Abstract: The present invention describes plastic materials and food additives that are free or substantially free from endocrine disruptive chemicals. The plastic materials may be used in products which are exposed to individuals in which endocrine disruptive activity is particularly disadvantageous, such as baby bottles, baby toys, food containers, medical containers, animal cages and medical products. The food additives may be used in food products that are ingested by individuals in which endocrine disruptive activity is particularly disadvantageous, such as newborns or the physically infirm. The present invention also describes a series of assays which, when performed in combination, provide a novel method for determining the presence of endocrine disruptive activity.

Abstract: The present invention relates to curable coating compositions containing acetoacetylated polyvinyl polymers obtained from polyvinyl polymers, such as polyvinyl butyrals. These coating compositions are especially suitable for use as wash primers in automotive OEM and refinish coating applications.

Abstract: Disclosed are (1) a porous polymer particle comprising a polymer substrate having ester bonds connected to a group containing a quaternary ammonium structure through a spacer molecule, (2) an alkali-resistant, high-strength porous polymer particle having ester bonds connected to a group containing a quaternary ammonium structure through a spacer molecule, a part of the ester bonds being saponified and converted to a hydroxyl group(s), (3) a porous polymer particle comprising a polymer substrate having ester bonds connected to a group containing a quaternary ammonium structure through a spacer molecule, the porous polymer particles being treated with an alkaline solution to generate a hydroxyl and/or a carboxyl group on a surface of the substrate, (4) an anion exchanger comprising any one of the particles (1) to (3) above, (5) a packing material for anion chromatography comprising the anion exchanger (4) above, (6) a column for anion chromatography using the anion exchanger (4) above, and (7) a method for meas

Abstract: A post-treatment process for making a water-resistant polymeric composition which is inkjet printable, or in the form of a strongly-swellable gel, includes providing a stable, aqueous two-phase polymeric composition by the steps of forming a reaction mixture in a reaction vessel which includes a water-soluble vinyl monomer, optionally with one or more water-soluble comonomers, a first amount of a multi-vinyl crosslinking agent, and water, heating the mixture, then periodically adding a predetermined amount of a free radical initiator, and polymerizing the reaction mixture, optionally removing the resultant two-phase polymeric composition from the reaction vessel, adding a predetermined amount of a post-treatment crosslinker, optionally blending with a proteinaceous or other water compatible polymer material thereto, optionally coating the mixture onto a support, and optionally heating at room temperature or above, to increase the viscosity of the composition in a predetermined manner.

Abstract: Polymers for cement dispersing admixtures, which show different performing properties in concrete are described. All polymers are based on a composition of reactants, namely a) a poly(acrylic acid), b) a polyalkyleneglycol-monoalkylether and, optionally c) a ?-amino-polyalkylene-glycol-?-alkylether and/or d) a primary or secondary amine. By keeping the composition of reactants constant and varying only the reaction time, polymers with different properties can easily be achieved. Such polymers are suitable for pre-cast, readymix or for increasing workability over time, just depending on reaction time. Polymers of the invention can be used as single polymer or in polymer blends. For this, the kinetics of the used polymer analogous condensation reaction was intensively studied. Additionally, the benefit of amines as reactant regarding stability and hydrolysis velocity of cleavable side groups was investigated.

Abstract: High-density, miniaturized arrays including high surface areas. Arrays described include substrate with a coating of linking agents, as well as arrays with reactants affixed to the substrates. Methods of manufacturing high-density arrays of reactants. The methods include the use of oriented, heat shrink films and elastomeric materials. Methods of functionalizing a substrate with linking agents for subsequent affixation of reactants are also disclosed herein.

Abstract: A novel modified conjugated diene polymer is obtained by polymerizing a conjugated diene compound with a specified catalyst consisting of components (a)-(c) and then reacting with at least one specified compound selected from the group consisting of components (d)-(l), and has a content of cis-1,4-bond of not less than 85% and a ratio of weight average molecular weight to number average molecular weight of not more than 4. And also, a rubber composition comprises the modified conjugated diene polymer a rubber ingredient.

