RU2696859C1 - Aminoplastic resin - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to an aminoplastic resin used as a structural material both independently and in composites. Aminoplastic resin consists of melamine and glycoluril cross-linked with aldehydes and curable by heating at pH=3–6. Cross-linking agent used is 36.6 % aqueous solution of formaldehyde.

EFFECT: obtained aminoplast resin has high decomposition temperature and strength both individually and in composites.

6 cl, 4 dwg, 1 tbl, 5 ex

Description

The invention relates to the field of macromolecular compounds, namely, to condensation polymers of aldehydes or ketones with two or more other monomers, and can be used as a structural material both independently and in composites.

Known condensation polymer of aldehydes and ketones with two or more other monomers used for bonding particleboard compositions (patent EP 2807201, 2014-12-03, B27N 3/00). A disadvantage of the known polymer is that it is suitable for use only as an adhesive that cures at a relatively high temperature (140 ° C). In addition, there are problems with the homogenization of the polymer, which are partially solved by introducing polyesters into the composition, which can impair the physicomechanical properties of the compositions. The gel time of such a resin does not exceed 100 s., Which complicates the work with it.

Also known is the group of polymers used to make the films (US 4,540,735, September 10, 1985, C08G 12/266). A significant difference of this invention is that glycoluryl derivatives and melamine are used here not as an independent condensation polymer of aldehydes and ketones, but as crosslinking agents for polymers obtained by radical polymerisation in suspension. A significant disadvantage of this invention is the synthesis time, reaching 2 hours, multi-stage production of polymers, the use of emulsifiers and an inert atmosphere of nitrogen during the reactions.

Closest to the proposed invention in terms of technical nature and the achieved result is selected as a prototype aminoplastic resins used as a crosslinking agent for cellulose (patent EP 698627, 1996-02-28, C08B 15/10). However, known resins are prepared using expensive aldehydes of the formula R-CHO over a relatively long period of time (60-600 min).

The objective of the present invention is to obtain a polymer having a high temperature of destruction and strength both individually and in the composition of the composites.

The problem is solved in that glycoluryl is additionally introduced into the composition of the melamine-formaldehyde resin, or its derivatives and polycondensation are carried out in such a way that a transparent or translucent polymer with a given number of crosslinks is obtained. A comparative analysis of the proposed technical solution with the prototype shows that the claimed invention differs structurally, namely, the presence of less reactive aldehydes and ketones as a crosslinking agent. Thus, the claimed solution meets the criteria of the invention of "novelty."

A large number of aminoplastic resins are known in which the amino derivative is urea or melamine, and the aldehyde derivative is formaldehyde or glyoxal (see, in particular, Brown D., Sherdron G., Kern B. “A Practical Guide to the Synthesis and Study of Properties polymers ", Germany, 1971, Lane with it. Under the editorship of Doctor of Chemical Sciences V.P. Zubova. M.," Chemistry ", 1976, S. 213-215). These resins are widely used, in particular, in the production of paper-laminated plastics and wood-pressed boards. In a well-known manner, aminoplastic resins are prepared in two stages. At the first stage, in an alkaline medium (pH 8-9), oligomeric products of the interaction of urea and / or melamine with aldehydes are obtained. In the second stage, the resin is cured by acidification of the solution (pH 3.5-5) or by exposure at a temperature of 140-160 ° C. Upon thermal curing of the resin, material heterogeneity may occur, and the number of cross-links in the final polymer may also decrease. Along with methylene bonds, ether bonds are present in the cured resin. Aminoplastic resins obtained by polycondensation are characterized by shrinkage and a tendency to crack, which limits their independent use as a material. At temperatures above 250 ° C, ether and partially methylene bonds break, which indicates the destruction of the polymer resin.

In an attempt to solve the above problems, the applicant discovered that the aminoplastic resins, into which glycoluryl, or its derivatives are introduced, have a number of useful qualities. Therefore, the subject of the present invention is the production of melamine-glycoluryl-formaldehyde resins, characterized in that glycoluryl is directly integrated into the polymer chain, and in a certain way the selected conditions for producing the resin allow to obtain materials with desired properties.

