STRUCTURAL COMPOSITES WITH CONTINUOUS

POL YCARB AMIDE MATRIX WITH FUNCTIONAL PROPERTIES FOR STRUCTURAL APPLICATIONS

Technical Field

The present invention relates to a composite material that comprises a polycarbamide resin and a filler, to a method for preparing said composite material and to the elements obtained by means of said composite material. Background art

Composite materials comprise a continuous matrix having an organic polymeric base and a dispersed filler. Currently the most extensively used organic matrixes are the ones based on unsaturated polyester resins and the ones based on epoxy resins. The former have been used very widely in all applications requiring large volumes, typically in the construction sector and in the production of large manufactured articles, also thanks to interesting technical characteristics and to their relatively low cost. Their main limitation derives from the considerable environmental impact linked to the use of styrene as liquid monomer, which has the function of fluidifying the preformed unsaturated polyester resin and to take part, therefore, as reactive solvent, in the cross-linking process initiated by free radicals produced in situ. Epoxy resins have no volatile components and are much more eco-compatible in the step of composite production, but their cost is high. Both types of resin in any case yield cross-linked matrixes of the composite and this makes any recycling extremely difficult and onerous, since the resulting molecular structures cannot be melted, are insoluble and also very difficult to degrade by thermal means.

In general, the derived composites described in the background art, even with high contents of fillers of the inorganic type, have a low flame resistance, because a superficial layer of substantial thickness is constituted by organic substance.

Disclosure of the invention The aim of the present invention is to provide a composite material with low environmental impact which comprises a continuous matrix with an organic polymeric base and a dispersed filler.

An object of the present invention is to provide a method for preparing said material that is eco-compatible, can be provided on an industrial scale and at low cost.

Another object of the present invention is to provide structures and manufactured articles that comprise a micro- or nanostructural composite material that is adapted also for use in the construction of structural manufactured articles, particularly if they are large.

This aim and these and other objects that will become better apparent hereinafter are achieved by means of a composite material comprising a filler of fiber or powder selected among glass filler, basalt filler, carbon filler and mixtures thereof and a polycarbamide resin obtained by means of a process that comprises reacting a diamine compound of formula A (reagent A) and a diisocyanate compound of formula B (reagent B), to obtain a polycarbamide resin of type C

Reagent A Reagent B

where

Ri and R ₂ can be independently H, an alkyl group unsubstituted or substituted with heteroaromatic groups, an aromatic group, an alkyl or aromatic ester, an alkyl or aromatic ether, siloxane groups or heteroaromatic groups, provided that Ri and R ₂ are not both H;

X is a linear or branched alkyl group or an aromatic group, which can be optionally substituted with amine functional groups; Y is an alkyl group, an aromatic group, a polyisocyanate group; and m and n are independently an integer comprised between 2 and 20.

The aim and objects of the present invention are achieved, moreover, by means of an element made of composite material obtained by depositing successive layers of filler and of a polycarbamide resin obtained by means of a process that comprises reacting a diamine compound of formula A (reagent A) and a diisocyanate compound of formula B (reagent B), to obtain a polycarbamide resin of type C

Reagent A Reagent B

where

Ri and R ₂ can be independently H, an alkyl group unsubstituted or substituted with heteroaromatic groups, an aromatic group, an alkyl or aromatic ester, an alkyl or aromatic ether, siloxane groups or heteroaromatic groups, provided that Ri and R ₂ are not both H;

X is a linear or branched alkyl group or an aromatic group, optionally substituted with amine functional groups;

Y is an alkyl group, an aromatic group, a polyisocyanate group; and m and n are independently an integer comprised between 2 and 20.

The aim and objects of the present invention are also achieved by means of a composition that comprises a diisocyanate compound in which at least one additive selected among a glassy, metallic, saline, organic material or mixtures thereof is dispersed and in which the diisocyanate compound has the formula B (reagent B), in which Y is an alkyl group or a polyisocyanate group; and m is an integer comprised between 2 and 20.

The aim and objects of the present invention are also achieved by means of a method for obtaining a material that comprises the following steps:

a) mixing of the composition comprising the reagent B as described above and an additive selected among a glassy, metallic, saline, organic material or mixtures thereof with a diamine compound of formula A (reagent A), where the reagent A has the following formula:

Reagent A

in which Ri and R ₂ can be independently H, an unsubstituted alkyl group, an alkyl ester, an alkyl ether or siloxane groups, provided that i and R ₂ are not both H;

X is a linear or branched alkyl group that can be optionally substituted with amine functional groups; and

n is an integer comprised between 2 and 20 and

b) polymerization of the mixture obtained in step a).

