Abstract:
A fabric is coated with a composition which comprises a thermoplastic polyurethane and 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane derivative having the following general formula ##STR1## wherein each n1 and n2 represents zero or a positive integer and n1 + n2 is zero or one of the integers from 1 to 8, and preferably a polyisocyanate as a cross-linking agent.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a flame retardant coating composition, particularly relates to a flame retardant polyurethane coating composition having a good light fastness. This invention also relates to a coated fabric therewith. 
     Heretofore, it has been widely practiced to apply thermoplastic polyurethane composition to various fabrics, particularly to light fabrics such as polyamide and polyester fabrics. However, those coated fabrics are extremely flammable and therefore, it is necessary to make them flame retardant. Many attempts have been made to obtain flame retardant polyurethane coating composition, but satisfactory results could not have been obtained. Among them a method wherein phosphoric esters containing halogen atoms such as tris(dibromopropyl)phosphate are used in combination with polyurethane is said to be a relatively preferable method. However, those compositions lower the light fastness of the finished fabrics to a great extent though exhibit a good flame resistance. Therefore, this method is only applicable to the limited materials and rather impractical. 
     The principal object of the invention is to provide a polyurethane coating composition superior in flame resistance and light fastness. 
     A further object of the invention is to provide an improved flame retardant coated fabric. 
     The other objects and advantage of the invention will partly be apparent and partly become clear from the following detailed description of the invention. 
     SUMMARY OF THE INVENTION 
     The flame retardant coating composition according to the invention comprises a thermoplastic polyurethane and 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane derivative; 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane derivative is an adduct of ethylene oxide with 2,2-bis(4-hydroxy-3,5-dipromophenyl)propane which has the following general formula (I) ##STR2## wherein each n1 and n2 represents zero or a positive integer and n1+n2 is zero or one of the positive integers from 1 to 8. 
     The mixing ratio of 2,2-bis(4-hydroxy-3,5-dibromophenyl) propane derivative to polyurethane is not limited, but it is preferable that 3-30 parts by weight, most preferably 7-20 parts by weight, of 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane derivative is mixed with 20 parts by weight of polyurethane. 
     The flame retardant polyurethane coating composition is applied to fabrics to obtain polyurethane coated fabrics superior in flame resistance. 
     DETAILED DESCRIPTION OF THE INVENTION 
     As a polyurethane useful in the invention, any one which is generally used as fiber treating agent and coating component can be utilized, regardless of its type or kind such as polyether polyurethane, polyester polyurethane and polyurethane polyurea. The polyurethanes useful herein are conventional and well known in the art as disclosed in &#34;Textile Chemist and Colorist&#34; Vol. 5 No. 8 pages 151-159 (1973). The coating composition according to the invention may be prepared in the forms of a solution in organic solvents such as dimethylformamide, methylethylketone, tetrahydrofuran, benzene and toluene, or an aqueous dispersion. The coating composition being an organic solvent solution is preferred. 
     The coating composition of the invention may further contain coloring agents and other additives. When a polyisocyanate compound is used in the coating composition as a cross linking agent, the physical property of the resultant polyurethane coating is found to be further improved, and the light fastness and the flame resistance are increased. 
     The isocyanate compounds useful as cross linking agent may be any compounds which have a relatively low molecular weight and contain at least two isocyanate groups in its molecule. Among them there may be included polyisocyanates such as diphenylmethane diisocyanate and triphenylmethane triisocyanate; addition products of polyisocyanate to triols such as trimethylol propane; and other active polyisocyanate prepolymers. In addition, such compounds that have temporally blocked isocyanate groups with phenol which can be converted to active isocyanate groups by heating. 
     The coating composition of the invention can be applied to a wide variety of textile goods such as natural fibers, synthetic fibers, fabrics and non-woven fabrics by the conventional coating method such as a doctor knife coating method, a dipping method, a spraying method and a transferring method. 
     The coating compositions according to the invention show a good flame resistance which is equal or superior to that of the composition which is obtained with use of tris(2,3-dibromopropyl)phosphate. In addition, the coated fabrics of the invention have a good light fastness and are superior in other physical properties. 
    
