The present invention relates to a method for making a solid electrolytic capacitor having a low equivalent series resistance by impregnating a porous capacitor pellet with conductive polymer. An oxidized pellet is dipped in a high concentration conductive polymer solution to deposit the polymer in doped (conductive) form. The solution also contains a crosslinking agent to prevent redissolution of the polymer when the pellet is re-dipped. After dipping, the solvent in the polymer solution is evaporated and a conductive film formed. In order to evaporate the solvent quickly, the solvent should have a boiling point of 80-220xc2x0 C. and preferably a boiling point of 100-150xc2x0 C. The conductive polymer film has a low resistivity (less than 1 ohm-cm, preferably less than 0.2 ohm-cm).

This invention relates to solid electrolytic capacitors and methods for fabricating the same, and more particularly to solid electrolytic capacitors in which conductive polymers are used as solid electrolytes and which have a low equivalent series resistance.
A solid state electrolytic capacitor is made from a porous pellet of sintered tantalum powder, a dielectric tantalum oxide layer formed on the surface of the sintered tantalum powder, a solid-state conductor impregnated into the volume of the pellet, and external connections such as silver paint, etc. The tantalum forms the positive electrode of the capacitor, and the solid-state conductor forms the negative electrode (also called the cathode or counter-electrode).
Manganese dioxide has been utilized as the cathode of choice for solid tantalum capacitors since the commercial introduction of this style of capacitor in the early 1950""s. A key property of manganese dioxide is its self-healing ability. At defective portions of the dielectric film, the manganese dioxide becomes non-conductive. This is due to the manganese dioxide transforming to a lower manganese oxide because of joule heating at the defect site. This mechanism allows capacitors with low leakage currents to be produced. It also allows small dielectric defects that occur during manufacture and use to be isolated. However, if the dielectric defect is too large, the dielectric can crack. Manganese dioxide is a powerful oxidizing agent. When it comes in direct contact with tantalum through a crack in the oxide, the capacitor can ignite, leading to destruction of the capacitor and possible destruction of other components in the circuit. It is desirable to replace the manganese dioxide with a solid-state conductor that does not cause the tantalum to ignite while maintaining the self-healing ability.
The use of tantalum capacitors in high frequency circuits has become more important. This has led to the need for tantalum capacitors having low equivalent series resistance (ESR). The best manganese dioxide has a resistivity of 0.5 to 10 ohm-cm. It is desirable to replace the manganese dioxide with a solid-state conductor metals and oxides do not have a self-healing ability and thus are not suitable for solid-state tantalum capacitors.
Conductive polymers such as polypyrroles, polyanilines, and polythiophenes have resistivities 10 to 100 times less than that of manganese dioxide. Since they are much less powerful oxidizing agents than manganese dioxide, these materials do not cause the capacitor to ignite upon failure. Polypyrrole was shown to have a self-healing mechanism (Harada, NEC Technical Journal, 1996). Due to favorable properties of conductive polymer compounds, these compounds are being investigated as possible replacement materials for manganese dioxide in solid-state tantalum capacitors.
Three methods have been used to deposit the conductive polymer in the porous tantalum pellet:
1. Chemical oxidative polymerization;
2. Electrolytic oxidative polymerization; and
3. Deposition of a polymer from solution followed by oxidation and/or doping.
In chemical oxidative polymerization, a monomer, an oxidizing agent, and a dopant are reacted inside the porous pellet to form the conductive polymer. Monomers include pyrrole, aniline, thiophene, and various derivatives of these compounds. The oxidizing agent can be either an anion or a cation. Typical anion oxidizers are persulfate, chromate, and permanganate. Typical cations are Fe(III) and Ce(IV). The best dopants are anions of strong acids such as perchlorate, toluenesulfonate, dodecylbenzenesulfonate, etc. The reaction between monomer, oxidizing agent, and dopant can take place in a solvent such as water, an alcohol, a nitrile, or an ether.
Several methods have been used to get the monomer, oxidizing agent, and dopant into the porous pellet and carry out the conversion to conductive polymer. In one method, the pellet is first dipped in a solution of the oxidizing agent and dopant, dried, and then dipped in a solution of the monomer. After the reaction is carried out, the pellet is washed and then the process is repeated until the desired amount of polymer is deposited in the pellet. In this method, it is difficult to control the morphology of the final polymer. It is also difficult to control the exact reaction stoichiometry between the monomer and the oxidizing agent. Control of this stoichiometry is critical to achieve the highest conductivity polymer (Satoh et al., Synthetic Metals, 1994). Cross contamination of the dipping solutions is a problem. Since the pellet must be dipped twice for each polymerization, the number of process steps is greatly increased. The excess reactants and the reduced form of the oxidizing agent need to be washed out of the part. This adds even more process steps and complexity to the process.
In a related method, the sequence is reversed so that the pellet is dipped in the monomer solution first and the solvent is evaporated away. The pellet is then dipped in the oxidizing agent/dopant solution and the reaction is carried out. This method suffers from all the disadvantages of the previous method. In addition, some monomer may be lost in the solvent evaporation step.
In yet another method, all components are mixed together and the pellet is dipped in the combined solution. This method reduces the number of dips and allows more precise control over the reaction stoichiometry. However, the monomer and oxidizing agent can react in the dipping bath, causing premature polymerization and loss of reactants, adding some cost and complexity to the process. This problem is especially significant with pyrrole monomer and Fe(III) oxidizing agents. To overcome this problem to some extent, the dipping bath can be kept at cryogenic temperature (Nishiyama et al., U.S. Pat. No. 5,455,736). However, use of cryogenic temperatures adds considerable equipment and operational complexity to the process. The pyrrole/Fe(III) can be replaced with a monomer/oxidizing agent combination that is less reactive, such as 3,4-ethylenedioxythiophene and an Fe(III) salt of an organic acid (Jonas et al., U.S. Pat. No. 4,910,645).
In electrolytic oxidative polymerization, the monomer is oxidized to polymer at an electrode and the dopant is incorporated from the electrolyte. This polymerization method produces high conductivity polymer films. There is no chemical oxidizer to wash out of the film after polymerization.
Direct electrolytic oxidation of monomer to polymer on the tantalum anode is difficult because of the high resistance dielectric oxide layer. Various methods have been proposed to circumvent this problem. One method is to form the polymer on the tantalum and then to form the oxide layer (Saiki et al., U.S. Pat. No. 5,135,618). In another method, the polymer and the oxide layer are formed at the same time (Saiki et al., European Patent Application 0 501 805 A1). However, the electrolytes best suited for depositing conductive polymer and tantalum oxide films are quite different; therefore, these methods produce neither an optimum polymer nor an optimum oxide.
Another method is to deposit a thin film of conductive material by chemical methods, followed by contacting this layer with an electrode to carry out the electrolytic oxidative polymerization. Manganese dioxide prepared by pyrolysis of manganese nitrate (Tsuchiya et al., U.S. Pat. No. 4,943,892), manganese dioxide prepared by pyrolysis of permanganate (Kudoh et al., J. Power Sources, 1996), and conductive polymer prepared by chemical oxidative polymerization (Yamamoto et al., Electronics and Communications in Japan, 1993) have been used for this thin layer. Contacting this thin layer of conductive material with an auxiliary electrode is difficult to achieve in practice. Thus, Tsuchiya et al. propose bridging the anode lead to the conductive layer. This bridging layer must be removed after the polymer has been deposited by electrolytic oxidative polymerization. A complicated series of insulating washers under the bridging layer is used to accomplish this. Kojima et al. (U.S. Pat. No. 5,071,521) propose contacting the thin conductive layer with an auxiliary electrode. Use of an auxiliary electrode greatly increases process complexity, especially with sintered pellet-type anodes where an individual electrode must be provided for each individual anode. Contacting the thin conductive layer with an auxiliary electrode can cause damage to the tantalum oxide layer.
In principle, direct deposition of polymer from solution involves dipping the capacitor in the polymer solution, then evaporating the solvent away to form a conductive film. This operation would be repeated several times to deposit the required amount of polymer in the pellet. This direct deposition strategy would reduce the number of process steps compared to the chemical oxidative polymerization approach and would eliminate the cumbersome auxiliary electrodes used in the electrolytic oxidative polymerization approach. However, capacitance efficiency is poor with this process, due to the difficulty of impregnating small pores with a liquid containing a dispersed solid phase.
Furthermore, technical limitations on conductive polymer solutions prevent this ideal process from being achieved in practice. For example, polyaniline is soluble in N-methyl-2-pyrrolidone (xe2x80x9cNMPxe2x80x9d) in the emereldine base form (PANI-EB), but not in the doped form. A solution of PANI-EB is impregnated into a pellet followed by solvent evaporation to leave a low-conductivity PANI-EB film. The pellet must then be further soaked in a solution of a dopant to change the film into the conducting emereldine salt (ES) form. This doping reaction takes a considerable amount of time, and the excess dopant must be washed from the pellet. In addition, PANI-EB solutions are very viscous in concentrations above 5 wt % and tend to gel with standing. Thus, Sakata et al. (U.S. Pat. No. 5,457,862) state that PANI-EB in NMP can be used to coat the outside of the porous pellet and is not suitable for internal impregnation. Even after doping, the resistivities of PANI-ES prepared using this method are only about 1 ohm-cm.
