RU2534544C1 - Method of manufacturing phenol-formaldehyde oligomer - Google Patents

Abstract

FIELD: woodworking industry.

SUBSTANCE: manufacturing method comprises loading phenol, loading water, loading the first portion of caustic soda, loading formalin and loading the second portion of caustic soda. At that, formalin before loading to the reaction mixture and adding the second portion of caustic soda is mixed with paraformaldehyde solution followed by neutralisation of the mixture with granulated caustic soda.

EFFECT: reduction of amount of free volatiles, reduction of alkalinity, and increase in the degree of cure of these oligomers, improvement of qualitative characteristics of the plywood and chipboard obtained on their basis.

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Description

The invention relates to the woodworking industry and can be used in the manufacture of phenol-formaldehyde oligomer used in the manufacture of waterproof plywood.

A known method of manufacturing a phenol-formaldehyde oligomer, in which phenol and water are pre-heated to 30-35 ° C, then 65.2% of the total sodium hydroxide solution provided for in the recipe is first loaded into the reactor. After that, the reactor stirrer is turned on and the mixture is kept at a temperature of 30-35 ° C for 10-15 minutes. Then the heating of the reactor is stopped, cold water is fed into the jacket of the reactor and formalin is charged. Due to the exothermic reaction, the mixture is heated to a temperature of 44-46 ° C. If the temperature of the reaction mixture does not reach 44-46 ° C, then the mixture is heated to this temperature by letting steam into the jacket of the reactor. At a temperature of 44-46 ° C, the mixture is condensed for 90 minutes, and then steam is turned on and the temperature of the reaction mixture is adjusted to 97-100 ° C, i.e. to a boiling point at which the condensation process of the reaction mixture continues for 30 minutes After that, the reaction mixture is cooled for 25-30 minutes to a temperature of 40-45 ° C and the remaining sodium hydroxide solution provided for in the recipe is introduced into the cooled mixture. The resulting mixture is heated to a temperature of 83-85 ° C for 40-45 minutes, condensed at this temperature for 5 minutes, and then the finished resin is cooled to a temperature of 25-30 ° C for 35-40 minutes, and then poured into a receiver . (See Shvartsman G.M., Schedro D.A. Production of chipboards. 4th ed. Rev. and add. - M.: Lesn. Prom-st, 1987.-320 s; p. 58-59) .

The closest technological solution is the method of manufacturing the phenol-formaldehyde oligomer SFZh-3014, which includes the following steps: phenol, water and sodium hydroxide are charged into the reaction flask according to the recipe and the mixture is heated to 38-50 ° C with a continuously working stirrer. Then the mixture is cooled to 24-32 ° C, after dissolving the phenol load the calculated amount of formalin.

Then raise the temperature of the reaction mixture to 60-70 ° C and incubated for 90 minutes. After the exposure time, a resin sample is taken to determine the refractive index, viscosity and pH, which should be in the following ranges: refractive index - 1,450-1,460; viscosity according to VZ-4 - 10-16 s; pH 10.2-10.4.

Next, the temperature of the mixture is gradually brought to a boiling point of 94-98 ° C, after which the mixture is kept for 25-30 minutes.

The end of the process at this stage is determined by the following indicators: refractive index - 1,468-1,474; pH = 10.5-10.9; viscosity according to VZ-4 - 25-90 s.

Upon reaching these indicators, a second portion of caustic soda is introduced, with stirring, for 5 minutes. Then, at a temperature of 80-85 ° C, the mixture is incubated for 5-10 minutes. The resulting resin is cooled to 25-40 ° C and poured into a receiving container, an analysis is carried out for compliance with the requirements of GOST. (See V.E. Tsvetkov, Yu.V. Pasko, K.V. Kremnev, and O.P. Machneva. Polymers in the production of wood materials: workshop. - M.: GOU VPO MGUL, 2007. - 55 p., pg. 34-35).

The disadvantages of the known solutions are the insufficient degree of cure at 100-105 ° C and the high alkalinity associated with the synthesis conditions of the low viscosity resin, as well as the insufficient reduction in the toxicity of the oligomer and waterproof plywood obtained using this oligomer. And, in addition, the enterprises producing synthetic oligomers are faced with the acute problem of the safe utilization of paraformaldehyde, which is formed during the storage of formalin at the bottom of tanks.

