Process for preparing flame-retardant acrylic powder compositions

Abstract

A process for making a multi-stage acrylic composition includes providing a multi-stage acrylic polymer latex by emulsion polymerization, the multi-stage acrylic polymer including a first stage acrylic polymer and a final stage acrylic polymer formed on or around the first stage acrylic polymer. At least one of the first stage acrylic polymer and the final stage acrylic polymer includes structural units of at least one organophosphorus monomer. The multi-stage acrylic polymer is isolated by coagulation and dried to form a powder.

Description

[Technical Field]

[0001] The present invention relates generally to a process for preparing a multi-stage acrylic polymer composition useful as an impact modifier, the composition containing an organophosphorus monomer in at least one stage of the multi-stage acrylic polymer. [Background technology]

[0002] Acrylic impact modifiers are often prepared in the form of core-shell rubber (CSR), which has a soft acrylic core coated with a harder grafted shell. Core-shell rubber acrylic impact modifiers are typically prepared by conventional emulsion polymerization and isolated into a powder.

[0003] Acrylic impact modifiers can be used in a variety of thermoplastic resins, including polycarbonate (PC).

[0004] It has long been desirable to incorporate flame-resistant moieties, molecules, or atoms into acrylic impact modifiers, however, such attempts have met with limited success due to the difficulties associated with incorporating such flame-resistant moieties, molecules, or atoms.

[0005] U.S. Patent No. 11,254,990 discloses a composition comprising an aqueous dispersion of submicron-sized particles and micron-sized polymer beads, where either the polymer particles or the beads or both are functionalized with phosphorus-containing acid groups. However, this composition is an aqueous dispersion rather than a powder.

[0006] EP 2235077(B1) discloses an aqueous composition comprising an emulsion polymer composition containing a phosphorus-containing monomer.

[0007] U.S. Pat. No. 7,820,754 discloses an aqueous polymer composition obtained from a mixture of monomers including at least one ethylenically unsaturated monomer bearing at least one second functional group selected from phosphoric acid, phosphonic acid, or phosphinic acid.

[0008] U.S. Pat. No. 7,803,858 discloses an aqueous composition containing pigment particles, particles of an acrylic polymer containing phosphoric or phosphonic groups, and at least one compound containing pyrophosphate bonds and having 12% or less carbon.

[0009] Each of these prior art attempts provides an aqueous composition rather than a powder.

[0010] It would be desirable to provide a flame retardant multi-stage acrylic composition in powder form. Summary of the Invention

[0011] The present invention provides a process for making a multi-stage acrylic composition comprising providing a multi-stage acrylic polymer latex by emulsion polymerization, wherein the multi-stage acrylic polymer composition comprises a first stage acrylic polymer and a final stage acrylic polymer formed on or around the first stage acrylic polymer. At least one of the first stage acrylic polymer and the final stage acrylic polymer comprises structural units of at least one organophosphorus monomer. The multi-stage acrylic polymer is isolated by coagulation and dried to form a powder. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graph showing total burn time after ignition for polycarbonate formulations according to embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present inventors have surprisingly found that the incorporation of an organophosphorus monomer in the final stage of a multi-stage acrylic polymer can improve the flammability of the acrylic polymer. Furthermore, the present inventors have found that the multi-stage acrylic polymer can be formed as a powder and can provide desirable impact resistance when used in resins such as polycarbonates.

[0014] As used herein, the term "polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. The generic term "polymer" includes the terms "homopolymer," "copolymer," "terpolymer," and "resin." As used herein, the term "structural unit" refers to the remnants of the listed monomers after polymerization. As used herein, the term "(meth)acrylate" refers to either acrylate or methacrylate, or a combination thereof, and the term "(meth)acrylic" refers to either acrylic or methacrylic, or a combination 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 "acrylic polymer" refers to a polymer in which more than 50% by weight of the structural units comprising the polymer comprise (meth)acrylic acid monomers or (meth)acrylate monomers. Preferably, at least 60% by weight of the structural units of the acrylic polymer are (meth)acrylic acid monomers or (meth)acrylate monomers. More preferably, at least 70% by weight of the structural units of the acrylic polymer are (meth)acrylic acid monomers or (meth)acrylate monomers. Even more preferably, at least 80% by weight of the structural units of the acrylic polymer are (meth)acrylic acid monomers or (meth)acrylate monomers. Even more preferably, at least 90% by weight of the structural units of the acrylic polymer are (meth)acrylic acid monomers or (meth)acrylate monomers.

