DE1496646A1 - Pigment frit for varnishes, paints, plastics, paper and the like. - Google Patents

Description

E> I. DU PONT DE NEMOURS ά COMPANY Wilmington, Delaware 19 S98 / USA

applicable:
^ Pigment frit for varnishes, paints, plastics, paper and the like. '

The invention relates to the use of glass frits as Pigments in lacquers and paints and as fillers in Papers, plastics, man-made fibers and the like. The pigment frit is a glass mass of a certain grain size with embedded fine crystals of titanium dioxide and zirconium dioxide is.

In the production of enamels that are resistant to corrosive substances and high temperature loads, a mixture of inorganic oxides - including TiO ₂ and ZrO /, - * together with minerals, fluorides or salts is placed in a melting vessel until it melts and the starting products are converted into a homogeneous one heated glassy mass. the

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The temperatures used here depend on the particular composition of the desired glasses. In general, the temperatures are between 1100 ° and 1400 ° C. After melting, the glass melt is quenched by pouring it into cold water. It disintegrates into an easily friable mass, which can then be ground to the desired grain size in a ball mill with water, clay and an electrolyte. The aqueous slurry or the slurry is then applied as a coating on a metal object or another substrate and fired "at relatively low temperatures (about 100 to 15O ⁰ C) dried and then for the glazing. During firing, the glass particles melt together and form a uninterrupted glass coating, in this crystallized TiO ₂ as a separate phase, which clouds the enamel.

Commercially available powder enamel made from Britten containing titanium oxide are manufactured according to a process of the glass industry, are set aside for special applications and as pigments unsuitable because they have a low durability and a show undesirably high oil absorption.

In the production of such low-melting glasses, large amounts of fluxes, such as Na _£ Q, K ₂ O, Li ₂ O, fluorides, etc., are used, which are leached out during the wet grinding. If such powder enamel or glass frits are used for enamelling, TiO ₂ crystallizes out in a not entirely clear manner and leads to gray-colored products.

There are enamel powder (British patent specification 966 451) known, which are used for the production of cover enamels on various objects by means of an enamel firing. at These enamels are glass frits, with the glass

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is devitrified to some extent, i.e. an excretion of e.g. titanium dioxide in the glass particles. Will now such an enamel powder as a powder enamel or as a slip applied and enameled in the context of the Eraall firing a complete melting takes place and flowing of the glass components to form a glassy, dense one Coating. The firing temperature for this enamelling is sufficiently high and the time during which the Glass components are at the same temperature, sufficient long that the already opacifying or undissolved substances from the enamel raw materials have sufficient time to recrystallize «These cover materials are characterized by good quality Whiteness and opacity.

It should be noted that the frits according to the above British patent specification were used solely for the purpose of producing enamel.

The invention now relates to the use of grass frits as pigments in lacquers and paints and as pigment filler in plastic and rubber objects and as filler and glue for paper. The glass frit used according to the invention has a grain size between 1 and 60 ax and contains crystallites of titanium dioxide or zirconium dioxide embedded in the glass mass with a crystallite size between 0.01 and lyU.

The pigments used according to the invention are are therefore substances in which the actual pigments, i.e. the crystals of titanium dioxide or zirconium dioxide, are completely encased and thus stabilized by a glass mass. This has significant advantages on "the areas of application with themselves, they would, however, when applying "

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in the enamelling technique to no particular effect to lead.

For the use according to the invention, for example, fries are suitable the following glass additive (in wt .- ^):

SiO ₂ ZrC ₂ , Li ₂ C) 30 - 60 B ₂ O ₃ - BaO, ZnO) 0 - 15th * 2 , K ₂ O 0 - Y TiO ₂ or 4gO, 5 - 40, preferably 20-30 Ai ₂ C ₃ O - 15th H ₂ O (Ka ₂ O. b - 15 - RO (CaO, ί 0 - 15th P 0 0 - 10

Preferred frits contain 44 % SiO ₂ , 11-25 % _{TiO 2} , 4 £ K ₂ O, 3 / S ZnO, 9 % Na ₂ O and 4

The pigments used according to the invention have excellent properties Opacity, very good resistance, favorable oil absorption values and other important pigment properties. They are best used as a dispersion and, if necessary, mixed with other pigments or extenders in paints and varnishes, the carrier of which is e.g. linseed oil - ^^ varnish, turpentine and plastic. or in plastic or rubber compounds as fillers and in papermaking as a filler or for gluing.

