Method for preparing modified thermoplastics having germ-repellent properties and a product thereof, and a composition for preparing the modified thermoplastics

Abstract

This disclosure discloses a preparing method of transforming commercial base thermoplastics into germ-repellent resins or functional masterbatch through plasma and (melt)mixing assisted grafting process. The resins or masterbatch concentrate composition enable a number of product reforming processes, including but not limited to thermoforming, profile extrusion, injection molding, blow molding, blow filming, film casting, and spinning into articles of different shapes and geometries or overmolding on plastic substrates that can resist surface adsorption of microbes after solidification.

Claims

1. A method for preparing modified thermoplastics having a germ-repellent property, comprising: (a) providing base thermoplastics; (b) treating the base thermoplastic with plasma to obtain treated thermoplastics; (c) directly melt-extruding the treated thermoplastics with a chemical modifier with/or without additives to form a masterbatch of modified thermoplastics.

2. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein said base thermoplastics is selected from a group consisting of homopolymers, copolymers and blends of polyolefins, cyclic polyolefins, acrylics, acetates, styrenics, polyesters, polyimides, polyaryletherketones, polycarbonates, polyurethanes and thermoplastic elastomers.

3. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein said base thermoplastics is selected from a group consisting of poly(methyl methacrylate) (PMMA), polystyrene (PS), polyethylene terephthalate (PET), polycarbonate (PC), polymethylpentene (PMP), polysulfone, polyamide (PA), polyvinyl chloride (PVC), styrene acrylonitrile (SAN), styrene-methacrylate based copolymer, polypropylene based copolymer, acrylonitrile butadiene styrene (ABS), polyimide (PI) cellulosic resins, methyl methacrylate butadiene styrene (MBS), thermoplastic polyurethane (TPU), styrene ethylene butylene styrene block thermoplastic elastomer (SEBS), polyolefin elastomers (POE), thermoplastic polyester elastomers (TPEE), and thermoplastic vulcanizates (TPV).

4. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein a form of said thermoplastics is selected from a group consisting of powder, granule, flake and filament.

5. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein in step (b) and step (d), said plasma includes atmosphere plasma or vacuum plasma; and/or said plasma is formed from a gas selected from a group consisting of oxygen, argon, nitrogen, carbon dioxide and combinations thereof; and/or a duration of plasma treatment ranges from 10 s to 600 s, and/or power of plasma treatment ranges from 10 W to 1000 W.

6. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein in step (c), said chemical modifier is selected from a group consisting of one or more of linear and/or multi-armed structures of non-ionic surfactants.

7. The method for preparing modified thermoplastics having a germ-repellent property according to claim 6, wherein said non-ionic surfactants are one or more selected from a group consisting of fatty alcohol polyoxyalkylene ethers, polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan/sorbitol fatty acid esters, polyether glycols and their derivatives.

8. The method for preparing modified thermoplastics having a germ-repellent property according to claim 7, wherein said non-ionic surfactants, each having a polyoxyethylene moiety, are one or more selected from a group consisting of polyoxyethylene sorbitol hexaoleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene hydrogenated castor oil and polyoxyethylene cetyl/stearyl ether, and their derivatives; or said non-ionic surfactants are one or more selected from a group consisting of polyoxyethylene acrylate, polyoxyethylene methacrylate, and polyoxyethylene vinyl ethers; or said non-ionic surfactants, each having a polyoxypropylene moiety, are one or more selected from a group consisting of polyoxypropylene glycol, polyoxypropylene amine and polyoxypropylene acrylate, polyoxypropylene methacrylate, polyoxypropylene glycerol ether and their derivatives.

9. The method for preparing modified thermoplastics having a germ-repellent property according to claim 8, wherein the polyoxyethylene moiety or polyoxypropylene moiety has a molecular weight ranging from 132 Da to 4400 Da.

10. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein in step (c), said chemical modifier is in standalone form or diluted form.

11. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein in step (c), the masterbatch of modified thermoplastics comprises treated thermoplastics at 70-99 wt %, chemical modifiers at 0.5-29 wt %, and other additives at 0.01-1 wt %.

12. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, further comprising (d) applying post-treatment with plasma to the masterbatch of modified thermoplastics.

13. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein in step (c), said melt-extruding is either performed via a twin-screw extruder, a Banbury mixer or other heat-assisted blend process and subsequently pelletized into a granule form.

14. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein in step (c), additives are added to be blended with the treated thermoplastics and chemical modifiers, said additives being selected from a group consisting of an antioxidant, a brightener, a nucleator and an anti-transesterification.

15. The method for preparing modified thermoplastics having a germ-repellent property according to claim 1, wherein said step (d) further comprises rinsing the composition after said post-treatment.

16. The method for preparing modified thermoplastics having a germ-repellent property according to claim 15, wherein said rinsing is performed by employing water, ethanol, centrifugation and compressed air to remove unlinked surface modifiers.

17. A method for preparing a product having a germ-repellent property, comprising: (e) providing base thermoplastics; (f) providing the masterbatch of modified thermoplastics made according to claim 1; (g) blending the base thermoplastic with the masterbatch of modified thermoplastics to form a mixture; (h) molding said mixture into an article with a desired shape and dimension.

18. The method for preparing a product having a germ-repellent property according to claim 17, wherein said molding is selected from profile extrusion, injection molding, blow molding, blow filming, film casting, spinning and overmolding on a plastic substrate.

19. The method for preparing a product having a germ-repellent property according to claim 17, wherein step(h) is performed with a molding temperature from 170° C. to 260° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a principle schematic diagram of a method of modifying base thermoplastics according to the present disclosure.

(2) FIG. 2 is a work flow diagram of modifying base thermoplastics using a one-step method and a two-step method provided by the present disclosure.

(3) FIG. 3 is a flow diagram of subjecting a sample to a microbial adsorbing test, wherein this flow is based on the revised ISO22196 standard.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(4) References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

(5) Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a concentration range of “about 0.1% to about 5%” should be interpreted to include not only the explicitly recited concentration of about 0.1 wt. % to about 5 wt. %, but also the individual concentrations (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, and 3.3% to 4.4%) within the indicated range.

(6) As described herein, the term “a” or “an” is used to include one or more than one and the term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. In addition, it is to be understood that the phraseology or terminology employed herein, without being otherwise defined, is for the purpose of description only and not of limitation. Furthermore, all publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

(7) In the methods of manufacturing described herein, the steps can be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited. Recitation in a claim to the effect that first a step is performed, and then several other steps are subsequently performed, shall be taken to mean that the first step is performed before any of the other steps, but the other steps can be performed in any suitable sequence, unless a sequence is further recited within the other steps. For example, claim elements that recite “Step A, Step B, Step C, Step D, and Step E” shall be construed to mean step A is carried out first, step E is carried out last, and steps B, C, and D can be carried out in any sequence between steps A and E, and that the sequence still falls within the literal scope of the claimed process. A given step or sub-set of steps can also be repeated.

(8) Furthermore, specified steps can be carried out concurrently unless explicit claim language recites that they be carried out separately. For example, a claimed step of doing X and a claimed step of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.

Definitions

(9) The singular forms “a,” “an” and “the” can include plural referents unless the context clearly dictates otherwise.

(10) The term “about” can allow for a degree of variability in a value or range, for example, within 10%, or within 5% of a stated value or of a stated limit of a range.

(11) The term “independently selected from” refers to referenced groups being the same, different, or a mixture thereof, unless the context clearly indicates otherwise. Thus, under this definition, the phrase “X1, X2, and X3 are independently selected from noble gases” would include the scenario where, for example, X1, X2, and X3 are all the same, where X1, X2, and X3 are all different, where X1 and X2 are the same but X3 is different, and other analogous permutations.

(12) The present disclosure is not to be limited in scope by any of the following descriptions. The following examples or embodiments are presented for exemplification only.

(13) Modification of base thermoplastics according to the present disclosure can be processed in either one-step or two-step method (FIG. 2). The base polymer is firstly activated by plasma prior to being blended and reacted with chemical modifiers and/or without auxiliary additives either before or during mixing and subsequent plasma post treatment to create functional polymer (one-step) or masterbatch (two-step). Representative examples of base thermoplastics include thermoplastic polyurethane (TPU) and thermoplastic vulcanizate (TPV), styrene ethylene butylene styrene block thermoplastic elastomer (SEBS), polypropylene, and polyolefin elastomers (POE). Plasma treatment can be either performed in vacuum plasma or atmosphere plasma with proper source and processing condition. Blending can be achieved on either in a mixer or melt processing such as single/twin-screw extrusion or a Banbury mixing operated with a proper processing temperature window. The extruder can be equipped with an underwater pelletizer to obtain solid standalone or a masterbatch concentrate resin prior to article reforming by injection molding, for example. The processing temperature ranges from 80° C. to 260° C. for base thermoplastics and other main components for modifying the same.

