GB2596345A

GB2596345A - Synthetic stone

Info

Publication number: GB2596345A
Application number: GB2009794.5A
Authority: GB
Inventors: Christopher Apsey Glenn; Fisher Adam
Original assignee: Perspex International Ltd
Current assignee: Perspex International Ltd
Priority date: 2020-06-26
Filing date: 2020-06-26
Publication date: 2021-12-29
Also published as: GB202009794D0; WO2021260393A1; WO2021260393A8; EP4172127A1

Abstract

There is described an article comprising polymer particles, wherein at least some of the polymer particles are in the form of an agglomerated network of polymer particles; and ≥70% of inorganic filler by total weight of the article,. Also described is a composition for use in forming an article by compression moulding and a method of forming an article where the polymer material used comprises ≥ 80% by weight of polymer particles. The polymer particles may comprise (co)polymers selected from acrylic, styrene methyl methacrylate (SMMA), general purpose polystyrene (GPPS), high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), methyl methacrylate-butadiene-styrene (MBS), styrene acrylonitrile (SAN), polylactic acid (PLA), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and/or polyvinyl butyral (PVB).

Description

SYNTHETIC STONE

FIELD

[1] The present invention relates to synthetic stone. More specifically, the present invention relates to synthetic stone for use as exterior building cladding.

BACKGROUND

[2] Synthetic stone is the term used to describe industrially manufactured products designed to replicate the aesthetics and performance of natural stone such as granite and marble. However, due to the extensive range of raw materials that can be used synthetic stone offers a wider range of aesthetics and performance characteristics than natural stone. Imperfections often found in natural stone can be eliminated giving higher performing and more consistent products. In addition, synthetic stone can be produced which is less expensive and of lower density to facilitate handling.

[3] It is known to manufacture synthetic stone by binding reactive organic resins, particularly unsaturated polyesters, with a mix of natural and/ or artificial filler optionally including colouring pigments to attain the required aesthetic. The most predominantly used manufacturing process involves the production of engineered stone by pouring of a mix of unsaturated polyester resin, filler and pigments into a mould. The contents are subject to a process that includes exposure to a vacuum together with vibrational and compressive forces to produce a deaerated and compacted slab. The slab is then exposed to a high temperature to allow for the curing of the unsaturated polyester resin typically using a peroxide initiator.

[4] There are several drawbacks to this process. The use of unsaturated polyester resins means that there needs to be suitable engineering controls to limit exposure to styrene and to reduce environmental emissions. There also need to be suitable safety controls to manage the storage and handling of peroxides and transition metal accelerators. Controlled cooling of the cured slabs needs to take place which adds a further step and additional plant equipment to the process. Additionally, there are economic limitations to the thickness of slabs that can be produced since thinner gauge products have a higher proportion of associated waste principally as a result of grinding to the required dimensions. As a result thicknesses are limited to at least 12mm.

[5] Another route to the manufacture of synthetic stones is to use an inorganic material to bind filler mixes by a high temperature sintering process. The pressures and temperatures used are much higher than those employed using reactive organic resins. These conditions allow the minerals to fuse together into a compacted stone.

[6] However, this process also has several drawbacks. There are limitations in the number and type of pigments that can be used due to the high processing temperatures employed. There are also high energy costs due to the elevated temperatures used which are typically 1000t or higher. The resultant slabs have poor impact and chipping resistance in comparison with products made using unsaturated polyester resins. In addition fabrication and installation is more difficult due to the nature of the resultant surface.

[7] Thus, there remains a requirement to produce a synthetic stone without the aesthetic, mechanical and processing drawbacks of sintered stone and without the need to handle hazardous and volatile monomers within organic resins and their associated curing agents or the additionally cited processing steps to achieve acceptable products.

[8] It is thereof an object of the present invention to address one or more of the above mentioned, or other, problems.

SUMMARY OF THE INVENTION

[9] According to a first aspect of the present invention there is provided an article comprising: i. polymer particles, wherein at least some of the polymer particles are in the form of an agglomerated network of polymer particles; and 7094, of inorganic filler by total weight of the article.

[10] According to a second aspect of the present invention there is provided an article obtained by compression moulding a composition comprising: i. polymer material, wherein the polymer material comprises nO% of polymer particles by total weight of the polymer material; and 70% of inorganic filler by total weight of the composition.

[11] According to a third aspect of the present invention there is provided a composition for use in forming an article by compression moulding, the composition comprising: i. polymer material, wherein the polymer material comprises 80% of polymer particles by total weight of the polymer material; and 70°/0 of inorganic filler by total weight of the composition.

[12] According to a fourth aspect of the present invention there is provided a method of forming an article, comprising the steps: a optionally, forming polymer particles; b contacting polymer particles with filler to form a composite composition, wherein the composite composition comprises: i. polymer material, wherein the polymer material comprises 80% of the polymer particles by total weight of the polymer material; and H. 700/0 of inorganic filler by total weight of the composition; and c. compression moulding the composite composition to form the article. DETAILED DESCRIPTION OF THE INVENTION [13] It has surprisingly been found that compression moulding a composition according to the present invention results in a synthetic stone-type article that can be produced using a significantly simplified and lower cost manufacturing process while achieving good physical properties such as strength and flexibility. The present invention can also provide a significantly higher manufacturing output than other methods of forming synthetic stone-type articles, such as the cure-type method used to form engineered stone. In addition, the present invention can provide a greener product than engineered stone by reducing the hazardous emissions that are produced during manufacture and by reducing waste by not requiring a post-moulding reduction in the thickness of the article to achieve the desired properties.

[14] The article of the first aspect of the present invention comprises polymer particles, wherein at least some of the polymer particles are in the form of an agglomerated network of polymer particles. The phrase 'agglomerated network of polymer particles' as used herein may refer to a network that comprises particle-like regions of polymer material in which there will typically be some coalescence between the particle boundaries of adjacent polymer particles.

