MXPA99011767A

MXPA99011767A - High gloss high impact monovinylidene aromatic polymers

Info

Publication number: MXPA99011767A
Application number: MXPA/A/1999/011767A
Authority: MX
Inventors: Schrader David; Demirors Mehmet; M Black Steven
Original assignee: M Black Steven; Demirors Mehmet; Schrader David; The Dow Chemical Company
Priority date: 1997-08-13
Filing date: 1999-12-15
Publication date: 2000-06-01

Abstract

The present invention is a rubber modified monovinylidene aromatic polymer having a bimodal particle size distribution comprising:a) rubber particles of a star or branched low viscosity rubber having a volume average particle size of from 0.1 to 2&mgr;, and a cellular or core shell morphology or mixture thereof, and b) rubber particles of a star or branched low viscosity rubber, linear diene rubber or block copolymer rubber having a volume average particle size of from 0.5 to 10&mgr;, characterized in that the rubber particles of b) are more dense than the rubber particles of a), having a smaller occluded monovinylidene aromatic polymer content than the particles of a), wherein the particles of a) are from 50 to 99 weight percent of the total diene rubber content.

Description

* - -J HIGH BRIGHTNESS AROMATIC ONOV1N1LIDENO POLYMERS, HIGH IMPACT ~ DECRIPTION OF THE INVENTION The present invention relates to rubber-modified aromatic monovinylidene polymers, particularly polymers containing two different average particle sizes in rubber volume, hereinafter referred to as bimodal compositions, and to a process for their preparation. The rubber-modified monovinylidene aromatic polymers have typically been prepared from aromatic vinyl monomers by polymerizing the aromatic vinyl monomer in the presence of a dissolved rubber. The aromatic vinyol monomer is polimerized, forming a discontinuous phase, dispersed through a continuous phase of rubber dissolved in monomer. As the aromatic vinyl monomer continues to polymerize, the discontinuous polymer phase becomes a larger volume, thus forming a continuous phase, while the rubber forms a discontinuous phase, dispersed therethrough. This phenomenon, referred to as "phase inversion", is, therefore, the conversion of the polymer from a discontinuous phase dispersed in the continuous phase of the rubber / monomer solution, through the point where there is no continuous phase or discontinuous different in the polymerization mixture, to a continuous polymer phase having the rubber dispersed through it. ^ Several bimodal compositions containing two different sizes of rubber particle have been produced to try to balance and effectively obtain a high brightness. , while still maintaining the high impact properties using several types of huje. U.S. Patent No. 4,334,039, issued to Dupree et al. And the U.S. patent. 4,153,645 issued to Lanza and others describe the use of butadiene rubbers to obtain polymers having a bimodal rubber particle size distribution. Said polymers, although having a good tenacity, do not have the desired level of glass. EP-048,389 by Echte discloses the use of styrene / butadiene block copolymer rubbers, wherein small particles of a 40/60 styrene / butadiene block copolymer are made and are of core-shell type morphology. Although such products have the desired balance of gloss and impact, they are economically disadvantageous because of the high cost due to the use of block copolymer rubbers. In addition, higher amounts of the block copolymer should be used in order to obtain a level of polybutadiene, increasing the cost additionally. It is well known in the art that the brightness and impact resistance balance of high impact monovinylidene aromatic polymers depends on the particle size of the rubber, the level of rubber and the flow properties of the product. Typically, resins that contain a smaller rubber particle have a "higher brightness and lower impact, while resins that contain a larger rubber particle have a lower brightness and a higher impact. , usually known as the butadiene homopolymer type, can not be dimmed small enough to make the desired high-gloss products Block copolymers usually lead to small rubber particles but are more expensive Other aspects have been used to solve the problem. The problem of obtaining small particles using polybutadiene rubbers EP-277,687 describes a rubber-modified polymer containing a radial or branched polybutadiene rubber having an average volume diameter of 0.1 to 1.2 microns (μ) and rubber particles containing rubber. be radial, branched