[0016] As used herein, the term "organophosphorus" refers to an organic compound containing 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 (formula P m O 3m -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. Alkali phosphates include alkali metal orthophosphates, alkali metal polyphosphates, and alkali metal metaphosphates. Alkali 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.

[0017] As used herein, the term "multistage polymer" refers to a polymer made by forming (i.e., polymerizing) a first polymer, referred to as the "first stage" or "first stage polymer," and then forming a second polymer, referred to as the "second stage" or "second stage polymer," which may be an intermediate or final stage, in the presence of the first stage and on or around the first stage. A multistage polymer has at least a first stage and a final stage, and optional intermediate stages formed between the first and final stages. Each intermediate stage is formed in the presence of the polymer resulting from the polymerization of the stage immediately preceding it. In such embodiments, where each subsequent stage forms a partial or complete shell around each particle remaining from the previous stage, the resulting multistage polymer is known as a "core / shell" polymer, where the first stage polymer comprises the core, each subsequent stage comprises a shell on the preceding stage, and the final stage forms the outermost shell.

[0018] As used herein, "weight average molecular weight" or "Mw The 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" means the dry weight of the polymer.

[0019] As used herein, "glass transition temperature" or "T g The term "glass transition temperature" refers to the temperature 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)

[0020] 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 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 EH 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 multi-stage polymer g is a characteristic of the polymer that forms the step, T g (i.e., the T observed when the polymer forming that stage is formed and measured separately from other stages. g ) can be the same as a monomer with a specific T g When a homopolymer made from that monomer is said to have that T g It means having.

[0021] As used herein, when it is said that a "polymeric composition contains little or no 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 wt. % or less, based on the weight of the polymeric composition. Among embodiments described herein as having "little or no" a particular substance, embodiments are contemplated in which none of the particular substance is present.

[0022] The polymer composition of the present invention contains a multi-stage acrylic polymer 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.

[0023] 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. Initiators are 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 a combination thereof. Some suitable initiators form one or more free radicals when exposed to radiation, such as ultraviolet light or electron beam radiation. Combinations of suitable initiators are also suitable.

[0024] Preferably, the multi-stage acrylic polymer is made by emulsion polymerization to form a latex. The latex preferably has an average particle size of 50 nm or more, or 100 nm or more. The latex preferably has an average particle size of less than 1 micrometer, or less than 800 nm, or less than 600 nm.

[0025] The emulsion polymerization may optionally include the use of at least one organophosphorus soap containing an anionic phosphate surfactant. Each anionic phosphate surfactant has a cation associated therewith, forming an alkali metal salt of the phosphate surfactant, including, for example, 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 alkylphenyl ether phosphate salts, polyoxyalkylene alkyl ether phosphate salts, polyoxyethylene alkylphenyl ether phosphate salts, and polyoxyethylene alkyl ether phosphate salts. The alkali metal salt of the phosphate surfactant may include polyoxyethylene alkyl ether phosphate salts. The weight of the phosphate surfactant present during the emulsion polymerization of the multistage polymer, characterized by the weight of the phosphate surfactant based on the weight of the total monomers added to the polymerization, 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. When present during the emulsion polymerization of the multi-stage acrylic polymer, the weight of the phosphate surfactant, characterized by the weight of the phosphate surfactant based on the total monomer weight added to the polymerization, can be in the range of 5% by weight or less, preferably 4% by weight or less, and more preferably 3% by weight or less. 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.

