WO2019233822A1

WO2019233822A1 - A thermoplastic elastomer composition

Info

Publication number: WO2019233822A1
Application number: PCT/EP2019/063775
Authority: WO
Inventors: Yusuf YUSUFOGLU; Tugce ONER; Beyza DEMIR; Metehan CIHANGIR; Beste PAMUKOGULLARI
Original assignee: Arcelik Anonim Sirketi
Priority date: 2018-06-08
Filing date: 2019-05-28
Publication date: 2019-12-12

Abstract

The present invention relates to an antibacterial/antimicrobial thermoplastic elastomer composition and to its use.

Description

A THERMOPLASTIC ELASTOMER COMPOSITION

The present invention relates to a hydrogenated triblock copolymer based antimicrobial thermoplastic elastomer composition, and to using said composition in domestic appliances (washing machines, dishwashers, refrigerators, dryers, etc.).

In the state of the art, hydrogenated triblock copolymer (hydrogenated triblock copolymer - SBS, SEBS, SIS, SEP, SEPS) based thermoplastic elastomers are commonly used in the industry due to combining the features of rubbers such as elasticity and high elongation ratios with the typical features of thermoplastics such as formability by heat and recyclability. Hydrogenated triblock copolymer based elastomers also substitute materials resistant to oils and heat, depending on the used di- and triblock copolymer which create a good touching sensation.

In applications in contact with water and/or other liquids likely to cause organism growth, in which elastomeric properties are sought for, development of microorganism such as microbes and fungus is not desired. In domestic appliances industry utilizing elastomeric materials, particularly in household appliances such as washing machines and dishwashers, there always is the risk of being contaminated by microorganisms and rapid growth thereof due to being in contact with dirty laundry/items. For example, on a dishwasher door gaskets, bacterial plaque and mold formation is observed on the sealing member as a result of repetitive washing processes. Said bacterial plaque or plate poses a problem in terms of hygiene in the washing process. Therefore, the cleaning process to be backed up by materials with antimicrobial properties is of utmost importance.

State of the art international patent application no. WO 2006/023232 A1 discloses an elastomer composition with antimicrobial properties and the method to obtain said composition. In this document, silicone is used as the elastomer and silver oxide is used as the antimicrobial agent.

State of the art Chinese patent application no. CN 104109332 discloses an antimicrobial thermoplastic elastomer and the preparation method of said elastomer. This elastomer composition comprises in percentage by weight, 15-30% of SEBS, 10-30% of rubber filling oil, 10-25% of polyurethane (PU), 5-30% of antimicrobial master batch, 5-25% of inorganic filler, 5-15% of compatibilizer and 0-2% of other assistant additives.

The aim of the present invention is to produce domestic appliances (washing machines, dishwashers, refrigerators, dryers, etc.) utilizing high-performance hydrogenated triblock copolymer thermoplastic elastomer composition exhibiting antimicrobial properties.

The elastomer composition realized to achieve the aim of the present invention and disclosed in the first claim and the dependent claims, comprises at least one hydrogenated triblock copolymer, at least one polyolefin, at least one non-aromatic oil, at least one inorganic filler, at least one thermal protector and antioxidant mixture, at least one natural essential oil or at least one antimicrobial organic additive, and at least one compatibilizer agent.

This elastomer composition is used in domestic appliances (washing machines, dishwashers, refrigerators, dryers, etc.) requiring hygiene.

The antibacterial/antimicrobial thermoplastic elastomer composition of the invention comprises a hydrogenated triblock copolymer, a polyolefin, at least one non-aromatic oil, at least one inorganic filler, at least one thermal protector and antioxidant mixture, and at least one compatibilizer agent.

The antibacterial/antimicrobial thermoplastic elastomer composition of the invention comprises at least one natural essential oil and/or at least one antimicrobial organic additive.

