Tung, Fai LO. (12 rue de Horgnes, Agincourt, Agincourt, F-60940, FR)
| 1. | Antistatic agent for a polymer composition, characterized in that it consists of a combination of: (a) a first additive chosen from poly (ethylene glycols) with a weightaverage molar mass M w of from 500 to 15,000 and mixtures thereof, and (b) Nalkylsulphonates and mixtures thereof, the weight ratio of the second additive to the first additive being not more than 0.50. |
| 2. | Antistatic agent according to Claim 1, characterized in that the weight ratio of the second additive to the first additive ranges from 0.30 to 0.50, preferably from 0.35 to 0.50. |
| 3. | Antistatic agent according to Claim 1 or 2, characterized in that the poly (ethylene glycols) have a weightaverage molar mass of from 11,000 to 14,000, preferably from 9000 to 11,000. |
| 4. | Antistatic agent according to any one of Claims 1 to 3, characterized in that, in the Nalkylsulphonates, the alkyl groups are C8C20, preferably CioCis, alkyl groups. |
| 5. | Polymer composition, characterized in that it comprises from 1.5 to 2%, preferably 1.5 to 1.7%, by weight of an antistatic agent according to any one of Claims 1 to 4, relative to the total weight of the polymers. |
| 6. | Composition according to Claim 5, characterized in that the second additive of the antistatic agent represents 0.5% by weight and the first additive of the antistatic agent represents 1 to 1.5% by weight relative to the total weight of the polymers in the composition. |
| 7. | Composition according to Claim 5 or 6, characterized in that the polymer is chosen from olefin polymers and copolymers and alloys thereof, styrene polymers and alloys thereof, acrylic and methacrylic polymers and copolymers and alloys thereof, vinyl polvmers and copolymers and alloys thereof, poly (oxyphenylenes) and mixtures of these polymers and copolymers. |
| 8. | Composition according to Claim 7, characterized in that the styrene polymers are chosen from polystyrenes, polyalkylstyrenes, high impact polystyrenes, emulsion and bulk acrylonitrile/butadiene/stvrene (ABS) resins, styrene/acrylonitrile resins, stvrene/butadiene/st ! rene resins, synthetic butyl rubbers and alloys thereof. |
| 9. | Composition according to Claim 8, characterized in that the polymer is an ABS resin, preferably a flameretardant resin. |
| 10. | Composition according to Claim 8 or 9, characterized in that the polymer composition comprises an ABS resin comprising from 4 to 70% by weight of butadiene relative to the total weight of the ABS resin. |
| 11. | Composition according to Claim 10, characterized in that the ABS resin contains 4 to 40% by weight of butadiene and is in the form of granules. |
| 12. | Composition according to Claim 10, characterized in that the ABS resin contains 10 to 70% by weight of butadiene and is in the form of powder. |
| 13. | Composition according to any one of Claims 10 to 12, characterized in that the polymer resin comprises 10 to 80 parts by weight of a grafted ABS resin and 90 to 20 parts by weight of SAN resin. |
| 14. | Composition according to Claim 13, characterized in that the polymer resin comprises 30 parts by weight of grafted ABS resin and 70 parts by weight of SAN resin. |
| 15. | Composition according to any one of Claims 7 to 14, characterized in that it comprises one or more adjuvants chosen from lubricants, pigments, dyes, UV stabilizers, antioxidants, flame retardants and extending and reinforcing fillers. |
It is known practice, in order to avoid the deposition of dust on articles moulded from polymer compositions, such as moulded articles made of acrylonitrile-butadiene-styrene (ABS) resin, to incorporate an antistatic or dust-repellent agent into these compositions.
The antistatic agent usually used in moulding compositions, in particular those based on ABS resin, is ethoxylated Cm-C ; amines. These ethoxylated amines are in liquid form.
In industrial production, the liquids are difficult to manipulate.
The liquid antistatic agent is generally injected during the extrusion of the polymer composition close to the die, which entails risks of ignition.
