Patent Application
20050043461
This application claims the priority of Japanese Patent Application NO. 2001-023768 filed on Jan. 31, 2001, NO. 2001-023939 filed on Jan. 31, 2001, NO. 2001-194507 filed on Jun. 27, 2001, NO. 2001-194509 filed on Jun. 27, 2001, and NO. 2001-312885 filed on Oct. 10, 2001. This application is a continuation-in-part application of U.S. patent application Ser. No. 10/058,327 filed on Jan. 30, 2002.
The present invention relates to a flame-retardancy-imparting material capable of ensuring a material composed of a resin or so an excellent flame retardancy, a flame-retardant polymer material, and a method for imparting flame retardancy.
Resin materials are used in a wide variety of fields and demands therefor are still growing for their desirable chemical and physical properties, and for excellent moldability and processability. Most of resin materials are however highly combustible enough to limit the application range thereof, so that there has been a strong demand for providing flame retardancy to such resin materials.
While halogen-base flame retarder has been most popular as a flame retarder for flame retarding finish for resin materials, this type of flame retarder is now understood as undesirable from an environmental viewpoint since it can generate dioxin or furan. So that there is a strong demand for development and practical application of ecological flame retarder. Also phosphorus-base flame retarder, which is of non-halogen-base, is undesirable since it can emit phosphine, a hydride of phosphorus.
There is also known inorganic flame retarder such as aluminum hydroxide and magnesium hydroxide, and in particular aluminum hydroxide enjoys a large demand of all flame retarders since it is advantageous in low hazardousness, low fuming property, electric insulation property and low cost. In approaches of imparting flame retardancy through addition of inorganic flame retarder such as aluminum hydroxide and magnesium hydroxide to a resin or the like, a satisfactory level of flame retardancy is obtainable only when it is added in a large amount to the resin, wherein it is necessary to mix it typically in an amount of 150 parts by weight or more per 100 parts by weight of the resin. This is a most critical drawback of the inorganic flame retarder, and is consequently a reason why the inorganic flame retarder cannot widely be accepted. More specifically, blending of such large amount of inorganic flame retarder to the resin undesirably lowers mechanical strength of the resin, and tends to degrade the waterproof property. Addition of a large amount of inorganic flame retarder raises another problem of increase in viscosity of the compound, which is causative of an adverse effect on moldability of the resin, and raises still another problem in that the combustion of the resin blended with such inorganic flame retarder for the purpose of disposal or so may result in a large amount of deposited combustion residue derived from such inorganic flame retarder.
It is also disadvantageous for the inorganic flame retarders that they need be mixed with other flame retarder since independent use thereof can attain only a small degree of flame retardant effect. There is also known a vitreous flame retarder using a low-melting-point glass, but problems reside in that demanding complicated production process, large amount of addition to the resin and high production cost, and in that achieving only a poor waterproof property.
It is therefore an object of the present invention to solve the foregoing problems and to provide a flame-retardancy-imparting material and a flame-retardant polymer material containing thereof, both of which being aimed at achieving excellent flame retardancy at a low amount of addition to resin or so without degrading various properties of such resin, and low production of combustion residue when such resin or so is combusted for disposal.
A flame-retardancy-imparting material of the present invention proposed to solve the foregoing problems is such that being used for ensuring a target object, which mainly comprises a polymer material, flame retardancy as being dispersed therein or immobilized on the surface thereof, and wherein the flame-retardancy-imparting material contains a group expressed as NxOy (where, x and y are positive integers) (for example, ammonium nitrate) and a group capable of generating water upon heating (for example, aluminum hydroxide).
Such flame-retardancy-imparting material containing a group expressed as NxOy (where, x and y are positive integers) and a group capable of generating water upon heating can be compounded (added) with a target object such as resin by mixing or immobilization. When such target object is exposed to a high temperature (e.g., 500° C. or above), both of a water component generating group and a nitrogen-containing, combustion-inhibitory gas generated by heating from the group expressed as NxOy (where, x and y are positive integers) are responsible for providing the target object an excellent flame retardancy in a cooperative manner. More specifically, this successfully allows provision of flame retardancy satisfying a level from V-0 to V-2 when tested in compliance with the procedures of UL-94 combustibility test (this specification follows the fifth edition, Oct. 26, 1996).
In one more preferred embodiment, the group expressed as NxOy (where, x and y are positive integers) is contained in a form of a compound selected from the group consisting of nitric acid compound, nitrous acid compound and hyponitrous acid compound. More specifically, a compound selected from the group consisting of metal nitrate, nitric acid ester and ammonium nitrate is available. The metal nitrate can be exemplified by zinc nitrate hexahydrate, nickel nitrate hexahydrate, copper nitrate hexahydrate, iron nitrate nonahydrate, aluminum nitrate nonahydrate, cerium nitrate hexahydrate and ammonium cerium nitrate.
The metal nitrate or organic/inorganic nitric acid compound generates nitrogen oxide (NxOy) upon heating. Possible examples of the organic/inorganic nitric acid compound include acetyl nitrate (C2H3NO4); aniline nitrate (C6H8N2O3); nitric acid esters (RONO2) such as methyl nitrate (CH3ONO2), ethyl nitrate (C2H5ONO2), butyl nitrate (C4H9ONO2), isoamyl nitrate ((CH3)2CHCH2CH2ONO2), isobutyl nitrate ((CH3)2CHCH2ONO2) and isopropyl nitrate ((CH3)2CHONO2); ammonium nitrate (NH4NO3); guanidine nitrate (CH6N4O3); nitroacetylcellulose; nitrocellulose; urea nitrate (HNO3.CO(NH2)2); hydrazinium nitrate (N2H5NO3); hydroxylammonium nitrate ([NH3OH]NO3) and benzendiazonium nitrate (C6H5N3O3). The nitrous acid compound is also available, and examples thereof include ammonium nitrite (NH4NO2); and nitrous acid esters (RONO) such as methyl nitrite (CH3ONO), ethyl nitrite (C2H5ONO), propyl nitrite (C3H7ONO), isopropyl nitrite ((CH3)2CHONO), butyl nitrite (C4H9ONO), isobuthyl nitrite ((CH3)2CHCH2ONO) and isoamyl nitrite (amyl nitrite) ((CH3)2CHCH2CH2ONO). Also the hyponitrous acid compound can be exemplified by metal salt and ammonium salt of hyponitrous ion (N2O22−). The nitrogen compound represented by such metal nitrate, and organic/inorganic nitric acid compound is preferably used in a form of dry preparation. Non-dried preparation may degrade moldability and physical properties of the product due to lowered decomposition temperature. While the nitrogen compound is preferably used in a grain form with an average grain size of 0.01 to 100 ìm, those in a form of liquid or solution are also available.
