Title of Invention

METHOD FOR PREPARING AND COAGULATING GRAFT RUBBER LATEX HAVING HIGH THERMAL STABILITY

Abstract

The present invention relates to a preparation method of a graft rubber latex, more precisely to a preparation method of a graft rubber latex by polymerization of a monomer mixture comprising one or more compounds selected from the group consisting of a rubber latex, an aromatic vinyl compound, a vinyl cyan compound and an acrylate compound, characterized by using a first hydrophobic peroxide-based polymerization initiator before the polymerization conversion rate of the monomer mixture reaches 50% and a second hydrophobic peroxide-based polymerization initiator thereafter. The graft rubber latex prepared by the method of the present invention has excellent thermal stability without using an additional thermo-stabilizer and increased efficiency in applying to a screw type dewatering machine.

Full Text

METHODS FOR PREPARING AND COAGULATING GRAFT RUBBER LATEX HAVING HIGH THERMAL STABILITY Technical Field The present invention relates to a preparation method of a graft rubber latex, more precisely a method of preparing and coagulating a graft rubber latex having excellent thermal stability without using an additional thermo-stabilizer and having increased efficiency in applying to a screw type dewatering machine. Background Art A rubber-reinforced resin such as acrylonitrile-butadiene-styrene (ABS), methacrylate-butadiene-styrene (MBS) and acrylonitrile-styrene-acrylate (ASA), etc. is obtained by preparing a rubber-reinforced latex by emulsion polymerization, coagulating and drying into a powder. The prepared powder is added in an extruder together with a resin such as styrene-acrylonitrile copolymer (SAN), polyvinylchloride (PVC) and polycarbonate (PC), etc. leading to the primary process to produce a pellet and the secondary process to inject the pellet At this time, it is generally preferred to add rubber-reinforced powder having moisture content of less than 1% into the extruder for the primary process. In some cases, the rubber-reinforced latex is coagulated without drying to prepare a powder containing moisture. This powder is placed in an extruder and moisture of the powder is eliminated therein. Then, the powder is mixed with a resin such as styrene-acrylonitrile copolymer (SAN), polyvinylchloride (PVC) and polycarbonate (PC), etc. to produce a pellet At this time, the moisture content in the rubber-reinforced resin powder is around 30%. If the moisture content is higher than that, water elimination process in a dehydrator is extended, resulting in errors of product quality and decrease of productivity. Accoridingly, when the powder including moisture is loaded in an extruder, it is essential to minimize water content to increase productivity. However, the conventional centrifugal dehydration has its limits in minimizing water content To overcome the above problem, an alternative method was proposed, that is water content was reduced by using a screw type dewatering machine. But, in that case, an additional high temperature - high pressure process is required, resulting in the decrease of thermal stability of a resin and further deformity of the resin. Thus, in the rubber-reinforced resin production industry, it is important to maximize the productivity of the rubber-reinforced resin to increase price competitiveness, in addition to increase the quality of a product As a method for increasing the productivity of a rubber-reinforced resin, a method to increase the extrusion productivity has been proposed. Precisely, the amount of each major and minor ingredient to be loaded in an extruder is increased and screw rpm and a temperature in the extruder are up-regulated considering the increased each major and minor ingredient content, so that the discharging resin is increased. If necessary, a specially designed screw can be used to strengthen the mixing process of the ingredients. This method to increase the extrusion productivity favors the increase of the productivity and improvement of properties including impact strength owing to the secured dispersity of rubber particles, but has disadvantages of reducing thermal stability by the increased friction of a resin resulted from the high shear force and accelerating thermal degradation due to the increased temperature. The decrease of thermal stability by thermal degradation causes color change in a final product. Even if the color change might not be significant, color change and gloss reduction will be resulted during the secondary process of injection, making errors in products. To solve the above problem and to maximize the productivity, thermal stability of a resin prepared by emulsion polymerization has to be fundamentally improved and at the same time a method to improve thermal stability during the process needs to be developed. The conventional method to improve thermal stability of a resin prepared by emulsion polymerization is focused on graft-polymerization forming a shell, particularly in the case of using a rubber-reinforced resin having a core-shell structure, and secondly on the selection and introduction method of an antioxidant to prevent the resin from being oxidized by thermal history during coagulation and drying process. Besides, the conventional method to secure thermal stability during extrusion is generally focused on the minimization of friction between a resin and a barrel during the process by the addition of a thermo-stabilizer or a lubricant. However, the effect of the above conventional methods is vulnerable according to the extrusion productivity requested. That is, to guarantee equal quality of a product before and after increasing the productivity, an antioxidant has to be used excessively or various lubricants have to be added or if one