WO2010066642A1

WO2010066642A1 - Polymer-containing composition comprising a layered double hydroxide in a matrix

Info

Publication number: WO2010066642A1
Application number: PCT/EP2009/066392
Authority: WO
Inventors: Rudolf Anthonius Maria Venderbosch; Hendrika Petronella Maria Verlaan-Hooft; Johannes Petrus Jozef Verlaan; Auke Gerardus Talma; Rudolph Overbeek
Original assignee: Akzo Nobel N.V.
Priority date: 2008-12-08
Filing date: 2009-12-04
Publication date: 2010-06-17

Abstract

The invention relates to a polymer-containing composition which comprises a layered double hydroxide in a polymer matrix, wherein the layered double hydroxide, comprising stacks of individual platelets, comprises carbonate as charge -balancing anion and wherein the individual platelets have an average L/D value above (150), and the polymer comprises a thermoset polymer and/or a nonhalogen-containing thermoplastic polymer. The invention further relates to the use of said layered double hydroxide for improving properties of the polymer-containing composition; the use of the polymer-containing composition in a coating, ink, cleaning, rubber or rubber formulation, drilling fluid, cement formulation, plaster formulation, or paper pulp,- a polymer formulation, a coating composition or article comprising the polymer-containing composition; and a process for preparing the polymer-containing composition.

Description

POLYMER-CONTAINING COMPOSITION COMPRISING A LAYERED DOUBLE HYDROXIDE IN A MATRIX

The invention relates to a polymer-containing composition which comprises a layered double hydroxide in a polymer matrix.

It is known to use layered double hydroxides that comprise carbonates as charge-balancing anions as filler materials in polymer compositions such as polyvinylchloride-containing compositions. These carbonates are used as part of a thermal stabilisation package.

Surprisingly, it has now been found that various properties of a polymer composition can be considerably improved when use is made of a layered double hydroxide carbonate having a particular average L-D value.

Accordingly, the present invention relates to a polymer-containing composition which comprises a layered double hydroxide in a polymer matrix, wherein the layered double hydroxide, comprising stacks of individual platelets, comprises carbonate as charge-balancing anion and wherein the individual platelets have an average length over thickness ratio (L/D value) above 150, and the polymer matrix comprises a thermoset polymer and/or a nonhalogen-containing thermoplastic polymer.

Such polymer-containing compositions display an improved transparency, improved adhesion properties, and/or improved flame retardancy properties when compared with similar types of polymer compositions that contain conventional layered double hydroxide (LDH) carbonates.

The layered double hydroxides to be used in accordance with the present invention differ from the LDHs comprising carbonate known in the art in that the average L/D ratio of the individual platelets of the LDHs of the invention is considerably higher than the values observed for the known LDHs - the latter being well below 100.

It is noted that for LDHs comprising carbonate known in the art, an L/D ratio is often defined as being the ratio of the length (L) of a fibre, being composed of stacks of individual platelets, to the diameter (D) of said fibre. US 4,351 ,814 for example discloses the use of fibrous or needle-like shaped hydrotalcites as a fire retardant for thermoplastic and thermosetting resins, said fibres having a length-to-diameter ratio, determined under an electron microscope, of at least about 10, in many cases about 30 to about 50 or more. JP 56-074137 discloses the use of a fibrous hydrotalcite in a resin, the fibre having a length/diameter ratio of 20-200, preferably 40-180.

The LDHs according to the present invention, on the other hand, do not form fibres. Hence, the choice was made to define an L/D ratio for the individual platelets, with the length (L) being the largest size of the platelets in the direction perpendicular to the stacking direction and the thickness (D) referring to the thickness of the individual clay particles in the stacking direction.

The average length over thickness ratio (L/D ratio) of the individual platelets in the LDH to be used according to the present invention exceeds 150, preferably the L/D ratio is at least 175, more preferably the L/D ratio is at least 200, and even more preferably the L/D ratio is at least 250. The L/D ratio can be determined using electron microscopy such as scanning electron microscopy (SEM) and/or TEM. It is noted that the average length and the average diameter can be determined by taking the average length and the average diameter of 20 clay particles, for example. The number of clay particles may also be larger or smaller, as long as the average values are statistically justifiable.

The individual platelets of the LDHs according to the present invention form stacks of which the height is preferably at most 50 platelets, more preferably at most 30 platelets. Alternatively or additionally, the LDHs of the invention generally have an average length of the individual platelets of at least 400 nm; preferably, the average length is at least 500 nm, and most preferably the average length is at least 600 nm. The average length is defined and determined using the methods described for the L/D value above.

