MXPA99006711A - Polymers containing highly grafted rubbers - Google Patents

Abstract

The present invention is directed to rubber modified polymers which contain a non-block grafted rubber having a degree of grafting of at least 30 percent at the point of phase inversion and a specified amount of grafted vinyl aromatic polymer.

Description

POLYMERS CONTAINING HIGHLY GRAFTED RUBS This invention relates to highly grafted rubber and modified rubber polymers produced from these. Modified rubber polymers such as high impact polystyrene (HIPS) and acrylonitrile / butadiene / styrene (ABS) are typically produced by polymerizing styrene or styrene / acrylonitrile in the presence of a dissolved rubber, such that rubber is dispersed within the polymer matrix in the form of discrete rubber containing matrix polymer occluded therein. The occluded rubber particles can have a variety of morphologies including lamellar (onion skin), cellular (multiple occlusions), and heart shell (single occlusion). Rubber particles having small cell morphology and heart shell are particularly advantageous in improving pass properties of the brightness balance and impact resistance of modified rubber polymers. Additionally, the physical properties of modified rubber polymers can be improved with increasing levels of rubber grafting. The block copolymer rubbers can be highly grafted and have been used in previous modified rubber polymers. However, block copolymer rubbers are more expensive than different versions to block ones making this method economically unattractive. There have been many attempts to increase the level of grafting on rubber other than block. One approach includes hydroxyperoxidation of rubber using oxygen with simple bond (SO) which results in an aggregate number of reactive grafting sites on the rubber structure. The generation of SO photochemically in a rubber / styrene mixture containing dissolved oxygen has been reported in US-A-4,717,741 by Hahnfeld et al. However, the number of reactive grafting sites is limited by the solubility of oxygen in the rubber / styrene mixture. Additionally, photosensitizers must be used which act as contaminants in the final polymer causing discoloration. Additionally, the solubilizers are used by the photosensitizers that end the recycle stream and must be separated from the styrene monomer, making this process economically unattractive. Another approach involves the generation of SO in a rubber / styrene mixture by heating a compound that liberates SO, such as bisquinone peroxide as described in US-A-4,895,907 by Priddy et al. However, relatively low levels of grafting were achieved and the bisquinone peroxides are not available for commercial use. Still another approach involves the generation of single bond oxygen from triphenyl phosphite ozonides to increase grafting on polybutadiene rubber for the preparation of modified polybutadiene polystyrene, as described in "Polybutadiene Hydroperoxide by Singlet Oxygen: Its Grafting and Morphology in Polystyrene Matrix ", Journal of Applied Polymer Science, Vol., 31, 1827-1842 (1986) by Peng. However, the process described does not achieve high levels of grafting as hypothesized by Peng. Therefore, it remains highly desirable to obtain rubber modified vinyl aromatic polymers containing highly grafted non-block rubber particles utilizing an efficient and commercially viable process. In one aspect of the present invention a modified rubber polymer is obtained comprising a) a vinyl aromatic polymer matrix, and b) a non-block grafted rubber having a grafting degree of 30 to 100% at the point phase inversion, where the total amount of grafted vinyl aromatic polymer ranges from 20 to 75% of the total amount of vinyl aromatic polymer, wherein the grafted rubber is dispersed within the vinyl aromatic polymer matrix in the form of discrete rubber particles containing matrix polymer occluded therein. In the rubber-modified vinyl aromatic polymer containing a non-highly grafted block rubber combined with the defined graft / matrix ratio has improved physical properties and economic advantages when compared to the modified vinyl aromatic polymers containing rubbers of the ordinary technique. Another aspect of the present invention is a transparent rubber modified vinyl aromatic polymer wherein the dispersed rubber is in the form of dense particles containing substantially non-occluded matrix polymer therein, having an average particle size of less than 0, 1 μm. This aromatic vinyl modified rubber polymer can be used to produce transparent films. Another aspect of the present invention is a rubber modified polymer comprising a) an aromatic vinyl copolymer and nitrile restored matrix, b) a graft rubber different from a block having a degree of grafting ranging from 30 to 100% before of the phase inversion, wherein the total amount of grafted vinyl aromatic copolymer and unsaturated nitrile ranges from 25 to 90% of the total amount of vinyl aromatic copolymer and unsaturated nitrile, such that the rubber is dispersed within the polymer matrix in the form of rubber particles. This unsaturated rubber / vinyl modified vinyl aromatic polymer containing a differently grafted block rubber combined with a defined graft / matrix polymer ratio has improved physical properties when compared to the modified vinyl aromatic polymer / unsaturated nitrile polymer which contains rubbers of the ordinary technique. Yet another aspect of the present invention is an unsaturated rubber / nitrile modified vinyl aromatic polymer containing highly grafted rubber produced using a bulk polymerization process, wherein the polymer comprises: a) a vinyl aromatic and unsaturated nitrile copolymer matrix , and b) a grafted rubber that has a degree of grafting of to 100% before phase inversion, wherein the total amount of grafted vinyl aromatic copolymer and unsaturated nitrile is from 25 to 90% of the total amount of vinyl aromatic copolymer and unsaturated nitrile, such that the rubber is dispersed within the polymer matrix in the form of rubber particles. This unsaturated rubber / vinyl aromatic modified vinyl aromatic polymer produced by a dough process and similar in character to the unsaturated rubber / nitrile modified vinyl aromatic polymer produced using an emulsion polymerization process, having excellent gloss and impact resistance properties. Yet another aspect of the present invention is an improvement of a dough process for the production of a rubber modified vinyl aromatic polymer wherein the improvement comprises the production of grafting sites on rubber different from block using polymerization of a vinyl aromatic monomer , so that at least 25% of the rubber is grafted with the vinyl aromatic polymer at the point of phase inversion. This process allows the production of vinyl aromatic modified rubber polymers containing different block grafts highly grafted with improvement of the physical properties of the modified rubber polymer produced. The modified rubber polymers of the present invention comprise a matrix polymer, a non-grafted block rubber and any polymer. The graft polymer is grafted to the rubber, which is dispersed through the matrix polymer in the form of rubber particles. The matrix polymer can be any polymer produced from vinyl aromatic monomer. Suitable vinyl aromatic monomers include, but are not limited to, those vinyl aromatic monomers known to be used in polymerization processes, such as those described in US-A-4,66,987, US-A4,572,819 and US-A- 4,585,825. Preferably, the monomer is of the formula: R 'i Ar-C = CH2 wherein R' is hydrogen or methyl, Ar is an aromatic ring structure having from 1 to 3 aromatic rings with or without alkyl, halo or haloalkyl substitution, wherein the alkyl group contains 1 to 6 carbon atoms and haloalkyl refers to an alkyl group substituted by halo. Preferably, Ar is phenyl or alkylphenyl, wherein the alkylphenyl refers to a phenyl group substituted by alkyl, the phenyl being the most preferred. Typical vinyl aromatic monomers that can be used include: styrene, alpha methyl styrene, all isomers of vinyltoluene, especially paravinyltoluene, all isomers of ethyl styrene, propyl styrene, vinyl biphenyl, vinyl naphthalene, vinylanthracene, and mixtures thereof. The vinyl aromatic monomers may also be combined with other copolymerizable monomers. Examples of such monomers include, but are not limited to acrylic monomers such as acrylonitrile, methacrylonitrile, methacrylic acid, methyl methacrylate, acrylic acid, and methylacrylate; maleimide, phenylmaleimide, and maleic anhydride. The products containing impact modified or grafted rubber are further described in US-A-3,123,655, US-A-3,346,520, US-A-3,639,522 and US-A-4,409,369. The average weight molecular weight (Mw) of the matrix polymer is typically 50,000 to 500,000, preferably 60,000 to 400,000 and more preferably 80,000 to 350,000. The rubber other than grafted block comprises a rubber substrate other than block containing graft polymer grafts. The rubber substrate may be any rubber polymer other than unsaturated block having a glass transition temperature not greater than 0 ° C, preferably not greater than -20 ° C, as determined by ASTM D-756-52T. Typically, the rubber can be any rubber other than block having unsaturated bonds of at least 0.1% or more of the rubber structure. The term rubber other than block refers to a rubber wherein substantially blocks within the rubber and rubber structure is substantially a homopolymer or a copolymer containing 10% or less of block copolymer. Suitable rubbers include diene rubbers, butyl rubbers, ethylene-propylene-diene monomer rubbers (EPDM), and silicone rubbers. Examples of suitable diene rubbers include but are not limited to mixtures of conjugated 1,3-diene, for example, butadiene, isoprene, piperylene, chloroprene, etc. Suitable rubbers also include homopolymers of 1,3-conjugated dienes and interpolymers of 1,3-dienes conjugated with one or more copolymerizable monoethylenically unsaturated monomers, for example, copolymers of isobutylene and isoprene. Preferably, the rubber is a 1,3-conjugated diene homopolymer such as butadiene, isoprene, piperylene, and chloroprene, a copolymer of a conjugated diene with one or more vinyl