The problem solved by the claimed invention is to reduce toxicity, while improving the physico-mechanical properties of plywood, as well as simultaneously solving two problems: environmental (paraformaldehyde, being a harmful toxic substance containing formaldehyde, is not released into the environment) and production (paraformaldehyde " is utilized ”in the synthesis of phenol-formaldehyde oligomer as a substance containing formaldehyde, thereby saving formalin).

The solution to this problem is provided by the fact that in the method of manufacturing phenol-formaldehyde oligomers, including loading phenol, loading water, loading the first portion of caustic soda, loading formalin, loading the second portion of caustic soda, formalin, before loading into the reaction mixture and before introducing the second portion of caustic soda, mixed with a solution of paraformaldehyde, followed by neutralization of the mixture with granular sodium hydroxide.

The technical essence of the claimed invention lies in the fact that in the synthesis of phenol-formaldehyde oligomers can be used dissolved paraformaldehyde, which is a clear, colorless or slightly yellowish liquid with a pungent odor of formaldehyde. The main properties of paraformaldehyde solution are as follows: refractive index - 1.375, pH - 0.80, density - 1.121 kg / m ³ , free formaldehyde content - 21.0%. The processing of paraformaldehyde is difficult because it does not dissolve in water and melts with decomposition in the high temperature range (T = 120-150 ° C). The formaldehyde content in paraformaldehyde is up to 95%.

A characteristic feature of paraformaldehyde is that when heated, monomer molecules are split off. This decomposition process is usually called depolymerization, in contrast to degradation, a decomposition process that is not accompanied by the release of volatile products, which leads to a sharp decrease in the molecular weight of the polymer. Both of these processes can occur simultaneously, and in this case the overall picture of destruction is noticeably complicated.

The mechanism of destruction of paraformaldehyde can proceed as an elementary reaction - thermooxidative destruction under the influence of ammonium salts - ammonolysis.

The destruction of paraformaldehyde under the action of ammonium salts can proceed according to the following mechanism:

, легко растворимых в воде. Образовавшиеся продукты деструкции способны вступать в реакцию с компонентами фенолоформальдегидного олигомера с образованием более высокомолекулярных олигомерных продуктов - взаимодействие функциональных групп олигомера с продуктами аммонолиза.The presented mechanism can lead to the formation of amino alcohols and polyoxymethylene glycols with a degree of polymerization $$n=2÷6$$

easily soluble in water. The resulting degradation products are able to react with the components of the phenol-formaldehyde oligomer to form higher molecular weight oligomeric products — the interaction of the functional groups of the oligomer with ammonolysis products.

A similar mechanism for the destruction of paraformaldehyde allows them to be modified during the synthesis of phenol-formaldehyde oligomers. The presence of phenol as an acceptor of formaldehyde and a synthesis temperature of 94-100 ° C create the prerequisites for the implementation of this mechanism.

The presented method for the modification of phenol-formaldehyde oligomers makes it possible to reduce the amount of free volatile substances (phenol and formaldehyde), as well as reduce alkalinity and increase the degree of curing of these oligomers and, therefore, increase the quality characteristics of plywood and particle board.

The invention is illustrated by the following examples.

Example No. 1.

The phenol necessary for the synthesis is dosed in an amount of 100 mass parts, water is dosed in an amount of 150 mass parts and sodium hydroxide is dosed in an amount of 20 mass parts, then the mixture is heated to 50 ° C with a continuously working stirrer. Then the reaction mixture is cooled to 30 ° C, after dissolving phenol, a pre-prepared mixture consisting of 200 parts by weight of formalin and 50 parts by weight of paraformaldehyde solution is loaded and which was neutralized by 5 parts by weight of granular sodium hydroxide.

Then raise the temperature of the reaction mixture to 70 ° C and incubated for 90 minutes. After the exposure time, a resin sample is taken to determine the refractive index, viscosity and pH, which should be in the following ranges: refractive index - 1,450-1,460; viscosity according to VZ-4 - 10-16 s; pH 10.2-10.4.

Next, the temperature of the mixture is gradually brought to a boiling point of 94-98 ° C. After which the mixture can withstand 25-30 minutes.

The end of the process at this stage is determined by the following indicators: refractive index - 1,468-1,474; viscosity according to VZ-4 - 25-90 s; pH is 0.5-10.9.

Upon reaching these indicators enter the second portion of caustic soda - 10 mass parts, with stirring, for 5 minutes. Then, at a temperature of 80-85 ° C, the mixture is incubated for 5-10 minutes. The resulting resin is cooled to 25-40 ° C and poured into a receiving container.

