ITMI20130469A1 - ANTIBACTERIAL POLYMERS AND METHOD OF OBTAINING THEM - Google Patents

Description

DESCRIPTION

â € œANTIBACTERIAL POLYMERS AND METHOD FOR OBTAINING THEMâ €

FIELD OF THE INVENTION

The present invention relates to polymers having antibacterial properties and their uses for the preparation of articles intended to come into contact with the skin. The invention also relates to a process for the preparation of such polymers.

BACKGROUND OF THE INVENTION

Bacteria are found everywhere in the environment and can be beneficial or carry diseases. The latter are normally transmitted by sick people or animals, water and food contamination and other external sources of pollution.

It is possible to become contaminated with bacteria responsible for the development of pathologies through contact with objects or surfaces previously handled by people or animals carrying these bacteria.

The problem of safety against bacterial proliferation has now reached a global dimension. The development of different types of pathogenic bacteria on the surfaces of objects / artefacts is favored by particular environmental conditions.

Generally, microorganisms must reach certain concentrations to cause damage to the organism, that is, to cause disease. It is therefore important to prevent the occurrence of suitable conditions for their development. In addition to the normal rules of hygiene by now established, the need to develop materials with intrinsic antibacterial properties to be used for the preparation of products of large consumption and use, in particular intended to come into contact with the skin, is becoming more and more widespread. . The combination of the common rules of hygiene and the use of antibacterial materials allows to achieve optimal results in terms of reduction of bacterial contamination and therefore of the pathologies connected to it.

Nowadays thermoplastic polymers are the most used materials for the manufacture of products in any sector. It therefore becomes important to be able to have products made of plastic material able to counteract bacterial proliferation.

Historically speaking, the antibacterial properties of silver have been known since ancient times.

In fact, although the bacteria were obviously not known, the antibacterial and healing effects of some metals such as silver were known since ancient times.

From these first applications we arrived at the union of nano-particles of silver, or colloidal silver (liquid suspension of microscopic silver particles) with polymeric plastic materials, to give the latter antiseptic and antibacterial properties.

However, it is known that the prolonged use of colloidal silver or silver particles can cause chronic poisoning, called "argyria".

There is also extensive scientific documentation on the side effects of colloidal silver, which is capable of causing skin necrosis if kept in contact with the skin for a long time.

However, the metals that have antimicrobial properties are different, for example copper, nickel and zinc. However, copper and nickel have severe legislative limitations due to their high toxicity.

The toxicity of free metallic zinc is well known, as are the neurological problems it can induce. However, zinc ion compounds are less toxic than metallic zinc and retain antibacterial properties. Over the last few years, numerous studies have confirmed the antimicrobial and antiviral properties of zinc ions, especially against Gram + bacteria such as Staphylococcus Aureus, one of the most common pathogenic bacteria responsible for skin infections, and against the main bacteria of the oral cavity such as Streptococci and Actinomycetes.

In fact, zinc ions possess bacteriostatic properties, that is, they inhibit bacterial growth as they are able to penetrate inside the bacterial cell blocking various biological processes fundamental for the survival of the bacterium itself.

Polymers are known having antibacterial properties obtained by mixing the polymer with zinc salts in which the antiseptic properties are due to the ions of these metals. The mixing of the polymeric macromolecule with the zinc salts, although it achieves the pre-established result, that is to give the polymers antiseptic and antibacterial properties, typical of the metal ion, thus fighting the proliferation of microbes and bacteria, however it has an important disadvantage

This disadvantage is linked to the release of zinc ions over time due to the fact that the salts of these metals are simply mixed with the polymer and not incorporated into the polymer structure. In fact, even if the mixing is performed in an optimal way, over time phenomena of release of metal ions occur in quantities exceeding the limits allowed by the European law in force on the subject, which regulates the maximum limits of metals that can migrate from a polymer to the € ™ surrounding environment. This standard sets the maximum migration limit for the zinc ion at a value equal to 21 ppm.

In light of the above considerations there is a need in the sector to provide polymers with antibacterial and antiseptic properties to be used for the production of products intended to come into contact with human or animal skin, characterized by low toxicity and a release of zinc ions lower than the legal limits.

