DE2215947B1 - Process for the production of phenolic resin glues - Google Patents

Description

ORIGINAL KSf- _GT

It has now been found that alkaline condensed aqueous phenol-formaldehyde resins of the above described type, which are suitable as binders for wood-based materials and are more satisfactory Have properties than before, due to the gradual condensation of phenol with formaldehyde in the presence an alkaline agent with a final phenol to formaldehyde to alkali molar ratio of 1 to (1.5 to 2.5) to (0.4 to 1.5) is obtained when one

a) in a first stage, phenol, formaldehyde and 0.1 to 0.3 mole of alkali per mole of phenol mixed, the reaction mixture is as long at a temperature below 6O ⁰ C until 30 to 60 ° / ₀ of the formaldehyde originally present free are bound, and then maintains a temperature between 8O ⁰ C and the boiling point of the mixture until the viscosity of the solution at 2O ⁰ C reaches a value of about 700 to 3000 cP, and

b) in a known manner in at least one further stage, adding the remaining amount of alkali and as long as further condensed until a viscosity of 100 to 60OcP when measured at 2O ⁰ C and based on a 50% solution is achieved.

According to a particular embodiment of the invention, the temperature in the first stage is kept below 60 ^° C. until 40 to 50% of the originally free formaldehyde is bound, 0.15 to 0.25 mol of alkali per mol of phenol being initially present , and adds the remaining amount of alkali at a temperature below 80 ^° C. in at least one further stage.

According to a further, likewise particularly advantageous embodiment of the invention, 0.25 to 0.3 mol of alkali per mole of phenol is used in the first stage and the remaining amount of alkali is added in at least two further stages. It is expedient to maintain a temperature between 80 and 95 ^° C. in at least one of the further stages.

It has further proved to be advantageous to add the final amount of alkali in the final stage at a temperature below 7O ⁰ C and to refrain from further heating.

The viscosity data used above to characterize the state of condensation relate to the resin contents of the finished solutions which are customary in industry, d. H. about 48 to 50%> which can be determined as the dry residue of the solution. Solutions with a different concentration naturally show correspondingly higher or lower viscosities, which can be determined by setting up calibration curves in known Way can be determined.

Knowledge of the unbound content of the reaction mixture in each case is essential for carrying out the invention of free formaldehyde is important.

Methods of determination for free formaldehyde, especially in the presence of alkali, are known. However, it has been found advantageous in the practice of the invention, according to Pfeil und S c h r ο t h, magazine for analytical Chemie, 134, 333 (1952), or after J.I. de Jο η g, Recueil des Traveaux de Chimie, 72, 356 (1953) procedure:

1. Basics of the method

Formaldehyde combines with KCN or HCN to form glycolonitrile, a known one is used Amount of KCN and back-titrate the KCN excess with adjusted Hg (II) nitrate solution. as The metal indicator is diphenylcarbazone with a change from colorless to purple.

2. Reagents

a) Ο, ΐη-KCN solution;

b) 0.1 In-Hg (NO ₃ ) ₂ solution;

c) ln sodium hydroxide solution;

d) 2N nitric acid;

ίο e) sodium acetate (solid);

f) 1% methanolic ^e diphenylcarbazone solution.

3. Determination of the titer of the cyanogen potassium solution

6.5 g of KCN are dissolved in 1000 ml of distilled water. To produce the titer, 50 ml of this solution are made alkaline with 5 ml of η-sodium hydroxide solution and then _{titrated with O, ln-silver nitrate solution with a known normal factor (n x} ). End point:

Permanent white haze against a black surface. Consumption in ml = V (ImI 0, In-AgNO ₃ ^ 2 ml Ο, ΐη-KCN solution).

4. Titer determination of the mercury nitrate solution

16.25 g of Hg (II) nitrate are dissolved in a 1000 ml volumetric flask with slightly nitric acid distilled water. To determine the titer, 50 ml of the adjusted KCN solution are placed in a pipette, 5 ml of normal sodium hydroxide solution and 8 to 10 drops of diphenylcarbazone solution are added. The color of the alkaline solution is reddish. The solution is diluted to about 100 ml with water, and 2N nitric acid is added dropwise until the solution just changes from orange-red to colorless. Then immediately titrate with the Hg (II) nitrate solution to be adjusted until it remains purple (at least 1 minute). Consumption in ml = V ₂ . The change in the metal indicator diphenylcarbazone is strongly pH-dependent. If the Hg (II) nitrate solution is strongly acidic, the excess acid must be neutralized with ln sodium hydroxide solution shortly before the end point is reached in order to get a sharp change from colorless to purple.
ImI 0, In-KCN ^ 1 ml of O, ln-Hg (II) nitrate solution.

