Method for modifying polycarbonate

Abstract

Provided is a method of modifying polycarbonate comprising blending the polycarbonate with composite particles, wherein the composite particles comprise (I) a crosslinked polyolefin core, and (II) a full or partial shell comprising polymerized units of one of more vinyl monomers.

Claims

1. A method of modifying polycarbonate comprising blending the polycarbonate with composite particles, wherein the composite particles comprise (I) a crosslinked polyolefin core, wherein the crosslinked polyolefin core has gel fraction of 10% or more by weight, wherein the gel fraction is measured in toluene at 90° C. for 1 hour, and (II) a full or partial shell comprising polymerized units of one of more vinyl monomers.

2. The method of claim 1, wherein the vinyl monomer comprises one or more (meth)acrylic monomer.

3. The method of claim 1, wherein the vinyl monomer comprises one or more unsubstituted alkyl ester of (meth)acrylic acid.

4. The method of claim 1, wherein the crosslinked polyolefin core comprises one or more hydrocarbon polyolefin and one or more non-hydrocarbon polyolefin.

5. The method of claim 1, wherein the crosslinked polyolefin core has Tg of −30° C. or lower.

6. The method of claim 1, wherein the crosslinked polyolefin core is present in an amount of 60% to 90% by weight based on the sum of the weight of the crosslinked polyolefin core and the weight of the shell.

7. The method of claim 1, wherein the composite particles are present in an amount of 0.5% to 20% by weight based on the sum of the weight of the composite particles plus the weight of the polycarbonate.

8. The method of claim 1, wherein the method comprises blending the polycarbonate with the composite particles and with a process stabilizer.

Description

PREPARATIVE EXAMPLE 1: MAKING AQUEOUS DISPERSION OF INITIAL POLYOLEFIN PARTICLES

(1) An aqueous polyolefin dispersion was prepared utilizing a twin screw extruder (25 mm screw diameter, 48 L/D rotating at 450 rpm) using the following procedure. The hydrocarbon polyolefin and the non-hydrocarbon polyolefin were supplied to the feed throat of the extruder via a Schenck Mechatron loss-in-weight feeder and a Schenck volumetric feeder, respectively. The liquid crosslinking agent was injected into the polymer melt zone using Isco dual syringe pumps (from Teledyne Isco, Inc. (Lincoln, Nebr., USA)). The polymers were then melt blended, and then emulsified in the presence of a first aqueous stream and surfactant. The emulsion phase was then conveyed forward to the dilution and cooling zone of the extruder where additional dilution water was added to form the aqueous dispersions having solid level contents in the range of from less than 70 weight percent. The initial aqueous stream, and the dilution water were all supplied by Isco dual syringe pumps. The barrel temperature of the extruder was set to 140-150° C. After the dispersion exited the extruder, it was further cooled and filtered via a 200 μm mesh size bag filter. Particle size analysis was done with the Beckman Coulter LS 13320 Laser Light Scattering Particle Sizer (Beckman Coulter Inc., Fullerton, Calif.) using the standard procedure. Volume average particle size was obtained.

EXAMPLE 2: MAKING A DISPERSION OF CROSSLINKED POLYOLEFIN PARTICLES IN AN AQUEOUS MEDIUM

(2) Crosslinked polyolefin particles were produced in a modified emulsion polymerization according to the following procedure. The polyolefin dispersion from Preparative Example 1 was diluted to 40 wt % solids with a pH of 4-7. Then 5 ppm FeSO.sub.4 dissolved in water (based on polyolefin dispersion weight) was added into the dispersion prior to reaction. The dispersion was then charged into a 250 mL three-neck flask fitted with a condenser and a mechanical stirrer. The flask was placed in an oil bath at 65-100° C. The stirring rod was inserted through the Teflon adaptor and glass sleeve and connected to the center of the flask. The stirrer rate was set at 200 rpm. Nitrogen was slowly purged through the reactor, and cooling water was turned on to flow through the condenser. Redox initiator was tert-Butyl hydroperoxide (t-BuOOH) and a reducing agent. The reducing agent was isoascorbic acid (IAA) unless otherwise specified. The t-BuOOH and the reducing agent were dissolved in deionized water respectively and then fed into the reactor slowly using separate syringe pumps. Finally, the hybrid emulsion was collected by filtration through a 190 micron filter.

(3) The gel fraction of the resulting dispersions were measured using two different methods. As defined above, in all methods, gel fraction=100*WGEL/WTOT. First, the dispersion was dried to remove water, and the weight of dried dispersion was WTOT.