(14) One or more of linear and/or multi-armed structures of non-ionic surfactants is/are selected as the non-fouling modifiers. The non-ionic surfactants are chosen from one or more of fatty alcohol polyoxyalkylene ethers, polyoxyalkylene sorbitan/sorbitol fatty acid esters, polyether glycols and their derivatives. Polyoxyethylene sorbitol hexaoleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene lauryl ether and polyoxyethylene cetyl/stearyl ether, allyl PEG and polyoxyethylene (meth)acrylate are preferred non-fouling modifiers. Proper ratio and combination of functional modifiers is key to the anti-biofouling performance and retention of physical properties of base thermoplastic materials. Typical ratio is adjusted from 0.5 to 10% on a weight basis with respect to the total weight of the composition. In a specific embodiment, the the polyoxyethylene in PEG sorbitol hexaoleate has a molecular weight ranging from 132 to 4,400 Da.

(15) Other additives, such as anti-oxidant, optical brightener, color masterbatch, etc. are chosen to control the appearance and scent of the articles. The anti-oxidant is preferred to be selected from butylated hydroxytoluene, IRGANOX® 1010, IRGANOX® 1076, IRGANOX® 1098, IRGAFOS® 168 or IRGANOX® B 225 with a weight percentage to the total weight of the composition from 0.1 to lwt %. The brightener is preferred to be selected HOSTALUX® KS, HOSTALUX® KS 1, KEYFLUOR® WHITE OB, KEYFLUOR® WHITE OB-1, KEYFLUOR® WHITE RWP with a weight percentage to the total weight of the composition from 0.01 to 0.05 wt %.

(16) The protocol for germ repellent tests on the molded circular plate samples is herein described by the schematic diagram in FIG. 3. The protocol is based on ISO 22196 with modification. The starting inoculum concentration of E. coli (ATCC® 8739™) and S. aureus (ATCC® 6538P™) was about 8×10.sup.8 and 8×10.sup.7 cells/ml in 1/500 NB solution (1/500 NB refers to the 500× diluted Nutrient Broth with pH adjusted to 6.8-7.2) for challenging the sample surface. Result of the adsorption tests are illustrated in the following examples.

(17) The embodiments of the present disclosure can be better understood by reference to the following examples which are offered by way of illustration. The present disclosure is not limited to the examples given herein.

Example 1

(18) This example provides a method of modifying a segmented block copolymer TPU: treating TPU resin with vacuum argon plasma and directly extruding a compound of 96% treated TPU resin with 4% Polysorbate 80 on a weight basis with a processing temperature ranging from 190° C. to 210° C. to obtain functional resin directly. The modified formulation is re-pelletized as standalone resin and post treated with vacuum argon plasma (herein annotated as TPU-M) that can be fed into an injection molding machine (with processing temperature of 210° C.) to obtain plastic samples dictated by the mold tooling design.

(19) With an untreated TPU as a control, testing is carried out with respect to the hardness, density, mechanical performance, and microbial repellent property of the modified TPU-M. Characterization results are summarized in Table 1, wherein the microbial repellent property is directed to the E. coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria). Compared with the control (TPU), after being incubated for 24 hours, the residual bacterial counts on the TPU sample surface show a reduction of 99%, such that the TPU-M passes the antibacterial requirement in the revised ISO22196. Meanwhile, the hardness, density and mechanical property of the thermoplastic plastic before and after modification vary little. In other words, the hardness, density, and mechanical performance of the modified thermoplastic plastic are all well preserved.

(20) TABLE-US-00001 TABLE 1 Hardness Tensile % reduction % reduction (Shore Density Izod impact Elongation at strength of E. coli ofS. aureus Samples Hardness) (g/cm.sup.3) strength (KJ/m.sup.2) break (%) (MPa) adsorption(%) adsorption (%) TPU 71 1.08 NB 832 30.04 — — TPU-M 71 1.07 NB 860 29.10 99% 99%

Example 2

(21) TPV is a PP/EPDM vulcanized system. This example provides a method of modifying TPV: treating TPV resin with vacuum oxygen plasma and extruding a compound of treated 85% TPV resin with 15% polyoxyethylene allyl ether (molecular weight around 1000) on a weight basis with a processing temperature ranging from 190° C. to 200° C. to obtain a functional masterbatch concentrate (herein, annotated as TPV-M) after palletization. The masterbatch was dry blended at a ratio of 1:9 w/w with TPV, during which the atmosphere plasma is applied to the blending system, and subsequently fed into an injection molding machine (with processing temperature of 200° C.) to obtain plastic samples.