Moreover, when the technique of master batches is used, i. e. the technique which consists in preparing a premix of adjuvants with some of the resinous components of the polymer composition, the premix has a tendency to form aggregates which stick to the walls of the supp and metering system during the formulation of the final composition on a twin-screw extruder.
Furthermore, the liquid antistatic agent is packaged in drums and it is not possible to extract all of the content of the drum, resulting in a loss of starting material and an increase in manufacturing costs.
Finally, when such a liquid antistatic agent is used dispersed in an article made of moulded plastic, for example one based on ABS resin, the additive has a tendency to migrate faster towards the surface of the moulded article and to form a whitish film thereon, which reduces the sheen and the aesthetics of this moulded article.
In order to overcome the drawbacks of liquid antistatic agents, the use of solid antistatic agents has been envisaged. Solid antistatic agents which have been envisaged are ethoxylated Ci6-Cis amines which are in pasty form. Another solid antistatic agent which is commercially available from the company CECA consists of 75 parts by weight of ethoxylated C16-Cl8 amines and 25 parts by weight of calcium stearate.
However, these solid antistatic agents still have the drawback of forming aggregates when they are used in the master-batch technique, in particular with ABS resins loaded with pigments and dyes such as TiO.
The formation of these brittle aggregates greatly disrupts the supply and metering of the master batch during the formulation of the final composition on a twin-screw extruder.
Another solid antistatic agent which has been proposed to overcome the drawbacks mentioned above is a mixture of an ethoxylated Ci5-C2o amine and of a solidifying component chosen from Mg, Zn and Ti oxides, barium sulphate, talc, ethylenebis (stearamide) wax and synthetic hydrotalcites.
However, articles moulded from polymer compositions, in particular from compositions based on acrylonitrile-butadiene-styrene,
incorporating such an antistatic agent generally exhibit pronounced yellowing.
One object of the present invention is thus to provide an antistatic agent for polymer compositions, in particular for compositions based on ABS resin and more particularly for compositions based on standard ABS resins (i. e. resins free of a-methylstyrene) OR flame- retardant resins, which overcomes the drawbacks of the prior art, in particular which avoids yellowing during the injection-moulding and the heat treatment in an oven.
A subject of the invention is also a polymer composition, in particular a composition based on ABS resin, incorporating such an antistatic agent.
The antistatic agent according to the invention is characterized in that it consists of a combination of a first additive chosen from poly (ethylene glycols) with a weight-average molar mass M w ranging from 500 to 15,000, and mixtures thereof, and a second additive chosen from N-alkylsulphonates and mixtures thereof, the weight ratio of the second additive to the first additive being not more than 0.50.
Preferably, the weight ratio of the second additive to the first additive ranges from 0.30 to 0.50 and better still from 0.35 to 0.50.
Poly (ethylene glycols) (PEGs) with a weight-average molar mass M w ranging from 500 to 15,000 are known products and are commercially available. Preferably, the PEGs which are suitable for the present invention have a weight-average molar mass M,, of from 1100 [sic] to 14,000 and better still from 9000 to 11,000.
A PEG which is particularly recommended is the PEG sold by the company ICI under the name Pluronico F88 (M w = 10800).
The N-alkylsulphonates of the antistatic agent are preferably N- alkylsulphonates in which the alkyl group is a C6-C20 alkyl and better still a Cic-Cts alkyl group, and mixtures thereof.
The present invention also relates to a polymer composition incorporating the above antistatic agent.
Among the polymers of the compositions according to the invention which may be mentioned are olefin polymers and copolymers such as poly (ethylenes), poly (propylenes), ABS resins and alloys thereof, styrene polymers and alloys thereof such as polystyrene, vinyl polymers and alloys thereof such as poly (vinyl chloride), (meth) acrylic polymers and copolymers and alloys thereof, poly (oxyphenylenes), and mixtures of these polymers and copolymers.
The compositions which are preferred according to the invention are compositions of ABS resins and of ABS/SAN, ABS/ASA and ABS/PC, PC/ABS, ABS/PA and ABS/PBT alloys and in particular of flame-retardant ABS resins.
