WO2022135501A1

WO2022135501A1 - Mechanically-strong, biocompatible, food-contact safe and germ-repellent engineering plastics

Info

Publication number: WO2022135501A1
Application number: PCT/CN2021/140642
Authority: WO
Inventors: Wenjun MENG; Shengchang TANG; Kevin Tsai; Deryck Hin Yeung Li
Original assignee: Nano And Advanced Materials Institute Limited
Priority date: 2020-12-23
Filing date: 2021-12-22
Publication date: 2022-06-30

Abstract

A mechanically-strong, biocompatible, food-contact safe and germ-repellent engineering plastic and a method for preparing this engineering plastic: this engineering plastic comprising one or more base engineering plastic resins and one or more germ-repellent modifiers incorporated with one or more carrier agents, where the plastic optionally includes one or more additives of compatibilizers, reinforcing fillers, heat stabilizers, and/or antioxidants. The plastic before and after the introduction of the germ-repellent modifier (s) with the carrier agent (s) has no significant difference in mechanical properties of less than approximately 20%, biocompatibility of no observed in-vitro cytotoxicity, and at least one-year shelf life at room temperature without any alteration of germ repellent efficacy, mechanical properties and biocompatibility.

Description

MECHANICALLY-STRONG, BIOCOMPATIBLE, FOOD-CONTACT SAFE AND GERM-REPELLENT ENGINEERING PLASTICS

Inventors: Wenjun MENG; Shengchang TANG; Kevin TSAI; Deryck Hin Yeung LI

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from a U.S. provisional patent application number 63/129,617 filed December 23 ^rd, 2020, and the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to the field of engineering plastic for biocompatible and food-contact safe articles. In particular, it relates to the engineering plastic which is mechanically-strong and germ-repellent for biocompatible and food-contact safe articles.

BACKGROUND

It is a common problem in a biocompatible and food-contact safe plastic that the mechanical properties are not comparable to those of other plastics because it has to comply with certain standards required by the corresponding authorities. The standards for these kinds of plastics are usually more stringent than those for other plastics, especially in terms of toxicity or likelihood that the release of the constituents from the article to the object in contact with the article will affect the quality of the object or have adverse effect on the health of the consumer of the object. These articles include food containers, machinery for food processing, packaging for food, kitchenware and tableware, medical device, etc.

To meet those standards while introducing some germ-repellent modifiers to the plastics, some of these biocompatible and food-contact safe plastics need to sacrifice their mechanical properties, e.g., tensile strength, such that they are usually more brittle than some other plastics.

A conventional way to impart germ repellency onto a plastic is by melt blending with a hydrophilic agent, but doing so would severely affect the mechanical properties of the plastic itself and it is hard to select a matching hydrophilic agent to the plastic of interest due to other external factors such as manufacturing limitations, e.g., an unmatched hydrophilic agent can lead to slipping at the screw surface during the manufacturing. For example, in US 10,525,614, a chemical linker is introduced into the polymer backbone of the plastic resin to link the anti-fouling agent. In a later application, i.e., US 10,548,314, an alternative method to extrude a dry blend of base plastic and anti-fouling agent in a single step is provided, but still involving a chemical linker. A subsequent application, under the Patent Application Publication No. US 2020/0107545, further provides introducing an intermediate plastic including a polystyrene and maleic anhydride repeating units to be grafted on the base plastic to impart the germ repellency in the presence of the anti-fouling agents.

In US 10,836,890, a method for modifying a transparent grade base thermoplastic to gain anti-biofouling property with mechanical reinforcement of an article formed from that thermoplastic is provided, where the transparent thermoplastic is either directly blended with at least a non-ionic surfactant and with or without other additives, or form a masterbatch concentrate having the non-ionic surfactant and/or other additives before melt processing the thermoplastic with the masterbatch. A subsequent application, under the Patent Application Publication No. 2020/115534, further provides a composition for forming a functional polymer or a masterbatch concentrate from the transparent thermoplastics.

Alternatively, some prior arts teach using some non-chemical methods to modify the base plastic. For example, in US 10,030,108, a linker-free/initiator-free method is used by plasma treating thermoplastic resin to introduce a functional group to the resin before adding any bacteria repelling agent. Another patent by the same applicant, under the Patent No. 11,136,439, also provides a method for preparing a modified thermoplastics having the germ repellency including treating the thermoplastics with plasma before melt extruding with a chemical modifier, and also a method of blending base thermoplastics with a masterbatch of the modified thermoplastics treated by plasma before molding into an article. However, this kind of non-chemical modification methods may introduce some other unwanted modifications to the plastic during the treatment before engaging the bacterial repelling agent, leading to some uncertain/unexpected modifications which may impose some potential negative effects on the germ repellency of the modified plastic.

A germ-repellent elastomer is also provided in a U.S. Patent Application Publication No. 2020/017658, where a careful selection of germ-repellent agents which are polyethoxylated non-ionic surfactants is required in order to impart germ repellency to the corresponding modified elastomer selected from thermoplastic PU, SEBS, LSR or HCR.

