Title of Invention	"A PROCESS FOR PREPARATION OF PAINTABLE OR PRINTABLE POLYPROPYLENE COMPOSITION"
Abstract	A process for preparation of paintable or printable polypropylene composition by melt blending 40 to 98 wt% polypropylene, 0 to 35 wt% nylon 6, 2.5 to 37.5 wt% of maleic anhydride-grafted polypropylene or 5 to 30 wt% of maleic anhydride grafted ethylene - propylene -diene monomer and antioxidant 0.01 to 1.5 phr and dispersing agent 0.05 to 1.0 phr, at a temperature in the range of 180 to 265°C.

Full Text

The present invention relates to a process for the preparation of paintable or printable polypropylene composition. Polypropylene, which is one of the most widely used commodity plastics have excellent combination of properties like rigidity, flex resistance, chemical and heat resistance, lowest density and excellent cost to performance ratio. These combination of properties enables polypropylene to be the leading contender in vast array of moulded articles especially in automobiles and appliance sector. However, being non polar in nature it suffers from an inherent defect of poor paintability which restricts its applications and aesthetics. Current painted polypropylene based exterior automotive parts and appliances are pretreated and primed before a top coat is applied. These pretreatments can be solvent/chlorofluoro washes, flame treatment or plasma treatment. Pretreatments add cost to be final product and pretreatment equipments take up valuable space in the factory. Chlorofluoro carbons are also beginning to come under pressure from governmental agencies due to environmental concerns. There is a need for polypropylene compositions that are directly paintable with primer less or water borne paint systems. The present invention aims at the development of polypropylene compositions which are directly paintable with primer less or water borne paint systems. Reference may be made to (Victoria Graves, Modern Plastics Encyclopedia Mid-November'95 Pg.B-6) and (Charles Capshew, Modern Plastics Encyclopedia Mid-November'96 Pg.B-6) wherein it is mentioned that polypropylene resin has been used in a wide range of fields since long because it is in expensive and has good moulding quality and mechanical characteristics. However, coating of or printing on polypropylene could not be done satisfactorily, because it does not have a polar group or reactive functional group in its molecular structure and the resin has poor solubility in solvents. Secondary processing, like coating or printing, used to peel off easily. Various methods have been suggested to improve this aspect of the resin as described below : One such method is to chemically activate the surface of polypropylene resin mouldings by treating it with ozone, corona discharge or plasma (Tokka-isho Japanese Patent No. 5 6-82825, 61-204239 etc.). Oxidising the surface using chromium sulphuric acid has also been suggested. These methods, however, have the shortcoimings of requiring a complex treatment process or treatment facilities. As the surface pretreatment for coating, printing or bonding, various methods such as sandblast treatment, chromic acid mixture treatment, flame treatment, corona discharge treatment, plasma treatment, a method of imparting a surface with a functional group or a surface optical grafting method have been proposed. However, none of these methods have provided a satisfactory results. The sandblast treatment is a surface-roughening method which is carried out by allowing particulate abrasives to collide with a material surface. However, the drawback of this treatment is that the particulate abrasives soil working environments and products. It is hence required to wash the material surface with water. Another problem is that the material surface is opacified due to the sandblast treatment, and abrasives driven into the surface cannot be removed. The chromic acid mixture treatment is carried out by heating a chromic acid mixture (75 parts of potassium dichromate, 120 parts of water and 1,500 parts of concentrated sulfuric acid) to about 100°C, and immersing a material to be treated in the chromic acid