The present invention refers to a polyester composition of reduced flammability based on an unsaturated polyester resin containing an unsaturated free radical copolymerizable polyester and a cross-linking monomer, and on a specially selected multi-component mixture of flammability reducing modifiers.

There are known in the art low-flammable polyester compositions based on unsaturated polyester resins with halogen atoms, mainly chlorine or bromine atoms, embedded into an unsaturated polyester's chain or into molecules of a cross-linking monomer. There is also known a flame retardant polyester composition, where flame retardancy effect is obtained by introduction into final polyester resins of halogen anti-flammable modifiers and flammability reducing inorganic modifiers with significant content of crystalline water, such as hydrated aluminum oxide or hydrated zinc borate.

It is possible to obtain the required flammability reduction by embedding halogens into one of the basic components of an unsaturated polyester resin if a significant quantity of one of these elements is introduced, which results in a necessity to use complex chemical compounds hindering a synthesis of an unsaturated polyester and causes serious environmental problems. Similar environmental doubts arise from the use of flammability reducing halogen modifiers used for modification of final unsaturated polyester resins. On the other hand, compounds with crystalline water must be introduced in such large quantities that it makes it significantly difficult to manufacture reinforced products with glass fiber, synthetic fiber or carbon fiber.

Toxic properties of flammability reducing halogen modifiers have recently led to limited use of these flame retarding modifiers.

Phosphorous compounds should be mentioned among halogen-free flammability reducing modifiers used for unsaturated polyester resins. Yet, the commonly used and effective phosphorous modifier in the form of tris-/2,3- dibromopropyl/ phosphate has turned out to be a toxic compound, and the use of phosphoric acid esters has made it difficult to harden polyester resins and has reduced their hydrolysis resistance.

Some publications and few related patent descriptions suggest the use of flammability reducing phosphoric modifiers with nitrogen compounds as well as complex mixtures and products of reaction of compounds containing these phosphoric-nitrogen function groups slowing down reactions in the polymer burning zone. For example, US patent US 7,205,346 discloses compositions where phosphoric acid ester amides are used as flammability reducing modifiers with the compounds containing nitrogen, such as piperazine, with inorganic acid salts and metal salts. This modification does indeed reduce flammability of resins, yet it is complicated from a technological point of view and has not found its industrial application. In the art, halogen-free polyester flammability reducing modifiers comprise metal oxides and hydroxides as important ones. Unsaturated polyester resins known from the Polish patent PL 192 427 with tin-zinc compounds added as modifiers are characterized by improved resistance to fire and reduced emission of smoke. However, the target to be achieved is strongly dependent on a necessity of using specific flame retarder molecule sizes and a relatively high concentration thereof, which makes the end products significantly more expensive.

Organic nitrogen flammability reducing modifiers based on melamine or guanidine and derivatives thereof, for example melamine cyanurates and polyphosphates, have impact on the release of gases in the first phase of polyester resins burning, which has effect on the formation of a porous coke layer. It is described in US patent no. US 0065304 with reference to the modifications of the specially engineered copolyesters. It has been demonstrated necessary to use them in high concentrations, especially in the case of melamine polyphosphate, in order to reach a favorable oxygen index (01), which is characteristic of a sufficient flame retardancy level. The quoted patent does not describe any modifications of classical structural types of unsaturated polyester resins.

Based on the conducted research and the analysis of the results of works as described above it has turned out that a lot of aforementioned difficulties can be avoided if a multi-component combination of halogen-free flammability-reducing modifiers is used in the form of melamine salt with selected nanofillers. The invention is based on effective cooperation of classical flammability modifiers with the compounds characterized by molecules which, at nanometric level, have a well developed structure from the viewpoint of size, shape and solubility. It should be added that users of such polymeric materials as polyester compositions expect a "ready to use" product, which means that even if it has multiple components it should have homogenous phases, be relatively easy to add and should not disrupt the conversion processes.

Montmorillonite /MMT/, being an aluminosilicate of a fine crystalline structure, has turned out to be one of the most popular and practically effective nanocomposite reinforcing thermoplastic polymers and reducing this-type flammability, as described in the US patent US 0326133, among others. However, the disclosed invention is limited to MMT having a capillary tubular microstructure and to the addition after specific previous processing. No results have been presented regarding the modification of unsaturated polyester resins with such a reduced flammability modifier.

