WO2014017933A1

WO2014017933A1 - Composition containing polyamide, silica and silver nanoparticles, and stabilizing additives

Info

Publication number: WO2014017933A1
Application number: PCT/PL2012/000086
Authority: WO
Inventors: Grażyna RYMARZ; Krzysztof BORTEL; Barbara CICHY; Marta Stechman
Original assignee: Splast Sp Z Oo Sp K
Current assignee: Splast Sp Z Oo Sp K
Priority date: 2012-07-23
Filing date: 2012-09-11
Publication date: 2014-01-30
Anticipated expiration: 2015-01-23
Also published as: PL400101A1; CZ2015119A3; PL221727B1

Description

COMPOSITION CONTAINING POLYAMIDE, SILICA AND SILVER NANOPARTICLES , AND

STABILIZING ADDITIVES

Field of the invention

The subject of the invention is a new kind of composition containing polyamide and 5 stabilizing additives. The stabilizers are: an antioxidant, UV absorber, UV stabilizer, synthetic precipitated silica having a nanometer particle sizes and silver nanoparticles. This

composition is characterized by increased mechanical strength, reduced susceptibility to contamination, hydrophobic surface and antibacterial properties. The composition may be used in particular for household appliances production, furniture and other products exposed 10 to weather conditions.

State of the art

There are known in the state of the art various compositions based on polyamides (in particular polyamide 6), which improve their mechanical properties, resistance to heat 15 and resistance to UV radiation.

The Polish patent PL203810 describes composition containing polyamide and an antioxidant. The composition according to the invention contains polyamide and 0.01 -5 wt% of antioxidant relative to the total mass of polyamide. The antioxidant is a sterically hindered phenol.

20 Polyamide resistant to heat and light was also described in the international patent

application WO 99/46323. According to the patent application, such resistance provides polyamide which contains derivative of a hindered piperidine. Polyamide with hindered piperidine derivatives was obtained in the polymerization process in the presence of aliphatic dicarboxylic acid as a chain length regulator.

25 According to the patent application US 2010/0028580 A1 , the invention is to produce the injection molded and extruded products from a polyamide composition. This polyamide composition includes a polyalcohol co-stabilizer form a group of secondary aryl amines, not specified enhancers and supplement with functional groups: compatibilizer. The composition of the invention is resistant to an elevated temperature and light.

30 A process of preparing a polyamide composition was described also in the patent application US 2010/0029820. Such composition was obtained by the condensation reaction of aromatic dicarboxylic acids with aliphatic diamines and included polyalcohols with more than two hydroxyl groups and not specified enhancers in an amount up to 60% by mass.

Composition based on polyamides with increased protection against degradation due to UV radiation (PA 6, Pa 6.6, PA 11 , PA 12, etc.) was described in the patent EP 0430650. This effect is achieved by the use of an antioxidant additives and UV stabilizers. As antioxidants are used:

a) tetrakis-(methylene-(3,5-di-(tert)-butyl-4-hydrocinnamate))methane in an amount of from 0.05% to 1.0%

b) bis (2,4-di-t-butylphenyl) pentraerythritol diphosphite (ULTRANOX 626) in an amount of from 0.05% to 1.5%

a stabilizer system:

a) bis(1 ,2,2,6,6-pentamethylpiperidin-4-yl) butyl(3,5-di-tert-butyl-4- hydroxybenzyl)malonate (eg. Tinuvin 144) in an amount of from 0.05% to 1.5% b) optional 2-[2-hydroxy-3,5-di-(1 ,1 -dimethylbenzyl)]-2H-benzotriazole in an amount of from 0.05% to 1.5% (eg. Tinuvin 234)

The methods for obtaining the polyamide composition comprising glass fiber are known from industrial practice. This type of reinforcement provides higher strength compared with the material without the addition of glass fiber. The relevant preparations of the fiber surface (siloxanes, titanates and other) and suitable compatibilizers with an affinity to the polymer as well as glass fiber were used for such composition in order to obtain good dispersibility glass fiber in polymer matrix and adhesion of the fibers with the polymer.

In the above documents relating to state of the art, there were only described polyamide compositions resistant to the high temperature and light (the UV radiation). The prior art does not disclose solutions characterized by the increased mechanical strength, reduced susceptibility to contamination, hydrophobic surface nor antibacterial properties.

In recent decades it is observed increased use of all kind of plastics in various fields of technology and development of the market of plastic products with a wide range of user requirements. One of the most important requirement is long-term resistance to changing weather conditions at the same time desired characteristics such as: smooth surface with hydrophobic properties (no wettable by water), increased mechanical strength properties or antibacterial properties (biostatic).