5. Execution of the determination

a) Formalin solution

3 g 36% ^'e g formaldehyde solution are weighed on the analytical balance, transferred to a 500 ml volumetric flask and made up with distilled water. An aliquot (25 ml) is pipetted into a 300 ml Erlenmeyer flask, 50 ml of adjusted KCN solution and 5 ml (burette) η sodium hydroxide solution are added, diluted to about 100 ml with distilled water and 8 drops after standing for 5 minutes Diphenylcarbazone solution added; the sample is adjusted to colorless, weakly acidic with 2N nitric acid (burette) and then titrated with Hg (II) nitrate solution until it changes to violet blue. Consumption in ml = V ₃ . The acid of the added Hg (II) nitrate solution is expediently trapped with a few drops of sodium hydroxide solution shortly before the envelope, or it is buffered by adding 2 to 3 g of sodium acetate.

(De Jong recommends 90% strength aqueous pyridine solution ^e as a buffer which is not used on the basis of existing tests, because the buffer capacity is too low.)

b) phenolic resin

400 to 1500 mg phenolic resin solution (depending on the free formaldehyde content) are placed on the analytical balance weighed and placed in a 300 ml conical flask convicted. The further determination is carried out as described under 3 a) for the formaldehyde solution.

6. Calculation

n ₂ =

50
50 η ₂

= 0.04 x F ₁ x n _x ;

C = 6000 x n _x

Vi (K, - F ₃ )
V ₉ -E

For Ti ₁ = 0.1000 the simplified form applies:
C = 600 % free formaldehyde.

V ₂ -E

It means:

Ti ₁ - normal factor of the silver nitrate solution;

n ₂ = normal factor of the KCN solution;

n ₃ = normal factor of the Hg (II) nitrate solution;

V ₁ = consumption in ml of 0.1 In-AgNO _s solution
per 50 ml of KCN solution;

F ₂ = consumption in ml of 0.1 ln-Hg (NO ₃ ) ₂ solution
per 50 ml of KCN solution;

F ₃ = consumption in ml of 0.1 ln-Hg (NO ₃ ) ₂ solution
for the examined sample solution upon presentation of 50 ml of 0.1n-KCN solution;

C = free formaldehyde content in percent by weight;
ίο E = weight in mg per titrated sample.

Phenolic resins according to the invention have a molar ratio of phenol to formaldehyde with particular advantage like 1: 1.8 to 1: 2.2 with an alkali content (based on on phenol) from 0.5 to 1.3 mol. They have a resin content of 40 to 60, especially 45 to 55%

For example, in the condensation of phenol with formaldehyde in a molar ratio of 1: 2 in a three-stage process, 0.25 mol of NaOH was added per stage and the gelling times listed in the table below were achieved: The gelling time in minutes is achieved without adding hardener to the undiluted Solutions (about 50% resin content) ^{measured at 100 0} C in such a way that a sample of the resin solution in a suitable test tube is immersed in a boiling water bath and the time is measured which elapses until a clear gel formation.

Tabel

Condensation time
(Minutes) 30th
145
15th 45
125
10 55
65
70 60
55
15th 70
20th
0 One step procedure 400 412 360 350 332 (Comparison) 30th 31 31 31 30th 300-450 55-50

1st stage (end of 100 ° C)

2nd stage (8O ⁰ C)

3rd stage (50 ⁰ C)

Viscosity (cP) at 20 ^° C

Gelling time at 100 ⁰ C without hardener
(Minutes)

The parts and percentages contained in the examples below relate to the extent that not otherwise noted, on weight.

example 1

1185 parts of phenol, 1920 parts of 40% formaldehyde and 630 parts of water are initially introduced. At 40 ° C., 155 parts of 50% strength sodium hydroxide solution are added over the course of 5 minutes. The molar ratio of phenol to formaldehyde to NaOH is 1: 2: 0.15, with a free formaldehyde content of 19.8% being present at the start of the reaction. While maintaining a temperature of 40 ^° C., condensation was carried out for a total of 150 minutes and the decrease in free formaldehyde was measured continuously (see A b b. 1; in the figure, the solid line denotes the temperature profile, the dashed line denotes the free formaldehyde content).