[15] The polymer particles, and in particular the agglomerated network of polymer particles, typically forms adherent interactions with the filler. As such, the polymer particles, and in particular the agglomerated network of polymer particles, may be considered to provide binding of the filler.

[16] The agglomerated network of polymer particles of the present invention is typically formed by compression moulding a composition that comprises a high proportion of polymer particles in the polymer material at a temperature that is above the glass transition temperature (Tg) of the polymer particles. Using such a technique, the resulting article may comprise an observable agglomerated network of polymer particles. The article may comprise one or more agglomerated networks of polymer particles and may additionally include discrete polymer particles.

[17] A synthetic stone-type article of the present invention can be distinguished over cure-type polymer systems that are commonly used in applications such as the production of engineered stone. In such cure-type systems, a liquid polymer resin is typically mixed with a filler and a curing-type step is applied to set the polymer material into a continuous polymer matrix. 'Cure-type steps' can include setting, crosslinking, and the like. Typically, such cure-type systems use an initiator composition to effect the curing. The resulting polymer matrix will substantially be in the form of a continuous polymer matrix that does not comprise polymer particles, wherein at least some of the polymer particles are in the form of an agglomerated network of polymer particles.

[18] Similarly, a synthetic stone-type article of the present invention can be distinguished over synthetic stone-like articles that are produced by extrusion. The present invention requires only low shearing forces. In the present invention the ability to use only low shear forces means that even when the moulding temperature is above the melting point of the polymer particles, the polymer particles are not fully blended. In contrast, the high sheer forces required for production by extrusion result in full blending of the polymer particles into a single continuum.

[19] The agglomerated network of polymer particles of the present invention is readily distinguishable from a polymer matrix such as that produced using a cure-type liquid polymer resin method using normal tools of the art, including visual observation.

[20] UV fluorescent marking of the polymer material can be used to further enhance visibility of the agglomerated network of polymer particles. As shown in Figures 3 and 4, in the agglomerated network of polymer particles of the present invention a large number of delineated particle-like regions are clearly identifiable in the article, whereas for the cure-type method few, if any, particle boundaries in the matrix polymer material can be observed.

[21] Accordingly, the article of the present invention may be substantially formed in the absence of a cure-type step.

[22] The article of the second aspect of the present invention may comprise polymer particles, wherein at least some of the polymer particles are in the form of an agglomerated network of polymer particles.

[23] The composition of the second, third and fourth aspects of the present invention may be operable to form an article comprising polymer particles, wherein at least some of the polymer particles are in the form of an agglomerated network of polymer particles, suitably by compression moulding.

[24] In the article of the present invention, 50% of the polymer particles may be in the form of an agglomerated network of polymer particles, by weight of the polymer particles, such as 70% or 90°./..

[25] The polymer particles may have a D50 particle size of pm, such as 20 pm, or 50 pm.

D50 particle size as used herein was measured prior to compression moulding and determined according to ASTM D1921 -18 "Standard Test Methods for Particle Size (Sieve Analysis) of Plastic Materials".

[26] The polymer particles may have a D50 particle size of 51000 pm, such as 5750 pm, or 5600 Pm.

[27] The polymer particles may have a D50 particle size of from 1 to 1000 pm, such as from 20 to 750 pm, or from 50 to 600 pm.

[28] The polymer particles may comprise a first fraction of polymer particles having a D50 particle size of 5100 pm, such as 590 pm, or 580 pm, and a second fraction of polymer particles having a D50 particle size of >100, such as 200 pm, or n00 pm.

[29] The first fraction of polymer particles may have a D50 particle size of ?1, such as pm, or 20 pm.

[30] The second fraction of polymer particles may have a DSO particle size of 51000 pm, such as 5750 pm, or 5600 pm.

[31] The first fraction of polymer particles may have a D50 particle size of from 1 to 100 pm, such as from 10 to 90 pm, or from 20 to 80 pm. The second fraction of polymer particles may have a D50 particle size of from >100 to 1000 pm, such as from 200 to 750 pm, or from 300 to 600 pm.

[32] At least 5% of the polymer particles may have a D50 particle size according to the first fraction, by weight of the polymer particles, such as L10 wt% or 20 wt%.

[33] At least 10% of the polymer particles may have a DSO particle size according to the second fraction, by weight of the polymer particles such as 20 wt% or nO wt%.

[34] Advantageously, it has been found that the combination of a first polymer particle fraction and a second polymer particle fraction having the above-mentioned particle sizes results in a synthetic stone-type article having improved properties, in particular properties such improved water resistance, improved flexural strength and unique aesthetic properties.

[35] The polymer particles may have a weight average molecular weight (Mw) of 10,000 Da, such as 20,000 Da, or n0,000 Da.

[36] The polymer particles may have a Mw of 55,000,000 Da, such as 52,000,000 Da, or 51,000,000 Da.

[37] The polymer particles may have a Mw of from 10,000 to 5,000,000 Da, such as from 20,000 to 2,000,000 Da, or from 30,000 to 1,000,000 Da.

[38] The polymer particles may have a weight average molecular weight (Mw) of ?250 kDa, such as 500 kDa, or 750 kDa.

[39] As reported herein, the Mw was determined by gel permeation chromatography using a polystyrene standard according to ASTM D6579-11("Standard Practice for Molecular Weight Averages and Molecular Weight Distribution of Hydrocarbon, Rosin and Terpene Resins by Size Exclusion Chromatography". UV detector; 254nm, solvent: unstabilised THF, retention time marker: toluene, sample concentration: 2mg/m1).

[40] The polymer particles may have a Tg of 55 °C, such as 65 °C, or 75 °C.

[41] The polymer particles may have a Tg of 5150 °C, such as 5130 °C, or 5110 °C.

