Bishop, Timothy D. (186 Wedgewood Road, Oxford, PA, 19363, US)
Bersted, Bruce (6470 Ivey Hill Drive, Cumming, GE, 30040, US)
Bishop, Timothy D. (186 Wedgewood Road, Oxford, PA, 19363, US)
| 1. | Safety equipment to protect a wearer comprising a polymer composition comprising: an aromatic polyamide having a melting point, and above 10 wt. %, based on the total weight of the polymer composition, of at least one functionalized polyolefin impact modifier having a glass transition temperature below10°C. |
| 2. | Safety equipment according to claim 1, characterized in that it is a protective face or head gear. |
| 3. | Safety equipment according to claim 1 or 2, characterized in that it is a welding helmet or mask. |
| 4. | Safety equipment according to anyone of claims 1 to 3, characterized in that the aromatic polyamide is a polyphthalamide. |
| 5. | Safety equipment according to anyone of claims 1 to 4, characterized in that the aromatic polyamide has a melting point greater than 280 °C. |
| 6. | Safety equipment according to anyone of claims 1 to 5, characterized in that the functionalized polyolefin impact modifier is a functionalized ethylene/propylene/diene terpolymer. |
| 7. | Safety equipment according to anyone of claims 1 to 6, characterized in that the polymer composition comprises at least about 15 % by weight, based on the total weight of the polymer composition, of the functionalized polyolefin impact modifier. |
| 8. | Safety equipment according to anyone of claims 1 to 7, characterized in that the polymer composition further comprises an aliphatic polyamide. |
| 9. | Safety equipment according to anyone of claims 1 to 7, characterized in that the polymer composition further comprises a lactamderived aliphatic polyamide. |
| 10. | Safety equipment according to claim 9, characterized in that the lactamderived aliphatic polyamide is nylon 12. |
| 11. | Safety equipment according to either claim 9 or 10, characterized in that the lactamderived aliphatic polyamide is comprised in the polymer composition in an amount of at least about 2.5 % by weight, based on the total weight of the polymer composition. |
| 12. | Safety equipment according to anyone of claims 9 to 11, characterized in that the lactamderived aliphatic polyamide is comprised in the polymer composition in an amount of up to about 10 % by weight, based on the total weight of the polymer composition. |
| 13. | Polymer composition comprising: an aromatic polyamide having a melting point, and above 10 wt. %, based on the total weight of the polymer composition, of at least one functionalized polyolefin impact modifier having a glass transition temperature below10°C. |
| 14. | Polymer composition according to claim 13, characterized in that the aromatic polyamide is a polyphthalamide. |
| 15. | Polymer composition according to either claim 13 or 14, characterized in that the functionalized polyolefin impact modifier is a functionalized ethylene/propylene/diene terpolymer. |
| 16. | Polymer composition according to anyone of claims 13 to 15, characterized in that the polymer composition further comprises an aliphatic polyamide. |
| 17. | Polymer composition according to anyone of claims 13 to 15, characterized in that the polymer composition further comprises a lactamderived aliphatic polyamide. |
| 18. | Polymer composition according to claim 17, characterized in that the lactamderived aliphatic polyamide is nylon 12. |
| 19. | Polymer composition according to either claim 17 or 18, characterized in that the lactamderived aliphatic polyamide is comprised in the polymer composition in an amount of at least about 2.5 % by weight, based on the total weight of the polymer composition. |
| 20. | Polymer composition according to anyone of claims 17 to 19, characterized in that the lactamderived aliphatic polyamide is comprised in the polymer composition in an amount of up to about 10 % by weight, based on the total weight of the polymer composition. |
60/547,840, filed February 27,2004.
BACKGROUND OF THE INVENTION Safety equipment to protect a wearer is required by many occupations. In particular, safety equipment can be used to protect the wearer from mechanical impact, exposure to temperature extremes, and protection from actinic radiation.
The wearer should usually be understood as the living body, in general a person, who wears the safety equipment as a body covering.
An example of safety equipment is protective face and head gear, such as welding helmets and masks. For comfort and ease of use it is desirable that wearable safety equipment be light weight. Polymeric compositions are useful for making light-weight wearable safety equipment.
Three characteristics are paramount in protective face and head gear, such as welding helmets and masks. First, the helmet/mask must have thermal characteristics that protect the wearer from molten metal and sparks during welding. Second, the helmet/mask must have an opacity level such that no damaging ultraviolet (UV) light is transmitted through the welding helmet/mask and damages the welder's eyesight. Third, the helmet/mask must have good impact properties.
SUMMARY OF THE INVENTION In order to provide a wearable robust safety equipment that would consistently meet or exceed end use requirements and solve the problems associated with long flow lengths, inconsistent impact strength, and poor surface aesthetics, new and improved polymer compositions were investigated.