[0026] The multi-stage acrylic polymer of the present invention comprises a first stage acrylic polymer and a final stage acrylic polymer formed on or around the first stage acrylic polymer, wherein at least one of the first stage acrylic polymer and the final stage acrylic polymer contains structural units of at least one organophosphorus monomer.

[0027] 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 phosphate group. Examples of organophosphorus monomers include:

[0028] [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 that also contain polymerizable vinyl or olefinic groups, such as allyl phosphate, monophosphate or diphosphate of bis(hydroxy-methyl) fumarate or itaconate, 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.

[0029] Other suitable organophosphorus monomers are CH═C(R)—C(O)—O—(R′O), such as, for example, the methacrylates SIPOMER™ PAM-100, SIPOMER™ PAM-200, SIPOMER™ PAM-400, SIPOMER™ PAM-600 and the acrylate, SIPOMER™ PAM-300, available from Solvay. n -P(O)(OH)2, where R=H or -CH3, R'=alkyl, and n=1-5.

[0030] Other suitable organophosphorus monomers are the phosphonate-functional monomers disclosed in WO 99 / 25780 A1, including vinylphosphonic acid, allylphosphonic acid, 2-acrylamido-2-methylpropanephosphonic acid, α-phosphonostyrene, 2-methylacrylamido-2-methylpropanephosphonic acid. Further suitable organophosphorus monomers are the 1,2-ethylenically unsaturated (hydroxy)phosphinylalkyl(meth)acrylate monomers disclosed in U.S. Pat. No. 4,733,005, including (hydroxy)phosphinylmethyl methacrylate.

[0031] Preferably, the organophosphorus monomer has the formula CH═C(R)—C(O)—O—(R′O) n More preferably, R is —CH 3 , R′ is an alkyl group containing 1 to 6 carbon atoms, and n=1.

[0032] At least one of the first stage acrylic polymer and the final stage acrylic polymer contains structural units of 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 acrylic polymer in that stage. At least one of the first stage acrylic polymer and the final stage acrylic polymer contains polymerized units derived from at least one organophosphorus monomer in an amount of 5 wt% or less, 4 wt% or less, 3 wt% or less, 2.5 wt% or less, or 2.0 wt% or less, based on the total weight of the acrylic polymer in that stage. Preferably, the first stage acrylic polymer, the final stage acrylic polymer, or both contain structural units of at least one organophosphorus monomer in an amount ranging from 0.25 to less than 5 wt%, based on the total weight of the acrylic polymer in the respective stage. More preferably, the first stage acrylic polymer, the final stage acrylic polymer, or both contain structural units of at least one organophosphorus monomer in an amount ranging from 0.5 to 3 wt%, based on the total weight of the acrylic polymer in the respective stage.

[0033] The first-stage acrylic polymer comprises structural units of one or more substituted or unsubstituted (meth)acrylate monomers. Preferably, the first-stage polymer comprises structural units of one or more alkyl (meth)acrylate monomers, where the alkyl of the alkyl (meth)acrylate monomer is selected from straight- and branched-chain alkyl groups having 1 to 12 carbon atoms. More preferably, the first stage comprises structural units of at least one monomer selected from butyl acrylate, ethylhexyl acrylate (e.g., 2-ethylhexyl acrylate), ethyl acrylate, methyl methacrylate, butyl methacrylate, and isooctyl acrylate. Even more preferably, the first stage comprises structural units of at least one monomer selected from butyl acrylate and ethylhexyl acrylate.

[0034] The first-stage acrylic polymer may be polymerized in the presence of a crosslinking or graft-linking monomer. Examples of crosslinking and / or graft-linking monomers useful in the first-stage acrylic polymer include, but are not limited to, butanediol diacrylate, butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, divinylbenzene, diethylene glycol diacrylate, diethylene glycol dimethacrylate, diallyl maleate, allyl methacrylate, diallyl phthalate, triallyl phthalate, and trimethylolpropane triacrylate. Preferably, the first-stage acrylic polymer contains structural units of allyl methacrylate. If present, the first-stage polymer may contain structural units of the crosslinking or graft-linking monomer in an amount of 0.1 to 10 weight percent, based on the total weight of the first-stage acrylic polymer. Preferably, the first-stage polymer contains structural units of the crosslinking or graft-linking monomer in an amount of 0.2 to 5 weight percent, based on the total weight of the first-stage acrylic polymer.

