Tannin staining and fungus growth inhibitor pigment and manufacturing procedure

A process of inhibiting of the staining of a film forming finish applied to a tannin containing wood substrate includes the step of applying to the wood substrate prior to or concurrently with the film forming finish, a protective coating containing an effective amount of zinc cyanamide to inhibit the migration of tannins from the substrate into the finish.

BACKGROUND OF THE INVENTION 
Tannin staining, an undesirable process which results in aesthetic 
degradation and loss of decorative value of protective coatings is a 
problem frequently encountered, for example, with white coatings applied 
on wood substrates. It is observed usually as yellow-brown coloration or 
as randomly distributed brown colored spots on freshly applied aqueous 
white coatings and more particularly, on white coated wood substrates 
exposed to high, typically condensing, humidity conditions. 
Water soluble tannins or tannic acids, natural compounds of complex and 
non-uniform composition, are the staining species involved, which are 
abundantly present, especially in redwood substrates. 
A significant example of such materials is the group known as hydrolyzable 
tannins which are esters of hexozes (normally glucose) formed with benzoic 
acid or its derivatives in variable mole ratios. Their complex chemical 
composition and structure is consistent with their intricate chemical 
behavior and physical properties, some of which are relevant to the tannin 
staining process, i.e.: solubility in water and polar organic solvents, 
tendency to darken in the presence of air (more specifically in alkaline 
media) and to form soluble or insoluble, usually dark colored combinations 
with various metal cations. Similarly, the formation of colored tannate 
species are observed in the presence of insoluble or partially soluble, 
various (pigment grade) mineral products, in which case, apparently, the 
anionic species involved interfere as well with the related process. 
Notably, tannins' mild acidic character is also well known. 
A complex phenomenon, tannin staining includes several concurrent 
processes: water or vapor penetration of wood substrates, solubilization, 
diffusion into the coating and darkening of the deposited air-exposed 
tannin species, among others. It is significant to observe in this sense 
that the rate of staining is diffusionally controlled and its extent is 
significantly dependent on the substrate's tannin concentration. 
By definition, staining inhibition in the above specified sense implies 
such capacities of the specialized coating systems, as to interact with 
dissolved tannin species and to interfere with related diffusion 
processes, thus causing "in situ" immobilization of the formers and 
resulting in overall obstruction of the staining process. 
There are specialized pigment grade products known by the prior art as 
"blockers of tannin" or "stain inhibitors", which as functional components 
of water or solvent based paint formulations, provide such protective 
capacity to white coatings systems applied on wood substrates. Also used 
for this purpose, for example, are pigment grade Bametaborate, known in 
the prior art, or Mg(OH).sub.2 which is recommended as a stain inhibitor 
by U.S. Pat. No. 4,218,516, issued Aug. 19, 1980. Also, U.S. Pat. No. 
3,846,148, issued November 1974, discloses the chemical composition and 
manufacturing procedure of such products, comprising base pigments which 
essentially consist of wollastonite, talc or mica in combination with 
phosphate or borate of Ca or Zn and as a doping agent or active additive, 
one amphoteric metal hydrate of Al, Ti, Zr, Zn or Si. While the 
above-identified '516 Patent, refers to all of the specified metal 
hydrates as amphoteric, it is believed that Si hydrate is typically 
acidic, whereas Ti and Zr hydrates are considered compounds of basic 
character. Consequently, the tannin stain blocking activity of pigment 
compositions, as claimed, is not necessarily correlatable with the 
components' amphoteric character. In a related sense, it will be also 
observed (as documented in the literature) that totally or partially 
dehydrated metal hydrates (such as alumina, silica, zirconia, etc., 
essentially the above-specified doping agents) are characterized by 
variable and considerable degrees of (Bronsted and Lewis) surface acidity. 
Based on that, it is reasonable to suppose that no significant chemical 
reaction could occur between such substrates, characterized by surface 
acidity and dissolved, weakly acidic tannin species, and thus it is 
believed that the stain blocking capacity of composite pigments according 
to the above identified U.S. Patent results primarily from their barrier 
function and absorption capacity. 
It can be concluded that stain inhibitors containing the specified metal 
hydrates as functionally active additives, according to the above 
identified U.S. patent, function essentially by reducing the permeability 
of coating systems and, thus display relatively limited tannin stain 
inhibitive capacity. 
SUMMARY OF THE INVENTION 
It was learned according to the present invention that white pigment grade 
zinc cyanamide products obtained pursuant to my U.S. Pat. Nos. 5,176,894, 
issued Jan. 5, 1993, or patent application Ser. No. 195,783 filed Feb. 14, 
1994, now U.S. Pat. No. 5,378,446, issued Jan. 3, 1995, displays 
remarkable tannin stain inhibitive activity as a functional pigment 
component of wood protective coatings. It will be noted in this respect, 
that the chemical aspects of interaction of solid ZnNCN with solubilized 
tannin species has not been heretofore documented in the scientific 
literature. 
Any attempt, however, to explain the remarkable stain inhibitive capacity 
of pigment grade ZnNCN, as disclosed hereinafter, should consider, in 
addition to the barrier function thereof, the possibility of chemical 
interaction thereof with dissolved tannin species. Taking into account the 
relative strength of the involved acids (comparatively acidic tannin 
species and weakly acidic H.sub.2 NCN, characterized by 
K=4.04.times.10.sup.-11 respectively) this postulated chemical interaction 
appears plausible, logically resulting in free H.sub.2 NCN and more 
specifically of insoluble, light colored tannates which ultimately are 
accountable for the effective immobilization of dissolved tannin species 
"in situ" by ZnNCN containing protective coatings. In this sense, it will 
be observed as well, that free H.sub.2 NCN thus generated is quite 
reactive and presumably able to further interfere with such intricate 
staining processes. 
In conclusion, it is reasonable to suppose that complex blocking 
mechanisms, including chemical interactions, as above discussed, are 
accountable for the effective tannin staining inhibition capacity of 
pigment grade ZnNCN, and thus for the remarkable service of wood 
protective coating formulated with such products. 
