Patent Publication Number: US-2002002117-A1

Title: Compositions and articles containing styrene polymers and copolymers and blends thereof

Description:
[0001] The present application is a U.S. non-provisional application based upon and claiming priority from French Patent Application No. 0006695, which is hereby incorporated by reference.  
       FIELD OF THE INVENTION  
       [0002] The present invention relates to compositions containing styrene polymers and copolymers and blends and moulded articles obtained from these composition.  
       BACKGROUND OF THE INVENTION  
       [0003] Compositions containing styrene polymers and copolymers, such as impact polystyrenes and acrylonitrile-butadiene-styrene resins (ABS resins), are widely used for the manufacture of moulded articles, including but not limited to consumer goods such as food utensils, for example meal plates, dishes, cups, etc., or housings of electrical household appliances, such as, for example, irons, refrigerators, vacuum cleaners, food processors, etc.  
       [0004] One fault of articles moulded from these compositions containing styrene polymers and copolymers or their blends is their low resistance to surface marking by impacts or rubbing, e.g., between the moulded articles themselves during their handling and/or use. Thus, during their manufacture, moulded articles are often transported by means of conveyor belts to storage and/or packing sites. During this transportation, among other things, the articles frequently knock and rub against each other, resulting in the appearance of marks on their surfaces such as scratches or traces, which results in a large number of articles being rejected.  
       [0005] Lubricants are incorporated into plastics materials primarily to improve processability of the material compounded by lowering melt viscosity and/or by preventing the polymer from sticking to the metal surface of the processing equipment. There are two different types of plastic lubricants depending on the mode of action and consequently the application in which each type would be used: either internal or external lubricants. Internal lubricants are soluble in the polymer system and alter the cohesive forces between polymer chains so as to improve the flow of polymer chains past one another, thus lowering melt viscosity and improving flow properties. External lubricants are insoluble in the polymer melt and as such have a tendency to migrate to the surface of the polymer, forming a mono-layer on the surface of the polymer, and providing lubrication between the molten and fused plastic composition and metallic parts of the processing equipment. The amount of lubricant external to the polymer is critical when the polymer is processed. Too much lubricant causes slippage, eliminating the friction necessary for the movement of polymer through the barrel of an extruder and poor aesthetic aspects in the finished application. This results in a decrease in output and torque. Polymers are more sensitive to external over-lubrication than to internal over-lubrication. The concentration of external lubricants is typically generally much lower than that of internal lubricants in the prior art.  
       [0006] In references employing lubricants, European Patent Publication No. 177096 discloses the use of an internal lubricant mineral or silicone oil in the amount of 0.1 to 3 wt. % in a composition containing styrene polymers and copolymers or their blends for high impact resistance and flowability. Canadian Patent No. 992235 discloses the use of about 5 -20 wt. % petroleum jelly, which is a micro-crystalline wax with about 2 to 10 wt. % of oil, in a composition containing styrene polymers and copolymers or their blends for a composition with improved flow property and high impact strength.  
       [0007] The prior art references employing internal lubricants do not remedy the problem of surface marking articles moulded from compositions containing styrene polymers and copolymers or their blends. Applicant in European Patent Publication No. EP 877054A found that the use of about 3 to 10 wt. % paraffin wax as an external lubricant in compositions containing styrene polymers, styrene copolymers, or their blends for compositions and moulded articles having increased resistance to surface marking.  
       [0008] A growing demand has been noted in recent years, particularly in the household appliance sector, for products in bright, deep colors, and, therefore, a particular interest in offering consumers the choice of a very extensive palette of colors. However, styrene polymer and copolymer compositions that contain paraffin waxes do not permit the manufacture of moulded articles having bright, intense colors, and particularly in highly saturated green, blue, red, or yellow shades. In fact, the presence of paraffin results in subdued coloring. The high opacity of paraffin wax generates a background whiteness that attenuates the intensity of the color, resulting in a dull-colored finished product. A certain range of colors is therefore excluded for the manufacture of moulded articles resistant to abrasion and friction.  
       [0009] Thus the subject of the present invention is new compositions containing styrene polymers and copolymers or their blends that make it possible to obtain glossy, colored articles in bright, intense colors, all the while having increased resistance to surface marking and the moulded articles thus obtained.  
       SUMMARY OF THE INVENTION  
       [0010] The inventors discovered that by incorporating from 2% to 10% by weight of vaseline oil, as an external lubricant, in relation to the total weight of the polymers and/or copolymers in the composition, in a composition containing styrene polymers, styrene copolymers, or their blends containing less than 2% by weight of internal lubricant in relation to the total weight of the polymers and/or copolymers in the composition, a composition was obtained that makes it possible to make moulded articles in bright, intense colors, all the while having increased resistance to surface marking, in a wide choice of colors, particularly highly saturated colors, without harming the other properties.  