In one more preferred embodiment, the nitric acid compound, nitrous acid compound and hyponitrous acid compound are non-metallic. This desirably prevent a resin, the target substance, from being colored due to addition of the flame-retardancy-imparting material. Coloring is probably ascribable to metal ion. For example, non-metallic ammonium nitrate (NH4NO3) is proper as the nitric salt used in the present invention since it is inexpensive and is not causative of such coloring of the target substance. In contrast, intentional use of coloring by the metal nitrate will be valuable for the case the coloring of the target substance is desired. Some of the metal nitrate have a decomposition temperature higher than that of non-metallic nitrate, so that they are advantageous in that allowing setting of the molding temperature of the resin material at a relatively higher level. It is thus recommendable to selectively use the non-metallic nitrate or metallic nitrate by purposes. Anyway such coloring by no means indicates ruining of the flame retardancy and moldability of the target object.
In one more preferred embodiment, the nitric acid compound, nitrous acid compound and hyponitrous acid compound are subjected to surface treatment for improving the affinity with the target object. The surface treatment is preferably given by using any one agent selected from the group consisting of those of Si-base, Ti-base, Al-base, olefin-base, fatty-acid-base, oil-and-fat-base, wax-base and surfactant-base. Specific examples thereof include those using silane coupling agent, titanate-base coupling agent or aluminate-base coupling agent; those using fatty-acid such as stearic acid, oleic acid, linoleic acid, linolenic acid or eleostrearic acid; those using salt of fatty-acid such as Ca salt or Zn salt of the foregoing fatty-acids; those using nonionic surfactant such as polyethylene glycol derivative; those using polyethylene-base or polypropylene-base wax; carboxylate-base coupling agent and phosphate-base coupling agent.
It is also allowable to subject the nitric acid compound, nitrous acid compound and hyponitrous acid compound to surface treatment with silica, in order to improve the moisture-proof property. In particular for the case where ammonium nitrate is used as the nitric acid compound, it is preferable to grind it so as to achieve an average grain size of 0.01 to 100 μm, and to further subject it to the surface treatment (moisture-proofing treatment) with silica.
More specifically, the surface treatment may be coating with a vitreous precursor composition capable of generating vitreous ceramic upon heating onto such nitrogen compound. When the target object is exposed to a high temperature (e.g., 500° C. or above), such vitreous precursor composition produces vitreous ceramic, and such vitreous ceramic serves as a protective film to thereby allow the target object to have an excellent flame retardancy.
The vitreous precursor composition is such that containing silicon component and/or metal component together with oxygen, and the resultant vitreous ceramic obtained by heating is such that being mainly composed of silicon oxide and/or metal oxide. Since the silicon component and/or metal component is likely to produce a vitreous ceramic through oxidation by heating, and the resultant vitreous ceramic mainly composed of silicon oxide and/or metal oxide is excellent in heat resistance, so that the vitreous precursor composition used for the surface treatment in the present invention is particularly preferable when it contains silicon component and/or metal component together with oxygen. The metal component herein can be any one or combination of two or more of Ti, Cu, Al, Zn, Ni, Zr and other transition metals. The vitreous ceramic may preliminarily be contained in the compound as a part thereof, or may exist in a form such that allowing conversion into such vitreous ceramic only after a part or the entire portion of the compound is heated. So-called sol-gel process is one possible method for the surface treatment with such vitreous precursor composition.
Another surface treatment relates to such that coating the nitrogen compound using stearic acid as a fatty-acid-base agent. Thus surface-treated nitrogen compound will be improved in the compatibility (affinity) with the target object such as resin or so, which allows the nitrogen compound to be dispersed in or immobilized on the target object in a uniform manner. The surface treatment with stearic acid can be effected by, for example, mixing 100 parts by weight of the nitrogen compound with 0.01 to 1 parts by weight of stearic acid under stirring, and then heating the mixture within a temperature range from 70 to 80° C.
The flame-retardancy-imparting material of the present invention may also be such that containing a product obtained by reacting a compound having a group expressed as NxOy (where, x and y are positive integers) with a compound having a group capable of generating water upon heating. For example, it may be a nitric-acid-base composite compound obtained by reacting a hydroxide with nitric acid, and more specifically, a compound having in a single molecule at least a hydroxyl group and/or a group with crystal water, and a group expressed as NxOy (where, x and y are positive integers).
In one more preferred embodiment, the group capable of generating water upon heating is contained in a form of a hydroxyl-group-containing compound. Metal hydroxide is recommendable for such hydroxyl-group-containing compound. More specifically, it is exemplified by a compound mainly comprising at least one compound selected from the group consisting of aluminum hydroxide, magnesium hydroxide and calcium hydroxide. That is, any mixtures comprising two or more compounds selected from aluminum hydroxide, magnesium hydroxide and calcium hydroxide are also allowable. It is still also allowable to use a compound having in its composition two or more metal elements. Possible examples thereof include calcium aluminate hydrate (3CaO.Al2O3.6H2O) and hydrotalcite (Mg6Al2(OH)16CO3.4H2O). Now such hydrotalcite (Mg6Al2(OH)16CO3.4H2O) is referred to as a compound which contains hydroxyl groups and crystal waters, and contains a plurality of metal elements in the composition thereof. The hydroxyl-group-containing compound and hydrate compound used herein preferably have a granular form with an average grain size of 0.1 to 100 μm.
