MXPA99008076A - Improved modifiers of impact of metacrylate-butadiene-style - Google Patents

Abstract

Disclosed is a process and composition for methacrylate-butadiene-styrene (MBS) modifiers, which have (A) an elastic core, (B) an internal grafting stage, comprising mainly a hard polymer, (C) an intermediate sealing step, comprised primarily of an alkyl acrylate monomer and / or a polyunsaturated crosslinker, and, (D) an outer shell, to provide compatibility of the core-shell polymer with the matrix polymer. It is also disclosed a process for preparing MBS impact modifiers that have a surprisingly improved impact performance on matrix polymers. Also described in the present invention are articles prepared from mixtures of matrix polymers and core-shell polymers.

Description

IMPROVED AMENDERS OF IMPACT OF METACRYLATE-BUTADIENE-EST1RENE BACKGROUND There is a need for core-shell emulsion polymers with a core or elastic stage, based on butadiene homopolymers or copolymers, for use as impact modifiers in matrix polymers, such as acrylonitrile-butadiene-styrene (" ABS "), for styrene-acrylonitrile copolymers, in polymers of methyl methacrylate, in poly (vinyl chloride) ("PVC"), in various engineering resins, such as polycarbonate, polyesters or polyamides, and in thermosetting resins, such as epoxies. Such copolymers containing impact modifiers of butadiene and styrene and at least one step or shell of poly (methyl methacrylate) are known in the art as core-shell polymers of methacrylate-butadiene-styrene ("MBS"). Although MBS impact modifiers are commercially available, there is a constant need to reduce the manufacturing cost of these impact modifiers, while maintaining or improving properties. of the matrix resins that are used. The improved properties may include increased impact properties (for example, PVC bottles that can withstand greater dropping heights without breaking) and improved clarity and color in clear matrix polymer blends. The reduction of manufacturing costs can arise from shorter process times and / or reducing the cost of dust recovery processes. It is convenient to use emulsion-efficient recovery processes known in the art, such as spray-drying or coagulation. The coagulated MBS emulsions produce an aqueous slurry of coagulated core-shell particles of various sizes, which must be further dried to produce the MBS powders, which are easily handled and added to the matrix resins during the mixing processes and composition. The average particle sizes of the aqueous paste, commercially available, for generating powders, are typically in the range of about 100 microns to less than about 300 microns and preferably between about 200 and 2500 microns. A preferred average particle size of the aqueous paste is necessary to avoid problems related to the dispersion in matrix polymers, dust formation when handled, powder compaction, flowability and drying of the wet mass. U.S. Patent No. 5,534,594 to Troy et al. Discloses an improved process for preparing core-shell MBS modifiers, in which the charges of the monomers, which form the polymers of the second and / or third stages, they are added before completing the polymerization of the previous steps. Although the Troy process substantially reduces the polymerization time, the inventor has discovered that commercially viable latex polymer-coated polymer emulsions having a butadiene-based fraction of the weight of the core of more than 70 % and a conversion of core monomers of the first stage of less than 75%, provides aqueous pastes inconveniently having an average particle size greater than about 300 microns, when coagulated at temperatures higher than about 20 ° C. Because the particle size of the aqueous paste typically increases with increasing temperature, impact modifiers, commercially viable, which follow the Troy process require temperatures of coagulation below 20 ° C, in order to supply aqueous pastes having a convenient average particle size of less than about 300 microns. Coagulation below about 20 ° C is a problem that prevents the use of efficient cooling processes on a commercial scale. While Troy reveals coagulation ("Method B") As a possible method of isolation, Troy is not intended to maintain a convenient average particle size of the aqueous paste. When the core-shell polymers, obtained according to Troy, coagulate at temperatures of or above about 20 ° C, the average particle size of the aqueous paste frequently exceeds about 300 microns. Also, the process of isolation of "Method A", described by Troy (drying by freezing the emulsion, followed by vacuum drying) is not recommended for commercial production. The ability of a particular MBS core-shell polymer to increase the impact strength of a matrix polymer generally increases, up to a point, as the weight fraction of the elastic core increases, generally to at least 70%. However, as the fraction by weight of the core increases, there is a corresponding decrease in the fraction by weight, thickness and hardness of the polymer outer shell. IF the cover becomes too thin, it will not properly cover the rubber core. Improper cover coverage also emerges as described in Makromol. Chem. , Mac romo 1. Symp. 35/36, 307-325 (1990). Improper coverage of the shell in the MBS polymers is also aggravated by the presence of unreacted monomers in the shell, which reduce the glass transition temperature ("Tg") of the shell. Finally, inadequate coverage of the cover leads to problems with dust insulation (for example the inability of spray or coagulum drying, or a very large particle size of the aqueous paste), and reduced impact resistance in the mixtures of the matrix polymer. These problems usually become evident when the elastic fraction of the core weight exceeds about 70 to 75%. The inventor has discovered that a certain amount of an alkyl acrylate and / or polymerized crosslinker monomer between the internal graft stage and the outer shell decreases the particle size average of the aqueous slurry of the multi-stage, coagulated MBS core-shell polymers having a weight fraction of the elastic core exceeding 70% to a commercially viable range (less than about 300 microns at coagulation temperatures above) 20 ° C). The inventor also discovered that core-shell polymers, prepared at reaction temperatures in the range of 60 to 70 ° C, provide a surprisingly large improvement in impact properties in matrix polymer blends. The object of the present invention is to provide MBS core-shell polymers having a weight fraction of the elastic core exceeding 70% and a particle size of the aqueous paste of less than 300 micras when coagulated above 20 °. C, for use as modifiers of the impact on matrix resins. A further object is to provide an improved impact modifier, having a weight fraction of the elastic core exceeding 70% and a particle size of the aqueous paste less than 300 microns, when it coagulates above 20 ° C and for optically clear PVC compositions. Another object of the invention is to provide thermoplastic mixtures and articles comprising the matrix polymers and MBS core-shell polymers of this invention, which have a surprisingly large improvement in impact properties. Still another object is to provide a process for preparing MBS, core-shell impact modifiers, having a weight fraction of the elastic core exceeding 70%, a particle size of the aqueous paste less than 300 microns, when it coagulates above 20 ° C, and a surprisingly large improvement in impact properties, when mixed with matrix resins. These and other objects, which will become apparent from the following description, are achieved by the present invention.

