FI106307B - Process for producing hollow particles from latex polymers - Google Patents

Description

1 106307

Process for the manufacture of hollow-core latex polymers It is an object of the present invention to provide an efficient process for the preparation of hollow-core latex polymers. Hollow particles are useful as opacifying agents in coating applications such as paints or paper coatings. The use of cavity particle latex in such coatings reduces the need for expensive pigments, such as TiO 2, without excessive and undesirable weight gain of the coating. The hollow latex particle provides opacity because the cavity structure in the latex particle scatters light more efficiently than the corresponding uniform density particle. The light scattering properties are relative to the refractive index of the refractive index between the shell and the cavity inside. Such cavity particle latexes are also useful in fields other than coatings, such as microencapsulation processes, for example, for the manufacture of controlled release materials.

Thus, the present invention is an effective method for producing hollow latex particles. The process comprises preparing cavity particulate latex polymers and characterized in that the monomers are polymerized in a single step in the presence of hydrocarbons, wherein: 25 (1) the initial reactor comprising a first batch of organic phase and an aqueous phase (a) comprising ) an effective amount of a water-soluble initiator, and the first batch of organic phase 30 comprises (a) an effective amount of at least one monomer having a solubility in the aqueous phase of less than 3% under polymerization conditions, and (b) an effective amount of inert, non-polymerizable hydrocarbon, wherein the polymer formed during monomer polymerization has a solubility in hydrocarbon under 3% polymerization conditions and the hydrocarbon solubility in aqueous phase is less than 1% under polymerization conditions and the monomer is mixed with the hydrocarbon under polymerization conditions; (2) polymerizing the monomer under conditions leading to a low molecular weight polymer so that when the low molecular weight polymer reaches a high enough molecular weight to separate from the charge of the first organic phase to the low molecular weight organic phase, the low molecular weight organic phase a polymer-containing phase; (3) supplying to the vessel a second reactor charge, comprising a second organic phase charge, into the aqueous phase when the low molecular weight polymer formation reaches a step of up to 80% by weight conversion of the monomer to the second organic phase charge further comprising a crosslinking agent a monomer, wherein the crosslinking monomer is incorporated into the low molecular weight polymer phase; and (4) polymerizing the crosslinking monomer with the low molecular weight polymer under polymerization conditions such that a hollow polymer-latex particle is formed.

As used herein, the term "hollow polymer latex particles" is intended to include latex particles which are not completely uniform. Such a particle shape may include various pore structures, such as homogeneous micro-cavities or hemispherical particles having a central cavity. More preferred hollow polymer latex particles are those having a center in the cavity and a ratio of the inside diameter to the outside diameter such that the particle wall becomes 0.1 to 0.9 µτα. Hollow polymer latex particles having a central cavity are more useful in coatings than micro-cavity structures or hemispherical particles with a central cavity.

As used herein, the term "aqueous phase" refers to an organic phase medium. The aqueous phase typically comprises water, an effective amount of a chain exchange agent, and an effective amount of a water-soluble initiator. The aqueous phase may optionally contain one or more surfactants and / or seed particles. Water is typically present in an amount of 100 to 65% by weight based on the total amount of the aqueous phase. "Water-soluble initiators" suitable for use in the aqueous phase are those typically known in the art, for example, oxidation-reduction couples including sodium bisulfite and sodium persulfate; iron (II) ions and peroxide (Fenton's reagent); Copper (i) ions and peroxide; and iron (II) ions and sodium persulfate, wherein the peroxide may be benzoyl peroxide, hydrogen peroxide or t-butyl peroxide. These initiators may be combined with non-water-soluble thermal initiators, such as higher alkyl peroxides or azo compounds, or water-soluble thermal initiators, such as persulfate. Examples of water-insoluble thermal initiators include azobisisobutyronitrile and t-butyl peroctoate.

An effective amount of initiator may be from 0.1 to 25% at most 2% by weight of the total polymer. The effective amount of initiator is preferably 0.4 to 1.0% by weight based on the total amount of polymer.