SUMMARY OF THE INVENTION

In general terms, the present invention relates to a polymer having antibacterial and antiseptic properties obtained or obtainable by adding at least one zinc salt to the solution or dispersion in aqueous or organic solvent of the monomers used for the synthesis of the polymer. Alternatively, at least one zinc salt can be added during the polymerization reaction of the starting monomers.

The invention also relates, in general terms, to a process for obtaining the antibacterial polymer comprising a step for adding at least one zinc salt to the solution or dispersion in aqueous or organic solvent of the monomers used for the synthesis of the polymer by means of a polymerization reaction. In particular, this addition is carried out before the start of the polymerization reaction or during the reaction and before its completion.

The invention also relates to an antibacterial and antiseptic product obtained starting from the antibacterial polymer of the invention by, for example, extrusion, molding (for example, male-female molding, injection molding), hot forming, etc. This product can for example, computer mice, computer keyboards, covers for phones and tablets, door handles, plastic handrails, antibacterial coatings for panic bars, antibacterial film for surfaces that must have a high degree of cleanliness, frames for glasses, etc.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for the preparation of an antibacterial and antiseptic polymer comprising the steps of:

a) solubilizing or dispersing at least one zinc salt in an organic or aqueous solvent;

b) adding the dispersion or solution thus obtained to the solution or dispersion in organic or aqueous solvent of at least one monomer;

c) polymerize at least one monomer.

All the percentages indicated in the patent application are intended as percentages by weight calculated with respect to the final weight of the antibacterial polymer to be obtained.

The antibacterial polymer is a thermoplastic polymer, for example polypropylene (PP), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), nylon and polystyrene.

If an antibacterial polypropylene is to be made, the at least one monomer is propylene which is subjected to polymerization according to step c) of the process after adding the at least one zinc salt. The polymerization of propylene is carried out with the usual techniques known in the field which use suitable catalysts to obtain isotactic or syndiotactic propylene.

Polycarbonate is obtained from the polymerization of at least one monomer diol selected for example from: bisphenol A, 1,1-bis 1,1-bis (4-hydroxyphenyl) cyclohexane, dihydroxybenzophenone and tetramethyl cyclo-butanediol with a source of carbonate groups, for example fonsgene and diphenylcarbonate. The polymerization conditions are known in the art and therefore will not be further illustrated.

ABS is a copolymer, that is a polymer made by polymerization, not of a single monomer, but of several monomers.

For the production of an antibacterial ABS polymer, a mixture of acrylonitrile, butadiene and polymerized styrene (polystyrene) in a certain range of percentages:

acrylonitrile, in a percentage comprised between 12% and 40%, preferably between 20% and 35%.

butadiene, in a percentage between 2% and 35%, preferably between 10% and 20%.

polymerized styrene (polystyrene) in a percentage comprised between 30% and 70%, preferably between 40% and 60%.

For the realization of the ABS polymer with antibacterial properties, appropriate aliquots of the different components are taken, in the proportions indicated and polymerized according to the traditional polymerization and synthesis methods of the ABS polymer.

The polystyrene used to prepare ABS can already possess antibacterial properties if made and polymerized according to the process described in this patent.

In particular, polystyrene is obtained from the polymerization (carried out according to the processes and conditions known in the field) of styrene monomers to which the dispersion or solution of at least one zinc salt has been added. The polyvinyl chloride is obtained from the polymerization of the vinyl chloride monomer under the conditions known in the art.

Polyethylene terephthalate is obtained from the polymerization of the monomers terephthalic acid and ethylene glycol, or dimethyl terephthalate and ethylene glycol, under the conditions known in the art.

Nylon is obtained by condensation reaction of diamines with carboxylic acids using reaction procedures and conditions known in the art. The at least one zinc salt is added to the dispersion or solution of the at least one monomer necessary for the polymerization or to the dispersion or suspension of a mixture of two or more monomers.

The solvent used to prepare the solution or dispersion of the at least one zinc salt is preferably selected from: water, ethyl alcohol, methanol, acetone, isopropyl alcohol or a mixture of two or more solvents.