aromatic monomers such as styrene, alpha.beta-ethylenically unsaturated nitriles such as acrylonitrile; alpha-olefins such as ethylene or propylene. Other rubbers include branched rubbers and low solution viscosity rubbers containing vinyl aromatic polymer blocks. The most preferred rubbers are 1,3-butadiene homopolymers. Small amounts of block copolymer rubbers can be combined with different block grafts highly grafted used in modified rubber polymers of the present invention. The average weight molecular weight (Mp) of the rubber polymer is generally from 10,000 to 600,000, typically from 30,000 to 500,000, preferably from 40,000 to 400,000, more preferably from 45,000 to 400,000, and more preferably from 50,000 to 350,000 as measured by gel permeation chromatography (GPC). The grafting polymer may be the same as or different from the matrix polymer. The grafting polymer can be produced from a variety of monomeric materials including vinyl aromatic monomers such as styrene, alpha-methylstyrene, 2,4-dimethylstyrene, 4-butyltinrene, etc .; alkyl substituted ring styrenes, for example, ortho-, meta- and para-vinyl toluene haloestyrenes with substituted ring, vinylnaphthalene, vinylanthracene, etc. Alkyl substituents generally have from 1 to 4 carbon atoms and may include isopropyl and isobutyl groups. If desired, mixtures of 1 or more vinylaromatic monomers can be used. The preferred monomers for use of the grafting polymer are styrene, acrylonitrile and methacrylate. Also suitable for use in the formation of graft polymers are the radically free polymerizable olefinically unsaturated monomers. Examples of such monomers include methyl methacrylate, and ethyl methacrylate; acrylonitrile, methacrylonitrile, and ethacrylonitrile and ethylene, propylene. The Mp of the grafting polymer will depend on the desired polymer product. For example, in a polymer having dense particles containing substantially non-occluded matrix polymers, the molecular weight of the graft polymer will be as low as possible, preferably less than 300,000, more preferably less than 250,000, and more preferably less than 200,000. . For products containing rubber particles having a heart shell morphology, the Mp of the grafting polymer will be close or equal to the Mp of the matrix polymer. Typically the grafting polymer will have an Mp from about 20,000 to about 800,000, preferably from 30,000 to about 700,000, more preferably from 40,000 to about 600,000 and even more preferably from 50,000 to about 500,000. If the polymer matrix and the grafting polymer are different, they must be compatible. In other words, a mixture of two polymers must have a glass transition temperature. A mixture of two incompatible polymers would have two distinct vitreous transition temperatures corresponding to each individual polymer. In one embodiment of the present invention, both the matrix polymer and the graft polymer are copolymers of styrene and acrylonitrile and the rubber is a polybutadiene. In this embodiment, the weight ratio of styrene to acrylonitrile ranges from 99: 1 to about 60:40. In another embodiment, both the matrix polymer and the graft polymer are polystyrene and the rubber is a polybutadiene. The rubber is typically present in amounts such that the modified rubber polymer contains from 2 to about 30, generally from 4 to about 25, preferably from 5 to about 20, and more preferably from 8 to about 20% by weight of rubber, based on the total weight of the monomer and the rubber components. The amount of the rubber present also depends on the final product of the desired polymer. Typically, for polymers such as HIPS, the total amount of rubber ranges from 5 to about 15% by weight. ABS polymers typically contain from 5 to about 30% by weight rubber. Another aspect of the present invention relates to a polymerization process, improved mass for the production of rubber modified vinyl aromatic polymer. In general, the modified vinyl aromatic rubber polymers of the present invention are produced by means of a continuous bulk polymerization as described in US-A-4,640,959 combined with a grafting process such as at least 25%, preferably at less 30% degree of grafting is achieved at the point of phase inversion. It is noted that additional grafting can occur after the phase inversion, where up to 10 or even 20% additional grafting can occur. Therefore, the modified vinylaromatic rubber polymers produced by this process would contain rubbers having at least 35%, preferably at least 40%, and up to 100% degree of grafting. The mass polymerization can be conducted in the presence of additives such as initiators, chain transfer agents, lubricants, etc. Typical initiators include peroxides such as t-butyl hydroxy peroxide, di-t-butyl peroxide, eumeno hydroperoxide, dicumyl peroxide, 1,1-bis (t-butylperoxy) cyclohexane, benzoyl peroxide, 1,1-bis (4,4-di- t-butyl peroxy cyclohexane) propanone; and azo compounds such as azo-bisisobutyrate and cyanovaleric bis azo acid. Typically chain transfer agents include mercaptans such as n-dodecyl mercaptan and t-codecilmercaptan, alphamethylstyrene dimer, 