BIOCIDAL POLYAMIDE-COMPOSITIONS, METHODS FOR PREPARING THE SAME AND USES THEREOF

Abstract

The invention relates to the field of polymers, in particular to polymer systems based on polyamide (PA) having broad spectrum biocidal activity and the use thereof in the manufacture of biocidal products. The blends are produced by hot melt extrusion. Provided is a miscible blend of polyamide-iodine (PA-I), preferably comprising at least 0.1 iodine, preferably at least 0.5 wt % iodine. Also provided is a biocidal product comprising a blend according to the invention.

Claims

1. A method for providing a biocidal polyamide-iodine (PA-I) blend comprising mixing polyamide (PA) with a suitable source of iodine (I) and optional further ingredients, followed by solubilizing the mixture by subjecting the mixture to a hot melt extrusion process to obtain in a homogeneous blend in which all ingredients are uniformly distributed throughout the polyamide-iodine complex matrix.

2. The method of claim 1, wherein the PA is an aliphatic polyamide, a nylon, a semi-aromatic polyphthalamide and aromatic aramide, or any mixture thereof.

3. The method of claim 2, wherein the PA is selected from the group consisting of Polyamide 6, Polyamide 11, Polyamide 12, Polyamide 5-10, Polyamide 6-6, Polyamide 6-9, Polyamide 4-10, Polyamide 6-10, Polyamide 6-12, Polyamide 10-10, Polyamide 10-12, Polyamide 4-6 and Polyamide 12-12.

4. The method according to claim 1, wherein the source of iodine is selected from the group consisting of elemental iodine, iodide and iodate salts, polyvinylpyrrolidone-iodine (PVP-I), and mixtures thereof.

5. The method according to claim 4, wherein the iodine source is elemental iodine, PVP-I, or a mixture thereof.

6. The method according to claim 5, wherein said PVP-I contains 1-25% available iodine and 2-45% total iodine.

7. The method according to claim 1, wherein said polyamide and/or iodine source is/are of bio-based origin.

8. The method according to claim 1, comprising mixing PA with a suitable source of iodine and one or more further polymer(s), small molecule(s), additives(s), plasticizer(s), biocidal agent(s) and/or antibiotic(s).

9. The method according to claim 1, wherein the hot melt extrusion process comprises the use of a multiple screw extruder.

10. The method according to claim 9, wherein the temperature in the mixing zones of the extruder is in the range of from 150° C. to 260° C., preferably while operating the multiple screw extruder at 300 to 500 rpm.

11. A homogenous biocidal PA-I blend obtained by a method according to claim 1, comprising at least 0.1 wt % iodine.

12. The biocidal PA-I blend according to claim 11, comprising 60-99% wt % polyamide.

13. A biocidal composition comprising a homogeneous PA-I blend according to claim 11, and one or more further polymer(s), small molecule(s), additives(s), plasticizer(s), biocidal agent(s) and/or antibiotic(s).

14. The biocidal composition according to claim 13, comprising one or more of the following biocidal agents: silver, copper, gold, zinc metals and their salts; quaternary amino compounds (e.g. benzalkonium chloride and cetylpyridinium chloride); phenols and cresols; halophenols (e.g. p-chloro-m-xylenol); biguanides (e.g. chlorhexidine); anilides (e.g triclocarbon) and triclosan.

15. The biocidal Composition according to claim 13, comprising polyvinyl-pyrrolidone.

16. A method for manufacturing a biocidal material, comprising incorporating into the material the PA-I blend according to claim 11.

17. The method of claim 16, wherein said biocidal material is active against bacteria, viruses, yeasts, fungi, mold, spores and/or protozoa.

18. A biocidal product comprising the biocidal PA-I blend according to claim 11.

19. The biocidal product according to claim 18 selected from the group consisting of air filters, water and solution filters, mouth caps, tooth brush bristles, equipment or device housing, sutures, garments, curtains, blankets, hard surface coatings, dentistry articles, building materials, construction materials, carpets, medical devices, wound coating gauze, light switches, door handles, operating and endo-scopes, catheters, tubes, breathing tubes, endotracheal tubes, intravascular catheters, deep intravenous lines, shoes and shoe soles, sponges, cutting planks, masks, syringe housings, hospital containers, synthetic sheets and covers, food and device packaging, countertops, flexible surface coatings, key boards, upholstery, plates, diapers, tissues, handkerchiefs, fasteners and flooring.

20. A biocidal product comprising the biocidal composition according to claim 13.

Description

LEGEND OF THE FIGURES

[0060] FIG. 1: Clearing zone studies of PA:PVP-I (80:20) pellets with Staphylococcus aureus. Right hand panel shows a magnification of the area comprising the pellets.