"Chain-exchange agent" is typically any component of the polymerization mixture known in the art as a chain-exchange agent, such as an aliphatic alcohol, for example methanol or isopropanol; carbon tetrachloride; mercaptan such as dodecyl mercaptan; or any other water or hydrocarbon soluble material having the ability to control the molecular weight of the polymers. To optimize the 35 methods of the present invention, the polymerization rate as well as the molecular weight of 4,106,307 polymers are important for hollow particle formation. The molecular weight of the polymer may be controlled by the content of initiator and / or the chain-changing agent. The polymerization rate is controlled by the initiator type 5 and the concentration and temperature. If the initiators are selected to optimize the molecular weight of the latex polymer particle, a chain exchange agent may not be necessary.

An effective amount of a chain exchange agent is the amount that causes the low molecular weight polymer to reach a sufficient molecular weight to separate the low molecular weight polymer from the first organic feed phase to form a low molecular weight polymer.

An effective and qualitative amount of any of the 15 chain exchange agents is typically from 0.1 to 50% by weight of the total amount of polymer. Some chain exchange agents are known in the art to be more effective than other chain exchange agents. More effective chain exchange agents are effective at lower concentrations. Mercaptans are one example of 20 more potent chain exchange agents. An effective amount of a more effective chain exchange agent is 0.1 to 1.0% by weight based on the total amount of polymer. The effective amount of a more effective chain exchange agent is most preferably from 0.1 to 0.5% by weight of the total amount of polymer.

·: 25 Less effective chain altering agents, such as aliphatic alcohols, are required at higher concentrations than more effective chain altering agents to achieve the same degree of chain exchange as with a lower concentration of the more effective chain exchange agent. An effective amount of less than 30 effective chain exchange agents is 2 to 50% by weight of the total amount of polymer. Most preferably, the effective amount of the less effective chain exchange agent is 20 to 35% by weight of the total amount of polymer.

Aliphatic alcohols such as methanol are thought to contribute to the regulation of the molecular weight of the polymer formed and also to interact with the initiator system, sodium persulfate, so that the polymerization rate is reduced.

"Surfactants" in this context include those conventional surfactants known in the art to be used in polymerization processes. The surfactant or surfactants are typically added to the aqueous phase. An effective amount of surfactant is, in the seed process, an amount that helps stabilize the particle into a colloid, minimize contact between the particles, and prevent coagulation. In a seedless process, an effective amount of a surfactant is an amount that affects the particle size. The type and concentration of surfactant are also selected according to the polymer solids content used in the process. Higher polymer solids content increases the need for a surfactant.

Typical surfactants include alkylated diphenyl oxide disulfonates, sodium dodecyl 20 benzenesulfonates, and sodium sulfomer succinic acid dihexyl esters.

The seed process for producing hollow latex polymer particles is carried out in the same manner as the seed-free process. However, 25 seeds having a particle size of 0.02 to 0.10 µm are used. The seed content is determined by the desired size of the finished hollow polymer latex particle. The preferred size of the hollow polymer latex particle to optimize the opacity of the latex in the coating is 0.4 to 0.5 µm.

The seed particles are typically in the form of an aqueous dispersion and are introduced into the polymerization process in the aqueous phase up to a concentration of 2% by weight, preferably less than 1% by weight, based on the total amount of monomer present. The polymer composition of the seed particles may be either similar to or different from the polymer composition of the resulting hollow particle latex polymer.

The term "organic phase" as used herein refers to two batches of polymerization phase, each comprising an effective amount of at least one monomer having an aqueous solubility less than 3% under polymerization conditions, and an effective amount of inert non-polymerized hydrocarbon, wherein the polymerization of the monomer 3% Polymerin-10 under thio conditions. The hydrocarbon solubility in the aqueous phase should also be less than 1% under polymerization conditions. In addition, the monomer and hydrocarbon should be miscible under polymerization conditions.

The term "polymerization conditions" as used herein refers to conditions at a temperature of 25 to 95 ° C in a pressurized jacketed reactor in which each component used in the polymerization process (e.g., monomer, water, hydrocarbon) is present in the concentration used in the polymerization. The pressure 20 in the reactor is mainly determined by the vapor pressure of the selected monomer and hydrocarbon at the reaction temperature.

"Solubility" as used herein means that a substance defined as soluble is soluble in the dissolution medium under polymerization conditions and results in a transparent (i.e.