Abstract: The invention provides a method of making a number of different multifunctional acrylic materials from a limited number of starting materials. The method of the invention requires the product of a masterbatch of an acrylic oligomer or polymer having two or more cyclic carbonate functional groups. A first portion of the masterbatch is then reacted with ammonia and a grafting material (c) in either successive or simultaneous reactions to provide a first multifunctional acrylic oligomer or polymer. Additional portions of the masterbatch may be reacted with ammonia and other grafting materials (c), different from the first grafting material (c), in either successive or simultaneous reactions to provide different multifunctional acrylic oligomers or polymers.

Abstract: A crosslinkable second-order nonlinear optical polymer having one or more polarizable chromophore moieties, one or more diene moieties, and one or more dienophile or dienophile precursor moieties, wherein the diene and dienophile moieties are reactive to form 4+2 cycloaddition products; a crosslinked second-order nonlinear optical polymer having aligned, polarizable chromophore moieties and one or more 4+2 cycloaddition moieties, wherein the 4+2 cycloaddition moieties are reversibly, thermally reactive to provide diene moieties and dienophile moieties; lattices and devices that include the crosslinkable second-order nonlinear optical polymer; lattices and devices that include the crosslinked second-order nonlinear optical polymer; and methods for making the crosslinked second-order nonlinear optical polymer.

Abstract: Disclosed is a method of preparing terminally functionalized telechelic polymers using a cationic living polymer product or a terminal tert-chloride chain end of a carbocationic quasiliving polymer product, which comprises quenching the polymer product with an N-substituted pyrrole to thereby functionalize the N-substituted pyrrole at the terminal reactive polymer chain end(s). Also disclosed are the terminal functionalized polyisobuyl N-substituted pyrrole compounds where the polyisobutyl group is substituted at the 2 and 3 position of the N-substituted pyrrole.

Abstract: Process for the preparation of a derivative of a polymer having at least one functional group, characterized in that the process comprises the following step (i): (i) reaction of the polymer having at least one functional group, with at least one activating reagent or at least one derivative of an activating reagent in homogeneous phase.

Abstract: The invention relates to a method of making waterborne multifunctional materials, especially waterborne multifunctional materials comprising at least one primary carbamate group and a grafting moiety (cii). The method of the invention requires the successive or simultaneous reactions of a material P with a grafting material (c) and ammonia. Material P comprises two or more cyclic carbonate groups (bi). Grafting material (c) comprises at least one amine group (ci) and a grafting moiety (cii). The amine group (ci) is selected from primary amines, secondary amines, and mixtures thereof. The resulting waterborne multifunctional materials may be water dispersible, water soluble and/or useful in electrodeposition coatings.

Abstract: These compounds contain an oxetane functionality and a maleimide functionality. The oxetane functionality is homopolymerizable in reactions that undergo cationic or anionic ring opening, and the maleimide functionality is homopolymerizable, or polymerizable with compounds such as electron donor compounds. The dual functionality allows for dual cure processing.

Abstract: A process for the preparation of novel polyamides, the use of such polyamides for the production of fibers, sheets and moldings, and fibers, sheets and moldings obtainable from such polyamides, are provided.

Abstract: The invention relates to a method of making multifunctional materials, especially materials comprising at least one primary carbamate group and a grafting moiety (cii). The method of the invention requires the successive or simultaneous reactions of a material P with a grafting material (c) and ammonia. Material P comprises two or more cyclic carbonate groups (bi). Grafting material (c) comprises at least one amine group (ci) and a grafting moiety (cii). The amine group (ci) is selected from primary amines, secondary amines, and mixtures thereof. The resulting multifunctional materials are useful in a variety of curable coating compositions, including solventborne, waterborne, electrodeposition, liquid solvent free coatings, powder, and powder slurry.

Abstract: The present invention provides: a process for producing a water-absorbing agent at low temperature in a short time, wherein the water-absorbing agent has excellent balance between the absorption capacity without load and the absorption capacity under a load, high fluidity under a hygroscopic atmosphere, and excellent safety; and a novel water-absorbing agent and a novel crosslinking agent particularly suitable for crosslinking water-absorbent resins. The water-absorbing agent, having excellent balance between the absorption capacity without load and the absorption capacity under a load, high fluidity under a hygroscopic atmosphere, and excellent safety, can be obtained by using an oxetane compound and/or an imidazolidinone compound for a water-absorbent resin.