If a mixture of solvents is used, the individual solvents are preferably used in the following percentages:

water: it is used inside the mixture in a percentage between 5% and 100%, preferably between 20% and 100% by weight.

ethyl alcohol: it is used inside the mixture in a percentage between 5% and 15%, preferably between 5% and 10% by weight.

methanol: it is used inside the mixture in a percentage between 5% and 10%, preferably between 5% and 7% by weight.

acetone: it is used inside the mixture in a percentage between 3% and 70%, preferably between 10% and 65% by weight.

isopropyl alcohol: it is used inside the mixture in a percentage between 2% and 20%, preferably between 5% and 15% by weight. In a preferred embodiment, the solution or dispersion of the at least one zinc salt is added dropwise to the monomer solution or dispersion. In the polymerization phase c) the polymer incorporates the at least one salt inside the polymer structure, thus giving the obtained polymer product remarkable antibacterial and antiseptic properties.

This is due to the use of the additive based on zinc ions which, thanks to its properties, contrasts and fights the microbial and bacterial proliferation on the polymer surface obtained, regardless of the polymer used or the shape of the product obtained.

Preferably, the at least one zinc salt is selected from: zinc PCA (zinc salt of pyrrolidon-carboxylic acid), zinc oxide, zinc hydroxide, zinc pyrrolidone, zinc pyrithione or their mixtures.

The amounts of the at least one zinc salt added to the at least one monomer are comprised between 0.1 and 10% by weight, preferably between 0.1% and 5%, more preferably between 0.2% and 4%.

For example, PCA zinc is used in a percentage between 0.1% and 10%, preferably between 2% and 5%.

Zinc oxide is used in a percentage between 0.1% and 2%, preferably between 0.2% and 0.6%.

Zinc hydroxide is used in a percentage between 0.1% and 4%, preferably between 0.2% and 1%.

Zinc pyrithione is used in a percentage between 0.1% and 2%, preferably between 0.1% and 0.7%. Zinc pyrrolidone is used in a percentage between 0.01% and 3%, preferably between 0.1% and 1%.

In a preferred embodiment, the at least one zinc salt is ZnPCA or Zn pyrithione or a mixture thereof. In another embodiment all the zinc salts listed above are used in a mixture.

For the synthesis of the antibacterial polymer of the invention, the amounts of salts reported above are dissolved in one or more solvents as previously described.

The slightly soluble salts, for example zinc oxide and zinc hydroxide, are instead finely dispersed in one or more solvents as described above.

Once the solution or dispersion of one or more salts has been obtained, this is added to the suspension or solution of the at least one monomer, or alternatively, it is added during the polymerization process. The at least one monomer is preferably dissolved or suspended in solvents selected from: acetone, dichloromethane, chloroform or their mixtures.

Once added, the solution or dispersion of the at least one zinc salt is stirred together with the monomers of the polymer until the polymer is obtained by polymerization of the monomers. The reaction time is preferably between 20 minutes and 3 hours, more preferably between 60 minutes and 90 minutes.

In a second aspect, the invention relates to an antibacterial polymer obtainable from the process described above in which at least one zinc salt is dispersed inside the polymeric structure, giving the polymer antiseptic properties.

The antibacterial polymer of the invention is characterized by having a release of zinc ions lower than the legal limits equal to 21 ppm, as evidenced by the release tests carried out and reported below. This represents a considerable advantage for the health and safety of the end user of these polymers. Furthermore, the antibacterial properties of the polymer are optimal as demonstrated by the bacterial proliferation measurement tests below.

The antibacterial polymer of the invention is effective to contain or eliminate the bacterial proliferation of Gram- and Gram + bacteria, for example Escherichia Coli Staphylococcus Aureus, Pseudomonas aeruginosa, Acinetobacter baum, Ent. Cloacae, C. albicans and Clostriudim difficile.

The antibacterial polymers thus obtained can be used directly to prepare artifacts with antiseptic properties or mixed with polymers of the same chemical nature or of other chemical nature to give an antibacterial polymer which can then be used to prepare antibacterial products.

The manufactured articles can preferably be obtained by molding (for example by means of a male-female mold or by injection molding), hot forming or extrusion of the antibacterial polymer.

Such artifacts can be, for example, computer mice, computer keyboards, covers for phones and tablets, door handles, plastic handrails, antibacterial coatings for panic bars, antibacterial film for surfaces that must have a high degree of cleaning, frames for glasses, etc.

