Patent Application
20240317968
The invention relates to a thermoplastic composition (P) having low haze, high clarity and UV resistivity, a process for its preparation, shaped articles made therefrom and its use for various applications, in particular outdoor applications in the construction and automotive sector. It also relates to high clarity and low haze UV stabilized styrene-methyl methacrylate copolymers (SMMA) with very low (minimal) yellowness change to high UV exposure.
Clear and transparent polymer materials are of considerable importance for many technical applications. It is often desirable to make transparent packaging materials such as films (e.g. for food packaging) or plastics moldings (e.g. bottles, boxes, etc.), transparent parts of buildings (e.g. window panes, films, signboards), transparent parts of cars (e.g. panes, screens, exterior lamp cases), transparent parts of electronics (e.g. screen surfaces, cases, lamps), optical fibers or transparent parts of varnish, toys, sports equipment or medical and laboratory equipment. Particularly desirable are such polymers or compositions which are transparent for at least visible light, e.g. in a wavelength range of from 380 nm to 800 nm, and remain stable even after being exposed to UV light.
Polymethyl methacrylate polymers (PMMA) bear the desired transparent properties. In particular, PMMA is transparent for visible light and stable towards UV light. However, the technical applicability of PMMA is limited, e.g. by its low dimensional stability due to water absorption, which is associated with the high polarity of the polymer. Furthermore, said water absorption also leads to a change in the refractive index of the polymer, which is particularly undesired in optical applications requiring high precision and accuracy.
In contrast to PMMA, vinylaromatic polymers, such as, e.g., polystyrene or polymers based on derivatives of styrene or copolymers bear desirable properties regarding dimensional stability. Furthermore, such vinylaromatic polymers are non-polar, therefore having no issues with high humidity applications, such as refractive index changes.
WO 2015/118142 discloses styrene/methyl methacrylate (SMMA) copolymers comprising 20 to 50 wt.-% of methyl methacrylate and 50 to 80 wt.-% of styrene for producing UV-translucent products. Specific UV absorbers or light stabilizers are not mentioned.
However, the vinylaromatic moieties absorb light in the range of the nearer UV light, in particular in the range of from 250 nm to 370 nm.
Therefore, the copolymers comprising typical amounts of vinylaromatic moieties bear impaired transparency properties, especially in this range. Furthermore, due to the absorption of UV light, vinylaromatic polymers can be partially damaged over time, thus that the shaped articles prepared therefrom can become hazy and discolored and lose transparency, even for light in the spectral range outside of the absorbed range. These issues lead to limitations for the use of polymers derived from vinylaromatic monomers, especially in applications where the polymers are exposed to UV light.
These issues can be partially overcome by the use of specific additives in the vinylaromatic polymer compositions, such as light stabilizers.
U.S. Pat. No. 5,624,982 discloses non-yellowing styrenic polymers stabilized with a stabilizer system which comprises a benzotriazole UV absorber (e.g. Tinuvin® 328; BASF), a hydroxyl-benbenzylisocyanurate primary antioxidant and a hindered amine light stabilizer (HALS). As HALS, an oligomeric condensation product of N,N′(2,2,6,6-tetramethylpiperidinyl)alkylene diamine and 6-amino-2,4-dichloro-1,3,5-s-triazine which triazine amine group is preferably derived from morpholine (e.g. Cyasorb® 3346), or bis(2,2,6,6,-tetramethyl-4-piperidinyl) sebacate (e.g. Tinuvin® 770), or bis(1,2,2,6,6,-pentamethyl-4-piperidinyl) ester of (3,5-di-tert-butyl-4-hydroxybenzyl)-butylmalonate (e.g. Tinuvin 144) is used.
In a long list of suitable styrenic polymers SMMA copolymers are generally mentioned. In all examples of U.S. Pat. No. 5,624,982 a stabilized blend of SAN-copolymers with ASA- and AES-graft copolymers is used which additionally comprises TiO2 (pigment, inorganic UV-absorber). One of the 50 Examples shows a SAN-copolymer blend comprising a stabilizer system, comprising 0.4 pbw Tinuvin 328, 0.4 pbw Tinuvin 144 and 0.4 pbw Cyasorb 3346.
The balance in yellowing performance and weatherability and the transparency of these known blends are still in need of improvement.
WO 2006/057355 discloses resin compositions comprising 100 pbw of a SMMA-copolymer (MMA: 80 to 50 wt.-%), 0.1 to 2 pbw, of a HALS compound and 0.1 to 2 pbw of a benzotriazole compound. As HALS compound one or more derivatives of bis(1,2,2,6,6-pentamethyl-4-piperidiyl)- or bis(2,2,6,6-tetramethyl-4-piperidiyl)dicarboxylic acid di-esters may be used. In all examples one HALS compound (Tinuvin 770) and a UV-absorber (Tinuvin 329) are used in a 1:1 weight ratio.
KR 2010/0070143 discloses a styrene resin composition comprising 100 pbw of a methylmethacrylate styrene copolymer (styrene: 50 to 80 wt.-%), 0.05 to 1.0 pbw of a HALS stabilizer, and 0.05 to 1.0 pbw of a benzotriazole UV absorber (all examples: Tinuvin 329, 0.2 pbw). The HALS absorber is of the bis(1,2,2,6,6-pentamethyl-4-piperidiyl)- or bis(2,2,6,6-tetramethyl-4-piperidiyl)dicarboxylic acid diester type (all examples: Tinuvin 770, 0.2 pbw).