(22) With an untreated TPV as a control, testing is carried out with respect to the hardness, density, mechanical performance, and microbial repellent property of the modified TPV-M. Characterization results are summarized in Table 2, wherein the microbial repellency property is directed to the E. coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria). Compared with the control (TPV), after being incubated for 24 hours, the remnant bacteria counts on the TPV-M sample surface read a reduction of 99%, such that the TPV-M passes the antibacterial requirement in the revised ISO22196. Meanwhile, the hardness, density and mechanical property of the thermoplastic plastic before and after modification vary little. In other words, the hardness, density, and mechanical performance of the modified thermoplastic plastic are all well preserved.

(23) TABLE-US-00002 TABLE 2 Hardness Tensile % reduction % reduction (Shore Density Izod impact Elongation at strength of E. coli of S. aureus Samples Hardness) (g/cm.sup.3) strength (KJ/m.sup.2) break (%) (MPa) adsorption(%) adsorption (%) TPV 69 0.95 NB 470 6.50 — — TPV-M 68 0.93 NB 492 5.98 >99% >99%

Example 3

(24) This example provides a method of modifying SEBS (styrene ethylene butylene styrene block thermoplastic elastomer): treating SEBS resin with vacuum plasma with oxygen and argon as the gas source (flow ratio O.sup.2:Ar=3:1), then mixing 80% treated resins with 20% polyoxyethylene cetyl ether on a weight basis in a Banbury mixer with processing temperature ranging from 170° C. to 220° C. The mixture was then transferred to an extruder and sequentially pelletizer to form a functional masterbatch. The masterbatch was dry blended at a ratio of 1:9 w:w with SEBS in a rotary vacuum argon plasma and subsequently fed into an injection molding machine (with processing temperature of 200° C.) to obtain plastic samples.

(25) With the untreated SEBS as a control, testing is carried out with respect to the hardness, density, mechanical performance, and microbial repellent property of the modified SEBS-M. Characterization results are summarized in Table 3, wherein the microbial repellency property is directed to the E. coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria). Compared with the control, after being incubated for 24 hours, the remnant bacteria counts on the SEBS-M sample surface read a reduction of 99%, such that the SEBS-M passes the antibacterial requirement in the revised ISO22196. Meanwhile, the hardness, density and mechanical property of the thermoplastic plastic before and after modification vary little. In other words, the hardness, density, and mechanical performance of the modified thermoplastic plastic are all well preserved.

(26) TABLE-US-00003 TABLE 3 Hardness Tensile % reduction % reduction (Shore Density Izod impact Elongation at strength of E. coli ofS. aureus Samples Hardness) (g/cm.sup.3) strength (KJ/m.sup.2) break (%) (MPa) adsorption(%) adsorption (%) SEBS 46 0.88 NB 1052 7.02 NA NA SEBS-M 44 0.90 NB 1100 6.90 >99% >99%

Example 4

(27) This example provides a method of modifying polypropylene (PP): applying vacuum plasma treatment to PP resins with ambient air as the gas source, then mixing the 97.89% treated resin with 1% of poly(ethylene glycol) sorbitol hexaoleate, 1% polyoxyethylene allyl ether (Mw˜1000), 0.1% MILLAD® 3988 and 0.01% Keystone® OB-1 at 80° C. for 30 mins, and applying the vacuum air plasma to the mixture for post-treatment. The treated resins are rinsed by water and dried to form the functional pellets. The dried pellets are then directly subjected to injection molding (with processing temperature of 200° C.) to get molded samples.