Therefore, selecting a matching biocompatible and food-contact safe and germ-repellent modifier with one or more constituents to stabilize or even enhance the mechanical properties of the engineering plastic after the surface modification is of utmost importance.

SUMMARY OF THE INVENTION

In view of the foregoing problem, a first aspect of the present disclosure relates to a mechanically-strong, biocompatible, food-contact safe, and germ-repellent engineering plastic including a base engineering plastic resin modified by one or more germ-repellent modifiers incorporated with one or more carrier agents to impart germ repellency onto the engineering plastic. The introduction of the one or more germ-repellent modifiers with the one or more carrier agents to the engineering plastic does not significantly change the mechanical properties, e.g., less than 20%change in the mechanical strength, heat deflection temperature, and biocompatibility, e.g., no observed in-vitro cytotoxicity, which complies with ISO 10993-5. In the presence of the germ-repellent modifiers with the carrier agents in the engineering plastic, biofilm formation is substantially avoided. The germ-repellent engineering plastics of the present invention with substantially the same germ repellency and other mechanical and biocompatible properties have a shelf-life of about 1 year or more at room temperature.

Accordingly, a first aspect of the present invention provides a mechanically-strong, biocompatible, food-contact safe and germ-repellent engineering plastic comprising:

one or more base engineering plastic resins selected from polyamides, polyesters, polycarbonates, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polyphenylene ether, polyphenylene sulfide, acrylonitrile butadiene styrene, polyoxymethylene, methyl methacrylate butadiene styrene, polyetherketone, and/or, polyetheretherketone, or any polymer alloys having no less than 50 wt. %of the one or more base engineering plastic resins;

one or more germ-repellent modifiers selected from poly (ethylene glycol) , poloxamer, polyethylene glycol sorbitan monolaurate, poly (ethylene glycol) sorbitol hexaoleate, polypropylene glycol glycerol ether, ceteareth, polysorbate, alkyl polyglycol ether C16-C20, and/or any combination thereof, at approximately 1 to 20 wt. %, and incorporated with one or more carrier agents comprising stearyl palmitate, stearyl behenate, stearyl stearate, palmityl palmitate, myristyl palmitate, and/or myristyl myristate; and

the engineering plastic optionally further comprising one or more additives including compatibilizers, reinforcing fillers, heat stabilizers, and/or antioxidants; and each of the additives being at approximately 0.5 to 20 wt. %,

the engineering plastic before and after introduction of the one or more germ-repellent modifiers with the one or more carrier agents having no significant difference in mechanical properties including tensile strength and impact strength as well as heat deflection temperature (HDT) of less than approximately 20%, biocompatibility including no observed in-vitro cytotoxicity, and at least one-year shelf life at room temperature without any alteration of germ repellent efficacy, mechanical properties and biocompatibility.

In one embodiment, the compatibilizers comprise maleic anhydride and glycidyl (meth) acrylate grafted polymers at approximately 1 to 20 wt. %.

In another embodiment, the reinforcing fillers comprise silica nanoparticles untreated or treated with the one or more germ-repellent modifiers at about 0.1 to 5 wt. %.

In another embodiment, the antioxidants comprise one or both of sterically hindered phenols and phosphites.

In yet another embodiment, the heat stabilizer comprises organophophites, phenolic compounds and metallic stearates.

In a further embodiment, the present engineering plastic further comprises a slip agent tolerant of high temperature for imparting hydrophilicity to the surface of the base engineering plastic resins and/or facilitating dispersion of the germ-repellent modifiers and other additives across polymer matrix of the base engineering plastic resins during a high temperature extrusion thereof.

In an embodiment, the present engineering plastic further comprises an antistatic agent for lowering friction on the surface of the base engineering plastic resins.

In another embodiment, the present engineering plastic further comprises one or more specialty additives, where one of the specialty additives is selected from stearyl stearate, stearyl behenate, behenyl behenate, ethylene glycol distearate, ethyl behenate, behenyl acetate, palmityl myristate, or palmityl palmate.

A second aspect of the present invention relates to a method for preparing a mechanically-strong, biocompatible, food-contact safe and germ-repellent engineering plastic comprising:

providing a masterbatch by comingling one or more germ-repellent modifiers with the one or more base engineering plastic resins, in an extrusion process, and further comingling the masterbatch with the one or more base engineering plastic resins, wherein the masterbatch is optionally provided by incorporating the one or more germ-repellent modifiers with one or more additives before comingling with the one or more base engineering plastic resins; or

comingling the one or more germ-repellent modifiers with the one or more base engineering plastic resins directly, wherein the one or more additives are optionally incorporated into the one or more germ-repellent modifiers and comingled with the one or more base engineering plastic resins altogether; and

processing the obtained resins.

In an embodiment, the one or more germ-repellent modifiers are incorporated with one or more carrier agents comprising stearyl palmitate, stearyl behenate, stearyl stearate, palmityl palmitate, myristyl palmitate, and/or myristyl myristate during said providing the masterbatch, said direct comingling the one or more germ-repellent modifiers with the one or more base engineering plastic resins, or said processing the obtained resins.

