JPS6134749B2 - - Google Patents

Description

[Detailed description of the invention]

Since the issuance of U.S. Pat. No. 3,028,365 in April 1962, aromatic polycarbonates have become well-known as thermoplastic resins suitable for a wide variety of applications, including injection molding, extrusion, and film formation. It is accepted. The chemistry, synthesis, properties, and applications of these polycarbonates are described in the book Chemistry and Physics of Polycarbonates by Schnell.
Polycarbonates, Interscience, 1964 and Christopher and Fox, Polycarbonates, Reinhold, 1962. Although polycarbonate has some inherent flame resistance and is self-extinguishing, the ever-increasing flame retardant requirements have led to many attempts to improve this property. .
Two general methods are being pursued. One method has been to add significant amounts of halogen, particularly bromine or chlorine, to the polycarbonate composition. Halogens may be added via polycarbonate polymer chains, as in US Pat. Nos. 3,751,400 and 3,334,154, or by monomeric compounds, as in US Pat. No. 3,382,207. However, the presence of significant amounts of halogens has been found to be detrimental to the properties of polycarbonate, and a number of additives, such as those proposed in U.S. Pat. No. 3,647,747, have overcome these adverse effects. It is proposed to. Another method is to add various organic and inorganic metal salts to impart the desired flame retardancy.
U.S. Pat. No. 3,775,367 discloses the use of about 0.01 to 1% by weight of alkali metal perfluoroalkane sulfonate salts and shows that the presence of halogens on the polymer backbone or by additive compounds increases the flame retardant efficiency of these salts. It shows. U.S. Patent No. 3836490
The No. 2003-2011 designates the use of 0.00005 to 0.1% by weight of selected organic alkali salts of carboxylic acids in halogen-free or halogen-containing polycarbonates. In this case the salt is soluble in the polycarbonate melt. In contrast, German patent no. 2149311 has approx.
Indicates the use of 0.05 to 3.0% by weight of insoluble alkali metal salts, especially salts of minerals, phosphonic acids and sulfonic acids. U.S. Pat. No. 3,535,300 discloses that small amounts of specific metal salts (not including alkali metal salts) attached to the polymer backbone or additives are about 0.01 to 1.
Indicates use in combination with weight percent halogen.
Halogens are said to interact "synergistically" with salts. In either the halogen method or the salt method, two aspects of flame retardancy must be considered. The UL Item 94 test, which has become widely accepted for testing the flame resistance of organic polymers, evaluates a polymer's resistance to being quenched by flame and the ability of the polymer to emit flames when exposed to flame. It is a measure of both the tendency of particles to drip. The latter phase, dripping, has been found to be more difficult to control. U.S. Patent No. 3,876,580 is 2-6% by weight
of glass fibers in combination with 1-3% by weight of halogen (chlorine or bromine) or 0.01-1% by weight of nickel or alkali metal salts have been shown to achieve both flame-retardant properties. . This patent states that if both salt and halogen are added,
It is noted that smaller amounts of each are sufficient to achieve the desired flame retardancy. Finally, DE 25 35 262 A1 shows the addition of fluorinated polyolefins, such as polytetrafluoroethylene, to polycarbonates containing organic alkali metal salts to prevent dripping. All of the above methods have been tried and found to some extent to meet the three main objectives of flame retardancy of thermoplastics. (1) the improvement in the fire resistance of the polymer, measured both by composition and instillation; (2) the improvement of the flame retardant polymer's (3) the use of a very inexpensive system that meets the other two objectives; Clearly, these three objectives are somewhat predetermined and a balance must be sought. For example, certain additives in sufficient amounts may achieve any desired degree of flame retardancy, but with an unacceptable loss of other properties of the polymer. The flame retardancy of polycarbonates can be improved by increasing either the amount or the efficiency of the flame retardant system. The former method is less attractive since other properties of the polymer, especially mechanical properties, usually decrease as the level of chemically introduced halogen or additive increases. The efficiency of the flame retardant system may be increased by reducing the rate of polycarbonate melt flow (thus increasing the relative viscosity and molecular weight). Resins with lower melt flows generally have better mechanical properties and can tolerate higher additive levels. More importantly, however, resins with lower melt flows have an inherent greater resistance to dripping, which, as discussed above, is one of the two aspects of flame retardancy. Unfortunately, reduced resin melt flow has drawbacks. As melt flow decreases, it becomes more difficult to process polycarbonate into finished shapes, especially by injection molding, one of its most important end uses. In addition, processing polycarbonate with lower melt flow typically requires exposing the resin to higher temperatures and for longer periods of time, thus increasing the likelihood that the resin will undergo some degradation during processing. Conversely, the adverse effects of the flame retardant system can be reduced by lowering its amount or by using a system that is better tolerated by polycarbonate. The amount of flame retardant can be reduced by using a more effective system.