EXPOSITION OF THE INVENTION In the present invention, the impact resistance of matrix polymers, such as acrylonitrile-butadiene-styrene ("ABS"), styrene-acrylonitrile copolymers, polymers of methyl methacrylate, PVC, polycarbonate, polyesters or polyamides, and the like, or combinations of these matrix polymers, is substantially increased by the addition of small amounts of certain core-shell modifiers, having a fraction of the elastic core greater than about 70%. Additionally, the present invention provides an MBS core-shell composition, having a weight fraction of the elastic core exceeding about 70% and having an average particle size of the aqueous paste of less than about 300 microns, when coagulates above 20 ° C, as does the provision of improvements in the properties of the impact to matrix polymers on those taught in the prior art. Specifically, the present invention provides core-shell MBS impact modifiers, which have a weight fraction of the elastic core which exceeds about 70%, and have an average particle size of the aqueous paste of less than about 300 microns, when coagulated above 20 ° C, which, when mixed with PVC to prepare plastic bottles, they have excellent transparency, low fogging, low color inversion and high impact resistance, evident by the reduced breakage when they drop The impact modifier of this invention is a core-shell polymer with (A) an elastic core, such as a copolymer containing a diolefin, (B) an internal grafting step, comprised mainly of a hard polymer, such as a polymer containing a vinyl aromatic monomer, (C) an intermediate sealing step, comprised primarily of a monomer of alkyl acrylate and / or a polyunsaturated crosslinker, and (D) an outer shell, comprised primarily of alkyl methacrylate monomers (such as methyl methacrylate) to provide compatibility of the core-shell polymer with the matrix polymer. The impact modifier of the present invention comprises: (A) about 70 to 85 parts of a core comprising about 15 to 35 weight percent of units derived from at least one vinyl aromatic monomer, and about 65 at 85 weight percent of units derived from at least one diolefin monomer. (B) about 8 to 14 parts of an internal grafting step, comprising at least one vinyl aromatic monomer or at least one C1-C4 alkyl methacrylate monomer; (C) about 0.1 to 5 parts of an intermediate sealing step, comprising at least one monomer selected from a C 1 -C 8 alkyl acrylate or a polyunsaturated crosslinker; and (D) about 10 to 16 parts of an outer shell, comprising at least one Cl-C4 alkyl (meth) acrylate monomer, or at least one vinyl aromatic monomer.

Another aspect of the invention is the mixing of the impact modifier composition with at least one matrix polymer, in a weight ratio of about 99: 1 to 70:30 of the matrix polymer: impact modifier. Still another aspect of the invention comprises molded parts, bottles, sheets, films, tubes, foams, containers, profiles or other prepared articles, according to the aforementioned compositions and mixtures. The inventor also discovered a process for preparing core-shell impact modifiers, which have an average particle size of aqueous paste below about 300 microns, when they coagulate above 20 ° C, which comprises: (A) polymerizing in emulsion, about 70 to 85 parts of a first mixture of monomers, comprising approximately 65 to 85% of a monomer of diolefin and about 15 to 35% of at least one vinyl aromatic monomer, in the presence of an emulsifier and a free radical initiator, until a 60 to 90% conversion of the monomers to the polymer has been achieved; (B) continuing the polymerization of the first monomer mixture, while adding about 8 to 14 parts of a second monomer mixture, this mixture comprises at least one vinyl aromatic monomer or a C1-C4 alkyl methacrylate monomer; (C) continuing the polymerization of the second monomer mixture until at least 90% conversion to the polymer has been achieved; (D) add approximately 0.1 to 5 parts of a third monomer mixture and a radical initiator free, this mixture comprises at least one monomer selected from a C 1 -C 8 alkyl acrylate or a polyunsaturated crosslinker; and (E) adding approximately 10 to 16 parts of a fourth monomer mixture, this mixture comprising at least one alkyl methacrylate or Cl-C4 monomer, or at least one vinyl aromatic monomer, adding a free radical initiator and continuing polymerization until at least 95% conversion to the polymer has been achieved, wherein the reaction temperature, during steps (A) to (E), is in the range of 20 to 100 ° C.

The inventor also discovered a process for preparing core-shell impact modifiers that provide surprisingly improved impact properties in matrix polymer blends, which comprises: (A) polymerizing in emulsion, approximately 70 to 85 parts of a first mixture of monomers, comprising approximately 65 to 85% of a diolefin monomer and approximately 15 to % of at least one vinyl aromatic monomer, in the presence of an emulsifier and free radical initiator, until a 60 to 90% conversion of the monomers to the polymer has been achieved;; B continuing the polymerization of the first monomer mixture, while adding about 8 to 14 parts of a second monomer mixture, this mixture comprises at least one vinyl aromatic monomer or a C1-C4 alkyl methacrylate monomer; (C) continuing the polymerization of the second monomer mixture until at least 90% conversion to the polymer has been achieved; Y; D) adding approximately 10 to 16 parts of a third monomer mixture, which comprises at least one Cl-C4 alkyl methacrylate monomer or at least one vinyl aromatic monomer, adding a free radical initiator and continuing the polymerization to that a conversion of at least 95% to the polymer has been achieved. wherein the reaction temperature, during steps (A) to (D), is in the range of 60 to 70 ° C. A further variant in any process of preparing the core-shell impact modifiers is to polymerize the first monomer mixture in the presence of a polymer dispersion previously formed "sowing" latex) for the control of the desired particle size or for the Modification structure of the resulting polymer. The "sowing" latex is often of small particle size, such as below 100 nm. The dispersion of the preformed polymer can be a polymer of an elastic material, such as poly (butadiene), and can be similar or different in composition to the core polymer. Alternatively, it may be a hard, non-elastic polymer, for example polystyrene or poly (methyl methacrylate), present to adjust the refractive index, as taught by Myers et al., U.S. Patent No. -3, 971, 835. Yet another variant in any process is the addition of an agglomeration people during stage (A), after the conversion of 60 to 90% of the first mixture of monomers to the polymer, having a particle size of 70 to 110 nm. As used herein, the term "step" is intended to encompass its broadest possible meaning, including the meanings of the prior art, such as in US Patent No. 3,793,402, US Patent No. 3,971,835, US Patent No. 5,534,594 and US Patent No. 5,599,854, which offer several resources to achieve the polymers "in stages". As used in this document, the term of "mixture" is intended to encompass a combination of one or more chemical compounds. As used herein, the term "parts" is intended to mean "parts by weight". In addition, the invention encompasses additional steps or steps, which polymerize after the formation of the complete internal graft stage and the excess pressure is discharged. Such steps may include an additional elastic step of a diolefin polymer or a poly (alkyl acrylate), or additional outer layers of the polymer, mainly or exclusively polymerized from styrene, methyl methacrylate, or the styrene / methyl methacrylate copolymer.

