. Since physical adsorption and, in particular, chemical adsorption of the pigment and silane intermediates of formula (I) usually occur through this residue, this residue is hereinafter referred to as BV residue. The BV moiety is preferably halogen or C 1 -C 10 alkoxy, preferably fluoro, chloro, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy or decoxy. 12 3 4

Furthermore, at least one of R 1, R 2, R 2 and R 2 is an alkyl group having from 1 to 30, preferably from 5 to 30, preferably from 10 to 30, carbon atoms, with one or two non-adjacent -CH 2 - groups being in this radical. optionally substituted with groups of formula -CH = CH- and / or -O-. Since, in less frequent cases, physical adsorption occurs especially between the pigment surface and the silane of the general formula I via this residue (in particular oxalkyl, alkenyl or oxaalkenylayl), the remainder is hereinafter referred to as NBV residue, as opposed to BV residue. The NBV radical is preferably an alkyl group containing more than 8 carbon atoms, in particular, for example, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosanyl, docosanyl, tricosanyl, tetracosanyl, pentaco. -sanyl, hexacosanyl, heptacosanyl, octacosanyl, nonacosanyl, triacontanyl, 12,12-trimethyltetradecyl, 12-methyl-12-ethyltetradecyl, 12,12-dipropyltetradecyl, 11-propyl-12-butylpentadecyl or 8,8-dimethyl-12- propyl-13-propylhexadecyl.

The remaining two residues may have the same meaning as those given for BV residue or NBV residue. The silane of the formula can be bonded to the pigment surface by physical adsorption or chemistry. Physical adsorption typically involves van der Waals interactions between the polar pigment surface and the polar groups BV and NBV residues, particularly BV residues. In the case of chemisorption interactions, the hydrolytic cleavage of one or more of the BV residues usually results in the formation of one or more silane-pigment surface bonds. Pigments according to the invention, in which the si-lane compounds of the general formula (I) are added by chemisorption, are usually preferred over pigment-silane complexes stabilized by physical adsorption based interaction because they have a higher stability. Since it is generally desirable to produce more chemisorption bonds than one, for example two or even three such bonds, to increase pigment-silane complex stability, the silanes of general formula I preferably contain two or preferably three BV residues. it is possible to avoid those silanes of the formula I in which two or three BV residues have a comparable chain length. It is preferred that the length of these chains does not differ by more than 2 methylene groups. Particular preference is given to silanes containing 2 or 3 BV residues, at least two of which are identical. Further preferred is also the silanes of formula I which contain 3 BV residues with shorter chains than six carbon atoms. Particular preference is given to the silanes of the formula I which contain 3 BV residues selected from the group consisting of methoxy or ethoxy groups.

The silanes of formula (I) may contain 1 to 3 NBV residues. However, they are usually not more than 2, preferably less than 1. At least one of the NBV radicals is preferably a relatively long chain alkyl group containing more than 5 carbon atoms, more preferably less than 10 carbon atoms. carbon atoms. This NBV residue serves, on the one hand, to anchor the pigment-silane complex in the plastic system and, on the other hand, serves as a first barrier against diffusion of the stabilizer molecule or anti-aging agent to the surface since it extends to a relatively large distance from the pigment-silane complex. In order to increase the steric hindrance, the NBV may also be branched, especially the outward end of the chain. Silanes of general formula (I) containing such branched NBV radicals are preferred. Particular preference is given to silanes which, as NBV radical, contain the remainder of the general formula CH gH vzorce vzorce or when the silane contains more than 1 NBV radical, have additional NBV preferably the residues are shorter chains, i.e. chains of from 1 to 15 carbon atoms, which may be branched or unbranched. The silanes of formula (I) are either known or can be prepared by methods known per se, such as those described in standard inorganic chemistry textbooks (see, for example, Holleman-Wiberg, Lehrbuch der anorganischen Chemie, Berlin 1976, p. 555 or R. Steudel, Chemistry der Nichtmetalle (Chemie nekovů) Berlin 1974, p. 426). Other procedures not explicitly mentioned herein may also be used.