[0035] Preferably, the first stage polymer has a T of 40° C. or less, 20° C. or less, 0° C. or less, −20° C. or less, or −35° C. or less, or −50° C. or less. g The first stage polymer preferably has a Tg It has.

[0036] The multi-stage polymer may, for example, contain 70% or more, or 80% or more, or 90% or more by weight of the first stage polymer, based on the total weight of the multi-stage polymer. The multi-stage polymer may contain 98% or less, or 95% or less by weight of the first stage polymer, based on the total weight of the multi-stage polymer.

[0037] The first stage acrylic polymer may further include polymerized units derived from at least one organophosphorus monomer.

[0038] When present, polymerized units derived from at least one organophosphorus monomer in the first stage acrylic monomer may be present in an amount of 0.25 wt% or more, or 0.5 wt% or more, based on the total weight of the first stage polymer. The first stage may contain polymerized units derived from at least one organophosphorus monomer in an amount of 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, or 1 wt% or less, based on the total weight of the first stage polymer.

[0039] The final stage is formed on or around the first stage acrylic polymer either directly on or around the first stage acrylic polymer or indirectly by forming the final stage on an intermediate stage. Preferably, the final stage acrylic polymer is grafted to the first stage acrylic polymer via the graft-linker used to form the first stage acrylic polymer.

[0040] The final stage acrylic polymer preferably comprises structural units of one or more aryl (meth)acrylate or alkyl (meth)acrylate monomers, where the alkyl of the alkyl (meth)acrylate monomer is selected from straight- and branched-chain alkyl groups having 1 to 12 carbon atoms. Preferably, the final stage acrylic polymer comprises structural units of one or more monomers selected from butyl acrylate, ethylhexyl acrylate, ethyl acrylate, methyl methacrylate, butyl methacrylate, cyclohexyl (meth)acrylate, cyclopentyl methacrylate, tetrahydrofurfyl methacrylate, and benzyl (meth)acrylate. More preferably, the final stage acrylic polymer comprises structural units of methacrylate.

[0041] The final stage acrylic polymer may further comprise one or more substituted or unsubstituted styrene structural units. Suitable substituted styrenes include, for example, alpha-alkylstyrenes (e.g., alpha-methylstyrene). When present, the one or more substituted or unsubstituted styrene structural units may comprise up to 40 wt.% of the total weight of the final stage acrylic polymer. For example, the one or more substituted or unsubstituted styrene structural units may comprise 5 wt.%, 10 wt.%, 20 wt.%, 30 wt.%, or 40 wt.% of the total weight of the final stage acrylic polymer.

[0042] The final stage acrylic polymer may further include polymerized units derived from at least one organophosphorus monomer.

[0043] When present, polymerized units derived from at least one organophosphorus monomer in the final stage acrylic monomer may be present in an amount of 0.25 wt% or more, or 0.5 wt% or more, based on the total weight of the final stage polymer. The final stage may contain polymerized units derived from at least one organophosphorus monomer in an amount of 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, or 1 wt% or less, based on the total weight of the final stage polymer.

[0044] When both the first stage acrylic polymer and the final stage acrylic polymer contain at least one organophosphorus monomer, the at least one organophosphorus monomer in the first stage acrylic polymer can be the same as or different from the at least one organophosphorus monomer in the final stage acrylic polymer. Preferably, the at least one organophosphorus monomer in the first stage acrylic polymer and the at least one organophosphorus monomer in the final stage acrylic polymer are the same. Without wishing to be bound by theory, it is believed that incorporating an organophosphorus monomer in both the first stage acrylic polymer and the final stage acrylic polymer may further improve flammability.

