The present invention relates to a process for the productipn of
variously decorated plastered structural and/or decorative elements, in particular
for the building field, such as covering panels, false ceilings, partitions and
the like, with excellent characteristics of stability to light and weathering
and polluting agents, as well as of mechanical strength.
The present invention also relates to the so obtained structural
and decorative plastered elements.
The decoration or painting of mortar plasters, utilized especially
in the building field, is usually carried out according to known decoration and
coloring techniques, such as brush or spray or roll varnishing or painting directly
coated on walls.
On panels having also complex size and sections composed of concrete
or mortars obtained as coatings on any materials, the decoration and painting
techniques range from silk-screen techniques, known also in ceramics, to the more
recent painting techniques making use of photomechanical processes or the like.
The characteristic shared by these techniques is that of allowing
the decoration and the painting on the surface of the mortar plaster by operating
directly on the surface of the same once the artifact has been obtained either
in the form of a wall or a panel covering.
The paints adhere to the surface of the plaster, restraining all
the process and resistance limits to the environment conditions, well known to
everybody as deteriorating even art masterpieces.
Object of the present invention is to realize a process for the production
of plastered and decorated panels, partitions, door and window frames, false ceilings
and the like, to be used as structural and decorative elements in the building
field, for internal fittings, town-fittings, and the like.
Another object of the invention is to realize a process for the production
of plastered panels and the like for the building field and fittings in general,
said panels bearing a decoration resistant to weathering and light as well as to
mechanical stresses, such as bending, impacts, etc.
A further object is to provide plastered structural elements for
the building field and fittings bearing multi-color decorations and also "antique-imitation"
decorations, i.e. decorations that imitate and/or reproduce paintings realized
in ancient times, as they appear at present.
These and still other objects and related advantages that will be
apparent from the following description are achieved by a process for the realization
of structural and/or decorating elements for the building field, internal fittings,
town-fittings, such as panels, partitions, door and window frames, false ceilings
and the like, bearing one- or multi-color decorations, which process, according
to the present invention, consists in the transfer and incorporation in a plaster
layer coated on a backing from rigid or semi-rigid material a sublimable color
decoration employing the transfer decoration technique.
As is known, the transfer decoration technique consists in the transfer
of a decoration realized with sublimable colors on a flexible backing such as
paper, fabric, plastics or the like, from said backing to the article to be decorated
by means of the combined action of pressure and temperature applied to the flexible
backing, which is caused to adhere to the article by suitable means, as described
for instance in the European Patent no. 0817728 owned by the same applicant, as
well as by FR 2203321, EP 544603, etc.
More particularly, said process comprises the following steps:
- submitting said backing from rigid or semi-rigid material to one or more degreasing,
cleaning, surface conversion treatments, and anti-corrosion treatments in the
case of metals, and anodizing in case of aluminum and alloys thereof;
- submitting said so treated backing to one or more operations of pre-painting
with colored paints, either opaque or transparent, suitable to form a primer base
- transferring on said treated and pre-painted backing a preparatory decoration
with sublimable colors from a suitable flexible backing, by means of the transfer
- coating said sublimable color decoration transferred on said backing with a
plaster mortar layer;
- submitting to drying and heating said backing comprising said decoration and
said layer of plaster mortar, according to a pre-fixed program, with ensuing hardening
of said plaster and diffusion, surfacing and curing of said decoration on the
surface of said hardened plaster.
The material which said rigid or semi-rigid backing is made from
is selected from among ferrous metals, non-ferrous metals and light alloys, marble,
stone, ceramics, bricks, cement type materials, glass, wood plates, and wood derivatives,
special plastic materials and composites.
Said backing from rigid or semi-rigid material may be in the form
of sheets, slabs, tubes, tapes, sections or the like, and may have a size of up
to 8000x2000 mm. In general, any material may be used, provided it is resistant
to temperatures of up to 250°C, i.e. the temperatures at which the sublimable
color transfer operations are carried out.