(28) With the untreated PP as a control, testing is carried out with respect to the hardness, density, mechanical performance, and microbial repellent property of the modified PP-M. Specific characterization testing results are summarized in Table 4, wherein the microbial repellency property is directed to the Escherichia coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria). Compared with the control, after being incubated for 24 hours, the remnant bacteria counts on the PP-M sample surface read a reduction of 99%, such that the PP-M passes the antibacterial requirement in the revised ISO22196. Meanwhile, the hardness, density and mechanical property of the thermoplastic plastic before and after modification vary little. In other words, the hardness, density, and mechanical performance of the modified thermoplastic plastic are all well preserved.

(29) TABLE-US-00004 TABLE 4 Hardness Tensile % reduction % reduction (Shore Density Izod impact Elongation at strength of E. coli ofS. aureus Samples Hardness) (g/cm.sup.3) strength (KJ/m.sup.2) break (%) (MPa) adsorption(%) adsorption (%) PP 68 0.90 3.1 220 34.20 NA NA PP-M 68 0.92 4.2 260 32.68 >99% >99%

Example 5

(30) This example provides a method of modifying polyolefin elastomers POE: treating POE resins with vacuum argon plasma, and extruding a compound of 90% treated TPU resin with 10% polyoxyethylene cetyl ether on a weight basis with a processing temperature ranging from 190° C. to 210° C. to obtain functional masterbatch. The masterbatch is dry blended at a ratio of 1:9 w:w with POE in a vacuum air plasma with rotary drum, and subsequently fed into an injection molding machine (with processing temperature of 200° C.) to obtain plastic samples.

(31) With the untreated POE as a control, testing is carried out with respect to the hardness, density, mechanical performance, and microbial repellent property of the modified POE-M. Characterization results are summarized in Table 5, wherein the microbial repellency property is directed to the Escherichia coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria). Compared with the control, after being incubated for 24 hours, the remnant bacteria counts on the POE-M sample surface read a reduction of 99%, such that the POE-M passes the antibacterial requirement in the revised ISO22196. Meanwhile, the hardness, density and mechanical property of the thermoplastic plastic before and after modification vary little. In other words, the hardness, density, and mechanical performance of the modified thermoplastic plastic are all well preserved.

(32) TABLE-US-00005 TABLE 5 Hardness Tensile % reduction % reduction (Shore Density Izod impact Elongation at strength of E. coli ofS. aureus Samples Hardness) (g/cm.sup.3) strength (KJ/m.sup.2) break (%) (MPa) adsorption(%) adsorption (%) POE 29 0.87 NB 852 15.2 NA NA POE-M 28 0.87 NB 900 14.4 >99% >99%

Example 6

(33) This example provides a method of modifying thermoplastic polyester elastomers (TPEE): treating TPEE resin/powder with vacuum argon plasma; extruding a compound of 95 wt % treated TPEE resin, 4.4 wt % of polysorbate 80, 0.3 wt % of sodium dihydrogen phosphate and 0.3 wt % of IRGANOX® 1010 at 190˜230° C. to obtain modified resin TPEE-M; then, adding the modified resin into an injection molding machine (processing temperature 230° C.) to obtain a plastic sample.

(34) With the untreated TPEE as a control, testing is carried out with respect to the hardness, density, mechanical performance, and microbial repellent property of the modified TPEE-M. Characterization results are summarized in Table 6, wherein the microbial repellency property is directed to the Escherichia coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria). Compared with the control, after being incubated for 24 hours, the remnant bacteria counts on the TPEE-M sample surface read a reduction of 99%, such that the TPEE-M passes the antibacterial requirement in the revised ISO22196. Meanwhile, the hardness, density and mechanical property of the thermoplastic plastic before and after modification vary little. In other words, the hardness, density, and mechanical performance of the modified thermoplastic plastic are all well preserved.

(35) TABLE-US-00006 TABLE 6 Hardness Tensile % reduction % reduction (Shore Density Izod impact Elongation at strength of E. coli ofS. aureus Samples Hardness) (g/cm.sup.3) strength (KJ/m.sup.2) break (%) (MPa) adsorption(%) adsorption (%) TPEE 55 1.19 NB 350 15.0 NA NA TPEE-M 54 1.17 NB 380 14.8 >99% >99%

(36) The examples above are only for clearly illustrating the present disclosure, not for limiting the embodiments of the present disclosure. To a person of normal skill in the art, variations or changes of other different forms may also be made based on the description above. It is unnecessary to exhaust all embodiments herein. Any modifications, equivalent substitutions and improvements within the spirit and principle of the present disclosure should be included within the protection scope as limited in the claims of the present disclosure.