mixture for about 5 minutes. The deficiency of this treatment is that making its waste liquid harmless costs too much. The flame treatment is a method of roughening a molded article surface with an oxidative flame (1,000 to 2,500°C) of a gas containing an excess amount of air. In this method, however, deformation and fusion sometimes take place. The corona discharge treatment is a surface roughening method which is carried out by applying a high voltage to a film or filmy material fed through a gap between an electrode and a metal roll. In this method, however, no materials other than a film or filmy material can be treated. The plasma treatment is a method in which low-temperature plasma is allowed to act on a plastic surface thereby to cause a chemical reaction on the surface with a gas in an ionized state and UV ray. Plasma of oxygen or air is used in the treatment. The disadvantage of this method is that the cost for a treatment apparatus is large. The method of imparting a surface with a functional group is carried out, e.g. by irradiating a material with UV ray in a chlorine gas, and treating the material with an alkali. The problem of this method is that dangerous chlorine gas is used. The surface optical grafting method is carried out, e.g. by kneading benzophenone into a polypropylene film and photograftpolymerizing acrylamide under oxygen-free atomosphere. The drawback of this method is that the treatment step is complicated in view of economic benefit. To simplify the process and the treatment facilities in the above methods, blending various kinds of rubber with polypropylene have also been tried. For example, blending of styrene-butadiene block copolymer, ethylene vinyl acetate copolymer, ethylene propylene rubber with or without an inorganic powder is described in Tokkaisho 55-3472, 58-213043, 61-43650 etc.. The blending of an organic peroxide along with a rubber like styrene polymer, ethylene-vinyl acetate copolymer, and/or ethylene-acrylic acid ester copolymer, ethylene propylene copolymer etc. is described in Tokkaisho 55-50007, 56-122849 etc.. The addition of rubber-like substance in the above methods, however significantly lowers the rigidity and heat resistance of the polypropylene composite. The main object of the present invention is to provide a process for preparation of paintable/printable polypropylene composition. Another object of the present invention is to provide polypropylene compositions which are directly paintable/printable without any surface treatments. Another object of the present invention is to improve the coating and printing performance without adversely affecting the original physico-mechanical properties ot he polypropylene resin composition. Yet another object of the present invention is to use simple method i.e., blending, requiring simple facilities, for the purpose. Accordingly, the present invention provides a process for preparation of paintable or printable polypropylene composition which comprises melt blending (A) 40 to 98 wt% polypropylene (B) 0 to 35 wt% nylon 6, (C) 2.5 to 37.5 wt% of maleic anhydride-grafted polypropylene or 5 to 30 wt% of maleic anhydride grafted ethylene - propylene -diene monomer and antioxidant 0.01 to 1.5 phr and dispersing agent 0.05 to 1.0 phr, at a temperature in the range of 180 to 265°C. In an embodiment of the present invention polypropylene used may have melt flow index in the range of 10 gm/10min to 25gm/10min. In another embodiment of the present invention the Nylon-6 may have tensile strength in the range of 700 kg/cm2 to 800kg/cm2 and impact strength in the range of 3kg.cm/cm to 5kg.cm/cm. Yet in another embodiment of the present invention maleic anhydride grafted propylene (MAH-g-PP) can have melt flow index (MFI), 20gm/10min. to 80 gm/10min. and extent of grafting 0.1 to 2, prepared by melt mixing polypropylene with maleic anhydride and dicumyl peroxide in an extruder in the temperature range of 190-230°C. Yet in another embodiment, the dispersing agent used may be calcium state, zinc stearate, barium stearate. Yet in another embodiment, the antioxidant used may be tris nonyl phenyl phosphate, octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate, Butylated hydroxyl toluene etc. The present invention provides paintable/printable polypropylene compositions and mouldings which comprises a polypropylene composition that contains (A) 60-90 wt% polypropylene, (B) 5-30 wt% nylon 6 and (C) 5-10 wt% of maleic anhydride-grafted polypropylene having Melt Flow Index (MFI) 20g/10min.