JP 2006/154445 discloses a light diffusing plate which layer (B) consists of a resin composition consisting of a SMMA copolymer (MMA: 5 to 50 wt.-%), and further 0.1 to 1 pbw of an UV absorber and 0.1 to 1 pbw of a HALS stabilizer. The UV-absorber can be i.a. of a benzophenone type, cyano acrylate type, salicylic ester type, benzotriazole type, triazine type, and oxal anilide type.
The afore-mentioned resin compositions comprising SMMA copolymers and stabilizer systems according to the prior art often offer a good indoor UV resistance but their outdoor UV resistance is not satisfying. A stronger UV resistance of said materials is needed in many demanding outdoor applications, in particular applications in the construction or automotive sector.
However, especially in construction and automotive applications, it is difficult to obtain sufficient UV resistance while maintaining clarity and transparency of the articles, since the right combination and concentration of UV additives can increase UV performance, but at the same time deteriorate the color and optical properties of the resin. Additionally, without the correct combination of UV additives, increasing concentrations of UV additives often will only minimally increase UV performance, but reduce optical quality to a significantly greater extent. Therefore, in order to achieve high UV stability with as low of concentration of additives as possible, the functionality and purpose of each UV additive needs to be optimized to optimize the performance and appearance of the resin.
SMMA copolymers combine advantageous properties, such as dimensional stability, and good processability. Furthermore, the presence of methyl methacrylate contributes to the UV stability of the polymers. Still, the UV stability is often insufficient for outdoor applications. Furthermore, even the applicability of light stabilizing and UV-absorbing additives is limited due to potential solubility issues, since they may lead to haziness and discoloration of the polymer compositions, if introduced in higher amounts that may be required for the stabilization against UV-induced deterioration in outdoor applications.
In view of the above, there is a technical need to provide better resin compositions comprising SMMA copolymers that have an increased outdoor UV stability and a good balance of optical properties and UV-resistance. Often desired are a haze according to ASTM D1003 of 1.5% or less before weathering, measured on samples having a thickness of 3.175 mm (⅛ inch), and an increase of the yellowness index according to ASTM method E313 (test specimens of 3.175 mm (⅛ inch) thickness) by less than 1.3, preferably less than 1.0, more preferably less than 0.89 (measured from the CIE color space values using a D65 light source (observation angle 10°) according to ASTM E1348:2015) after outdoor stability testing according to SAE J2527 (issued 2004-02) through SAE J1960 at a radiant exposure of 5000 KJ/m2 (Xenon irradiance (340 nm) of 0.55 W/m2).
Surprisingly, it was found that a thermoplastic composition (P) as described below bears such desired properties.
Therefore, one aspect of the present invention is a thermoplastic composition (P) comprising (or consisting of) components (a), (b), (c) and optionally (d):
The number average molecular weight of HALS component (b1) and (b2) can be determined by common analytical methods such as Liquid chromatography-mass spectrometry (LC-MS), Gas chromatography-mass spectrometry (GC-MS) and gel permeation chromatography/size exclusion chromatography (GPC/SEC). Furthermore, NMR-methods can be used. In some cases, the HALS components (b1) and (b2) have distinct molecular weight, rather than a distribution. In these cases, the number average molecular weight is identical to the distinct molecular weight (formula weight) of the respective component. Often, the HALS components (b1) and (b2) are commercially available. In these cases, the molecular weights are published by the supplier. Where the HALS component has a molecular weight distribution, the number average molecular weight is preferably determined by NMR methods (nuclear magnetic resonance spectroscopy), in particular 1H NMR spectroscopy, as described, e.g., in “Polymer Molecular Weight Analysis 35 by 1H NMR Spectroscopy” (Josephat U. Izunobi and Clement L. Higginbotham, J. Chem. Educ. 2011, 88, 8, pp. 1098-1104).
Thermoplastic compositions according to the invention and shaped articles thereof have a high outdoor UV stability (UV-resistance), e.g. they can be used for a longer period of time (such as months or years) outdoor with changing temperatures and sun-light.
In the context of the present invention, the outdoor UV stability testing is conducted according to SAE J2527 (issued 2004-02) through SAE J1960 at a radiant exposure of 5000 KJ/m2 with Xenon irradiance (wavelength 340 nm) of 0.55 W/m2 at 70° C. for light cycle and 38° C. for dark cycle.
In the context of the present invention, the term “high outdoor UV stability” means that after outdoor stability testing as described above, the yellowness index according to ASTM method E313 (test specimens of 3.125 mm (⅛) inch thickness) increases by less than 1.3, preferably less than 1.0, more preferably less than 0.89 (measured from the CIE color space values using a D65 light source (observation angle 10°) according to ASTM E1348:2015).
Furthermore, in the context of the present invention, the term “good optical properties” means that the haze of the thermoplastic composition before outdoor stability testing as described above is 1.5% or less, preferably 1.2% or less (measured according to ASTM D1003 using CIE illuminant C, test specimens of 3.125 mm (⅛ inch) thickness).
Another aspect of the invention is a process for the preparation of a thermoplastic composition (P) according to the invention by mixing copolymer (a) with HMw-HALS (b1), LMw-HALS (b2), UV absorber (c1) having a peak absorption at a wavelength from 310 nm to 380 nm, UV absorber (c2) having a peak absorption at a wavelength from 260 nm to less than 310 nm, and, if present, at least one further additive (d).
