U.S. patent application number 12/228566 was filed with the patent office on 2008-12-11 for coating material with biocide microcapsules.
Invention is credited to Dagmar Antoni-Zimmermann, Rudiger Baum, Hans-Jurgen Schmidt, Thomas Wunder.
Application Number | 20080305137 12/228566 |
Document ID | / |
Family ID | 29797085 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080305137 |
Kind Code |
A1 |
Baum; Rudiger ; et
al. |
December 11, 2008 |
Coating material with biocide microcapsules
Abstract
The invention relates to a coating material for protection
against microorganism invasion on surfaces which are exposed to the
effects of damp or water. The coating material has either a
pH-value of at least 11.0 or is provide with a base material for
the coating whereby the pH-value is at least 11. The coating
material is characterized in that it contains a biocide which bonds
to solid particles in a carrier material and is released in a
delayed manner therefrom.
Inventors: |
Baum; Rudiger; (Waghausel,
DE) ; Antoni-Zimmermann; Dagmar; (Speyer, DE)
; Wunder; Thomas; (Neustadt/Weinstrasse, DE) ;
Schmidt; Hans-Jurgen; (Speyer, DE) |
Correspondence
Address: |
HEDMAN & COSTIGAN P.C.
1185 AVENUE OF THE AMERICAS
NEW YORK
NY
10036
US
|
Family ID: |
29797085 |
Appl. No.: |
12/228566 |
Filed: |
August 14, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10489842 |
Mar 15, 2004 |
7429392 |
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PCT/EP2002/006806 |
Jun 19, 2002 |
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12228566 |
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Current U.S.
Class: |
424/408 ;
514/188; 514/245; 514/372; 514/394; 514/478 |
Current CPC
Class: |
C09D 5/14 20130101; C04B
2103/67 20130101; C04B 2103/67 20130101; C04B 2111/2092 20130101;
C04B 20/1018 20130101; C04B 2111/00112 20130101; A01N 25/28
20130101; C04B 20/1018 20130101; C09D 5/1606 20130101; C04B 20/1018
20130101; C04B 20/1018 20130101; C04B 14/047 20130101; C04B
2111/00482 20130101; C04B 14/301 20130101; C04B 14/12 20130101;
C04B 2103/67 20130101 |
Class at
Publication: |
424/408 ;
514/188; 514/372; 514/478; 514/394; 514/245 |
International
Class: |
A01N 25/26 20060101
A01N025/26; A01N 55/02 20060101 A01N055/02; A01N 43/80 20060101
A01N043/80; A01N 47/10 20060101 A01N047/10; A01N 43/52 20060101
A01N043/52; A01N 43/68 20060101 A01N043/68; A01P 15/00 20060101
A01P015/00 |
Claims
1-12. (canceled)
13. Biocide, bound in a carrier material composed of particulate
solids, wherein the carrier material contains a
formaldehyde-melamine resin and the biocide is zinc pyrithion,
4,5-dichloro-2-octylisothiazolin-3-one, 3-iodo-2-propynyl
N-butylcarbamate, methyl 1H-benzimidazol-2-ylcarbamate, or
N.sup.2-t-butyl-N.sup.4-ethyl-6-methylthio-1,3,5-triazin-2,4-diyldiami-
ne or a mixture of two or more of these compounds.
14. Biocide according to claim 13, wherein the particulate solids
of the carrier material are granular particles having cavities.
15. Biocide according to claim 14, wherein the granular particles
having cavities are microcapsules.
16. Biocide according to claim 13, wherein the wall material of the
microcapsules is composed primarily of a formaldehyde-melamine
resin.
17. Biocide according to claim 13, wherein the particulate solids
have a diameter of from 30 to 40 .mu.m.
18. A method of protecting a coating material against microorganism
infestation comprising the step of incorporating a biocide
according to claim 1 in said coating.