An aspect of the present invention concerns a safety equipment to protect a wearer comprising a polymer composition comprising an aromatic polyamide having a melting point, and above 10 wt. %, based on the total weight of the polymer composition, of at least one functionalized polyolefin impact modifier having a glass transition temperature below-10°C. Another aspect of the present
invention concerns a polymer composition which is well suited for making a safety equipment to protect a wearer.
DETAILED DESCRIPTION OF THE INVENTION It is an objective of the present invention to provide a robust safety equipment to protect a wearer that consistently meets or exceeds end use requirements and solves the problems associated with long flow lengths, inconsistent impact strength, and poor surface aesthetics.
With this end in view, the present invention concerns a safety equipment to protect a wearer comprising a polymer composition comprising : - an aromatic polyamide having a melting point, and - above 10 wt. %, based on the total weight of the polymer composition, of at least one functionalized polyolefin impact modifier having a glass transition temperature below-10°C.
In certain embodiments of the present invention, the safety equipment is a protective face or head gear. In certain embodiments of the present invention, the safety equipment is a welding helmet or mask.
In certain embodiments of the present invention, the safety equipment comprises more than 10 wt. %, based on the total weight of the safety equipment, of the polymer composition. In certain embodiments of the present invention, the safety equipment comprises more than 25 wt. %, based on the total weight of the safety equipment, of the polymer composition. In certain embodiments of the present invention, the safety equipment comprises more than 50 wt. %, based on the total weight of the safety equipment, of the polymer composition. In certain embodiments of the present invention, the safety equipment comprises more than 65 wt. % of the polymer composition.
To the purpose of the present invention,"aromatic polyamide"is intended to denote any polymer comprising at least 50 mole % of recurring units formed by the polycondensation reaction between at least one aromatic diacid and at least one diamine. The diamine can be either aliphatic or aromatic Metaxylylenediamine is an example of aromatic diamine. The aromatic polyamide may optionally comprise less than 50 mole % of aliphatic recurring units comprising an amide group, such as recurring units derived from an aliphatic diacid and an aliphatic diamine, recurring units derived from an aliphatic amino-acid and/or recurring units derived from an aliphatic lactam.
In certain embodiments of the present invention, the aromatic polyamide is a polyphthalamide, i. e. an aromatic polyamide comprising recurring units formed
by the polycondensation reaction between at least one phthalic diacid and at least one diamine.
The aromatic polyamide has a melting point. Aromatic polyamides having a melting point are usually semi-crystalline. In certain embodiments of the present invention, the aromatic polyamide has a melting point greater than 280 °C, preferably greater than 285°C and more preferably greater than 290°C ; besides, in these embodiments, the aromatic polyamide has a melting point advantageously below 310°C, preferably below 305°C and more preferably below 300 °C.
The melting point of the aromatic polyamide can be measured by any suitable technique known from the skilled in the art; very often, it is measured by Differential Scanning Calorimetry. Precisely, Universal V3.7A Instruments DSC calorimeter was used by the Applicant to measure the melting point of the aromatic polyamide. For this purpose, it was preliminarily checked that the calorimeter was well-calibrated by means of a calibration sample. Then, the aromatic polyamide of which the melting point had to be measured was submitted to the following heating/cooling cycle: 1"heating from room temperature up to 350°C at a rate of 10°C/min, followed by cooling from 350°C down to room temperature at a rate of 20°C/min, followed by 2"d heating from room temperature up to 350°C at a rate of 10°C/min. The melting point was measured during 2"heating. Melting is an endothermic first-order transition that appears as a negative peak on the DSC scan. The melting point is advantageously determined by a construction procedure on the heat flow curve : the intersection of the two lines that are tangent to the peak at the points of inflection on either side of the peak define the peak temperature, namely the melting point.
Suitable polyphthalamides included within the scope of invention include any partially aromatic polyphthalamide, in particular any polyphthalamide further comprising recurring units formed by the polycondensation reaction between at least one aliphatic diacid and at least one diamine. Suitable polyphthalamides for certain embodiments of the present invention comprise recurring units formed by the polycondensation reaction between at least one phthalic diacid and at least one aliphatic diamine. In certain embodiments, the phthalic acid is terephthalic acid. In certain other embodiments of the present invention, the phthalic acid comprises terephthalic acid and isophthalic acid. In other certain embodiments of the present invention, the polyphthalamide further
comprises recurring units formed by the polycondensation reaction between at least one aliphatic diacid, such as adipic acid, and at least one aliphatic diamine.
