Integral skin foams employing 1,1,1,3,3-pentafluoropropane as blowing agent

The invention relates to integral skin foams and in particular to integral skin foams that are prepared using 1,1,1,3,3-pentafluoropropane (HFA-245fa) alone or in combination with water as the blowing agent. The foams exhibit physical characteristics such as resistance to abrasion and cracking on flex comparable to conventional chlorinated fluorocarbon blown foams. The foams of the present invention are suitable for use in many applications including, for example, shoe soles.

EXAMPLES The same general procedure commonly referred to as “handmixing” is used to prepare all foams. For each blowing agent, a master batch of the premix combining all the components except blowing agent was prepared. About 2 kg is blended to insure that all of the foams in a given series are made with the same master batch of premix. The premix is blended in a one-gallon paint can, and stirred at about 1500 rpm with a Conn 2″ diameter ITC mixer until a homogenous blend was achieved. When mixing is complete the material is transferred to a one-gallon glass bottle and sealed. The bottle was then placed in a refrigerator controlled at 50° F. The foam blowing agents were kept separately in the same refrigerator, along with the 32 oz. tin cans used for mixing vessels. The A-component, isocyanate, is kept in sealed containers at 70° F. For the individual foam preparations, an amount of B-component equal to the formulation weight is weighted into a 32 oz. tin can preconditioned at 50° F. The required amounts of the individual blowing agents, also preconditioned to 50° F. is added to the B-component. The contents are stirred for two-minutes with a Conn 2″ ITC mixing blade turning at about 1000 rpm. Following this, the mixing vessel and contents are reweighed. If there is a weight loss, the lower boiling blowing agent is added to make up the loss. The contents are then stirred for an additional 30 seconds, and the can replaced in the refrigerator. After the contents have cooled again to 50° F., approximately 10 minutes, the mixing vessel is removed from the refrigerator and taken to the mixing station. A pre-weighed portion of A-component, isocyanate, is added quickly to the B&square; component, the ingredients mixed for 10 seconds using a Conn 2″ diameter ITC mixing blade at 3000 rpm and poured into a 8″×8″×4″ cardboard cake box and allowed to rise. Cream, initiation, gel and tack free times were recorded for the individual polyurethane foam samples. The foams are allowed to cure in the boxes at room temperature for at least 24 hours. After curing, the blocks are trimmed to a uniform size and the densities are measured Any foam that did not meet the density specification are discarded, and new foams prepared using an adjusted amount of blowing agent in the formulation to obtain the specified density. For test purposes both molded and free rise foam samples were prepared. The necessary quantity of B-side required to obtain the targeted molded density were calculated. The foam components were weighed so that the final total weight is equal to the weight needed in the mold allowing for what ever hang up was present in the mixing vessel. After mixing the foam components per the above described procedure the foam was poured into a 6″×6″×1″ heated to 98° F. which has been lightly sprayed with silicone mold release. After 4 minutes, the plaque was demolded and trimmed. The net weight of the plaques was taken and the foam density calculated. After 24 hours curing time, physical properties were tested. The reactivity profiles and free rise densities for HFC-245fa and CFC-11 are reported in Tables I and II, respectively. HFC-245fa was evaluated at 50° F. for both the A- and B-sides in order to minimize evaporation of HEFC-245fa and frothing of the B-side. Attempts were made to run CFC-11 evaluation at 50° F. for the A- and B-sides. However, the reactivity was extremely slow and produced poor quality foam. Thus CFC-11 was evaluated at 70° F. The free rise density of HFC-245fa at 20 wt. % could not be determined since the cells were very coarse and the foam collapsed. 