Description
[0001] The invention relates to a coating material for protection
against microorganism infestation on surfaces which are exposed to
the effects of damp or water, said coating material either itself
having a pH of at least 11.0 or being intended for the coating of a
substrate material whose pH is at least 11.0. The invention
pertains in particular to plasters and paints which are to be
protected with biocides against attack by microorganisms.
[0002] It has long been known that fungicidal and/or algicidal
biocides are added to plasters and paints in order to preserve
films thereof. The purpose of this is to prevent unwanted
infestation of the films by microorganisms, e.g., fungi, such as
molds and yeasts, and also by bacteria, algae, and cyanobacteria
(see D. Antoni-Zimmermann, P. Hahn, "Wassrige
Siliconharz-Beschichtungssysteme fur Fassaden" [Aqueous silicone
resin coating systems for facades], expert verlag, volume 522,
pages 379 to 406). Such microorganism infestation occurs, for
example, in the case of building facades provided with
corresponding plasters and paints. These facades discolor as a
result of the growth of the microorganisms and therefore require a
new surface treatment after just a relatively short time, depending
on the weathering situation.
[0003] On the one hand this affects those masonry coatings whose pH
is in a range that allows the microorganisms to grow. The coating
systems in question here are normally synthetic-resin-bound coating
systems.
[0004] On the other hand, however, it also applies to
silicate-bound plasters or paints. It is true that the pH of such
systems is often in such a high range, owing to the high fraction
of alkaline compounds, that initially there is no infestation by
the microorganisms. Dispersion-based silicate coatings have a pH of
from 11 to 11.5 when applied to a masonry construction. Pure
silicate coatings or cementitious systems frequently have an even
higher pH.
[0005] However, these high pH values subside over the course of
time. This occurs on the one hand owing to neutralization of
alkaline constituents of the coating material by atmospheric carbon
dioxide. On the other hand, however, there are apparently further
causes of microorganism infestation even in the case of strongly
alkaline coatings. In recent times more and more cases have arisen
in which, despite an alkaline coating on building facades,
overgrowth by algae or fungi, for example, occurs after just a
relatively short time. One possible cause of this might lie in the
use of increasingly thicker or increasingly higher-quality heat
insulation materials which are fitted to the building facades
beneath the coatings, partly as a consequence of new heat
insulation provisions. The improved insulation reduces heat
exchange between the interior of the building and the outer surface
of the coating. This promotes condensation and retards the drying
of the exterior coating (see J. P. Blaich, "Die Gebaudehulle" [The
building shell], Fraunhofer IRB Verlag, pages 46 to 58, especially
pages 48 to 50, section 3, "Tauwasserniederschlag"
[Condensation]).
[0006] The better the thermal insulation of a building facade the
more quickly, and the greater the period of time, for which the
temperature will fall below the dew point there. The consequence of
this is the promotion of leaching of alkaline constituents from the
surface of the facade, whose pH consequently falls more rapidly
into a relatively lower range, in which the plaster or the paint
again allows microorganisms to grow. At the same time, owing to the
relatively long moisture cycles, there is also an increase in the
extent of infestation.
[0007] EP 1108824 A1 discloses a building material comprising
microcapsules containing hinokitiol as active substance. Said
active substance is intended to emerge from the microcapsules over
a prolonged period of time and to spread within the building
material in order thus to eliminate, for example, microbes and
bacteria. Hinokitiol is inadequate as a biocide for specifically
suppressing the growth of algae and fungi on building facades to a
sufficient extent.
[0008] EP 0758633 B1 describes porous granules which are loaded
with chemical substances in such a way as to act as a store for
these substances and to release them slowly. An example of one such
chemical substance is a biocide. The material of the granules can,
for example, be a porous ceramic material.
[0009] DE 432-4315 A1 reports on a final-coat plaster composition
which can where appropriate include an added biocide. In no way,
however, is this biocide protected from decomposition.
