SILICONE-ACRYLIC POLYMER PARTICLES

Abstract

Provided is a polymer particle comprising (a) a core polymer comprising (i) polymerized units of one or more Si-containing monomers; (ii) polymerized units of one or more monovinyl acrylic monomers (ii); and (iii) polymerized units of one or more graftlinkers that have no silicon atoms; (b) a shell polymer comprising polymerized units of one or more acrylic monomers.

Also provided is a composition comprising polyvinyl chloride and a plurality of the polyer particles.

Claims

1. A polymer particle comprising (a) a core polymer comprising (i) polymerized units of one or more monomers selected from monomers of structure (I), monomers of structure (II), and mixtures thereof, ##STR00011## wherein every R.sup.1 is independently hydrogen or a hydrocarbon group; n is 0 to 1,000; m is 2 to 1,000; p is 0 to 1,000; every Ra is independently an organic group that contains one or more ethylenically unsaturated group; (ii) polymerized units of one or more monovinyl acrylic monomers (ii); and (iii) polymerized units of one or more graftlinkers that have no silicon atoms; (b) a shell polymer comprising polymerized units of one or more acrylic monomers.

2. The polymer particle of claim 1, wherein the polymer particle has a measured glass transition temperature of −90° C. or lower and a measured glass transition temperature of from −80° C. to −10° C.

3. The polymer particle of claim 1, wherein the shell polymer has a calculated glass transition temperature of 50° C. to 120° C.

4. The polymer particle of claim 1, wherein the weight ratio of monomer (i) to the sum of monomer (ii) and monomer (iii) is from 0.7:1 to 19:1.

5. The polymer particle of claim 1, wherein the shell polymer is present in an amount of from 5% to 40%, by weight based on the weight of the polymer particle.

6. A polymer composition comprising polyvinyl chloride and a plurality of the polymer particles of claim 1, wherein the polymer particles of claim 1 are present in an amount of 1 to 10 parts by weight per hundred parts by weight of the polyvinyl chloride.

Description

EXAMPLE 1

[0081] A mixture (M0) was prepared of 99.3 parts by weight BA and 0.7 parts by weight ALMA. Then a mixture (M1) was prepared of 75 parts by weight TSO-1 and 25 parts by weight of the BA/ALMA mixture (M0). The mixture (M1) was combined with water and SLS (0.5% SLS by weight based on the weight of M1). The mixture M1 was emulsified with an ultrasonic processor which works on the principle of cavitation to form emulsion E1. The amount of mixture M1 was 25% by weight based on the weight of emulsion E1. The emulsion E1 was transferred to a round bottom flask and polymerized with a redox initiation system of t-butyl hydroperoxide (tBHP), ferrous sulfate and sodium formaldehyde sulfoxylate (SFS). The system also contained Trigonox 125 (t-amyl peroxypivalate) at 1% based on total monomer, an oil soluble thermal initiator with a half-life of about 1 hour at 72° C. This stage was heated to 45° C. and exothermed to about 65° C. The result was a dispersion of core polymer particles.

[0082] An emulsion of MMA was made and added, at 20 parts by weight MMA to 80 parts by weight of solid core polymer, and the mixture was heated to 80° C., and NaPs was added. The mixture was held at 85° C., then cooled to 23° C. The result was a dispersion of core/shell polymeric particles in water. The dispersion was then freeze dried to obtain the polymeric particles in solid form.

[0083] Example 1 was analyzed with DSC as described above, and all of the detected glass transitions are reported. Example 1 was also analyzed as described above for the soluble fraction (SF) of the core polymer and % grafting (% G) of the shell polymer. The dispersion of core/shell polymer was also analyzed by dynamic light scattering for the volume-average diameter (D). Also measured was the solids (% by weight). Results are in Tables Ia and Ib.