Using natural essential oil contributes to achieving an environmentally friendly composition. Natural essential oils exhibit antifungal, antibacterial, antiviral properties thanks to carvacrol, thymol and eugenal which are the biologically active compounds in their structure, as well as an antioxidant effect thanks to their phenolic structure. Essential oils' activity on materials act on microorganisms by means of the surface film which forms due to the terpenes consisting the hydrophilic structure of the oils, moving towards the surface. Similar to essential oils, antimicrobial organic additives act against Aspergillus nilger (fungi), Escherichia coli (E. Coli, gram negative bacteria) and Staphylococcus aureus (S. Aureus, gram positive bacteria) which are the microorganisms targeted by the produced material, and prevent bacterial and fungus biofilm formation on surface by means of surface migration and enhance protecting the features.

The natural essential oil(s) used in the invention are of antimicrobial properties, and enable the thermoplastic composition to maintain its activity by settling therein. In addition, this enables avoiding fungus and bacteria formation likely to occur on the material comprising the thermoplastic composition of the invention, due to water, heat and humidity or due to being in contact with food, thereby providing a better hygienic environment.

The antibacterial/antimicrobial thermoplastic elastomer composition comprises at least one natural essential oil selected from the group comprising: sage oil, thyme oil, peppermint oil, rosemary oil, lavender oil, cinnamon oil, bergamot oil, tea tree oil, lemon balm oil, clove oil, cardamom oil, laurel oil, garlic oil and basil oil.

These oils used in the formulation migrate towards the surface of the thermoplastic elastomer over time, thereby preventing bacteria and mold biofilm growth on the surface. Hygiene properties of the material is thus utilized.

In the preferred embodiment of the invention, the thermoplastic elastomer composition comprises: 20-70 wt% (w/w) of hydrogenated poly(styrene-b-(ethylene-co-butylene)-b-styrene copolymer (SEBS, 31-34 styrene), 10-30 wt% (w/w) of polypropylene (PP), 10-60 wt% (w/w) of non-aromatic oil, 0-20 wt% (w/w) of inorganic filler, 1-5 wt% (w/w) of thermal protector and antioxidant mixture, 0-10 wt% (w/w) of compatibilizer, 5-30 wt% (w/w) of natural essential oil, and 1-10 wt% (w/w) of organic antimicrobial additive.

The ethylene group in SEBS structure enables achieving a better water, ozone and solvent resistance and therefore a better aging performance thanks to being resistant to water, humidity and temperature conditions. Furthermore, the styrene groups (hard domains) in SEBS structure form physical crosslinks by combining in crystal structures, and the ethylene-butylene domains which are rubbery structures are in fact amorphous rubbery structures and assume form to create elasticizing links between crystal structures. Using PP as thermoplastic phase in the invention enables achieving the desired high heat performance in usage temperatures, and also brings the production and formability of thermoplastics to an elastomer based material. In addition, thermoplastic phase also has a significant effect in improving the tensile and tearing strength of the material. The thermal protectors and antioxidants defined in the invention, are mixed in specific proportions in the formulation and then used in thermoplastic elastomer production process in the stated proportions.

SEBS/PP proportion fundamentally effects the tensile strength, tearing strength and the elasticity module of the material. The amount of PP in the material structure has a significant effect particularly in determining the rigidity and mechanical values of the thermoplastic elastomer composition. In addition, polypropylene facilitates processing and injection molding of the elastomer composition, while also enabling recyclability of the elastomer composition of the invention. PP is the material enabling features such as processability, injection moldability and recyclability. The amount of SEBS as the elastomeric phase, affects determining the features such as the elongation value until tearing, the deformation amount under compression and tensile forces, elasticity and low temperature performance of the TPE. Taipol 6151 is used in the invention as the hydrogenated triblock copolymer (SEBS). It contains 32% styrene hard block polymer structure, to 68% soft ethylene-butylene elastomer. As per its structure, this material has a high molecular weight, and excellent weathering and heat resistance. It exhibits good conformity with polyolefins.

In an embodiment of the invention, the non-aromatic oil is a paraffinic oil or a mixture of paraffinic-naphthenic oil.