DETAILED DESCRIPTION OF THE INVENTION It has been found that the impact strength of matrix polymers, such as acrylonitrile-butadiene-styrene ("ABS") copolymers, styrene-acrylonitrile copolymers, methyl methacrylate polymers, poly (chloride) of vinyl) ("PVC"), various engineering resins, such as polycarbonate, polyesters or polyamides, and thermosetting resins, such as epoxies, or combinations of these matrix polymers, are substantially increased by the addition of small amounts of certain core-deck modifiers of MBS. These MBS core-shell modifiers of the present invention have a core weight fraction greater than about 70%, a particle size of the aqueous paste less than about 300 microns, when coagulated above 20 ° C, and they provide improvements in the properties of the impact to the matrix polymers on those taught in the prior art. These impact modifiers have (A) an elastic core, such as a copolymer containing a diolefin, (B) an internal grafting step, comprised primarily of a hard polymer, such as a polymer containing a vinyl aromatic monomer or a C 1 -C 4 alkyl methacrylate, (C) a sealing step intermediate, comprised primarily of an alkyl acrylate monomer and / or a polyunsaturated crosslinker, and (D) an outer shell, comprised primarily of a C 1 -C 4 alkyl methacrylate or vinyl aromatic monomers (such as methyl methacrylate), to provide compatibility between the core-shell polymer and the matrix polymer. The core of the impact modifier composition of the present invention is an elastic polymer and generally comprises a copolymer of a diolefin and a vinyl aromatic monomer. Preferred diolefin monomers include the 1,3-dienes, such as butadiene and isoprene. The elastic polymer may include the 1,3-diene rubber copolymers (for example the butadiene-styrene copolymer, butadiene-styrene- (meth) acrylate terpolymers, butadiene-styrene-acrylonitrile terpolymers, isoprene-styrene copolymers, etc.) . Of the elastic polymers, mentioned above, are especially convenient those that can be produced as a latex. In particular, the latex of the butadiene-vinyl aromatic copolymer, obtained as a result of the emulsion polymerization, is preferred. In the core, a partially entangled polymer can be employed if the entanglement is moderate. In addition, entangled or linked graft monomers, otherwise described as multifunctional unsaturated monomers, may also be copolymerized in the core. Such entangled or linked graft monomers include divinylbenzene, diallyl maleate, butylene glycol diacrylate. ethylene glycol dimethacrylate, allyl methacrylate, and the like. The ratio of the comonomers in the core depends on the desired refractive index ("Rl") of the core-shell polymer and the desired hardness of the rubber phase. The range of the ratio of the diolefin to the vinyl aromatic in the core polymer is from 95: 5 to 20:80, preferably from 85:15 to 65:45 (parts by weight). If the amount of the butadiene is below 20 parts by weight, it is difficult to improve the impact resistance. If the amount of butadiene exceeds 95 parts by weight, on the other hand, it can be difficult to obtain a modifier having a Rl high enough to correspond to that of the matrix polymer for blends of clear polymers, modified on impact, such as clear PVC. Optionally, a small concentration, of about 0 to 5 weight percent of an interlacing monomer, such as divinylbenzene or butylene glycol dimethacrylate, is included, and optionally about 0 to 5 weight percent of a linker monomer by grafting, to ligate the core and cover each other, such as allyl maleate, can be included in the elastic core polymer. Additional examples of crosslinking monomers include polyacrylates or polyanoacrylic polymethacrylates, such as ethylene glycol diacrylate, diethylene glycol dimethacrylate, butylene glycol diacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate, trimethylolpropane diacrylate. , trimethylolpropane dimethacrylate, trimethylolpropane triacrylate or trimethylolpropane trimethacrylate, and unsaturated allyl esters of the carboxylic acid, such as allyl acrylate, allyl methacrylate or diallyl maleate.

The particle sizes of the core can be as low as 90 nm, and as high as 300 nm, although 120 to 240 nm are preferred for the polymer blends modified on impact. As the internal grafting step of the impact modifier composition, polymers or copolymers with a Tg above room temperature can generally be used. Hard polymers or copolymers of vinyl aromatic monomers and C1-C4 alkyl methacrylate, they are preferred. This step is present in an amount of about 8 to 14 parts. Examples of vinyl aromatic monomers suitable for the internal grafting stage include alpha-methyl-styrene, para-methyl-styrene, chlorostyrene, vinyl-toluene, dibromostyrene, tribromostyrene, vinyl-naphthalene, isopropenyl-naphthalene, divinyl-benzene and, preferably, styrene. Examples of C1-C4 alkyl methacrylate monomers are ethyl methacrylate, propyl methacrylate, butyl methacrylate and, preferably, methyl methacrylate. Optionally, one or more additional copolymerizable monomers can also be used with the methacrylate Cl-C4 alkyl, and vinyl aromatic monomers, in the internal grafting stage. The additional monomer may include one or more of any of the following monomers: acrylonitrile, methacrylonitrile, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, methacrylate of ethyl, divinylbenzene, alpha-methyl-styrene, para-methyl-styrene, chlorostyrene, vinyl-toluene, dibromostyrene, tribromostyrene, vinyl-naphthalene, isopropenyl-naphthalene, as well as methacrylates and higher alkyl acrylates with C 12 to C 20 atoms carbon, such as lauryl methacrylate, lauryl acrylate, stearyl methacrylate, stearyl acrylate, isobornyl methacrylate. Additionally, the Cl-C4 alkyl methacrylate monomers and the vinyl aromatic monomers can be used, alone or in combination with each other. Optionally, one or more additional monomers can be added to the internal graft stage to adjust the Rl. This additional monomer may be any monomer that copolymerizes with the other two monomers used in the core polymer and produces a terpolymer which allows the Rl of the modifier to correspond to that of the matrix polymers with which it is mixed. The intermediate sealing step is added to ensure that the impact modifiers of the present invention have an average particle size of the aqueous paste of less than about 300 microns when coagulated above 20 ° C. This step is present in an amount of approximately 0.1 to 5 parts, preferably 0.5 to 2 parts. Useful monomers for forming the intermediate sealing step include at least one monomer selected from the C 1 -C 8 alkyl acrylate or a polyunsaturated crosslinker. Surprisingly, intermediate sealing step amounts within the range of 0.1 to 5.0 parts, added to the core-shell composition, improve the coverage of the outer shell in the inner stage and the core, which results in smaller average particle sizes. of the aqueous paste. Suitable monomers of C 1 -C 8 alkyl acrylate in 1 intermediate sealing step include methyl acrylate, ethyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and preferably butyl acrylate.

Suitable polyunsaturated crosslinkers in the intermediate sealant stage include butylene glycol dimethacrylate, polyacrylate or polyanoacrylate polyanacrylates, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, oligoethylene glycol diacrylate, dimethacrylate. of oligoethylene glycol, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate or trimethylolpropane trimethacrylate, and the allyl esters of unsaturated carboxylic acids, such as allyl acrylate, allyl methacrylate or diallyl maleate, and preferably divinyl -benzene. As the outer shell of the impact modifier composition, hard polymers or copolymers with a Tg above room temperature are suitable, and polymers prepared with the C 1 -C 4 alkyl methacrylate and aromatic vinyl monomers are preferred. Examples of suitable vinyl aromatic monomers include styrene, alpha-methyl-styrene, para-methyl-styrene, chlorostyrene, vinyl-toluene, dibromostyrene, tribromostyrene, vinyl-naphthalene, isopropenyl-naphthalene, divinyl-benzene and the like. Examples of C 1 -C 4 alkyl methacrylate monomers are ethyl methacrylate, propyl methacrylate, butyl methacrylate and, preferably, methyl methacrylate. Optionally, one or more additional monomers, copolymerizable with the C 1 -C 4 alkyl methacrylate and vinyl aromatic monomers can also be used in the outer shell composition. The additional monomer may include one or more of any of the following monomers: acrylonitrile, methacrylonitrile, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, ethyl methacrylate, divinyl-benzene, alpha-methyl-styrene, para methyl-styrene, chlorostyrene, vinyl-toluene, dibromostyrene, tribromostyrene, vinyl-naphthalene, isopropenyl-naphthalene, as well as methacrylates and higher alkyl acrylates with C 12 -C 20 carbon atoms, such as lauryl methacrylate, lauryl acrylate stearyl methacrylate, stearyl acrylate, isobornyl methacrylate In addition, the C1-C4 alkyl methacrylate monomers and the vinyl aromatic monomers can be used alone or in combination with each other.

Optionally, one or more additional monomers may be added to the cover to adjust the RI. These additional monomers can be any monomer that copolymerizes with the other two monomers used in the core polymer and produces a terpolymer which allows the Rl of the modifier to match that of the matrix polymers with which it is mixed. For example, when the matrix polymer is PVC, it is preferred that the general R1 of the core-shell polymer be in the range of 1.52 to 1.55 to prepare clear, modified PVC blends. When preparing an emulsion of the core-shell impact modifier, having a weight fraction of the elastic core exceeding 70%, and an average particle size of the aqueous paste less than 300 microns, when it coagulates above 20 ° C, the first step involves polymerizing a first mixture of monomers of a diolefin monomer and at least one aromatic vinyl monomer, in the presence of an emulsifier and a free radical initiator, at a temperature between 20 and 100 ° C in emulsion, until achieving the conversion of 60 to 90% of the monomers to the polymer, to form the elastic core.