[42] The polymer particles may have a Tg of from 55 to 150 °C, such as from 65 to 130 °C, or from 75 to 110 °C.

[43] As reported herein, the Tg was measured according to ASTM D6604-00(2013) ("Standard Practice for Glass Transition Temperatures of Hydrocarbon Resins by Differential Scanning Calorimetry". Heat-flux differential scanning calorimetry (DSC), sample pans: aluminium, reference: blank, calibration: indium and mercury, sample weight: 10mg, heating rate: 20°C/min).

[44] The polymer particles may be formed from monomers selected from acrylic, acrylonitrile, other vinyl; unsaturated aliphatic, such as ethylene, propylene, butadiene; lactic acid; polyacid, such as terephthalic acid; and/or polyol.

[45] Acrylic monomers may be (hetero)aliphatic(alk)acrylate or (alk)acrylic acid, such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, t-butyl acrylate, n-butyl methacrylate, iso-butyl methacrylate, t-butyl methacrylate, 2-ethylhexy methacrylate, 2-ethylhexyl acrylate, lauryl methacrylate, lauryl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methacrylic acid or acrylic acid; hydroxyl-functional acrylates such as 2-hydroxyethyl methacrylate, hydroxypropylethyl methacrylate, 2-hydroxyethyl acrylate, or hydroxypropyl acrylate; allyl methacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,4-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol dimethacrylate and/or 1,6-hexanediol diacrylate.

[46] Other vinyl monomers may be selected from styrene, vinyl pyrrolidinone, vinyl pyridine and/or divinyl benzene.

[47] The polymer particles may be (co)polymers selected from acrylic, styrene methyl methacrylate (SMMA), general purpose polystyrene (GPPS), high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), methyl methacrylatebutadiene-styrene (MBS), styrene acrylonitrile (SAN), polylactic acid (PLA), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and/or polyvinyl butyral (PVB). Suitably, polyethylene and polypropylene polymer particles have a Tg of above 55°C.

[48] Acrylic polymer particles may be a homopolymer of a poly(hetero)aliphatic(alk)acrylate or (alk)acrylic acid or copolymers of a (hetero)aliphatic(alk)acrylate or (alk)acrylic acid with one or more other vinyl monomers. Suitably, at least 50% of the monomer residues are acrylic monomer residues, more typically, at least, 70% thereof, most typically, at least 80% thereof, especially, methyl methacrylate residues at such levels. Typically, a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate with one or more other vinyl monomers is used. By other vinyl monomers is included a further (hetero)aliphatic(alk)acrylate or (alk)acrylic acid such as ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, t-butyl acrylate, n-butyl methacrylate, iso-butyl methacrylate, t-butyl methacrylate, 2-ethylhexy methacrylate, 2-ethylhexyl acrylate, lauryl methacrylate, lauryl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methacrylic acid or acrylic acid; hydroxyl-functional acrylates such as 2-hydroxyethyl methacrylate, hydroxypropylethyl methacrylate, 2-hydroxyethyl acrylate, or hydroxypropyl acrylate; vinyl compounds such as styrene, vinyl pyrrolidinone or vinyl pyridine; and compatible crosslinking monomers such as ally! methacrylate, divinyl benzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,4-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol dimethacrylate or 1,6-hexanediol diacrylate, particularly the compatible acrylic crosslinking monomers.

[49] The polymer particles may be thermoplastic or thermoset. Suitably the polymer particles comprise crosslinked thermoset particles.

[50] The polymer particles may comprise cast or bead polymer particles. Beads may be produced by suspension, solution or emulsion polymerisation, suitably suspension polymerisation. Suitably the particles may comprise cast polymer particles, in particular cell cast polymer particles, such as by grinding cell cast polymer sheet.

[51] The polymer particles may comprise crushed, milled, and/or ground particles.

[52] The composition or article may comprise 530% polymer material by total weight of the composition or article, such as 520 wt% or 515 wt%.

[53] The composition or article may comprise n% polymer material by total weight of the composition or article, such as wt% or 0 wt%.

[54] The composition or article may comprise from 1 to 30% polymer material by total weight of the composition or article, such as from 5 to 20 wt% or from 10 to 15 wt%.

[55] The polymer material of the composition or article may comprise 50°/0 polymer particles by weight of the polymer material, such as 70 wt%, wt% or 90 wt%.

[56] Advantageously, it has been found that a higher proportion of polymer particles in the polymer material allows for shorter processing times. A higher proportion of polymer particles can also lead to reduced shrinkage and thereby a reduced requirement for surface grinding required post-moulding.

[57] The polymer material may comprise a polymer resin. Optionally, the polymer material may be substantially free of polymer resin.

[58] The polymer material of the composition may comprise 515% monomers by weight of the polymer material, such as 510 wt%, or 55 wt%.

[59] The polymer material of the article may comprise 55°/0 monomers by weight of the polymer material, such as 53 wt%, or 51 wt%.

[60] The polymer material of the composition or article may comprise low shrinkage monomer or oligomers; and/or other additives to enhance the performance of the article, such as lubricants and/or UV stabilisers.

[61] The polymer material of the composition or article may comprise 5071, acrylic monomer residues by total weight of the polymeric material, such as 75 wt% or nO wt%.

[62] The polymer material of the composition or article may comprise 20,10 crosslinked polymer by total weight of the polymer material, such as N.0 wt% or 60 wt%.

[63] The polymer material of the composition or article may comprise ?50% cast polymerised polymer by total weight of the polymer material, such as 75 wt% or 90 wt%.

[64] Advantageously, it has been found that the use of cast acrylic polymer material results in a synthetic stone-type article having improved properties, such as improved UV, solvent and chemical resistance [65] The composition may comprise S1 % of polymerisation initiator by weight of the composition, such as s0.5 wt% or S0.1 wt%. The composition may be substantially free of polymerisation initiator.

