The production of novolac oligomers

The paper presents the improvement of production technology of novolac phenol-formaldehyde oligo-mers by introducing the new scheme of capture of exhaust gases due to waste production, which leads to a reduction of costs and increase economic efficiency. The calculation of the material balance of the pro-duction of novolac phenol-formaldehyde oligomer at 300 kg/h of technical product is performed, the technological calculation of the basic equipment and selection of auxiliary equipment is produced. The apparatus scheme of production is made and the description of the process is represented. The draft of the main reactor is made.


Introduction
Phenol-formaldehyde oligomers is the first plastic mass obtained by the reaction of polycondensation.They are prepared from phenols and aldehydes, primarily formaldehyde.Cresols, xylenols, polyatomic phenols, alkylphenols, polynuclear compounds, such as bisphenol etc., are used as phenolic raw material along with the use of phenol.Depending on the ratio of reactants and catalysis method either novolacs (excess of phenols with catalysis by acids) or resoles (excess of formaldehyde with catalysis by bases) are made.
In the period of rapid development of the plastics it's hard to give a prediction about the future of phenol-formaldehyde oligomers -the oldest of polymeric materials; it is safe to say that at the present time they not only lost their value, but there is reason to expect long-term, although the slight absolute increase in the production of phenolic plastics despite the decrease in their relative part in the total output of plastics.
Phenol-formaldehyde oligomers were the first synthetic industrial thermosetting plastics.The deficit of natural raw materials and the need to replace natural materials with synthetic served as the impetus for their production.
Noteworthy is the fact that the socalled classical phenol-formaldehyde thermosetting plastics and thermoplastics despite the decline in their relative part in the world production of plastics not only lost their positions, but on the contrary have assumed much greater importance.In this regard and with the much tougher ecological standards, the search for the most economical and ecological technology for the production of phenol-formaldehyde oligomers, in particular novolacs, requires what this work is devoted.

Brief characteristics and main fields of applications of phenol-formaldehyde novolac oligomers
The color of the non-cured oligomers is from light-yellow to dark brown; the average molecular weight is 400-1000 g/mol, the melt density is 1.14-1.22g/cm 3 , viscosity is 00-200 Pa•s.The density of the solid resins is 1.22 to 1.27 g/cm 3 , Ubbelode dropping point is 70-130 °C.The unhardened oligomers are soluble in phenols and alkaline solutions, in organic solvents [1].
The unhardened oligomers exposed to partial swelling under prolonged contact with water, they are practically insoluble in organic solvents, although the contained in them oligomers can be partially recovered by extraction.Resites slowly dissolve with decomposition under the influence of aqueous alkali or phenol melts.They are resistant to most acids, except concentrated sulphuric and acidoxidants.
At full or partial replacement of phenol to cresol or xylenol oligomers when cured have improved dielectric properties.
The properties of filled oligomers are caused to a large extent by the filler.
The unhardened oligomers are stable for a long time when heated up to 200 °C and partially are able to resist the action of higher temperatures (days at 200-250 °C, hours at 250-500 °C, minutes at 500-1000 °C, a few seconds at 1000-1500 °C).The decomposition of the unhardened resins begins at temperatures around 300 °C and is accompanied by the release of pyrolysis products (homologs of phenol and benzene, carbon dioxide, etc.).
The oxidizers and acids accelerate this process.At higher temperature the charring occurs with the formation of coke.The presence of substituents in the phenolic nuclei reduces the thermal stability of resins: oligomers obtained from phenols quickly begin to decompose already at 230 °C.

Main fields of application of the PFO [2]:
Foams plastics and foam blocks They are obtained by the gas filling of resoles with fillers by hydrocarbons (technology is similar to the production of polystyrene), are used as heat-and soundinsulation material having high thermostability and fire resistance compared to geofoam.

Glues and adhesive materials
The glues based on phenol-formaldehyde resins intended to associate the wood fibers (matrix fiberboard, particleboard, plywood) are widespread.The viscous PFO use for cold welding of light metals and plastic products (for example, seaming of linoleum pieces), the compositions on their basis with modifications are able to work in extreme conditions; their solutions in ethanol or other volatile solvents are used as medical adhesives for wound healing.