In the context of the present application the term "charge-balancing anion" refers to anions that compensate for the electrostatic charge deficiencies of the crystalline clay sheets of the LDH. As the clay typically has a layered structure, the charge-balancing anions may be situated in the interlayer, on the edge or on the outer surface of the stacked clay layers. Such anions situated in the interlayer of stacked clay layers are referred to as intercalating ions.

The LDHs comprising charge-balancing organic anions preferably have a layered structure corresponding to the general formula (I):

[M^⁺ (OH)_2m+2n Jx-- bH₂O (I)

wherein M²⁺ is a divalent metal ion such as Zn²⁺, Mn²⁺, Ni²⁺, Co²⁺, Fe²⁺, Cu²⁺, Sn²⁺, Ba²⁺, Ca²⁺, and Mg²⁺, M³⁺ is a trivalent metal ion such as Al³⁺, Cr³⁺, Fe³⁺, Co³⁺, Mn³⁺, Ni³⁺, Ce³⁺, and Ga³⁺, m and n have a value such that m/n = 1 to 10, and b has a value in the range of from 0 to 10. It is also contemplated to use three or more different metal ions in the layered double hydroxide prepared with the process of the invention. Of the above metal ions the combination of Mg²⁺ and/or Zn²⁺ as divalent metal ions and Al³⁺ as trivalent metal ion is preferred. X is carbonate (CO3^2") or a mixture of carbonate and one or more inorganic or organic anions known in the art. Examples of suitable inorganic anions other than carbonate include hydroxide, bicarbonate, nitrate, chloride, bromide, sulfonate, sulfate, bisulfate, vanadates, tungstates, borates, and phosphates. For the purpose of this specification, carbonate and bicarbonate anions are defined as being of inorganic nature. Examples of suitable organic anions can be found in US 5,728,366 and US 2005/020749.

The LDH to be used in accordance with the present invention includes hydrotalcite and hydrotalcite-like anionic LDHs. Examples of such LDHs are meixnehte, manasseite, pyroauhte, sjόgrenite, stichtite, barberonite, takovite, reevesite, and desautelsite.

In one suitable embodiment of the invention, the layered double hydroxide has a layered structure corresponding to the general formula (II):

[Mg² _m ⁺Air(OH)_2m+2nJX_n7_z- bH₂O (II)

wherein m and n have a value such that m/n = 1 to 10, preferably 1 to 6, more preferably 2 to 4, and most preferably a value close to 3; b has a value in the range of from 0 to 10, generally a value of 2 to 6, and often a value of about 4. X is a charge-balancing ion as defined above. It is preferred that m/n should have a value of 2 to 4, more particularly a value close to 3.

In another suitable embodiment of the invention, the layered double hydroxide has a layered structure corresponding to the general formula (III):

[Mg² _m ⁺ ZnI⁺ AI³;(OH)_2m+2n+2p]x- . bH₂O (III)

wherein m and n have a value such that (m+n)/p = 1 to 10, preferably 1 to 6, more preferably 2 to 4, and most preferably a value close to 3; b has a value in the range of from 0 to 10, generally a value of 2 to 6, and often a value of about 4. X is a charge-balancing ion as defined above. It is preferred that (m+n)/p should have a value of 2 to 4, more particularly a value close to 3. The LDH may have any crystal form known in the art, such as described by Cavani et al. (Catalysis Today, 11 (1991 ), pp. 173-301 ) or by Bookin et al. (Clays and Clay Minerals, (1993), Vol. 41 (5), pp. 558-564), such as 3Hi, 3H₂, 3Ri, or 3R₂ stacking. In one embodiment, the LDH has 3Ri stacking.

In the polymer-containing composition according to the present invention, the polymer comprises a thermoset polymer and/or a nonhalogen-containing thermoplastic polymer. Preferably, it comprises only a thermoset polymer.

When the polymer matrix (i.e. resin formulation) to be used in accordance with the present invention comprises a thermoset polymer, the thermoset polymer is preferably selected from the group consisting of unsaturated polyester resins, acrylate resins, methacrylate resins, polyimides, epoxy resins, fenol formaldehyde resins, urea formaldehyde resins, melamine formaldehyde, bis/tris allyl ethers, and polyurethanes. More preferably, the thermoset polymer is selected from the group consisting of polyurethanes, unsaturated polyester resins, and epoxy resins. The skilled person will appreciate which particular thermoset polymer can be selected from each of the above-mentioned categories of thermoset polymers.