The pigments are preferably coated with the silanes of the general formula in a very simple manner, which is also the subject of the present invention. In this process, the pigments and silane are mixed in an dry state, i.e. without addition of solvent and other substances, such as coupling agents, carrier liquids, and the like. Mixing is carried out intensively in a mixer at a temperature of from 50 to 100 ° C, typically up to 10 to 10,000 minIn rare cases, longer mixing times than one hour must be used. Usually, further processing of the resulting mixture is not necessary, although it may be performed if desired.

The pigments can also be reacted with silanes in a suspension of organic solvents, as described, for example, in DE 2 543 962 or JP 49-099,328. In this case, after removal of the solvent, the coated pigment has to be heat treated, for example at a temperature of 50 to 200 ° C.

The silane content by weight relative to the non-specific surface of the pigmented pigment is usually in the range of 0.0001 to 0.1 and in particular of 0.001 to 0.07 g.m. Particularly good results are obtained with a silane concentration of up to 0.002 to 0.004 g.m

The pigments reactively coated with the silanes of the formula I have good mechanical properties (for example agglomerate tendency and dispersion properties), so that their incorporation into most different plastic systems is not associated with any difficulty and can be carried out by conventional methods. The systems of the invention based on thermoplastic polymers or elastomers are preferred. Especially preferred are plastic systems for baseipolyethylene, polypropylene, polyvinyl chloride, polyamides, polycarbonates and polyacrylates. However, a substantial increase in long-term color stability can also be achieved in thermosetting systems such as epoxy resins, and in particular phenolic resins, so that pigments which are reactively coated with silanes of the general formula I can also be used successfully.

Using the pigments coated with the silanes of the present invention, effective suppression of yellowing-related reactions in plastic systems can be achieved. This yellowing inhibition has been observed in the presence of all conventional anti-aging stabilizers and agents, but particularly good results can be obtained with systems containing phenolic antioxidants and anti-aging agents.

The invention is further illustrated by the following example. This example is purely illustrative and is not intended to limit the scope of the invention in any way. EXAMPLE 8 kg of titanium dioxide (TiCl4) was vigorously mixed with 160 gsilane of formula C11H14Si at 80 DEG C. for 10 minutes using a Lodige mixer, 270 rpm.

To demonstrate the resistance of the coated pigment to yellowing in the dark, a model experiment is performed by adding 1 g of the coated pigment to 5 ml of a 1% solution of propyl gallate kept in the dark. There will be no yellowing in the dark.

The coated pigment and uncoated pigment (in both cases titanium white) is incorporated into the polyethylene plastic system. The system to which the pigment of the invention has been added exhibits significantly lower yellowing in the dark compared to the system to which conventional uncoated titanium white has been added. For both systems, the following CIE color parameters are measured.

Conventional System The System of the Invention L * 69.2 76.1 Me and 2.3 1.4 b * 10.8 6.9

Claims (4)

PATENT CLAIMS 1. Pigments coated with a general formula (I) wherein R @ 1, R, R @ 1 or R @ 4 are at least one carbon atom or an alkoxy group having from 1 to 20 carbon atoms, wherein one or two non-adjacent carbon atoms are present. optionally, -CH = CH-, -O-, -CO-, -COO- or -OCO-, at least one other radical of the radical R 1, R 2, R 2 and R 6 before is an alkyl group containing from 1 to 30 carbon atoms, wherein one or two non-adjacent -C (2) groups are respectively an alkyl group; replaced by -HC = CH- and / or -O-, and the remaining two radicals independently of one another are halogen or C 1 -C 30 alkyl or C 1 -C 30 alkoxy, wherein 1 or 2 non-adjacent C 1 -C 4 groups they are optionally replaced by groups of the formula -CH = CH-, -O-, -CO-, -COO- or -OCO-. 2. A plastic system comprising pigments coated with a silane of the formula (I) for yellowing purposes. 3. A process for the production of pigments coated with a silane of the general formula (I), characterized in that the inorganic pigment is mixed with one or more silanes of the general formula (I) without the addition of a solvent or other additives. 4. Use of pigments coated with silanes of the general formula I for the purpose of inhibiting yellowing in plastics. MP-1185-91-HO