[0045] The final polymer is heated to a temperature of 50°C or higher or 90°C or higher. g The final stage polymer may have a T g may have:

[0046] The multi-stage polymer may contain the final stage polymer in an amount of 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 final 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.

[0047] Preferably, the final 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 final stage polymer. g The polymerized units are derived from a monomer having the formula:

[0048] The weight ratio of the first stage polymer to the final stage polymer can range from 0.1:1 or greater, or 0.2:1 or greater, or 0.4:1 or greater, or 1:1 or greater, or 1.5:1 or greater, or 3:1 or greater, or 4:1 or greater. The weight ratio of the first stage polymer to the final stage polymer can range from 50:1 or less, or 25:1 or less, or 20:1 or less.

[0049] The 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% by weight or more, or 2% by weight or more, or 5% by weight or more, or 10% by weight 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% by weight or less, or 2% by weight or less, or 5% by weight or less, or 10% by weight or less, based on the total weight of the multi-stage polymer. As with the final stage polymer in a multi-stage polymer, one or more intermediate stage polymers may also contain polymerized units derived from one or more organophosphorus monomers.

[0050] In the process of the present invention, the multi-stage polymer latex can be isolated by coagulation or spray drying to form a powder. Preferably, the multi-stage polymer latex is isolated by coagulation.

[0051] If present, the organophosphorus soap may be retained on the surface of the multi-stage polymer upon coagulation. Suitable coagulation methods include, for example, coagulation with divalent cations.

[0052] 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 cations present are calcium(+2), 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.

[0053] 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.

[0054] 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 procedures: 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 have complex structures, and water cannot easily access every part of the coagulated polymer. While not wishing to be bound by theory, it is contemplated that significant amounts of divalent cations and residual organophosphate soaps are left behind. Therefore, the compositions of the present invention may contain organophosphate 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 organophosphate 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.

[0055] Preferably, the dried multi-stage polymer has a moisture content of less than 1.0% by weight, based on the weight of the dried multi-stage polymer.

[0056] The polymer composition of the present invention may also contain 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, such as esters of thiopropionic acid), esters of phosphorous acid (HPO), and hydroxylamines. Suitable metal deactivators include, for example, chelating agents (e.g., ethylenediaminetetraacetic acid).

[0057] 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 a mixture of the multi-stage acrylic polymer powder and the matrix resin into a solid article, the impact resistance of the article will be better than the same solid article made using a matrix resin that has not been mixed with the multi-stage polymer. The multi-stage polymer can be provided in a solid form, such as pellets or powder, or a mixture thereof. The matrix resin can also be provided in a solid form, such as pellets or powder, or a mixture thereof. The solid multi-stage acrylic polymer powder can be mixed with the solid matrix resin at room temperature (20°C) or at an elevated temperature (e.g., 30°C to 90°C). Alternatively, the solid multi-stage acrylic polymer powder can be mixed with the molten matrix resin in, for example, an extruder or other melt mixer. The solid multi-stage acrylic polymer powder can also be mixed with the solid matrix resin, and then the solid mixture can be heated sufficiently to melt the matrix resin, or the mixture can be further mixed, for example, in an extruder or other melt processing device.

[0058] The weight ratio of matrix resin to the multi-stage acrylic polymer powder of the present invention can range, for example, from 1:1 or greater, or from 1.1:1 or greater, or from 2.3:1 or greater, or from 4:1 or greater, or from 9:1 or greater, or from 19:1 or greater, or from 49:1 or greater, or from 99:1 or greater.

[0059] 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 containing polymerized units of BPA together with one or more other polymerized units.

[0060] The matrix resin may include at least one polyester. Suitable polyesters include, for example, polyethylene terephthalate and polybutylene terephthalate.

[0061] 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.

[0062] The matrix resin composition containing the multi-stage acrylic polymer and the matrix resin may contain one or more additional materials added to the mixture. Any one or more of such additional materials can be added to the multi-stage polymer or the matrix resin before forming the final mixture of all materials. When the matrix resin is in solid or molten form, each of the additional materials (if used) can be added to the matrix resin (singly 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.