More specifically, the polymers which are useful in the antistatic compositions according to the invention comprise olefin polymers and copolymers, and styrene polymers and copolymers, acrylic and methacrylic polymers and copolymers, and vinyl polymers and copolymers, and alloys thereof.
Among the olefin polymers and copolymers which are useful in the compositions of the present invention, mention may be made of
polyolefins such as polyethylenes, polypropylenes, polybutvlenes and olefin copolymers such as ethylene-propylene copolymers.
Among the styrene polymers and copolymers which are useful in the compositions of the present invention, mention may be made of styrene homopolymers, homopolymers of alkylstyrene such as a- methylstyrene, high impact polystyrenes (HIPS) and grafted styrene polymers.
A recommended class of styrene polymers which is useful in the compositions of the present invention is high impact polystyrenes (HIPS and PPO/HIPS). These high impact polymers are generally prepared by polymerization by grafting mixtures of styrene and optionally of one or more additional copolymerizable vinyl monomers in the presence of a rubbery polymer trunk. It is also possible to prepare similar resins by mixing a polymer of rigid matrix with a grafted rubbery trunk. The comonomers which can be used in mixtures with styrene for the preparation of rigid styrene copolymers, as well as for a use as grafting monomers, comprise monomers chosen from ethyl styrene, halostvrenes, vinylalkylbenzenes, such as vinyltoluene, vinylxylene and butvlstyrene, acrylonitrile, methacrylonitrile, lower alkyl esters of methacrvlic acid and mixtures thereof. In the high impact styrene resins, the rubbery polymer trunk normally constitutes from 5 to 80%, preferably 5 to 50%, of the total weight of the grafted polymer, and comprises rubbery copolymers chosen from polybutadiene, polyisoprene, rubbery styrene-diene copolymers, acrylic rubber, nitrile rubber and olefinic rubbers, such as PDM and PR. In addition, other styrene polymers known in the art can be used in the alloy compositions of the invention.
As specific examples of grafted polymers which are useful in the compositions of the present invention, mention may be made of resins
of emulsion and bulk acrylonitrile/butadiene/styrene (ABS) polymer type, methyl methacrylate/butadiene/acrylonitrile/styrene (MABS) resins, resins of grafted styrene/butadiene (HIPS) polymer type and methyl methacrylate/butadiene/styrene (MBS) resins.
As specific examples of styrene polymers which can be used in the present invention, mention may be made of polystyrene and styrene copolymers such as styrene/acrylonitrile (SAN) copolymers, styrene/ methacrylic ester copolymers, resins of styrene/acrylonitrile/maleic anhydride (SAMA) terpolymer type, resins of styrene/maleic anhydride (SMA) copolymer type, similar polymers comprising differently and similarly substituted N-phenyl-substituted maleimides and mixtures thereof. In addition, it is also possible to use styrene-butadiene-styrene (SBS) copolymers and synthetic butyl rubbers (SBR). Moreover, it is also possible to use similar copolymer resins in which some of the stvrene monomer component is replaced with other styrene monomers such as ct- methylstyrene, halostyrenes or vinyltoluene. It is also possible to use mixtures or alloys of the above styrene polymers. Finally, it is also possible to use mixtures of the above styrene polymers and of one or more polyphenylene ethers, polymers of polyvinyl chloride type, polyamides, polycarbonates and other polymers generally known in the art for the alloy with styrene polymers. These additional polymers are generally known in the art and are described in Modern Plastic Encyclopedia, 1986- 1987, McGraw-Hill, Inc., New York, USA.
The styrene polymers which are useful in the present invention also comprise polymers of core-shell structure. The styrene polymers are generally prepared by emulsion or bulk polymerization, emulsion-bulk polymerization or bulk-suspension polymerization.
The styrene polymers which are particularly recommended for the compositions of the present invention are ABS resins, in particular ABS resins containing from 4 to 70% by weight of butadiene relative to the total weight of the resin, and alloys of ABS resins and of styrene/acrylonitrile (SAN) copolymers. When the ABS resin is in the form of powder, it preferably contains 10 to 70% by weight of butadiene. When the ABS resin is in the form of granules, it preferably contains 4 to 40% bv weight of butadiene and better still 4 to 30% by weight.