lubricant is used, the amount has to be excessive. Therefore, mechanical properties and appearances are to be changed and at the same time price competitiveness might be rather decreased. To overcome the problems of the conventional methods, it is an object of the present invention to provide a preparation method of a graft rubber latex having excellent thermal stability without using an additional tiiermo-stabilizer and having increased efficiency in applying to a screw type dewatering machine, and a coagulation method of the same. The above object and other objects of the present invention can be achieved by the following embodiments of the present invention. To achieve the above object, the present invention provides a preparation method of a graft rubber latex by polymerization of a monomer mixture comprising one or more compounds selected from the group consisting of a rubber latex, an aromatic vinyl compound, a vinyl cyan compound and an acrylate compound, characterized by the use of a first hydrophobic (oil soluble) peroxide-based polymerization initiator before the polymerization conversion rate of the monomer mixture reaches 50% and the use of a second hydrophobic peroxide-based polymerization initiator after the above time point The present invention also provides a coagulation method of the graft rubber latex, which is characterized by the following steps: early coagulation induced by adding a metal salt to the graft rubber latex; and late coagulation induced by adding an acid to the coagulated latex above, leading to coagulation and aging. The present invention further provides a preparation method of a graft rubber latex composition, comprising the steps of coagulating the prepared graft rubber latex by the above coagulation method; preparing a rubber resin containing moisture by reducing water content of the coagulated rubber latex to the level of up to 2 -10 % by using a screw type dewatering machine; and mixing and melting the rubber resin containing moisture with one or more resins selected from the group consisting of styrene-acrylonitrile copolymer, polyvinylchloride and polycarbonate, and a lubricant A preparation method of a graft rubber latex by polymerization of a monomer mixture comprising one or more compounds selected from the group consisting of a rubber latex, an aromatic vinyl compound, a vinyl cyan compound and an acrylate compound, characterized by treating a first hydrophobic peroxide based polymerization initiator before the polymerization conversion rate of the monomer mixture reaches 50% and then treating a second hydrophobic peroxide based polymerization initiator after the polymerization conversion rate reaches 50%, The present invention is described in detail hereinafter. The present inventors have used a rubber latex with high gel content and a hydrophobic polymerization initiator stepwise to prepare the thermoplastic graft rubber latex applicable to a screw type dewatering machine. As a result, a graft rubber latex was prepared by emulsion polymerization with increasing grafting efficiency. Then the present inventors completed this invention by confirming that the rubber resin having excellent thermal stability even at high temperature and under high shear force can be prepared without additional use of a thermo-stabilizer by treating one or more coagulators stepwise. (A) Preparation of a graft rubber latex A graft rubber latex of the present invention is prepared by graft-polymerization of 50 - 70 weight part of a rubber latex (mean diameter: 2,500 - 5,000 A, gel content: 80 - 99%) and 30 - 50 weight part of a monomer mixture comprising one or more compounds selected from the group consisting of an aromatic vinyl compound, a vinyl cyan compound and an acrylate compound. (a) Preparation of a rubber latex A polybutadiene rubber latex having small diameter is first prepared and then enlarged to prepare a polybutadiene rubber latex having large diameter, which is used as the rubber latex of the invention. To prepare the polybutadiene rubber latex having small diameter, a mixture of 100 weight part of 1,3-butadiene, 1 - 4 weight part of an emulsifier, 0.1 - 0.6 weight part of a polymerization initiator, 0.1-1.0 weight part of an electrolyte, 0.1 - 0.5 weight part of a molecular weight regulator and 90 -130 weight part of ion exchange water was reacted at 50 - 65 °C for 7 -12 hours, to which 0.05 -1.2 weight part of a molecular weight regulator was added, followed by further reaction at 55 -70°C for 5 -15 hours. The preferable mean diameter of the rubber latex having small diameter is 600 - 1500 A and the gel content is 80 - 99%. To prepare the rubber latex having large diameter, 1.0 - 4.0 weight part of acetic acid solution was added to 100 weight part of the rubber latex having small diameter slowly for one hour to enlarge the particles. The preferable mean diameter of the rubber latex having large diameter is 2500 - 5000 A and the gel content is 80 - 99%. Within the above gel content range, graft-copolymerization can be effectively finished in the outside of rubber particles, resulting in the excellent impact strength and thermal stability and more over mechanical properties and color can be protected under the high temperature and high shear force set for increasing the productivity. (b) Preparation of a graft rubber latex The graft rubber latex of the present invention is prepared by graft-copolynieri2ation of 50 -70 weight part of the polybutadiene rubber latex of (a) and 30 - 50 weight part of a monomer mixture, and at this time a polymerization initiator is added thereto at different time points, before and after the polymerization conversion rate of the monomer mixture reaches 50%. The monomer mixture is prepared by mixing one or at least two compounds selected from the group consisting of an aromatic