[0061] FIG. 2: Clearing zone studies of PA:PVP-I (80:20) pellets with Aspergillus brasiliensis. Right hand panel shows a magnification of the area comprising the pellets.

[0062] FIG. 3: Clearing zone studies of PA:PVP-I (80:20) pellets with Candida albicans. Right hand panel shows a magnification of the area comprising the pellets.

[0063] FIG. 4: Clearing zone studies of PA:PVP (80:20) pellets with (A) Staphylococcus aureus, (B) Aspergillus brasiliensis or (C) Candida albicans (comparative example).

[0064] FIG. 5: Clearing zone studies of PA pellets with (A) Staphylococcus aureus, (B) Aspergillus brasiliensis or (C) Candida albicans (comparative example).

[0065] FIG. 6: Clearing zone studies of PA-I sample strands from Example 2 with (A) Staphylococcus aureus—common strain or (B) Staphylococcus aureus—MRSA resistant strain.

[0066] FIG. 7: (left hand side) PP-I extruded material, Comparative Sample 34, and (right hand side) PA-I complex, Sample 27, of the invention in sample bags after extrusion.

EXPERIMENTAL SECTION

Extrusion Studies and Thermal Analysis:

[0067] The raw materials used were Polyamide 6 (PA6; Lanxess Durethan® 29), elemental iodine 99.8% purity (Sigma Aldrich/Merck), personal care grade PVP K30 having K-value of 30 (Boai NKY Pharmaceuticals Ltd. PolyViscol™ K30), Polyamide 11 (Sigma Aldrich/Merck), Polyamide 12 (Sigma Aldrich/Merck), Polyamide 6,6 (Sigma Aldrich/Merck), polypropylene and EP pharmaceutical grade PVP-I (Boai NKY Pharmaceuticals Ltd. KoVidone®-I) having an available iodine content from 9-12%. If required, larger granule polymers were milled before use and used without additional drying. The iodine was ground into a fine powder before use. Both PVP K30 and PVP-I were used as received. The powders blends were dry mixed in a mixer and then fed into the extruder.

[0068] 400 Gram extrusion studies were conducted in a Thermo Prism Eurolab 16 twin screw extruder having 16 mm screw diameter and 25 cm barrel length. The extruding barrel had five heating zones that were set in the range of 150-240° C. The rotation speed of the screws was fixed at 400 rpm.

[0069] Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were conducted on Netzsch 204-F1 and TA instrument Q500, respectively.

[0070] The compatible PA-I complexes formed during the melt blending resulted in an extrudate in the form of a molten strand that was cooled and pelletized. All extrusion experiments were conducted under a nitrogen atmosphere. The pellets or cooled strands were used “as is” in subsequent bacterial growth studies. The following table is a summary of the various extrusion experiments conducted.

Example 1: Extrusion Test Trial 1

[0071] Hot melt extrusion compounding studies wore carried out with PA6 and PVP and PVP-I systems.
The summary is outlined on the following Table 1

TABLE-US-00001 Wt. ratio of Ingredients Biocidal Sample PA6 PVP PVP-I Activity Observations  1 99 1 — − Miscible blend  2* 95 5 — − Miscible blend  3* 90 10 — − Miscible blend  4* 80 20 — − Miscible blend  5* 70 30 — − Miscible blend  6* 60 40 — − Miscible blend  7* 50 50 — − At the limit of mechanical properties  8 99 — 1 + Miscible blend  9 95 — 5 + Miscible blend 10 90 — 10 + Miscible blend 11 80 — 20 + Miscible blend 12 75 — 25 + Miscible blend 13 70 — 30 + Reaction of iodine with cooling bath 14 90 5 5 + Miscible blend 15 80 10 10 + Miscible blend 16* 100 — — − control *Reference/comparative sample

[0072] As can de derived from the results in Table 1 above, compatible blends were obtained up to 40 w % PVP addition in which the PA-PVP blend could still be extruded to give a fiber that did not break. Above 40 w % PVP, the blend is still compatible, but the mechanical properties are greatly compromised. For biocidal PA-PVP-I blends, the upper limit of PVP-I incorporation was about 25 weight %. Whereas the mechanical properties were still acceptable, the water-cooling bath seemed to react and discolor the resultant PA-PVP-I fiber. It is expected that incorporation of an increased amount PVP-I would be possible if an alternative cooling system is employed.

The following Table 2 gives a summary for the DSC and TGA analysis of samples 10 and 11.