Suitable diolefin monomers, which form the elastic core, include 1,3-dienes, preferably butadiene, suitable vinyl aromatic monomers, which copolymerize with the diolefin monomers in the elastic core include para-methyl-styrene, alpha- methyl-styrene, chlorostyrene, vinyl-toluene, bromostyrene, dibromostyrene, tribromostyrene, isopropenyl-naphthalene, vinyl-naphthalene and, preferably, styrene. In the first step, the first monomer mixture can be added in batches or fed continuously to the reactor over time. Continuous feeding is preferred, since it allows the best control of the reaction temperature. Typically, the first monomer mixture is fed into the reactor in a time between 2 and 12 hours. Suitable emulsifiers include those conventionally used in the emulsion polymerization, especially the diolefin monomers, and include the salts of alkyl, aryl, aralkyl or alkaryl sulfates or sulfonates, alkylpoly (alkoxyalkyl) ethers, alkylpoly (alkoxyalkyl) sulfates or salts alkalines of long-chain fatty acids, such as potassium oleate. If the latex of the butadiene polymer is going to agglomerate (see below), it is preferred to use an ionic emulsifier and it is especially preferred to use a fatty acid soap, whose systems have a pH above 7. to be partially destabilized and microagglomerates decreasing this pH. The free radical initiators, which can be used in the various steps of the process, are those conventionally used in free radical polymerizations, conducted in the temperature range from about room temperature to about 100 ° C, preferably 55 ° C. 80 ° C. Suitable initiators include thermally activated initiators, such as persulfates, peroxides or peroxyesters. Suitable initiators also include "redox" initiators, such as oxidants, for example hydroperoxides, persulfates or peroxides, in combination with reducing agents, such as sodium formaldehyde sulfoxylate, sodium sulfite, sodium hydrosulfite or isoascorbic acid. An oil soluble initiator, which has a lower water solubility of styrene (3.5 mM at 25 ° C - 50 ° C), is preferred, examples of which include diisopropylbenzene hydroperoxide, t-butyl perbenzoate, tere isopropylcarbonate. butyl peroxy, t-butyl peroxyisobutyrate, t-butyl peroctoate, diisopropyl-peroxy dicarbonate, di (2-ethylhexyl) peroxy dicarbonate, and the like. Redox reactions can also be promoted by reagents, such as iron salts, for example ferrous iron ethylene diamine tetraacetic acid (Fe-EDTA). The second step involves continuing the polymerization of the first monomer mixture, while adding a second monomer mixture, having at least one vinyl aromatic monomer or a C1-C4 alkyl methacrylate monomer, to form the internal grafting step. The second mixture is added after the first monomer mixture for the core has reached a conversion of 60 to 90%. This interval of core monomer conversion is important to control the overall efficiency of the process. If the conversion of the core monomer is greater than 90%, before the addition of the second monomer mixture, then the reaction time of the core becomes very long, leading to a higher cost. If the monomer conversion of the core is less than 60%, when the second mixture is As monomers are added, then 1 outer cover coverage will become poorer, leading to lower coagulation temperatures and reduced compatibility with the matrix resin. Suitable vinyl aromatic monomers of the C 1 -C 4 alkyl methacrylate for the second mixture were described above. The second monomer mixture can be added in batches or fed continuously with time in the reactor, to form the internal grafting stage. Continuous feeding is preferred since it allows the best control of the reaction temperature. Additional emulsifier and initiator can also be added simultaneously: suitable emulsifiers and initiators are listed above for the stage of preparing the core and can be the same or different. Typically, the second mixture of monomers, emulsifiers and initiators was fed into the reactor at times between 1 and 10 hours at temperatures between 20 and 100 ° C. It is preferred that the reaction temperatures are between 55 and 85 ° C; below 55 ° C, the reaction rates become low, and above 85 ° CV, an increased amount of self-entanglement in the core occurs. The interlacing increased in the core, or promoted by the interlacing monomer or promoted by self-entanglement by high reaction temperatures inconveniently leads to reduced impact properties. The third step involves continuing the polymerization of the second monomer mixture for the internal grafting step, until at least 90% of the total monomers have been converted to the polymer. This step usually takes 1 to 24 additional hours at temperatures between 20 and 100 ° C, preferably for 2-6 hours at temperatures between 55 and 80 ° C. It is also convenient to feed additional initiator and emulsifier to achieve a conversion of at least 90%. The degree of conversion was determined by the analysis of the fraction of solids of the emulsion. After achieving a conversion of at least 90%, the reactor can be vented to prevent the polymerization of the unreacted butadiene in subsequent steps. If the conversion is greater than 99%, then this ventilation is not required. However, because to achieve a conversion greater than 99% it is necessary to take an inconveniently long amount of time, the The reactor is preferably cooled to conversions in the range of 90 to 98%. The fourth step involves adding a third monomer mixture having at least one monomer selected from the C1-C8 alkyl acrylate or a polyunsaturated crosslinker, and initiator, to form the intermediate sealing step. This intermediate sealing step is added to ensure that the impact modifiers of the present invention have an average particle size of the slurry of less than about 300 microns when coagulated above 20 ° C. This step is present in an amount of approximately 0.1 to 5 parts, preferably 0.5 to 2 parts. Useful monomers for forming the intermediate sealing step include at least one monomer selected from the C 1 -C 8 alkyl acrylate and a polyunsaturated crosslinker, as described above. Preferably, the alkyl acrylate monomer is butyl acrylate and the polyunsaturated crosslinker is divinylbenzene. When the degree of conversion of the core is between 60 and 80%, it is preferred to use a mixture of 0.4 to 1.5 parts of butyl acrylate and 0.1 to 0.5 parts of divinylbenzene. The third monomer mixture is added to the reactor at a temperature between 20 and 100 ° C, preferably between 55 and 80 ° X and the reaction is between 30 minutes and 4 hours, preferably between 1 and 2 hours. Preferably, the additional initiator and emulsifier is fed into the reactor with the monomers. This additional initiator and emulsifier can be mixed with the monomers to form an emulsified monomer mixture, when added to the reactor, or added separately. The initiators and emulsifiers suitable for this step are the same as described above and may be the same or different from those of the other steps. The fifth step involves adding a fourth mixture of monomers, having at least one C1-C4 alkyl methacrylate monomer or an aromatic vinyl monomer, adding an initiator and continuing the polymerization until at least 95% conversion to the polymer is achieved, to form the outer shell and complete the preparation of the core-shell polymer. The fourth monomer mixture is added to the reactor at a temperature between 20 and 100 ° C, preferably between 55 and 80 ° C, and the reaction between 30 minutes and 4 hours, preferably between 1 and 2 hours. It is also preferred to feed an initiator and emulsifier in the reactor with the monomers. This additional initiator and emulsifier can be mixed with the monomers to form an emulsified monomer mixture when added to the reactor, or added separately. Suitable monomers for preparing the outer shell of the impact modifier composition are those which form hard polymers or copolymers with a Tg above room temperature, and are preferably selected from Cl-C4 alkyl methacrylate monomers and vinyl aromatics. Examples of suitable monomers and optional additional monomers, copolymerizable with the C1-C4 alkyl methacrylate and vinyl aromatics are those given above. Optionally, one or more chain transfer agents can be incorporated during any of the aforementioned process steps, to control the degree of polymerization. Common transfer agents or their mixtures are known in the art, such as alkyl mercaptans, and are used to control molecular weight. To prepare core-shell impact modifiers, which provide impact properties Surprisingly improved to the matrix polymer blends, the core-shell polymers are obtained at a temperature in the range of 60 to 70 ° C. Preferably, an oil soluble initiator is used during this process. The following variations apply to the aforementioned composition, as well as to both processes: Optionally, one or more additional monomers can be added to the cover to adjust the Rl. This additional monomer can be any monomer, which copolymerizes with the fourth monomer mixture, to allow the Rl of the modifier to correspond to that of the matrix polymer in which it is mixed. Additional suitable monomers to control the Rl are those provided above. The first monomer mixture can be polymerized in the presence of a pre-formed polymer dispersion ("seed" latex), to control the desired particle size or for structural modification of the resulting polymer. The "sowing" latex is often of a small particle size, such as below 100 nm, and a composition similar to that of the Rubber phase will be formed. The dispersion of the preformed polymer may be a polymer of a rubber material, such as poly (butadiene) and may be similar or different in composition to the core polymer. Alternatively, it may be a hard, non-elastic polymer, for example, polystyrene or poly (methyl methacrylate) = present to adjust the refractive index, as taught by Myers et al., E patent. U. A., No. 3,971,835. An agglomerating agent can also be added to control the particle size of the core, after conversion of 60 to 90% of the first monomer mixture to the polymer, having a particle size of 70 to 110 nm. The agglomeration can also be achieved in various ways, such as the controlled adjustment of solids, by extensive cutting of the emulsion or by the carefully controlled addition of electrolytes, such as the water-soluble salts of inorganic acids, such as sodium chloride, potassium hypophosphite, potassium chloride or sodium phosphate. It is preferred to use as the emulsifier an alkaline salt of a fatty acid, when agglomeration is used or not, and it is separately preferred that the agglomerating agent be an acid, such as hydrochloric acid, acetic acid or phosphoric acid. If the acid is used, it is preferred that, after agglomeration, sufficient alkali hydroxide is added to restore the pH to the present value before the agglomeration step. The acids used to adjust the pH and / or achieve agglomeration can be any number of organic or inorganic acids, preferably soluble in water, such as hydrochloric, sulfuric, phosphoric, acetic acids., methanesulfonic or tartaric. The agglomeration can also be achieved by the controlled addition of the salts, such as sodium chloride or potassium chloride. It is known to agglomerate with polymeric acids, such as ethyl acrylate / methacrylic acid copolymers, but this tends to cause excessive dilution of the reaction and to create a wider particle size distribution of the agglomerate, sometimes less convenient in certain applications of "clear" polymer mixture. The core-shell polymers can be isolated from the emulsion in various ways, the preferred methods being spray drying or coagulation, such as with the addition of the electrolyte. Any of the various techniques revealed in the literature, such as in the US Patent No. 4,897,462 can be applied to the emulsion during isolation to produce a spheroidal product which, when dried, exhibits an outstanding flux of "dust, under dusting, and a higher bulk density than isolated powders conventionally, the average particle size of the aqueous paste is in the approximate range of 100 to 300 microns, preferably in the approximate range of 200 to 250 microns.A preferred average particle size of the aqueous paste is necessary to avoid the related problems with dispersion in the matrix polymers, dusting when handled, powder compaction, flowability and drying of the wet mass.In the conventional coagulation processes for MBS core-shell polymers, the average particle size of the aqueous paste generally increases at the coagulation temperature, because the butadiene polymers are sensitive to desco Thermal deposition when drying or processing at high temperatures, one or more thermal stabilizers may be added during the insulation and during mixing with a matrix polymer. Stabilizers suitable thermal include octadecyl 3, 5-di-t-butyl-4-hydroxyhydrocinnamate, and the reaction product of 2-t-butyl-5-methylphenol with crotonaldehyde. The thermal stabilizers may also contain additional emulsifiers, such as epoxidized soybean oil, to aid emulsification. The core-shell polymers of the present invention can be used in various ways. They can be mixed with poly (vinyl chloride) to improve impact resistance for many uses, such as glossy sheets, injection molded articles, blow molded articles or extruded articles. When the component monomers of the core-shell polymer are aggregated in a manner such that the refractive indexes coincide carefully, the resulting polymers are useful in clear packaging applications, such as the containers surrounding the articles of sale, for use in storage. , to pack food and for clear bottles for the packaging of liquids, such as water. The core-shell modifiers of the present invention are especially useful for PVC bottles, where impact resistance of fall is necessary.