The polymer-containing compositions containing such a thermoset polymer display improved transparency, improved adhesion and/or improved flame retardancy properties when compared with similar types of polymer compositions that contain a conventional LDH. The improved transparency is of importance in top layer applications such as finishing coatings for wood floors and metal objects. As regards the adhesion properties, it has been found that the present polymer-containing compositions display an improved adhesion to metal surfaces such as the surfaces of, for instance, aluminium and iron. The improved adhesion properties have the advantage that they lead to improved durability of the object onto which the coating of the polymer-containing composition is applied. When the polymer matrix to be used in accordance with the present invention comprises a nonhalogen-containing thermoplastic polymer, the nonhalogen-containing thermoplastic polymer is preferably selected from the group consisting of polyethylene terephthalate, polyimides, polycarbonates, polyaryl ethers, polysulfones, polysulfides, polyamides, polyether imides, polyether esters, polyether ketones, polyether ester ketones, polysiloxanes, polyurethanes, polyepoxides, polystyrene, acetal (co)polymers, butadiene nitrile rubber, silicon rubbers, and ethylene vinyl acetate rubber. More preferably, the nonhalogen-containing thermoplastic polymer is ethylene vinyl acetate rubber.

The polymer-containing compositions containing such a nonhalogen- containing thermoplastic polymer display improved flame retardancy when compared with similar types of polymer compositions that contain a conventional LDH.

When the polymer in the present polymer-containing compositions comprises a thermoset polymer, the thermoset polymer is suitably present in an amount in the range of from 3-95 wt.%, based on total composition. Preferably, the thermoset polymer is present in an amount in the range of from 30-95 wt.%, more preferably in an amount in the range of from 70-90 wt.%, based on total composition.

When the polymer in the present polymer-containing compositions comprises a nonhalogen-containing thermoplastic polymer, the nonhalogen- containing thermoplastic polymer is suitably present in an amount in the range of from 30-80 wt.%, based on total composition. Preferably, the nonhalogen-containing thermoplastic polymer is present in an amount in the range of from 40-80 wt.%, more preferably in an amount in the range of from 50-70 wt.%, based on total composition. One of the major advantages of the present invention is that less LDH can be used when compared with a conventional thermoplastic composition, into which normally more than 60 wt.% of LDH needs to be incorporated to ensure sufficient flame retardancy properties. Moreover, this leads in addition to improved physical properties such as toughness and strength. Additionally, the present polymer-containing composition may also contain MDH (Magnesium Double Hydroxide) and/or ATH (Aluminium trihydroxide), leading to similar improved properties.

In contrast to known processes for the preparation of LDHs such as for example described in DE 102 17 364, the process for the preparation of LDHs according to the present invention comprises a first step wherein a slurry or solution is prepared comprising a thvalent metal ion source, a divalent metal ion source, and a suspending medium, and wherein in a second step, a solvothermal treatment is performed to form the LDH. More particularly, the slurry or solution comprising a thvalent metal ion source prepared in step (a) of the presently claimed process is a precursor slurry for the formation of a layered double hydroxide. From this precursor slurry the layered double hydroxide is formed via a solvothermal treatment. In more detail, the production process of the LDHs according to the present invention, which is described in WO 2008/034835, comprises the steps of: a) preparing a precursor slurry or solution comprising a trivalent metal ion source, a divalent metal ion source, and a suspending medium, the divalent metal ion source being a source free of carbonate and/or a source containing carbonate; b) solvothermally treating said precursor slurry or solution at a temperature of at least 100°C, and optionally adding a carbonate source to the slurry during or after the solvothermal treatment, to form the layered double hydroxide comprising carbonate; and if the slurry or solution does not contain a divalent metal ion source containing carbonate, a carbonate source is added to the slurry or solution during or after the solvothermal treatment. It is noted that said process does not comprise a hydrothermal after-treatment of the LDH (also generally referred to as an aging step). The process is preferably carried out in the absence of sodium hydroxide so that the sodium ion content in the produced LDH will be as low as possible, and preferably below 1 wt.%, more preferably below 0.1 wt.%, based on the total weight of the LDH. In Figure 1 a SEM image of the thus obtained LDH is depicted.

The process can be conducted by preparing a slurry or solution comprising a trivalent metal ion source, a carbonate-containing divalent metal ion source, and a carbonate-free divalent metal ion source. If in such case the amount of carbonate in the slurry or solution is sufficient to form an LDH with the desired amount of carbonate in the interlayer, the addition of a carbonate source is not necessary. However, if the amount of carbonate is not sufficient, a carbonate source is generally added before, during or after step b) of the process. Preferably, the carbonate source is added during or after step b).

Alternatively, if a carbonate-containing divalent metal ion source is absent in the slurry or solution of step a), the addition of the carbonate source before, during or after step b) is necessary in order to obtain an LDH comprising carbonate as charge-balancing anion. In a preferred embodiment, the carbonate source is added during or after step b).