In certain other embodiments of the present invention, the diamine is an aliphatic diamine comprising from 4 to 12 carbon items, such as hexamethylenediamine (HMDA), nonanediamine, 2-methyl-1, 5 pentadiamine, and 1, 4-diaminobutane.
In certain embodiments of the present invention, from at least about 40 mole % to about 100 mole % of dicarboxylic acid used in fonning the aromatic polyamide is chosen from aromatic dicarboxylic acids. In certain embodiments of the present invention, the aromatic polyamide comprises: - from about 50 mole % to about 100 mole % of terephthalamide recurring units (i. e. recurring units formed by the polycondensation reaction between terephthalic acid and at least one aliphatic diamine, in particular hexamethylene diamine), - from about 35 mole % to about 0 mole % of isophthalamide recurring units (i. e. recurring units formed by the polycondensation reaction between isophthalic acid and at least one aliphatic diamine, in particular hexamethylene diamine), and - from about 50 mole % to about 0 mole % of recurring units formed by the polycondensation reaction between at least one aliphatic diacid and at least one aliphatic diamine (in particular adipamide recurring units, i. e. recurring units formed by the polycondensation reaction between adipic acid and at least one aliphatic diamine, in particular hexamethylene diamine).
In certain embodiments of the present invention, the aromatic polyamide comprises up to about 75 mole % terephthalamide recurring units. In certain other embodiments of the present invention, the aromatic polyamide comprises up to about 60 mole % terephthalamide units. In certain embodiments of the present invention, the aromatic polyamide comprises at least about 10 mole % adipamide recurring units. In certain other embodiments of the present invention, the aromatic polyamide comprises at least about 30 mole % adipamide recurring units. In certain other embodiments of the present invention, the aromatic polyamide comprises at least about 40 mole % adipamide recurring units. In certain embodiments of the present invention, the aromatic polymer comprises up to about 10 mole % isophthalamide recurring units.
Suitable aromatic polyamides for embodiments of the present invention in the present invention are available as AMODEL polyphthalamides from Solvay Advanced Polymers, L. L. C.
Suitable polyphthalamides for certain other embodiments of the present invention are disclosed in U. S. Patent Nos. 5,436, 294; 5,447, 980; and Re34,447, the entire disclosures of which are incorporated herein by reference. hi certain embodiments of the present invention, the polymer composition comprises at least about 30 % by weight of the aromatic polyamide. In certain embodiments of the present invention, the polymer composition comprises at least about 50 % by weight of the aromatic polyamide. In certain embodiments of the present invention, the polymer composition comprises up to about 80 weight % of the aromatic polyamide.
In certain embodiments of the present invention, the polymer composition comprises at least about 15 % by weight, based on the total weight of the polymer composition, of the functionalized polyolefin impact modifier. In certain embodiments of the present invention, the polymer composition comprises up to about 35 weight % of the functionalized polyolefin impact modifier. In certain embodiments of the present invention, the polymer composition comprises up to about 30 weight % of the functionalized polyolefin impact modifier. In certain embodiments of the present invention, the polymer composition comprises up to about 25 weight % of the functionalized polyolefin impact modifier. In certain embodiments of the present invention, the polymer composition comprises about 20 weight % of the functionalized polyolefin impact modifier.
Any functionalized polyolefin impact modifier that has a glass transition temperature lower than-10 °C is suitable for this invention.
The glass transition temperature of the functionalized polyolefin impact modifier can be measured by any suitable technique known from the skilled in the art, in particular by Differential Scanning Calorimetry. For example, a Mettler DSC 30 calorimeter can be used to measure the glass transition temperature of the functionalized polyolefin impact modifier. For this purpose, it is advantageously preliminarily checked that the calorimeter is well-calibrated by means of a calibration sample. Then, the functionalized polyolefin impact modifier of which the the glass transition temperature has to be measured is submitted to the following cooling/heating cycle: 15t cooling from room temperature down to-100°C at a rate of 20°C/min, followed by 1 St heating from - 100°C up to +100°C at a rate of 10°C/min, followed by 2nd cooling from +100°C down to-100°C at a rate of 20°C/min, followed by 2nd l1eating from- 100°C up to +100°C at a rate of 10°C/min. The glass transition temperature is measured during 2nd heating. The glass transition temperature is advantageously
determined by a construction procedure on the heat flow curve: a first tangent line to the curve above the transition region is constructed; a second tangent line to the curve below the transition region is also constructed; the temperature on the curve halfway between the two tangent lines, or l/2 delta Cp, is the glass transition temperature. hi certain embodiments of the present invention, the functionalized polyolefin impact modifier has one and only one glass transition temperature. In certain other embodiments of the present invention, the functionalized polyolefin impact modifier is a block copolymer which has two or still more glass transition temperatures, at least one of them being lower than-10°C. To the purpose of the present invention, functionalized polyolefin impact modifiers having one and only one glass transition temperature are preferred over functionalized polyolefin impact modifiers having two or more glass transition temperatures.