Given the nature of MMT microstructure, the use of this nanof ^' iller for thermosetting polyester resins becomes more effective after the modification of MMT with a relevant amount of organic compounds or selected ammonium salts and when it is used together with conventional flammability reducing modifiers from the group of phosphorous and nitrogen flame retarders - as demonstrated by the conducted works and as claimed in this invention. Such compositions flammability reducing modifiers have never been used before for making polyester resins flame retardant.

Synergy-based cooperation with traditional flammability reducing modifiers has also been noticed in the case of using precipitated nanosilica or expandable graphite. Precipitated silica, as synthetic silica, has been treated before as a thickener and a tixotropic agent of chemosetting resins, which is confirmed in the US patent US 0136672 Al. However it has turned out that taking advantage of specific properties of nanosilica or expandable graphite makes it possible to use them as additions that support the flammability reducing action.

Said nanofillers when exposed to heat catalyze the formation of a coke layer on the surface of a polymeric material, although the mechanism of action of these two nano-compounds is different. So far these results have not been confirmed for phosphorous-nitrogen flammability reducing modifiers and for polyester resins.

The purpose of this invention was to obtain a halogen-free polyester composition showing an effective flame retardancy level with the use of relatively small amounts of flammability reducing modifiers and maintaining the strength properties of end products after their cross-linking by multi-radical polymerization method.

Unexpectedly it has turned out that a composition containing an unsaturated polyester resin in the amount of 5.0-40.0 parts by weight /as per 100 parts by weight of a resin/, halogen-free multi-component flammability reducing modifiers with melamine salts, mainly melamine polyphosphate and/or melamine cyanurate with nanofillers in the form of: MMT/modified MMT or synthetic precipitated silica or expandable graphite / surface-modified expandable graphite shows significantly reduced flammability and significantly reduced emission of toxic smoke while keeping a favorable set of mechanical properties of hardened products.

A polyester composition according to the invention contains unsaturated polyester resins where the main ingredients are unsaturated polyester and a cross- linking manomer. Unsaturated polyesters are used, which are composed with the maleic and fumaric acid rests, glycol rests such as ethylene glycol, 1,2-propylenene-, dimethylene-, dipropylene- and neopentyl- glycol, as well as etoxyl- and propoxyl- diane and dicarboxylic acid rests such as phthalic, isophthalic, terephthalic, adipine acid and acid relative to maleic anhydride adduct with diene such as butadiene, cyclobutadiene, anthracene and β-naphthol. A product of addition of methacrylic acid to epoxy resin can also be used.

A polyester composition according to the invention contains styrene and p- methylstyrene, methylmethacrylane and triethylene glycol dimethacrylane as a cross-linking monomer. Unsaturated polyester may contain embedded chlorine or bromine atoms, for example in the form of rests of tetrabromophthalic acid, HET acid, dibromoneopentyl glycol or glycol derived from epichlorhydrine. Also monomers with embedded chlorine or bromine are used, e.g. chlorostyrenes or bromostyrenes. A polyester composition according to the invention as flammability reducing modifiers contains water dissoluble melamine salts, favorably with phosphoric acids, isocyanurate acid, boric acid or oxalic acid; mainly melamine polyphosphate and melamine cyanurate with nanofillers: in the form of montmorollonite or its modified form, mainly ammonium salts, expandable graphite, synthetic precipitated silica.

Silica belongs to the substances of high chemical resistance especially to acids and oxidizers and it also increases resistance to abrasion and cracking. Admixtures of silica increase resistance to thermal aging, reduce heat give-off and loss of mass. These properties of silica have been used in this invention, even though never before has silica been regarded as a flammability reducing modifier of polyester resins. Precipitated silica containing a number of silanol groups and silica after proper modification is characterized by better compatibility with polymers which in practice translates into a possibility to obtain a homogenous mixture of a polymer and a filler.

The present invention describes the use of precipitated silica characterized by a nanometric microstructure (grain size of lOOnm) obtained by reacting a silicate with an acidifier.