After 150 minutes the free formaldehyde content is 10.3%. This corresponds to a binding of 48% of the formaldehyde used. The reaction mixture is ^{heated to 100 °} C. within 7 minutes and held at this temperature for 33 minutes, a viscosity of about 1000 cP ( ^{measured at 20 °} C.) being achieved. During this time, the remaining amount of formaldehyde is quantitatively bound. After rapid cooling to 80 ⁰ C, 360 parts quickly entered ° / ₀ sodium hydroxide solution at 80 ⁰ C and 50 (measured at 20 ⁰ C) for 30 minutes at 80 ⁰ C up to a viscosity of about 750 cP condensed. The total molar ratio of phenol to formaldehyde to NaOH at this point in time corresponds to 1: 2: 0.5. The resin solution is then cooled to 50 ° C. within a further 10 minutes. Under further cooling, 258 parts of 50 ° / ₀ sodium hydroxide solution metered in below 50 ^0C. The phenolic resin thus obtained has a final molar ratio of 1: 2: 0.75. About 4500 parts of an aqueous phenolic resin with a solids content of 48%, an alkali content of 8.57% NaOH and a viscosity of 285 cP (measured at 20 ° C.) are obtained. The gel time at 100 ° C without the addition of hardener is 29 minutes.

Example 2

To a mixture of 1120 parts of phenol, 1780 parts of a 40% (weight percent) solution and 527 parts of unstabilized formaldehyde water under cooling at 55 ° C within 5 minutes 241 parts of a 50% strength aqueous sodium hydroxide ^en