In certain embodiments of the present invention, the functionalized polyolefin impact modifier has a glass transition temperature of less than about- 20 °C. In certain embodiments of the present invention, the functionalized polyolefin impact modifier has a glass transition temperature of less than about- 30 °C. In certain embodiments of the present invention, the functionalized polyolefin impact modifier has a glass transition temperature of above about- 65 °C.
Suitable functionalized polyolefin impact modifiers for use in certain embodiments of the present invention, are soft and rubbery.
Suitable functionalized polyolefin impact modifiers for use in certain embodiments of the present invention, comprise polar functional groups. In certain embodiments of the invention, the functionalized polyolefin impact modifier comprises carboxyl functionality. hi certain embodiments of the invention, the functionalized polyolefin impact modifier comprises at least about 0.1 weight %, and preferably at least about 0.5 weight %, of carboxyl functionality. In certain embodiments of the invention, the functionalized polyolefin impact modifier comprises up to about 5 weight %, and preferably up to about 2.0 weight %, of carboxyl functionality.
The functionalized polyolefin impact modifier that may be used in certain embodiments of the present invention include those having a melt flow rate (MFR) of at least about 0.5 g/10 min. The MFR of the functionalized polyolefin impact modifier according to certain embodiments of the present invention may be up to about 200 g/10 min. The MFR of the functionalized
polyolefin impact modifier is usually measured according to conventional methods, e. g. in accordance with ISO standards. For example, as concerns functionalized polyolefin impact modifiers comprising recurring units derived from ethylene, ISO 1133 (1991) is advantageously used, and the MFR is then usually measured at a temperature of 190°C and under a load of 5 kg.
In certain embodiments of the present invention, the functionalized impact modifier is dispersed in the aromatic polyamide. In certain polymer compositions used to form embodiments of the present invention, the functionalized impact modifier comprises polar groups that react with the aromatic polyamide, which results in enhanced adhesion to the aromatic polyamide matrix.
Suitable functionalized polyolefin impact modifiers are available from various commercial sources, notably: - maleic anhydride-functionalized ethylene-propylene copolymer rubbers comprising pendant succinic anhydride groups available as EXXELOR VA from the Exxon Mobil Chemical Company, such as EXXELOR VA 1801, - maleic anhydride-functionalized styrene/ethylene-butylene/styrene block copolymer rubbers available as KRATON FG from Kraton Polymers, such as KRATONe FG19OlX, - maleic anhydride-functionalized ethylene-propylene-diene terpolymer rubbers (EPDM rubber), such as ROYALTUF 498, a 1% maleic anhydride functionalized EPDM rubber, available from the Crompton Corporation.
Suitable functionalized polyolefin impact modifiers for use in certain embodiments of the present invention comprise recurring units derived from ethylene and/or propylene. Suitable functionalized polyolefin impact modifiers for use in certain embodiments of the present invention comprise further recurring units derived from one or more monomers chosen from monoolefins comprising from 4 to 12 carbon atoms like 1-butene and 1-hexene, diolefins like butadiene, (meth) acrylic monomers such as (meth) acrylic acid and its alkali (like sodium) or alkaline-earth (like zinc) metal salts and (meth) acrylic acid ester (s).
Recurring units derived from diolefins can be hydrogenated ; an example of a functionalized polyolefin impact modifier wherein recurring units derived from butadiene have been hydrogenated is KRATON FG19OlX, a 1% maleic anhydride grafted styrene/ethylene-butylene/styrene block copolymer comprising about 30 wt. % of polystyrene blocks available from Kraton Polymers.
The functionality of the functionalized polyolefin impact modifiers can be obtained by copolymerizing one or more functional monomers and/or by grafting one or more functional monomers. In particular, carboxyl functionality of the functionalized polyolefin impact modifiers can be obtained by copolymerizing one or more acrylic monomers chosen from acrylic acid and methacrylic acid, their alkali (like sodium) or alkaline-earth (link zinc) metal salts, acrylic acid esters and methacrylic acid esters. It can also be obtained by grafting one or more of said monomers, or anhydrides like maleic anhydride. Carboxylic acid groups can be partially or totally neutralized by an alkaline or alkaline-earth hydroxide or salt subsequent to the copolymerization or the grafting step.
In certain embodiments of the present invention functionalized polyolefin impact modifiers comprise recurring units derived from ethylene and propylene, with a ratio of ethylene radicals to propylene recurring units of from 40: 60 to 65: 30.