[0010] It is an object of the invention to specify a coating
material, in particular a plaster or paint, for protection against
microorganism infestation on surfaces exposed to the effects of
damp or water. The aim here is that microorganism infestation
should be retarded or prevented even when on the surface that is to
be protected an initially high pH falls in the course of time.
[0011] This object is achieved by the invention by means of a
coating material of the type specified at the outset which is
characterized in that the coating material comprises a biocide
which is bound in a carrier material composed of particulate solids
and is released retardedly therefrom.
[0012] In accordance with a first embodiment the coating material
of the invention has a pH of at least 11. This has the advantage
that, following application to the surface that is to be protected,
the coating material, by virtue of its alkaline-range pH, initially
halts the growth of microorganisms, particularly of algae and
fungi. A further advantage is that when over the course of time, as
a result of the effect of atmospheric carbon dioxide and also of
condensation and rainwater, the alkaline constituents of the
coating material become more and more neutralized and are leached
from the coating material, and the pH of the material reduced as a
result would allow microorganisms to grow again, the carrier
material used in accordance with the invention gradually releases
the biocide it contains and so prevents further growth of the
microorganisms. All in all, therefore, the coating material
maintains a flawless appearance of the surface that is to be
protected, and does so for a relatively long time. Absent the
invention, a silicate-bound coating material, which by its nature
has a relatively high pH, could not be provided from the start with
a biocide mixed in in the usual way, since the biocide would be
decomposed in the strongly alkaline environment. Additionally,
absent the invention, such a coating material would also lose its
biocidal activity within a relatively short time, through leaching
of the alkaline constituents, and would again allow algal or fungal
growth.
[0013] In accordance with a second embodiment of the invention the
coating material may also have a pH of well below 11.0, such as a
pH of 8.5. In that case it is envisaged for application to a
strongly alkaline substrate, e.g., to concrete or to the
cement-bound reinforcing plaster of an exterior insulation and
finishing system. In this case, alkaline compounds gradually
penetrate from the substrate material into the coating containing
the biocide, and as a result of the increase in pH would normally
decompose an unprotected biocide therein. This would be the case,
for example, if the coating were applied to the strongly alkaline
substrate before its pH had fallen, as a result of atmospheric
carbon dioxide, to a level at which the biocide remains stable. In
the case of isothiazolinones as active biocidal substances, for
example, the pH would have to fall to about 4 to 9.
[0014] If in such a case, namely that of a strongly alkaline
substrate, the biocide were to be added to the coating in
conventional manner, i.e., without the particulate-solids carrier
material used in accordance with the invention, as is the case, for
example, with known synthetic-resin-bound plasters and paints, the
biocidal effect achieved would be inadequate, or there would be
none at all. The reason is that the strongly alkaline constituents
penetrating the coating from the substrate decompose the biocide
and/or convert it into a soluble form. The substances produced in
this process no longer have a biocidal effect and/or are rapidly
leached. Since only a few biocides with high stability in the
strongly alkaline range are known, and in this range, therefore,
the activity spectrum with respect to microorganisms is greatly
restricted, the invention provides a substantial improvement in
this respect.
[0015] The coating material of the invention is preferably a
silicate-bound or mineral plaster having a pH of at least 11 or a
synthetic-resin-bound or silicone-resin-bound plaster having a pH
of below 11.
[0016] In addition it is preferable for the coating material to be
a silicate-bound paint having a pH of at least 11 or a
synthetic-resin-bound or silicone-resin-bound paint having a pH of
below 11.
[0017] In accordance with the microorganisms which occur primarily
in the environment of plasters and paints, it is preferred in
accordance with the invention for the biocide to be a fungicide, an
algaecide or a combination of the two. It is also possible here to
use more than two biocides simultaneously.
