Abstract:
A resin which may be cured to form a polymeric resin which is diffcultly inflammable and resistant to high temperatures, said resin being a mixture of 
     (a) a resin component comprising at least one thermically curable 1-oxa-3-aza tetraline group containing compound and optionally a curable epoxy compound; and of 
     (b) a second component comprising at least one flame retardant selected from the group consisting of: aluminum hydroxide; hydrated calcium magnesium carbonate; magnesium hydroxide; element red phosphorus, oxygen acids of phosphorus; inorganic salts of oxygen acids of phosphorus; organic salts of oxygen acids of phsophorus; polyphosphates; boric acid; salts of boric acid.

Description:
TECHNICAL FIELD 
     This invention relates to resins which may be cured to form polymeric resins which are difficultly inflammable an resistant to high temperatures, as well as to processes for preparing such polymeric resins More particularly, this invention relates to mixtures of 1-oxa-3-aza tetraline group containing compounds and flame retardants and to polymeric resins obtained by curing such mixtures. 
     BACKGROUND OF THE INVENTION 
     Compounds containing 1-oxa-3-aza tetraline groups and their prepolymers (hereafter called &#34;oxazene resins&#34; by convenience) are known, for example form Swiss Patents Nos. 574,978, 579,113 and 606,169. They can be obtained, for example, from phenols by reaction with formaldehyde and an amine, according to formula (A): ##STR1## wherein R is, for example, hydrogen, halogen, alkyl or alkoxy, and R&#39; is an aliphatic or aromatic group. 
     However, they can also be prepared by other processes leading to similar products. 
     In contrast to other known condensation reactions of phenols, amines and formaldehyde, in the reaction outlined above phenolic OH groups are consumed, it is thereby possible, according to the formula (A) hereinabove, to determine the amount of the synthesized 1-oxa-3-aza tetraline groups from the analytic determination of the said OH groups in the reaction mixture. 
     Prepolymers of 1-oxa-3-aza tetraline group containing compounds are also useful in preparing said oxazene resins. Since some of the 1-oxa-3-aza tetraline groups may react during polymerization, these prepolymers may contain a fewer number of said 1-oxa-3-aza tetraline groups than provided by the monomers used to form such prepolymers. It is essential, however, that the intermediately formed or hypothetic monomer reaction product does in fact contain 1-oxa-3-aza tetraline groups. This can easily be calculated by a person skilled in the art from the functionality. An oxazene resin, or its prepolymer, useful in accordance with the invention is, for instance, formed if the molar ratio is kept within the limits defined in Swiss Patent No. 606,169. 
     Phenol and phenol derivatives, respectively, as well as amines and formaldehyde are used as starting or basic materials for preparing the oxazene resin. 
     Preferably, for the present invention, 1-oxa-3-aza tetraline group containing compounds are used which are formally derived from a phenol and an amine, one of said components being more than monofunctional. 
     Examples of phenols that can be used include: 
     Monovalent phenols, such as phenol, m and p-cresol, m- and p-ethyl phenol, m- and p-isopropyl phenol, m- and p-isopropyloxy phenol m- and p-chloro phenol and betanaphthol. Meta-substituted phenols are preferred, since they do not include any blocked reactive positions. 
     Bivalent phenols, such as 4,4&#39;-dihydroxydiphenylmethane, 3,3&#39;-dihydroxy-diphenylmethane, 2,2&#39;-bis-(4-hydroxyphenyl)-propane, 4,4&#39;-dihydroxy-stilbene, hydroquinone, pyrocatechol, and resorcin. 
     Low-condensed phenol formaldehyde novolak resins, eventually mixed with a phenol. 
     Examples of amines that are particularly useful include: 
     Aniline, o-, m- and p-phenylene diamine, benzidine, 4,4&#39;-diaminodiphenyl methane, cyclohexylamine, ethylenediamine, and propylenediamine. 
     Polymeric resins on the basis of 1-oxa-3-aza tetraline group containing compounds are resistant to high temperatures of more than 200 ° C., and up to more than 300 ° C. The flame resistance, despite the fact that it compares favorably with that of other polymeric resins resistant to high temperatures, such as for instance epoxy resins is still not sufficient for many uses. The attempt to improve said flame resistance by incorporating of halogen would result in the drawback that highly toxic gases of combustion are formed in case of fire. 