or linear having an average particle diameter in volume of 1 to 5 μ However, although these properties have a high gloss, they do not have sufficient tenacity. Therefore, there is a need to produce monovinuidene-modified aromatic polymers with rubber having similar gloss and impact properties to those products that use block copolymer rubbers., but without the high cost of block copolymer rubbers. The present invention is an aromatic monovinylidene polymer modified with rubber having a size distribution of the bimodai particle comprising "a) rubber particles of a star or branched rubber. low viscosity having a volume average particle size of 0.1 to 2 μ, and a cell morphology or - core shell or mixture thereof, and b) rubber particles of a low density star or branched rubber, linear diene rubber or block copolymer rubber having a volume average particle size of 0.5 to 10 μ, characterized in that the rubber particles of b) are denser than the rubber particles of a), having a content of = monovinylidene aromatic polymer occluded smaller than the particles of a), where the particles of a) are of 50 to 99% by weight of the total content of diene huie. This product has excellent shine and impact properties. It has the balance of gloss and impact properties of a resin that contains a block copolymer without the high cost. Such products are highly desirable to replace higher cost products in injection molding and extrusion applications. The present invention relates to monovinylidene aromatic polymers modified with rubber. Polymers modified with monovinylidene rubber are derived from one or more aromatic vinyl monomers Representative aromatic vinyl monomers include styrene, alkyl-substituted styrenes such as alpha-alkyl styrenes, for example, alpha-methylstyrene, alpha-ethylstyrene; ring-substituted styrenes; -SF-for example, vinyltoluene, particularly p-vinyltoluene, or -ethylstyrene; and 2,4-substituted styrenes; -dimethylstyrene; halo-substituted radicals on the ring such as chlorostyrene and 2,4-d-chloro-styrene; styrene subsituted with both halogen and alkyl groups, such as 2-chloro-4-methylstyrene, vinyl anthracene and mixtures thereof Preferably, the styrene and / or alpha-methyl styrene is used as the aromatic vinyl monomer, with styrene being very preferred. Comonomers can also be used in the ombination with the aromatic vinyl monomer, preferably in TTrTa amount up to 40% by weight of the polymerizable monomer mixture. Representative comonomers include unsaturated nitriles, such as acrylonitrile; alkyl acrylates and alkyl meta-plates such as methyl methacrylate or n-buπyl acrylate; ethylenically unsaturated carboxylic acids; and ethylenically more saturated carboxylic acid derivatives, including anhydrides and imides, such as maleic anhydride, and N-phenyl m a I m a d i. The rubber suitable for use in the production of rubber particles having a volume average particle size of 0.1 to 2 μ, as described in a), is a low viscosity rubber having a solution viscosity (5% in styrene) at 20 ° C) on a scale of 20 to 120 centipoise (cps) and a Mooney viscosity (ML + 1, 100 ° C) from 30 to 80. Suitable rubbers include so-called radial or star rubbers that have three or more polymer segments attached to an element or compound (individual polyfunctional T, such as branched rubbers having a cis content of less than 75% and at least one, or a significant number of subordinate chains of sufficient length, so that the viscosity of the rubber is less than the viscosity of a linear polymer of the same monomeric components and of the same molecular weight, said rubbers useful in a), typically have a relatively high average molecular weight, a viscosity of relative solution. Highly high and a high Mooney viscosity. In general, the viscosity of solution for the rubber will be below 120 cps, while the viscosity of Mooney will be less than 80 cps. The radial or branched rubber preferably employed in a) of the present invention typically exhibits a secondary order transition temperature not greater than 0 ° C, and preferably not greater than -20 ° C. Such rubbers include alkadienes, which include conjugated 1,3-dies such as butadiene, isoprene, chloroprene or piperylene. Very preferred are homopolymers prepared from 1,3-conjugated dienes, with homopolymers of 1 being especially preferred., 3-butadiene. Alkdiene copolymer rubbers containing small amounts, for example up to 10 to 15% by weight, of other monomers such as aromatic vinyl can also be employed if the rubbers satisfy the other characteristics described herein. 