DE1433942B2 - Binders for foundry cores and molds - Google Patents

Description

1 2

The invention relates to an improved ker about 5 to 50 parts, urea formaldehyde about 35 parts

Binders for use in foundries for up to 75 parts, furfuryl alcohol for about 5 to 50 parts and

Manufacture of cores and molds. The inventively sufficient water to dissolve the constituents

proper binder is extremely suitable for urea and formaldehyde can be a simple

the production of sand cores, especially those, 5 a mixture of substances, a urea-formaldehyde

which are condensate or a combination thereof after the so-called »hot-sleeve process«. A

be made. highly polymerized urea-formaldehyde product

For years, foundry cores and molds on the other hand would not be desirable the hot-canning process, whereby under the term "sugar" are those Sand and binding agent brought to a heated model, io saccharides of aldose or ketose character hardened, Ejected from the model and stood, which are usually called reducing sugars Casting metals can be used. This reducing or as such non-reducing saccharides, which Driving has the advantage of faster mass production of hydrolyzing, nuclei, with the formation of reducing sugars and molds for metal casting. are known. Examples of sugars and sugars ent- So far are the most useful binders in these 15 holding materials useful for the invention Processes that have been so-called furan resins are dextrose, starch hydrolysates such as corn syrup, which consists of a mixture of urea formaldehyde arabinose, xylose, ribose, galactose, mannose, and furfuryl alcohol and in combination fructose, maltose, lactose, sucrose, invert sugar, with a suitable catalyst, usually Am-molasses, Hydrol and the like compounds such as sorbitol monium chloride, for the mass production of foundry 20 and mannitol on the other hand, which are not aldehyde or Cores and forms are applied (see e.g. contain or result in ketose groups are not very British patent specification 889 166). These resins are effective in the invention. Hydrol, known from time to time however, certain disadvantages. On the one hand, they are behaved as corn molasses, which is the liquid that moderately costly, and cost is an essential one after dextrose is left over crystallization Point of the 25, which is in fierce competition, is particularly suitable for the new binders, especially the foundry industry. Also, the freshly made are special from an economic point of view. Furan resins very viscous, only slightly soluble in water. The catalyst can be any mineral acid and tend to solidify without the addition of a kata or a salt, which produces a lysators when left to stand for a period of acidic environments under the conditions of hardening about 6 months. 30 dissociated. Oxalic acid can also be used. It is the aim of the invention to overcome these drawbacks but in general the organic acids are not Creation of a new water-soluble binder effective. Acid substances, which are particularly effective To overcome, which a substantial improvement has been found, are ammonium sulfate, versus ammonium the furan resins in terms of hardness chloride, aluminum chloride, femchlorid, aluminumder finished cores, speed of hardening, 35 sulfate, ferric sulfate and zinc sulfate. Stability in storage and economy represent- The molar ratio of formaldehyde to urea represents. should be between about 1.8: 1 to about 3.0: 1. Of the The foundry binder of the invention, which preferred range is about 2.0: 1 to about 2.5: 1. However, a urea-formaldehyde mixture and / or is known to be a mixture of urea - Contains condensate and furfuryl alcohol is marked and formaldehyde is listed as having such a low mole by a further content of a reduced ratio of formaldehyde to urea in a very short time ornamental sugar and / or a sugar, which polymerize or resinify time. So it would hydrolyzed to form reducing sugars. not be useful a binder with this Ver-Doing the sugar is to be produced in an amount of about 5 to ratio. This difficulty was according to about 50 parts by weight (dry basis) present. 45 of the invention overcome in that part of the The agent is used in the form that it is used in urea with the acidic component, a binder component and a catalyst component; In other words, it becomes the new binder in such constituent, wherein the binder constituent is prepared in a manner that the molar ratio form composition according to the two preceding aldehyde to urea between about 2.8: 1 to about Sedimentation and water and the catalyst 50 is 5.0: 1, within which range little or none constituent urea, water and an acidic material has a tendency to polymerize; next to it is a comprises and wherein the molar ratio of form-separated mixture produced which catalyst aldehyde to urea in the final agent component is called and from an aqueous one is between about 1.8: 1 to about 3.0: 1. Solution of the acidic catalyst plus sufficient The binder according to the invention is simply made up of urea to the final molar ratio easy to use and extremely beneficial - from formaldehyde to urea, if the binder economic. It allows an exceptional high and the catalyst component to each other in the Core and mold making speed. Used in making cores or molds It delivers harder cores and shapes than those that will, in the desired range of about 1.8: 1 which can be obtained with the known furan resin binders from 60 to about 3.0: 1.

will. This new binder has a low A number of modifications are possible, Higher viscosity and better shelf life For example, all of the urea could be in the than the currently available binders. Catalyst component are used. Another In a counter-modification, the binder according to the invention supplies water from the composition waiting to be completely let out of water and an acidic catalyst. With regard to economically drawn sand cores in an extremely short time. ease, ease of manufacture, handling and Preferably, the ingredients are present in the following use, however, is that in the aforementioned paragraph lowing proportions (by weight, dry basis): Zu- specified preferred process for the production of the

Binder and catalyst component are the most satisfactory.