7 8

dosing solution. To keep this ratio in front of phenol, where after this line: a content: \ όγ ^ι λ5 ^η '"formaldehyde ζ ι; NaOK amount; 1: 2: 0.25. Which exist in free formaldehyde. Corresponding to this! one of this mixture contained an amount of free form-binding of 47 "" of the formaldehyde aidehyde used; at the beginning of the reaction 19.4 ", .. The (A b b The overhead drawn line shows the temperature, the dashed line is measured, and in the diagram in Fig. 2, the free formaldehyde content is entered as a function of the reaction time ;. Within a reaction time of .30 minutes at 55 ° C. or 30 minutes, the residual amount of formaldehyde only holds 9 "," free form - is condensed in. After the reaction mixture aidehyd. ie. of the formaldehyde used has been heated for 45 minutes at 100 to 102 ° C. has bound at this point in time. Within 5 minutes, the resin solution has a viscosity of about 300 ° ^{C., the mixture increases from 55 to 100:} C. ie (at 20 "C. measured) after a quick Cooling to boiling point, heated. Here the rest is set to 80 ^; C 2S6 parts 50 ^r _{'/ 0} sodium hydroxide solution free formaldehyde within 20 minutes ago quantitative within 5 minutes was added. . After a further tively linked (see A b b 2: in the image loading 15 10 minutes at 80 ^C again 228 parts of the solid line indicates the Temperaturver- 50 °, quickly metered ₀ sodium hydroxide solution and run as long dashed the Free formaldehyde content is further condensed until the resin solution has a viscosity hyd). After a total reaction time of 3 minutes of about 50 ° C. at 20 ° C., a viscosity of about 140 ° C. is reached (measured at 20 ° C. rapid cooling to room temperature). Then it quickly drops to 80 ^: C- 20 95 parts 50 °. _n iger sodium hydroxide solution added. It is cooled and the reaction mixture at 80'C with 4560 parts of resin solution having a dry residue of 241 parts offset 50 ° _o aqueous sodium hydroxide solution. After 10 minutes of 45.4% and a viscosity of 310 cP at 20 ² C, another 232 parts of 50% sodium hydroxide are obtained. The gel time at 100 ^c C without addition of hardener caustic at 80 ^: C added. The total molar ratio is 27 minutes. The resin solution has an end from phenol to formaldehyde to NaOH in a 25 molar ratio of phenol to formaldehyde to NaOH at this stage is 1: 2: 0.75. At 80 ^c C it will increase from 1: 2: 0.84 for as long. The temperature profile and the condenses until a viscosity of about 850 cP formaldehyde binding is achieved during the condensation ( ^{measured at 20:} C 1 is reached. For this purpose are shown at in A b b. 3. The alkali content is 8.6%. 80 '"C takes about 85 minutes. After that, it quickly...
cooled and the resin solution with 88 parts of a 30 13 e 1 s ρ 1 e 1 4
50% sodium hydroxide solution and 343 parts of water were added. To 1,600 parts of phenol were 2546 parts of an 4570 are parts of a Flarzlösung with a 40% aqueous formaldehyde unstabilized dry residue of 46 ⁽ "'and an NaOH content solution and metered in 750 parts of water. To get this Lövon p.64%. The final molar ratio of solution is 345 parts of phenol to formaldehyde to NaOH continuously with stirring is 1: 2: 0.84. 35 of a 50% aqueous sodium hydroxide solution '"C measured) and a gel time of 31 minutes addition increases from room temperature to 60" C, at 100 ° C without the addition of hardener. In A b b The molar ratio of phenol to the course of the condensation is shown: 40 Formaldehyde to NaOH at this point in time is ... 1: 2: 0.254 mperatur (100 ^G C) and heated up to a temperature of 1120 parts, which takes about 80 minutes, are condensed in a stirrer apparatus to give a mixture of 1120 parts at a room viscosity of about 125 ° cP (measured at 20 ° C.). Phenol, 1780 parts of 40 "strength formaldehyde solution and 45" C. It is then rapidly cooled to 80 "C. Within 870 parts of water within 50 minutes 190 parts of 10 minutes, a further 345 parts of 50% sodium hydroxide solution are added in the manner, 50% sodium hydroxide solution is added and further that the temperature in the first 30 minutes to 10 minutes at 80 ^: C held until the solution ^{rises to 40:} C and then has a viscosity of 75OcP (measured at 20 C) by cooling at 40 "C). Is hooked. The molar ratio of phenol to form-50 after being cooled rapidly to 3O ⁰ C aldehyde to NaOH is 1: 2: 0.2. The content of a further 330 parts of 50% sodium hydroxide solution free formaldehyde is added at the beginning of the reaction. There are 5900 parts of a 48.2% strength before the addition of the sodium hydroxide solution 18.9%. while the phenolic resin solution with a final molar ratio of the sum of the free and bound formaldehyde phenol to formaldehyde to NaOH of 1: 2: 0.75 received 18% 55 after addition of the first amount of sodium hydroxide solution. A gel time of this resin is without results. The reaction mixture is hardened for 33 minutes, the alkali content is 8.6%. de Vissamtreaktionsdauer of 130 minutes at 4O ⁰ C overall viscosity by 260 cps at ^20: C.

1 sheet of drawings

COPY 309 539 528

Claims (1)