vinyl compound, a vinyl cyan compound and an acrylate compound. And 0.1 - 2 weight part of an emulsifier, 0.05 - 2.0 weight part of a polymerization initiator, 0.1 - 0.5 weight part of an electrolyte and 0.2 -1.0 weight part of a molecular weight regulator can be additionally included in the above. The aromatic vinyl compound can be one or a mixture of at least two compounds selected from the group consisting of styrene, a-methylstyrene, p-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene and their substituents. The vinyl cyan compound can be one or a mixture of at least two compounds selected from the group consisting of acrylonitrile, methacrylonitrile and their substituents. The acrylate compound can be one or a mixture of at least two compounds selected from the group consisting of ethylacrylate, methylacrylate, butylacrylate and ethylhexylacrylate. The emulsifier can be one or a mixture of at least two compounds selected from the group consisting of alkyl aryl sulfonate, alkalimethyl alkyl sulfate, sulfonated alkylester, and other general adsorptive emulsifiers such as fatty acid soap or rosin alkali salt To guarantee thermal stability of the latex more effectively, a reactive emulsifier and a high molecular reactive emulsifier can be added independently or together with the adsorptive emulsifier. As a polymerization initiator of the invention, hydrophobic peroxide such as cumenehydro peroxide, diisopropyl benzenehydro peroxide, tertiary butylhydro peroxide, paramethane hydro peroxide and benzoyl peroxide can be used together with an oxidative-reductive polymerization initiator. The first hydrophobic peroxide-based polymerization initiator is added within the time point where the polymerization conversion rate of the monomer mixture reaches 50% and the second hydrophobic peroxide-based polymerization initiator is added after the above time point Upon completion of the reaction, a hydrophobic peroxide based polymerization initiator and an oxidative-reductive polymerization initiator are added together to eliminate non-reacted monomers. The first hydrophobic peroxide based polymerization initiator is exemplified by strong hydrophobic compounds such as cumene hydro peroxide or diisopropyl benzenehydro peroxide. The second hydrophobic peroxide based polymerization initiator is exemplified by comparatively weak hydrophobic compounds such as tertiary butyl hydro peroxide. The oxidative-reductive polymerization initiator can be selected from the group consisting of metal salts including Fe(n), Fe(III), Co(II) and Ce(IV). The reducing agent can be selected from the group consisting of polysaccharides such as dextrose, glucose and fructose, dihydroxy acetone and polyamines. To help a metal catalyst not to loose its activity under various alkali conditions, such compounds as tartaric acid, citric acid, pyrrolephosphoric acid or ethylene diamine tetraacetate can be additionally used. The electrolyte herein can be one or a mixture of at least two compounds selected from the group consisting of KC1, NaCl, KHCO3, NaHCO3, K2CO3 Na2CO3, KHSO3, NaHSO3, K4P2O7, K3P04, Na3PO4 K2HPO4 and Na2HPO4. The molecular weight regulator is preferably one or a mixture of at least two mercaptan compounds selected from the group consisting of n-octylmercaptan, n-dodecylmercaptan and t- dodecylmercaplan. In general, the addition of a monomer mixture for the graft polymerization is performed by serial injection, batch injection or the combination of these two methods selectively. And, the serial injection is preferred for shell graft reaction, but not always limited thereto. In some cases, 5 - 30% of a monomer mixture is added at a time and the rest portion of the mixture is added serially. At this time, the monomer mixture for the batch injection in the early reaction stage is preferably added alone and the monomer mixture for the serial injection in the late stage is preferably added in an emulsion form supplemented with an emulsifier, ion exchange water and a polymerization initiator. The reaction time for the graft polymerization is preferably within 3 hours and the polymerization conversion rate after the reaction is preferably at least 98.5 % and the preferable molecular weight is 50,000 -150,000. The graft rubber latex prepared above can additionally include an anti-oxidant for the prevention of oxidation during the process. The anti-oxidant herein can be one of the conventional phenol based, phosphorous based or sulfur based anti-oxidants and is preferably added in the emulsified form (mean diameter: 0.5 - 2 fzm). The preferable content of such anti-oxidant is 0.2 - 2 weight part for 100 weight part of the graft rubber latex. The said anti-oxidant content is effective to keep thermal stability during the late reaction stage and does not cause any changes in mechanical properties and color expression. It is preferred to add an anti-oxidant with stirring and slowly to the graft rubber latex at 40 -80 °C continuously until coagulation. (B) Coagulation of a graft rubber latex The coagulation method of the graft rubber latex of the invention is characteristically composed of the following steps: early coagulation induced by adding a metal salt to the graft rubber latex prepared by the method of claim 1; and late coagulation induced by adding an acid to the coagulated latex above, leading to coagulation and aging. The metal salt herein is exemplified by MgSO4, CaCl2 or Al2(SO4)3 and particularly MgSO4 or CaCl2 is preferred. The acid herein is exemplified by sulftiric acid, phosphoric acid or hydrochloric acid, and particularly sulftiric acid is preferred. In general, either acid or metal salt is added for coagulation, but it is more preferred in order to guarantee oxidative stability and improve color quality (whiteness) of a final product to induce early coagulation