The manufacture of sand cores and molds using the new binder is unusually simple. The preferred method is to first mix the sand with the catalyst (the amount of catalyst is about 25 percent by weight of the binder), then add the binder in the ratio of about 1 to 5 ⁰ I ₀ based on the weight of the sand, and to mix again. The mixture is then pushed or blown into a model, which ^{is heated to a temperature of about 121 to 316 °} C., and allowed to harden in situ until the core or mold has hardened sufficiently to be pushed out of the model (dwell time). Once brought out, an exothermic reaction continues until the core or mold is fully cured.

British Patent 807 044 teaches a means for binding core sand, which is a cereal, a Includes sugar, water and an inorganic additive. The problem there was to create a binder which gives a freshly formed wet core with sufficient green strength to hold its shape to keep from baking. The solution to this problem is based on the unexpected discovery that, when certain sugars are used in combination with a cereal binder and certain salts or acids inorganic additive can be used instead of conventional kernel oils, satisfactory green strength and high dry strength can be obtained.

The present invention solves an entirely different problem on the same general technical one Area. The invention is based on the creation of a new water-soluble furan binder which the Difficulties overcome that the furan resins so widely used in foundry are very viscous and are only sparingly soluble in water. The invention was also not supported by the prior art, viz the well-known furfuryl alcohol-urea-formaldehyde resin binders and the well-known sugar-urea-formaldehyde resin binders suggested. The considerable superiority of the binders according to the invention About these known binders could be proven numerically. It should also be noted that these known binders are intended for hardening without heating, while the binders according to the invention Find their application in the hot box process, in which an exothermic reaction by heating is initiated. The prior art also gives no indication that the application of the known Binder or a modification of this in the hotbox process or another hot process is advantageous may be.

The following examples illustrate the invention even better. They are just for illustration and not given for restriction.

example 1

Laboratory tests were made to compare different binders made according to both of the invention as well as outside its limits with three different commercially available furan binders. In this and the following examples, the commercial products with the letters A, B_ and C are designated. The attempted binders are indicated by a number. When the controls were 25 percent by weight of the binder used on the catalyst recommended by the manufacturer. In The experimental examples were 25 percent by weight of the binder on the following catalyst composition used:

Ammonium sulfate 20%, urea 40%, water 40%. The urea-formaldehyde component was a commercial concentrate. It had a formaldehyde to urea molar ratio of about 4.6 up to 4.8: 1 and contained about 15% water. The hydrol had a solids content of about 70%.

Cores were made in the following way:

Sand 3000 g

Catalyst 15 g

Mix for 1 minute

Binder 60 g

Mix for 3 minutes

Table 1

A. B. C. 1 2 3 4th 5 6th 7th 8th 52.3 45.3 35.8 32.4 29.6 42.2 0 35.8 23.1 20.0 15.8 14.3 13.0 0 15.8 15.8 13.8 16.0 18.9 20.0 20.9 22.5 25.3 18.9 10.8 18.7 29.5 33.3 36.5 35.3 58.9 29.5 27.1 25.7 30.6 30.2 32.0 31.3 29.9 21.1 33.7 0 31.3 94 90 96 96 96 96 96 96 96 - 96 3.8 2.4 3.45 2.4 1.7 1.4 6.8 0 0 - 1.3 7.7 7.7 7.7 5.6 4.6 2.8 1.8 0.8 - - 2.7 14.4 16.2 17.2 13.0 10.9 4.6 3.4 2.1 0 ⁴ > ⁷ 420 700 680 720 1080

% Urea formaldehyde
(Dry basis)

% Furfuryl alcohol

% Water

% Hydrol (dry basis) ...

% Sucrose (dry basis) ..