Functionalized ethylene/acrylate copolymers and ethylene/acrylic acid/acrylate terpolymers, as well as the corresponding co-and terpolymers with methacrylic derivatives, may be used in certain embodiments of the present invention provided they have a glass transition temperature below-10°C.
Examples thereof are functionalized rubbery ethyl acrylate-ethylene copolymers.
Other functionalized polyolefin impact modifiers that may be used in the practice of the invention include ethylene-higher alpha-olefin polymers that have been provided with reactive functionality by being grafted or copolymerized with suitable reactive carboxylic acids or their derivatives such as, for example, acrylic acid, methacrylic acid, maleic anhydride or their esters (impact modifiers (IM1)) ; they will have advantageously a tensile modulus up to about 50, 000 psi determined according to ASTM D-638. Suitable higher alpha-olefins include C3 to C8 alpha-olefins such as, for example, propylene, 1-butene, and 1-hexene.
Examples of suitable functionalized ethylene-higher alpha-olefin polymers are ethylene-1-octene elastomers available as ENGAGEO from DuPont (such as ENGAGE" 8550), on which maleic anhydride has been grafted.
Alternatively, functionalized polyolefin impact modifiers having structures comprising similar units may also be obtained through the hydrogenation of recurring units derived from a diene monomer, for example a 1-3 diene monomer (impact modifiers (IM2)). For example, ethylene-butadiene copolymers may be hydrogenated to provide ethylene-butylene copolymers structures. Similarly, hydrogenation of ethylene-isoprene copolymers may be employed to provide
equivalent ethylene-isobutylene copolymers.
A class of functionalized polyolefin impact modifiers of particular interest consists of polymers comprising recurring units from ethylene, at least one higher alpha-olefin polymer and at least one diene, and that have been provided with reactive functionality by being grafted or copolymerized with suitable reactive carboxylic acids or their derivatives such as, for example, acrylic acid, methacrylic acid, maleic anhydride or their esters (impact modifiers (IM3)), especially functionalized ethylene/propylene/diene terpolymers (commonly known as EPDM rubbers). Diene monomers that can be used for synthesizing functionalized polyolefin impact modifiers of this class include notably conjugated dienes, such as isoprene and 1,3-butadiene, non conjugated dienes of 4 to 24 carbon atoms, such as 1,4-butadiene, 1,4-hexadiene, 1,5-hexadiene, 2, 5-dimethyl-1, 5-hexadiene and 1,4-octadiene, cyclic dienes, such as cyclopentadiene, cyclohexadiene, cyclooctadiene and dicyclopentadiene, alkenylnorbornenes, such as 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5-norbornene and 2-isopropenyl-5-norbornene, and tricyclodienes, such as 3-methyltricyclo- [5. 2.1. 0.2. 6] deca-3,8-diene. The content of recurring units derived from diene monomer in the functionalized polyolefin impact modifiers of this class is preferably from about 0.5 % to about 10 % by weight, and in particular from about 1 % to about 5 % by weight, based on the total weight of the functionalized polyolefin impact modifier. Mole fractions of ethylene units and higher alpha-olefin units in the ethylene-higher alpha-olefin copolymer rubbers generally range from about 40: 60 to about 95: 5.
Also suitable are functionalized block copolymers comprising at least two polymeric blocks, at least one block (B 1) being a block of a polymer chosen from (IM1), (IM2) and (IM3) impact modifiers and at least one block (B2) being a block of an optionally substituted styrene, especially a block of a polystyrene homopolymer. Examples thereof are functionalized styrene-monoolefins block polymers like functionalized SEBS, functionalized SEB, functionalized SEPS and functionalized SEP (where S is for styrene, E is for ethylene, P is for propylene and B is for butylene obtained by the hydrogenation of recurring units derived from butadiene).
Suitable functionalized polyolefin impact modifiers for use in certain embodiments of the present invention do not comprise recurring units derived from ethylene and/or propylene. Examples thereof are functionalized styrene-
diolefins block polymers like functionalized Sp, fimctionalized SPS, functionalized SIS and functionalized ABS (where S is for styrene, P is for butadiene, I is for isoprene and A is for acrylonitrile).
The functionalized polyolefin impact modifiers suitable for preparing the polymer compositions from which are made the safety equipments of the present invention are not limited the above described ones.
In certain embodiments of the present invention, the polymer composition can comprise additional components, notably mold release agents, plasticizers, lubricants, and thermal stabilizers, light stabilizers, antioxidants, opacifying agents like pigments, and fillers.
The levels of these optional additives will be determined for the particular use envisioned, with up to about 50 weight %, based on the total weight of the polymer composition, of such additional additives considered to be within the range of ordinary practice in the extrusion art.
