JPS62285945A - Production of phenolic resin binder - Google Patents

Abstract

PURPOSE:To obtain the title binder which does not cause environmental pollution, has excellent curability, storage stability and working efficiency and is suitable for use in shell molds, by blending a specified liquid resol type phenolic resin contg. no free HCHO with a solid phenolic resin. CONSTITUTION:A phenol compd. (a) (e.g., phenol) is condensed with HCHO (b) in a molar ratio of 1:3-8 in an alkaline aq. medium contg. 0.02-0.2mol [per mol of the component (a)] of NaOH (c) dissolved in water at 40-100 deg.C (reflux temp.) for 1-10hr. The reaction mixture is cooled and the pH thereof is adjusted to 4-7 with an acid, NH3 and/or an ammonium salt [e.g., (NH4)2CO3] are/is added thereto to convert the remaining free HCHO into hexamethyleneteramine. If desired, the mixture is dehydrated in a vacuum to obtain a liquid resol type phenolic resin (B) contg. no free HCHO. At least one solid phenolic resin (A) such as novolak, resol or benzyl ether type phenolic resin is blended with at least 2wt% (on a solid basis) component B.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Application Field The present invention is for producing a phenolic resin binder that has excellent curing performance and does not pollute the working environment during use. This relates to the method of

More specifically, the present invention is applicable to molds, molds or core adhesives, riser heat insulation materials, refractories, building materials, industrial laminated materials, molding materials, grindstones, and friction materials. ,
The present invention relates to a method for producing an industrial phenolic resin binder with improved properties that can be suitably used in a wide range of applications such as inorganic fiber insulation materials and ceramics.

Conventional technology Conventionally, in the casting industry, resin-coated sand grains for Elmold are used to manufacture molds or cores (hereinafter referred to as molds, etc.). Sand grains coated with a thermosetting resin binder are generally classified into novolac resin-hexamine-based resin-coated sand grains and resol-based resin-coated sand grains depending on the type of resin binder. Xamine-based resin-coated sand grains are manufactured using hexamethylenetetramine, or hexamine, which has excellent properties as a hardening agent. Resole-based resin-coated sand grains coated with a mixed resin binder containing resol resin and a small amount of novolac resin are also characterized by excellent mold performance and curing performance.

However, on the other hand, harmful gases, mainly ammonia and formaldehyde, generated by the thermal decomposition of hexamine during the manufacturing of molds, etc., can significantly pollute the working environment.
There is a problem in that it has a large negative impact on the body of workers, such as causing rashes, and requires a lot of money to counteract the pollution. -The resol-based resin-coated sand grains proposed to solve these problems are effective in improving the working environment, but as mentioned above, the curing speed during the production of molds, etc. The disadvantage is that production efficiency inevitably decreases because the process becomes extremely slow.

As described above, a phenolic resin binder that does not contaminate the working environment and also exhibits excellent performance as a binder when used in the production of molds, etc., has not been realized to date, and the technology in question Its development has been strongly desired in this field.

Problems to be Solved by the Invention The present invention satisfies these demands, does not pollute the working environment, reduces pollution control costs, and improves the molding performance of molds, that is, the curing performance. The present invention aims to provide a soaked phenolic resin binder.

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have conducted intensive research and found that the substantially solid phenolic resin used in the past has a specific property obtained by a specific manufacturing method. When used as a binder for shell molds, for example, a binder containing a liquid resol resin has an improved working environment than the conventional novolac resin-hexamine binder (
/'C1 It has been found that the moldability of resol resins, particularly cylinders, can be greatly improved, and based on this knowledge, the present invention has been completed.

That is, according to the present invention, the phenolic compound and formaldehyde are mixed in a molar ratio of 1 in the presence of an alkaline aqueous medium.
Condensation reaction is carried out at a ratio of :3 to 1:8, and the resulting reaction mixture is adjusted to pH 4 to 7 with an acid, and then at least one compound selected from ammonia and ammonium salts is added thereto. The process converts free formaldehyde into hexamethylenetetramine to obtain a liquid resol-type phenolic resin substantially free of free formaldehyde, which is then selected from a novolac-type phenolic resin, a resol-type phenolic resin, and a benzyl ether-type phenolic resin. The liquid resol-type phenolic resin (in terms of solid content) is blended with at least one solid phenolic resin in a ratio of at least 2 weights based on the total solid weight (thus, the desired phenolic resin bonding is achieved). can be manufactured.