TABLE-US-00001 TABLE IA Example 1 TSO BA/ALMA mixture lowest Tg highest Tg Example p (pbw) (pbw) (° C.) (° C.) 1 198 20 60 −129 −48

TABLE-US-00002 TABLE Ib Example 1 Core Total shell Example D (nm) solids (%) SF (%) SF (%) grafting (%) 1 241 27.3 5.1% 13.5% 58

EXAMPLE 2

[0084] A variety of additional core/shell polymers were made. Each was similar to Example 1. Various telechelic silicone oils (TSO) were used, all having the same structure as TSO-1, with various values of p. Variations were made in the relative amounts of different ingredients in the core polymer. In every example, the BA/ALMA ratio was 99.3/0.7 by weight, the amount of SLS was 0.5% by weight based on the dry weight of the core/shell polymer, and the weight ratio of core polymer to shell polymer was 80/20.

[0085] The examples were was analyzed with DSC as described above, and all of the detected glass transitions are reported. The examples were also analyzed as described above for the soluble fraction (SF) of the core polymer and % grafting (% G) of the shell polymer. The dispersions of core/shell polymer were also analyzed by dynamic light scattering for the volume-average diameter (D). Also measured were the solids (% by weight). Results are shown in Tables II and III.

TABLE-US-00003 TABLE II TSO BA/ALMA mixture lowest Tg highest Tg Example p (pbw) (pbw) (° C.) (° C.) 1 198 20 60 −129 −48 2-1 183 10 70 −125 −47 2-2 183 20 60 −128 −46 2-3 95 10 70 −125 −46 2-4 95 20 60 −128 −48

TABLE-US-00004 TABLE III Core Total shell Example D (nm) solids (%) SF (%) SF (%) grafting (%) 1 241 27.3 5.1 13.5 58.0 2-1 208 27.8 6.2 18.6 38.0 2-2 250 29.8 5.7 16.8 44.5 2-3 236 33.4 5.7 15.2 52.5 2-4 239 32.8 5.4 20.0 27.0

EXAMPLE 3—IMPACT TESTING

[0086] The examples were also tested for effectiveness as impact modifiers in PVC. A typical formulation of nonplasticized PVC was used, with 4, 5, or 6 phr of dry modifier per 100 parts by weight of PVC. The formulation was mixed and then milled on a heated plastics-processing two-roll mill, then pressed into a plaque. Impact resistance was tested by the notched Izod impact test (ASTM D256, American Society of Testing and Materials, Conshohocken Pa., USA) at 23° C. Ten replicate samples were tested for each example.

[0087] Also tested were PVC samples formulated with a comparative impact modifier. The comparative modifier was a core/shell polymer made by conventional two stage emulsion polymerization. A core polymer of BA/ALMA was polymerized, and then a shell polymer of MMA was polymerized, with a core/shell weight ratio of 80/20.

[0088] Impact results are (1) the energy required to break the sample and (2) the percentage of the replicate samples that broke in a ductile fashion rather than a brittle fashion. Higher energy and higher percent ductile breaks each indicate better impact resistance. Impact results are shown in Table IV.

TABLE-US-00005 TABLE IV Energy Example phr (N*m/cm (ft*lb/in)) % ductile comparative 4 3.34 0 1 4 3.49 0 2-1 4 5.52 10 2-2 4 5.86 10 2-3 4 7.62 20 2-4 4 11.70 50 comparative 5 3.18 0 1 5 21.85 100 2-1 5 22.83 100 2-2 5 21.28 100 2-3 5 24.00 100 2-4 5 18.86 90 comparative 6 17.22 70 2-1 6 22.13 90 2-2 6 22.67 90 2-3 6 25.56 100 2-4 6 24.04 100

[0089] When comparisons are made among modifiers used at equal phr levels, it is clear that all of the inventive examples show better impact resistance than the comparative example.

EXAMPLE 4: ATOMIC FORCE MICROSCOPY (AFM)

[0090] Examples 2-1 and 2-2 were tested as follows. An aqueous dispersion of polymer particles was freeze dried to produce a collection of the polymer particles in solid form. The solid sample was pressed into a film, and the surface was studied by AFM. Both samples showed three phases: a phase rich in silicone, a phase rich in poly(BA), and a phase rich in poly(MMA). In Example 2-2, the size of the domains of the phase rich in silicone were larger than in Example 2-1.