In a further aspect, the invention relates to an article which can be obtained from the antibacterial polymer by, for example, molding (for example injection molding and male-female molding), hot forming or extrusion.

In a preferred embodiment, the manufactured article is prepared by bringing the antibacterial polymer to the melting temperature. This temperature is obviously different depending on the polymer to be used. Once melted, this is injected, preferably through special nozzles, into a mold which has the shape of the final product to be made. Once filled, the mold is then brought to a temperature between 150 ° C and 350 ° C, preferably between 160 ° C and 220 ° C, at which the mold is opened in order to be able to remove the manufactured article.

EXAMPLES

For the realization of the PP with antibacterial properties we start from the propylene monomer.

An initial quantity of propylene (50 grams) is dispersed in a mixture of solvents comprising: ethyl alcohol 10%, water 90%, and having a total weight equal to 1 kg.

A solution of zinc salts is added to the monomer solution comprising: 2 g of ZnPCA. The solution thus obtained is subjected to a synthesis temperature between 55 ° C and 65 ° C.

To this mixture it is necessary to add the appropriate catalyst indispensable for the polymer synthesis.

For the realization of PVC with antibacterial properties we start from vinyl chloride. An initial quantity of vinyl chloride (50 grams) is dispersed in a mixture of organic solvents composed of: 9% ethyl alcohol, 10% water, 7% methanol, 60% acetone and 14% isopropyl alcohol, and having a total weight equal to to 1 kg.

A zinc salt solution is added to the monomer solution containing: 1 g of ZnPCA, 0.1g zinc oxide, 0.2g zinc hydroxide, 0.2g zinc pyrrolidone and 0.2g zinc pyrithione. The mixture is heated to the synthesis temperature between 50 ° C and 65 ° C.

To make PET with antibacterial properties, we start from the ethylene monomer.

An initial quantity of Ethylene (50 grams) is dispersed in the mixture of solvents: 10% ethyl alcohol, 80% water, and 10% isopropyl alcohol, having a total weight of 1 kg.

A solution containing: 1 g of ZnPCA, 0.2g Zinc Oxide, 0.2g Zinc hydroxide, 0.2g Zinc pyrrolidone and 0.2g zinc pyrithione is added to the monomer solution. The mixture thus obtained is heated to the synthesis temperature as obtained between 60 ° C and 65 ° C.

To this mixture it is necessary to add the appropriate catalyst indispensable for the polymer synthesis.

For the realization of the PP with antibacterial properties we start from the propylene monomer.

An initial quantity of propylene (50 grams) is dispersed in a mixture of solvents comprising: ethyl alcohol 10%, water 90%, and having a total weight equal to 1 kg.

A solution of zinc salts is added to the monomer solution comprising: 1 g of ZnPCA, 0.2g Zinc Oxide, 0.2g Zinc hydroxide, 0.2 g Zinc pyrrolidone, and 0.2 g of zinc pyrithione. The mixture thus obtained is subjected to a synthesis temperature between 55 ° C and 65 ° C.

To this mixture it is necessary to add the appropriate catalyst indispensable for the polymer synthesis.

For the synthesis of PC with antibacterial properties we start from two different raw materials: Bisphenol A and phosgene.

A quantity equal to 221 g of Bisphenol A is dissolved in water. Once the dissolution process has taken place, soda is added to the aqueous solution to basify the solution and make the polymerization process possible.

At the same time an aqueous solution containing zinc and formed by 2 g of ZnPCA, and 0.2 g of zinc pyrithione is prepared.

The two aqueous solutions are then mixed.

A solution of phosgene (99 g) in CH2Cl2 is then prepared.

The two solutions are kept separate and the synthesis of the PC polymer takes place at the interface.

The temperature at which the process takes place is between 20 ° C and 60 ° C; in particular, a temperature between 30 ° C and 40 ° C was used.

To make nylon with antibacterial properties, a polymerization of 116 g of hexadethylamine with 185 g of adipic acid acyl chloride is carried out.

Hexadiethylamine is dissolved in a suitable quantity of water.

At the same time an aqueous solution containing zinc and formed by 2 g of ZnPCA, and 0.2 g of zinc pyrithione is prepared.

The two aqueous solutions are then mixed.