Service conditions (high humidity, warm microclimate) which promote tannin 
staining, also support the growth of various fungi (including mold and 
algae) which typically form colonies of dark color on attacked surfaces 
causing aesthetic degradation and accelerated physical breakdown of the 
coating systems and ultimately of the protected wood substrates. 
Consequently, fungus growth control capacity is considered an essential 
function of modern paint and coating formulations intended for wood 
protection, which extend the service life and improve the overall 
protective performance of such systems. Typically, fungicides of various 
chemical composition and toxicity, are employed as special paint additives 
to increase fungal growth inhibition capability of wood protective 
coatings containing traditional stain inhibitor pigments. 
Briefly, in accordance with the invention there is provided a process of 
inhibiting of the staining of a film forming finish applied to a tannin 
containing wood substrate includes the step of applying to the wood 
substrate prior to or concurrently with the film forming finish, a 
protective coating containing an effective amount of zinc cyanamide to 
inhibit the migration of tannins from the substrate into the finish. 
In addition to wood substrates, the compositions and process of this 
invention have also been found effective in blocking other stains, for 
example, those caused by smoke damage on structural materials such as 
drywall, or graffiti coverage. Stain blockers in accordance with the 
invention include at least one, and preferably more than one, white 
colored stain blocking component selected from the group consisting of 
zinc cyanamide, calcium cyanamide, magnesium cyanamide, strontium 
cyanamide, zinc carbonate, cerium carbonate, zirconium carbonate, calcium 
carbonate, strontium carbonate, zirconium phosphate and titanium phosphate 
.

DETAILED DESCRIPTION 
It was learned according to the present invention, that pigment grade ZnNCN 
displays dual functionality as a component of wood protective coatings: 
more specifically, in addition to tannin staining inhibition, it presents 
remarkable fungus growth control activity, as well. As a consequence, 
ZnNCN, by providing both protective qualities, contributes considerably to 
the overall service performance of such coating systems. 
It is preferred according to the present invention to prepare pigment grade 
ZnNCN by wet procedures, such as those disclosed in my U.S. Pat. No. 
5,178,894, issued Jan. 5, 1993, and U.S. patent application Ser. No. 195, 
783 filed Feb. 14, 1994, now U.S. Pat. No. 5, 378, 446, which typically 
are characterized by high assay, narrow particle size distribution, high 
specific surface area and relatively "open", porous texture 
The chemical composition of such products, considered "neutral" zinc salts 
of di-basic H2NCN is consistent with ZnNCN formula. Depending on the 
manufacturing process, however, ZnNCN is obtainable in "typical" or 
"atypical" (symbolized hereafter by (T) or (A-T), respectively) crystal 
form (as disclosed in the above identified U.S. Patent Application). 
It was also learned pursuant to the present invention that the "basic" zinc 
salt of H.sub.2 NCN, which is further referred to as basic zinc cyanamide, 
displays a tannin staining and fungus growth inhibitive activity as a 
pigment component of wood coating formulations. The chemical composition 
of basic zinc cyanamide is consistent with a ZnNCN.ZnO.H.sub.2 O formula. 
It is obtainable in pigment grade quality essentially by reacting 
dispersed and hydrated ZnO, in an aqueous medium, with H.sub.2 NCN at 
appropriate stoichiometrical ratio, according to: 
EQU 2ZnO+H.sub.2 NCN.fwdarw.ZnNCN.ZnO.H.sub.2 O 1. 
A detailed description of the manufacturing procedure and pertinent 
analytical data are presented in Example No. 4. 
It will be observed that basic zinc cyanamide, similarly to neutral ZnNCN, 
can be obtained in both "typical" (T) or "atypical" (A-T) crystal form, 
identifiable by characteristic IR spectra, as disclosed in aforementioned 
U.S. patent application Ser. No. 195,783. Predictably, Reaction 1 yields 
the former, whereas partially carbonated ZnO (as aqueous suspension, 
subject to similar reaction conditions) even at as low as 2-3% ZnCO.sub.3 
content, is the typical precursor of the latter crystal structure. The 
ZnNCN.ZnO.H.sub.2 O formula, which is in agreement with obtained 
analytical data, suggests the presence of free ZnO as a constituent of 
such products. The chemical behavior of basic zinc cyanamide, however, is 
inconsistent with that: as for example, it was observed, according to the 
present invention, that an aqueous suspension of the freshly formed 
compound, unlike ZnO, does not react with gaseous CO.sub.2 to form basic 
zinc carbonate. Nevertheless, basic zinc cyanamide is readily convertible 
into neutral zinc cyanamide according to: 
EQU ZnNCN.ZnO.H.sub.2 O+H.sub.2 NCN.fwdarw.2ZnNCN+2H.sub.2 O 2. 
The initial objective of the present invention to develop composite pigment 
systems was to maximize the active ZnNCN phases's specific surface area by 
incorporation of finely divided support constituents. The development of 
ZnNCN based composite pigments characterized by synergistic behavior in 
respect of tannin stain inhibitive activity is an object of the present 
invention. 
In accordance with a related aspect of the invention, specifically prepared 
or commercially available products, characterized by adequate physical, 
(i.e. white color), and chemical properties and able to promote synergy as 
support constituents of ZnNCN based composite pigments, are identified. 