TABLE-US-00002 DSC* TGA (°C.) Melt Temp Onset Temp Melt Cryst @ Initial temp. Tm Enthalpy Temp 5% wt. start of of Sample (°C.) AH (J/g) T.sub.c (°C.) loss decomp. decomp. 100% PA6 222 75.5 186 383 292 416 (reference 16) PA6/10% 217 68 181 344 286 385 PVP-I (sample 10) PA6/20% 209 53 169 324 279 365 PVP-I (sample 11) *Aluminum DSC pans used for DSC analysis
As can be seen in Table 2, the resultant DSC and TGA analysis show the resultant materials are stable and homogeneous. Increasing incorporation of the amorphous PVP-I causes a decrease in the both the melt temperature and melt enthalpy, showing the polymers are behaving as miscible blends. Biocidal activity was realized for samples compounded with PVP-I and not PVP alone.

Example 2: Extrusion Test Trials 2

[0073] The following table 3 is a summary of the various extrusion experiments conducted.

TABLE-US-00003 Wt. ratio of Ingredients Total Biocidal Sample PA6 I PVP PVP-I Iodine Activity Observations 17 95 — — 5 0.5% + Miscible blend 18 92.5 2.5 — 5 3.0% + Miscible blend 19 90.5 4.5 — 5 5.0% + Miscible blend 20 85.5 9.5 — 5  10% + Miscible blend 21 81 9 — 10  10% + Miscible blend 22 95 5 — —   5% + Miscible blend 23 93 5 2 —   5% + Miscible blend 24 90 5 5 —   5% + Miscible blend 25 85 5 10 —   5% + Miscible blend 26 85 10 5 —  10% + Miscible blend 27 90 10 — —  10% + Miscible blend

[0074] As can be derived from the results in table 3, all systems gave miscible blends, resulting in stable PA-I complexes. The iodine was tightly bound to the PA matrix with no iodine release or discoloration of surrounding materials. All PA-I complexes showed biocidal activity.

Clearing zone photos for a number of the samples are included in FIG. 6 showing the PA-1 systems show strong activity against both natural occurring and Methicillin-resistant strains of Staphylococcus aureus.
The following table 4 is a summary of thermal properties as determined by TGA and DSC for a number of the samples.

TABLE-US-00004 DSC* TGA (°C.) Melt Cryst. Temp @ Initial Onset Melt Temp Enthalpy Temp 5% wt. start of temp. of Sample Tm (°C.) AH (J/g) Tc (°C.) loss decomp. decomp. 100% PA6 220 71 165.5 383 292 416 (reference) 18 211 69 170 340 288 392 19 207 64 164 321 280 380 20 202.5 58 158 318 269 378 22 206.0 66 165.0 336 279 387 23 214.5 74 176 352 258 397 24 204.5 58 162 316 266 381 25 199.0 53 156 327 268 381 26 198.5 55 154 297 266 361 27 203.5 64 161.5 319 280 374 * Pressurized steel pans used for DSC analysis.
As can be seen from table 4, the resultant DSC and TGA analysis show the resultant PA-I materials are stable and homogeneous. The resultant stable PA-I blends can be directly molded into desired end products or can be further extruded with additional ingredients for final use.

Example 3: Extrusion Test Trials 3

[0075] Besides PA6, other base PA polymers were extruded to give the PA-I blends. The PA materials extruded in this example were Polyamide 11, 12 or 6,6. The following table 5 is a summary of the extruded materials.

TABLE-US-00005 Wt. ratio of Ingredients Biocidal Sample PA PVP-I I.sub.2 Activity Observations 28 92.5 PA11 5 2.5 + Compatible blend 29 97 PA12 — 3 + Compatible blend 30 95 PA6.6 5 — + Compatible blend 31 92.5 PA6.6 5 2.5 + Compatible blend
All extrusion reactions resulted in compatible blends on which the complexed iodine formed a stable complex within the PA matrix. All systems showed biocidal activity.

Example 4: Extrusion Test Trials 4 (Comparative Example)

[0076] Following the teaching described in U.S. Pat. No. 7,659,344, Polypropylene (PP) was extruded with PVP-I or with elemental iodine. The following Table 6 gives a summary of the results.

TABLE-US-00006 Wt. ratio of Ingredients Biocidal Sample PP PVP-I I.sub.2 Activity Observations 32 95  5 — − Inhomogeneous blend 33 90 10 — − Inhomogeneous blend 34 97 — 3 Not Unstable complex tested
The extrusion of PP with PVP-I (samples 32 and 33) resulted in the physical mixing of the PVP-I powder within the melted PP matrix. Upon cooling, the resultant strands were rough and of poor mechanical integrity. The PVP-I powder structure could be visually detected as being embedded and encased on the PP matrix upon cooling, which resulted in two incompatible materials. Bacterial testing on these systems showed no biocidal activity.
The direct extrusion of PP with elemental iodine resulted in a clearly visible unstable complex. Once the PP-I strands were obtained from the extrusion process, the material was granulated and placed in plastic bags for keeping. The surrounding materials become quickly colored due to the escaping iodine vapors. There was no complex formed and thus no stable PP-!complex could be produced. FIG. 7 shows a photographic image of either the comparative PP-I material (Sample 34) or the PA-I complex (Sample 27; see Example 2) of the invention that were stored in plastic bags. Both materials were extruded at about the same time. The PP-I material immediately showed discoloration of surrounding materials, while the PA-I complexes of this invention remain stable and free of any color release after immediate production and over time, even though the total iodine loading was more than 3× the amount as for the PP system, 10% and 3%, respectively.