1-phenyl-butane-2-fluorene, terpinon, and chloroform. Other additives such as lubricants, for example stearic acid, behenic acid, stearoamide, oxidation inhibitors, for example plasticizer rear phenols, for example mineral oil, polyethylene glycol flame retardant agents, light stabilizers, coloring agents, fiber reinforcing agents, and fillers can also be used. Solvents can also be used in mass polymerization processes. Typically the solvents include aromatic hydrocarbons such as toluene, benzene, ethyl benzene, xylene, hydrocarbons such as heptane, hexane, and octane. Preference is given to using ethylbenzene or toluene. In general, the. solvent is used in sufficient quantities to improve processability and heat transfer during polymerization. Such amounts will vary depending on the rubber, monomer and solvent used, the process equipment and the desired degree of polymerization. If employed, the solvent is generally employed in an amount of up to 35% by weight, preferably 2 to 25% by weight, based on the total weight of the solution. Preferably the mass polymerization is conducted in one or more reactors of the so-called "plug flow" type or substantially linear stratified flow such as that described in US-A-2,727,884 or alternatively, in a stirred tank reactor where the The content of the reactor is essentially uniform throughout its volume, whose stirred tank reactor is generally used in combination with one or more "plug flow" type reactors. The temperatures at which the polymerization is most advantageously conducted depend on a variety of factors including the type of specific initiator and the concentration of rubbers, and the comonomer and reaction solvent, if any. In general, the polymerization temperatures vary from 60 to 160 ° C before the phase inversion with temperatures ranging from 100 to 190 ° C being used for phase inversion. The grafting process of the rubber, such as at least 25% or preferably at least 30% degree of grafting is achieved at the point of phase inversion, this is also used during the mass polymerization process. The degree of grafting refers to the proportion of grafted rubber of the total amount of rubber present. In other words, if a rubber has at least 30% degree of grafting, then at least 30% of the rubber contains at least one engrafted graft polymer chain. If the degree of grafting can be obtained through any process that produces the desired number of reactive sites on the rubber during the polymerization process before the phase inversion. For example, the use of low viscosity rubbers combined with increasing amounts of initiators, for example greater than 500 ppm. (parts per million), can increase the level of grafting on rubber to a desirable level. However, this method can also cause increased reactivity making the reaction difficult to control. The in-situ generation of single bond oxygen will increasingly increase the level of grafting as desired. The generation of single bond oxygen within the mass polymerization can be accompanied by several methods that include stoppage are not limited to the decomposition of phosphite ozonides in the polymerization feed, generating single bond oxygen gas by combining chlorine and peroxides from Basic hydrogen and come into contact with the polymerization feed, microwave discharges of dissolved oxygen in the polymer feed, or generate simple bonding oxygen gas by discharging oxygen plasma and an inert gas and coming into contact with the polymerization feed. In one embodiment of the process of the present invention, the single bond oxygen is used to achieve the desired degree of grafting on the decomposition rubber of the ozonide phosphites in the vinyl aromatic and rubber monomer feed of a bulk polymerization process. The ozonide phosphites can be produced by dissolving a phosphite, for example triphenyl phosphite, in an organic solvent at low temperature, typically below -60 ° C, in the presence of an excess of ozone. Typically solvents include inert solvents such as toluene, and ethylbenzene. An excess of ozone refers to a higher concentration of ozone than the concentration of phosphite in the reaction mixture. It is important to have an excess of ozone present in order to increase the production of ozonide phosphite at colder temperatures such as 80 ° C, which is typically the temperature used in the preparation of phosphorous ozonides. It has been found that if the phosphite is in excess it decomposes part of the ozonide, reducing the production of the reaction. Typically ozonide phosphites are known in the art and include but are not limited to those described by the general formula: OR3 RO-P-OR2 wherein R1, R2 and R3 are Ci to C20 alkyl, aryl or combinations of alkyl and aryl groups, wherein the aryl groups may contain from 1 to 3 rings. These compounds can also be of the cyclic type wherein the phosphorus atom is part of a mono, bicyclic or tricyclic structure. The ozonide phosphite is advantageously cooled to temperatures lower than -50 ° C, more preferably lower than -60 ° C and more preferably -80 ° C or less, to decrease decomposition of the produced ozonide and increase production.