[0018] Fungicides preferred in the context of the invention are
isothiazolinones, carbamates, pyrithiones, aldehydes, ketones,
quinones, amines, amidines, guanidines, hydrazo and azo compounds,
aromatic carbonitriles, carboxylic esters, carboxamides and
carboximides, benzimidazoles, quinoxalines, imidazoles, triazoles,
pyrimidines, triazines, halogenated and nitrated alcohols and
phenols, perhaloalkyl mercaptan derivatives, phosphoric and
phosphonic esters, tetrahydro-1,3,5-thiadiazinethiones,
thiocyanates and isothiocyanates, thiophenes, antibiotics, and
active plant substances. Specific examples of fungicides highly
suitable in accordance with the invention are methyl
1H-benzimidazol-2-ylcarbamate (carbendazim), 2-pyridinethiol
1-oxide zinc (zinc pyrithione), 2-n-octylisothiazolin-3-one (OIT),
4,5-dichloro-octylisothiazolin-3-one (DCOIT), and 3-iodo-2-propynyl
N-butylcarbamate (IPBC).
[0019] Algicides preferred in the context of the invention are
triazines, N,N-dimethylureas, and uracils. Specific examples of
algicides highly suitable in accordance with the invention are
N.sup.2-t-butyl-N.sup.4-ethyl-6-methylthio-1,3,5-triazine-2,4-diyldiamine
(terbutryn), 2-chloro-4,6-bis(isopropylamino)-s-triazine,
2-t-butylamino-4-ethylamino-6-methoxy-s-triazine,
2-methylthio-4-butylamino-6-cyclopropylamino-s-triazine,
4-butylamino-2-chloro-6-ethylamino-s-triazine,
3-(4-isopropylphenyl)-1,1-dimethylurea,
N'-(3,4-dichlorophenyl)-N,N-dimethylurea, and
3-t-butyl-5-chloro-6-methyluracil.
[0020] The particulate solids of the carrier material are
preferably granular particles with cavities.
[0021] It is advantageous for these granular particles to be in the
form of microcapsules. Within these microcapsules the biocides are
enclosed in a finely dispersed, liquid or solid phase. Suitable
wall materials for the microcapsules include a very wide variety of
substances: natural, semisynthetic, and synthetic materials.
[0022] Natural materials preferred in the context of the invention
for the microcapsule walls are gum arabic, agar, agarose,
maltodextrin, sodium alginate, calcium alginate, dextran, fats,
fatty acids, cetyl alcohol, milk solids, molasses, gelatine,
gluten, albumin, shellac, starches, caseinates, stearins, sucrose,
and also waxes, such as beeswax, carnauba wax, and spermaceti
wax.
[0023] Preferred semisynthetic materials for the microcapsule walls
are cellulose acetate, cellulose acetate butyrate, cellulose
acetate phthalate, cellulose nitrate, ethylcellulose,
hydroxypropylcellulose, hydroxypropylmethyl-cellulose,
hydroxypropylmethylcellulose phthalate, methyl-cellulose, sodium
carboxymethylcellulose, hydrogenated tallow, myristyl alcohol,
glyceryl mono- or dipalmitate, hydrogenated castor oil, glyceryl
mono- or tristearates, and 12-hydroxystearyl alcohol.
[0024] Preferred synthetic materials for the microcapsule walls are
formaldehyde-melamine resins, acrylic polymers and copolymers, such
as polyacrylamide, polyalkyl cyanoacrylate, and poly(ethylene-vinyl
acetate), aluminum monostearate, carboxyvinyl polymers, polyamides,
poly(methyl vinyl ether-maleic anhydride), poly(adipyl-L-lysine),
polycarbonates, polyterephthalamide, poly(vinyl acetate phthalate),
poly(terephthaloyl-L-lysine), polyaryl sulfones, poly(methyl
methacrylate), poly(.epsilon.-caprolactone), polyvinylpyrrolidone,
polydimethylsiloxane, polyoxyethylenes, polyesters, polyglycolic
acid, polylactic acid and copolymers thereof, polyglutamic acid,
polylysine, polystyrene, poly(styrene-acrylonitrile), polyimides,
and polyvinyl alcohol.
