# Patent

## Title
Enhanced heat stability polypropylene

## Abstract

A process forming a high MFR polypropylene includes providing a reactor powder polypropylene, the reactor powder polypropylene having a melt flow rate of less than 100 dg/min. The process also includes mixing the reactor powder polypropylene with a free-radical initiator to form a powder/initiator mixture and subjecting the powder/initiator mixture to post-reactor forming. The present disclosure further provides for a vis-broken polypropylene and a polymer article.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No. 62/808,152, filed Feb. 20, 2019, which is incorporated herein by reference in its entirety for all purposes.


BACKGROUND
Polyolefins, particularly polypropylene, may be used in a variety of applications. Polypropylene with good thermal stability may be useful in such applications as composites and compounding. Composites may be formed by wetting a fiber, such as a glass fiber, with polypropylene. Polypropylene with good thermal stability may also be used in nonwovens, such as for automobiles and in filtration. Polypropylene with good thermal stability may also be used in durable good applications where high temperature resistance is desirable. Such durable goods include, but are not limited to, coffee makers, hair dryers, washing machines and dish washers.
SUMMARY
The present disclosure provides for a process forming a high MFR polypropylene. The process includes providing a reactor powder polypropylene, the reactor powder polypropylene having a melt flow rate of less than 100 dg/min. The process also includes mixing the reactor powder polypropylene with a free-radical initiator to form a powder/initiator mixture and subjecting the powder/initiator mixture to post-reactor forming. The present disclosure further provides for a vis-broken polypropylene and a polymer article.



BRIEF DESCRIPTION OF DRAWINGS
The present disclosure may be understood from the following detailed description when read with the accompanying figures.
FIG. 1 is a graph of Percent Weight-Loss versus Time for Compounds with Irgafos 168 consistent with certain embodiments of the present disclosure.
FIG. 2 is a graph of Percent Weight-Loss versus Time for Compounds with Doverphos S9228T consistent with certain embodiments of the present disclosure.
FIG. 3 is a graph of TGA Time at 2% Weight-loss versus Weight Percent of secondary antioxidant consistent with certain embodiments of the present disclosure.
FIG. 4 is a graph of TGA Time at 2% Weight-loss versus secondary antioxidant with Curve-Fits consistent with certain embodiments of the present disclosure.
FIG. 5 is a graph of Recrystallization Temperature versus Weight Percent of Talc consistent with certain embodiments of the present disclosure.