The rubber is typically dissolved in a mixture of vinyl aromatic monomer and a solvent, such as ethylbenzene, before feeding the bulk polymerization processes. The phosphite ozonide is added to the rubber solution under appropriate conditions for the proper administration of the ozonide within the rubber solution. The rubber solution is typically maintained at room temperature, for example about 25 ° C, since the ozonide phosphite is mixed rapidly with the rubber solution. The rubber solution can be cooled to a temperature of -25 ° C or less to allow good distribution of the ozonide phosphite in the rubber solution.

The ozonide phosphite produces a simple bonding oxygen that reacts with the rubber to produce hydroperoxide groups on the rubber structure. These hydroperoxide groups serve as grafting sites on the rubber during polymerization of the vinyl aromatic monomer and rubber feed. The amount of simple bonding oxygen necessary to achieve the desired grafting sites on the rubber depends on the product of the polymer and the desired degree of grafting. Polymers in which a high degree of grafting is desired, require a greater amount of simple bonding oxygen. In an embodiment wherein the single bond oxygen is generated from an ozonide phosphite from 25 ppm to 1.0% by weight of single bond oxygen is typically required, based on the total weight of the polymerization feed. The amount of single bond oxygen required is determined by the grafting requirements of the phase reversal point. Typically less than half of the single bond oxygen units added to the bulk polymerization result in a grafting site on the rubber. Typically, to achieve a degree of 30% grafting further, at least 50 ppm of hydroperoxide units based on the weight of the diene rubber in the polymerization feed are necessary. Generally, preferably from 100, more preferably from 150 and more preferably from 200 to about 2,000, preferably about 1,800, more preferably about 1,500 and more preferably about 1,200 ppm of hydroperoxide units, based on the total weight Rubber polymerization mixture can be used. In one embodiment of the present invention, a transparent high impact polystyrene polymer is produced which contains particles having an average particle size volume of 0.1 μm or less. In this embodiment, at least 600 ppm, more preferably at least 1,000 ppm or more hydroperoxide units based on the rubber weight of the solution are present in the rubber structure. In another embodiment of the present invention, ABS polymers are produced. In this embodiment, the ozonide concentration is typically from 20% to 30% less than that required for HIPS products at a given rubber level. The efficiency of the grafting process is improved in such polymers due to the presence of polar components, for example acrylonitrile. Therefore, less ozonising is necessary to achieve the same level of grafting in an ABS polymer as is necessary in a HIPS polymer. In HIPS polymers, typically about 30% of the hydroperoxide units present result in a grafting site on the rubber, while about 50% result in grafting sites in ABS polymers. The rubber modified vinyl aromatic polymers of the present invention contain a rubber dispersed through the vinyl aromatic polymer matrix in the form of particles which may have a variety of average particle size volume. The methods and conditions necessary for the production of an average particle size of desired volume are well known to those skilled in the art. As used here, the average average particle size volume refers to the diameter of the rubber particles that include all the vinyl aromatic polymer occlusions within the rubber particles. The volume of average particle sizes and distributions can be measured using conventional techniques such as Coulter Counter ™ or electron microscopy image analysis. Generally, the rubber particles obtained can vary from 0.01 to 5 μm. The ABS polymers of the present invention may have rubber particle sizes of volume average in the range of 0.01 to 1 μm, preferably 0.05 to 0.9 μm and more preferably 0.05 to 0.8 μm . Additionally, rubber particles can have a variety of morphologies including lamellar, cellular and heart shell. It has been surprising to discover that using the improved bulk processes of the present invention, the ABS products can be obtained which closely resemble the modified rubber ABS products obtained in emulsion polymerization processes. In particular, dense rubber particles and rubber particles of heart shell morphology can be obtained in an ABS polymer, which has not been previously met using the dough process of the present invention.