For example, replacing chlorine with bromine (Canadian Patent No.
725726 teaches). The less flame retardant that is present, the better the polycarbonate will usually be able to withstand it, but certain flame retardants, such as combinations of iron salts and bromine, have been found to pose special problems of high temperature stability. . Naturally, one should choose a flame retardant system that achieves both the desired flame retardancy and the desired mechanical properties and is also inexpensive. Generally, flame retardants that are more readily available or more easily synthesized are somewhat less expensive. For example, the organic alkali metal carboxylates of US Pat. No. 3,836,490 are cheaper and more readily available than the alkali metal perfluoroalkane sulfonates of US Pat. No. 3,775,367. However, increasingly more stringent requirements are making it even more difficult to meet both criteria 1 and 2. Many conventional flame retardant systems are unable to achieve the required flame retardancy;
Still retains suitable mechanical properties. for example,
A high degree of flame retardancy, such as 94V-0 in UL item 94, is required at a thinner cross section, such as 1.6 mm. As the cross-sectional thickness decreases, the difficulty of achieving the required flame retardancy increases. The combination of polytetrafluoroethylene (PTFE) and certain alkali metal salts of inorganic acids interact synergistically to give polycarbonates with them a high degree of flame retardancy, even when these additives are present in small amounts. It was found here that it gives It has also been found that the presence of small amounts of halogens, particularly chlorine or bromine, synergistically increases the effectiveness of the PTFE and salt combination. The polytetrafluoroethylene must be of a type that forms fibrils when sheared and is present in an amount sufficient to reduce the tendency of the polycarbonate to drip, preferably about 0.01 based on the weight of the total composition.
~1% by weight must be present. The alkali metal salt should be present in an amount sufficient to reduce the flame extinction, ie, ability to support combustion, of the polycarbonate, preferably from about 0.01 to 1% by weight, based on the weight of the composition. In embodiments using chlorine or bromine, the halogen is attached to a carbon atom attached to an aromatic ring and should be present in an amount sufficient to enhance the flammability of the polycarbonate, alkali metal salt, and PTFE composition. Preferably, the halogen should be present at about 0.05 to 1% by weight, based on the weight of the total composition. Polytetrafluoroethylene suitable for use in the present invention is well known and commercially available. It should have the property of forming fibrils when subjected to shear. Among the suitable polytetrafluoroethylenes are those described in US Pat. Nos. 3,005,795 and 3,671,487 and German Pat. PHFE
A particularly preferred form is available from DuPont as Teflon Type 6 and designated Type 3 by ASTM. Conveniently, polytetrafluoroethylene is used in an amount up to about 2% by weight, based on the weight of the total composition. However, it is preferred to use between about 0.01 and 1% by weight, and more preferably between about 0.05 and 0.2% by weight. Inorganic acid alkali metal salts useful in the present invention include:
K ₃ ALF ₆ /KAlF ₄ , KPF ₆ , Na ₂ S ₂ O ₅ , NaSbF ₆ ,
_{They are Na2B4O7} , _{K2SiF6 , K4P2O7 and KBF4 .} Salts may be used in effective amounts up to about 2% by weight, based on the weight of the total composition. It is preferred to use less than about 0.01% by weight, more preferably no less than about 0.1% by weight. It is preferred to use no more than about 1% by weight, and more preferably no more than about 0.5% by weight. More than 2% by weight of salt does not reduce its effect on flame retardancy, but it reduces other properties of the polycarbonate to a greater extent than is justified by the flame retardant improvement achieved. Salts suitable for use in the present invention are substantially insoluble in polycarbonate. It is believed that such salts will have very limited mobility in polycarbonate matrices at room temperature and will therefore be less susceptible to problems such as leaching. These salts should also reduce the tendency to concentrate on the surface or plate out during molding. The