In the method of the present invention, the phenolic compounds used in the production of the liquid resol resin include, for example, monophenols such as haphenope resorcinol, catechol, hydroquinone, and pyrogallol, cresol,
When producing xylenol, cumylphenol, alkylphenols such as nonylphenol, arylphenols such as phenylfer, nobisphenols such as bisphenol A and bisphenol F, as well as monophenols, alkylphenols, arylphenols, and bisphenols. Examples include one type or a mixture of two or more types, such as by-produced purification residues.

Further, as the formaldehyde to be reacted with these phenolic compounds, an aqueous solution such as formalin is usually used, but other substances that generate formaldehyde during the reaction, such as paraformaldehyde and trioxane, can also be used. If necessary, it can also be used in combination with glyoxal, furfural, etc.

The phenolic compound and formaldehyde are used in a ratio of 3 to 8 moles of the latter per 1 mole of the former. If the amount of formaldehyde is less than this, the curing of the obtained liquid resol resin will be slow, and even if it is blended with the solid novolak resin, it will not be able to function as a modifier or a crosslinking agent. Further, when the amount of formaldehyde is increased more than this, there is no particular problem in terms of the physical properties of the liquid resol resin, but the substantial resin content 1 in one reaction mixture decreases, which is economically disadvantageous.

The condensation reaction between the phenolic compound and formaldehyde is carried out in the presence of an alkaline water-injecting medium, and the alkali of the catalyst used in this alkaline water-injecting medium includes, for example, sodium, potassium, lithium, magne 7, etc.
Alkaline inorganic arsenic compounds such as hydroxides, oxides, carbonates, and hydrogen carbonates such as aluminum, calcium, strontium, and barium, and tertiary amines such as trimethylamine, triethylamine, tribenzylamine, and triphenylamine. Examples include alkaline organic compounds such as. These may be used alone or in combination of two or more.

The amount of these catalysts used varies depending on the type, reaction temperature, production scale, etc.9 - Generally speaking, it is not limited, but when carrying out production on an industrial scale, it is
A range of 0.02 to 0.2 mol is suitable.

Furthermore, in the condensation reaction between a phenol compound and formaldehyde carried out in the presence of the catalyst, formaldehyde is added to the phenol compound as much as possible to reduce the residual amount of unreacted phenols, and to avoid excessively high It is necessary to suppress molecularization. The reaction is therefore usually carried out in an aqueous medium at a temperature in the range from 40 to ioo<0>C (reflux temperature), preferably from 50 to 90[deg.]C.

The reaction time may vary depending on the reaction temperature, amount of catalyst, and other conditions, but is usually about 1 to 10 hours.

Furthermore, the end point of the condensation reaction varies depending on the reaction conditions, but is generally not limited to a range in which the degree of dilution with water of the reaction mixture produced by the reaction is from 2 to 8/2.

The degree of water dilution here means that the unit weight (2) of the condensate liquid is 3
The amount of water required to make the sample cloudy at 0° C. is shown by (-).

Next, the reaction mixture obtained in this way is cooled and adjusted to pH 4 to 7 with acids, but this pH adjustment is due to the large heat generated when residual formaldehyde is treated with ammonia or ammonium salt in the next step. This is very important in suppressing excessive polymerization of the reaction mixture and obtaining a liquid resol resin having good storage stability and mold strength.

Examples of organic acids or inorganic acids with a dissociation constant of 10 or more that are usually used in alkali neutralization, such as sulfuric acid, hydrochloric acid, phosphoric acid, oxalic acid, benzoic acid, salicylic acid, and lactate. can be mentioned. These may be used alone or in combination of two or more.

Furthermore, when using a large amount of catalyst, it is desirable to select an acid that forms a salt that is difficult to bathe or is insoluble in water, and to remove the formed salt by filtration.