In an embodiment, the one or more base engineering plastic resins are selected from polyamides, polyesters, polycarbonates, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polyphenylene ether, polyphenylene sulfide, acrylonitrile butadiene styrene, polyoxymethylene, methyl methacrylate butadiene styrene, polyetherketone, and/or, polyetheretherketone, or any polymer alloys that contain no less than 50 wt. %of the one or more engineering plastics.

In an embodiment, the extrusion is carried out in a twin-screw extruder.

In an embodiment, the one or more germ-repellent modifiers are selected from poly (ethylene glycol) , poloxamer, polyethylene glycol sorbitan monolaurate, poly (ethylene glycol) sorbitol hexaoleate, polypropylene glycol glycerol ether, ceteareth, polysorbate, alkyl polyglycol ether C16-C20, and/or any combination thereof, at approximately 1 to 20 wt. %.

In an embodiment, the one or more additives include compatibilizers, reinforcing fillers, heat stabilizers, and/or antioxidants, and each of the additives is at approximately 0.5 to 20 wt. %.

In an embodiment, the compatibilizers comprise maleic anhydride and glycidyl (meth) acrylate grafted polymers at approximately 1 to 20 wt. %.

In an embodiment, the reinforcing fillers comprise silica nanoparticles untreated or treated with the one or more germ-repellent modifiers at about 0.1 to 5 wt. %.

In an embodiment, the antioxidants comprise one or both of sterically hindered phenols and phosphites.

In an embodiment, the heat stabilizers comprise organophophites, phenolic compounds and metallic stearates.

In an embodiment, the one or more additives further comprise a slip agent tolerant of high temperature for imparting hydrophilicity to the surface of the base engineering plastic resins and/or facilitating dispersion of the germ-repellent modifiers and other additives across the polymer matrix of the base engineering plastic resins during a high temperature extrusion thereof.

In an embodiment, the one or more additives further comprise an antistatic agent for lowering friction on the surface of the base engineering plastic resins.

In an embodiment, the one or more additives further comprise one or more specialty additives, where one of the specialty additives is selected from stearyl stearate, stearyl behenate, behenyl behenate, ethylene glycol distearate, ethyl behenate, behenyl acetate, palmityl myristate, or palmityl palmate.

In an embodiment, said processing the obtained resins includes injection molding.

There is also provided a mechanically-strong, germ-repellent, biocompatible and food-contact safe engineering plastic prepared by the method of the second aspect of the present invention.

There is also provided a mechanically-strong, germ-repellent, biocompatible and food-contact safe article comprising the plastic of the first aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus not limitative of the disclosure, wherein:

FIG. 1 is a schematic diagram depicting an embodiment of the present invention involving the use of a processing aid to assist the orientation of hydrophilic moiety of the hydrophilic additives to the surface of the base plastic at the molten state followed by cooling stage after extrusion.

FIG. 2 illustrates schematically a typical example of a twin-screw extrusion process of preparing a germ-repellent polymer structure from base resin with germ-repellent modifiers according to an embodiment of the present invention.

FIG. 3 illustrates a process workflow of how to conduct a germ repellent efficiency test for plastic samples.

Definitions

The terms “a” or “an” are 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, and not 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.

In the methods of preparation 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. 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.

DETAILED DESCRIPTION

The present invention will be described in detail through the following embodiments /examples with appending drawings. It should be understood that the specific embodiments are provided for an illustrative purpose only, and should not be interpreted in a limiting manner.

EXAMPLES

Example 1

400g of polyethylene terephthalate (PET) base plastic is comingled with 20g poly (ethylene glycol) (PEG) antifouling compound and 16g maleic anhydride grafted polypropylene intermediate plastic. The antifouling compound, intermediate plastic, and the base plastic are comingled in a twin-screw extruder with temperatures ranging from 180℃ to 270℃.

The comingled plastic is then injection molded to form a germ-repellent plastic (A) .

The weight percentage in the final plastic of (A) is: 91.74%PET base plastic, 4.59%PEG antifouling compound, and 3.67%maleic anhydride grafted polypropylene intermediate plastic.

A comparative plastic (Control A) made of PET is also prepared in an identical manner, except that the comparative sample did not contain any antifouling compound. The comparative plastic (Control A) is used as an unmodified control for comparison with germ-repellent plastic (A) .