(4) In gel fraction method A, the dried sample of crosslinked polyolefin particles was extracted with xylene in a Soxhlet extractor for 18 hours under reflux. The dry weight of the material after extraction was WGEL.

(5) In gel fraction method B, the dried sample of crosslinked polyolefin particles was stirred in toluene for 1 hour at 90° C. The mixture of solid material and toluene was filtered through a 75 μm filter. The weight of material retained on the filter, after drying, was WGEL.

(6) The resulting crosslinked polyolefin particles are described in Table 1 below. The crosslinking reaction is characterized by reaction time (RXTIME) and reaction temperature (RXTEMP). The amounts of ingredients used are characterized as “phr,” which is parts by weight based on 100 parts by weight of dry initial polyolefin particles.

(7) TABLE-US-00001 TABLE 1 Making Crosslinked Polyolefin Particles C1 C2 Ex. 1 Ex. 2 Ex. 3 Ex. 4A Ex. 5 Ex 4B Ex 4C E/OCT-1 81 72 72 72 E/OCT-2 67.5 75 75 75 75 PE/MAH-1 15 15 15 15 5 5 5 5 PE/MAH-2 15 10 10 10 10 EPDM 8 8 8 13.5 PBD 2 TAIC 2 2 2 SLES 4 4 4 4 4 4 4 4 4 Peroxide (phr) 0.8 0 0.4 0.8 0.8 0.3.sup.(a) 0.3 0.3.sup.(b) 0.3.sup.(c) RXTIME (h) 4 0 2 4 3 1 1 1 1 RXTEMP (° C.) 95 — 95 95 95 65 65 65 65 .sup.(a)t-BuOOH/sodium formaldehyde sulfoxylate (SFS) redox pair .sup.(b)hydrogen peroxide/isoascorbic acid (IAA) redox pair .sup.(c)tert-butyl peroctoate/SFS redox pair
C1 is comparative because no crosslinking agent was used. C2 is comparative because the initial polyolefin particles were not subjected to the crosslinking reaction with peroxide.

(8) The crosslinked polyolefin particles were characterized, as shown in Table 2 below, using methods described above. The gel fraction (“gel frac”) was characterized by method A or method B or both. The diameter (“diam”) was measured as described above. The notation “nm” means “not measured.”

(9) TABLE-US-00002 TABLE 2 Characterizing Crosslinked Polyolefin Particles C1 C2 Ex. 1 Ex. 2 Ex. 3 Ex. 4A Ex. 5 Ex 4B Ex 4C gel frac A (%) 0 0 31 34 51 nm nm nm nm gel frac B (%) nm nm nm nm 36 87   60.sup.(1) 12 36 diam (nm) 335 335 335 335 408 335 335 335 335 .sup.(1)approximately

(10) The comparative samples had no gel fraction, while the working examples had significant level of crosslinked material.

(11) Additional initial polyolefin particles were made and then crosslinked by the methods described above. Compositions were as shown in Table 3. Crystallinity was measured by DSC, at a scan rate of 10° C./minute, using the area under the crystallization exotherm. The terms “low” and “medium” are comparative terms to compare samples within Table 3, as follows: “low” means crystallization exotherm less than or equal to 30 J/gram; and “medium” means crystallization exotherm above 30 J/gram but less than or equal to 45 J/gram.

(12) TABLE-US-00003 TABLE 3 Making Additional Initial Polyolefin Particles Ex. 6 Ex. 7 Ex. 8 Ex.9 E/OCT-2 67.5 67.5 79 E/OCT-3 79 PE/MAH-1 15 5 5 5 PE/MAH-2 10 10 10 EPDM 13.5 13.5 TAIC 2 2 SLES 4 4 4 2 ETHOX 2 crystallinity medium low low low diam (nm) 299 340 326 434

(13) The initial polyolefin particles described in Table 3 were crosslinked using the methods described above. The resulting compositions were as shown in Table 4. The suffix “X” denotes the result of the crosslinking reaction. The label “gel frac” refers to the gel fraction in the crosslinked polyolefin particle, measured by method “B” defined above. All of the samples labeled “Ex” had sufficient crosslinking to qualify as working examples of the present invention. “diam” is the volume-average diameter of the crosslinked polyolefin particle prior to emulsion polymerization.