[0025] Particularly preferred microcapsule wall materials are
formaldehyde-melamine resins. The microcapsule walls may also be
composed of two or more of the aforementioned materials.
[0026] There are numerous known methods of preparing the
microcapsules used as carrier material in the context of the
invention (see, for example, C. A. Finch, R. Bodmeier,
Microencapsulation, Ullmann's Encyclopedia of Industrial Chemistry,
6th Edition 2001, Electronic Release). The appropriate method in
each case can be selected in accordance with the desired biocide
and the microcapsule wall material to be employed.
[0027] It is also advantageous if the granular particles with
cavities that are used are particles whose cavities are, for
example, pores formed by foaming of the material, as in the case of
a foamed ceramic material or in the case of expanded clay, or if
the cavities are structural cavities, such as are present in
zeolites.
[0028] Suitable granular particles in the form of a foamed ceramic
material, and a variety of methods of preparing them, are known
from EP 0758633 B1, for example. Further carrier materials, such as
zeolites, are described in DE 4337844 A1.
[0029] The aforementioned particulate solids of the carrier
material, e.g., as microcapsules, foamed ceramic material, zeolite,
and the like, preferably have a size in the range from 30 to 40
.mu.m.
[0030] In addition to the above-mentioned biocides and the
materials for the microcapsule walls or for the porous granules,
the coating material of the invention may include any substances
which are commonly known and conventional in dependence on the
intended use of the material. This includes, on the one hand, the
corresponding binders and film formers, such as polyacrylates,
polystyrene acrylates or silicone resins, and, on the other hand,
the known auxiliaries, such as pigments, fillers, solvents,
thickeners, defoamers, plasticizers, dispersants, emulsifiers, and
agents for adjusting the pH of the coating material.
[0031] The examples illustrate the invention.
[0032] Preparation Examples 1 to 3 illustrate the preparation of
microcapsules in which an active biocidal substance is
enclosed.
[0033] Preparation Example 4 illustrates the preparation of a
silicate-bound exterior plaster, Preparation Example 5 that of a
synthetic-resin-bound float plaster.
[0034] Inventive Examples 1 to 4 and Comparative Examples 1 to 4
elucidate the superior stability of the plasters of the invention
with respect to leaching of the biocide they contain.
[0035] Inventive Examples 5 and 6 and Comparative Examples 5 to 7
elucidate the growth of fungi on different plaster surfaces and the
advantage achieved by the invention.
PREPARATION EXAMPLE 1
[0036] The substances indicated below were used to prepare
microcapsules enclosing zinc pyrithione (2-pyridinethiol 1-oxide
zinc) as active biocidal substance.
TABLE-US-00001 Substances used Amounts, g Water 389.6 Polyacrylate
1.5 (Coatex BR 3, Dimed) Gum arabic 0.6 Silicone defoamer 0.3
(Aspumit AP, Thor GmbH) Zinc pyrithione powder 60.0 Concentrated
hydrochloric acid 4.0 Formaldehyde-melamine resin 144.0 (Quecodur
DMQ, Thor GmbH) 600.0
[0037] For the preparation of the microcapsules the water was
introduced first. Polyacrylate, gum arabic, silicone defoamer and
the zinc pyrithione were stirred into the water. The resultant
mixture was adjusted with hydrochloric acid to a pH of 3 and then
heated to a temperature of 70.degree. C. Subsequently the
formaldehyde-melamine resin was added dropwise over 1 h. The
mixture was subsequently stirred at the same temperature for a
further 2 h.
[0038] The mixture obtained comprised the desired microcapsules and
was used unchanged in preparing the microcapsule plaster.
PREPARATION EXAMPLE 2
[0039] The substances indicated below were used to prepare
microcapsules enclosing DCOIT
(4,5-dichloro-2-octylisothiazolin-3-one) as active biocidal
substance.