: 25 clear) or at least a translucent blend. Further, the term "solubility", as used herein, means that a substance defined as soluble must be separated from a different substance which, when added to the same solubilizing medium under similar conditions, only disperses in the leach medium, giving the dispersion a white, milky appearance.

"Miscibility", as used herein, means that the substance defined as miscible is soluble in the dissolution medium under polymerization conditions and results in a mixture which is transparent (i.e., clear) or at least translucent. In addition, the term "miscibility" as used herein, means that the substance defined as miscible must be distinguished from a different substance which, when added to the same solubilizing medium under similar conditions, only disperses in the solubilizing medium, giving the dispersion a distinctive white, milky appearance.

The term "first batch of organic phase" as used herein means the first addition of an organic phase to the aqueous phase. Similarly, the term "second organic phase batch" as used herein refers to the second addition of the organic phase to the aqueous phase.

The term "second batch of organic phase" is also intended to include the crosslinking monomer and optionally one or more other monomers and hydrocarbons.

The term "hydrocarbon" is intended to include inert non-polymerized hydrocarbons having a solubility of less than 1% in the aqueous phase used in this hollow particle latex production process. The hydrocarbon to be used depends on the monomer chosen. The hydrocarbon should be completely miscible with the monomer. Examples of suitable hydrocarbons include hexane, heptane, iso-octane, nonane, decane; Hydrocarbons containing 25 or more alkyl chains and mixtures of such hydrocarbons.

The first batch of organic phase typically contains from 50 to 5% by weight of the total amount of the first batch of organic phase hydrocarbon used.

, The term "crosslinking monomer" is intended to include monomers known in the art as a crosslinking agent for polymerizable monomers. Typical examples of such monomers include typically di- or trifunctional monomers such as divinylbenzene, ethylene glycol dimethacrylate, 1,3-butylene glycol diacetate, trimethylolpropane trimethacrylate, 5-allyl methacrylate, allyl methacrylate, allyl methionyl methacrylate. The crosslinking monomer may be present in the second organic phase batch in an amount of 100 to 4% by weight of the total amount of the second organic phase batch.

Suitable monomers and monomer mixtures for use in this invention include aromatic monovinyl monomers, aliphatic conjugated diene monomers, acrylate monomers, vinylidene halide di- or vinyl halide monomers such as 1 to 18 carbon atoms, A monoethylenically unsaturated carboxylic acid monomer could also be used.

The term "aromatic monovinyl monomer" as used herein is intended to include monomers having a group of the formula

R

ch 2 = c- (wherein R is a hydrogen atom or a lower alkyl group such as an alkyl group containing 1 to 4 carbon atoms) directly attached to an aromatic ring having 6 to 10 carbon atoms, including monomers wherein the aromatic ring is substituted with alkyl or halo substituents. Examples include styrene, alpha-methyl styrene, p-methyl-styrene, t-butyl styrene, vinyl toluene and halogen. you styrene. The preferred monomer is styrene.

The amount of aromatic monovinyl monomer present in the first batch of organic phase typically depends on the monomer selected; however, a typical range 35 is from 0 to 97% by weight of the total amount of the first organic m 9 106307 batch. The amount of aromatic monomer in the second batch of organic phase depends on the monomer selected and the degree of crosslinking required for the resulting polymer; however, the typical range is 0 to 97% by weight of the total amount of the second organic phase charge.

As used herein, the term "aliphatic conjugated diene" is intended to include monomeric compounds such as isoprene, 1,3-butadiene, 2-methyl-1,3-butadiene, piperylene (1,3-pentadiene), and other 1,3 hydrocarbons analogous to butadiene. The amount of aliphatic conjugated diene monomer in the first batch of organic phase typically depends on the monomer selected; however, a typical range is from 15% to 50% by weight of the total amount of the first organic phase batch. The amount of aliphatic conjugated diene monomer in the second batch of organic phase depends on the monomer selected and the degree of crosslinking of the resulting polymer; However, the typical range is 0-100% by weight of the total amount of the second organic phase charge.

Suitable "vinylidene halide di- and vinyl halide monomers" for the present invention include vinylidene dichloride and vinyl chloride, which are very preferred.

; Vinylidene bromides and vinyl bromide may also be used.