The sublimation transfer of the preparatory decoration to the surface
of the rigid backing may be carried out by means of processes and apparatuses
such as: a press with a flat compressing element, a calender, a two-frame press
with flexible and impermeable membranes, plus vacuum utilization, a sucking rigid
platen with a flexible and impermeable membrane, plus vacuum utilization, a sucking
platen or impermeable plastic films bearing the decoration to be transferred,
utilized in combination with vacuum and without contact elastic membranes. Said
films are of the heat-formable type and of the heat-retractable type. These films
are available in the form of tubes, tapes and sheets. Besides, also silicone rubber
tubes may be utilized wherein the backings to be decorated may be inserted wrapped
up in papers, yielding fabrics bearing the preparatory pattern to be transferred,
also in this case in combination with vacuum.
The conditions of the transfer process for the preparatory decoration
may be the following:
- a temperature from 150°C to 230°C,
- a time from 30 sec. to 30',
- a pressure from 0,1 Ate to 7 Ate.
Plaster is a plastic mixture of various inorganic and organic ingredients
and binders with water, that hardens upon drying and heating and the various chemical
reactions that occur between the various ingredients and binders, creating a cured
and hardened layer.
The plaster according to the invention may be coated on the backing
by roll, brush, knife, trowel, spray or other coating means.
The thickness may be obtained by one or more layers, and the same
may range from 0,5 mm to about 5 mm.
Once the plaster has been coated on the backing and dried at room
temperature and moisture for a time ranging from 1 hour to 24 hours, the same is
introduced in a hot and dry air oven, finally hardened and dried at a temperature
comprised between 60°C and 250°C for a time comprised between 1' and 30'.
By such treatment, the previously printed preparatory decoration
spreads through the thickness of the plaster, which has a porosity and a permeability
suitable for the purpose. It must allow, in fact, the diffusion of the pigments
through its thickness up to the surface. Besides, the plaster according to the
invention is also very resistant to the formation of fractures, thermal shocks
and the bending of the backing up to very low angles of less than some millimeters.
According to an alternative embodiment of the invention, said step
of submitting to drying and heating said backing comprising said decoration and
said plaster layer is carried out under pressure.
Pressure is applied either by compressing means such as internally
heated rolls or pads that are pressed against the surface of the plaster during
the heating step, or, when the size and shape of the structural elements allow
it, by introducing said element in heated pressurized containers, such as autoclaves
or the like.
Generally, the pressure applied is comprised in the range between
0,1 Ate and 7 Ate.
Surprisingly, it has been found, in fact, that by carrying out the
drying and heating step under pressure, the curing times of plaster and stabilization
of the decoration on the surface of the plaster markedly reduce, up to 20%, with
ensuing additional advantages of productivity and reduction in process costs.
The flow of a sublimation-generated gas that transports the pigments
from the preparatory pattern to the backing surface through the solid porous means,
such as a plaster mortar, is caused, according to the present invention, by the
continuity and motion equations already known and typical of the processes that
describe the passage of a fluid, a liquid or a gas, through a solid porous means,
such as plaster mortar.
The main parameters that must be controlled in the present invention
may be grouped into two main groups:
- a) parameters of the materials: pigments and plaster mortar;
- b) process parameters: temperature and pressure and thickness of the plaster.
- a) The parameters of the pigment material include: viscosity of their gas at
sublimation temperature; specific weight (or density) at sublimation temperature;
the parameters of the plaster mortar material include: porosity (or the actual
surface gone through in their inside, which is given by the void and solid ratio)
which is at the origin of the permeability of the sublimation gas that goes though
it at a given temperature and pressure.
- b) The process parameters include: the temperature associated to the sublimation
transition of the various pigments, the pressure necessary to originate and complete
the sublimation gas flow through the plaster mortar thickness and the thickness
of the plaster mortar that is supposed to be very constant. The plaster surface
is a parameter that is fixed by the size of the equipment, but does not fall directly
within the parameters of the process control. In fact, once the dimensional characteristics
of the artifact to be realized according to the present invention have been fixed,
said characteristics are no longer subject to control.
