Multi-stage impact modifier with organophosphorus in the later stages

Abstract

A multi-stage polymer composition is provided, comprising (a) an early stage polymer and (b) a late stage polymer, the late stage polymer comprising polymerized units derived from at least one alkyl (meth)acrylate monomer, a styrene monomer, and at least one organophosphorus monomer. The at least one organophosphorus monomer is in acid form as a salt of a phosphoric acid group. The weight ratio of the at least one alkyl (meth)acrylate monomer to the styrene monomer in the late stage polymer ranges from 50:50 to 90:10. Also provided are matrix resin compositions and methods for making the multi-stage polymer compositions, comprising such polymer compositions and a matrix resin.

Description

[Technical field]

[0001] The present invention relates generally to a multi-stage polymer composition useful as an impact modifier, the composition containing polymerized organophosphorus monomers in the late stage polymer. [Background technology]

[0002] In manufacturing products, it is generally desired to achieve ease of manufacturing as well as light weight, i.e., reduction in the weight of the product. Both of these objectives are achieved through the use of plastics relative to the use of metals or ceramics. Meanwhile, it is generally desired that the manufactured article have low to no flammability, which is provided by the use of metals or ceramics and generally not provided by the use of plastics.

[0003] Recently, plastic formulations with improved (i.e. lower) levels of flammability have been developed. Typically, these formulations contain high levels of flame retardant additives in addition to drip-proof additives. These formulations can achieve certain standards specified by UL (Underwriter Laboratories), allowing their use in the manufacture of electrical articles as well as articles for use under the hood of automobiles.

[0004] These plastic formulations generally have a requirement for substantial impact strength in use. However, the additives used to achieve lower flammability typically reduce the impact strength of the molded product. It is very common to add core-shell polymer impact modifiers to these formulations to achieve the required level of impact strength. However, the polymers used to make these core-shell impact modifiers are highly flammable and increase the flammability of the formulation in direct correlation with the amount utilized in the formulation. Therefore, there is a problem in the field of plastic formulations to achieve the appropriate balance between impact strength and flammability.

[0005] U.S. Patent No. 5,219,907 discloses the use of core-shell emulsion polymers containing phosphate monomers as part of the shell, which can be used in polycarbonate formulations. The phosphate monomers are C1-C8 alkyl or unsubstituted or substituted C6-C alkyl groups containing no halogen on the phosphate group. 20 Aryl substituents are required. Impact modifiers should be used at 5-40% in the polycarbonate formulation.

[0006] EP 0663410 discloses the use of high concentrations of phosphorus monomers located in the shell to provide improved flammability. The phosphorus monomer requires an alkyl or aryl substituent on the phosphate group. The phosphorus monomer is present in an amount ranging from 15 to 25 weight percent, based on the total weight of the final polymer.

[0007] US Patent No. 6,710,161 discloses acrylic polymers prepared with phosphoethyl methacrylate (PEM). However, a pH of less than 2 is required to copolymerize PEM with the acrylic polymer. At higher pH, the PEM is in a neutralized form that is too water soluble and ends up as homopoly PEM in the serum phase, which may lead to coagulation or flocculation of the latex.

[0008] US Patent No. 9,346,970 discloses vinyl acetate polymers and copolymers with butyl acrylate prepared with PEM in conventional emulsion polymerization. Vinyl acetate hydrolyzes rapidly at low pH and cannot be polymerized according to the conditions required in US Patent No. 6,710,161. Vinyl acetate was successfully incorporated into the backbone polymer at pHs ranging from 5 to 7 without producing homopolyPEM in serum. The unique behavior of vinyl acetate is believed to be due to its high water solubility and very different vinyl copolymer reactivity ratios with butyl acrylate and PEM.

[0009] Therefore, there is a need to develop new processes and impact modifier polymer compositions that do not suffer from the shortcomings of the prior art, namely, the use of alkyl or aryl substituted phosphate monomers or the use of highly acidic conditions. Summary of the Invention

[0010] One aspect of the invention provides a multi-stage polymer composition comprising (a) an early stage polymer and (b) a late stage polymer. The late stage polymer comprises polymerized units derived from at least one alkyl (meth)acrylate monomer, a styrene monomer, and at least one organophosphorus monomer. The at least one organophosphorus monomer is in the acid form or as a salt of a phosphoric acid group.

[0011] In another aspect, the invention provides a matrix resin composition comprising: (A) a multi-stage polymer composition comprising (i) an early stage polymer and (ii) a late stage polymer; and (B) one or more matrix resins. The late stage polymer comprises polymerized units derived from at least one alkyl (meth)acrylate monomer, a styrene monomer, and at least one organophosphorus monomer. The at least one organophosphorus monomer is in the acid form or as a salt of a phosphoric acid group.