The amount of vinylidene halides and vinyl halides in the first batch of organic phase depends on the monomer selected, however, a typical range is 0-97% by weight of the first organic phase. 'Total stake. The amount of vinylidene halides and vinyl halides in the second organic phase batch depends on the monomer selected and the degree of silylation of the resulting polymer required; however, a typical range is 0 to 10 106307 97% by weight of the total amount of the second organic phase charge.

As used herein, the term "acrylate" is intended to include monovinyl acrylate or methacrylate monomers in a first batch of organic phase 5. Monovinyl or divinyl acrylates can be used in another batch consisting of organic phase. Additionally, monovinyl or divinyl acrylates may include acids, esters, amides, and substituted derivatives thereof. Preferred monovinyl acrylates are generally C1-6 alkyl acrylates or methacrylates. Examples of such acrylates include butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, t-butyl acrylate, methyl methacrylate, butyl methacrylate, ethyl methacrylate, hexyl methacrylate, isobutyl methacrylate, and the like. Preferred monovinyl acrylates are butyl acrylate and methyl methacrylate.

The amount of acrylate in the first batch of organic phase-20 will typically depend on the monomer selected, but a typical range will be 0-97% by weight of the total amount of the first batch of organic phase. The amount of acrylate in the second batch of organic phase depends on the monomer selected and the degree of crosslinking of the resulting polymer. However, a typical concentration range of acrylate present in the second organic phase batch is from 0 to 97% by weight of the total amount of the second organic phase batch.

The term "monoethylenically unsaturated carboxylic acid monomer" as used herein includes monocarboxylic monomers such as acrylic acid and methacrylic acid and dicarboxylic monomers such as itaconic acid, fumaric acid and their maleic acid.

«11 106307

The amount of monoethylenically unsaturated carboxylic acid monomer in the first batch of organic phase is typically the amount required to stabilize the latex particles. One typical example of such an amount is 2 to 10% by weight of the total amount of the first batch of organic phase.

As used herein, the term "low molecular weight polymer" is intended to include polymers of first stage monomers having a lower molecular weight than the polymer of the resulting latex particles but sufficient to allow the polymer to precipitate from the organic phase and begin to separate dynamically from the organic phase. phase. The low molecular weight polymer typically has a number average molecular weight of 1,000 to 100,000.

A "low molecular weight polymer phase" is defined as a phase consisting essentially of a concentrated low molecular weight polymer and an unreacted monomer and is located at the boundary between the aqueous phase and the first batch of organic phase.

In the polymerization process, be it seed; 25 method, or without the seed particles, the temperature range used depends on the initiators selected and is typically 50 to 90 ° C. One typical temperature range for the use of persulfate initiators for polymerization initiation is 60 to 90 ° C.

The method comprises a cavity particle lattice according to the invention. The preparation of '' involves two emulsion polymerization steps, each of which may be a continuous or batch addition, thiopolymerization step. The monomers of the first stage are polymerized in an aqueous medium containing a chain exchange agent and a hydrocarbon which is mixed with the monomer 12106307 under polymerization conditions but which has a solubility in the aqueous phase of less than 1% under polymerization conditions. The second step can be started at almost any point during the polymerization and a second batch of organic phase containing the crosslinking monomer and optionally additional monomer and hydrocarbon is added. Preferably, the second step begins when the monomer begins to polymerize and forms a low molecular weight polymer. More preferably, the second step is initiated when the low molecular weight polymer 10 has begun to separate from the charge of the first organic phase and is deposited on the surface of the formed particle.

Quantitatively, the second batch of organic phase may be added when the monomer conversion to low molecular weight polymer reaches a maximum of 80%. The second batch of organic phase may advantageously be added when the conversion of the first-stage monomer to the polymer reaches a value of 2 to 80%. More preferably, the second batch of organic phase may be added at a conversion of the first monomer of 20 to 10% to 40% polymer.

When polymerization occurs, the low molecular weight polymer phase is separated from the hydrocarbon because the polymer is insoluble in the organic phase under polymerization conditions. As the monomer further polymerizes, the poly-; The mer is easily deposited on the aqueous surface of the particle and away from the hydrocarbon monomer phase to form a latex having a hollow core and a polymer shell or various cavities within the latex polymer.

