WO2017046126A1

WO2017046126A1 - Impact modified polycarbonate composition

Info

Publication number: WO2017046126A1
Application number: PCT/EP2016/071638
Authority: WO
Inventors: Zhenyu Huang; Qing Liu
Original assignee: Covestro Deutschland Ag; Covestro Polymers (China) Co., Ltd.
Priority date: 2015-09-17
Filing date: 2016-09-14
Publication date: 2017-03-23
Also published as: TW201723082A; CN108350258A

Abstract

The present invention relates to a polycarbonate composition, and the process for producing the same. In particular, the present invention relates to an impact modified polycarbonate composition having improved chemical resistance and resistance against coatings.

Description

Impact modified polycarbonate composition

Field of invention

The present invention relates to a polycarbonate composition, the process for preparing the same, and the use thereof in housing parts of electric and electronic devices. In particular, the present invention relates to an impact modified polycarbonate composition having improved chemical resistance and resistance against coatings.

Background of invention

Most of the housing parts in consumer electronic devices such as mobile phones need coating after injection molding. The coating materials usually contain some chemicals that are harmful to polycarbonate, thereby dramatically affecting the mechanical properties of the polycarbonate materials. In general, it is required for mobile phone models to have the resistance to some cosmetics like sun lotion and sweat, which contain many kinds of chemicals that might be not good to polycarbonate. Due to its short chain length and intermediate polarity, polycarbonate molecules have a high affinity to many organic solvents. Furthermore, since polycarbonate is an amorphous material, it can be easier penetrated by chemicals with small molecules compared with semi- crystalline polymeric materials such as Nylon, PE (polyethylene), PP (polypropylene), and polyester (PBT (polybutylene terephthalate) and PET (polyethylene terephthalate) etc.). All of these factors make polycarbonate a material with poor chemical resistance.

A common way to improve chemical resistance is to mix polycarbonate with polyester (PBT, PET, or any polyester copolymer). Due to the semi-crystalline structure of many polyesters, the chemical resistance can be improved greatly. However, adding polyester to polycarbonate will lead to a lower heat distortion temperature, which may block some applications that require a high working temperature. A lower impact strength at low temperature is another disadvantage of such a polycarbonate/polyester blend. Therefore, impact modified polycarbonate materials have been widely used in some equipment housing applications and electric & electrical devices, such as mobile phones, tablets, adaptors/chargers, sockets, and switches. These materials provide good toughness and can prevent the damage caused by dropping and hitting. Moreover, they also possess higher heat resistance as compared to other engineering polymers such as HIPS (high impact polystyrene), ABS (acrylonitrile butadiene styrene), and polycarbonate/ABS etc., allowing them to withstand higher working temperatures in electrical devices.

However, the resistance against coatings and the chemical resistance in general of impact modified polycarbonate using regular impact modifiers, such as MBS, acrylic rubber based impact modifiers, and most of the impact modifiers with a silicone/acrylic rubber based core-shell structure alone, are not satisfying.

US patent No. 8,314,168 discloses that syndiotactic polystyrene (SPS) was added into a polycarbonate system impact modified by MBS or silicone/acrylate rubber based core-shell structure impact modifier. Some phosphate esters, such as PX-200 or TPP (triphenyl phosphate), were added to improve flowability. The chemical resistance was improved due to the crystalline structure of SPS that has good miscibility with polycarbonate. However, it is expected that low temperature impact performance will be sacrificed with adding SPS.

US 2004/0186233 Al discloses that acrylic rubber based, silicone/acrylate rubber based core-shell structure impact modifiers, SEBS (styrene-ethylene-butylene-styrene), and PP were found to be able to improve chemical resistance and low temperature impact performance of polycarbonate. SEBS and PP seem more effective on improving chemical resistance than silicone/acrylate rubber based core-shell structure impact modifiers. However, both of them are expected to have a poor miscibility and thus it is not very practical to use them. US 2014/0107262 Al discloses that some small amounts of alkyl ketene dimer were added to polycarbonate to improve chemical resistance effectively. However, this additive led to poor hydrolysis stability.

Since electronic device businesses for consumers grow fast, especially the smartphone market in recent years, there is a demand for impact modified polycarbonate suitable for the housings of these devices with good impact performance, good resistance against coatings and chemical resistance in general. The present invention provides a solution for this need.

Summary of the invention

The invention relates to an impact modified polycarbonate composition that has special properties, such as improved resistance against coatings and chemical resistance. In particular, the invention relates to a polycarbonate composition comprising a combination of different types of impact modifiers. Technical synergistic effects have been observed for the polycarbonate composition with the impact modifiers.

The present invention provides a polycarbonate composition comprising the combination of special impact modifiers, thereby providing beneficial synergistic effects on resistance against coatings and resistance against sun lotion, and which can balance other properties such as low temperature impact performance.

The present invention provides a polycarbonate composition comprising: A) at least one thermoplastic, aromatic polycarbonate in an amount ranging from 85% by weight to 97% by weight based on the total weight of the composition; and

B) at least two impact modifiers selected from the group consisting of

Bl) ethylene acrylate copolymers, preferably in an amount of 3% to 5% by weight based on the total weight of the composition;

B2) silicone-acrylate rubbers with a core-shell structure, preferably in an amount of 3% to 6% by weight based on the total weight of the composition;

B3) acrylate rubber based core-shell impact modifier, preferably in an amount of 2.5% to 3.4% by weight based on the total weight of the composition, with the proviso that the amounts of the impact modifiers Bl, B2 and/or B3 sum up to 3-15 % by weight based on the total weight of the composition.

