Description

POLYCARBONATE-POLYSILOXANE COPOLYMER RESIN

COMPOSITION WITH HIGH IMPACT STRENGTH AT LOW

TEMPERATURE AND MECHANICAL STRENGTH

Technical Field

[1] The present invention relates to a polycarbonate-polysiloxane copolymer resin composition with high impact strength at low temperature and high mechanical strength. More particularly, the present invention relates to a polycarbonate- polysiloxane copolymer resin composition which comprises a polycarbonate resin and an organic siloxane polymer having a primary amine group.

[2]

Background Art

[3] Polycarbonate-polysiloxane copolymers and methods for preparing the same have been widely studied for many years.

[4] In general, polycarbonate-polysiloxane copolymers have been prepared by in- terfacial polymerization. U.S. Patent No. 5,530,083 discloses a method for preparing a silicone polycarbonate block copolymer using an interfacial phosgenation reaction in which an aromatic dihydroxy compound, phosgene and a catalyst are reacted with a hydroxyaryl terminated polydiorganosiloxane. However, this method has the problem of using a chlorinated solvent that is harmful to the environment.

[5] U.S. Patent No. 4,994,532 discloses a process of preparing a polycarbonate- silicone block copolymer by melt-blending a polycarbonate resin and a polydimethylsiloxane having a functional carboxylic acid group.

[6] In addition, U.S. Patent No. 5,194,524 discloses a process for producing a copolymer by melt-mixing siloxane compounds having at least one secondary amine group and polycarbonate resins through a conventional extruder. According to the above-mentioned patent, the polysiloxane having the secondary amine functional group is more effective for the reactive extrusion than a polysiloxane having a primary amine, due to relatively low hydrolytic stability of primary amine. The method using a melt mixing process has some advantages of proceeding in a conventional melt extruder and being a simple process, however, the method also has the problems of low impact strength at low temperature and low mechanical strength.

[7] Accordingly, in order to solve those problems, the present inventors have developed a polycarbonate-polysiloxane copolymer resin composition with high impact strength at low temperature as well as high mechanical strength and a method for preparing the same by introducing an organic siloxane polymer having a primary amine group to a

polycarbonate resin. [8]

Disclosure of Invention

Technical Problem

[9] An object of the present invention is to provide a polycarbonate-polysiloxane copolymer resin composition with high impact strength at low temperature and high mechanical strength.

[10] Another object of the present invention is to provide a polycarbonate-polysiloxane copolymer resin composition having a good balance of physical properties such as impact resistance, thermal stability, workability and appearance.

[11] Other objects and advantages of this invention will be apparent from the ensuing disclosure and appended claims.

[12]

Technical Solution

[13] The polycarbonate-polysiloxane copolymer resin composition according to the present invention comprises (A) about 100 parts by weight of a thermoplastic polycarbonate resin and (B) about 0.1 to 30 parts by weight of an organic siloxane polymer having a primary amine group.

[14] In an exemplary embodiment of the invention, the polycarbonate-polysiloxane copolymer resin composition has an impact strength of about 35 kgf-D/D or more measured at 23 ⁰ C for 1/4" specimens in accordance with ASTM D-256, an impact strength of about 18 kgf-D/D or more at -20 ⁰ C and about 15 kgf-D/D or more at -30 ⁰ C measured in accordance with ASTM D-256 for 1/4" specimens, respectively, and a flexural modulus of about 21,000 Kgf/Dor more measured in accordance with ASTM D790 using a 1/4" thick test specimens.

[15] The resin composition may further comprise an impact modifier to improve the impact strength. The preferable impact modifier may be present in the composition in an amount of less than about 10 parts by weight.

[16] In an exemplary embodiment of the invention, the impact modifier is a core-shell graft copolymer.

[17] In the exemplary embodiment, the polycarbonate-polysiloxane copolymer resin composition has an impact strength of about 70 kgf-D/D or more measured at 23 ⁰ C for 1/4" specimens in accordance with ASTM D-256, an impact strength of about 55 kgf-D/D or more at -20 ⁰ C and about 34 kgf-D/D or more at -30 ⁰ C measured in accordance with ASTM D-256 for 1/4" specimens, and a flexural modulus of about 21,000 Kgf/Dor more measured in accordance with ASTM D790 using a 1/4" thick test specimens.