Polymers can be mixed with many polymeric matrices, such as polymers of methyl methacrylate, with styrene-acrylonitrile copolymers, with aromatic polyesters, such as poly (ethylene terephthalate) or poly (butylene terephthalate), with polycarbonates, with polyamides or with polyacetals. The utility of such mixtures is varied, but include panels and equipment housings, such as for appliances or computers, and automobile parts, such as panels.

EXAMPLES APPARATUS AND GENERAL PROCEDURES In the following examples, the core-shell polymers were prepared in an appropriate stirred pressure vessel, capable of withstanding a pressure of 1360 kPa, and equipped with a pressure bursting disc, agitator, ventilating element the reactor, element for dropping the emulsion of the formed polymer into a container, element for recording the temperature, element for adding the emulsifier solution, element to add the initiator and element to add monomers under pressure. The particle size of the emulsion particles was measured using the Nanosizer BI-90 apparatus. The size of the emulsion particles was 175 nm ± 10 nm for all the examples. The stabilizing system used in all of the following examples was a mixture of epoxidized soybean oil, octadecyl 3, 5-di-t-butyl-4-hydroxyhydrocinnamate and the reaction product of 2-t-butyl-5-methylphenol with the crotonaldehyde The core-shell polymers for each example were coagulated by adding the emulsions to a solution of hydrochloric acid, well stirred, at 0.3 - 1%, at a temperature between 20 and 35 ° C, adding 2.5 parts of a diluted latex of MMA / ethyl acrylate (90/10 emulsion, followed by a pH adjustment of 5.5, heating the water paste at 60 ° C, dehydrating the wettest, rewashing this wet mass with water, adjusting the H to 2.7 and refiltering and drying.The average particle size of the aqueous paste was determined using a Melvern 2600 Series Particle Size device Analyzer (Malvern Instruments, Worcestershire, England).

The core-shell polymers were mixed in a PVC bottle formulation, indicated in Table 1, in a high-speed rotary mixer. These mixtures were composed in a single screw extruder of 31.75 mm and forming pellets. The pellets were extrusion blow molded in Boston round bottles of 473 ml. The bottles were tested for fall impact as described in ASTM D-2463, Procedure C, Accumulative Fall Impact Method. Adonally, the panelees cut from these bottles were tested in the transmission of light and color, as described in ASTM D-1003, using the Hunter Lab D-25 colorimeter. The blue / yellow tint of the bottle panels was measured in two ways. First, the "b" value of the Hunter L, a, b scale was measured. The value "b" Hunter measures the blue-yellow, and the procedure for determining this value is given in the instruction manual: HUNTERLAB TRISTIMULUS COLORIMETER MODEL D25P-9 (rev A). Hunter "b" values for all tested PVC / core-shell bottles varied between 0.5 and 1.1. The second measured parameter is referred to as the Scattered Yellowness Index ("SYI"). This SYI was calculated according to the procedure of Yellowness Index ("YI") of the ASTM-D-1925 standard, using the diffuse (scattered) transmission values, instead of the total transmission values. The SYI values for all tested PVC / core-shell bottles ranged between -54.3 and -23.2. The total light transmission "Y" and the fogging percentage "% Fogging" were also measured; Y values for all tested PVC / core-shell bottles varied between 87.1 and 89.9 and the% fogging values for all tested PVC / core-shell bottles varied between 3.0 and 4.6. These optical results indicate that all the core-shell polymers tested were suitable for preparing clear PVC bottles.