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The opacity and thus the opacity of white pigments - like TiOp - is known to be based on diffuse reflection, • Diffraction and scattering of most of the incident visible light. The coloring and covering power of a pigment Is a function of the pigment concentration and the quality of the dispersion or distribution of the pigment particles in the Carrier. In the context of many applications, flocculation or agglomeration or assembly of the pigment particles occurs on, which leads to an undesirable reduction in hiding power.

The refractive indices of pigment and carrier as well as the pigment fineness have a great influence on the light scattering, as is well known. In the case of titanium oxide, the particle diameter must be somewhat smaller than half the wavelength of the light K /% . Since the pigments should be effective over a wide spectral range, a certain particle size distribution is necessary. Average particle sizes of the T10g of 0.2 to 0.35 M are generally effective in visible light and from 0.01 to 0.1 λΐ in UV light.

Another important factor in titanium dioxide pigments is the pigment concentration in paint, plastic, paper or the like. At relatively high volume concentrations, the effectiveness and hiding power of the pigment decrease. For this reason, pigment concentrations above 25 #, that is 40% by weight, are rare _{in TiO 2 pigments.} A higher effectiveness is in the range of 10 to 15 vol.-Ji, that is 16 to 24 wt. With increasing volume concentration, the pigment particles agglomerate so strongly that air-pigment interfaces develop on the surface of the carrier material. Since air has a very low refractive index, • it "improves the opacity, but the appearance

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of the product unsightly, which can also be achieved with cheaper streak agents and does not have to use expensive TiO ₂ pigment. At a pigment concentration of 10% by volume, a distance between the pigment particles of, for example, 0.25 yU grain size, corresponding to their grain size, is obtained. This is the optimal distance, as the effective scattering diameter is slightly more than twice the physical diameter. Agglomeration of the pigment therefore regularly leads to a deterioration in quality.

The pigment used according to the invention is produced by forming crystal nuclei in a first heat treatment of titanium dioxide from a metastable solution in the quenched glass mass, i.e. the frit, and TiO _{2 is} precipitated * whereupon the product for further crystal growth is a heat treatment with a precisely calculated and adhered to Temperature is subjected. The cloudy mass is then ground to a small grain size, essentially as fine as a pigment.

In order to develop the required TiO ₂ particles of precisely adjusted size in the glass mass, the glass frit is fired at temperatures between 600 and 1000 ° C., preferably 700 and 800 ° C., depending on the melting point of the glass. A temperature of 400 to 700 ^° C. below the melting temperature of the glass is preferred. Depending on the type of glass and the temperature, TiO ₂ precipitates as anatase, rutile or phase mixture.

In order to ensure the preferred rutile modification, the. Temperature above the transition point from anatase to rutile. The burning time can vary and is generally between a few minutes and a few hours, approx. 30 minutes

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a firing temperature of 800 ° C. is generally _{sufficient for the formation of TiO 2} particles with length and width dimensions between 0.1 and lyu in the glass mass. If the same glass mass is fired at lower temperatures, for example 700 ^° C., but for a longer time, titanium dioxide particles embedded in a similarly pigment-fine manner are obtained. You can also use higher temperatures for shorter times.

Once the desired crystallite size has been reached in the glass, the frit in the usual mills, e.g. ball mills, pin mills, Roller mills, pan mills, shaking or vibration

suf
Mill to ground, namely / an average particle size of the pigment of 1 to 60 ai, preferably 2 to 15yU. The pigment is therefore a glass frit with finely dispersed embedded TiO ₂ or ZrO ₂ crystal "

It is known that a mixture of rutile and anatase modification is present in the glass mass which was fired at relatively low temperatures (ea, 750 ° ^C. ), that is to say below the transition point. Anatase crystals do not grow to a particle size of about 0.25 to 0.35 M * Rutikristalle can at higher firing temperatures, for example about 85O ⁰ C, relatively large dimensions and reach lyu to approx in length.

The pigment frits are preferably transparent systems with a particle size of about 1 to 15 yu and a titanium dioxide crystal size of 0.01 to 1 ax, preferably 0.1 to 0.3 / U.

The TiO ₂ crystallites are advantageously dispersed in a glass mass with a refractive index between 1.46 and 1.96.