TABLE-US-00002 Substances used Amounts, g Water 389.6 Polyacrylate
1.5 (Coatex BR 3, Dimed) Gum arabic 0.6 Silicone defoamer 0.3
(Aspumit AP, Thor GmbH) DCOIT, 98% form 60.0 Concentrated
hydrochloric acid 4.0 Formaldehyde-melamine resin 144.0 (Quecodur
DMQ, Thor GmbH) 600.0
[0040] For the preparation of the microcapsules the water was
introduced first. Polyacrylate, gum arabic, silicone defoamer and
the zinc pyrithione were stirred into the water. The resultant
mixture was adjusted with hydrochloric acid to a pH of 3 and then
heated to a temperature of 70.degree. C. Subsequently the
formaldehyde-melamine resin was added dropwise over 1 h. The
mixture was subsequently stirred at the same temperature for a
further 2 h.
[0041] The mixture obtained comprised the desired microcapsules and
was used unchanged in preparing the microcapsule plaster.
PREPARATION EXAMPLE 3
[0042] The substances indicated below were used to prepare
microcapsules enclosing IPBC (3-iodo-2-propynyl N-butylcarbamate)
as active biocidal substance.
TABLE-US-00003 Substances used Amounts, g Water 338.4 Gum arabic
0.6 Silicone defoamer 3.0 (Aspumit AP, Thor GmbH) IPBC, 50% aqueous
132.0 dispersion (Acticide IPW 50, Thor GmbH) Citric acid, 12% 60.0
Formaldehyde-melamine resin 66.0 (Quecodur DMQ, Thor GmbH)
600.0
[0043] For the preparation of the microcapsules the water was
introduced first. Polyacrylate, gum arabic, silicone defoamer and
IPBC dispersion were stirred into the water. Subsequently the
mixture was adjusted with the citric acid to a pH of 1 to 2 and
heated to a temperature of 55 to 60.degree. C. Then the
formaldehyde-melamine resin was added dropwise over 1 h.
Subsequently the mixture was stirred at 55 to 60.degree. C. for 2
h.
[0044] The mixture obtained comprised the desired microcapsules and
was used unchanged in preparing the microcapsule plaster.
PREPARATION EXAMPLE 4
[0045] A silicate-bound white exterior plaster with a grain size of
1.5 to 2 mm was prepared. Prepared first of all was a premix, which
was then processed further to form a final mix, i.e., the
plaster.
a) Premix
[0046] The following substances are mixed for 15 minutes in order
to achieve integration or dissolution.
TABLE-US-00004 % by weight Water 9.3 Dispersant (Sapetin D 20) 0.1
Silicate stabilizer (Betolin Quart 20) 0.3 Rheological additive
(Rhodopol 50 MD) 0.1 Titanium dioxide (Bayertitan R-KB-5) 3.0
Defoamer (TEGO-Foamex KS 10) 0.2
[0047] The following substances are added with stirring to the
mixture obtained:
TABLE-US-00005 % by weight Styrene-acrylate copolymer dispersion,
6.0 50% by weight (Mowilith SDM 765 A) Al Mg silicate, D 50 300
.mu.m 2.5 (Plastorit 05) Reinforcing fiber filler 0.5 (Arbocel B
400) Calcium carbonate, D 50 5 .mu.m 4.0 (Omyacarb 5-GU) Calcium
carbonate, D 50 7 .mu.m 5.0 (Omyacarb 10-GU) Calcium carbonate, D
50 23 .mu.m 10.0 (Omyacarb 40-GU)
[0048] The following substances were added in succession with
stirring to the mixture obtained:
TABLE-US-00006 % by weight Hydrophobicizer 0.5 (TEGO Phobe 1040)
Additive to prevent surface cracking 0.5 (Lubranil A 1520)
Stabilized potassium silicate 10.0 (waterglass, Betolin P 35, 29%
by weight)
b) Final Mix
[0049] The premix indicated above under a) was aged for 3 days.