DETAILED DESCRIPTION
A detailed description will now be provided. The following disclosure includes specific embodiments, versions and examples, but the disclosure is not limited to these embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the disclosure when the information in this application is combined with available information and technology.
Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents. Further, unless otherwise specified, all compounds described herein may be substituted or unsubstituted and the listing of compounds includes derivatives thereof.
Further, various ranges and/or numerical limitations may be expressly stated below. It should be recognized that unless stated otherwise, it is intended that endpoints are to be interchangeable. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.).
Embodiments of the present disclosure generally relate to high melt flow rate controlled polypropylene with good thermal stability. Certain embodiments of the present disclosure relate to a process of forming a high melt flow rate (MFR) polypropylene with long term thermal performance characteristics, referred hereinafter as “forming a high MFR polypropylene.” In such embodiments, the process of forming a high MFR polypropylene includes providing a reactor powder polypropylene and subjecting the reactor powder polypropylene to post-reactor forming. MFR is measured herein using ASTM D1238.
Reactor Powder Polymer
The reactor powder polypropylene may be a homopolymer that may contain up to 5% of another alpha-olefin, including but not limited to C2-C8 alpha-olefins such as ethylene and 1-butene. The polypropylene homopolymer may be atactic polypropylene, isotactic polypropylene, hemi-isotactic, syndiotactic polypropylene, or combinations thereof. A polymer is “atactic” when its pendant groups are arranged in a random fashion on both sides of the chain of the polymer. In contrast, a polymer is “isotactic” when all of its pendant groups are arranged on the same side of the chain and “syndiotactic” when its pendant groups alternate on opposite sides of the chain. In hemi-isotactic polymer, every other repeat unit has a random substituent.
In certain embodiments, the reactor powder polymer is a heterophasic polypropylene. In other embodiments, the polypropylene copolymer may be a polypropylene heterophasic copolymer (PPHC) wherein a polypropylene homopolymer phase or component is joined to a copolymer phase or component. The PPHC may comprise from greater than 6.5 wt. % to less than 20 wt. % ethylene by total weight of the PPHC, alternatively from 8.5 wt. % to less than 18 wt. %, alternatively from 9.5 wt. % to less than 16%.
The copolymer phase of a PPHC may be a random copolymer of propylene and ethylene, also referred to as an ethylene/propylene rubber (EPR). PP heterophasic copolymers show distinct homopolymer phases that are interrupted by short sequences or blocks having a random arrangement of ethylene and propylene. In comparison to random copolymers, the block segments comprising the EPR may have certain polymeric characteristics (e.g., intrinsic viscosity) that differ from that of the copolymer as a whole. Without wishing to be limited by theory, the EPR portion of the PPHC has rubbery characteristics which, when incorporated within the matrix of the homopolymer component, may function to provide increased impact strength to the PPHC. In an embodiment, the EPR portion of the PPHC comprises greater than 14 wt. % of the PPHC, alternatively greater than 18 wt. % of the PPHC, alternatively from 14 wt. % to 18 wt. % of the PPHC.
The amount of ethylene present in the EPR portion of the PPHC may be from 38 wt. % to 60 wt. %, alternatively from 40 wt. % to 45 wt. % based on the total weight of the EPR portion. In an embodiment, the PPHC may have a melt flow rate (MFR) of from 1 g/10 min. to 100 g/10 min., alternatively from 1.5 g/10 min. to 50 g/10 min.
In another embodiment, the reactor powder polymer is a polypropylene homopolymer with a density of from 0.895 g/cc to 0.920 g/cc, alternatively from 0.900 g/cc to 0.915 g/cc, and alternatively from 0.905 g/cc to 0.915 g/cc as determined in accordance with ASTM D1505. In certain embodiments of the present disclosure, the propylene homopolymer may have a MFR of between 10 and less than 100 dg/min, between 20 and 90 dg/min or between 30 and 70 dg/min as measured by ASTM D1238. In certain embodiments, the MFR of the propylene homopolymer is less than 100 dg/min. U.S. Pat. No. 4,822,546 teaches that polypropylenes with a MFR above about 40 are difficult to pelletize. U.S. Patent Application No. 2017/0051118 discloses similar results with examples where 50 MFR polypropylene results in misshapen pellets. Such difficulties in pelletization increase as MFR increases from 50 dg/min. In addition, fines production may increase with higher MFRs, as shown in WO 2006025917. Polypropylenes having a MFR of 80 dg/min or greater may be difficult to manufacture, lowering production rates by 20% or more. Difficulties in pelletization of high melt flow polyolefins are described in U.S. Pat. No. 5,611,983, WO 2007126994 A1, and U.S. Pat. No. 6,423,800. Fines generation are described in U.S. Pat. No. 8,232,358, WO2006025917 and WO 2000042077.
Post-Reactor Forming
The reactor powder polypropylene may be subjected to post-reactor forming. In post-reactor forming, the reactor powder polypropylene is formed into larger, discrete particles. Post reactor forming may be accomplished by, for example, extrusion into pellets, compaction into a fused/physically bonded pellet, prill bead manufacturing, pastillation, or melt atomization.
Post-reactor forming may provide such advantages as reducing or eliminating explosion hazards found with dust handling, increasing bulk density, improving material handling, and improved product consistency such as by improving particle-to-particle consistency. Other post-reactor forming advantages may include increasing manufacturing versatility and intimate dispersion of additives within the polypropylene molecules, such as when the post-reactor forming step involves melting the polypropylene in making the larger, discrete particle.
In certain embodiments, MFR of the polypropylene is increased during post-reactor forming by mixing the reactor powder polypropylene with a free radical initiator, such as a peroxide to form a powder/initiator mixture and then subjecting the powder/initiator mixture to post-reactor forming. In certain embodiments, the peroxide is an organic peroxide. Examples of organic peroxides may include, but are not limited to, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, commercially available from AKZONOBEL® under the tradename TRIGONOX® 301 (CAS #24748-23-0); 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, commercially available from AKZONOBEL® as LUPERSOLTM 101, 2,5-dimethyl 2,5 bis-(t-butylperoxy) hexyne-3 and 4 methyl 4 t-butylperoxy-2 pentanone, 3,6,6,9,9-pentamethyl-3-(ethyl acetate), 1,2,4,5-textraoxy cyclononane, 4-(t-amylperoxy)-4-methyl-2-pentanol, dihexylene glycol peroxide, 4-(t-hexylperoxy)-4-methyl-2-pentanol, 4-(t-octylperoxy)-4-methyl-2-pentanol, 2-methyl-2-t-amylperoxy-4-pentanone, di-t-butyl peroxide, di-t-hexyl peroxide; di-t-octyl peroxide, dicumyl peroxide, and α,α′ bis-(tert-butylperoxy) diisopropyl benzene. In certain embodiments, where the large, discrete particle is to be free of tertiary butyl alcohols, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane is not used and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane is used.
The peroxide may be present in the powder/initiator mixture in an amount ranging from greater than 0 ppm to 1500 ppm, or 50 ppm to 1500 ppm, or 100 ppm to 750 ppm, or 250 ppm to 500 ppm (all by weight), for example.
Post-reactor forming of the powder/initiator mixture may result in vis-breaking of the polypropylene, resulting in an increased MFR of the vis-broken polypropylene. In certain embodiments, the vis-broken polypropylene may have a melt flow rate of 50 dg/min to 500 dg/min, from 70 dg/min to 300 dg/min or from 80 dg/min to 150 dg/min. In some embodiments, the ratio of the large, discrete particle MFR to reactor powder polypropylene may be from 1.25:1 to 25:1, from 2:1 to 15:1 or from of 2.5:1 to 12:1. In certain embodiments, the amount of initiator may be adjusted to achieve the desired MFR.
In certain embodiments, the powder/initiator mixture may include an antioxidant, such as a primary antioxidant or a secondary antioxidant. As used herein, a primary antioxidant is a radical scavenger. Examples include sterically hindered phenols, such as Irganox 1010 (CAS 6683-19-8), Irganox 1076 (CAS 2082-79-3), Irganox 3114 (CAS 27676-62-6), Irganox 1330 (CAS 1709-70-2), and Cyanox 1790 (CAS 40601-76-1). As used herein, a secondary antioxidant is a hyperoxide decomposing compound. The secondary antioxidant may aid in reducing premature weight loss in the propylene homopolymer, particularly at elevated temperatures. Examples of secondary antioxidants include, but are not limited to phosphites, hindered amine stabilizers and hydroxylamines. Phenol-free antioxidants are suitable as well, such as for example those based on hindered amine stabilizers, phosphites, hydroxylamines. Examples of suitable secondary antioxidants are BNX DSTDP (Dioctadecyl 3,3′-thiodipropionate) (CAS 693-36-7), Irgafos 168 (CAS 31570-04-4), Doverphos S9228T (CAS 154862-43-8), Ultranox 626 (CAS 26741-53-7), Weston 618F (CAS 3806-34-6), TNPP (CAS 26523-78-4), Hostanox P-EPQ (CAS 119345-01-6), and Irgastab FS-042 (CAS 143925-92-2). The secondary antioxidant may be present in the powder/initiator mixture between, for instance, 0.1% to 3% by weight, between 0.2% and 1.5% by weight, or between 0.15% and 0.75% by weight.
In certain embodiments, talc may be added to the powder/initiator mixture. Talc may be present in the powder/initiator mixture between 0.1 wt % to 2 wt % or between 0.3% to 1%, all by weight. In certain embodiments, talc may increase the recrystallization temperature of the polypropylene.
In certain embodiments, by vis-breaking the reactor powder polypropylene in post-reactor forming, a higher MFR polypropylene may be formed without adversely affecting the production rate of the reactor powder polypropylene while maintaining the long term heat aging performance (LHTA) of the polypropylene. One measure of LHTA is Isothermal Thermo-Gravimetric Analysis (TGA). TGA measures weight loss of the polypropylene at an elevated temperature. To measure TGA, a sample is started at 25° C. steadily heated to 230° C. over 15 minutes. The sample is held at 230° C. for 4 hours. An air purge gas atmosphere is used throughout the procedure. Weight loss may be calculated based on difference between the weight of the sample after four hours compared to the initial weight of the sample. Results of TGA multiple measurement may be averaged. In one measure of TGA, the time at a pre-determined elevated temperature to achieve a predetermined weight loss may be found. In certain embodiments of the present disclosure, following post-reactor forming, at 230° C., have a 1% loss in weight from between 25 and 250 minutes, or between 50 and 150 minutes, a 2% loss in weight between 50 minutes and 300 minutes or between 75 and 200 minutes, and a 3% loss in weight between 50 minutes and 300 minutes or between 77 and 210 minutes.
Articles
In some embodiments, the pellets may be processed to make an article, such as by methods known to those of ordinary skill in the art. For example and without limitation, the pellets may be processed by injection molding, fiber extrusion, film extrusion, sheet extrusion, pipe extrusion, blow molding, rotomolding, slush molding, injection-stretch blow molding or extrusion-thermoforming to produce an article. The article may be a motor vehicle component, appliance, or filter media, for example.
EXAMPLES
The disclosure having been generally described, the following examples show particular embodiments of the disclosure. It is understood that the example is given by way of illustration and is not intended to limit the specification or the claims. All compositions percentages given in the examples are by weight.
Example 1
Samples of powder/initiator mixture were prepared in accordance with Table 1. Sample 1 is a comparative reactor grade 100 melt flow rate propylene homopolymer fluff. Samples 2-26 are a controlled rheology grade 30 melt flow propylene homopolymer fluff with xylene solubles targeted at 2 consistent with the present disclosure as described herein above.