Other examples available for the present invention include metal hydroxide selected from zinc hydroxide, cerium hydroxide, iron hydroxide, copper hydroxide, titanium hydroxide, barium hydroxide, beryllium hydroxide, manganese hydroxide, strontium hydroxide, zirconium hydroxide and gallium hydroxide; mineral such as boehmite containing such metal hydroxide; and basic magnesium carbonate.
Of course the foregoing surface treatment can be applied to the hydroxyl-group-containing compound composing the flame-retardancy-imparting material. In particular for the case where aluminum hydroxide is used as the hydroxyl-group-containing compound, it is preferable to grind it so as to achieve an average grain size of 0.1 to 100 μm, and to further subject it to the surface treatment with a fatty-acid-base treatment agent. This facilitates blending with the polymer material.
Next, a flame-retardant polymer material of the present invention is such that having a matrix which comprises a polymer material and has dispersed therein a flame-retardancy-imparting material which contains a group expressed as NxOy (where, x and y are positive integers) and a group capable of generating water upon heating.
Another flame-retardant polymer material of the present invention is such that having a matrix which comprises a polymer material and has immobilized on the surface thereof a flame-retardancy-imparting material which contains a group expressed as NxOy (where, x and y are positive integers) and a group capable of generating water upon heating. Such flame-retardancy-imparting material can partially be immobilized on the surface of the matrix and can partially be dispersed in such matrix.
Still another flame-retardant polymer material of the present invention is such that having a matrix which comprises a polymer material and has immobilized thereon a flame-retardancy-imparting material which contains a compound selected from the group consisting of nitric acid compound, nitrous acid compound and hyponitrous acid compound, together with a hydroxyl-group-containing compound.
Such polymer materials having added thereto the flame-retardancy-imparting material of the present invention can retain an excellent moldability without ruining the intrinsic properties thereof. The present invention can also provide a masterbatch which is a grain-formed molded product containing a polymer matrix having dispersed therein the flame-retardancy-imparting material, and which is used for molding to thereby obtain a product having a secondary form and a volume larger than that of the individual grain.
It is to be noted that the flame-retardancy-imparting material of the present invention can be used in combination with conventional inorganic and/or organic flame retarders. Specific examples of such known flame retarders include inorganic flame retarders typified by micas such as muscovite, phlogopite, biotite and sericite; minerals such as kaoline, talc, zeolite, borax, diaspore and gypsum; metal oxides such as magnesium oxide, aluminum oxide, antimony oxide and silicon dioxide; metal compounds such as calcium carbonate; zinc-base flame retarders such as zinc borate, zinc sulfate and zinc stannate; phosphorus-base compounds such as red phosphorus, ester of phosphoric acid and ammonium polyphosphate; and vitreous flame retarders containing low-melting-point glass; organic flame retarders typified by those of phosphorus-base, silicone-base and nitrogen-base; and metal powders.
In another aspect, the flame-retardancy-imparting material of the present invention is such that being used for ensuring a target object, which mainly comprises a polymer material, flame retardancy as being dispersed therein or immobilized on the surface thereof, wherein the flame-retardancy-imparting material contains a combustion-inhibitory oxidative decomposition accelerator which oxidatively decomposes such polymer material upon heating to thereby ensure such target object combustion-inhibitory property.
Another flame-retardancy-imparting material of the present invention is such that being used for ensuring a target object, which mainly comprises a polymer material, flame retardancy as being dispersed therein or immobilized on the surface thereof, wherein the flame-retardancy-imparting material contains a combustion-inhibitory oxidative decomposition accelerator which oxidatively decomposes such polymer material at the combustion temperature of the polymer material or at a lower temperature than such combustion temperature to thereby ensure such target object combustion-inhibitory property.
The flame-retardancy-imparting material containing such combustion-inhibitory oxidative decomposition accelerator can be compounded (added) with a target object by, for example, mixing or immobilization. When such target object is exposed to a high temperature (e.g., approx. 200 to 500° C., or higher), the combustion-inhibitory oxidative decomposition accelerator is activated by the heat to oxidatively decompose the target object (thermal oxidative decomposition), to thereby provide the target object an excellent flame retardancy. Here the flame retardancy is provided through oxidation without being associated with flame before the target object starts to burn in flame, and the combustion-inhibitory oxidative decomposition is supposed to proceed during the temperature elevation and before combustion in flame. In more detail, the combustion-inhibitory oxidative decomposition accelerator oxidatively decomposes the target object during or immediately before the combustion of such target object to thereby denature the target object into non-combustible components such as CO2 and H2O. It is to be understood now that combustion in the context of the present invention typically refers to such that proceeding in the air and being associated with flame. Such flame-retardancy-imparting material of the present invention can provide an excellent flame retardancy in a small amount of addition, which is advantageous in that avoiding degradation of various properties of the target object and reducing the production cost.
The combustion-inhibitory oxidative decomposition accelerator can contain an oxidant. In this case, flame retardancy is provided through oxidative decomposition of the target object by such oxidant. Such oxidant can be at least one compound selected from the group consisting of nitric acid, nitric acid compound, permanganate, chromic acid, chromic acid compound, peroxide, salt of peroxoacid, salt of sulfuric acid, oxygen-base substance and oxide. Specific examples thereof include HNO3, HNO2, N2O3, N2O4, KMnO4, MnO2, Mn(CH3CO2)3, CrO3, Na2Cr2O7, H2O2, Na2O2, (C6H5CO)2O2, CH3CO3H, C6H5CO3H, K2S2O8, Fe2(SO4)3, O2, PbO, HgO, AgO and Ag2O.
