Abstract:
A process for dispersing one or more powdered ignition resistant or flame retardant additives into carbonate polymers which comprises the steps of preparing a base concentrate having about 5 to about 50 weight per cent of said additives by blending said additives with a carbonate polymer having a melt flow rate from about 3 to about 20, pelletizing said base concentrate having said ignition resistant additive dispersed therein, dry blending said concentrate pellets with carbonate pellets having a melt flow rate from about 1 to about 80 whereby said polymer/concentrate blend has an amount of said additive dispersed therein effective to render said blend ignition resistant, and pelletizing or molding said carbonate polymer/concentrate blend. The use of this method gives ignition resistant carbonate polymers with improved impact properties as measured by Izod impact tests.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of Ser. No. 286,918 filed Dec. 20, 1988 which is a continuation-in-part of Ser. No. 132,495 filed Dec. 14, 1987 all now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a composition and a process for the production of ignition resistant or flame retardant polycarbonates and/or carbonate polymers wherein the ignition resistant additives are first compounded into a polycarbonate carrier resin then blended with a low molecular weight or moldable polycarbonate. 
     It is known from U.S. Pat. No. 4,626,563 that aromatic sulfimide metal salts, monomeric or polymeric halogenated aromatic compounds, metal salts of inorganic acids having a pKa from 1 to 5, and fibril forming polytetrafluoroethyene are useful to render carbonate polymers ignition resistant or flame retardant. Other flame retardant additives are known from and listed in U.S. Pat. No. 4,650,823. These patents are incorporated by reference herein. 
     SUMMARY OF THE INVENTION 
     The present invention is broadly directed to a process for dispersing one or more powdered ignition resistant or flame retardant additives into carbonate polymers wherein the impact properties of the ignition resistant carbonate polymers is improved. 
     More specifically, the invention is directed to a process for dispersing one or more powdered ignition resistant or flame retardant additives into carbonate polymers which comprises the steps of preparing a base concentrate having about 5 to about 50 weight percent of said additives by blending said additives with a carbonate polymer having a melt flow rate from about 3 to about 80 and preferably a MFR in the range of 3 to 20, pelletizing said base concentrate having said ignition resistant additive dispersed therein, dry blending said concentrate pellets with carbonate polymer pellets having a melt flow rate from about 1 to about 80 whereby said polymer/concentrate blend has an amount of said additive dispersed therein effective to render said blend ignition resistant, and pelletizing or molding said carbonate polymer/concentrate blend. 
     The process of this invention has the following steps: 
     (A) making a polymer/concentrate by pelletizing a carbonate polymer having a melt flow rate in the range from about 3 to about 80 with the composition comprising, 
     (i) 2.0 to 10% by weight of a metal salt of an aromatic sulfur containing compound, 
     (ii) 10 to 80% by weight of a monomeric, oligomeric or polymeric halogenated aromatic compound, 
     (iii) 2.0 to 10.0% by weight of compound selected from the group consisting of a metal salt of an inorganic compound and a free aromatic sulfimide, and 
     (iv) 6 to 40% by weight of a fibril forming polytetrafluoroethyene, 
     (B) blending said concentrate pellets with carbonate polymer pellets having a melt flow rate from about 1 to about 80 and substantially lower than said first carbonate polymer whereby said polymer/concentrate blend has an amount of said additives dispersed therein effective to render said blend ignition resistant, and 
     (C) pelletizing or molding said carbonate polymer/concentrate blend. 
     The advantages of the invention over the known techniques are that significant improvement is seen in the toughness of the final product as measured by improved Izod impact tests when the polymer concentrate is first made and diluted down with additional polymer. In addition, the generation of dust particles which is commonly found in additive compounding is eliminated. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The carbonate polymers employed in the present invention are advantageously aromatic carbonate polymers such as the trityl diol carbonates described in U.S. Pat. Nos. 3,036,036; 3,036,037; 3,036,038 and 3,036,039; polycarbonates of bis(ar-hydroxyphenyl) alkylidenes (often called bisphenol-A type diols) including their aromatically and aliphatically substituted derivatives such as disclosed in U.S. Pat. Nos. 2,999,835; 3,038,365 and 3,334,154; and carbonate polymers derived from other aromatic diols such as described in U.S. Pat. No. 3,169,121. 
     It is understood, of course, that the polycarbonate may be derived from (1) two or more different dihydric phenols or (2) a dihydric phenol and a glycol or a hydroxy- or acid-terminated polyester or a dibasic acid in the event a carbonate copolymer or heteropolymer rather than a homopolymer is desired. Also suitable for the practice of this invention are blends of any one of the above carbonate polymers. Also included in the term carbonate polymer are the ester/carbonate copolymers of the types described in U.S. Pat. Nos. 3,169,121; 4,105,633; 4,156,069; 4,225,556; 4,260,731; 4,287,787; 4,330,662; 4,355,150; 4,360,656; 4,374,973; and 4,388,455. Of the aforementioned carbonate polymers, the polycarbonates of bisphenol-A and derivatives, including copolycarbonates of bisphenol-A, are preferred. Methods for preparing carbonate polymers for use in the practice of this invention are well known, for example, several suitable methods are disclosed in the aforementioned patents which are hereby incorporated by reference in their entirety. 