Comparative properties of phenol-formaldehyde oligomers are shown in table 1.

Example No. 2.

The phenol required for the synthesis is dosed in an amount of 100 mass parts, water is dosed in an amount of 100 mass parts and sodium hydroxide is dosed in an amount of 20 mass parts, then the mixture is heated to 50 ° C with a continuously working stirrer. Then the reaction mixture is cooled to 30 ° C, after dissolving the phenol, a pre-prepared mixture consisting of 180 parts by weight of formalin and 100 parts by weight of paraformaldehyde solution is loaded and which was neutralized by 8 parts by weight of granular sodium hydroxide.

Then raise the temperature of the reaction mixture to 70 ° C and incubated for 90 minutes. After the exposure time, a resin sample is taken to determine the refractive index, viscosity and pH, which should be in the following ranges: refractive index -1,450-1,460; viscosity according to VZ-4 - 10-16 s; pH 10.2-10.4.

Next, the temperature of the mixture is gradually brought to a boiling point of 94-98 ° C. After which the mixture can withstand 25-30 minutes.

The end of the process at this stage is determined by the following indicators: refractive index - 1,468-1,474; viscosity according to VZ-4 - 25-90 s; pH is 10.5-10.9.

Upon reaching these indicators enter the second portion of caustic soda - 10 mass parts, with stirring, for 5 minutes. Then, at a temperature of 80-85 ° C, the mixture is incubated for 5-10 minutes. The resulting resin is cooled to 25-40 ° C and poured into a receiving container.

Comparative properties of phenol-formaldehyde oligomers are shown in table 1.

Example No. 3.

The phenol required for the synthesis is metered in an amount of 100 mass parts, water is metered in an amount of 50 mass parts and sodium hydroxide is metered in an amount of 20 mass parts, then the mixture is heated to 50 ° C with a continuously working stirrer. Then the reaction mixture is cooled to 30 ° C, after dissolving the phenol, a pre-prepared mixture consisting of 150 parts by weight of formalin and 150 parts by weight of paraformaldehyde solution is loaded and which has been neutralized by 10 parts by weight of granular sodium hydroxide.

Then raise the temperature of the reaction mixture to 70 ° C and incubated for 90 minutes. After the exposure time, a resin sample is taken to determine the refractive index, viscosity and pH, which should be in the following ranges: refractive index - 1,450-1,460; viscosity according to VZ-4 - 10-16 s; pH 10.2-10.4.

Next, the temperature of the mixture is gradually brought to a boiling point of 94-98 ° C. After which the mixture can withstand 25-30 minutes.

The end of the process at this stage is determined by the following indicators: refractive index - 1,468-1,474; viscosity according to VZ-4 - 25-90 s; pH is 10.5-10.9.

Upon reaching these indicators enter the second portion of caustic soda -10 mass parts, with stirring, for 5 minutes. Then, at a temperature of 80-85 ° C, the mixture is incubated for 5-10 minutes. The resulting resin is cooled to 25-40 ° C and poured into a receiving container.

Comparative properties of phenol-formaldehyde oligomers are shown in table 1.

Table 1 Comparative properties of phenol-formaldehyde oligomers Properties of Oligomers Example 1 Example 2 Example 3 The closest analogue Appearance Homogeneous clear liquid from reddish brown to dark cherry color VZ-4 viscosity, sec at 20 ° C 17-90 Dry residue,% 46-52 The content of free formaldehyde,% 0.12 0,098 0.14 no more than 0,15 The content of free phenol,% no more than 0.10 Mass fraction of alkali,% 3.8 3.2 4.1 6.5-7.5 The tensile strength when chipping along the adhesive layer of plywood after boiling in water for 1 h, MPa 1,61 1,66 1,64 1.4

Thus, the invention allows to reduce the toxicity and alkalinity of phenol-formaldehyde resins while improving the tensile strength when chipping plywood along the adhesive layer after boiling in water for 1 hour, while solving the environmental problem of using oligomeric production waste by recycling it in the synthesis process.

Claims (1)

A method of manufacturing a phenol-formaldehyde oligomer, comprising loading phenol, loading water, loading the first portion of caustic soda, loading formalin and loading a second portion of caustic soda, characterized in that formalin is mixed with a solution of paraformaldehyde before being introduced into the reaction mixture and before the second portion of caustic soda is added, followed by neutralization of the mixture with granular sodium hydroxide.