In the process of preparing polyester compositions according to the invention flammability reducing modifiers are introduced into unsaturated polyester resins before curing. This procedure enables the use of modifications of different types of polyester resins at the polymers producer's and processor's. Mixing of compositions is done in stages in a low speed rotation mixer, and then using an ultrasonic turbine impeller mixer (rotation speed of 4500 rev/min) and finally using a homogenizer in some cases. This method assures that a homogenous composition is obtained which does not show any tendency to sedimentation.

Polyester compositions are cured by known methods by radical polymerization which is initiated by methyiethylketone (MEK) peroxides or hydroperoxides, favorably in the presence of accelerants such as tertiary aliphatic-aromatic amines, cobalt salts or vanadium salts. Polymerization can also be initiated by the use of ultraviolet or visible radiation, wherein relevant sensitizers are then injected into a resin.

Polyester compositions of reduced flammability according to this invention, when subjected to curing, are characterized by an average increase of 25%-35% in oxygen index as defined in ASTM D 2863-97, a decrease of 45% in heat release rate (HRR) and an average increase of 15% in heat deflection temperature (HDT) determined as per PN-EN ISO 75-2 compared to analogous parameters of polyester resin subjected to curing but without these flame retarders.

These compositions find application in the production of reinforced materials, details produced from the molded pressed thermosetting mixture, thick- layer coatings or castings. Polyester compositions according to the invention are used for the supersaturation of glass fibers in the form of glass rowing, glass mat or glass textile. Usually 30g of glass fiber (of an example grammage of 450g/m ² ) with 70g of polyester composition are used. Polyester-glass laminates are usually cured at room temperature with MEK peroxide and cobalt naphthenate. Polyester-glass laminates obtained according to the invention are applied in construction industry, transport, shipbuilding, boatbuilding and for the production of the elements of sanitary accessories.

Other types of products obtained with the use of the polyester composition according to the invention are flame retardant, thick-layered seamless floor liners, coatings on wooden or wood-like surfaces or flame retardant details produced from the molded pressed thermosetting mixture for which thermosetting is carried out in special molds at an increased temperature.

Example constituents of a polyester composition according to the invention and methods of obtaining and applying thereof are described in more detail in the below embodiments which do not limit the scope of the invention or its application in any way whatsoever.

Example I.

Polyester composition:

- polyester resin Polimal 109 - 100 g - melamine polyphosphate - 15g

- montmorillonite modified with ammonium salts (M T-1) - 5g

15 g of melamine polyphosphate with phosphorous content of 14.8%, nitrogen content of 44.1% and 5 g of MMT 1 (montmoryllonite modified with ammonium salts) are introduced to lOOg of maleic-phthalic-propylene polyester resin Polimal 109, of a viscosity of 620 mPas, containing 36% of styrene. All is mixed in stages: in a low speed rotation mixer, then in an ultrasonic turbine impeller mixer. Thanks to that a homogenous composition is guaranteed after around 25 minutes of stirring.

Thus obtained composition is subjected to curing at room temperature by addition of 3g of MEK peroxide and 0.4 g of cobalt naphthenate (NK) with 1% of Co. The composition is seasoned at room temperature for 24 hours, and then cured at 40°C for 16 hours. The composition after curing is characterized by an oxygen index (as per ASTM D 2863-97) of 27.1%, wherein the resin without the flame retarders has an oxygen index of 20.9%. Modified products after curing are additionally characterized by heat deflection temperature (HDT) (as per PN-EN ISO 75-2) of 66.5 °C and impact strength (without notch) of 9.5 kJ/m2 (as per PN-EN IS0179).

Example II.

Polyester composition:

- polyester orhtophthalic resin Polimal 109-32K - lOOg - melamine cyanurate - 10 g

- surface-modified expandable graphite - 3g

10 g of melamine cyanurate and 3g of expandable graphite (surface modified before) are added to lOOg of polyester orhtophthalic resin Polimal 109- 32K of a viscosity of 395 mPas. The composition is mixed in stages as described in example I and, additionally, using a high rotation speed homogenizer at the end of this process.

Afterwards, thus obtained homogenous mixture is subjected to curing at room temperature in the presence of 2.5g of MEK peroxide and 0.5% of NK (l%Co). The composition is seasoned at room temperature for 24 hours and then cured additionally for 15 hours at 40°C. After curing the composition is characterized by a high oxygen index 01= 28.2% (as per ASTM D 2863-97), which means an increase in this value by 23% compared to polyester orthophthalic resin Polimal 109-32 K before the modification in same testing method. Additionally, the hardened polyester resin is characterized by 38% reduction in HRR determined by a cone calorimeter. The composition shows a ball pressure hardness of 132 MPa (as per PN-EN ISO 2039-1).

