AU659344B2

AU659344B2 - Thermoplastic resin composition containing a polycarbonate resin and a multi-layer polymer, and moulded article made therefrom

Info

Publication number: AU659344B2
Application number: AU47416/93A
Authority: AU
Inventors: Tatsuo Fujii; Kazuhiko Ishii; Makoto Muzutani; Junji Oshima; Goro Shimaoka; Takao Teraoka
Original assignee: Mitsubishi Gas Chemical Co Inc; Takeda Chemical Industries Ltd
Current assignee: Mitsubishi Gas Chemical Co Inc; Takeda Pharmaceutical Co Ltd
Priority date: 1990-05-11
Filing date: 1993-09-16
Publication date: 1995-05-11
Anticipated expiration: 2011-05-08
Also published as: AU4741693A

Description

-j i~lrrur-r*~- -1- P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 659344

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: THERMOPLASTIC RESIN COMPOSITION CONTAINING A POLYCARBONATE RESIN AND A MULTI-LAYER POLYMER, AND MOULDED ARTICLE MADE THEREFROM r a o ~otr c rrrtr a I r rrre a rrr

I

rr a rre r a rrc r Irrr c tr ct r PI d tl'C a c(f P i CS i: r I

I

The following statement is a full description of this inverition, including the best method of performing it known to me/us: t C rC t C I&CO REF: P21819B:PJW -I I~ 1A This application is a divisional of application nc.

76419/91.

Field of the Invention The present invention relates to a thermoplastic resin composition which comprises a polycarbonate resin and a multi-layer polymer as an impact modifier, and to a moulded article made from the thermoplastic resin composition.

Background of the Invention Being tough, excellent in impact and electrical characteristics, and high in dimensional stability, polycarbonate resin has been used as a versatile engineering plastic. However, this resin has several drawbacks, namely high melt viscosity, poor mouldability, thickness dependency of impact resistance, and poor chemical resistance as evidenced by the incidence of cracks in contact with chemicals. For instance, brittle fracture occurs when a test piece of more than 1/4 inch thick is given impact; even with a test piece of 1/8 inch thick, the lower the temperature, the small the impact rength. All these defects delimit its application.

Therefore, many attempts have been made to overcome the above-mentioned disadvantages. For example, Japanese Patent Laid-opens Nos. 56-45946 and No. 56-45947 propose a resin composition composed of aromatic polycarbonate resin and an acrylic polymer as an impact modifier which is particularly improved in impact resistance at low temperatures. It is true that this resin composition has an improved impact resistance, but is coloured unevenly 30 when it contains a colouring agent. This phenomenon is known as pearlesscence in the trade, and is particularly pronounced when a high shear load is added to the resin composition, for example, in the neighbourhood of a gate of a mould. Therefore, the use of the resin composition is limited unless a surface coating or like treatment is applied thereto. Furthermore, when the resin composition AALI is moulded, the resultant moulded articles are very often 3 accompanied by delamination where the resin composition N1w

C-,

AI r-.ii i -2receives a high shear load, for example, in the gate region, to provide moulded articles infeasible for practical use.

Meanwhile Japanese Patent Publication No. 61-9982 discloses a resin composition composed of polycarbonate resin and a multi-layer polymer composed of a first stage polymer of an aromatic vinyl monomer, a second stage polymer of an alkyl acrylate wherein the alkyl has 1-8 carbons and a third stage polymer or copolymer of an aromatic vinyl monomer which has a glass transition temperature of not less than 50 0 C to improve impact resistance without reduction of transparency of polycarbonate resin. However, neither mention was made of elimination of unevenness in colour, nor of thickness dependency of impact resistance and impact resistance at low temperatures.