Several pigment grade white extenders of various chemical compositions were 
incorporated in composite pigments according to the invention and 
evaluated for their synergistic contribution to the tannin staining 
inhibitive activity of the related composites. In accordance with the 
invention it was learned that ZnNCN, or basic zinc cyanamide, is generally 
compatible, as expected, with extenders of various chemical compositions 
and crystal structure; several tested extenders, however, displayed no 
synergistic behavior in the above-specified sense or actually did affect 
unfavorably the overall tannin stain inhibitive activity of the pertinent 
composite pigments. In this respect it will be observed that a few mineral 
fillers widely used by the paint industry, i.e. talc, chlorite (hydrous 
magnesium aluminum silicate), MgO, as well as wollastonite (calcium 
silicate), were found to belong to the latter category; apparently 
Mg.sup.2+ and/or silicate species released by these products into the 
staining process are accountable for the noticeable adverse interference 
with the tannin stain inhibitive activity of ZnNCN, the active component 
of the composite pigments. Furthermore, no significant synergy was 
observable in relation to pigment composites (according to the present 
invention) containing TiO.sub.2 (Rutile), precipitated BaSO.sub.4, mica, 
silica, kaolin clay (hydrated aluminum silicate), nepheline syenite 
(anhydrous sodium potassium aluminum silicate) or Zn.sub.3 
(PO.sub.4).sub.2.2H.sub.2 O, SrHPO.sub.4.H.sub.2 O, MgHPO.sub.4.H.sub.2 O, 
Ca.sub.3 (PO.sub.4).sub.2, as well as precipitated CaCO.sub.3, SrCO.sub.3. 
Nevertheless, composites comprising the above-enlisted support 
constituents are generally characterized by excellent pigmentary 
properties, comparable to ZnNCN in respect to tannin stain inhibition. 
Several products of various chemical composition and appropriate physical 
properties (solubility, color) were identified according to the present 
invention to function as synergistic substrate constituent of ZnNCN based 
composite pigments. In intricate physical association with ZnNCN, or basic 
zinc cyanamide, such products form solid composite systems, characterized 
by excellent overall pigmentary properties, which typically display fungus 
growth control activity and synergism in respect to tannin stain 
inhibition. It was learned, pursuant to the present invention, that few 
selected carbonates characterized by appropriate color and solubility, and 
more specifically: basic zinc carbonate, basic zirconyl carbonate and 
Ce.sup.3+ or La.sup.3+ carbonate display synergy in the above-specified 
sense. It will be observed that carbonates typically are non-reactive 
under the reaction conditions subsequently specified. In this sense, 
however, basic zinc carbonate (dry product normally corresponds to 
ZnCO.sub.3.1.6Zn(OH).sub.2.0.6H.sub.2 O formula and contains approximately 
40-42% ZnCO.sub.3) represents a "non-typical" case: as disclosed in my 
U.S. patent application Ser. No. 195,783, it does react with H.sub.2 NCN, 
forming ZnNCN and CO.sub.2 ; consequently, it is employed pursuant to the 
present invention in appropriate stoichiometrical ratio. Basic zirconyl 
carbonate, unlike basic zinc carbonate, does not react with H.sub.2 NCN; 
it is characterized, however, by limited heat stability, being convertible 
by drying (performed at moderate temperature ranges of 
80.degree.-100.degree. C.) into zirconium oxide (hydrated to variable 
degrees) and ultimately into ZrO.sub.2 with total loss of carbonate 
content. It was observed pursuant to the present invention that pigment 
composites containing basic zirconyl carbonate as a support constituent, 
dried at the same moderate temperature conditions, retain a relatively 
high carbonate content, presumable due to a stabilizing effect of the 
related matrix. Lanthanide carbonates, corresponding to Ln.sub.2 
(CO.sub.3).sub.3.3-4 H.sub.2 O, where Ln=Ce.sup.3+, La.sup.3+, and more 
preferable Ce.sub.2 (CO.sub.3).sub.3.3H.sub.2 O, are non-reactive as well, 
in the above-specified sense. Commercially available Ce.sup.3+ carbonate 
(from Molycorp., Inc.), a relatively heat stable product, usually 
characterized by variable carbonate content (due to the presence of 
Ce.sup.4+, as well as the bicarbonate or basic carbonate species), is 
applicable as support constituent of pigment composites according to the 
present invention. Efficient U.V. radiation absorbers (300-400 nm range) 
cerium compounds are known inhibitors of photo degradation processes of 
various, specifically organic, mediums. Presumably ZnNCN based pigment 
composites, containing cerium carbonate as support constituent, 
additionally to tannin stain inhibiting and fungus growth control 
activity, provide improved photostability to coating systems by inhibiting 
the degradation of related resin matrixes. Additionally to carbonates as 
above-specified, selected phosphates, hydrated metal oxides and Zeolites 
or molecular sieves were identified as synergistic support constituents of 
pigment composites according to the present invention. 
Ti(HPO.sub.4).sub.2.H.sub.2 O.sub.x and more specifically, 
Zr(HPO.sub.4).sub.2.H.sub.2 O.sub.x known for its layered structure, ion 
exchange capacity and ability to form intercalates with organic species, 
along with NaY or HY of ZSM-5 type molecular sieves or Zeolites of various 
Si/Al ratios, characterized (preferable but not exclusively) by large 
intersecting pore system and related absorption capacity, as well as 
hydrated aluminum oxide, Al(OH).sub.3 and hydrated Zirconium oxide, were 
found to display synergy in association with ZnNCN or basic zinc cyanamide 
in the above specified respect. 
In order to achieve intimate association between ZnNCN, the active 
component and the support constituent of such composite pigment, the 
former typically was prepared by gradual and simultaneous introduction of 
H.sub.2 NCN and ZnO suspension, into well dispersed aqueous suspension 
(containing the whole amount) of the latter. 
It will be observed, however, that, when applicable, "in situ" and 
concurrent formation of both phases, the active component and the support 
constituents, is the preferred procedure of ZnNCN based composite pigment 
synthesis according to the present invention. 
As for example, a previously prepared aqueous mixed suspension of ZnO and 
MeO (carbonate precursor) is simultaneously converted into ZnNCN and 
MeCO.sub.3 (or basic carbonate) respectively, by concurrent introduction 
of H.sub.2 NCN and CO.sub.2 gas into the reaction system as follows: 
EQU ZnO+MeO+H.sub.2 NCN+CO.sub.2 .fwdarw.MeCO.sub.3 /ZnNCN+H.sub.2 O3. 