Furthermore, the pH-adjusted reaction mixture is treated with ammonia, an ammonium salt, or a mixture thereof to convert the formaldehyde remaining in the system into hexamic acid, and then, if necessary, is decanted or concentrated under reduced pressure to obtain the desired amount. By adjusting the resin concentration, a liquid resol resin according to the present invention substantially free of formaldehyde can be obtained.

Furthermore, the resol four fingers may be diluted with an organic solvent such as methanol or acetone depending on the purpose of use.

Examples of the ammonium salt include ammonium carbonate,
Fd! Examples include ammonium rubamate, ammonium hydrogen carbonate, ammonium benzoate, ammonium salicylate, ammonium acetate, ammonium citrate, ammonium chloride, ammonium sulfate, etc., and each of these may be used alone or in combination of two or more. It can also be used with ammonia. When an ammonium salt is used, there is an advantage that neutralization of the inorganic alkali catalyst and treatment of free formaldehyde can be carried out simultaneously.

Treatment of a pH-adjusted reaction mixture with ammonia or ammonium salt generally generates a large amount of heat.
It is preferable to carry out the process so as not to exceed 0°C, and
It is desirable to carry out the same procedure when adjusting the desired resin concentration by removing water under reduced pressure as necessary.

As described above, the liquid resol resin according to the present invention obtained by treating the pH-adjusted reaction mixture with ammonia or an ammonium salt has improved solubility in aqueous systems, and has better storage stability than conventional resol resins. It has the advantage of improving properties.

The liquid resol resin according to the present invention obtained in this way can be made of substantially all the common novolac type phenol resins, resol type phenol resins, benzyl ether type phenol resins, and mixed resins thereof, which are obtained by conventionally known methods. When blended with solid phenolic resin, it not only improves its curing performance, but also significantly reduces the generation of harmful gases and improves the working environment. Incidentally, the same effect can be exerted on a festival prepared by dissolving the solid phenol resin in an organic solvent such as methanol depending on the purpose of use.

In the method of the present invention, the liquid resol resin is added to the substantially solid phenol resin, the solid content of which is at least 2% by weight based on the total solid content of the phenol, Preferably, the proportion is at least 5% by weight. If this amount is less than 2% by weight, curing performance will not be sufficiently improved.

The phenolic soy sauce binder obtained in the present invention may optionally contain additives such as a silane coupling agent and an amide lubricant, organic or inorganic disintegration modifiers such as loge/chemicals, resorcinol, Curing accelerators such as catechol, benzoic acid, salicylic acid, and bisphenols, mold release agents, and synthetic resins such as epoxy resins, xylene resins, vinyl acetate resins, and acrylic resins may be mixed within the scope of the invention. can be used.

Function The reason why the phenolic resin binder obtained by the present invention exhibits better curing properties and performance in reducing harmful gases than conventionally known phenolic resin binders is not necessarily clear. However, one of the reasons for this is that the liquid resol resin used as a resin binder component has a curing function similar to that of hexamine, which is formed by adding as much formaldehyde as possible to a phenolic compound in a condensation reaction. Because it contains many crosslinkable methylol groups and has a resin structure bound to hexamine, which is formed by treating free formaldehyde with ammonia or ammonium salt, it can be combined with conventional phenolic resins as a modifier or crosslinking agent. When using, conventional clear resin,
Compared to bulking agents, it has many crosslinking functional groups with a curing function, so the amount of hexamine used, which generates harmful gases, can be substantially reduced, improving the curing speed and reducing harmful gas emissions. It is presumed that this has the effect of reducing the occurrence.

EXAMPLES Next, the present invention will be explained in more detail with reference to examples. In addition, the parts and sections in the Examples and Comparative Examples are key 9 unless otherwise specified.
It is based on weight.

In addition, evaluation of the four-finger coated sand grains (Rcs) was carried out according to the following test method.

Folding Crab J-S-6910 Pend: , TACT test method 5M-3 Melting point: , TAOT test method 0-1 Temperature strength according to J-K S-6910, mold temperature 25
The test piece was baked at 0° C. for a predetermined time and the transverse rupture strength was measured 10 seconds after demolding.