Then the following substances were mixed in with slow stirring:
TABLE-US-00007 % by weight Calcium carbonate, D 50, 160 .mu.m 11.0
(Omyacarb 130-GU) Calcium carbonate grains, D 50 1200 .mu.m 37.0
(Austro-tec 10/15)
[0050] The total amount of the quantities indicated above for the
premix and the final mix makes 100.0% by weight.
[0051] The finished final mix was the exterior plaster. The
biocides were then each mixed into this plaster in accordance with
the examples below.
PREPARATION EXAMPLE 5
[0052] A synthetic-resin-bound white float plaster was prepared in
conventional manner from the following substances.
TABLE-US-00008 % by weight Polyacrylate 13.2 (Acronal 290 D, BASF
AG) Sodium polyphosphate, 0.8 25% strength solution Preservative
0.3 (Acticide MBS, Thor GmbH) Defoamer 0.3 (Agitan 280) Thickener,
polyacrylate, 0.8 8% strength ammoniacal solution (Latekoll D, BASF
AG) White spirit 1.0 (180-210.degree. C.) Butyl diglycol 1.0
Basophob WDS (BASF AG) 0.6 Titanium dioxide, rutile 2.8 (Kronos
2044, Kronos Titan GmbH) Calcium carbonate 39.5 (Omyacarb 40-GU)
Calcium carbonate 25.5 (Omyacarb 130-GU) Al Mg silicate 6.5
(Plastorit 05) Quartz shingle 4.5 Water 3.2 100.0
[0053] The float plaster obtained had a pH of from 8.5 to 9.
INVENTIVE EXAMPLE 1 AND COMPARATIVE EXAMPLE 1
[0054] The microcapsule-containing mixture of Preparation Example 1
was added to the synthetic-resin-bound plaster obtained in
Preparation Example 5, which has a pH of 8.5. The amount of biocide
in the plaster was 578 ppm.
[0055] The plaster biocidally treated in this way was used to
produce test specimens in the form of plaster disks for the water
storage tests. For this purpose the plaster was coated into a
circular plastic mold having a diameter of about 5 cm and a depth
of 3 mm. The coat thickness corresponded to the grain size of the
plaster. The plaster sample was then dried and fully cured.
Thereafter the test specimen was removed from the mold and
conditioned for the water storage test.
[0056] For comparison, plaster disks which differ from the above
samples only in that the zinc pyrithione had been mixed into the
plaster not in microencapsulated form but instead in normal powder
form were produced.
[0057] For each sample, the amount of zinc pyrithione in the
plaster before and after water storage for various periods of time
was measured.
[0058] The samples were subjected to static water storage in 1 l of
DIBT solution, the solution being replaced completely every 24 h
with the exception of the 7th day.
[0059] The DIBT solution is an alkaline solution specified by the
Deutsches Institut fur Bautechnik (DIBT) [German Institute of
Construction Engineering] for the water storage of samples. The
solution has a pH of 12.5 and is composed of the following
substances:
TABLE-US-00009 Sodium hydroxide 0.88 g Potassium hydroxide 3.45 g
Calcium hydroxide 0.48 g Water remainder to 1 l
[0060] The results are reported below.
TABLE-US-00010 Residual biocide in plaster (pH 8.5), ppm Storage in
DIBT solution, days None 2 5 10 Inventive Example 1 578 478 259 187
Comparative 560 21 4 0 Example 1
INVENTIVE EXAMPLE 2 AND COMPARATIVE EXAMPLE 2
[0061] Inventive Example 1 and Comparative Example 1 were repeated
but with the modification that now the silicate-bound float plaster
of Preparation Example 5, with a pH of 11.5, was used and storage
in water took place for 1, 2 and 7 days.
[0062] The results are reported below.