The carbonate source can be any suitable carbonate source known in the art. Examples of such a carbonate source are carbon dioxide (CO2), an alkali metal carbonate such as sodium or potassium carbonate, and an alkali metal bicarbonate such as sodium or potassium bicarbonate. It is also contemplated to use one or more carbonate sources. These sources may be added simultaneously or at different stages in the process. Of these carbonate sources carbon dioxide is preferred, as no salt, which will end up in the waste stream and which needs to be removed, is added to the slurry or solution. The terms "solvothermal treatment" and "solvothermally" refer to the treatment of the precursor suspension/slurry or solution at a pressure above atmospheric pressure and a temperature which generally is above the boiling point of the precursor suspension or solution at atmospheric pressure. The pressure generally is from 1 bar to 200 bar, preferably from 2 bar to 100 bar, and most preferably from 3 bar to 10 bar. Generally, the temperature is from 100⁰C to 300⁰C, more preferably from 110°C to 250⁰C, and most preferably from 120°C to 200°C. The suspending medium used in the process of the invention can be any suitable suspending medium known in the art. The suspending media include water, an organic solvent or mixtures thereof. Suitable examples of organic solvents include alcohols such as methanol, ethanol, 1 -propanol, and isopropanol; and alkoxylated alcohols such as propylene glycol monomethyl ether and propylene glycol monoethyl ether; and alkanes such as pentane, hexane, and heptane; and aromatic hydrocarbons such as benzene, toluene, and xylene. Preferably, the suspending medium comprises water, an alcohol and/or an alkoxylated alcohol.

A solvothermal treatment in a suspending medium comprising water and an organic solvent or containing only water is also referred to as a "hydrothermal treatment".

The divalent metal ion source containing carbonate, the trivalent metal ion source, and the divalent metal ion source free of carbonate used in the process can be any source known to the man skilled in the art. These sources include soluble salts of the divalent and/or trivalent metal ions as well as insoluble or partially insoluble divalent and trivalent metal ion sources, or mixtures thereof.

Soluble salts of metal ion sources include nitrates, chlorides, perchlorates, and also aluminates. The insoluble or partially insoluble divalent and trivalent metal ion sources generally include oxides or hydroxides, carbonates of the divalent or thvalent metal ions. Preferably, the sources are insoluble or partially soluble. Most preferably, the further divalent and trivalent metal ion sources are oxides and/or hydroxides.

In the context of the present application "soluble salts" refers to divalent and trivalent metal ion sources that dissolve completely and form a clear solution at room temperature. In the context of the present application the wording "insoluble or partially insoluble" refers to sources that do not dissolve completely and form a suspension at room temperature.

Examples of divalent metal ions are Zn²⁺, Mn²⁺, Ni²⁺, Co²⁺, Fe²⁺, Cu²⁺, Sn²⁺, Ba²⁺, Ca²⁺, and Mg²⁺. Examples of trivalent metal ions are Al³⁺, Cr³⁺, Fe³⁺, Co³⁺, Mn³⁺, Ni³⁺, Ce³⁺, and Ga³⁺. It is also contemplated to use three or more different metal ions in the layered double hydroxide prepared with the process of the invention. Of the above metal ions the combination of Mg²⁺ and/or Zn²⁺ and Al³⁺ is preferred.

The magnesium source containing carbonate is generally selected from the group consisting of magnesium hydroxycarbonate, hydromagnesite (Mg₅(COs)₄(OH)₂), magnesium carbonate, magnesium bicarbonate, and dolomite. A combination of two or more carbonate-containing magnesium sources is also contemplated.

Examples of suitable magnesium sources which are insoluble or partially insoluble include magnesium oxide, magnesium hydroxide, magnesium hydroxycarbonate, hydromagnesite (Mg₅(COs)₄(OH)₂), magnesium carbonate, magnesium bicarbonate, dolomite, and sepiolite. The magnesium source free of carbonate may be magnesium oxide or magnesium hydroxide. A combination of two or more magnesium sources is also contemplated. The zinc source containing carbonate is generally selected from the group consisting of zinc hydroxycarbonate, zinc carbonate, and zinc bicarbonate. A combination of two or more carbonate-containing zinc sources is also contemplated.

Examples of suitable zinc sources which are insoluble or partially insoluble include zinc oxide, zinc hydroxide, zinc hydroxycarbonate, zinc carbonate, and zinc bicarbonate. The zinc source free of carbonate may be zinc oxide or zinc hydroxide. A combination of two or more zinc sources is also contemplated. It is also contemplated to use a combination of at least one magnesium source and at least one zinc source.

The aluminium source which is insoluble or partially insoluble typically is a hydroxide or an oxide of aluminium. Examples of such an aluminium source are aluminium trihydroxides such as gibbsite and bayerite, aluminium oxohydroxides such as boehmite, diaspore or goethite, and transition aluminas, which are known to the man skilled in the art.

