RU2106368C1 - Method for production of epoxy nitrates of cellulose for polymer base of solid polymer coatings, adhesives and solid fuel - Google Patents

Abstract

FIELD: production of polymers for solid polymer coatings, adhesives and solid fuel having decreased combustion rate. SUBSTANCE: nitrocellulose (nitrogen content in it being 12.5-13.5 %) or pyroxylin gunpowder is mixed with epoxy resin, peptizing agent and with stabilizing agent, the process is carried out in solution. Thus prepared product is affected by thermal mechanical treatment on heated rolls, the process takes place within 15-20 min at 70-80 C. Then fabric is rolled out and cooled, ratio of nitrocellulose and epoxy resin being (80:20)-(20:80). EFFECT: increased rate of reaction without using catalyst; simplified method for production of epoxy nitrates of cellulose; increased degree of epoxidation; increased degree of utilization of nitrocellulose gunpowder after their prolonged storage. 1 tbl

Description

 The invention relates to the field of producing polymers for solid polymer coatings, adhesives and solid fuels with a reduced burning rate.

 The patent literature contains information on the production of nitrocellulose (SC) with other polymers by chemical plasticization, for example, from the collection of articles "High molecular weight compounds. Cellulose and its derivatives." M., ed. USSR Academy of Sciences, 1965, p. 100-106. In particular, chemical plasticization was carried out by interacting with flexible-chain polymers compatible with SC - polymethyl methacrylate with practically no formation of a homopolymer with a maximum content of the latter in the copolymer of 28.5%, while the copolymer had an increased initial elastic modulus.

 The disadvantage of this method is the long duration of the process and the low yield of the product, in addition, this literature does not describe a method for producing cellulose epoxynitrates (ESCs).

 The prototype of the method is a method that describes the process of condensation of 1,2-epoxides on nitrocellulose (see French Patent N 1259546 from 03.20.61. (A) Journal of Chemistry, 1963, 12 T, 55 A). According to the prototype, the condensation of 1,2-epoxides on an SC is carried out in a homogeneous medium in a common solvent of 1,2-epoxide, an SC and a catalyst. The reaction resulted in a product containing 10.44% nitrogen, esterified at 1.94%.

 The disadvantage of this method is the need to use a catalyst and its subsequent separation, which complicates the production technology, as well as a low degree of epoxidation. In addition, the prototype does not describe the production of ESCs from the secondary SC contained in nitrocellulose powders after they are rejected after the expiration of storage periods.

 The objective of the invention is to accelerate the reaction of obtaining ESCs without a catalyst, simplifying the production process, increasing the degree of epoxidation and disposal of nitrocellulose powders (NCP) after their long storage and rejection.

This is achieved by the fact that a high-nitrogen SC with a nitrogen content of 12.5 to 13.5%, including that contained in the NCP after the end of their shelf life, is dissolved in an organic solvent, a plasticizer and a stabilizer are introduced into it and mixed with epoxy in the ratio from 80:20 to 30:70 in mass parts, and then the resulting mechanical mixture is rolled on horizontal rollers with two heated rollers at a temperature of rolls from 70 to 80 ^o C. Duration of rolling - 15-20 minutes with the number of repeated rolling 15-20 and the gap between the rolls 0.8-1.2 mm. The resulting material in the form of a "stocking" on the roll is cut with a special knife on the rollers, straightened on a flat table surface and cooled. This material is the product of a chemical reaction between NC and epoxy resin in the presence of a plasticizer and a chemical stability stabilizer. It is a thermoplastic capable of curing at temperatures from 80 to 120 ^o C and holding for 3-18 hours in the form of a light brown transparent homogeneous film or coating. After receiving in the ESC, the content of nitrogen and epoxy groups was determined by known methods by titration.

 Let us give an example of obtaining an ECC.

To obtain an ECC at a ratio of NTs: ES of 50:50, take a high-nitrogen SC or 14/7 pyroxylin powder with a nitrogen content of 13%, dissolve it in an organic solvent at a ratio of SC: solvent 1: 3 in mass parts. Then we introduce a liquid plasticizer and stabilizer, mixing them with a solution of SC for 3-3.5 minutes. After that, a weighed portion 30 is taken, diluted with the same solvent to the ES: solvent ratio 2: 1, it is discharged into the dissolved SC, and it is stirred for 2-3 minutes at room temperature. The resulting mixture is gradually unloaded from the mixing chamber onto the rollers and rolled onto the rollers with two horizontally located rolls at a temperature of from 70 to 80 ^° C for 15-20 minutes with the number of repeated rolling of 15-20 and the gap between the rolls of 0.8-1 , 2 mm. During rolling, the solvent evaporates and is captured, condensed and reused as a solvent. After machining, the obtained ESC is cut from the work roll with a special knife. Then the ESCs are cooled and samples are taken from it to analyze the chemical composition and determine its physicochemical and mechanical properties.