[0012] In yet another aspect, the invention provides a process for preparing a multi-stage polymer composition comprising emulsion polymerizing a later stage polymer in the presence of an early stage polymer, where emulsion polymerizing the later stage polymer comprises polymerizing a reaction mixture comprising at least one alkyl (meth)acrylate monomer, a styrene monomer, and at least one organophosphorus monomer at a pH of at least 4, where the at least one organophosphorus monomer is in the acid form or as a salt of a phosphoric acid group. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The inventors have surprisingly found that organophosphorus monomers, in acid form or as salts of phosphate groups, can be incorporated into later stages of multi-stage polymers at higher pH than previously thought possible. This result is surprising since it has been traditionally understood that highly acidic conditions are required to incorporate such monomers. The inventors have observed that the multi-stage polymer compositions of the present invention have improved stability at higher pH conditions. The incorporation of organophosphorus monomers is expected to provide significantly improved flammability.

[0014] As used herein, the term "polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. The general term "polymer" includes the terms "homopolymer," "copolymer," "terpolymer," and "resin." As used herein, the term "polymerized units derived from" refers to a polymer molecule synthesized according to a polymerization technique in which the product polymer contains "polymerized units derived from" the constituent monomers that are the starting materials for the polymerization reaction. As used herein, the term "(meth)acrylate" refers to either acrylate or methacrylate or combinations thereof, and the term "(meth)acrylic" refers to either acrylic or methacrylic or combinations thereof. As used herein, the term "substituted" refers to having at least one attached chemical group, such as an alkyl group, an alkenyl group, a vinyl group, a hydroxyl group, a carboxylic acid group, other functional groups, and combinations thereof.

[0015] As used herein, the term "organophosphorus" refers to an organic compound that contains phosphorus. As used herein, the term "phosphate" refers to an anion composed of phosphorus and oxygen atoms. Orthophosphate (PO4 -3 ), polyphosphate (P n O 3n+1 -(n+2) , where n is 2 or more), and metaphosphates (of formula P m O3m -m where m is 2 or greater). As used herein, "alkali phosphate" refers to a salt of an alkali metal cation and a phosphate anion. Alkaline phosphates include alkali metal orthophosphates, alkali metal polyphosphates, and alkali metal metaphosphates. Alkaline phosphates also include partially neutralized salts of phosphate acids, including, for example, partially neutralized salts of orthophosphate acids, such as, for example, monosodium dihydrogen phosphate and disodium hydrogen phosphate.

[0016] As used herein, the term "multi-stage polymer" refers to a polymer made by forming (i.e., polymerizing) multiple polymers in a stepwise or stepwise manner. A multi-stage polymer may include two or more stages. For example, a multi-stage polymer may include two stages, including a first stage and a second stage formed on the first stage. Alternatively, a multi-stage polymer may include a first stage, one or more intermediate stages, and then a final stage, with the final stage forming the outermost layer of the multi-stage polymer. A first polymer, referred to as the "first stage polymer" or "initial stage polymer," may form the core of the multi-stage polymer. An additional polymer, referred to as a "later stage," which may be an intermediate or final stage of the multi-stage polymer, is then formed on the initial stage polymer in the presence of the initial stage polymer. A multi-stage polymer may include additional stages, which may be formed before or after the later stage polymer. Each intermediate stage is formed in the presence of a polymer resulting from polymerization of the stage immediately preceding the intermediate stage. In such embodiments, where each subsequent stage forms a partial or complete shell around each of the particles remaining from the previous stage, the resulting multi-stage polymer is known as a "core / shell" polymer, where the initial stage polymer comprises the core and each subsequent stage comprises a shell on the preceding stage with the final stage forming the outermost shell. Thus, the later stage polymers constitute at least a portion of the shell in the core / shell multi-stage polymer.

[0017] As used herein, "weight average molecular weight" or "M wThe term "weight of polymer" refers to the weight average molecular weight of the polymer as measured by gel permeation chromatography (GPC) for acrylic acid polymers against polystyrene calibration standards according to ASTM D5296-11 (2011) and using tetrahydrofuran (THF) as the mobile phase and diluent. As used herein, the term "weight of polymer" refers to the dry weight of the polymer.