During the first step, an aqueous phase consisting of water, an effective amount of a water-soluble chain exchange agent and an effective amount of a water-soluble initiator is added. The aqueous phase components may optionally comprise one or more surfactants 35 and / or seed particles. The aqueous phase is fed with a first batch of 106307 13 organic phases containing at least one monomer and an effective amount of an inert, non-polymerized hydrocarbon. The solubility of the monomer (s) in the aqueous phase should be less than 3% under polymerization conditions. The hydrocarbon solubility in the aqueous phase should be less than 1% and should be miscible with the monomer under polymerization conditions. The polymer forming the monomer polymerization should have a solubility in hydrocarbon below 3% under polymerization conditions. The monomer (s) is then polymerized under conditions whereby a low molecular weight polymer phase is formed. Such conditions include chain-exchange agent, initiators, temperature and monomer selected to give a low molecular weight polymer having a number average molecular weight of 1000 to 100,000.

When the low molecular weight polymer reaches sufficient molecular weight, it separates first from the organic phase introduced, accumulates on the surface of the organic phase introduced into the mixture and forms the low molecular weight polymer phase.

When the conversion of the monomer to the low molecular weight polymer reaches at most 80%, the second step is initiated. During the second step, a second batch of organic phase is introduced into the aqueous phase. The second batch of organic Vasia contains a crosslinking monomer and optionally; 25 other monomers and more hydrocarbon. The monomer, one or more, is predominantly incorporated into the low molecular weight polymer phase and polymerizes within the low molecular weight polymerization conditions to form hollow polymer-30 latex latex particles. Such polymerization conditions are generally known to depend on such polymerization parameters as the polymerization temperature and on the reactor. pressure, depending on the concentrations and types of selected polymerization mixture components.

t, · 106307 14

The opacity-enhancing properties of the latexes of the invention can be determined by blending cavity-particle latex with a film-forming styrene-butadiene latex binder at a mass-to-binder ratio of 30:70. The latex mixture is applied to a pure mylar film using a Meyer bar # 30 and dried in an oven at 100 ° C for 1 min. The film opacity is then measured using a Diano Corporation BNL-2 Opaci-meter. This opacimeter measures the TAPPI guideline-10, which is defined as the ratio of the luminous flux reflected from a paper sample with a completely black background to the luminous flux reflected from a sample with a white body with a refractive index of 89%. Refraction from the cavity to the particle shell on the air-polyreneer-15 surface is the main source of scattered light or opacity. The thinner the shell, the more scattering sites there are per unit mass of polymer.

The following, for example, illustrate embodiments of the present invention and are not intended to limit the scope of the method of the invention.

Example 1

The stainless steel jacketed reactor (3.8 L) is charged with 379 g of methane; 25 l of water, 943 g of water, 3.9 g of sodium persulfate, 4 g of surfactant, alkylated diphenyloxide disulfonate and 0.96 g of seed leading to particles of 0.4000 µm. To this mixture are added 225 g of styrene, 37.1 g of methacrylic acid and 115 g of isooctane. The resulting mixture is stirred and heated. After one hour, another batch of monomer is added to the mixture. The second monomer charge comprises 385 g of styrene, 53 g of divinylbenzene with 80% vinyl content and 68 g of isooctane. The resulting mixture is stirred and heated until the reaction is complete. Polymer particles 106107 are examined by transmission electron microscopy and hydrodynamic chromatography. The polymer particles are hollow and have an inner diameter of 0.1500 to 0.2000 µm and an average total diameter of 0.4000 µm. The hydrocarbons are removed by stripping, and the structure of the stripped polymer remains unchanged.

The opacity of the latex is determined as follows. The latex prepared in Example 1 (30% by weight) is mixed with a film-forming binder latex such as styrene-bu-10 tadene latex (70% by weight). The latex mixture is applied as a film to a pure mylar film using a Meyer bar # 30 and dried in an oven at 100 ° C for 1 min. Film opacity is measured using a Diano Corporation BNL-2 Opacimeter. This opacimeter measures the opacity of a TAPPI-15, which is defined as the ratio of the luminous flux reflected from a paper sample with a completely black background to the luminous flux reflected from a sample with a white body having a reflectance of 89%. In Example 1, the opacity readings are in the range 33-38. that the light scattering ratio of the hollow polymer particle is greater than that of the homogeneous polymer particle.