Summary of the Invention In a first aspect, the present invention provides a thermoplastic resin composition which comprises: 100 parts by weight of a polycarbonate resin; 9% and 0.5 60 parts by weight of a multi-layer polymer which is composed of 12 42% by weight, with respect to the multilayer polymer, of a core layer formed from styrene or a substituted styrene; (ii) 50-65% by weight, with respect to the multit layer polymer, of an intermediate rubbery polymer layer formed from an alkyl acrylate monomer, wherein <J 30 the alkyl moiety has 2-8 carbons; and (iii) 10-40% by weight, with respect to the multilayer polymer, of a glassy polymer shell layer which has a glass transition temperature of not less than and which is formed from a styrene or substituted styrene and a non-aromatic monomer in an amount of not more than 30% by weight with respect Sto the total monomer used for the shell layer, and wherein the shell layer is cross-linked with a S:218198/703 i; 4 II I I 3 cross-linking monomer in an amount at 5-15% by weight with respect to the total monomer used for the shell layer.

In a second aspect, the present invention provides a moulded article made from a composition according to the first aspect of the present invention.

Detailed Description of the Invention The polycarbonate resin used in the present invention is commonly utilised for engineering plastics.

Preferred is an optionally branched thermoplastic polycarbonate resin which is produced by reacting an aromatic dihydroxy compound 4..

4 4

C

SC

cC Cr C a I a

I

4 i 1 i -1 i i i

I

A]

c.9 1 a QR/7n 4 as such or a mixture thereof with a small proportion of a polyhydroxy compound with phosgene or a carbonic diester.

Examples of said aromatic dihydroxy compound are 2,2-bis(4-hydroxyphenyl)propane (also known as bisphenol A), tetranethylbisphenol A, tetrabromobisphenol A, his (4hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, 4,4-dihydroxydiphenyl and so on. Particularly preferred is bsphenol A.

To prepare a branched aromatic polycarbonpte resin, phloroglucinol, 4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptene-2, 4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptane, 2,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptene-3, 1,3,5tri(4-hydroxyphenyl)benzene, 1,1,1-tri(4-hydroxyphenyl)ethane, 3,3-bis(4-hydroxyaryl)oxyindole (also known as sct isatin bisphenol), 5-chloroisatin, 5,7-dichloroisatin, 15 or the like is used to substitute said dihydroxy compounds in part (for example about 0.1 to 2 mole As the aromatic monohydroxy compound suited for *2 ~molecular weight adjustment, m- or p-methylphenol, m- or p-propylphenol, p-bromophenol, p-tert-butylphenol, p-long chain alkyl-substituted phenols, etc. can be used with advantage. Among typical examples of the polycarbonate resin are these based on bis(4-hydroxyphenyl)alkane dihydroxy compounds, particularly bisphenol A. The polycarbonate copolymer obtainable by using two or more different aromatic dihydroxy compounds in combination or the branched polycarbonate obtainable by using a small proportion of a trihydroxy phenol compound in conjunction can also be employed. Furthermor, two or more different polycarborate resins can be used as a mixture.

The multi-layer polymer e*the present invention can be produced by a multi-stage saed emulsion polymerization method in which a polymer formed in a preceding stage is serially covered with a polymer formed in the following N I stage in a continuous sequence. In the practice of the present invention, three-stage emulsion polymerization is generally carried out.

The first-stage polymerization, which provides said S core layer, is carried out using an aromatic vinyl monomer, rP-o i-t c 44My_ mon-omer- u s- i n styrene az 4 a substituted styrene such as vinyltoluene, ao-methylstyrene, monochlorostyrene, 3,4-dichlorostyrene or bromostyrene. e. by s prnen'r-eA..

1 n In this first-stage polymerization, a non-aromatic monomer copolymerizable with said aromatic vinyl monomer may be optionally employed. Its proportion is preferably not more than 50% by weight based on the total monomer for the first-stage polymerization. The more useful proportion o 2- 15 is not more than 20% by weight. The non-aromatic monomer mentioned above includes, inter alia, alkyl acrylates such as ethyl acrylate, butyl acrylate, etc., alkyl methacrylate such as methyl methacrylate, butyl methacrylate, etc., and vinyl cyanides or vinylidene cyanide such as acrylonitrile 20 and methacrylonitrile.