     It is known to improve the flame resistance of some inflammable polymeric resins, such as epoxide resins and unsaturated polyester resins, by addition of a flame retardant which is not mixable with the polymeric resin. However, for achieving self-extinguishing properties such a high amount of additive is necessary, for instance 200 phr and more, that the good mechanical properties of these resins are lost. 
     As usual, in the present specification &#34;phr&#34; means &#34;parts by weight of additive per 100 parts by weight of resin&#34;. 
     Therefore, such systems are practically unsuitable for preparing highly reinforced polymeric resins. Difficultly inflammable phenolic resins are also out of the question for said use, since, per se, they already show much lower mechanical properties. In spite the serious toxicological doubts, no satisfying alternative to halogenated systems was found so far. 
     SUMMARY OF THE INVENTION 
     It now was found that oxazene resins can already be made self-extinguishing by addition of much lower amounts of flame retardants, for instance with such low amounts as 30 phr of ammonium polyphosphate aluminum hydroxide, and that products which are chemically stable and inflammable can be produced on this basis. 
     Broadly stated, the present invention provides for a resin which may be cured to form a polymeric resin which is difficultly inflammable and resistant to high temperatures of up to more than 280° C., said resin being a mixture of 
     (a) a resin component comprising at least one thermically curable 1-oxa-3-aza tetraline group containing compound; and of 
     (b) a second component comprising at least one flame retardant selected from the group consisting of: 
     aluminum hydroxide; 
     hydrated calcium magnesium carbonate; 
     magnesium hydroxide; 
     elemental red phosphorus; 
     oxygen acids of phosphorus; 
     inorganic salts of oxygen acids of phosphorus; 
     organic salts of oxygen acids of phosphorus; 
     polyphosphates; 
     boric acid; and 
     salts of boric acid. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In a preferred embodiment of the invention the second component (b) of said resin comprises one or several compounds selected from the group consisting of: 
     aluminum hydroxide; 
     hydrated calcium magnesium carbonate; 
     magnesium hydroxide; 
     elemental red phosphorus; 
     oxygen acids of phosphorus; 
     inorganic salts of oxygen acids of phosphorus; 
     organic salts of oxygen acids of phosphorus; 
     polyphosphates; 
     boric acid; 
     salts of boric acid. 
     Resin component (a) may also comprise a curable epoxy compound. 
     The forming of bubbles at higher temperatures may be avoided by curing or tempering said resin at temperatures of above 180° C., and preferably at a temperature of 180° to 200° C. 
     These findings were highly surprising to one skilled in the art for various reasons. 
     As it is generally known, epoxy resins show a much worse flame resistance than resins on the basis of phenol formaldehyde condensates. Therefore, it was the fear of that good flame resistance properties might be destroyed by the addition of epoxide compounds. As a matter of fact, this supposition proved to be a fallacy. 
     On the other hand, it was to be expected that bubble formation would happen already at temperatures of more than 180° C. This supposition too proved to be a fallacy. Calcium magnesium carbonate hydrate, for instance, decomposes at 230° C., so that bubble formation was to be expected at temperatures above said temperature. However, it was found that polymeric resins on the basis of 1-oxa-3-aza tetraline group containing compounds and calcium magnesium carbonate hydrate, with or without an epoxide compound, not only remains completely stable at 280° C. but also does scarcely show any bubble formation above the place of burning. 
     Therefore, calcium magnesium carbonate hydrate is particularly useful for polymeric resins having no addition of epoxide compounds. 
     It was particularly surprising to note that with oxazene resins the desired result can by obtained with much less flame retardant than with epoxide resins alone or with oxazene/epoxide resins. For instance, outstanding results may already be obtained with the following amounts of aluminum hydroxide (Al(OH) 3 ): 
     
         ______________________________________Oxazene resin     40       phr Al(OH).sub.3Oxazene/epoxide resin             90       phr Al(OH).sub.3Epoxide resin     about 200                      phr Al(OH).sub.3______________________________________ 
    
     There is no upper limit for the amount of additive, except that of processing technology. Amounts up to 300 phr aluminum hydroxide may be used for molding compositions. 