Another aspect of the invention is a process for the preparation of a shaped article comprising the thermoplastic composition (P). A further aspect of the invention is a shaped article comprising a thermoplastic composition (P).
Furthermore, an aspect of the invention is the use of components (a), (b), (c) and optionally (d), as defined herein, for the preparation of a thermoplastic composition (P) or a shaped article with the following properties:
In the following, the invention and the components are described in more detail.
The term “copolymer” as used herein for copolymer (a) may be understood in the broadest sense as any polymer obtainable from two or more different types of monomers (i.e., (a1) at least one kind of vinylaromatic monomer and (a2) at least methyl methacrylate (MMA)) by polymerization. The terms indicating that the copolymer (a) comprises monomers or the polymer consists of monomers will be understood by those skilled in the art as meaning that the monomers in this context are monomeric moieties embedded into the copolymer strand, i.e. repeating units derived from the respective monomers.
Furthermore, a repeating unit derived from a certain monomer will be understood as a repeating unit obtained from said monomer during polymerization, i.e., “derived” does not mean that the repeating unit is obtained from a derivative of said monomer. For example, a repeating unit obtained by polymerization of alpha-methyl styrene is not considered a repeating unit derived from styrene in the context of the present invention.
In a preferred embodiment, the vinylaromatic monomer (a1) and methyl methacrylate (a2) in the copolymer (a) are not bound to rubber monomers such as butadiene moieties. Particularly preferably, the vinylaromatic monomer (a1) is styrene.
Preferably, the melt flow index (MFI) (determined at a temperature of 200° C. and at a load of 5 kg according to ASTM procedure D1238-20) of the copolymers (a) according to the present invention is less than 50 g/10 min, more preferably less than 20 g/10 min, more preferably of less than 10 g/10 min, often less than 5 g/10 min.
In a copolymer (a), the different types of repeating units may be either statistically and homogeneously distributed over the copolymer (random copolymer) or may be located at distinct areas of the polymer strand(s) arranged in blocks (block copolymer).
The term “block copolymer” may be understood in the broadest sense as any copolymer having distinct areas of the polymer strand(s) arranged in blocks. Preferably, the copolymer (a) however is a random copolymer.
Optionally, the copolymer (a) according to the present invention may also contain one or more methacrylate derivatives other than MMA such as, e.g. ethyl methacrylate (EMA), butyl methacrylate (BMA) and 2-ethyl hexyl methacrylate (2-EHMA), and methacrylic acid. Preferably, such methacrylate derivatives and methacrylic acid constitute for not more than 25 wt.-% of the copolymer mass, more preferably not more than 10 wt.-% of the copolymer mass, often not more than 5 wt.-% of the copolymer mass. More preferably, the copolymer (a) does not contain any further methacrylate derivative other than MMA or methacrylic acid. Particularly preferably, the copolymer (a) does not contain any further methacrylate derivative other than MMA.
Optionally, the copolymer (a) according to the present invention may also contain one or more cross-linking moiety/moieties such as, e.g., divinylbenzene, in its polymer strand. Preferably, such cross-linking agents constitute for not more than 25 wt.-% of the copolymer mass, more preferably not more than 10 wt.-% of the copolymer mass, often not more than 5 wt.-% of the copolymer mass. Preferably, the copolymer (a) does not contain any cross-linking moieties.
The copolymer (a) according to the present invention may bear a linear, circular or branched structure. A circular structure is a copolymer strand wherein both ends are connected with another. As used herein, the term “branched structure” may be understood in the broadest sense as any structure deviating from a plain linear or circular structure. Accordingly, in a polymer of branched structure, there is at least one monomer binding to three or more other monomer(s). Preferably, the copolymer (a) of the present invention is an essentially linear or circular copolymer, more preferably an essentially linear copolymer, in particular a linear random copolymer.
The thermoplastic composition (P) is transparent or at least partly transparent. In particular, when the thermoplastic composition (P) is once heated above the glass transition temperature Tg, subsequently molded and finally cooled below the glass transition temperature Tg, the obtained molding is transparent or at least partly transparent. The Tg-value of the thermoplastic composition (P) can be determined by classical methods.
As used throughout the present invention, the term “transparent” may be understood in the broadest sense as ability of letting light pass through.
Preferably, transparency means, that, at a thickness of a sample of ⅛ inch (3.175 mm), at least 70%, preferably of at least 80%, more preferably of at least 85%, more preferably of at least 90%, of visible light passes through. Particularly preferably, transparency means that, in a sample of 0.5 mm, 1 mm, 3.175 mm, 5 mm or even 1 cm, at least 70%, preferably at least 80%, more preferably at least 85%, more preferably at least 90% of visible light passes through. In some preferred embodiments, light having certain wavelengths outside the visible light spectrum, e.g. starting above 380 nm or up to 800 nm, also passes through, to an extent of at least 70%, preferably at least 80%, more preferably at least 85%, more preferably at least 90%. Accordingly, in some preferred embodiments, at least 70%, preferably at least 80%, more preferably at least 85%, more preferably at least 90% of all light in the range from 380 nm to 800 nm passes through a sample having a thickness of ⅛ inch (3.175 mm).