[18] In another exemplary embodiment of the invention, the impact modifier is an

ethylene/alkyl (meth) acrylate copolymer.

[19] The resin composition of the invention may further include additives selected from the group consisting of flame retardants, flame retardant aids, lubricants, releasing agents, nucleating agents, antistatic agents, stabilizers, modifiers, inorganic fillers, pigments, dyes, and mixtures thereof.

[20] Another aspect of the present invention relates to a method for preparing a poly- carbonate-polysiloxane copolymer. The method comprises melt-blending a thermoplastic polycarbonate resin and an organic siloxane polymer having a primary amine group and extruding the melt-blended mixture through an extruder.

[21] The copolymer of the present invention now will be described more fully hereinafter in the following detailed description of the invention.

[22]

Best Mode for Carrying Out the Invention

[23] (A) Polycarbonate Resin

[24]

[25] The polycarbonate resin of the present invention is prepared by reacting a diphenol represented by the following Chemical Formula 1 with a phosgene, a halogen formate or a carbonic diester.

[26]

[27] [Chemical Formula 1]

[28]

[29] wherein A is a single bond, a C alkylene group, a C alkylidene group, a C cy-

1-5 1-5 5-6 cloalkylidene group, -S- or -SO . [30] Examples of the diphenol shown in Chemical Formula 1 may include 4,

4'-dihydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl)-propane,

2,4-bis-(4-hydroxyphenyl)-2-methylbutane,l,l-bis-(4-hydro xyphenyl)-cyclohexane,

2,2-bis-(3-chloro-4-hyroxyphenyl)-propane,

2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and the like. [31] Preferable examples of diphenols are 2,2-bis-(4-hydroxyphenyl)-propane,

2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane, and l,l-bis-(4-hydroxyphenyl)-cyclohexane. The most preferable diphenol is

2,2-bis-(4-hydroxyphenyl)-propane called 'bisphenol A' commonly used in industry as an aromatic. [32] In the present invention, it is preferable that the polycarbonate resin has a weight

average molecular weight (Mw) of about 10,000 to about 500,000, more preferably about 25,000 to about 100,000.

[33] In accordance with various embodiments of the invention, suitable polycarbonates incorporated into the composition of the present invention may be branched in a known manner, in particular, preferably by incorporating about 0.05 to about 2 mol%, based on the total quantity of diphenols used, of tri- or higher functional compounds, for example, those with three or more phenolic groups.

[34] A homopolymer of polycarbonate, a copolymer of polycarbonate, or mixtures thereof may be used in the preparation of resin composition of the present invention.

[35] [36] (B) Organic Siloxane Polymer Having a Primary Amine Group [37] [38] The organic siloxane polymer of the present invention is the organic siloxane polymer containing a primary amine group represented by the following Chemical Formula 2.

[39] [40] [Chemical Formula 2] [41]

[42] wherein R is independently a hydrogen atom, a C alkyl group, a C aryl group,

6-30 or a C 1-15 alky ^J l-substituted C 6-30 ary ^J l g ^to rou ^r p; R 2 is a C 1-8 alky ^J lene g ^to rou ^r p; R 3 is inde- pendently a hydrogen atom, a C alkyl group, a C aryl group, or a C alkyl- substituted C aryl group; p is 0 or 1; k is an integer from of about 1 to 5.

[43] Preferably R and R are independently a hydrogen atom or a C alkyl group. More preferably, R and R may include a hydrogen atom, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, isobutyl, isoamyl, t-amyl, etc.

[44] Preferably R is methylene, ethylene, propylene, isopropylene, butylene, sec- butylene or t-butylene. [45] The organic siloxane polymer containing a primary amine group may include, but is not limited to, a secondary amine group as shown in Chemical Formula 2.

[46] In the above, m and n represent the ratio of repeating units, m : n is about 99.9 : 0.1 to about 50 : 50, preferably about 99.5 : 0.5 to 55 : 45.

[47] The viscosity of the organic siloxane polymer having a primary amine group used in the preparation of the resin composition may be, but is not limited to, about 1-100,000 cSt at 25 ⁰ C, more preferably about 10-80,000 cSt considering the workability.

[48] The organic siloxane polymer having a primary amine group (B) of the present invention is used in an amount of about 0. l~30 parts by weight, preferably about 0.2~20 parts by weight, more preferably about 0.5~15 parts by weight. In those ranges, good physical properties mechanically may be obtained.

[49]

[50] (C) Impact Modifier

[51]

[52] In embodiments, a conventional impact modifier may be optionally used to improve the impact strength.

[53] In exemplary embodiments of the invention, the impact modifier may be a core- shell graft copolymer.

[54] The core-shell graft copolymer can be prepared by grafting the rubber polymer with a monomer such as aromatic vinyl compound, cyanide vinyl compound, C 1 -C 8 (meth) acrylic acid alkyl ester, maleic anhydride, maleimide, or mixtures thereof. [55] The core-shell graft copolymer may be preferably prepared by graft copolymerizing

5 to 95 % by weight of at least one monomer selected from the group consisting of styrene, α-methylstyrene, halogen- or C -C alkyl-substituted styrene, C -C methacrylic acid alkyl ester, C -C acrylic acid alkyl ester, acrylonitrile, methacry-

1 8 lonitrile, maleic anhydride, C -C alkyl- or phenyl N-substituted maleimide and mixtures thereof onto 5 to 95 % by weight of a rubber polymer selected from the group consisting of butadiene rubber, acrylic rubber, ethylene/propylene rubber, styrene/ butadiene rubber, acrylonitrile/butadiene rubber, isoprene rubber, ethylene- propylene-diene terpolymer (EPDM), polyorganosiloxane/polyalkyl(meth)acrylate rubber complex and mixtures thereof.

[56] The C -C methacrylic acid alkyl ester or C -C acrylic acid alkyl ester can be obtained from a methacrylic acid or an acrylic acid respectively and a monohydric alcohol containing 1 to 8 carbon atoms. Examples of the acid alkyl ester may include methacrylic acid methyl ester, methacrylic acid ethyl ester, acrylic acid ethyl ester, acrylic acid methyl ester or methacrylic acid propyl ester.

[57] One embodiment of the core-shell graft impact modifier is a graft copolymer obtained by graft polymerizing a mixture of styrene, acrylonitrile and optionally (meth) acrylic acid alkyl ester onto butadiene rubber, acrylic rubber, or styrene/butadiene

rubber. [58] Another embodiment of the core-shell graft impact modifier is a graft copolymer obtained by graft polymerizing (meth)acrylic acid alkyl ester monomer onto the rubber mixture of polyorganosiloxane/polyalkyl (meth) acrylate rubber with butadiene rubber, acrylic rubber, and styrene/butadiene rubber. [59] The rubber polymer may have preferably an average particle size of about 0.05 ~4 D considering the impact strength and the appearance of a molded article. [60] The graft impact modifier according to the present invention can be prepared through a conventional polymerization process such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization. Among these processes, emulsion or bulk polymerization in which said monomers are added to the rubber polymer using an initiator is preferable. [61] In another embodiment of the invention, the impact modifier may be a linear impact modifier, for example, an ethylene/alkyl (meth) acrylate copolymer. [62] The ethylene/alkyl (meth) acrylate copolymer may be represented by the following

Chemical Formula 3. [63]

[64] [Chemical Formula 3]

[65]

[66] wherein R is a hydrogen atom or a methyl group; R is a C -C alkyl group, a and b are the degree of polymerization, and a : b is about 300 : 1 to 10 : 90.

[67] Preferably, R is methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, isobutyl, isoamyl, or t-amyl.

[68] The ethylene/alkyl (meth) acrylate copolymer may be a random copolymer, a block copolymer, a multiblock copolymer, a graft copolymer, or mixtures thereof. The ethylene/alkyl (meth) acrylate copolymer may be prepared by one of ordinary skill in the art.

[69] In the present invention, the core-shell graft copolymer and the ethylene/ alkyl(meth)acrylate copolymer can be mixed together.

[70] The impact modifier according to the invention comprises favorably about 10 parts

by weight or less in the aspect of mechanical strength, more preferably 0.1 to 7 parts by weight, most preferably 0.5 to 5.5 parts by weight.

[71] Polycarbonate-polysiloxane copolymer resin composition of the invention may further comprise conventional additives such as flame retardants, flame retardant aids, lubricants, releasing agents, nucleating agents, antistatic agents, stabilizers, modifiers, inorganic fillers, pigments, dyes, etc. These additives can be used alone or in combination with one another. The inorganic additives may be present in the composition in an amount of about 0 to about 60 parts by weight, preferably about 1 to about 40 parts by weight, per 100 parts by weight of the base resin of (A) and (B).

[72] The polycarbonate-polysiloxane copolymer of the invention may be prepared by melt-blending a thermoplastic polycarbonate resin and an organic siloxane polymer having a primary amine group and extruding the melt-blended mixture. The mixture is extruded at about 200-300 ⁰ C, preferably about 250-280 ⁰ C. Extruded products can be prepared in the form of pellets. The pellets can be prepared by a conventional process and can be molded into the interior/exterior parts of electric and electronic goods such as TV housings, washing machines, telephones, audio sets, video players, CD players, and the like.

[73] The invention may be better understood by reference to the following examples which are intended for the purpose of illustration and are not to be construed as in any way limiting the scope of the present invention, which is defined in the claims appended hereto.

[74]

Mode for the Invention

[75] Examples

[76]

[77] The compound specifications of (A) the polycarbonate resin, (B) the organic siloxane polymer containing a primary amine group, and (C) the impact modifier used in Examples and Comparative Examples will be described more fully hereinafter.

[78]

[79] (A) Polycarbonate Resin

[80]

[81] Bisphenol-A based polycarbonate with a weight average molecular weight of

25,000 (Mw) was used.

[82]

[83] (B) Organic Siloxane Polymer Containing a Primary Amine Group

[84]

[85] (B-I) The organic siloxane polymer having a dynamic viscosity of 1,000 cSt at 25

⁰ C and represented by the above Chemical Formula 2 in which the ratio of m to n is 98.7 : 1.3; R is methyl group; R is propylene; R is hydrogen atom; p is 0; k is 2 was used.

[86] (B-2) polydimethylsiloxane having a dynamic viscosity of 100 cSt at 25 ⁰ C manufactured by Shinetsu Co. of Japan (KF-96) was used.

[87] (B-3) Siloxane polymer containing a secondary amine group represented by the following Chemical Formula 4 was used.

[88]

[89] [Chemical Formula 4]

[90]

[91] (d : e is 98 :2 and the dynamic viscosity is 1,000 cSt at 25 ⁰ C)

[92]

[93] (C) Impact Modifier

[94]

[95] MBS based core-shell graft impact modifier (Metablen C223A) manufactured by

MRC Co. of Japan was used.

[96]

[97] Examples 1~2 and Comparative Examples 1~4

[98]

[99] The components as shown in Table 1 added with antioxidants, thermal stabilizers were mixed in a conventional mixer and the mixture was extruded through a twin screw extruder (L/D=35, φ=45 mm) in pellets. The resin pellets were molded into test specimens using a 10 oz injection molding machine at 280~300 ⁰ C.

[100]

[101] The physical properties of the test specimens were measured as follow and were shown in Table 1 below.

[102]

[103] (1) Izod Impact Strength at room temperature: The notch Izod impact strength was measured for 1/4" specimens (inch, kgf-D/D), after exposure at 23 ⁰ C and 50 % of

relative humidity for 48 hours in accordance with ASTM D-256.

[104] (2) Izod Impact Strength at low temperature: The notch Izod impact strength was measured for 1/4" specimens (inch, kgf-D/D), after exposure at -20 ⁰ C and at -30 ⁰ C respectively for 48 hours in accordance with ASTM D-256.

[105] (3) Flexural Modulus: The flexural modulus was measured after exposure at 23 ⁰ C and 50 % of relative humidity for 48 hours in accordance with ASTM D790 using a 1/4" thick test specimens at 2.8 mm/min velocity.

[106] [107] Table 1

[108] [109] As shown in Table 1, Examples 1-2 employing the organic siloxane polymer containing a primary amine group show high impact strength at low temperature and high mechanical strength, compared to Comparative Examples 1-4 employing the organic siloxane polymer without the functional group or the organic siloxane polymer substituted for a secondary amine group.

[HO] [111] In the above, the present invention was described based on the specific preferred embodiments, but it should be apparent to those ordinarily skilled in the art that various changes and modifications can be added without departing from the spirit and scope of the present invention which will be defined in the appended claims.