The use of the above insoluble or partially soluble divalent metal ion and trivalent metal ion sources provides a process that is more environment- friendly, as considerably less salt - if any - remains in the waste stream resulting from the process. Moreover, the divalent and trivalent metal ion sources, and in particular the magnesium, zinc, and aluminium sources, generally are less expensive than the corresponding salts commonly used in the production of layered double hydroxides. In addition, the process of the invention generally is simpler, as it requires fewer steps and/or does not require an after-treatment of the waste stream. Furthermore, these processes may be performed in a much shorter time, which in turn may lead to a higher production rate of the layered double hydroxide compared to conventional processes. In a preferred embodiment of the process for preparing the LDH, the trivalent metal ion source is aluminium trihydroxide or boehmite and the divalent metal ion source is selected from the group consisting of magnesium oxide, hydromagnesite, magnesium carbonate, and nesquehonite.

The pH of a suspension of the LDH is preferably lower than 9, more preferably below 8.5.

In a preferred embodiment of the process for preparing the LDH, the insoluble or partially soluble divalent and/or trivalent metal ion sources, and in particular the magnesium, zinc and/or aluminium sources, are milled prior to step (b). These metal ion sources may be milled in the presence of the suspending medium or without the suspending medium. In the preparation process the divalent and/or trivalent metal ion sources generally have a d50 value of less than 20 μm and a d90 value of less than 50 μm. Preferably, the d50 value is less than 15 μm and the d90 value is less than 40 μm, more preferably the d50 value is less than 10 μm and the d90 value is less than 30 μm, even more preferably the d50 value is less than 8 μm and the d90 value is less than 20 μm, and most preferably the d50 value is less than 6 μm and the d90 value is less than 10 μm. The particle size distribution can be determined using methods known to the man skilled in the art, e.g. laser diffraction in accordance with DIN 13320. This milling step allows the formation of the layered double hydroxide to proceed faster. It further may reduce the amount of impurities such as gibbsite or brucite if the divalent and trivalent metal ion sources are magnesium and aluminium sources.

Generally, at least 10% of the total amount of charge-balancing anions is carbonate, preferably at least 30%, more preferably at least 60%, and most preferably at least 90% of the total amount of charge-balancing anions is carbonate. It is also envisaged that 100% of the total amount of charge- balancing anions is carbonate.

In one embodiment, a mixture of the divalent metal ion source containing carbonate and the further divalent metal ion source free of carbonate is used. The weight ratio of the carbonate-containing to the carbonate-free divalent metal ion sources is generally from 100:1 to 1 :100, preferably from 50:1 to 1 :50, and most preferably from 10:1 to 1 :10.

In a preferred embodiment of the present invention, the LDH is treated with a compatiblising agent in order to render the LDH more hydrophobic. Such a coating agent can be any coating agent known in the art. Examples of such coating agents include mono-, di- or polycarboxylic acids, sulfonic acids, phosphonic acids, and sulfate acids, thiols, benzothiols, phenols, and salts thereof. Suitable examples are fatty acids or salts thereof having from 8 to 22 carbon atoms. In the context of this application the wording "fatty acid" refers to the acid as well as the salt of the acid. Such a fatty acid may be a saturated or unsaturated fatty acid. Suitable examples of such fatty acids are caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, decenoic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, and mixtures thereof. A preferred fatty acid is stearic acid and the salt thereof. The coating agent is used in order to increase the hydrophobic nature of the LDH and improve its compatibility with polymeric matrices such as polyvinyl chloride (PVC). This fatty acid treatment can be conducted in any way known in the art. The fatty acid can be added before, during or after step b) of the preparation process. After the LDH is formed, the fatty acid can be added to the slurry in a molten state or in solid form. The fatty acid may also be added to the slurry or solution before or during the solvothermal treatment of step b). This latter route is preferred over the former because the resulting product is more hydrophobic and its compatibility with a polymeric matrix such as PVC is improved. Moreover, the treated LDH may form fewer agglomerates and may be more finely and uniformly distributed throughout a polymeric matrix. It is believed - without wishing to be bound by any theory - that the treated LDH is coated more efficiently and more extensively compared to a treated LDH obtained via the after-treatment route. Alternatively, the fatty acid can be added to the slurry or solution as a magnesium or zinc salt in step a) or during step b) of the preparation process. This has the advantage that the magnesium and/or zinc ions of the fatty acid salt can be used in the formation of the LDH, so that no salts remain in the waste stream. Suitable examples of such fatty acid salts are magnesium stearate and zinc stearate.

The amount of coating agent used is in the range from 0.01 to 10 wt.%, preferably from 0.1 to 8 wt.%, and most preferably from 0.2 to 5 wt.%, based on the weight of the divalent and thvalent metal ion sources.