A swab test to evaluate the germ repellent efficacy is conducted on both samples by the following protocol. The germ repellent efficacy or germ repellency of a plastic can be determined by the amount of bacterial adhesion on samples fabricated from germ repellent base plastic blend compared to the base plastic without any germ repellent additives. Plastic samples are prepared in specific dimensions and first incubated for a fixed period of time against inoculums containing a known cell number of bacteria. The inoculum preparation and the bacterial incubation procedures follow the experimental protocol of industrial standards JIS Z 2801 or ISO 22196, whereby the test and the control work pieces are incubated at 35℃ ± 1℃ and relative humidity of not less than 90%for 24h ± 1h. One Gram-positive bacteria strain (e.g. Staphylococcus aureus) and one Gram-negative bacteria strain (e.g. Escherichia coli) are used as representative test microbes as outlined in the said standard. After incubation, the sample will undergo a bacteria clearance step by draining off the test inoculums from the samples, rinsing with 0.9%saline solution to completely remove the inoculums. The adherent bacteria from the sample surfaces are collected by swab applicator and the collected bacteria will be representative of the degree to which the plastic sample is susceptible to colonization and biofilm growth. After serial dilution, the collected bacteria will then be cultured on agar plates in standard 90mm diameter Petri dishes and are quantified in terms of colony forming units per volume of broth per specimen. FIG. 3 illustrates the process workflow of an in-house germ repellent efficiency test.

In this example, six 5cm x 5cm replicates of each sample are prepared. Bacterial suspension solutions for both S. aureus and E. coli are prepared. 1mL of each bacterial suspension is inoculated on the surface of three replicates of each plastic sample. The inoculated samples are incubated at 35℃ for 24 hours for both S. aureus and E. coli. Afterwards, the samples are retrieved and washed with 8mL saline. Samples inoculated with S. aureus are washed three times; samples inoculated with E. coli, one time. A rayon-tipped swab is used to collect remaining surface bacteria and transfer them to 1mL of Letheen neutralizing buffer. The contents of the buffer are plated on agar plates and incubated at 35℃ for 24 hours. Colonies formed on the agar plate after incubation are then counted.

Table 1: E. coli bacterial counts on sample replicates of germ-repellent plastic (A) and comparative plastic (Control A)

As can be seen in Table 1, with E. coli, the germ-repellent plastic (A) of the present invention provides a >99.99%reduction in the swab test as compared to the comparative plastic (Control A) .

Table 2: S. aureus bacterial counts on sample replicates of germ-repellent plastic (A) and comparative plastic (Control A)

As can be seen in Table 2, with S. aureus, the germ-repellent plastic (A) of the present invention provides a >99.99%reduction in the swab test as compared to the comparative plastic (Control A) .

Example 2

400g of polyethylene terephthalate (PET) base plastic is comingled with 20g poly (ethylene glycol) (PEG) antifouling compound and 1.6g maleic anhydride compatibilizer. The antifouling compound, intermediate plastic, and the base plastic are comingled in a twin-screw extruder with temperatures ranging from 180℃ to 265℃.

The comingled plastic is then injection molded to form a germ-repellent plastic (B) .

The weight percentage in the final plastic of (B) is: 94.88%PET base plastic, 4.74%PEG antifouling compound, and 0.38%maleic anhydride intermediate plastic.

A comparative plastic (Control B) made of PET is also prepared in an identical manner, except that the comparative sample did not contain any antifouling compound. The comparative plastic (Control B) is used as an unmodified control for comparison with germ-repellent plastic (B) .

A swab test to evaluate the germ repellent efficacy is conducted on both samples by the following protocol. Six 5cm x 5cm replicates of each sample are prepared. Bacterial suspension solutions for both S. aureus and E. coli are prepared. 1mL of each bacterial suspension is inoculated on the surface of three replicates of each plastic sample. The inoculated samples are incubated at 35℃ for 24 hours for both S. aureus and E. coli. Afterwards, the samples are retrieved and washed with 8mL saline. Samples inoculated with S. aureus are washed three times; samples inoculated with E. coli, one time. A rayon-tipped swab is used to collect remaining surface bacteria and transfer them to 1mL of Letheen neutralizing buffer. The contents of the buffer are plated on agar plates and incubated at 35℃ for 24 hours. Colonies formed on the agar plate after incubation are then counted.

Table 3: E. coli bacterial counts on sample replicates of germ-repellent plastic (B) and comparative plastic (Control B)

As can be seen in Table 3, with E. coli, the germ-repellent plastic (B) of the present invention provides a 99.6%reduction in the swab test as compared to the comparative plastic (Control B) .

Table 4: S. aureus bacterial counts on sample replicates of germ-repellent plastic (B) and comparative plastic (Control B)

As can be seen in Table 4, with S. aureus, the germ-repellent plastic (B) of the present invention provides a >99.99%reduction in the swab test as compared to the comparative plastic (Control B) .

Example 3

400g of polycarbonate (PC) base plastic is comingled with 20g poly (ethylene glycol) (PEG) antifouling compound and 16g maleic anhydride grafted polypropylene intermediate plastic to form a masterbatch. The antifouling compound and the base plastic are comingled in a twin-screw extruder with temperatures ranging from 220℃ to 280℃.

The masterbatch is then combined with PC base plastic. The weight ratio of base plastic: masterbatch is 75: 25. The two are injection molded together to form a germ-repellent plastic (C) .

The weight percentage in the final plastic of (C) is: 97.94%PC base plastic, 1.15%PEG antifouling compound, and 0.82%polypropylene, and 0.09%maleic anhydride intermediate plastic.

A comparative plastic (Control C) made of PC is also prepared in an identical manner, except that the comparative sample did not contain any antifouling compound. The comparative plastic (Control C) is used as an unmodified control for comparison with germ-repellent plastic (C) .