[66] The article may comprise S0.1°/0 of polymerisation initiator or residue thereof by weight of the article, such as S0.05 wt% or S0.01 wt%. The article may be substantially free of polymerisation initiator or residue thereof [67] The composition or article may comprise inorganic filler in an amount of aO % by weight of the composition or article, such as 85 wt%.

[68] The composition or article may comprise inorganic filler in an amount of s97 % by weight of the composition or article, such as 95 wt% or 90 wt%.

[69] The composition or article may comprise inorganic filler in an amount of from 70 to 97 % by weight of the composition or article, such as from 80 to 95 wt% or from 85 to 90 wt%.

[70] The type and level of inorganic fillers used will depend on the aesthetic and performance requirements in the final product. Any filler may be used as long as they are compatible with the polymeric material. The inorganic filler may comprise natural aggregate. As used herein, the term "natural aggregate" primarily means crushed or milled natural stone and minerals. The natural aggregate may be selected from calcium carbonate, quartz, cristobalite, granite, feldspar, marble, quartzite, dolomite, basalt, and ferrosilicon. Marble, granite, and quartz are particularly preferred, more preferably quartz.

[71] The term "inorganic filler" may also be understood to include or be completely made up of other materials, often added to polymeric compositions. Such fillers may include one or more of fumed silica, clay, fly ash, cement, broken ceramics, mica, silicate flakes, broken glass, glass beads, glass spheres, mirror fragments, steel grit, aluminium grit, carbides, barium sulfate, aluminium trihydrate, aluminum hydroxide, aluminum oxides, aluminum silicates, calcium carbonate, magnesium hydroxide, iron oxide, iron hydroxide, pigments, and/or colorants.

[72] The filler may be selected from natural aggregate, such as quartz, fumed silica and/or an inorganic pigment, such as Ti02.

[73] The size of the filler particles may vary depending upon the end use of the material. The size of the filler may depend on the aesthetic required. Plain colours will usually have smaller particles sizes whereas granites will contain a combination of different sizes depending on the effect required. Some stones may also contain large particle mirror glass. In most processes the average size D50 of the filler is 550 mm, preferably 540 mm, more preferably 530 mm. The filler may comprise a filler fraction having an average particle size within the range 0.01 to 100 mm, such as between 0.01 and 5 mm, 0.03 and 4 mm, or between 0.03 and 3 mm. Suitably, these sizes are particularly applicable to the natural aggregate in the filler. Particle size may be determined by using a laser process such as a Sedigraph III 5120 particle size analyser or by sieve sizes.

[74] The composition or article may comprise a flame-retardant inorganic filler, such as aluminium trihydrate and/ or magnesium hydroxide.

[75] The filler may comprise a filler material, optionally a first filler material, having a Mohs hardness of a5, such as a6 or a7.

[76] The filler may comprise a second filler material in addition to a first filler material having a lower Mohs hardness than the first filler material, such as a Mohs hardness of 57, such as 55 or 53.

[77] The filler may comprise a first filler material an amount of a30 % by weight of the filler, such as a 40 wt°/o, or a 50 wt%.

[78] The filler may comprise a first filler material an amount of 5 95% by weight of the filler, such as 5 90 wt%, or 5 85 wt%.

[79] The filler may comprise a first filler material an amount of from 30 to 95% by weight of the filler, such as from 40 to 90 wt%, or from 50 to 85 wt%.

[80] The filler may comprise a second filler material an amount of a5 % by weight of the filler, such as a 10 wt%, or a 15 wt%.

[81] The filler may comprise a second filler material an amount of 5 50% by weight of the filler, such as 5 40 wt%, or 5 35 wt%.

[82] The filler may comprise a second filler material an amount of from 5 to 50% by weight of the filler, such as from 10 to 40 wt%, or from 15 to 35 wt%.

[83] The first filler material may comprise filler selected from quartz.

[84] The second filler material may comprise material selected from aluminium trihydrate and/or magnesium hydroxide [85] Advantageously, it has been found that the combination of a first inorganic filler material and a second inorganic filler material having different Mohs hardness results in a synthetic stone-type article having improved properties.

[86] The composition or article may comprise inorganic filler that is at least partially encapsulated by polymer material.

[87] The at least partially encapsulated inorganic filler may be filler according to the second filler material and/or a flame-retardant filler.

[88] The composition or article may comprise at least partially encapsulated filler in an amount of % by weight of the composition or article, such as MO wt% or M5 wt%.

[89] The composition or article may comprise at least partially encapsulated filler in an amount of E30 % by weight of the composition or article, such as 60 wt% or 30 wt%.

[90] The at least partially encapsulated filler may be formed by polymerising a monomer composition in the presence of the said filler, for example in a cast polymerisation.

[91] The composition may have a solids content of nO % by total weight of the composition, such as 95vvt%, n8wt% 99wt% or 99.9wt%.

[92] The article may further comprise a dye. Suitably, the polymer material may comprise a dye, for example a dye absorbed into the polymer material. For example, the dye may be applied by dye sublimation. As used herein, the term "dye" is intended to refer to colouring materials that can dissolve in a liquid, such as water and/or liquid polymer material.

[93] The dye may be applied during formation of the article, suitably during compression moulding of the article. The dye may be applied by dye sublimation during moulding of the article.

[94] Advantageously, a dye design can be formed on the articles of the present invention during moulding of the article, without requiring any post-moulding steps. Dye sublimation can be carried out simultaneously during moulding to produce a myriad of printed surface effects in which the dye is embedded within the surface.