    
     PREFERRED EMBODIMENTS OF THE INVENTION 
     This invention will be further illustrated by the following examples. 
     EXAMPLE 1 
     10 parts by weight of 2,2-bis(4-hydroxyethoxy-3,5-dibromophenyl)propane was added to 100 parts by weight of thermoplastic polyurethane solution (solid content: 20% by weight, solvent:methylethylketone/toluene =1/1 by weight, viscosity at 25° C.: 15000 cps) which was obtained by the reaction of polyester prepared from 1,4-butanediol and adipic acid with methylenebisphenol isocyanate (MDI), and mixed thoroughly. The polyurethane solution is a hydroxy-terminated polyurethane solution of polyurethane 3922 produced by Nikon Polyurethane Kogyo Kabushiki Kaisha. 
     The resultant mixture solution was applied to nylon taffeta (65 g/m 2 ) with use of doctor knife. The coated nylon taffeta was dried at a room temperature for 30 minutes and then at 110° C. for 3 minutes with hot air. After allowing to stand at a room temperature for additional 24 hours, the product was examined with respect to flame resistance and light fastness. The thickness of the coating formed on nylon taffeta was calculated according to the gravimetric method and found to be 25 microns. The results of the above examination are shown in Table 1. 
     EXAMPLE 2 
     The same procedure as in Example 1 was repeated except that 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane derivative having the general formula (I) in which n1+n2 is 4 was used instead of 2,2-bis(4-hydroxyethoxy-3,5-dibromophenyl) propane to obtain a coated fabric. The coated fabric was examined in the same manner as in Example 1, and the resultants are shown in Table 1. 
     Control 1 
     The same procedure as in Example 1 was repeated except that tris(2,3-dibromopropyl)phosphate (TBPP) was used instead of 2,2-bis(4-hydroxyethoxy-3,5-dibromophenyl)propane to obtain a coated fabric. Obtained fabric was examined in the same manner as in Example 1, and the results are also shown in Table 1. 
     EXAMPLE 3 
     10 parts by weight of 2,2-bis(4-hydroxyethoxy-3,5-dibromophenyl)propane and 5 parts by weight of ethyl acetate solution of triisocyanate compound (solid content of 75%) which was prepared from 1 mole of trimethylpropane and 3 moles of toluene diisocyanate were added as a cross linking agent to 100 parts by weight of the same polyurethane solution as in Example 1, and mixed thoroughly. 
     The resultant mixture solution was applied to nylon taffeta in the same manner as in Example 1. 
     The same examination as in Example 1 was carried out, and the results are shown in Table 1. 
     EXAMPLE 4 
     The same procedure as in Example 3 was repeated except that 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane derivative having the general formula (I) in which n1+n2 is 6 was used instead of 2,2-bis(4-hydroxyethoxy-3,5-dibromophenyl)propane to obtain a coated fabric. The coated fabric was examined in the same manner as in Example 1 and the resultants are shown in Table 1. 
     Control 2 
     The same procedure as in Example 3 was repeated except that tris(2,3-dibromopropyl)phosphate was used instead of 2,2-bis(4-hydroxyethoxy-3,5-dibromophenyl)propane to obtain a coated fabric. This coated fabric was examined in the same manner as in Example 1 and the results are shown in Table 1. 
     
                       Table 1______________________________________       Light fastness                   Flame resistance______________________________________Example 1     4th grade     4-5Example 2     4th grade     5Control 1     1st grade     4Example 3     4th grade     4-5Example 4     4th grade     5Control 2     1st grade     4______________________________________ (notes): Light fastness : JIS L 0842 Carbon arc lamp method Flame resistance : JIS L 10911973 R D method (Coil method)? 
    
     The flame resistance is measured by the following steps according to Japanese Industrial Standard (JIS) L 1091--1973, D method. 
     A sample sheet having a width of 100 mm and a weight of 1 g is prepared. The sheet is rolled with a width of 100 mm. The rolled sample is placed in a coiling supporter maintained at an angle of 45°. The bottom end of the rolled sample is contacted with the flame of a burner to heat the sample until the burning of it stopped. This burning step is repeated. The number of burning steps required to burn up 90 cm of the rolled sample from the bottom of it are measured. 
     The light fastness is measured by the following steps according to Japanese Industrial Standard (JIS) L 0845. 
     A sample sheet is attached to a test holder with a blue scale having eight grades and exposed to carbon arc lamp light. Then, the colour fastness of the sample sheet is measured in terms of the grade of the blue scale which indicates the most similar discoloration to that of the sample sheet. The larger the grade, the more superior the colour fastness.