An essentially similar principle (as will be later exemplified) can be 
alternatively realized by precipitation of selected carbonates, phosphates 
or hydroxides, mixed with previously dispersed ZnO and by subsequent 
conversion of the latter into ZnNCN. Support constituents or their 
precursors, when applicable, are employed according to the present 
invention in finely divided form, characterized by average particle size 
of 1-10 nm. 
It was subject of consideration to optimize the support constituent/active 
component ratio of the composite pigments: no measurable benefit in 
respect of functional activity was observable, however, at or above 50% of 
support content levels. 
EXAMPLES 
For simplicity reasons with no intention however to limit the applicability 
of the present invention, all examples hereinafter presented disclose 
manufacturing procedures of composite pigments having the support 
constituent content limited to practically one selected value, typically 
of 30-40% by weight. 
Various pigment components realized pursuant to the present invention, are 
symbolized by a "phase composition" formula, which identifies the support 
constituents' chemical composition (basic or neutral) and crystal 
structure (typical(T) or atypical (A-T)) of the zinc cyanamide phase. 
In order to maximize the ZnO.fwdarw.ZnNCN conversion, optimal process 
conditions were applied: approximately 10% molar excess of H.sub.2 NCN 
(except in the case of basic zinc cyanamide), 70.degree.-85.degree. C. 
temperature range and intensive agitation. However, "in situ" preparation 
of the carbonate support constituents by gaseous CO.sub.2 introduction 
into the reaction system was preferable performed at lower temperature 
range of 20.degree.-50.degree. C. 
All synthesized composite pigments were analyzed for N, Zn, and carbonate 
contents (when applicable) by Kjeldahl, complexometric and gas volumetric 
analytical techniques, respectively. 
Primer or topcoat paint formulations intended for wood protection are 
typically water based, often solvent based systems of considerably 
complexity. Such water based formulations usually contain water reducible 
alkyd or acrylic resins as film forming component, filler pigments and 
water as major components. They also contain several functional components 
such as: staining inhibitor pigment, coalescent solvent, dispersants, 
defoamers, thickeners, neutralizers and biocides in appropriate amounts. 
All functional characteristics, including to some extent, tannin stain 
blocking capacity, of wood protective coatings are dependent on the major 
components' (such as fillers and polymer matrixes) chemical composition, 
respectively cross-linking density. It will be observed, however, it is 
the stain inhibitor pigment component, representing only about 5-6% of the 
solid phase, which determines the tannin stain blocking performance of the 
resultant coatings. 
A primer formulation prepared in accordance with Example 11, with varieties 
of composite pigments obtained according to the present invention, was 
employed as a test system to estimate and to quantify the tannin staining 
inhibitor activity of such ZnNCN based products. To that purpose, the 
related variations of the primer formulation were applied by a 3 mil. let 
down bar on surface finished redwood panels, aged for several days and 
subsequently subjected to condensing humidity conditions for 24 hours. By 
measuring the magnitude of the resulted discolorations of the test panels 
by means of a computer assisted reflectance spectrophotometer, results 
were obtained and expressed in FMCII color measurement system versus 
related and unexposed control exhibits, where the pertinent formulations 
were applied on white non-staining substrates. The primer variations' 
protective performance and the pertinent composite pigment varieties' 
tannin staining inhibitive activities were thus evaluated and quantified. 
Fungus growth retarding activity of pigment grade ZnNCN and of selected 
ZnNCN based composite pigments were evaluated on pine and gypsum test 
panels as above described following the specialized test procedure 
recommended by ASTMD-3273. 
Example 1 
Composite pigments, characterized by excellent tannin staining inhibitive 
and fungus growth control activity were prepared, symbolized by phase 
composition formulas: 
1.1: Ce.sub.2 (CO.sub.3).sub.3.3H.sub.2 O/ZnNCN (T) 
1.2: Al(OH).sub.3 /ZnNCN(T) 
1.3: Molecular sieve Valfor CBV-400/ZnNCN(T). 
The support constituents according to 1.1, 1.2, 1.3 are available from 
Molycorp, Inc., Nyco Minerals, Inc. and the PQ Corporation, respectively. 
The composites were synthesized pursuant to the following procedure: 
Well dispersed and hydrated aqueous suspensions of selected varieties of 
the selected substrate constituents and separately, of highly reactive 
ZnO, were concurrently prepared by introducing in small increments 300.0 
g. of any such product, as specified, and 543.0 g. (6.67 moles) of AZO 66 
grade ZnO (from American Smelting and Refining Co.) respectively, onto two 
separate volumes of hot water 1,000 ml. each, by intensive stirring. 
The dispersion and hydration process of all (various substrate constituents 
and ZnO) such suspensions was completed by maintaining the same conditions 
for one hour at 75.degree.-85.degree. C. 
Subsequently, composite pigment varieties were produced by simultaneously 
introducing in about 60 minutes, the previously prepared ZnO suspension 
(as above described) and 313.0 g. (7.45 moles) of H.sub.2 NCN (employed as 
aqueous solution of 25% available from S.K.W.--Germany) into the 
previously prepared, intensively stirred suspensions of any substrate 
constituent. The ZnO conversion into ZnNCN was finalized by keeping the 
same reaction conditions (intensive stirring, 75.degree.-85.degree. C.) 
for approximately 1 hour after the reactants introduction was completed. 
Subsequently the solid phases of the resultant product suspensions were 
separated by vacuum filtration, and without washing, the obtained press 
cakes were dried at 105.degree.-110.degree. C. for 12 hours and pulverized 
to a fineness of 100% +270 mesh. 
The process waters collected were entirely recyclable. Since the products 
selected as support constituents are essentially nonreactive under the 
above disclosed reaction conditions yields obtained were all approximately 
1002.0-1060.0 g. 