halogen bearing can be any monomeric or polymeric compound having a chlorine or bromine atom directly attached to a carbon atom attached to an aromatic ring. Compounds containing high concentrations of chlorine or bromine are preferred because they provide the same halogen content at lower additive concentrations. It is believed that the chlorine or bromine atoms are the active parts of these additives with respect to flame retardancy. Among monomeric compounds, those having a phenyl or diphenyl structure are preferred, and those having an ester or carbonate bond are particularly preferred. Among the polymeric compounds, polyesters or polycarbonates derived from aromatic monomers substituted with chlorine or bromine are preferred, such as 2,2-bis-
(3,5-dichloro-4-hydroxyphenyl)
Particular preference is given to polycarbonate copolymers based on halogen-substituted or halogen-free aromatic dihydroxy compounds such as -propane and 2,2-bis-(4-hydroxyphenyl)-propane. Suitable polymers include the oligomers shown in US Pat. No. 3,855,277 and the high molecular weight polymers of US Pat. Nos. 3,334,154 and 3,751,400. Of course, the halogen may be directly attached to the polycarbonate skeleton that constitutes the majority of the composition. Chlorine or bromine may be present in effective amounts up to about 3% by weight. In this embodiment, it is preferred to use at least about 0.05% by weight of halogen;
It is also preferred to use no more than about 1.0% by weight. It is particularly preferred to limit the halogen content to between about 0.1 and 0.5% by weight. Higher halogen contents are bad because they tend to cause resin decomposition, as discussed in US Pat. No. 3,876,580. In the present invention, such high amounts are not justified by the improved flame retardancy thereby achieved. The polycarbonates useful in this invention are based on aromatic dihydroxy monomers and are thermoplastics. These include those described in the US patents discussed above in the Background of the Invention, the descriptions of which are incorporated herein by reference. Suitable polycarbonates include, for example, U.S. Pat.
Also included are branched polycarbonates such as those described in US Pat. No. 3,799,953 and 3,897,392 and US Pat. Preferred polycarbonates are those which can be prepared from di-(monohydroxyaryl)-alkanes and derivatives of carbonic acid, such as phosgene or chloroformates. Particularly preferred polycarbonates are those which can be prepared from 4,4'-dihydroxydiarylmethane. The most preferred polycarbonate is 2,2-bis-
It is based on (4-hydroxyphenyl)-propane. The polycarbonate should have a molecular weight such that it is a thermoplastic solid at room temperature. Preferably polycarbonate is about 10000~
It has a weight average molecular weight of between 200,000 and more preferably exhibits a melt flow of between about 1 and 24 grams per 10 minutes (measured according to ASTM Standard D1238, Condition 0). The polycarbonate compositions of the present invention may also contain other conventional stabilizers such as pigments, dyes, UV stabilizers, heat stabilizers, mold release agents and fillers. However, reinforcing agents such as fillers and glass fibers tend to reduce some mechanical properties such as impact strength, and their addition may also lead to desirable improvements in other mechanical properties such as stiffness. If it does not occur, it must be avoided. especially,
The addition of glass fibers is unnecessary to achieve satisfactory flame retardancy. The compositions of the present invention may be made by any method commonly known in the art. For example, various additives may be dry mixed with polycarbonate pellets and the mixture may be extruded. Alternatively, additives may be metered into the devolatilizing extruder as the polymer is being recovered from solution. of course,
Additives soluble in the polycarbonate process solvent may be added to the polycarbonate solution, and polycarbonate soluble may be added to the melt. The only requirement is that the additives are completely dispersed and
The added polytetrafluoroethylene undergoes sufficient shear to form fibrils in the polycarbonate matrix. The polytetrafluoroethylene may be subjected to shearing prior to addition to the polycarbonate, and it is believed that such prefibrillation increases flame retardancy and makes the additive effective at lower levels.