The present invention also provides a polycarbonate composition comprising:

A) at least one thermoplastic, aromatic polycarbonate in an amount ranging from 85% by weight to 97% by weight based on the total weight of the composition; and

B) at least two impact modifiers selected from the group consisting of

Bl) ethylene acrylate copolymers in an amount ranging from 1% to 8% by weight, preferably 3% to 6% by weight, particularly preferred 3% to 5% by weight based on the total weight of the composition;

B2) silicone-acrylate rubbers with a core-shell structure in an amount ranging from 1% to 8% by weight, preferably 3% to 6% by weight based on the total weight of the composition;

B3) acrylate rubber based core-shell impact modifier in an amount ranging from 1% to 8% by weight, preferably 3% to 6% by weight, particularly preferred 2.5% to 3.4% by weight based on the total weight of the composition, with the proviso that the amounts of the impact modifiers Bl, B2 and/or B3 sum up to 3-15 % by weight based on the total weight of the composition.

A preferred composition is a composition comprising:

A) at least one thermoplastic, aromatic polycarbonate in an amount ranging from 85% to 97% by weight based on the total weight of the composition; and B) at least two impact modifiers selected from the group consisting of

B2) silicone- acrylate rubbers with a core-shell structure in an amount ranging from 1% to 8% by weight, preferably 3% to 6% by weight based on the total weight of the composition, with the proviso that the amount of the impact modifiers Bl and B2 sum up to 3-15 % by weight based on the total weight of the composition.

Another preferred composition is a composition comprising:

A) at least one thermoplastic, aromatic polycarbonate in an amount ranging from 85% to 97% by weight based on the total weight of the composition; and

B) at least two impact modifiers selected from the group consisting of

Bl) ethylene acrylate copolymers in an amount ranging from 1% to 8% by weight preferably 3% to 6% by weight, particularly preferred 3% to 5% by weight based on the total weight of the composition;

B3) acrylate rubber based core-shell impact modifier in an amount ranging from 1% to 8% by weight, preferably 3% to 6% by weight, particularly preferred 2.5% to 3.4% by weight based on the total weight of the composition, with the proviso that the amounts of the impact modifiers Bl and B3 sum up to 3-15 % by weight based on the total weight of the composition.

Another preferred composition is a polycarbonate composition comprising:

B) at least two impact modifiers selected from the group consisting of

B2) silicone- acrylate rubbers with a core-shell structure in an amount ranging from 1% to 8% by weight, preferably 3% to 6% by weight based on the total weight of the composition; B3) acrylate rubber based core-shell impact modifier in an amount ranging from 1% to 8% by weight, preferably 3% to 6% by weight, particularly preferred 2.5% to 3.4% by weight based on the total weight of the composition, with the proviso that the amounts of the impact modifiers B2 and B3 sum up to 3-15 % by weight based on the total weight of the composition.

As the impact modifiers sum up to 15 wt.-% at most, it is clear that the amounts of the impact modifiers Bl, B2 and/or B3 have to be chosen accordingly. Where "8 wt.-%" is mentioned as an upper limit, it is only the maximum amount for each group of impact modifier in the composition described in the preceding paragraph.

In another aspect, the present invention provides a housing for electric or electronic apparatus parts prepared from the above polycarbonate composition.

Detailed description of the invention

The objects and advantages of the invention will be better understood from the following detailed description of the preferred embodiments thereof. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

One aspect of the present invention is to provide a polycarbonate composition comprising A) polycarbonate and B) at least two impact modifiers selected from the components Bl), B2) and/or B3).

Component A

For the purposes of the present invention, thermoplastic, aromatic polycarbonates are not only homopolycarbonates but also copolycarbonates; as is known, the polycarbonates can be linear or branched polycarbonates, a polyester-carbonate copolymer, and a siloxane-carbonate copolymer. The thermoplastic, aromatic polycarbonates have mean weight-average molecular weights (Mw, measured by GPC using a polycarbonate calibration and dichloromethane as eluent) of from 10,000 to 200,000 g/mol, preferably from 15,000 to 80,000 g/mol, particularly preferably from 24,000 to 32,000 g/mol.

A portion, up to 80 mol%, preferably from 20 mol% to 50 mol%, of the carbonate groups in the polycarbonates suitable according to the invention can have been replaced by aromatic dicarboxylic ester groups. These polycarbonates which incorporate, into the molecular chain, not only acid moieties from carbonic acid but also acid moieties from aromatic dicarboxylic acids are termed aromatic polyester carbonates. For simplicity, the present application subsumes them within the umbrella term "thermoplastic, aromatic polycarbonates". The polycarbonates are produced in a known manner from diphenols, carbonic acid derivatives, and optionally chain terminators and optionally branching agents, and production of the polyester carbonates here involves replacing a portion of the carbonic acid derivatives with aromatic dicarboxylic acids or derivatives of the dicarboxylic acids, and specifically in accordance with the extent to which aromatic dicarboxylic ester structural units are intended to replace carbonate structural units in the aromatic polycarbonates.