 To confirm the suitability of the ESC for the declared purpose, we give a specific example of its use as a polymer base for hard coatings.

To obtain a polymer coating proposed the following composition, wt. hours:
ENC with the content of epoxy groups of 2.5% - 80
Epoxy resin ED-20 - 5
Hardener - polyethylene polyamine - 5
Filler - Magnesium Carbonate - 10
The prepared mechanical mixture after rolling at a temperature of 80 ^o C was pressed by a hydraulic press to a metal surface to be coated (steel 3), previously degreased with ethyl alcohol, kept for 30 min at a pressure of 5 MPa, the coating was cooled to room temperature and placed in a heating cabinet for curing in within 48 hours

 The coating test results are as follows.

 Appearance - the coating is light brown in color, smooth, without visible external defects, easy to grind.

The adhesive strength at the border with the metal (shear) is 150 N / cm ² .

Peeling strength of the coating is 240 N / cm ² .

 Moisture absorption during exposure to water for 24 hours to increase the weight to the initial weight of the coating is 0.001%.

 After storage at room conditions for 12 months, the appearance of the coating and its technical characteristics remained unchanged.

 The results of experiments to obtain the ESC and the study of its properties are shown in the table.

 After obtaining the ESC, the content of epoxy groups was determined in it by the known titration method. For this, a predetermined amount of hydrochloric acid was added to the ESC in the solution, which reacted, and part of it remained unreacted. This part of hydrochloric acid is titrated with 0.1 N. a solution of caustic soda, and the content of epoxy groups with an accuracy of 0.1% was calculated from the difference between the consumed caustic soda in the control experiment and in the experiment with the ESC.

The results of the analysis of the reaction mass after rolling (Table 1) for the content of epoxy groups show that in all experiments except the fifth, their content decreased. This means that in this case a chemical reaction of the NTs with the ES occurs with the consumption of part of the reactive groups in the ES on the interaction with the NTs with the formation of the ENTs. Evidence of the formation of ESCs is also that on the thermograms of differential thermal analysis of the initial SC isolated from pyroxylin gunpowder, the temperature of the onset of intensive decomposition was 187 ^o C, while in the ESC it was 179 ^o C in the absence of any other peaks in the DTA thermogram.

 The reaction of the formation of an ECC proceeds during rolling with a component ratio of at least 20:80 in the SC: ES system. If the resin is taken less than 20 wt. hours, the reaction mass is too rigid, which increases the fire hazard during rolling due to the large force of external friction and high temperature. When in the reaction mass there is a lot of ES and little SC at a ratio of 80:20 wt. h, respectively, the formation of the EEC does not occur and the number of epoxy groups in the ES remains unchanged (see experiment 5 in table 1). In this case, the sample is a mechanical mixture in the form of a pasty mass, capable of further delamination.

 Physico-mechanical properties, in particular tensile strength, adhesive shear strength of two smooth surfaces glued together “lap”, were determined on a tensile testing machine RMU-0.05-1 with an electronic force meter. Tear specimens were obtained from the web in the form of a double-sided spatula. The burning rates of an 1-mm thick ECC web were determined by recording the propagation velocity of the flame front.

 The proposed method for producing ESCs allows to obtain ESCs with sufficient mechanical strength, good adhesion to wood, metal and plastic in accelerated mode from nitrocellulose powders to be disposed of.

Claims (1)

A method of producing cellulose epoxynitrates for a polymer base of solid polymer coatings, adhesives and solid fuels using the interaction of epoxides and nitrocellulose in an organic solvent, characterized in that high-nitrogen nitrocellulose with a nitrogen content of 12.5 to 13.5% or pyroxylin powder after long-term storage dissolved in an organic solvent, mixed with a stabilizer and plasticizer, and then mixed with epoxy resin, subjected to rolling on rollers with two heated rollers with Temperature of from 70 to 80 ^o C for a duration of rolling of from 15 to 20 minutes with the number of repeated rollings 15 and 20 and with the magnitude of the roll gap of 0.8 to 1.2 mm in the following ratio, mass parts .:
Nitrocellulose - 30 - 80
Epoxy resin - 20 - 70
Organic solvent - 80 - 240k

Images