Table 1: Formulation of PVC Bottles to Test Physical Properties The following examples and comparative examples are presented to illustrate the invention, but this invention is not limited by these examples. All parts and percentages are by weight, unless indicated otherwise. The following breviations are used in the Examples: Bd = butadiene.

BA = butyl acrylate MMA = methyl methacrylate St = styrene DVB = divinyl-benzene CHP = eumeno hydroperoxide DIBHP = isopropylbenzyl hydroperoxide TBIC = tere isopropylcarbonate. -butylperoxy t-BHP = tere hydroperoxide. -butyl TSPP = tetrasodium pyrophosphate Fe-EDTA = ferrous iron - ethylene diamine tetraacetic acid SFS = sodium formaldehyde sulfoxylate KOL = potassium oleate.

In the description of the compositions, a simple diagonal ("/") implies a copolymer, the numbers separated by a single diagonal within parentheses indicate the relation of the copolymer of the particular stage, while a double diagonal "//") implies a separate stage. The general format for describing the core-shell polymer compositions is thus a "core composition" // "composition of the stage of internal graft "//" intermediate sealing stage "//" external cover composition ".

EXAMPLE 1 The composition of this example is Bd / Sty // Sty // MMA in a weight ratio of 76 (75/25) // 11 // 13 and does not contain an intermediate sealing step. The conversion of the core monomer was 70%. 6310 parts of deionized water were charged to a suitable reactor. 118 parts of TSPP of a 5.0% solution, 722 parts of the sowing of Bd / Sty 7/3 in a 33% emulsion, 13 parts of sodium hydroxide from a 2.5% solution (or, as necessary for a Target pH of 9.8 to 10.0), 0.15 parts of Fe-EDTA and deionized water 250 parts to rinse, while stirring. The reactor was heated to 65 ° C. At this temperature of 65 ° C, Bd 4845 parts were fed to the reactor simultaneously and Sty 1615 parts of a 2.0% solution and KOL 469 parts of a 15.5% solution; this step prepared the nucleus of the core-shell polymer. In a monomer conversion of core of 70%, 935 part of styrene was fed to the reactor with the DIBHP (53% active) 28 parts, SFS 342 parts of a 2.0% solution and KOL 275 parts of a 15.5% solution, to form the grafting stage internal An additional 166 SFS parts of a 2.0% solution of DIBHP (53% active), 14 parts, were added at the end of the styrene loading. The reaction was conducted at 65 ° C for about 13 hours, to ensure a conversion of styrene > 95% The reactor was ventilated at the end of this internal grafting stage. Then, 1105 parts of MMA and 350 parts of deionized water were added. Eighteen parts of DIBHP (53% active) and 208 parts of SFS of a 2.0% solution were fed simultaneously to form the outer shell. This reaction was conducted for 4-5 hours until a conversion of 97-100%. The reaction was cooled to 40 ° C and then stabilized as previously described. An emulsion of 48-50% solids was obtained.

EXAMPLE 2 The composition of this example is Bd / Sty // Sty // BA / DVB // MMA, in a weight ratio of 76 (75/25) // 11 // 1.5 (67/33) // 13. The conversion of the monomer from core was 70%. The core-shell polymer in this example was prepared in a manner similar to Example 1, with the following exceptions: after ventilating at the end of the internal grafting stage, 80 parts of BA, 72.5 parts of DVB ( 55% active), 27 parts of t-BHP of a 2.0% solution and 19 parts of SFS of a 2.0% solution, at a temperature of 65 ° C, to prepare the intermediate sealing step. Likewise, 312 parts of t-BHP were used from a 2.0% solution instead of DIBHP, in the preparation of the outer shell.

EXAMPLE 3 The composition of this example is Bd / Sty // Sty // BA / DVB // MMA, in a weight ratio of 76 (75/25) // 11 // 2 (50/50) // 13. The conversion of the core monomer was 70%. The core-shell polymer in this example was prepared in a manner similar to Example 2, with the following exceptions: after ventilating at the end of the internal grafting stage, 80 parts of BA, 145 parts of DVB ( 55% active), 40 parts of t-BHP from a 2.0% solution and 28 parts of SFS from a solution at 2.0%, at a temperature of 65 ° C, to prepare the intermediate grafting stage.

EXAMPLE 4 The composition of this example is Bd / Sty // Sty // BA // MMA, in a weight ratio of 76 (75/25) // 11 // 1 // 13. The conversion of the core monomer was 75%. The core-shell polymer in this example was prepared in a manner similar to Example 1, with the following exceptions: after ventilating at the end of the internal grafting step, 80 parts of BA were fed to the reactor, I part of DIBHP (53% active (and 10 parts of SFS of a 2.0% solution at a temperature of 65 ° C, to prepare the intermediate sealing stage.

EXAMPLE 5 The composition of this example is Bd / Sty // Sty // BA / DVB // MMA, in a weight ratio of 76 (75/25) // II // 4.4 (91/9) // 13. The conversion of the core monomer was 75%. The core-shell polymer in this example was prepared in a manner similar to Example 1, with the following exceptions: after venting at the end of the internal grafting stage, 340 parts of BA, 62 parts of DVB (55% active), 4 parts of DIBHP (53% active) and 50 parts of SFS of a 2.0% solution, at a temperature of 65 were fed to the reactor. ° C, to prepare the intermediate sealing stage.

EXAMPLE 6 The composition of this example is Bd / Sty // Sty // BA / DVB // MMA, in a weight ratio of 76 (75/25) // 11 // 1.1 (91/9) // 13. The conversion of the core monomer was 68%. The core-shell polymer in this example was prepared in a manner similar to Example 1, with the following exceptions: after ventilating at the end of the internal grafting stage, 80 parts of BA, 15.5 parts of DVB ( 55% active), 1 part of DIBHP (53% active) and 12 parts of SFS of a 2.0% solution, at a temperature of 65 ° C, to prepare the intermediate sealing stage.

EXAMPLE 7 The composition of this example is Bd / Sty // Sty // MMA, in a weight ratio of 76 (75/25) // 11 // 13. The core-shell polymer in this example was prepared in a manner similar to Example 1, with the exception that the conversion of the core monomer was 75%.

EXAMPLE 8 The composition of this example is Bd / Sty // Sty // BA / DVB // MMA, in a weight ratio of 76 (75/25) // 11 // 1.2 (83/17) // 13. The conversion of the core monomer was 75%. The core-shell polymer in this example was prepared in a manner similar to Example 1, with the following exceptions: after ventilating at the end of the internal grafting stage, 80 parts of BA, 31 parts of DVB ( 55% active), 1 part of DIBHP (55% active) and 15 parts of SFS of a 2.0% solution, at a temperature of 65 ° C, to prepare the intermediate sealing stage.

EXAMPLE 9 The composition and process of this example were the same as those of Example 6, with the exception that the conversion of the core monomer was 80%, before adding the internal grafting step.