A swab test to evaluate the germ repellent efficacy is conducted on both samples by the following protocol. Three 5cm x 5cm replicates of each sample are prepared. Bacterial suspension solution for S. aureus is prepared. 1mL of the bacterial suspension is inoculated on the surface of three replicates of each plastic sample. The inoculated samples are incubated at 35℃ for 24 hours. Afterwards, the samples are retrieved and washed with 8mL saline three times. A rayon-tipped swab is used to collect remaining surface bacteria and transfer them to 1mL of Letheen neutralizing buffer. The contents of the buffer are plated on agar plates and incubated at 35℃ for 24 hours. Colonies formed on the agar plate after incubation are then counted.

Table 5: S. aureus bacterial counts on sample replicates of germ-repellent plastic (C) and comparative plastic (Control C)

As can be seen in Table 5, with S. aureus, the germ-repellent plastic (C) of the present invention provides a 96.7%reduction in the swab test as compared to the comparative plastic (Control C) .

Example 4

400g of polycarbonate (PC) base plastic is comingled with 2.8g Incromax 300 antifouling compound. The antifouling compound and the base plastic are comingled in a Babyplast injection molding machine with temperatures ranging from 305℃ to 310℃ to form a germ-repellent plastic (D) .

The weight percentage in the final plastic of (D) is: 99.30%PC base plastic and 0.70%Incromax 300 antifouling compound.

A comparative plastic (Control D) made of PC is also prepared in an identical manner, except that the comparative sample did not contain any antifouling compound. The comparative plastic (Control D) is used as an unmodified control for comparison with germ-repellent plastic (D) .

A swab test to evaluate the germ repellent efficacy is conducted on both samples by the following protocol. Three 5cm x 5cm replicates of each sample are prepared. Bacterial suspension solution for E. coli is prepared. 1mL of the bacterial suspension is inoculated on the surface of three replicates of each plastic sample. The inoculated samples are incubated at 35℃ for 24 hours. Afterwards, the samples are retrieved and washed with 8mL saline one time. A rayon-tipped swab is used to collect remaining surface bacteria and transfer them to 1mL of Letheen neutralizing buffer. The contents of the buffer are plated on agar plates and incubated at 35℃ for 24 hours. Colonies formed on the agar plate after incubation are then counted.

Table 6: E. coli bacterial counts on sample replicates of germ-repellent plastic (D) and comparative plastic (Control D)

As can be seen in Table 6, with E. coli, the germ-repellent plastic (D) of the present invention provides a 93.1%reduction in the swab test as compared to the comparative plastic (Control D) .

Example 5

400g of polybutylene terephthalate (PBT) base plastic is comingled with 32g polyoxyl 20 cetostearyl ether (ceteareth-20) antifouling compound, 32g poly (ethylene glycol) sorbitol hexaoleate (PEG SHO) antifouling compound, 16g Incromax 100 friction reduction additive, and 4g hexamethyldisilazane-treated fumed silica mechanical reinforcer to form a masterbatch. The antifouling compounds, friction reductive additive, mechanical reinforcer and the base plastic are comingled in a twin-screw extruder with temperatures ranging from 220℃ to 260℃.

The masterbatch is then combined with PBT base plastic. The weight ratio of base plastic: masterbatch is 80: 20. The two are injection molded together to form a germ-repellent plastic (E) .

The weight percentage in the final plastic of (E) is: 96.53%PBT base plastic, 1.32%ceteareth antifouling compound, 1.32%PEG SHO antifouling compound, 0.66%Incromax 100 friction reduction additive, and 0.17%hexamethyldisilazane-treated fumed silica mechanical reinforcer.

A comparative plastic (Control E) made of PBT is also prepared in an identical manner, except that the comparative sample did not contain any antifouling compound or processing aid. The comparative plastic (Control E) is used as an unmodified control for comparison with germ-repellent plastic (E) .

A swab test to evaluate the germ repellent efficacy is conducted on both samples by the following protocol. Six 5cm x 5cm replicates of each sample are prepared. Bacterial suspension solutions for both S. aureus and E. coli are prepared. 1mL of each bacterial suspension is inoculated on the surface of three replicates of each plastic sample. The inoculated samples are incubated at 35℃ for 24 hours. Afterwards, the samples are retrieved and washed with 8mL saline one time. A rayon-tipped swab is used to collect remaining surface bacteria and transfer them to 1mL of Letheen neutralizing buffer. The contents of the buffer are plated on agar plates and incubated at 35℃ for 24 hours. Colonies formed on the agar plate after incubation are then counted.

Table 7: E. coli bacterial counts on sample replicates of germ-repellent plastic (E) and comparative plastic (Control E)

As can be seen in Table 7, with E. coli, the germ-repellent plastic (E) of the present invention provides a 98.4%reduction in the swab test as compared to the comparative plastic (Control E) .