[0018] As used herein, "glass transition temperature" or "T g The term "temperature at or above which a glassy polymer undergoes segmental motion of the polymer chains. The glass transition temperature of a copolymer can be estimated by the Fox equation (Bulletin of the American Physical Society, 1(3) p. 123 (1956)) as follows: 1 / T g =w1 / T g(1) +w2 / T g(2) For copolymers, w1 and w2 refer to the weight fractions of the two comonomers, and T g(1) and T g(2) refers to the glass transition temperature of the two corresponding homopolymers made from a monomer. For polymers containing three or more monomers, additional terms are added (w n / T g(n) The glass transition temperatures of homopolymers can be found, for example, in "Polymer Handbook" edited by J. Brandrup and E.H. Immergut (Interscience Publishers). g can also be measured by a variety of techniques, including, for example, differential scanning calorimetry (DSC). As used herein, "calculated T gThe phrase "glass transition temperature" is intended to mean the glass transition temperature as calculated by the Fox equation. g When two or more T g can be observed. T observed in one stage of a multistage polymer g is a characteristic of the polymer that forms the rung, T g (i.e., the T observed when the polymer forming that stage is formed and measured separately from the other stages. g ) can be the same as the monomer T g When a homopolymer made from that monomer is said to have that T g It means having

[0019] A compound is considered herein to be "water-soluble" if the amount of the compound that can be dissolved in water at 20°C is 5 g or more per 100 ml of water. A compound is considered herein to be "water-insoluble" if the amount of the compound that can be dissolved in water at 20°C is 0.5 g or less per 100 ml of water. A compound is considered herein to be "partially water-soluble" if the amount of the compound that can be dissolved in water at 20°C is 0.5 g to 5 g per 100 ml of water.

[0020] As used herein, when a polymeric composition is described as having "little or no part of a particular substance," it means that the polymeric composition does not contain any of that substance, or, if any of that substance is present in the composition, the amount of that substance is 1% by weight or less, based on the weight of the polymeric composition. Among embodiments described herein as having "little or no part" of a particular substance, embodiments are contemplated in which none of the particular substance is present.

[0021] The multi-stage polymers of the present invention contain late stage polymers that contain polymerized units derived from at least one organophosphorus monomer. As used herein, the term "organophosphorus monomer" refers to a phosphorus-containing monomer. The organophosphorus monomer may be in the acid form or as a salt of a phosphoric acid group. Examples of organophosphorus monomers include:

[0022] [ka] wherein R is an organic group containing an acryloxy, methacryloxy, or vinyl group, and R' and R'' are independently selected from H and a second organic group. The second organic group can be saturated or unsaturated. Suitable organophosphorus monomers include dihydrogen phosphate functional monomers, such as dihydrogen phosphate esters of alcohols which also contain polymerizable vinyl or olefinic groups, such as allyl phosphate, mono- or diphosphates of bis(hydroxy-methyl)fumarates or itaconates, derivatives of (meth)acrylic acid esters, such as phosphates of hydroxyalkyl (meth)acrylates, including 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and the like.

[0023] Other suitable organophosphorus monomers include CH2=C(R)-C(O)-O-(R'O) n -P(O)(OH)2 (where R=H or -CH3, R'=alkyl, and n=1-5), such as methacrylates SIPOMER™ PAM-100, SIPOMER™ PAM-200, SIPOMER™ PAM-400, SIPOMER™ PAM-600 and acrylates, such as SIPOMER™ PAM-300, available from Solvay.

[0024] Other suitable organophosphorus monomers are the phosphonate functional monomers disclosed in WO 99 / 25780 A1, including vinyl phosphonic acid, allyl phosphonic acid, 2-acrylamido-2-methylpropane phosphonic acid, α-phosphonostyrene, 2-methylacrylamido-2-methylpropane phosphonic acid. Further suitable organophosphorus monomers are the 1,2-ethylenically unsaturated (hydroxy)phosphinyl alkyl (meth)acrylate monomers disclosed in U.S. Pat. No. 4,733,005, including (hydroxy)phosphinyl methyl methacrylate.

[0025] Preferably, the organophosphorus monomer has the formula CH2=C(R)-C(O)-O-(R'O) n More preferably, R is -CH3, R' is an alkyl group containing 1 to 6 carbon atoms, and n=1.

[0026] The late stage polymer may contain polymerized units derived from at least one organophosphorus monomer in an amount of 0.25 wt% or more, or 0.5 wt% or more, based on the total weight of the late stage polymer. The late stage polymer may contain polymerized units derived from at least one organophosphorus monomer in an amount of 20 wt% or less, 15 wt% or less, or 10 wt% or less, based on the total weight of the late stage polymer. Preferably, the late stage polymer contains polymerized units derived from at least one organophosphorus monomer in an amount ranging from 0.5 to 20 wt%, based on the total weight of the late stage polymer. More preferably, the late stage contains polymerized units derived from at least one organophosphorus monomer in an amount ranging from 2 to 10 wt%, based on the total weight of the late stage polymer.

[0027] The later stage polymer further comprises polymerized units derived from one or more substituted or unsubstituted styrene and one or more substituted or unsubstituted alkyl (meth)acrylate monomers.

[0028] Suitable alkyl groups in the at least one alkyl (meth)acrylate monomer include linear or branched C1-C12 The alkyl group may include methyl, ethyl, propyl, butyl, hexyl, 2-ethylhexyl, and octyl groups. Preferably, the alkyl (meth)acrylate monomer comprises methyl methacrylate.