Ammonia: Resin-coated sand grains 2.
52 was charged and fired for 70 seconds, the concentration of ammonia gas generated was measured using a kita type detection tube (measurement range 25 to 900 pprn).

Formaldehyde: The resin-coated sand grains used are 152, and the formaldehyde gas concentration side is a fixed-type detection tube (1llll fixed range 1 to 35 ppm).
) was measured according to the method for measuring ammonia gas concentration described above.

Production Example 1 100 parts of phenol and 238 parts of 47% formalin were placed in a three-necked flask equipped with a reflux condenser and a stirring device.
While stirring, add 8.5 parts of 50% sodium hydroxide and react at a reaction temperature of 80°C for 3 hours (water dilution at 30°C is 3.5 parts).
After the reaction (0d/P), the mixture was cooled and the pH was adjusted to 5.6 with salicylic acid.

Furthermore, 59 parts of 25% ammonia water was added while cooling the resin liquid so that the temperature did not exceed 60°C, and dehydration was performed under reduced pressure.
A liquid resol resin (hereinafter abbreviated as resin A) according to the present invention was obtained.

The resulting resin A had a solid content of 60%, a viscosity of 130 centiboise (30°C), and a free phenol content of 0.1%.
No free formaldehyde was detected. Note that free phenol was determined by liquid chromatography, and free formaldehyde was determined by the hydroxylamine hydrochloride method.

Production Example 2 Phenol xoo parts and 373 parts of 47% formalin were placed in a three-neck flask equipped with a reflux condenser and a stirring device, and while stirring, 4.3 parts of 50% sodium hydroxide was added, and the mixture was heated at a reaction temperature of 80°C for 2 hours ( After the reaction (water dilution rate at 30° C. was 5.6 ml/9), the mixture was cooled and the pH was adjusted to 4.5 with acetic acid. Furthermore, while cooling the resin liquid so that the temperature does not exceed 60℃, 25% ammonia water 144
1, and dehydration was performed under reduced pressure to obtain a liquid resol resin (hereinafter abbreviated as resin B) according to the present invention.

Resin B obtained had a solids content of 59%, a viscosity of 90 centivoise (30° C.), and no free phenol or free formaldehyde was detected.

Production Example 3 Add too much phenol and 509 parts of 47% Volf 9 to a three-bottle flask equipped with a reflux condenser and stirring device, add 4.32 parts of hydroxide with stirring, and reduce to 2.5 at a reaction temperature of 80°C. time (water dilution at 30°C is 3.
177r) After the reaction, cool and then adjust the pH with hydrochloric acid.
After adjusting the temperature to 6.5 and leaving it still, the neutralized salt was removed. Next, while cooling the resin liquid so that it does not exceed 60℃, 25%
239 parts of ammonia water was added and dehydration was performed under reduced pressure to obtain a liquid resol resin (hereinafter abbreviated as resin C) according to the present invention.

Resin C obtained had a solid content of 60%, a viscosity of 75 centipoise (30° C.), and free phenol and free formaldehyde were not detected.

Production Example 4 244 parts of phenol water dilution of 4.2
m//? ) After the reaction, the mixture was cooled and then adjusted to pH 5.1 with salicylic acid. Furthermore, while cooling the resin liquid so that the temperature does not exceed 60℃,
1 part and dehydrated under reduced pressure to obtain a liquid resol resin (hereinafter abbreviated as resin) according to the present invention.

The resulting resin had a solids content of 60%, a viscosity of 55 centipoise (30° C.), free phenol of 2.1 g, and no free formaldehyde detected.

Production Example 5 A control liquid resol resin (hereinafter abbreviated as Resin E) was obtained in the same manner as Production Example 1 except that neutralization with salicylic acid was not performed.

The resulting resin E had a solid content of 60 inches, a viscosity of 230 centiboise (30°C), and a free phenol content of 0.2 inches.
No free formaldehyde was detected.

Production Example 6 A control liquid resol resin (hereinafter abbreviated as Resin F) was produced in the same manner as Production Example 1 except that 25% ammonia water was not added.
I got it.

The obtained resin F had a solid content of 60% and a viscosity of io.

centiboise (30℃), free phenol 0.2t,
Free formaldehyde was 11.3%.