The subject of the invention is to obtain a new polyamide-based composition intended for processing by standard methods of production (injection and extrusion) and characterized by increased strength parameters, relatively low degree of filling strengthening additives (glass fiber in the amount of 10% wt), increased resistance to UV radiation, biostatic properties and hydrophobic surface.

All these features were obtained through the use of prescription systems with synergistic effects.

Detailed description of the invention

The subject of the invention is the polyamide-based composition containing additives such as antioxidant, UV absorber and UV stabilizer, synthetic precipitated silica having a nanometer particle sizes and silver nanoparticles, characterized in that it containing:

a) from 0.2 to 1.0 mass fraction of stabilizing additives, wherein:

i. as an antioxidant is derivative of hindered phenol

(N,N' -Hexamethylene-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionamide)) of formula 1 :

as UV absorber is derivative of benzotriazole of formula 2:

iii. as UV stabilizer is HALS-3 compound (Polymer of N, N'-Bis(2, 2,6,6- tetramethyl-4-piperidinyl)1 ,6-hexanediamine 8t 2,4,6-trichloro-1 ,3,5-triazine & 2,4,4-trimethyl-1 ,2-pentanamine) of formula 3:

b) from 2 to 10 mass fraction of synthetic precipitated silica having a nanometer particle sizes

Preferably, when the composition containing from 0.4 to 0.8 mass fraction (m/m) of stabilizing additives. Also preferably, when ratio of an antioxidant, UV absorber and UV stabilizer is from 1 :1 :1 to 1 :1 :2.5.

Preferably, when the surface of synthetic precipitated silica is modified with fatty amines of formula 4:

H₂

C ^fatty amine

FT ^iv wherein: R means C8 to C22 alkane or C8 to C22 alkene and the modification occurs by reaction of isolated silanol groups with fatty amines, as a replacement of hydrogen in silanol group by amine group with substituent R. Especially preferred when the surface of synthetic precipitated silica is modified with fatty amines of formula 4, wherein: R means C12 to C18 alkane or C12 to C18 alkene and concentration of fatty amines is from 0.2 to 5%.

Preferably, when the composition contains 3 to 6 mass fraction of synthetic precipitated silica nanoparticles or organic precipitated silicates nanoparticles.

Also preferably, when the composition contains from 0.005 to 0.03 mass fraction of silver nanoparticles, and especially preferred composition contains from 0.01 to 0.02 mass fraction of silver nanoparticles.

A most important aspect of the present invention is to enrich the standard polyamide

(especially Polyamide 6: polycaprolactam) with or without conventional strengthening materials (glass fiber, microspheres) with use of following enriching additives:

1 ) A mixture of stabilizing additives in the proportions given above as: an antioxidant, UV absorber and UV stabilizer, whereas the antioxidant is derivative of hindered phenol of formula 1 , as the UV absorber is derivative of benzotriazole of formula 2, and the UV stabilizer is from the group of substituted aromatic amine of formula 3. Increase of resistance to UV radiation was observed during the experiments. Such polyamide-based composition has even 5 to 6 times longer time of use compared to composition without such additives (as a suitability time for use assumed the change of 50% of the selected parameter which is characteristic of the product).

) The addition of the synthetic precipitated silica nanoparticles in size in the

proportions given above. As a result of the experiments it turned out that the addition of surface-modified silica to polyamide 6, the strength parameters improved by about 30-35%. Increase of tensile strength and impact resistance by Charpy's method as well as decrease of elongation at break were observed. Moreover the surface of product has become hydrophobic: a drop of water has not spilled on the surface of the plate - such surfaces are called self-cleaning.

Amorphous silica is composed of silicon -oxygen tetrahedra (Si0 )^4", which build very small particles agglomerating into larger clusters or chains of inorganic polymer structure. The structure of silica is responsible for its ability to exchange ions.

Inorganic polymer is based on a nonpolar siloxane groups (Si-O-Si) and silanol groups. The latter group is distinguished by the free silanol groups, the even silanol groups and the associated silanol groups. Isolated silanol groups (Si-OH) are the most surface reactive groups, and provide a location for the physical adsorption of molecules and easily react with many substituents. Moreover the ability to detach the proton (Si-O^' and H⁺) in silanol groups causes the acidic properties of the product surface. Silanol groups are responsible for the surface modification by the substitution of new groups of atoms. The surface of silica with the silanol groups could react with a variety of chemical compounds such as: silanes, metals halides, non-metals halides, alcohols. According to electron structure and properties of the Si-0 bonds can be determined that those are processes of nucleophilic and electrophilic substitutions.

