JPH08192101A - Method for treating surface-coated powder - Google Patents

Abstract

PURPOSE: To provide a method for treating powder coated with organohydrogen polysiloxane which generates almost no hydrogen. CONSTITUTION: Powder, after being reacted with organohydrogen polysiloxane for surface treatment, is contacted with at least one kind selected from among water and lower alcohols to replace the unreacted reactive hydrogen atoms of the organohydrogen polysiloxane left in the coating layer with a chemically stable functional group.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for treating surface-coated powder.

[0002]

2. Description of the Related Art Conventionally, there are many methods for hydrophobizing powders, and it is well known to utilize the hydrophobic property of silicone oil.

Among the above-mentioned silicone compounds, especially the organohydrogenpolysiloxane compound is coated on the surface of the powder and then heat-treated in air to form a powder on the surface of the powder.
It has the characteristics that it does not elute with solvents and oils, and it does not easily fall off by mechanical force, and it forms a strong silicone resin-like coating layer. It is used for coating the powder surface for the purpose of making the powder hydrophobic, and the surface-coated powder is often used in cosmetics, toners, paints, inks and the like.

The organohydrogenpolysiloxane compound used for the powder surface coating is a polysiloxane compound containing a polysiloxane chain and an organohydrogensiloxane group in the molecule, and the Si--H (hydrosilyl) bonding portion thereof is When the surface of the powder is coated, the Si-H bond portions of the adjacent organohydrogenpolysiloxane molecules react with oxygen in the air to crosslink and polymerize to form a network polysiloxane structure. When the metal oxide has a surface hydroxyl group such as a metal oxide, the hydrogen atom in the Si-H bond portion of the organohydrogenpolysiloxane also reacts with the surface hydroxyl group of the metal oxide to form a chemical bond with the powder surface. It is believed that various coating layers are formed.

The adjacent organohydrogenpolysiloxane molecules generate hydrogen gas during the crosslinking reaction. Further, when the powder itself such as an inorganic oxide has a surface hydroxyl group, the organohydrogenpolysiloxane molecule at the time of coating is composed of a part which is directly adsorbed on the powder surface and a part which is laminated thereon. However, in the part where the organohydrogenpolysiloxane molecule is directly adsorbed on the powder surface, Si
The hydrogen atom of the —H bond portion and the hydrogen atom of the OH bond portion of the hydroxyl group on the powder surface undergo a binding reaction, and as a result, hydrogen gas is generated.

Conventionally, in order to perform surface coating treatment on powder using the above-mentioned organohydrogenpolysiloxane compound, first,
A method in which the surface of the powder is physically coated with an organohydrogenpolysiloxane compound by a known method, and then the coated powder is heat-treated in air to cross-link and polymerize the organohydrogenpolysiloxane compound on the surface of the powder. Was being done.

However, when the surface of the powder is coated with the organohydrogenpolysiloxane compound and then heat-treated in the air, the crosslinking reaction between the molecules and the bonding reaction with the base material proceed, but the reaction proceeds to form a network. When the polysiloxane structure in the form of a ring is formed, developed, and fixed, some of the isolated reactive hydrogen atoms are left behind because there is no partner for the crosslinking reaction in the vicinity of itself.

Although it is very difficult to remove the above-mentioned residual hydrogen atoms by heat treatment in industrial production, a part of the hydrogen atoms remains in the atmosphere over time when viewed from a long-term viewpoint of several months. Reacts with water and other substances, gradually forming and desorbing hydrogen gas.

Therefore, when the powder is subjected to the surface coating treatment using the organohydrogenpolysiloxane compound by the conventional technique, a large number of unreacted reactive hydrogen atoms remaining in the surface coating layer remain in the air. The water may cause a dehydrogenation reaction gradually over a long period of time, or the composition may cause a dehydrogenation reaction within a short period of time by water, alcohol, amine, etc. in the presence of an acid or a base. When the above surface-coated powder is used as it is for various composition components such as cosmetics, toners, paints, and inks, hydrogen gas is generated in the composition at the application stage to cause various harmful effects. Was there.

That is, when hydrogen gas is generated in the use stage, specifically, for example, in the case of cosmetics, product package expansion, product cracking, peeling, deterioration of water repellency over time, etc. However, in the case of paints, problems such as swelling of the product package and unevenness of the coating film occur when deterioration of various properties such as chargeability occurs.