Pertinent analytical data typical for tannin staining inhibitor composite 
pigments 1.1, 1.2 and 1.3, all containing about 70% by weight of ZnNCN as 
active component and about 30% by weight of selected synergistic support 
constituent, are presented in Table 1. 
TABLE 1 
______________________________________ 
Determined/Calculated Values of 
Phase Composition 
Quality Parameters 
of Synthesized Support 
Specific 
No. Pigments N % Zn % % Gravity 
______________________________________ 
1.1 Ce.sub.2 (CO.sub.3).sub.3.3H.sub.2 O/ 
16.05 51.8 9.5(as 3.0 
ZnNCN(T) CO.sub.3) 
1.2 Al(OH).sub.3 /ZnNCN(T) 
15.2 45.1 29.4 2.6 
1.3 CBV-400/ZnNCN(T) 
15.5 45.5 30.0 2.3 
______________________________________ 
Yields obtained and the correspondent chemical compositions (based on the 
presented analytical data) are disclosed below: 
______________________________________ 
Chemical Composition of Synthesized Pigments 
Yield, g. 
______________________________________ 
1.1: 0.09 Ce.sub.2 (CO.sub.3).3H.sub.2 O/ZnNCN.0.38ZnO 
1058.0 
1.2: 0.73 Al(OH).sub.3 /ZnNCN.0.27ZnO.0.04H.sub.2 O 
1020.0 
1.3: 30% CBV-400/ZnNCN.0.26ZnO 
1002.0 
______________________________________ 
IR Spectrum characteristic to 1.3, CBV400/ZnNCN(T) is presented in FIG. 1. 
Example 2 
Composite pigment corresponding to basic zinc carbonate/ZnNCN(A-T) was 
synthesized as follows: 
Basic zinc carbonate (which corresponds to ZnCO.sub.3 
1.6Zn(OH).sub.2.0.6H.sub.2 O as available from Aldrich Chemical Co.) 
suspension was prepared by dispersing 1050.0 g. of finely ground material 
in 2000 ml. intensively stirred hot water and by keeping the same 
conditions at 75.degree.-85.degree. C. for 1 hour. 
Composite pigment according to the present invention, was synthesized by 
introducing in about hour, 306.0 g. (7.28 moles) of H.sub.2 NCN, employed 
as 5% aqueous solution, into the previously prepared, intensively stirred 
basic zinc carbonate suspension, while keeping the temperature of the 
reaction mixture at 75.degree.-85.degree. C. The conversion process was 
finalized by maintaining the same process conditions for 1 additional 
hour. 
The resultant pigment grade composite suspension was further processed in 
identical manner as disclosed in the relevant part of Example 1. 
Pertinent analytical data typical for composite pigment containing ZnNCN 
(A-T) as active component and basic zinc carbonate as support constituent, 
(in this case in approximately 60% to 40% weight ratio, respectively) are 
presented below. 
TABLE 2 
______________________________________ 
Analyzed/Tested Parameter 
Determined Values 
______________________________________ 
Specific gravity 2.94 
N % as N 16.22 
Zn % as Zn 60.04 
ZnCO.sub.3 % 17.0 
Yield 997.0 g. 
______________________________________ 
Based on the above presented analytical data the composite pigment's 
chemical composition corresponds to ZnNCN.0.23ZnCO.sub.3.0.35Zn(OH).sub.2 
O.17H.sub.2 O. 
Relevant IR spectrum is presented in FIG. 2. 
Example 3 
Composite pigment of similar chemical composition and physical structure as 
disclosed in Example 1, corresponding to CaCO.sub.3 /ZnNCN(A-T) phase 
composition formula, was produced by performing the synthesis of the 
active ZnNCN component and of the synergistic support constituent, 
simultaneously "in situ" of the reaction medium using the following 
procedure: 
A well-dispersed, hydrated and reactive mixed suspension was prepared by 
introducing in small increments, 543.0 g. ZnO (AZO-66 grade preferable) 
and the appropriate amount, 168.0 g. of CaO, the carbonate precursor 
oxide, into intensively stirred 2000.0 ml. hot water at 
75.degree.-85.degree. C. 
The reactive mixed suspension of ZnO and CaO, the carbonate precursor 
oxide, was subsequently converted into composite pigment by introducing 
continuously for about 1 hour into the intensively stirred reaction 
medium, CO.sub.2 gas at a manageable rate, and with approximately 5 
minutes relative delay (but essentially simultaneously), 295.0 g. (7.0 
moles) of HnNCN as 25% aqueous solution of the same quality as specified 
in Example 1. 
Subsequently, the conversion process was finalized by keeping the 
temperature of the obtained suspension at 30.degree.-40.degree. C. and by 
continuous agitation for about 2 hours. More importantly, however, the 
reaction medium's pH were continuously monitored and periodically 
corrected to pH=7-7.5 by additional CO.sub.2 introductions, performed 
intermittently, as necessary. Typically, after two hours stable pH=7-8 
values of the reaction mediums were observed. 
The obtained pigment composite suspension was further processed in 
identical fashion as discussed in the applicable section of Example 1. 
Relevant analytical data are presented below. 
TABLE 3 
______________________________________ 
Analyzed/Tested Parameter 
Determined Values 
______________________________________ 
Specific Gravity 2.64 
N % as N 16.7 
Zn % as Zn 42.16 
CaCO.sub.3 % 30.0 
Yield: 997.0 g. 
______________________________________ 
Based on the above presented analytical data the composite pigment chemical 
composition corresponds to 0.5 CaCO.sub.3 /ZnNCN(A-T).0.08ZnO.0.3H.sub.2 
O. 
