23  US 6,930,141 B2  24  In Example 6, the relative scrub resistance value of the  dry coating,  RS,  which is prepared from the aqueous poly- Total Improvement Factor  Dry coating samples are prepared from the aqueous  polymer blend composition, Example 5.1, and the compara› tive aqueous polymer composition, Comparative C and are  evaluated according to the procedure for the dirt pickup  resistance test. The dirt pickup resistance for the dry coating  prepared from the aqueous polymer blend composition of  this invention, Example 5.1, is greater than 110% of the dirt  pickup resistance of the dry coating prepared from the  comparative aqueous polymer composition, Comparative C.  Thus, the relative dirt pickup resistance value,  RL,  is greater  than 1.1. This result demonstrates improved dirt pickup  resistance for the dry coating prepared from the aqueous  polymer blend composition containing the hard polymer  particles and the select soft polymer particles compared to  the dry coating prepared from the comparative aqueous  polymer composition containing the soft polymer particles,  but not containing the hard polymer particles.  Evaluation of Dirt Pickup Resistance  3.  The aqueous polymer blend composition according to  claim  2  wherein said redox polymerization is effected in the  presence of 0.0025 to 0.025 moles chain transfer agent per  kg weight of said soft polymer particles.  4.  The aqueous polymer blend composition according to  claim  1  wherein said redox polymerization is effected at a  pH of 4 to 8.  5.  The aqueous polymer blend composition according to  claim  1  further comprising pigment, wherein said aqueous  polymer blend composition has a pigment volume concen- tration of less than or equal to 40 and has volatile organic  compound level of less than 5% by weight based on the total  weight of said aqueous polymer blend composition.  6.  The aqueous polymer blend composition according to  claim  1  further comprising pigment, wherein said aqueous  polymer blend composition has a pigment volume concen› tration greater than or equal to 35 and has volatile organic  compound content of less than 3% by weight based on the  total weight of said aqueous polymer blend composition.  7. The aqueous polymer blend composition according to  claim  1  further comprising pigment, wherein said aqueous  polymer blend composition has a pigment volume concen› tration of less than or equal to 85 and has volatile organic  2.  The aqueous polymer blend composition according to  claim  1  wherein said redox polymerization is effected in the  presence of 0.001 to 0.05 moles chain transfer agent per kg  weight of said soft polymer particles.  ii) from 70 to 98 weight % of soft polymer particles;  based on the total weight of said hard polymer particles and  said soft polymer particles;  What is claimed is:  i) from 2 to 30 weight % of hard polymer particles; and  1.  An aqueous polymer blend composition comprising:  mer blend composition of this invention, is greater than 1.1.  In Example 7, the relative dirt pickup resistance value of the  dry coating, RL, which is prepared from the aqueous poly› mer blend composition of this invention, is greater than 1.1.  The total improvement factor of the dry coating, which is  prepared from the aqueous polymer blend composition  containing the select soft polymer particles, is greater than  1.2.  Evaluation of Scrub Resistance  Dry coating samples are prepared from the aqueous  polymer blend composition, Example 4.1, and the compara› tive aqueous polymer blend composition, Comparative B,  and are evaluated according to the procedure for the scrub  resistance test. The scrub resistance for the dry coating  prepared from the aqueous polymer blend composition of  this invention, Example 4.1, is greater than 110% of the  scrub resistance of the dry coating prepared from the com› parative aqueous polymer blend composition, Comparative  B. Thus, the relative scrub resistance value,  RS,  is greater  than 1.1. This result demonstrates improved scrub resistance  for the dry coating prepared from the aqueous polymer blend  composition containing the hard polymer particles and the  select soft polymer particles compared to the dry coating  prepared from the comparative polymer blend composition  containing the hard polymer particles and the comparative  soft polymer particles.  TABLE 5.1  EXAMPLE 8  EXAMPLE 7  b) at least 40 weight % of each of said soft polymer  particles is polymerized in the presence of at least 5  weight % of added monomer that remains unreacted,  based on accumulated weight of said added monomer,  said added monomer being selected from said mono› ethylenically unsaturated (meth)acrylic monomer, said  monoethylenically unsaturated acid monomer, said  third monomer, and mixtures thereof.  a) at least 40 weight % of each of said soft polymer  particles, based on weight of said soft polymer  particles, is formed by redox polymerization; or  wherein:  wherein said hard polymer particles have a weight aver› age molecular weight of at least 100,000; and  wherein said soft polymer particles comprise as copoly› merized units, from 70 to 99.7 weight % monoethyl› enically unsaturated (meth)acrylic monomer, from 0.3  to 10 weight % monoethylenically unsaturated acid  monomer; and from Oto 29.7 weight% third monomer,  based on weight of said soft polymer particles;  wherein said soft polymer particles have a glass transition  temperature (Tg) in the range of from -20°  C. to 25°  C.,  and said hard polymer particles have a  T  g  of greater  than 25°  C. and at least 10°  C. greater than said  T  g  of  said soft polymer particles;  EXAMPLE 6  Aqueous Polymer Blend Composition and Comparative Aqueous  Polymer Composition  Ingredient  Example 5.1  Comparative C  titanium dioxide dispersion  344.07 g  344.07 g  Water  20.00 g  20.00 g  propylene glycol  16.50 g  Example 1 (soft)  430.1 g  Example 3 (hard)  115.26 g  Surfyno  1  TM  CT-111 surfactant  1.00 g  ammonia (28%)  0.70 g  Polyphase  TM  AF-1 biocide (Troy  8.00 g  Corporation)  Acrysol  TM  RM-2020 NPR rheology  29.00 g  modifier (Rohm and Haas Co.)  Acrysol  TM  RM-SW rheology modifier  5.60 g  (Rohm and Haas Co.)  water  104.2 g  voe (weight %)  <2.25  16.50 g  537.65 g  1.00 g  0.70 g  8.00 g  29.00 g  5.60 g  113.62 g  <2.25 