The core layer may be cross-linked with a cross-linking mo;.omer. The cross-linking monomer may be used in an amount of not more than 30% by weight, preferably in an amount of 0.5-20% by weight, more preferably in an amount of 5-15% by weight, based on the total monomer for the first-stage polymerization. As said cross-linking monomers, monomers each containing two or more ethylenic unsaturation may be employed. More particularly there may be employed aromatic divinyl monomers such as divinylbenzene etc. and alkane polyol poly(meth)acrylates such as ethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, hexanediol di(meth) acrylate, olygoethylene glycol di(meth)acrylates, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc., among these is preferred divinylbenzene.

L LI V" _1 r 7 useful, among these is preferred divinylbenzene. The proportion of such monomers is 0.01-5% by weight, preferably 0.1-2% by weight based on the total monomer for the second-stage polymerisation.

The grafting monomers mentioned hereinbefore may also be employed. Particularly preferred is allyl methacrylate. The proportion of such monomers not more than 5% by weight, preferably 0.1-2% by weight based on the total monomer for the second-stage polymerisation.

The third-stage polymerisation for the shell layer is carried out in such a manner that a rigid polymer with a glass transition temperature of not less than 50 0 C will cover the rubbery polymer. The third-layer polymerisation is carried out using an aromatic vinyl monomer, namely styrene or a substituted styrene such as vinyltoluene, a-methylstyrene, monochlorostyrene, 3,4dichlorostyrene or bromostyrene. Styrene is particularly preferred.

In this third-stage polymerisation, non-aromatic monomers copolymerisable with said aromatic vinyl monomers are also employed. The proportion of such monomers is not more than 30% by weight, based on the total monomer for the third-stage polymerisation. Among such copolymerisable non-aromatic monomers are alkyl acrylates such as ethyl acrylate, butyl acrylate, etc., Salkyl methacrylates such as methyl methacrylate, butyl methacrylate, etc., and vinyl or vinylidene cyanides such Sas acrylonitrile, methacrylonitrile and so on.

SA cross-linked monomer is used in the third-stage polymerisation in an amount of 5-15% by weight with respect to the total monomers used in the third-stage polymerisation. The cross-linking monomers mentioned in relation to the first-stage polymerisation may be used in the third-stage polymerisation. Particularly, divinylbenzene and butylene glycol dimethacrylate may be preferably used, and divinylbenzene is preferred.

ALl The hard shell layer is more preferably composed of O a styrene-acrylonitrile copolymer.

S:21819B/703 -8- A hard intermediate polymer layer may be interposed between the intermediate rubbery polymer layer and the hard shell layer. This hard intermediate polymer layer is preferably composed on a rigid polymer with a glass transition temperature of not less than 50 0 C and is preferably formed by using, inter alia, an alkyl methacrylate preferably of 1-5 carbons such as methyl methacrylate, butyl methacrylate and so on.

The cross-linking monomers mentioned in relation to the first-stage polymerisation may be used for the I preparation of the hard intermediate layer in an amount of not more than 30%- by weight, preferably 0.5-20%- by weight, more preferably 5-15% by weight, based on the total monomer used for the hard intermediate layer.

Particularly preferred are divinylbenzene and butylene glycol methacrylate, the former being most preferred.

The grafting monomers mentioned in relation to the first-stage polymerisation may also be used for the preparation of the hard intermediate layer in an amount of not more than 5% by weight, preferably not more than f t 1% by weight based on the total monomer used for the hard intermediate layer.

It is preferred that the core and hard intermediate layers are cross-linked with the cross-linking monomers ;25 in an amount of about 5-15% by weight of the monomers S| cr' used in each layer, respectively, in contrast to the multi-layer polymer of prior art which contains in each S( layer, if any, only a small amount of cross-linking monomers to prevent reduction of impact strength.