Table 8: S. aureus bacterial counts on sample replicates of germ-repellent plastic (E) and comparative plastic (Control E)

As can be seen in Table 8, with S. aureus, the germ-repellent plastic (E) of the present invention provides a 95.9%reduction in the swab test as compared to the comparative plastic (Control E) .

Example 6

400g of polybutylene terephthalate (PBT) base plastic is comingled with 20g poly (ethylene glycol) (PEG) antifouling compound and 16g maleic anhydride grafted polypropylene intermediate plastic. The antifouling compound, intermediate plastic, and the base plastic are comingled in a twin-screw extruder with temperatures ranging from 220℃ to 260℃.

The comingled plastic is then injection molded to form a germ-repellent plastic (F) .

The weight percentage in the final plastic of (F) is: 91.74%PBT base plastic, 4.59%PEG antifouling compound, 3.30%polypropylene, and 0.37%maleic anhydride intermediate plastic.

A comparative plastic (Control F) made of PBT is also prepared in an identical manner, except that the comparative sample did not contain any antifouling compound. The comparative plastic (Control F) is used as an unmodified control for comparison with germ-repellent plastic (F) .

Table 9: E. coli bacterial counts on sample replicates of germ-repellent plastic (F) and comparative plastic (Control F)

As can be seen in Table 9, with E. coli, the germ-repellent plastic (F) of the present invention provides a 78.3%reduction in the swab test as compared to the comparative plastic (Control F) .

Table 10: S. aureus bacterial counts on sample replicates of germ-repellent plastic (F) and comparative plastic (Control F)

As can be seen in Table 10, with S. aureus, the germ-repellent plastic (F) of the present invention provides a >99.99%reduction in the swab test as compared to the comparative plastic (Control F) .

Example 7

Similar to Example 2, the only difference in this example is an addition of pentaerythritol tetrakis [3- [3, 5-di-tert-butyl-4-hydroxyphenyl] propionate at about 0.5 phr, and the rest of the components and their content in the composition, and the preparation thereof are substantially the same as those in Example 2. In addition to the swab test for showing the germ repellency against two different bacterial strains, mechanical properties of the germ-repellent plastic in this example are also tested such as the tensile strength and impact strength. The following Table 11 summarize the germ repellent performance against E. coli and S. aureus; and Table 12 summarizes the tensile and impact strengths, and heat deformation of this example. The change in percentage of bacterial CFU reduction or various mechanical properties in the sample plastic sheet prepared according to this example is compared with those in a control (i.e., the engineering plastic without the corresponding germ-repellent modifiers) .

Table 11:

SA: S. aureus

EC: E. coli

CFU Reduction by comparing CFU in sample with that in control

Table 12:

Table 13

SA: S. aureus

EC: E. coli

*CFU Reduction by comparing CFU in sample with that in control

Table 14

SA: S. aureus

EC: E. coli

*CFU Reduction by comparing CFU in sample with that in control

From Table 11, the plastic sample in this example is shown to have over 99.99%bacterial reduction in terms of CFU of S. aureus and about 99.6%bacterial reduction in terms of CFU of E. coli compared to those in the control (without germ-repellent modifier) . The mechanical test results shown in Table 12 suggest that there is no significant in mechanical properties, e.g., less than 20%, in the sample of this example compared to the control; the changes in impact strength and heat deformation of the sample is not very significant compared to the control (only a small reduction observed in both impact strength and heat deformation temperature in the sample) . Results of Tables 13 and 14 demonstrate that there is no significant change in germ repellent efficacy and various mechanical properties of the plastic sample in this example under a stability assay for about a year, meaning that the shelf-life of the germ repellent engineering plastics of the present invention is stable for at least one year at room temperature in terms of at least the properties as above mentioned.

A Minimal Essential Media (MEM) Elution test is also carried out in this example to determine its cytotoxicity of any extractable materials from the plastic, which is according to ISO 10993-5. An extract of the sample in this example was added to cell monolayers and incubated. The cell monolayers were examined and scored based on the degree of cell destruction. As compared to a negative control (polypropylene pellets) , media control, and positive control (latex natural rubber) , the cell monolayers incubated with the extract of the sample in this example scored 0 in this test (positive control scored 4; negative and media controls scored 0) , which indicates that there was no cell lysis /in-vitro cytotoxicity observed. The plastic sample in this example under a stability assay for about a year was also scored 0 in the in-vitro cytotoxicity test according to ISO 10993-5 , indicating that there is no cytotoxicity observed on the sample after at least one-year storage at room temperature.

The sample in this example is further subjected to food contact safety tests in compliance with the Commission Regulation EU 2020/1245 of 2 September 2020 amending and correcting Regulation EU No. 10/2011 for plastic materials and articles intended to come into contact with food, EC No. 1935/2004 for sensorial examination of odor and taste, and US FDA under 21 CFR 177.1630 for determination of amount of next chloroform solution extractives. The results show that the sample in this example passed all the foregoing food contact safety tests.