3JL0S polymers having random branching, as well as methods for their preparation, are known in the art and are referenced therefor for the purpose of this invention. Branched rubbers and representative methods for their preparation are described in Great Britain Patent No. 1, 130, 485 and in Macromolecules, Vol. II No. 5, p. 8, by R. N. Young and C. J. Fetters. Radial or star-shaped polymers, commonly referred to as polymers having designated branching, are conventionally prepared using a polyfunctional coupling agent or a polyfunctional initiator. Methods for preparing star or radial polymers having designated branching are well known in the art. The methods for preparing a butadiene polymer using an assembly agent are illustrated in the U.S. Patents. 4,183,877; 4,340,690; 4,340,691; and 3,668,162, while methods for preparing a butadiene polymer using a polyfunctional initiator are described in US-A-4, 82,818; US-A-4,264,749; US-A-3, 668, 263 and US-A-3, 787, 510. As is known to those skilled in the art, various techniques such as branching control and molecular weight control can be used to adjust and designing polymers to obtain the necessary solution and Mooney viscosities. As well as to relation of these two. -The rubber suitable for use in the production of rubber particles having an average particle size in volume of 0.5 to 10 μ, as described in b), may be rubber like that used to produce the smallest rubber particles, as described in a), a different rubber or a mixture thereof. Typically, the rubber can be any rubber polymer, which can be dissolved in the aromatic vinyl monomer. Preferred rubber polymers include a homopolymer or afcadiene copolymer or an ethylene-propylene copolymer optionally containing a non-conjugated diene. Most preferably, the rubber is a mopolimer of a 1,3-conjugated diene such as butadiene, isoprene, piperylene, and chloroprene, or a copolymer of a conjugated diene with one or more aromatic vinyl monomers such as styrene; alpha, ethylenically unsaturated beta-nitriles such as acrylon itp lo; and alpha-oiefins such as ethylene or propylene. Very preferred rubbers with 1,3-butadiene homopolymers and block or random copolymers of at least 30, most preferably from 50 to 90% by weight of 1,3-butadiene and up to 70, most preferably from 5 to 50% by weight of an aromatic vinyl compound, preferably styrene. The rubber used to produce large rubber particles of b) is preferably a polybutadiene. The rubber used to produce small rubber particles of a) is preferably a polybutadiene or a block copolymer of poly (butadiene-styrene). The small rubber particles of a) typically have a core-shell (individual occlusion, major) or cellular morphology (smaller multiple occlusions) or a mixture thereof. The rubber particles of b) are also characterized because they have a dense rubber structure when compared to the typical salami structure observed in other products. The proirfédio ratio of the monovinylidene aromatic polymer to the rubber occlusion content of the rubber particles of b) is smaller than that of the smaller particles of a), as can be more clearly distinguished from an electron micrograph. Typically, the particles of b) have an average content of monovinylidene aromatic polymer to rubber occlusion of 0.5 to 3, preferably 0.5 to 2.8, most preferably 0.5 to 2.5, while a standard particle type has an average content of aromatic polymer ^ of monovinylidene to rubber occlusion typically from 3.1 to 6, as in the rubber particles of a). The rubber feet as two sizes lead to rubber particles that have two groups of modules. Such compositions are capable of causing cracking on a wide range of applied stresses leading to a more rigid material without significant loss of gloss property. As used herein, the average particle size and volume refers to the diameter of the rubber particles, including all occlusions of the aromatic vinyl polymer within the rubber particles. The average volume particle sizes and distributions can be measured using conventional techniques such as Coulter Counter ™ or electronic transmission microscope image analysis. Large particles are measured using a 50 μm tute using a 30 micron tube. The amount of rubber initially dissolved in the aromatic vinyl monomer depends on the desired rubber concentration in the final rubber-reinforced polymer product., the degree of conversion during polymerization and the viscosity of the solution. The rubber is typically used in amounts so that the rubber reinforced polymer product contains from 2 to 20%, preferably from 3 to 17%, and most preferably from 3 to 15% by weight of rubber, based on the total weight of aromatic vinyl monomer and rubber components, expressed as rubber or rubber equivalent. The term "rubber" or "rubber equivalent" as used herein, means, for a rubber homopolymer, such as polybutadiene, simply the amount of rubber, and for a block copolymer, the amount of copolymer made of the monomer that when homopolymerized forms a rubber polymer (hulose), tai comot for a butadiene-styrene block copolymer, the amount of butadiene component of the block copolymer. The polymerization is preferably conducted in one or more substantially linear stratified flow reactors or the so-called sealed flow type, as described in US-A-2,727,884. The techniques of bulk polymerization and the conditions necessary to produce the desired average particle sizes are well known to those skilled in the art. The temperature at which the polymerization is conducted will vary according to the specific components, particularly the initiator, but in general, it will vary from 60 to 19 ° C. ll * w -Typically, the bimodal composition of the present invention is produced by polymerizing an augmentation of the desired components and a graft initiator in a series of reactors, wherein the rubber particles of a) are formed and stabilized within the ppmer reactor, are then fed to the top of a second reactor. ~ A portion of the initial feed is additionally added to the second reactor, at about the midpoint of the reactor, so that mixing of the polymerization mixture containing the rubber particles of a) is rapidly combined with the feed not polymerized in the second reactor and the rapid phase reversal of the second feed results in the dense-type morphology of the rubber particles in b) .To obtain the dense-type morphology, the polymerization mixture containing the small particles of a) is mixed with the non-polymerized feed in the second reactor, under conditions such that the resulting mixture of a) and the unpolymerized feed has a solids content of at least 4 to 5 times the rubber content. of the dense, large particles of b) can be controlled by controlling the agitation and the solids content in the second actor, as is well known in_Ja technique. "The polymerization is preferably carried out in the presence of an initiator, preferably for the particles of a). Suitable initiators include any initiator capable of imparting the desired graft of polymer to the rubber particle under the polymerization conditions and accelerating the polymerization of the vinyl aromatic monomer. Representative initiators include peroxide initiators such as peresters, for example, tertiary butyl peroxybenzoate and tertiary butyl peroxyacetate, tertiary butyl peroxyolate, dibenzoyl peroxide, dilauryl peroxide, 1,1-tert-butyl butyl cyclohexane, cyclohexane 1. 3-bis-tertiary butyl-peroxy-3,3,5-trimethyl, and dicumyl peroxide. If desired, photochemical initiation techniques can be employed. Preferred initiators include tertiary butyl peroctoate, tertiary butyl isopropyl perchloride, dibenzoyl peroxide, tertiary butyl peroxybenzoate, tertiary bis-butyl peroxycyclohexane, and tertiary butyl peroxyacetate. The initiators can be employed on a scale of concentrations depending on a variety of factors including the specific initiators employed, the desired levels of polymer damage and the conditions at which bulk polymerization is conducted. Specifically, the initiators can be employed in amounts of 0 to 2JJ00, preferably 100 to 1500 parts by weight per million parts by weight of aromatic vinyl monomer. -Also, a solvent can be used in the polymerization. Acceptable solvents include normally liquid organic materials, which form a solution with the rubber, aromatic vinyl monomer and ef polymer thereof. Solvents i: Representative include aromatic hydrocarbons and aromatic substitutes such as benzene, ethylbenzene, toluene, xylene or the like; saturated straight or branched chain aliphatics, substituted or unsubstituted of 5 or more carbon atoms, such as heptane, hexane, octane or the like; substituted alicyclic or alicyclic hydrocarbons having 5 or 6 carbon atoms, such as cyclohexane. Preferred solvents include substituted aromatics, with ethylbenzene and xylene being most preferred. In general, the solvent is used in sufficient amounts to improve processability and heat transfer during polymerization. Said 