To avoid the gelling problem, Abe et al. (U.S. Pat. No. 5,436,796) use a solution of polyaniline in the leuco emereldine base form (PANI-LEB). This allows higher concentrations of PANI to be used without the problems of gelling, and the ultimate film resistivity is lower. However, in order to be converted into the conducting PANI-ES form, the PANI-LEB films must be oxidized and doped inside the capacitor pellet. The oxidizing/dopant reaction takes a considerable amount of time, and both the excess dopant and excess oxidizer mush be washed from the pellet.
Other prior art efforts include Cao et al. (U.S. Pat. No. 5,624,605) who teach the use of functionalized protonic acids to induce processibility of electrically conductive substituted or unsubstituted polyanilines with average molecular weight greater than 10,000 Daltons. Cao et al. also disclose the use of these functionalized protonic acids to induce solubility of polyanilines in organic liquids. The functionalized protonic acid solutes are well known as dopants and are defined as acids that protonate polyaniline to form a miscible or soluble complex with conductivity approximately equal to or greater than 10xe2x88x923 S/cm. The preferred functionalized protonic acid is dodecylbenzene sulfonic acid because as the degree of protonation increases, the solubility also increases. Cao et al. combine one or more substituted or unsubstituted polyanilines, an organic substrate phase, and one or more functionalized protonic acid solutes with a compatible counter ion to produce electrically conductive, co-continuous polymeric solutions that contain around 1 wt % of monomer.
Cao et al. teach that the substituted or unsubstituted polyanilines in protonated form can be dissolved in organic liquids and, due to their high molecular weight, coated onto surfaces and spun into fibers without binders. The organic substrate phase is either an organic liquid, an organic solid or semisolid, or the protonic acid. These liquids, solids, semi-solids or acids can be substituted or unsubstituted aromatic hydrocarbons, such as xylene, higher alkanes, cyclic alkanes, halogenated alkanes, higher alcohols, higher ketones, heterocyclics, or perfluorinated hydrocarbons.
One limitation of these prior art solutions (or dispersions) has been the low concentration of doped polymer that can be dissolved. For example, one commercially available dispersion of polyaniline contains only 0.5 wt % doped polymer (ORMECON Dispersion 900132). Likewise, a commercially available dispersion of poly-(3,4-ethylenedioxythiophene) contains only 1.3 wt % doped polymer (Bayer, Baytron P). The use of such low concentration dispersions would require that the capacitor be dipped many times, resulting in a low process throughput.
Another limitation on prior art solutions has been the redissolution of the deposited polymer film in the dipping solution. Smith et al. (U.S. Pat. No. 5,470,505) describe a solution of up to 20 wt % doped polyaniline in concentrated sulfuric acid. However, they state that the deposited polyaniline films are re-soluble in the sulfuric acid solution. Even if the films do not redissolve, the solvent will soften the film on re-dipping, leading to separation of the film from the tantalum oxide dielectric. Kinlen (U.S. Pat. No. 5,567,356) describes polyaniline salts soluble in organic solvents (sold under the Monsanto trade name XICP-OS01). Without modification, these salts also redissolve in solvent.
It is therefore an object of the present invention to deposit a conductive polymer in a porous capacitor pellet directly from solution in the final conductive form. This eliminates secondary doping, oxidation, and washing steps, thereby reducing the process complexity. In the past, technical limitations of these doped polymer solutions have made them unsuitable for depositing polymer in a capacitor.
It is another object of the present invention to deposit a solution containing a high concentration of conductive polymer in a porous capacitor pellet. The high concentration solution enables a conductive polymer film to be applied in a fewer number of dipping steps.
It is a further object of the present invention to deposit a conductive polymer film in a porous capacitor such that the polymer film does not redissolve or does not substantially redissolve during subsequent dipping steps.
It is yet a further object of the present invention to deposit a conductive polymer film in a porous capacitor pellet such that the film has a conductivity of greater than 5 S/cm and a long range of thermal stability.
One aspect of the present invention involves a process for forming a solid electrolytic capacitor having a conductive polymer counter electrode, the process comprising:
(a) providing an oxidized porous capacitor pellet;
(b) dipping the pellet in a solution comprising a solvent, a conductive polymer, and a crosslinking agent; and
(c) applying heat to the pellet so as to evaporate the solvent and crosslink the polymer, thereby forming a conductive polymer film.
Another aspect of the present invention involves additionally:
(d) re-dipping the pellet in the solution of step (b); and
(e) applying heat to the pellet so as to evaporate the solvent;
wherein the crosslinked polymer is substantially insoluble in the solvent.
According to the present invention, a high concentration polymer solution, preferably having a concentration of at least 5 wt % polymer, more preferably at least about 8 wt % polymer, most preferably from about 10 wt % to about 30 wt % polymer, effectively and rapidly impregnates a porous capacitor pellet. Upon evaporation of the solvent, the polymer is deposited in the doped (conductive) form. To prevent redissolution of the polymer in the dipping solution, the polymer film is rendered insoluble in the original polymer solution. This can be accomplished by including an agent that crosslinks the polymer during the solvent evaporation stage. The conductive polymer film which is formed has a resistivity of less than 1 ohm-cm and preferably less than 0.2 ohm-cm. For ease of handling in an industrial process, it is desirable that the solvents have boiling points in the range of 80 to 220xc2x0 C., most preferably in the range of 100 to 150xc2x0 C. In a preferred embodiment, a mixed solvent of xylene and propylene glycol propyl ether is employed.
The process of the present invention realizes a substantial reduction in the number of process steps through the use of a high polymer concentration dipping solution and by preventing redissolution of the deposited polymer film. The invention further eliminates the need for additional doping, oxidation and washing steps by depositing a polymer film in the doped form, and eliminates the need for auxiliary electrodes as is required in electrolytic oxidative polymerization. The deposited polymer film is highly conductive, i.e., more than 5 S/cm. In addition, the conductive polymer solution has relatively no pot life limitations.
A porous pellet is prepared by pressing charged powder and sintering to form a porous body. Preparation of porous pellets is well known in the art, for example as taught by U.S. Pat. No. 5,729,428 to Sakata et al., incorporated by reference herein in its entirety. The pellet may be made from tantalum, niobium, aluminum, hafnium, zirconium, titanium, or alloys of these elements, tantalum being the preferred material. An oxide film is then formed using a phosphoric acid or phosphate-containing electrolyte solution with a voltage of from about 14 V to about 150 V being applied. The formation voltage ranges from 2.5 to 4.5 times the rated voltage of the part and most preferably from 3 to 3.5 times the rated voltage of the part. The porous pellet can be of any size that is suitable for producing a surface mount or leaded-style tantalum capacitor. The porous pellet body typically has a thickness of 0.5 mm to 3 mm, a width of 0.9 mm to 5 mm, and a length of 1 mm to 5.5 mm.
A conductive polymer solution is prepared containing a conductive polymer and a suitable crosslinking agent. The concentration of the conductive polymer in the solvent is preferably at least 5 wt %, more preferably at least about 8 wt %, and most preferably from about 10 wt % to about 30 wt %. Various conductive polymers may be used in accordance with the invention, such as polyaniline, polythiophene, polypyrrole, and derivatives of these materials. The preferred conductive polymer is polyaniline. Conductive polymers are well known in the art, for example as taught by U.S. Pat. No. 5,624,605 to Cao et al., incorporated by reference herein in its entirety.
The conductive polymer is dissolved in a solvent, preferably a solvent having a boiling point in the range of 80 to 220xc2x0 C., most preferably in the range of 100 to 150xc2x0 C. The selection of a suitable solvent for a particular conductive polymer is well within the level of skill in the art. In a preferred embodiment of the invention, a mixed solvent of xylene and propylene glycol propyl ether containing a crosslinking agent (trade name Monsanto XICP-OS06N) is used to dissolve polyaniline.
The particular crosslinking agent used is not critical to the invention. For example, Jonas et al. (DE 195 07 413 A1) teach the use of glycidoxypropyltrimethoxysilane to crosslink poly (3,4-ethylenedioxythiophene) doped with poly (styrene sulfonic acid). Here the glycidoxy functionality on the silane reacts with the excess sulfonic acid groups in the dopant to crosslink the polymer and make it substantially water-insoluble after curing. The crosslinking agent is chosen to react either with the polymer chain or with the dopant molecules. The crosslinking agent can have a concentration ranging from less than 0.1% by weight to greater than 10% by weight, depending on the degree of crosslinking required. The degree of crosslinking is set high enough so that the polymer remains insoluble after curing but low enough so that the conductivity of the final polymer film is not degraded. The selection of a suitable crosslinking agent for a particular conductive polymer is well within the level of skill in the art.
The porous pellet is then dipped in the conductive polymer solution. The pellet is removed from the solution and heated to a temperature of from about 100xc2x0 C. to about 180xc2x0 C., preferably about 160xc2x0 C. Heat is applied until such time that the solvent has evaporated and crosslinking of the polymer has been completed, which normally is about fifteen minutes. Since the polymer film is in the conductive form, an additional step of doping is not needed.
The steps of dipping, solvent removal and crosslinking are repeated as necessary to build up the conductive polymer film to yield a capacitor having desired electrical characteristics. Crosslinking of the polymer prevents redissolution or substantial redissolution of the polymer in the dipping solution. The conductive polymer film which is formed has a resistivity of less than 1 ohm-cm and preferably less than 0.2 ohm-cm.