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The pigment frits used according to the invention have special advantages in the Aristrichtechnlk and paper industry. A first class white pigment for paints and papers must have good covering power, high opacity and high coloring power. In addition, it should very fine, chemically inert, free of soluble salts, it should be insoluble in all media used in the relevant technology and should ultimately be under normal temperature conditions are not attacked. In addition, it should be easy to disperse not be toxic and must show a low oil absorption. Due to the special properties, the inventive applied pigments especially in matt lacquers and in areas of application with normally poor dispersion, e.g. in the paper industry, as cheap.

When used in papers and with .matte or glossy Lacquers or paints can be achieved with the inventive Pigments significant improvements.

The invention is explained in more detail by means of the following examples. In these examples, specific amounts of TiOg or ZrOg are given for white pigments, but these amounts can generally be between 5 to 40% by weight , preferably 15 to 10% . The pigments can be used either alone or in various combinations and mixtures.

Color pigments can contain different types and amounts of coloring metal oxides, for example cobalt, nickel and manganese. Small amounts of these can be introduced into the glass offset together with TiO ₂ and the other components.

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The following examples illustrate the invention. The specified Parts are parts by weight.

Example 1 1 .

A glass frit with 18.5% by weight TiO ₂ was prepared by melting 82 parts of borax, 840 parts of resin, 156 parts of NaNO, 24 parts of NagoiF ^, 156 parts of K ₂ JiIg, Ö4 parts of Na ₂ HPO ₁ ^ and 378, parts of TiO ₂ at 1250 ° C in 5.5 n .. ■ ... '. ".'".

The melt was quenched in cold water, - the friable mass was dried and ^{burned for 60 min at 700 0} G to recrystallize the TiO ₂ , cooled - the lumps were broken up dry, to a grain size of about 0.149 now and then wet (with a ratio from 1 part glass to 3 parts water) ground in a ball mill to a grain size of 1 to 10 yes. in 21 h. 1 liter of a sodium aluminate solution (40 parts of AigOw) was added to this slip to flocculate the pigment. The whole was then heated to 90 ° for 1 h and then cooled. The pH was adjusted to 7 by adding 1.2 HCl, then filtered, and the pigment was washed and dried.

An alkyd matt varnish (soya and castor oil-modifier-tös phthalic anhydride resin in licking gasoline with 40 % pesticide content) was applied to a reflection using commercially available rutile pigment for comparison with various extenders in a weight ratio of 1: J, colored with carbon black 0.8 (measured with a "Hunter reflectometer" with a green filter. J. Opt. Sog. of America, 50 , 44-48-1960), the paints with the inventive

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and comparative pigment were applied to standard white and standard black test papers for opacity
in a layer thickness of 0.1 ozw. 0.15 mm. After drying, the lacquers were saturated with a colorless mineral oil
and the contrast ratio was determined by the "Kuuelka and Munk" test method (National Bureau of Standards, Research Paper = -1026). The light scattering ^{coefficients 0} S "were determined, which _{indicate the actual light scattering ability of TiO 0} in the paints. - -. '■"'

If mm compares the results of the ~ according to the invention
Pigment rides with products with the addition of calcium carbonate or silicon dioxide as trecKnittel with an equivalent pigment volume concentration, then according to the invention higher values result for 5 and thus higher deck craft per weight unit of TiOo. ·

TABEL

TiO ₂ , hü. Rutile pigment (g) SiO ₂ extender (g) GaCO, extender (g) required according to pigment (g) carbon black (mg)
Alkyd resin cnr naphtha (g)

Pigment volume conc. ⁺⁺ in the dry coat

12th

- ■ 2 2 - 5.95 5.95 5> 0 L., 75 _: 1.9 1.0 2.5 4.0 66.5 66.5 70 70 / Cont TABLE I - 11 -

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iA-30 γ42 - li -

torts, to TUKLLE I

__A BCD

Streukoerfizierit J ■

(dry). 2.31 2.79 3.83- 9.29

StreuicoeiTisdeut J

(in 01) * 1.34 2.19 3.03 3.76

Gli-'tiz at layer-.
thickness 0.152 mm

dry 0.910 O / f44 0.812 '€, 856-

Oil ^? 0.910 .0.704 0.778 0.740

⁺ containing 2.2 g

Layer thickness on paper 0.1 ram each

Example 2

Commercially available Titaridioxid pigment with 20 wt .- ^ TiO ₂ was baked for crystallization I5 min at 800 ^0C. Rutile particles were obtained in a glass matrix with a size substantially smaller than that of the commercially available titanium dioxide with a preferred scattering of blue light. The fired material was ground wet according to Example 1 to an average grain size of 5 Ai and the pH value was maintained at 4 by adding hydrochloric acid.