     As used throughout this specification, &#34;aluminum hydroxide&#34; stands for the compound of the chemical formula Al(OH) 3 . This compound is not identical with the compounds known as fillers and having the composition AlO-OH (aluminum oxide monohydrate, bauxite, et al). 
     Throughout this specification. &#34;calcium magnesium carbonate hydrate&#34; stands for &#34;hydrated calcium magnesium carbonate&#34;. A suitable compound for instance, shows the following analytical results for its main components: 
     38% MgO 
     8% CaO 
     53% ignition loss (=44% CO 2  +9% H 2  O). 
     Elemental red phosphorus is preferably used in microencapsulated form. Suitable encapsulation compounds are, for instance, epoxide compounds. 
     Advantageously, resin component (a) further comprises at least one curable epoxy compound preferably in an amount of at least 5 parts by weight, and particularly of 5 to 60 parts by weight per 100 parts by weight of the 1-oxa-3-aza tetraline group containing compound. 
     For this purpose, mono- or polyfunctional epoxide compounds which may be cured thermically, catalytically or by means of hardeners, and which generally are called epoxide resins, are suitable. Such suitable epoxide compounds are described in: 
     Sidney H. Goodman, Handbook of Thermoset Plastics, Noyes Publications, Park Ridge, NJ; 
     W. G. Potter, Epoxide Resins, Ilife Books, London; 
     Henry Lee and Kris Neville, Handbook of Epoxy Resins, McGraw-Hill Book Company, New York/San Francisco/Toronto/London. 
     Preferabky, aluminium hydroxide is used in an amount of at least 40 phr, calcium magnesium carbonate hydrate in an amount of at least 50 phr, ammonium polyphosphate and melamine phosphate in an amount of at least 20 phr. These additives can also be applied in coated form, for instance with a stearate or silane coating. 
     By thermally curing said curable resins at temperatures above 100° C., preferably at a temperature from 140° to 220° C., difficulty inflammable polymeric resins which are resistant to high temperatures and heat are obtained. 
     Advantageously, the cured polymeric resins, especially those containing aluminum hydroxide but no epoxide compounds, are subject to a thermal aftertreatment, preferably at temperatures of 180° to 220° C. The duration of this tempering depends on the temperature level. The following guide values may serve as clues, however, the duration may be extended at will without damage of the polymer resins: 
     24 h at 180° C.; or 
     4 h at 200° C.; or 
     30 min at 220° C. 
     These durations can be proportionally combined at will. For instance, the following tempering cycle has proved successful: 
     30 min at 200° C.+30 min at 220° C.+30 min at 230° C.+30 min at 250° C. 
     By using systems containing melamine phosphate self-extinguishing foam plastics can be produced without addition of a special foaming agent. This finding too was surprising for a person skilled in the art, since melamine phosphate in the absence of the resin is stable up to temperatures of 300° C. 
     The properties of the polymeric resins produced as described above can be tailored for certain applications by addition of usual additives. The following additives are of particular importance: 
     reinforcement fibers, such as glass, quartz, carbon, mineral and synthetic fibers, int he usual forms of short fibers, staple fibers, threads, fabrics or mats; 
     plasticizers, especially phosphorus compounds; 
     carbon black or graphite; 
     fillers; 
     dyestuffs; 
     micro hollow spheres; 
     metal powder. 
     The processes known for phenol formaldehyde resins or epoxy resins, such as hot-pressing of prepregs, SMC (Sheet Molding Compound); or molding; casting; filament winding; or vacuum impregnating are suitable for processing the resins according to the invention. With respect to vacuum impregnating, very fine additives having a particle size of less than 0.001 mm are particularly suitable. 
     EXAMPLES 
     In the following Examples, the starting compounds and materials specified hereafter were used. 