Preferably the obtained thermoplastic composition (P) is transparent when a shaped article obtained therefrom is more than 0.5 mm, preferably more than 1 mm, more preferably more than 2 mm, often from 3.175 mm to 10 mm thick. The light transmittance for visible light, at a layer thickness of 3.175 mm preferably is higher than 85%, often higher than 90%., measured according to ASTM D1003 using CIE illuminant C.
As used herein, methyl methacrylate (MMA) (a2) is understood in the broadest sense. Herein, the terms “methyl methacrylate”, “methyl methacrylate moiety”, “methyl methacrylate monomer”, “methyl methacrylate monomer moiety”, and similar terms are understood interchangeably.
As used herein, a vinylaromatic monomer (a1) may be understood in the broadest sense as any as any moiety bearing at least one vinyl residue (—CH═CH2) in its monomeric form and at least one monocyclic or polycyclic aromatic residue known in the art. The person skilled in the art will notice that upon polymerization, the double bond of the vinyl residue is cleaved and is thereby embedded into the polymeric strand. In accordance with international common designation standards, the monomeric moiety as well as the moiety embedded into the polymeric strand is designated as vinylaromatic monomer. Herein, the terms “vinylaromatic”, “vinylaromatic moiety”, “vinylaromatic monomer”, “vinylaromatic monomer moiety”, “aromatic vinyl”, “aromatic vinyl moiety”, “aromatic vinyl monomer”, “aromatic vinyl monomer moiety” and similar terms may be understood interchangeably. Preferably, the vinylaromatic monomer bears one vinyl residue (—CH═CH2) and one monocyclic or polycyclic aromatic residue.
More preferably, the vinylaromatic monomer bears one vinyl residue (—CH═CH2) and one monocyclic aromatic residue, such as styrene.
In a preferred embodiment, the one or more vinylaromatic monomers (a1) comprise(s) styrene and/or one or more styrene derivative(s). As used herein, a styrene derivative may be any derivative of styrene known in the art such as, e.g.
Particularly preferably, the one or more vinylaromatic monomer according to the present invention is alpha-methylstyrene or styrene, in particular styrene.
In a preferred embodiment, the one or more vinylaromatic monomers (a1) comprise styrene.
In a more preferred embodiment, the one or more vinylaromatic monomers (a1) comprise at least 50 wt.-% styrene, preferably at least 70 wt.-% styrene, more preferably at least 80 wt.-% styrene, more preferably at least 90 wt.-% styrene, based on the total weight of (a1). In a preferred embodiment, the only vinylaromatic monomer (a1) in said copolymer (a) is styrene.
It is preferable that the copolymer (a) comprises 40 to 70 wt.-% of repeating units derived from vinylaromatic monomers (a1), in particular styrene, and 30 to 60 wt.-% of repeating units derived from methyl methacrylate (a2); more preferable that it comprises 50 to 69 wt.-% of repeating units derived from vinylaromatic monomers (a1), in particular styrene, and 31 to 50 wt.-% of repeating units derived from methyl methacrylate (a2); more preferable that it comprises 51 to 65 wt.-% of repeating units derived from vinylaromatic monomers (a1), in particular styrene, and 35 to 49 wt.-% of repeating units derived from methyl methacrylate (a2); even most preferred that it comprises 52 to 60 wt.-% of repeating units derived from vinylaromatic monomers (a1), in particular styrene, and 40 to 48 wt.-% of repeating units derived from methyl methacrylate (a2), based on the total weight of copolymer (a).
Preferably, the copolymer does not comprise any further monomer moieties than MMA and one or more, preferably one, vinylaromatic monomers, in particular styrene. Thus, preferred copolymer (a) consists of repeating units derived from vinylaromatic monomers (a1), in particular styrene, and of repeating units derived from methyl methacrylate (a2) in the afore-mentioned amounts.
Therefore, preferred are thermoplastic compositions (P) as afore-mentioned, wherein copolymer (a) consists of 31 to 50 wt.-%, preferably 35 to 49 wt.-%, more preferably 40 to 48 wt.-%, based on the total weight of copolymer (a), of repeating units derived from methyl methacrylate (a2), and 50 to 69 wt.-%, preferably 51 to 65 wt.-%, more preferably 52 to 60 wt.-%, based on the total weight of copolymer (a), of repeating units derived from styrene.
In general, a copolymer (a) according to the present invention may be obtained by any means suitable therefore known in the art. The person skilled in the art knows numerous methods suitable for obtaining such copolymer (a). Well-known conventional polymerization procedures may be employed in the preparation of such copolymer (a) according to the present invention.
Component (a) is e.g. obtained in a known manner by bulk, solution, suspension, precipitation or emulsion polymerization. Details of these processes are described, for example, in Kunststoffhandbuch, ed. R. Vieweg and G. Daumiller, Vol. V “Polystyrol”, Carl-Hanser-Verlag Munich, 1969, p. 118 ff.
Exemplarily, the copolymer (a) may be prepared by emulsion polymerization, solution polymerization or bulk polymerization. Preferably, heat or radical initiation may be used (including living polymerization methods).