       [0011] In addition, the compositions according to the invention increase the Izod impact strength, the Vicat temperature (thermal characteristics), and the ease with which moulded articles are removed from the mould.  
       [0012] The incorporation of vaseline oil in the compositions according the invention also increases the fluidity of the compositions, which is advantageous in the manufacture of articles by injection molding.  
       [0013] In one embodiment of the invention in low-temperature moulding of about 150-250° C., vaseline oil has a cleansing effect on the barrels of injection molding machines or extrusion lines.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0014] Compositions containing styrene polymers, styrene copolymers, or their blends according to the invention are characterized in that they comprise, in relation to the total weight of the polymers and/or copolymers in the composition:  
       [0015] a) less than 2% of internal lubricant; and  
       [0016] b) 2 to 10%, preferably 3 to 7%, of vaseline oil as an external lubricant.  
       [0017] The composition of the present invention improve resistance to the surface marking of articles manufactured therefrom.  
       [0018] Component A—Styrene Polymers and Copolymers  
       [0019] Among the styrene polymers and copolymers that are useful in the compositions of the present invention, styrene homopolymers, alkylstyrene homopolymers such as α-methylstyrene, high impact strength polystyrenes (HIPS), and grafted styrene polymers can be cited.  
       [0020] In one embodiment of the invention, styrene polymers and copolymers include high impact strength polystyrenes (HIPS). These high impact strength polymers are generally prepared by polymerization by grafting of mixtures of styrene and possibly one or more additional copolymerizable vinyl monomers in the presence of a rubbery polymer backbone. Analogous resins can also be prepared by mixing a rigid-matrix polymer with a grafted rubbery backbone. The comonomers that are useful in mixtures with styrene for the preparation of rigid styrene copolymers, and thus for use as grafting monomers, include monomers chosen from among the ethylstyrene form, halogenostyrenes, vinylalkylbenzenes, such as vinyltoluene, vinylxylene and butylstyrene, acrylonitrile, methacrylonitrile, lower alkyl esters of methacrylic acid, and mixtures thereof. In high impact strength styrene resins, the rubbery polymer backbone normally constitutes from 5 to 80%. In another embodiment of high impact strength styrene resins, the rubbery polymer backbone constitutes about 5 to 50% of the total weight of the grafted polymer, and comprises rubbery copolymers chosen from among 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 are useful in the blend compositions of the invention.  
       [0021] In another embodiment of the invention, grafted polymers and copolymers are used, including resins of the bulk and emulsion acrylonitrile/butadiene/styrene (ABS) polymer type, methyl methacrylate/butadiene/acrylonitrile/styrene (MABS) resins, resins of the styrene/butadiene grafted polymer type (HIPS), and methyl methacrylate/butadiene/styrene (MBS) resins can be cited. Examples of styrene polymers and copolymers include styrene/acrylonitrile (SAN) copolymers, styrene/methacrylic ester copolymers, resins of the styrene/acrylonitrile/maleic anhydride (SAMA) terpolymer type, acrylonitrile/styrene/butyl acrylate (ASA) copolymers, resins of the styrene/maleic anhydride (SMA) copolymer type, similar polymers comprising N-phenyl substituted maleimides and differently substituted maleimides, and similar mixtures thereof can be cited. 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 analogous copolymer resins in which a portion of the styrene monomer component is replaced by other styrene monomers such as α-methylstyrene, halogenated styrenes, or vinyltoluene. It is also possible to use mixtures or blends of the above styrene polymers and copolymers. Finally, it is also possible to use mixtures of the above styrene polymers and copolymers and of one or more polyphenylene ethers, polymers of the polyvinyl chloride type, polyamides, polycarbonates, polybutylene alone or blends thereof, and other polymers generally known in the art for blending 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.  
       [0022] Styrene polymers that are useful in the present invention also include polymers with the Core-Shell structure. Styrene polymers are generally prepared by emulsion or bulk, emulsion-bulk, or bulk-suspension polymerization.  
       [0023] In one embodiment of the invention, the styrene polymers for the compositions of the present invention are ABS resins. In another embodiment, they are ABS resins containing from 4 to 70% by weight of butadiene in relation to the total weight of the resin, and blends of ABS resins and of styrene/acrylonitrile (SAN) copolymers. In a third embodiment when the ABS resin is in granular form, it contains 4 to 40% by weight of butadiene. It yet another embodiment, the ABS resin contains 4 to 30% by weight of butadiene.  
       [0024] In another embodiment of the invention, the compositions of the invention contain ABS/SAN blends containing 10 to 80 parts by weight of ABS resin and 90 to 20 parts by weight of SAN copolymer. In another embodiment, the resins are ABS/SAN blends containing 10 to 40 parts by weight of ABS resin and 90 to 60 parts by weight of SAN copolymer. In yet another embodiment, ABS/polycarbonate blends and ABS/polybutylene terephthalate blends are used.  