[0063] The matrix resin composition can be used to form useful articles by, for example, 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.

[0064] The multi-stage polymers of the present invention can provide significant improvements in the flammability of matrix resin compositions.

[0065] Some embodiments of the present invention are described in detail in the following examples. [Example]

[0066] Preparation of multistage acrylic polymers A 5-liter, four-necked round-bottom flask equipped with a mechanical stirrer, thermometer, condenser, and electric heating mantle was charged with 1873 g of deionized water, 1.5 g of tetrasodium pyrophosphate, and 0.2 g of alkyldiphenyloxide diphosphonate. The reactor contents were sparged with nitrogen and heated to 45°C with stirring. In a separate vessel, 91 g of butyl acrylate, 30 g of 2-ethylhexyl acrylate, and 1 g of allyl methacrylate were mixed. The monomer mixture was then added as a shot to the kettle. This was immediately followed by the addition of 0.3 g of tert-butyl hydroperoxide and 0.25 g of sodium formaldehyde sulfoxylate. The reaction contents were held until the reaction exotherm was complete, then the reaction contents were brought to 50°C and a mixture of 91g butyl acrylate, 30g 2-ethylhexyl acrylate, and 1g allyl methacrylate was added, followed by 0.1g tert-butyl hydroperoxide and 0.1g sodium formaldehyde sulfoxylate. The reaction contents were held until the reaction exotherm was complete, then 2.0g alkyl diphenyloxide disulfonate was added to the reactor, then the reaction contents were brought back to 50°C. A mixture of 327g butyl acrylate, 109g 2-ethylhexyl acrylate, and 3g allyl methacrylate was added, followed by 0.3g tert-butyl hydroperoxide and 0.3g sodium formaldehyde sulfoxylate. The reaction contents were held until the reaction exotherm was complete, then 4.0 g of alkyldiphenyloxide disulfonate was added to the reactor, and the reaction contents were returned to 50° C. A mixture of 327 g of butyl acrylate, 109 g of 2-ethylhexyl acrylate, and 3 g of allyl methacrylate was then added, followed by 0.3 g of tert-butyl hydroperoxide and 0.3 g of sodium formaldehyde sulfoxylate. The reaction contents were held until the reaction exotherm was complete, then a redox couple of 0.1 g of tert-butyl hydroperoxide and 0.1 g of sodium formaldehyde sulfoxylate was added, followed by 1.3 g of alkyldiphenyloxide disulfonate, and held for 20 minutes.The reaction contents were returned to 50°C, and then 97g of methyl methacrylate was added to the reactor, followed by 0.3g of tert-butyl hydroperoxide and 0.3g of sodium formaldehyde sulfoxylate. After the exotherm was complete, the reaction contents were held for 10 minutes. After the hold, the batch was cooled to 40°C, after which the emulsion was characterized and found to have a particle size of 308nm and a solids content of 34.9%.

[0067] In examples where the phosphate monomer (SIPOMER™ PAM-600, phosphoethyl methacrylate) was added to the core, half of the charge was used in each of the third and fourth monomer mixture additions, and the alkyldiphenyloxide disulfonate was replaced, on an active basis, with organophosphorus soap. In examples where the phosphate monomer was added to the shell, the corresponding amount of methyl methacrylate was replaced with the charge.

[0068] Control samples (Comparative Example 1) and inventive samples (Examples 1-4) were prepared using compositions according to Table 1 below, where values ​​are provided in terms of weight percent of monomer in the first stage acrylic polymer.

[0069] Multi-stage acrylic polymer coagulation Preparation of antioxidant emulsion To a 250 mL plastic container was added 1.5 g of Dowfax 2A1 (25%), 12.7 g of Irganox 1076, and 70.9 g of deionized water. The mixture was heated to 60° C. and homogenized at 10,000 rpm for 5 minutes.