Embodiments A class of mold release agents of interest in certain embodiments (E-1) of the present invention consists of aliphatic polyamides; one or more aliphatic polyamides may be comprised in the polymer composition.
To the purpose of the present invention,"aliphatic polyamide"is intended to denote any polymer comprising more than 50 mole % of recurring units formed by the polycondensation reaction between at least one aliphatic diacid and at least one aliphatic diamine, and/or of at least one aliphatic amino-acid, and/or of at least one aliphatic lactam.
Among other aliphatic polyamides as above defined, there are polymers comprising more than 50 mole % of recurring units formed by the polycondensation reaction between at least one aliphatic diacid and at least one aliphatic diamine, hereafter referred to as"diacid/diamine-derived aliphatic polyamides" ; an exemplary diacid/diamine-derived aliphatic polyamide is nylon 12,12, because it gave superior results over shorter-chain homologues like nylon 6,6.
In embodiments (E-1), the amount of the aliphatic polyamide in the polymer composition is advantageously up to about 20 % by weight (based on the total weight of the composition), and preferably up to about 10 % by weight ; besides, it is advantageously at least about 1.0 % by weight, and preferably at least about 2.5 % by weight.
Embodiments (E-2).
A class of mold release agents of particular interest in certain embodiments (E-2) of the present invention consists of aliphatic polyamides of a specific type [hereadter, type (T) ] ; one or more aliphatic polyamides of type (T) may be comprised in the polymer composition.
Polyamides of type (T) are those comprising more than 50 mole % of recurring units formed by the polycondensation reaction of at least one aliphatic amino-acid and/or at least one aliphatic lactam.
Among other aliphatic polyamides of type (T), are polymers comprising more than 50 mole % of recurring units formed by the polycondensation reaction of at least one aliphatic amino-acid, hereafter referred to as"amino-acid-derived aliphatic polyamides" ; an exemplary amino-acid-derived aliphatic polyamide is nylon 11 (which is the homopolymer formed by the condensation reaction of -aminoundecanoic acid).
In embodiments (E-2), the amount of the aliphatic polyamide of type (T) in the polymer composition is advantageously up to about 20 % by weight (based on the total weight of the composition), and preferably up to about 10 % by weight; besides, it is advantageously at least about 1.0 % by weight, and preferably at least about 2.5 % by weight.
Embodiments (E-3).
A class of mold release agents of very particular interest in certain embodiments (E-3) of the present invention consists of aliphatic polyamides of a very specific type, hereafter referred to as"lactam-derived aliphatic polyamides" ; one or more lactam-derived aliphatic polyamides may be comprised in the polymer composition.
To the purpose of the present invention, a lactam-derived aliphatic polyamide is intended to denote any polymer comprising more than 50 mole % of recurring units formed by the polycondensation reaction of at least one aliphatic lactam.
The lactam-derived aliphatic polyamide comprises preferably more than 90 mole % of recurring units formed by the polycondensation reaction the aliphatic lactam; more preferably, all the recurring units of the lactam-derived aliphatic polyamide are formed by the polycondensation reaction of the aliphatic lactam.
Non limitative examples of suitable aliphatic lactams are y-butyrolactam, s-caprolactam, a-methylcaprolactam, (3-methylcaprolactam, y-methylcaprolactam, 6-methylcaprolactam, s-methylcaprolactam,
N-methylcaprolactam, p. y-dimethylcaprolactam, y-ethylcaprolactam, y-isopropylcaprolactam, s-isopropylcaprolactam, y-butylcaprolactam, s-nantholactam, co-enantholactam, rj-caprylolactam, co-caprylolactam, co-aurolactam (also referred to as 2-azacyclotridecanone), 2-azacyclopentadecanone and 2-azacycloheptadecanone.
The aliphatic lactam has advantageously at least 4, preferably at least 7, more preferably at least 10 and still more preferably at least 12 carbon atoms- Besides, it has advantageously at most 18 carbon atoms, preferably at most 15 carbon atoms and more preferably at most 12 carbon atoms. The most preferred aliphatic lactam is co-laurolactam.
The lactam-derived aliphatic polyamide has advantageously a melting point. Lactam-derived aliphatic polyamides having a melting point are usually semi-crystalline. The melting point of the lactam-derived aliphatic polyamide is preferably above 150°C and more preferably above 165°C ; besides, it is preferably below 210°C and more preferably below 190°C.
Excellent results were obtained when the lactam-derived aliphatic polyamide was nylon 12. Nylon 12 is the homopolymer formed by the polycondensation reaction ofm-laurolactam. Nylon 12 is a semi-crystalline lactam-derived aliphatic polyamide having a melting point of about 178°C. An exemplary nylon 12 is VESTAMID L-1700, available from Degussa.