Methyl methacrylate (MMA) monomers (a) as well as numerous vinylaromatic monomers are commercially available. Others can be easily obtained by standard chemical processes. As indicated above, a vinyl monomer is characterized by its vinyl group (—CH═CH2) in its monomeric form. Therefore, vinyl monomers may also be obtained from precursor molecules. Exemplarily, precursor molecules bearing an ethyl residue (—CH2—CH3) may be oxidized/dehydrated, halogenated precursor molecules bearing a halogemethyl residue (e.g., —CHCl—CH3, —CH2—CH2Cl) may be dehalogenated by eliminating the respective acid (e.g., HCl) or hydroxylated precursor molecules bearing a hydroxyethyl residue (e.g., —CHOH—CH3, —CH2—CH2OH) may be dehydrogenated by eliminating water (e.g., H2O). Then, the respective vinyl monomers are obtainable.
Copolymerization for the preparation of copolymer (a) may optionally be carried out in the presence of, e.g., one or more solvent(s) and/or one or more initiator(s) (e.g., one or more radical starter(s)).
The initiation of copolymerization may e.g. be started by thermal decomposition of an initiator (e.g an organic peroxide (e.g., dicumyl peroxide) or an azo compound), photolysis (e.g., with metal iodides, metal alkyls or azo compounds (e.g., azoisobutylnitrile (AIBN))), a peroxide initiator (e.g., benzoyl peroxide), an initiator composition enabling a redox reaction (e.g., reduction of hydrogen peroxide or an alkyl hydrogen peroxide by means of iron ions or other reductants such as, e.g, Cr2+, V2+, Ti3+, Co2+ or Cu+), persulfate activation, ionizing radiation (e.g., by means of α-, β-, γ- or x-rays), electrochemical activation, plasma activation, sonication (e.g., at around 16 kHz) or a ternary Initiator (e.g., benzoyl peroxide-3,6-bis(o-carboxybenzoyl)-N-isopropylcarbazole-di-η5-indenylzicronium dichloride optionally in combination with a metallocene (e.g., indenylzirconium) and/or a peroxide (e.g., benzoyl peroxide).
In a preferred embodiment, the copolymerization comprises heating of the reaction mixture comprising the monomers above a temperature above 100° C. and/or adding one or more polymerization initiator(s) to said reaction mixture.
The reaction mixture can be maintained or brought to conditions allowing chain elongation of the polymer. For instance, the temperature is set according to the monomer/copolymer content of the reaction mixture. Exemplarily, as indicated above, the temperature may optionally also be varied during incubation, such as, e.g., constantly or stepwise increased during the polymerization process.
Exemplarily, methods for producing copolymer (a) of the present invention may be used as shown in any of GB 464688, GB 531956, GB 863279 and WO 2003/051973.
As component (b) a combination of at least two hindered amine light stabilizers (HALS) is used which consists of: (b1) at least one high molecular weight hindered amine light stabilizer (HMw-HALS) having a number average molecular weight (Mn) of ≥(equal to or greater than) 1800 g/mol, preferably ≥1900 g/mol; more preferably ≥2000 g/mol, and (b2) at least one low molecular weight hindered amine light stabilizer (LMw-HALS) having a number average molecular weight (Mn) of ≤(equal to or less than) 1000 g/mol, preferably ≤900 g/mol, more preferably ≤800 g/mol.
The hindered amine light stabilizers used in the thermoplastic composition (P) according to the invention are generally based on 2,2,6,6-tetramethyl-piperidine derivatives, in particular derivatives of 2,2,6,6-tetramethyl-4-piperidyl-substituted organic compounds.
LMw-HALS compounds (b2) are mostly composed of one or two units comprising a 2,2,6,6-tetramethyl-piperidine group.
HMw-HALS compounds (b1) mostly are (oligomeric) reaction products based on 2,2,6,6-tetramethyl-piperidine derivatives, often (oligomeric) reaction products based on 2,2,6,6-tetramethyl-piperidine derivatives and 1,3,5-triazine derivatives.
The number average molecular weight (Mn) of the HMw-HALS (b1) often is in the range of 1800 to 15000 g/mol, preferably in the range of 1900 g/mol to 10000 g/mol; more preferably in the range of 2000 to 5000 g/mol.
Suitable compounds which may be used as HMw-HALS (b1) are one or more compounds selected from the group consisting of:
Preferred as HMw-HALS (b1) are oligomeric reaction products of a 2,2,6,6-tetramethyl-4-piperidyl-substituted organic compound (includes its derivatives) and a 1,3,5-triazine derivative, such as in particular poly[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]).
Suitable compounds which may be used as LMw-HALS (b2) are one or more compounds selected from the group consisting of:
Preferably the at least one LMw-HALS (b2) is a derivative of a bis(2,2,6,6-tetramethyl-4-piperidyl)dicarboxylic acid diester, in particular preferred is bis(2,2,6,6,-tetramethyl-4-piperidyl)sebacate.
In the thermoplastic composition (P) according to the invention the at least one, preferably one, HMw-HALS (b1) and the at least one, preferably one, LMw-HALS (b2) are generally used in a weight ratio (b1):(b2) of from 12:1 to 1:2, more preferably from 6:1 to 1.5:2, more preferably from 4:1 to 1:1, in particular from 3:1 to 1:1. Particularly preferably, no further HALS except for (b1) and (b2) are present in component (b).
As the at least one organic UV absorber (c) (=component (c)) two or more compounds are used, wherein at least one, preferably one UV absorber (c1) has a peak absorption at a wavelength from 310 nm to 380 nm, and at least one, preferably one UV absorber (c2) has a peak absorption at a wavelength from 260 nm to less than 310 nm, measured by UV/VIS spectroscopy. Particularly preferably, no further UV absorbers other than (c1) and (c2) are present in component (c).
