Abstract:
A fire-retardant and radiation resistant molded resin product is prepared by blending a resin with a halogenated acenaphthylene compound of the formula: ##STR1## wherein X is chlorine or bromine and R is alkyl, alkoxy or alkylester of 1 to 4 carbon atoms such that when m is 0, n is an integer of 2 to 8; when m is an integer of 1 to 4, n is an integer of 2 to 7 and n+m is ≦8 and when m is more than 2, R may be the same or different; and, after molding said blend, generating free radicals within said blend.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a fire retardant resin molded product, and to a process for preparing the same. 
     From a viewpoint of safety in an atomic power station, a demand for improvement of the reliability on and the health of electric cable for light-water type power reactor is now going on increasing. Saturated hydrocarbon polymers such as polyethylene and ethylene-propylene copolymer have been used as an insulating material for electric cable. These materials are widely used because of being relatively excellent in radiation resistance in addition of insulation ability, workability and economy. However, their mortal defect lies in combustibility. 
     Today a combustible resin such as polyethylene, polypropylene and ethylene-propylene rubber is mixed with various fire retardant additives for the purpose of making the resin fire retardant. As a fire retardant additive, a halogenated aliphatic compound such as chlorinated paraffine and chlorinated polyethylene and a halogenated aromatic compound such as hexabromo benzene and decabromo diphenylether are known. However, the halogenated aromatic compound, from the molecular structural point of view, is wanting in compatibility with resins and often blooms to the surface of resin during use for a long term and volatilizes at elevated temperatures and thereby has a tendency to bring on a change in fire retardance of resin. 
     Further, recently, in an electric wire, cable and various machinery and tools used for a nuclear reactor, breeder reactor and ionizing radiation generator, from the viewpoint of safety, it has become indispensable to be fire retardant. Therefore, various resin compositions used as insulating materials for electric wires and cables, packings and sealing materials, are required to be not only fire retardant but also radiation resistant. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a fire retardant resin molded product capable of maintaining a fire retardance stable over a long period and a property as not volatilizing nor blooming when used at elevated temperatures for a long time. 
     Further, an object of the present invention is to provide a resin molded product having a remarkably improved fire retardance and simultaneously having a radiation resistance. The present inventors have found that a specific acenaphthylene compound melts and disperses relatively uniformly into a resinous material when milling to the resinous material or molding under heat and polymerizes by subjecting to a treatment with free radical generation and partially grafting to the resinous materials and thereby provide a high fire retardance thereto and thereby the resulting molded product is prevented from volatilization and leaching on use, and have accomplished the present invention. 
     That is, the fire retardant resin molded product of the present invention is obtained by blending a resin with a halogenated acenaphthylene represented by the formula ##STR2## , wherein X is chlorine or bromine atom; Q is O or Rm wherein R is an alkyl, alkoxy or alkylester group having 1 to 4 carbon atoms; when Q is O, n is an integer of 2 to 8 and when Q is Rm, n is an integer of 2 to 7, m is an integer of 1 to 4; and n+m≦8, in case m is more than 2 R may be the same or different, and, after molding, subjecting the resin to a treatment with free radical generation. X in the formula of fire retardant additive is chlorine or bromine which may coexist in the same molecule. In case of n=1 the fire retardant effect is scarcely recognized. The substitution of above n=2 is required for fire retardant effect. A resin composition with a fire retardant additive high in polymerizability displays very high fire retardant properties because such fire retardant additive is distributed homogeneously and fixed completely in the resin. The compatibility of fire retardant additive and resin is improved by introducing an alkyl group, a methoxy group, or a methylester group thereinto. Thereby the workability in milling and molding and such a property as not volatilizing nor blooming on use at elevated temperatures for a long period are increased. An acenaphthylene derivative having more than four alkyl groups is difficult to synthesize and also the derivative having a longer alkyl chain than limited length should not be used because it lowers the fire retardant properties and the radiation resistance. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The concrete example corresponding to Rm in the formula of fire retardant additive includes 3-methyl, 5-methyl, 3-ethyl, 4-ethyl, 3,5-dimethyl, 3,5-diethyl, 5,6-dimethyl, 5-butyl, 3-methoxy, 5-methoxy, 5-ethoxy, 3,5-dimethoxy, 5,6-dimethoxy, 5-butoxy, 3,5-dimethylester, 5-methylester, etc. 
     The resinous material to be improved its fire retardant properties according the present invention includes, for example, polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-ethylacrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinylchloride copolymer, ethylene-vinylacetate-graft vinylchloride copolymer, ethylene-propylene-graft vinylchloride copolymer, chlorinated polyethylene, chlorinated polyethylene-graft vinyl chloride copolymer, polyurethane, polyamide, polyester, acrylic resin, butyl rubber, chloroprene rubber, nitrile rubber, natural rubber, silicone rubber, chlorosulfonated polyethylene, styrene-butadiene rubber, styrene-butadiene-acrylonitrile copolymer, acrylonitrile-styrene copolymer, polyester-ether elastomer, etc. The fire retardant resin molded product of the present invention can be prepared by subjecting the fire retardant resin composition to a treatment with free radical generation. In order to increase the yield of polymer of acenaphthylene derivative in the resin by the treatment with free radical generation, it is effective to mix an appropriate amount of acenaphthylene and other radical polymerizable compounds or radical polymerizable fire retardant additives into the acenaphthylene derivative and to make them copolymerize or cograft. 
     The amount of fire retardant additive to be mixed is preferably determined within the range of about 5 to 150 parts, by weight, per 100 parts, by weight, of resin for good fire retardant properties in lower limit and sufficient extensibility and flexibility of resin in upper limit. With regard to the radiation resistance, an effect is recognized in the resin composition added with more than 0.5 parts, by weight, of acenaphthylene derivative and the more the amount is the greater the effect is. 
     As a concrete means for treatment with free radical generation, so called &#34;heating method&#34; as blending an organic peroxide such as dicumyl peroxide, 1,3-bis (t-butyl peroxide), 1,3-bis(t-butyl peroxy isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexyne-3, di-t-butyl peroxide, etc. into the resin composition and heating and the irradiation of ionizing radiation such as β ray, γ ray and accelerated electron beams are included. From the viewpoint of operation effect it is preferable for some kinds of resin to mix a polyfunctional monomer such as trimethylolpropane trimethacrylate, polyethylene glycol dimethacrylate, triarylisocyanurate, etc. in the treatment with free radical generation. And also it is preferable for fire retardant properties to add an inorganic filler such as antimony trioxide, aluminium hydroxide, talc, etc. Further, there is no harm in adding a reinforcing agent, a filler, a pigment, a lubricant and a heat or light stabilizer, etc. 
    