Abstract: Surface-treated superabsorbent polymer particles obtained by mixing 100 parts by weight of superabsorbent polymer particles with 0.001 to 10 parts by weight of a hydroxyalkylamide, and heating the surface-treated superabsorbent polymer particles to crosslink molecular chains existing at least in the vicinity of the surfaces of the superabsorbent polymer particles is disclosed. Surface crosslinking the superabsorbent polymer particles with a hydroxyalkylamide substantially increases both the rate of liquid absorption and the quantity of liquid absorbed and retained by the superabsorbent particles.

Abstract: Disclosed is an ink composition which comprises water, a colorant, and a lightfastness agent which is a polysiloxane having thereon a hydrophilic moiety and a lightfastness moiety. Also disclosed are printing processes using the ink.

Abstract: The present invention relates to the prevention of scorching before crosslinking of a thermoplastic and/or elastomeric composition with peroxides or azo compounds. This is achieved by using a family of specific nitroxides as additive.

Abstract: A crosslinking agent is provided, prepared by reacting (A) an aminoplast resin; (B) a reactive urethane group-containing adduct of a polyfunctional polymer and monoisocyanate, and (C) at least one other compound having active hydrogen groups reactive with aminoplast resin (A). Compound (C) is selected from: (i) compounds having the structure (I):  wherein X is aromatic; R1, R2, and R3 each independently represents H, (cyclo)alkyl having from 1 to 12 carbon atoms, aryl, alkaryl, aralkyl, or an active hydrogen-containing group, (ii) compounds having the structure (II) or (III):  where R′ and R″ each independently represents an aromatic group or an alkyl group having 1 to 12 carbon atoms; and (iii) compounds different from (i) and (ii), having a melting point of at least 80° C. Further provided are methods for preparing the crosslinking agent, curable compositions containing the crosslinking agent, and coated substrates.

Abstract: A composition comprising a fluoropolymer comprising interpolymerized units derived from a nitrogen-containing cure site monomer; and a catalyst composition comprising a compound having the general formula: wherein the group HA is an acid, and each R1, R2, and R3 is, independently, the same or a different C1-C20 alkyl group, a C3-C20 cyclic or heterocyclic group, Rf(CH2)x—wherein Rf is a C1-C8 linear or branched and at least partially fluorinated alkylene, cycloalkylene, or oxyalkylene, and x is 1 to 4, or a bond to another R group such that the nitrogen is bonded to or part of an imino or heterocyclic group; wherein two or more R groups may be linked to form a cyclic, bicyclic or aromatic group, optionally comprising a heteroatom. Also provided are a method of making a fluoropolymer composition and articles prepared from the compositions.

Abstract: A process for preparing a fluorine-containing elastomeric copolymer, a vulcanizing agent and a vulcanization accelerator, said process comprising the step of coagulating the copolymer from an aqueous dispersion of the fluorine-containing elastomeric copolymer and drying the resulting coagulate of the copolymer while kneading, wherein a mixture of mutually soluble components consisting of the vulcanizing agent and the vulcanization accelerator is added to the coagulate, can give a fluororubber composition having stable vulcanization physical properties, wherein the vulcanizing agent and the vulcanization accelerator are homogeneously dispersed in the fluororubber.

Abstract: This invention provides a method for producing a derivatized resin useful in the arts of solid-phase peptide synthesis, combinatorial chemistry, and peptide or protein purification and separation. Methods for synthesizing the derivatized resin, the prototypical example of which is hydrazyl-carbonyl-amino methylated polystyrene, are provided by this invention disclosure.

Abstract: A microencapsulated adhesive component, comprising a cross-linking constituent microencapsulated with a silanized polybutadiene, wherein the reactive constituent has been first reacted in the melt with cross-linking, thereby resulting in a cross-linkable hot-melt adhesive component for coating and/or laminating surface formations.

Abstract: The present invention is directed to a thermally curable polymer composition, and a photolithographic substrate coated therewith, the composition comprising a hydroxyl-containing polymer, an amino cross-linking agent and a thermal acid generator. The thermally curable polymer composition may be dissolved in a solvent and used as an undercoat layer in deep UV lithography.