[0029] Suitable substituted styrenes include, for example, alpha-alkylstyrenes (eg, alpha-methylstyrene).

[0030] Preferably, the weight ratio of the at least one alkyl (meth)acrylate in the later stage polymer to styrene ranges from 5:95 to 95:5. For example, the weight ratio of the at least one alkyl (meth)acrylate in the later stage polymer to styrene can be at least 10:90, at least 20:80, at least 30:70, at least 40:60, or at least 50:50, and the weight ratio of the at least one alkyl (meth)acrylate in the later stage polymer to styrene can be up to 90:10, up to 80:20, or up to 70:30.

[0031] The later stage polymers have a T of 50°C or higher or 90°C or higher. g The late stage polymer may have a T of 200° C. or less, or 150° C. or less. g may have:

[0032] The multi-stage polymer may contain the late stage polymer in an amount of, for example, 2% by weight or more, or 10% by weight or more, or 20% by weight or more, based on the total weight of the multi-stage polymer. The multi-stage polymer may contain the late stage polymer in an amount of, for example, 50% by weight or less, or 25% by weight or less, or 10% by weight or less, based on the total weight of the multi-stage polymer.

[0033] Preferably, the late stage polymer has a T of 50° C. or greater in an amount of 50 wt. % or greater, or 75 wt. % or greater, or 90 wt. % or greater, based on the total weight of the late stage polymer. g The monomer comprises polymerized units derived from a monomer having the formula:

[0034] Preferably, the late stage polymer is the final stage polymer of a multi-stage polymer.

[0035] The multi-stage polymer may contain the initial stage polymer in an amount of, for example, 10% by weight or more, or 20% by weight or more, or 50% by weight or more, based on the total weight of the multi-stage polymer. The multi-stage polymer may contain the initial stage polymer in an amount of 98% by weight or less, or 95% by weight or less, or 90% by weight or less, based on the total weight of the multi-stage polymer.

[0036] The initial stage of the multi-stage polymer may contain polymerized units derived from one or more multifunctional monomers. Multifunctional monomers contain two or more functional groups capable of participating in a polymerization reaction. Suitable multifunctional monomers include, for example, divinylbenzene, allyl methacrylate, ethylene glycol methacrylate, and 1,3-butylene dimethacrylate. If present, the initial stage may contain polymerized units derived from multifunctional monomers in an amount of 0.01 wt% or more, or 0.03 wt% or more, or 0.1 wt% or more, based on the weight of the total weight of the initial stage polymer. If present, the initial stage may contain polymerized units derived from multifunctional monomers in an amount of 5 wt% or less, or 2 wt% or less, based on the weight of the total weight of the initial stage polymer.

[0037] The initial stage of the multi-stage polymer may contain polymerized units derived from one or more diene monomers. Suitable diene monomers include, for example, butadiene and isoprene. The initial stage may contain polymerized units derived from diene monomers in an amount of 2 wt% or more, or 5 wt% or more, or 10 wt% or more, or 20 wt% or more, or 50 wt% or more, or 75 wt% or more, based on the total weight of the initial stage polymer. The initial stage contains polymerized units derived from diene monomers in an amount of 100 wt% or less, or 98 wt% or less, or 90 wt% or less, based on the total weight of the initial stage polymer.

[0038] The initial stage polymer of the multi-stage polymer may contain polymerized units derived from one or more of styrene, substituted styrene, or mixtures thereof. The initial stage polymer may contain polymerized units derived from one or more of styrene and substituted styrene in an amount of 1 wt% or more, or 2 wt% or more, or 5 wt% or more, or 10 wt% or more, based on the total weight of the initial stage polymer. The initial stage polymer may contain polymerized units derived from one or more of styrene and substituted styrene in an amount of 80 wt% or less, or 50 wt% or less, or 25 wt% or less, or 10 wt% or less, or 5 wt% or less, based on the total weight of the initial stage polymer.

[0039] The initial stage polymer of the multi-stage polymer may contain polymerized units derived from an acid functional monomer. An acid functional monomer is a monomer having an acid group, such as a sulfonic acid group or a carboxylic acid group. Suitable acid functional monomers include, for example, acrylic acid and methacrylic acid. The initial stage polymer may contain polymerized units derived from one or more acid functional monomers in an amount of 3% by weight or less, or 2% by weight or less, or 1% by weight or less, or 0.5% by weight or less, based on the total weight of the initial stage polymer.

[0040] The early stage polymers of the multi-stage polymer may further include phosphorus-organic derived polymerized units as described above for the later stage polymers. Without wishing to be bound by theory, it is believed that flammability may be further improved by incorporating organophosphorus monomers in both the early and later stage polymers.

[0041] When present, the initial stage polymer may contain polymerized units derived from at least one organophosphorus monomer in an amount of 0.25% by weight or more, or 0.5% by weight or more, based on the total weight of the initial stage polymer. The initial stage polymer may contain polymerized units derived from at least one organophosphorus monomer in an amount of 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less, based on the total weight of the initial stage polymer.