Using a low polarity paraffinic oil is preferred due to the structure of the utilized base polymers and the desired features. In addition, the highly saturated bond structure of these non-aromatic oils enables the polymer to stay more stable when subjected to UV light and heat, and to gain resistance against oxidation and discoloration. Mixture of two oils is used in the invention due to not being able to acquire high paraffinic purity in oil structure. The process assisting oil has a pour point of -36/-9˚, an aniline point of 95/115˚C, a flash point of 220-270˚C, a density of 850/950 kg/m³, and a viscosity of 8/18 mm²/s at 100˚C.

In an embodiment of the invention, as the inorganic filler, at least one is selected from the group comprising: calcium carbonate, precipitated silica, fumed silica, bentonite, kaolin, talc, carbon black, halloysite, graphite, wollastonite.

In addition to contributing in improving thermal stability which is the fundamental problem in thermoplastic elastomer compositions, the inorganic additives also enable facilitating processability of the composition. Furthermore, this contributes to enhancing the mechanical properties of the elastomer composition, thereby reducing material costs. Moreover, in order to enable antimicrobial properties to maintain their effectiveness for a longer duration, increase in effectiveness may be provided by impregnating the functional additive to the filler particularly in systems with liquid additives prior to formulation works. In such systems, particularly halloysites of tubular structure provide a longer effect for retaining the additive and for oscillating.

In the preferred embodiment of the invention, the thermal protector is a phosphite based process stabilizer and/or a phenol based antioxidant.

Thermal protectors are used to provide thermal endurance of said thermoplastic elastomer composition.

The thermal protectors introduced to the formulation act as a process stabilizer, and prevent degradation of the polymer during hot melt mixing while protecting the polymer against thermal-oxidative degradation by preventing thermal degradation for a longer time by enhancing the effectiveness of the phenolic primary antioxidants added to the structure.

In the preferred embodiment of the invention, polypropylene-grafted-maleic anhydride (PP-g-MA) and/or styrene-ethylene-butylene-styrene-grafted-maleic anhydride (SEBS-g-MA) is used as the compatibilizer.

The compatibilizer introduced to the polymer formulation and the elastomer which is base polymer, enable forming an effective interface between olefinic phase and fillers. Improvement is thus observed in the mechanical properties of the material.

The elastomer composition of the invention is produced by a method comprising the process steps of
(i) Mixing liquid oil phase and rubber based material,
(ii) Extruding said premix with polyolefin which is thermoplastic phase and the other additives,
(iii) Obtaining the physical crosslinked thermoplastic elastomer mixture,
(iv) Passing the mixture material in filament form leaving the extruder port, through cooling water,
(v) Cutting the material passed through cooling water, by cutter blades and obtaining granulated elastomer composition.

If an extruder with liquid dosing is used, oil and rubber based material are mixed from the front regions of the extruder prior to mixing with polyolefin, and if an extruder system without liquid dosing is used, two materials are mixed in a mixer before being loaded in the feeding unit.

All oils (process assisting oil and aromatic oils) should be mixed in the process step (i).

Physical crosslinking in material structure and the material obtaining 3D web structure occur by formation of polystyrene structures under the effects of heat and the shear forces applied during extruding process, and by these structures forming PS domains in elastomeric phase.

Depending on usage purposes, coloring agent, light and/or heat sensitive chromic material, flame-retardant material, foaming material, UV protector, surface characteristic enhancing additive, or process facilitating lubricant/wax may be introduced to the elastomer composition.

In an embodiment of the invention, obtained elastomer composition is used in hygiene requiring domestic appliances.

Using the elastomer composition of the invention in domestic appliances, enables avoiding likely bacteria/microbe/fungi formation on the material due to water, heat and humidity, or due to contact with dirty items/laundry or food.

In an embodiment of the invention, the material comprising said antibacterial/antimicrobial thermoplastic elastomer composition is used in washing machines.

A more effective hygiene environment is provided and likely bacteria/microbe/fungi formation due to dirty/contaminated laundry is avoided in washing machines utilizing the elastomer composition of the invention. The elastomer composition of the invention may be used in washing machine door gasket which is one of the elastomer based components requiring antimicrobial properties in washing machines.