The HIPS polymers of the present invention typically contain chunk particles having an average particle size volume in the range of 0.1 to about 5 μm, more preferably 0.2 to 4 μm, and more preferably close to 0.2 to 3 μm. Preferred morphologies include cellular, lamellar and heart shell with the heart shell being the most preferred. Additionally, transparent HIPS products (TIPS) can be obtained where the rubber particles are dense, without having matrix polymer occlusions and being less than 0.1 μm. Another important aspect of the present invention, in addition to the degree of grafting, belongs to the embodiments wherein the matrix polymer and the grafting polymer are the same. This aspect is the ratio of the grafted matrix polymer to the total amount of matrix polymer. In this case the amount of matrix polymer present as a graft in the rubber also depends on the degree of grafting desired in the final polymer product. In one embodiment of the present invention, the HIPS polymer containing rubber particles having an average particle size of 0.4 to 1 μm and a cell morphology can be produced where the degree of grafting is advantageous from 30 to 60% at the point of phase inversion. Phase inversion is a term well known in the art and refers to the process wherein vinyl aromatic monomer polymerizes by forming a discontinuous phase dispersed through the continuous phase of the rubber dissolved in monomer. As the vinyl aromatic monomer continues to polymerize, the discontinuous polymer phase becomes larger in volume thus forming a continuous phase while the rubber forms a discontinuous phase dispersed throughout its volume. This phenomenon refers to the "phase inversion", which is, therefore, the conversion of the polymer of a discontinuous phase dispersed in the continuous phase of the rubber / monomer solution through the point where continuous phase is not different or discontinuous in the polymerization mixture, for a continuous polymer phase having the rubber dispersed throughout its volume. The investment phase point can be defined by the formula: s = 2, 5 x RP wherein Rp is the weight percentage based on rubber on the total polymerization mixture and s is the sum of rubber and polymer formed (both grafted and free polymer matrix). Similarly, the proportion of matrix polymer grafted to the total matrix polymer in the above solids content is advantageously in the range of 25 to 50%. These proportions can be achieved by polymerizing the vinyl aromatic monomer with a rubber having from 50 to 2,000 ppm of hydroperoxide units, based on the total amount of rubber, on the structure of the rubber. Rubbers containing such levels of hydroperoxide units can be produced by mixing an approximate amount of ozonide phosphite equal to about three times the stoichiometric amount of single bond oxygen required. Due to its high reactivity, some, for example up to about two thirds of the single bond oxygen is wasted in collateral reactions, leaving the remaining phosphorous ozonide to produce hydroperoxide units in the rubber structure. In another embodiment of the present invention, wherein the high impact polymer containing the rubber particles having a heart shell morphology and an average particle size volume of 0.1 to 0.5 μm is obtained, the Grafting degree is advantageously in the range of 40 to 80% in the ratio of graft matrix polymer to total matrix polymer is from 35 to 65%. These levels can be achieved by polymerizing vinyl aromatic monomer and rubber in the presence of an amount of ozonide phosphite that produces three to four times the molar equivalent of the single bond oxygen necessary for the desired degree of grafting. Typically, approximately 40 to 2,000 ppm of single bond oxygen, based on the total feed weight, can be used, which would typically lead to 250 to 800 ppm of hydroperoxide units, based on the weight of rubber on the rubber structure. In the embodiments where the rubber particles having a heart shell morphology are obtained, the polymerization is typically conducted in the presence of a chain transfer agent. Generally, at least 200 ppm of the chain transfer agent, for example n-dodecyl mercaptan, based on the total weight of the polymerization feed, are added at the start of the polymerization reaction, or before the phase inversion, to obtain a well-defined heart shell structures. In another embodiment of the present invention wherein the rubber particles of the average particle size volume of 0.1 μm or less and not having occluded matrix polymer are obtained, the level of grafting is advantageously 50 to 100% in the point of phase inversion. The grafted matrix component at the phase reversal point is advantageously 50% or more. The specific grafting parameters usually a rubber containing 600 ppm or higher levels of hydroperoxide units on the rubber structure based on the weight of rubber. These levels can be achieved by mixing an amount of ozonide phosphite at a level sufficient to generate 100 ppm of simple oxygen in a feed containing 5% by weight of a low cis diene rubber. If a rubber containing more than the typical cis content of 45% is used, the ozonide phosphite levels should be reduced as rubbers with a higher cis content usually leading to improved productions of hydroperoxidation. If the additional peroxide initiators are used in the polymerization processes, the hydroperoxide content to achieve the degree of specific grafting for any structure will decrease, to the extent that the activities of the hydroperoxide units on the rubber structure and the initiators of grafting with complementary. The modified rubber vinylaromatic polymers of the present invention can be used in a number of applications such as small appliance housings, electronic equipment, and office equipment. The improved bulk polymerization process used to produce such polymers is an economically and commercially viable process for producing vinylaromatic modified rubber polymers containing highly grafted rubbers and exhibiting improved physical properties. The following examples are provided to illustrate the present invention. The examples are not intended to limit the scope of the invention and they should not be so interpreted. The amounts are in parts by weight or percentages by weight unless otherwise indicated.

