Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1999-01-11
2001-10-30
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C106S002000, C106S038220, C106S287130, C106S287140, C106S287150, C106S287160, C264S333000, C264S338000
Reexamination Certificate
active
06309577
ABSTRACT:
The present invention relates to a process for moulding and rendering water-repellent building materials, such as moulded components made of concrete, mortar, cement or terracotta, for example tiles or bricks. Another subject-matter of the invention is the moulded objects thus obtained, as well as compositions for removing from the mould and rendering water-repellent.
Modern structures very often make use of moulded components made of concrete or mortar. These components can be moulded on site or prefabricated in specialized plants, with or without heating the item in an oven in order to accelerate its drying.
In order to facilitate removal from the mould and to minimize the defects which these items can contain, the moulds generally have a wash applied to them comprising a substance called a mould-release agent. Good removal from the mould is particularly important because it avoids the cost of correcting the defects, a cost which can reach up to 15% of the cost of the building shell. The mould-release agents are generally mineral oils, whereas the moulds are generally made of steel, of wood or of plastic. Silicone resins are rarely used because of their high cost.
Once put in place, in particular when they constitute building facades, these items are generally protected from the damage caused by moisture (rain, mist, and the like) by a water-repellent treatment. This operation of rendering water-repellent is expensive because of the manpower cost and the scaffolding cost.
Provision has already been made in the past for compositions given as facilitating removal from the mould and, at the same time, rendering water-repellent the items thus moulded. This relates to Patent Application FR-A-2,231,488, which provides for the application, to the surfaces of the moulds, of a mixture composed of water-repellent curable organosilicon compounds, finely divided solid inorganic matter and, optionally, solvents. Repeating the examples of this application has made it possible to obtain satisfactory water-repellency of the moulded product but has not made it possible to obtain good removal from the mould, the surface of the moulded item exhibiting pits as well as numerous off-white blemishes.
Patent Application FR-A-2,474,518 also discloses a composition based on silicone resins which can be crosslinked at ambient temperature in the presence of moisture, making it possible to obtain a non-stick water-repellent film which is easy to detach and which is resistant to staining. This composition can be used in a great many applications, for example as coating agent for separation or removal from the mould or as agent for coating the surface of materials to be protected from the light, from air, from water, and the like. It can be applied in particular to cement, concrete, brick, tile and slate, as well as to structures such as bridges and buildings. However, this document does not provide for simultaneously removing from the mould and rendering water-repellent moulded building components.
In addition, as regards the application with which the present invention is concerned, the composition according to this document cannot be applied on a large scale for reasons of cost. This is because this complex composition is composed of a mixture
a) of an organopolysiloxane resin,
b) of an &agr;,&ohgr;-dihydroxydiorganopolysiloxane,
c) of a crosslinking agent based on an organosilane containing hydrolysable functional group(s) or its partial condensation and/or hydrolysis product, which is used to cure the composition at ambient temperature.
In addition, a curing catalyst can also be provided.
The object of the present invention is to provide a novel process which makes it possible simultaneously to removal from the mould and to render water-repellent moulded components made of concrete, mortar, cement and the like, which makes it possible both faultlessly to remove the moulded components from the mould and to render them water-repellent under conditions which are entirely satisfactory, while observing the economic criteria which have to be observed in this type of activity.
More specifically, the object of the invention is to render economically acceptable the use of silicone resins for removing building components from the mould by providing a simple composition which provides fully for both removal from the mould and for rendering water-repellent.
These objects are achieved in accordance with the invention by a process based very carefully on the ability of concrete, mortar, cement and the like, by their alkaline nature, to themselves provide for the curing of the silicone resin according to the invention.
The subject-matter of the present invention is thus a process for simultaneously moulding and rendering water-repellent moulded components made of concrete, mortar, cement or the like, characterized in that, before pouring the concrete, mortar, cement or the like, the interior of the mould is covered with a composition comprising a resin which is a silicone copolymer of following formula (I):
M
&agr;
D
&bgr;
T
&ggr;
Q
&dgr;
(OR)
&egr;
(I)
where:
M=R
1
R
2
R
3
SiO
½
D=R
4
R
5
SiO
2/2
T=R
6
SiO
3/2
Q=SiO
4/2
R
1
, R
2
, R
3
, R
4
, R
5
and R
6
, which are identical to or different from one another, each represent a C
1
-C
12
and more particularly a C
1
-C
8
hydrocarbon-comprising residue;
R is a hydrogen atom or a linear or branched C
1
-C
4
alkyl radical;
the copolymer exhibits, in its structure, at least one T or Q unit;
the &agr;, &bgr;, &ggr; and &dgr; symbols represent the molar fractions (or the proportion by number) of the silicon atoms respectively of M, D, T and Q types for one silicon atom; the &egr; symbol represents the molar fraction (or the proportion by number) of the ≡SiOR ends per silicon atom; these symbols varying within the following ranges:
&agr;: 0-0.5
&bgr;: 0-0.95
&ggr;: 0-0.9
&dgr;: 0-0.8
&egr;: 0.05-2
with &agr;+&bgr;+&ggr;+&dgr;=1
in the absence of crosslinking agent of hydrolysable silane type and of curing catalyst in the composition.
The M units, when there are several of them, can be identical to or different from one another; the same comment also applies to the D and T units.
According to a preferred embodiment of the invention, the resin is a copolymer of formula (I) where:
R
1
to R
6
, which are identical to or different from one another, each represent a linear or branched C
1
-C
8
alkyl radical;
the copolymer exhibits, in its structure, at least one T unit, the &dgr; symbol then being a number other than zero;
at least 25% by number of one or more of the R
1
to R
6
substituents represent a linear or branched C
3
-C
8
alkyl radical.
More preferably, the copolymer is of type:
D
&bgr;
T
&ggr;
(OR)
&egr;
where:
R
4
to R
6
, which are identical to or different from one another, each represent a linear or branched C
1
-C
8
alkyl radical;
at least 25% by number of one or more of the R
4
to R
6
substituents represent a linear or branched C
3
-C
8
alkyl radical;
&bgr;: 0.2-0.9
&ggr;: 0.1-0.8
&egr;: 0.2-1.5.
More preferably still, the copolymer is of type:
D
&bgr;
T
&ggr;
(OR)
&egr;
where:
R
4
and R
5
, which are identical to or different from one another, each represent a linear or branched C
1
-C
2
alkyl radical;
R
6
, which are identical to or different from one another, each represent a linear or branched C
3
-C
8
alkyl radical;
R is a hydrogen atom or a linear C
1
-C
3
alkyl radical;
&bgr;: 0.2-0.6
&ggr;: 0.4-0.8
&egr;: 0.3-1.0.
Generally, each of the R
1
to R
6
radicals can be a linear or branched alkyl radical, for example methyl, ethyl, propyl, butyl or isobutyl; and alkenyl radical, such as, for example, vinyl; an aryl radical, for example phenyl or naphthyl; an arylalkyl radical, such as, for example, benzyl or phenylethyl; an alkylaryl radical, such as, for example, tolyl or xylyl; or an araryl radical, such as biphenylyl.
The silicone copolymer according to the invention is sufficient by itself to provide simultaneously for the faultless removal from the
Garcin Eric
Goubet Sandrine
Rhodia Chimie
Seugnet Jean-Louis
Vargot Mathieu D.
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