[95] In contrast, generating dye designs on other types of synthetic-type stone, such as engineered stone and ceramic stone, have required the use of further steps after moulding, which are energy and time consuming. For example, the amount of liquid that is used in the production of engineered stone (i.e. the liquid resin) and ceramic stone (i.e. water present in ceramic materials before firing) means that dye sublimation cannot be used during moulding because the dye would be dissolved before pressing, thereby ruining the design. In addition, for engineered stone shrinkage of the resin during cure deforms the intended pattern. Furthermore, due to the post-moulding grinding and polishing that is required for engineered stone the surface of the sheet is a mixture of quartz particles and polymer. This means that even if dye sublimation is attempted after producing engineered stone slabs the result would not be as clear or have as good coverage as the image produced by the present invention because the dye would only absorb into the polymer material and not into the exposed filler. For ceramic stone the temperatures employed are too high for the dyes which necessitates a separate printing process once the product has been manufactured. This printing process does not absorb the ink into the surface in the way sublimation does. Typically to sublimate on ceramic surfaces a polymer coating must first be applied to a ceramic finished product.

[96] Polymer particles may be formed by polymerising a monomer composition in the presence of a filler, for example in a cast polymerisation. Where required, particles may then be formed from the polymerisation product, such as by crushing, milling and/or grinding. Suitably, the filler may be a second filler material as defined above and/or a flame-retardant filler.

[97] Polymer particles may be mixed with the filler such as to form a substantially homogenous composite composition.

[98] The composite composition may be compression moulded by arranging the composition into a suitable mould, optionally levelling the composition, and then applying heat and pressure to the composition.

[99] The composition may be compression moulded at a temperature that is greater than the glass transition temperature (Tg) of the polymer particles, suitably of the polymer material. It will be understood that the appropriate temperature will depend on the specific polymer material, but typically the composition may be compression moulded at a temperature of a85°C, such as a120°C, or a150°C.

[100] The composition may be compression moulded at a temperature that is less than the melting temperature of the polymer particles, suitably of the polymer material. The composition may be compression moulded at a temperature of 5230°C, such as 5200°C, or 5180°C.

[101] The composition may be compression moulded at a temperature of from 85 to 230°C, such as from 120 to 200°C, or from 150 to 180°C.

[102] The composition may be compression moulded at a pressure of a10 bar, such as a25 bar of a40 bar.

[103] The composition may be compression moulded at a pressure of 5200 bar, such as 5100 bar, or 570 bar.

[104] The composition may be compression moulded at a pressure of from 10 to 200 bar, such as from 25 to 100 bar, or from 40 to 70 bar.

[105] The composition may be compression moulded for a10 seconds, such as a30 seconds or a60 seconds.

[106] The composition may be compression moulded for 5300 seconds, such as for 5200 seconds, or for 5100 seconds.

[107] The composition may be compression moulded for from10 to 300 seconds, such as for from 30 to 200 seconds, or for from 60 to 100 seconds.

[108] The article may have a density that is 94°/0 of the theoretical density based on the components used to form the article during the moulding step, such as 95°/0 or 96°/0.

[109] Advantageously, it has been found that present invention can produce a synthetic stone-type article having a density that is closer to the theoretical density than the cure-type method used to produce engineered stone. This allows for thinner articles to be produced while still achieving the desired physical properties.

[110] In contrast, previous methods of producing synthetic stone-type articles have been found to suffer from a significant difference between the density achieved and the theoretical density. Other methods can also require complex processing to reduce air from the article during production. For example, the production of engineered stone requires vacuum and vibration to be applied. Similarly, in extrusion and injection moulding the process typically involves use of a vacuum to remove air and volatiles due to the high temperatures used. Vacuum can also be required to remove air from a mould as the melt is injected.

[111] The present invention can be produced with a density that is closer to the theoretical density than these other methods of production without requiring use of vacuum or special vent grooves. The air can also be removed to form a substantially void free article without the propensity for flashing observed in the moulding of plastics.

[112] The density can also be improved by the fact that unlike in engineered stone there need not be a curing process. A curing process can lead to dimensional changes and the formation of voids between the polymer and filler particles (shrinkage).

[113] The present invention is especially suitable for manufacturing synthetic stone-type articles for use outdoors, such as for the production of tabletops, countertops, architectural facings such as cladding, walkways, patio furniture, decorative stone, outdoor tile, flooring, mantles, wall facings, and imitation stone structures, among others.

[114] The article of the present invention may be for use as a cladding material, suitably for exterior wall cladding.

[115] The article, such as cladding material, may have an average thickness of 0 mm.

[116] Definitions [117] For the purpose of the present invention, an aliphatic group is a hydrocarbon moiety that may be straight chain (i.e. unbranched), branched, or cyclic and may be completely saturated, or contain one or more units of unsaturation, but which is not aromatic. The term "unsaturated" means a moiety that has one or more double and/or triple bonds. The term "aliphatic" is therefore intended to encompass alkyl, cycloalkyl, alkenyl cycloalkenyl, alkynyl or cycloalkenyl groups, and combinations thereof The term "(hetero)aliphatic" encompasses both an aliphatic group and/or a heteroaliphatic group.

[118] An aliphatic group is optionally a C1_30 aliphatic group, that is, an aliphatic group with 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,29 or 30 carbon atoms. Optionally, an aliphatic group is a C1-15 aliphatic, optionally a C1-12 aliphatic, optionally a C1_10 aliphatic, optionally a C1-8 aliphatic, such as a Cl_8aliphatic group. Suitable aliphatic groups include linear or branched, alkyl, alkenyl and alkynyl groups, and mixtures thereof such as (cycloalkyl)alkyl groups, (cycloalkenyl)alkyl groups and (cycloalkyl)alkenyl groups.

[119] A heteroaliphatic group (including heteroalkyl, heteroalkenyl and heteroalkynyl) is an aliphatic group as described above, which additionally contains one or more heteroatoms. Heteroaliphafic groups therefore optionally contain from 2 to 21 atoms, optionally from 2 to 16 atoms, optionally from 2 to 13 atoms, optionally from 2 to 11 atoms, optionally from 2 to 9 atoms, optionally from 2 to 7 atoms, wherein at least one atom is a carbon atom. Optional heteroatoms are selected from 0, S, N, P and Si. When heteroaliphatic groups have two or more heteroatoms, the heteroatoms may be the same or different. Heteroaliphatic groups may be substituted or unsubstituted, branched or unbranched, cyclic or acyclic, and include saturated, unsaturated or partially unsaturated groups.