Example 8

The base plastic and processing conditions used in this example are the same as those used in example 3, except the germ-repellent modifier and additive are different. 2 phr methyoxypoly (ethylene glycol) (mPEG) (MW: 2000Da) and 1.73 phr n-phenylmaleimide are comingled with the mPEG to form a masterbatch and then subjected to extrusion by a twin-screw extruder under 220 to 270 degrees Celsius. The plastic sheet sample is tested with germ-repellency by the same swab test outlined in other examples described herein and certain mechanical properties as those tested in example 7. Corresponding results are summarized in the following Tables 15 and 16.

Table 15

SA: S. aureus

EC: E. coli

*CFU Reduction by comparing CFU in sample with that in control

Table 16:

An additional feature of using polycarbonate as the base plastic is that it is still transparent after comingled with the germ-repellent modifier and additive. Table 17 below shows that the change in optical transmittance of the sample is very minimal compared to control.

Table 17:

Sample	Average Transmittance	Change
Control	89.88 ± 0.25 %	-
Example 8	82.91 ± 0.19 %	-6.64%

Although the sample in this example exhibits excellent germ repellency against S. aureus and E. coli with no significant change in optical transmittance, changes in mechanical properties have been observed, in particular the most significant change is in the impact strength which is reduced by about 90%compared to the control.

The next example will demonstrate a solution to this significant change in impact strength of the polycarbonate sample plastic sheet.

Example 9

Similar to example 8, polycarbonate is used as the base plastic and comingled with mPEG (MW: 2000Da) and n-phenylmaleimide, but the amount of mPEG and n-phenylmalemide is halved than that used in example 8, and an additional component methacrylate butadiene styrene (MBS) as a mechanical reinforcing agent is comingled together before extrusion in order to maintain impact strength of the base plastics. Germ-repellency of the sample sheet and its mechanical properties are summarized in the following Tables 18 and 19, respectively.

Table 18:

SA: S. aureus

EC: E. coli

*CFU Reduction by comparing CFU in sample with that in control

Table 19:

Table 20:

As compared to example 8, the sample in this example not just has comparable germ repellency against S. aureus and E. coli to that in example 8, but also the reduction in impact strength is much improved by the additional component, even it is still a slight decrease in impact strength. The change in other mechanical properties in the sample compared to the control are not very significant, so it is acceptable. Similar to Example 7, the result of Table 20 demonstrates that the germ repellent engineering plastic of the present invention has at least about one-year shelf life at room temperature without significant change in germ repellent efficacy.

Cytotoxicity of the sample in this example is also tested according to the MEM Elution test described in example 7. The cytotoxicity result of the MEM Elution test on this sample shows that the score is 0 according to ISO 10993-5. The plastic sample in this example under a stability assay for about a year was also scored 0 in the in-vitro cytotoxicity test according to ISO 10993-5, indicating that there is no cytotoxicity observed on the sample after at least one-year storage at room temperature.

The sample is also subjected to a series of food contact safety tests used in example 7, and it passed all the tests.

Table 21 below summarizes the composition, chemicals used and corresponding germ repellency in terms of the inhibition of colony formation of two different bacterial strains on the germ-repellent plastic of the above examples.

Table 21: Summary of example composition and germ-repellent efficacy

SA: S. aureus

EC: E. coli

INDUSTRIAL APPLICABILITY

The present invention is applicable in various food-contact safe plastic products in substantially all shapes and dimensions with durable and effective germ-repellent properties while mechanical properties and biocompatibility are substantially unchanged or the change is minor after the introduction of the germ-repellent modifiers with the carrier agents. The articles comprising the plastic of the present invention should meet the corresponding standards for food-contact safe articles such as EC No. 1935/2004 and for biocompatible articles such as ISO10993.

Claims

A mechanically-strong, biocompatible, food-contact safe and germ-repellent engineering plastic comprising:

one or more base engineering plastic resins selected from polyamides, polyesters, polycarbonates, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polyphenylene ether, polyphenylene sulfide, acrylonitrile butadiene styrene, polyoxymethylene, methyl methacrylate butadiene styrene, polyetherketone, and/or, polyetheretherketone, or any polymer alloys having no less than 50 wt. %of the one or more base engineering plastic resins;

one or more germ-repellent modifiers selected from poly (ethylene glycol) , poloxamer, polyethylene glycol sorbitan monolaurate, poly (ethylene glycol) sorbitol hexaoleate, polypropylene glycol glycerol ether, ceteareth, polysorbate, alkyl polyglycol ether C16-C20, and/or any combination thereof, at approximately 1 to 20 wt. %, and incorporated with one or more carrier agents comprising stearyl palmitate, stearyl behenate, stearyl stearate, palmityl palmitate, myristyl palmitate, and/or myristyl myristate; and