The present invention also relates to the use of a layered double hydroxide as described hereinbefore in a polymer-containing composition which comprises a thermoset polymer for improving the transparency and/or adhesion properties of the polymer-containing composition.

Moreover, the present invention also relates to the use of a layered double hydroxide as described hereinbefore in a polymer-containing composition which comprises a nonhalogen-containing thermoplastic polymer for improving the flame retardancy of the polymer-containing composition.

The present invention also relates to the use of a present polymer- containing composition in a coating, ink, cleaning, rubber or rubber formulation, drilling fluid, cement formulation, plaster formulation, paper pulp, or glass fibre reinforced, carbon fibre reinforced or natural fibre reinforced composites. In addition, the present invention provides a polymer formulation which comprises a polymer-containing composition according to the present invention.

The present invention further relates to a coating composition comprising the polymer-containing composition according to the present invention. Such coatings include finishing or top coatings and cable coatings.

The present invention also relates to an article comprising a polymer- containing composition according to the present invention. Suitable articles include, for instance, printed circuit boards, and any article which includes reinforced polyester material(s), such as pieces of furniture, yachts, etc.

The present invention further provides a process for preparing the present polymer-containing composition, which process comprises the steps of: a) providing a thermoset polymer and/or nonhalogen-containing thermoplastic polymer; b) adding the layered double hydroxide to the thermoset polymer or one or more of its components or to the nonhalogen-containing thermoplastic polymer under stirring/mixing conditions; and c) recovering the polymer-containing composition.

The present invention is further illustrated by means of the following Examples.

Examples

Preparation of hydrotalcite carbonate (HTC-CO₃) in thermoplastic polymers The fire retardancy of additives was tested in a polymer compound. The test was performed as described below, which is similar to the UL-94 test method. The polymer compounds and additives were milled for 15 minutes in a Haake Rheocord 90 with a Rheomix 600 internal mixer/ mixing chamber at 16O⁰C and 40 revs. After this the mixture was pressed in a Fontijne Holland press. For this pressing the material was weighed, put in a mould, and pressed at 180⁰C. The waiting time was 1 minute at < 10 kN so the polymers could melt. Then the mixture was pressed for 1 minute at < 50 kN and 3 minutes at 150 kN and cooled down for 30 minutes at 150 kN. The pressed plates were cut into strips of 1.27 x 12.7 cm. The strips were hung in the UL-94 test chamber one by one and the flame was held under them for 10 seconds. If the strip burned, it had to extinguish before the flame could be held under it again for 10 seconds. There are three classifications: VO, V1 , and V2, which depend on the flame retardancy behaviour.

- V2: burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed. - V1 : burning stops within 30 seconds on a vertical specimen; no drips allowed. - VO: burning stops within 10 seconds on a vertical specimen; no drips allowed.

The polymer used was Escorene Ultra EVA UL00328. Several additives were tested in several polymer/additive ratios:

- Magnesium dihydroxide (MDH, Magshield UF) - Aluminium trihydroxide (ATH, Alumill F505 or martinal OL-104IE)

- Hydrotalcite (HTC-OH, AkzoNobel, AN, product)

- Hydrotalcite carbonate (HTC-CO3, AkzoNobel product)

- Hydrotalcite carbonate (HTC-CO3, Alcemizer 1 ex Kisuma Chemicals)

From Table 1 it will be clear that the compositions according to the present invention meet the VO classification, which means that they stopped burning within 10 seconds on a vertical specimen and that no dripping occurred, whereas the compositions falling outside the scope of the present invention (the Comparative Examples with a L/D of smaller than 100) did not meet any of the V0-V2 classifications because they burned for a long time and showed dripping. Hence, it can only be concluded that the present invention constitutes a clear improvement over the known compositions. Preparation of hydrotalcite carbonate (HTC-CO₃) samples in thermosetting resins

All twelve samples were prepared using a high-speed dissolver of the type Dispermat CN 20 F2 marketed by VMA Getzmann GmbH. A resin, or a resin solution, was weighed into a beaker and next dry hydrotalcite carbonate powder was added. The HTC powder was mixed in at low speed/low shear, to prevent it being blown away. Once all the HTC had been mixed in, the stirring speed was increased to a maximum of 10,000 rpm depending on the type and viscosity of the resin or resin solution to be modified. The various compositions and process conditions are shown in Table 2.

Cure behaviour: The clay-modified resins were tested for cure behaviour in several systems. Polyamines were cured with epoxy resins at 80⁰C for 1 hour in a circulation oven. Clay-modified epoxy resins were cured with amines at 80⁰C for 1 hour in a circulation oven. Clay-modified polyester polyols were cured with isocyanates at 140°C for 1 hour in a circulation oven. The polyol-isocyanate reactions were catalysed with dibutyltin dilaurate.