TABLE 1





TOTAL PETROCHEMICALS ENHANCED HEAT


STABILITY CRED PP WITH A HIGH MFR

























1
2
3
4
5
6
7
8
9





DSTDP
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4


Irganox 1010
0.45
0.45
0.45
0.45
0.45
0.45
0.45
0.45
0.45


Irganox 1076
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005


Hydrotalcite
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07


Irgafos 168
0.2
1.5
1.5
1.5


1.5
1.25
0.95


Trigonox 301

0.074
0.08
0.08
0.074
0.08
0.08
0.08
0.08


IMI Fabi Talc BT



0.5







Doverphos S9228T




0.75
0.75












Sample #

















10
11
12
13
14
15
16
17
18





DSTDP
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4


Irganox 1010
0.45
0.45
0.45
0.45
0.45
0.45
0.45
0.45
0.45


Irganox 1076
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005


Hydrotalcite
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07


Irgafos 168
0.7



0.95
0.95





Trigonox 301
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08
0.08


IMI Fabi Talc BT




0.3
1
0.3
1



Doverphos S9228T

0.35
0.27
0.2


0.27
0.27
0.16












Sample #

















19
20
21
22
23
24
25
26






DSTDP
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4



Irganox 1010
0.45
0.45
0.45
0.45
0.45
0.45
0.45
0.45



Irganox 1076
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005



Hydrotalcite
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07



Irgafos 168


0.2




1.5



Trigonox 301
0.08
0.08
0.08
0.07
0.08
0.09
0.08
0.08



IMI Fabi Talc BT
0.3
1









Doverphos S9228T
0.16
0.16

0.27
0.27
0.27
0.2









Values provided for components of the powder/initiator mixture are in weight percent of the total powder/initiator mixture weight. Trigonix 301, as used in Table 2, is based on a 41% mixture of Trigonix 301, e.g., a 800 ppm loading of 41% Trignoix 301 is 328 ppm of peroxide.
Example 2
Samples from Example 1 were subjected to post-reactor forming and molding. Results are shown in Table 2:














TABLE 2













After Compounding
After Molding





























GC



GC














Additives
MFR
GPC
Active
GPC
Active





















Irgafos
Trig
Talc
Dover
MFR
Mn
Mw
Mz
Peroxide
Mn
Mw
Mz
Peroxide


#
%
%
%
%
dg/min
Daltons
Daltons
Daltons
ppm
Daltons
Daltons
Daltons
ppm























1
0.2



103
22555
144293
686180







2
1.5
0.074


102
30141
179651
625411







3
1.5
0.08


116
30123
177736
607270







4
1.5
0.08
0.5

112
30117
178797
622089







5

0.074

0.75
104
30096
178636
610805







6

0.08

0.75
113
29762
179695
663599







7
1.5
0.08


112
30904
188677
707374
227
30183
176105
608175
122.9


8
1.25
0.08


120
30637
188192
680674
224
30057
173057
576910
127.9


9
0.95
0.08


118
30956
183891
643708
230
30070
173565
581917
126.5


10
0.7
0.08


130
30828
184539
647249
222
30040
171494
575858
121


11

0.08

0.35
122
30624
184850
662387
224
29757
167825
548760
116.8


12

0.08

0.27
124
30630
186673
677449
228
29216
155300
479965
95.5


13

0.08

0.2
130
30767
184756
657247
222
29810
165165
522529
111.7


14
0.95
0.08
0.3

130
30811
190011
761662
237
30284
180774
632070
143


15
0.95
0.08
1

130
30781
188180
686716
238
30331
176347
595963
121.2


16

0.08
0.3
0.27
134
30541
184066
670980

30018
164549
519389



17

0.08
1
0.27
124
30446
182072
644894

30109
166058
525467



18

0.08

0.16
120
30548
189579
709814

30361
172528
568530



19

0.08
0.3
0.16
110
30551
186276
683907

30242
171094
568825



20

0.08
1
0.16
130
30517
183947
668936

30078
166009
531130



21
0.2
0.08


133
30537
187328
730193







22

0.07

0.27
102
30557
184081
660742
188






23

0.08

0.27
121
30821
185897
662044
197






24

0.09

0.27
138
30696
184648
675854
260






25

0.08

0.2
130
30652
185801
690027







26
1.5
0.08


121
30735
187231
683896









The effect of peroxide on long term heat performance is shown in the data presented in Tables 3 and 9. TGA measurement and DSC results for the Samples from Example 1 are shown in Table 3.
The TGA data is presented in the format Weight-Loss versus Exposure Time at 230° C. for compounds containing Irgafos 168 (FIG. 1) and Doverphos 59228T (FIG. 2). Performance increases for increasing loading for both Irgafos 168) and Doverphos 59228T. Most loading levels studied exceeded the  ̃100 minute to 2% weight-loss that is typical of Sample 1. Irgafos 168 exhibits a greater initial weight-loss rate than the Doverphos 59228T. FIG. 3 depicts the Time at 2% Weight-Loss versus anti-oxidant weight for Irgafos 168 and Doverphos 59228T in pellet and molded form. FIG. 4 depicts compounds using no talc and 800 ppm of Trigonox 301. Doverphos 59228T generally outperforms Irgafos 168 by a ratio of 3:1 with identical additive weight.
FIG. 5 illustrates the recrystallization temperature versus talc loading. FIG. 5 shows that including talc increases the recrystallization temperature by 3-8° C.













TABLE 3












After Compounding
After Molding




























TGA





TGA












Time





Time

























at
DSC
at
DSC after Molding




























2%
2nd




2%
2nd

























Additives
wt.
Melt
□H2
Recry
□H
%
wt.
Melt
□H2
Recry
□H
%
























Irgafos
Trig
Talc
Dover
loss
Peak
Melt
Peak
Recry
Crystal
loss
Peak
Melt
Peak
Recry
Crystal


