CH508678A - Thermo stable resins for mouldings - Google Patents

Abstract

Resins are formed by reaction of an N,N-dicarboxylic bis-imide (I):- (where D is a divalent group containing a double bond, A is a divalent group containing at least 2C) with a diamine H2NBNH2 (B is a less than 30 C divalent gp.) in the presence of a strong acid or free radical inhibitor.

Description

  

  Process for the preparation of new thermostable resins The main patent relates to a process for the preparation of novel crosslinked thermostable resins, characterized in that an unsaturated dicarboxylic acid N, N'-bis-imide of the general formula is reacted.
EMI0001.0003
    in which D represents a divalent radical containing a carbon-carbon double bond and A is a divalent radical having at least two carbon atoms, with a bi-primary diamine of general formula H2N - B - NH2 (II)

    in which B represents a divalent radical having no more than 30 carbon atoms.



  The amounts of N, N'-bis-imide and diamine are chosen so that the ratio
EMI0001.0009
    is between 1.2 and 50.



  The object of the present invention is an improvement in the preparation of the resins according to the main patent, characterized in that the reaction between the bis-imide (I) and the diamine (II) is carried out in the presence of an inhibitor. free radicals.



       The use of a free radical inhibitor is above all advantageous, for obtaining prepolymers of tines to be used in the form of solutions or else in the molten state, for example for the production of composite materials or else casting molding. In fact, the prepolymer solutions thus obtained exhibit increased resistance to oxidation by oxygen in the air and their viscosity remains practically constant during storage at ordinary temperature.

   The use of an inhibitor also considerably prolongs the time during which the prepolymer can be maintained in the molten state, which makes it possible to perform cast moldings without being dependent on the precariousness of the liquid state of the product. to comply.



  As inhibitor, hydroquinone, picric acid or diphenylpicrylhydrazine are preferably used in proportions by weight identical to those mentioned above for the initiator. A strong acid can optionally be combined with the inhibitor, mainly for obtaining prepolymers intended for the preparation of layered assemblies.



  By strong acids is meant in the Brönsted sense mono- or polyacids of which at least one of the functions has an ionization constant pKa of less than 4.5. They may be inorganic acids such as hydrochloric, sulfuric, nitric or phosphoric, optionally substituted by an organic radical and among the latter there may be mentioned sulfonic and phosphonic acids.

   They can also be carboxylic acids, these can be of simple structure or have groups which do not disturb the reaction between the bisimide (I) and the diamine (II).



  The preferred acid is maleic acid. We generally use amounts by weight of acid which represent 0.5 to 5% relative to the weight of the bis-imide (I) used.



       The examples below illustrate the invention <I> Example 1: </I> An intimate mixture prepared by shooting - 8.95 g of N, N'-4,4'-diphenylmethane- is brought to 1500 ° C. maleic bisimide - 1.98 g bis (4-amino phenyl) methane - 0.018 g picric acid.



  After 2 min, the mixture liquefies and it still appears in liquid form after 45 min under these temperature conditions.



  When picric acid is replaced by the same amount of N, N-diphenyl-N'-picrylhydrazine, the mixture is still in liquid state after 1 hour at 150c, C.



  By way of comparison, when operating without an inhibitor, the mixture becomes pasty after 17 min at 1500 ° C. and at this stage it is already unusable for performing a cast molding.



  <I> Example 2: </I> We mix intimately
EMI0002.0006
  
    - <SEP> 89.5 <SEP> g <SEP> of <SEP> N, N'-4,4'-diphenylmethane-bis-imide
<tb> maleic <SEP> with
<tb> - <SEP> 19.8 <SEP> g <SEP> of <SEP> bis (4-amino-phenyl) methane)
<tb> - <SEP> 0.179g <SEP> picric acid <SEP>
<tb> - <SEP> 1.79 <SEP> g <SEP> of maleic acid <SEP>. The mixture is heated at 150 ° C. for 30 min. After cooling, the prepolymer is ground, then dissolved in 190 g of N-methylpyrrolidone.

      With 79 g of the solution thus obtained, a stratified assembly is prepared in the manner indicated in Example 4 of the main application; this laminate has the following properties at 250 C - resin content .._ <B> -------------------- </B> ... .. 22 - flexural strength at break ...... 53 kg / mm2 The residual solution was stored in the light and without special precautions;

   during this storage, its coloring and its viscosity hardly changed.

 

Claims (1)

CLAIM Process for the preparation of crosslinked thermostable resins according to claim 1 of the main patent, characterized in that the reaction is carried out in the presence of a free radical inhibitor. SUB-CLAIM A method according to claim in which a strong acid is combined with the free radical inhibitor.