I 30 However, the multi-layer polymer used in the present invention has a shell layer, and optionally core and hard tintermediate layers, which is/are cross-linked with the ,cross-linking monomers in such a V t J 1 .CO

,J

large amount as above mentioned, and the incorporation of such a multi-layer polymer into a polycarbonate resin provides a polymer composition which has improved evenness in color without deterioration of impact strength.

It is preferred, however, tha' the total amount of the cross-linking monomers used in the core, hard intermediate and shell layers is 1-30% by weight, preferably 3-20% by weight, based on the total amount of the monomers used in the core, hard intermediate and shell layers.

c The multi-layer polymer used in the invention may be obtained as follows. From the latex formed by the known seed emulsion polymerization process, the polymer is separated by a freeze-thaw or salting-out procedure and cI subjected to centrifugal dehydration and drying to give granules, flakes or powders. By the spray-drying technique, /the polymer may be directly harvested from the latex. If desired, the multi-layer polymer thus obtained is further processed into pellets with an extruder and pelletizer or be used as it is.

It is preferred that the multi-layer p.olymer has a toluene soluble portion of not more than 10% by weight, most preferably not more than 6% by weight. The use of such a multi-layer polymer in a polycarbonate resin composition provides a shaped article having improved evenness in color. The toluene soluble rtion is defined i herein the amount of the polymer in percentage by weight dissolved in toluene in an amount one hundred times in weight the amount of the polymer when the polymer is dispersed in the toluene and left standing at room temperature for 48 hours.

It is also desirable that the multi-layer polymer has a particle size of 100-700 nm, preferably 200-500 nm so that the resultant resin composition has satisfactorily improved impact resistance. i The multi-layer polymer st-i4h\invention is compopsed

COZEM

of 12-42% by weight of \core layer, \by weight of intermediate rubbery polymer layer, and 10-40% by weight of -a;f gassy polymer shell layer. More preferably, the multi-layer polymer is composed of 15-30% by weight of the core layer, 50-65% by weight of the intermediate rubbery polymer layer and 15-25% by weight of the shell layer.

The multi-layer polymer may contain the hard intermediate polymer layer. The amount of the hard intermediate polymer layer ssuch that the total amount of this layer and the shell layer accounts for 10-40% by weight, preferably 15-25% by weight, based on the whole multi-layer polymer. Further, the amount should be within the range of 0-100 parts by weight based on 100 parts by weight of Sthe outer shell layer.

The total of the proportions of said core, intermediate, hard intermediate polymer layer and shell layers is 100 weight percent.

The resin composition of the invention contains to 60 parts by weight, preferably 1 to 25 parts by weight, of the above multi-layer polymer in relation to 100 parts 20 by weight of the polycarbonate resin.

o The resin composition of the invention is markedly improved in impact resistance at low terperature and markedly reduced in temperature dependency of impact resitance while it holds inherent dynamic and electrical characteristics and dimensional stability of polycarbonate resin.

The resin composition of the invention may be produced by blending a polycarbonate resin together with the multilayer polymer in the proportions defined herein.

There is virtually no restriction on the blending process and technique but melt-blending is a preferred procedure. Melt-blending is generally carried out at a temperature of 200 to 300'C by means of a hot roil, a Banbury mixer or a single-screw or twin-screw extruder.

The resin compositions of the invention may contain I3LL V i :j 11 additives in appropriate proportions. For example, stabilizers, pigments, flame retardants, lubricants, inorganic fillers, antistatic agents, mold releases, ultraviolet absorbers and so on may be incorporated.

Referring to the pigments, in particular, a variety of pigments including titanium oxide, iron oxide and other types of inorganic pigments, organic dyes and pigments such as azo and phthalocyanine dyes, etc., carbon black and so on may be employed. These pigments may be used in an amount of 0.01 to 20 parts by weight in relation to 100 parts by weight of the resin composition.