The combustion-inhibitory oxidative decomposition accelerator may be such that containing a nitrogen compound and a hydroxyl-group-containing compound. In this case, the target object is given with the flame retardancy through a process in which, during or before the combustion of such target object, the nitrogen compound generates a nitrogen oxide, the hydroxyl-group-containing compound generates water, such nitrogen oxide and water then react with each other to produce nitric acid, and such nitric acid denatures the polymer material by thermal oxidation to produce non-combustible components such as CO2 and H2O. It is to be understood now that “denaturalization” in the context of this specification also includes changes caused by chemical reaction associated with breakage of covalent bond.
More specifically, for the case a metal hydroxide is used as the hydroxyl-group-containing compound, the nitrogen compound is preferably a nitric acid compound having a decomposition temperature of 50 to 600° C. Since most of metal hydroxide have a decomposition temperature at approx. 400° C. or below, and will cause dehydration when heated to approx. 400° C. So that using such nitric acid compound having a decomposition temperature of 50 to 400° C. as the nitrogen compound allows smooth progress of the reaction between the independently generated nitrogen oxide and water. For the case that aluminum hydroxide (decomposition temperature is approx. 300° C.) is used as the metal hydroxide, the nitrogen compound preferably has a decomposition temperature of 50 to 350° C., and more preferably 100 to 300° C. For the case that magnesium hydroxide (decomposition temperature is approx. 350° C.) is used as the metal hydroxide, the nitrogen compound is preferably a nitric acid compound having a decomposition temperature of 50 to 400° C., and more preferably 200 to 400° C. for the same reason. The nitric acid compound can be selected from those listed in the above. The same will apply to the foregoing hydroxyl-group-containing compound.
The combustion-inhibitory oxidative decomposition accelerator can be contained in an amount of 150 parts by weight or below per 100 parts by weight of the target object. In the conventional procedure for adding an inorganic flame retarder such as aluminum hydroxide, a necessary amount of blending thereof was as much as 150 to 200 parts by weight or around per 100 parts by weight of the target object. On the contrary, the flame-retardancy-imparting material of the present invention containing a nitrogen compound and a hydroxyl-group-containing compound can efficiently provide the flame retardancy, so that an amount of addition of such combustion-inhibitory oxidative decomposition accelerator of only as small as 150 parts by weight or below per 100 parts by weight of the target object will successfully result in a sufficient level of flame retardancy, which may be even attainable by the addition of 100 parts by weight or below, and even by 50 parts by weight or less in some cases. More specifically, the amount of addition of the combustion-inhibitory oxidative decomposition accelerator is preferably within a range typically from 5 to 150 parts by weight, more preferably 10 to 100 parts by weight, and still more preferably 20 to 80 parts by weight, where a particularly preferable range resides in a range from 30 to 70 parts by weight. The more the amount of addition increases, the more the target object becomes sensitive to property changes and the cost becomes large. On the contrary, too small amount of addition may fail in providing a sufficient level of flame retardancy, so that the amount of addition is preferably adjusted within the foregoing ranges.
That is, the flame-retardancy-imparting material of the present invention is preferably added to 100 parts by weight of the target object to be provided with flame retardancy so as to attain contents of the nitrogen compound of 0.1 to 50 parts by weight and hydroxyl-group-containing compound of 10 to 100 parts by weight. A content of the nitrogen compound of less than 0.1 parts by weight may degrade the efficiency in providing flame retardancy, and exceeding 50 parts by weight may result in cost increase. A preferable range of content of the nitrogen compound is 1 to 20 parts by weight or around. On the other hand, a content of the hydroxyl-group-containing compound of less than 10 parts by weight may degrade the efficiency in providing flame retardancy, and exceeding 100 parts by weight may undesirably modify properties of the target object. More specifically, mechanical strength or moldability of the target object may be ruined. This is also disadvantageous in that a large amount of combustion residue may deposit within an incinerator. A preferable range of content of the hydroxyl-group-containing compound is 30 to 70 parts by weight or around.
The flame-retardancy-imparting material of the present invention preferably has a content of the nitrogen compound (for example, ammonium nitrate ) of 0.05 to 0.2 parts by weight per one part by weight of the hydroxyl-group-containing compound (for example, aluminum hydroxide). The content of the nitrogen compound of less than 0.05 parts by weight per one part by weight of the hydroxyl-group-containing compound may result in a degraded imparting ability of flame retardancy. On the other hand, the content of the nitrogen compound exceeding 0.2 parts by weight may result in only a limited range of improvement in the flame retardant ability against expectation as judged from the amount of addition, or may result in modified properties of the target material.
Since the flame-retardancy-imparting material preferably has the content of the nitrogen compound of 0.05 to 0.2 parts by weight per one part by weight of the hydroxyl-group-containing compound, when the content of the hydroxyl-group-containing compound (for example, aluminum hydroxide) is in the range from 10 to 100 parts by weight per 100 parts by weight of the polymer material, the content of the nitrogen compound (for example, ammonium nitrate) is preferably in the range from 0.5 to 20 parts by weight. In the same manner, when the content of the hydroxyl-group-containing compound is in the range from 30 to 70 parts by weight per 100 parts by weight of the polymer material, the content of the nitrogen compound is preferably in the range from 1.5 to 14 parts by weight.
In another aspect, the flame-retardant polymer material of the present invention is such that mainly comprising a polymer component, wherein such flame-retardant polymer material shows in a spectrum of TDS analysis (thermal decomposition spectroscopy) in vacuo a peak attributable to a combustion-related gas component generated within a combustion temperature range of the polymer component, and a peak attributable to a combustion-inhibitory gas component containing at least a group expressed by COx (x is a positive integer) and generated within a temperature range lower than the combustion temperature range of the polymer component.