In embodiments (E-3), the amount of the lactam-derived aliphatic polyamide in the polymer composition is advantageously up to about 20 % by weight, preferably up to about 10 % by weight, more preferably up to 8% by weight, and still more preferably up to about 6.0 % by weight (based on the total weight of the polymer composition). Besides, the amount of the lactam-derived aliphatic polyamide in the polymer composition is advantageously at least about 1.0 % by weight, preferably at least about 2.5 % by weight, and more preferably at least about 3.5 % by weight (based on the total weight of the composition).
In embodiments (E-3), the lactam-derived aliphatic polyamide can be used as sole aliphatic polyamide, or in combination with an amino-acid-derived aliphatic polyamide and/or a diacid/diamine-derived aliphatic polyamide ; it is preferably used as sole aliphatic polyamide, or in combination with an amino- acid-derived aliphatic polyamide and/or a diacid/diamine-derived-aliphatic polyamide, wherein the diacid/diamine-derived-aliphatic polyamide over the amino-acid-derived aliphatic polyamide ratio ranges from 0 to 45% ; it is more preferably used as sole aliphatic polyamide, or in combination with an amino-
acid-derived aliphatic polyamide. The weight of the lactam-derived aliphatic polyamide, based on the total weight of the aliphatic polyamide, ranges advantageously from 45% to 100%; it ranges preferably from 75% up to 100% ; still more preferably, the aliphatic polyamide consists of the lactam-derived aliphatic polyamide.
Suitable pigments for use in the present invention include carbon black. In certain embodiments, the pigment is present in the polymer composition in an amount of up to about 10 % by weight.
Fillers can be notably in fibrous or in particulate form. Fibrous fillers useful in forming certain safety equipments may include glass fiber, carbon or graphite fibers, as well as fibers formed from high temperature engineering resins such as, for example, poly (benzothiazole), poly (benzimidazole), polyarylates, poly (benzoxazole), polyarylethers and the like, and may include mixtures comprising two or more of such fibers. Suitable fibers will be preferably selected from glass fibers, carbon fibers and aramide fibers such as the fibers sold by the DuPont Company under the trade name KEVLAR@. Particulate fillers are preferably nucleating agents such as talc and mica.
The amount of fibrous filler, and preferably the overall amount of filler too (whatever its form), is advantageously less than 20 wt. %, preferably less than 10 wt. %, more preferably less than 5 wt. % and still more preferably less than 3 wt. %, based on the total weight of the polymer composition. Filler-free polymer compositions gave excellent results.
While, in general, there is no absolute limitation as to the nature of the optional additional components, certain components are usually disliked because they have sometimes an adverse effect upon the desired properties of the safety equipment. Among such ingredients are polyphenylethers like poly (2,6- dimethylphenylene-1, 4-ether) s; thus, the polymer composition comprises advantageously from 0 to 5 wt. % of polyphenylether and the polymer composition is preferably free of polyphenylether.
It is another objective of the present invention to provide a polymer composition which is well suited for a making robust safety equipment to protect a wearer that consistently meets or exceeds end use requirements and solves the problems associated with long flow lengths, inconsistent impact strength, and surface defects.
With this end in view, the present invention concerns a polymer composition comprising : - an aromatic polyamide having a melting point, - above 10 wt. %, based on the total weight of the polymer composition, of at least one functionalized polyolefin impact modifier having a glass transition temperature below-10°C.
The polymer composition according to the present invention has the same characteristics as the polymer composition comprised in the safety equipment according to the present invention as above detailed, in all its embodiments.
Examples El to E9 (polymer composition according to the invention) and comparative example CE1 (polymer composition to the contrary) Three levels of functionalized polyolefin impact modifier and three types of flow modifier underwent testing. The various polymer compositions tested are listed in Table 1. Polyphthalamide (PPA1) is a polyphthalamide consisting of about 55 wt. % of recurring units formed by the polycondensation reaction between phthalic diacid, essentially terephthalic diacid, and hexamethylene diamine, and about 45 wt. % of recurring units formed by the polycondensation reaction between adipic acid and hexamethylene diamine.
The various polymer compositions were evaluated for use in welding helmets/masks and the test data is given in Table 2. The flow modifiers evaluated included a linear low density polyethylene (LLDPE), an alkaline-earth salt of a long chain carboxylic acid, and nylon 12.
It was observed that an aliphatic polyamide, such as nylon 12, improved the surface appearance of the safety equipment molded from the aromatic polyamide composition. Safety equipments to protect a wearer, according to certain embodiments of the present invention, such as welding helmets, formed from polymer compositions that comprise nylon 12 as an additive, have more regular surface characteristics than welding helmets formed from polymer compositions without nylon 12.