[0042] Preferably, the initial stage polymer comprises butadiene, more preferably crosslinked butadiene.

[0043] The weight ratio of early stage polymer to later stage polymer can be in the range of, for example, 0.1:1 or more, or 0.2:1 or more, or 0.4:1 or more, or 1:1 or more, or 1.5:1 or more, or 3:1 or more, or 4:1 or more. The weight ratio of early stage polymer to later stage polymer can be in the range of, for example, 50:1 or less, or 25:1 or less, or 20:1 or less.

[0044] A multi-stage polymer may contain one or more intermediate stage polymers. The total of the intermediate stage polymers may be present in an amount of 1 weight percent or more, or 2 weight percent or more, or 5 weight percent or more, or 10 weight percent or more, based on the total weight of the multi-stage polymer. The total of the intermediate stage polymers may be present in an amount of 60 weight percent or less, or 2 weight percent or less, or 5 weight percent or less, or 10 weight percent or less, based on the total weight of the multi-stage polymer. As with the later stage polymers in a multi-stage polymer, one or more intermediate stage polymers may also contain polymerized units derived from one or more organophosphorus monomers.

[0045] The multi-stage polymers are made by aqueous emulsion polymerization. In aqueous emulsion polymerization, water forms the continuous medium in which polymerization occurs. The water may or may not be mixed with one or more additional compounds that are miscible with or dissolved in water. The continuous medium may contain 30% or more water by weight, or 50% or more water by weight, or 75% or more water by weight, or 90% or more water by weight, based on the weight of the continuous medium.

[0046] Emulsion polymerization involves the presence of one or more initiators. An initiator is a compound that forms one or more free radicals that can start the polymerization process. The initiator is usually water-soluble. Some suitable initiators form one or more free radicals when heated. Some suitable initiators are oxidizing agents that form one or more free radicals when mixed with one or more reducing agents, or when heated, or combinations thereof. Some suitable initiators form one or more free radicals when exposed to radiation, such as, for example, ultraviolet light or an electron beam. Combinations of suitable initiators are also suitable.

[0047] Preferably, the multi-stage polymer is made by emulsion polymerization to form a latex. As used herein, the term "latex" refers to the physical form of the polymer in which the polymer exists in the form of small polymer particles dispersed in water. The latex may have, for example, an average particle size of 50 nm or more, or 100 nm or more. The latex may have an average particle size of 1,000 nm or less, or 800 nm or less, or 600 nm or less.

[0048] The emulsion polymerization may involve the use of at least one organophosphorus soap, including an anionic phosphate surfactant. Each anionic phosphate surfactant has a cation associated therewith, forming, for example, an alkali metal salt of the phosphate surfactant, including alkyl phosphate salts and alkylaryl phosphate salts. Suitable cations include, for example, ammonium, alkali metal cations, and mixtures thereof. Suitable alkali metal salts of phosphate surfactants include, for example, polyoxyalkylene alkyl phenyl ether phosphate salts, polyoxyalkylene alkyl ether phosphate salts, polyoxyethylene alkyl phenyl ether phosphate salts, and polyoxyethylene alkyl ether phosphate salts. The alkali metal salts of the phosphate surfactant may include polyoxyethylene alkyl ether phosphate salts. The weight of the phosphate surfactant present during the emulsion polymerization of the multi-stage polymer may range from 0.5% by weight or more, preferably 1.0% by weight or more, and more preferably 1.5% by weight or more, characterized by the weight of the phosphate surfactant based on the total monomer weight added to the polymerization. The weight of the phosphate surfactant present during the emulsion polymerization of the multi-stage polymer can be in the range of 5% by weight or less, preferably 4% by weight or less, more preferably 3% by weight or less, characterized by the weight of the phosphate surfactant based on the total monomer weight added to the polymerization.In addition to the anionic phosphate surfactant described above, one or more anionic surfactants can be utilized in the emulsion polymerization.Suitable additional anionic surfactants include, for example, carboxylates, sulfosuccinates, sulfonates, and sulfates.

[0049] In the process of the present invention, the multi-stage polymer latex can be isolated by coagulation or spray drying to retain the organophosphorus soap on the surface of the multi-stage polymer. Suitable coagulation methods include, for example, coagulation with divalent cations.

[0050] Suitable divalent cations include, for example, divalent metal cations and alkaline earth cations. Suitable divalent cations include, for example, calcium(+2), cobalt(+2), copper(+2), iron(+2), magnesium(+2), zinc(+2), and mixtures thereof. Preferably, the multivalent cation is selected from calcium(+2) and magnesium(+2). More preferably, any divalent cation present is calcium(+2), or magnesium(+2), or mixtures thereof. Even more preferably, the divalent cation comprises calcium(+2). The divalent cation may be present in an amount of 10 ppm or more, or 30 ppm or more, or 100 ppm or more, based on the dry weight of the multistage polymer. The divalent cation may be present in an amount of 3 wt % or less, or 1 wt % or less, or 0.3 wt % or less, based on the dry weight of the multistage polymer.