% Invert sugar (dry basis)

Cold tensile strength, kg / cm ²
(30 seconds dwell time)

Scratch hardness

Hot tensile strength, kg / cm ²
(15 seconds dwell time)

Hot tensile strength, kg / cm ²
(30 seconds dwell time)

Hot tensile strength, kg / cm ²
(60 seconds dwell time)

Brookfield viscosity 25 ° C, cP

Viscosity - 128 days

Viscosity - 9 months

The sand mixture was bubbled with 4.2 to 5.6 kg / cm in ^a a heated at 177 ⁰ C standard shell-core test model. After a residence time of 20 seconds, the cores were removed from the test model, allowed to cool to 25 ° C. and the tensile strength and scratch hardness determined. In addition, sand mixtures were blown into a heated model and tensile strengths on the hot cores were determined in situ after dwell times of 15, 30, 45 and 60 seconds using a Dietert hot tensile strength tester. These values are reported as hot tensile strength and are an indication of the rate of cure. The results are shown in Table 1.

According to Table 1, cores made with the binders of the invention generally had one higher cold tensile strength and scratch hardness than those made with known products, which indicated that stronger nuclei were being formed. The hot tensile strengths were comparable or lower, the lower values indicated a slower cure rate. Most of them, however were found to be satisfactory for general foundry purposes, those are those being exceptional high production speed is not required. The binders according to the invention showed no tendency to solidify even after 9 months of storage. Binders 6 and 7 wherein furfuryl alcohol or urea-formaldehyde was omitted, were unusable. In trusses 8 and 9 were Sucrose and invert sugar are used in place of hydrol in 3. The results do not show any conspicuous Difference in properties resulting from the use of other sugars in the batch.

Example 2

Example 1 was repeated with the modification that the amount of furfuryl alcohol was changed. The results are shown in Table 2.

Table 2

% Urea formaldehyde

% Furfuryl alcohol (dry basis) ...

% Water

% Hydrol (dry basis)

Cold tensile strength, kg / cm ² (30 second residence time)

Scratch hardness

As can be seen, varying amounts of furfuryl alcohol do not noticeably change the properties the binder.

Eg play1 3

In some foundries, an extraordinarily high hardening rate is required. It was

ίο suspects that a system could be developed which would lead to higher hardening speeds, but with greater use of sugar, by changing the molar ratio of formaldehyde to urea in binders from 4.6: 1 to 3.5: 1. Because a urea-formaldehyde concentrate having a molar ratio of 3.5: is not commercially available 1 was prepared by mixing such a commercial product having 7.85% urea by heating at 74 ⁰ C. One

ao complete solution with some reactant content of about 88% was obtained in 15 minutes. Enough water was added to make the water content up bring about 15%. Various binders have been made by simply mixing the ingredients together. In this series, the proportions of furfuryl alcohol and the proportions of sugar were kept constant and urea-formaldehyde were changed. The catalytic systems were the same as in the Example 1. Cores were made in the following manner.

30th

Sand 3000 g

Catalyst 15 g

Binder 60 g

35

The mixing procedure was as follows: Catalyst

and sand were mixed in for 1 minute, then the binder was mixed in in 3 minutes. The sand was blown with 4.2 to 5.6 kg / cm ^a in a ⁰ to 190 C, heated to 177 standard shell core test model. After a residence time of 45 seconds, the cores were removed from the model and allowed to cool to 25 ° C. for 1 hour, after which the tensile strength was determined.

Hot tensile strength (the hardening rate of the binder-sand mixture was measured with a hot tensile strength tester certainly.

The results are shown in Table 3.

Table 3

C. 12th 13th 14th 15th 16 36.96 45.76 63.36 73.92 54.56 - 15.68 15.68 15.68 15.68 15.68 - 17.96 16.16 12.56 10.40 14.36 - 29.40 22.40 8.40 0 15.40 30.6 22.5 29.5 24.6 14.8 30.9 3.4 0 1.7 4.8 5.1 3.4 7.7 0.9 3.9 14.1 15.1 12.3 17.2 2.7 8.4 15.5 16.2 17.6 - 6.3 6.5 6.5 7.1 6.85 - 840 890 980 1110 250

% Urea-formaldehyde concentrate

3.50: 1.0 mole ratio (dry basis).

% Furfuryl alcohol (dry basis)

% Water

% Hydrol (dry basis)

Cold tensile strength, kg / cm ² (45 seconds

Dwell time at 177 ° C)

Hot tensile strength, kg / cm ² (15 seconds

Dwell time at 177 ° C)

Hot tensile strength, kg / cm ² (30 seconds

Dwell time at 177 ° C)

Hot tensile strength, kg / cm ² (60 seconds

Dwell time at 177 ° C)

pH at 25 ^° C

Brookfield viscosity at 25 ^° C., cP

50.00 15.68 15.00 19.32

32.7

13.4 6.70 310

According to Table 3, most of the test cores were as hard or harder than the control and the cure rate was considerably higher in most cases. At number 15 where the sugar is completely left out the core hardened quickly, but it was considerably less hard and noticeably less Tensile strength than the kernels made with a sugar. The above approaches were more costly than those of Examples 1 and 2, but still much cheaper to produce than furan resin binders.

