Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2001-12-07
2004-01-20
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S412000, C428S442000, C428S520000, C428S522000
Reexamination Certificate
active
06680111
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of composite materials and more particularly to composite materials comprising, on at least one of their surfaces, an impact-resistant primer layer and at least one abrasion-resistant (scratch-resistant) coating layer deposited on the primer layer. The impact-resistant primer layer is formed from polymer particles dispersed in water. The scratch-resistant coating may consist, for example, of a photocrosslinkable or thermally crosslinkable varnish according to EP 0,035,609 or WO 83/0125. The composite materials intended by the present invention are intended for various applications. By way of non-limiting indication, applications in the building industry, such as windows, in the automobile industry, such as windows and headlight lenses, and in the sanitaryware industry, such as shower trays and bathtubs, may be mentioned.
BACKGROUND OF THE INVENTION
Known composite materials have their impact-resistance properties altered by the presence of a hard surface layer. Moreover, in certain applications good solvent resistance is demanded.
It is well known that those composite materials intended for the applications described above with no primer layer have a low impact resistance and a limited resistance to the action of solvents when these composite materials are under stress (“stress cracking”).
The prior art discloses impact-resistant layers of various kinds. Thus, Japanese patents 6,314,001 and 6,387,223 describe an impact-resistant primer layer based on a thermoplastic polyurethane resin.
U.S. Pat. No. 5,015,523 recommends the use of acrylic impact-resistant primers, however European Patent EP-0,404,111 describes the use of impact-resistant primers based on a thermosetting polyurethane.
Document U.S. Pat. No. 5,316,791 describes the use of an impact-resistant primer layer formed from an aqueous polyurethane dispersion applied directly to one surface of an organic glass substrate. The impact-resistant primer layer may be obtained by drying and curing, in air, an aqueous dispersion or latex of a polyurethane which may possibly contain an anionically stabilized acrylic emulsion.
Although these impact-resistant primer layers of the prior art ensure both acceptable adhesion of the abrasion-resistant hard coating and a degree of impact resistance, the latter is not sufficient for the applications intended.
DESCRIPTION OF THE INVENTION
It has now been found that it is possible to improve the impact-resistance of composite materials by using, for the impact-resistant primer layer, an aggregate of multiphase structured particles, one of the phases of which is formed by a polymer having a soft character and another phase is formed by a polymer having a hard character, these phases having glass transistion temperatures lying within defined ranges.
According to the invention, a multilayer composite material is produced which comprises a substrate, at least one impact-resistant primer layer deposited on at least one of the faces of the substrate, and at least one abrasion-resistant coating layer deposited on the primer layer, characterized in that the said primer layer comprises an aggregate of multiphase polymer particles, each particle comprising two separate phases:
a first phase formed by a polymer P1 with a soft character having a glass transition temperature (T
g
1) below 20° C., and
a second phase formed by a polymer P2 with a hard character having a glass transition temperature (T
g
2) above 50° C.
Preferably, the particles are two-phase particles and possess a core/shell structure.
Preferably, the core contains the polymer P1 and the shell contains the polymer P2.
Also preferably, the polymer P1 has a T
g
1 below 0° C. and the polymer P2 has a T
g
2 above 60° C.
Again preferably, the polymer P1 is dispersed in the form of nodules in a matrix formed by the polymer P2.
Preferably, the polymer P1 has a hydrophobicity greater than that of the polymer P2.
In general, the impact-resistant primer layer consists of 70 to 90% by weight of the polymer P1 with a soft character and 10 to 30% by weight of the polymer P2 with a hard character.
Advantageously, the polymers P1 and P2 of the primer layers according to the invention contain:
90 to 100% by weight of units obtained by the polymerization of at least one monomer chosen from the group (I) consisting of (C
1
-C
8
)alkyl esters of (meth)acrylic acid, such as methyl (meth)acrylate and butyl (meth)acrylate; vinyl esters of linear or branched carboxylic acids, such as vinyl acetate and vinyl stearate; styrene; alkylstyrenes, such as &agr;-methylstyrene; haloalkylstyrenes, such as chloromethylstyrene; conjugated dienes, such as butadiene and isoprene; (meth)acrylamide; acrylonitrile; vinyl chloride; (meth)acrylic acids and their derivatives, such as anhydrides; and
0 to 10% by weight of units obtained by the polymerization of at least one monomer chosen from the group (II) consisting of allyl esters of &agr;, &bgr;-unsaturated monocarboxylic or dicarboxylic acids, such as allyl acrylate, allyl methacrylate and diallyl maleate; conjugated dienes, such a butadiene and isoprene; polyol poly(meth)acrylates, such as ethylene glycol dimethacrylate, 1,3-butylene glycol diamethacrylate, 1,4-butenediol diacrylate and pentaerythritol tetraacrylate; polyvinylbenzenes, such as divinylbenzene or trivinylbenzene; and polyallyl derivatives, such as triallyl cyanurate and triallyl trimesate.
The monomers of group (II) act as crosslinking agents in the polymers P1 and P2.
In general, the polymer P1 with a soft character consists mostly of units coming from the polymerization of at least one monomer chosen from butyl acrylate, butadiene and isoprene, however the polymer P2 with a hard character in general consists mostly of units coming from the polymerization of at least one monomer chosen from methyl methacrylate, styrene and vinyl chloride.
In the case of a core/shell structure, preferably only the core is crosslinked, the preferred crosslinking monomers being butadiene and 1,4-butanediol diacrylate and the content of crosslinking monomers being between 0 and 10% by weight with respect of the total weight of the particles.
The hard polymer P2 may be grafted directly onto the polymer P1 or by introducing into the latter residues of monomer units. These residues of monomer units are obtained by the incorporation, into the soft polymer P1, of grafting monomers chosen either from conjugated dienes, the residues of monomer units resulting from the partial 1,2-incorporation of the diene during polymerization, or from allyl esters of &agr;, &bgr;-unsaturated carboxylic or dicarboxylic acids, which possess two copolymerizable functional groups of different reactivities.
The preferred grafting monomers according to the invention are butadiene, allyl methacrylate and diallyl maleate.
The polymers P1 and P2 according to the invention may be prepared by two-step emulsion polymerization, as described below, using monomers chosen from group (I) and possibly group (II) above.
The selection of the monomers both for the soft polymer P1 and for the hard polymer P2 depends on properties, such as the hydrophobicity and the glass transition temperature, that it is desired to confer on the polymers in question.
The primer layer according to the invention may be obtained in particular from a latex containing particles of the polymers P1 and P2, particularly hydrophobic and core/shell-structured polymers P1 and P2. When the mass contribution of the shell in total weight of the polymer particles does not exceed 30%, the latex applied to one surface of an organic glass substrate gives, after low-temperature drying, and without the intervention of either coalescing agents or of volatile organic compounds, a continuous film, structured in the form of soft nodules dispersed in a homogeneous, hard matrix, having no surface tack and having good mechanical strength.
In general, hydrophobicity is the property of being insoluble in water or the absence of affinity for water. According to the invention, this lack of affinity may be hier
Boumera Jean-Marc
Leibler Ludwik
Meunier Gilles
Verzaro Francis
Vuillemin Bruno
At fina
Nakarani D. S.
Smith , Gambrell & Russell, LLP
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