Example 5: Bacterial Tests

[0077] In this example, the biocidal activity of a representative PA-I blend (Sample 11) was determined using clearing zone studies of PA-PVP-I (80:20) pellets with either Staphylococcus aureus (Gram+bacteria), Aspergillus brasiliensis (fungus) or Candida albicans (yeast).
Bacterial Test 1: Clearing Zone Studies with S. aureus.
A suspension of 10.sup.6 cfu/ml S. aureus was prepared. The suspension was then used to inoculate TSA and SDA agar by dipping a cotton swab in the test suspension and rubbing the swab against the agar plates. After the suspension treatment, the PA-PVP-I (80:20) pellets were transferred on the plates and the plates incubated. Clearing zones were observed after 2 and 4 days around the pellets. FIG. 1 shows the PA-PVP-I pellets (80:20) after 4 days incubation. Biocidal activity was observed for the PA-PVP-I pellets.
Bacterial Test 2: Clearing Zone Studies with A. brasiliensis.
A suspension of 10.sup.6 cfu/ml A. brasiliensis was prepared. The suspension was then used to inoculate TSA and SDA agar by dipping a cotton swab in the test suspension and rubbing the swab against the agar plates. After the suspension treatment, the PA-PVP-I (80:20) pellets were transferred on the plates and the plates incubated. Clearing zones were observed after 2 and 4 days around the pellets. FIG. 2 shows the PA-PVP-I pellets (80:20) after 4 days incubation. Biocidal activity was observed for the PA-PVP-I pellets.
Bacterial Test 3: Clearing Zone Studies with C. albicans.

[0078] A suspension of 10.sup.6 cfu/ml C. albicans was prepared. The suspension was then used to inoculate TSA and SDA agar by dipping a cotton swab in the test suspension and rubbing the swab against the agar plates. After the suspension treatment, the PA-PVP-I (80:20) pellets were transferred on the plates and the plates incubated. Clearing zones were observed after 2 and 4 days around the pellets. FIG. 2 shows the PA-PVP-I pellets (80:20) after 4 days incubation. Biocidal activity was observed for the PA-PVP-I pellets.

Bacterial Test 4: Reference Sample 4 Clearing Zone Studies of PA:PVP (80:20) Pellets.

[0079] Suspensions of 10.sup.6 cfu/ml S. aureus, A. brasiliensis and C. albicans were prepared. The suspensions were then used to inoculate TSA and SDA agar by dipping a cotton swab in the test suspension and rubbing the swab against the agar plates. After the suspension treatment, PA-PVP (80:20) pellets were transferred on the plates and the plates incubated. Clearing zones were not observed after 2 and 4 days around the pellets. FIG. 2 shows the PA-PVP pellets (80-20) after 4 days incubation. The PA-PVP pellets did not have any biocidal activity against these microorganisms.

Bacterial Test 6: Reference Sample 16 Clearing Zone Studies of PA Pellets.

[0080] Suspensions of 10.sup.6 cfu/ml S. aureus, A. brasiliensis and C. albicans were prepared. Each of the suspensions were then used to inoculate TSA and SDA agar by dipping a cotton swab in the test suspension and rubbing the swab against the agar plates. After the suspension treatment, PA pellets were transferred on the plates and the plates incubated. Clearing zones were not observed after 2 and 4 days around the pellets. FIG. 2 shows the PA pellets after 4 days incubation. Clearly, PA pellets did not have any biocidal activity against these microorganisms.

Example 6: Biocidal Activity of Extruded Strands of PA-I Against Natural Strain or Methicillin-Resistant Strain (MRSA) S. aureus

[0081] Suspensions of a natural strain or a Methicillin-resistant strain of Staphylococcus aureus were inoculated on agar plates. After treating the plates, extruded strands of PA-I blends with increasing iodine content (samples 17, 18, 19, 20, 22 and 26 of Example 2) were placed on the plates and incubated. All samples were found to be biocidal, with the PA-I samples containing higher levels of iodine loading showing larger clearing zones.