The polycarbonates in the present application are added in the composition in an amount ranging from 85% to 97% by weight of total composition weight, preferably, from 90% to 95% by weight of total composition weight.

Dihydroxyaryl compounds suitable for the production of polycarbonates are those of the formula (2)

HO-Z-OH (2), in which

Z is an aromatic radical having 6 to 30 carbon atoms, it being possible for said radical to comprise one or more aromatic rings, to be substituted, and to contain aliphatic or cycloaliphatic radicals and/or alkylaryls or heteroatoms as bridging members.

Z in formula (2) is preferably a radical of the formula (3)

in which

R6 and R7 independently of one another are H, Ci- to Cis-alkyl, Ci- to Cis-alkoxy, halogen such as CI or Br, or aryl or aralkyl each of which is optionally substituted, and preferably are H or

Ci- to Ci₂ alkyl, more preferably H or Ci- to Cs-alkyl, and very preferably H or methyl, and X is a single bond, -SO2-, -SO-, -CO-, -0-, -S-, Ci- to C6-alkylene, C2- to Cs-alkylidene or C5- to C6-cycloalkylidene which may be substituted by Ci- to C6-alkyl, preferably methyl or ethyl, or else is Ce- to Ci₂-arylene, which may optionally be fused with aromatic rings containing further heteroatoms.

X is preferably a single bond, Ci- to Cs-alkylene, C₂- to Cs-alkylidene, C5- to C6-cyclo-alkylidene, - 0-, -SO-, -CO-, -S-, -SO2- or a radical of the formula (3b)

Examples of diphenols suitable for producing the polycarbonates for use in accordance with the invention include hydroquinone, resorcinol, dihydroxybiphenyl, bis(hydroxyphenyl)alkanes, bis(hydroxyphenyl)cycloalkanes, bis(hydroxyphenyl) sulphides, bis(hydroxyphenyl) ethers, bis(hydroxyphenyl) ketones, bis(hydroxyphenyl) sulphones, bis(hydroxyphenyl) sulphoxides, α,α'- bis(hydroxyphenyl)diisopropylbenzenes, and also their alkylated, ring-alkylated and ring- halogenated compounds.

Preferred diphenols are 4,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)-l-phenyl-propane, 1,1- bis(4-hydroxyphenyl)phenylethane, 2,2-bis(4-hydroxyphenyl)propane, 2,4-bis(4-hydroxyphenyl)- 2-methylbutane, l,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene (bisphenol M), 2,2-bis(3-mefhyl-4- hydroxyphenyl)propane, bis(3,5-dimethyl-4-hydroxyphenyl)methane, 2,2-bis(3,5-dimethyl-4- hydroxyphenyl)propane, bis(3,5-dimethyl-4-hydroxyphenyl) sulphone, 2,4-bis(3,5-dimethyl-4- hydroxyphenyl)-2-methylbutane, l,3-bis[2-(3,5-dimethyl-4-hydroxyphenyl)-2-propyl]benzene and l,l-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC).

Particularly preferred diphenols are 4,4'-dihydroxybiphenyl, l,l-bis(4- hydroxyphenyl)phenylethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4- hydroxyphenyl)propane, l,l-bis(4-hydroxyphenyl)cyclohexane and l,l-bis(4-hydroxyphenyl)- 3,3,5-trimethylcyclohexane (bisphenol TMC).

In the case of the homopolycarbonates, only one diphenol is used; in the case of copolycarbonates, two or more diphenols are used. The diphenols used, and also all other auxiliaries and chemicals added to the synthesis, may be contaminated with the impurities originating from their own synthesis, handling and storage. It is desirable, however, to work with extremely pure raw materials.

As monofunctional chain terminators are needed in order to regulate the molecular weight, phenols or alkylphenols, especially phenol, p-tert-butylphenol, isooctylphenol, cumylphenol, the chlorocarbonic esters thereof or acyl chlorides of monocarboxylic acids, and/or mixtures of these chain terminators, are used.

Branching agents or mixtures of branching agents are selected from the group comprising trisphenols, quaterphenols or acyl chlorides of tricarboxylic or tetracarboxylic acids, or else mixtures ofpolyphenols or ofacyl chlorides. Examples of aromatic dicarboxylic acids suitable for producing the polyestercarbonates include ortho-phthalic acid, terephthalic acid, isophthalic acid, tert-butylisophthalic acid, 3,3'- biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4-benzophenonedicarboxylic acid, 3,4'-benzophenonedicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenyl sulphone dicarboxylic acid, 2,2-bis(4-carboxyphenyl)propane and trimethyl-3-phenylindane-4,5'- dicarboxylic acid. Used with particular preference among the aromatic dicarboxylic acids are terephthalic acid and/or isophthalic acid.

Derivatives of the dicarboxylic acids are the dicarboxylic dihalides and the dicarboxylic dialkyl esters, especially the dicarboxylic dichlorides and the dicarboxylic dimethyl esters.

The replacement of the carbonate groups with the aromatic dicarboxylic ester groups takes place substantially stoichiometrically and also quantitatively, and so the molar ratio of the reactants is also found in the completed polyestercarbonate. The incorporation of the aromatic dicarboxylic ester groups may occur either randomly or in blocks.