       [0025] Among the acrylic and methacrylic polymers and copolymers that can be used in the present invention include the copolymers of acrylic acid derivatives, for example acrylic esters, with styrene, vinyl chloride, methacrylic acid derivatives and acetic acid esters, poly(alkyl methacrylate)s such as poly(methyl methacrylate), and poly(alkyl acrylate)s can be cited.  
       [0026] Among the vinyl polymers and copolymers, poly(vinyl chloride), poly(vinyl acetate), poly(vinylbenzene)s, ethylene-vinyl acetate copolymers, and poly(vinyl alcohol)s can cited.  
       [0027] Component B—Lubricants  
       [0028] The external lubricant of the invention is a transparent lubricant selected from the group consisting of: a) oily solvents of mineral or vegetable oil, such as olive oil, peanut oil, paraffin oil, vaseline oil or mixtures of several oils; b) a liquid silicone such as dimethicone or simethicone; c) a glycol polymer such as polyethylene glycol 600, 800 or 1200; and d) a glycol such as ethylene glycol, propylene glycol or glycerol.  
       [0029] In one embodiment of the invention, the external lubricant is a vaseline oil, which is understood to mean any product comprising at least 95% by weight of vaseline oil having a viscosity of about 10 to 150 mm 2 /s at 40° C. In one embodiment of the invention, the external lubricant is used in the amount about 3 to 10%. In a second embodiment, it is in the range of about 3 to 7 wt. %. For contents of less than 3% by weight of the external lubricant, the desired effect of resistance to surface marking is not obtained, while for amounts greater than 10% by weight there is no significant improvement in this property.  
       [0030] By way of example, one such external lubricant is a vaseline oil marketed by MERKUR under the trademark MERKUR PHARMA 240 B.  
       [0031] Internal lubricants can be used in the compositions of the invention in amounts of about less than 4% by weight in relation to the total weight of the polymers and copolymers present in the compositions. The internal lubricants of compositions containing styrene polymers and copolymers are well-known adjuvants and, by way of example, metal stearates and ethylene bis-steramide wax can be cited.  
       [0032] In one embodiment of the invention, the internal lubricant represents less than 2 wt. %. In a third embodiment, it is less than 0.1% by weight. In yet another embodiment, the compositions are totally devoid of internal lubricants.  
       [0033] Optional Components  
       [0034] The compositions according to the invention can also contain the adjuvants that are generally used in compositions containing styrene polymers, such as pigments, dyes, UV stabilizers, antioxidants, flame retardants, antistatic agents, and extending and/or reinforcing fillers.  
       [0035] Among the inorganic fillers that can be used in the compositions of the invention, talc, barium sulphate, calcium carbonate, magnesium aluminum hydroxycarbonate, and calcium aluminum hydroxycarbonate can be cited.  
       [0036] The flame retardants that can be used in the compositions of the present invention are any flame retardant or mixture of flame retardants known to confer a flame-retardant nature to polyolefin-based or styrene polymer-based compositions. Among the flame retardants, flame-retardant organic compounds such as tetrabromobisphenol, bistribromophenoxyethane, polybromodiphenyl ether, polybromophenol, polybromophenyl alkyl ethers, polybromobenzyl acrylate or polyacrylate, polybromocyclododecane, polybromostyrene, polybromophenylmaleimide, brominated epoxy monomers or epoxy polymers, copolycarbonates derived from a halo-substituted diphenol and from a diphenol, the halogen preferably being chlorine or bromine, can be cited.  
       [0037] Phosphate compounds, in particular organic phosphates, can also be used as a flame retardant. In one embodiment, the halogenated organic flame retardant is used in combination with a synergistic compound such as an antimony compound, for example antimony oxide.  
       [0038] The compositions of the present invention can also contain dyes and pigments, such as, for example, titanium oxide, ultramarine blue, or carbon black.  
       [0039] Preparation of the Composition.  
       [0040] The production of the composition of the invention is done by any of the operations known for the blending and extrusion of compositions containing styrene polymers and copolymers, such as impact polystyrenes and acrylonitrile-butadiene-styrene resins (ABS resins), e.g. mixing or blending the ingredients in a two-roll mill, a Banbury mixer, a single screw extruder or twin-screw extruder.  
       [0041] The composition of the present invention can be formed into useful articles with improved resistance to the surface marking. The articles are formed by a variety of known processes such as, for example, profile extrusion, sheet extrusion, extrusion blow molding and thermoforming, and injection molding. 