The aim and objects of the present invention are also achieved by means of a micro- and nanocomposite structural material having a continuous polycarbamide matrix that can be obtained by way of said process.

The aim and objects of the present invention are also achieved by using said material to produce manufactured articles (or elements).

The aims and objects of the present invention are also achieved by means of a composite material that comprises a filler and said micro- and nanocomposite structural material having a continuous polycarbamide matrix and by means of a panel-shaped structure of composite material obtained by means of a method that comprises the deposition of successive layers of a fiber with weft and of said composite material. Ways of carrying out the invention

Within the scope of the present invention, the term "filler" designates a material that is not chemically reactive with respect to a resin and in suitable physical form, for example as fiber or powder, which can be added to the resin in order to give desired proprieties. Examples of fillers of glassy, metallic, saline, organic material and derivatives thereof that can be used in the present invention are: glass fiber, basalt fiber, carbon fiber.

Within the scope of the present invention, the expression "nanostructured particle" is understood to reference a particle of an organic or inorganic material in which at least one of the dimensions is on the order of nanometers, such as synthetic or natural alumosilicates (montmorillonite) .

Within the scope of the present invention, the expression "structural composite material with continuous matrix" is understood to reference a two-phase material constituted by a polymeric phase in which fillers are dispersed and on the surface of which adhesive forces occur with respect to the polymer that constitutes the continuous matrix.

Within the scope of the present invention, the expression "coupling agent" is understood to reference a multifunctional molecule with two or more functionalities, added to the formulation of the resin, capable of forming bonds with amine groups and/or isocyanic groups, for example triisocyanates - polyols - carboxylic acids, polyamines.

Within the scope of the present invention, the term "nanocomposite" is understood to reference a composite material that comprises particles of nanometric size.

Within the scope of the present invention, the expression "alkyl group" references a linear or branched chain of saturated aliphatic hydrocarbons C1-C20 and the term "polyisocyanate" references a molecule with more than one isocyanic group -NCO.

Within the scope of the present invention, the expressions "organophilically modified montmorillonite" and "organophilically modified hydrocalcites" respectively designate synthetic and natural alumosilicates treated with alkyl ammonium salts.

An aspect of the present invention relates to a composite material that comprises a fiber or powder filler selected among glass filler, basalt filler, carbon filler and mixtures thereof and a polycarbamide resin obtained by means of a process that comprises reacting a diamine compound of formula A and a diisocyanate compound of formula B, to obtain a polycarbamide resin of type C Reagent A Reagent B

where

Ri and R ₂ can be independently H, an alkyl group unsubstituted or substituted with heteroaromatic groups, an aromatic group, an alkyl or aromatic ester, an alkyl or aromatic ether, siloxane groups or heteroaromatic groups, provided that Ri and R ₂ are not both H;

X is a linear or branched alkyl group or an aromatic group, which can be optionally substituted with amine functional groups;

Y is an alkyl group, an aromatic group, a polyisocyanate group; and m and n are independently an integer comprised between 2 and 20.

Preferably, in said material the filler has the form of filament or fabric, with dimensions from 1 cm to 100 cm in length.

Preferably, in said material the filler has the appearance of powder with dimensions from 0.1 to 100 nanometers.

Preferably, in said material the filler is contained in a quantity comprised between 1% and 80% by weight on the total weight of the composition. An aspect of the present invention relates to an element made of composite material obtained by means of the deposition of successive layers of filler and of a polycarbamide resin obtained by way of a process that comprises reacting a diamine compound of formula A and a diisocyanate compound of formula B to obtain a polycarbamide resin of type C

Reagent A Reagent B

where

Ri and R ₂ can be independently H, an alkyl group unsubstituted or substituted with heteroaromatic groups, an aromatic group, an alkyl or aromatic ester, an alkyl or aromatic ether, siloxane groups or heteroaromatic groups, provided that Ri and R ₂ are not both H;

X is a linear or branched alkyl group or an aromatic group, optionally substituted with amine functional groups;

Y is an alkyl group, aromatic group, a polyisocyanate group; and m and n are independently an integer comprised between 2 and 20.