In the present context, peak absorption refers to the absorption maximum with the highest absorbance (i.e. absolute maximum) in the UV/VIS spectrum, when measured in a chloroform solution of the respective UV absorber at a concentration of 10 mg/L.
The UV absorbers (c1) and (c2) are preferably selected from the group consisting of substituted benzotriazoles, substituted benzophenones, substituted triazines, oxalanilides, substituted resorcinols, salicylates and cyanoacrylates, more preferably from the group consisting of 2-(2-hydroxyphenyl) benzotriazoles, 2-hydroxy-benzophenones and hydroxyphenyl-s-triazines, which fulfill the peak absorption wavelength requirements.
For example, the at least one UV absorber (c1) having a peak absorption at a wavelength from 310 nm to 380 nm may be selected from the group consisting of 2-(2-hydroxyphenyl) benzotriazoles and 2-hydroxy-benzophenones, and the at least one UV absorber (c2) having a peak absorption at a wavelength from 260 nm to less than 310 nm may be selected from the group consisting of hydroxyphenyl-s-triazines and other triazines.
Preferably, (c1) is a 2-(2-hydroxyphenyl) benzotriazole and (c2) is hydroxyphenyl triazine. More preferably, (c1) is 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, which is, e.g., commercially available as “Tinuvin® 329” (BASF) and has a peak absorption at 343 nm, and (c2) is 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxy phenol, which is, e.g., commercially available as “Tinuvin® 1577” (BASF) and has a peak absorption at 274 nm.
Furthermore, the weight ratio (c1):(c2) is preferably from 8:1 to 1:4, more preferably from 6:1 to 1:2, more preferably from 4:1 to 2:3, more preferably from 3:1 to 1.5:2, more preferably from 2:1 to 1:1.
The weight ratio (b):(c) in the composition of the invention is preferably from 5:1 to 1:5, more preferably from 4:1 to 1:2, more preferably from 3:1 to 1:1, more preferably from 3:1 to 4:3.
Furthermore, the total weight of UV additives (b) and (c) is preferably 1.5 wt.-% or less, more preferably 1.2% or less, more preferably 1.0% or less, based on the total weight of the thermoplastic composition (P).
Preferred is a thermoplastic composition (P) as afore-mentioned, wherein the weight ratio (b1):(b2) is from 12:1 to 1:2, preferably from 6:1 to 1.5:2, more preferably from 4:1 to 1:1 more preferably from 3:1 to 1:1, the weight ratio (c1):(c2) is from 6:1 to 1:2, preferably from 4:1 to 2:3, more preferably from 3:1 to 1.5:2, more preferably from 2:1 to 1:1, and the weight ratio (b):(c) is from 5:1 to 1:5, preferably from 4:1 to 1:2, more preferably from 3:1 to 1:1, more preferably 3:1 to 4:3.
Preferred are thermoplastic compositions (P) comprising:
Optionally the thermoplastic composition (P) according to the invention may comprise up to 2.0 wt.-%, preferably up to 1.0 wt.-%, more preferably up to 0.5 wt.-%, more preferably up to 0.3 wt.-%, based on the total weight of the thermoplastic composition (P), of at least one further additive (d) (=component (d)), which is different from HALS and UV absorbers. Preferably, the at least one further additive (d) does not contain any pigments or fillers.
The amount of component (d), if present, is preferably at least 0.01 wt.-%, more preferably at least 0.02 wt.-%, more preferably at least 0.05 wt.-%, particularly preferably at least 0.1 wt.-%, based on the total weight of the thermoplastic composition (P).
Suitable additives (d) include all substances customarily employed for processing or finishing the polymers, except of pigments and fillers (see e.g. “Plastics Additives Handbook”, Hans Zweifel, 6th edition, Hanser Publ., Munich, 2009).
Exemplarily, an additive may be a stabilizer for improving thermal stability, a stabilizer for enhancing hydrolysis resistance and chemical resistance, a process stabilizer, a radical scavenger, an antioxidant, an anti-thermal decomposition agent, a glossing agent, a metal deactivator, an antistatic agent, a flow agent, an anti-sticking agent, metal ions, a flame retardant, a dispersing agent, a dye, and/or a (external/internal) lubricant.
These additives may be admixed at any stage of the manufacturing operation, but preferably at an early stage in order to profit early on from the stabilizing effects (or other specific effects) of the added substance.
Preferably component (d) is at least one lubricant and/or at least one antioxidant. More preferably, component (d) is at least one antioxidant.
Suitable lubricants (glidants/demolding agents) include stearic acids, stearyl alcohol, stearic esters, amide waxes (bisstearylamide, in particular ethylenebisstearamide (EBS)), polyolefin waxes and/or generally higher fatty acids, derivatives thereof and corresponding fatty acid mixtures comprising 12 to 30 carbon atoms.