[0051] Preferably, most or all of the divalent cations present in the composition are in the form of water-insoluble phosphate salts. The molar amount of polyvalent cations present in the form of water-insoluble phosphate salts can be 80% or more, or 90% or more, or 95% or more, or 98% or more, or 100%, based on the total moles of divalent cations present in the composition.

[0052] Preferably, most or all of the water remaining with the isolated polymer is removed from the isolated polymer by one or more of the following operations: filtration (including, for example, vacuum filtration) and / or centrifugation. The isolated polymer may optionally be washed with water one or more times. It is known that coagulated polymers are complex structures and water cannot easily contact every part of the coagulated polymer. Without wishing to be bound by theory, it is contemplated that significant amounts of divalent cations and residual organophosphorus soaps are left behind. Thus, the compositions of the present invention may contain organophosphorus soaps in an amount of 50 ppm or more, or 100 ppm or more, or 500 ppm or more, based on the dry weight of the multistage polymer. The compositions of the present invention may contain organophosphorus soaps in an amount of 10,000 ppm or less, or 7,500 ppm or less, or 5,000 ppm or less, based on the dry weight of the multistage polymer.

[0053] Preferably, the dried multi-stage polymer has a moisture content of less than 1.0 weight percent, based on the weight of the dried multi-stage polymer.

[0054] The polymer composition of the present invention may also contain a flow aid. The flow aid is a hard material in the form of a powder (average particle size 1 micrometer to 1 mm). Suitable flow aids are, for example, hard polymers (i.e., those with a T of 80° C. or higher). g The polymer may be a polymer having a structure similar to that of the compound having the formula (I) or a mineral (e.g., silica).

[0055] The polymer composition of the present invention may also include a stabilizer. Suitable stabilizers include, for example, radical scavengers, peroxide decomposers, and metal deactivators. Suitable radical scavengers include, for example, hindered phenols (e.g., those having a tertiary butyl group attached to each carbon atom of the aromatic ring adjacent to the carbon atom to which a hydroxyl group is attached), secondary aromatic amines, hindered amines, hydroxylamines, and benzofuranones. Suitable peroxide decomposers include, for example, organic sulfides (e.g., divalent sulfur compounds, e.g., esters of thiopropionic acid), esters of phosphorous acid (H3PO3), and hydroxylamines. Suitable metal deactivators include, for example, chelating agents (e.g., ethylenediaminetetraacetic acid).

[0056] As noted above, one aspect of the present invention utilizes the polymer composition described herein as an impact modifier in a matrix resin composition containing a multi-stage polymer composition and a matrix resin. After mixing, melting, and forming the mixture of multi-stage polymer and matrix resin into a solid article, the impact resistance of the article will be better than the same solid article made with a matrix resin that is not mixed with the multi-stage polymer. The multi-stage polymer may be provided in a solid form, such as pellets, or powder, or a mixture thereof. The matrix resin may also be provided in a solid form, such as pellets, or powder, or a mixture thereof. The solid multi-stage polymer may be mixed with the solid matrix resin at room temperature (20° C.) or at elevated temperatures (e.g., 30° C. to 90° C.). Alternatively, the solid multi-stage polymer may be mixed with the molten matrix resin, for example, in an extruder or other melt mixer. The solid multi-stage polymer may also be mixed with a solid matrix resin, the solid mixture may then be heated sufficiently to melt the matrix resin, and the mixture may be further mixed, for example, in an extruder or other melt processing device.

[0057] The weight ratio of matrix resin to the multi-stage polymer of the present invention can be in the range of, for example, 1:1 or more, or 1.1:1 or more, or 2.3:1 or more, or 4:1 or more, or 9:1 or more, or 19:1 or more, or 49:1 or more, or 99:1 or more.

[0058] Suitable matrix resins include, for example, polyolefins, polystyrene, styrene copolymers, poly(vinyl chloride), poly(vinyl acetate), acrylic polymers, polyethers, polyesters, polycarbonates, polyurethanes, and polyamides. Preferably, the matrix resin contains at least one polycarbonate. Suitable polycarbonates also include, for example, homopolymers of polymerized units derived from bisphenol A ("Bisphenol A, BPA"), and copolymers that include polymerized units of BPA together with one or more other polymerized units.

[0059] The matrix resin may include at least one polyester. Suitable polyesters include, for example, polyethylene terephthalate and polybutylene terephthalate.