Preferably, in said element the filler is at least a fiber with weft selected among a glass fiber, a basalt fiber or a carbon fiber, comprising a fabric with fibers arranged in a manner that is not prearranged and a fabric with ordered and crossed wefts.

In one aspect, the present invention relates to a composition that comprises a diisocyanate compound in which at least one additive selected among a glassy, metallic, saline, organic material or mixtures thereof is dispersed and in which the diisocyanate compound has the formula B (reagent B)

OC N— (-Y-)— NC O

m

Reagent B in which Y is an alkyl group or a polyisocyanate group; and m is an integer comprised between 2 and 20.

Preferably, in said composition the additive is present in a quantity comprised between 0.5% and 5% by weight on the total weight of the composition.

Preferably, in said composition the filler is at least one among: glass fiber, basalt fiber, carbon fiber. Moreover, in said composition the additive is preferably selected among organophilically modified montmorillonite, sodium montmorillonite, aluminum hydroxide, magnesium hydroxide, organophilically modified hydrocalcites, bohemites, aluminum oxide. Preferably, in said composition the additive is of micrometric size or in nanostructured form, in powder or liquid.

Preferably, in said composition the additive is pretreated with a coupling agent, such as an aminosilane, before being dispersed in the reagent B.

An aspect of the present invention relates to a method for obtaining a material that comprises the following steps:

a) mixing of the composition according to one of claims 7-12 with a diamine compound of formula A (reagent A), where the reagent A has the following formula:

Reagent A

in which i and R ₂ can be independently H, an unsubstituted alkyl group, an alkyl ester, an alkyl ether or siloxane groups, provided that Ri and R ₂ are not both H;

X is a linear or branched alkyl group that can be optionally substituted with amine functional groups; and n is an integer comprised between 2 and 20 and b) polymerization of the mixture obtained in step a).

Preferably, in said method the diamine compound A has the following formula (I);

where: X is a linear, branched or cyclic alkyl group, optionally substituted with amine functional groups; Rio-Ro, equal or mutually different, are selected independently among linear, cyclic or branched aliphatic groups.

Preferably, in said method the reagents A and B comprise no more than two reactive functionalities in the reaction of polymerization per molecule of reagent.

In one aspect, the present invention relates to a micro- and nanocomposite structural material with continuous polycarbamide matrix that can be obtained by way of said method.

Preferably, in said method the additive added in dispersion in the reagent B is present in a percentage comprised between 0.1% and 5% by weight on the total weight of the material.

In one aspect, the present invention relates to a manufactured article that is suitable for the construction of hulls, pipes, beams, car and motorcycle parts, tanks, which comprises the micro- and nanocomposite structural material with continuous polycarbamide matrix that can be obtained by way of said method or to a composite material that comprises a filler and the micro- and nano composite structural material with continuous polycarbamide matrix that can be obtained by way of said method.

In one aspect, the present invention relates to a panel-shaped structure of composite material obtained by means of a method that comprises the deposition of successive layers of a fiber with weft and of the micro- and nanocomposite structural material with continuous polycarbamide matrix that can be obtained by way of said method.

Preferably, in said structure the fiber with weft is at least one among a glass fiber, a basalt fiber, a carbon fiber and mixtures thereof, comprising a fabric with fibers arranged in a manner which is not prearranged and a fabric with ordered and crossed wefts.

The filler used in the material, in the element, in the structure, in the composition and in the method of the invention may have dimensions that vary from micro (10 ^"5 to 10 ^"6 m) to nano (10 ^"7 to 10 ^"9 m) and the particles that constitute it may have different shapes (for example spheres, fibers, planar particles).

The present invention, thanks to the nature of the resins and of the specific steps of synthesis, allows to prepare a composite material using volatile toxic substances in minimal or negligible quantities and therefore can be performed in high eco-compatible production conditions. The method of the present invention, moreover, allows to prepare composite materials with excellent functional proprieties with the ultimate purpose of obtaining manufactured articles of different kinds, comprising resin ones, thanks also to the considerable efficiency of the polycarbamide resins used in the present invention in bonding as continuous matrixes a large number of reinforcing fillers with ample structural possibility, in particular by varying conveniently the chemical structures of the diamine component, of the diisocyanate component and of the chain extenders and/or cross-linking agents.

The diamine and the diisocyanate used in the method of the present invention may both have reactive functionalities in a number of no more than two per molecule. The use of reagents with these characteristics allows to provide a completely thermoplastic continuous matrix.