Unsaturated polyesters, dissolved in styrene, were cured with MEK-peroxide (1.2 wt. % of a 50 wt. % solution) catalysed by cobalt (II) 2-ethylhexanoate (0.15 wt.% of a 6 wt.% solution in mineral spirit ex Aldrich) at room temperature for 24 h. Curing was followed by a post-cure of 16 h at 80⁰C. Material was cured in a test tube with a height of 15 cm and a diameter of 1.5 cm. The clay did not settle during polymerisation, and its composition was the same at the top of the tube as at the bottom of the tube. Measurements were performed with thermogravimetric analysis (TGA). The following results were obtained:

• Curing of epoxy resins modified with carbonate HTCs (samples 4/5) with amines was not negatively affected by the presence of the clay. • Curing of polyamines with epoxy resins was not negatively affected by the presence of the clay.

• Curing of polyester polyol (sample 8) with toluene diisocyanate was not negatively affected by the presence of the clay. • Curing of polyester polyol (sample 12) with Desmodur W was not negatively affected by the presence of the clay.

• Curing of polyester polyol (sample 11 ) with TDI was not negatively affected by the presence of the clay.

• Curing of unsaturated polyester was not negatively affected by the presence of the clay.

It is further observed that all cured coatings in accordance with the invention gave hard transparent films containing only a slight haze. Unsaturated polyesters containing more than 10 wt.% of the clay were found to be less transparent.

Fire retardancy:

Fire retardancy was tested on unsaturated polyester resins according to a UL-94 procedure (except for the dimensions of the test specimen). The test tube was placed 1 cm above the burner. After ignition the specimen was kept in the flame for 10 seconds and then removed. If the test specimen did not burn, the procedure was repeated. The sample containing no HTC-CO3 burned already after 10 seconds in the flame. All other samples according to the present invention and containing respectively 10, 30, and 40 wt.% HTC- CO3, based on total composition, did not burn after 10 seconds in the flame. It can therefore be concluded that the polymer-containing compositions in accordance with the present invention display an improved performance when compared with the known compositions. Table 1

^(a) Aid is ex Kyowa Kisuma Table 2 HTC-CO₃ modified resins

1 ) Thiocure PETMP ex Bruno Bock

2) Setal 291 high solid alkyd resin ex AkzoNobel

3) Ancamine 830 ex Air Products

4) Epikote 828 ex Resolution

5) Thioplast G131 ex AkzoNobel

6) Mono methoxypolyethylene glycol (Mn=350) modified with succinic anhydride

7) Polyesterpolyol of Elastogran

8) Synolite 1967 ex DSM Comparative Example A: Production

4,492 g of cold (20⁰C) water were put into a container. Into it were dispersed 841 g of MgO (Zolitho 40). Cold water was used in order to prevent an immediate reacting to Mg(OH)₂. The thus obtained magnesium oxide suspension was passed over a rotator ball mill (Dynomill Type KDL-Pilot Bachofen with Pearls 0.5 mm Type Y Zr O₂; throughput 70 g/min), followed by washing with washing water. After the intensive grinding the mean particle size came to about 0.65 μm (D₅₀). 1 ,157 g of the ground MgO suspension (Mg content 15w%) were diluted in 2,121 g of demineralised water. 123 g of CO₂ were introduced from the bottom (at room temperature). The introduction took place over about 2 hours in all. In a separate container 354 g of aluminium hydroxide (Alumil F505) were dissolved in 647 g of caustic soda (50% NaOH content) at 100⁰C to form sodium aluminate.

Next, the magnesium hydroxycarbonate dispersion formed as stated above was mixed with 427 g of the Na-aluminate solution. During the mixing there was intensive stirring for 14 hours. The temperature of the mixing suspension came to about 80°C. The resulting product was subjected to a hydrothermal treatment for 6 hours at 180⁰C and cooled to 80°C within 10 hours. The obtained hydrotalcite crystals were filtered off and dried in a vacuum oven at 80°C for 16 h.

The thus obtained product was analysed using XRD, which showed that the product contained significant amounts of Na₂COs and NaAICOs(OH)₂ (Dawsonite), which are hygroscopic and alkaline.

The product was furthermore analysed with SEM, which showed that the L/D ratio was about 100. Figure 2 is a SEM image of said product.

B: Resin modification

Subsequently, the product was ground in a mortar to very fine powder which was used for modifying epoxy resin Epikote 828 and polyamine resin lnca 830. Epikote resin 828 was modified with 20 wt.% of the product prepared in Comparative Example A (see Table 3). The sample looked very smooth and did not show large aggregates, lnca 830 was modified with 15 wt.% of the product prepared in Comparative Example A, but gave a less smooth dispersion. The modified Epikote sample was subsequently mixed with the modified lnca 830 sample. The mixture appeared to give some larger aggregates which became worse when a film was drawn on a glass plate. Although the film itself was transparent, large aggregates were visible, destroying the appearance of the film. Furthermore, the film did not adhere well to the glass plate and was water- sensitive.