#
%
%
%
%
min
° C.
J/g
° C.
J/g
%
min
° C.
J/g
° C.
J/g
%


























1
0.2



94
164
105
121
102
50.4








2
1.5
0.074


172
164
104
120
100
49.5








3
1.5
0.08


198
164
104
120
100
49.6








4
1.5
0.08
0.5

200
165
108
127
102
51.5








5

0.074

0.75
265
165
107
121
104
51.1








6

0.08

0.75
265
164
101
120
99
48.4








7
1.5
0.08


204
164
111
123
107
52.9
190
163
111
123
107
53


8
1.25
0.08


178
163
110
121
106
52.4
164
162
112
121
108
53.3


9
0.95
0.08


166
163
109
120
104
52.2
186
162
112
120
107
53.3


10
0.7
0.08


139
162
109
119
107
52.2
121
163
109
119
105
52.1


11

0.08

0.35
177
162
111
120
108
52.9
196
162
111
120
107
52.9


12

0.08

0.27
148
162
110
119
108
52.8
166
162
110
119
106
52.7


13

0.08

0.2
112
162
111
119
109
53.0
80
161
111
119
109
53.3


14
0.95
0.08
0.3

181
164
112
127
109
53.6
169
164
113
127
110
54.3


15
0.95
0.08
1

174
164
113
128
109
53.8
165
164
114
128
110
54.6


16

0.08
0.3
0.27
161
164
112
127
109
53.7

165
129
127
126
61.7


17

0.08
1
0.27
148
164
114
128
110
54.4

164
128
128
123
61.1


18

0.08

0.16
77
163
115
123
110
55.0

165
121
122
121
57.8


19

0.08
0.3
0.16
77
165
114
126
109
54.4

165
126
126
121
60.1


20

0.08
1
0.16
92
164
113
128
109
53.8

167
120
127
119
57.3


21
0.2
0.08


66
162
115
121
110
55.0








22

0.07

0.27
150
163
112
120
109
53.7








23

0.08

0.27
135
162
116
121
111
55.3








24

0.09

0.27
135
162
113
120
109
54.1








25

0.08

0.2
114
162
113
121
109
54.0








26
1.5
0.08


206
162
111
120
109
53.1









Table 4 depict a subset of data from Table 3. As shown in Table 4, the controlled rheology sample #21 matches sample #1 in formulation, except with Trigonox 301 peroxide addition to increase the MFR from 30 to the 100 MFR target. With the balance of the additive package held constant, TGA is reduced to 66 minutes in comparison to the reactor grade #1 baseline of 94 minutes. An antagonistic effect exists between vis-breaking and long term heat stability. As shown with respect to sample #18, a similar effect is observed when using Doverphos S9228T at a similar loading level of 1600 ppm, even though Doverphos S9228T shows much higher efficacy in conventional polymer formulations. Replacing 2000 ppm Irgafos 168 with 1600 ppm Doverphos S9228T is not sufficient to match sample 1 performance. Only by using a 1:1 replacement of Doverphos S9228T for Irgafos 168, as shown with sample #13, does a vis-broken PP formulation match or exceed that of the sample #1 baseline.










TABLE 4









Additives
TGA















Irgafos
Trig.

Dover.
Time at 2%




168
301
Talc
S9228T
wt. loss



#
%
%
%
%
min


















1
0.2



94



21
0.2
0.08


66



18

0.08

0.16
77



13

0.08

0.2
112










As shown in Table 5, increasing Irgafos 168 leads to a TGA result that exceeds sample #1's TGA measurement of 94 minutes. Using the results of samples #7, #8, #9, #10 and #21, an interpolated TGA time of 94 minutes is determined at 0.425% Irgafos 168. However, at 0.08% Trigonox 301 this yields a 131 MFR, well above the 100 MFR target of sample #1.













TABLE 5












TGA








Time












Additives
at 2%















Irgafos 
Trig.

Dover.
wt.
MFR



168
301
Talc
S9228T
loss
MFR


#
%
%
%
%
min
dg/min
















1
0.2



94
103


21
0.2
0.08


66
133


10
0.7
0.08


139
130


9
0.95
0.08


166
118


8
1.25
0.08


178
120


7
1.5
0.08


204
112


Interpolated Fit
0.425
0.08


94
131









Table 6 depicts samples #2, #3, and #26 and an interpolated fit using 0.45% Irgafos 168 and 0.068% Trigonox 301, yielding a balance of TGA performance and a nominal 100 MFR pellet. These results matching the Sample #1.













TABLE 6












TGA








Time












Additives
at 2%















Irgafos
Trig.

Dover.
wt.
MFR



168
301
Talc
S9228T
loss
MFR


#
%
%
%
%
min
dg/min
















1
0.2



94
103


21
0.2
0.08


66
133


10
0.7
0.08


139
130


9
0.95
0.08


166
118


8
1.25
0.08


178
120


7
1.5
0.08


204
112


3
1.5
0.08


198
116


26
1.5
0.08


206
121


2
1.5
0.074


172
102


Interpolated Fit
0.45
0.068


98
102









Achieving a balance of TGA performance and a nominal 100 MFR pellet is shown in Table 7 with Doverphos 59228T, a higher performance phosphite-based melt stabilizer. Higher performance melt stabilizers may reduce the amount of additive used. For example, adding >0.4% Irgafos 168 could present additive feeding challenges and problems with product consistency. If a high performance antioxidant can be used for similar efficacy as, for instance, Irgafos 168, industrial performance may improve.
The results in Table 7 use of a high performance antioxidant like Doverphos S9228T. As shown in Table 7, an interpolated fit to the data indicate similar efficacy at only  ̃33% the loading needed with Irgafos 168. Adding 0.16% Doverphos S9228T would be similar to adding 0.2% Irgafos 168, making use of Doverpos S9228T feasible. Table 7 show a match of Sample #1 TGA and MFR measurements using a balance of peroxide and Doverphos S9228T.