[0070] Emulsion preparation To a 1 liter bottle was added 481.6 g of emulsion (CP7605 - "First Comparative Example", EXL-2390 control) diluted to 30% TS with 85.1 g of deionized water and heated to 51°C in a water bath. Once at the target temperature, 34.2 g of the antioxidant emulsion listed above was added to the diluted emulsion and mixed thoroughly. The emulsion was stored at 51°C until ready to solidify.

[0071] coagulation To a 3-liter beaker, 4.76 g of calcium chloride powder and 1133.3 g of deionized water were added. The contents of the beaker were heated to 51°C while stirring at 350 rpm. Once the contents reached 51°C, the preheated emulsion was slowly added to the beaker over 45-60 seconds. This resulted in phase separation of the mixture into an aqueous phase and a solid polymer phase. 79.3 g of a 10% aqueous calcium chloride solution was added to complete the coagulation. After 1 minute, 30.6 g of K-120 (diluted to 10% TS) was slowly added to the beaker. The mixture was then heated to 81°C and held at 81°C for 30 minutes. After this time, the mixture was cooled, dewatered, and washed in a Buchner funnel. The sample was washed with deionized water until the conductivity of the filtrate was less than 30 μS / m, and then dewatered. After dewatering, the resulting wet cake was treated with phosphate spray. The phosphate spray consisted of 0.9 g of a 6% solution of monosodium phosphate and 7.43 g of a 20% solution of disodium phosphate. The samples were dried overnight in a vacuum oven at 65° C. The particle size of the powder is measured with a Malvern Mastersizer 2000.

[0072] In other examples, the above process was modified to include additional ingredients.

[0073] [Table 1]

[0074] Comparative Example 2 Preparation of Comparative Polymer Composition M732 The multi-stage acrylic polymer powder of the present invention was compared with a commercially available flame-retardant impact modifier (product name M-732, manufactured by Kaneka Corporation). The rubber component of M-732 is polybutadiene, a core / shell type methacrylate-butadiene-styrene copolymer.

[0075] Polycarbonate Compounds Polycarbonate formulations were prepared using the multistage acrylic polymer powders (AIM) of Comparative Example 1 and Examples 1 to 4, and M732 powder (MBS) of Comparative Example 2. The formulations according to Table 1 were compounded in an extruder to produce pellets for injection molding.

[0076] [Table 2]

[0077] PC Lexan 141: Polycarbonate manufactured by SABIC AIM / MBS: AIM powders of Examples 1 to 4 and Comparative Example 1, or M732 powder of Comparative Example 2 FR-2025a: 100% potassium perfluorobutanesulfonate manufactured by 3M IRGANOX® 1076 and IRGANOX® 168: antioxidants manufactured by BASF The polycarbonate formulations were injection molded to form double-end gated 1.5 mm ASTM burn bars for flammability testing using the UL94 flammability test method. The injection molding conditions are shown in Table 3 below.

[0078] [Table 3]

[0079] The results of the UL94 test are shown in the graph of Figure 1, which shows the total burn time after a 5 bar torch. As can be seen from the graph of Figure 1, the multi-stage acrylic powder formulations of Examples 1-4 performed well in the UL94 test, with each sample receiving a V-1 rating or better. Examples 2 and 4 received a V-0 rating for flammability in the UL94 test, which is an improvement over Comparative Example 1, and had significantly better t2 and t1 + t2 burn times compared to Comparative Example 2.

[0080] The Notched Izod Impact results are shown below in Table 4. As can be seen in Table 4, the impact strength of the inventive examples showed improvement over Comparative Example 2.

[0081] [Table 4]

Claims

1. 1. A process for making a multi-stage acrylic composition comprising: (i) a multi-stage acrylic polymer latex, the multi-stage acrylic polymer comprising: (a) a first stage acrylic polymer; (b) a final stage acrylic polymer formed on or around the first stage acrylic polymer; providing by emulsion polymerization a multi-stage acrylic polymer latex, wherein at least one of said first stage acrylic polymer and said final stage acrylic polymer comprises structural units of at least one organophosphorus monomer; (ii) isolating the multi-stage acrylic polymer by coagulation; (iii) drying the multi-stage acrylic polymer to form a powder.