[0011]

In order to reduce the above-mentioned unreacted reactive hydrogen atoms, for example, a metal hydroxide serving as a catalyst for initiating cross-linking polymerization of organohydrogenpolysiloxane is mixed with the powder to be treated. After milling, a method of utilizing a mechanochemical reaction (Japanese Patent Publication No. 56-43264, etc.) or a method of adding an acidic substance when reacting an organohydrogenpolysiloxane on the surface of powder (Japanese Patent Laid-Open No. Sho 60-60)
No. 163809, etc.) has been tried.

The above-mentioned methods have some effects, but there are problems that the process is complicated and the catalyst remains in the product powder.

Further, for the purpose of reducing unreacted reactive hydrogen atoms, a solid material is coated with a silicone polymer film having a Si--H (hydrosilyl) group portion, and then a pendant group is attached to the Si--H group portion. A method of bonding (Japanese Patent Laid-Open No. 63-168346, etc.), and
A specific silicone compound is allowed to act directly on the powder to be treated in a gaseous state, and the excess is removed in a gaseous state so that unreacted reactive hydrogen atoms are not directly adsorbed on the powder surface and hydrogen is removed. For example, a modified powder that does not generate gas is obtained (Japanese Patent Publication No. 1-54381).

Although these improved methods have some effects, they are not versatile and costly because new processes need to be added and only silicone compounds having a specific structure can be used. There are drawbacks such as

From the above, there has been a strong demand for an organohydrogenpolysiloxane-coated powder which is inexpensive and easy to produce in various applications and which does not have the problem of hydrogen generation.

[0016]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that after reacting an organohydrogenpolysiloxane compound on the powder surface, Si
The unreacted reactive hydrogen atom remaining in the organohydrogenpolysiloxane coating layer is replaced with a chemically stable functional group by causing a substance having a reactive activity to the —H group to act on the treated powder. Then, they have found that a powder which does not cause the problem of hydrogen gas generation can be obtained in the later application, and thus reached the present invention.

That is, according to the present invention, the surface of the powder is reacted with an organohydrogenpolysiloxane compound to carry out a surface coating treatment, and then one or more compounds selected from water and lower alcohols are coated on the powder. A method for treating a surface-coated powder, which comprises contacting and replacing unreacted reactive hydrogen atoms of an organohydrogenpolysiloxane remaining in a coating layer with a chemically stable functional group. .

The powder in the present invention mainly means an inorganic powder, among them, metal oxides such as titanium oxide, fine particle titanium oxide, zinc oxide, alumina and silica, talc, sericite and kaolin. , Natural minerals such as mica, carbonates such as calcium carbonate, calcium sulfate and barium sulfate, and sulfates are preferably used, but organic powders may be used.

In the organohydrogenpolysiloxane compound used in the present invention, a methyl group is usually used as the organo group when, for example, the coating-treated powder is required to have hydrophobicity, methylhydrogenpolysiloxane or methylhydrogen is used. Gencyclosiloxane and the like can be preferably used. Further, various organo groups may be used instead of the above methyl group depending on the required characteristics.

In addition, the polysiloxane chain in the organohydrogenpolysiloxane compound may be in the form of a chain having a terminal group or a ring, and the content or distribution of the organohydrogensiloxane group contained in the polysiloxane chain is not limited. Absent.

Since the present invention is characterized in that the powder is coated with the organohydrogenpolysiloxane compound and then treated, any method may be used until the powder is coated with the organohydrogenpolysiloxane compound. You may perform a coating process.

As a coating treatment method, for example, an organic solvent in which an organohydrogenpolysiloxane compound is previously dissolved and powder are dispersed using a disperser such as a stirrer, a homogenizer, a sand grinder mill, and an attritor. Wet method of removing solvent, dry method of coating while mixing organohydrogenpolysiloxane compound and powder in Henschel mixer, ball mill, etc., after mixing organohydrogenpolysiloxane compound and powder , A method of pulverizing with a pulverizer, a pin mill, a jet mill, or the like, but the coating treatment by any of the above-mentioned methods does not impair the characteristics of the present invention.

When the powder is coated with the organohydrogenpolysiloxane compound, the crosslinking reaction is usually completed by heat treatment in air at 100 to 200 ° C. for 0.5 to 10 hours. The step of causing a substance having a reaction activity to the —H group to act on the treated powder may be performed before or after the heat treatment step as long as the powder is coated with the organohydrogenpolysiloxane compound. Further, it does not matter even during the heat treatment step.