-80g/10min. and extent of grafting 0.1 to 2, and antioxidant 0.01 to 1.5, phr and dispersing agent 0.05 to 1.0, phr, prepared by melt blending in a single screw or double screw extruder at temperature range of 235°C to 265°C or a polypropylene composition that contains (A) 80-98 wt% of polypropylene and (B) 2-20 wt. of maleic anhydride grafted polypropylene having MFI 20g/10m-80g/10min. with extent of grafting 0.1 to 2, and an antioxidant 0.01 to 1.5, phr and dispersing agent 0.05 to 1.0, phr. prepared by melt blending in a single screw or double screw extruder at temperature range of 180-235°C or a polypropylene composition that contains (A) 70-95 wt% polypropylene and (B) 5-30 wt% of maleic anhydride grafted ethylene-propylene-diene monomer and an antioxidant 0.01 to 1.5, phr and dispersing agent 0.05 to 1.0, phr., prepared by melt blending in a single screw or double screw extruder at 180-235°C. The pellets of PP & Nylons are cut into small granules in conduce cutter. For the preparation of various grades of maleic anhydride grafted polypropylene 100 parts by weight of the propylene homopolymer as a starting material,0.05 -2 parts of maleic anhydride, 1-2 part by weight of a radical initiator like dicumyl peroxide, benzoyl peroxide and 0.1 part by weight of irganox 1010 as stabilizer were mixed in a high speed mixer. The resultant mixtures were melt kneaded in an extruder in the temperature range of 180-220°C to give maleic anhydride grafted polypropylene of varying Melt Flow Index and extent of grafting. This graft polypropylene is mentioned as (MAH-g-PP) maleic anhydride grafted polypropylene herein after 30-95 wt% of PP having Melt Flow Index 6 to 20g/10min. were mixed with an antioxidant i.e., trisnonyl phenyl phosphite (0.05 phr), a dispersing agent i.e., calcium stearate (O.lphr), 5-70 wt. % nylon 6 and 0.1 to 10 wt. % of MAH-g-PP having Melt Flow Index 20 to 80 gm/10 min. in a high speed mixer. The melt blending of the compositions were carried out in an extruder at temperatures ranging from 235° - 265 °C. Compositions were also prepared by mixing 80 - 98 wt. % of PP resin having Melt Flow Index 6-20 g/10 min. with an antioxidant i.e., trisnonyl phenyl phosphite (0.5 phr), a dispersing agent, calcium stearate (0.1 phr) and 2-20 wt. % of MAH-g-PP having melt flow index 20-80 g/10 min. in a high speed mixer. The melt blending of the compositions were carried out in an extruder at temperatures range of 180-235°C. Also, 70 - 98 wt. % of PP resin having melt flow index = 6-20 g/lOmin. were mixed with an antioxidant, trisnonyl phenyl phosphite (0.05 phr) & dispersing agent, calcium stearate (0.1 phr) and 2-30 wt. % of maleic anhydride grafted ethylene propylene diene monomer i.e. maleated EPDM in a high speed mixer. The melt blending of the compositions were carried out in an extruder at temperatures ranging from 180-235°C. Polypropylene though have excellent combinations of properties like stiffness, impact strength, chemical resistance, low density etc., have got poor paintability being non-polar in nature. The poor paintability/coatability of polypropylene can be improved by introducing polar groups without adversely affecting the original physical properties of polypropylene resin, while using blending technique, which is simple and requires only simple facilities which in turn is achieved by providing functional groups on the surface of chemically inert polypropylene resin. Incorporation of polar groups by blending with Nylon-6 though results in enhancement of paintability markedly but there is a markable in deterioration in mechanical properties. Due to the difference of polarity of PP & Nylon-6 the system usually separates into two distinct phases with poor interfacial