Process of preparing a solid electrolytic capacitor containing a conductive polymer counter electrode


A futon couch/bed frame is constructed for ease of shipping, assembly and use. It comprises a base with first and second tubular end members joined together in parallel, spaced-apart relation by front and rear rails which frictionally join to the end members without the use of screw fasteners. Pivotally supported on the base are first and second seat members that hinge together this seat assembly attaches to the base using only two bolts that pivotally join the seat assembly to the spaced-apart tubular end portions.

I. Field of the Invention
This invention relates generally to an item of furniture, and more particularly to a frame for a futon couch/bed.
II. Discussion of the Prior Art
Arrangements for tilting a sofa bed between a bed position and a couch position are quite well known in the art. In bi-fold arrangements, there is provided a frame having two sections that are pivotally movable with respect to one another between a "couch" position, in which the sections are disposed at an angle to one another so as to form a seat and back rest combination, and a "bed" disposition where the two sections become coplanar and form a futon supporting surface. The couch/bed futon supporting sections are typically mounted on a base member so that the couch/bed futon supporting sections will be elevated relative to the floor. Typical of prior art futon couch/bed frames are described in the following United States patents:
______________________________________ Newton 5,485,638 Dodge 5,513,398 Stoler et al. 5,664,268 Meade 5,429,415 Fitts 5,303,432 Meade 5,170,519 Withers 5,129,114 ______________________________________
A common shortfall of the prior art futon couch/bed frames is that they typically incorporated somewhat complicated linkages for coupling the futon support segments to the base making the unit difficult to assemble and generally requiring two persons to accomplish such assembly. Moreover, the base and futon support segments in prior art futon couch/bed arrangements tend to be quite bulky when disassembled making packaging and shipping of the parts in disassembled form relatively difficult and expensive.
A need, therefore, exists for a futon couch/bed combination that has a minimum of parts and which can fit into a relatively flat carton during shipment and which can be readily assembled by a single person in only a manner of minutes. The present invention meets that need.


A shield for shielding a capacitive touch screen from external noise arising from stray capacitance is located between the exterior housing of a touch screen device and the touch screen itself. The shield comprises a thin piece of conductive material such as aluminum foil laminated between two layers of insulating material such as a polycarbonite and is secured to the upper surface of the touch screen, as by an adhesive. The shield has a central opening which is smaller than an opening in the housing of the touch screen device that is provided to enable the touch screen to be contacted for entry of data, and to enable a user to view a display that is located beneath the touch screen, which is transparent. Portions of the shield are thus visible, and the central opening of the shield thus defines the portion of the display which can be viewed. Different sizes of displays can therefore be used in the touch screen device by using shields with different sizes of central openings, without the need for redesigning the exterior housing of the touch screen device.

The present invention relates to a touch screen device and more particularly to a shield used in the touch screen device to shield the touch screen from external noise due to stray capacitance.
Capacitive touch screens have become one of the major touch screen technologies in marketplaces such as the hospitality and quick-service point of sale marketplaces, mainly due to their extremely high durability and their resistance to interference from foreign objects on the screen, such as dirt and grease.
Capacitive touch screens calculate touch points by measuring the amount of current that the body of a user of the screen draws from the screen. This current drain is caused by capacitive coupling of the user's finger (and body) from a conductive film layered on the glass of the screen. A capacitor is defined as being two conductive surfaces separated by a thin insulating surface. In the case of a capacitive touch screen, as shown in FIG. 1, the two conductive surfaces are the user's finger 10 and a conductive coating 12 on the glass 14 of the touch screen. The insulating substance is a thin protective covering 16 layered on top of the conductive coating 12. This combination forms a capacitor, represented symbolically in FIG. 1 by the capacitor 18.
The touch point is calculated by measuring the current drain at the four corners of the touch screen. The closer a user's touch is to a corner, the more current drain will be measured from that corner. A microprocessor circuit compares the current drain from the four corners and calculates an X, Y coordinate for the touch point.
It is the fact that the hand does not actually touch the conductive coating that makes capacitive touch screens so durable, for reasons which include the following. The insulating coating can be made very strong so that it protects the conductive coating from scratching and wearing over time. Any foreign objects on the insulating coating (dirt, grease, etc.) will not degrade the performance of the touch screen. The touch screen assembly has no moving parts; therefore it can be sealed to the bezel of the touch screen device to prevent leakage of liquids into the device.
Unfortunately, it is also the fact that the hand does not touch the conductive coating of the touch screen that makes capacitive touch screens susceptible to interference. For example, as shown in FIG. 2, a left hand 20 of a user placed on the bezel 22 of a touch screen device 24 will induce enough stray capacitance to cause error, as shown by point 26, in the X, Y coordinates which are calculated by the system to represent a point 28 touched on the touch screen 30 by a finger 32 of the right hand 34 of the user.
The reason that the touch screen 30 so easily picks up the capacitance (C') of the hand 20 is that the active area of the touch screen 30 is only approximately 75% of the entire area of the glass. The 25% unused area of glass (hidden from view under the bezel 22) is required to distribute charge evenly throughout the conductive coating. Although this portion of+the touch screen is unused, it is still sensitive to capacitance. Therefore it easily picks up the large capacitance of the hand 20 since only the thin bezel 22 separates the hand 20 from the glass of the touch screen 30.
Current methods to shield this sensitive unused portion of the touch screen 30 from stray capacitance induced by the hand 20 of a user of the touch screen device 24, which includes the touch screen 30 and an associated display 34, include covering the unused portion of the screen with a piece of conductive tape 33 beneath the bezel 22, as shown in FIG. 3. The touch screen 30 typically comprises a glass base 36 having a conductive coating 38 and an insulating coating 40 disposed thereover. The conductive tape 33 typically comprises a plastic tape base 42 with a silkscreened conductive pattern 44 on its surface. The tape 33 is driven with the same signal that is used to drive the four corners of the touch screen glass. Although the conductive tape certainly is an improvement over the unshielded glass, and insulates the touch screen from a large portion of any outside interference, it still allows some stray capacitance to get through. Two other drawbacks of the tape shield method are that it is visually unattractive, and that it must be electrically isolated from grounding sources since it carries a signal.
One effective type of shield which may be employed to shield a touch screen is the subject of U.S. patent application Ser. No. 08/234,881, filed Apr. 28, 1994, Docket No. 5948, assigned to the assignee of the present application, and incorporated herein by reference. This shield comprises two interconnected rectangular metal elements which are disposed on either side of the touch screen. However it would be desirable to provide a shield which is even less expensive than such a shield, and which can be assembled to the touch screen in a very simple manner.

