GB2102820A

GB2102820A - Method for the production of phenol-aldehyde resins

Info

Publication number: GB2102820A
Application number: GB08122285A
Authority: GB
Inventors: Geoffrey Norman Swailes; Arthur Anthony Cutler
Original assignee: REVERTEX IND
Current assignee: REVERTEX IND
Priority date: 1981-07-20
Filing date: 1981-07-20
Publication date: 1983-02-09
Also published as: AU7316681A

Abstract

In one form of the invention, the method includes reacting a phenol and aldehyde at a temperature of between 80 DEG C and 90 DEG C for a period of at least 30 minutes, thereafter increasing the temperature of the reaction to between 90 DEG C and 97 DEG C for a further period of at least 90 minutes. In a further form of the invention, the method includes the split charge of phenol aldehyde. Thus, the phenol is initially reacted with an aldehyde at between 80 DEG C to 90 DEG C for a period of at least 30 minutes, and thereafter additional phenol is added and reacted with the resultant mixture for a further period of at least 30 minutes at a temperature of between 60 DEG C and 90 DEG C. Following this, further heating takes place for a period of at least 90 minutes at a temperature of between 90 DEG C and 97 DEG C.

Description

SPECIFICATION Improvements in and relating to phenol-aldehyde resins This invention relates to a method for the production of phenol-aldehyde resin. The invention also relates to a resin formed by the abovesaid method.

In particular, this invention relates to a resole type phenol-aldehyde (preferably formaldehyde or paraformaldehyde) resin which contains benzyl ether linkages situated ortho to the hydroxy group on the benzene ring. It is well known in the art that certain water soluble metal salts of organic mono carboxycyclic acids, in particular zinc acetate, are suitable catalysts to effect this type of steric placement in a phenol-formaldehyde polymer.

Thermo-setting phenol-aldehyde resins are known and basically relate to the reaction of phenol and formaldehyde in the presence of a suitable catalyst, and at a suitable temperature, until the polymer so formed has reached a predetermined molecular weight as defined by a simple in-process test.

Various methods and processes for the production of such phenol-formaldehyde resins are known, for example as those disclosed in New Zealand Patent Specifications Numbers 175042, 177241 and 177267.

It has been found however, that the processes and methods known up until this time and such as described in the aforesaid New Zealand Patent Specifications, are not always as commercially or practically advantageous as stated.

It is an object of at least one form of the invention to provide an efficient method of producing a phenol-aldehyde resin.

It is a further object of at least one form of this invention to provide a phenol-aldehyde resin.

According to one aspect of this invention, there is provided a method of producing a phenol-aldehyde resin, including: 1. reacting phenol and aldehyde, at a temperature of from 80"C to 90"C for a period of at least 30 minutes and thereafter 2. increasing the temperature of said reaction to between 90"C and 97"C for a further period of at least 90 minutes.

According to a further aspect of th is invention, there is provided a method of forming a phenol-aldehyde resin including: 1. reacting phenol with an aldehyde at between 80"C and 90"C for a period of at last 30 minutes.

2. introducing additional phenol and reacting the resultant mixture for a further period of at least 30 minutes at a temperature of between 80"C and 90"C, thereafter 3. further heating said mixture to a temperature of between 90"C and 97"C for a period of at least 90 minutes.

The invention will now be described by way of example only and with reference to the accompanying examples.

The present invention relates to the use of aldehydes, but specifically, in preferred forms of the invention, to formaldehyde and paraformaldehyde.

In order to produce a resin (both commercially viable and technically acceptable), phenol and a formaldehyde are first reacted for a predetermined period of time and at a predetermined temperature in the presence of a catalyst (such as for example, zinc acetate or a mixture of acetic acid and zinc oxide).

The reaction of the formaldehyde and phenol in the presence of the acidic catalyst takes place in an appropriate apparatus such as for example a reactor equipped with stirrer, condenser and thermometer.

The phenol and formaldehyde are reacted for an initial period of time of at least 30 minutes at a temperature of between about 80"C and about 90"C.

Preferably, the mixture or batch is held at a temperature of between about 80"C and about 85"C for about 50 to 70 minutes.

Following this initial step, the mixture or batch is then further heated to a higher temperature of between about 90"C and about 95"C for a period of at least about 90 minutes and until such time as the batch separates into two phases, being a lower resinous phase and an upper aqueous phase. At some point after this time, the reaction is stopped and the resinous phase is allowed to settle. The resinous phase is then withdrawn.

Preferably, the reaction at a temperature of between about 90"C and about 97"C continues until such time as the viscosity of the resinous phase of the batch is between about 2 poise and about 20 poise at 500C. It has been found that a desirable viscosity level is 5 poise at 50"C.

Following the separation of the resinous phase, the resinous phase can be mixed with a suitable solvent compound (for example:- diethylene glycol) to give a mobile, resinous composition of low viscosity.

In one form of the invention, a method is provided whereby the addition of phenol is made in at last two stages of application so as to provide a split charge. While the invention is described with reference to the phenol being split into two stages of application, this is by way of example only. If desired, the phenol could be added in one, or more than two, stages; for example, three or four. In this form of the invention and by way of example, not less than 50% (by weight) of the desired phenol is reacted with formaldehyde in the presence of a suitable catalyst (for example a metal salt of a mono carboxycyclic acid) for a period of at least 30 minutes (preferably about 60 minutes), at a temperature between about 80"C and about 90"C.

Preferably, the quantities of phenol and formaldehyde are such that the mole ratio of these components in this initial reaction between formaldehyde to phenol, is less than 2.5 and preferably between 1.5:2.2.

Following this reaction, the remaining amount of phenol is added to the mixture and reacted for a further period of at least 30 minutes (preferably about 60 minutes) at a temperature between about 80"C and about 90"C, such that the final mole ratio of formaldehyde to total phenol is less than 1.7:1.0.

Following this, the mixture is then further heated to a temperature of between about 90"C and about 97"C for a period of at least 90 minutes and until such time as the desired viscosity of the resinous phase (as referred to hereinbefore) of the mixture is reached.

It has been determined that by splitting or delaying parts of the phenol charge, the resulting resin has an improved bond quality, which is applicable in particular (but not solely) when the resin is being used with plywood veneers and when mixed with certain tannin solutions.

In the present invention, it has been found preferable that the reactant solids content be above about 50% (by weight) and below about 75% (by weight) of the batch charge. The high reactant solids content provides greater utilisation of reactor capacity because the yield of product is thereby increased. A preferred solids content (by way of example) is 60% (by weight).

It has been found possible to use formaldehyde solution containing above 7% (by weight) methanol, (preferably between 7% and 8% (by weight) methanol), although formaldehyde solution with lesser methanol content may be used.

The present invention provides for the phenol to formaldehyde mole ratio to be below 1.7:1 and preferably to be between 1.2:1.5. This has been found to provide improved viscosity stability of the resin; in particular whenmixed with certain tannin solutions. It also provides an improved bond quality, in comparison to those resins currently available and made by known methods and processes.

The present invention is able to use as a catalyst, a stoichiometric mixture of zinc oxide and acetic acid which is found to be more commercially acceptable than zinc acetate dihydrate itself, because of its more ready availability and lower cost. However, other metal salts of organic mono carboxycylic acids may be used to equal advantage and these are well known in the art.

Certain forms of the present invention are able to be carried out with paraformaldehyde as it has been found that the use of paraformaldehyde, in place of formaldehyde permits the economic recovery of other products separated in the process. This avoids resorting to concentration by methods which involve expensive equipment and high energy input.

It has therefore been found that the use of paraformaldehyde allows the straight forward and economic recovery of other by-products generated in the process, without having to use expensive and time consuming extraction processes. The invention will now be described by way of the following Examples: Example 1.

This relates to the preparation of a resole type phenolic resin. To a 10 litre glass reactor equipped with a stirrer, reflux condenser and thermometer, was charged: Water: (858 grams) Zinc acetate-Di Hydrate: (263 grams) Formaldehyde (44%wiw): (3551 grams) Phenol: (2446 grams) The mass was heated by means of a hot water bath, with constant stirring to a temperature of 80"C over a period of 60 minutes.

An exothermic temperature rise was observed when the temperature reached 80"C.

With the heating bath temperature held at 800C the batch temperature peaked at 85"C after 15 minutes and thereafter fell to 80"C over a further 45 minutes.

At this point phenol (816 grams) and water (544 grams) were added to the reactor.

The mixture was then heated and reacted for a further period of 60 minutes at 85"C.

The mixture was then heated to 95"C and the batch was held at 95"C for 90 minutes.

The batch then separated into two phases.

Samples were taken of the lower resinous phase at intervals during the continuing reaction and the viscosity measured using a Brookfield viscometer.

When the viscosity of the resinous phase reached 5 poise at 500C the reaction was terminated by application of rapid cooling, by passing cold water around the reactor.

Stirring was maintained until the batch temperature reached 60"C at which time the stirring was stopped.

The resinous phase was then allowed to settle.

The resin was then withdrawn and mixed with diethylene glycol (433 grams) to give a mobile, resinous composition of viscosity 20 poise at 259C.

By way of example the formulation of the batch was calculated on the following parameters: Initial period to formaldehyde mole ratio: 1.0:2.0 Overall phenol to formaldehyde mole ratio: 1.0:1.5 Total reactant solid charged: 60% (by weight) Zinc acetate mole percentage on phenol (initial charge) 4.6% Zinc acetate mole percentage on phenol (overall charge) 3.45% Example 2: In this example the formulation and process set out in the above Example 1 were followed, except that: formaldehyde(37%W) containing between 7% and 8% (by weight) methanol: (4223 grams) and water: (186 grams) were charged in place of: formaldehyde (44%WZW) (3551 grams) and water: (858 grams) as in Example 1.