Preferred modes of producing the polycarbonates for use in accordance with the invention, including the polyestercarbonates, are the known interfacial process and the known melt transesterification process (cf. e.g. WO 2004/063249 Al, WO 2001/05866 Al, WO 2000/105867,

US 5,340,905 A, US 5,097,002 A, US-A 5,717,057 A). In the first case, acid derivatives are preferably phosgene and optionally dicarboxylic dichlorides; in the latter case they are preferably diphenyl carbonate and optionally dicarboxylic diesters. Catalysts, solvents, work-up, reaction conditions, etc. for polycarbonate production and polyestercarbonate production have been widely described and are well known in both cases.

The polycarbonates, polyestercarbonates and polyesters can be worked up in a known way and processed to mouldings of any desired kind, by means of extrusion or injection moulding, for example. Component B

Component B is at least two modifiers selected from the group consisting of Bl) ethylene acrylate copolymer, preferably ethylene- alky 1 (meth)acrylate copolymer, B2) silicone-acrylate rubber with a core-shell structure, B3) acrylate rubber based core-shell impact modifier . Bl) ethylene acrylate copolymer

For the purposes of the present invention, component Bl) preferably is an ethylene-alkyl (meth) acrylate copolymer of the formula (I),

(I), wherein

Ri is methyl or hydrogen,

R2 is hydrogen or a Ci- to Ci2-alkyl moiety, preferably methyl, ethyl, propyl, isopropyl, butyl, sec- butyl, tert-butyl, isobutyl, hexyl, isoamyl, or tert-amyl, each of x and y is an independent degree of polymerization (integer), and n is an integer >= 1.

The ratios of the degrees of polymerization x and y are preferably in the range x:y = from 1:300 to 90: 10.

The ethylene-alkyl (meth)acrylate copolymer can be a random, block or multiblock copolymer or a mixture of the said structures. In one preferred embodiment, branched and unbranched ethylene - alkyl (meth) acrylate copolymer, particularly linear ethylene-alkyl (meth) acrylate copolymer, is used.

Preferably, component Bl is ethylene-methyl acrylate copolymer or, alternatively, ethylene-methyl acrylate copolymer is one of the components Bl. For example, the component Bl) is selected from a group consisting of ethylene acrylate copolymers including Elvaloy AC1820, AC1224, AO 125, AC 1330 from Dupont, and Lotyl 18MA02, 20MA08, 24MA02, 24MA005, 29MA03, 30BA02,

35BA40, 17BA04, 17BA07 etc. from Arkema. The melt flow rate (MFR) of the ethylene- alky 1 (meth)acrylate copolymer (measured at 190°C for 2.16 kg load, ASTM D1238) is preferably in the range from 0.5 to 40.0 g/(10 min.), particularly preferably in the range from 0.5 to 10.0 g/(10 min.), most particularly preferably in the range from 2.0 to 8.0 g/(10 min). Component Bl) in the present application is preferably added to the composition in an amount ranging from 1% to 8% by weight, preferably from 1% to 6% by weight, more preferably 3% to 6% by weight, particularly preferred 3% to 5% by weight based on the weight of the total composition.

B2) Silicone-acrylate rubber with a core-shell structure: For the purposes of the present invention, component B2) is a silicone-acrylate rubber with a core- shell structure.

These are preferably composite rubbers with graft-active sites containing 10 - 90 wt.-% silicone- rubber component and 90 wt.-% to 10 wt.-% polyalkyl-(meth)acrylate-rubber component, the two components permeating each other in the composite rubber, so that they cannot be substantially separated from one another.

The silicone rubber is preferably produced by emulsion polymerization, wherein siloxane monomer units, cross-linking or branching agents (IV) and optionally grafting agents (V) are employed.

Dimethylsiloxane or cyclic organosiloxanes with at least 3 ring members, preferentially 3 to 6 ring members, are employed, for example, and preferably, as siloxane-monomer structural units, such as, for example, and preferably, hexamethyl cyclotrisiloxane, octamethyl cyclotetrasiloxane, decamethyl cyclopentasiloxane, dodecamethyl cyclohexasiloxane, trimethyltriphenyl

cyclotrisiloxanes, tetramethyltetraphenyl cyclotetrasiloxanes, octaphenyl cyclotetrasiloxane.

The organosiloxane monomers may be employed singly or as mixtures of 2 or more such monomers. The silicone rubber preferably contains not less than 50 wt.-%, and particularly preferably not less than 60 wt.-%, organosiloxane, relative to the total weight of the silicone-rubber component.

Use is preferentially made of silane-based cross-linking agents with a functionality of 3 or 4, particularly preferably 4, by way of cross-linking or branching agents (IV). The following are preferred trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane and tetrabutoxysilane. The cross-linking agent may be employed singly or in a mixture of two or more such agents. Tetraethoxysilane is particularly preferred. The cross-linking agent is employed in an amount of 0.1 to 40 wt.%, relative to the total weight of the silicone-rubber component. The quantity of cross-linking agent is selected in such a way that the degree of swelling of the silicone rubber, measured in toluene, is 3 and 30, preferably 3 and 25, and particularly preferably 3 and 15. The degree of swelling is defined as the weight ratio of the quantity of toluene that is absorbed by the silicone rubber when it is saturated with toluene at 25 °C to the quantity of silicone rubber in the dried state. The ascertainment of the degree of swelling is described in detail in EP 0 249 964 A2.