Abstract: A thermosetting composition that includes an ungelled copolymer composition and a crosslinking agent. The ungelled copolymer composition includes a functional group-containing copolymer that includes segments of alternating residues derived from a donor monomer composition comprising an acceptor monomer composition. The donor monomer composition includes one or both of isobutylene and diisobutylene, and the acceptor monomer composition includes acrylic monomers and monomers containing functional groups. The ungelled copolymer composition is substantially free of transition metals and Lewis acids, and the copolymer is substantially free of maleate-type monomer residues and fumarate-type monomer residues. The crosslinking agent has at least two functional groups that are reactive with the functional groups of the copolymer. The thermosetting composition may be in liquid, powder, or dispersed form and may be applied by traditional or electrocoating methods.

Abstract: A process for the preparation of novel polyamides, the use of such polyamides for the production of fibers, sheets and moldings, and fibers, sheets and moldings obtainable from such polyamides, are provided.

Abstract: There is provided a process for producing a modified polymer rubber having modified both ends, which comprises the steps of: (1) reacting a compound represented by the following formula (1) with an organic alkali metal compound to produce a chemical species, (2) polymerizing a conjugated diene monomer or a combination of a conjugated diene monomer with an aromatic vinyl monomer in the presence of the chemical species to produce an active polymer having an alkali metal at an end thereof, and (3) reacting the active polymer with a functional group-carrying modifying agent in a hydrocarbon solvent to produce the modified polymer rubber having modified both ends.

Abstract: The present invention relates to vulcanization accelerators constituted by compounds, derived from secondary amines, belonging to the class of enamines and to a process for their preparation.

Abstract: A thermoplastic elastomer composition includes: a thermoplastic elastomer having a carbonyl-containing group and a nitrogen-containing heterocycle in a side chain thereof; and an amino group-containing compound. The thermoplastic elastomer composition retains excellent recycle property, and also has excellent mechanical characteristics and compression set (shape retention). Thus, it is of extremely superior industrial applicability and environmental protection effect.

Abstract: A device containing a support member, a cross-linked polymer, and a pH buffer agent. A surface of the support member is coated with the cross-linked polymer in which the pH buffer agent is embedded.

Abstract: The invention discloses a protective coating solution suitable for forming a resinous protective coating layer on a patterned resist layer in the manufacture of semiconductor devices having, in particular, crowdedly hole-patterned areas and areas of an isolated hole pattern. The essential ingredients of the solution are (A) a resinous compound such as an acrylic resin and (B) a crosslinking compound such as a triazine compound which are combined in such a proportion of 2:8 to 4:6 by weight that the overall weight-average molecular weight of the components (A) and (B) is in the range from 1300 to 4500. This inventive coating solution is advantageous in respect of evenness in the thickness of the coating layer even on a patterned resist layer having a crowdedly hole-patterned area and an isolatedly hole-patterned area and absence of unfilled voids within the hole patterns.

Abstract: The present invention relates to a process for preparing novel, monodisperse ion exchangers having chelating functional groups, and their use for adsorbing metal compounds, in particular, heavy metal compounds and noble metal compounds, and also for extracting alkaline-earth metals from saline solutions from alkali metal chloride electrolysis.

Abstract: The present invention relates to compositions which comprise one or more polymer conjugates having the formula: wherein T is a heterocyclic unit which is capable of inhibiting one or more proteolytic enzymes; L is a linking group; [Poly] is a polymeric unit, i indicates the number of said heterocyclic units which comprise said conjugate and has the value of from 1 to 100; z is 0 or 1, said polymer conjugates suitable for use in preventing skin irritation resulting from exposure of the skin to body fluids, inter alia, feces, menstrual fluid. The conjugates of the present invention are useful in diapers, dressings, sanitary napkins, and the like.

Abstract: In a production process for a water-absorbent resin, comprising the steps of: blending a liquid material and a water-absorbent resin; and heating the resultant mixture in order to produce a modified water-absorbent resin, the present invention is to provide: a method for uniformly and efficiently treating a water-absorbent resin favorably in view of industry, and as a result, a good-balanced water-absorbent resin having various excellent properties, such absorption capacity without a load, absorption capacity under a load, and single-layer absorption capacity under a load in contact with an aqueous liquid. The production process comprises the step of spray-blending a water-absorbent resin (A) and a liquid material (B) with a blending apparatus equipped with a spray nozzle (C), wherein the liquid material (B) is sprayed from the spray nozzle (C) and its spray pattern is a circular and hollow cone shape or a double-convex-lens and elliptic cone shape.