using a metal salt and then late coagulation using an acid for complete coagulation and aging. In the late coagulation, pH of the graft rubber latex is preferably 3-7. This pH range has been confirmed to be effective, precisely the latex in this pH range exhibited neither damage on whiteness of a resin usually caused by acid-treatment nor decrease of thermal stability caused by the metal remaining on the resin. The coagulated graft rubber latex is turned into a solid type having 20 - 40% water content, for which excessive water content is reduced by a dehydrator, followed by hot-air drying to give a powder-type latex. The latex powder is placed in an extruder or the moisture containing solid latex is placed in an extruder where it is through with dehydration and evaporation. Then the latex can be mked with a resin added as a matrix and a lubricant to produce a pellet. (C) Preparation of a graft rubber resin composition The preparation method of the graft rubber latex composition of the present invention is composed of the following steps: coagulating the graft rubber latex prepared in the above (A) by the method of (B); preparing a rubber resin containing moisture by reducing water content of the coagulated rubber latex using a screw type dewatering machine to the level of up to 2 -10%; melting and mixing the prepared moisture containing rubber resin with one or more resins selected from the group consisting of styrene-acrylonitrile copolymer, polyvinylchloride and polycarbonate and a lubricant In the step of reducing water content of the coagulated graft rubber latex using a screw type dewatering machine, it is preferred to reduce water content to the level of up to 2 - 10% and more preferably up to 5%. With this water content, extruding for dehydration and drying can be omitted and at the same time extrusion productivity can be increased. Best Mode for Carrying Out the Invention Practical and presently preferred embodiments of the present invention are illustrative as shown in the following Examples. However, it will be appreciated that those skilled in the art, on consideration of this disclosure, may make modifications and improvements within the spirit and scope of the present invention. [Examples] Example 1 Preparation of a graft rubber latex To a nitrogen substituted polymerization reactor were added 60 weight part (solid content) of polybutadiene rubber latex (rubber particle diameter: 3,200 A, gel content: 98%), 92 weight part of ion exchange water, and 0.2 weight part of a fatty acid soap. The temperature of the reactor was maintained at 50 °C, and 0.1 weight part of cumene hydro peroxide, 0.09 weight part of sodium pyrophosphate, 0.12 weight part of dextrose, and 0.003 weight part of FeS were added to the reactor at once. When the polymerization conversion rate reached 55%, emulsion containing 28.8 weight part of styrene, 11.2 weight part of acrylonitrile, 15 weight part of ion exchange water, 0.3 weight part of tertiary dodecyl mercaptan, 0.6 weight part of a fatty acid soap, and 0.2 weight part of tertiary butylhydro peroxide was added continually for 2 hours with increasing the temperature to 70 °C. Upon completion of the continual addition, 0.05 weight part of cumenehydro peroxide, 0.043 weight part of sodium pyrophosphate, 0.055 weight part of dextrose and 0.001 weight part of FeS were added at a time at 80 °C, and Ihen the reaction mixture was maintained for 60 minutes. The unreacted monomers were removed to complete the polymerization. Coagulation of a graft rubber latex To the graft rubber latex finished with the above reaction was added 0.5 weight part of an antioxidant emulsion (Wingstay-L, mean diameter: 1.0 ym), followed by primary coagulation at 78 °C in the presence of 1.5 weight part of MgSO4. Then, 0.5 weight part of sulfuric acid was added additionally, followed by secondary coagulation and aging at 90 °C. The coagulation was washed to obtain the graft polymer powder having 25% water content. Preparation of a graft rubber resin composition The prepared graft copolymer powder having 25% water content was loaded in a screw type dewatering machine to reduce the water content to 5%. Styrene-acrylonitrile (SAN) copolymer having 28% acrylonitrile content and 100,000 of weight average molecular weight and a lubricant were added to the above powder, and the resins mixture was extruded and then molded in an injector to give a sample having the final rubber content of 14%. The physical properties of the sample were tested. Example 2 To the nitrogen substituted polymerization reactor of the Example 1 were added 60 weight part (solid content) of a polybutadiene rubber latex (rubber particle diameter: 3,200 A, gel content: 98%), 92 weight part of ion exchange water, 7.2 weight part of styrene, 2.8 weight part of acrylonitrile and 0.4 weight part of a fatty acid soap. The temperature of the reactor was maintained at 50 °C, and 0.1 weight part of cumene hydro peroxide, 0.09 weight part of sodium pyrophosphate, 0.12 weight part of dextrose, and 0.003 weight part of FeS were added at a time to the reactor, and the temperature was raised up to 70 °C for 20 minutes. An experiment was performed in the same manner as described in Example 1 except that, with maintaining the raised temperature, emulsion comprising 21.6 weight part of styrene, 8.4 weight part of acrylonitrile, 15 weight part of ion exchange water, 0.3 weight part of dodecylmercaptan, 0.6 weight part of a fatty acid soap, and 0.2 weight part of tertiary butylhydro peroxide were continually added for 1 hour and 40 minutes. Example 3 An experiment was performed in the same manner as described in the Example 1 except that 60 weight part of a polybutadiene rubber latex (rubber particle diameter: 3200 A, gel content: 70%) was used and only 2 weight part of MgSO4 was added to