Visible and touchable touch screen shield

AT&T Global Information Solutions Company


Thermoplastic molding compositions comprise

The invention relates to thermoplastic molding compositions, comprising
A) from 5 to 96% by weight of a polyester,
B) from 1 to 30% by weight of a nitrogen compound, excluding melamine cyanurate,
C) from 0.1 to 30% by weight of a phosphinate of formula I or of a diphosphinate of formula II or of polymers of these or mixtures of these
xe2x80x83where:
R1 and R2 are hydrogen, linear or branched alkyl having from 1 to 6 carbon atoms or phenyl, with the proviso that at least one of the radicals R1 and R2 is hydrogen,
R3 is linear or branched C1- to C10-alkylene or is arylene, alkylarylene or arylalkylene,
M is an alkaline-earth metal or alkali metal, Al, Zn, Fe or boron,
m is an integer from 1 to 3,
n is an integer from 1 to 3, and
x is 1 or 2
D) from 0 to 5% by weight of at least one ester or amide of saturated or unsaturated aliphatic carboxylic acids having from 10 to 40 carbon atoms with saturated aliphatic alcohols or amines having from 2 to 40 carbon atoms, and
E) from 0 to 60% by weight of other additives,
where the total of the percentages by weight of components A) to E) is 100%.
The invention further relates to the use of the novel molding compositions for producing fibers, films or moldings, and also to the resultant moldings of any type.
The market is increasingly interested in halogen-free flame-retardant polyesters. Significant requirements placed upon the flame retardant are: pale intrinsic color, adequate heat stability for incorporation into thermoplastics, and also effectiveness in reinforced and unreinforced polymer (wicking effect of glass fibers).
The UL 94 fire test for unreinforced polyesters should be passed here at the V-0 level. For reinforced polyesters, at least the V-2 classification should be obtained and/or the glow-wire test passed.
Besides the halogen-containing systems there are in principle four halogen-free FR systems used in thermoplastics:
Inorganic flame retardants, which have to be used in large amounts to be effective.
Nitrogen-containing FR systems, such as melamine cyanurate, which has limited effectiveness in thermoplastics, e.g. polyamide. In reinforced polyamide it is effective only in combination with shortened glass fibers. Melamine cyanurate by itself is not effective in polyesters.
Phosphorus-containing FR systems, which are generally not very effective in polyesters.
Phosphorus/nitrogen-containing FR systems, such as ammonium polyphosphates or melamine phosphates, which do not have sufficient thermal stability for thermoplastics processed at temperatures above 200xc2x0 C.
JP-A 03/281 652 has disclosed polyalkylene terephthalates which comprise melamine cyanurate and glass fibers, and also a phosphorus-containing flame retardant. These molding compositions comprise derivatives of phosphoric acid, such as phosphoric esters (valence state +5), which tend to bleed out on exposure to heat.
These disadvantages are also seen for the combination of melamine cyanurate (MC) with resorcinol bis(diphenyl phosphate), known from JP-A 05/070 671. These molding compositions also have high phenol values during processing and do not have adequate mechanical properties.
JP-A 09/157 503 has disclosed polyester molding compositions with MC, phosphorus compounds and lubricants, comprising less than 10% of reinforcing agents. Molding compositions of this type have flame-retardant and mechanical properties which are not fully satisfactory. The same applies to migration and phenol formation during processing.
EP-A 699 708, DE-A 19614424 and BE-A 875 530 have disclosed salts of phosphinic acid as flame retardants for polyesters.
WO 98/17720 has disclosed combinations of MC with phosphorus-containing compounds and lubricants for polyesters.
It is an object of the present invention to provide flame-retardant polyester molding compositions which achieve an adequate UL 94 classification and an improved LOI value. In addition there should be a very high degree of retention of mechanical properties. Thermal stability during processing should, furthermore, be improved, and phenol emission reduced.
We have found that this object is achieved by means of the thermoplastic molding compositions defined at the outset. Preferred embodiments are given in the subclaims.
The novel molding compositions comprise, as component A), from 5 to 96% by weight, preferably from 10 to 70% by weight and in particular from 10 to 60% by weight, of a thermoplastic polyester.
Use is generally made of polyesters based on aromatic dicarboxylic acids and on an aliphatic or aromatic dihydroxy compound.
A first group of preferred polyesters is that of polyalkylene terephthalates having from 2 to 10 carbon atoms in the alcohol moiety.
Polyalkylene terephthalates of this type are known per se and are described in the literature. Their main chain contains an aromatic ring which derives from the aromatic dicarboxylic acid. There may also be substitution in the aromatic ring, e.g. by halogen, such as chlorine or bromine, or by C1-C4-alkyl, such as methyl, ethyl, iso- or n-propyl or n-, iso- or tert-butyl.
These polyalkylene terephthalates may be prepared by reacting aromatic dicarboxylic acids, or their esters or other ester-forming derivatives, with aliphatic dihydroxy compounds in a manner known per se.
Preferred dicarboxylic acids are 2,6-naphthalenedicarboxylic acid, terephthalic acid and isophthalic acid, and mixtures of these. Up to 30 mol %, preferably not more than 10 mol %, of the aromatic dicarboxylic acids may be replaced by aliphatic or cycloaliphatic dicarboxylic acids, such as adipic acid, azelaic acid, sebaccic acid, dodecanedioc acids and cyclohexanedicarboxylic acids.
Preferred aliphatic dihydroxy compounds are diols having from 2 to 6 carbon atoms, in particular 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethylanol and neopentyl glycol, and mixtures of these.
Particularly preferred polyesters A) are polyalkylene terephthalates derived from alkanediols having from 2 to 6 carbon atoms. Among these, particular preference is given to polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate, and mixtures of these. Preference is also given to PET and/or PBT comprising, as further monomer units, up to 1% by weight, preferably up to 0.75% by weight, of 1,6-hexanediol and/or 5-methyl-1,5-pentanediol.
The viscosity number of the polyester A) is generally in the range from 50 to 220, preferably from 80 to 160 (measured in 0.5% strength by weight solution in a phenol/o-dichlorobenzene mixture (in a weight ratio of 1:1 at 25xc2x0 C.) in accordance with ISO 1628.
Particular preference is given to polyesters whose carboxyl end group content is up to 100 mval/kg of polyester, preferably up to 50 mval/kg of polyester and in particular up to 40 mval/kg of polyester. Polyesters of this type may be prepared, for example, by the process of DE-A 44 01 055. The carboxyl end group content is usually determined by titration methods (e.g. potentiometry).
Particularly preferred molding compositions comprise, as component A), a mixture of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). The proportion of the polyethylene terephthalate in the mixture is preferably up to 50% by weight, in particular from 10 to 30% by weight, based on 100% by weight of A).
Novel molding compositions of this type have very good flame-retardant properties and improved mechanical properties.
It is also advantageous to use recycled PET materials (also termed scrap PET) in a mixture with polyalkylene terephthalates, such as PBT.
Recycled materials are generally:
1) Those known as post-industrial recycled materials: these are production wastes during polycondensation or during processing, e.g. sprues from injection molding, start-up material from injection molding or extrusion, or edge trims from extruded sheets or films.
2) Post-consumer recycled materials: these are plastic items which are collected and treated after utilization by the end consumer. Blow-molded PET bottles for mineral water, soft drinks and juices are easily the predominant items in quantity terms.
Both types of recycled material may be used either as regrind or in the form of pellets. In the latter case, the crude recycled materials are isolated and purified and then melted and pelletized using an extruder. This usually facilitates handling and free-flowing properties, and metering for further steps in processing.
The recycled materials may either be used as pellets or as regrind. The edge length should not be more than 6 mm, preferably less than 5 mm.
Because polyesters undergo hydrolytic cleavage during processing (due to traces of moisture) it is advisable to predry the recycled material. The residual moisture content after drying is preferably from 0.01 to 0.7%, in particular from 0.2 to 0.6%.
Another class to be mentioned is that of fully aromatic polyesters deriving from aromatic dicarboxylic acids and aromatic dihydroxy compounds.
Suitable aromatic dicarboxylic acids are the compounds previously mentioned for the polyalkylene terephthalates. The mixtures preferably used are made from 5 to 100 mol % of isophthalic acid and from 0 to 95 mol % of terephthalic acid, in particular from about 50 to about 80% terephthalic acid and from 20 to about 50% of isophthalic acid.
The aromatic dihydroxy compounds preferably have the formula III
where Z is alkylene or cycloalkylene having up to 8 carbon atoms, arylene having up to 12 carbon atoms, carbonyl, sulfonyl, oxygen or sulfur or a chemical bond, and m is from 0 to 2. The phenylene groups in the compounds may also have substitution by C1-C6-alkyl or alkoxy and fluorine, chlorine or bromine.
Examples of parent compounds for these compounds are
dihydroxydiphenyl,
di(hydroxyphenyl)alkane,
di(hydroxyphenyl)cycloalkane,
di(hydroxyphenyl) sulfide,
di(hydroxyphenyl) ether,
di(hydroxyphenyl) ketone,
di(hydroxyphenyl) sulfoxide,
xcex1, xcex1xe2x80x2-di(hydroxyphenyl)dialkylbenzene,
di(hydroxyphenyl) sulfone, di(hydroxybenzoyl)benzene, resorcinol, and
hydroquinone, and also the ring-alkylated and ring-halogenated derivatives of these.
Among these, preference is given to
4,4xe2x80x2-dihydroxydiphenyl,
2,4-di(4xe2x80x2-hydroxyphenyl)-2-methylbutane,
xcex1,xcex1xe2x80x2-di(4-hydroxyphenyl)-p-diisopropylbenzene,
2,2-di(3xe2x80x2-methyl-4xe2x80x2-hydroxyphenyl)propane, and
2,2-di(3xe2x80x2-chloro-4xe2x80x2-hydroxyphenyl)propane,
and in particular to
2,2-di(4xe2x80x2-hydroxyphenyl)propane,
2,2-di(3xe2x80x2,5-dichlorodihydroxyphenyl)propane,
1,1-di(4xe2x80x2-hydroxyphenyl)cyclohexane,
3,4xe2x80x2-dihydroxybenzophenone,
4,4xe2x80x2-dihydroxydiphenyl sulfone, and
2,2-di(3xe2x80x2,5xe2x80x2-dimethyl-4xe2x80x2-hydroxyphenyl)propane, and mixtures of these.
It is, of course, also possible to use mixtures of polyalkylene terephthalates and fully aromatic polyesters. These generally comprise from 20 to 98% by weight of the polyalkylene terephthalate and from 2 to 80% by weight of the fully aromatic polyester.
For the purposes of the invention, polyesters include polycarbonates which have been obtained by polymerizing aromatic dihydroxy compounds, in particular 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and its derivatives, e.g. with phosgene. Corresponding products are known per se and are described in the literature, and many of them are also commercially available. The amount of the polycarbonates is up to 90% by weight, preferably up to 50% by weight, based on 100% by weight of component A).
It is, of course, also possible to use polyester block copolymers, such as copolyetheresters. Products of this type are known per se and are described in the literature, e.g. in U.S. Pat. No. 3,651,014. Corresponding products are also available commercially, e.g. Hytrel(copyright) (DuPont).
The novel thermoplastic molding compositions comprise, as component B), from 1 to 30% by weight, preferably from 5 to 20% by weight, and in particular from 5 to 15% by weight, of a nitrogen compound as flame retardant, excluding melamine cyanurate.
Suitable nitrogen compounds (also frequently termed salts or adducts) are:
Compounds for the purposes of the present invention include benzoguanamine itself and its adducts or salts, and also the nitrogen-substituted derivatives and their adducts or salts.
Other suitable compounds are ammonium polyphosphate (NH4PO3)n, where n is from about 200 to 1000, preferably from 600 to 800, and tris(hydroxyethyl) isocyanurate (THEIC) of formula IV
and its reaction products with aromatic carboxylic acids Ar(COOH)m, where
Ar is a mono-, bi- or trinuclear aromatic six-membered ring system and
m is 2, 3 or 4.
Examples of suitable carboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, pyromellitic acid, mellophanic acid, prenitic acid, 1-naphthoic acid, 2-naphthoic acid, naphthalenedicarboxylic acids and anthracenecarboxylic acids.
They are prepared by reacting the tris(hydroxyethyl) isocyanurate with the acids, or with their alkyl esters or their halides using the process of EP-A 584 567.
Reaction products of this type are a mixture of monomeric and oligomeric esters which may also have been crosslinked. The degree of oligomerization is usually from 2 to about 100, preferably from 2 to 20. Preference is given to the use of THEIC and/or its reaction products in mixtures with phosphorus-containing nitrogen compounds, in particular (NH4PO3)n. The mixing ratio, for example of (NH4PO3)n to THEIC is preferably 90xe2x88x9250:50xe2x88x9210% by weight, in particular 80xe2x88x9250:50xe2x88x9220% by weight, based on the mixture of components B) of this type.
Other suitable compounds are benzoguanamine (compounds) of formula V
where R and Rxe2x80x2 are straight-chain or branched alkyl having from 1 to 10 carbon atoms or preferably hydrogen, and in particular adducts of these with phosphoric acid, boric acid and/or pyrophosphoric acid.
Preference is also given to allantoin compounds of formula VI
where R and Rxe2x80x2 are as defined in formula V, and also the salts of these with phosphoric acid, boric acid and/or pyrophosphoric acid, and also
glycourils of formula VII or salts of these with the abovementioned acids
where R is as defined in formula V.
Suitable products are available commercially or obtainable as in DE-A 196 14 424.
The cyanoguanidine (formula VIII) which can be used according to the invention is obtained, for example, by reacting calcium cyanamide with carbonic acid, whereupon the cyanamide produced dimerizes at a pH of from 9 to 10 to give cyanoguanidine.
The product obtained commercially is a white powder with a melting point of from 209 to 211xc2x0 C.
The novel molding compositions comprise, as component C), from 0.1 to 30% by weight, preferably from 1 to 25% by weight and in particular from 10 to 20% by weight, of a phosphinate of formula (I) and/or of a diphosphinate of formula (II) or polymers of these or mixtures of these
where:
R1 and R2 are hydrogen, phenyl, C1-C6-alkyl, preferably C1-C4-akyl, linear or branched, e.g. methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl or n-pentyl, with the proviso that at least one of the radicals R1 and R2 is hydrogen, in particular R1 and R2 are hydrogen,
R3 is C1-C10-alkylene, linear or branched, e.g. methylene, ethylene, n-propylene, iso-propylene, n-butylene, tert-butylene, n-pentylene, n-octylene or n-dodecylene; arylene, e.g. phenylene or naphthylene; alkylarylene, e.g. methylphenylene, ethylphenylene, tert-butylphenylene, methylnaphthylene, ethylnaphthylene or tert-butylnaphthylene; aralkylene, e.g. phenylmethylene, phenylethylene, phenylpropylene or phenylbutylene;
M is an alkaline-earth metal or alkali metal, Al, Zn, Fe or boron;
m is an integer from 1 to 3;
n is an integer from 1 to 3; and
x is 1 or 2.
Particular preference is given to compounds of formula II where R1 and R2 are hydrogen, where M is preferably Al or Zn, and very particular preference is given to calcium phosphinate.
Products of this type are available commercially, e.g. as calcium hypophosphite.
Suitable salts of formula I or II where only one of the radicals R1 and R2 is hydrogen are sodium benzenephosphinate and calcium benzenephosphinate.
Preparation processes are known from EP-A 699 708 and BE-A 875 530.
The novel molding compositions may comprise, as component D), from 0 to 5% by weight, preferably from 0.01 to 5% by weight, particularly preferably from 0.05 to 3% by weight and in particular from 0.1 to 2% by weight, of at least one ester or amide of saturated or unsaturated aliphatic carboxylic acids having from 10 to 40 carbon atoms, preferably from 16 to 22 carbon atoms, with saturated aliphatic alcohols or amines having from 2 to 40 carbon atoms, preferably from 2 to 6 carbon atoms.
The carboxylic acids may be mono- or dibasic. Examples which may be mentioned are pelargonic acid, palmitic acid, lauric acid, margaric acid, dodecanedioc acid, behenic acid and, particularly preferably stearic acid, capric acid and montanic acid (a mixture of fatty acids having from 30 to 40 carbon atoms).
The aliphatic alcohols may be mono- to tetrahydric. Examples of alcohols are n-butanol, n-octanol, stearyl alcohol, ethylene glycol, propylene glycol, neopentyl glycol and pentaerythritol. Glycerol and pentaerythritol are preferred.
The aliphatic amines may be mono- to tribasic. Examples of these are stearylamine, ethylenediamine, propylenediamine, hexamethylenediamine and di(6-aminohexyl)amine. Ethylenediamine and hexamethylenediamine are particularly preferred. Correspondingly, preferred esters or amides are glycerol distearate, glycerol tristearate, ethylenediamine distearate, glycerol monopalmitate, glycerol trilaurate, glycerol monobehenate and pentaerythritol tetrastearate.
It is also possible to use mixtures of different esters or amides or combinations of esters with amides. The mixing ratio may be as desired.
The novel molding compositions may comprise, as component E), from 0 to 60% by weight, in particular up to 50% by weight, of other additives.
Examples of usual additives E) are amounts of up to 40% by weight, preferably up to 30% by weight, of elastomeric polymers (also frequently termed impact modifiers, elastomers or rubbers).
These are very generally copolymers which have preferably been built up from at least two of the following monomers: ethylene, propylene, butadiene, isobutene, isoprene, chloroprene, vinyl acetate, styrene, acrylonitrile and acrylate and/or methacrylates having from 1 to 18 carbon atoms in the alcohol component.
Polymers of this type have been described, for example, in Houben-Weyl, Methoden der organischen Chemie, Vol. 14/1 (Georg-Thieme-Verlag, Stuttgart, 1961), pages 392-406, and in the monography by C. B. Bucknall, xe2x80x9cToughened Plasticsxe2x80x9d (Applied Science Publishers, London, 1977).
Some preferred types of such elastomers are described below.
Preferred types of such elastomers are those known as ethylene-propylene (EPM) and ethylene-propylene-diene-(EPDM) rubbers.
EPM rubbers generally have practically no residual double bonds, whereas EPDM rubbers may have from 1 to 20 double bonds per 100 carbon atoms.
Examples of diene monomers for EPDM rubbers are conjugated dienes, such as isoprene and butadiene, nonconjugated dienes having from 5 to 25 carbon atoms, such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene and 1,4-octadiene, cyclic dienes, such as cyclopentadiene, cyclohexadienes, cyclooctadienes and dicyclopentadiene, and also 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[5.2.1.02,6]-3,8-decadiene, or mixtures of these. Preference is given to 1,5-hexadiene, 5-ethylidenenorbornene and dicyclopentadiene. The diene content of the EPDM rubbers is preferably from 0.5 to 50% by weight, in particular from 1 to 8% by weight, based on the total weight of the rubber.
EPM and EPDM rubbers may preferably also have been grafted with reactive carboxylic acids or with derivatives of these. Examples of these are acrylic acid, methacrylic acid and derivatives thereof, e.g. glycidyl (meth)acrylate, and also maleic anhydride.
Copolymers of ethylene with acrylic acid and/or methacrylic acid and/or with the esters of these acids are another group of preferred rubbers. The rubbers may also include dicarboxylic acids, such as maleic acid and fumaric acid, or derivatives of these acids, e.g. esters and anhydrides, and/or monomers containing epoxy groups. These dicarboxylic acid derivatives or monomers containing epoxy groups are preferably incorporated into the rubber by adding, to the monomer mixture, monomers containing dicarboxylic acid groups and/or containing epoxy groups and having the formulae I, II, III or IV
xe2x80x83R1C(COOR2)xe2x95x90C(COOR3)R4xe2x80x83xe2x80x83(I)

where R1 to R9 are hydrogen or alkyl having from 1 to 6 carbon atoms, m is an integer from 0 to 20, g is an integer from 0 to 10 and p is an integer from 0 to 5.
R1 to R9 are preferably hydrogen, where is m is 0 or 1 and g is 1. The corresponding compounds are maleic acid, fumaric acid, maleic anhydride, allyl glycidyl ether and vinyl glycidyl ether.
Preferred compounds of the formulae I, II and IV are maleic acid, maleic anhydride and (meth)acrylates containing epoxy groups, such as glycidyl acrylate and glycidyl methacrylate, and the esters with tertiary alcohols, such as tert-butyl acrylate. Although the latter have no free carboxyl groups their behavior approximates to that of the free acids and they are therefore termed monomers with latent carboxyl groups.
The copolymers are advantageously composed of from 50 to 98% by weight of ethylene, from 0.1 to 20% by weight of monomers containing epoxy groups and/or of methacrylic acid and/or monomers containing anhydride groups, the remaining amount being (meth)acrylates.
Particular preference is given to copolymers made from
from 50 to 98% by weight, in particular from 55 to 95% by weight, of ethylene,
from 0.1 to 40% by weight, in particular from 0.3 to 20% by weight, of glycidyl acrylate and/or glycidyl methacrylate, (meth)acrylic acid and/or maleic anhydride, and
from 1 to 45% by weight, in particular from 10 to 40% by weight, of n-butyl acrylate and/or 2-ethylhexyl acrylate.
Other preferred (meth)acrylates are the methyl, ethyl, propyl, isobutyl and tert-butyl esters.
Besides these, comonomers which may be used are vinyl esters and vinyl ethers.
The ethylene copolymers described above may be prepared by processes known per se, preferably by random copolymerization at high pressure and elevated temperature. Appropriate processes are well known.
Preferred elastomers also include emulsion polymers whose preparation is described, for example, by a Blackley in the monograph xe2x80x9cemulsion polymerizationxe2x80x9d. The emulsifiers and catalysts which may be used are known per se.
In principle it is possible to use homogeneously structured elastomers, or those with a shell construction. The shell-type structure is a result of the sequence of addition of the individual monomers. The morphology of the polymers is also affected by this sequence of addition.
Monomers which may be mentioned here, merely as examples, for the preparation of the rubber fraction of the elastomers are acrylates, such as n-butyl acrylate and 2-ethylhexyl acrylate, and corresponding methacrylates, and butadiene and isoprene, and also mixtures of these. These monomers may be copolymerized with other monomers, such as styrene, acrylonitrile, vinyl ethers and with other acrylates or methacrylates, such as methyl methacrylate, methyl acrylate, ethyl acrylate or propyl acrylate.
In the elastomers, the soft or rubber phase (with a glass transition temperature below 0xc2x0 C.) may be the core, the outer enveloping shell or an intermediate shell (in the case of elastomers whose structure has more than two shells). Elastomers having more than one shell may also have more than one shell made from a rubber phase.
If one or more hard components (with glass transition temperatures above 20xc2x0 C.) are involved, besides the rubber phase, in the structure of the elastomer, these are generally prepared by polymerizing, as principle monomers, styrene, acrylonitrile, methacrylonitrile, xcex1-methylstyrene, p-methylstyrene, or acrylates or metharylates, such as methyl acrylate, ethyl acrylate or methyl methacrylate. Besides these, it is also possible to use relatively small proportions of other comonomers.
It has proven advantageous in some cases to use emulsion polymers which have reactive groups at their surfaces. Examples of groups of this type are epoxy, carboxyl, latent carboxyl, amino and amide groups, and also functional groups which may be introduced by concomitant use of monomers of the formula
where:
R10 is hydrogen or C1-C4-alkyl,
R11 is hydrogen, C1-C8-alkyl or aryl, in particular phenyl,
R12 is hydrogen, C1-C10-alkyl, C6-C12-aryl or xe2x80x94OR13,
R13 is C1-C8-alkyl or C6-C12-aryl, if desired with substitution by Oxe2x80x94 or N-containing groups,
X is a chemical bond or C1-C10-alkylene or C6-C12-arylene, or
Y is Oxe2x80x94Z or NHxe2x80x94Z, and
Z is C1-C10-alkylene or C6-C12-arylene.
The graft monomers described in EP-A 208 187 are also suitable for introducing reactive groups at the surface.
Other examples are acrylamide, methacrylamide and substituted acrylates or methacrylates, such as (N-tert-butylamino)ethylmethacrylate, (N, N-dimethylamino) ethyl acrylate, (N,N-dimethylamino)methyl acrylate and (N,N-diethylamino)ethyl acrylate.
The particles of the rubber phase may also have been crosslinked. Examples of crosslinking monomers are 1,3-butadiene, divinylbenzene, diallyl phthalate and dihydrodicyclopentadienyl acrylate, and also compounds described in EP-A 50 265.
It is also possible to use the monomers known as graft-linking monomers, i.e. monomers having two or more polymerizable double bonds which react at different rates during the polymerization. Preference is given to the use of compounds of this type in which at least one reactive group polymerizes at about the same rate as the other monomers, while the other reactive group (or reactive groups), for example, polymerize(s) significantly more slowly. The different polymerization rates give rise to a certain portion of unsaturated double bonds in the rubber. If another phase is then grafted onto a rubber of this type, at least some of the double bonds present in the rubber react with the graft monomers to form chemical bonds, i.e. the phase grafted on has at least some degree of chemical bonding to the graft base.
Examples of graft-linking monomers of this type are monomers containing allyl groups, in particular allyl esters of ethylenically unsaturated carboxylic acids, for example allyl methacrylate, diallyl maleate, diallyl fumarate and diallyl itaconate, and the corresponding monoallyl compounds of these dicarboxylic acids. Besides these, there is a wide variety of other suitable graft-linking monomers. For further details reference may be made here, for example, to U.S. Pat. No. 4,148,846.
The proportion of these crosslinking monomers in the impact-modifying polymer is generally up to 5% by weight, preferably not more than 3% by weight, based on the impact-modifying polymer.
Some preferred emulsion polymers are listed below. Mention is made firstly of graft polymers with a core and at least one outer shell and the following structure:
These graft polymers, in particular amounts of up to 40% by weight of ABS and/or ASA polymers, are used in particular for the impact-modification of PBT, if desired in a mixture with up to 40% by weight of polyethylene terephthalate. Corresponding blend products are commercially available under the tradename Ultradur(copyright)S (previously Ultrablend(copyright)S) from BASF AG. ABS/ASA mixtures with polycarbonates are commercially obtainable with the trademark Terblend(copyright) (from BASF AG).
Instead of graft polymers whose structure has more than one shell it is also possible to use homogeneous, i.e. single-shell, elastomers made from 1,3-butadiene, isoprene and n-butyl acrylate or from copolymers of these. These products, too, may be prepared via concomitant use of crosslinking monomers or of monomers having reactive groups.