Example III.

Polyester composition:

- maleic-phthalic-epichlorohydrine resin Polimal 160 - lOOg - melamine polyphosphate of the same characteristics as in example I - 21g

- synthetic precipitated silica - 4g

21 g of melamine phosphate of the characteristics as mentioned in Example I with 4 g of synthetic precipitated silica are introduced to lOOg of maleic-phthalic- epichlorhydrine polyester resin Polimal 160, containing 31% of styrene. All the ingredients are mixed for 35 minutes, as described in Example I.

Then, the resultant homogenous mixture is cured by an addition of 2% MEK hydroperoxide and 0.4% NK (l%Co). Additional curing of a composition at a higher temperature is carried out as described in example I. After curing, the composition demonstrates a 28% increase in 01 and a 15% increase in heat deflection temperature (HDT) (as per PN-EN ISO 75-2).

Example IV.

Polyester composition:

- polyester resin Polimal 162 - lOOg,

- melamine polyphosphate of an average grain size οίΐθμιη - 5g

- precipitated silica of an average grain size of 100 nm - 5g

5 g of melamine polyphosphate of an average grain size of ΙΟμητι and 5g of precipitated silica of an average grain size of 100 nm are added to lOOg of polyester resin Polimal 162 obtained with the use of HET acid and containing 33% of styrene. All the ingredients are mixed as described in Example II.

A composition is cured at room temperature using the curing configuration of example III. After complete curing a polyester composition is characterized by 01=29,1% and HDT=69,2 °C. A composition produced and cured this way belongs co V=0 category in UL-94 test which qualifies the product as a flame retardant.

Example V.

Polyester composition:

- polyester resin Polimal 103 - lOOOg

- melamine polyphosphate of an average grain size of ΙΟμι ^η - 200g

- synthetic precipitated silica of an average grain size of 100 nm - 20g

200 g of melamine phosphate as in Example III and 20 g of precipitated synthetic silica as in Example IV are added to lOOOg of maleic-phthalic-propylene polyester resin Polimal 103 of a viscosity of 380 mPas and styrene content of 33%. All the ingredients are mixed for 35 minutes, in stages, as described in Example I.

Thus obtained homogenous composition is used for contact forming of a polyester-glass laminate using a glass mat of a grammage of 450g/m2. While preparing a laminate a standard recipe is used: 70g of a polyester composition and 30 g of glass mat. Laminate is cured using a curing configuration of Example I. After curing the polyester-glass laminate shows an oxygen index of 41.8% and V=0 category in UL-94 flammability test. Moreover, laminate is characterized by HDT of 125 °C and impact strength of 83.4 kJ/m ² (as per PN-EN ISO 179).

Example VI.

Composition as in Example I containing additionally 0.1% of paraffin is poured out in stages, in two layers every 30 minutes to the surface of a wooden panel. After curing at room temperature as in Example I a matt hard coating is obtained of a thickness of 0.6 mm. When ignited directly by a gas flame, the coating gives out once the flame is removed.

Example VII.

Polyester composition:

- polyester resin Polimal 160 - lOOOg

- dicumyl peroxide - lOg ,

- short-cut glass fiber - 700g,

- magnesium oxide - 30g,

- kaolin - 750g,

- zinc stearate - 30g, - melamine cyanurate - 250g

- precipitated silica - 50g

A thermosetting polyester molding mixture is prepared using a polyester composition obtained by mixing lOOOg of polyester resin Polimal 160, lOg of dicumyl peroxide, 700 g of short-cut glass fiber, 30 g of magnesium oxide, 750 g of kaolin, 30g of zinc stearate, 250 g of melamine cyanurate and 50 g precipitated silica.

Thus obtained molding mixture is used for the preparation of details by pressing at a temperature of 150 °C under 10 MPa pressure, with pressing time of 50 s per 1 mm of pressed detail's thickness. Pressed pieces are difficult to ignite with a gas flame and they go out once it is removed.