Because laboratory tests can only give an indication of the usefulness of a foundry binder, tests were carried out on a larger scale to find the product according to the invention below the actual Try out foundry conditions. Examples 4, 5 and 6 show the results of these experiments.

Example 4

This test was made in an aluminum foundry and the core selected for the tests was about 71.1 cm high and 22.9 cm in diameter and weighed about 18.1 kg. Used at the time of the trial The foundry made a common resin with catalyst, designated C. The following procedure was used to produce Manufacture of the cores applied: '

Sea sand: ■ ·. 454 kg

Silicia sand 227 kg

Catalyst 3.06 kg

Binder C 10.2 kg

used a common binder, designated B, using the following procedure:

Kleankore sand 454 kg

Catalyst 2.7 kg

Mix 3 minutes

Binder B 9.1 kg:

Mix 6 minutes

IO cores were blown at a can temperature of about 246 ^{° C.} The process (blow to eject) took 16 seconds. Test cores were made using Binder 16 and ammonium sulfate-urea catalyst. Only 2.3 kg of catalyst was used, but in all other respects the proportions and procedures were the same as the control. The test cores were harder than the control and the casts made from them were excellent. The cycle was then shortened to 13 seconds and the catalyst level increased to 30%. The test cores were equal to or superior to the controls.

Example6

The following experiment was made in a gray cast iron foundry. The core chosen was small and measured about 1.3 x 1.8 x 14 cm and weighed about 180 g.

'Cores were manufactured using the following methods:

35

The sand and catalyst were mixed for 3 minutes, then resin was added and mixed for an additional three minutes. The cores were blown at a can temperature between 232 and 249 ° C. A manufacturing cycle was 14 seconds with the can under the blower and 15 seconds waiting for the can to open for ejection or 29 seconds total curing time. . The cores were made using the same procedure except for using test binder 16 and the ammonium sulfate-urea catalyst component; instead of the commercially available binder and. Catalyst were used. In addition, test cores were produced using a waiting time of 10 seconds, i.e. reducing the total residence time to 24 seconds. Tensile strengths of a number of the baked cores were measured. The controls showed an average tensile strength of 17.6 kg / cm ² , the cores made with binder 16, 22.5 kg / cm ² . Aluminum castings were made and visual inspection indicated the cores made a superior cast. Even with a higher strength of the test cores, no difference in the shaking out between them and the controls could be detected.

Example 5

. This attempt was made in a gray cast iron foundry. The core selected for the tests measured 63.5 x 20.3 x 10.15 cm and weighed 7.48 kg. The foundry

Silica sand 31.8 kg

local sand 13.6 kg

Water 0.24 kg

Catalyst, 0.18 kg

Binder C 1.1 kg

... sand and water were mixed for 1 minute then the catalyst added and mixing for more Continued for 3 minutes. The resin binder was added and mixed again for an additional 3 minutes so that was mixed for a total of 7 minutes.

The core box temperature was between 171 and 227 ° C and the residence time was 10 seconds. if the binder 16 and the ammonium sulfate urea catalyst instead of the commercially available products were used, cores of comparable quality were obtained. The residence time was then with the Trial binders reduced to 5 seconds and completely satisfactory cores were obtained again.

Example 7

This example shows the effectiveness of other sugars in the invention. A number of ties was made the same as Binder 16 of Example 3, except that different sugars were used in place of the hydrol became. Test cores were made as in Example 3, and hot tensile strengths were determined by residence times determined by 15, 30, 45 and 60 seconds. The results are shown in Table 4.