Abstract: The present invention relates to novel templates useful for generating novel compounds and to compounds produced utilizing the templates. The templates comprise quaternary amino acids that may be linked to solid supports. These templates make possible the production of novel classes of chemical compounds through a plurality of chemical reactions. The templates are advantageous for use in drug discovery regimes.

Abstract: A post-treatment process for making a water-resistant polymeric coating composition or a strongly-swellable polymeric gel includes providing a stable, aqueous two-phase polymeric composition by the steps of forming a reaction mixture in a reaction vessel which includes a water-soluble vinyl monomer, optionally with one or more water-soluble comonomers, first amount of a crosslinking agent, and water, heating the mixture, then periodically adding a predetermined amount of an initiator, and polymerizing at about 30-130° C., optionally removing the resultant two-phase composition from the reaction vessel, adding a predetermined amount of an additional crosslinker or proteinaceous compound thereto, optionally coating the mixture onto a support, and optionally heating to further polymerize the mixture.

Abstract: Hetero-telechelic polymers having the formula: FG—(Q)d—Z—J—[A(R1R2R3)]x  (I) wherein FG is a protected or non-protected functional group; Q is a saturated or unsaturated hydrocarbyl group derived by incorporation of a compound selected from the group consisting of conjugated diene hydrocarbons, alkenylsubstituted aromatic hydrocarbons, and mixtures thereof; d is an integer from 10 to 200; Z is a branched or straight chain hydrocarbon group which contains 3-25 carbon atoms, optionally containing aryl or substituted aryl groups; J is oxygen, sulfur, or nitrogen; [A(R1R2R3)]x is a protecting group, wherein A is an element selected from Group IVa of the Periodic Table of Elements; R1, R2, and R3 are each independently selected from the group consisting of hydrogen, alkyl, substituted alkyl groups containing lower alkyl, lower alkylthio, and lower dialkylamino groups, aryl or substituted aryl groups containing lower alkyl, lower alkylthio, and lower dialkylam

Abstract: A curable powder coating composition is disclosed comprising a film-forming polymer having reactive functional groups, a curing agent having functional groups reactive with the functional groups of the polymer, the curing agent being present in an amount sufficient to cure the coating composition, and a tricarbamoyl triazine compound. The curable powder coating composition has improved mar resistance properties.

Abstract: Hetero-telechelic polymers having the formula: FG—(Q)d—Z—J—[A(R1R2R3)]x  (I) wherein FG is a protected or non-protected functional group; Q is a saturated or unsaturated hydrocarbyl group derived by incorporation of a compound selected from the group consisting of conjugated diene hydrocarbons, alkenylsubstituted aromatic hydrocarbons, and mixtures thereof; d is an integer from 10 to 200; Z is a branched or straight chain hydrocarbon group which contains 3-25 carbon atoms, optionally containing aryl or substituted aryl groups; J is oxygen, sulfur, or nitrogen; [A(R1R2R3)]x is a protecting group, wherein A is an element selected from Group IVa of the Periodic Table of Elements; R1, R2, and R3 are each independently selected from the group consisting of hydrogen, alkyl, substituted alkyl groups containing lower alkyl, lower alkylthio, and lower dialkylamino groups, aryl or substituted aryl groups containing lower alkyl, lower alkylthio, and lower dialkylam

Abstract: The present invention provides: a process for producing a water-absorbing agent at low temperature in a short time, wherein the water-absorbing agent has excellent balance between the absorption capacity without load and the absorption capacity under a load, high fluidity under a hygroscopic atmosphere, and excellent safety; and a novel water-absorbing agent and a novel crosslinking agent particularly suitable for crosslinking water-absorbent resins. The water-absorbing agent, having excellent balance between the absorption capacity without load and the absorption capacity under a load, high fluidity under a hygroscopic atmosphere, and excellent safety, can be obtained by using an oxetane compound and/or an imidazolidinone compound for a water-absorbent resin.

Abstract: Novel solid supported intermediate products of the general formula 1

Abstract: A composition comprising: (a) polyethylene; (b) as a scorch inhibitor, [1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione]; (c) a thioester; (d) a hindered amine stabilizer; and (e) an organic peroxide.