Example 4 
Pigment grade basic zinc cyanamide, having chemical composition 
correspondent to ZnNCN.ZnO. H.sub.2 O, characterized by enhanced tannin 
staining and fungus growth inhibitive activity was produced according to 
the following procedure: 
A well hydrated, reactive suspension, containing 407. g (5.0 moles) ZnO in 
1000.0 ml. H.sub.2 O was prepared in a similar fashion as disclosed in the 
correspondent part of Example 1, cooled to 30.degree.-40.degree. C. and 
subsequently converted to basic zinc cyanamide (suspension) by introducing 
into it in about 1 hour, 105.0 g. (2.5 moles) of H.sub.2 NCN, added as 25% 
solution, while keeping the temperature of the reaction medium at 
20.degree.-50.degree. C. The conversion process can be finalized in about 
1 hour at 20.degree.-85 C. under intense agitation 
After separation, the solid phase was washed with limited amounts of 
H.sub.2 O, dried overnight at critical, 75.degree.-80.degree. C. and 
further processed as disclosed in the applicable part of Example 1. 
Relevant analytical data and IR spectrum are presented below, respectively 
in FIG. 3. 
TABLE 4 
______________________________________ 
Analyzed/Tested Quality Parameters 
Determined Values 
______________________________________ 
Specific Gravity 3.38 
N % as N 13.6 
Zn % as Zn 62.6 
ZnCO.sub.3 % as ZnCO.sub.3 
1% 
H.sub.2 O % 10.5% 
Yield: 490.0 g. 
______________________________________ 
Based on the above presented analytical data, the chemical composition of 
the product corresponds to ZnNCN.0.97ZnO..1.2H.sub.2 O. 
Example 5 
Composite pigment correspondent to basic zinc carbonate/basic zinc 
cyanamide (A-T) was prepared according to the procedure as follows: 
Well dispersed, hydrated and reactive suspension of ZnO was prepared by 
introducing 298.0 g. (3.66 moles, AZO 66 grade) of such product into 1500 
ml. hot water of 75.degree.-85.degree. C., keeping the same conditions for 
one hour, then cooling it to about 40.degree. C. 
The prepared ZnO suspension was divided by weight into two parts, A and B, 
containing practically 178.0 g. and 120.0 g. ZnO, respectively. 
Subsequently, B containing 120.0 g. ZnO was converted into basic zinc 
carbonate suspension by introducing continuously into it for about one 
hour, under intense agitation, CO.sub.2 gas at manageable rate. 
A mixed ZnO--basic zinc carbonate suspension was obtained by unifying A and 
B, which, first heated to 70.degree.-80.degree. C., was further converted 
into composite pigment suspension. 
To that purpose, under intense agitation and at 70.degree.-80.degree. C., 
48.0 g. (1.14 moles) of H.sub.2 NCN (as 25% aqueous solution) were 
introduced into the mixed suspension in about 15-20 minutes. The 
conversion process was finalized by keeping the same conditions for one 
additional hour, and subsequently, the obtained composite pigment 
suspension was processed in identical fashion as presented in the 
applicable part of Example 1. 
Relevant analytical data are presented below: 
TABLE 5 
______________________________________ 
Analyzed/Tested Parameter 
Determined Values 
______________________________________ 
Specific Gravity 2.92 
N % 7.91 
Zn % 61.15 
ZnCO.sub.3 % 23.7 
Yield: 379.1 g. 
______________________________________ 
Based on the above presented analytical data, the composite pigment's 
chemical composition corresponds to: 0.67 ZnCO.sub.3.0.64 ZnO.0.2H.sub.2 
O/ZnNCN. ZnO.H.sub.2 O. 
Related IR spectrum is presented in FIG. 4. 
Example 6 
Composite pigment corresponding to basic zinconyl carbonate/ZnNCN (T) phase 
formula, was obtainable according to as follows: 
Well dispersed, hydrated and reactive ZnO suspension, containing 220.0 g 
(2.7 moles) such product in 1000 ml. H.sub.2 O, was prepared in the above 
already presented typical fashion. 
Concurrently, zirconyl sulfate solution was prepared by dissolving 245.0 g. 
of such product (available from Magnesium Elektron, Inc. as H.sub.2 
ZrO(SO.sub.4).sub.2.3H.sub.2 O, assay: 32% ZrO.sub.2) in approximately 
1000 ml. H.sub.2 O and converted into basic zirconyl carbonate suspension 
by Na.sub.2 CO.sub.3 addition (about 195.0200.0 g required) until a 
constant pH=8.5-9.0 was achieved. 
Composite pigment was produced by adding the basic zirconyl carbonate 
suspension to the ZnO suspension, stirring the mixed suspension for 
approximately 30 minutes at 40.degree.-50.degree. C. and by subsequent 
introduction into it, in about 30 minutes, of 120.0 g. (2.85 moles) 
H.sub.2 NCN (as 25% solution). 
The conversion process was finalized by keeping the same conditions for an 
additional hour, after which the solid phase was separated by filtration, 
washed to salt free conditions and further processed in similar fashion as 
described in the applicable section of Example 1. 
Pertinent analytical data are presented below: 
TABLE 6 
______________________________________ 
Analyzed/Tested Parameter 
Determined Values 
______________________________________ 
Specific Gravity 2.84 
N % 16.58 
Zn % 43.83 
carbonate as Co.sub.3 % 
5.92 
carbonate as 
ZrO(OH) (CO.sub.3).sub.0.5 % 
30.4 
Yield: 391.1 
______________________________________ 
Based on the above disclosed analytical data, the synthesized composite 
pigment's chemical composition corresponds to: 
0.33ZrO(OH)(CO.sub.3).sub.0.5 /ZnNCN.0.13 ZnO.0.07H.sub.2 O. 
Example 7 
Composite pigments, containing basic zinc cyanamide as active component, 
corresponding to phase composition formulas: 
7.1 HY Zeolite/basic zinc cyanamide (T) 
7.2 Diatomaceous silica/basic zinc cyanamide (T), were produced pursuant 
essentially to the procedure disclosed in Example 1, except that the 
employed raw material molar ratios were as follows: 
TABLE 7 
______________________________________ 
Amounts in grams per synthesized 
products 
Raw Materials 7.1 7.2 
______________________________________ 
ZnO(AzO 66 grade) 
178.0 178.0 (2.18 
moles) 
H.sub.2 NCN (SKW, Germany) 
48.0 48.0 (1.14 
moles) 
HY Zeolite (CBV-760 
165.0 -- 
from the PQ Corp.) 