TABLE 7












TGA








Time












Additives
at 2%















Irgafos
Trig.

Dover.
wt.
MFR



168
301
Talc
S9228T
loss
MFR


#
%
%
%
%
min
dg/min
















1
0.2



94
103


22

0.07

0.27
150
102


23

0.08

0.27
135
121


24

0.09

0.27
135
138


25

0.08

0.2
114
130


11

0.08

0.35
177
122


12

0.08

0.27
148
124


13

0.08

0.2
112
130


18

0.08

0.16
77
120


Interpolated Fit

0.065

0.16
99
99









In certain embodiments, it may be desirable to manufacture molded parts from CRed polypropylene that have LTHA performance that matches or exceeds that of sample #1. The results, set forth in Table 8, demonstrate such performance with an additive package. After molding, all compounds but one retain TGA values higher than that of sample #1. Adding an additional melt processing step and consuming more residual active peroxide is tenable. Any modest loss in TGA performance between compounding and molding as shown in Table 8 may be compensated by formulation optimization.









TABLE 8








After Compounding
After Molding






















TGA




TGA






GC
Time at



GC
Time at














GPC
Active
2% wt.
GPC
Active
2% wt.


















Mn
Mw
Mz
Peroxide
loss
Mn
Mw
Mz
Peroxide
loss


#
Daltons
Daltons
Daltons
Ppm
min
Daltons
Daltons
Daltons
ppm
min




















7
30904
188677
707374
227
204
30183
176105
608175
122.9
190


8
30637
188192
680674
224
178
30057
173057
576910
127.9
164


9
30956
183891
643708
230
166
30070
173565
581917
126.5
186


10
30828
184539
647249
222
139
30040
171494
575858
121
121


11
30624
184850
662387
224
177
29757
167825
548760
116.8
196


12
30630
186673
677449
228
148
29216
155300
479965
95.5
166


13
30767
184756
657247
222
112
29810
165165
522529
111.7
80


14
30811
190011
761662
237
181
30284
180774
632070
143
169


15
30781
188180
686716
238
174
30331
176347
595963
121.2
165









Tensile strength, flexural modulus and HDT were measured for samples selected from Example 2. The results are shown in Table 9. As shown in Table 9, tensile strength at yield, HDT of samples #2-#20, the controlled rheology polymer subject to post reaction forming of the present disclosure, are consistent with that of sample #1, the comparative reactor grade 100 melt flow rate propylene. Specifically, in applications requiring the modulus and HDT value to match sample 1, use of a nucleating agent like talc in these examples achieves that requirement without adversely impacting TGA or MFR performance.














TABLE 9












Tensile
Flex
HDT
























Tensile
Stress
Strain
Stress
Strain
Flex
Std.
HDT



Irgafos
Trig
Talc
Dover
Modulus
@Yield
@Yield
@Break
@Break
Modulus
Dev.
Value


Compound
%
%
%
%
ksi
psi
%
psi
%
kpsi
kpsi
° F.






















1
0.2



252.7
5271
5.9
5015
8
228
1.7
239


2
1.5
0.074












3
1.5
0.08


241.1
5152
6.8
4513
11
205
3.8
219


4
1.5
0.08
0.5

264.4
5333
5.9
4617
10
235
2.6



5

0.074

0.75










6

0.08

0.75
247.3
5258
6.5
4715
11
211
2
225


7
1.5
0.08


247.3
5261
6.7
3624
14
220
3.7
234


8
1.25
0.08


237.4
5132
6.9
3822
14
206
1.8
224


9
0.95
0.08


234.5
5126
7.1
3764
15
204
2.5
219


10
0.7
0.08


237.0
5157
7
4062
14
207
3.5
218


11

0.08

0.35
238.4
5172
6.8
4105
13
208
2.6
217


12

0.08

0.27
235.7
5149
6.9
4090
14
202
3.2
218


13

0.08

0.2
231.2
5105
7.1
4078
14
204
2.5
213


14
0.95
0.08
0.3

254.6
5347
6.3
4332
11
229
3.6
240


15
0.95
0.08
1

258.5
5312
6
4524
11
238
1.4
243


16

0.08
0.3
0.27
273.3
5438
5.8
4660
11
240
4



17

0.08
1
0.27
280.3
5419
5.4
4743
9
249
2.1



18

0.08

0.16
264.3
5402
6.2
4289
11
230
1.1



19

0.08
0.3
0.16
273.9
5448
5.7
4687
10
239
5.2



20

0.08
1
0.16
281.1
5426
5.4
4674
10
245
2.5









Certain TGA and MFR performance only, as shown above, will meet some application needs, but other applications will require a performance level in other physical properties. These physical properties include stiffness, tensile stress at yield and heat deflection temperature. As shown in Table 9 and highlighted in the following table below, the Cred grades often are slightly lower than the Sample #1 comparative. As shown in Table 10, modulus for certain samples is 10 to 20 kpsi lower, tensile strain at yield averages 0.9% higher and HDT averages 18° F. lower than sample #1.


















TABLE 10















Time













at













2%




Irgafos
Trig.

Dover.
Tensile
Stress
Strain
Flex
HDT
wt.