Abstract: A radical-modified polymer having a free radical compound stable in the presence of oxygen at an ordinary temperature at the end of the molecule thereof or in the molecular chain thereof and a polymer composition containing the same.

Abstract: The present invention relates to a process for preparing novel, monodisperse ion exchangers having chelating functional groups, and their use for adsorbing metal compounds, in particular, heavy metal compounds and noble metal compounds, and also for extracting alkaline-earth metals from saline solutions from alkali metal chloride electrolysis.

Abstract: Thermally cured undercoat for use in lithography of a thermally cured composition comprising a hydroxyl-containing polymer, an amino cross-linking agent and a thermal acid generator, wherein the hydroxyl containing polymer is a polymer comprising units m, n and o of the following formula: 1

Abstract: A process for producing scratch-resistant coatings, especially scratch-resistant multicoat finishes, involving use of coating compositions which after curing have a storage modulus E′ in the rubber-elastic range of at least 107.5 Pa and a loss factor tan &dgr; at 20° C. of at least 0.05, the storage modulus E′ and the loss factor having been measured by dynamic mechanical thermoanalysis on free films having a film thickness of 40±10 &mgr;m, and comprise as binders one or more polyacrylate resins having a hydroxyl number of from 100 to 240, an acid number of from 0 to 35, and a number-average molecular weight of from 1500 to 10,000, and as crosslinkers one or more free or blocked isocyanates and/or triazine-based components which crosslink with the hydroxyl groups of the binder to form ether and/or ester structures.

Abstract: Thermally cured undercoat for use in lithography of a thermally cured composition comprising a hydroxyl-containing polymer, an amino cross-linking agent and a thermal acid generator, wherein the hydroxyl containing polymer is a polymer comprising units m, n and o of the following formula: wherein R1 is H or methyl; R2 is a substituted or unsubstituted C6-C14 aryl acrylate or C6-C14 aryl methacrylate group wherein the substituted groups may be phenyl, C1-4 alkyl or C1-4 alkoxy; R3 is a hydroxyl functionalized C1-C8 alkyl acrylate, methacrylate or C6-C14 aryl group, R4 is a C1-C10 linear or branched alkylene; p is an integer of from 1 to 5 with the proviso that there are no more than thirty carbon atoms in the [—R4O—]p; R5 is a C1-C10 linear, branched or cyclic alkyl, substituted or unsubstituted C6-C14 aryl, or substituted or unsubstituted C7-C15 alicyclic hydrocarbon; and m is about 40 to 70, n is about 15 to 35 and o is about 15 to 25.

Abstract: The present invention provides a chlorine-containing polymer vulcanizing composition with improved preservation stability. The present invention is a chlorine-containing polymer vulcanizing composition obtained by blending (a) a zeolite compound, (b) a vulcanizing agent, and (c) an optional organic vulcanization accelerator. The zeolite compound can be natural zeolite, an A-type, X-type, or Y-type synthetic zeolite, a sodatite, natural or synthetic mordenite, ZSM-5, or a metal substitution product thereof. The zeolite compound is preferably an activated zeolite compound. With respect to 100 parts by weight of chlorinated polyethylene, (a) preferably 0.5 to 30 parts by weight, more preferably 5 to 25 parts by weight, of the zeolite compound, (b) preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, of the vulcanizing agent, and (c) preferably 0.5 to 3 mol, more preferably 0.7 to 1.5 mol, of the vulcanization accelerator with respect to 1 mol of (b) the vulcanizing agent are blended.

Abstract: Fine silica particles surface-treated with a silane and having primary particles having a particle diameter of from 0.01 to 5 &mgr;m, which fine silica particles fulfill the following conditions (i) and (ii), a process for their production and an organic resin composition containing such particles as a component are provided. (i) When an organic compound which is liquid at room temperature and has a dielectric constant of from 1 to 40 F/m and fine silica particles are mixed in a weight ratio of 5:1 and shaked, the fine silica particles disperse uniformly in the organic compound, and (ii) the quantity of primary particles remaining as primary particles when methanol is evaporated under heating by means of an evaporator from a dispersion prepared by dispersing the fine silica particles in methanol and thereafter the particles are held at a temperature of 100° C. for 2 hours, is in a percentage of at least 20% based on the quantity of primary particles originally present.