The surface silicon atom connected to the electrically neutral hydroxyl group can be used as a center for nucleophilic reagent. Substituent enters into the group located in the surface layer while the surface of silica is an electron acceptor.

The surface of silica may have also electron donor properties in the case of interacting with electron acceptor substances. This is the result of inseparable pair of electrons presence in oxygen atom from hydroxyl group.

These concern both the silica obtained by precipitation or pyrogenic methods.

However, the preparation affects the properties of the obtained silica. Pyrogenic silica is characterized by more regular shapes of particles, which are similar to the spherical forms as well as reduced the content of silanol group responsible for silica reactivity. Reduced silanol groups content causes not only a reduced amount of water but also increased the presence of stable siloxane bonds. Precipitated silica has a much more (50%) of silonol groups responsible for silica reactivity. The modification of precipitated silica surface by a fatty amine of formula 4 is the most preferred for the preparation of polyamide composition, which also improves the compatibility of the polyamide - silica system.

3) The addition of silver nanoparticles in the proportions given above. The addition of silver nanoparticles enables to obtain the biostatic properties of polyamide products (limit of growth of fungi and mildew).

Products with these additives may be colored with conventional colorants used for polyamides.

Summary of the invention

The subject of the invention is the composition based on polyamide containing various enrichment additives such as: stabilizing additives as antioxidant, UV absorber and UV stabilizer, and/or synthetic precipitated silica or organic silicates having a nanometer particle sizes and nanoparticles of silver. The new polyamide material is characterized by strongly increased mechanical strength parameters in a long time of usage under weather conditions as well as new traits such as reduced susceptibility to contamination, hydrophobic surface and biostatic properties (antibacterial).

The composition formed in pellet may be used for further processing by any technique used in plastics processing.

Composition according to the invention is shown in detail in the following examples. The examples should not be interpreted as a limitation of its scope.

Example 1

Polyamide 6 for injection molding processing was dosed by the main loading hopper into the plastizing system of the twin-screw extrusion machine (compander) with selected configuration of the screw segments. The polyamide was pre-dried to moisture content of 0.1%. Gravimetric auxiliary feeders dosed the additives:

a) the stabilizing additives composition (antioxidant, UV absorber, UV stabilizer) against degrading effects of UV radiation, previously prepared in planetary mixer, with ratio 1 :1 :1 and amount 0,5 m/m

b) newly precipitated silica in amount of 4,5 m/m. The silica was previously obtained by the reaction of sodium silicate solution with an inorganic acid and next elutriated of sodium sulphate. The silica surface was modified by fatty amines in amount of 1% (m/m). Next the silica was dried and ground. The specific surface area of final product was about 125 m²/g and the particle size was 150 - 350 nm.

c) Silver nanoparticles powder in amount of 0.01 m/m

The polymer composition was plastized and homogenized at a temperature of about 220- 245°C. Then the composition was extruded as threads, which were pelletized by granulator in technological line. From such granulated products the injection molding fittings were made for study the mechanical strength properties. Part of these fittings were subjected to accelerated aging in weatherometer with xenon light source and cycle corresponding to the Mediterranean climate conditions. The test was carried out to the point where 50% change in tensile strength was achieved. Such decrease in strength occurred after 3500 hours. The fittings made from pure polyamide 6 (without additives) the 50 % decrease of tensile strength occurred after 600 hours.

The physical and mechanical properties characteristic of both, obtained polyamide composition and standard polyamide, which was the base for prepared multifunctional composition, is shown in table 1. Researches were performed for non -conditioned samples.

Table 1. The physical and mechanical properties characteristic of polyamide composition and standard polyamide

Polyamide 6 Composition of

Property [unit]

without additives example 1

Tensile strength [MPa] 78.0 99.6

Relative tensile elongation [%] 62.0 42.0

Impact resistance by Charpy's method [kJ/m2] No fracture No fracture

Impact resistance with notch by Charpy's method

12.0 16.8

[kJ/m2]

Water contact angle Θ [deg] 68 105

Accelerated aging [number of hours to 50% tensile

600 3500 strength initial value]

Number of bacteria E. coli after test [cfu/mL]

(initial number of bacteria in solution 5 x 108 Very numerous 0 cfu/mL)

Number of bacteria S. aureus after test [cfu/mL]

(initial number of bacteria in solution 1 x 108 Numerous 0 cfu/mL)