Some of the conventional flame-retardant polymer material have added therein a metal hydroxide, such as aluminum hydroxide, which decomposes upon heating to generate water. Heating of such polymer materials can generate H2O within a temperature range lower than the combustion temperature range thereof. Heating of the flame-retardant polymer material of the present invention will produce at least combustion-inhibitory gas expressed as COx, which is typified by CO and CO2. The combustion-inhibitory gas also contains other components such as H2O and NOx (where, x represents a positive integer, and typically NO, NO2, etc.). Since COx is non-combustible as being generally understood, it can be responsible for creating a flame-retardant atmosphere and inhibiting combustion (drastic oxidation) of the polymer material. Flame-retardant effect of the flame-retardant polymer material of the present invention can thus be confirmed also from the TDS analysis. The combustion-related gas component can be exemplified at least by those having a group expressed as CnHm (where, n and m are positive integers, and typically CH4, C2H6, C3H8, etc.). It is to be noted now that COx detected in the TDS analysis is not ascribable to residual COx remaining after the measurement apparatus is evacuated from the normal atmosphere to vacuum.
The temperature range lower than the combustion temperature range of the polymer component can typically be a range lower by 50 to 400° C. Note that such difference of the temperature range depends on the rate of temperature elevation in the TDS analysis, and the foregoing range is attained at a standard rate of temperature elevation in TDS analysis of the polymer material, which is typified as 500° C./min. The combustion initiation temperature of the polymer component can be defined as a temperature whereat hydrocarbon or CO2 vigorously starts to generate when the polymer component is heated in the air.
In another aspect, the flame-retardant polymer material of the present invention is such that mainly comprising a polymer component, wherein such flame-retardant polymer material shows a spectrum of TDS analysis (thermal decomposition spectroscopy) in vacuo in which a peak profile attributable to a combustible gas component generated by decomposition reaction of the polymer component; and a peak profile attributable to a non-combustible gas component generated as a decomposition product of the polymer component within a temperature range lower than that responsible for the start of the generation of such combustible gas component.
The target object of the measurement will never ignite nor burn when the combustion temperature thereof is attained in the TDS analysis in vacuo, since there is almost no oxygen. The target object of the measurement which is no more combustible will then cause breakage of the covalent bonds, and elimination of the decomposition products. The same will apply to a polymer without being provided with flame retardancy. The flame-retardant polymer material of the present invention can generate the non-combustible gas in the temperature range lower than the temperature range in which such decomposition and elimination occur. This allows the polymer material to be exposed to a flame-retardant atmosphere, to thereby exhibit the flame-retardant effect in the air. Similarly in the lower temperature range, a part of the polymer material is decomposed and emitted as the non-combustible gas component. Such process competes with the combustion (drastic oxidation) to thereby inhibit the combustion, which results in a desirable flame-retardant effect.
Best embodiments for carrying out the present invention will be detailed referring to the attached drawings.
The compound 531 can be molded into a grain form such as pellet or the like which is available as a masterbatch grain 32. The masterbatch grain 32 typically has a grain size of approx. 0.1 to 10 mm (more specifically approx. 1 to 4 mm) as being expressed by the diameter of an equivalent virtual sphere. While the shape of the masterbatch grain 32 is not specifically limited, the masterbatch grain 32 can typically be obtained by extruding the softened compound in a strand form, and then cutting the obtained strand into a predetermined length so as to form a columnar (cylindrical) grain, as shown in
The ammonium nitrate powder (ammonium nitrate grain) 10 and aluminum hydroxide powder (aluminum hydroxide grain) 39 may be subjected to surface treatment. One possible surface treatment agent is such that containing at least carbon component and that being capable of improving affinity between the polymer material 41 and ammonium nitrate powder (ammonium nitrate grain) 10. More specifically, any one compound selected from the group consisting of those of silane-base, titanate-base, aluminum-base, zirco-aluminum-base, olefin-base, fatty-acid-base, oil-and-fat-base, wax-base and surfactant-base is available.
It is also allowable to subject the ammonium nitrate powder (ammonium nitrate grain) 10 to surface treatment with silica for the purpose of improving the moisture-proofing property. On the other hand, it is particularly preferable to subject the aluminum hydroxide powder (aluminum hydroxide grain) 39 to surface treatment with a fatty-acid-base treatment agent for the purpose of improving the affinity with the polymer material 41.
One possible example of such surface treatment relates to coating of a vitreous precursor composition based on the sol-gel process, where the composition contains silicon component and/or metal component together with oxygen, and capable of producing vitreous ceramic typically by heating.
In the example shown in
Next, an exemplary production process of molded product (secondary molded product) using the masterbatch shown in
In an example shown in
In the injection apparatus 503, a feeding screw 509 driven by a hydraulic motor 513 as being transmitted by a shaft 512 is housed in a heating cylinder 507 which is heated by a heat source such as a band heater 508, and a hopper 510 for feeding masterbatch P is attached thereto. The masterbatch P is fed from the hopper 510 as the screw 509 rotates, and a polymer matrix is melted by heating within the heating cylinder 507 to produce a molten compound, which is then pooled in a pooling portion 507a. Advancing now the screw 509 in a predetermined length with the aid of the hydraulic cylinder 511 allows a predetermined amount of the molten compound to be injected within the die 505 through the runner 521.
As shown in
While the masterbatch grain 32 can independently be used to obtain the molded product as shown in
The content of the compound grain in the masterbatch grain to be diluted is as high as 20 to 67 wt % on the weight basis, so that it is preferable to blend a dispersion aid so as to uniformly disperse the compound grain at such a high content. Metallic soap is an example of preferable dispersion aid. The metallic soap can be exemplified as those having an organic acid component selected from naphthenic acid (naphthenate), lauric acid (laurate), stearic acid (stearate), oleic acid (oleate), 2-ethylhexanic acid (octate), fatty acid in linseed oil or soybean oil (linolate), tall oil (tollate) and rosin (rosinate) Examples of metal component are as listed below:
Of these, copper stearate and zinc stearate can be exemplified as specific examples of the metallic soap particularly excellent in dispersion effect (stearic acid treatment). It is to be noted that an excessive compounding of the metallic soap will raise a problem in material strength and homogeneity, and too small amount of compounding will result in insufficient dispersion effect, so that it is preferable to select the amount of compounding within a range typically from 0.01 to 3 wt % (more specifically, 0.3 wt %) so as to avoid such disadvantages.
Besides the foregoing examples, it is also allowable to separately prepare masterbatch A (not shown) having blended therein ammonium nitrate powder 10 and polymer material 41, and masterbatch B (not shown) having blended therein aluminum hydroxide powder 39 and polymer material 41, and then to mix both masterbatches A and B to thereby obtain a molded product. It is still also allowable to blend masterbatch A with aluminum hydroxide powder 39, or to blend masterbatch B with ammonium nitrate powder 10.
It is also allowable to compose the flame-retardant polymer material having compounded therein the flame-retardancy-imparting material of the present invention with a molding resin material, adhesive or paint of two-part-mixing type, which individually comprises a principal agent containing an uncured resin component such as epoxy resin, urethane resin (including urethane rubber) or silicone resin, and a curing agent for curing such uncured resin component.
A specific example of production of such molding material using epoxy resin will be explained referring to
The flame-retardancy-imparting material can also be immobilized on the surface of the polymer matrix.
In the present invention, the polymer material or polymer component composing the matrix is preferably selected from those mainly containing saturated hydrocarbon group, which are exemplified as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer and ethylene-polypropylene-diene copolymer (EPDM). Addition of the flame-retardancy-imparting material of the present invention into a polymer material mainly containing unsaturated hydrocarbon groups such as aromatic ring may be successful in providing flame retardancy but only in a limited degree as compared with the case it was added to a polymer material mainly containing saturated hydrocarbon groups, since oxidative decomposition of such polymer material cannot proceed smoothly due to the unsaturated hydrocarbon groups.
The flame-retardancy-imparting material of the present invention was subjected to the following experiments.
15 g of ammonium nitrate, 150 g of aluminum hydroxide and 300 g of polypropylene resin (PP) were mixed, and the obtained mixture was made into a polymer molded product (sample 1) using an extrusion/injection molding machine. Independently, 60 g of ammonium nitrate, 210 g of aluminum hydroxide and 300 g of polyethylene resin (PE) were mixed, and the obtained mixture was made into a polymer molded product (sample 2) using an extrusion/injection molding machine. Still independently, ammonium nitrate grain preliminarily subjected to SiO2 coating by the sol-gel process as shown in
Thus obtained samples 1 to 4 were tested by Determination of Burning Behavior by Oxygen Index (JIS K-7201), UL94 combustibility test (fifth edition, Oct. 26, 1996), moldability (judged as good if no oily bloom observed), coloring of resin (visual inspection) and tensile strength (JIS K-7113). Results were shown in Table 1.
All samples showed good results both in the oxygen index test and UL 94 test, which proved sufficient flame retardancy. Also the moldability was found to be desirable in all samples. No sample showed coloring of the resin. Samples 3 and 4, having the ammonium nitrate grain coated with SiO2 by the sol-gel process and with stearic acid, respectively, showed higher tensile strength as compared with that shown by samples 1 and 2. Also samples using ammonium nitrite in place of ammonium nitrate gave almost similar good results in the same test.
Next, sample 1a which is similar to sample 1 except that containing no ammonium nitrate, and sample 1b which is similar to sample 1 except that containing zinc nitrate in place of ammonium nitrate were similarly tested and compared with sample 1. Results were shown in Table 2.
Sample 1a containing no ammonium nitrate showed almost no flame-retardant effect, and sample 1b containing zinc nitrate in place of ammonium nitrate showed an almost equivalent level of flame retardancy with sample 1 but resulted in slight coloring of the resin. It is to be noted that addition of aluminum hydroxide and ammonium nitrate to the resin can produce white color ascribable to aluminum hydroxide. Such resin allows arbitrary coloring thereafter.
Next, sample 2a which is similar to sample 2 except that containing no ammonium nitrate, and sample 2b which is similar to sample 2 except that containing zinc nitrate in place of ammonium nitrate were similarly tested and compared with sample 2. Results were shown in Table 3.
Sample 2a containing no ammonium nitrate showed almost no flame-retardant effect, and sample 2b containing zinc nitrate in place of ammonium nitrate showed an almost equivalent level of flame retardancy with sample 2 but resulted in slight coloring of the resin.
Moreover, sample 5 which is similar to sample 1 except that containing guanidine nitrate in place of ammonium nitrate, sample 6 which is similar to sample 1 except that containing magnesium hydroxide in place of aluminum hydroxide, and sample 7 which is similar to sample 6 except that containing guanidine nitrate in place of ammonium nitrate were similarly tested and compared with sample 1. Results were shown in Table 4.
Samples 1 and 5 to 7 were found to have excellent flame retardancy, and cause no coloring of the resin. It is thus known from the findings that the polymer material, which is obtained by blending a polymer component (target object) such as resin with the flame-retardancy-imparting material containing a group expressed by NxOy (where, x and y are positive integers) (e.g., ammonium nitrate, ammonium nitrite, guanidine nitrate, zinc nitrate) and a group capable of generating water, exhibits excellent flame retardancy while successfully keeping properties of the resin before such compounding almost intact.
The flame-retardancy-imparting material of the present invention was further subjected to the following experiments.
The individual nitric acid compounds as the nitrogen compound, and the individual hydroxyl-group-containing compounds, both of which being listed in Table 5, were mixed with any of the target objects which are exemplified as polypropylene (PP: product of Grand Polymer Co., Ltd., J708), polyethylene (PE: product of Japan Polychem Corporation, LJ800) and ethylene-vinyl acetate copolymer (EVA: product of Tosoh Corporation, U-537), and polymer molded products were obtained using an extrusion/injection molding machine (Examples 1 to 10). The obtained molded products were tested according to Determination of Burning Behavior by Oxygen Index (JIS K-7201) and UL94 combustibility test (fifth edition, Oct. 26, 1996). Results were shown in Table 5. Decomposition temperature of the individual compounds measured in the thermal analyses were shown in Tables 6 and 7.
Decomposition temperature of dry preparations of the individual compound was measured as 204° C. for zinc nitrate, 248° C. for nickel nitrate, 236° C. for copper nitrate, 286° C. for ammonium nitrate, 500° C. or above for lithium nitrate and potassium nitrate, approx. 300° C. for aluminum hydroxide and approx. 350° C. for magnesium hydroxide. The individual molded products obtained in Examples 1 to 7 gave good results in the oxygen index (OI) test and UL94 test, which proves sufficient flame retardancy. It was also confirmed that the individual molded products obtained in Examples 1 to 7 can ensure a desirable degree of flame retardancy in an amount of addition of as low as 55 to 60 parts by weight per 100 parts by weight of the resin, where the nitric acid compound accounts for 5 to 10 parts by weight, and the hydroxyl-group-containing compound accounts for 50 parts by weight. All molded products obtained in Examples 1 to 7 were found to be excellent in the moldability. On the other hand, all molded products obtained in Examples 8 to 10, in which decomposition temperatures largely differ between the nitric acid compound and hydroxyl-group-containing compound, showed flame retardancy only to a degree smaller than that shown in Examples 1 to 7.
Findings of the thermal analyses listed in Table 7 proved advantage of drying treatment (alcohol dehydration) of the nitric acid compound. Metal nitrate without drying treatment will start to decompose at a temperature at approx. 70° C. or lower, which undesirably reduces a ratio of such metal nitrate decomposable at the decomposition temperature of the hydroxyl-group-containing compound, which results in only a limited degree of flame retardancy. So that the decomposition temperature of the metal nitrate as close as possible to that of the hydroxyl-group-containing compound will give better results. Such condition ensures most efficient production of nitric acid through reaction between a nitrogen compound and water generated by the decomposition. Thus produced nitric acid eventually allows rapid progress of thermal decomposition of the polymer. Care should be taken since the decomposition of the metal nitrate in an excessively low temperature range may degrade the intrinsic moldability or various properties of the polymer material due to generated nitrogen oxide. The thermal analysis herein was performed using a thermogravimetric differential thermal analyzer (TG-DTA) apparatus manufactured by Rigaku International Corporation, at a temperature elevation rate of 10° C./min. The same condition for the temperature elevation in the DTA measurement was applied also to the experiments thereafter.
Next, the molded product of Example 1 listed in Table 5, the molded product of Example 11 listed in Table 8, which product contains the same components as in Example 1 and wherein the nitric acid compound is coated with SiO2 by the foregoing sol-gel process, and a polypropylene molded product (Comparative Example 1) were subjected to tensile strength test, elongation test, Izod impact test, and combustion test based on oxygen index. Results were shown in Table 8.
As for mechanical properties such as tensile strength (in Pa), elongation percentage (in %) and Izod impact value (in J/m2), Examples 1 and 11 were found to be lowered in the elongation percentage as compared with Comparative Example 1, but no considerable decrease in the tensile strength and impact strength were observed. In particular for Example 11 in which zinc nitrate is coated with SiO2 by the sol-gel process gave better results in the elongation percentage and Izod impact value. The obtained oxygen indices indicated that desirable flame retardancy was attained both in Examples 1 and 11.
From these findings, the polymer material, which is obtained by blending a polymer component (target object) such as resin with the flame-retardancy-imparting material containing a group expressed by NxOy (where, x and y are positive integers) (e.g., ammonium nitrate, ammonium nitrite, guanidine nitrate, zinc nitrate) and a group capable of generating water, exhibits excellent flame retardancy while successfully keeping properties of the resin before such compounding almost intact.
Ammonium nitrate and aluminum hydroxide individually in the amounts shown in Table 9 below were mixed with 100 parts by weight of polypropylene resin, and the burning test (JISK-7201) by an oxygen index method and UL94 combustibility test were performed. According to these tests, sample 8 containing neither ammonium nitrate nor the aluminum hydroxide did not show flame retardancy. Samples 9 to 11 containing either one of ammonium nitrate and aluminum hydroxide were also burned and did not show flame retardancy. On the other hand, both of sample 12 having 5 parts by weight of ammonium nitrate and 50 parts by weight of aluminum hydroxide mixed with 100 parts by weight of the polypropylene resin, and sample 13 having 7 parts by weight of ammonium nitrate and 70 parts by weight of aluminum hydroxide mixed with 100 parts by weight of the polypropylene resin showed a high flame retardancy ranked at V2 in the UL94 combustibility test. From comparison among samples 9, 10 and 12, it was found that samples 9 and 10 containing only either one of ammonium nitrate and aluminum hydroxide did not show flame retardancy, but sample 12 containing both of ammonium nitrate and aluminum hydroxide showed a high flame retardancy, even under the amounts of addition of ammonium nitrate and aluminum hydroxide remained unchanged. It was confirmed from the above experiment that the combined addition of ammonium nitrate and aluminum hydroxide can provide an excellent flame retardancy even in a small amount of addition thereof.
More specifically, an approach of imparting a sufficient level of flame retardancy through addition only of aluminum hydroxide to the resin will be successful only when aluminum hydroxide is blended in an amount of 150 parts by weight or more per 100 parts by weight of the resin. On the contrary, the combined addition of aluminum hydroxide and ammonium nitrate to the resin makes it possible to achieve a sufficient level of flame retardancy and to sharply decrease the overall amount of mixing to the resin, such as being typified by a total amount of aluminum hydroxide and ammonium nitrate of 55 parts by weight (sample 12) and 77 parts by weight (sample 13), per 100 parts by weight of the resin. In other words, a sufficient level of flame retardancy is obtainable through the combined addition of aluminum hydroxide and ammonium nitrate, even under such small amount of mixing of the flame retarder to the resin.
The following measurements were carried out to elucidate the exhibition mechanism of the flame retardancy in the flame-retardancy-imparting material of the present invention. First, gases emitted during the temperature elevation were examined by TDS (thermal desorption spectroscopy) measurement. In the measurement, the individual samples were heated by infrared radiation at a speed of 50° C./min using a thermal desorption analyzer manufactured by Denshi Kagaku K.K. (the same will apply to all TDS analyses thereafter). At the same time, the emitted gases were also examined by mass spectroscopy (abbreviated as MS, hereinafter) Three samples were used herein, which were simple polyethylene (PE) also used in the foregoing Experiment, a composition containing such polyethylene and aluminum hydroxide (PE+Al(OH)3), and a composition containing such composition and ammonium nitrate (PE+Al(OH)3+NH4NO3). Results were expressed as graphs in
Next, the ternary (PE+Al(OH)3+NH4NO3) system was examined by MS at a predetermined temperature. Results were shown in
Next, to analyze generation conditions specific to m/z=30 (NO) and m/z=46 (NO2), each of polyethylene (PE), the composition of polyethylene and aluminum hydroxide (PE+Al(OH)3), and the composition of polyethylene and aluminum hydroxide and ammonium nitrate (PE+Al(OH)3+NH4NO3) was examined for the amount of generation of m/z=30 (NO) and m/z=46 (NO2) at the individual temperatures.
Similarly, to analyze generation conditions specific to m/z=28 (CO) and m/z=44 (CO2), the individual systems of (PE), (PE+Al(OH)3) and (PE+Al(OH)3+NH4NO3) were examined for the amount of generation of m/z=28 (CO) and m/z=44 (CO2).
To further analyze generation conditions specific to m/z=18 (H2O), m/z=28 (CO), m/z=30 (NO), m/z=44 (CO2) and m/z=46 (NO2), the composition of polyethylene and aluminum hydroxide and ammonium nitrate (PE+Al(OH)3+NH4NO3) was examined for the amount of generation of such individual gases.
Next, to identify gas component of m/z=28 generated at around 300° C., components ascribable to m/z=26 to 28 of the (PE+Al(OH)3+NH4NO3) system were examined by the TDS measurement.
From these findings, the composition of polyethylene and aluminum hydroxide and ammonium nitrate (PE+Al(OH)3+NH4NO3) can sharply emit CO and CO2 at around 300 to 350° C., which suggests that oxidative decomposition of polyethylene can proceed before the combustion (500 to 700° C.) occurs. Since H2O, NO and NO2 (also N2O may be included) were found to generate almost at the same time with CO and CO2, it is supposed that HNO3 generated from H2O, NO and NO2 instantaneously decomposes polyethylene.
More specifically, as shown in
The next effort was directed to identify the decomposition products through TG-MS measurement. The gases emitted when the foregoing composition comprising polyethylene and aluminum hydroxide and ammonium nitrate (PE+Al(OH)3+NH4NO3) was thermally decomposed in the TG-DTA apparatus were measured in situ by GC/MS measurement.
The first TG-MS measurement was carried out in a He atmosphere in order to identify the decomposition products generated at 300° C. Results were shown in
On the other hand, similar TG-MS measurement of the decomposition products generated at 480° C. revealed that, as shown in
Weight changes during the temperature elevation were then measured individually in a He atmosphere and O2 atmosphere. Results were shown in
Based on the findings from the TDS and TG-MS measurements, the exhibition mechanism of the flame retardancy of the flame-retardancy-imparting material according to the present invention can be explained as follows. That is, as shown in
Next, the experiment below was made for the purpose of confirming preferable ratio of weight between ammonium nitrate and aluminum hydroxide. First, aluminum hydroxide was grinded so as to adjust the average grain size thereof to 0.1 to 100 μm, and then subjected to surface treatment with a fatty-acid-base treatment agent. Next, ammonium nitrate was grinded so as to adjust the average grain size thereof to 0.01 to 100 μm, and then subjected to surface treatment with silica. Thus obtained aluminum hydroxide and ammonium nitrate were mixed in the amounts of mixing listed in Table 10 below with 100 parts by weight of polypropylene resin, to thereby obtain flame-retardant polymer materials. Measured values of oxygen index (OI) (based on JIS K-7201) of the individual samples and contents of ammonium nitrate per one part by weight of aluminum hydroxide (NH4NO3/Al(OH)3) are shown in Table 10.
A graph (
Now, UL94 combustibility test will be explained briefly. First, a rectangular-plate-shaped test piece made of flame-retardant polymer material is prepared. As shown in
Next, JIS K 7201 combustion test by oxygen index method is explained briefly. With this JIS K 7201 test, minimum oxygen concentration necessary for the test piece to burn with flame (afterflame) is measured by an apparatus as shown in
A: Lower O2 concentration if combustion time exceeds 3 minutes.
B: Raise O2 concentration if combustion time is 3 minutes or shorter.
C: Repeat operations A and B, obtain O2 concentration when the combustion time is 3 minutes, and determine the obtained O2 concentration as oxygen indexes OI.
It is to be noted that expression of “principal component” or “mainly comprising” was used to specify a component which accounts for a largest content on a weight basis unless otherwise than as specifically described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2001-023768 | Jan 2001 | JP | national |
| 2001-023939 | Jan 2001 | JP | national |
| 2001-194507 | Jun 2001 | JP | national |
| 2001-194509 | Jun 2001 | JP | national |
| 2001-312885 | Oct 2001 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10058327 | Jan 2002 | US |
| Child | 10934367 | Sep 2004 | US |