Suitable antioxidants are, e.g., one or more compounds selected from monophosphite-based antioxidants, diphosphite-based antioxidants and sterically hindered phenolic antioxidants. If one or more antioxidants are present, they are preferably selected from monophosphite-based antioxidants, such as trisubstituted monophosphite derivatives, diphosphite-based antioxidants, such as substituted pentaerythrirol diphosphite derivatives and sterically hindered phenolic antioxidants, such as 2,6-di-tertbutylphenolic derivatives. More preferably, the antioxidant used as component (d) is one or more compounds selected from tri-phenyl substituted monophosphite derivatives, di-phenyl substituted pentaerythritol diphosphite derivatives and mono-substituted 2,6-di-tertbutylphenolic derivatives. In particularly preferred embodiments, the one or more antioxidants are one or more of tris(2,4-di-tert-butylphenyl)phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite and octadecyl-3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate.
In preferred embodiments, the thermoplastic composition (P) according to the invention consists of the components (a), (b), (c) and optionally (d).
Preferably, the thermoplastic composition (P) of the invention comprises, more preferably consists of:
As indicated above, a further aspect of the invention is a process for the preparation of a thermoplastic composition (P) according to the invention by mixing copolymer (a) with HMw-HALS (b1), LMw-HALS (b2), UV absorber (c1) having a peak absorption at a wavelength from 310 nm to 380 nm, UV absorber (c2) having a peak absorption at a wavelength from 260 nm to less than 310 nm, and, if present, at least one further additive (d).
Component (b) comprising HMw-HALS (b1) and LMw-HALS (b2) can be added to copolymer (a) by separate addition of HMw-HALS (b1) and LMw-HALS (b2), or by addition of a mixture of both.
Furthermore, Component (c) comprising UV absorber (c1) having a peak absorption at a wavelength from 310 nm to 380 nm and UV absorber (c2) having a peak absorption at a wavelength from 260 nm to less than 310 nm, can be added to copolymer (a) by separate addition of UV absorber (c1) and UV absorber (c2), or by addition of a mixture of both.
Preferably, in the process according to the invention, copolymer (a) is provided in a molten state and components (b), (c) and, if present, (d) are added to a melt of copolymer (a).
Components (b), (c) and, if present, (d) may be added to the copolymer (a) in their pure form, or admixed thereto as masterbatches or as a single masterbatch in a polymeric carrier. Preferably, components (b), (c) and, if present, (d), are added to the copolymer (a) as one or more masterbatches in a polymeric carrier.
When components (b), (c) and, if present, (d) are added as one or more masterbatches in a polymeric carrier, the polymeric carrier preferably comprises, more preferably consists of copolymer (a). Also, the concentration of the respective component(s) in the polymeric carrier is preferably from 20 to 80 wt.-%, more preferably from 25 to 60 wt. %, more preferably from 30 to 50 wt.-%, based on the total weight of the respective masterbatch.
Where components (b), (c) and, if present, (d) are added as a masterbatch, their amounts based on the total weight of the thermoplastic composition (P), as specified above, refer to the respective pure component, and not to the masterbatch. Furthermore, where the polymeric carrier comprises or consists of copolymer (a), the amount of copolymer (a) in the masterbatch is counted towards the amount of copolymer (a) based on the total weight of the thermoplastic composition (P), as specified above. For example, a thermoplastic composition prepared from 96 wt.-% of copolymer (a), 2 wt. % of a masterbatch of component (b) (50 wt.-% in copolymer (a)), and 2 wt.-% of a masterbatch of component (c) (50 wt.-% in copolymer (a)) corresponds to a thermoplastic composition (P) consisting of 98 wt.-% of copolymer (a), 1 wt.-% of component (b) and 1 wt.-% of component (c).
The mixing of the components can be performed by suitable means such as e.g. a mixer, a kneader or an extruder, preferably a twin screw extruder.
Preferably, if antioxidants are present as component (d), they are added to copolymer (a) separately from components (b), (c) and any further optional additives used as component (d). More preferably components (b), (c) and optional further additives used as component (d) are introduced into the thermoplastic composition (P) during secondary compounding, whereas antioxidants, if present, are introduced into the reactor during the polymerization of copolymer (a).
The thermoplastic composition (P) according to the present invention may be used to produce a shaped article therefrom.
Thus, a further aspect of the invention is a process for the preparation of a shaped article comprising the thermoplastic composition (P) according to the invention wherein the shaped article is formed by extrusion, injection molding, casting, blow molding, spraying, spinning, rolling or weaving, in particular extrusion or injection molding.
In this context, the person skilled in the art will know several means for producing one or more of such shaped articles from such molding compositions. Producing a shaped article may e.g. be performed by extrusion, injection molding, casting, blow molding, spraying, spinning, rolling, weaving, forming a suspension from an emulsion etc. or a combination of two or more thereof. The person skilled in the art will know which method(s) to apply for producing the respective shaped article.
The person skilled in the art will also notice that a shaped article in the sense of the present invention may be obtained from at least one thermoplastic composition (P) according to the present invention, which molding composition may either be a melt or present as a raw material for molding processes (e.g. in the form of pellets, powder and/or blocks) or may be dissolved in a suitable solvent.
Accordingly, a further aspect of the present invention relates to a shaped article comprising (or consisting of) a thermoplastic composition (P) according to the present invention.
Thermoplastic compositions (P) according to the invention and shaped articles thereof are generally transparent or at least partly transparent. Thermoplastic compositions (P) according to the invention and shaped articles thereof in particular have a high outdoor UV stability. As outlined above, the outdoor UV stability testing is conducted according to SAE J2527 (issued 2004-02) through SAE J1960 at a radiant exposure of 5000 KJ/m2 with Xenon irradiance (wavelength 340 nm) of 0.55 W/m2 at 70° C. for light cycle and 38° C. for dark cycle.
