JP7563005B2 - METHOD FOR PRODUCING GRANULAR METAL SOAP, AND GRANULAR METAL SOAP OBTAINED BY THE PRODUCTION METHOD - Google Patents

Description

The present invention relates to a method for producing granular metal soap, and to the granular metal soap obtained by said method.

Metal soaps are salts of higher fatty acids and organic acids with metals other than alkali metals, and are used for various purposes such as stabilizers for polyvinyl chloride resin. In recent years, in response to regulations on heavy metals such as lead, the design of low-toxicity stabilizers for polyvinyl chloride resin that use metal soaps as the main raw material has become mainstream. For this reason, it has become even more important to improve the efficiency of metal soap production and reduce costs.

As a method for producing metal soap, a direct melting method (dry method) is known in which a metal oxide and/or metal hydroxide are directly reacted with a fatty acid. The dry method is a simple method and produces few by-products. However, since the reactants need to be stirred in a molten state, in order to produce powdered metal soap, the reactants in the molten state need to be cooled to form flakes, and the resulting flakes need to be crushed and pulverized. Another known method for producing metal soap is a pressurized method in which a metal oxide and/or metal hydroxide is reacted with a fatty acid at a temperature below the melting point of the metal soap under a constant pressure using a pressurized container to obtain granular metal soap. In these methods, the metal soap is produced using an excess amount of metal oxide and/or metal hydroxide relative to the stoichiometric ratio of fatty acid to metal (for example, Patent Document 1). This results in a high content of free fatty acid, which is an unreacted product, and furthermore, the transparency of the molten metal soap is reduced due to the influence of the excess metal used.

Japanese Unexamined Patent Publication No. 55-136244

The present invention has been made to solve the above problems, and its main objective is to provide a method for producing granular metal soap at low cost and with good production efficiency, and to provide metal soap obtained by this method.

The method for producing a powdery metal soap of the present invention comprises stirring and mixing a fatty acid, at least one selected from the group consisting of a metal oxide, a metal hydroxide, and a metal carbonate, and water while heating under pressure. The amounts of the fatty acid and at least one selected from the group consisting of a metal oxide, a metal hydroxide, and a metal carbonate charged are chemically equivalent to the amount of the resulting metal soap. This heating is performed by using a combination of indirect heating and direct heating.
In one embodiment, the direct heating is direct heating with steam.
In one embodiment, the heating temperature is below the melting point of the resulting metal soap.
In one embodiment, the fatty acid is at least one selected from the group consisting of fatty acids having 8 to 28 carbon atoms.
In one embodiment, the metal contained in the metal oxide, metal hydroxide, and metal carbonate is at least one metal selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, strontium, barium, tin, and zinc.
In another aspect of the present invention, there is provided a metal soap, which has a transparency of 1 in a melt transparency evaluation test of a metal soap when heated at 160° C. for 1 hour.

The method for producing powdered metal soap of the present invention includes stirring and mixing fatty acid, at least one selected from the group consisting of metal oxides, metal hydroxides, and metal carbonates, and water under pressure while heating, and the heating is performed by combining indirect heating and direct heating. In the production method of the present invention, the fatty acid as the raw material and at least one selected from the group consisting of metal oxides, metal hydroxides, and metal carbonates can react in a stoichiometric molar ratio. Therefore, the amount of unreacted substances (free fatty acid and excess metal) that may be contained in the obtained metal soap can be reduced. Furthermore, since there is no need to use an excess of raw material, costs can be reduced.

Furthermore, the metallic soap obtained by the manufacturing method of the present invention has a low content of impurities such as unreacted materials. Therefore, the transparency of the metallic soap in a molten state can be improved. Therefore, it can be suitably used in applications where transparency is required. Furthermore, it can prevent the occurrence of defects due to unreacted materials (e.g., free fatty acids) in products using the metallic soap.

1 is a photograph showing the results of a melt transparency evaluation test of the metal soaps obtained in the Examples and Comparative Examples.