coagulate the prepared graft rubber latex. Example 4 An experiment was performed in the same manner as described in Example 3 except that 0.1 weight part of tertiary butylhydro peroxide was added as a polymerization initiator in the early reaction stage instead of 0.1 weight part of cumene hydro peroxide, and 0.05 weight part of tertiary butylhydro peroxide was added instead of 0.05 weight part of cumene hydro peroxide after the monomer emulsion was added. Example 5 An experiment was performed in the same manner as described in Example 4 except that a mixture of 30 weight part of polybutadiene rubber latex having gel content of 98%, and rubber particle diameter of 3200 A and 30 weight part of polybutadiene rubber latex having gel content of 70% with the same rubber particle diameter was used. [Measurements] The physical properties of the samples prepared in the above examples were tested and the results are shown in Table 1. *Izod impact strength: measured with a sample of 1/4" in thickness by ASTM D256. *Scorch: powders containing 25% moisture content prepared from the graft rubber latex were placed in aluminum foil with exposing on the air to be able to contact oxygen, which was left in a 190 °C hot air oven. Sampling was performed over the time and color change of each sample was investigated. The time of carbonization was measured to evaluate comparative thermal stability. *Maximum oxidation time: samples were left at 190 °C in the presence of oxygen and the time point when the weight change was most significant was checked and calculated as a value point. *Residence gloss: the pellet obtained from the extruder was loaded in an injection molding machine and stayed there for 15 minutes at 250 °C to give a gloss sample. 45 degree gloss was measured for both the gloss sample and the other sample ejected at 200 °C without staying. The results were compared and bias value was calculated. The lower the bias value, the greater the residence gloss was. *Residence discoloration (AE): a gloss sample was prepared by the same manner as described above for measuring residence gloss and L, a, b values of before and after staying were calculated by using Suga color computer and residence discoloration was calculated by the following mathematical formula [Mathematical Formula 1] (Formula Removed) [Table 1] (Table Removed) As shown in Table 1, the graft rubber latex was prepared by treating the first hydrophobic peroxide based polymerization initiator before the polymerization conversion rate reached 50% and then treating the second hydrophobic peroxide based polymerization initiator when the polymerization conversion rate was over 50%. The graft rubber resin compositions of Example 1 and Example 2 were prepared by double coagulation processes using the first and second hydrophobic peroxide based polymerization initiators, which were confirmed to have excellent physical properties and thermal stability, compared with another sample of Example 3 prepared by a single coagulation process and using the both first and second hydrophobic peroxide based polymerization initiators and also other samples of Examples 4 and 5 prepared by a single coagulation process without the polymerization initiators. Industrial Applicability As explained hereinbefore, the present invention provides a method of preparing and coagulating a graft rubber latex having excellent thermal stability without using an additional thermo-stabilizer and excellent applicability to a screw type dewatering machine. Those skilled in the art will appreciate that the conceptions and specific embodiments disclosed in the foregoing description may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims. We claim: 1. A preparation method of a graft rubber latex by polymerization of a monomer mixture comprising one or more compounds selected from the group consisting of a rubber latex, an aromatic vinyl compound, a vinyl cyan compound and an acrylate compound, wherein the graft rubber latex is prepared by treating a first hydrophobic peroxide based polymerization initiator before the polymerization conversion rate of the monomer mixture reaches 50% and then treating a second hydrophobic peroxide based polymerization initiator after the polymerization conversion rate reaches 50%]_ by copolymerization of 50 - 70 weight part of a rubber latex having gel content of 80 - 99% and mean diameter of 2,500 - 5,000 A and 30 - 50 weight part of a monomer mixture comprising one or more compounds selected from the group consisting of an aromatic vinyl compound, a vinyl cyan compound and an acrylate compound; and by additional use of one or more anti-oxidants selected from the group consisting of phenol based, phosphorous based and sulfur based anti-oxidants. 2. The preparation method of graft rubber latex as claimed in claim 1, wherein the first hydrophobic peroxide based polymerization initiator is one or more compounds selected from the group consisting of cumene hydro peroxide and diisopropyl benzenehydro peroxide. 3. The preparation method of a graft rubber latex as claimed in claim 1, wherein the second hydrophobic peroxide based polymerization initiator is tertiary butyl hydro peroxide. 4. The preparation method of a graft rubber latex as claimed in claim 1, wherein the first and second hydrophobic peroxide based polymerization initiator is used with an oxidative-reductive polymerization initiator. 5. The preparation method of a graft rubber latex as claimed in claim 1, wherein the anti-oxidant is 0.5-2 µm in particle diameter as an emulsion and added by 0.2 - 2 weight part to 100 weight part of the graft rubber latex. 6. The preparation method of a graft rubber latex as claimed in claim 1, wherein the anti-oxidant is slowly added to the graft rubber latex at 40 - 80°C and continuously stirred until coagulation.