As outlined above, the term “high outdoor UV stability” means that after outdoor stability testing as described above, the yellowness index according to ASTM method E313 (test specimens of 3.125 mm (⅛) inch thickness) increases by less than 1.3, preferably less than 1.0, more preferably less than 0.89 (measured from the CIE color space values using a D65 light source (observation angle 10°) according to ASTM E1348:2015), and the term “good optical properties” means that the haze of the thermoplastic composition before outdoor stability testing as described above is 1.5% or less, preferably 1.2% or less (measured according to ASTM D1003 using CIE illuminant C, test specimens of 3.125 mm (⅛ inch) thickness).
Accordingly, a further aspect of the invention is the use of a thermoplastic composition (P) according to the invention and of shaped articles comprising it for outdoor applications, preferably for applications in the construction and automotive sector, in particular for exterior automotive parts, such as e.g. exterior rear combination lamps.
Yet another aspect of the invention is the use of components (a), (b), (c) and optionally (d), as defined above in the amounts specified above, for the preparation of a thermoplastic composition (P) or a shaped article with following properties:
The invention is further outlined by the following examples and the patent claims.
UV stability testing was conducted according to SAE 2527 through SAE 1960 with xenon irradiance (340 nm) of 0.55 W/m2 at 70° C. for light cycle and 38° C. for dark cycle.
Haze was measured for ⅛″ (3.125 mm) thickness specimen according to ASTM D 1003.
YI was calculated according to ASTM E313 from measured CIE L*a*b* color space values.
CIE color space values measured using a D65 light source (observation angle 10°) according to ASTM E1348.
A continuous feed of 55 wt.-% (a1) styrene and 45 wt.-% (a2) methyl methacrylate—each based on the total weight of (a1) and (a2), a free radical initiator, and antioxidants (0.1 wt.-% Irgafos® 126 and 0.03 wt.-% Irganox® 1076, each based on the entire molding composition) were added to a stirred tank reactor at a temperature of 150° C.
The polymerization reaction was thermally initiated and conducted to a conversion in the range of 60 to 85%.
The copolymer product stream leaving the polymerization reactor was sent to a preheater, then to a devolatizer to remove volatile components from the molten polymer.
The devolatizer operates at temperatures of from 200 to 245° C. and a pressure less than 20 mbar.
Then, at a temperature of 210° C. the obtained copolymer (a) was compounded in a twin screw extruder with (b1) a high molecular weight hindered amine light stabilizer (Chimassorb® 944, Ciba, Mn=2000-3100 g/mol, CAS-RN: 71878-19-8), (b2) a low molecular weight hindered amine light stabilizer (Tinuvin® 770 DF, BASF, Mn=480.7 g/mol, CAS-RN: 52829-07-9), (c1) a UV-absorber with a peak absorption at a wavelength of 343 nm (Tinuvin® 329, BASF, CAS-RN: 3147-75-9), and (c2) a UV absorber with a peak absorption at a wavelength of 274 nm (Tinuvin® 1577, BASF, CAS-RN: 147315-50-2) in the amounts as shown in the Table 1 below, and an EBS wax (0.05 wt.-%, based on the entire molding composition).
The obtained SMMA copolymer molding composition was injection molded into the desired shaped article (preparation of various test specimens of ⅛ inch (3.175 mm) thickness).
The obtained test specimens were subjected to haze measurement according to ASTM D 1003, and then to an (outdoor) UV stability test according to SAE J2527 through SAE J1960 at a radiant exposure of 5000 KJ/m2 with Xenon irradiance (wavelength 340 nm) of 0.55 W/m2 at 70° C. for light cycle and 38° C. for dark cycle. Under these conditions, the CIE L*a*b* color space values and yellowness index (YI) calculated from the CIE color space values were measured before (initial) and after (final) exposure, to examine the UV-induced change in yellowness (ΔYI) and b* value (Δb*). The experimental results are shown in Table 1 below.
From these Examples 1 to 15 it can be seen that all specimens had a haze of 1.5% or less before weathering, and at the same time experienced a change in Yellowness Index of less than 1.3. This shows that the compositions of the invention and the articles prepared therefrom have a good balance of optical properties and UV resistance. The compositions of the invention were further compared with compositions (comparative examples C1 to C6), wherein the UV absorber (c2) having a peak absorption at a wavelength of from 260 to less than 310 nm was not present, and optionally the HMw HALS (b2) was not present.
From the direct comparison of compositions with the same UV additive loading (0.3 wt. %, 0.45 wt.-%, 0.7 wt.-%, 0.9 wt.-% or 1.2 wt.-%), it can be seen that the compositions comprising each of (b1), (b2), (c1) and (c2) have significantly higher weathering stability than compositions lacking at least one of the UV additives, even if the missing additives are compensated with a larger amount of the additives present.
The compositions of the invention showed high utility for out-door equipment and articles used with exposure to e.g. sun-light, humidity and temperature changes.
Exemplary articles using the prepared compositions are: films, food packaging, bottles, boxes, window panes, signboards, screens, exterior lamp cases, optical fibers, sports equipment, medical and laboratory equipment, which have the above optical and weathering properties.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21196690.8 | Sep 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/075367 | 9/13/2022 | WO |