If the degree of swelling is less than 3, i.e. if the content of cross-linking agent is too high, the silicone rubber does not display adequate rubber-like elasticity. If the swelling index is greater than 30, the silicone rubber does not form a domain structure in the matrix polymer and therefore does not enhance impact strength; the effect would then be similar to a simple addition of polydimethylsiloxane.

Tetrafunctional cross-linking agents are preferred over trifunctional cross-linking agents, because the degree of swelling is then easier to control within the limits described above. Suitable as grafting agents (V) are compounds capable of forming structures conforming to the following formulae:

CH2=C(R²)-COO-(CH2)p-SiR¹„0(3-„)/2 (V-l)

CH₂=CH-SiR¹„0(3-„)/2 (V-2) or

HS-(CH₂)p-SiR¹„0₍3-„)/2 (V-3) wherein

R¹ denotes Ci-C t-alkyl, preferably methyl, ethyl or propyl, or phenyl,

R² denotes hydrogen or methyl, n is 0, 1 or 2 and p is a number from 1 to 6. Acryloyloxysilanes or methacryloyloxysilanes are particularly suitable for forming the aforementioned structure (V-l), and have a high grafting efficiency. As a result, an effective formation of the graft chains is enabled, and the impact strength of the resulting resin composition is favored. The following are preferred : β-methacryloyloxy-ethyldimethoxymethyl-silane, γ-methacryloyloxy- propylmethoxydimethyl-silane, γ-methacryloyloxy-propyldimethoxymethyl-silane, γ- methacryloyloxy-propyltrimethoxy-silane, γ-methacryloyloxy-propylethoxydiethyl-silane, γ- methacryloyloxy-propyldiethoxymethyl-silane, δ-methacryloyl-oxy-butyldiethoxymethyl-silane or mixtures thereof.

The silicone rubber may be produced by emulsion polymerization, as described in US 2,891,920 and US 3,294,725 incorporated herein by reference. In this case the silicone rubber is obtained in the form of an aqueous latex. For this, a mixture containing organosiloxane, cross-linking agent and optionally grafting agent is mixed, subject to shear, with water, for example by means of a homogenizer, in the presence of an emulsifier based on sulfonic acid, such as, for example, alkylbenzenesulfonic acid or alkylsulfonic acid, whereby the mixture polymerises to form silicone- rubber latex. Particularly suitable is an alkylbenzenesulfonic acid, since it acts not only as an emulsifier but also as a polymerization initiator. In this case a combination of the sulfonic acid with a metal salt of an alkylbenzenesulfonic acid or with a metal salt of an alkylsulfonic acid is favourable, because the polymer is stabilized by this means during the later graft polymerization.

After the polymerization the reaction is terminated by neutralizing the reaction mixture by adding an aqueous alkaline solution, for example an aqueous solution of sodium hydroxide, potassium hydroxide or sodium carbonate.

Suitable poly alky l(meth)acrylate-rubber components of the silicone-acrylate rubbers may be produced from alkyl methacrylates and/or alkyl acrylates, a cross-linking agent and a grafting agent. Exemplary and preferred alkyl methacrylates and/or alkyl acrylates in this connection are the Ci- to C$- alkyl esters, for example methyl, ethyl, n-butyl, t-butyl, n-propyl, n-hexyl, n-octyl, n- lauryl and 2-ethylhexyl esters; halogen alkyl esters, preferentially halogen Ci- to Cs-alkyl esters, such as chloroethyl acrylate, and also mixtures of these monomers. Particularly preferred is n-butyl acrylate.

Monomers with more than one polymerizable double bond may be used as cross-linking agents for the polyalkyl-(meth)acrylate-rubber component of the silicone-acrylate rubber. Preferred examples of cross-linking monomers are esters of unsaturated monocarboxylic acids with 3 to 8 carbon atoms and of unsaturated monohydric alcohols with 3 to 12 carbon atoms, or saturated polyols with 2 to 4 OH groups and 2 to 20 carbon atoms, such as ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate and 1,4-butylene glycol dimethacrylate. The cross-linking agents may be used singly or in mixtures of at least two cross-linking agents. Exemplary and preferred grafting agents are allyl methacrylate, triallyl cyanurate, triallyl isocyanurate or mixtures thereof. Allyl methacrylate may also be employed as cross-linking agent. The grafting agents may be used singly or in mixtures of at least two grafting agents.

The quantity of cross-linking agent and grafting agent is 0.1 wt. % to 20 wt. %, relative to the total weight of the polyalkyl-(meth)acrylate-rubber component of the silicone-acrylate rubber.

The silicone-acrylate rubber is produced in the form of an aqueous latex. This latex is subsequently enriched with the alkyl methacrylates and/or alkyl acrylates, cross-linking agent and grafting agent, and a polymerization is carried out. Preferred is a radically initiated emulsion polymerization, initiated for example by a peroxide initiator, an azo initiator or a redox initiator. Particularly preferred is the use of a redox initiator system, especially a sulfoxylate initiator system produced by combination of iron sulfate, disodium methylenediamine tetraacetate, rongalite and hydroperoxide.

The grafting agent which is used in the production of the silicone rubber results in the polyalkyl- (meth)acrylate-rubber component being covalently bonded to the silicone-rubber component. In the course of polymerization, the two rubber components permeate each other and form the composite rubber which after polymerization no longer separates into its constituents components.