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. Other materials may also be present in the process of the present invention, including plasticizers, for example, mineral oil; flow promoters, lubricants, antioxidants, catalysts, mold release agents, or polymerization aids, such as chain transfer agents, including alkyl mercaptans, for example, n-dodecyl mercaptan. If employed, a chain transfer agent may be present in an amount of 0.001 to 0.5% by weight based on the total weight of the polymerization mixture to which it is added. The entanglement of the rubber in the resulting product and the removal of the unreacted monomers, as well as any solvent, if employed, and other volatile materials, are advantageously conducted using conventional techniques, such as introducing the polymerization mixture into a devolatilizer, vaporizing the monomer and other volatiles at elevated temperature, for example, from 200 to 300 ° C under vacuum and remove them from the devolatilizer. -In bimodal compositions, two different average volume particle sizes are produced and combined. In particular, the rubber particles have different average particle sizes by volume, wherein one contains small rubber particles of cell type, core-shell or mixture thereof, having a volume average particle size of 0.1 to 2 microns. , and the other contains large, dense rubber particles, having an average particle size in volume of 0.5 to 10 microns. In bimodal compositions, the desired elation of small to large particles depends on the properties desired in the final rubber reinforced polymer. Typically, the amount of small particles ranges from 51 to 99, preferably from 75 to 96 and most preferably from 80 to 95% of the total amount of rubber particles in the rubber reinforced polymer. For products that require high gloss properties, the amount of small particles is 80 to 98% and the number of large particles is 2 to 20%. Other polymers where a much higher impact strength is desirable can be 65 to 75% of small particles and 25 to 35% of large particles. In one embodiment of the present invention, a high impact polystyrene (HIPS) composition is produced comprising a polymerized aromatic vinyl monomer, with dispersed rubber particles, having a bimodal particle size distribution. The size of the rubber particles depends on the desired brightness and the impact properties of the polymer product. For bimodal HIPS compositions, the small rubber particles are typically in the range of 0.1 to 2 μ, preferably from "0.2 to 1.5 and most preferably from 0.3 to 1.2, and preferably from 0.3 to 1.1 μ.The small particles are of a cell type morphology The ratio of polystyrene to polybutadiene occlusion content is typically from 3.1 to 6. The large rubber particles are typically from 0.5"to 10, preferably from 1.0 to 8, preferably from 1.2 to 7 and most preferably 1.3 to 6 μ. The large rubber particles are denser than the smaller rubber particles, having a polystyrene to rubber content, occluded, of only 0.5 to 3. Alternatively, the present invention may be an acrylonitrile-butadiene-styrene type composition ( ABS), wherein an alkenyl nitrile, generally acrylonitrile, is used as a comonomer. For bimodal ABS compositions, the small particles are typically in the range of 0.2 to 1, preferably 0.3 to 1, preferably 0.4 to 0.9 and most preferably 0.5 to 0.8 μ, and the large rubber particles are typically in the scale from 0.8 to 10, preferably from 0.9 to 6, preferably from 1 to 4 and most preferably from 1 to 4 μ. Due to the excellent balance of gloss and stiffness properties, these rubber-reinforced bimodal compositions are useful in a wide variety of applications such as consumer electronics, small household items, toys and furniture. These polymers are also useful in coextrusion applications such as in the preparation of a gloss layer using coextrusion techniques for cooler linings. As used in this, the volume average particle size refers to the diameter of the rubber particles, including all the aromatic vinyl polymer occlusions within the rubber particles. Average particle sizes and distributions can be measured using conventional techniques such as Coulter Counter ™ or electronic transmission mTcroscopy image analysis. Large particles are measured using a 50 μ tube. The following examples are provided to illustrate the present invention. The examples are not intended to limit the scope of the present invention and should not be so interpreted. The amounts are by weight unless otherwise indicated.