The alloys which are particularly recommended for the compositions of the invention are ABS/SAN alloys comprising 10 to 80 parts by weight of ABS resin and 90 to 20 parts by weight of SAN copolymer. Preferably, the resins recommended for the compositions of the invention are ABS/SAN alloys containing 10 to 40 parts by weight of ABS resin and 90 to 60 parts by weight of SAN copolymer.
Among the acrylic and methacrylic polymers and copolymers which are useful in the present invention, mention may be made of copolymers of acrylic acid derivatives, for example of acrylic esters, with styrene, vinyl chloride, methacrylic acid derivatives and acetic acid esters, poly (alkyl methacrylates) such as poly (methyl methacrylate) and poly (alkyl acrylates).
Among the vinyl polymers and copolymers which may be mentioned are poly (vinyl chloride), poly (vinyl acetate), poly (vinylbenzenes), ethylene-vinyl acetate copolymers and polyvinyl alcohols.
In general, the compositions according to the invention comprise from 1.5 to 2%, preferably 1.5 to 1.7%, by weight of antistatic agent relative to the total weight of polymers in the composition.
Preferably, the second additive (N-alkylsulphonate) of the antistatic agent represents 0.5% by weight of the polymer composition and the first additive represents 1 to 1.5% by weight relative to the total weight of the polymers. The antistatic or dust-repellent effect can also be improved by the presence of hydrotalcite as acidity neutralizer, and this agent is generally used in proportions of from 0.025 to 0.4% by weight.
The compositions according to the invention can also contain adjuvants generally used in polyolefin compositions and styrene polymers, such as lubricants, pigments, dyes, UV stabilizers, antioxidants, flame retardants and extending and/or reinforcing fillers.
Among the lubricants which can be used in the compositions of the present invention, mention may be made, by way of example, of magnesium stearate, zinc stearate, polyethylene wax, paraffin wax, ethylene oxide-propylene oxide wax, butyl stearate, glyceryl monostearate, barium stearate, sodium stearate, stearyl alcohol and octyl behenate.
Among the mineral fillers which can be used in the compositions of the present invention, mention may be made of talc, barium sulphate, calcium carbonate, magnesium aluminium hydroxycarbonate and calcium aluminium hydroxycarbonate.
The flame retardants which can be used in the compositions of the present invention are any flame retardant or mixture of flame retardants which is known to give a flame-retardant nature to compositions, in particular to compositions based on polyolefins or styrene polymers. Among the flame retardants which may be mentioned are organic compounds such as tetrabromobisphenol, bis (tribromophenoxy) ethane, polybromodiphenyl ether, polybromo-
phenol, polybromophenyl alkyl ethers, polybromobenzyl acrylate or polyacrylate, polybromocyclododecane, polybromostyrene, polybromo- phenylmaleimide, brominated epoxy monomers or epoxy polymers, copolycarbonates derived from a substituted halodiphenol and from a diphenol, the halogen preferably being chlorine or bromine.
Flame retardants which can also be used are phosphate compounds, in particular organic phosphates.
Preferably, also, the haloorganic flame retardant is used in combination with a synergistic compound such as an antimony compound, for example antimony oxide.
The compositions of the present invention can also contain dyes and pigments, such as, for example, titanium oxide, ultramarine blue or carbon black.
The examples which follow illustrate the present invention.
In the examples, all the percentages and parts are on a weight basis except where otherwise indicated.
Comparative Examples A, B and C and Example 1 The flame-retardant ABS compositions in Table I below were prepared conventionally by mixing together the various ingredients. For each of the compositions, in addition to the conventional properties, the 180/1A Izod impact strength, hot fluidity (220°C-10 g/minute) and Vicat B 120°C hardness, the yellowing and the antistatic properties were determined.