Table 1 Components EXAMPLES 1 2 3 4 5 6 7 8 9 CE1 Polyphthalamide (PPA1) 74.3 70.5 74.8 69.5 65.7 79.5 79.0 75.3 70.0 74.1 (wt. %) ROYALITUF# 498 19 19 19 23.8 23.8 14.3 14.3 14.3 23. 8 0 1 % maleic anhydride functionalized EPDM rubber (wt. %) EXXELOR PO 1015 0 0 0 0 0 0 0 0 0 9.7 Maleic anhydride functionalized polypropylene (wt. %) KRATON"'FG1901X000000 000 9.7 1 % maleic anhydride functionalized SEBS block copolymer (wt. %) LLDPE (wt. %) 1 0 0 1 0 0 1 0 0 0 Nylon 12 (wt. %) 0 4.8 0 0 4.8 0 0 4.8 0 4.8 Alkaline-earth salt of a long 0 0 0.5 0 0 0.5 0 0 0.5 0 chain carboxylic acid (wt. %) Carbon black (wt. %) 5 5 5 5 5 5 5 5 5 0 Other conventional 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 1.7 ingredients of polyphthalamide compositions (antioxidant, mold release,...) (wt. %) Total (wt. %) 100 100 100 100 100 100 100 100 100 100 Table 2 Izod Dynatup Dynatup Impact Dynatup # Energy Max Total Kayeness (ft-Ductile Load Energy viscosity T5 MFR Examples Ibs/in) Breaks (ft-lbs) (ft-lbs) (poise) g/10min 1 6.1 5 of 5 18.8 28.2 2880 9.9 2 4.0 5 of 5 19.8 31.8 2550 9.5 3 2.3 4 of 5 16.2 24.7 2180 29.9 4 18.4 5 of 5 20.4 32.5 3880 1.5 5 11.2 5 of 5 18.3 30.7 3230 4.4 6 2.9 5of5 13.2 13.5 1810 51 7 2.8 5 of 5 23.4 35.9 2670 19.9 8 3.3 5 of 5 20.9 30.3 2550 19.9 9 4.2 0 of 5 4.5 4.5 2850 5.4 CE1 0.77 4 of 5 24.0 37.0 2570 5.1 The Izod impact test was run at standard ASTM conditions. The Dynatup impact test was run according to ASTM D3763 on 1/8 inch plaques. The BB test comprises shooting a number of BBs at various velocities and then inspecting the test sample for damage from the BB impact. The polymer compositions were evaluated for use in protective face and head gear based on three criteria: 1. Impact data based on Izod, Dynatup impact maximum energy and the number of ductile breaks, 2. flow properties measured by melt flow rate (MFR), and viscosity as measured with a Kayeness capillary viscosimeter, in which the viscosity was measured at 394 sec-1 after 5 minutes (referred to as T5) according to ASTM D3835, and 3. internal injection molding evaluations.
All 12 formulations were molded in an insert plaque mold where processing, surface appearance and weld line aesthetics were evaluated and compared.
The following observations were made based on the molding trials.
Example E10 (safety equipment according to the invention) and comparative example CE2 (safety equipment to the contrary) Welding helmets were made from the polymer composition according to example E5 (welding helmets E10) on one hand, and from the polymer
composition according to comparative example CE1 (welding helmets CE2) on the other hand.
Example E10 was processed initially exactly according to the same conditions as Comparative Example CE2. The melt temperature was 618 °F. In these conditions, the surfaces of the welding helmets E10 were similar in appearance to the surfaces of the control welding helmets CE2 except the flow lines were more pronounced. However, reducing the injection speed improved the flow lines, so that after optimizing the process conditions, the surface appearance of the welding helmets E10, according to the invention, was similar to the surface appearance of the control welding helmets CE2. In the case of example E10, no part sticking was detected.
A welding helmet E10 was tested and passed successfully the 300 ft/sec BB impact test.
Example Ell (safety equipment according to the invention) Welding helmets were also made from the polymer composition according to example E2 (welding helmets Ell).
Example Ell was processed initially exactly under the same conditions as comparative example CE2. In these conditions, the surface appearance of the welding helmets Ell was cleaner and clearer than the surface appearance of the welding helmets E10, and the flow lines were less apparent. As for example E10, the injection speed was reduced to minimize flow lines. After optimizing the process conditions, the surface appearance of the welding helmets El 1, according to the invention, was similar to the surface appearance of the control welding helmets CE2. In the case of example El 1, no part sticking was detected.
A welding helmet El l was tested and passed successfully the 300 ft/sec BB impact test.
Welding helmets (in particular protective faces and head gears) E10 and El l, according to the invention, dramatically demonstrated improved impact strength relative to control welding helmets CE2.
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