Example 2

The second example is otherwise carried out in the same manner as Example 1, but the hydrocarbon is heptane instead of isooctane. Concentrations and results are the same or similar. Guides determined as described in Example 1. teaette readings range from 33 to 38.

16 106307

Example 3

The stainless steel jacketed reactor (3.8 L) is charged with 488 g of methanol, 1013 g of water and 2.3 g of sodium persulfate. To this 5 mixture is added 174 g of styrene, 23.4 g of acrylic acid and 54 g of isooctane. The resulting mixture is stirred and heated under nitrogen. After stirring for 3 hours at 70 ° C, a second batch of monomer is added. The second monomer charge comprises 174 g of styrene, 29.8 g of 80% vinylbenzene and 54 g of isooctane. The resulting mixture is stirred and heated until the reaction is complete. Polymer particles are examined by transmission electron microscopy and hydrodynamic chromatography. The polymer particles are hollow and have a total diameter of 0.5500 µm and an inner diameter of 0.1700 µm. The hydrocarbons are removed by stripping, and the structure of the stripped polymer remains the same as that of the Strip-free. Opacity readings determined as described in Example 1 are in the range of 33-38.

Example 4

The stainless steel jacketed reactor (3.8 L) is charged with 488 g of methanol, 1013 g of water and 2.24 g of sodium persulfate. To this mixture are added 174 g of styrene, 22.4 g of acrylic acid and; 54 g of isooctane. The resulting mixture is stirred and heated under nitrogen. After stirring for 3 hours at 70 ° C, a second batch of monomer is added. The second monomer charge comprises 87 g of styrene, 87 g of methyl methacrylate, 30.0 g of divinylbenzene having an 80% vinyl content and 54 g of isooctane. The resulting mixture is stirred and heated until the reaction is complete. The polymer particles are examined by transmission electron microscopy and hydrodynamic chromatography. The polymer particles are hollow and have a total diameter of 0.5000 µm and an inner diameter of 0.1500 to 0.2000 µm.

• 17 106307

The hydrocarbons are removed by stripping, and the structure of the stripped polymer remains unchanged. Opacity readings determined as described in Example 1 are in the range of 33-38.

Example 5

The latex particles are otherwise prepared as described in Example 1, but 0.3 g of t-dodecylmercaptan is added to the first monomer charge. The opacity number determined as described in Example 1 is 45.

Example 6

A stainless steel jacketed reactor (3.8 L) is charged with 593 g of methanol, 1544 g of water, 3.4 g of sodium persulfate, 8 g of surfactant, alkylated diphenyl oxide disulfonate 15 and 0.96 g of seed which leads to particles having a size of 0.400 µm. To this mixture are added 96.6 g of styrene, 96.6 g of methyl methacrylate, 31.8 g of methacrylic acid, 98.4 g of isooctane and 1.8 g of an effective chain exchange agent. The resulting mixture is stirred and heated under nitrogen. After stirring for 1 hour at 70 ° C, another batch of monomer is added. The second monomer charge comprises 330 g of methyl methacrylate, 52 g of allyl methacrylate and 68 g of isooctane. The resulting mixture is stirred and heated until the reaction is complete; 25 gone. The polymer particles are examined by transmission electromicroscope and hydrodynamic chromatography. The polymer particles are hollow and have a total diameter of 0.4000 µm and an inside diameter of 0.1700 µm. The hydrocarbons are removed by stripping, and the structure of the stripped polymer remains unchanged. Opacity readings determined as described in Example 1 are in the range of 33-38.

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Claims (17)