Examples of preferred emulsion polymers are n-butyl acrylate-(meth)acrylic acid copolymers, n-butyl acrylate-glycidyl acrylate or n-butyl acrylate-glycidyl methacrylate copolymers, graft polymers with an inner core made from n-butyl acrylate or based on butadiene and with an outer shell made from the abovementioned copolymers, and copolymers of ethylene with comonomers which supply reactive groups.
The elastomers described may also be prepared by other conventional processes, e.g. by suspension polymerization.
Preference is also given to silicone rubbers, as described in DE-A 37 25 576, EP-A 235 690, DE-A 38 00 603 and EP-A 319 290.
It is, of course, also possible to use mixtures of the types of rubbers listed above.
Fibrous or particulate fillers which may be mentioned are carbon fibers, glass fibers, glass beads, amorphous silica, asbestos, calcium silicate, calcium metasilicate, magnesium carbonate, kaolin, chalk, powdered quartz, mica, barium sulfate and feldspar, used in amounts of up to 50% by weight, in particular from 1 to 40% by weight, particularly from 20 to 35% by weight.
Examples of preferred fibrous fillers are carbon fibers, aramid fibers and potassium titanate fibers, and particular preference is given to glass fibers in the form of E glass. These may be used as rovings or in the commercially available forms of chopped glass.
The fibrous fillers may have been surface-precoated with a silane compound to improve compatibility with the thermoplastic.
Suitable silane compounds have the formula:
(Xxe2x80x94(CH2)n)kxe2x80x94Sixe2x80x94(Oxe2x80x94CmH2m+1)4xe2x88x92k
where:
n is an integer from 2 to 10, preferably of 3 or 4,
m is an integer from 1 to 5, preferably 1 or 2, and
k is an integer from 1 to 3, preferably 1.
Preferred silane compounds are aminopropyltrimethoxysilane, aminobutyltrimethoxysilane, aminopropyltriethoxysilane, and aminobutyltriethoxysilane, and also the corresponding silanes which contain a glycidyl group as substituent X.
The silane compounds are generally used for surface-coating in amounts of from 0.05 to 5% by weight, preferably from 0.5 to 1.5% by weight and in particular from 0.8 to 1% by weight (based on D)).
Acicular mineral fillers are also suitable.
For the purposes of the present invention, acicular mineral fillers are mineral fillers with pronounced acicular character. An example is acicular wollastonite. The mineral preferably has an L/D (length to diameter) ratio of from 8:1 to 35:1, preferably from 8:1 to 11:1. The mineral filler may, if desired, have been pretreated with the abovemetioned silane compounds, but the pretreatment is not essential.
Other fillers which may be mentioned are kaolin, calcined kaolin, wollastonite, talc and chalk.
The novel thermoplastic molding compositions may comprise, as component E), conventional processing aids, such as stabilizers, oxidation inhibitors, agents to prevent decomposition by heat or by ultraviolet light, lubricants, mold-release agents, colorants, such as dyes and pigments, nucleating agents, plasticizers, etc.
Examples of oxidation inhibitors and heat stabilizers are sterically hindered phenols and/or phosphites, hydroquinones, aromatic secondary amines, such as diphenylamines, various substituted representatives of these groups, and mixtures of these in concentrations of up to 1% by weight, based on the weight of the thermoplastic molding compositions.
UV stabilizers which may be mentioned and are usually used in amounts of up to 2% by weight, based on the molding composition, are various substituted resorcinols, salicylates, benzotriazoles and benzophenones.
Colorants which may be added are inorganic pigments, such as titanium dioxide, ultramarine blue, iron oxide and carbon black, and also organic pigments, such as phthalocyanines, quinacridones and perylenes, and also dyes, such as nigrosine and anthraquinones.
Nucleating agents which may be used are sodium phenylphosphinate, alumina, silica and preferably talc.
Lubricants and mold-release agents which differ from D) and are usually used in amounts of up to 1% by weight are preferably long-chain fatty acids (e.g. stearic acid or behenic acid), salts of these (e.g. calcium stearate or zinc stearate) or montan waxes (mixtures of straight-chain saturated carboxylic acids having chain lengths of from 28 to 32 carbon atoms), and also low-molecular-weight polyethylene waxes and low-molecular-weight polypropylene waxes.
Examples of plasticizers which may be used are dioctyl phthalates, dibenzyl phthalates, butyl benzyl phthalates, hydrocarbon oils and N-(n-butyl)benzenesulfonamide.
The novel molding compositions may also comprise from 0 to 2% by weight of fluorine-containing ethylene polymers. These are polymers of ethylene with a fluorine content of from 55 to 76% by weight, preferably from 70 to 76% by weight.
Examples of these are polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymers and tetrafluoroethylene copolymers with relatively small proportions (generally up to 50% by weight) of copolymerizable ethylenically unsaturated monomers. These are described, for example, by Schildknecht in xe2x80x9cVinyl and Related Polymersxe2x80x9d, Wiley-Verlag, 1952, pp. 484-494 and by Wall in xe2x80x9cFluoropolymersxe2x80x9d (Wiley Interscience, 1972).
These fluorine-containing ethylene polymers have homogeneous distribution in the molding compositions and preferably have a particles size d50 (number average) in the range from 0.05 to 10 xcexcm, in particular from 0.1 to 5 xcexcm. These small particle sizes may particularly preferably be achieved by the use of aqueous dispersions of fluorine-containing ethylene polymers and the incorporation of these into a polyester melt.
The novel thermoplastic molding compositions may be prepared by methods known per se, by mixing the starting components in conventional mixing apparatuses, such as screw extruders, Brabender mixers or Banbury mixers, and then extruding them. The extrudate may be cooled and comminuted. It is also possible to premix individual components and then to add the remaining starting materials individually and/or likewise in a mixture. The mixing temperatures are generally from 230 to 290xc2x0 C.
In a preferred method, components B) to D), and also, if desired, conventional additives E), are mixed with a polyester prepolymer, compounded and pelletized. The resultant pellets are then condensed to the desired viscosity in the solid phase under an inert gas, continuously or batchwise, at a temperature below the melting point of component A).
The novel thermoplastic molding compositions have good mechanical and flame-retardant properties and also improved LOI values. Their processing takes place with very little change in the polymer matrix, and mold deposits are markedly reduced. They are suitable for producing fibers, films or moldings, in particular for applications in the electrical and electronics sectors. Particular applications are lamp parts, such as lamp sockets and lamp holders, plugs and multipoint connectors, coil formers, casings for capacitors or connectors, and circuit-breakers, relay housings and reflectors.

Flame-retardant polyester molding compositions containing flame retardant nitrogen compounds and diphosphinates

Abstract: xe2x80x83as defined in the specification


The alarm system is capable of detecting both conductive and non-conductive liquid level increases, designed for indoor operation, and ideally suited for detecting basement flooding or leaky domestic steel oil tanks or other fluid containment devices. A float, positioned above any surface such as a contained area (sump or drip pan), rises with the presence of a liquid, allowing a spring-loaded switch to rise, triggering a 9-volt powered battery electric circuit. The electric circuit, enclosed in a plastic enclosure, activates an audible pulsating alarm when triggered. A battery voltage monitor incorporated in the electric circuit, tests the battery voltage on a continuous bases, and will trigger the unit into the alarm mode when the battery voltage is insufficient to sustain continuous operation. A simple convenient self check feature allows the user to simply check the unit at any time. An external connection is provided to allow the unit to be connected to a home security system or other external device to allow extended protection or secondary operations.

1. Field of the Invention
The present invention relates to a liquid detection and alarm system for detecting the presence of oil or water leaks from indoor domestic appliances or domestic furnace oil tanks, for example, or for basement flooding. The invention may also be used for industrial applications where the detection of leaking liquids are desirable to prevent environmental or other unwanted results. The invention is typically placed over a drip pan or low point of a surface where the liquid is likely to collect. The invention uses an electrical circuit with an audible alarm device, enclosed in housing, with an attached float.
Oil leaks from domestic 909 liter steel oil tanks or connections can cause serious damage to a home and create an environmental disaster if the oil finds its way under the building foundation. In most cases the oil must be reclaimed from the soil at a considerable expense. If the ground water becomes contaminated, cost for the clean up is higher, and in most cases the property is devalued. There is no accurate prediction device or method, which will determine with accuracy when a tank will fail, or when fittings will leak. There is therefore a need for an alarm system which will be reliable, compact, and will warn the residents that their oil tank is leaking.
The invention will operate for liquids with a density greater then 775 kg/m3 and a flash point no less then 38 degrees Celsius. Typical heating oil found in domestic steel tanks would meet or exceed these minimum limitations.
2. Description of the Prior Art
Prior art includes an Oil Alert system designed by Dorlen Products Inc. of Milwaukee, U.S.A., which features xe2x80x9cOil Alert Sensing Modulesxe2x80x9d which are absorbing cells which after insertion into a housing, are placed on the floor and will activate an audible alarm after the cells have detected oil. This prior art has limitations, which the invention will overcome. For example, this prior art requires cell replacement after triggering and cannot be easily self checked. The unit must be placed on a level surface, thus cannot act as an adjustable level alarm.
There are other oil detection systems used in industrial applications such as detecting a liquid level between double-wall storage tanks. However, this prior art is intended to be used in this specific industrial application. These known devices do not have an easy self-check mechanism, are not portable, and are typically not equipped with an audible alarm.
Other water detection alarm systems use a conducting sensing method which cannot be used to detect the presence of oil due the fact that oil is a poor electrical conductor.
The invention may be distinguished from the other prior water detection alarms in significant respect. Prior art includes a variety of patents pertaining to water leak detection devices which are designed to detect water and automatically shut down an appliance or valve. Many prior art devices use conductivity sensing probes, strips or cells to detect the presence of water from a leaking basement, appliance, or back-up pipe. An audible alarm will sound when moisture is detected. Representatives of this prior art are patents such as:
Canadian patent no. 1261940 Otterhof
Canadian patent no. 2124907 Janesky
Canadian patent no. 1244533 Leblanc
Canadian patent no. 2023376 Shih
Canadian patent no. 2228517 Isaacson
Canadian patent no. 2175005 Leger
U.S. Pat. No. 5,539,383 Chin
U.S. Pat. No. 5,058,421 Alexander
U.S. Pat. No. 5,091,715 Murphy
U.S. Pat. No. 4,297,686 Tom
U.S. Pat. No. 5,898,374 Schepka
U.S. Pat. No. 5,655,561 Wendal
U.S. Pat. No. 5,557,263 Fisher
U.S. Pat. No. 5,550,532 Marshall
U.S. Pat. No. 4,805,662 Moody
U.S. Pat. No. 4,246,575 Purtell
U.S. Pat. No. 5,517,174 Barrows
U.S. Pat. No. 4,800,372 Poteet
U.S. Pat. No. 4,973,947 Tax
Other prior art utilizing conductive type detective systems can easily false alarm when condensation forms on the probes. Absorption type units, which sit on the floor, will become submerged if the water level quickly rises, thus damaging the unit and causing it to malfunction. The invention is intended to be mounted directly above the monitoring surface. The float can rest at any desired height above the monitoring surface, however the component housing should be mounted a minimum distance of 7 cm above the float and up to 807 cm directly above the liquid surface. The minimum distance can be lowered if required, although for most application this is not desired. Most prior art devices are fixed units, which are not adjustable once set in place. The length of the conductivity leads limits the range of these prior art devices.
Other prior art devices generally may not incorporate a fail-safe mechanism, in the event the sensing device becomes disabled for any reason. If a dielectric capacitor, or absorbent cell becomes disabled for any reason, then the unit will not indicate a fault in the alarm unit. Some prior art devices do include a battery low voltage-checking device.
The invention provides a simple water or oil leak detection alarm system which is capable of producing an audible alarm when the liquid level increases above the point at which the unit is set to trigger. The invention would typically be used in a domestic home application for detecting water flooding, or a leaking oil tank installation. The invention can also be adapted for many industrial applications where the presence of a conductive or non-conductive liquid requires alarming. In combination with its audible alarm, connections preferably are provided for external monitoring, such as a home security system or relay controller. The invention uses a float, which can be adjusted to various heights above the area, which requires monitoring. The invention is portable and can be easily moved from one monitoring position to another, or from one liquid service to another. The invention requires a 9-volt battery, which is checked continuously for sufficient voltage. The unit will sound an alarm when insufficient voltage is detected. A 120 volt ac/9-volt dc external supply can also be used to power the invention. The triggering mechanism of the invention requires a positive liquid level increase of approximately 5 mm after contact with the float to activate the alarm. This ensures the unit does not false alarm with the presence of moisture, like many prior art devices. The invention is ideally suited for monitoring oil leaks from domestic furnace tanks, which can leak at any time. By simply attaching the unit on the side of a pan (located under the tank), with hook and pile fastening material (e.g. Velcro (trademark)) or other commonly known fastening means, the unit will be fixed into position ready to detect a leak. The invention has a simple self-check feature. By the touch of a fingertip, the unit can be self checked to ensure all circuits are fully operational. A fail-safe design ensures that in the event the float becomes disabled for any reason, the unit will sound the alarm.
The invention does not require conductive water detection systems for a triggering mechanism. It uses a float, attached to a lever switch, which upon coming in contact with a rising liquid, will cause the lever switch to rise, activating a spring-loaded switching mechanism.
The invention is portable and can be moved from place to place, or it can be used to service different types of liquid applications. Today when areas become flooded, this alarm will enable a homeowner to set the positioning and height so that the house can be vacated when the alarm sounds. This would be a safety feature in areas under threat of potential flooding. The alarm offers portability and flexibility, along with a reliable simple safety check for operability.
As stated, the invention has a simple self check mechanism. A simple motion of raising the lever switch with a finger will allow the unit to be checked for all operational features. Other prior art devices with self-check mechanisms may require submersion in the water or liquid to be self-checked. This would, typically, be messy and difficult to perform.
The invention incorporates a fail-safe feature. Should the sensing device (float) become detached for any reason, the unit will automatically go into alarm mode.
The invention incorporates a low voltage battery monitoring system which will trigger the alarm circuitry should the battery fall below 7.4 volts. The unit will sound an audible alarm for a minimum of 24 hours in this condition, and will also trigger, if equipped, the external monitoring circuitry. The improvement of the 24-hour continuous alarm along with the triggering of the external circuit for low voltage conditions is an improvement over prior art devices. A new 9-volt alkaline battery will last a minimum of 1 year, in a non-triggered operation mode. The unit may also operate continuously with an external 120 volt AC /9 volt DC adapter.
The alarm system is capable of detecting both conductive and non-conductive liquid level increases, designed for indoor operation, and ideally suited for detecting basement flooding or leaky domestic steel oil tanks or other fluid containment devices. A float, positioned above any surface such as a contained area (sump or drip pan), rises with the presence of a liquid, allowing a spring-loaded switch to rise, triggering a 9-volt powered battery electric circuit. The electric circuit, enclosed in a plastic enclosure, activates an audible pulsating alarm when triggered. The alarm system is capable of generating a sound pulsating at the 85 dB level, preferably every 10 seconds. The alarm system is portable, and can be moved from one site to another, or from one service to another. The unit must sit directly above the site to be monitored, with a clear unencumbered path to the float mechanism. The height above the monitored surface where the alarm is placed can vary according to preference, from a minimum of 7 cm to maximum of 807 cm. The adjustment in height can be accomplished by utilizing 6.80 kg (breaking strength ) braided nylon string which can be cut and tied to the desired length. A battery voltage monitor incorporated in the electric circuit, tests the battery voltage on a continuous bases, and will trigger the unit into the alarm mode when the battery voltage is insufficient to sustain continuous operation. A simple convenient self check feature allows the user to simply check the unit at any time. An external connection is provided to allow the unit to be connected to a home security system or other external device to allow extended protection or secondary operations. which continues to alarm at approximately 10 seconds intervals until the alarm system is reset or the battery voltage is insufficient to sustain the alarm performance.