1 2 Considerations and a change in other Claim: important properties of the binders are limited. It is therefore an object of the invention Process for the production of alkaline, particularly high-performance phenolic resins condensed aqueous phenol-formaldehyde resins to create 5 such measures that only the cookers are suitable as binders for wood-based materials, relate to the positioning process. by stepwise condensation of phenol with Now it is known that the average condensation formaldehyde in the presence of an alkaline degree - i.e. the average molecular size - agent with a final molar ratio of phenol and its composition of low molecular weight to formaldehyde to alkali of 1 to (1.5 up to 2.5) to io and higher molecular proportions the property profile (0.4 to 1.5), characterized by the fact that condensate resins essentially determine:
that a phenolic resin is generally cured in the same way a) in a first stage phenol, formaldehyde and faster, the further condensation d. H. the higher mol- Mixes 0.1 to 0.3 moles of alkali per mole of phenol, ^{kular it 1} ^. ? ° ^ch _f ^k . ^on ? ° ^si f ^te _τ ^ΗαΓΖ ^ ^ηί ΐ ^es _T ^md f ^ch the reaction mixture for so long at a ¹ S responsible for the fact that the glue m the Lerrnfuge keeps temperature below 60 ° C, up to 30 ^ ^ble J> t ^{and thus} seme actual task Erbis 60% of the initially present free ^{fu can "en} / unerwunschterweise instead of the timber a m-formaldehyde are bonded, and then a zudringen O ^ s the glue joint chip away") changes temperature between 8O ⁰ C and the boiling hand, is a certain amount of impregnation, ie Empunkt complies with the mixture until the viscosity of ² ° dringfahigkeit of Leimharzes compared to the a value of about Denden wood entirely desirable to binder solution at 20 ⁰ C because achieved in this way 700 to 3,000 cP, and ^{dle Nei} S ^Un S of the wood to swell in a damp or even humid environment is reduced. b) in a known manner in at least one £) _am i _t increasing degree of condensation, but the further step, the remaining amount of alkali _to-25 viscosity of the resins increases sharply, the Kondenfügt and further condensed until a sationsgrad by the processing technique (which AufViskosität from 100 to 600 cP, measured when the resin solution is applied to the wood). 20 ⁰ C and relative to 50% solution, _e j _b j _{s NEN} 45. ER- 50% Spanplattenleim suitable is sufficient. _z . b. a processing viscosity of about 120 to 30 450 cP, measured at 20 ⁰ C. Phenol-formaldehyde glues are commonly called about 40 to 60% strength aqueous solutions by reacting phenol with formaldehyde in a molar ratio 1: 1.5 to 1: 2.5 in the presence of about 7 to 14% The invention relates to a process for the production of alkali - preferably sodium hydroxide solution - obtained. In this case, storage-stable, fast-curing phenol-formaldehyde is generally added to the mixture of phenol hyd resins, in which phenol and formaldehyde in and formaldehyde, the required amount of alkali is condensed into an alkaline aqueous solution and the mixture is condensed to 60% by heating will. to 100 ⁰ C to achieve the desired viscosity Alkaline condensed phenolic resins are condensed as 40. It can be also present with the entire phenolic binder for the production of wood-based materials used and the amount of alkali ent- (chipboard, fiberboard, plywood) at 40 to 100 ⁰ C. Add adequate amount of formaldehyde. The Kon-Die resins are used for this purpose as approximately 40 to densation is traded at 80 to 100 ⁰ C up to a viscosity of 60% aqueous solutions. In this connection from about 200 to 60OcP, measured at 20 ⁰ C, stood by the phenolic resins consist of a mixture of 45 out. low molecular weight methylol compounds of phenol One has also already used multistage processes and higher molecular weight condensates in the form of their alkaline phenolic resins, such as those that are water-soluble Alkali salts, as described in British patent specification 1023 882 Is used for the production of wood-based materials. In particular, a method has recently been used in the German Offenlegungsschrift 1 570 899 such that the amount of resin is about 50 to 120 g per square, according to which phenol is 1.5 to three meters of glue area. In the case of chipboard, 3.5 molar equivalents of formaldehyde in the presence of the resin content about 5 to 15 percent by weight of the alkali is condensed in such a way that initially wood, which is added up to 0.4 equivalents of alkali from a dilute glue liquor, is then added together curing agents, hydrophobing agents. ä u. ₅₅ continuously a further 0.2 to 2.0 moles of alkali with an be applied to the loose chips. Rate of 0.3 to 5% per minute can be added and The technical bottleneck in the manufacture of wood-based materials - as soon as the condensation to the desired molar position is generally the dwell time that the weight has advanced, so much alkali added Binder together with the wooden parts in that its total content - based on Plate press must spend to the chip association 60 phenol - 0.2 to 2 mol is. To manufacture the said open; This is why the production of rapid hardening refers to other techder Resin types an essential task of the Harz niken of the gradual condensation, which ultimately all manufacturer. aim to improve the reactivity of the resins. Experience has shown that highly reactive, i.e. H. fast - to other suggestions, for example that of the USA. - hardening Resins for instability in storage. 65 Patent 2,988,536, alkaline earth metal hydroxides as Kon-Zwar can be used both the reactivity and the dense agent, should not go into detail-stability influence by additives; usually be accepted as they are the subject of the invention these measures will, however, stand further through economic ones.