Preferred silicon-acrylate rubbers that may be used are those described in JP 08259791 A, JP 07316409 A, EP-A 0315035, US Pat. 4,963,619, and EP315035, which are incorporated herein by reference.

Preferably, the component B2) is selected from a group consisting of silicone-acrylate rubber grafted with styrene-acrylonitrile copolymer such as Metablen SX-006 and Metablen SRK200 from Mitsubishi Rayon Co. Ltd.

Component B2) in the present application is added in the composition in an amount ranging from 1% to 8% by weight based on the total weight of the composition, preferably, from 1% to 6% by weight, particularly preferred from 3% to 6% by weight based on the weight of the total composition.

Silicone-acrylate rubbers are known and are described, for example, in U.S. pat. no. 5,807,914, EP 430 134 and U.S. pat. no. 4,888,388 all incorporated herein by reference.

B3) Acrylate rubber based core-shell impact modifier:

For the purposes of the present invention, component B3) is an acrylate rubber based core-shell impact modifier. Preferably, the component B3) is selected from the group consisting of acrylate rubber grafted with methylmethacrylate including, e.g., Paraloid® EXL2311, EXL2313, EXL2315, EXL2300, EXL2390 from Dow Chemical, and Durastrength® 410, 440, and 480 from Arkema.

Component B3) in the present application is added to the composition in an amount ranging from 1% to 8% by weight based on the total weight of the composition, preferably, from 1% to 6% by weight, preferably 3% to 6% by weight, particularly preferred 2.5% to 3.4% by weight based on the total weight of the composition.

Component C - Additives

The polycarbonate compositions may also be admixed with additives customary for the stated thermoplastics, such as flame retardants fillers, antioxidants, heat stabilizers, antistatic agents, colorants and pigments, mold release agents, UV absorbers and IR absorbers, in the customary amounts.

The amount of additives is preferably up to 5 wt.-%, more preferably 0.01 to 3 wt.-%, based on the overall composition. Examples of suitable antioxidants or heat stabilizers are alkylated monophenols,

alkylthiomethylphenols, hydroquinones and alkylated hydroquinones, tocopherols, hydroxylated thiodiphenyl ethers, alkylidenebisphenols, 0-, N- and S-benzyl compounds, hydroxybenzylated malonates, aromatic hydroxybenzyl compounds, triazine compounds, acylaminophenols, esters of -(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, esters of -(5-tert-butyl-4-hydroxy-3- methylphenyl)propionic acid, esters of -(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid, esters of 3,5-di-tert-butyl-4-hydroxyphenylacetic acid, amides of -(3,5-di-tert-butyl-4- hydroxyphenyl)propionic acid, suitable thio synergists, secondary antioxidants, phosphites and phosphonites, benzofuranones and indolinones.

Preference is given to organic phosphites such as triphenylphosphine, tritolylphosphine or 2,4,6-tri- tert-butylphenyl 2-butyl-2-ethylpropane-l,3-diyl phosphate, phosphonates and phosphanes, usually those in which the organic radicals consist entirely or partly of optionally substituted aromatic radicals.

Especially suitable additives are IRGANOX® 1076 (octadecyl 3,5-di-tert-butyl-4- hydroxyhydrocinnamate, CAS No. 2082-79-3) and also triphenylphosphine (TPP). Examples of suitable mold release agents are the esters or partial esters of mono- to hexahydric alcohols, more particularly of glycerol, of pentaerythritol or of Guerbet alcohols. Monohydric alcohols are, for example, stearyl alcohol, palmityl alcohol and Guerbet alcohols. A dihydric alcohol is, for example, glycol; a trihydric alcohol is, for example, glycerol; tetrahydric alcohols are, for example, pentaerythritol and mesoerythritol; pentahydric alcohols are, for example, arabitol, ribitol and xylitol; hexahydric alcohols are, for example, mannitol, glucitol (sorbitol) and dulcitol.

The esters are preferably the monoesters, diesters, triesters, tetraesters, pentaesters and hexaesters or mixtures thereof, more particularly statistical mixtures, of saturated, aliphatic Cio- to C36- monocarboxylic acids and optionally hydroxymonocarboxylic acids, preferably with saturated aliphatic C14- to C32-monocarboxylic acids and optionally hydroxymonocarboxylic acids. The fatty acid esters commercially available, especially those of pentaerythritol and of glycerol, may comprise < 60% of various partial esters as a consequence of the preparation process.

Examples of saturated aliphatic monocarboxylic acids having 10 to 36 carbon atoms are capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, hydroxystearic acid, arachidic acid, behenic acid, lignoceric acid, cerotinic acid and montanic acids. PETS (pentaerythritol tetrastearate) is a typical mold release agent for polycarbonate resin to facilitate the compounding process and help the molded part release from the mold.

The polycarbonate composition of the present invention can be prepared by a common process known to a person skilled in the art, such as the process comprising the following steps: 1) premix of impact modifiers and other additives, such as, e.g., lubricant and anti-oxidant agents; 2) compounding for blend of polycarbonate resin and premix; 3) pelletize to obtain the pellets.

Another aspect of the present invention is to provide a molded part obtainable from the above polycarbonate composition, preferably a housing for electric and electronic parts.

In one example of the present invention, the housing is the housing part of a mobile phone, laptop, adaptor, charger, socket, or switch.