The acyl chloride of adipic acid is dissolved in a suitable aliquot of organic solvent, for example chloroform.

The two solutions are kept separate and the nylon synthesis takes place at the interface.

The temperature at which the process takes place is between 5 ° C and 70 ° C, in this case a temperature between 25 ° C and 35 ° C was used, temperature at which the polymerization process takes place at the interface of the two solutions.

To make polystyrene with antibacterial properties, the polymerization of the styrene monomer is carried out.

A suitable quantity of styrene (30 g) is solubilized in a suitable quantity of water (1 kg).

At the same time an aqueous solution containing zinc and formed by 2 g of ZnPCA, and 0.2 g of zinc pyrithione is prepared.

The two solutions are then combined in the presence of suitable catalysts such as peroxides, at a polymerization temperature between 50 ° C and 150 ° C, preferably between 70 ° C and 120 ° C.

Production of polypropylene (PP) phone covers

An initial quantity of polypropylene (PP) obtained according to the process described above, is loaded at the entrance of the machine suitable for the formation of telephone covers.

A heating apparatus brings the PP polymer granules to a temperature of 180 ° C, melting them.

The mass of polymer thus prepared is then inserted into special molds through preheated nozzles.

The molds (male and female) give the molten polymer the desired shape, which corresponds to that of the phone covers.

Once the molding has taken place, the mold undergoes a cooling process that lasts a few seconds, at the end of which it is opened to allow the manufactured article to come out.

In the course of a second preferred embodiment, a heating apparatus brings the PP polymer granules to a temperature of 180 ° C, melting them.

The mass of polymer thus prepared is then injected into special molds through preheated nozzles.

The mold gives the molten polymer the desired shape.

Once the injection has taken place, the mold undergoes a cooling process that lasts a few seconds, at the end of which it is opened to allow the manufactured article to come out.

RELEASE TEST OF ZINC IONS

To carry out these release tests, the product (for example the telephone cover of the previous example) made with an antibacterial polymer described in the present patent, was introduced into a beaker and completely submerged with a known volume of food simulant.

Subsequently, the beakers thus composed were placed inside a thermostated oven at 70 ° C for a total time of 2 hours.

At the end of the time (defined by current legislation regarding the global and specific migration of metals and dyes in products suitable for food contact), the beaker was removed from the stove. The simulant taken from the beaker and was analyzed by ICP to determine any zinc present inside the simulant.

The simulants used were water and 3% acetic acid.

In the following table the migration results obtained:

zinc migration (ppm) in the simulants used

water acetic acid typology

polymer

antibacterial

<0.001 <0.001 PVC

<0.001 <0.001 polystyrene

<0.001 <0.001 nylon

0.100 <0.001 PET

0.109 0.177 PP

0.332 0.332 ABS

<0.001 0.402 PC

The results obtained show that the release of zinc is lower than the 21 ppm permitted by law.

ANTIBACTERIAL ACTIVITY

A phone cover obtained by molding the antibacterial ABS polymer prepared above has been tested to evaluate the effectiveness of the polymer against the main microbial strains, defined by the regulations in force regarding plastic products that must come into contact with the skin. The product was tested for 2 types of bacterial strains (Escherichia Coli ATCC 8739 (Gram-) and Staphylococcus Aureus ATCC 6538 (Gram +)) using the international standard method for the evaluation of the antibacterial activity of plastic and non-porous surfaces.

Inoculum Printed Inoculum

CEPPI Reduction Initial reduction in polymeric control

MICROBIALS log%

(cfu / ml) Incubation (cfu / ml) (cfu / ml)

Escheriachia 2.5 x at 37 ° C for <7>

<6> 6.2 x 107 1.0 x 10 0.79 83.87% coli 10 24 h

Staphylococcus 1.7 x <6>

<6> 2.3 x 107 1.4 x 10 1.2 93.91% Aureus 10

The starting bacterial suspensions were diluted in order to obtain a known bacterial concentration expressed in colony forming units - cfu / ml. The covers analyzed were suitably sectioned, in order to create small pieces of the optimal size for carrying out the test. These were treated with the reference microbial strains, covered with sterile polyethylene film and placed in an incubator at a temperature of 37 ± 1 ° C for 24 hours. At the end of the incubation period, the samples were washed with a neutralizing solution on which the residual microbial load was then determined.