EXAMPLES EXAMPLE 1"A feed stream of styrene monomer, HX565 (a branched rubber star with a low cis content available from Bayer AG of Germany), 1000 ppm of zinc stearate and 1200 ppm of Irganox 1076 was polymerized according to the procedure described in EP-0096447. The resin was compression molded in order to obtain the physical properties listed below. ~ Comparative Example 1 is the same as Example 1, except that the rubber is a polybutadiene rubber.

Example 1 Comparative % Total Rubber 10 10% rubber as large particles with 6 6 base in total rubber content Small particle size (μ) 0.8 0.8 Large particle size (μ) 3 3 Impact Izod cm kg / cm 12.53 9.81 Impact Gadner kg.m 19.87 17.39 Gadner brightness 60 degrees (%) 93 92 Gadner brightness 20 degrees (%) 60 45 The Izod impact was measured in accordance with ASTM D-256. The Gadner impact was measured in accordance with ASTM D-3029 and Gadner brightness measurements were obtained in accordance with ASTM D 791.

-The greater the difference between the brightness of 60m degrees and the brightness of 20 degrees, the more sensitive to brightness is the material The Example of the present invention has better impact properties and is less sensitive to brightness than the Comparative Example

Claims

CLAIMS 1. An aromatic modified rubber monovinylidene polymer having a bimodal particle size distribution, comprising: a) rubber star or branched rubber particles having a viscosity in solution (5% in styrene) at 20 ° C) from 20 to 120 centipoise and a Mooney viscosity (ML + 1 at 100 ° C) from 30 to 80 centipoise, a volume average particle size of 0.1 to 2 μ, a content - occlusion of average monovinylidene aromatic polymer to rubber of 3.1 ^ to 6, and a cell or core shell morphology or mixture thereof, and b) rubber particles of a low density star or branched rubber, rubber linear diene or block copolymer rubber having a solution viscosity (5% in styrene at 20 ° C) of 20 to 120 centipoise and a Mooney L viscosity (ML + 1 at 100 ° C) of 30 to 80 centipoise, one size particle average in volume from 0.5 to 10 μ, characterized in that the rubber particles of b) are denser than the rubber particles of a), having an occlusion content of monovinylidene aromatic polymer to rubber of 0.5 to 3, wherein the particles of a) are from 50 to 99% by weight of the total content of diene rubber 2. The composition according to claim 1, wherein the rubber of a) is a butadiene homopolymer. 3. The composition according to claim 1, wherein the rubber of b) is a butadiene homopolymer. 4. The composition according to claim 1, wherein the polymer in a HIPS polymer and the rubber particles of a) are from 0.2 to 1.5 μ 5. The composition according to claim 4, in where the rubber particles of a) are from 0.2 to 1.4 [mu] 6. The composition according to claim 5, wherein the rubber particles of a) are from 0.3 to 1.4 [mu] 7.- The composition according to with claim 5, wherein the polymer is a HIPS polymer and the rubber particles of b) are "1.0 to 8 μ. 8. The composition according to claim 7, wherein the rubber particles of b) are from 1.2 to 7 μ. f9.- The composition according to claim 8, wherein the rubber particles of b) are from 1.3 to 6 μ. J10.- The composition according to claim 1, wherein the polymer is a polymer of ABS and the rubber particles of a) are from 0 2 to 1 μ. 11. The composition according to claim 10, wherein the rubber particles of a) are from 0.3 to 1 μ. 12. The composition according to claim 11, wherein the rubber particles of a) are from 0.4 to 0.9 μ. 13. - The composition according to claim 12, wherein the rubber particles of a) are from 0.4 to 0.8 μ. 14. The composition according to claim 1, wherein the polymer is a polymer of ABS and the rubber particles of b) are from 0.8 to 10 μ. 15. The composition according to claim 14, wherein the rubber particles of b) are from 0.9 to 6 μ. 16. The composition according to claim 15, wherein the rubber particles of b) are from 0.9 to 4 μ 17. The composition according to claim 16, wherein the rubber particles of b) they are from 1 to 4 μ 18. The composition according to claim 1, wherein the rubber particles of a) have a core-shell morphology. The composition according to claim 1, in where the rubber particles of a) have a cell morphology JQ.0 - The composition according to claim 1, wherein the rubber particles of a) have a mixture of core-shell and cellular morphology. process to produce the polymer of the claim 1, which comprises. jA) polimeporating a polymerization mixture (1) comprising a vinyl aromatic monomer and a star or branched low viscosity rubber, dissolved, in a first reactor, so as to produce rubber particles having a particle size average of 0.1 to 2 μ and a cell or core-shell morphology or mixture thereof and an aromatic monovinylidene to rubber polymer content, occluded, from 3.1 to 6, and are produced within a partially polymerized polymer matrix, b) mixing the product of A) with a polymerization mixture (2) comprising an aromatic vinyl monomer and a low viscosity rubber. of star or branched, dissolved, a linear diene rubber or block copolymer rubber, under conditions such that the resulting mixture has a solids content of at least 4 times the total rubber content of the mixture, and large dense particles having an average particle size in volume of 0.5 to 1_0 μ and an occlusion content of aromatic monovinylidene polymer to rubber, average, of 0.5 to 3, and 1C) further polymerizing the product of B) to produce a rubber modified aromatic monovinylidene polymer having a bimodal particle distribution. 22. The process according to claim 21, wherein the polymerization mixture (1) further comprises an initiator. J.23.- The process according to claim 22, wherein the initiator is selected from the group comprising tertiary butyl peroctoate, tertiary butyl perbenzoate and bs- (peroxybutyrate) peroxycyclohexamoate. ^ 24. The process according to claim 21, wherein the polymerization mixture (1) further comprises a chain transfer agent. -25.- The process according to claim 24, wherein the chain transferring agent is n-dodecyl mercaptan.