Press mass
The pressed powders are used for casting of finished goods (which are used less in recent years) and for the preparation of composite materials with different fillers; widely used in composition of building mixtures to create coatings or adhesive layers.
Lacquer resins Used as replacement of natural shellac, as dielectric coatings and protection of metals from corrosion."Liquid novolac", a solution of novolak in ethylene glycol, which is used as anti-corrosion coating in shipbuilding, is produced increasingly at the present time.
Laminates Composites based on phenol-formaldehyde oligomers are used as a light strong material to facilitate construction as well as materials resistant to adverse conditions and have good dielectric properties.Also they are used for forming tubes and rods of various types.

Ion exchange resins
Practically all range of cationic, anionic, amphoteric and other resins, containing aromatic monomer of substituted benzene, are widely used in wastewater treatment, water treatment and catalysis in the chemical industry.
Brief characteristic of raw materials used in the production of phenol-formaldehyde novolac oligomers Phenol shipbuilding, is produced increasingly

Laminates
Composites based on phenol-formalde struction as well as materials resistant they are used for forming tubes and rod

Ion exchange resins
Practically all range of cationic, anion substituted benzene, are widely used in cal industry.

OH
Colorless crystalline substance with th is 181.8 °C, the density is about 1030 k significantly reduce the melting point o to 84 °C it mixes with water in any rati Colorless crystalline substance with the specific smell of gouache, MP is 40.9 °C, the boiling temperature is 181.8 °C, the density is about 1030 kg/m 3.Under air oxidation phenol becomes pink.The impurities significantly reduce the melting point of the phenol.The solubility in water is of about 8 %; under heating to 84 °C it mixes with water in any ratio.The aqueous solutions of alkalis easily dissolve the phenol with the formation of phenolates.Phenol is soluble in formalin, ethanol, diethyl ether, glycerol, benzene, turpentine, fatty acids and their esters [2].
The chemical activity of phenol in the synthesis of phenol aldehyde resins is explained by the presence of three active protons in its molecule or two in the ortho-and one in para-position to the hydroxyl group.
Cresols (Methylphenols) Phenols attach formaldehyde only to the ortho-and para-position to the hydroxyl group, therefore, m-cresol with three active protons giving thermoreactoplastics are more functionalized; o -and p-cresols, which are only bifunctional, give thermoplastics.
Because of the difficulty of separation of cresols, the mixture of three isomers called tricresol is often uses: the density of liquid is 1044 kg/m 3 , boiling point is 185-205 °C depending on the content of isomers and impurities.Tricresol is soluble in ethanol, diethyl ether and alkaline solutions, about 2.5 % of tricresol dissolves in the water.The fraction of coal tar, boiling in the range of 160-250 °C, which is cleaned from a large part of the naphthalene, can be used for tricresol manufacturing.

OH
Xylenol has six isomers.The technical xylenol is the mixture of isomers, it's the viscous oil of a brownish-black color with a strong unpleasant odor, the boiling point is 200-220 °C, the density is 1040 kg/m 3 , it's soluble in 10 % aqueous alkali solution.The main source of xylenols is the cresol fractions of resins obtained from the thermal processing of fuels.In view of its bifunctionality, it's not able to form the mesh structure and without the introduction of additional raw materials is suitable only for thermoplastic oligomers manufacturing.
Bisphenol A and its derivatives The condensation products of phenols and acetone under catalysis by mineral acids, which have several active centers (up to 4), and as a consequence, are able to link oligomeric chains by adding to the basic raw material to improve their heat resistance and rigidity.

O OH
Derivative of furfural, which increases the thermosetting properties and the viscosity of the polymer; has a highly active center in the 5-position of the furan cycle.

Chlorophenols
Mono-, di-and trisubstituted products of chlorination of phenol.They are less active than phenols and cresols, but more acidity, and at the same time they give the higher combusting resistance to the product due to the presence of chlorine atoms.

The highest phenols
This group includes hydroxynaphthalenes, phenolic derivatives of anthracene, phenanthrene, etc.By the addition to oligomers they give them high thermal stability (up to 400 °C), growing with increasing number of condensed cycles in phenol.