adhesion. The major component forms the matrix & minor component forms the domains. This type of incompatible polymeric pair requires a compatibilizing agent to achieve satisfactory interfacial adhesion & interfacial phase transfer between the phases. One approach to polymer blend compatibilization is to manipulate the interaction at the interface by the addition of interfacial agents that facilitates graft reaction. Functionalized polypropylene compatibilizer are popular third component that are added to aid both adhesion and mixing in the PP/nylon system. Various grades of MAH-g-PP have been used for the purpose. In Polypropylene / Polyamide - 6 (Nylon - 6) blends, the MAH-g-PP i.e., the compatibilizer forms a chemical linkage through the reaction of anhydride groups with the polyamide end groups. Consequently, a graft copolymer with segments of PP and PA are formed in situ in the interface. It has been observed that incorporation of MAH-g-PP in PP and nylon by blending technique, which is simple and requires only simple facilities results in PP composition having excellent paintability without adversely affecting the original physical properties of polypropylene resin. Functional groups could be provided on the surface of the PP resin by incorporating functionalized PP that contains a, P unsaturated dicarboxylic acid anhydride only. The functionalized PP in the PP resin provides parts that are firmly integrated with the PP resin, PP/MAH-g-PP also show good paintability without any deterioration in physico-mechanical properties. The PP/PP-g-EPDM blends also show excellent paintability with reduced stiffness or tensile strength and enhanced impact strength. These compositions categorizes application where impact toughness of PP is required. Method of preparation of test piece The resulting polypropylene resin compositions are compression moulded (Nuchem compression moulding machine) at 230°C to make a flat sheet of 6" width, 6" length and 3mm thickness which is subjected to various tests. Tensile Property This is measured according to ASTM D-638 using dumbell shaped specimen cut out from compressed sheet. Izod Impact Strength This is measured according to ASTM D-256 using a notched specimen at 30°C. Specific Gravity This is measured according to ASTM D-792 Hardness Shore D of the specimens are measured according to ASTM D-2240 Melt flow Index This is measured according to ASTM D-1238 Paint Adhesion Test A 50x50x3mm sample piece was taken from the central portion of a plate shaped molded article. A surface of the sample piece was cleansed by wiping the surface with isopropanol and the surface was then air dried, The surface was coated with an acrylic-urethane based paint and dried at 80°C for 2-4 hrs. The coating adhesion was tested according to ASTM D-3359-93. The following examples are given by way of illustration of present invention and therefore should not be construed to limit the scope of the present invention. Example -1 60 wt. % of polypropylene having melt flow index (MFI) 10g/10 min, 10 wt. % of maleic anhydride modified polypropylene (MAH-g-PP) having melt flow index ( MFI) 53g/10 min. and extent of grafting 1.13, 30 wt. %, Nylon-6 (dried at 90°C for 6 hrs. in an vacuum oven), 0.05 wt. %, Trisnonylphenyl phosphite and 0.1 wt. %, calcium stearate were mixed in a high speed mixer. The mixture was then melt blended in a single screw extruder at 245°C. The pellets of the blends were then compression moulded and evaluated for various properties. The results are shown in Table-1. Example -2 60 wt. % of polypropylene having melt flow index (MFI) 10g/10 min, 10 wt. % of maleic anhydride modified polypropylene (MAH-g-PP) having melt flow index ( MFI)22g/10 min. with extent of grafting 0.93, 30 wt. %, Nylon-6 (dried at 90°C for 6 hrs. in an vacuum oven), 0.05 wt. %, Trisnonylphenyl phosphite and 0.1 wt. %, calcium stearate were mixed in a high speed mixer. The mixer was then melt blended in a single screw extruder at 245°C. The pellets of the blends were then compression moulded and evaluated for various properties. The results are shown in Table - 1. Example-3 60 wt. % of