RU2284212C2 - Composition for preparing microporous phenoplastic filter material - Google Patents

Abstract

FIELD: filter materials.

SUBSTANCE: invention relates to technology of preparing porous materials appropriate for cleaning liquid and gaseous media and which can be used in a variety of technical areas when manufacturing filters and sorption materials. Preparation of composition: predetermined amount of compounds from group of liquid thermosetting phenol-formaldehyde resins is loaded into mixer and predetermined amount (to 66-75%) of saturated solution of oxalic acid in polyatomic alcohol is dozed thereto, after which mixture is thoroughly stirred until mutual dissolution of components and cured for 1 h on heating to 50-70°C. Solidified mass is unloaded, washed with hot running water to remove oxalic acid and polyatomic alcohol, and dried.

EFFECT: enabled development of porosity, formation of microsphero-porous structure of material with increased specific surface of finished material with improved sorption characteristics.

2 dwg, 1 tbl

Description

The present invention relates to the field of obtaining porous materials used for the purification of industrial liquid and gaseous media, and can be used in the chemical, engineering, gas producing, petrochemical and related fields in the production of filters or sorbent materials.

A known composition for producing microporous material from a phenolic material for filters, closest to the claimed composition, comprising phenol-formaldehyde resin as a binder, powdered oxalic acid as a catalyst and blowing agent (RF patent No. 2101075, IPC B 01 D 39/04, publ. BI No. 1/98 g., Dated 10.01.98 g.).

The disadvantages of the prototype include the underdeveloped specific surface area of the finished material, the high viscosity of the initial composition, which is not technologically advanced for cases of manufacturing products of complex shapes, the insufficiently high rate of washing out of the blowing agent (oxalic acid), which significantly lengthens the process as a whole and leads to overuse of raw materials, and a high minimum size then, which narrows the scope of the finished material. In addition, the finished product obtained by the known composition has a mesh structure (figure 1), which does not allow to obtain material for fine filters.

The objective of the inventors is to develop a formulation of the composition for producing a microporous material with a new microsphere-porous structure for filters or adsorption materials with a higher specific surface area, the possibility of producing smaller pores in such a material, characterized by a higher rate of removal of the blowing agent from the product than achieved in the prototype.

A new technical result achieved by using the proposed composition is to ensure the development of porosity, transformation of the structure of the finished material into microsphere-porous with an increase in the specific surface of the finished material, leading to an improvement in its sorption characteristics and uniformity of porosity and physico-mechanical properties in terms of the volume of the finished product, as well as ensuring the production of material with a smaller pore size than in the prototype.

These tasks and a new technical result are ensured by the fact that in the known composition for obtaining microporous phenolic material for filters, including phenol-formaldehyde resin as a binder, oxalic acid as a catalyst, in accordance with the proposed formulation contains a solution of oxalic acid in one of the compounds from the group of polyatomic alcohols as a complex agent of a catalyst-modifier-emulsifier-blowing agent in the following ratio of ingredients, parts by weight:

saturated oxalic acid solution in polyhydric alcohol 66-75 phenol formaldehyde resin rest

The invention is illustrated as follows. Initially, a composition is prepared, for which a calculated amount of a binder — liquid rezol thermosetting phenol-formaldehyde resin — is loaded into the mixer, and the calculated amount of a saturated solution of oxalic acid in polyhydric alcohol is metered into it. The resulting mixture has a long duration of mobility (up to 5-10 hours), which makes it possible to form large volumes of mass. Then the mixture is poured into a mold and cured at a temperature of 20-70 ° C. In the heat treatment process, polycondensation of the resin occurs to form a resin emulsion. The resulting spherical particles of the emulsion gradually harden. Hardened spherical particles have weak cohesive bonds, dumbbell-shaped particles form in places. After curing, a saturated solution of oxalic acid in polyhydric alcohol is removed from the workpiece by dissolution in water, optimally in hot and flowing. As a result of the washing of the blowing agent, an open-porous phenoplastic filter material with a rigid porous structure with a certain average size of porous channels is formed. The total porosity and pore size of such a material is controlled by the amount of a saturated solution of oxalic acid in polyhydric alcohol introduced into the phenol-formaldehyde resin. During heating, moisture and residues of oxalic acid are removed from the preform, which sublimates or decomposes to water and carbon dioxide, even in closed pores, opening them.

In the process of removing the modifier, pores are formed in the material, alternating with microspherical structural elements, uniformly distributed over the volume of the finished material, with the formation of a complex developed regular open-porous structure consisting of microspheres with a diameter of 1-15 μm having cohesive bonds (Fig. 2). In contrast to the prototype (Fig. 1) having a mesh structure, the material obtained using the proposed composition implements a microsphere-porous structure, which solves the problems of producing filters and fine chemical adsorbents.

In the prototype, the oxalic acid powder with a predetermined particle size contained as a pore-forming agent is not distributed uniformly enough in the material, as a result of which the degree of uniform distribution of pores in the volume of products is not high enough. In addition, in this case, the molding composition is characterized by a large initial viscosity at a high rate of its growth in time, which makes it difficult to manufacture thin-layer products of complex shape.