2. 10. The process of claim 1, wherein said powder of said multi-stage acrylic polymer has a moisture content of less than 1% by weight, based on the weight of said dry multi-stage polymer.

3. 3. The process of claim 1 or 2, wherein the first stage polymer comprises structural units of one or more alkyl (meth)acrylate monomers, the alkyl of the alkyl (meth)acrylate monomers being selected from straight and branched chain alkyl groups having from 1 to 12 carbon atoms.

4. 4. The process of claim 3, wherein the first stage polymer comprises structural units of at least one monomer selected from butyl acrylate, ethylhexyl acrylate, ethyl acrylate, methyl methacrylate, butyl methacrylate, and isooctyl acrylate.

5. 5. The process of any one of claims 1 to 4, wherein the first stage polymer comprises structural units of at least one monomer selected from butanediol diacrylate, butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, divinylbenzene, diethylene glycol diacrylate, diethylene glycol dimethacrylate, diallyl maleate, allyl methacrylate, diallyl phthalate, triallyl phthalate, trimethylolpropane triacrylate.

6. 6. The process of any one of claims 1 to 5, wherein the final stage acrylic polymer comprises structural units of one or more aryl (meth)acrylate or alkyl (meth)acrylate monomers, the alkyl of the alkyl (meth)acrylate monomer being selected from straight and branched chain alkyl groups having 1 to 12 carbon atoms.

7. 7. The process of any one of claims 1 to 6, wherein the first stage acrylic polymer and the second stage acrylic polymer comprise structural units of at least one organophosphorus monomer, and the at least one organophosphorus monomer in the first stage acrylic polymer is the same as or different from the at least one organophosphorus monomer in the final stage acrylic polymer.

8. 8. The process of claim 7, wherein the final stage acrylic polymer comprises structural units of one or more monomers selected from butyl acrylate, ethylhexyl acrylate, ethyl acrylate, methyl methacrylate, butyl methacrylate, cyclohexyl (meth)acrylate, cyclopentyl methacrylate, tetrahydrofurfyl methacrylate, and benzyl (meth)acrylate.

9. The at least one organophosphorus monomer in the final stage acrylic polymer has the formula CH ２ =C(R)-C(O)-O-(R'O) ｎ -P(O)(OH) ２ (Wherein R is H or —CH ３ and R' is alkyl and n is in the range of 1 to 5.

10. R is -CH ３ 10. The process of claim 9, wherein R' is an alkyl group containing 1 to 6 carbon atoms.

11. 11. The process of any one of claims 1 to 10, wherein the first stage polymer is present in an amount of 70 to 98 weight percent, based on the total weight of the multi-stage polymer, and the final stage polymer is present in an amount of 2 to 30 weight percent, based on the total weight of the multi-stage polymer.

12. 12. The process of any one of claims 1 to 11, wherein the at least one organophosphorus monomer is present in the multi-stage acrylic polymer in an amount of less than 5 weight percent, based on the total weight of the multi-stage acrylic polymer.

13. 13. The process of claim 12, wherein said at least one organophosphorus monomer is present in said multi-stage acrylic polymer in an amount of less than 3 weight percent, based on the total weight of said multi-stage acrylic polymer.

13. 13. The process of any one of claims 1 to 12, wherein the emulsion polymerization of step (i) is carried out in the presence of at least one organophosphorus soap.

14. 14. The process of claim 13, wherein the at least one organophosphorus soap comprises one or more of a polyoxyalkylene alkyl phenyl ether phosphate salt, a polyoxyalkylene alkyl ether phosphate salt, a polyoxyethylene alkyl phenyl ether phosphate salt, and a polyoxyethylene alkyl ether phosphate salt.

15. The process of any one of claims 1 to 14, wherein the multi-stage acrylic polymer latex has an average particle size of from 50 nm to 1 micrometer.

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