Documents:

1768-del-2007-1-Correspondence Others-(25-05-2012).pdf

1768-DEL-2007-Abstract-(06-03-2012).pdf

1768-DEL-2007-Abstract-(25-05-2012).pdf

1768-del-2007-abstract.pdf

1768-DEL-2007-Assignment-(06-03-2012).pdf

1768-DEL-2007-Claims-(06-03-2012).pdf

1768-DEL-2007-Claims-(25-05-2012).pdf

1768-del-2007-claims.pdf

1768-DEL-2007-Correspondence Others-(06-03-2012)..pdf

1768-DEL-2007-Correspondence Others-(06-03-2012).pdf

1768-DEL-2007-Correspondence Others-(25-05-2012).pdf

1768-DEL-2007-Correspondence Others-(28-02-2012).pdf

1768-del-2007-correspondence-others.pdf

1768-del-2007-description (complete).pdf

1768-del-2007-form-1.pdf

1768-del-2007-Form-18 (25-02-2008).pdf

1768-del-2007-form-2.pdf

1768-del-2007-form-26.pdf

1768-DEL-2007-Form-3-(28-02-2012).pdf

1768-del-2007-form-3.pdf

1768-del-2007-form-5.pdf

1768-DEL-2007-GPA-(06-03-2012).pdf

1768-DEL-2007-Petition-137-(06-03-2012).pdf