EXAMPLES Trifenilphosphate Ozonolysis The triphenyl phosphate (listed in Table I) is dissolved in 60 ml of methylene chloride. The solution is then cooled in a solid C02 bath at a temperature of about -78 ° C. The ozone gas is slowly bubbled through the solution using an ozonator (Ozobloc ™ OC1 (available from Envico Environment Control BV of the Netherlands) .The reaction is considered complete once the blue color of dissolved ozone is observed to be consistent. Ozonized triphenyl phosphate is then mixed with the polymerization feed as listed in Table 1 which has been cooled to a temperature of about -20 ° C using a cryostatic bath.The solution is mixed for approximately 30 minutes and then placed at room temperature environment to heat slowly for about two hours During the heating process, the phosphorous ozonide decomposes to generate a simple bonding oxygen which in turn reacts with the polybutadiene of the feed to form the hydroperoxides on the structure of the rubber. The hydroperoxide structure of the rubber structure is then measured in accordance n Method ASTM D-2340-82 by taking a small portion of the polymerization feed solution, precipitating the polybutadiene rubber using solvent precipitation, reacting with sodium iodide in isopropyl alcohol and titrating the released iodide with standard thiosulfate solution of sodium.

Polymerization The polymerization feed solution is then fed into a 2.5 liter Auger type batch reactor fitted with heating elements and an agitator. At the intervals specified in Table I, a sample is removed from the reactor and analyzed for solids and grafting. Once the desired conversion level is reached, the polymerization molasses is then devolatilized in a vacuum oven at 240 ° C for about one hour. The polymer is then cemented and extruded into granules.

Physical tests Physical tests are determined by injection of molded samples produced using an Arbug 170 injection molding machine. The tensile test is made in accordance with ASTM D-638. The Izod impact test is made in accordance with ASTM D-256. The Charpy impact test is made in accordance with ISO-179-2C. The particle size of rubber is measured by means of a Coulter Counter Multisizer using a 20 μm tube. The rubber level of the final products is measured using IR spectroscopy. Gloss measurements are determined using an All Rounder 170 CM tree under typical molding conditions listed below. Gardner (60 degrees). The measurements are made using a Dr. Lange device. The molding conditions and sample weights are maintained for comparison of materials.

Mass temperature (° C) 230-220-210-190 Molding temperature (° C) 40 injection speed (cm3 / min) 25 maintenance pressure (Pa) 600x10b to 650X10- in steps of c and • (weight of the sample (g) 6.65 Grafting measures are done on reactor samples. For this purpose, well-known solvent precipitation techniques are used, the components are precipitated by changing the solubility parameter of the solvent gradually. The free weights of the polybutadiene (PBD), free polystyrene (PS) and the polybutadiene-polystyrene graft copolymer (PBD-g-PS) are measured and the grafted polybutadiene and the grafted polystyrene are calculated. The weight of the grafted polystyrene = Total weight PS - ((weight PBD-gPS + free weight PBD) - total weight PBD). The weight of the grafted polybutadiene = (weight PBD-g-PS - grafted PS weight). The percentage of grafted polystyrene = (grafted Ps weight / total PS weight) x 100. The percentage of grafted polybutadiene (graft PBD / total PB) x 100.