the engineering plastic before and after introduction of the one or more germ-repellent modifiers with the one or more carrier agents having no significant difference in mechanical properties including tensile strength and impact strength of less than approximately 20%, biocompatibility including no observable in-vitro cytotoxicity, and at least one-year shelf life at room temperature without any alteration of germ repellent efficacy, mechanical properties and biocompatibility.
The engineering plastic of claim 1, further comprising one or more additives including compatibilizers, reinforcing fillers, heat stabilizers, and/or antioxidants; and each of the additives being at approximately 0.5 to 20 wt. %.
The engineering plastic of claim 2, wherein the compatibilizers comprise maleic anhydride and glycidyl (meth) acrylate grafted polymers at approximately 1 to 20 wt. %.
The engineering plastic of claim 2, wherein the reinforcing fillers comprise silica nanoparticles untreated or treated with the one or more germ-repellent modifiers at about 0.1 to 5 wt. %.
The engineering plastic of claim 2, wherein the antioxidants comprise one or both of sterically hindered phenols and phosphites.
The engineering plastic of claim 2, wherein the heat stabilizer comprises organophophites, phenolic compounds and metallic stearates.
The engineering plastic of claim 1, further comprising a slip agent tolerable in high temperature for imparting hydrophilicity to the surface of the base engineering plastic resins and/or facilitating dispersion of the germ-repellent modifiers and other additives across polymer matrix of the base engineering plastic resins during a high temperature extrusion thereof.
The engineering plastic of claim 1, further comprising an antistatic agent for lowering friction on the surface of the base engineering plastic resins.
The engineering plastic of claim 1, further comprising one or more specialty additives, wherein one of the specialty additives is selected from stearyl stearate, stearyl behenate, behenyl behenate, ethylene glycol distearate, ethyl behenate, behenyl acetate, palmityl myristate, or palmityl palmate.
A method for preparing a mechanically-strong, biocompatible, food-contact safe and germ-repellent engineering plastic comprising:

providing a masterbatch by comingling one or more germ-repellent modifiers with the one or more base engineering plastic resins, in an extrusion process, and further comingling the masterbatch with the one or more base engineering plastic resins; or

comingling the one or more germ-repellent modifiers with the one or more base engineering plastic resins directly; and

processing the obtained resins.
The method of claim 10, wherein the one or more additives are optionally incorporated into the one or more germ-repellent modifiers during said providing the masterbatch or before said direct comingling with the one or more base engineering plastic resins.
The method of claim 11, wherein the one or more germ-repellent modifiers are incorporated with one or more carrier agents comprising stearyl palmitate, stearyl behenate, stearyl stearate, palmityl palmitate, myristyl palmitate, and/or myristyl myristate during said providing the masterbatch, said direct comingling the one or more germ-repellent modifiers with the one or more base engineering plastic resins, or said processing the obtained resins.
The method of claim 10, wherein the one or more base engineering plastic resins are selected from polyamides, polyesters, polycarbonates, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polyphenylene ether, polyphenylene sulfide, acrylonitrile butadiene styrene, polyoxymethylene, methyl methacrylate butadiene styrene, polyetherketone, and/or, polyetheretherketone, or any polymer alloys that contain no less than 50 wt. %of the one or more engineering plastics.
The method of claim 10, wherein the extrusion is carried out in a twin-screw extruder.
The method of claim 10, wherein the one or more germ-repellent modifiers are selected from poly (ethylene glycol) , poloxamer, polyethylene glycol sorbitan monolaurate, poly (ethylene glycol) sorbitol hexaoleate, polypropylene glycol glycerol ether, ceteareth, polysorbate, alkyl polyglycol ether C16-C20, and/or any combination thereof, at approximately 1 to 20 wt. %.
The method of claim 11, wherein the one or more additives comprise compatibilizers, reinforcing fillers, heat stabilizers, and/or antioxidants; each of the additives is at approximately 0.5 to 20 wt. %.
The method of claim 16, wherein the compatibilizers comprise maleic anhydride and glycidyl (meth) acrylate grafted polymers at approximately 1 to 20 wt. %.
The method of claim 16, wherein the reinforcing fillers comprise silica nanoparticles untreated or treated with the one or more germ-repellent modifiers at about 0.1 to 5 wt. %.
The method of claim 16, wherein the antioxidants comprise one or both of sterically hindered phenols and phosphites.
The method of claim 16, wherein the heat stabilizer comprises organophophites, phenolic compounds and metallic stearates.
The method of claim 16, wherein the one or more additives further comprise a slip agent tolerable in high temperature for imparting hydrophilicity to the surface of the base engineering plastic resins and/or facilitating dispersion of the germ-repellent modifiers and other additives across polymer matrix of the base engineering plastic resins during a high temperature extrusion thereof.
The method of claim 16, wherein the one or more additives further comprise an antistatic agent for lowering friction on the surface of the base engineering plastic resins.
The method of claim 16, wherein the one or more additives further comprise one or more specialty additives, and

wherein one of the specialty additives is selected from stearyl stearate, stearyl behenate, behenyl behenate, ethylene glycol distearate, ethyl behenate, behenyl acetate, palmityl myristate, or palmityl palmate.
The method of claim 10, wherein said processing the obtained resins comprises injection molding.
A germ-repellent, mechanically-strong, biocompatible and food-contact safe engineering plastic prepared by the method of any one of claims 10 to 24.
A germ-repellent, mechanically-strong, biocompatible and food-contact safe article comprising one or more of the engineering plastics according to any one of claims 1 to 9.