Com-
168
301
Talc
S9228T
Modulus
@Yield
@Yield
Modulus
Value
loss
MFR


pound
%
%
%
%
ksi
psi
%
kpsi
° F.
min
dg/min


























1
0.2



252.7
5271
5.9
228
239
94
103


3
1.5
0.08


241.1
5152
6.8
205
219
198
116


6

0.08

0.75
247.3
5258
6.5
211
225
265
113


7
1.5
0.08


247.3
5261
6.7
220
234
204
112


8
1.25
0.08


237.4
5132
6.9
206
224
178
120


9
0.95
0.08


234.5
5126
7.1
204
219
166
118


10
0.7
0.08


237.0
5157
7
207
218
139
130


11

0.08

0.35
238.4
5172
6.8
208
217
177
122


12

0.08

0.27
235.7
5149
6.9
202
218
148
124


13

0.08

0.2
231.2
5105
7.1
204
213
112
130


18

0.08

0.16
264.3
5402
6.2
230

77
120














Average for vis-broken compounds:
241.4
5191
6.8
210
221
166
121









In certain samples, talc was used as a nucleator although other nucleators are permissible. Adding talc improved stiffness, yield stress and HDT, which, on average as shown below in Table 11, exceeded those of the sample #1 reactor grade comparative. Likewise, strain at yield was reduced to 5.8% on average, closely resembling sample #1. No antagonistic effects were observed in TGA or MFR results. The use of a nucleator, such as talc, makes it possible to make a vis-broken LTHA PP compound that mirrors sample 1 for long term thermal stability, MFR, stiffness, TGA and percent strain at yield.


















TABLE 11















Time













at













2%




Irgafos
Trig.

Dover.
Tensile
Stress
Strain
Flex
HDT
wt.



Com- 
168
301
Talc
S9228T
Modulus
@Yield
@Yield
Modulus
Value
loss
MFR


pound
%
%
%
%
ksi
psi
%
kpsi
° F.
min
dg/min


























1
0.2



252.7
5271
5.9
228
239
94
103


4
1.5
0.08
0.5

264.4
5333
5.9
235

200
112


14
0.95
0.08
0.3

254.6
5347
6.3
229
240
181
130


15
0.95
0.08
1

258.5
5312
6
238
243
174
130


16

0.08
0.3
0.27
273.3
5438
5.8
240

161
134


17

0.08
1
0.27
280.3
5419
5.4
249

148
124


19

0.08
0.3
0.16
273.9
5448
5.7
239

77
110


20

0.08
1
0.16
281.1
5426
5.4
245

92
130














Average for vis-broken compounds w/ talc:
269.4
5389
5.8
239.3
241.5
148
124









Example 3
A 30 melt flow rate propylene homopolymer fluff was produced in a commercial reactor and subjected to post-reactor forming to achieve a 100 melt flow rate polypropylene. Multiple lots were tested. Results are shown in Table 12. Trigonix 301 was used as the peroxide, with the amount of peroxide in Trigonix 301 reflected in Table 12. The TGA data for the runs is presented in the format Weight-Loss versus Exposure Time at 230° C.











TABLE 12











TGA













Formulation
Weight
















Melt Flow
Irganox


Doverphos
Loss
Exposure
















Fluff
Pellet
1010
DSTDP
Peroxide
S9228T
Threshold
Time


Name
MFR
MFR
(%)
(%)
(%)
(%)
%
(min)


















Lot 1

79.5
0.45
0.424
0.025
0.241
2
94.04


Lot 2
28.09
87.9
0.45
0.392
0.025
0.240
2
93.18


Lot 3
35.33
94.4
0.45
0.432
0.025
0.245
2
97.76


Lot 4
34.07
107.7
0.45
0.504
0.025
0.250
2
90.01


Lot 5
34.07
105.1
0.45
0.444
0.025
0.245
2
89.67


Lot 6
33.85
102.2
0.45
0.392
0.025
0.240
2
87.25


Average
33.082 
96.13833 
0.45
0.431333
0.025
0.243542
2
91.985









As shown in Table 12, TGA performance for 30 melt flow rate propylene homopolymer fluff produced in a commercial reactor and subjected to post-reactor forming to achieve a 100 melt flow rate polypropylene is consistent with Sample 1 of Examples 1 and 2.
Example 4
Samples of a 30 melt flow propylene homopolymer fluff with xylene solubles targeted at 2 were mixed with the additive packages as shown below in Table 13. The TGA data is presented in the format Weight-Loss versus Exposure Time at 230° C.









TABLE 13







TGA at 2%


Sample
Description
(min)

















A
Lupersol 101 + no secondary antioxidant
15.13


B
Trignox 301 + 0.05% Irg 168 (no peroxide)
15.05


C
no Peroxide + no secondary antioxidant
14.94









As is shown in Table 13, an unbalanced additive package in combination with the homopolymer fluff, i.e., with peroxide but without a secondary antioxidant, or without peroxide but with antioxidants, or without peroxide or antioxidants does not perform as shown above with properly balanced additive packages. Specifically, samples with the unbalanced additive package in combination the homopolymer fluff have much lower TGA performance than sample 1 and samples 20-26.
Depending on the context, all references herein to the “disclosure” may in some cases refer to certain specific embodiments only. In other cases it may refer to subject matter recited in one or more, but not necessarily all, of the claims. While the foregoing is directed to embodiments, versions and examples of the present disclosure, which are included to enable a person of ordinary skill in the art to make and use the disclosures when the information in this patent is combined with available information and technology, the disclosures are not limited to only these particular embodiments, versions and examples. Other and further embodiments, versions and examples of the disclosure may be devised without departing from the basic scope thereof and the scope thereof is determined by the claims that follow.