The Pigment Frifete was then used with a commercially available

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Anatas pigment as paper filler, compared and added to 100 parts of a 4% paper pulp with 5 ecm of a 4% alum solution. The superiority of the pigment frits according to the invention with regard to opacity in the dry state compared to the comparison was shown. The opacity (sized) was almost the same as that of anatase, although the grain size of the pigment used according to the invention was below the optimal values for maximum opacity. In addition, as was to be assumed by its bluish appearance, there was a substantial increase in gloss when a white fluorescent color was added to the paper pulp. This showed that the smaller TiO ₂ particles in the glass mass reflect and do not absorb the UV light required to excite the dye.

Example 3

50 g of commercially available zirconium dioxide pigment frit with 18% ZrO ₂ were burned for recrystallization at 750 ° C. for 15 minutes and then ground for Γ6 h in a ball mill. The slurry was adjusted to pH 5.5 by addition of hydrochloric acid, filtered, washed and the solid dried. A pigment frit with a particle size of 3 μm embedded in glass was obtained. 7.2 g of this pigment frit were dispersed in 8 ecm of an alkyd resin as a carrier for "a matt lacquer and the opacity of the dry coating was determined using a green filter according to Example 1." The results are compiled in Table II.

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TABLE E. II

Reflection on white, dry reflection on black, dry reflection on white, with oil Reflection on black, with oil opacity, dry Opacity, damp

0.860 0.738 O.75 ² * 0.428 0.858 0.560

Example 4

A glass melt produced according to Example 1 was quenched in water and fired individual portions in an oven at 75O ⁰ C different lengths namely 10, 20, 30, 40, 50 and 60 min. Each portion was milled to a particle size below 0.149 mm, and then examined by electron microscopy to determine the crystallite size of the rutile. The material fired for 10 minutes contained both anatase and rutile in a crystallite size of up to 0.1 yes.

A larger batch of Pigmentfritte was prepared as above, 10 min fired at 75O ⁰ C and then 20 h wet-ground, wherein a ratio was maintained 1 Tell frit to 3 parts water. After filtering the solids, washing and drying, a pigment frit with a grain size of 1 to was obtained

A paint batch was made up by mixing the Pigment frit with an acrylic resin lacquer binder (methyl meth

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acrylate polymer in solvent mixture) with a solids content of 36 yi in a proportion of 0.8 parts of Pritte to 1 part of resin solids, the whole thing was mixed for 26 h and then on black and white test sheets to determine the opacity in a layer thickness of 0.2 inch applied to paper. All test sheets were air-dried for 1/2 hour, then baked ^{at 150 ° C. for 1/2 hour.} The pigmented and unpigmented paints were essentially transparent and almost water-clear, but the pigmented paint showed very slight opalescence.

It test sheets were produced on a carrier provided with a pattern, the pattern in the near and distant ultraviolet fluorescent. Under UV exposure, the fluorescence pattern was clear in the case of the unpigmented leak visible, but not in the case of the varnish pigmented according to the invention, so one obtained one that was opaque in the UV Coating which, however, was transparent in visible light.

The accelerated weathering showed that the invention pigmented coatings the non-pigmented and with Superior to commercially available Rütil pigment pigmented paint are.

PATENT CLAIMS:

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Claims (3)

Use a glass frit with a grain size between 1 and bO / U containing titanium dioxide or zirconium dioxide in a crystallite size between 0.01 and l / U as pigment in lacquers and paints, plastic and Kexitschukmateria lien as well as papers. · 2) Use a glass frit from JO up to 60 yä up to Vj ρ BpO ^, up to γ % F ₀ ,> up to 4θ # TiO ₂ or ZrO ₀ , up to 15 J> Al ₂ O ^, j up to 13 # R ₂ O, to I5> a RO and to 10 ^ P ₂ Ö _r - according to claim 1.. 3) Use of a glass frit made of 44 % 3iO ₂ , 11 % 25 ⁰ Jy TiO ₂ , 4 ^ Ii ₂ O ,, 3 # ZnO, 9 ^ Ui.gO and 4 ^ P ₂ O, according to claim 1. SAD New documents (αλ * Τι 1 / VA r