Preferably, in the method of the invention the diamine compound A is a ester derivative of aspartic acid with formula (I)

Preferably, X is a linear alkyl group constituted typically by 6 methylene groups or by the methylene-dicyclohexane group, where X is a linear, branched or cyclic alkyl group, and both can be optionally replaced with other functional groups of formula (II):

(Π)

In formula I, the groups ₁₀ to R ₁₃ can be mutually identical or different and are selected among aliphatic groups. Preferably, the groups R ₁₀ to R ₁₃ are of linear or branched alkyl nature in beta position with respect to the oxygen of the ester group, more preferably the groups R ₁₀ to R ₁₃ are ethyl groups (Formula II).

The use of derivatives of aspartic acid with groups X of different kinds allows to modulate the drying time of the polycarbamide, allowing the application of this formulation to the obtainment of manufactured articles suitable for different applications.

As an alternative, it is also possible to use aliphatic amines that are commercially available with the general formula (III) with n comprised between 1 and 3, Rl and R2 equal independently from H, methyl, ethyl, isopropyl or other linear or branched aliphatic groups that comprise 3 to 8 atoms of carbon

H ₂ N-^CH-CH ₂ -0^-CH ₂ -CH-NH ₂

R, n R ₇

(III)

In a preferred embodiment, the diisocyanate compound B is selected among 1,6-hexamethylene diisocyanate (HDI), l-isocyanate-3- isocyanatomethyl- 3,5,5-trimethylcyclohexane (isophorone diisocyanate, IPDI) and 4,4'-dicyclohexylmethane diisocyanate (H12MDI).

HDI

IPDI

H12MDI

However, it is preferable to use the dimers and trimers of the diisocyanates shown previously because they have the characteristic to be less volatile and therefore less toxic than the corresponding monomers. Some examples of aliphatic polyisocyanates based on 1,6-hexamethylene diisocyanate (HDI) are:

Biuret Isocvanurate

Uretdione

The composite material that can be obtained by way of the method of the invention can be further modulated in its structure and molecular weight and optionally strengthened by means of a post-reaction process, in which suitable non-volatile coupling agents, characterized by the presence of functional groups that are reactive with those of the primary resin, increase the network of the final product, allowing to increase the distortion temperature (HDT) of the final manufactured article to temperatures of 75°C or more.

Preferably, the method for preparing the resin according to the invention comprises the addition to the reaction mixture that comprises the reagents A and B of a non-volatile additive (coupling agent) in order to obtain a composite material with a higher degree of cross-linking.

This agent is usually added as an additive to the diisocyanate component before the forming of the resin and can belong to the class of bisoxazolidines. More preferably, said non-volatile coupling agent is a bisoxazolidine with the formula (IV), where: R ₃ = H, linear or branched alkyl group, aromatic group; ₄ = linear or branched alkyl group, aromatic group, poly-ester group, poly-ether group, siloxane group, urethane group or carbon group.

( IV) (V)

These molecules, by hydrolyzing for example due to the action of atmospheric humidity, generate alkoxyamines. The amine groups and the hydroxyl groups thus formed can then react with amine and/or isocyanate groups that have remained free during polycondensation in stages, leading to an increase in the density of the lattice of the final resin. Moreover, it is possible to use cross-linking agents that can react in a reversible manner with suitable functional groups present on the main resin so as to provide for the possibility of lowering the molecular weight at the end of the life of the manufactured article, which therefore can be disposed and/or recycled more easily. For this purpose, a derivative of the bismaileimide of formula (VI) can be added, for example, to the formulation and can increase the polymeric network by a Diels-Alder reaction with suitable dienes present in the main resin.

The filler selected among at least one glassy, metallic, saline, organic material or mixtures thereof used in the method of the present invention can be based on nanodispersible silicates in a quantity from 1% to 5% by weight on the total weight of the composition, in order to obtain a matrix that belongs to the REI flammability class. Said filler can also be a flame suppressant or flame retardant, for example an organophilic phylosilicate such as montmorillonite, which can be added together with the amine component in a quantity from 1% to 10% by weight on the total weight of the composition.

In another aspect, the present invention relates to the use of said material for producing manufactured articles.

Preferably, said composite material is used for the production of manufactured articles for the nautical sector and in particular for forming boat hulls; in the construction sector, with particular reference to light beams, in the transportation sector, for example in the construction of body parts for cars and trains, or in the provision of small manufactured articles for series such as for example car mirrors, motorcycle fairings, spoilers for trucks, and in the industrial field, such as for example for providing pipes for liquids of different types, tanks of different shape and size.