In the claimed invention, the aminoplastic resin consists of melamine and glycoluryl crosslinked with aldehydes and heat cured at pH = 3-6, but unlike the prototype, a 36.6% aqueous solution of formaldehyde is used as a crosslinking agent, in the following ratio of components, wt. %:

melamine - 30.5-33.1%

glycoluryl - 4.9-5.3%

stabilizer - 0.02-2.4%

hardener - 1.7-7.3%

NSON - the rest.

As a stabilizer use a 20% aqueous solution of ammonia in an amount of 2.4-2.5 wt. % or sodium hydroxide in an amount of 0.02-0.034 wt. %

As a hardener use a 35-37% aqueous solution of hydrochloric acid in an amount of 7-7.3 wt. % or 85% aqueous solution of formic acid in an amount of 3.3-3.4 wt. %, and can also be used ammonium sulfate in an amount of 1.7 wt. %

Figure 1 shows the scheme for producing melamine-formaldehyde resins. Figure 2 shows the structure of melamine-glycoluryl-formaldehyde resin.

Example 1:

To prepare the aminoplastic resin, a mixture of 0.624 g (0.0044 mol) of glycoluril, 3.876 g (0.03 mol) of melamine and a sufficient amount of caustic soda to obtain a pH of about 9 were dissolved in 7 ml (0.0854 mol) of a 36.6% formaldehyde solution with stirring at a temperature of 70-80 ° WITH.

After 30 minutes, the homogeneous solution was cooled to 50-60 ° C and a hardener was added. After 2-3 minutes, the solution gelatinizes, and after 10 minutes it hardens.

Example 2:

To prepare the aminoplastic resin, a mixture of 0.624 g (0.0044 mol) of glycoluril and 3.876 g (0.03 mol) of melamine is dissolved in 7 ml (0.0854 mol) of a 36.6% formaldehyde solution with 0.3 ml (0.0035 mol) of a 20% ammonia solution with stirring at a temperature of 70-80 ° C.

After 30 minutes, cool the homogeneous solution to 50-60 ° C and add the hardener. After 2-3 minutes, the solution gelatinizes, and after 10 minutes it hardens.

Example 3:

To prepare the aminoplastic resin, a mixture of 0.624 g (0.0044 mol) of glycoluril, 3.876 g (0.03 mol) of melamine and a sufficient amount of stabilizer to obtain a pH of about 9 are dissolved in 7 ml (0.0854 mol) of a 36.6% formaldehyde solution with stirring at a temperature of 70-80 ° С .

After 30 minutes, we cool the homogeneous solution to 50-60 ° C and add 0.4 ml (0.0087 mol) of an 85% aqueous solution of formic acid. After 2-3 minutes, the solution gelatinizes, and after 10 minutes it hardens.

Example 4:

To prepare the aminoplastic resin, a mixture of 0.624 g (0.0044 mol) of glycoluril, 3.876 g (0.03 mol) of melamine and a sufficient amount of stabilizer to obtain a pH of about 9 are dissolved in 7 ml (0.0854 mol) of a 36.6% formaldehyde solution with stirring at a temperature of 70-80 ° C .

After 30 minutes, we cool the homogeneous solution to 50-60 ° C and add 0.9 ml (0.0086 mol) of a 35% aqueous hydrochloric acid solution. After 2-3 minutes, the solution gelatinizes, and after 10 minutes it hardens.

Example 5:

To prepare the aminoplastic resin, a mixture of 0.624 g (0.0044 mol) of glycoluril, 3.876 g (0.03 mol) of melamine and a sufficient amount of stabilizer to obtain a pH of about 9 are dissolved in 7 ml (0.0854 mol) of a 36.6% formaldehyde solution with stirring at a temperature of 70-80 ° C .

After 30 minutes at a temperature of 70 ° C, add 0.2 g (0.0015 mol) of ammonium sulfate. After 4-5 minutes, the solution gelled, and after 10 minutes it hardens. The method is suitable for the production of opaque temperature-controlled composites by curing.