     The monomeric, oligomeric or polymeric halogenated aromatic compound used in this invention can be virtually any halogenated organic compound commonly used as a fire retardant additive. The preferred compounds are the halo-substituted aromatic compounds (halo is fluoro, chloro, or bromo). Suitable compounds include, for example, decabromo diphenyloxide, tris(tribromophenoxy) triazine, decabromodiphenylcarbonate, an oligomer or polymer of tetrabromobisphenol A, and a copolymer of bisphenol A/tetrabromobisphenol A. Combinations of the above identified compounds can be employed. Examples of other suitable monomeric and polymeric halogenated compounds are disclosed in U.S. Pat. No. 4,263,201, which is incorporated herein by reference. 
     The metal salts of sulfur compounds used herein include metal salts of aromatic sulfonates, sulfates, sulfonamides, and sulfimides. Suitable metals are the metals of Groups I and IIA of the Periodic Chart as well as copper, aluminum, and antimony. The preferred metal is an alkali metal such as sodium or potassium. 
     The preferred group of aromatic sulfur compounds are sulfimides having the formula ##STR1## wherein Ar is an aromatic group and M is a metal cation. 
     Examples of the sulfimide salts are the alkali metal salts of saccharin, N-(p-tolylsulfonyl)-p-toluene sulfimide, N-(N&#39;-benzylaminocarbonyl)sulfanilimide, N-(phenylcarboxyl)-sulfanilimide, N-(2-pyrimidinyl)-sulfanilimide, and N-(2-thiazolyl)sulfanilimide. These salts and similar ones are disclosed in U.S. Pat. No. 4,254,015 which is incorporated herein by reference in its entirety. 
     The free aromatic sulfimides useful in this invention are those having a pKa in the range from about 1 to about 3. Examples of such free aromatic sulfimides are saccharin, N-(p-tolylsulfonyl)-p-toluene sulfimide, N-(N&#39;-benzylaminocarbonyl)sulfanilimide, N-(phenylcarboxyl)-sulfanilimide, N-(2-pyrimidinyl)sulfanilimide, and N-(2-thiazolyl)sulfanilimide. They are further illustrated by the formula ##STR2## wherein R is carbonyl, arylcarbonyl, arylaminocarbonyl, aralkylaminocarbonyl, or arylsulfonyl. Specific examples of these groups are benzoyl, benzylaminocarbonyl and tolylsulfonyl groups. 
     In general, the additive package has a fixed weight ratio of components so that after the polymer concentrate is made it can be readily shipped without dust formation to desired locations where it can be diluted down or let down with more polymer to the final ignition resistant product. The preferred ratio of components is; metal salt of an aromatic sulfur containing compound:monomeric, oligomeric or polymeric halogenated aromatic compound:metal salt of an inorganic compound:fibril forming polytetrafluoroethyene (1:10:1:3). For example, a 15% additive/polymer concentrate is blended with more polymer at a 10:1 ratio to give a useful ignition resistant blend. 
     In addition to the aforementioned fire retardant additives, other additives can be included in the carbonate polymer composition of the present invention such as fillers (i.e. glass fibers), pigments, dyes, antioxidants, stabilizers, ultraviolet light absorbers, mold release agents, impact modifiers and other additives commonly employed in carbonate polymer compositions. 
     The following examples and controls are presented to further illustrate the invention. 
     EXAMPLE 1 
     A fifteen percent ignition resistant (IR) polycarbonate concentrate is prepared by adding 1 gram (1%) potassium paratolylsulfimide (KPTSM) 1 gram (1%) potassium bisulfate (KHSO 4 ), 3 grams (3%) fibril forming polytetrafluoroethylene (Teflon 6C) and 10 grams (10%) tetrabromobisphenol-A oligomer (TBBPA), all in one masterbatch, to 85 gms (85%) heat stabilized polycarbonate resin having a 22 gms/10 min MFR (melt flow rate). The KPTSM is represented by the formula: ##STR3## wherein Ar is a paratolyl group and M is potassium. 
     The additive masterbatch and polycarbonate pellets are blended on a rotating blender (Lightnin blender) for one minute with agitation. The resultant blended material is gradually fed to a 30 mm twin screw extruder having a 250° C. barrel temperature. The extruded pellets are post blended on a paint shaker to ensure uniform mixing. 
     The 15% IR concentrate is let down in or blended with a base polycarbonate at 10 to 1 ratio. The base polycarbonate had a 15 gms/10 minute melt flow rate (MFR). The mixture was blended on Lightnin blender for 1 minute. The blended pellets are extruded on 30 mm twin screw extruder at 275° C. barrel temperature to make a 15 MFR ignition resistant polycarbonate product. The final product is dried in an oven for 3 hours at 125° C. and molded into bars for flammability and Izod impact tests. If desired the IR concentrate and base polycarbonate can be fed separately into the twin screen extruder or can be directly molded into various parts. 
     EXAMPLE 2 
     The procedure for Example 1 was repeated using 1 gm (1%) paratolylsulfimide (HPTSM) in place of the KHSO 4 . 
     EXAMPLE 3 
     The procedure for Example 1 was repeated using a 30 weight % IR concentrate. This concentrate contained: 
     2% potassium paratolylsulfimide, 
     2% potassium bisulfate, 
     6% fibril forming polytetrafluoroethylene and 
     20% tetrabromobisphenol-A oligomer. 
     This 30% concentrate was blended with a base polycarbonate at a 20 to 1 letdown ratio. 
     EXAMPLE 4 
     The procedure for Example 2 was repeated using the above 30% IR concentrate at a 20 to 1 letdown ratio. 
     Control A 
     The procedure for Example 1 was repeated using only the base resin without either IR concentrate or IR masterbatch. 
     Control B 
     The procedure for Example 1 was repeated using only 1.5% IR additive masterbatch without concentrate. 
     The above examples and controls were tested for Izod impact strength and the results are shown in Table I. 
     