1 TABLE I Free Rise Data for HFC-245fa (T A &equals; T B &equals; 50° F.) Example FR-1 FR-2 FR-3 FR-4 Polyol Premix (g) 100.14 84.52 63.04 60.00 HFC-245fa (g) 5.32 9.41 11.17 14.98 Wt. % HFC-245fa 5 10 15 20 ISO (g) 46.8 41.0 28.8 27.0 Mix Time (sec) 10 10 10 10 Cream Time (sec) 42 38 35 34 Gel Time (sec) 70 80 90 108 Rise Time (sec) 28 52 53 74 Tack Free Time (sec) 93 106 118 173 Foam Weight (g) 83.7 47.2 31.8 — Foam Volume (cc) 500 500 500 — Overall Density (pcf) 10.43 5.88 3.96 — 2 TABLE II Free Rise Data for CFC-11 (T A &equals; T B &equals; 70° F.) Example FR-5 FR-6 FR-7 FR-8 Polyol Premix (g) 100 84.5 63 60 CFC-11 (g) 5.3 9.4 11.1 15 Wt. % CFC-11 5 10 15 20 ISO (g) 46 39 28.2 27.0 Mix Time (sec) 10 10 10 10 Cream Time (sec) — 38 37 37 Gel Time (sec) 50 55 65 65 Rise Time (sec)* — — — — Tack Free Time (sec) 70 73 82 90 Foam Weight (g) 81.2 69.2 54.0 39.7 Foam Volume (cc) 250 400 500 500 Overall Density (pcf) 20.3 10.8 6.7 5.0 *Not measured. FIG. 1 shows the gel time as a function of blowing agent concentration for both HFC-245fa and CFC-11. As expected, the gel times for the HFC-245fa formulation were longer than for the CFC-11 formulation. This can be attributed to two factors: the lower boiling point of HFC-245fa and the lower processing temperature (50° F.). The free rise density was plotted versus blowing agent concentration for both blowing agents evaluated. These results are shown in FIG. 2 . Noted here is the substantial reduction in free rise density for HFC-245fa foam versus CFC-11 blown foam, particularly at low blowing agent weight percent. For example, at 5 wt. % blowing agent, the density of the HFC-245fa foam is nearly one-half that of CFC-11 foam. This cannot be attnbuted to the molecular weight difference of the two blowing agents (134 g/mole for HFC-245fa vs. 137.4 g/mole for CFC-11). One explanation may be the difference in the processing temperatures used in the study. The lower temperature for HFC-245fa used during processing produces a longer gel time. This means that the foam would rise for a longer period of time before it gels. The rise time was not measured for the CFC-11 free rise study. The results for the poured foam samples of HFC-245fa and CFC-11 are given in Table III and IV. A 6″×6″×1″ mold was used for these samples. The typical mold temperature was 98° F. As in the free rise density work, HFC-245fa foams were prepared at 50° F. for both the A- and B-sides while the CFC-11 foams were prepared at 70° F. The molded foam at 30 pcf and 15 and 20 wt. % HFC-245fa could not be formed since the force of the rising foam caused the foam to squeeze out of the mold. This can be attributed to the density difference between the formulations. Just pouring the required mass of the HFC-245fa formulation in the mold to achieve 30 pcf would almost fill the mold prior to reaction and subsequent expansion. This was no the case for CFC-11 foams. 3 TABLE III Molded Foam Data for HFC-245fa (T A &equals; T B &equals; 50° F.; Mold T &equals; 98° F.) Example Mold-1 Mold-2 Mold-3 Mold-4 Mold-5 Mold-6 Molded 20 20 20 20 30 30 Density Target (pcf) Wt. % 5 10 15 20 5 10 HFC-245fa Polyol Premix 165 160 155 150 215 205 (g) ISO (g) 75.7 73.0 31.0 68.0 96.0 90.4 Target Weight 189 189 189 189 284 284 (g) Foam Weight 188.9 189.3 184.6 178.3 286.1 276.1 (g) Overall Density 20.0 20.0 19.5 18.9 30.2 29.2 (pcf) 4 TABLE IV Molded Foam Data for CFC-11 (T A &equals; T B &equals; 70° F.; Mold T &equals; 98° F.) Example Mold-9 Mold-10 Mold-11 Mold-12 Mold-13 Mold-14 Mold-15 Mold-16 Molded 20 20 20 20 30 30 30 30 Density Target (pcf) HFC-245fa 5 10 15 20 5 10 15 20 (wt %) Polyol 165.2 160.1 155.2 150 215.2 205 195 190 Premix (g) ISO (g) 74.7 71.2 71.0 68.7 97.0 94.6 89.4 85.2 Target 191.4 188.4 192.0 181.6 280.8 279.8 282.6 280.1 Weight (g) Foam 191.4 188.4 192.0 181.6 280.8 279.8 282.6 280.1 Weight (g) Overall 20.2 19.9 20.3 19.2 29.6 29.6 29.9 29.6 Density (pcf) 5 TABLE V Physical Property Comparison of Foams Blown with CFC-11, H 2 O and HFC-245fa Index &equals; 100 CFC-11 H 2 O HFC-245fa Hand mix free rise density 3.5 8.5 3.5 (pcf) Molded Density (pcf) 7.0 15 20 25 7.0 Core Tensile Strength (psi) 838 180 250 375 895 Core Elongation (%) 95 180 190 180 110 Trouser Tear Strength (pli) 102 48 66 95 131 6 TABLE VI Comparison of Physical and Mechanical Properties of Foam Samples Made Using HFC-134a and HFC-245fa for a Polyether Polyol System HFC-134a HFC-134a HFC-245fa HFC-245fa Ratio (R/A) 100/50.5 100/51.8 100/50.5 100/51.9 Index 95 97 97 100 Density (pcf) 38.7 37.4 36.8 38.0 Shore A 65 63 63 65 Tensile Strength &commat; 642 620 618 772 Break (psi) Elongation &commat; 505 430 525 560 Break (%) Trouser Tear (pli) 46 38 40 35 7 TABLE VII Aging Study on HFC-245fa in Medium Density Polyether Polyol System Closed Container Vapor Space Above Polyol ˜ 60% (Stored at Room Temperature) Aging Study Initial 21 Days Polyol weight (g) 230 230 Isocyanate weight (g) 118 118 Cream time (sec) 15 16 Rise Time (sec) 35 35 Gel Time (sec) 46 57 Tack Free Time (sec) 70 75 Indent Recovery Time (sec) 125 130 Cup Density (pcf) 18.6 19.8 While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the spirit thereof