A process for producing hollow particles of latex polymers, characterized by a single-stage emulsion polymerization of monomers in the presence of hydrocarbons, by: (1) introducing into an polymerization vessel an initial reactor charge comprising a first charge of organic phase and a aqueous phase, wherein the aqueous phase comprises (a) water and (b) an effective amount of water-soluble initiator and wherein the first organic phase charge comprises (a) an effective amount of at least one monomer having a solubility of less than 3% in the aqueous phase under polymerization conditions, and (b) an effective amount of an inert, non-polymerizable hydrocarbon, the polymer formed from the polymerization of the monomer being less than 3% soluble in the hydrocarbon under polymerization conditions and wherein the hydrocarbon has less than 1% solubility in the aqueous phase under polymerization conditions and the monomer is miscible with co. hydrogen under polymerization conditions; (2) polymerizing the monomer under conditions to form low molecular weight polymer such that when the low molecular weight polymer achieves a molecular weight sufficient: to cause the low molecular weight polymer to phase separate from the first charge of organic phase, the phase separates with low molecular weight polymer from the organic phase and concentrated at the surface of the organic phase to form a low molecular weight polymer phase; (3) introducing into the vessel a second reactor charge comprising a second charge of the organic phase to the aqueous phase when the conversion of monomer to low molecular weight polymer reaches a value equal to or less than 80% by weight, the second charge of the organic phase further comprises a cross-linking monomer, <23 1 0 6 3 0 7 wherein the cross-linking monomer is absorbed in the low molecular weight polymer phase; and (4) polymerizing the cross-linking monomer with the low molecular weight polymer under polymerization conditions sufficient to form a hollow polymer latex particle. 2. The method of claim 1, wherein the aqueous phase further comprises an effective amount of chain transfer agent 10. Method according to claim 2, characterized in that the chain transfer agent is present in an amount of from 0.1 to 50% by weight, based on the total weight of the polymer. 4. A process according to claim 1, characterized in that the water-soluble initiator is present in an amount of from 0.4 to 1.0% by weight, based on the total weight of the polymer. 5. A process according to claim 1, characterized in that the monomer in the first batch of the organic phase is a monovinyl aromatic monomer, aliphatic conjugated diene monomer, acrylate monomer, vinylidene halide or vinyl halide monomer, vinyl ester monomer of a carboxylic acid containing to 18 carbon atoms, metacrylonitrile, acrylonitrile or monoethylenically unsaturated carboxylic acid; 25 xylic acid monomer. 6. A process according to claim 2, characterized in that the second charge of the organic phase further comprises a monomer which is a monovinyl aromatic monomer, acrylate monomer, aliphatic conjugated diene monomer, vinyl idenhalide or vinyl halide monomer, vinyl ester monomer of a carboxylic acid containing from 1 to 18 carbon atoms, methacrylonitrile, acrylonitrile or monoethylenically unsaturated carboxylic acid monomer. 7. A process according to claim 1, characterized in that the sufficient molecular weight of the low molecular weight polymer is a number average molecular weight of from 1000 to 100,000. 8. A process according to claim 6, characterized in that the second charge of the organic phase further comprises hydrocarbon. 9. A process according to claim 2, characterized in that the chain transfer agent is an aliphatic alcohol and the aliphatic alcohol is present in the aqueous phase in an amount of from 2 to 50 weight percent, based on the total weight of the polymer. the initiator is present in an amount of less than or equal to 2% by weight based on the total weight of the polymer, and the water is present in an amount of from 100 to 65% by weight based on the total weight of the aqueous phase. 10. A process according to claim 1, characterized in that the monomer in the first charge of the organic phase is a mixture of a monovinyl aromatic monomer and a monoethenically unsaturated carboxylic acid monomer. 20 11. A process according to claim 10, characterized in that the monovinyl aromatic monomer is present in an amount of from 0 to 97% by weight and the monoethylenically unsaturated carboxylic acid monomer is present in an amount of from 2 to 10% by weight; Total weight of the first charge of the organic phase. 12. A process according to claim 8, characterized in that the monomer in the second batch of the organic phase is a monovinyl aromatic monomer and the cross-linking monomer is divinylbenzene. 30 13. Process according to claim 12, characterized in that the monomer in the second batch of the organic phase is a mixture of the monovinyl aromatic monomer and an aliphatic conjugated diene monomer. 14. A process according to claim 12, characterized in that the monovinyl aromatic monomer is 106307 present in an amount of from 0 to 97% by weight and di-vinylbenzene is present in an amount of from 4 to 100% by weight. the total weight of the second batch of the organic phase. 5 15. A process according to claim 8, characterized in that the aqueous phase further comprises a surfactant. 16. A process according to claim 15, characterized in that the aqueous phase further comprises germ particles. 17. A method according to claim 16, characterized in that the polymer composition in the seed particles is similar to that of the polymer composition in the resulting hollow polymer latex particles and the seed particles are present in the aqueous phase at a concentration equal to or less than 1% by weight. calculated on total monomer. ». ·, M