Total number of fungi [cfu/25cm2] Fungal colonies 1 Example 2

Polyamide 6 with 10% of glass fiber (GF) for injection molding processing was dosed by the main loading hopper into the plastizing system of the twin screw extrusion machine (compander) with selected configuration of the screw segments. The polyamide was pre-dried to moisture content of 0.1%. Gravimetric auxiliary feeders dosed the additives:

a) the stabilizing additives composition against degrading effects of UV radiation,

previously prepared in planetary mixer, with ratio 1 :1 :1 and amount 0,5 m/m b) newly precipitated silica in amount of 4,5 m/m. The silica was previously obtained by the reaction of sodium silicate solution with an inorganic acid and next elutriated of sodium sulphate. The silica surface was modified by fatty amines in amount of 1%

(m/m). Next the silica was dried and ground. The specific surface area of final product was about 125 m²/g and the particle size was 150 - 350 nm.

c) Silver nanoparticles powder in amount of 0.010 m/m

The physical and mechanical properties characteristic of both, obtained polyamide composition and standard polyamide (with 10% content of glass fiber), which was the base for prepared multifunctional composition, is shown in table 2. Researches were performed for non-conditioned samples.

Table 2. The physical and mechanical properties characteristic of polyamide composition and standard polyamide with 10% GF

Composition of

Property [unit] Polyamide 6 with

example 2

Tensile strength [MPa] 90.0 145

Relative tensile elongation [%] 2,5 12,6

Impact resistance by Charpy's method [kJ/m²] 30 65

Impact resistance with notch by Charpy's

5,6 9,8 method [kJ/m²] Water contact angle Θ [deg] 72 105

Accelerated aging [number of hours to 50%

600 3500 tensile strength initial value]

Number of bacteria f. co/i after test [cfu/mL]

(initial number of bacteria in solution 5 x 108 Very numerous 0 cfu/mL)

Number of bacteria S. aureus after test

[cfu/mL] (initial number of bacteria in solution Numerous 0

1 x 108 cfu/mL)

Total number of fungi [cfu/25cm²] Fungal colonies 2

The accelerated aging studies found that the most effective is the arrangement of all three additives (HALS, phenol derivative, benzotriazole) in proportions according to the invention. The 50% initial values of mechanical strength parameters (from 20 to 50%) were reached more easily in the case of use of these components separately than use all the additives of the stabilizer mixture. Similar, the use of two of the components is also less advantageous. The 50% mechanical strength properties change time was 40 - 75 % of time of all stabilizer mixture additives. Synergistic effect is obtained as a result of the combination of all three components. This allows the use of lower amounts of the compounds than should be if the stabilized material with one type of stabilizer.

Claims

1. The composition based on polyamide containing additives as an antioxidant, UV

absorber, UV stabilizer, synthetic precipitated silica having a nanometer particle sizes and silver nanoparticles, characterized in that it containing:

a. from 0.2 to 1.0 mass fraction of stabilizing additives, wherein:

i. as an antioxidant is derivative of hindered phenol

(N,N'-Hexamethylene-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionamide)) of formula 1 :

ii. as UV absorber is derivative of benzotriazole of formula 2:

iii. as UV stabilizer is HALS-3 compound (Polymer of N, N' -Bis(2,

2,6,6- tetramethyl-4-piperidinyl)1 ,6-hexanediamine & 2,4,6-trichloro-1 ,

3,5- triazine & 2,4,4-trimethyl-1 ,2-pentanamine) of formula 3:

b. from 2 to 10 mass fraction of synthetic precipitated silica having a particle size 150 - 350 nm

The composition according to claim 1 , characterized in that it containing from 0.

4 to 0.8 mass fraction (m/m) of stabilizing additives.

The composition according to claim 1 , characterized in that ratio of an antioxidant, UV absorber and UV stabilizer is from 1 :1 :1 to 1 :1 :2.5.

The composition according to claim 1 , characterized in that the surface of synthetic silica is modified with fatty amines of formula 4:

H₂

C ^fatty amine wherein: R is C8 to C22 alkane or C8 to C22 alkene,

and the modification occurs by reaction of isolated silanol groups with fatty amines, as a replacement of hydrogen in silanol group by amine group with substituent R.

5. The composition according to claim 4, characterized in that the surface of synthetic precipitated silica is modified with fatty amines of formula 4, wherein: R means C12 to C18 alkane or C12 to C18 alkene and concentration of fatty amines is from 0.2 to 5%.

6. The composition according to claim 1 , characterized in that it containing from 3 to 6 mass fraction of the synthetic precipitated silica with particles 150 - 350 nm in size

7. The composition according to claim 1 , characterized in that it containing from 0.005 to 0.03 mass fraction of silver nanoparticles.

8. The composition according to claim 7, characterized in that it containing from 0.01 to 0.02 mass fraction of silver nanoparticles.