Example 3: The formulation and process of Example 1 were followed in this case, except that: paraformaldehyde (91%w/w): (1717 grams) and water: (2692 grams) were charged in place of: formaldehyde (44% w/w) (3551 grams) and water: (858 grams) Example 4: In this case, the process and formulation of Example 1 were also followed, except that: zinc oxide: (97.6 grams) acetic acid (glacial): (144.3 grams) were used in place of: zinc acetate: (263 grams) Example 5 This example demonstrates the preparation of a resole type phenolic resin using a single phenol addition rather than the split or double addition or charge, as described in the earlier examples.

Thus, to a 10 litre glass reactor equipped with stirrer, reflux condenser and thermometer, was charged: water: (858 grams) zinc acetate dihydrate: (263 grams) formaldehyde (44 %ww): (3551 grams) phenol: (3272 grams) The mass was heated by means of a hot water bath with constant stirring to 80"C over a period of about 60 minutes.

Following this, the temperature was then raised to about 95"C for a period of at least 90 minutes and until such time as the batch separated into two phases.

Samples were then taken of the lower phase and the viscosity was measured using a Brookfield viscometer.

When the viscosity of the resinous phase reached 5 poise at 50"C, the reaction was terminated by application of rapid cooling.

Stirring was maintained until the batch temperature reached 60"C at which point it was stopped and the resinous phase allowed to settle. The resin was then withdrawn and mixed with diethylene glycol (433 grams) to give a mobile resinous composition of low viscosity.

The total reactant solids charged were 60% (by weight) of the charged batch weight.

The overall mole ratio phenol to formaldehyde was 1.0:1.5.

Claims

CLAIMS 1. A method of producing a phenol-aldehyde resin including: 1. reacting phenol and an aldehyde at a temperature of from 80"C to 90"C for a period of at least 30 minutes and thereafter 2. increasing the temperature of said reaction to between 90"C and 97"C for a further period of at least 90 minutes. 2. A method of producing a phenol-aldehyde resin including:

1. reacting phenol with an aldehyde at a temperature of between 80"C and 90"C for a period of between at least 30 minutes, thereafter

2. subjecting said reaction to a temperature of between 90"C to 97"C for a further period of at least 90 minutes, and until such time as the viscosity of a resinous phase from said reaction reaches from 2 to 20 poise at 50"C.

3. A method as claimed in claim 2 and wherein the viscosity of said resinous phase is 5 poise at 500C.

4. A method of forming a phenol-aldehyde resin including:

1. reacting phenol with an aldehyde at between 80"C and 90"C for a period of at least 30 minutes.

2. introducing additional phenol and reacting the resultant batch for a further period of at least 30 minutes at a temperature of between 80"C and 90"C, thereafter

3. further heating said mixture to a temperature of betwen 90"C and 97"C for a period of at least 90 minutes.

5. A method of forming a phenol-aldehyde resin including:

1. initially reacting phenol with an aldehyde at between 80"C and 90"C for a period of at least 30 minutes in quantities such that the mole ratio of aldehyde to phenol is between 1.5 and 2.2:1.0.

2. introducing additional phenol and reacting the resultant batch for a further period of at least 30 minutes at a temperature of between 80"C and 90"C such that the mole ratio of aldehyde to total phenol is below 1.7:1.0.

3. further heating said mixture to a temperature of between 90"C to 97"C for a period of at least 90 minutes.

6. A method of forming a phenol-aldehyde resin including:

1. reacting phenol with an aldehyde at between 80"C and 90"C in at least two stages, for a period of upto 140 minutes; thereafter

2. further heating said mixture to a temperature of between 90"C and 97"C for a period of at least 90 minutes.

7. A method as claimed in any of claims 4, 5 or 6, wherein the heating of said mixture to a temperature of between 90"C and 97"C continues until the viscosity of the resinous phase of said batch reaches from 2 to 20 poise at 50"C.

8. A method as claimed in claim 7 and wherein the viscosity is 5 poise at 50"C.

9. A method as claimed in any one of the preceding claims and wherein the resinous phase of the resultant batch is mixed with diethylene glycol.

10. A method as claimed in any one of the preceding claims, including formaldehyde.

11. A method as claimed in any one of the preceding claims, 1 to 9 including paraformaldehyde.

12. A method as claimed in claim 10, and wherein said formaldehyde solution contains above 7% (by weight) of methanol.

13. A method as claimed in any one ofthe preceding claims, and wherein the reaction is carried out at a total reactant solids concentration of between 50% and 75% (by weight).

14. A method as claimed in claim 13, wherein the total reactant solids concentration is 60% (by weight).

15. A method as claimed in any one of the preceding claims, including a catalyst in the form of a stoichiometric mixture of acetic acid; and zinc oxide and/or zinc acetate.

16. A method substantially as hereinbefore described with reference to any one of the preceding claims.

17. A resin formed by the method claimed in any one of the preceding claims.

18. A method, substantially as hereinbefore described with reference to any of the Examples.