     1-Oxa-3-aza tetraline compound 1 
     prepared by reacting 4,4&#39;-diamino-diphenylmethane with phenol and formaldehyde in a molar ratio of 1:2:4. Structural formula: ##STR2## 
     1-Oxa-3-aza tetraline compound 2 
     prepared form the reaction product of 2 mols phenol and 1 mol formaldehyde by a second reaction with 2 mols aniline and 4 mols formaldehyde. Mean composition: ##STR3## 
     1-Oxa-3-aza tetraline compound 3 
     prepared by reaction phenol with aniline and formaldehyde in a molar ratio of 1:1:2. Structural formula: ##STR4## 
     Epoxide compound 1 
     Liquid bisphenol A gycidylether, epoxide equivalent weight=200 (Trade name &#34;Epikote 828&#34;). 
     Epoxide compound 2 
     3,4 epocyclohexylmethyl-3,4-epoxy-cyclohexade carboxylate 
     (Trade name &#34;Araldite CY 179&#34;). 
     Butandiol-diglycidyl-ether (Trade name &#34;Araldite DY 026&#34;) 
     Aluminum hydroxide 1 
     Al(OH) 3 . Mean particle size 0.0008 mm. 
     Aluminum hydroxide 2 
     Al(OH) 3 . Mean particle size 0.020 to 0.025 mm. 
     Calcium magnesium carbonate 
     Hydrated calcium magnesium carbonate, 38% Ca. 8% Mg, ignition loss (700° C.) 53% (44% CO 2 , 9% H 2  O) mean particle size 0.00016 mm. 
     Magnesium hydroxide 
     Mg(OH) 2 , mean particle size 0.0012 mm, ignition loss (1000° C.) 32%. 
     Ammonium polyphosphate 
     (NH 4 ) n+2  P n  O 3n+1 , phosphorus content 32%, mean particle size 0.03 mm. 
     Melamine phosphate 
     C 3  H 6  N 6 .H 3  PO 4 , particle size &lt;0.075 mm. 
     Dimelamine phosphate 
     (C 3  H 6  N 6 ) 2 .H 3  PO 4 , particle size &lt;0.075 mm. 
     Red phosphorus 
     Amorphous, particle size 0.001 to 0.050 mm. 
     Phosphorus acid 
     H 3  PO 3 , crystalline, ground. 
     Orthophosphoric acid 
     H 3  PO 4 , liquid. 
     Boric acid 
     H 3  BO 3 , crystalline, ground. 
     Glass fabric 1 
     200 g/m 2 , number of ends/cm=7×7, aminosilane finish. 
     Glass fabric 2 
     110 g/m 2 , number of ends/cm=24×24, aminosilane finish. 
     Test plates were prepared by curing the resin/additive mixtures for 2 hours at 200° C. between teflonized glass plates. For specimens containing glass fabrics, the glass fabric was first vacuum impregnated with the resin/additive mixture at 120° C., then the plate was cured between glass plates. 
     Inflammability was tested in accordance with Specification UL 94 vertical Test. When judging the results, the thickness of the specimens is to be taken into consideration, since thicker specimens more easily meet the classifications UL 94 V than thinner ones. 
     Heat resistance was tested by heating the specimens for 15 hours to 280° C. and thereafter determining the change of volume. 
     All specimens with a negative change of volume do not show any bubble formation or other damages. 
     EXAMPLES 1 TO 27 
     The test results are compiled in Tables 1 and 2 hereafter. 