Formalin
The aqueous 37 % solution of formaldehyde at room temperature or up to 50 % at increased temperature.During reaction with the phenols it enters into electrophilic aromatic substitution, "stitching" between the aromatic nuclei and thereby forming oligomers.The solid derivatives of formaldehyde -paraform and urotropin (methenamine) -are sometimes used as a replacement for the unstable solution in the production.

Lignin
Natural oligomer, which is part of the wood.It has phenolic centers, linked by saturated hydrocarbon chains (3-4 atoms).The oligomer obtained using lignin contains less quantity of free phenol and is also biodegradable, that facilitates its disposal and does less harm to the environment.The production of lignin-based oligomers is currently becoming increasingly important in developed countries in connection with stricter of ecological regulations.
Novolac phenolformaldehyde oligomers are obtained, as a rule, by the polycondensation of phenol and formaldehyde (in form of formalin) in an acidic aqueous mass; the various additives to the starting materials have only the limited application.The production is carried out by periodic or continuous scheme [3].In this paper the device and further improvements in the continuous production schemes were in detail considered.

H OH OH 6
The average molecular weight is 730,86 g/mol Molecular formula is С 42 Н 42 О 7 The characteristics of the original sample: 1.The standard sample is approved in accordance with the established procedure.
2. The standard sample should be replaced by newly prepared and approved after 6 months.
3. Validity period, its extension and storage of the standard sample is estab-

Description of the technological process
The production of novolac phenolformaldehyde oligomers is the multistage continuous process.The block scheme of technological process is shown in Fig. 1, the technological scheme is shown in Fig. 2.

Checking and preparing equipment for work
All equipment is periodically visually checked on the integrity of the coating of apparatus, the isolation valves, the lack of reaction mass.The tightness of the devices is checked by creatign 2 ATM pres-sure inside the reactor, the compressed air supply should be closed.Upon exposure of 10 minutes the pressure should not decrease.The operation of the mixers, the flow of steam to the casing are checked at idling.The devices of IA, control panel are inspected.

TP-1. Preparation of raw materials
The raw materials and intermediates adopted by the input control with the appropriate mark of quality are passed in the production (table 2).Periodically all Fig. 1.Block scheme of technological process storages must fill out the appropriate raw materials.

TP-1.1. Preparation of the starting mixture
Apparatus design for stage: 1. Storage of phenol (St-1) is the apparatus, heated by tube bundle, made of steel 1Х18Н9Т, with a capacity of 63 m 3 , connected with PC, equipped with the remote measuring glass.
2. Dosimeter of phenol (Dos-2) is the apparatus, heated by shirt, made of steel 1Х18Н9Т, with capacity 40 L, connected with PC , equipped with the remote measuring glass.
3. The mixing tank (Re-3) is the apparatus made of steel 1Х18Н9Т, with a capacity of 1 m 3 , connected with PC, equipped with the remote measuring glass.4. The storage of phenolic water (Re-12) is the apparatus made of steel 1Х18Н9Т, with a capacity of 25 m 3 , connected with PC, equipped with the remote measuring glass and coil cooling.

Heater (H-4
) is shell-and-tube apparatus made of steel 1Х18Н9Т, with the cross section of the tube space 0,089 m 2 .
From the storage St-1 the molten phenol and the phenolic water recycling from the collector SB-12 is pumped to the dosimeter Dos-2, where it is periodically drained into the mixing tank Re-3, in which 50 % formalin from the methanol oxidation facility is flowing continuously under the control of the flow meter.The mass resides in the mixer for 1.5 hours, continuously entering to the next stage through the heat exchanger H-4 heated to 70 °C (table 3-4).

TP-1.2. The catalyst preparation
Apparatus design for stage: 1. Reactor for preparation of catalyst (R-10) is a apparatus made of steel 1Х18Н9Т, with a capacity of 0.32 m 3 , connected with PC, equipped with a remote measuring glass, thermometer, coil cooling and propeller stirrer.2. The dosimeter of the catalyst (Dos-11) is the apparatus made of steel 1Х18Н9Т, with a capacity of 1L, connected with PC, equipped with a remote measuring glass.
Simultaneously with the preparation of the starting mixture, catalyst (an aqueous suspension of oxalic acid) is drained into the dosimeter Dos-11 from the reactor R-10, which is loaded once per day by ox- alic acid and water, which is then drained by gravity to the next stage.The addition of acid is regulated on the temperature and level of the mixture in the main reactor (table 5-6).