    
     The present invention will be explained more in detail in the following Examples. 
     EXAMPLES 1 TO 5 AND COMPARATIVE EXAMPLES 1 TO 3 
     All components were milled uniformly on a hot roll and thereafter were heated and pressed by a hot press at 180° C. for 20 minutes to mold a sheet of 1 to 3 mm in thickness. 
     The loading unit of each component is shown by part by weight. 
     
         ______________________________________Example 1Polyethylene                100Chlorinated polyethylene (Chlorinecontent 40%)                353,5-dibromoacenaphthylene   30 ##STR3##Antimony trioxide           102,6-di-t-butylphenol        0.5Dicumylperoxide             3Example 2Polyethylene                100Chlorinated polyethylene (Chlorinecontent 40%)                353,5,6,8-tetrabromoacenaphthylene                       30 ##STR4##Antimony trioxide           202,6-di-t-butylphenol        0.5Dicumylperoxide             3Example 3Ethylene-vinylacetate copolymer (Combinedvinylacetate 30%, by weight)                       1003,5,6,8-tetrachloracenaphthylene                       35 ##STR5##Antimony trioxide           152,6-di-t-butylphenol        0.5Dicumylperoxide             2Example 4Polyethylene                100Chlorinated polyethylene (Chlorinecontent 40%)                351,3,5,6,8-pentachloracenaphthylene                       30 ##STR6##Antimony trioxide           202,6-di-t-butylphenol        0.5Dicumylperoxide             3Example 5Ethylene-propylene copolymer (Combinedpropylene 40% by weight)    1001,3,5,6,8-pentabromacenaphthylene                       30 ##STR7##Antimony trioxide           202,6-di-t-butylphenol        0.5Dicumylperoxide             3Talc                        100Comparative Example 1Polyethylene                100Chlorinated polyethylene (Chlorine content 40%)                       35Hexabromobenzene            30 ##STR8##Antimony trioxide           202,6-di-t-butylphenol        0.5Dicumylperoxide             3Comparative Example 2Polyethylene                100Chlorinated polyethylene (Chlorine content 40%)                       0.52,4,3&#39;,5&#39;-tetrabromosalicylanilide                       2 ##STR9##Antimony trioxide           202,6-di-t-butylphenol        0.5Dicumylperoxide             3Comparative Example 3Ethylene-propylene copolymer                       1003,5,3&#39;,5&#39;-tetrabromodiphenyl                       30 ##STR10##Antimony trioxide           202,6-di-t-butylphenol        0.5Dicumylperoxide             3Talc                        100______________________________________ 
    