TABLE I * Control based on copolymer of 60% butadiene and 40%) of styrene, is not an example of the present invention.

The data in Table I indicate that high-gloss HIPS can be serviced using hyperoxidized rubber with properties similar to those obtained from very expensive block copolymers.

Table II: Grafting data for EXAMPLE 2 1Based on total polystyrene. Based on the total polybutadiene.

Table III: Grafting data for EXAMPLE 3 1Based on total polystyrene. 2 Based on the total polybutadiene.

The graft data show that the graft levels at the point of phase inversion are in the claimed range. At the phase immersion point it is usually at 2.5 x the level of rubber in the feed. At 5.5% rubber, the phase inversion is typically about 14% conversion. The control and example are repeated and the resulting product is mixed with a HIPS product of large particles having an average particle size of 3.5 microns to make bimodal HIPS with high gloss and impact properties. The properties are given in table IV.

Table IV 'Controls, is not an example of the present invention.

The bimodal versions based on the HIPS and HIPS control block copolymers of the present invention show similar properties.

Claims (20)

1. A modified rubber polymer comprising: a) a vinyl aromatic polymer matrix, and b) dispersed within the polymer matrix, a rubber It is noted that it has a degree of grafting of 30 to 100% at the point of phase inversion, wherein the total amount of grafted vinyl aromatic polymer is from 20 to 75% of the total weight of vinyl aromatic polymer.

2. A modified rubber polymer comprising: a) a vinyl aromatic matrix and unsaturated nitrile copolymer, and b) dispersed within the polymer matrix, a grafted rubber having a grafting degree of 30 to 100% in the point of investment phase, wherein the total amount of grafted vinyl aromatic copolymer and unsaturated nitrile ranges from 25 to 75% of the total weight of vinyl aromatic copolymer and unsaturated nitrile.

3. The modified rubber polymer of claim 1 or 2, wherein the rubber is a diene rubber.

4. The modified rubber polymer of claim 3, wherein the rubber is a polybutadiene.

5. The modified rubber polymer of claim 1 or 2, wherein the dispersed rubber has a particle size of 0.3 to 1 μm.

6. The modified rubber polymer of claim 1 or 2, wherein the dispersed rubber has a cellular morphology.

7. The modified rubber polymer of claim 1 or 2, wherein the dispersed rubber has a heart shell morphology.

8. The modified rubber polymer of claim 1 or 2, wherein the dispersed rubber has a lamellar morphology.

The modified rubber polymer of claim 1 or 2, wherein the dispersed rubber is in the form of dense particles having an average particle size of less than 0.1 μm.

The modified rubber polymer of claim 1, wherein the dispersed rubber has a heart shell morphology and an average particle size ranging from 0.1 to 0.5 μm.

The rubber modified polymer of claim 1, wherein the polymer additionally contains rubber particles having an average particle diameter of 1.5 to 10 μm in an amount of 3 to 50% of the weight based on the total amount of rubber present.

The modified rubber polymer of claim 2, wherein the dispersed rubber is in the form of dense particles having an average particle size ranging from 0.05 to 0.2 μm.

The modified rubber polymer of claim 2, wherein the dispersed rubber has a heart shell morphology with an average particle size of 0.1 to 0.6 μm.

The rubber modified polymer of claim 2, wherein the polymer additionally contains rubber particles having an average particle diameter of 1.5 to 5 μm in an amount of 3 to 50% by weight based on the total amount of rubber present.

15. A molded article produced from modified rubber polymer of claim 1 or 2.

16. An extrudate produced from modified rubber polymer of claim 1 or claim 2.

17. An improvement of the dough polymerization process for the production of a vinyl aromatic rubber polymer in which the vinyl aromatic monomer and the rubber mixture are fed into a bulk polymerization vessel and polymerized, the improvement comprises using a grafting process such that at least 30% of the rubber is injected with a graft polymer at the point of phase immersion during the mass polymerization process.

18. The process of claim 17, wherein the ABS polymer is produced.

The process of claim 17, wherein the improvement comprises contacting the vinyl aromatic monomer and the rubber mixture with simple bonding oxygen prior to polymerization such that the hydroperoxide groups are formed on the rubber structure.

20. The process of claim 17, wherein the single bond oxygen is generated from a phosphorous ozonide.