Diatomaceous Silica 
-- 165.0 
(Ultra Block grade 
from Eagle Picher Min- 
erals, Inc.) 
______________________________________ 
Pertinent analytical data are presented below: 
TABLE 8 
______________________________________ 
Determined/Calculated Values of 
Phase Composition 
Quality Parameters 
of Synthesized Support 
Specific 
No. Pigments N % Zn % % Gravity 
______________________________________ 
7.1 HY Zeolite/Basic 
7.1 39.02 43.7 2.45 
ZnNCN(T) 
7.2 Silica/basic 7.83 38.18 44.0 2.58 
ZnNCN(T) 
______________________________________ 
Yields recovered and the correspondent chemical compositions (based on the 
above presented analytical data) are given below: 
______________________________________ 
Chemical Composition of Synthesized Pigments 
Yield, g. 
______________________________________ 
7.1 43.4% Zeolite HY/ZnNCN. 
380.0 
1.35ZnO.1.6H.sub.2 O 
7.2 44% Silica/ZnNCN. 375.0 
1.08ZnO.1.31H.sub.2 O 
______________________________________ 
Example 8 
Composite pigment containing basic zinc cyanamide as active component, 
corresponding to phase composition of hydrated zirconyl oxide/basic ZnNCN 
was obtained essentially the same way in all details as disclosed in 
Example 7, except that in this case the support constituent was prepared 
by precipitating dissolved zirconyl species as Zr(OH).sub.2.H.sub.2 
O.sub.x. 
TO that purpose 415.0 g. of zirconyl sulfate (see also Example 6), 
dissolved in 1,500 ml. H.sub.2 O was converted into ZrO(OH).sub.2.H.sub.2 
Ox suspension by 210.0 g. (5.25 moles) of NaOH addition to a stable 
pH=8.59.0, subsequently incorporated into composite pigment and further 
processed as described in Example 7, respectively, in Example 1. 
Pertinent analytical data are presented below: 
TABLE 9 
______________________________________ 
Analyzed/Tested Parameter 
Determined Values 
______________________________________ 
Specific Gravity 3.28 
N % 7.8 
Zn % 36.0 
Basic Zinc Cyanamide % 
56.39 
Substrate % 43.6 
Yield: 410.0 g. 
______________________________________ 
Based on the above disclosed data, the synthesized pigment's chemical 
composition corresponds to: 
1.07.ZrO.sub.2.2.5H.sub.2 O/ZnNCN.0.97 (ZnO.H.sub.2 O). 
Example 9 
Composite pigments comprising basic zinc cyanamide as active component, 
zirconyl or titanyl phosphate as support constituent and corresponding to 
phase composition formulas of: 
9.1 Zr(HPO.sub.4).sub.2 /Basic ZnNCN(T) 
9.2 Ti(HPO.sub.4).sub.2 /Basic ZnNCN(T) were produced essentially in 
similar fashion as presented in Example 7, except that in these cases the 
support constituents were prepared according to as follow: 
Zirconyl sulfate (9.1) or Titanyl sulfate (9.2) solution was obtained by 
solubilizing 223.0 g. of the former (available from Magnesium Electron, 
Inc., with an assay of 32% ZrO.sub.2) or 650.0 g. the latter (available 
from Kemira, Inc., with an assay of 9.8% TiO.sub.2) product, respectively, 
in approximately 2,000 ml.H.sub.2 O. 
Consecutively Zr(HPO.sub.4).sub.2.H.sub.2 O.sub.x or 
Ti(HPO.sub.4).sub.2.H.sub.2 O.sub.x aqueous suspensions were produced by 
introducing, under intense agitation 170.0 g. (1.47 moles) of H.sub.3 
PO.sub.4 (as 40% solution) into each solution and by further NaOH addition 
to a stable pH=8.0-9.0. 
The incorporation of the support constituents into the correspondent 
composite pigments 9.1 and 9.2, respectively, was subsequently performed 
in all details as described in Example 7, including washing the products 
to salt-free conditions as described in Example 1. 
Related analytical data are presented below: 
TABLE 10 
______________________________________ 
Determined/Calculated Values of 
Quality Parameters 
Phase Composition of Support 
Specific 
No. Synthesized Pigments 
N % Zn % % Gravity 
______________________________________ 
9.1 Zr(HPO.sub.4).sub.2 /Basic 
7.94 36.14 43.37 2.80 
ZnNCN(T) 
9.2 (Ti) (HPO.sub.4).sub.2 /Basic 
7.54 34.65 47.0 2.73 
ZnNCN(T) 
______________________________________ 
Yield, IR spectrum relevant to 9.1 and the correspondent chemical 
compositions (based on the above presented analytical data) are shown 
below, respectively, in FIG. 5. 
______________________________________ 
Chemical Composition of Synthesized Pigments 
Yield, g. 
______________________________________ 
9.1 2.04Zr(HPO.sub.4).sub.2.0.38H.sub.2 O/ZnNCN.0.95 
395.0 
(ZnO.H.sub.2 O) 
9.2 2.96Ti(HPO.sub.4).sub.2.0.2H.sub.2 O/ZnNCN.0.96 
415.0 
(ZnO.H.sub.2 O) 
______________________________________ 
Example 10 
Composite pigment based on ZnNCN and three component mixed support 
constituent according to the phase composition formula of Ce carbonate, 
basic (Zn +Zr) carbonate/ZnNCN(A-T), was prepared pursuant to the 
following procedure. 
Previously prepared (see pertinent and applicable section of Example 1) 
well dispersed, hydrated and reactive ZnO suspension, containing 300.0 g. 