ίο

Tabel

sugar

15sec kg / cm ²

30sec kg / cm ² 45sec
kg / cm ^s

60sec
kg / cm ²

Brookfield viscosity
at 25 ° C

pH
at 25 ° C

Corn syrup

Dextrose

lactose

Maltose

80 _^0/0 invert
Sorbitol

3.9 3.8 4.5 5.1 4.2 2.4

10.5 10.2 11.2 11.2 12.0 8.5 14.1
13.2
13.2
14.1
12.7
11.1

16.2

.10.9

14.4

13.7

12.1

6.3

240
160
160
640
140
140

6.85
7.30
7.45
4.65
6.95
7.00

Example 8

This example shows the effectiveness of acidic catalysts other than the ammonium sulfate of the previous one Examples. Binder 16 was used, and

Cores were restored in the same way as 20 follow in Table 5.

according to Example 3. The catalyst comprised proportion of urea 40 ° / _0, water 40 ° / _0, 20% acid salt. As in the previous example, the cores were produced and their hot tensile strengths were determined after residence times of 15, 30, 45 and 60 seconds. The results

Table 5 Sour salt 15sec
kg / cm ² 30sec
kg / cm ² . 45sec
kg / cm ² 60sec
kg / cm ² Aluminum sulfate 1.3
0
1.0
3.1
4.2
0
0
0 1.7
1.0
5.6
10.5
7.6
0.6
5.3
0 10.6
2.7
8.8
12.4
11.2
3.0
14.3
2.3 14.2
5.2
16.2
14.5
7.3
6.1
16.2
3.4 Zinc sulfate Ferric sulfate>. Ammonium chloride Aluminum chloride Zinc chloride Ferric chloride Ammonium oxalate

Example 9

In this example cores were made as in Example 3 using Binder 16 with the the only difference is that the urea was omitted from the catalyst component. The hot tensile strengths at 15, 30, 45 and 60 seconds were zero.

B e i s ρ i e 1 10

The previous examples were of cores made by the hot can process. This Example shows that the binder according to the invention is also extremely suitable for conventional core production processes and is superior to furan resins in green strength and baked strength.

The following approach and mixing procedure were used to prepare the sand mix:

Sand 3000 g

Cereal binder 50 g

Southern bentonite 15 g

Water 75 g

Test binder 30 g

Catalyst 7.5 g

Kerosene 3.5 g

. Sand, cereal binder and bentonite were mixed for 2 minutes, then added to the water and mixed for another 3 minutes. The inventive binder and catalyst were added to before mixed with the sand mixture and mixed in for 3 minutes. Kerosene was added and mixing during continued for another minute. The mixture was placed in a 1 gallon pail and covered. Baking was then done in a standard convection oven at about 218 ° C for various times according to table 6.

In addition, kernels were made using a commercially available kernel oil in place of the binder. The results can also be seen from Table 6.

Tabel

control
C. 16 Binder according to the invention 5 Pumpkin seed oil 0.06 0.06 0.06 0.09 Green strength, kg / cm ² 0.04 0.05 0.05 0.07 Green Shear Strength, kg / cm ² ... (baked) tensile strength 12.3 10.9 6.7 <2.8 5 minutes at 218 ° C / kg / cm ² 14.1 11.2 13.4 <2.8 10 minutes at 218 ° C / kg / cm ^a 9.1 6.3 11.2 .3.2 15 minutes at 218 ° C / kg / cm ² 8.1 5.3 11.2 4.2 20 minutes at 218 ° C / kg / cm ² <3.5 <3.5 9.3 5.3 25 minutes at 218 ° C / kg / cm ² <3.5 <3.5 8.4 6.3 30 minutes at 218 ° C / kg / cm ² Dietert scratch hardness 93 95 85 60 5 minutes at 218 ° C 95 92 97 75 10 minutes at 218 ° C 78 70 92 82 15 minutes at 218 ° C 65 50 87 80 20 minutes at 218 ° C 40 <40 78 79 25 minutes at 218 ° C <40 <40 74 79 ' 30 minutes at 218 ° C ° / ₀ baked 41 47 42 22nd 10 minutes at 218 ° C 70 79 79 38 20 minutes at 218 ° C 100 100 100 41 30 minutes at 218 ° C - - - 58 45 minutes at 218 ° C ■ - - - 89 60 minutes at 218 ° C 3 0.06 0.05 13.4 15.1 13.7 11.6 11.6 10.5 97 98 97 94 92 88 41 81 100 - -

Claims (3)

Patent claims: 1. Foundry binder, which is a urea-formaldehyde mixture and / or condensate and furfuryl alcohol, characterized by a further content of a reducing agent Sugar and / or a sugar which hydrolyzes to form reducing sugar. 2. Foundry binder according to claim 1, characterized in that the sugar in one Amount from about 5 to about 50 parts by weight (dry basis) is present. 3. Means for use in the manufacture of cores and molds for foundry purposes, thereby characterized in that it comprises a binder component and a catalyst component, wherein the binder component comprises a composition according to claim 1 or 2 and water and the catalyst component comprises urea, water and an acidic material and wherein the Formaldehyde to urea molar ratio in the final average between about 1.8: 1 to is about 3.0: 1.