Examples:

In the present invention, some typical coating materials for mobile phone housings from the market and Nivea sun lotion are used as chemicals to test the resistance against coatings and the chemical resistance in general.

Methods and materials: Preparation steps of composition (general introduction):

The compounding was performed at a Coperion ZSK26MS extruder with barrel temperature from 240°C to 265°C and output 32-35 kg/h.

The impact modifiers and other additives (mold release agent) are all commercially available.

Paraloid® EXL-2650A is MBS (methylmethacrylate-butadiene-styrene) from Dow Chemical.

Paraloid® EXL-2311 is an acrylate rubber based core-shell impact modifier from Dow Chemical. SX-006 is a silicone-acrylate rubber with a core-shell structure from Mitsubishi Rayon Co. A series of ethylene methyl acrylate copolymers (EMA) with different comonomer content and melt flow were used, including Elvaloy® AC1820, AC1125, and AC1330 from Dupont. Material and agents: component

A polycarbonate resin BPA based polycarbonate, available from Covestro

Makrolon® 2600 (PC

2600)

B Metablen® SX-006 silicone/acrylate rubber with a core-shell structure with SAN

(styrene-acrylonitrile copolymer) graft, the rubber content is around 50% and particle size is around 100 nm, available from Mitsubishi Rayon Co.

Elvaloy® AC 1820 ethylene-methyl acrylate copolymer (EMA) with methyl acrylate content 20 wt.-% and melt flow index 8 g/(10 min) (testing conditions 190°C, 2.16 kg, ISO 1133-1 :2011), used as impact modifier, available from Dupont.

Elvaloy® AC 1125 ethylene-methyl acrylate copolymer (EMA) with methyl acrylate content 25 wt.-% and melt flow index 0.5 g/(10 min) (testing conditions 190°C, 2.16 kg, ISO 1133-1:2011), used as impact modifier, available from Dupont.

Elvaloy® AC1330 ethylene-methyl acrylate copolymer (EMA) with methyl acrylate content 30 wt.-% and melt flow index 3 g/(10 min) (testing conditions 190°C, 2.16 kg, ISO 1133-1 :2011), used as impact modifier, available from Dupont. Paraloid® EXL-2311 acrylate rubber based core-shell impact modifier with PMMA graft, available from Dow Chemical Co.

Paraloid® EXL-2650A Methacrylate-butadiene-styrene (MBS) core-shell impact modifier, which contains butadiene rubber core and PMMA (polymethylmethacrylate) graft, available from Dow Chemical Co. c PETS pentaerythritol tetrastearate, used as lubricant, available from

FACI Asia Pacific Pte Ltd. (Singapore)

Table 1 : The composition of examples 1 to 7

Examples

Components

1 2 3 4 5 6 7

A PC 2600 wt.-% 93.4 91.4 90.4 93.4 93.4 93.4 93.4

Metablen® SX-006 wt.-% 3 3 6 3 3 3

Elvaloy® AC 1820 wt.-% 3 5 3 3

B Elvaloy® AC 1125 wt.-% 3

Elvaloy® AC 1330 wt.-% 3

Paraloid® EXL-2311 wt.-% - - - - - 3 3

C PETS wt.-% 0.6 0.6 0.6 0.6 0.6 0.6 0.6

Table 2: The composition of Comparative examples 1

Testing methods:

1. IZOD notched impact strength of the examples and comparative examples was measured at 2 different temperatures (23°C and -20°C) according to ISO180/A: 2000. The sample bars were cut with the dimension of 80 mm x 10 mm x 3 mm. The radius of notcher was 0.25 mm. 10 specimens were tested for each experimental condition. The impact strength values are shown together with the break type (P or C) in Tables 3 and 4. P stands for partial break, indicating the ductile behavior. C stands for complete break, corresponding to the brittle behavior. The results are shown in Tables 3 and 4 for examples and comparative examples, respectively.

2. The resistance against coatings is characterized by measuring the difference between the puncture energy in multiple axial impact (MAI) test before and after coating for both examples and comparative examples. The coating materials are obtained from the market. The relative change of puncture energy (%) is calculated and shown in the Tables 3 and 4 for examples and comparative examples, respectively.

Table 3: The IZOD notched impact strength values and resistance against coatings characterized by the change of MAI puncture energy after coating of the examples Examples

Testing Testing

items conditions

1 2 3 4 5 6 7

Izod 23°C 60P 65P 64P 60P 62P 60P 57P

notched

impact

strength,

-20°C 53P 54P 53P 55P 54P 54P 50P

3 mm

(kJ/m²)

Before

51.3 47.1 49.9 51.6 49.9 49.2 51.8

coating

MAI

puncture after

49.8 44.6 46.5 46.6 46.4 44.3 47.6

energy coating

(J)

change

-2.9 -5.3 -6.8 -9.7 -7.0 -10.0 -8.1

(%)

Table 4: The IZOD notched impact strength values and resistance against coatings

characterized by the change of MAI puncture energy after coating of the

comparative examples

Comparative Examples

Testing items Testing conditions

1 2 3 4 5 6 7 8

Izod notched 23°C 60P 57P 64P 59P 66P 59P 64P 68P impact strength, 3

mm (kJ/m²) -20°C 57P 54P 57P 53P 35C 39C 41C 56P

Before coating 52.5 51.4 50.6 50.8 53 52.5 51.8 32.2

MAI puncture

after coating 29.2 32.6 34.4 36.9 43 55.3 31.7 32.0 energy (J)

change (%) -44.4 -36.6 -32.0 -27.4 -18.9 5.3 -38.8 -0.6 Tables 3 and to 4 show the performance comparisons among the examples and the comparative examples regarding the notched impact properties and resistance against coatings characterized by the MAI puncture energy change after coating.