The resin compositions of the invention may be-,=em outdin intc articles of desired shapes, by ordinary\, techniques such as injection extrusion mold Si 15 compression and so on, at a temperature of 200'C to 300'. The resulting shaped articles find application as automotive parts such as bumpers, fenders, door-handles, etc., office automation equipment parts, household electrical appliance parts and so on.

Meanwhile in the production of colored articles, the resin compositions of the invention insure a marked improvement in evenness in color, free from whitening and other colorimetric drawbacks.

As a further improvement, there takes place substantially no delamination 9f molded articles in the neighborhood of gate of a moB4\when the resin compositions are ~*ev4* .A Examples The following examples and comparative examples are intended to illustrate the invention in further detail and should by no means be construed as being limitative of the scope of the invention.

In the examples and comparative examples, all parts to as A pa t s as b e f d r a e et. ofic auoaineupetprshueodeetia 4 12 are by weight and the abbreviations used therein have the following meanings.

2-Ethylhexyl acrylate 2EHA n-Butyl acrylate

BA

Methyl methacrylate MMA Styrene St Acrylonitrile AN Allyl methacrylate A1MA 1,4-Butylene glycol acrylate BGA Divinylbenzene DVB Deionized water DIW Sodium dioctyl sulfosuccinate SSS 1 s Sodium persulfate SPS 5 Sodium hydrogen carbonate SHC *ff: i5 Glass transition temperature Tg Poiycarbonate PC The weight average particle size of the multi-layer polymer was measured with a laser particle analyzer (Ohtsuka Electronics Co., Ltd., LPA-3000).

Production of Multi-layer Polymer Example 1 Ic Production of Multi-layer Polymer A A 5-liter polymerization equipment equipped with a reflux condenser was charged with 448 g of DIW, 12 g of 1% aqueous solution of SSS, and 32 g of 1% aqueous solution of SHC and the charge was heated to 70"C in a nitrogen stream with stirring. Then, 30 g of MMA was added and dispersed over a period of 10 minutes, after which 80 g of 2% aqueous solution of SPS was added for seed polymerization.

Ii First-stage monomer emulsion: St 332 g DVB 36 g A1MA 2 g SSS, 1% aq. soln. 308 g SHC, 1% aq. soln. 48 g DIW 192 g The temperature was then increased to 75°C and io10 918 g of the above first-stage monomer emulsion was continuously fed over a period of 60 minutes, followed by ageing at 80°C for one hour. Thereafter, 80 g of 2% aqueous solution of SPS was added and then 2320 g of the following second-stage monomer emulsion was fed over a period of 180 minutes to carry out the second-stage polymerization at 80"C followed by ageing at 80C for one hour.

:2 0 e 4 Second-stage monomer emulsion: 2EHA 1176 g DVB 18 g AIMA 6 g SSS, 1% aq. soln. 960 g SC, 1% aq. soln. 80 g DIW 80 g Then 50 g of 2% aqueous solution of SPS and 580 g of the following third-stage monomer emulsion was fed over a period oi 60 minutes to carry out the third-stage polymerization at 80C, followed by ageing at 80' for one hour.

Third-stage monomer emulsion: Third-stage monomers 240 g 100 g 14 DVB 60 g SSS, 1% aq. soln. 100 g SHC, 1% aq. soln. 40 g DIW 40 g After cooling to room temperature, the reaction mixture was filtered through a 300-mesh stainless steel sieve to yield a core-shell polymer latex with a solid content of 44.4% and a weight average particle size of 276 's '10 nm. This latex was precipitated by freeze-thaw, rinsed, dehydrated and dried to provide a multi-layer polymer A.

Examples 2 to 4 Production of Multi-layer Polymers B to D In accordance with the formula shown in Table 1, the procedure of Example 1 comprising emulsion polymerization, freeze-thaw, rinse, dehydration and drying steps was followed to give multi-layer polymers B to D.

Comparative Example 1 Production of Multi-layer Polymer E A 2-liter polymerization equipment equipped with a reflux condenser was charged with 600 g of DIW, 20 g of 2% aqueous solution of SSS and 40 g of 1% aqueous solution of S: '25 SHC and the mixture was heated to 70'C in a nitrogen stream t,,f with constant stirring. Then, 40 g of the following firststage monomers were added and dispersed over a period of minutes, after which 80 g of 2% aqueous solution of SPS was added for seed polymerization.

First-stage monomers: 2EHA 792 g AlMA 4 g BGA 4 g Then 1080 g of the following first-stage monomer emulsion was added continuously over a period of 180 minutes, and the mixture was heated to 90'C, followed by ageing at for one hour.

First-stage monomer emulsion: First-stage monomers 760 g SSS, 2% aq. soln. 280 g SHC, 1% aq. soln. 40 g After the mixture was cooled to 70'C, 20 g of 2% aqueous solution of SPS were added and then 360 g of the E following second-stage monomer emulsion were fed over a tperiod of 45 minutes to carry out the second-stage R 15 polymerization, followed by ageing at an elevated temperature of 90°C for one hour.

Second-stage monomer emulsion: MMA 200 g SSS, 1% aq. soln. 60 g SHC, 1% aq. soln. 20 g DIW 80 g After cooling to room temperature, the reaction S 25 mixture was filtered through a 300-mesh stainless steel t sieve to yield a core-shell polymer latex with a solid content of 44.7% and a weight average particle size of 293 nm. This latex was precipitated by freeze-thaw, rin.ed, dehydrated and dried to provide a multi-layer polymer E.

Comparative Examples 2 to 4 Production of Multi-layer Polymers F to H In accordance with the charge formulations indicated in Table 1, the procedure of Example 1 comprising emulsion 16 polIymeriz at ion, f reeze- thaw precipi tat ion, rinse, dehydration and drying steps was followed to provide multi-layer polymers F to 11.

2 0 r*r.

41., 41 41414~ 4 Table 1 Example Comparative Example 1 2 3 4 1 2 3 4 Multi-layer polymer A B C D E F G H Construction (wt. ratio) SCore layer 20 '0 30 30 80 35 20 Intermediate rubbery layer 60 60 50 50 30 60 Hard intermediate layer Shell layer 20 15 20 20 20 35 20 Core layer monomer, composition (wt. ratio) 2EHA 99 St 83 91 86.4 86.4 96 83 MMA 7.5 5 5 96 BGA 0.5 3.5 DVB 9 8.5 8.4 8.4 9 AlMA 0.5 0.5 0.2 0.2 0.5 0.5 0.5 Intermediate rubbery layer (wt. ratio) 2EHA 98 98 97.8 98 BA 97.8 98 98 DVB 1.5 1.5 1.8 1.8 1.5 1.5 AlMA 0.5 0.5 0.2 0.2 0.5 0.5 I [1111111 I I I n C ft 1 Sw 0* A abC i Table 1 (Continued) 4" ir Example Comparative Example 1 2 3 4 1 2 3 4 Multi-layer polymer A B C D E F G Hard intermediate layer (wt. ratio) MMA DVB AIMA Shell layer (wt. ratio) St 60 90 70 70 90 AN 25 23 23 MMA 100 100 PVB 15 10 7 7 10 Particle size (nm) 276 283 320 432 293 290 273 310 Toluene soluble portion (wt. 3.32 3.26 2.69 3.95 25.3 3.51 7.22 4.20 19 Polycarbonate Base Resin Composition Example Production of Thermoplastic Resin Composition (1) To 100 parts by weight of a resin mixture consisting of 95 parts by wei-ght of, bisphenol A-based polycarbonate resin (Mitsubishi Gas Chemical, lupilon S-3000; hereinafter referred to as S-3000) and 5 parts by weight of multi-layer polymer A was added 0.1 part by weight of carbon black, and the mixture was melt-blended and extruded Swith a 40 mm single-screw extruder at a cylinder temperature of 240-260"C to give pellets of thermoplastic resin composition Examples 6 to 8 Production of Thermoplastic Resin Compositions to (4) The procedure of Example 5 was repeated except that multi-layer polymers B to D were respectively used in lieu Si' of multi-layer polymer A to provide pellets of thermoplastic t, ,20 resin compositions to Comparative Examples 5 to 7 Production of Thermoplastic Resin Compositions to (7) The procedure of Example 5 was repeated except that t': t 25 multi-layer polymers E, F and H were respectively used in lieu of multi-layer polymer A to provide pellets of thermoplastic resin compositions to Comparative Example 8 Production of Thermoplastic Resin Composition (8) To 100 parts by weight of polycarbonate resin (S-3000) were added 0.1 part by weight of carbon black and the resultant mixture was melt-blended and extruded with a mm single-screw extruder at a cylinder temperature of 240- 260"C to give pellets of thermoplastic resin composition 410 Test Example 1 Test For Impact Resistance Pellets of thermoplastic resin compositions to were respectively dried at.l 1OC for not less than 6 hours and then injection-eo4- 4ea at 240-260C to prepare test specimens. Each specimen was notched by machining to give a 1/8 inch-thick and a 1/4 inch-thick test piece for Izod impact test as directed in JIS K7113.

The impact resistance was measured at 23°C with the 1/4 inch-thick test piece, and at -40C with the 1/8 inchthick test piece in accordance with JIS K7113. The results are shown in Table 2.

The delamination of the article at the gate was visually evaluated.

Test Example 2 Pellets of thermoplastic resin compositions to Cl0 were respectively dried at l10C for not less than 6 hours and then injection-m 4-4edat 240-260"C into test specimens of three graded thicknesses (2 mm, 3 mm, 4 mm).

The L value of the 4 mm thick portion and the color difference (AE value between the 2 mm and 4 mm thick portions were determined with a Suga Testing Machine SM color computer. The results are shown in Table 2. The L value represents the depth of color, and the smaller the value of the color, the nearer to perfect black the color is; while AE value represents the degree of unevenness of color, and the larger the value, the larger the difference in color between the 2 mm and 4 mm thick portions of the test specimen. Accordingly, it is desirable that both values are as small as possible so that resin compositions are excellent in colorability.

Table 2 Exampl e 6 7 8 Resin Composition (4) Formulation (wt. parts) PC (S30)I 95.0 95.0 95.0 95.0 Multi-layer polymer A B C D

E

F

II

Carbon black 0.1 0.1 0.1 0.1 Izod impact (Kgf .cm/cm) 1/4 inch 23 C MG.5 74.2 75.1 74.2 1/8 inch -40 C 68.9 65.4 66.0 65.0 L value 7.2 6.8 6.9 6.7 ABE value 0.64 0.78 0.67 0.64 Delamination at gate"z) Q 0 0 0 NOTE *1 *2: Mitsubishi Gas Chemical, polycarbonate, 1upilon S-3000 0O=Good (no delamina tion) A=Crust formation X=Surface delamination L 1 0* *0 S S S S S S C S* S S S S 4 5 0 aS *5 S S 5 4* 5 'Table (C~tiiued) 555 5 5 55 5* 54 S S S 45 4 *54 4 4 S 5 5 4 54 9 5 #45

F-

I

Comparative 6 (6) Example 7 (7) 8 R~esin Composition Formulation (wt. parts) PC (S-3000'*I Multi-layer polymer A 95.0 95.0 95.0 100 Carbon black 0.1 0.1 0.1 0.1 Izod impact (Kgf .cm/cm) 1/4 inch 23'C 75.8 Sl 7 73.5 15.5 1/8 inch -40 C 67.2 64.0 18.1 L value 10.6 698.9 6.4 A E value 2.34 Q,64 1.73 0.61 Delamination at gate*') X C0 A 0 NOTE Mitsubishi Gas Chemical, polycarbonate, Iupilon S-3000 0==Good (no delamination) A =Crust formation X Surface delamination