polypropylene having melt flow index (MFI) l0g/10 min, 10 wt. % of maleic anhydride grafted polypropylene (MAH-g-PP) having melt flow index (MFI) 37g/10 min. with 0.85 extent of grafting , 30 wt. %, Nylon-6 (dried at 90°C for 6 hrs. in an vacuum oven), 0.05 wt. %, Trisnonylphenyl phosphite and 0.1 wt. %, calcium stearate were mixed in a high speed mixer. The mixer was then melt blended in a single screw extruder at 245°C. The pellets of the blends were then compression moulded and evaluated for various properties. The results are shown in Table - 1. Example-4 64 wt. % of polypropylene having melt flow index (MFI) l0g/10 min, 6 wt. % of maleic anhydride modified polypropylene (MAH-g-PP) having melt flow index (MFI) 48g/10 min. with 0.85 extent of grafting, 30 wt. %, Nylon-6 (dried at 90°C for 6 hrs. in an vacuum oven), 0.05 wt. %, Trisnonylphenyl phosphite and 0.1 wt. %, calcium stearate were mixed in a high speed mixer. The mixer was then melt blended in a single screw extruder at 245°C. The pellets of the blends were then compression moulded and evaluated for various properties. The results are shown in Table - 1. Example-5 70 wt. % of polypropylene having melt flow index (MFI) l0g/10 min, 10 wt. % of maleic anhydride grafted polypropylene (MAH-g-PP) having melt flow index (MFI) 53g/10 min. and extent of grafting 1.13, 20 wt. %, Nylon-6 (dried at 90°C for 6 hrs. in an vacuum oven), 0.05 wt. %, Trisnonylphenyl phosphite and 0.1 wt. %, calcium stearate were mixed in a high speed mixer. The mixer was then melt blended in a single screw extruder at 245°C. The pellets of the blends were then compression moulded and evaluated for various properties. The results are shown in Table - 1. Example-6 90 wt % of Polypropylene having melt flow index (MFI) 10g/10min., 10 wt. % of MAH-g-PP having melt flow index (MFI) 23 g/10 min. and extent of grafting 0.61, 0.05% Trisnonylphenyl phosphite and 0.1 wt % of calcium stearate were mixed in high speed mixer. The mixer was then melt blended in single screw extruder at 200°C. The pellets are compression moulded in compression moulding machine & evaluated for physico-mechanical properties. The results are shown in table-1. Example-7 92 wt % of Polypropylene having melt flow index (MFI) 10g/10min., was blended with 8 wt. % of MAH-g-PP having melt flow index (MFI) 48 g/10 min. and extent of grafting 0.85, 0.05% Trisnonylphenyl phosphite and 0.1 wt % of calcium stearate were mixed in high speed mixer. The mixer was then melt blended in single screw extruder at 200°C. The pellets are compression moulded in compression moulding machine & evaluated for physico- mechanical properties. The results are shown in table-1. Example-8 80 wt % of Polypropylene having melt flow index (MFI) 10g/10min., was blended with 20 wt. % of MAH-g-PP having melt flow index (MFI) 16 g/10 min. and extent of grafting 0.49, 0.05% Trisnonylphenyl phosphite and 0.1 wt % of calcium stearate were mixed in high speed mixer. The mixer was then melt blended in single screw extruder at 200°C. The pellets of the blends were then compression moulded and evaluated for various properties. The results are shown in table-1. Example-9 80 wt % of Polypropylene having melt flow index (MFI) lOg/lOmin., 20 wt. % of MAH-g-EPDM, 0.05% Trisnonylphenyl phosphite and 0.1 wt % of calcium stearate were mixed in a high speed mixer. The mixer was then melt blended in a single screw extruder at 180°C. The pellets are compression moulded in compression moulding machine, by applying the pressure 150 kg/cm2 & were evaluated for various physico-mechanical, thermal and paintability test. The results are shown in table-1. Example-10 90 wt % of Polypropylene were blended with 10 wt. % of MAH-g-EPDM, 0.05% Trisnonylphenyl phosphite and 0.1 wt % of calcium stearate were mixed in high speed mixer. The mixer was then melt blended in a single screw extruder at 180°C. The pellets are compression moulded in compression moulding machine, by applying the pressure 150 kg/cm2 & were evaluated for various physico-mechanical, thermal and paintability test. The results are shown in table-1. Comparative Example -1 100 wt. % of