[120] The term "alkyl" and "alk" as used herein, refers to saturated, straight-or branched-chain hydrocarbon radicals derived by removal of a single hydrogen atom from an aliphatic moiety. An alkyl group is optionally a "C1_20 alkyl group", that is an alkyl group that is a straight or branched chain with 1 to 20 carbons. The alkyl group therefore has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19 or 20 carbon atoms. Optionally, an alkyl group is a C1-15 alkyl, optionally a C1-12 alkyl, optionally a C1_10 alkyl, optionally a C1-8 alkyl, optionally a C1_6 alkyl group. Specifically, examples of "C1_20 alkyl group" include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, sec-pentyl, iso-pentyl, npentyl group, neopentyl, n-hexyl group, sec-hexyl, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, npentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, 1-ethyl-2-methylpropyl group, 1,1,2-trimethylpropyl group, 1-ethylbutyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyl group, 3-methylpentyl group and the like.

[121] The term "alkenyl," as used herein, denotes a group derived from the removal of a single hydrogen atom from a straight-or branched-chain aliphatic moiety having at least one carbon-carbon double bond. The term "alkynyl," as used herein, refers to a group derived from the removal of a single hydrogen atom from a straight-or branched-chain aliphatic moiety having at least one carbon-carbon triple bond. Alkenyl and alkynyl groups are optionally "C2_20alkenyl" and "C2_20alkynyl", optionally "C2-15 alkenyl" and "C2-15 alkynyl", optionally "C2_12 alkenyl" and "C2-12 alkynyl", optionally "C2_10 alkenyl" and "C2_10 alkynyl", optionally "C2_8 alkenyl" and "C2_8 alkynyl", optionally "C2-6alkenyl" and "C2-5alkynyl" groups, respectively. Examples of alkenyl groups include ethenyl, propenyl, ally!, 1,3-butadienyl, butenyl, 1-methyl-2-buten-1-yl, ally!, 1,3-butadienyl and allenyl. Examples of alkynyl groups include ethynyl, 2-propynyl (propargyl) and 1-propynyl.

[122] The terms "cycloaliphatic", "carbocycle", or "carbocyclic" as used herein refer to a saturated or partially unsaturated cyclic aliphatic monocyclic or polycyclic (including fused, bridging and spiro-fused) ring system which has from 3 to 20 carbon atoms, that is an alicyclic group with 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 carbon atoms. Optionally, an alicyclic group has from 3 to 15, optionally from 3 to 12, optionally from 3 to 10, optionally from 3 to 8 carbon atoms, optionally from 3 to 6 carbons atoms. The terms "cycloaliphatic", "carbocycle" or "carbocyclic" also include aliphatic rings that are fused to one or more aromatic or nonaromatic rings, such as tetrahydronaphthyl rings, where the point of attachment is on the aliphatic ring. A carbocyclic group may be polycyclic, e.g. bicyclic or tricyclic. It will be appreciated that the alicyclic group may comprise an alicyclic ring bearing one or more linking or non-linking alkyl substituents, such as -CH2-cyclohexyl. Specifically, examples of carbocycles include cyclopropane, cyclobutane, cyclopentane, cyclohexane, bicycle[2,2,1]heptane, norborene, phenyl, cyclohexene, naphthalene, spiro[4.5]clecane, cycloheptane, adamantane and cyclooctane.

[123] An alicyclic group is a saturated or partially unsaturated cyclic aliphatic monocyclic or polycyclic (including fused, bridging and spiro-fused) ring system which has from 3 to 20 carbon atoms, that is an alicyclic group with 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 carbon atoms. Optionally, an alicyclic group has from 3 to 15, optionally from 3 to 12, optionally from 3 to 10, optionally from 3 to 8 carbon atoms, optionally from 3 to 6 carbons atoms. The term "alicyclic" encompasses cycloalkyl, cycloalkenyl and cycloalkynyl groups. It will be appreciated that the alicyclic group may comprise an alicyclic ring bearing one or more linking or non-linking alkyl substituents, such as -CH2-cyclohexyl. Specifically, examples of the C3-20 cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl and cyclooctyl.

[124] An aryl group or aryl ring is a monocyclic or polycyclic ring system having from 5 to 20 carbon atoms, wherein at least one ring in the system is aromatic and wherein each ring in the system contains three to twelve ring members. An aryl group is optionally a "C6_12 aryl group" and is an aryl group constituted by 6, 7, 8, 9, 10, 11 or 12 carbon atoms and includes condensed ring groups such as monocyclic ring group, or bicyclic ring group and the like. Specifically, examples of "C610 aryl group" include phenyl group, biphenyl group, indenyl group, anthracyl group, naphthyl group or azulenyl group and the like. It should be noted that condensed rings such as indan, benzofuran, phthalimide, phenanthridine and tetrahydro naphthalene are also included in the aryl group.

[125] As used herein, unless otherwise expressly specified, all numbers such as those expressing values, ranges, amounts or percentages may be read as if prefaced by the word "about", even if the term does not expressly appear. The term "about" when used herein means +/-10% of the stated value. Also, any numerical range recited herein is intended to include all sub-ranges subsumed therein. Singular encompasses plural and vice versa. For example, although reference is made herein to "a" filler, and the like, one or more of each of these and any other components can be used. As used herein, the term polymer" refers to oligomers and both homopolymers and copolymers, and the prefix "poly" refers to two or more. Including, for example and like terms means including for example but not limited to. Additionally, although the present invention has been described in terms of "comprising", the processes, materials, and coating compositions detailed herein may also be described as "consisting essentially of" or "consisting of'.