Claims

1. A thermoplastic resin composition which comprises: 100 parts by weight of a polycarbonate resin; and 0.5 60 parts by weight of a multi-layer polymer which is composed of 12 42% by weight, with respect to the multi- layer polymer, of a core layer formed from styrene or a substituted styrene; (ii) 50-65% by weight, with respect to the multi- layer polymer, of an intermediate rubbery polymer layer formed from an alkyl acrylate monomer, wherein the alkyl moiety has 2-8 carbons; and (iii) 10-40% by weight, with respect to the multi- layer polymer, of a glassy polymer shell layer which has a glass transition temperature of not less than 500C and which is formed from a styrene or substituted styrene and a non-aromatic monomer in an amount of not more than 30% by weight with respect 9 L to the total monomer used for the shell layer, and wherein the shell layer is cross-linked with a cross-linking monomer in an amount at 5-15% by weight with respect to the total monomer used for L 25 the shell layer.

2. A composition as claimed in claim 1 wherein the multi-layer polymer is composed of 15-30% by weight with respect to the multi-layer polymer of the core layer; by weight with respect to the multi-layer polymer of r 30 the intermediate rubbery polymer; and 15-25% by weight with respect to the multi-layer polymer of the shell Slayer. t

3. A composition as claimed in claim 1 wherein the multi-layer polymer further contains a hard intermediate layer between the intermediate rubbery polymer layer and the shell layer, the hard intermediate layer being formed from a polymer of an alkyl methacrylate, wherein the /ALIq alkyl moiety has 1-5 carbons, and wherein the amount of N 1 :21819B/703 The resin compositions of the invention may contain 24 24 the hard intermediate layer and the shell layer is 10-40% by weight with respect to the multi-layer polymer.

4. A composition as claimed in claim 3, wherein the amount of the hard intermediate layer and the shell layer is 15-25% by weight with respect to the multi-layer polymer. A composition as claimed in any one of the preceding claims wherein the intermediate rubbery polymer layer is formed from at least one of 2-ethylhexyl acrylate and butyl acrylate.

6. A composition as claimed in any one of the preceding claims wnerein the glassy polymer shell layer is composed of a styrene-acrylonitrile copolymer.

7. A composition as claimed in any one of claims 3-6 whereii the alkyl methacrylate is methyl methacrylate or butyl methacrylate.

8. A composition as claimed in any of the preceding claims comprising 100 parts by weight of the polycarbonate resin and 1-25 parts by weight of the multi-layer polymer. S9. A thermoplastic resin composition substantially Sas herein described with reference to any one of the S 1 Examples excluding the Comparative and Test Examples. A moulded article made from a composition as S 25 claimed in any one of the preceding claims. Dated this 15th day of February 1995 TAKEDA CHEMICAL INDUSTRIES LTD AND MITSUBISHI GAS CHEMICAL COMPANY, INC. 9By their Patent Attorney GRIFFITH HACK CO. S I f 1 4 y /703 'AL L 1 ABSTRACT OF THE DISCLOSURE There is disclosed a mul.ti-layer polymer which comprises

12-42% by weight of a core layer formed from styrene or a substituted styrene, 48-78% by weight of an intermediate rubbery polymer layer formed from an alkyl acrylate monomer wherein the alkyl has 2-8 carbons and 10-40% by weight of a glassy polymer shell layer formed from styrene or a substituted styrene and a non-aromatic monomer in an amount of not more than 30% by weiglt based on the monomer used for the shell layer, and having a glass transition tempera- ture of not less than 50C the amount of each layer being S t i r t based on the multi-layer polymer. I There is also disclosed a polycarbonate resin compo- sition which contains the multi-layer polymer as an impact modifier. The resin composition provides shaped articles which have improved impact resistance, andalso high evenness in color when the composition contains a coloring agent.