TP-2. Polycondensation
Apparatus design for stage: 1.The polycondensation reactor (R-5) is the apparatus made of steel 1Х18Н9Т, with a capacity of 2 m 3 , connected with PC is supplied by a kinked pipe, level gauge, temperature and pressure gauges, plain jacket and anchor stirrer.
2. Backflow condenser (C-8) is shelland-tube apparatus made of 1Х18Н9Т steel, with a cross section of the tube space 0,013 m 2 .
The original mixture and the catalyst are mixed, going into the main reactor R-5 from the previous stage in a predeter-mined amount through the upper fittings, resulting in beginning of the chemical reaction of phenol and formaldehyde.The reaction takes place under the cooling of the reactor walls with water while maintaining a temperature of 98-100 °C for all time the mass stays in the apparatus (est. 2 hours), while it is continuously drained through the bottom fitting.The volatile starting materials evaporating in the reaction condense at the condenser C-8 and thus flow back to the reaction mass.Product samples are periodically taken from the reactor outlet.If the product becomes excessively viscous, the feed rate of the catalyst reduces.
The reactor is equipped with pipe displacement for an emergency evacuation of the mixture from the reactor.During the installation starting the primary quan- tity of the initial mixture is heated by dead steam (6 ATM) to reaction temperature and only then the water could be let in a jacket (table 7-8).

TP-3. Aqueous phase separation
Apparatus design for stage: 1. Florentine vessel (Dec-6) is a apparatus made of steel 1Х18Н9Т, with a capacity of 2 m 3 , connected with PC, equipped with a sight glass and a plain jacket.
The obtained mixture of the product, precursors and formed water from the reactor R-5 is fed to a continuous sedimentation in a steam-heated (6 bar) florentine vessel Dec-6.The mixture in the vessel is separated into aqueous and organic phase; the first is drained through the upper fitting and is led to utilization or resol resins production, the second is compressed with gear pump to the drying stage through the lower fitting (table 9-10).

TP -4. Drying and decarboxylation
Apparatus design for stage: 1. Dryer (Dr-7) is shell-and-tube apparatus made of 1Х18Н9Т steel, with a cross section of the tube space 0,259 m 2 , equipped by vacuum manometer at the outlet from tube space.
The resin is pumped from the separation stage into the dryer Dr-7, made in the form of shell-and-tube exchanger heated by high pressure steam (12 ATM) to create a temperature of 140-180 °C.The resin is fed into the tubular space, where the medium vacuum is created, and moves in the form of a film due to the   Because of high pressure steam heating, the polymerized resin remains on the tubes and must be periodically removed.

TP-5. Heat treatment
Apparatus design for stage: 1. Resin collector (Re-8) is the apparatus made of steel 1Х18Н9Т, with a capacity of 2 m 3 , connected with PC, is supplied by a kinked pipe, tank gauge, temperature and pressure gauges, coil semi-tube jacket and anchor stirrer.
The molten dried resin is poured into resin collector Re-8, a capacitive apparatus with jacket and mixer.Resin is fed to a predetermined filling level after which the incoming stream is transferred to another resin collector, and the live steam (6 bar) is flown to the apparatus through the kinked pipe.Under heating by both live and dead steam (12 bar) the temperature is maintained in the range of 130-190 °C, resulting in the excess phenol steam-distilling and going to condensation and disposal.Samples are collected periodically from the apparatus to verify compliance with standardized parameters.After the process is finished the marketable resin is supplied to the granulation and bagging (table 13-14).

Conclusion
This paper presents the modification of the technological scheme of production of novolac phenol-formaldehyde oligomers.Analytical review presents brief characteristics of raw materials, starting materials and the impact of each type of phenol and formaldehyde raw materials on technological and physicomechanical properties of the product.In the technological part the characteristic of finished products, raw materials and materials are given, a detailed description of technology and technological scheme of production is shown (table 15).

Table 3
Loaded on the stage ТP-1.1

Table 6
Obtained at the stage of TP-1.2

Table 8
Obtained at the stage of TP-2 Obtained