EXAMPLE 10 The composition of this example is Bd / Sty // Sty // MMA / DVB, in a weight ratio of 76 (75/25) // 11 // 13 (99/1) and does not contain an intermediate sealing step .. The conversion of the target monomer was 70%, before adding the internal grafting stage. The core-shell polymer in this example was prepared in a manner similar to Example 1, with the following exceptions: after ventilating at the end of the internal grafting stage, 1105 parts of MMA, 22 parts of DVB ( 55% active) and 350 parts of deionized water. 22 parts of DIBHP (53% active) and 270 parts of SFS in a 2.0% solution were simultaneously fed to the reactor to form the outer graft shell.

EXAMPLE 11 The composition of this example is Bd / Sty // Sty // MMA, in a weight ratio of 76 (75/25) // 11 // 13 and does not contain intermediate sealing step. The reaction temperature was 85 ° C, during most of the process. To a suitable reactor were charged 6310 parts of deionized water, 118 parts of TSPP of a 5.0% solution, 700 parts of the planting of Bd / Sty, 7/3, of a 33% emulsion, 13 parts of sodium hydroxide of a 2.5% solution (or, as needed, for the target pH of 9.8 to 10.0), 0.15 parts of Fe-EDTA and 250 parts of deionized water to rinse while shake The rector was heated to 85CC. At this temperature of 85 ° C, 4845 parts of butadiene and 1615 parts of styrene were fed to the reactor, simultaneously with 16 parts of t-BHP, 548 parts of SFS of a 2.0% solution and 876 parts of KOL of a solution of 15.5% to form the internal graft stage. Additional t-BHP was added to reach a monomer conversion of 85%, this step prepared the nucleus of the core-shell polymer. Next, 935 parts of styrene were fed to the reactor with 9 parts of t-BHP, 322 parts of SFS of a 2.0% solution and 500 part of KOL of a 15.5% solution, to form the internal grafting stage. This reaction was conducted at a temperature of 85 ° C for about 9 hours. During the last hour, the reaction was cooled to 70 ° C. The conversion for this stage was 95%. The reactor was vented at the end of the internal grafting stage. Then, 1105 parts of MMA and 200 parts of deionized water were added. 232 parts of a solution were simultaneously fed to the 2. 0% and 155 parts of SFS of a 2.0% solution inside the reactor to form the outer shell. The reaction was maintained at 75 ° C for 2 hours and cooled to 65 ° C over the last hour. The final conversion was 97-100%. This reaction was cooled to 40 ° C and then stabilized as previously described. An emulsion of 48-50% solids was obtained.

EXAMPLE 12 The composition of this example is Bd / Sty // Sty // MMA, in a weight ratio of 76 (75/25) // 11 // 13 and does not contain an intermediate sealing step .. The core-shell polymer in this example was prepared in a manner similar to Example 1, except that the initiator in the external cover stage was the TBIC (6 parts) instead of the DIBHP. The reaction temperature was 50 ° C during most of the process.

EXAMPLE 13 The composition of this example is Bd / Sty / DVB // Sty // MMA, in a weight ratio of 76 (75/25/1) // 11 // 13 and does not contain intermediate sealing stage. Temperature of reaction was 50 ° C, during most of the process. To a suitable reactor were charged 6310 parts of deionized water, 118 parts of TSPP of a 5.0% solution, 722 parts of the butadiene seeding of a 33% emulsion, 13 parts of sodium hydroxide of a 2.5% solution ( or, as necessary, for the target pH of 9.8 to 10.0), 0.15 parts of Fe-EDTA and 250 parts of deionized water to rinse while stirring. The rector was heated to 50 ° C. At this temperature of 50 ° C, 4845 parts of butadiene, 1615 parts of styrene and 14 parts of DVB were fed to the reactor, simultaneously with 49 parts of DIBHP, 582 parts of SFS of a 2% solution and 469 parts of KOL of a 15.5% solution, to form the internal grafting stage. The core monomer took more than 24 hours to reach 95%, then the reactor was ventilated. Continuing at 50 ° C, 935 parts of styrene were fed into the reactor for three hours with 28 parts of DIBHP (53% active), 342 parts of SFS of a 2.0% solution and 275 parts of KOL of a 15.5% solution, to form the internal graft stage. An additional 166 SFS parts of a 2.0% solution and 14 parts of DIBHP (53% active) for three more hours at the end of the styrene load. The reactor was ventilated at the end of the stage at the end of this internal grafting stage. Then, 1105 parts of MMA and 350 parts of deionized water were added. Eighteen parts of DIBHP (53% active) and 208 parts of SFS of a 2.0% solution were fed simultaneously to form the outer shell. This external shell reaction was conducted for 5-6 hours at 100% conversion & The reaction was cooled to 40 ° C and then stabilized as previously described. An emulsion of 46% solids was obtained.

COMPARATIVE EXAMPLE A A core-shell impact modifier was prepared, based on Example 6 of U.S. Patent No. 5,534,594, with minor modifications. This comparative example illustrates that the Bd / Sty // Sty // MMA three-core core-shell polymer of composition 70 (75/25) // 14 // 16 does not contain an intermediate sealing step and has a size of average particles of the aqueous paste greater than 300 micras, when it coagulates above 20 ° C.

To a suitable reactor were charged 6368 parts of deionized water, 122 parts of TSPP of a 5.0% solution, 67.5 parts of the seed of B / S, 7/3, of a 20% emulsion, 27 parts of sodium hydroxide from a 2.5% solution (or, as needed, for the target pH of 9.8 to 10.0), 0.15 parts of Fe-EDTA, 22.5 parts of SFS from a 6.0% solution, 2.7 parts of t-BHP and 150 parts of deionized water to rinse while stirring. The rector was heated to 85 ° C. At this temperature of 85 ° C, 5158 parts of butadiene and 1571 parts of styrene were fed to the reactor, simultaneously with 27 parts of t-BHP, 304 parts of SFS of a 6.0% solution and 761 parts of potassium oleate from a 15.5% solution to prepare the core. After the monomer conversion of about 77%, 1125 parts of styrene were fed to the reactor with 405 parts of t-BHP from a 5.0% solution, 281 parts of SFS from a 6.0% solution and 150 parts of deionized water. . The reaction was cooled to 65 ° C in at least two hours. The objective conversion for this stage it was 95% and then the reactor was vented and any butadiene was collected in a dry ice trap. After venting, 1012 parts of MMA, 112.5 parts of butyl acrylate, 110 parts of potassium oleate from a 15.6% solution and 150 parts of deionized water were added. 232 parts of a 2.0% solution and 155 parts of SFS of a 2.0% solution were simultaneously added. The reaction was maintained at 65 ° C for 3 hours. The final conversion was 100%. The reaction was cooled to 40 ° C and then stabilized in the previously described manner. An emulsion with 50 to 52% solids was obtained.

COMPARATIVE EXAMPLE B A core-shell impact modifier was prepared, based on Example 4 of U.S. Patent No. 5,534,594, with minor modifications. This comparative example illustrates that the three-stage core-shell polymer of Bd / Sty / DVB // Sty / MMA // MMA / Sty of composition 70 (75/25/1) // 15 (93/7) / / 15 (93/7), which does not contain an intermediate sealing step, has an average particle size of the aqueous paste greater than 300 microns, when it coagulates above 20 ° C.