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

A. Method for producing powdered metal soap
The method for producing a powdered metal soap of the present invention includes stirring and mixing a fatty acid, at least one selected from the group consisting of a metal oxide, a metal hydroxide, and a metal carbonate (hereinafter also referred to as a metal raw material), and water under pressure while heating. The amount of the fatty acid and the metal raw material charged is chemically equivalent to the amount of the metal soap to be obtained. That is, the amount of the metal raw material used is the chemical equivalent of the amount of the metal soap to the acid value of the fatty acid. Furthermore, in the method for producing a metal soap of the present invention, heating is performed by combining indirect heating and direct heating. By combining indirect heating and direct heating, the fatty acid and the metal raw material, which are raw materials, can react in a stoichiometric molar ratio. Therefore, it is possible to reduce unreacted substances (free fatty acid and excess metal) that may be contained in the obtained metal soap. Furthermore, since there is no need to use an excessive amount of raw material, it is possible to reduce costs.

A-1. Fatty Acids As the fatty acid, any appropriate fatty acid can be used depending on the desired metal soap. For example, at least one fatty acid selected from the group consisting of fatty acids having 8 to 28 carbon atoms can be used. Preferably, stearic acid, arachic acid, palmitic acid, myristic acid, lauric acid, undecanoic acid, capric acid, behenic acid, and montanic acid can be used. Metal soaps obtained by using these fatty acids can be widely used as raw materials for various industrial applications such as resin raw materials for paints, resin raw materials for soaps, resin raw materials, and various dielectrics. Only one type of fatty acid may be used, or two or more types may be used in combination.

A-2. Metal oxides, metal hydroxides and metal carbonates As the metal oxides, metal hydroxides and metal carbonates, any suitable metal oxides, metal hydroxides and metal carbonates can be used depending on the desired metal soap. Metal oxides are preferably used because they are inexpensive, chemically stable and contain few impurities. The metal oxides, metal hydroxides and metal carbonates may be used alone or in combination of two or more.

As the metal contained in the metal oxide, metal hydroxide, and metal carbonate, any suitable metal can be used depending on the desired metal soap. At least one metal selected from the group consisting of lithium, sodium, potassium, magnesium, calcium, strontium, barium, tin, and zinc is preferable, and zinc, calcium, magnesium, and barium are more preferable. By using these metals, it is possible to produce a powdered metal soap with a higher bulk density and flowability. Only one type of metal may be used, or two or more types may be used in combination.

A-3. Water Any suitable water can be used as the water. Examples include purified water, tap water, distilled water, and ion-exchanged water. In the production method of the present invention, water can function as a catalyst. Therefore, only a small amount of water is required. The water content can be, for example, 15% by weight or less of the total weight of the fatty acid and the metal raw material, and is preferably 5% by weight to 10% by weight of the total weight of the fatty acid and the metal raw material.

A-4. Other Components In the production method of the present invention, any other appropriate materials other than the fatty acid, the metal raw material, and water may be further included. Examples of the other components include a surfactant.

A-5. Stirring and mixing The production method of the present invention can produce a powdered metal soap by stirring and mixing a fatty acid, at least one selected from the group consisting of metal oxides, metal hydroxides and metal carbonates, water and any other components under pressure while heating by direct heating and indirect heating. In the production method of the present invention, the fatty acid and the metal raw material are used in a stoichiometric molar ratio (chemical equivalent to the resulting metal soap). By stirring and mixing under pressure while heating by direct heating and indirect heating, the fatty acid and the metal raw material can be reacted in a stoichiometric molar ratio, and the unreacted material contained in the resulting metal soap can be reduced.

Direct heating and indirect heating can be performed by any suitable method. Direct heating means that the object to be heated (reactant) is heated by contacting it with a high-temperature gas, and is a thermally efficient heating method performed by introducing a high-temperature gas into a reaction vessel containing the object to be heated (reactant). Examples of high-temperature gas used for direct heating include heated water vapor and inert gases such as heated nitrogen. Preferably, direct heating is performed by introducing heated water vapor into the reaction vessel. As described above, water can function as a catalyst. Therefore, water vapor functions as a catalyst while performing direct heating, and as a result, production efficiency can be improved.

Indirect heating means that the object to be heated (reactant) is heated by a method other than contact with high-temperature gas, for example by heating a container containing the object to be heated (reactant) using a jacket heater, etc.

Direct heating and indirect heating may be started simultaneously or may be performed in any suitable order. For example, the fatty acid, metal raw material, and water charged in the reaction vessel may be indirectly heated, and then direct heating may be performed while the indirect heating is still in progress. In one embodiment, the reaction vessel containing the fatty acid, metal raw material, and water may be indirectly heated, and heated steam may be introduced into the reaction vessel to perform heating. By performing direct heating in a state where the temperature has been raised by indirect heating, the introduced steam can be maintained in a gaseous state, and the reaction can be further promoted.

Direct heating and indirect heating are performed so that the temperature inside the reaction vessel is any appropriate temperature. The heating temperature can be set to any appropriate value. Preferably, the temperature is lower than the melting point of the resulting metal soap. For example, when producing zinc stearate as the metal soap, the temperature inside the vessel is heated to 110°C to 117°C. By setting the temperature below the melting point of the metal soap, the raw materials can be stirred and mixed in a slurry or solid state. Therefore, a powdered metal soap with a high bulk density and good flowability can be obtained. The heating temperature is preferably higher than the melting point of the fatty acid used.

In the manufacturing method of the present invention, direct and indirect heating is performed under pressure. The pressure inside the vessel can be set to any appropriate value depending on the pressure resistance of the reaction vessel. By heating under pressure, the raw materials can be stirred and mixed in a slurry or solid state. As a result, a powdered metal soap with a high bulk density and good flowability can be obtained.

As a reaction vessel, any suitable pressure-resistant vessel can be used. For example, a vessel that is pressure-resistant and equipped with any suitable stirring means can be used. Examples include a mixer, blender, autoclave, etc.

The stirring and mixing is carried out for any appropriate time depending on the conditions such as the heating temperature and pressure, and the amount of the fatty acid and at least one selected from the group consisting of metal oxides, metal hydroxides, and metal carbonates used. The stirring and mixing time can be set so that the reaction between the fatty acid and at least one selected from the group consisting of metal oxides, metal hydroxides, and metal carbonates is completed. For example, the reaction time can be shortened by increasing the pressure during the reaction.

A-6. Other Steps The production method of the present invention may further include any appropriate step other than the stirring and mixing. For example, it may include a drying step and a pulverizing step for forming the obtained metal soap into a desired granular shape. The pulverizing step can be carried out by any appropriate method. For example, the obtained metal soap can be pulverized using a pulverizing device such as a pin mill, a hammer mill, or an air mill. In the production method of the present invention, the raw materials are stirred and mixed in a slurry or solid state. Therefore, the bulk specific gravity value of the obtained powdery metal soap can be adjusted more easily.

B. Metal Soap The powdered metal soap of the present invention is obtained by the above-mentioned production method. As described above, in the production method of the present invention, the fatty acid and the metal raw material can be produced in a stoichiometric molar ratio. Therefore, the content of free fatty acid and unreacted substances such as excessively added metals in the obtained metal soap can be reduced. Specifically, the amount of free fatty acid in the obtained metal soap is preferably 0.20% by weight or less, more preferably 0.16% by weight or less. Therefore, the molten metal soap can have excellent transparency.

This metal soap can be used in any suitable application. The metal soap of the present invention has a low content of unreacted substances. Therefore, it can be suitably used in applications where free fatty acids and excessively administered metals may have adverse effects. In addition, the metal soap of the present invention has excellent transparency when melted. Therefore, it can be suitably used in applications where transparency is required. For example, it can be used as a stabilizer for vinyl chloride resin processed products such as wraps and corrugated sheets, for miscellaneous goods such as desk mats, and as a stabilizer for agricultural vinyl chloride resin processed products. It can also be used as an additive for paint resins and for various industrial applications such as various dielectrics.

In one embodiment, the metal soap has a transparency of 1 in a melt transparency evaluation test of the metal soap heated at 160°C for 1 hour. By having such transparency, the metal soap can be suitably used in applications where greater transparency is required. In this specification, the melt transparency evaluation test refers to a test performed by the following method.

<Transparency evaluation test>
5 g of the metallic soap is placed in a glass test tube (φ18 mm×180 mm, product number: rimmed A-18, Maruemu Co., Ltd.) and heated in a dryer at 160° C. for 1 hour to melt the metallic soap. The test tube is then removed from the dryer, and a black stainless steel plate is placed in close contact with the test tube. The black stainless steel plate is then visually observed through the test tube from a position 40 cm away. The transparency of the molten metallic soap is evaluated as follows: 1 if the molten metallic soap has good transparency and the black color of the stainless steel plate is clearly visible, 2 if the black color of the stainless steel plate is difficult to see, and 3 if the black color of the stainless steel plate is almost invisible.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[Example]
A 5L Combimix (manufactured by Primix) was charged with 1609 g of fatty acid (stearic acid, manufactured by Southern Acid (M) Berhad, trade name: POFAC1865L, acid value: 204 mg/KOH), 238.1 g of zinc oxide (zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd., trade name: zinc oxide type 2) (chemical equivalent of metal soap to the acid value of fatty acid), and 150 g of purified water, and stirred and mixed to 110°C by indirect heating using a jacket heated by passing steam through it. Next, maturation by stirring and mixing was performed for 15 minutes. Thereafter, steam of 0.3 MPa to 0.4 MPa was introduced into the container, and the inside of the container was kept at 110°C to 117°C, and maturation was performed for 15 minutes. The steam was controlled by the ON/OFF switch of the valve, and the pressure inside the container was adjusted to be constant between 0.10 MPa to 0.20 MPa. The container was then dried under reduced pressure to remove the water content, yielding a powdered metallic soap. Sampling was performed at three locations: the metallic soap, the container wall, and the rachis used for stirring. These were mixed together and used for evaluation.

(Comparative Examples 1 and 2)
Metal soaps were obtained in the same manner as in the Examples, except that direct heating was not performed and the heating temperature and heating time were changed as shown in Table 1.

(Comparative Examples 3 and 4)
A metallic soap was obtained in the same manner as in the Example, except that direct heating was not performed and that the amount of purified water used, the heating temperature and the heating time were changed as shown in Table 1.

<Evaluation>
The metal soaps obtained in the Examples and Comparative Examples were evaluated as follows.

1. Free fatty acid (FFA) analysis 1.0 g of the obtained metal soap was dissolved in a mixed solution of ether:ethanol = 1:1, and then filtered. The filtrate was then titrated with 0.1 mol/L potassium hydroxide solution (N/10) (ethanol standard solution) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and the percentage of free fatty acid contained in the obtained metal soap was calculated using the titration amount according to the following formula.

Percentage of free fatty acid (%) = (Potassium hydroxide titration (mL) × Factor of N/10 potassium hydroxide standard solution × Molecular weight of fatty acid/100) / Sample amount (g)

2. Melt Transparency Evaluation Test 5 g of the obtained metal soap was placed in a glass test tube (φ18 mm×180 mm, product number: rimmed A-18, Maruemu Co., Ltd.) and heated in a dryer at 160° C. for 1 hour. Next, the test tube was removed from the dryer, and a black stainless steel plate was placed in close contact with the test tube. The black stainless steel plate was then visually observed through the test tube from a position 40 cm away. The transparency of the molten metal soap was evaluated as follows: 1 for good transparency of the molten metal soap, where the black color of the stainless steel plate was clearly visible, 2 for difficult to see black of the stainless steel plate, and 3 for almost invisible black of the stainless steel plate. Photographs of the melt transparency evaluation test of the metal soap obtained in the examples and comparative examples are shown in FIG. 1.

The metallic soap obtained in the examples had a low ratio of free fatty acids. In addition, as shown in Figure 1, the black color of the stainless steel plate placed behind the test tube was clearly visible in the molten transparency evaluation. In Comparative Examples 3 and 4, in which the amount of purified water added was increased, the transparency was slightly improved, but the metallic soap in the molten state was cloudy, and there was room for improvement in transparency.

The method for producing powdered metal soap of the present invention makes it possible to efficiently produce metal soap with high transparency. The metal soap obtained by the method for producing the present invention can be suitably used as a stabilizer for polyvinyl chloride products.

Claims (4)

A method for producing a powdered metal soap, comprising: stirring and mixing stearic acid , zinc oxide , and water under pressure in a reaction vessel while heating the mixture,
The amounts of the stearic acid and the zinc oxide charged are chemically equivalent to the amount of the metal soap to be obtained,
the content of the water is 15% by weight or less of the total weight of the stearic acid and the zinc oxide;
A method for producing a powdered metal soap, wherein the heating is carried out by combining indirect heating and direct heating by introducing heated steam into the reaction vessel , and the temperature inside the reaction vessel during the indirect heating and direct heating is lower than the melting point of the resulting metal soap . 2. The method for producing a powdered metal soap according to claim 1, wherein the content of the water is 5% by weight to 10% by weight of the total weight of the stearic acid and the zinc oxide . 3. The method for producing a powdered metal soap according to claim 1 , wherein the temperature inside the reaction vessel during the indirect heating and the direct heating is equal to or higher than the melting point of the stearic acid . The method for producing a powdered metal soap according to any one of claims 1 to 3 , wherein the temperature inside the reaction vessel during the direct heating and the indirect heating is 110°C to 117°C .