[0060] The matrix resin may comprise a blend of polymers. Suitable blends of polymers include, for example, blends of polycarbonate and styrene resins, and blends of polycarbonate and polyester. Suitable styrene resins include, for example, polystyrene and copolymers of styrene with other monomers, such as acrylonitrile / butadiene / styrene (ABS) resins.

[0061] The matrix resin composition containing the multi-stage polymer and the matrix resin may contain one or more additional materials added to the mixture. Any one or more of such additional materials may be added to the multi-stage polymer or the matrix resin before forming a final mixture of all materials. When the matrix resin is in a solid or molten form, each of the additional materials (if used) may be added to the matrix resin (either alone or in combination with each other and / or in combination with the multi-stage polymer). Suitable additional materials include, for example, dyes, colorants, pigments, carbon black, fillers, fibers, lubricants (e.g., montan wax), flame retardants (e.g., borates, antimony trioxide, or molybdates), and other impact modifiers that are not the multi-stage polymers of the present invention.

[0062] The matrix resin composition can be used to form useful articles, for example, by film blowing, profile extrusion, molding, other methods, or combinations thereof. Molding methods include, for example, blow molding, injection molding, compression molding, other molding methods, and combinations thereof.

[0063] The multi-stage polymers of the present invention can provide significant improvements in the flammability of matrix resin compositions.

[0064] Some embodiments of the present invention are described in detail in the following examples. EXAMPLES

[0065] Particle size measurement The particle size of the oligomers was measured with a Malvern Zetasizer Nano S90 particle size analyzer.

[0066] Synthesis of core-shell polymers Preparation of polybutadiene initial stage emulsions. A stainless steel autoclave equipped with an agitator and several inlet ports was charged with 6300 parts deionized water, 170 parts 60 nm polymer preform, and 4 parts potassium oleate. After evacuating the reactor, 3200 parts butadiene, 4 parts divinylbenzene, 37 parts diisopropylbenzene hydroperoxide, 11 parts sodium formaldehyde sulfoxylate, and 30 parts additional potassium oleate were added and the mixture was allowed to react at 65° C. until the pressure no longer decreased. The reaction vessel was then evacuated to remove any remaining volatile materials. The final emulsion had a solids content of 32%.

[0067] Preparation of core-shell polymer emulsion EX1 To 1000 parts of the polybutadiene emulsion having a solids content of 32% prepared above, 144 parts of deionized water were added and the mixture was heated to 60° C. At 60° C., over 1 hour, 2.1 parts of Rhodafac® RS-610, 2.41 parts of sodium formaldehyde sulfoxylate (5% aqueous solution), and 1.69 parts of tert-butyl hydroperoxide (5% aqueous solution), followed by a monomer mixture of 84 parts of methyl methacrylate, 31.2 parts of styrene, and 4.3 parts of PAM600. Simultaneously with the start of the monomer mixture feed, 12 parts of sodium formaldehyde sulfoxylate (5% aqueous solution) and 8.45 parts of tert-butyl hydroperoxide (5% aqueous solution) were fed over 240 minutes while maintaining the reaction temperature at 60° C. After all feeds were completed, 11.29 parts of Rhodafac® RS-610 was added. The reaction mixture was then cooled to room temperature and determined to have a solids content of 33.6%.

[0068] Polymer Emulsion Coagulation Procedure Antioxidant Emulsion Preparation To a 100 ml plastic container was added 6.3 g of potassium oleate, 3.4 g of BNX® DLTDP, 3.4 g of butylated hydroxytoluene, 0.8 g of Irganox 245, and 23.3 g of deionized water. The mixture was heated to 60° C. and homogenized at 10,000 rpm for 10 minutes.

[0069] Emulsion coagulation preparation To a 1 liter bottle, 804g of emulsion was added and diluted with 96g of deionized water. The mixture was heated to 58°C in a water bath. Once the emulsion was >50°C, 31.7g of the antioxidant emulsion listed above was added and mixed thoroughly. The emulsion was stored at 58°C until ready to set.

[0070] coagulation To a 4 liter beaker, 3.6 g of calcium chloride powder and 1796.4 g of deionized water were added. The contents of the beaker were heated to 58°C while stirring at 350 rpm. When the contents reached 58°C, the above preheated emulsion was slowly added to the beaker over 45-60 seconds. This caused the mixture to phase separate into an aqueous phase and a solid polymer phase. 72 g of 10% aqueous calcium chloride solution was added to complete the coagulation. The mixture was then heated to 90°C and held at 90°C for 30 minutes. After holding, the mixture was cooled, dehydrated, and washed in a Büchner funnel. The sample was washed with deionized water until the conductivity of the filtrate was below 30 μS / m, and then dehydrated. The sample was dried overnight in a vacuum oven at 65°C. The particle size of the powder was measured with a Malvern Mastersizer 2000.

[0071] compound The polycarbonate formulations according to Table 1 were compounded in an extruder to make pellets for injection molding.