Table 3

Films based on Epikote 828 and lnca 830 containing the layered double hydroxide according to the present invention did not show any aggregates and gave a very smooth film on a glass plate having good adherence. Furthermore, this film was water-resistant.

Claims

1. A polymer-containing composition which comprises a layered double hydroxide in a polymer matrix, wherein the layered double hydroxide, comprising stacks of individual platelets, comprises carbonate as charge-balancing anion and wherein the individual platelets have an average length over thickness ratio (L/D ratio) above 150, and the polymer matrix comprises a thermoset polymer and/or a nonhalogen- containing thermoplastic polymer.

2. A composition according to claim 1 , wherein the L/D ratio is at least 200.

3. A composition according to claim 1 or 2, wherein the layered double hydroxide has a layered structure corresponding to the general formula

(I):

[M^⁺ (OH)_2m+2n Jx-- bH₂O (I)

wherein M²⁺ is a divalent metal ion such as Zn²⁺, Mn²⁺, Ni²⁺, Co²⁺, Fe²⁺,

Cu²⁺, Sn²⁺, Ba²⁺, Ca²⁺, and Mg²⁺, M³⁺ is a trivalent metal ion such as Al³⁺, Cr³⁺, Fe³⁺, Co³⁺, Mn³⁺, Ni³⁺, Ce³⁺, and Ga³⁺, m and n have a value such that m/n = 1 to 10, and b has a value in the range of from 0 to 10, and wherein X_n/_Z ^z" is CO3^2" or a mixture of CO3^2" and one or more anions selected from the group consisting of hydroxide, bicarbonate, nitrate, chloride, bromide, sulfonate, sulfate, bisulfate, vanadates, tungstates, borates, and phosphates.

4. A composition according to any one of claims 1 -3, wherein the layered double hydroxide comprises a hydrotalcite or a hydrotalcite-like anionic layered double hydroxide.

5. A composition according to any one of claims 1 -4, wherein the polymer matrix comprises a thermoset polymer which is present in an amount in the range of from 3-95 wt.%, based on total composition.

6. A composition according to any one of claims 1 -4, wherein the polymer matrix comprises a nonhalogen-containing thermoplastic polymer which is present in an amount in the range of from 20-70 wt.%, based on total composition.

7. A composition according to any one of claims 1 -5, wherein the thermoset polymer is selected from the group consisting of unsaturated polyester resins, acrylate resins, methacrylate resins, polyimides, epoxy resins, fenol formaldehyde resins, urea formaldehyde resins, melamine formaldehyde, bis/tris allyl ethers, and polyurethanes.

8. A composition according to any one of claims 1 -4 and 6, wherein the nonhalogen-containing thermoplastic polymer is selected from the group consisting of polyethylene terephthalate, polyimides, polycarbonates, polyaryl ethers, polysulfones, polysulfides, polyamides, polyether imides, polyether esters, polyether ketones, polyether ester ketones, polysiloxanes, polyurethanes, polyepoxides, polystyrene, acetal (co)polymers, butadiene nitrile rubber, silicon rubbers, and ethylene vinyl acetate rubber.

9. A composition according to any one of claims 1 -8, wherein the layered double hydroxide comprises two or more saturated or unsaturated fatty acids or salts thereof having from 8 to 22 carbon atoms.

10. Use of a layered double hydroxide as defined in any one of claims 1 -4 in a polymer-containing composition which comprises a thermoset polymer for improving the transparency and/or adhesion properties of the polymer-containing composition or which comprises a nonhalogen- containing thermoplastic polymer for improving the flame retardancy of the polymer-containing composition.

11. Use of a polymer-containing composition according to any one of claims 1 -9 in a coating, ink, cleaning, rubber or rubber formulation, drilling fluid, cement formulation, plaster formulation, paper pulp, or glass fibre reinforced, carbon fibre reinforced or natural fibre reinforced composites.

12. A polymer formulation which comprises a polymer-containing composition according to any one of claims 1 -9.

13. A coating composition comprising the polymer-containing composition according to any one of claims 1 -9.

14. An article comprising a polymer-containing composition according to any one of claims 1 -9.

15. A process for preparing a polymer-containing composition according to any one of claims 1 -9 comprising the steps of: a) providing a thermoset polymer and/or nonhalogen-containing thermoplastic polymer; b) adding the layered double hydroxide to the thermoset polymer or one or more of its components or to the nonhalogen-containing thermoplastic polymer under stirring/mixing conditions; and c) recovering the polymer-containing composition.