(14) TABLE-US-00004 TABLE 4 Characteristics of Crosslinked Polyolefin Particles Ex 6X Ex 7X Ex 8X Ex 9X initial PO particle Ex 6 Ex 7 Ex 8 Ex 9 gel fraction 20.sup.(1) 35 68.sup.(2) 45 .sup.(1)Approximately .sup.(2)Two samples were measured: both had either 68% or higher.

EXAMPLE 3: EMULSION POLYMERIZATION

(15) Composite particles were prepared by a seeded emulsion polymerization process. Each of the above crosslinked polyolefin particle dispersions of Table 4 was placed into a reactor to be used as a seed for polymerization of acrylic monomers. The monomers were premixed to form a monomer emulsion and then injected into the reactor over 60 min at 65° C. At the same time, a redox catalyst pair was fed separately into the reactor as a free radical initiator over 90 min. The reaction was maintained at 60° C. for 90 min and then allowed to cool to 25° C. and filtered through a 190 μm filter. In all cases the acrylic monomers were a mixture of methyl methacrylate (MMA) and butyl acrylate (BA), in a weight ratio of MMA:BA of 98.0:2.0.

(16) The characterization of the composite particles after emulsion polymerization is shown below in Table 5.

(17) Grafting was assessed as follows. Samples (approximately 0.2 gram) were dissolved in 5 g of tetrahydrofuran (THF) for approximately 16 hours at room temperature (approximately 23° C.). Then 5 g of acetonitrile (ACN) was added to the solution, which then stood for approximately 16 hours at room temperature. The solution was centrifuged at 70,000 revolutions per minute for 15 min. The supernatant was filtered and tested in a size exclusion chromatograph (SEC) apparatus, using styrene-divinylbenzene copolymer beads, flowing THF at 1 mL/min, with column temperature of 40° C., and differential refractive index detection. The extracted polymer was assumed to be ungrafted acrylic copolymer p(MMA/BA). The SEC curves of detector response versus time for each sample were compared to SEC curves for p(MMA/BA) standard samples of known concentrations. The graph of peak area vs. concentration for the p(MMA/BA) standard samples was fit to a standard line by the linear least-squares method. Using that standard line, the SEC peak area for each sample was converted to a concentration, which was used to calculate the amount of extractable polymer from each sample.

(18) In Table 5, the label “PO disp” refers to the polyolefin dispersion, defined in Table 4, that was used as seed for the emulsion polymerization. The suffix “-S” refers to the result of emulsion polymerization in the presence of a polyolefin dispersion. “Core: Shell” is the weight ratio of dry crosslinked polyolefin particles to total weight of (meth)acrylic monomers used. In some samples, Na.sub.3PO.sub.4 was added to the polyolefin dispersion prior to emulsion polymerization, and the amount shown is weight % based on the weight of the solid polyolefin particles.

(19) TABLE-US-00005 TABLE 5 Characterization of Composite Particles Ex. 6S Ex. 7S Ex. 8AS Ex. 8BS Ex. 9S C 7S PO-disp 6X 7X 8X 8X 9X C 7 grafting medium medium high high high medium Core:Shell 85:15 83:17 80:20 83:17 83:17 83:17 diam (nm) 299 340 326 326 434 340 Na.sub.3PO.sub.4 (%) 0 0 0.5 0.5 0.5 0.5
In Comparative C 7S, emulsion polymerization was performed on the non-crosslinked dispersion of initial polyolefin particles C 7.

EXAMPLE 4: COMPOUNDING OF COMPOSITE PARTICLES WITH MATRIX POLYMER

(20) The aqueous dispersions of composite particles were spray dried according to the following procedure. A two-fluid nozzle atomizer was equipped on a Mobile Minor spray dryer (GEA Process Engineering Inc. (Copenhagen, Denmark)). The nitrogen pressure to nozzle was fixed at 1 bar with 50% flow which is equivalent to 6.0 kg/hour of air flow. A glass jar was placed under the cyclone with the valve on the bottom of the cyclone open. Olefin-acrylic dispersion (approximately 40 wt % solid) was pumped into the heated chamber by an emulsion feed pump. The spray drying experiment was conducted in N.sub.2 environment with an inlet temperature fixed at 120° C., and the outlet temperature was controlled at 40° C. by tuning the feed rate of the dispersion. The volume mean particle diameter of the dry powder was measured to be in the range of 20-40 μm.