TABLE-US-00011 Residual biocide in plaster (pH 11.5), ppm Storage
in water, days None 2 5 10 Inventive Example 2 531 423 325 21
Comparative Example 2 568 2 0 0
INVENTIVE EXAMPLE 3 AND COMPARATIVE EXAMPLE 3
[0063] Inventive Example 1 and Comparative Example 1 were
essentially repeated, but with certain modifications. These were to
the effect that, instead of the zinc pyrithione microcapsules
obtained in accordance with Preparation Example 1, the
microcapsules containing DCOIT as active biocidal substance,
obtained in accordance with Preparation Example 2, were now used,
and instead of water storage the samples were heated at a
temperature of 54.degree. C. for 4 weeks. The silicate-bound
plaster of Preparation Example 4 was used, with a pH of 11.5.
[0064] The results are reported below.
TABLE-US-00012 Residual biocide in plaster (pH 11.5), and biocide
degradation after heat treatment at 54.degree. C. Heat treatment,
ppm None 4 weeks Degradation, % Inventive Example 3 508 474 6.7
Comparative Example 3 521 382 26.7
INVENTIVE EXAMPLE 4 AND COMPARATIVE EXAMPLE 4
[0065] Inventive Example 3 and Comparative Example 3 were repeated,
but with the modification that instead of the microcapsules of
Preparation Example 2, containing DCOIT, the microcapsules of
Preparation Example 3, containing IPBC, were now used.
[0066] The results are reported below.
TABLE-US-00013 Residual biocide in plaster (pH 11.5), and biocide
degradation after heat treatment at 54.degree. C. Heat treatment,
ppm None 4 weeks Degradation, % Inventive Example 4 280 256 8.6
Comparative Example 4 291 211 27.5
INVENTIVE EXAMPLES 5 AND 6 AND COMPARATIVE EXAMPLES 5, 6 AND 7
[0067] Fungal growth on the sample surface was investigated.
[0068] The silicate-bound plaster of Preparation Example 4, applied
to a support plate, was either biocide-free (Comparative Example 5)
or was admixed with 100 ppm of zinc pyrithione (Comparative Example
6), 200 ppm of zinc pyrithione (Comparative Example 7), 100 ppm of
microencapsulated zinc pyrithione (Inventive Example 5) or 200 ppm
of microencapsulated zinc pyrithione (Inventive Example 6).
[0069] The plaster samples were applied as a coat to calcium
silicate plates which measured 4.5 cm.times.9 cm and have undergone
water storage beforehand. The coat thickness of the plaster was
within the order of magnitude of its grain size, i.e., from 1.5 to
2 mm.
[0070] After the samples had cured, they were subjected to water
storage as in Inventive Example 1.
[0071] The test for fungal growth took place as follows:
[0072] The plaster samples were poured into a conventional agar
nutrient medium. Thereafter the samples were sprayed with a fungal
spore suspension. The suspension contained equal proportions of the
following test organisms: [0073] Alternaria alternata [0074]
Aspergillus niger [0075] Cladosporium cladosporoides [0076]
Penicillium funiculosum [0077] Ulocladium atrum
[0078] The total concentration of the fungal inoculum was 10.sup.6
spores/ml.
[0079] The samples were stored in the usual way over a relatively
long period of time under growth conditions optimum for fungi.
Thereafter the fungal growth on the sample surface was
evaluated.
[0080] The fungal growth on the sample surface was evaluated using
the following scale:
TABLE-US-00014 Growth rate Fungal growth 0 No growth visible x
Minimal growth (up to 25% surface coverage) xx Slight growth (up to
50% surface coverage) xxx Moderate growth (up to 75% surface
coverage) xxxx Severe growth (up to 100% surface coverage)
[0081] The results of the fungal growth test for the samples
investigated are reported below.
TABLE-US-00015 Fungal growth on the surface of the plaster (pH
11-12) without/with zinc pyrithione Zinc pyrithione Water storage
ppm None 2 days 5 days Comparative Example 5 0 xxx xxxx xxx
Comparative Example 6 100 x x xxx Comparative Example 7 200 0 x xx
Inventive Example 5 100 (encapsulated) 0 0 0 Inventive Example 6
200 (encapsulated) 0 0 0
* * * * *