After several theoretical-experimental verifications to verify the
continuity and motion equations as state equations that control the process of
the present invention, it is possible to synthesize that in practice the basic
relations are the following ones:
1) The basic equation of the motions of a gas through a porous material is reducible
to Darcy's formula:
V = f [Δ P / (Ps&peseta;d)]
- V = infiltration speed (m/s) referred to the gross section (full by void) gone
through by the sublimation gas in the plaster layer);
- Δ P = pressure jump (kg/m2) through the thickness of the entire
- Ps = specific weight (kg/m3) of the gas going through;
- d = thickness (m) of the material gone through;
- f = permeability of the material gone through (m/s) which is obviously bound
to the porosity of the mortar and also to the viscosity of the gas. By way of
example, to have some numerical references, the f value ranges from 2,10-5
m/sec for thin sand having bead diameters of 0,1-0,2 mm to 1x10-2 of
sand containing fine gravel having bead diameters of 1-3 mm.
Relation (1) may be expressed in practical terms also as:
W = Ps&peseta;V = f (Δ P/d)
W = Ps&peseta;V = capacity in weight [kg/ (m2&peseta;sec)] per mortar
surface gone through.
The experiments carried out on the present invention have allowed
to verify that the permeability of plaster mortar for a thickness from 0,2 to
5 mm is the mean of f value = 1,29,10-7 kg/(m2&peseta;sec)
at least with room temperature air (20°C) and pressures from 0,1 Ate to 7 Ate.
The experiments carried out with the same plaster thicknesses of
0,1-5 mm, the same pressures and temperatures in the range 175-250°C, have allowed
to find, instead, that the permeability of plaster mortar reached for the sublimation
gas of pigments a mean f = 1, 6, 10-4 kg/(m2&peseta;sec).
In other words, with respect to Darcy's law (1) it may be said that
the ablative gas of transfer pigments goes through plaster mortar with a permeability
higher by about 3 orders of magnitude.
In order to establish the concept, in the aforementioned conditions,
the mortar thickness of 0,2 mm is gone through by 5 g of ablative gas in 30 sec.
per m2 surface at the temperature of 180°C and for a pressure difference
of 0,7 kg/cm2.
This observation leads to specific considerations on the innovating
nature of the present invention because of the following reasons:
- 1. the permeability is rather high because of the high temperature at which
it takes place;
- 2. the flow of ablative gases goes through the selected plaster thickness until
it surfaces, and a large part of the same is absorbed on the internal surfaces
of the pores.
This may be attributed to the presence in the plaster of polymers
(2% by weight) and carbon fibers (0,3-0,5%). Carbon fibers, in particular, contribute
with their presence both to the porosity of the plaster between their links and
to the increase in porosity, given their intrinsically porous structure.
The inorganic material of the plaster has also a function of activation
of the absorption of the ablative gas such as to facilitate the transfer of dyes.
All these characteristics are at the base of the innovating concepts
of the present invention, and therefore the ablative pigments transferred to the
backing of a plaster operates as a pre-constituted deposit, like one on a paper,
to transfer on the polymerized surface (painted) of the pores of the same plaster
mortar, causing therefore the surfacing of the prefabricated patterns on its external
In particular, it may be inferred from formula (2) that, temperature
being constant, the flow of ablative gases linearly depend on pressure, inversely
proportionally on the thickness of plaster, but especially on its permeability
that depends on the material and especially its porosity and the specific weight
of the ablative gas; permeability is a property of the material, the specific
weight is a property of the ablative gas that, in its turn, depends on the process
The plaster mortar according to the present invention has convenient
porosity values ε through its thickness, and therefore a given permeability
f of the gas coming from the paint system of the preparatory patterns on the backing
surface. Such ablative gas at a given temperature has a determined specific weight
and succeeds in going through mortar porosity by means of an extraction flow caused
by the pressure difference Δρ applied on the plaster surface of the wall
facing the room.
Such flow of ablative air allows to realize the painting on the plaster
The one or multi-color decoration is realized on the plaster layer
according to the invention after having gone through the thickness of said plaster.
The decoration takes place because of the surfacing on the plaster
of colors coming by sublimation from pigments transfer-deposited on the plaster
backing surface and going through the thickness of plaster in the form of a gas
due to sublimation of the same.
Temperature T and pressure P are two variables that depend on the
process and that determine the time necessary and therefore the efficiency of the
Preferably, according to the present invention, said plaster has
a permeability f comprised between 10-4 and 10-7 kg/(m2&peseta;sec).