Preferably, the manufactured article of the invention comprises a superficially applied layer of a resin, preferably produced by polymerization of the reagents A and B, comprising a fluorescent color capable of emitting in the visible spectrum.

EXAMPLES

The following examples illustrate some embodiments of the invention without, however, intending to limit its aim.

Examples on material

EXAMPLE 1

100 parts by weight of diamine (e.g. of formula III), 65 parts by weight of polyisocyanate, constituted by a mixture that contains diisocyanate and/or cyclic derivatives thereof (e.g. a mixture of equal weights of Biuret, isocyanurate and Uretdione) and nanodispersible silicate- based nano-fillers from 1% to 5% by weight of the total, were mixed with a mechanical agitator machine at room temperature for approximately 1 minute to obtain a polycarbamide matrix that belongs to the REI flammability class. By applying this procedure, complete homogeneity of the mixture is ensured. Cross-linking occurs in 24 hours at the temperature of 25-30°C on a glass support and produces the polycarbamide resin. The compound will receive the addition, by slow mixing for 1 minute, in the isocyanate component, of 5% to 20% bisoxazolidine derivatives. This matrix is then used to provide composites filled with 30/60% by weight of different inorganic materials, mainly of the glassy type, as described in the examples given hereinafter.

EXAMPLE 2:

Like example 1, with the addition of a phillosilicate flame suppressant or flame retardant such as sodium montmorillonite added together with the amine component from 1% to 10% by weight with respect to the weight of the resin component in the composite.

EXAMPLE 3

Like example 1, with the addition of synthetic phillosilicate flame suppressant or flame retardant such as bohemite added together with the amine component from 1% to 10% by weight with respect to the weight of the resin component in the composite.

EXAMPLE 4

Like example 1 , with the addition of flame suppressant or flame retardant saline derivatives of phosphor added together with the amine component from 1% to 10% by weight with respect to the weight of the resin component in the composite.

EXAMPLE 5

A panel made of composite material obtained by depositing successive layers of polycarbamide resin with the addition of montmorillonite obtained in the example 1 and glass fiber of different kind by means of the following procedure:

a layer of polycarbamide resin with a thickness of approximately 1 mm was applied on a base of inert material covered by a PVC or LDPE film with release effect. On this layer, a layer of glass fiber known as Mat 450, constituted by glass fabric with fibers arranged in a non-prearranged manner, also known as random-type fabric, without size was applied. Subsequently, a new layer of polycarbamide resin was applied which was compressed with a suitable tool in order to remove any residual air bubbles.

A second layer of glass fiber of the random type was applied with the same method. A new layer of polycarbamide resin with montmorillonite was used as a binding agent for the applied fibers. A type of fabric with ordered and crossed wefts of the BAX 800 type is applied to the panel thus obtained, again without size. This material is known as "powder fiber". Again, in order to bind the glass fibers, the polycarbamide resin was deposited and any air bubbles were eliminated.

A last layer of random fiber overlapped by a layer of polycarbamide resin allows to obtain the final panel.

Summary of the construction sequence:

- 1 layer of polycarbamide resin with montmorillonite, 1 mm

- 1 layer of MAT 450 glass fiber of the random type, not sized

- 1 layer of polycarbamide resin with montmorillonite, 1 mm

- 1 layer of MAT 450 glass fiber of the random type, not sized

- 1 BIAX 800 crossed glass fiber without size or in powder form

- 1 layer of polycarbamide resin with montmorillonite, 1 mm

- 1 layer of MAT 450 glass fiber of the random type, not sized

- 1 layer of polycarbamide resin with montmorillonite

EXAMPLE 6

Like example 5, but using basalt fiber EXAMPLE 7

Like example 5, but using carbon fiber

EXAMPLE 8

Production of a composite panel as described in example 3, using the diamine A and the diisocyanate B but avoiding the use of amines or isocyanic components with reactive functionalities in a number of more than two per molecule in order to provide a completely thermoplastic continuous matrix.

The necessary thermomechanical performance will be reached by adding to the diamine component of the poly carbamide resin adhesive agents (aminosilanes) between the surface of the glass fiber and the matrix itself. The resulting mixture is then combined with the diisocynate and fillers like example 1 for the production of composite.

The disclosures in Italian Patent Application No. MI2010A002287 from which this application claims priority are incorporated herein by reference.