The results obtained show that after 24 hours of incubation at 37 ° C the zinc treated polymer reduces the bacterial load by 83.87% (in the case of Escherichia coli) and by 93.91% (in the case of staphylococcus aureus).

These tests were also repeated on the other polymers, obtaining a result in line with those indicated in the previous table.

Claims (16)

CLAIMS 1. Process for the preparation of an antibacterial polymer comprising the steps of: a) solubilizing or dispersing at least one zinc salt in at least one organic and / or aqueous solvent; b) adding the dispersion or solution thus obtained to the solution or dispersion in organic and / or aqueous solvent of at least one monomer; c) carrying out the polymerization of the at least one monomer. 2. Process according to claim 1, wherein said antibacterial polymer is a thermoplastic polymer, preferably selected from: polypropylene (PP), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), polyvinyl chloride (PVC) and polyethylene terephthalate ( PET), nylon and polystyrene. 3. Process according to claim 1 or 2, wherein said at least one monomer is propylene, polymerized in step c) to give the antibacterial polypropylene. 4. Process according to any one of claims 1 to 3, wherein said at least one monomer is a diol selected from: bisphenol A, 1,1-bis 1,1-bis (4-hydroxyphenyl) cyclohexane, dihydroxybenzophenone and tetramethyl cyclobutandiol , polymerized in step c) with a source of carbonate groups, preferably fonsgene or diphenyl carbonate, to give antibacterial polycarbonate. Process according to any one of claims 1 to 3, wherein said at least one monomer is a mixture of butadiene and acrylonitrile, polymerized in step c) in the presence of polystyrene to give antibacterial acrylonitrile butadiene-styrene (ABS). 6. Process according to any one of claims 1 to 3, wherein said at least one monomer is vinyl chloride, polymerized in step c) to give the antibacterial polyvinyl chloride. 7. Process according to any one of claims 1 to 3, wherein said at least one monomer is a mixture of terephthalic acid and ethylene glycol or dimethyl terephthalate and ethylene glycol, polymerized in step c) to give polyethylene terephthalate. Process according to any one of claims 1 to 7, wherein said solution or dispersion of the at least one zinc salt is added dropwise to the solution or dispersion of the at least one monomer, preferably before the start of the polymerization or during the polymerization reaction. Process according to any one of claims 1 to 8, wherein said at least one zinc salt is selected from: zinc PCA, zinc oxide, zinc hydroxide, zinc pyrrolidone, zinc pyrithione or their mixtures. 10. Process according to any one of claims 1 to 9, wherein said at least one zinc salt is added to the at least one monomer in an amount comprised between 0.1 and 10%, preferably between 0.1% and 5%, plus preferably between 0.2% and 2%. 11. Process according to claim 9 or 10, wherein said PCA zinc is added in a percentage comprised between 0.1% and 10%, preferably between 2% and 5%; said zinc oxide is added in a percentage comprised between 0.1% and 2%, preferably between 0.2% and 0.6%; zinc hydroxide is added in a percentage between 0.1% and 4%, preferably between 0.2% and 1%; said zinc pyrithione is used in a percentage comprised between 0.1% and 2%, preferably between 0.1% and 0.7%; said zinc pyrrolidone is used in a percentage between 0.01% and 3%, preferably between 0.1% and 1%. 12. Antibacterial polymer obtainable from the process according to any one of claims from 1 to 11, in which at least one zinc salt is dispersed inside the polymeric structure, giving the polymer antiseptic properties. 13. Antibacterial polymer according to claim 12, wherein said polymer is selected from: polypropylene (PP), polycarbonate (PC), acrylonitrile butadiene-styrene (ABS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET), nylon and polystyrene ( PS). 14. Use of the polymer according to claim 12 or 13 for the preparation of an antibacterial product or for mixing with other polymers. 15. An antibacterial product obtainable from the polymer according to claim 12 or 13, by molding, hot forming or extrusion of said polymer. 16. The product according to claim 15, selected from: computer mice, computer keyboards, covers for phones or tablets, door handles, plastic handrails, antibacterial coatings for panic bars, antibacterial film for surfaces that must have a high degree of cleanliness and eyeglass frames.