The intrinsic properties of the plaster mortar according to the present
invention must take into account three types of characteristics:
- a) porosity inter-communicating in the entire volume and suitable as much as
possible to have an intrinsic permeability k necessary to cause the ablative gas
coming from the paints of pigments of the preparatory pattern on the surface of
the plaster backing layer to pass easily. The temperature of the gas flow process
T and room temperature Δp are the process parameters according to formulae
(1) and (2), and have been confirmed by the experiments carried out;
- b) resistance to fracturing for environment reasons due to thermal or vibration
shocks with various levels of humidity and possible deterioration. Because of
the mechanical characteristics of standard mortar plasters, new types of mortars
have been experimented, mixed with special fiber reinforcements (composite technology)
and with plasticizers from plastics that render mortar less mechanically rigid;
- c) mortar must be easy to spray on the backing coating, in spite of its containing
reinforcing elements. from fibers, or anyhow they must have a workability possible
with the standard coating and spreading technologies, as that of the usually employed
plasters. The thickness of mortar must be very constant and comprised between 0,2
and 5 mm, with tolerances lower than 2%.
After several experiments with various mortars, at present the plaster
mortar called "Mighty CF" has proved particularly advantageous; said mortar is
produced by the MIGHTY KAGAKU Company, a Division of MIGHTY CHEMICAL CO, with
headquarters in Japan an has the following composition:
- a composite having as a main component a mixture of finely divided silica white
cement and carbon fibers; the white cement mainly contains calcium oxide, silica
and alumina; silanol groups between the finely divided silica promote the dispersion,
the adhesion on the backing materials and the resistance to corrosion;
- a water-soluble hardening material containing a mixture of cationic acrylic
resin, an anionic acrylic resin and an anti-coagulant agent as nonionic surfactant
to prevent gelling;
- optionally, an actiphenoxypolyethoxy alcohol and a fluorinated resin.
The above plaster mortar had demonstrated sufficient a, b, c properties
and a porosity such as to impart the ablative gas a permeability f that has given
good experimental results as a function of the specific weight of the ablative
gas at given temperatures T and pressures Δp of the experimented process.
Fracturing resistance and cracking resistance are high thanks to
the presence of carbon fibers and confirmed by the fact that no fracturing or
cracking appear on flexible backing panels, such as aluminum and steel panels,
even by 180° radius bending.
Resistance to weathering, UV and humidity with oxidation is similar
to that of standard plaster mortars.
The process according to the present invention is realized also by
utilizing different types of mortar, provided they satisfy the above indicated
According to a variant of the present invention, the process comprises
the following steps:
- possibly submitting said backing from rigid or semi-rigid material to one or
more degreasing, cleaning, possible surface conversion treatments, and anti-corrosion
treatments in the case of metals, possible anodizing in case of aluminum and alloys
- coating said backing with a plaster mortar layer;
- submitting to drying and heating said backing comprising said plaster mortar
layer until said plaster has hardened;
- transferring on the hardened plaster present on said backing a sublimable color
decoration from a suitable flexible backing, by means of the transfer technique.
This variant of the invention allows to simplify to some extent the
process; according to such variant, the diffusion of the pigments that form the
decoration occurs from the outside towards the inside of the plaster layer, instead
of from the inside towards the outside as described above.
Having selected a backing, for instance from aluminum, a transfer
preparatory pattern was deposited, taking care to leave it incomplete in order
to allow a subsequent ablation once the aforementioned mortar composition has been
coated. Such incomplete ablation is a variant of the process.
Also the thickness of the plaster mortar is a variable of the process,
and thicknesses have been selected in the range from 0,2 to 0,5 mm.
The plaster coating was realized by means of a spraying device particularly
suitable to obtain thickness uniformity and surface compactness.
After this operation, the panel is left in an oven, wherein the optimum
temperature and pressure conditions are created. See formula (2) for the transfer
of the preparatory pattern to the plaster surface through its thickness that after
some time appears even in intense colors.
According to the process subject matter of the present invention,
a variously decorated structural and/or decorative element is obtained for use
in the building field, fittings and the like, such as panels, partitions, false
ceiling and the like, which element comprises:
- a rigid or semi-rigid element in the form of a slab, a section or the like;
- a layer of hardened plaster coated on the surface of said backing or part thereof;
- a one or multi-color decoration realized on said plaster by means of sublimable