     
    
    
     EXAMPLES  
     [0042] The invention is illustrated by the following examples, which are not, however, to be construed as limiting in anyway. In the examples, except when otherwise indicated, all of the percentages and parts are expressed by weight. The compositions in Table I below were prepared by mixing the ingredients in the examples to form specimens for testing for various physical and mechanical properties as shown in Table I below.  
                                   TABLE I                                   Comparative   Comparative                   A   B   Example 1   Example 2                                                        Polymers                       ABS (1)     26   15   15   15       SAN (2)     74   85   85   85       Lubricants       Ethylene bis-   3   —   —   —       steramide wax       Paraffin wax (3)     —   5   —   —       Vaseline oil (4)     —   —   5   6       Antistatic agent       NOROPLAST ®   0.8   0.8   0.8   0.8       832       Silicone oil (5)     0.1   0.1   0.1   0.1       Dye/Pigment       TiO 2     0.24   0.24   0.24   0.24       Heliogen Blue FK   0.376   0.376   0.376   0.376       4207       Paliotol Yellow   0.32   0.32   0.32   0.32       PK 4190       Macr. Gelb G.   0.048   0.048   0.048   0.048       Yellow Pig.       Flow index   26   24   26   27       (220° C./10 kg),       g/10 minutes       Melting viscosity   183   200   175   171       at 230° C./1500s −1 ,       Pa.s       VICAT B 120   101   103   103   102       temperature, ° C.       IZOD/1A impact   11   8   10   12       strength, kJ/m 2         DIN EN 60068   0   ++   +   ++       abrasion test (a)         Width of marking   1.7   0.2   0.3   0.2       in mm (b)         Color measurement/       standard GN       1304 (c)         dL*   0.72   7.49   0.71   1.11       da   0.03   −9.01   0.06   0.09       db   0.35   1.32   0.5   0.65       dE   0.8   11.79   1.10   1.24       Gloss       20° angle   77   72   73   75       60° angle   93   91   91   92       “surfacing veil”   110   120   100   102       Blue shade dL*   29.41   36.43       31.21       a   6.53   8.75       9.56       b   −20.83   −37.94       −26.36       Green shade dL*   28.53   37.49       30.20       a   −3.67   −14.46       −4.07       b   −2.92   −9.1       −3.05                                                          
 
     [0043] The results show that the mechanical properties obtained with the compositions according to the invention are comparable to those of the compositions of the prior art with good impact strength. The tests were conducted as follows:  
     [0044] (a) DIN EN 60068 Abrasion Test  
     [0045] Plates with dimensions of 90 mm×70 mm×4 mm from compositions A, B, 1, and 2 in Table I above were moulded at 240° C.  
     [0046] These plates were subjected to abrasion by contact with a 80-cm wooden cylinder rotating for 600 rotations. A visual observation of the abrasion permitted an evaluation of the abrasion resistance:  
     [0047] 0=mediocre resistance; +=good resistance; ++=very good resistance  
     [0048] For examples 1 and 2, improved abrasion resistance was observed in relation to Comparative Example A, which did not contain vaseline oil, and equivalent abrasion resistance was noted in relation to Comparative Example B containing paraffin wax of the prior art.  
     [0049] (b) Test of Marking caused by Rubbing  
     [0050] Plates with dimensions of 90 mm×70 mm×4 mm from compositions A, B, 1, and 2 in Table I above were moulded at 240° C.  
     [0051] A plate of one composition was rubbed with the corner of another plate of the same composition 3 to 4 times at different points. The traces left on the rubbed plate were observed and the width of these traces was measured.  
     [0052] The narrower the traces, the better the resistance to marking of the composition by rubbing. The results show the excellent resistance of the compositions according to the invention compared to the prior art composition with internal lubricants.  
     [0053] (c) Color Measurement The color of the plates made above was compared to that of standard GN 1304.  
     [0054] It was observed that the tints obtained for examples 1 and 2 were very different from Comparative Example B. The color of the articles made with compositions 1 and 2 exhibited increased brightness and luster in relation to the much duller color of Comparative Example B with paraffin wax.  
     [0055] Colorability Measurement  
     [0056] The improvement in colorability in blue and green shades was determined. For blue shades, 0.5 p of Sandoplast Blue 2B was added to each of compositions A, B, and 2. For green shades, 0.5 p of Macrolex Green 5B was added to each of compositions A, B, and 2.  
     [0057] The colors were expressed in the CIELAB Lab color measuring system. In the green and blue shades, the absolute value of b must be as small as possible. This was the case of Comparative Example A (classic ABS performance) in relation to Comparative Example B (paraffin). The b values of Example 2 are close to those of Comparative Example A, indicating a roughly comparable colorability, but are different from Comparative Example B.  
     [0058] It should be noted that articles manufactured from classic ABS compositions exhibit quite satisfactory colorability.