     The sheets obtained from the above examples were testing on blooming and burning. In the blooming test a sheet was let alone stand in a thermostatic chamber at 121° C. for 168 hours and then, after allowing to cool to room temperatures, the sheet was observed on whether there is a bloom. The burning test was based upon ASTM D635-74. The burning times before and after the blooming test were measured. The test results are as shown in Table 1. 
     
                                           TABLE 1__________________________________________________________________________         Example        Comparative Example         1  2  3  4  5  1    2    3__________________________________________________________________________Blooming      none            none               none                  none                     none                        found                             found                                  foundBurning time  Before heat.         5  5  5  5  5  5    5    5(Second)  After heat.         5  5  5  5  5  &gt;20  &gt;15  &gt;10Oxygen index before heatingtest (%)      25 27 25 26 31 25   25   26__________________________________________________________________________ 
    
     EXAMPLES 6 TO 10 AND COMPARATIVE EXAMPLES 4 TO 7 
     All components other than a free radical generating agent were milled uniformly on a hot roll and thereafter added with a free radical generating agent, and then the resulting composition was heated under pressure by a hot press at 160° C. for 30 minutes to mold a sheet of 1 to 3 mm in thickness. 
     The loading unit of each component is shown by part by weight. 
     
         ______________________________________Example 6Polyethylene (ZF-30, made by Mitsubishi                        100Petrochem. Co.)Chlorinated polyethylene (Chlorinecontent 40%)                 353-methyl, 1,5,6,8-tetrabromacenaphthylene                        30 ##STR11##Antimony trioxide            202,6-di-t-butylphenol         0.5Dicumylperoxide              3Example 7Polyethylene (ZF-30 made by the samecompany)                     100Chlorinated polyethylene (Chlorinecontent 40%)                 355-butoxy, 1,3,6,8-tetrabromacenaphthylene                        50 ##STR12##Antimony trioxide            252,6-di-t-butylphenol         0.5Dicumylperoxide              5Example 8Ethylene-vinylacetate copolymer (Yukalon Eva25 K, made by the same company)                        1003-methyl, 1,5,6,8-tetrachloracenaphthylene                        35 ##STR13##Antimony trioxide            152,6-di-t-butylphenol         0.5Dicumylperoxide              3Example 9Ethylene-propylene-diene copolymer (EP-21 madeby Japan Synthetic Rubber Co.)                        1003,5-dimethyl, 1,6,8-tribromacenaphthylene                        30 ##STR14##Antimony trioxide            202,6-di-t-butylphenol         0.5Dicumylperoxide              3Talc                         100Example 10Ethylene-propylene-diene copolymer (EP-21made by Japan Synthetic Rubber Co.)                        1005-butoxy, 1,3,6,8-tetrachloracenaphthylene                        40 ##STR15##Antimony trioxide            252,6-di-t-butylphenol         0.5Dicumylperoxide              4Talc                         100Comparative Example 4Polyethylene (ZF-30)         100Chlorinated polyethylene (Chlorinecontent 40%)                 0.52,4,3&#39;,5&#39;-tetrabromsalicylanilide                        2 ##STR16##Antimony trioxide            202,6-di-t-butylphenol         0.5Dicumylperoxide              3Comparative Example 5Ethylene-propylene copolymer (EP-21)                        1003,5,3&#39;,5&#39;-tetrabromdiphenyl  30 ##STR17##Antimony trioxide            102,6-di-t-butylphenol         0.5Dicumylperoxide              3Comparative Example 7Polyethylene (ZF-30)         100Chlorinated polyethylene (Chlorinecontent 40%)                 351,3,5,6,8-pentabromacenaphthylene                        30 ##STR18##Antimony trioxide            202,6-di-t-butylphenol         0.5Dicumylperoxide              3Comparative Example 8Ethylene-vinylacetate copolymer (YukalonEva 25 K)                    1001,3,5,6,8-pentachloracenaphthylene                        35 ##STR19##Antimony trioxide            152,6-di-t-butylphenol         0.5Dicumylperoxide              2______________________________________ 
    