(On the other hand, the necessary shear may be imparted by some final molding operation, such as injection molding.) Without limiting the breadth of the invention, Applicant acknowledges that polytetrafluoroethylene may be used in the present invention. It is believed that it works by forming a fine fibrillar network in the matrix as described in US Pat. No. 3,005,795. Applicants are therefore open to any pretreatment or method of incorporation of polytetrafluoroethylene that would help to promote the formation of such networks. Examples Tables 1 and 2 include Examples 1-28. Tables 1 and 2 list the results of flammability tests according to the Underwriters Laboratory Item 94 (UL94) standard. Table 2 also includes
Contains test results using IBM6-0430-102. For UL94 testing, individual specimens of dimensions 120 mm x 12.7 mm x indicated thickness are clamped vertically and 20 mm high.
exposed to the blue gas flame twice for 10 seconds each,
Place the top of the gas burner approximately 10 cm from the bottom edge of the specimen. The specimen is covered with a horizontal layer of surgical cotton.
Place it 30.5cm above. To classify the substance, five specimens are tested. The following criteria are decisive for classification. 94V-2 Average combustion time after flame release 25 seconds Maximum allowable post flame release combustion time after any one flame contact 30 seconds Substance may drip while burning 94V-1 Post flame release combustion The time corresponds to that of 94V-2. Substances must not drip while burning. 94V-0 Average combustion time after flame separation 5 seconds Maximum allowable combustion time after flame separation 10 seconds Material must drip while burning. For the IBM6-0430-102 test, a specimen with dimensions of 120 mm x 10 mm x indicated thickness is hung vertically and
Expose to a 20mm Bunsen burner flame (no air supplied). The distance of the tip of the Bunsen burner from the bottom edge of the specimen is 10 mm. Expose the specimen to the flame without continuing to burn for more than 30 seconds after the flame has separated, and without burning particles dripping from the specimen and igniting the cotton wool ball placed below the specimen. Determine when you can. A substance separates from a Class A substance if, after a flame exposure time of 60 seconds, the substance disappears within 30 seconds without producing any flame droplets. Class B materials are those which extinguish after a flame exposure time of 5 seconds or longer but cannot withstand a flame exposure time of 60 seconds without exceeding those previously mentioned. Thus, for example, if a material extinguishes within 30 seconds for a flame exposure time of up to 45 seconds, it would be classified as Class B/Indicated Thickness/45 seconds. In the examples, the polycarbonate pellets described above are mixed in the dry state with various amounts of flame retardant additives by so-called shaking. The pellets are then extruded using a mixing screw at about 260°C to give ribbons and then shredded to give granules. Next, these fine particles are transformed into the required test piece using an injection molding machine at approximately 300°C. Melt flow values were determined according to ASTM D1238, condition 0. The base polycarbonate resin loaded with additives was a condensation product of phosgene and 2,2-bis-(4-hydroxyphenyl)-propane. The melt stability of the example compositions was determined at 300°C. The Instron stability test used measured the melt viscosity of the polymer (poise x 10 ^-4 ) and shear rate of 72 sec ^-1 on the polymer after 5, 35 and 65 minutes of residence time in an Instron barrel at 300°C. do. The change in viscosity measured between 5 and 65 minutes in this test is a good indication of the stability of the polymer tested. If there is a significant drop in viscosity between 5 and 65 minutes, the polymer is considered unstable. However, if the difference in viscosity is small between 5 and 65 minutes, the polymer is stable. All compositions were found to be stable.