Figure 3 shows thermogravimetry and differential scanning calorimetry of the cured acid polymer based on melamine and glycoluril.

According to thermogravimetry, the temperature of polymer degradation reaches 337.9 ° C. When the destruction temperature is exceeded, the methylene bonds in the polymer break and the melamine fragments decompose to cyanuric acid. Iodometric titration and thermogravimetry established the proportion of formaldehyde capable of being released when the polymer is heated to temperatures lower than the temperature of destruction, which does not exceed 1 wt. % Prior to the temperature of destruction, no noticeable deformation of both the individual polymer and composites based on it is observed.

Figure 4 shows the IR spectrum of a cured polymer based on melamine and glycoluril obtained in a crystal.

Based on the IR spectrum of the polymer, it is seen that, along with methylene bonds (2971 cm-1), ether bonds (1223 cm-1) are present. In addition, there are methylol groups (3258, 1373, 1314 cm -1 - primary alcohol). The complete binding of glycoluryl is indicated by the CH groups (2891 cm-1), C = O (1696 cm-1) and the absence of peaks of the N-H groups in the region of 3450-3300 cm-1.

Composites of a polymer resin based on melamine and glycoluryl with cellulose were also prepared by dipping followed by thermal pressing, and physical and mechanical tests of an individual polymer and its composite were carried out on a tensile testing machine GOTECH AI-7000M and GOTECH GT-7045-HMH. Table 1 shows a comparison of the physicomechanical properties of melamine-formaldehyde resin (60% reinforced with cellulose), a polymer based on melamine and glycoluryl, and a polymer based on melamine and glycoluryl (60% reinforced with cellulose). Values for melamine-formaldehyde resin (60% cellulose reinforced) are taken from the references.

According to table 1, composites with a matrix made of a polymer based on melamine and glycoluryl have greater strength (especially high impact strength) and are also not combustible.

The present invention has the following advantages. Firstly, due to the high temperature of polymer degradation, materials based on it can be used in those areas of technology where friction and elevated temperatures are associated, which means where materials from common thermoplastics are unsuitable. In addition, due to incombustibility, the polymer and composites based on it can be widely used in construction, as a guarantee of safety in case of fire. Secondly, due to the high physical and mechanical properties compared to other thermosetting plastics, polymer-based materials can be widely used as a structural material in the production of various kinds of products of an irregular shape. Thirdly, due to the simplicity of synthesis and the relative availability of the raw material base in the Russian Federation, it is possible to produce materials that do not have direct analogues in the world at low cost.

In the production of fibrous cellulose-containing composites, the glycoluryl and melamine with various aldehydes and ketones are used as the resin described in the prototype. Compared with the prototype, our polymer is more durable and economical in production, because the use of substituted aldehydes and ketones as cross-linking agents reduces the number of cross-links in the polymer, significantly complicates the process of polymer synthesis, which, moreover, will be relatively expensive.

Claims (11)

1. Aminoplastic resin, consisting of melamine and glycoluryl, crosslinked with aldehydes and cured by heating at pH = 3-6, characterized in that a 36.6% aqueous solution of formaldehyde is used as a crosslinking agent, in the following ratio, wt. %: melamine - 30.5-33.1%; glycoluryl - 4.9-5.3%; stabilizer - 0.02-2.4%; hardener - 1.7-7.3%; NSON - the rest. 2. The aminoplastic resin according to claim 1, wherein a stabilizer uses a 20% aqueous solution of ammonia in an amount of 2.4 wt. % 3. The aminoplastic resin according to claim 1, wherein sodium hydroxide in an amount of 0.02-0.034 wt. % 4. The aminoplastic resin according to claim 1, wherein a 35-37% aqueous solution of hydrochloric acid in an amount of 7-7.3 wt. % 5. The aminoplastic resin according to claim 1, where an 85% aqueous solution of formic acid in an amount of 3.3-3.4 wt. % 6. The aminoplastic resin according to claim 1, wherein ammonium sulfate is used as a hardener in an amount of 1.7 wt. %

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