     
                                           TABLE 1__________________________________________________________________________            Reference                    Example No.            1 1a                2 3 1 2 2a                          3 4  5  6  7 8 9 10                                             11  12__________________________________________________________________________Composition (Parts by weight)1-Oxa-3-aza-tetraline compound 1            30  30                  20                    30                      30  30                            20 20 20 --                                       --                                         20                                           24                                             30  201-Oxa-3-aza-tetraline compound 2            --  --                  ----                      --  --                            -- -- -- --                                       24                                         --                                           --                                             --  101-Oxa-3-aza-tetraline compound 3            --  --                  ----                      --  --                            -- -- -- 24                                       --                                         --                                           --                                             --  --Epoxide compound 1            --  --                  10                    --                      --  --                            10 10 10 --                                       --                                         --                                           --                                             --  --Epoxide compound 2            --  --                  --                    --                      --  --                            -- -- --  6                                        6                                         10                                            6                                             --  --Butandiol-diglycidyl-ether            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Aluminium hydroxide 1            --  --                  --                    10                      15  15                            10 10 15 12                                       10                                         10                                           10                                             --  --Aluminium hydroxide 2            --  --                  --                    --                      --  --                            10 10 -- 12                                       10                                         10                                           10                                             --  --Calcium magnesium carbonate            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             15  30Magnesium hydroxide            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Ammonium polyphosphate            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Melamine phosphate            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Dimelamine phosphate            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Red phosphorus   --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Phosphorous acid --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Orthophosphoric acid            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Boric acid       --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Glass fabric 1 (layers/mm)            --  --                  --                    --                      --  --                            -- 3.3                                  -- --                                       --                                         --                                           3.3                                             --  --Glass fabric 2 (layers/mm)            --  10                  --                    10                      --  10                            -- -- 10 --                                       --                                         --                                           --                                             --  --Tests (Unit)UL 94 Vertical Test:Thickness (mm)   4 1.0                1.0                  1.0                    0.9                      1.8 1.2                            1.0                               1.2                                  0.9                                     1.0                                       1.2                                         1.0                                           --                                             1.0 1.0Total burning duration (s)            --              --                --                  --                    80                       5  20                            20 17 185                                     18                                       25                                          5                                           --                                             10  80Longest burning duration (s)            --              --                --                  --                    14                       1   3                             3  3 19  7                                        7                                          3                                           --                                              1   9Burning up to the top            - + + + - -   - -  -  -  - - - - -   -Class UL 94      V1              --                --                  --                    V1                      V0  V0                            V0 V0 V1 V0                                       V0                                         V0                                           --                                             V0  V1Glass transition temperature.sup.(1) (°C.)            --    --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --after tempering 4 h/220° C. (°C.)            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Flexural strength (N/mm.sup.2)            --  --                  --                    --                      --  --                            -- -- -- --                                       --                                         --                                           --                                             --  --Annotations      --              --                --                  --                    (2)                      (2)                        (3)                          (2)                            -- -- -- --                                       --                                         --                                           --                                             --  --Volume change 15 h/280°  C. (%)            --              --                --                  --                    --                      80                         0                          --                            -8 -4 -4 --                                       --                                         --                                           --                                             -2.5                                                 -9__________________________________________________________________________ .sup.(1) Thermomechanical analysis (2) Swelling above the burning zone (3) Tempering: 30 min/200° C. + 30 min/220° C. + 30 min/230° C: no bubble formation after 15 h/280° C. 
    
     
                                           TABLE 2__________________________________________________________________________            Example No.            13 14 15                    16                      17 18                           19 20                                21                                  22                                    23                                      24                                        25                                          26                                            27__________________________________________________________________________Composition (Parts by weight)1-Oxa-3-aza tetraline compound 1            -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          --                                            --1-Oxa-3-aza tetraline compound 2            -- -- --                    --                      30 21                           21 30                                30                                  50                                    50                                      50                                        40                                          --                                            --1-Oxa-3-aza tetraline compound 3            30 24 24                    21                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          28                                            28Epoxide compound 1            --  6  6                     9                      --  9                            9 --                                --                                  --                                    --                                      --                                        --                                          --                                            --Epoxide compound 2            -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          --                                            --Butandiol-diglycidyl-ether            -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          