As clearly shown in Table 4, the MBS (EXL-2650A) modified polycarbonate

(comparative examples 1 and 2) lost a lot of puncture energy after coating was applied, suggesting its poor resistance against coatings. Further increasing the loading of MBS to 5% (all weight %, based on the total composition) in the polycarbonate does not improve the resistance against coatings indicated by Table 4. For the acrylate rubber based impact modifier EXL-2311, the resistance against coatings performance is similar to that of MBS although a little bit improvement can be observed but not significant enough.

Increasing the loading of EXL-2311 to 6% also has limited effect on improving the coating resistance (comparative example 4). For silicone-acrylate rubber based impact modifier SX-006 (SAN grafted), 3% loading (comparative example 5) will lead to improved resistance against coatings and increasing loading to 6% (comparative example 6) will further improve the resistance against coatings. However, at both 3% and 6% loading of SX-006, ductility cannot be achieved at -20°C for notched impact performance. For Evaloy® AC1820 (EMA), 3% loading cannot achieve ductility at 20°C for notched impact performance and also the resistance against coatings is not satisfied. At 6% loading of AC 1820, ductility can be achieved at -20°C. However, the MAI puncture energy will be significantly dropped to 32 J from original 51.8 J at 3% loading although the puncture energy level can be maintained after coating. Therefore, for all of these impact modifiers mentioned in comparative examples, no balanced properties can be achieved.

Interestingly, the examples in which the combinations of some impact modifiers are used show significantly improved resistance against coatings with ductile behavior at -20°C as disclosed in Table 3. The change ratio of MAI puncture energy after coating can be kept below 10% while the original puncture energy level can still maintain above 44J.

Metablen® SX-006 can be combined with Elvaloy® resins with different structure and flowability level (AC1820, AC1125, and AC1330) to achieve excellent resistance against coatings and good ductility level at low temperature. It can also work with

Paraloid® EXL-2311 very well (example 7). For Paraloid® EXL-2311, it can also work with Elvaloy® AC 1820 to achieve very good resistance against coatings and low temperature ductility. Therefore, any combinations of two impact modifiers from these three impact modifier categories (silicone-acrylate rubber based with a core-shell structure, and acrylate rubber based core-shell structure impact modifiers, and ethylene acrylate copolymer resins) can be used in the polycarbonate system to achieve excellent resistance against coatings and good low temperature impact performance (-20°C).

Claims

What is claimed is:

1. A polycarbonate composition comprising:

A) at least one thermoplastic, aromatic polycarbonate in an amount ranging from

85% to 97% by weight based on the total weight of the composition; and

B) at least two impact modifiers selected from the group consisting of

Bl) ethylene acrylate copolymer in an amount ranging from 1% to 8% by weight based on the total weight of the composition;

B2) silicone-acrylate rubber with a core-shell structure in an amount ranging from 1% to 8% by weight based on the total weight of the composition;

B3) acrylate rubber based core-shell impact modifiers in an amount ranging from 1% to 8% by weight based on the total weight of the composition with the proviso that the amounts of the impact modifiers Bl, B2 and/or B3 sum up to 3-15 % by weight based on the total weight of the composition.

2. The polycarbonate composition according to claim 1, wherein Bl is an ethylene - alkyl (meth) acrylate copolymer of the formula (I),

(I), wherein

Ri is methyl or hydrogen,

R₂ is hydrogen or a Ci- to Ci₂-alkyl moiety, and each of x and y is an independent degree of polymerization (integer), and n is an integer >= 1. The polycarbonate composition according to claim 2, wherein R2 is methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, isobutyl, hexyl, isoamyl, or tert-amyl.

The polycarbonate composition according to any one of the preceding claims, wherein the component Bl) is comprised in an amount ranging from 1% to 6% by weight based on the total weight of the composition.

The polycarbonate composition according to any one of the preceding claims, wherein the component B2) is contained in an amount ranging from 1% to 6% by weight based on the total weight of the composition.

The polycarbonate composition according to any one of the preceding claims, wherein the component B3) is contained in an amount ranging from 1% to 6% by weight based on the total weight of the composition.

The polycarbonate composition according to any one of claims 1 to 3, wherein the component Bl) is comprised in an amount ranging from 3% to 5% by weight based on the total weight of the composition, the component B2) is contained in an amount ranging from 3% to 6% by weight based on the total weight of the composition and the component B3) is contained in an amount ranging from 2.5 % to 3.4 % by weight based on the total weight of the composition, with the proviso that the amounts of the impact modifiers Bl, B2 and/or B3 sum up to 3-15 % by weight based on the total weight of the composition.

An electric/electronic apparatus part prepared from the polycarbonate composition according to any one of claims 1 to 7.

The electric/electronic apparatus part according to claim 8, wherein the electric/electronic apparatus part is a housing part of a mobile phone, laptop, adaptor, charger, socket, or switch.