[0072] [Table 1] PC Lexan 141: Polycarbonate from SABIC MBS: FR MBS powder of the present invention or M732 powder of the comparative example FR-2025a: 100% potassium perfluorobutanesulfonate from 3M INP449: A blend of 50% polytetrafluoroethylene and 50% SAN manufactured by SABIC IRGANOX® 1076 and IRGANOX® 168: antioxidants from BASF

[0073] The polycarbonate formulations were injection molded to form double end gated 1.0 mm ASTM burn bars for flammability testing using the UL 94 flammability test method.

[0074] Comparative Example Methyl butadiene styrene (MBS) core-shell rubber impact modifiers were prepared according to the process described above, except that the composition of the MBS impact modifier had the formula shown in Table 2. Comparative example results are shown in Table 2 below. As seen in Table 2, both comparative examples CE1 and CE2 coagulated during the later stage (shell) polymerization. Phosphoethyl methacrylate was believed to have homopolymerized in serum in accordance with the teachings of U.S. Patent No. 6,710,161. This result was consistent with the severe colloidal stability issues observed in the art when phosphoethyl methacrylate polymerization is carried out at neutral to high pH.

[0075] [Table 2]

[0076] Examples of the present invention Methylbutadienestyrene (MBS) core-shell rubber impact modifiers were prepared according to the process described above, and the compositions of the inventive examples are shown in Table 3 below. As shown in Table 3, the inventive examples showed excellent stability at high pH conditions and were able to successfully incorporate phosphoethyl methacrylate into the later stage (shell) polymer. The inventive examples also showed excellent flame resistance when tested under the UL-94 flammability test.

[0077] [Table 3]

Claims

1. 1. A multi-stage polymer composition comprising: (a) an initial stage polymer; (b) a later stage polymer, said later stage polymer comprising polymerized units derived from at least one alkyl (meth)acrylate monomer, a styrene monomer, and at least one organophosphorus monomer, said at least one organophosphorus monomer being in the form of an acid or as a salt of a phosphoric acid group, and wherein the weight ratio of said at least one alkyl (meth)acrylate monomer to styrene monomer in said later stage polymer is in the range of 5:95 to 95:

5.

2. 10. The polymer composition of claim 1, wherein the weight ratio of said at least one alkyl (meth)acrylate monomer to styrene monomer in said later stage polymer ranges from 10:90 to 90:

10.

3. The organophosphorus monomer is of the formula CH ２ =C(R)-C(O)-O-(R'O) ｎ -P(O)(OH) ２ where R=H or —CH ３ 2. The polymer composition of claim 1, wherein R′=alkyl and n=1-5.

4. R is -CH ３ 4. The polymer composition of claim 3, wherein R' is an alkyl group containing 1 to 6 carbon atoms.

5. 10. The polymer composition of claim 1, wherein said organophosphorus monomer is present in said late stage polymer in an amount ranging from 0.5 to 20 weight percent, based on the total weight of said late stage polymer.

6. 6. The polymer composition of claim 5, wherein said organophosphorus monomer is present in said late stage polymer in an amount ranging from 2 to 10 weight percent, based on the total weight of said late stage polymer.

7. The polymer composition of claim 1 , wherein the at least one alkyl (meth)acrylate monomer comprises methyl methacrylate.

8. The polymer composition of claim 1 , wherein the initial stage polymer comprises polymerized units derived from butadiene.

9. 10. The polymer composition of claim 1, wherein the early stage polymer comprises polymerized units derived from at least one organophosphorus monomer, and the at least one organophosphorus monomer in the early stage polymer is the same as or different from the at least one organophosphorus monomer in the later stage polymer.

10. 10. The polymer composition of claim 1, wherein said early stage polymer is present in an amount of 10 to 98 weight percent based on the total weight of said multi-stage polymer, and said late stage polymer is present in an amount of 2 to 50 weight percent based on the total weight of said multi-stage polymer.

11. A matrix resin composition comprising mixing one or more matrix resins with the multi-stage polymer composition of any one of claims 1-10.

12. 1. A process for preparing a multi-stage polymer composition comprising emulsion polymerizing a later stage polymer in the presence of an early stage polymer, wherein emulsion polymerizing said later stage polymer comprises polymerizing a reaction mixture comprising at least one alkyl (meth)acrylate monomer, a styrene monomer, and at least one organophosphorus monomer at a pH of at least 4, said at least one organophosphorus monomer being in the acid form or as a salt of a phosphoric acid group.

13. The organophosphorus monomer is of the formula CH ２ =C(R)-C(O)-O-(R'O) ｎ -P(O)(OH) ２ where R=H or —CH ３ 13. The process of claim 12, wherein R'=alkyl and n=1-5.

14. R is -CH ３ and R' is an alkyl group containing 1 to 6 carbon atoms.