## Claims

1. A process for forming a high melt flow rate (MFR) polypropylene comprising:
providing a reactor powder polypropylene, wherein the reactor powder polypropylene comprises a nucleator comprising talc, and wherein the reactor powder polypropylene has a MFR of less than 100 dg/min as determined by ASTM D1238;
mixing the reactor powder polypropylene with a free-radical initiator to form a powder/initiator mixture; and
subjecting the powder/initiator mixture to post-reactor forming to form discrete particle comprising a vis-broken polypropylene as the high MFR polypropylene, wherein the vis-broken polypropylene has a MFR greater than the MFR of the reactor powder polypropylene and in a range of from 80 dg/min to 150 dg/min.

2. The process of claim 1, wherein the reactor powder polypropylene is a homopolymer, a random copolymer, or an impact copolymer.

3. The process of claim 1, wherein the reactor powder polypropylene has a MFR greater than or equal to 10 and less than 100 dg/min as measured by ASTM D1238.

4. The process of claim 1, wherein the nucleator further comprises silica, a metallic-silicate hydrate, an organic derivative of dibenzylidene sorbitol, a sorbitol acetal, or a combination thereof.

5. The process of claim 1, wherein the free radical initiator is an organic peroxide.

6. The process of claim 5, wherein organic peroxide is 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, or 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane.

7. The process of claim 6, wherein the organic peroxide is 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane and no 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane is present.

8. The process of claim 5, wherein an amount of organic peroxide present in the powder/initiator mixture is between 50 ppm to 1500 ppm.

9. The process of claim 1, wherein a ratio of MFR of the vis-broken polypropylene to the reactor powder polypropylene is between 1.25:1 to 25:1.

10. The process of claim 9, wherein the ratio of MFR of the vis-broken polypropylene to the reactor powder polypropylene is between 2.5:1 to 12:1.

11. The process of claim 1, wherein the powder/initiator mixture is combined with a secondary antioxidant.

12. The process of claim 11, wherein the secondary antioxidant is a phosphite, hindered amine stabilizer or hydroxylamine.

13. The process of claim 12, wherein the secondary antioxidant is present in the powder/initiator mixture in an amount between 0.1% to 3 wt %.

14. The process of claim 1, wherein, following post-reactor forming, a TGA of the high MFR polypropylene at 230° C. has a 2% loss in weight of between 75 minutes and 200 minutes.

15. The process of claim 14, wherein, following post-reactor forming, the TGA of the high MFR polypropylene at 230° C. has a 3% loss in weight of between 77 minutes and 210 minutes.

16. The process of claim 1, wherein the post-reaction forming is accomplished by extrusion into pellets, compaction into a fused/physically bonded pellet, prill bead manufacturing, pastillation, or melt atomization.

17. A vis-broken polypropylene obtained by the process of claim 1.

18. The process of claim 1 further comprising forming the discrete particle into an article.

19. The process of claim 18, wherein the article is a motor vehicle component, appliance, or filter media.

20. A polymer article formed from the vis-broken polypropylene of claim 1.

21. The process of claim 1, wherein the MFR of the high MFR polypropylene is in a range of from about 100 dg/min to 150 dg/min.

22. A process for forming a high melt flow rate (MFR) polypropylene comprising:
providing a reactor powder polypropylene, the reactor powder polypropylene comprising a nucleator and having a MFR of less than 100 dg/min as determined by ASTM D1238;
mixing the reactor powder polypropylene with a free-radical initiator to form a powder/initiator mixture; and
subjecting the powder/initiator mixture to post-reactor forming to form discrete particle comprising a vis-broken polypropylene as the high MFR polypropylene, wherein the vis-broken polypropylene has a MFR greater than the MFR of the reactor powder propylene and in a range of from 80 dg/min to 150 dg/min;
wherein the nucleator is talc and the talc is present in the reactor powder polypropylene in an amount between 500 ppm and 20,000 ppm.

23. The process of claim 22, wherein the MFR of the high MFR polypropylene is in a range of from about 100 dg/min to 150 dg/min.

24. A process for forming a high melt flow rate (MFR) polypropylene comprising:
providing a reactor powder polypropylene, the reactor powder polypropylene having a MFR of less than 100 dg/min as determined by ASTM D1238;
mixing the reactor powder polypropylene with a free-radical initiator to form a powder/initiator mixture; and
subjecting the powder/initiator mixture to post-reactor forming to form discrete particle comprising a vis-broken polypropylene as the high MFR polypropylene, wherein the vis-broken polypropylene has a MFR greater than the MFR of the reactor powder polypropylene and in a range of from 80 dg/min to 150 dg/min;
wherein the powder/initiator mixture is combined with talc.

25. The process of claim 24, wherein the MFR of the high MFR polypropylene is in a range of from about 100 dg/min to 150 dg/min.