12                                            12Aluminium hydroxide 1            24 10 12                    12                      15 10                           12 --                                --                                  --                                    --                                      --                                        --                                          --                                            --Aluminium hydroxide 2            -- 20 24                    24                      -- 20                           24 --                                --                                  --                                    --                                      --                                        --                                          --                                            --Calcium magnesium carbonate            -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          --                                            --Magnesium hydroxide            -- -- --                    --                      -- --                           -- 30                                --                                  --                                    --                                      --                                        --                                          --                                            --Ammonium polyphosphate            -- -- --                    --                      -- --                           -- --                                 9                                  --                                    --                                      --                                        --                                          --                                            --Melamine phosphate            -- -- --                    --                      -- --                           -- --                                --                                  25                                    --                                      --                                        --                                          --                                            --Dimelamine phosphate            -- -- --                    --                      -- --                           -- --                                --                                  --                                    25                                      --                                        --                                          --                                            --Red phosphorus   -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                       1                                        --                                          --                                            --Phosphorous acid -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        10                                          --                                            --Orthophosphoric acid            -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          10                                            --Boric acid       -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          --                                            10Glass fabric 1 (layers/mm)            -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          --                                            --Glass fabric 2 (layers/mm)            -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          --                                            --Tests (Unit)UL 94 Vertical Test:Thickness (mm)   1.0               1.0                  1.0                    1.0                      0.8                         1.0                           1.0                              0.9                                0.8                                  1.0                                     2                                       2                                         3                                           3                                             3Total burning duration (s)            24 66 24                    90                      13 54                           20 15                                16                                  15                                    35                                       0                                         0                                           3                                             5Longest burning duration (s)             5 21  9                    24                       3 21                            4  2                                 4                                   3                                    10                                       0                                         0                                           8                                            10Burning up to the top            V0 V1 V0                    V1                      V0 V1                           V0 V0                                V0                                  V0                                    V0                                      V0                                        V0                                          V0                                            V0Class UL 94Glass transition temperature.sup.(1) (°C.)            103               108                  --                    --                      153                         --                           121                              --                                --                                  --                                    --                                      --                                        --                                          --                                            --after tempering 4 h/220°C. (°C.)            -- -- --                    --                      162                         --                           158                              --                                --                                  --                                    --                                      --                                        --                                          --                                            --Flexural strength (N/mm.sup.2)            -- -- --                    --                      140                         --                           100                              --                                --                                  --                                    --                                      --                                        --                                          --                                            --Annotations      -- -- --                    --                      -- --                           -- --                                --                                  (4)                                    (4)                                      --                                        (4)                                          (4)                                            (4)Volume change 15 h/280° C. (%)            -- -- --                    --                      -- --                           -- --                                --                                  --                                    --                                      --                                        --                                          --                                            --__________________________________________________________________________ .sup.(1) Thermomechanical analysis (4) Foamed after curing 
    
     EXAMPLE 28 
     An impregnating solution was prepared from 330 g 1-oxa-3-aza tetraline compound 1, 170 g epoxide compound 2, 200 g toluene, 390 g aluminum hydroxide 2 and 210 g aluminum hydroxide 1. Glass fabric 2 was lacquered with this solution and dried in a hot-air channel. 10 Layers of this prepreg were hot-pressed at 160° C. to form a laminate of 1 mm thickness which was cured for 1 h at 220° C. 
     The laminate showed the following properties: 
     
         ______________________________________Classification       UL 94-V0______________________________________Flexural strength:Warp direction       440     N/mm.sup.2Weft direction       385     N/mm.sup.2Modulus of elasticity                20000   N/mm.sup.2Specific volume resistance:at room temperature  10.sup.16                        Ohm · cmat 200° C.    4 · 10.sup.11                        Ohm · cmat 250° C.    5 · 10.sup.09                        Ohm · cmafter moist storage (95% rel. h.)                6 · 10.sup.13                        Ohm · cmSurface resistance:at room temperature  &gt;10.sup.15                        Ohmat 200° C.    5 · 10.sup.11                        Ohmat 150° C.    4 · 10.sup.10                        Ohmafter moist storage (95% rel. h.)                &gt;10.sup.15                        OhmDielectric constant (1 MHz)                5.5Loss factor (1 MHz)  0.02______________________________________ 
    
     EXAMPLE 29 
     In a manner analogous to that described in Example 28, a laminate of 1 mm thickness was prepared from 500 g 1-oxa-3-aza tetraline compound 2 and 300 g aluminum hydroxide. Curing: 1 h at 180° C. 
     The laminate showed the following properties: 
     
         ______________________________________Classification      UL 94-V0______________________________________Flexural strength   440     N/mm.sup.2Modulus of elasticity               22000   N/mm.sup.2______________________________________