     The sheets obtained from the above examples were tested in the same manner as in Examples 1 to 5. The test results are as shown in Table 2. Incidentally, the residual rate of fire retardant additive is meant by a percentage of fire retardant additive polymer obtained by Soxhlet extracting a small piece 1 mm square of molded sheet in toluene for the amount of fire retardant additive added. (Lower polymer components in the extraction liquid were recovered by reprecipitation with methanol and added to the residual rate.) 
     
                                           TABLE 2__________________________________________________________________________           Example        Comparative Example           6  7  8  9  10 4    5    6  7  8__________________________________________________________________________Blooming        none              none                 none                    none                       none                          found                               found                                    none                                       none                                          noneBurning time   Before heating           4  2  5  4  4  5    5    5  5  5(second)   After heating           4  2  5  4  4  &gt;15  &gt;10  5  5  5Oxygen index before heating test(%)             30 35 27 29 28 25   26   25 28 25Polymerization rate of fireretardant additive (%)           72 81 74 71 83 0    0    61 48 53__________________________________________________________________________ 
    
     EXAMPLES 11 AND 12 
     Fire retardant polyethylene sheet of 2 mm in thickness having the composition of Example 6 and fire retardant ethylene-propylene-diene copolymer sheet of 2 mm in thickness having the composition of Example 9 were irradiated with 100 Mrad of γ ray at room temperatures in air and were measured their mechanical properties before and after irradiation to evaluate the resistance to radiation. The results are as shown in Table 3. 
     
                       TABLE 3______________________________________                    Comparative            Example Example            11   12     4       5______________________________________Tensile strength     Before irradiation                  1.98   0.85 1.70  0.50(kg/cm.sup.2)     After irradiation                  2.10   0.90 1.65  0.45Elongation (%)     Before irradiation                  570    680  580   720     After irradiation                  310    370  190   170______________________________________ 
    
     As is evident from the table, according to the present invention, a fire retardant resin composition which is high in residue of elongation and excellent in resistance to radiation can be obtained. 
     EXAMPLE 13 
     100 parts of ethylene-propylene copolymer (EP-21), 30 parts of 1,3,5-tribromacenaphthylene as a fire retardant additive, 5 parts of ZnO, 0.4 part of S, 6 parts of Sb 2  O 3 , 1.5 parts of antioxidant, 1 part of lubricant and 100 parts of talc in weight were milled, and further 3 parts of dicumylperoxide as a free radical generating agent were added thereto and the fire retardant additive was polymerized at a condition of 160° C. and 100 kg/cm 2  and simultaneously molded to the desired shape. For comparison, each sample having used 3,5,3&#39;,5&#39;-tetrabromodiphenyl and decabromodiphenyl oxide, respectively, as a fire retardant addition was made. The test results for these samples are as shown in Table 4. 
     
                                           TABLE 4__________________________________________________________________________   Example of the   present invention            Comparative Examples__________________________________________________________________________Fire retardant additive    ##STR20##             ##STR21##                        ##STR22##Blooming   none     found      noneOxygen index   30       26         27   Tensile strength    Tensile strength   0.68Kg/mm.sup.2     0.55Kg/mm.sup.2Physical   Elongation 120%            --         Elongation 45%properties*   Bending test        Bending test   good                Broken__________________________________________________________________________ 
    
     As shown in the above description, the present invention can provide an excellent fire retardant resin molded product in which a fire retardant additive does not bloom nor volatilize by blending a specific fire retardant addition, and has no harmful effect on the aging behaviour.