[Table] (1) TetrachloroBPA/BPA copolymer (chlorine 10
wt%) Relative viscosity at 25℃ in methylene chloride is the solvent
1.281 measured with 0.5 g of resin in 100 ml (2) Bis-2,4-dichlorobenzoate (chlorine 40% by weight) of tetrachloroBPA with the following structure: (3) Teflon T-6 and 6C (ASTM Type 3 polytetrafluoroethylene powder) (4) N-methyltetrachlorophthalimide (chlorine 47.4% by weight) having the following structure:

【table】

[Table] Of particular interest in Table 1 is Example 12.
~15. As mentioned above, the melt flow of a polycarbonate has a significant influence on its flame retardancy, and generally high melt flow resins have considerably poorer flame retardant properties. However, all four of these compositions with fairly high melt flows are capable of achieving a UL-94 rating at 3.2 mm of 94V-0. Table 2 shows that the novel composition of the present invention consisting of aromatic polycarbonate/mineral acid salt/fibril-formed polytetrafluoroethylene/compound containing chlorine or bromine attached to an aromatic ring has a synergistic effect on the compositions of the prior art. It shows that it softens and has excellent flame retardant properties. As shown in Table 2, the same aromatic polycarbonates contained 0.25, 050 and 1.00% by weight, respectively.
KBF ₄ , blended (Examples 16, 17 and 18);
Blended with 0.10, 0.50 and 1.00 wt% fibril-forming polytetrafluoroethylene (Example
19, 20 and 21) and blended with 1.00 and 2.00% by weight of tetrachlorophthalic anhydride (52% by weight chlorine) (Examples 22 and 23). However, polycarbonate blended with one of these additives (and two of the three)
Types and blended polycarbonates (example
24, 25 and 26)), UL-94 test or IBM6
The flame retardant properties according to the -043-102 test are poor.
For this, 0.25% by weight of KBF ₄ 0.10% by weight of fibril-forming polytetrafluoroethylene and
The composition of Example 27 according to the invention containing 0.50% by weight of tetrachlorophthalic anhydride shows excellent flame retardant properties. It should be noted that although the composition of Example 27 contained minimal amounts of each of the three additives, it was improved over the composition containing 10 times as much of each additive alone as in Example 27. This means that it exhibits flame retardant properties. The compositions of the present invention thus represent an advance in the art in meeting the three criteria normally required of flame retardant systems. They provide high levels of flame retardancy at low levels of additives (less than 1% or even 0.5% by weight in some cases), but despite the use of inexpensive additives, they exhibit excellent thermal stability. Retains excellent mechanical properties. In particular, the compositions of the present invention have a 94 V-0 at 3.2 mm, or 1.6 in embodiments using small amounts of chlorine or bromine.
It has a UL94 rating of 94V-0 in mm,
Melt stability and good mechanical properties at 300°C are maintained.

Claims (1)

Claims: 1. (a) Thermoplastic aromatic polycarbonate; (b) 0.01 to 1% by weight, based on the weight of the total composition.
, K ₃ AlF ₆ /KAlF ₄ , KPF ₆ , Na ₂ S ₂ O ₅ ,
NaSbF ₆ , Na ₂ B ₄ O ₇ , K ₂ SiF ₆ , K ₄ P ₂ O ₇ and
at least one inorganic acid alkali metal salt selected from KBF ₄ ; (c) 0.01 to 1% by weight based on the weight of the total composition;
and (d) a compound containing chlorine or bromine attached to an aromatic ring, the amount of chlorine or bromine being from 0.05 to 1.0% by weight, based on the weight of the total composition. A flame-retardant molding composition characterized by: