DE2745549A1 - LIQUID CATALYST FOR CURING RESIN BINDERS - Google Patents

Description

MPD 213

Munich, Oct. 10, 1977 j

NS

Albright & Wilson Limited

POBox 3, Oldbury , Warley, West Midlands, England

Plushig catalyst for hardening synthetic resin binders

809815/0875

The invention relates to curing catalysts for synthetic resin binders, in particular for synthetic resins, used to make foundry molds.

Usually foundry molds are made of sand coated with a curable synthetic resin system, e.g. B. copolymers made of phenol, resorcinol and / or urea bound with formaldehyde and / or furfuryl alcohol. For example, phenol-formaldehyde, urea-formaldehyde, phenol-formaldehyde-furfuryl alcohol, urea-formaldehyde -Furfuryl alcohol-, phenol-urea-formaldehyde-furfuryl alcohol- or resorcinol-furfuryl alcohol copolymers are used. The invention is with all of the foregoing curable synthetic resin compounds applicable. The shape is fixed by curing the synthetic resin, whereby the effect of a curing catalyst is used, which is usually a low molecular weight aryl sulfonic acid, z. B. is one with 6-12 carbon atoms.

It has hitherto been customary to use toluenesulfonic acid or xylene, cumene or benzenesulfonic acids dissolved in water in concentrations of 65-70%. However, the curing speed that can be achieved with such solutions is undesirably slow in some applications.

The presence of water reduces the curing rate by means of the sulfonic acid catalyst. the The addition of sulfuric acid increases the curing speed, but worsens the mechanical resistance properties of the finished foundry core.

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In addition to a satisfactory curing effect, a must for Curing catalyst acceptable for foundry purposes must have sufficient fluidity so that it is pumpable and Remains liquid even when stored. Preferably, it should not crystallize during storage, namely not even at the low temperatures that occur in severe winters.

The reduction of the water content of the currently used sulfonic acid catalysts in order to increase their However, effectiveness has an increase in viscosity to unacceptably high values and brings the There is a risk that in most cases the catalyst will tend to crystallize. The use of thinners like methanol and acetone to overcome these problems, in turn, reduces the curing speed, increases the cost of the catalyst and can trigger the generation of toxic fumes.

In general, the most effective curing agents are those with the lowest molecular weight. At the same time, however, these are the most difficult to handle at high concentrations. Ζ. B. anhydrous benzene sulfonic acid is crystalline at temperatures below 45 ⁰ C, and aqueous solutions of benzenesulfonic acid can only be used in practice at concentrations below about 75 % . Toluenesulfonic acid also tends to crystallize at high concentrations. Xylene and cumene sulfonic acids, which are less active than benzene or toluene sulfonic acids, have less tendency to crystallize, but their viscosities at concentrations of more than 90 % are still as high (e.g. between

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1000 and 2000 cSt for 96 % cumene sulfonic acid at 20 ⁰ C) that they cannot be used in practice in these high concentrations. The higher molecular weight sulfonic acids are generally not sufficiently active.

It has been found that by using mixtures of aryl sulfonic acids it is possible to achieve some of the good curing properties of lower molecular weight Acids hate to combine with the lower melting points of higher molecular weight acids. Such mixtures however, they are still undesirably viscous and also often unstable; they particularly tend to low temperatures for crystallization.

Surprisingly, certain compounds have now been found which have a high degree of effectiveness with an unexpectedly high degree of effectiveness Combine fluidity and, in most cases, good stability.

The invention provides liquid catalysts for curing resin-containing binders, the catalysts consisting of up to 5% by weight of water, up to 10% by weight of sulfuric acid and a remainder of essentially a mixture of benzene and alkylbenzenesulfonic acids with up to 12 carbon atoms exist, wherein the mixture 20-80 wt .-% Benzoleulfonsäure and 20-80 wt -% contains alkyl benzene sulfonic acids with 8-9 carbon atoms..

These compositions are preferably essentially anhydrous, since the presence of water means that their

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Stability could be lowered. In practical use, commercial sulfonic acids normally contain "up to about 2 % water. The catalysts of the invention essentially retain adequate stability in the presence of up to 5 % water, although less than 4 % water, especially less than 3 % water , is preferred.

Sulfuric acid increases the stability of the catalysts, but too high a proportion of sulfuric acid weakens the hardened foundry cores. For this reason, the sulfuric acid content is preferably less than 10 %,

especially 0.5-5 %, e.g. B. 1-3 %.

Benzenesulfonic acid is an essential component of the catalysts according to the invention. She has a special one synergetic effect in connection with Cg and Cq sulfonic acids such as xylene or cumene sulfonic acids, which has not yet been observed with any other mixtures of sulfonic acids and an unexpectedly high fluidity and, in most cases, a satisfactory stability brings itself.

With proportions of benzenesulfonic acid below 20 wt .-? £, based on the total sulfonic acids, there is a risk of poor stability, especially with a high water content, and a relatively high viscosity; this also results in a lower activity than in the case of the preferred compounds. The proportion of benzenesulfonic acid is preferably above 30 %.

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27A5549

If the proportions are greater than 80 % , the result is a relatively poor stability at low temperatures. For most applications, the proportion is usually below 70% _t particularly when the rest of the active mixtures from a single Xylolisoioeren is, preferably the compounds are, therefore, at least 30 uew.- ^r / u, in particular at least 40 wt .-% benzenesulfonic acid, based on the total sulfonic acids, typically 40-60% by weight, e.g. B. 45-55: wt .-%.

All Cy and Cq sulfonic acids show a special synergetic effect with benzenesulfonic acid. If the mixture of sulfonic acids contains less than a total of 20 wt .- / 4 Cg- and Cq-sulfonic acids, the stability of the catalyst at low temperatures is insufficient. Concentrations of CG and Cq-sulfonic about 80 ^r '> result in poor stability at high water concentrations as well as high viscosity and relatively low activity. The compounds according to the invention preferably contain a total of 30-70 Cew .- '/ j of Cg and / or Cq sulfonic acids, based on the total sulfonic acid mixture. The proportion of Cg and / or Cq sulfonic acids is preferably between 40 and 60% by weight, and in particular the benzenesulfonic acid proportion is at least 5 times, in particular at least 10 times the water proportion.

The preferred Cg or Cq sulfonic acids are the commercially available mixture of Cg isomers, which came under the name Xylene sulfonic acid and cumene sulfonic acid (i.e. isopropylbenzenesulfonic acid) is distributed. Commercially available xylene sulfonic acid usually contains besides sulfonated Ortho-, meta- and paraxylene have a small proportion of

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Ethylbenzenesulfonic acid, ζ. B. 20 %. Ethylbenzenesulfonic acid in itself is a particularly effective synergist with benzenesulfonic acid, but is not as readily available commercially as so-called xylene sulfonic acid. In general, mixtures of Cg isomers should preferably be pure xylene isomers, both for reasons of cost and effectiveness. The xylene isomers by themselves cause premature crystallization if the proportion of benzenesulfonic acid exceeds approx. 65% by weight.

The presence of small amounts, e.g. B. less than a total of 50%, preferably less than 30 %, toluenesulfonic acid or higher acids such as. B. CjQ-arylsulfonic acids, in the mixture of sulfonic acids is not excluded. However, toluenesulfonic acid tends to lower the stability of the compound, and if it exceeds about 50 % , crystallization may be caused. The compounds are therefore preferably essentially free from toluenesulfonic acid. CJ ₀ " ^{and higher} acids tend to have high melting points and cannot be readily incorporated into liquid preparations according to the invention, but their presence in small amounts is not excluded. The catalysts according to the invention normally contain a small amount, e.g. B. up to 4 %, sulfones and sulfonated sulfones, which are usually present as impurities in commercially available sulfonic acids and do not have any adverse effect on the invention.

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The compositions according to the invention are prepared by using commercially available benzenesulfonic acid, e.g. B. is mixed with commercially available xylene and / or cumene sulfonic acids or that alternatively a suitable mixture of 6-12 carbon atoms containing aromatic hydrocarbons z. B. is sulfonated with sulfuric acid, oleum or sulfur trioxide, conventional sulfonation processes being used. Preferably, however, the compositions are formulated by reacting benzene with an excess of the sulfonating agent and then adding the alkylbenzenes along with any additional sulfonating agent required to complete the reaction.

The compositions of the invention are useful for curing a variety of synthetic resin binders including the curable synthetic resin systems already mentioned, especially for polymers of phenols with aldehydes such as formaldehyde, ζ. Β. for resole or Α-resins. They are particular about Suitable for use in foundry processes with rapid hardening (cf. e.g. GB-PS 1 441 572). Typically the catalysts are used in amounts of 10-80% by weight, preferably 20-60% by weight, e.g. B. 30-50 wt .-%, based on the resin weight, added. The resin is typically preferred with sand in amounts of 0.25-10 wt 0.5-5 wt. 96, e.g. B. 1-2 wt .- #, mixed.

The following examples serve to illustrate the invention.

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ΛΟ

A series of catalyst compositions were prepared by adding benzenesulfonic acid with commercially available Cumene sulfonic acid in those given in Table I. Amounts were mixed.

Tabel

example No. 1 5 No. 2 No. 3 No. t
4th 5 No. 5 Weight ratio 70:30 7th 60: 40 50: 50 40:60 7th 30: 70 Benzoil / cumene Molecular weight 168, 46 172 , 5 176 , 5 180, 65 185 , 2 Total acid 100, 7th 99 , 3 98 , 7 98 3 98 , 5 salary 5 6th H ₂ SO ₄ 1. 1.17 1 , 01 O ,8th O, 0.75 O .6 Sulfonic acid 95 93 95 ,8th 95 , 9 96, 176 95 , 9 Sulfones 1, 1 , 7 O , 5 1, 1 , 6 Water content 1. 35 1, 95 1, 19th viscosity 113 130 238 (cSt) at 20 ^° C

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ΛΑ

The foregoing viscosity figures are compared with benzene Bulfonsäure which is crystalline below 45 ⁰ C, and cumene sulfonic acid, which has a viscosity between 1000 and 2000 cSt at a concentration of 96% at 20 ⁰ C.

The stability of the compositions at different temperatures in the presence of added water was found and reported in Table II below.

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Table II

example

stability
at -2 ⁰ C

number 1

No.

No. No. 4

No. 5

no crystallization

stability
at -18 ⁰ C

crystallizes after 24 h

no crystallization crystallizes after 48 h

+ 0.5 % H ₂ O at
Ambient t emp ·

no crystallization

+ 2 % H ₂ O at
Ambient _{temp c}

no crystallization

+ 2 % H ₂ O
at -2 ⁰ C

no crystals. after 3 days

no crystals. after 3 days

Onset of crystallization after 3 days of crystallization onset
after 3 days

Crystallis,
after 3 days

+ 3 % H ₂ O at
Ambient _{temp c}

no crystallization after 3 days, slight crystallization, after 24 h

+ 3 % H ₂ O
at -2 ⁰ C

low crystals after 3 days

Kristal, after 2 days

no crystallization Krist.-Beg.
after 1 h

instant
Crystallization

+ 5 % H ₂ O at
ambient temp,

KriBt. after 24 h

Krist. after 24 h

Krist. after 3 days Krist.
after 5 h

instant
: installation

The activity of the compositions was determined by mixing 3 kg of sand with the catalyst (40% by weight, based on the synthetic resin weight) for 1 min and then for 1 min with the resol resin (viscosity 300 cP, pH = 6-6.4, Pesticides = 76-78 %) was mixed in an amount of 1.2% by weight, based on the weight of the sand. The workability time of the mixture and the parting time (the time for the foundry core or mold to become self-supporting) were determined and recorded in Table III, compared to aqueous toluene and benzenesulfonic acids.

Table III

number 1 No. 2 No. 3 No. 4 No. 5 65 % ; 72 % at Toluene- Benzene- game sulfone sulfone acid in acid ι Ver water water working 1 1 1.5 2 2.5 capability (min) 6th 5 Separating 8th 8th 11 14th 15th Time (min) 40 30th

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Mixtures of benzenesulfonic acid with commercially available xylene sulfonic acid were prepared. The properties these mixtures are given in Table IV below.

Tabel

IV

at No. 6 Ur. 7th No. 8 No. 9 Mr. 10 No. 11 No. 12 game Benzene: 20:80 30:70 40:60 50:50 60:40 70:30 80:20 Xylene viscosity (cSt) at 620 390 192 108 85 20 ⁰ C sta sta sta sta sta sta sta stability bil bil bil bil bil bil bil after a at at at at at at at week -20 ⁰ C -20 ⁰ C -20 ⁰ C -20 ⁰ C -20 ⁰ C -20 ⁰ C -20 ⁰ C

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To the stability and properties of mixtures of benzenesulfonic acid with individual Cg isomers To demonstrate, mixtures of the acids given in Table V were prepared:

Tabel

Visc. at
20 ⁰ C (cSt)

% H ₂ O

% Active ingredient

H ₂ SO ₄

benzene

Crystalline

1.8

94.5 2.02

Ethylbenzene

207

1.0

98.1

0.4

O-xylene

3

1.3 97.2

1.1

M-xylene

34 300 0.35

96.0 1.9

P-xylene

6 600 0.45

97.5 0.8

The following samples 13-32 were prepared by mixing the benzenesulfonic acid with each of the four Cg acids in Proportions of 70:30, 60:40, 50:50, 40:60 and 30:70 was mixed. The viscosities and proportions of water Examples 13-32 are given in Table VI.

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Table VI

1) Examples of
Benzene:
Ethylbenzene

viscosity
(cSt)
H ₂ O %

2) Examples of Benzene:
0-xylene

viscosity
H ₂ O %

3) Examples of Benzene:
P-XyIo1

viscosity
H ₂ O %

4) Examples of Benzene:
M-XyIo1

viscosity
H ₂ O %

70:30

13th

79 1.56

18th

60:40

14th

89 1.48

125

1.65

23

127 1.4

28

179 1.36

19th

180

1.6

24

195 1.26

29

272 1.22

0:50 , 4 40:60 15th 16 101
1 55 113
1 20th 21 277
1, 13th 434
1, 25th 26th 287
1, 08 445
1, 30th 31 451
1, 898
O, , 32 , 5 O 93

30:70

17th

134 1.24

22nd

671

1.45

27

700

0.9

32

1800 0.8

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These results mean that there is a significant synergistic viscosity improvement in all examples

was observed.

All samples 13-32 were tested with respect to stability at 20 ⁰ C and at -16 ⁰ C. At 20 ^° C., samples 18, 23, 28 and 29 crystallized in less than four days, but the others were still liquid even after two months. The compositions that crystallized were those with 70 % benzene and 30% ortho-, meta- or paraxylene sulfonic acids and with 60% benzene and 40 % metaxylene sulfonic acids. This illustrates that, in admixture with pure xylene isomers, the proportion of benzenesulfonic acid should not exceed 60% of the active mixture and preferably should not exceed 50 % . The mixtures containing ethylbenzenesulfonic acid were stable at room temperature in all proportions tested. The results of the tests at -16 ⁰ C are given in Table VII:

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Tabel

VII

sample 24 hours Kr. 13th - H - 15th - 16 - 17th
18th immediately
crystalline
sated 19th - 20th - 21 - 22nd 23 immediately
crystalline
sated 24 - 25th - 26th - 27
28
29 immediately
crystalline
sated
immediately
crystalline
sated 30th - 31 - 32

48 h

crystallizes Tg

3 weeks

crystallized

crystal!

2 months

crystallized

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Λ *

To test the effect of toluenesulfonic acid, samples were prepared by adding toluenesulfonic acid in proportions of 5, 10, 15, 20 and 50 % of the total active mixture to benzenesulfonic acid, to 50:50 mixtures of benzenesulfonic acid and commercially available xylenesulfonic acid or cumene sulfonic acid and to a mixture of benzene », commercial xylene and commercial cumene sulfonic acid in a ratio of 1: 1: 1 was added.

When admixed with benzenesulfonic acid, the toluenesulfonic acid produced very rapid crystallization. In the presence of the other acids, the addition took place of toluenesulfonic acid caused a slight increase in the viscosity of each sample, and at the 50–96 content occurred Signs of instability.

In comparison, mixtures of toluene and benzenesulfonic acid were unstable, while mixtures of xylene-ajumene, Toluene-aylene, toluene / cumene and toluene / xylene / cumene sulfonic acids were too viscous to be of practical use without organic diluents.

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Claims (1)

Claim Liquid catalyst for curing synthetic resin binders, consisting of a mixture of aryl sulfonic acids, characterized, that it consists of up to 5 wt -% of sulfuric acid and is a radical which is essentially a mixture of benzene sulfonic acid and alkyl benzene sulfonic acids having up to 12 carbon atoms, wherein the mixture 20-80 wt -.% water, up to 10 wt. #, preferably 30-70% by weight, benzenesulfonic acid, 20-80% by weight, # preferably 30-70% by weight, alkylbenzenesulfonic acids with 8-9 carbon atoms such as xylene and / or cumene sulfonic acids, optionally up to 50% by weight. -9i toluenesulfonic acid and optionally a small proportion of alkylbenzenesulfonic acids with 10-12 carbon atoms. 8Q9815 / 0875