[126] Where ranges are provided in relation to a genus, each range may also apply additionally and independently to any one or more of the listed species of that genus. For example, the polymer material may comprise a80% of polymer particles, by total weight of the composition, which polymer particles comprises acrylic polymer particles in an amount such that the polymer material comprises a80 of acrylic polymer particles, by total weight of the composition. Similarly, the composition may comprise from 70 to 97% of filler, by total weight of the composition, which filler comprises quartz and aluminium trihydrate in an amount such that the composition comprises from 70 to 97% of quartz and aluminium trihydrate, by total weight of the composition. Further examples of the abovementioned include the ranges provided for the filler fractions and the encapsulated filler, and all associated species, sub-genera and sub species.

[127] All of the features contained herein may be combined with any of the above aspects in any combination.

[128] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the following experimental data.

EXAMPLES

[129] Example 1

[130] 11.3%, Polyvinyl butyral (Mowital® B6OH), 88.7%, quartz (58.4%, Granucol® 9H and 30.3%, Dorsilit® 2500) and 1.1%, titanium dioxide, were mixed in a high shear mixer for 15 seconds. The resulting dry mix was then levelled in a die mould with a depth of 12mm and heated to 180°C. 8 Tonnes of pressure was then applied and held at pressure for 60 seconds. Pressure was then released and the sample cooled and removed.

[131] Example 2

[132] 11.3%, Poly(methyl methacrylate) (Elvacite® 4071), 88.7%, quartz (57.3%, Granucol® 9H and 30.3%, Dorsilit® 2500) and 1.1%, titanium dioxide, were mixed in a high shear mixer for 15 seconds, The resulting dry mix was then levelled in a die mould with a depth of 12mm and heated to 220°C. 50 Bar of pressure was applied for 45 seconds. Pressure was then released and the sample cooled and removed.

[133] Example 3

[134] Acrylic sheet containing 28.17%, methyl methacrylate, 1.36%, hydroxyethyl methacrylate, 0.3%, Solsperse® 41000, 0.13%, n-dodecylmercaptan, 68%, aluminium trihydroxide (Aluprem® TG-7), and 2%, titanium dioxide, was produced using a cell casting technique. This sheet was subsequently granulated to a D50 of 98 pm (using ASTM D1921 -18 "Standard Test Methods for Particle Size (Sieve Analysis) of Plastic Materials"). The resultant acrylic filled powder (42.7%), was then combined with 57.3%, quartz (Granucol® 9H) and mixed in a high shear mixer for 60 seconds at 80°C. The resulting dry mix was then levelled in a die mould with a depth of 12mm and heated to 220°C. 50 Bar of pressure was applied for 45 seconds. Pressure was then released and the sample cooled and removed. The final thickness of the sample was 6.3mm. The sample had a measured density of 2.20 g/cm3 (vs calculated of 2.25 g/cm3), a flexural strength of 25.6 ± 1.6 MPa and a flexural modulus of 15.1 ± 0.1 GPa.

[135] Example 4

[136] Acrylic sheet containing 28.17%, methyl methacrylate, 1.36%, hydroxyethyl methacrylate, 0.3%, Solsperse® 41000, 0.13%, n-dodecylmercaptan, 68%, aluminium trihydroxide (Aluprem® TG-7), and 2%, titanium dioxide, was produced using a cell cast technique. This sheet was subsequently granulated to a D50 of 98 pm (using ASTM D1921 -18 "Standard Test Methods for Particle Size (Sieve Analysis) of Plastic Materials"). The resultant acrylic filled powder (41%), was then combined with 59%, quartz (Granucol® 9H) and mixed in a high shear mixer for 60 seconds at 80°C, The resulting dry mix was then levelled in a die mould with a depth of 12mm and heated to 220°C. 50 Bar of pressure was applied for 45 seconds. Pressure was then released and the sample cooled and removed. The final thickness of the sample was 6.6mm. The sample had a measured density of 2.20 g/cm3 (vs calculated of 2.27 g/cm3) and a flexural strength of 34.6 ± 1 MPa and a flexural modulus of 14.3 ± 0.4 GPa.

[137] Density Differences Example Calculated Density Measured Density % Difference Comparative 2.46 2.30 6.5%

example 1

Example 3 2.25 2.20 2.2% Example 4 2.27 2.20 3.1% [138] Calculation for engineered stone comparative example 1: Component % Density g/cm3 Density Contribution Resin* 11.3 1.02 0.12 Dorsilite9H 57.3 2.62 1.50 Dorsilit® 2500 30.3 2.61 0.79 TiO2 1.1 4.23 0.05 Calculated Density 2.46 "ASTERITE® Liquid Acrylic Resin Series 300 containing methacrylate monomers

[139] Example 5

[140] 5% Fluorescent (optical brightener) doped PMMA sheet large particles (particle size from 425pm to 500pm), 10% PMMA sheet fine particles (particle size <90pm), 56.7% Quartz (Dorsilit® 9H) and 26.3 % Silica Flour (Dorsilit® 2500) were combined and pressed at 5 Tonnes. The sample produced is shown in Figures 1 and 3 as article 100.

[141] Engineered stone comparative example 2 [142] 11.3% Fluorescent (optical brightener) doped ASTERITE® Liquid Acrylic Resin Series 300 57.8 %, Quartz (Dorsilit® 9H) and 30.9 % Silica Flour (Dorsilit® 2500) were combined, pressed and then cured under standard engineered stone manufacturing conditions. The sample produced is shown in Figures 2 and 4 as article 200.

[143] Figures 1 and 2 show the articles 100 and 200 under normal light with no magnification. Differences between the articles can be observed. To further emphasise the differences between the structures of the polymer material in the articles, Figures 3 and 4 show articles 100 and 200 when exposed to UV light. It can be seen from Figures 3 and 4 that while the continuous polymer matrix of comparative example 2 is substantially devoid of discernible polymer particles, in contrast, the polymer material of example 5 is substantially formed of readily observable polymer particle-like regions. The polymer particles of polymer material in example 5 can be seen in Figure 3 to be in forms including discrete particles (102b), as well as small (102c) and larger (102a) areas of agglomerated polymer particle networks.

[144] The examples show that high density articles with thicknesses <10mm and having acceptable strength can be formed with the possibility of forming unique aesthetic effects via an agglomerated network of polymer particles.

[145] Mowital® is a trade mark of Kuraray [146] Granucol® and Dorsilit® are trade marks of Dorfner [147] Elvacite® is a trade mark of Lucite International [148] Aluprem® is a trade mark of Tor Minerals [149] Solsperse0 is a trade mark of Lubrizol [150] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[151] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[152] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[153] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. An article comprising: i. polymer particles, wherein at least some of the polymer particles are in the form of an agglomerated network of polymer particles; and 70% of inorganic filler by total weight of the article.
2. An article obtained by compression moulding a composition comprising: i. polymer material, wherein the polymer material comprises nO% of polymer particles by total weight of the polymer material; and 70% of inorganic filler by total weight of the composition.
3. A composition for use in forming an article by compression moulding, the composition comprising: i. polymer material, wherein the polymer material comprises nO% of polymer particles by total weight of the polymer material; and H. 70% of inorganic filler by total weight of the composition.
4. A method of forming an article, comprising the steps: a. optionally, forming polymer particles; b. contacting polymer particles with filler to form a composite composition, wherein the composite composition comprises: i. polymer material, wherein the polymer material comprises nO% of the polymer particles by total weight of the polymer material; and U. 70% of inorganic filler by total weight of the composition; and c. compression moulding the composite composition to form the article.
5. An article, composition or method according to any preceding claim, wherein the polymer particles have a D50 particle size of 20 pm.
6. An article, composition or method according to any preceding claim, wherein the polymer particles have a D50 particle size of 5750 pm.
7. An article, composition or method according to any preceding claim, wherein the polymer particles comprise a first fraction of polymer particles having a D50 particle size of 00 pm, and a second fraction of polymer particles having a D50 particle size of >100 pm.
An article, composition or method according to claim 7, wherein at least 5% of the polymer particles have a D50 particle size according to the first fraction, by weight of the polymer particles.
9. An article, composition or method according to claim 7 or 8, wherein at least 10% of the polymer particles have a D50 particle size according to the second fraction.
10. An article, composition or method according to any preceding claim, wherein the polymer particles have a Tg of 55 °C.
11. An article, composition or method according to any preceding claim, wherein the polymer particles comprise (co)polymers selected from acrylic, styrene methyl methacrylate (SMMA), general purpose polystyrene (GPPS), high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), methyl methacrylate-butadiene-styrene (MBS), styrene acrylonitrile (SAN), polylactic acid (PLA), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and/or polyvinyl butyral (PVB).
12. An article, composition or method according to any preceding claim, wherein the polymer particles comprise acrylic polymer particles selected from a homopolymer of a poly(hetero)aliphatic(alk)acrylate or (alk)acrylic acid or copolymers of a (hetero)aliphafic(alk)acrylate or (alk)acrylic acid with one or more other vinyl monomers.
13. An article, composition or method according to any preceding claim, wherein the polymer particles comprise cast polymer particles.
14. An article, composition or method according to any preceding claim, wherein the composition or article comprises 30% polymer material by total weight of the composition or article.
15. An article, composition or method according to any preceding claim, wherein the polymer material of the composition or article comprises 50°/0 polymer particles by weight of the polymer material.
16. An article, composition or method according to any preceding claim, wherein the polymer material of the composition comprises 15°/o monomers by weight of the polymer material.
17. An article, composition or method according to any preceding claim, wherein the polymer material of the composition or article comprises 50% cast polymerised polymer by total weight of the polymer material.
18. An article, composition or method according to any preceding claim, wherein the composition or article comprises inorganic filler in an amount of a0 % by weight of the composition or article.
19. An article, composition or method according to any preceding claim, wherein the inorganic filler comprises filler selected from natural aggregate, quartz, fumed silica, clay, fly ash, cement, broken ceramics, mica, silicate flakes, broken glass, glass beads, glass spheres, mirror fragments, steel grit, aluminium grit, carbides, barium sulfate, aluminium trihydrate, aluminium oxides, aluminium silicates, calcium carbonate, magnesium hydroxide, iron oxide, iron hydroxide, pigments, and/or colorants.
20. An article, composition or method according to any preceding claim, wherein the composition or article comprises a flame-retardant inorganic filler.
21. An article, composition or method according to any preceding claim, wherein the inorganic filler comprises a filler material having a Mohs hardness of
22. An article, composition or method according to claim 21, wherein the filler comprises a further inorganic filler material having a lower Mohs hardness than the first filler material.
23. An article, composition or method according to any preceding claim, wherein the composition or article comprises filler that is at least partially encapsulated by polymer material.
24. An article, composition or method according to claim 23, wherein the at least partially encapsulated filler is formed by polymerising a monomer composition in the presence of the said filler.
25. An article or method according to any preceding claim, wherein the article further comprises a dye.
26. An article or method according to any preceding claim, wherein dye is applied by dye sublimation during moulding of the article
27. An article or method according to any preceding claim, wherein the composition is compression moulded at a temperature that is greater than the glass transition temperature (Tg) of the polymer particles.
28. An article or method according to any preceding claim, wherein the article has a density that is n4% of the theoretical density based on the components used to form the article during the moulding step.
29. An article or method according to any preceding claim, wherein the article is for use as a cladding material.
30. An article or method according to any preceding claim, wherein the article has an average thickness of 10 mm.