To a suitable reactor were charged 8600 parts of deionized water, 339 parts of potassium oleate of a 15.5% solution, 117 parts of TSPP of a 5.0% solution, 0.25 parts of Fe-EDTA, 2 parts of NaOH of a solution to 20%, 0.24 parts of ferrous sulfate heptahydrate, 875 parts of styrene, DVB (55% active, 11 parts of DIBHP, 40 parts of SFS of a 5.0% solution and 2625 parts of butadiene.) The temperature was adjusted to 50 ° C and held for 5-6 hours until the conversions were 70%, then the temperature was raised to 870 ° C and 1125 parts of potassium chloride were added from a 10% solution, 800 parts of deionized water, 700 parts of styrene, 50 parts of MMA, 3.4 parts of eumeno hydroxide and 113 parts of SFS of a 2.0% solution and the temperature was maintained at 70 ° C. After three hours, 226 parts of a 15.5% solution of potassium oleate, 200 parts of sodium hydroxide of a 2.5% solution, 500 parts of deionized water, 7000 parts of MMA, 50 parts of styrene, 0.4 parts of eumeno hydroxide, 100 parts of deionized water, 169 parts of t-BHP of a 2.0% solution, and 112.5 parts of SFS of a solution 2.0%, and reacted for three hours. This The reaction was cooled to 65 ° C during the last hour, until a conversion of approximately 100% was reached. The reactor was vented and any unreacted butadiene was collected in an echo-funnel trap. The reaction was cooled to 40 ° C and then stabilized in the previously described manner. An emulsion of 48-50% solids was obtained.

Table 2. Results of the Coagulation: Effect of the Composition and Conditions of the Process Instrument that measures the particle size obturado of particles of aqueous paste greater than 300 microns Table 3. Results of the impact of the bottle fall: Effect of the composition of the intermediate sealing stage i'abla 4. Results of the impact of falling bottles Effect of the reaction temperature - The level of the core-covered impact modifier in these examples was 12 per. a - Average results for 40 impacts of modifiers prepared according to the Example 11 at 85 ° C. b - Average results for 8 impacts of modifiers prepared according to the Example 12 at 65 ° C. c - Average results for 5 impacts of modifiers prepared according to the ! Example 13 at 50 ° C.

The results in Table 2 show that the average particle size of the aqueous slurry of the core-coated polymers of coagulated MBS, as taught by Troy (Comparative Examples A and B), is more than 300 microns drawback. The results of Table 2 also show that the addition of an intermediate sealing step to the core-shell polymer of MBS conveniently supplies an average particle size of the aqueous paste well below 300 microns when coagulated at temperatures above 20. ° C. The results of Table 3 show that the PVC bottles in admixture with the core-shell polymers of MBS, taught by Troy (Comparative Examples A and B, which do not have an intermediate sealing stage and prepared at 50 ° C or 85 ° C) generally have a higher percentage of failures when they fall compared to PVC bottles in admixture with the MBS core-shell polymers of the present invention. The results in Table 4 show that several polymers of MBS, prepared at about 65 ° C, supply PVC bottles modified on impact, which have a Substantially lower failure rate when they fall, compared to core-shell polymers prepared either at 50 ° C or at 85 ° C.

Claims (11)

1. CLAIMS 1. A core-shell impact modifier composition, this composition comprises: (A) about 70 to 85 parts of a core comprising about 15 to 35 weight percent of units derived from at least one aromatic monomer of vinyl, and about 65 to 85 weight percent of units derived from at least one diolefin monomer; (B) about 8 to 14 parts of an internal grafting step, comprising at least one vinyl aromatic monomer or at least one C1-C4 alkyl methacrylate monomer; (C) about 0.1 to 5 parts of an intermediate sealing step, comprising at least one monomer selected from a C 1 -C 8 alkyl acrylate or a polyunsaturated crosslinker; and (D) about 10 to 16 parts of an outer shell, comprising at least one Cl-C4 alkyl (meth) acrylate monomer, or at least one vinyl aromatic monomer.
2. 2. The core-shell impact modifier of claim 1, wherein the polyunsaturated interlayer of the intermediate sealing step (C) is divinylbenzene and the C 1 -C 8 alkyl acrylate monomer is butyl acrylate.
3. 3. The core-shell impact modifier of claims 1 or 2, wherein the aromatic vinyl monomer is selected from styrene, para-methylstyrene, alpha-methyl-styrene, chlorostyrene, vinyl-toluene, bromostyrene, dibromostyrene, tribromostyrene, isopropenyl -naphthalene or vinyl-naphthalene, and where the diolefin monomer is butadiene.
4. 4. A mixture of polymers, which comprises: (A) one or more matrix polymers; (B) the composition of claims 1, 2 or 3; Y where the weight ratio of (A) © B) is approximately 99: 1 to 70:30.
5. 5. The polymer blend according to claim 4, wherein the matrix polymer is polyvinyl chloride.
6. 6. Products produced from the polymer mixture according to claims 4 or 5.
7. 7. A process for preparing a core-shell impact modifying emulsion, having a weight fraction of elastic core exceeding 70%, this process comprises: (A) polymerizing in emulsion, a first mixture of monomers, comprising approximately 65 1 85% of a diolefin monomer and about 15 to 35% of at least one vinyl aromatic monomer, in the presence of an emulsifier and a free radical initiator, until a conversion of 60 to 90% has been achieved from the monomers to the polymer; (B) continuing the polymerization of the first monomer mixture, while adding a second monomer mixture, which comprises at least one monomer vinyl aromatic or a C 1 -C 4 alkyl methacrylate monomer; (C) continuing the polymerization of the second monomer mixture until at least 90% conversion to the polymer has been achieved; (D) adding a third monomer mixture and a free radical initiator, this mixture comprising at least one monomer selected from a C 1 -C 8 alkyl acrylate or a polyunsaturated crosslinker; and (E) adding a fourth monomer mixture, this mixture comprises at least one Cl-C43 alkyl methacrylate monomer or at least one aromatic vinyl monomer, adding a free radical initiator, and continuing the polymerization until it has been achieved at least one 95% conversion to the polymer. wherein the reaction temperature, during steps (A) to (E), is in the range of 20 to 100 ° C.
8. 8. The process of claim 7, wherein the C 1 -C 8 alkyl acrylate monomer in step (D) is butyl acrylate.
9. 9. The process, according to claim 7, wherein the reaction temperature is in the range of 55 to 80 ° C.
10. 10. A process for preparing a core-shell impact modifying emulsion, having a weight fraction of the elastic core exceeding 70%, this process comprises: (A) polymerizing in emulsion, a first mixture of monomers, comprising approximately 65 al 85% of a diolefin monomer and about 15 to 35% of at least one vinyl aromatic monomer, in the presence of an emulsifier and a free radical initiator, until a conversion of 60 to 90% of the monomers to the polymer; (B) continuing the polymerization of the first monomer mixture, while adding a second monomer mixture, this mixture comprises at least one vinyl aromatic monomer or a C1-C4 alkyl methacrylate monomer; (C) continuing the polymerization of the second monomer mixture until at least 90% conversion to the polymer has been achieved; and (D) adding a third monomer mixture, this mixture comprises at least one C 1-4 alkyl methacrylate monomer or at least one vinyl aromatic monomer, adding a free radical initiator and continuing the polymerization until a conversion of at least 95% to the polymer. wherein the reaction temperature, during steps (A) to (D), is in the range of 60 to 70 ° C.
11. 11. A polymer product, produced by the process of claims 7 to 10.