Oxalic acid in the form of a solution of its polyhydric alcohol in the proposed composition exhibits the properties of a complex agent — both a structure modifier (since polyhydric alcohol chemically modifies phenol-formaldehyde resin) and an emulsifier (since the formation of a direct concentrated emulsion of the resin in a solution of oxalic acid in polyhydric alcohol ) and, as in the prototype, a pore former (since the pores between the emulsified resin particles cured during the polycondensation filled with a solution of oxalic acid in polyhydric alcohol), and a catalyst (because the process of interaction of the reagents is accelerated in the presence of oxalic acid).

The manifestation of such multifunctional properties in the cured mixture results in a finished phenoplastic material characterized by a more developed and evenly distributed microsphere-porous structure, a more developed surface, which expands the field of application of the finished material for fine filtering and adsorption processes.

With a decrease in the content of the solution of oxalic acid in polyhydric alcohol in the molding composition below the stated limits in the finished product, both net zones (as in the prototype) and microsphere-porous structure are observed simultaneously.

When the content of oxalic acid is exceeded over the declared limit, an unbound structure of the resulting finished product is formed due to the lack of cohesion between the microspherical elements of the structure.

Thus, the use of the proposed composition for the production of microporous material provides the development of porosity, the transformation of the structure of the finished material from mesh to microsphere-porous with an increase in the specific surface of the finished material, leading to an improvement in its sorption characteristics and uniformity of the distribution of porosity and physicomechanical properties over the volume of the product, as well as obtaining material with a smaller pore size.

The possibility of industrial application of the proposed composition is confirmed by the following examples of specific performance.

Example 1

The proposed composition was tested in laboratory conditions using the following conditions and laboratory equipment.

The preparation of the components of the composition was carried out by mixing rezol thermosetting phenol-formaldehyde resin brand SFF-302 as a binder in a container in an amount of 34 wt.h. with a modifier — a solution of oxalic acid in glycerol (EDKG) (as polyhydric alcohol) in an amount of 66 parts by weight

A solution of oxalic acid in glycerol (EDKG) is prepared at the rate of 3 wt.h. oxalic acid per 10 parts by weight glycerol, which is necessary to obtain a saturated solution that ensures the completeness of interaction of the components and the necessary direction of structure formation. The solution was brought to condition with thorough mixing of the components for at least 20 minutes.

The raw material mixture is poured into molds of a given size and placed in an oven (type "SNOL 3,5.3,5.3,5 / 3M") for curing at a temperature of 20-70 ° C.

In the process of heat treatment, polycondensation of the resin occurs with the formation of its emulsion. After curing, the products are washed in hot running water for 10-20 minutes to remove EDKG from them. Wet, cured, washed samples are placed in a closed form with a gas pipe and heated to a temperature of 150-300 ° C for drying.

Finished products are tested. The test results of the finished material are summarized in a table with comparative data on the prototype and the proposed composition.

Figure 2 shows the microstructure of the finished material obtained from the molding composition with the ratio of the ingredients of SFJ: EDKG - 34:66, respectively.

As experiments showed, the use of the proposed composition allows to obtain a microporous phenoplastic material with a more developed porosity, with a converted structure of the finished material from mesh to microsphere-porous, with an increased specific surface area of the finished material, leading to an improvement in its sorption characteristics and uniformity of porosity and properties throughout the product , with a smaller pore size than was achieved in the prototype.

Table Implementation examples The composition, wt.% Density, g / cm ³ Porosity,% The limit of compressive strength, kg / cm ² Specific surface, m ² / g Structure type one 2 3 four 5 6 7 Prototype The ratio of SFJ *: oxalic acid 33.3: 66.7 0.33 - 70 0.3-0.5 Mesh Example 1 The ratio of SFJ *: EDKG Mixed: Microsphere 43.5: 56.5 0.54 52.9 53 - porous + mesh Example 2 The ratio of SFJ *: EDKG 40:60 0.5 57.5 43 0.8 Microsphere-porous Example 3 The ratio of SFJ *: EDKG 33.3: 66.7 0.414 69.0 36 1-1.5 Microsphere-porous Example 4 The ratio of SFJ *: EDKG 25:75 0.31 92.0 25 1-1.5 Microsphere-porous Example 5 The ratio of SFJ *: EDKG 20:80 - - - - Unbound Microspherical Example 6 The ratio of SFJ *: EDKG 33.3: 66.7 0.42 71 twenty 0.7-1.0 Microsphere-porous * SFG - phenol-formaldehyde liquid resin.
** EDKG, EDKEG - a saturated solution of oxalic acid in glycerol and ethylene glycol, respectively.

Claims (1)

Composition for producing microporous phenolic plastic material for filters, including phenol-formaldehyde resin and oxalic acid, characterized in that oxalic acid is contained in its solution in one of the compounds from the group of polyhydric alcohols as a complex modifying agent in the following ratio of ingredients, wt.%: Saturated solution of oxalic acid in polyhydric alcohol 66-75 Phenol-formaldehyde resin Rest

Images