DD297826A5 - PHENOLIC COMPOSITIONS - Google Patents

Abstract

The invention relates to phenolic resin compositions, one of which comprises an ester-hardenable phenol-aldehyde resin in alkaline aqueous solution, wherein the phenol-aldehyde resin is a methylolated novolak phenolic resin. Preferably, unreacted phenol is removed during the preparation of the methylolated novolak phenolic resin. The composition can be used as a binder in the production of high strength molds and cores when reacted with an organic ester binder. The additional incorporation of an aryloxy alcohol in the novolak resin binder also improves the ultimate strength of products obtained by using a gasification method using ester vapor, such as ethylene oxide. Methyl formate vapor. {Phenolic Resin Compositions; ester-hardenable methylolated novolak phenolic resin; unreacted phenol; Harder; Binder; Gieszformen; aryloxy; gas curing}

Description

For this 1 page drawing

The invention relates to phenolic resin compositions. In particular, the invention relates to compositions containing a molybdenylated novolak phenolic resin as the phenolic resin component. The compositions are used to make molds and cores, phenolic foams, in casting, laminating, as molding sand binders, and in other applications where phenolic resins are commonly used.

Resole phenolic resole resins are used as binders for finely divided fire-resistant materials, for example, as binders for sand in the production of molds and cores. Cold-curing processes for the production of molds and cores have been described in which esters are used as crosslinking agents for alkaline resole phenolic resins for such fields of application. For example, European Patent Application 0027333 describes the use of compositions containing lactones as hardeners. EP-A 0085512 describes the use of compositions comprising certain resol resol phenol-formaldehyde resins, a silane and an ester curing agent for the resin for making molds and cores.

EP-A 0086615 describes a process for the production of molds and cores in that the vapor of a volatile ester is passed through the sand mixed with a binder containing a certain Resc I alkaline phenol-formaldehyde resin and a silane.

A particular advantage of these processes is that in the compositions described undesirable elements such as sulfur and nitrogen, which adversely affect the surface skins of the castings and can cause casting defects such as the formation of pinholes, are substantially absent are. Consequently, the described methods produce castings which are characterized by high surface quality and relative freedom from casting defects, in particular with regard to cast iron.

Cold-curing processes for making molds and cores using acid catalysts are also known. In such processes are usually phenolic or furan resins and acid catalysts, for. As paratoluene, used. However, the surface finish achieved with such acid catalyzed systems is generally lower than that achieved with the ester cured alkaline resole phenolic resin compositions described above. In addition, the acid-catalyzed systems usually cause unpleasant vapor evolution on contact with casting. Although the ester-cured alkaline resole-phenolic resin compositions have certain advantages over these acid-catalyzed systems, there is a disadvantage of the ester-cured alkaline resole-phenolic resin compositions. Settlements in that the strength of the molds and cores made from them does not in all cases meet the requirements.

The invention has for its object to provide an ester-cured alkaline phenolic resin composition, which overcomes this disadvantage and higher strengths than previously possible when used as a binder.

The invention is also based on the object, the sticking, in the manufacture of cores, in particular of

Horizontally split boxes, often a problem, exclude or largely avoid.

The invention is further the object lie lien to a phenolic resin composition by gassing with a

volatile organic ester can be cured to achieve high strength cured products.

It has been found that these objects are achieved by using a methylolated novolak phenolic resin as the ester-curable Phenol resin can be solved. Accordingly, the invention provides a phenolic resin composition comprising an ester-curable phenol-aldehyde resin in

alkaline aqueous solution and as the curing agent for the resin comprises an organic ester, characterized in that the ester-curable phenol-aldehyde resin is a methylolated novolak phenolic resin.

Consequently, it is apparent that the invention, in contrast to the prior art, by the use of a Resol phenol resin was characterized as ester-curable phenol component, a methylolated novolak phenolic resin as

ester-curable phenol component is used. The achieved higher strength during curing of the invention

Compositions over the prior art ester cure systems, as well as the higher tendency

The compositions of the invention for unwanted adhesion are based on the use of a methylolated

Novolac phenolic resin in these compositions. The terms "resol-phenol" and "novolak-phenolic" are of course phenolic-derived terms. Resoles are thermosetting, i. when heated, they form and become an infusible three-dimensional polymer

formed by condensing a phenol with an excess of aldehyde in the presence of a base catalyst. novolak

Phenolaldehydharze other hand, are chain polymers with phenol endings, by reacting an aldehyde with a Molar excess of a phenol normally formed in the presence of an acid catalyst. These novolak resins are

permanent fusible, non-hardening resins obtained by reaction with a curing agent, such as. B.

Hexamethylenetetramine, at elevated temperature. , Jr can be cured to an insoluble infusible resin. The novolak phenolic resin can be prepared by any known method. To get a resin that has the properties

of a novolak, that is, in order to obtain a product which does not cure when heated, it is necessary to have the

To use phenol and the aldehyde in a molar ratio of less than 1 mole of aldehyde per mole of phenol. The phenol used is preferably phenol itself or m-cresol or a mixture of phenol and

m-cresol. Other phenols with unsubstituted ring members ortho and para to the phenolic hydroxyl group, such as 3,5-xylene-1-oil and resorcinol, can completely or partially replace phenol.

Formaldehyde, which is preferably used in the form of its aqueous solution, is the preferred aldehyde for production

of the novolak phenolic resin. Formaldehyde can be completely or partially replaced by other aldehydes, such as. As acetaldehyde and

Furaldehyde or formaldehyde in the form of paraformaldehyde, be replaced. The novolak resin can be prepared using any of the catalysts commonly used for this purpose. Thus, novolac may be a conventional acid-catalyzed novolak in which the majority of the phenolic cores ortho-para or

para-para linkage, or it may be a so-called "high ortho" novolac in which the ortho-ortho linking of the nuclei outweighs and which is made using an ortho-directing catalyst, although it has been found that the high ortho-novolacs ortho novolacs generally have less satisfactory properties Suitable acid catalysts include strong mineral acids such as sulfuric, phosphoric and hydrochloric acids as well as organic acids such as oxalic and salicylic acids or anhydrides such as maleic anhydride Suitable ortho-directing catalysts include salts of divalent metals, such as zinc acetate and zinc borate.

As already stated, phenol and aldehyde are present in a molar ratio of less than 1 mole of aldehyde per mole Phenol reacted with each other. In general, the molar ratio of aldehyde to phenol is not less than 0.3: 1. at

however, the aldehyde used is preferably formaldehyde, which is best used in an amount of from 0.3 to 0.88 mole, most preferably from 0.4 to 0.88 mole per mole of phenol. Formaldehyde amounts greater than the indicated maximum molar ratio cause premature gelling of the resin. In the case of the high ortho-novolacs, the maximum useful ratio is about 0.75 mol of formaldehyde per mole of phenol, with 0.72 moles not exceeding. In both cases, a formaldehyde content below about 0.3 moles per mole of phenol is because of the unreacted large

Phenol amount uneconomical and unnecessary. In the production of a high ortho-novolak, I will ordinarily use an ortho-directing catalyst, e.g. B. a salt of a

divalent metal, in a proportion of 0.1 to 5, usually 0.4 to 1.2 parts by weight per 100 parts of the selected one

Phenols used on an anhydrous basis. In the case of an acid catalyzed novolak resin, it is sufficient to use a sufficient amount of acidic material to form a

To achieve satisfactory Verharzungsgeschwindigkeit. The required proportion depends on the type of acid used.

Trapping strong mineral acids, such as. As sulfuric acid or hydrochloric acid are used, this proportion moves in general

in the range from 0.02 to 1% by weight, preferably from 0.1 to 1.06% by weight, based on the phenol mass used. In organic

Acids, such as. Example, oxalic acid, or maleic anhydride, are usually amounts in the range of 0.1 to 10 wt .-%,

preferably from 1 to 5% by weight, based on the phenol composition used.

The methods for preparing acid catalyzed novolak resins are well known and are described e.g. in GB 1,210,239 and GB 1,

391,420.

The high ortho novolac phenolic resins referred to herein may be prepared by any known method

getting produced. Preferably, however, in their preparation, salts of divalent electropositive metals, such as

z. As zinc acetate, zinc borate, manganese borate, nickel borate, calcium acetate, manganese acetate, lead acetate and zinc benzoate, as

Catalysts used. The production method of high ortho resins using such salts as catalysts

in GB 757,392; GB 966,678 and GB1,114,004.

Regardless of whether the novacak resins formed are acid-catalyzed or high ortho resins

it is treated to remove the unreacted phenol when the reaction is substantially complete. The

most conveniently by steam distillation, but other methods for removing the unreacted phenol, such as. B. precipitation of the resin from solution and washing of the precipitate before drying, are applied. It is clear that the advantages of the invention can not fully develop when larger amounts of free phenol remain in the resin. On the other hand, it is generally uneconomical and impractical to remove all traces of free phenol from the resin. However, we have found that the strength can be substantially improved if the majority of the unreacted phenol is removed.

The composition of the present invention uses a methylolated novolak phenolic resin as the ester-curable phenolic component. By the term "methylolated novolak phenolic resin" it is meant that the novolak phenolic resin obtains by chemical reaction free methylol groups, ie hydroxymethylene groups, which are attached to at least some of the aromatic nuclei in the novolak resin which the novolak phenolic resin can be methylolated described.

After the phenol has been removed as described above, the novolak resin is made alkaline by reaction with formaldehyde and methylolated. Methylolation is accelerated by elevated temperatures. Since the resin formation can proceed under the conditions prevailing at this stage, a methylolation temperature of not more than 8O ⁰ C is preferred. The methylolation reaction is suitably carried out at a temperature between 50 and 70 ° C. The course of methylolation can be controlled by sampling at specific intervals and determining the level of free formaldehyde. When the proportion of free formaldehyde has dropped to an appropriate level, the reaction can be terminated by cooling. For practical reasons, the determination of the free formaldehyde can be replaced by a viscosity determination once the conditions for a particular resin have been established. In general, the reaction is complete in about 2 to 3 hours.

The alkali used to dissolve the novolak resin may be any alkali metal hydroxide, such as alkali metal hydroxide. As lithium, sodium or potassium hydroxide or mixtures thereof. The preferred alkali is potassium hydroxide. The amount of alkali used depends to some extent on the acidity of the novolak, but should generally be sufficient to provide from 0.4 to 1.2 moles, preferably from 0.6 to 0.8 moles of alkali hydroxide per mole of phenol. If necessary, a smaller amount of methylene chloride may be added and further alkali may be added at a subsequent stage prior to use.

The methylolated novolac resin prepared in this way in alkaline aqueous solution can be hardened by reaction with an organic ester. Examples of organic esters that can be used as the curing agent in the invention include low molecular weight lactones, such as those described in US Pat. Butyrolactone, propiolactone and caprolactone; Carboxylic esters, e.g. Diacetin, triacetin, ethylene glycol diacetate, propylene glycol diacetate, butylene glycol diacetate; and organic carbonates, such as. B. propylene carbonate. These curing agents in the form of esters can be used alone or in combination. As described in EP-A 0086615, it is also possible to use a low-boiling ester, such as. As methyl formate, in the form of a gas, steam or aerosol for curing the methylolated novolak phenolic resin use. In addition, when a gas-based curing method is employed, a liquid ester of the type described above may be incorporated in the composition to be cured.

It has been found that in the production of molds and cores by the fumigation process in which the vapor of a volatile or readily volatilizable ester, usually methyl formate, is passed through a composition used for molding or core manufacture, the methylolated novolak phenolic resin in alkaline aqueous solution, as a binder for sand or other finely divided fire-resistant material, greater strengths are achieved when an aryloxy alcohol is incorporated into the composition. Accordingly, according to another aspect of the invention, there is provided a phenolic resin composition suitable for curing by fuming with a volatile organic ester comprising a methylolated novolak phenolic resin in alkaline aqueous solution of from 1 to 20% by weight of aryloxyalcohol, based on the mass of the methylolated novolak resin.

Suitable aryloxy alcohols include e.g. G. phenoxyethanol, phenoxypropanol and methyleneoxyethanol. The preferred aryloxy alcohol is 2-phenoxy, ethanol.

The aryloxy alcohol is added to the methylolated novolak resin preferably in an amount of 2 to 10% of the mass of the methylolated novolak resin. However, even at a level of only 1%, some improvement in properties is evident. Amounts above about 20% are generally uneconomical and unnecessary. After mixing, the resin-sand composition may be formed into the required shape by introduction into a suitable mold or core box and passed through by passing ester vapor, which may optionally be in a carrier gas stream, generated with a per se known gas evolution apparatus be hardened for this purpose provided with a gassing and a vent opening form or core box. This process is described in detail in European patent 0086615. As already mentioned, if desired, the composition may also contain a liquid ester or a carbonate.

The compositions described above may also contain other additives to enhance or modify the properties of the mixture and / or the properties of the final cured compositions. So z. For example, an aminosilane may be incorporated in amounts generally known in the art for increasing the strength of the bond to the sand.

The invention is further illustrated by the following examples which, unless otherwise indicated, are parts by mass of all parts.

Examples 1 to 3 Preparation of an acid-catalyzed novolak phenolic resin

6110 parts of 100% phenol were placed in a jacket container equipped with stirrer, reflux and distillate cooler,

Steam heating, water cooling and vacuum device was equipped, and heated to 80 ° C under reflux. 138 parts Salicylic acid and 94 parts of a 24% [mass / mass] aqueous sulfuric acid solution were then added. 2339 parts

50% [mass / mass] aqueous formaldehyde solution was then added slowly over 90 minutes while maintaining the reflux conditions at atmospheric pressure, at which later stages of the reaction

Minimum steam was used to ensure gentle reflux cooling. After completion of the Formaldehyde addition, steam was added to the vessel to provide gentle reflux for a further 90 minutes

maintain.

Thereafter, distillate was removed at atmospheric pressure until the temperature rose to 11O ⁰ C. Then, a vacuum was gradually generated to 28 inches of mercury (-980mbar). During this time was further full with Steam heated. These conditions were maintained until the temperature reached 1SO ⁰ C, and then others

Maintain for 15 minutes.

Thereafter, under complete vacuum, it was heated with a heater sufficient to reach the temperature between 150 and 155 ⁰ C

Steam distillation was carried out until the content of free phenol content was less than 0.1%.

510 parts of the resin thus prepared were then dissolved in a mixture of 168.7 parts of potassium hydroxide and 473.2 parts of water. The resulting molar ratio of phenol: potassium was 1: 0.64.

The resin solution thus prepared was heated to 65 ° C and methylolated by adding 310.4 parts of a 50% (mass / mass) Formaldehyde solution were supplied over a period of 15 minutes, the temperature during the

total addition was kept below 67 ⁰ C. The product was then held for a further 130 minutes at 65-68 ⁰ C. During this time samples were taken at certain intervals and the viscosity was determined.

After 10 minutes the viscosity was at 25 ⁰ C 19OcP (Example 1). After 55 minutes, the viscosity at 25 ⁰ C 32OcP (Example 2). After 120 minutes, the viscosity was at 25 ⁰ C 38OcP (Example 3).

Verglelchsbelsplel Preparation of a conventional alkaline resole phenolic resin A conventional resole phenolic resole phenol resin, which is a typical example of commercial resins, was as follows

Prepared 100% phenol was dissolved in 50% aqueous solution of potassium hydroxide in an amount corresponding to a

Molar ratio (KOH: phenol) of 0.64: 1, and 50% formaldehyde solution was added in an amount equal to one Molar ratio (phenol: formaldehyde) of 1: 1.7, added slowly, keeping the temperature below 65 ⁰ C.

has been. Thereafter, the temperature was gradually raised to 100 ⁰ C, and the reaction mixture was heated under reflux until it had a viscosity of 900 centipoise at 25 ° C. The thus-prepared resin solution was then cooled to 40 ° C to give 3.77 parts of denatured industrial alcohol, 1 part of a 40% sodium ethylhexyl sulfate solution and 0.38 part of gamma.

Aminopropyltriethoxysilane was added to each 94.5 parts of the resin solution. For test purposes, compression strength specimens were prepared from the various resin compositions as follows:

1000g of Chelford 50 silica sand (AFS 50 is the fineness) at a temperature of 18 ⁰ C were placed in a laboratory-Ridsdale

Core sand mixer registered. 15g of a mixture of gamma-butyrolactone (40 parts) and triacetin (60 parts)

also registered and mixed for 30 seconds. 15 g of the resin to be tested were then added and mixed for 1 minute. The mixture was then removed and immediately using a standard rammer and

Precision tubes processed to AFS compression strength test specimens. (The test specimens are cylinders with one Diameter of 2 inches and a height of 2 inches, three times with a 14Ib. heavy weight, which has a fall travel of 2 inches

The results are shown in Table 1.

3.77 parts of denatured industrial alcohol and 0.38 part of gamma-aminopropyltriethoxysilane were added to each of 98.45 parts of the individual methylolated acid-catalyzed novolak resins in order to reduce the viscosity and the adhesion to the

Silica surfaces, and the products were compared to a conventional alkaline resis- Phenol resin composition tested as a core binder. The results are shown in Table 1. Table 1 Resin Example 1 Example 2 Example "Comparative Example Stand Chelford 50

% Resin on sand 1,5

Hardener gamma-butyrolactone 40 / triacetin 60 - -

% Hardener on resin 20

sand temperature

before mixing 17,5 17,5 18 18

after mixing 18 18 18.5 18.5

Processing time (min) 12 10 8-9 13 Setting time (min) 19 15 13 20

Compressive strength, kN / m ² 250 1085 1235 200 After an hour 1925 2370 2615 1380 After 1 hour 2715 3155 3155 2220 After 2 hours 4785 5575 5330 4245 After 24 hours

In Examples 1 to 3, there were no sticking problems. The resin of the comparative example caused some problems in this regard.

Examples 4 to 7

A salicylic acid-sulfuric acid novolak resin was prepared as described for Examples 1 to 3 and subjected to steam distillation to remove unreacted phenol. Prior to steam distillation and at intervals during the distillation process, resin samples were taken and the residual free phenol was measured. Each of these samples was then made alkaline by addition of potassium hydroxide in an amount sufficient to achieve a phenol: potassium ratio of 1: 0.64 and with formaldehyde in an amount having a P: F ratio of 1: 1 : 1.7, reacted.

As in the previous examples, 3.77 parts of denatured Industriealk Ml and 0.39 gamma-aminopropyltriethoxysilane were added to each 98.45 parts of the individual methylolated novolak resins to reduce the viscosity and increase the adhesiveness to the silica surfaces. The products were then tested as a core binder in comparison with a conventional resole phenol resin alkaline resin composition. The results are shown as Examples 4 to 6 in Table 2, which also contains a similar resin in which the phenol content of the novolak base was reduced to approximately 0% before methylolation (Example 7).

Table 2

Example 4 Examples Examples Example 7 18 18.5 18 18.5 Free phenol in novolak besis over 16% 9.1% 2.1% 0% 10 220 10 132 Sand% resin on sand · Hardener% hardener on resin - - - Chelford 50 1.5 - - - gamma-butyrolactone 40 / triacetin 60 20 2615 2960 4785 2615 3155 5330 Sand temperature before mixing after mixing 17,5 18 17,5 18 Setting time (min) Viscosity (cSt) 15 110 13 '/ 2 166 Compressive strength, kN / m ² After 1 hour After 2 hours After 24 hours 1725 2320 4145 2170 2515 4686

A conventional resole (the comparative example in Table 1) was tested before and after aging for comparison. It was found that similarly high final strengths are not attributable solely to setting time or viscosity effects. The results are shown in Table 3.

Table 3

comparison test Resol from aging Resol after aging Setting time (min) Viscosity (cSt) 14 138 11 '/ 2 174 Compressive strength wedge, kN / m ² After 1 hour After 2 hours After 24 hours 1480 2220 3945 1625 2565 3650

In Examples 4 to 7, there were no sticking problems. In the comparative examples, there were some problems in this regard. The resins of Examples 4 to 6 were also tested for use with methyl formate in a gassing process for making molds and cores as described in European Patent No. 0086615. They were used both with the described conventional resin (Resin A) and with a resole phenolic resin (Resin B, P: K = 1: 0.76, P: F = 1: 2.0), commercially available for this process available, compared. The results are shown in Table 4.

Although the strengths achieved with the resin of the invention are less clearly superior in this case, they are achieved with a lower P: K ratio and a lower P: E ratio, both of which are desirable.

Example 4 Example 5 Examples 2.1% Resin A Resin B Novolak-based free phenol over 16% 9.1% _ _ .... 1 D ............ I ₁ O ------------ W or or ...... ....... 220 Viscosity (cSt) 110 166 18.3 29 138 175 Bending strength, kg / cm ² Immediately after 24 hours 12.2 24.7 15.7 27.7 5.7 14 16.7 27.7

Example 8 Preparation of oxalic acid catalyzed resin An oxalic acid catalyzed novolak resin was prepared by reacting phenol and formaldehyde (as 50% strength by weight) Formaldehyde solution) in a molar ratio (P: F) of 1: 0.5 in the presence of 2.3% strength oxalic acid (based on the Phenolmasse) were implemented. For removal of water distillation was carried out in vacuo, and the content of

Free phenol was then reduced by steam distillation to 0.72%. The product (novolak base A) was then methylolated under alkaline conditions as described for Examples 1 to 3.

The product had a final molar ratio (P: F) of 1: 1.7 and a viscosity of 134 centistokes at 25 ⁰ C ai'i. This product was tested for compressive strength using a composition described in Table 2 Fumigation with methyl formate - as described in Table 4 - tested for flexural strength. The following results were achieved

(Table 5).

Table 5

Compressive strength, kN / m ² 2515 After 1 hour 3060 After 2 hours 5130 After 24 hours Flexural strength, kg / cm ² 22 Immediately 37 After 24 hours

As can be seen from Table 5, when using gaseous methyl formate as a curing agent, the flexural strengths obtained are substantially higher than those achieved with resole resins from which the low molecular weight material has not been removed.

While the products of this invention are primarily illustrated in terms of the production of molds and cores, they are also useful in many other applications where phenolic resins are commonly used.

Example 9

casting resins

Samples of the resin of example 3 and the comparative resin (above comparative example) were also treated with 20 parts of triacetin

mixed per 100 parts of resin, poured into block molds and allowed to stand at 20 ° C. The hardness was at intervals below

Using a Shore "D" hardness tester, the results are given in Table 6. As can be seen from these results (as well as the results for the cores described above), the

products of the invention significantly superior in terms of speed of development of strength and hardness.

Table 6

Hardness values (Shore, D ') 100 parts Comparative resin 10OTeHe Resin Example 3 200 parts 20 parts Hardener (Triacetin) 29 16 After 30 minutes 34 22 After 1 hour 45 30 After 1V2 hours 57 45 After 24 hours

Example 10 Use in laminates Glass fabric laminates were prepared using the acid catalyzed novolak of Example 3 with 20 parts Triethylene glycol diacetate prepared per 100 parts resin. They were compared with similar laminates under Use of the conventional alkaline resole phenolic resin and the same type of catalyst in the same amount

had been made. In both cases, the laminate contained 43% glass and 52% resin composition. The flexural strength of the laminates was measured after a resting period of 3 days at room temperature. The following results were determined:

Resin of Example 3 - 54.2 MN / m ²

Conventional resol - 39.8 MN / m '

Example 11 Use as carbonizable binder

Surprisingly, it has been found that the ester-cured methylolated novolak resins of the invention have greater oxidation resistance than conventional resols, making them particularly suitable for bonding fire-resistant carbon articles.

The attached drawing (Fig. 1) shows the thermogravimetric curves of a carbon specimen made using the resin of Example 3 as a binder and a comparative specimen made using a conventional resol (Resin A). For each resin a graph is given for the loss of mass under nitrogen and a curve for the loss of mass in air at increasing temperature. It is apparent that the resin of the present invention, when heated in air, has a much less pronounced decay than the prior art ester-cured resole (Resin A), indicating greater resistance to oxidation.

Example 12 Use as a wood glue

A composition of the invention was also tested as a wood adhesive using 1 inch (25.4 mm) wide beech wood specimens as defined in British Standard 1204.

For this purpose, 33 parts of the oxalic acid (novolak base A of Example 8) distilled with water vapor as described above were dissolved in 22 parts of a 50% potassium hydroxide solution. 19.5 parts of water were added and the temperature was raised to 65 ⁰ C. 20.75 parts of 50% formalin were then added, and the temperature was maintained at 65 ⁰ C until a viscosity of 30OcP at 25 ⁰ C was reached. Thereafter, the resin was cooled, and 3% denatured ethanol, 1% of 40% ethylhexyl sulfate solution and 0.4% of gamma-isopropyltriethoxysilane were added. The product thus obtained (Resin I) had a solids content of 55% (3 hours at 100 ° C) and a viscosity of 120 centistokes at 25 ° C.

This product was used to make the following size blend: Resin I 100 parts

Triethylene glycol diacetate 15 parts

1: 3Butylenglycoldiacetat lOTeile

Wood flour, sieve number 200 5 parts

Kaolin 5 parts

This glue mixture could be used in about 40 minutes at 20 ⁰ C.

A test according to BS 1204 (close contact) was carried out using a conventional ester-cured phenolic resin (Resin A prepared as described in the comparative example) as a comparison. The following results were obtained (figures in CN).

glue mixture dry soaked cold Cooked for 3 hours Cooked for 6 hours With Resin I (invention) 4.12 1.87 1.87 1.97 Resin A (comparison) 2.83 1.59 1.88 2.01 specification minimum 2.2 2.2 1.1 1.45

Although neither of the two resins met the minimum requirements of BS 1204 in the cold soak test, the test illustrates the superiority of the inventive resin over an ester-cured, conventional type resin.

Example 13

Preparation of an acid-catalyzed novolak phenolic resin

3340 parts of 100% phenol were charged into a jacketed vessel, fitted with stirrer, reflux and distillate condensers, steam heating, water cooling and vacuum apparatus, and heated under reflux to 80 ⁰ C. 79 parts of oxalic acid dissolved in 235 parts of water were then added. 1066 parts of a 50% [mass / mass] aqueous formaldehyde solution were then added slowly over 90 minutes while maintaining the reflux at atmospheric pressure, with a minimum of steam used in the later stages of the reaction to provide gentle reflux cooling to ensure. Upon completion of the formaldehyde addition, steam was added to the vessel to maintain the gentle reflux for another 90 minutes. Thereafter, distillate was removed at atmospheric pressure until the temperature rose to 14O ⁰ C. Thereafter, a vacuum was gradually generated to 28 inches of mercury (-980mbar), while still fully heated with steam. These conditions were maintained until the temperature reached 15O ⁰ C and then maintained for a further 15 minutes.

Thereafter, under full vacuum and with a heater sufficient to maintain the temperature between 150 and 155 ^° C, steam distillation was carried out until the product contained less than 1.0% of free phenol.

Under reflux in 1525 parts of water were gradually added to disperse the resin and to dissolve, and the mixture was cooled to below 8O ⁰ C. 1626 parts of potassium hydroxide were added, then the mixture was cooled down to 60-65 ° C. 1434 parts of a 50% formaldehyde solution over a period of 45 to 60 minutes were used for methylolation of the resin then added slowly while the temperature was maintained at less than 65 "C. This temperature was maintained until the viscosity at 25 ⁰ C 340- Reached 390 centipoise.

Finally, 309 parts of 2-phenoxyethanol and 31 parts of gamma-aminopropyltriethoxysilane were added. This preparation was repeated, however, for comparison purposes, 2-phenoxyethanol was replaced by the same mass of butylcarbitol

 For purposes of further comparison, a conventional resole phenolic resole phenolic resin (prepared as in the comparative example described above in connection with Examples 1-3) containing 4% by weight butylcarbitol (diethylene glycol monobutyl ether) and an otherwise identical one were used Resin containing 4Ma .-% 2-phenoxyethanol. The results of the flexural strength tests using 1.8% of the various resin compositions on Sigrano sand (AFS No. about 75) and gassing with methyl formate are summarized in the following table.

binder alcohol Flexural strength, kg / cm ² 1 hour 24 hours immediately 19 26 Conventional resole resin carbitol 13 24 28 Conventional resole resin 2-phenoxyethanol 16 31 37 Methylolated novolak resin carbitol 20 37 45 Methylolated novolak resin 3-phenoxyethanol 23

As can be seen from the table, the use of methylolated novolak resin with a low free phenol content in combination with an aryloxy alcohol causes a considerable improvement in the strength values, with approximately a doubling of the words obtained for a conventional butyl carbitol-containing resole resin.

FIG. 1

TPA-12 in nitrogen TPA-12inAir / ^ResinA

AK22A Nitrogen \ _. , _lo AK22AinLuft J ^Beis P ^iel3

Mass: 6.2782 mg

Scanning speed 25,007min

% weight = Ma%, temperature (C) = temperature ( ⁰ C)

Claims (24)

A phenolic resin composition containing an ester-curable phenol-aldehyde resin in alkaline aqueous solution and an organic ester as a curing agent for the resin, characterized in that the ester-curable phenol-aldehyde resin is methylolated novolak phenolic resin. Composition according to Claim 1, characterized in that the methylolated novolak phenolic resin is obtained by methylolating a novolak phenolic resin from which unreacted phenol has been removed. 3. A composition according to claim 2, characterized in that the novolak phenolic resin is subjected to a Wasserdampfdestillationsb6handlung before methylolation to remove unreacted phenol. 4. The composition according to any one of claims 1 to 3, characterized in that the methylolated novolak phenolic resin is a methylolated novolak-phenol-formaldehyde resin. Composition according to Claim 4, characterized in that the methylolated novolak-phenol-formaldehyde resin is prepared by methylolation of an acid-catalyzed novolak-phenol-formaldehyde resin in which the molar ratio of phenoh-formaldehyde is 1: 0.3 to 0.88. 6. The composition according to claim 4, characterized in that the methylolated novolak-phenol-formaldehyde resin is prepared by methylolation of a high ortho-novolak resin in which the molar ratio of phenohformaldehyde is 1: 0.3 to 0.72. Use of a methylolated novolak phenolic resin in alkaline aqueous solution as an ester-curable phenolic resin component in a curable composition for reaction by reaction with an organic ester, characterized in that the methylolated phenolic resin is recovered by removing novolak phenolic resin from which unreacted phenol has been removed , is methylolated. 8. Use - according to claim 7 - a methylolated novolak-phenol-formaldehyde resin in alkaline aqueous solution. A mold composition characterized by containing a mixture of finely divided fire resistant material and a methylolated novolak phenolic resin in alkaline aqueous solution, which composition is curable by reacting the methylolated novolak phenolic resin with a curing agent comprising an organic ester and wherein the methylolated one Phenolic resin is obtained by a novolak phenolic resin was removed from the unreacted phenol, methylolated. 10. A casting composition according to claim 9, characterized in that the organic ester is a liquid ester. 11. A casting composition according to claim 9, characterized in that it is organic ester methyl formate vapor. 12. A method for producing a Giebroi, τι or a core of sand, characterized in that sand, a methylolated novolak-phenol-formaldehyde resin in alkaline aqueous solution and a curing agent for the resin are mixed together in the form of a liquid ester, the mixture in the shape of Mold or the core is brought and cured, wherein the methylolated phenolic resin is recovered by methylolating a novolak phenolic resin, was removed from the unreacted phenol. 13. A method for producing a casting mold or a core of sand, characterized in that sand and a curable binder containing methylolated novolak-phenol-formaldehyde resin in alkaline aqueous solution are mixed together, brought the mixture into the shape of the mold or the core and thereafter the mixture is contacted with methyl formate vapor to cure the resin and thereby cure the mixture to recover the methylolated phenec resin by methylolating a novolak phenolic resin from which unreacted phenol has been removed. 14. The method according to claim 13, characterized in that the binder contains a methylolated novolak phenolic resin in alkaline solution and an aryloxy alcohol in an amount of 1 to 20Ma .-%, based on the resin composition. 15. The method according to claim 14, characterized in that the aryloxy alcohol in an amount of 2 to 10Ma .-%, based on the resin composition is included. 16. The method according to claim 14 or 15, characterized in that the aryloxy alcohol is 2-phenoxyethanol. 17. A phenolic resin composition which is suitable for curing by gassing with a volatile organic ester, characterized in that it methyloliertes a novolak phenolic resin in alkaline aqueous solution and an aryloxy in an amount of 1 bic 20%, based on the mass of ι ethylolated Novolak resin, contains. Composition according to Claim 17, characterized in that the methylolated novolak phenolic resin is obtained by methylolating a novolak phenolic resin from which unreacted phenol has been removed. 19. A composition according to claim 18, characterized in that the novolak phenolic resin is subjected to a Wasserdampfdestillationsbohandlung before methylolation to remove unreacted phenol. 20. The composition according to any one of claims 17 to 19, characterized in that the methylolated novolak phenolic resin is a methylolated novolak-phenol-formaldehyde resin. 21. A composition according to claim 20, characterized in that the methylolated novolak-phenol-formaldehyde resin is prepared by methylolation of an acid-catalyzed novolak-phenol-formaldehyde resin in which the molar ratio of phenol-formaldehyde is 1: 0.3 to 0.88. 22. A composition according to claim 17 to 21, characterized in that the aryloxy alcohol is 2-phenoxyethanol. 23. A casting composition containing a mixture of finely divided fire-resistant material and a curable binder which hardens upon reaction with a curing agent comprising a methyl formate vapor. κ is characterized in that the curable binder comprises a methylolated novolak phenolic resin in alkaline solution and an aryloxy alcohol in an amount of 1 to 20% based on the resin composition, wherein the methylolated novolak phenolic resin is recovered by reacting a novolak phenolic resin, was removed from the unreacted phenol, methylolated. 24. The composition according to claim 23, characterized in that the aryloxy alcohol is 2-phenoxyethanol.