Example 1 Fuuka silica sand 5 KP preheated to 150°C in a speed mixer manufactured by Enshu Tekko Co., Ltd., solid novolac resin (trade name: 5P70ONS manufactured by Keikaku Jizai Kogyo) 70F, and resin A30F obtained in Production Example 1 (compounding ratio 70:30) After adding and mixing for 30 seconds to fully melt and coat, mix for 40 seconds while rapidly cooling with cooling water 752 and air blower, then add calcium stearate 52 and mix for another 15 seconds to loosen the sand grains. Then, it was taken out to obtain resin-coated sand grains (hereinafter abbreviated as RC8). The obtained evaluation results of RC8 are shown in Table 1.

Examples 2 to 4 RC8 was obtained in the same manner as in Example 1 using the solid novolac resin SP70 ONS and Resin A obtained in Production Example 1 according to the formulation method listed in Table 1. The obtained evaluation results of RC8 are shown in Table 1.

Examples 5 to 7 RC8 was obtained in the same manner as in Example 1, except that resin A obtained in Production Example 1 was replaced with resin BD obtained in Production Examples 2 to 4. The obtained evaluation results of RC8 are shown in Table 1.

Comparative Example 1 -J (Shu tA Ko@Cracked speed mixer preheated to 150°C, Fuka silica sand 5 KP and solid novolac m fat sp7
After adding ONS 100 F and mixing for 30 seconds to fully melt and coat, add Hexame 7159 and cooling water 7.
59 was added thereto, and the mixture was mixed for 40 seconds while being rapidly cooled by blowing air. Then, calcium stearate 52 was added and mixed for another 15 seconds to loosen the sand grains, and then taken out to obtain RC3. The obtained evaluation results of RC8 are shown in Table 1.

Comparative Examples 2 to 3 RC8 was obtained in the same manner as in Example 1, except that resins E and F obtained in Production Example 5.6 were used in place of Resin A obtained in Production Example 1. The obtained evaluation results of RC8 are shown in Table 1.

The RCS evaluation results according to Examples 1 to 7 and Comparative Examples 1 to 5 are shown in Table 1. RCS using the resin binder of the present invention (Examples 1 to 7)
Compared to hexamine-based RC9 (Comparative Example 1), the generation of harmful gases during mold creation is significantly reduced, and the curing speed as shown in the hot strength and pend is significantly improved, and has a significant improvement effect.

In addition, RCS using acid-neutralized resin A (Example 1
) had significantly improved mold strength compared to RCS (Comparative Example 2) using Resin E without acid neutralization, and the effect of acid neutralization was clearly recognized. Furthermore, mold strength and curing speed were significantly improved compared to RCS (Comparative Example 3) using Resin F without ammonia treatment, and although ammonia was generated during mold creation, formaldehyde gas generation was significantly reduced. .

In addition, in Comparative Example 6, when manufacturing RCS, resin F
The generation of free formaldehyde was significant and the discomfort was unbearable and could not be put to practical use, and the effect of the ammonia treatment in the present invention was clearly recognized.

Example 8 5 kg of recycled No. 5 sand (fluidized roasted recycled sand) preheated to 150°C in a speed mixer manufactured by Enshu Iron Works and solid resol resin (trade name: 5P545N manufactured by Keiki Jizai Kogyo) 135 j
i and resin A25. obtained in Production Example 1. @ (Blending ratio 90
: Add 10) and mix for 30 seconds to fully melt and coat, then add 75.5% of cooling water. Mixing was performed for 40 seconds while quenching with i7 and air blowing, and then 5 g of calcium stearate was added and mixed for an additional 15 seconds to loosen the sand grains and then taken out to obtain RCS. The obtained RCS evaluation results are shown in Table 2.

Example 9 Solid resol resin 5P545N 120 g and Production Example 1
RCS was obtained in the same manner as in Example 8 except that the resin A50.9 (blending ratio 80:20) obtained in Example 8 was used. Obtained RC
The evaluation results for S are shown in Table 2.

Comparative Example 4 RCS was obtained in the same manner as in Example 8 except that only solid resol resin 5P545N was used as the binder. The obtained RCS evaluation results are shown in Table 2.