(21) The polycarbonate (PC) used was MAKROLON™ 2405 resin from Covestro. Before compounding, the resin was thoroughly dried for 2-4 hours at 110° C. in an oven. The polycarbonate (PC) resin and the composite particles were compounded with a JSW TEX28V co-rotating twin screw extruder (L/D=42). The resin and the composite particles were supplied to the feed throat of the extruder via the gravimetric K-Tron feeders and then melt blended. The extruded strand was then cooled and pelletized with a granulometer. The temperature profile of the extruder was set as 25-260-270-280-285-280-280-280-280-280-280-280-280° C. (from the hopper to the die) and the compounding was done with a screw speed of 150 rpm and an output of 10 kg/hr.

(22) The compounded pellets were dried 4 hours at 110° C. in a low pressure dryer and injection molded utilizing the Battenfield HM80/120 machine with the following temperature profile: 280-280-285-290° C. (from the hopper to the die). The holding pressure was set as 200 bars and the mold temperature was 80° C. The molds were ejected after a cooling time of 40 secs.

(23) The modifier materials compounded with the PC resin were the composite particles described above and, for comparison, PARALOID™ EXL-2629J methacrylate butadiene styrene impact modifier from the Dow Chemical Company, (herein “MBS”).

EXAMPLE 5: EXPERIMENTAL RESULTS WITH MODIFIER IN POLYCARBONATE

(24) Samples were compounded and molded as described in Example 4 above, with 95% by weight PC and 5% by weight various modifiers. The results of the MFR and the Izod impact tests at various temperatures were as shown in Table 6. “nt” means not tested. The conditions for MFR were 300° C. with 1.2 kg load. The amounts of modifier shown are percent by weight based on the total weight of the compounded PC. “Gate Defect” refers to the presence of surface delamination in the injection molded bar. Asterisk (*) denotes comparative example.

(25) TABLE-US-00006 TABLE 6 Results with 2.5% modifier in PC. Izod results in units of J/cm (ft*lb/in). Modifier: none* MBS* Ex. 7S Ex. 8BS MFR 20 20.3 19.6 22.8 (g/10 min) Izod at 23° C. 7.0 (13.2) 6.7 (12.5) 6.8 (12.8) 6.7 (12.6) Izod at 0° C. 6.5 (12.2) 6.0 (11.2) 6.7 (12.5) 6.5 (12.2) Izod at −20° C. 3.5 (6.5)  5.6 (10.4) 5.0 (9.3)  6.1 (11.5) Izod at −30° C. 1.5 (2.8)  3.3 (6.2)  2.4 (4.5)  5.2 (9.7)  Gate Defect no no low no

(26) As shown in Table 6, the compounds with modifier show acceptable MFR results. The compounds with modifier show equivalent Izod impact with the non-modified PC at 23° C. and 0° C., and the compounds with modifier show improved Izod impact at −20° C. and −30° C. The modifiers of the present invention (Ex. 7S and Ex. 8BS) show improvement to Izod impact that is equivalent to the improvement given by the commercial MBS impact modifier. It is known that MBS modifiers tend to degrade relatively quickly upon exposure outdoors because of the prevalence of unsaturated polybutadiene and aromatic rings in the MBS composition. In contrast, the modifiers of the present invention are expected to resist degradation due to outdoor exposure because of their polyolefin composition, which has few or no aromatic rings or unsaturations.

(27) TABLE-US-00007 TABLE 7 Results with 5% modifier in PC. Izod results in units of J/cm (ft*lb/in). Modifier: MBS* Ex 6S C 7S* Ex 7S Ex 8AS Ex 9S MFR (g/10 min) 17.9 19.4 25.5 20.7 20.8 20.3 Izod at 23° C. 6.1 (11.5) 6.1 (11.4) nt 6.7 (12.5) 6.5 (12.2) 6.4 (12.0) Izod at 0° C. 5.5 (10.3) 5.8 (10.9) 6.0 (11.2) 6.4 (11.9) 6.3 (11.8) 5.9 (11.1) Izod at −20° C. 5.7 (10.7) 5.7 (10.7) 5.7 (10.7) 5.8 (11.0) 5.5 (10.2) 5.8 (10.8) Izod at −30° C. 5.2 (9.8)  3.1 (5.8)  3.1 (5.9)  3.0 (5.6)  5.7 (10.6) 4.8 (9.0)  Gate Defect no high high low no no

(28) The modifiers of the present invention all gave acceptable MFR and Izod impact results. Example 6S had the lowest level of crosslinking in the crosslinked polyolefin particles prior to emulsion polymerization, and that Example had the least desirable outcome for Gate Defect, among the modifiers of the present invention.