(3.68 moles) of such product in 1,000 ml. H.sub.2 O, was converted in 
mixed suspension of hydroxides (precursors to cerium carbonate, basic 
zirconyl carbonate, basic zinc carbonate mixture) by first cooling it to 
40.degree.-50.degree. C. then introducing into it 125 0 g of zirconyl 
sulfate (as specified in Example 9), 140.0 g. of Ce(NO.sub.3).sub.3 (from 
Molycorp, Inc., characterized by assay of 34.5% CeO.sub.2) and after 
approximately 10 minutes, 83.0 g. of NaOH (2.07 moles) under intensive 
agitation. 
Carbonization of the mixed suspension of hydroxides was subsequently 
performed by introducing continuously into the intensively stirred 
reaction medium, at 25.degree.-35.degree. C. CO.sub.2 gas at a manageable 
rate for about one hour. 
Composite pigment, according to the phase composition formula above 
disclosed, was obtained by introducing consequently, in about 30 minutes 
141.0 g. of H.sub.2 NCN (3.36 moles, as 25% aqueous solution) into the 
reaction medium and finalizing the conversion process by agitation at 
25.degree.-40.degree. C., in about two hours. 
The obtained composite pigment was subsequently processed as described in 
the applicable section of Example 6, inclusively washing it to salt-free 
conditions. 
Related analytical data are presented below: 
TABLE 11 
______________________________________ 
Analyzed/Tested Parameter 
Determined Values 
______________________________________ 
Specific Gravity 2.82 
N % 15.91 
Zn % 47.66 
Total CO.sub.3 % (as CO.sub.3) 
5.6 
ZnNCN % 59.9 
Support % 40.1 
Yield: 510.0 g. 
______________________________________ 
Example 11 
A typical water based, stain blocking primer formulation (designed for wood 
protection) employed as test system (applied on redwood panels) pursuant 
to the present invention is presented below: 
TABLE 12 
______________________________________ 
Parts by 
Components Trade Names of Components 
Weight 
______________________________________ 
Stain Blocking 
Produced according to the 
33.0 
Composite Pigment 
present invention* 
TiO.sub.2 -- 300.0 
Dispersant Tamol 681 (1) 20.0 
Stabilizer Triton CF-10 (2) 2.0 
Thickener QR-708 (1) 6.0 
Anti-foam Agent 
Foamaster VL (3) 2.0 
Ammonia, 28% -- 1.0 
Coalescent Sol- 
Ethylene Glycol 20.0 
vents Texanol (4) 5.0 
Resin Rhoplex MV-23 (1) 520.0 
Water -- 200.0 
______________________________________ 
*except commercial products 
Suppliers of components are: (1) Rohm & Haas, (2) Union Carbide, (3) Henkel 
Co., and (4) Eastman Chemical Co. 
Following the test procedure earlier described, tannin stain blocking 
activity of various composite pigments (synthesized pursuant to the 
present invention and employed as functional components of the test 
formulation disclosed above in Table 12) was determined on redwood panels; 
pertinent results are presented in Table 13. 
.DELTA.E values measured, which qualify the magnitude of the observed color 
shifts, are also inversely proportional with the tested pigments' stain 
blocking activity. 
The above disclosed .DELTA.E values (observe control and commercial 
products for comparison) indicate remarkable tannin stain blocking 
activity of pigment grade ZnNCN and basic ZnNCN, as well as synergistic 
behavior, in the same sense, of related pigment composites synthesized 
according to the present invention. 
TABLE 13 
______________________________________ 
Related Tannin 
Tested Stain Blocking Pigments 
Stain Blocking 
According to Activity, Mea- 
Example # Phase Composition sured as .DELTA.E 
______________________________________ 
Control, with- 
N.A. 18.0 
out stain 
blocker* 
1.1 Ce.sub.2 (CO.sub.3)3.3H.sub.2 O/ 
7.0 
ZnNCN(T) 
--** ZnNCN(T) 9.5 
4. ZnNCN.ZnO.H.sub.2 O(T) 
9.0 
5. Basic Zinc Carbon- 7.5 
ate/basic ZnNCN(A-T) 
9.1 Zr(HPO.sub.4).sub.2 /basic ZnNCN(T) 
6.5 
1.2 Al(OH).sub.3 /ZnNCN(T) 
8.5 
1.3 Zeolite/ZnNCN(T) 8.0 
Commercial 
Borate Based 10.5 
Product 
Commercial 
Phosphate/Silicate 12.0 
Product Based 
______________________________________ 
*Compensated for by the same amounts of TiO.sub.2. 
**Produced according to U.S. Pat. No. 5,176,894. 
Example 12 
Fungus growth retarding activity of pigment grade ZnNCN was evaluated 
following the recommendations of the specialized test procedure by 
ASTM-3273. 
For that purpose, variations of paint formulation (as presented in Table 
12) containing pigment grade ZnNCN (produced according to U.S. Pat. No. 
5,176,894) borate based stain blocker pigment (available commercially, 
also recommended as fungicide in paint formulations) and control 
formulation without stain blocker, respectively, were applied on pine and 
gypsum substrates and subjected to test conditions. 
The extent of discoloration caused by fungal growth on the test coatings' 
surfaces, an indicator of the tested products' inhibitive activity, was 
visually evaluated and graded on a 10 (no disfiguration) to 1 (no fungus 
growth inhibition) scale. 
Pertinent results presented below indicate the manifestation of a 
remarkable fungus growth control activity for pigment grade ZnNCN. 
TABLE 14 
______________________________________ 
Grade of Fungus Growth Inhibi- 
tion on Substrates of: 
Inhibitor Pine Gypsum 
______________________________________ 
None(control formulation) 
2 2 
Modified Ba-metaborate 
3 1 
ZnNCN 7 7 
______________________________________ 
The foregoing is considered as illustrative only of the principles of the 
invention, since numerous modifications and changes will be apparent to 
those skilled in the art. The invention should not be considered to be 
limited to the exact compositions shown and described, and accordingly all 
suitable modifications and equivalents may be resorted to falling within 
the true scope of the invention.