In an embodiment of the invention, the material comprising said antibacterial/antimicrobial thermoplastic elastomer composition is used in dishwashers.

A more effective hygiene environment is provided and likely bacteria/microbe/fungi formation due to residue on dirty/contaminated kitchenware is avoided in dishwashers utilizing the elastomer composition of the invention. The elastomer composition of the invention maybe used in door gasket or O-rings in contact with dirty water in dishwashers.

In an embodiment of the invention, the material comprising said antibacterial/antimicrobial thermoplastic elastomer composition is used in refrigerators.

A more effective hygiene environment is provided and likely bacteria/microbe/fungi formation due to usage particularly in areas closer to food is avoided in refrigerators utilizing the elastomer composition of the invention. The elastomer composition of the invention may be used in refrigerators in areas with risk of microorganism growth such as refrigerator door gasket, water dispenser gaskets, or stopper components.

Claims

An antibacterial/antimicrobial thermoplastic elastomer composition comprising a hydrogenated triblock copolymer, a polyolefin, at least one non-aromatic oil, at least one inorganic filler, at least one thermal protector and antioxidant mixture and at least one compatibilizer agent, characterized by comprising at least one natural essential oil and/or at least one antimicrobial organic additive.
An antibacterial/antimicrobial thermoplastic elastomer composition characterized by the natural essential oil having antimicrobial properties.
An antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by the natural essential oil being at least one of those selected from the group comprising: sage oil, thyme oil, peppermint oil, rosemary oil, lavender oil, bergamot oil, tea tree oil, lemon balm oil, clove oil, cardamom oil and laurel oil.
An antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by the antimicrobial organic additive being selected amongst zinc pyrithione and/or phenol based structures.
An antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by the antimicrobial organic additive being zinc pyrithione and/or 5-chloro-2-(2,4 dichlorophenoxy)phenol.
An antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by comprising 20-70 wt% (w/w) of hydrogenated styrene-ethylene-butylene-styrene copolymer (SEBS, 31-34 styrene), 10-30 wt% (w/w) of polypropylene (PP), 10-50 wt% (w/w) of non-aromatic oil, 0-20 wt% (w/w) of inorganic filler, 1-5 wt% (w/w) of thermal protector and antioxidant mixture, 0-10 wt% (w/w) of compatibilizer, 5-30 wt% (w/w) of natural essential oil, and 1-10 wt% (w/w) of organic antimicrobial additive.
An antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by the non-aromatic oil being a paraffinic oil or a mixture of paraffinic-naphthenic oil.
An antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by the inorganic filler being at least one of those selected from the group comprising: calcium carbonate, precipitated silica, fumed silica, bentonite, kaolin, talc, carbon black, halloysite, graphite, wollastonite.
An antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by the thermal protector being a mixture of phosphide based process stabilizer and phenol based antioxidant.
An antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by the compatibilizer being polypropylene-grafted-maleic anhydride (PP-g-MA) and/or styrene-ethylene-butylene-styrene-grafted-maleic anhydride (SEBS-g-MA).
Production method of an antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1, characterized by the process steps of

(i) Mixing liquid oil phase and rubber based material,

(ii) Extruding said premix with polyolefin which is thermoplastic phase and the other additives,

(iii) Obtaining the physical crosslinked thermoplastic elastomer mixture,

(iv) Passing the mixture material in filament form leaving the extruder port, through cooling water

(v) Cutting the material passed through cooling water, by cutter blades and obtaining granulated elastomer composition.
A production method according to claim 11, characterized by introducing depending on usage purposes: coloring agent, light and/or heat sensitive chromic material, flame-retardant material, foaming material, UV protector, surface characteristic enhancing additive, or process facilitating lubricant/wax.
A domestic appliance characterized by comprising a material containing an antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1.
A washing machine characterized by comprising a material containing an antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1.
A dishwasher characterized by comprising a material containing an antibacterial/antimicrobial thermoplastic elastomer composition according to claim 1.