                       TABLE I______________________________________       PC       carrier              Izod Impact (10 mil       (MFR   notched at 25° C.; ASTM       in     D-259-84)         gms/10               %Sample        min.)    Izod Impact Brittle______________________________________Cntrl A       N.A.     15.0         0(Base Polymer)         ft.lb./in.Cntrl B       N.A.      3.0        100(Cntrl A + 1.5% IR     ft.lb./in.Masterbatch)Example 1     22       14.5         015% I.R.               ft.lb./in.concentrate with10:1 letdownExample 2     22       14.7         015% I.R.               ft.lb./in.concentrate with10:1 letdownExample 3     22       13.0        1030% I.R.concentrate with20:1 letdownExample 4     22       13.3        1030% I.R.concentrate with20:1 letdown______________________________________ 
    
     Table 1 shows that the use of IR concentrate at either 10 to 20 to 1 letdown (15 or 30%) resulted in improved Izod impact properties without any brittle breaks versus IR additive masterbatch which resulted in very low Izod impact with 100% brittle breaks. The improvement of Izod impact via the use of IR concentrate is attributed to more uniform additive dispersion using IR concentrate than using IR masterbatch. 
     The above examples and controls were further tested for ignition resistance or flammability using the well known UL-94 test. The results are shown in Table II. 
     
                       TABLE II______________________________________    UL-94 Test (1/16&#34;)                   Number      Avg. T-      ofSample     Sec          Drips    Rating______________________________________Control A  10.3         5/5      V-2Control B  1.0          0/5      V-0Example 1  1.2          0/5      V-0Example 2  1.5          0/5      V-0Example 3  1.1          0/5      V-0Example 4  1.3          0/5      V-0______________________________________ Note: TSec means time in seconds for a flame out 
    
     Table II shows the use of IR concentrate does not detract from the flammability properties of final product. 
     EXAMPLE 5 
     The procedure for Example 3 was repeated using a 20 MFR polycarbonate carrier. 
     EXAMPLE 6 
     The procedure for Example 4 was repeated using a 15 MFR polycarbonate carrier. 
     EXAMPLE 7 
     The procedure for Example 4 was repeated using a 10 MFR polycarbonate carrier. 
     Control C 
     The procedure for Example 3 was repeated using a 40 MFR polycarbonate carrier. 
     Control D 
     The procedure for Example 3 was repeated using a 80 MFR polycarbonate carrier. 
     The above examples and controls were tested for Izod impact strength and the results are shown in Table III. 
     
                       TABLE III______________________________________               Izod Impact (10 mil               notched at 25° C.;               ASTM D-259-84)                     Izod           PC        Impact           Carrier   (ft.lb./ %Sample          (MFR)     in)      Brittle______________________________________Cntrl A (Base   N.A.      15.0      0Polymer)Cntrl C (Cntrl A +           40        7.5      5030% IR concentrate at20 to 1 ratio)Cntrl D (Cntrl A +           80        3.0      10030% IR concentrate at20 to 1 ratio)Example 5 (Cntrl A +           20        13.0      030% IR concentrateat 20 to 1 ratio)Example 6 (Cntrl A +           15        14.5      030% IR concentrate at20 to 1 ratio)Example 7 (Cntrl A +           10        14.0     1030% IR concentrate at20 to 1 ratio)______________________________________ 
    
     The above controls and/or examples show that high melt flow rate polycarbonates are not effective as carriers as the low MFR carriers. 
     The above examples and controls were further tested for ignition resistance using the UL-94 test. The results are shown in Table IV. 
     
                       TABLE IV______________________________________    UL-94 Test (1/16&#34;)                   Number      Avg. T-      ofSample     Sec          Drips    Rating______________________________________Control A  10.3         5/5      V-2Control C  1.0          0/5      V-0Control D  2.0          0/5      V-0Example 5  1.0          0/5      V-0Example 6  1.0          0/5      V-0Example 7  1.0          0/5      V-0______________________________________ Note: TSec means time in seconds for a flame out 
    
     Tables III and IV show that lower MFR polycarbonate carriers help to improve the Izod impact strength of the polymer better than higher MFR PC carriers without sacrificing the flammability property of the final product.