The present invention relates to a polymer composition comprising a (meth)acrylic polymer. The invention further relates to a process for the production of such polymer composition. The invention also relates to an article produced using such polymer composition. Such polymer composition may for example be used in the production of shaped objects having a desired surface hardness.

(Meth)acrylic polymers are well-known polymers having have advantageous properties for a variety of applications. A particular advantageous property is the transparency. An example of a (meth)acrylic polymer is poly(methyl methacrylate), also referred to as PMMA. For certain applications, however, the surface hardness of objects produced using (meth)acrylic polymers according to the state of the art is not sufficient.

Exemplary applications thereof are display devices, transparent automotive parts such as lamp covers, windows and dashboard pars, and home appliances.

Various attempts have been made to improve the surface hardness of (meth)acrylic polymers. For example, it has been attempted to modify the surface hardness of PMMA by copolymerising a quantity of acrylonitrile monomer with PMMA, resulting in a P(MMA-co-AN) copolymer. Such polymer indeed shows improved surface hardness by their improved scratch and mar properties. However, a disadvantage of the production of such copolymer is that it involves a dedicated process for polymerisation. Furthermore, only a limited quantity of acrylonitrile can be incorporated into the copolymer.

Another option to produce a polymer composition comprising a (meth)acrylic polymer and polyacrylonitrile, also referred to as PAN, would be by melt compounding in for example a melt extruder. However, due to the thermal degradation of PAN before melting, such processing does not lead to compositions having the desired surface hardness properties.

For that reason, there is a need to develop a polymer composition comprising a

(meth)acrylic polymer and a polyacrylonitrile having a desired surface hardness, whilst allowing for the composition to be produced by a simple process, and allowing for flexibility in the production of homogeneously mixed compositions comprising both a high weight fraction of (meth)acrylic polymer and a low weight fraction of polyacrylonitrile, as well as comprising a high weight fraction of polyacrylonitrile and a low weight fraction of (meth)acrylic polymer.

This has now been achieved according to the present invention by a polymer composition comprising: (a) a (meth)acrylic polymer; and

(b) a polyacrylonitrile

wherein the polymer composition is prepared by a process comprising the steps:

(i) dissolving at least the (meth)acrylic polymer (a) and the polyacrylonitrile (b) in a

solvent; and

(ii) precipitating the dissolved material by addition of a precipitant.

Such polymer compositions have a desired surface hardness. Furthermore, such polymer compositions may be produced using simple processing equipment.

In the context of the present invention, surface hardness may for example include reduced susceptibility to scratching and marring. Scratching relates to the susceptibility of a material to penetration by a sharp object; marring relates to the susceptibility to occurrence of shallow defects due to contact with other objects. As indicators of surface hardness, the hardness and the modulus of elasticity of the composition may be used. The hardness may be determined as indentation hardness in accordance with ISO 14577-1 (2015). The modulus of elasticity may be determined as indentation modulus in accordance with ISO 14577-1 (2015).

The polymer composition prepared according to the present invention by a process comprising the steps:

(i) dissolving at least the (meth)acrylic polymer (a) and the polyacrylonitrile (b) in a

solvent; and

(ii) precipitating the dissolved material by addition of a precipitant

provides a particular benefit in that it allows for blending the (meth)acrylic polymer and the the polyacrylonitrile. Conventional blending methods, such as melt blending as for example performed by melt extrusion, do not allow for blending the (meth)acrylic polymer and the polyacrylonitrile, in particular a polyacrylonitrile homopolymer, as such polyacrylonitrile is not a thermoplastic material. When such polyacrylonitrile is subjected to melt extrusion in the presence of a (meth)acrylic polymer, for example the polyacrylonitrile being a polyacrylonitrile homopolymer and the (meth)acrylic polymer being poly(methylmethacrylate), the

polyacrylonitrile does not melt mix with the poly(methylmethacrylate) and a system is obtained comprising polyacrylonitrile particles embedded in a poly(methylmethacrylate) matrix. Even, due to the thermal degradation of PAN before melting, such processing does not lead to

compositions having the desired surface hardness properties as do the polymer compositions according to the present invention. Preferably, the (meth)acrylic polymer (a) is a polymer comprising ≥ 95.0 % by weight of polymer units according to formula I, with regard to the total weight of the (meth)acrylic polymer:

o

!

R2 formula I in which:

R1 is hydrogen or a hydrocarbon moiety comprising 1 -4 carbon atoms; R2 is a hydrocarbon moiety comprising 1-4 carbon atoms;

R3 is a hydrocarbon moiety comprising 1 -4 carbon atoms.

For example, R1 may be hydrogen or a methyl moiety. It is preferred that R1 is a methyl moiety.

R2 may for example be a methyl, ethyl, propyl or butyl moiety. It is preferred that R2 is a methyl moiety.

R3 may for example be a methyl, ethyl, propyl or butyl moiety. It is preferred that R3 is a methyl moiety.

In a preferred embodiment, each R1 , R2 and R3 are methyl moieties.

Preferably, the one or more (meth)acrylic polymer (a) is a polymer prepared using≥ 95.0 % by weight, more preferably≥ 98.0 % or≥ 99.0 % by weight, with regards to the total weight of the monomers used, of one or more monomers selected from methyl acrylate, methyl-2-methyl acrylate, methyl-2-ethyl acrylate, methyl-2-propyl-acrylate, methyl-2-butyl acrylate, ethyl acrylate, ethyl-2-methyl acrylate, ethyl-2-ethyl acrylate, ethyl-2-propyl acrylate, ethyl-2-butyl acrylate, propyl acrylate, propyl-2-methyl acrylate, propyl-2-ethyl acrylate, propyl-2-propyl acrylate, propyl-2-butyl acrylate, butyl acrylate, butyl-2-methyl acrylate, butyl-2-ethyl acrylate, butyl-2-propyl acrylate, butyl-2-butyl acrylate, t-butyl-2-methyl acrylate, isobutyl-2-methyl acrylate, isopropyl-2-methyl acrylate, or combinations thereof. More preferably, the one or more (meth)acrylic polymer (b) is a polymer prepared using≥ 95.0 % by weight, more preferably≥ 98.0 % or≥ 99.0 % by weight, with regards to the total weight of the monomers used of one or more monomers selected from methyl acrylate, methyl-2-methyl acrylate, butyl-2-methyl acrylate, ethyl acrylate, or combinations thereof. Preferably, the one or more (meth)acrylic polymer (a) is selected from

polymethylmethacrylate (PMMA), polybutylmethacrylate (PBMA), poly(methylmethacrylate- ethylacrylate (PMMA-co-EA), polyethyl acrylate (PEA), polybenzyl methacrylate, poly(n-butyl acrylate), poly(t-butyl acrylate), poly(cyclohexyl methacrylate), poly(1 ,3-dimethylbutyl methacrylate), poly(3,3-dimethylbutyl methacrylate), poly(diphenylethyl methacrylate), poly(diphenylmethyl methacrylate), poly(dodecyl methacrylate), poly(2-ethylbutyl methacrylate), polyethyl methacrylate, poly(trimethylpropyl methacrylate), poly(n-propylmethacrylate), polyphenyl methacrylate, poly(1 -phenylethyl methacrylate), polyoctyl methacrylate,

polyneopentyl methacrylate, poly(1 -methylpentyl methacrylate), polymethylbutyl methacrylate, polylauryl methacrylate, polyisopropyl methacrylate, polyisopentyl methacrylate, or

combinations thereof. More preferably, the one or more (meth)acrylic polymer (b) is selected from polymethylmethacrylate (PMMA), polybutylmethacrylate (PBMA), poly(methylmethacrylate- ethylacrylate (PMMA-co-EA), or polyethyl acrylate (PEA).

The (meth)acrylic polymer (a) may for example have a weight average molecular weight Mw Of≥ 25 kg/mol, alternatively≥ 50 kg/mol, alternatively≥ 75 kg/mol. The (meth)acrylic polymer (a) may for example have a weight average molecular weight of < 150 kg/mol, alternatively < 125 kg/mol. It is preferred that the (meth)acrylic polymer (a) has a weight average molecular weight of≥ 50 kg/mol and < 150 kg/mol, even more preferred≥ 75 kg/mol and < 125 kg/mol.

The weight average molecular weight M _w of the (meth)acrylic polymer (a) and the polyacrylonitrile (b) may be determined according to ASTM D5296-1 1 .

The polyacrylonitrile (b) preferably is a polymer comprising≥ 85.0 wt% of polymer units according to formula II, with regard to the total weight of the polyacrylonitrile:

formula II More preferably, the polyacrylonitrile (b) is a polymer comprising≥ 90.0 wt% of polymer units according to formula II, even more preferably≥ 95.0 w% or≥ 98.0 wt%, with regard to the total weight of the polyacrylonitrile (b).

The polyacrylonitrile may for example be a homopolymer or a copolymer of acrylonitrile. The polyacrylonitrile may for example be a homopolymer of acrylonitrile. It is particularly advantageous to use a homopolymer of acrylonitrile, also referred to as a polyacrylonitrile homopolymer, in the polymer composition of the present invention as such polyacrylonitrile homopolymers have a particularly desired effect on the surface hardness of the polymer composition.

Alternatively, the polyacrylonitrile may be a copolymer of acrylonitrile and one or more comonomers, where the polyacrylonitrile comprises≥ 85.0 wt% of polymer units derived from acrylonitrile. Preferably, the polyacrylonitrile comprises≥ 90.0 wt% of polymer units derived from acrylonitrile, more preferably≥ 95.0 wt%, even more preferably≥ 98.0 wt% or≥99.0 wt%.

The polyacrylonitrile may for example be produced using a comonomer selected from vinyl acetate, methyl acrylate, or methyl methacrylate.

The polyacrylonitrile (b) may for example have a weight average molecular weight of≥ 50 kg/mol, alternatively≥ 75 kg/mol, alternatively≥ 100 kg/mol. The polyacrylonitrile (b) may for example have a weight average molecular weight of < 200 kg/mol, alternatively < 175 kg/mol. For example, the polyacrylonitrile (b) may have a weight average molecular weight of≥ 75 kg/mol and < 200 kg/mol, alternatively≥ 100 kg/mol and < 175 kg/mol.

The polyacrylonitrile (b) may for example have an intrinsic viscosity as determined in accordance with ASTM D2857-95 (2007) of≥ 0.50 and < 5.00 dl/g, alternatively≥ 1 .00 and < 3.00. The polymer composition may for example comprise≥ 50.0 wt% of (meth)acrylic polymer

(a) with regard to sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile.

Alternatively, the polymer composition may comprise≥ 60.0 wt%, alternatively≥ 70.0 wt%, of (meth)acrylic polymer (a) with regard to sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile.

The polymer composition may for example comprise < 95.0 wt%, alternatively < 90.0 wt%, alternatively < 80.0 wt%, of (meth)acrylic polymer (a) with regard to sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile.

For example, the polymer composition may comprise≥ 50.0 wt% and < 95.0 wt% of (meth)acrylic polymer (a) with regard to the sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile. Alternatively, the polymer composition may comprise≥ 60.0 wt% and < 80.0 wt% of (meth)acrylic polymer (a) with regard to the sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile. The polymer composition may for example comprise≥ 5.0 wt% of polyacrylonitrile with regard to the sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile.

Alternatively, the polymer composition may comprise≥ 10.0 wt%, alternatively≥ 20.0 wt% of the polyacrylonitrile (b) with regard to the sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile.

The polymer composition may for example comprise < 50.0 wt%, alternatively < 40.0 wt%, alternatively < 30.0 wt%, of polyacrylonitrile (b) with regard to sum of the weight of the

(meth)acrylic polymer and the polyacrylonitrile.

For example, the polymer composition may comprise≥ 5.0 wt% and < 50.0 wt% of polyacrylonitrile (b) with regard to the sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile. Alternatively, the polymer composition may comprise≥ 20.0 wt% and < 40.0 wt% of polyacrylonitrile (b) with regard to the sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile.

For example, the polymer composition may comprise:

· ≥ 50.0 wt% and < 95.0 wt%, alternatively≥ 60.0 wt% and < 80.0 wt% of

(meth)acrylic polymer (a); and

• ≥ 5.0 wt% and < 50.0 wt%, alternatively≥ 20.0 wt% and < 40.0 wt% of

polyacrylonitrile (b)

with regard to the sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile. It is further preferred that the (meth)acrylic polymer (a) is a (meth)acrylic homopolymer or a (meth)acrylic copolymer, and/or that the polyacrylonitrile is a homopolymer of acrylonitrile or a copolymer of acrylonitrile. It is more preferred that the (meth)acrylic polymer (a) is

poly(methylmethacrylate) and the polyacrylonitrile (b) is a homopolymer of acrylonitrile. The polymer composition according to the present invention may for example be prepared by dissolving the (meth)acrylic polymer (a) and the polyacrylonitrile (b) in a solvent, and precipitating the dissolved material by addition of a precipitant. For example, the solvent may be selected from dimethyl sulfoxide, dimethyl formamide or dimethyl acetamide. It is preferred that the dissolution of (a) and (b) takes place at a temperature of≥ 70°C, preferably≥ 80°C. It is further preferred that the dissolving is performed during a period of 1 -6 hours, preferably 1-5 hours, more preferably 3-5 hours.

In a preferred embodiment, the polymer composition comprises≥ 50.0 wt% and < 95.0 wt% of the (meth)acrylic polymer and≥ 5.0 wt% and < 50.0 wt% of the polyacrylonitrile with regard to the sum of the (meth)acrylic polymer and the polyacrylonitrile, wherein the

(meth)acrylic polymer is poly(methylmethacrylate) and wherein the dissolving takes place at a temperature of≥ 80°C and < 100°C during 3-5 hrs. The polymer compositions according to the present invention may for example be converted into shaped objects via thermal moulding processes, such as injection moulding, extrusion, compression moulding, blow moulding, rotational moulding, melt spinning, clandering and/or thermoforming. The invention in a further embodiment also relates to a process for the production of a polymer composition comprising:

(a) a (meth)acrylic polymer; and

(b) a polyacrylonitrile

wherein the polymer composition is prepared by a process comprising the steps:

(i) dissolving at least the (meth)acrylic polymer (a) and the polyacrylonitrile (b) in a

solvent; and

(ii) precipitating the dissolved material by addition of a precipitant.

In this process, preferably:

· the solvent is selected from dimethyl sulfoxide, dimethyl formamide, or dimethyl acetamide; and/or

• the precipitant is a solution of an alcohol selected from methanol, ethanol or isopropanol in water.

The process may further comprise a step (iii) of drying the precipitate to obtain a dried polymer composition.

In this process, the polymer composition may for example comprise≥ 45.0 wt% and < 95.0 wt% of the (meth)acrylic polymer and≥ 5.0 wt% and < 55.0 wt% of the polyacrylonitrile with regard to the sum of the weight of the (meth)acrylic polymer and the polyacrylonitrile, wherein the (meth)acrylic polymer is poly(methylmethacrylate) and wherein the dissolving takes place a temperature of≥ 80°C and < 100°C during 3-5 hrs.

The polymer composition may optionally comprise further ingredients such as

antioxidants. These antioxidants may for example be phenolic antioxidants and/or phosphite antioxidants. A stabiliser composition comprising one or more phenolic antioxidant(s) and one or more phosphite antioxidant(s) may for example be used. Phenolic antioxidants may for example be selected from monophenolic antioxidants, i.e. antioxidants containing one phenolic group per molecule, bisphenolic antioxidants i.e. antioxidants containing two phenolic groups per molecule, and polyphenolic antioxidants, i.e. antioxidants containing more than two phenolic groups per molecule, including 1 ,1 ,3-tris(2-methyl-4-hydroxy-5-t-butyl phenyl) butane, pentaerythritol tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1 ,3,5-trimethyl-2,4,6- tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1 ,3,5-tris(3,5-di-t-butyl-4- hydroxybenzyl)isocyanurate, and 1 ,3,5-tris(4-t-butyl-2,6-dimethyl-3-hydroxybenzyl)isocyanurat e. Preferably, the phenolic antioxidant is pentaerythritol tetrakis(3-(3,5-di-t-butyl-4- hydroxyphenyl)propionate.

Phosphite antioxidants may for example be selected from trisnonylphenyl phosphite, trilauryl phosphite, tris(2,4-di-t-butylphenyl)phosphite, triisodecyl phosphite, diisodecyl phenyl phosphite, diphenyl isodecyl phosphite, and triphenyl phosphite. Preferably, the phosphite antioxidant is tris(2,4-di-t-butylphenyl)phosphite.

Preferably, the stabiliser that is introduced to the solution blend comprises pentaerythritol tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate.

The polymer composition may for example comprise≥ 0.10 and < 1 .00 wt% of antioxidant, with regard to weight of (meth)acrylic polymer and polyacrylonitrile, preferably≥ 0.20 and < 0.50 wt%.

The polymer composition may optionally comprise further ingredients such as heat stabilisers. The heat stabilisers may for example be a nitrogen-containing compounds. Such nitrogen-containing heat stabilisers may for example be one or more selected from the list consisting of aminotriazine compounds, allantoin, hydrazides, polyamids, melamines, and/or mixtures thereof.

The nitrogen-containing compound can be a low molecular weight compound or a high molecular weight compound. Examples of low molecular weight nitrogen-containing

compounds can include an aliphatic amine (e.g., monoethanolamine, diethanolamine, and tris- (hydroxymethyl)aminomethane), an aromatic amine (e.g., an aromatic secondary or tertiary amine such as o-toluidine, p-toluidine, p-phenylenediamine, o-aminobenzoic acid, p- aminobenzoic acid, ethyl o-aminobenzoate, or ethyl p-aminobenzoate), an imide compound (e.g., phthalimide, trimellitimide, and pyromellitimide), a triazole compound (e.g., benzotriazole), a tetrazole compound (e.g., an amine salt of 5,5'-bitetrazole, or a metal salt thereof), an amide compound (e.g., a polycarboxylic acid amide such as malonamide or isophthaldiamide, and p- aminobenzamide), hydrazine or a derivative thereof (e.g., an aliphatic carboxylic acid hydrazide such as hydrazine, hydrazone, a carboxylic acid hydrazide (stearic hydrazide, 12-hydroxystearic hydrazide, adipic dihydrazide, sebacic dihydrazide, or dodecane diacid dihydrazide; and an aromatic carboxylic acid hydrazide such as benzoic hydrazide, naphthoic hydrazide, isophthalic dihydrazide, terephthalic dihydrazide, naphthalenedicarboxylic dihydrazide, or

benzenetricarboxylic trihydrazide)), a polyaminotriazine (e.g., guanamine or a derivative thereof, such as guanamine, acetoguanamine, benzoguanamine, succinoguanamine, adipoguanamine, 1 ,3,6-tris(3,5-diamino-2,4,6-triazinyl)hexane, phthaloguanamine or CTU-guanamine, melamine or a derivative thereof (e.g., melamine, and a condensate of melamine, such as melam, melem or melon)), a salt of a polyaminotriazine compound containing melamine and a melamine derivative with an organic acid, a salt of a polyaminotriazine compound containing melamine and a melamine derivative with an inorganic acid, uracil or a derivative thereof (e.g., uracil, and uridine), cytosine or a derivative thereof (e.g., cytosine, and cytidine), guanidine or a derivative thereof (e.g., a non-cyclic guanidine such as guanidine or cyanoguanidine; and a cyclic guanidine such as creatinine), and urea or a derivative thereof.

The polymer composition may for example comprise≥ 0.10 and < 1.00 wt% of heat stabilisers, with regard to weight of (meth)acrylic polymer and polyacrylonitrile, preferably≥ 0.20 and < 0.50 wt%. The polymer composition may for example comprise 0.10-1 .00 wt% of one or more antioxidants and/or 0.10-1.00 wt% of one or more heat stabilisers with regard to the total weight of (meth)acrylic polymer and polyacrylonitrile.

The invention in one of its embodiments also relates to an article produced using the polymer composition according to the invention, wherein the article is produced via compression moulding at a mould temperature of≥ 210°C and < 250°C.

The invention will now be illustrated by the following non-limiting examples. Table 1 - Materials used

Using the materials as presented in table 1 , a number of polymer compositions were prepared according to the formulations as presented in table 2:

Table 2: Formulations

The values in table 2 represent the wt% of each compound with regard to the total weight of the polymer compositions. Samples 4-6 present formulations for comparative purposes.

The polymer compositions according to the formulations of samples 1 -3 of table 2 were prepared by dissolving PMMA and PAN in the weight ratio as presented in table 2 in dimethyl formamide according to a weight ratio of 1 part by weight of PMMA and PAN to 4 parts by weight of dimethyl formamide in a round bottom flask at 90°C under reflux, in a nitrogen atmosphere under mechanical stirring. The solution was kept under these conditions for 4 hrs. Subsequently, the solution was precipitated with a solution of 40% methanol in water and dried under vacuum at 60°C until a constant weight was obtained.

The preparation of sample 4 did not result in a polymer composition as the PMMA and the PAN according to this formulation were not miscible. The polymer composition according to samples 1-3, 5 and 6 were subjected to determination of material properties as indicated in table 3. The material properties were determined on specimens prepared by compression moulding of the polymer compositions, wherein in the preparation of each specimen a quantity of polymer composition was inserted into a mould, preheated for 1 min using a mould temperature of 225°C at a pressure of 380 kPa, followed by a breathing step at ambient pressure for 2 times 5 sec, subsequently subjected to compression at 640 kPa for 5 min at a mould temperature of 225°C, followed by a cooling for another 5 min under a pressure of 640 kPa, following which the specimen was removed from the mould.

Table 3: Determination of material properties

Hardness and modulus were determined as the indentation hardness and the indentation modulus in accordance with ISO 14577-1 (2015). Determination was performed using a

Berkovich indenter with a tip diameter of 20 nm. Indentations were made with a constant strain rate of 0.05 s ^"1 and indentation depth of 2 μηη. A Nano-lndenter XP, obtainable from Keysight Technologies, was used in the analysis.

From the above presented examples, it becomes apparent that polymer compositions according to the present invention have a desired good scratch resistance as indicated by the hardness, as well as a desired modulus, whilst avoiding the need for a copolymerisation process. This allows for flexibility in the desired formulations, i.e. in the ratio of PMMA to PAN, in the polymer composition without the need for production of different grades during a

polymerisation process.