The RCS evaluation results according to Example 8.9 and Comparative Example 4 are shown in Table 2, and the RCS using the resin binder of the present invention (Example 8.9)
Compared to (Comparative Example 4), the hot strength and pen door 5 were significantly improved, and the effect of improving the curing properties was remarkable.

Example 10 5 kg of fuka silica sand preheated to 150°C and solid novolac resin (trade name,
After adding 95 g of 5P500 (manufactured by Kyokai Jizai Kogyo) and 8.31 (blending ratio 95:5) of resin A obtained in Production Example 1 and mixing for 30 seconds to sufficiently melt and coat, 15 g of hexamine and 75 g of cooling water were added. Then, calcium stearate 51 was added and mixed for another 15 seconds to loosen the sand grains and then taken out to obtain RCS. Obtained RC
The evaluation results for S are shown in Table 3.

Example 11 Solid novolac resin 5p5oO? 0, p and production example 1
An RCS was obtained in the same manner as in Example 10, except that the resin A obtained in Example 10 was used at 16.79 (blending ratio 90:10).

The obtained evaluation results are shown in Table 3.

Comparative Example 5 RCS was obtained in the same manner as in Example 10 except that only solid novolac resin 5P500 was used as the binder.

The obtained RCS evaluation results are shown in Table 3.

Table 3 The RCS evaluation results according to Example 10.11 and Comparative Example 5 are as shown in Table 3. Compared with novolac resin-hexamine-based RC3 (Comparative Example 5), the
S (Examples 10 and 11) had significantly improved strength and bending at elevated temperatures, and the effect of improving the curing properties was remarkable.

In addition, resol resin A according to the present invention obtained in Production Example 1, control resol resin E obtained in Production Example 5.6, and ? Table 4 shows the results of a comparative study on the storage stability of

Table 4 *Storage stability: The resin was left in a constant temperature bath kept at 40°C, and the number of days until it separated into a water layer and a resin layer was determined.

As is clear from the above results, resol resin A according to the present invention was neutralized with acid and treated with ammonia.
has significantly improved storage stability over control resole resins, a property that is very useful for use on an industrial scale.

Effects of the Invention As is clear from the above explanation, the phenolic resin binder using the liquid resol resin of the present invention in combination as a crosslinking agent for a conventional solid phenolic resin binder has a higher performance than the conventional novolak type phenolic resin binder. It has extremely excellent curing performance and can significantly reduce the generation of harmful gases, so it not only improves the working environment, but also improves work efficiency and reduces pollution control costs. Further, when the liquid resol resin is used in combination as a modifier, it has remarkable effects such as being able to significantly improve curing performance compared to conventional solid phenol resin binders. Furthermore, since the liquid resol resin according to the present invention has excellent storage stability, it is extremely useful when used on an industrial scale.

The phenolic binder obtained by the present invention is suitably used for shell molds, and also for adhesion of casting molds or cores, for riser heat insulation materials, carbon materials, graphite materials,
For refractories such as unfired brick materials and blast furnace plugging materials, for building materials such as particle board, fiberboard, mineral board, and plywood, for industrial laminated materials, for molding materials, for grinding wheels, for friction materials, and inorganic fibers. It is also suitably used as an industrial resin binder in various applications such as heat insulating materials and ceramics.

Claims (1)

[Claims] 1 In the presence of an alkaline aqueous medium, a phenolic compound and formaldehyde are subjected to a condensation reaction at a molar ratio of 1:3 to 1:8, and the resulting reaction mixture is adjusted to pH 4 to 7 with an acid.
Then, at least one compound selected from ammonia and ammonium salts is added to the mixture to convert free formaldehyde into hexamethylenetetramine, thereby producing a liquid resol-type phenol substantially free of free formaldehyde. A resin is obtained, and then this liquid resol type phenol resin (in terms of solid content) is added to at least one solid phenol resin selected from novolac type phenol resin, resol type phenol resin, and benzyl ether type phenol resin. A method for producing a phenolic resin binder, characterized in that the binder is blended in a proportion of at least 2% by weight based on the total solid weight.