polypropylene having melt flow index (MFI) 10g/10min., 0.05 wt. % Trisnonylphenyl phosphite and 0.1 wt % of calcium stearate were mixed in a high speed mixer. The mixture was then melt blended in a single screw extruder at 200°C. The pellets of the blends were then compression moulded and evaluated for various properties. In the coating adhesion test, the coating came off from the entire area. The results are shown in table-1. TABLE- 1 (Table Removed) Comparative Example - II 70 wt % of polypropylene was blended with 30 wt. % of Nylon, 0.05% of Trisnonyl phenyl phosphite and 0.1 wt % of calcium stearate and were mixed in high speed mixer. The mixture was then melt blended in a single screw extruder at 245°C. The pellets of the blends were then compression moulded and evaluated for various properties. The composition though have good coating adhesion, have deteriorated and poor mechanical properties, shown in table-1. As exemplified the present invention provides PP compositions and its molded articles which have very good coatability/adhesion along with retained physico-mechanical properties such as impact resistance, stiffness, heat resistance and also exhibit excellent appearance. The compositions prepared are not mere admixture resulting in mere aggregation of the properties of individual properties but is a synergistic mixture resulting in excellent paintability / printability with reduced stiffness or tensile strength and enhanced impact strength. 1. The main advantages of the present invention are PP resin compositions defined by the new method as functional groups on the surface of the chemically inert PP resin. This improves the coating & painting technology remarkably. 2. The mouldings prepared from the compositions by injection moulding or extrusion moulding is not required by special pretreatment or even defatting of the solvent before coating or printing. 3. The compositions more over, retains the moldability and physical properties of PP resin. 4. The new method for the development of paintable PP without adversely affecting the original physical properties involves blending method which is simple & require only simple facilities. 5. The newly invented PP resin compositions can be used effectively in a wide range of application such as electrical parts, industrial parts of automobiles, parts of ordinary machines & tools, miscellaneous articles that requires surface decoration, packing materials etc. We claim : 1. A process for preparation of paintable or printable polypropylene composition which comprises melt blending (A) 40 to 98 wt% polypropylene (B) 0 to 35 wt% nylon 6, (C) 2.5 to 37.5 wt% of maleic anhydride-grafted polypropylene or 5 to 30 wt% of maleic anhydride grafted ethylene - propylene -diene monomer and antioxidant 0.01 to 1.5 phr and dispersing agent 0.05 to 1.0 phr, at a temperature in the range of 180 to 265°C. 2. A process as claimed in claim 1 wherein 60-90 wt% polypropylene resin, 5-30 wt% nylon 6 and 5-10 wt% of maleic anhydride-grafted polypropylene having melt flow index 20g/10min.-80g/10min. and extent of grafting 0.1 to 3, and antioxidant 0.01 to 1.5, phr and dispersing agent 0.05 to 1.0 phr. 3. A process as claimed in claims 1-2 wherein 70-95 wt% polypropylene resin and 5-30 wt% of maleic anhydride grafted ethylene-propylene-diene monomer and antioxidant 0.01 to 1.5, phr and dispersing agent 0.05 to 1.0 phr. 4. A process as claimed in claims 1-3 wherein the antioxidant used is selected from Trisnonyl phenyl phosphite octadecyl -3- (3,5-di-tert.butyl- 4-hydroxyphenyl)-propionate, Butylated hydroxyl toluene. 5. A process as claimed in claims 1-4 wherein the dispersing agent used is selected from calcium stearate, zinc stearate and barium stearate. 6. A process for preparation of paintable or printable polypropylene composition substantially as herein described with reference to the examples.

Documents:

114-del-2001-abstract.pdf

114-del-2001-claims.pdf

114-del-2001-correspondence-others.pdf

114-del-2001-correspondence-po.pdf

114-del-2001-description (complete).pdf

114-del-2001-form-1.pdf

114-del-2001-form-19.pdf

114-del-2001-form-2.pdf