The yellowing for the standard ABS was determined by moulding 75 x 60 mm test plates of each composition under the same
conditions and by placing the test plates in a ventilated oven for 3 days and 7 days at 90°C. The difference in coloration (Ab) before and after passage through the oven is determined by means of a Datacolor~ spectrocolorimeter. The yellowing can also be measured directly on a 75 x 60 mm plate moulded under normal injection conditions for a flame- retardant ABS (tmoulding = 220°C).
The antistatic properties were determined bv subjecting the sample plates of each composition, moulded under the same conditions, to a flow of iron powder for 1 minute, followed by fixing the iron powder to the plates with methyl ethyl ketone.
The surface is analysed by means of a conventional image analyser and the percentage of the surface of the plates not coated with iron powder is determined.
The results are given in Table 1.
TABLE I Ex A Ex B Ex C Ex 1 TAG 63E 38 38 38 38 SANS 2856 62 62 62 62 TBBA 21 21 21 21 Sb203 5 5 5 5 EBS Wax 1 1 1 1 MBTSF 0. 7 0. 7 0. 7 0. 7 T SAN 0. 2 0. 2 0. 2 0. 2 Noroplast 833 1. 6--- Pluronic F88 1. 6 1. 1 Hostastat HS1 1. 6 0. 5 DHT 4A - 0. 1 0.1 0.1 Irganox 1076 0.1 0.1 0.1 0.1 101010TiO210 g/10mn1814.113.316.8MFR220°C-5 VicatB120°C 88 90 90. 5 89 kJ/m210.89.710.49.7Izod180/1A Antistatic test % not coated 85 68 71 94 UL 94-1.6 mm VO-l0sec VO-12sec VO-20sec VO-9sec Ab colour (yellowing) 0-1.9-2-2.1 TAG 63E Grafted copolymer containing 48% butadiene SANS 2866 [sic] SAN copolymer (AN content = 28%) of intrinsic viscosity = 0.56 dl/g TBBA Flame retardant: tetrabromobisphenol A Sb203 Antimony oxide EBS Wax Wax of ethylenebis (stearamide) MBTSF Master batch of TAG 63E-silicone oil 1000 cops (87/13) T SAN SAN/Teflon powder = 50/50 anti-stillation agent Noroplast 833 Ethoxylated amine/calcium stearate/aluminium stearate/hydrotalcite 65/22/7/6 Pluronic F88 Polyethylene glycol MW = 10800 Hostastat HS1 N-alkyl sulphonate (alkyl = Qo-Cjs) DHT4A Hydrotalcite Ti02 Titanium dioxide Irganox 1076 Ciba-Geigy antioxidant
Comparative Examples D, E and F and Example 2 The process is as previously, but with standard ABS compositions.
The compositions and the results are given in Table II below: TABLE II ExD ExE ExF Ex2 TAG63E 30 30 30 30 SANS2856 70 70 70 70 Noroplast 832 1.6--- Pluronic F88-1. 6-1. 1 Hostastat -1.60.5- 0.10.10.1MgO- MBTSF 0. 7 0. 7 0. 7 0. 7 EBSWax 1 1 1 1 Ti02 8 8 8 8 Antistatic test % not coated 55 60 65 80 Notched Izod impact strength INI 180/1A-K [sic] J/m2 22 21 21.5 21.4 MFR 220°C/10 Kg 9/10 mm 24. 8 29 23 27. 8 Yellowing 3daysat90°C-Ab 0.52 0. 43 0. 45 0.49 7 days at 90°C-Ab 1.84 1 1. 3 1.12 VICAT B 120°C 102 100 102 101 TAG 63E Grafted copolymer containing 48% butadiene SANS 2866 [sic] SAN copolymer (AN content = 28%) of intrinsic viscosity = 0.56 dl/g Noroplast 832 Ethoxylated amine/calcium stearate/Mgc Pluronic F88 Polyethylene glycol MW = 10800 Hostastat HS1 N-alkyl sulphonate (alkyl = C10-C18) MgO Magnesium oxide MBTSF Master batch TAG 63E-oil EBS Wax Ethylenebis (stearamide) wax Ti02 Titanium dioxide The results show the superiority of the antistatic agent according to the invention.