In the present invention, a substance having a reaction activity with respect to a Si--H group is caused to act on an unreacted reactive hydrogen atom remaining in the organohydrogenpolysiloxane coating layer to form a chemically stable functional group. It is characterized by replacing
In addition to water (water vapor) and lower alcohols, higher alcohols, amines, and the like can be applied as long as they are substances having a reaction activity on the Si—H group.

The term "lower" in the present invention means C1 to
It refers to compounds up to C4, and lower alcohol specifically refers to, for example, methanol, ethanol, propyl alcohol, butanol and the like.

Regarding the form of water (steam) or lower alcohol which is brought into contact with the powder into the system, it may be introduced into the reaction system in a vapor or liquid state in accordance with the situation at the time of contact with the powder. Of course, the specific introduction place is preferably in a heatable mixer, a dryer, a crusher, or the like.

The temperature at the time of contact with the powder is 80 to 2
The temperature is 00 ° C, preferably 100 to 160 ° C, and the preferable contact time is 0.5 to 8 hours.

When the temperature of water (steam) or lower alcohol or the ambient temperature at the time of contact with the powder is low, a long contact time is eventually required to replace the hydrogen atom, and conversely at the time of contact. If the temperature is too high, the coating film of the organohydrogenpolysiloxane subjected to the coating treatment will be partially destroyed, which is not preferable.

Therefore, at the time of contact with the powder,
Although it is possible to perform treatment even when water (steam) or lower alcohol is in a liquid state, contacting in a gas state enables efficient treatment in a short time.

Further, since an alcohol having a large number of carbon atoms has a high boiling point, there arises a problem that the temperature becomes too high for contacting in a gaseous state. Therefore, for example, a solvent is used for coating treatment of the organohydrogenpolysiloxane compound. In this case, alcohol may be dispersed in the solvent after the coating treatment and before the removal of the solvent, and the alcohol may be brought into contact with the powder in a liquid state.

Further, as a special case, a jet mill using superheated steam can be used.

By applying the processing method of the present invention described above, the following advantages occur. 1. The purpose can be achieved simply by adding a simple and inexpensive substance such as water or lower alcohol. 2. Can be used as is without modifying existing equipment. 3. The costs incurred by applying the invention are small. 4. Additives such as catalysts do not remain in the powder to be treated. 5. No by-products are produced. 6. Even if the treatment of the present invention is performed, the basic powder characteristics of the powder to be treated are not affected at all, and the problem of hydrogen gas generation can be solved. 7. It can be introduced into the reaction system in either a liquid state or a gas state.

[0033]

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

Example 1 Fine Titanium Oxide (Taika MT-500B) 500
g, 10 g of methylhydrogenpolysiloxane (KF-99 manufactured by Shin-Etsu Chemical Co., Ltd.), and 1,000 g of toluene were put into a kneader capable of heating and reducing the pressure, and the mixture was heated and reduced in pressure with stirring to remove the solvent. Then, inside the device 120
After heating to 0 ° C., 50 g of water was added, and while maintaining the temperature, heating and stirring were performed at atmospheric pressure until the water content disappeared.
After that, it was pulverized with a pulverizer to obtain a surface-coated powder.

Example 2 A surface-coated powder was obtained in the same manner as in Example 1 except that the inside of the apparatus was kept at 120 ° C. for 2 hours before adding water.

Example 3 The surface was treated in the same manner as in Example 1 except that the powder was further pulverized with a pulverizer and then the powder was placed in a hot air circulation dryer and heat-treated at 120 ° C. for 2 hours. A coated powder was obtained.

Example 4 500 g of titanium oxide (JA-1 manufactured by Teika), 5 g of methyl hydrogen polysiloxane, 1,000 of toluene
g was put in a kneader capable of heating and depressurizing, and heating and depressurizing was performed while stirring to remove the solvent. Then, the powder was taken out, and 100 parts of water was placed in a hot air circulation dryer kept at 110 ° C.
It was allowed to stand for 2 hours with a beaker containing ml. After that, it was pulverized with a pulverizer to obtain a surface-coated powder.

Example 5 For the composition to be put into a kneader, the same treatment as in Example 1 was carried out except that 500 g of particulate titanium oxide was changed to 500 g of zinc oxide and the amount of methylhydrogenpolysiloxane was changed from 10 g to 5 g. A coated powder was obtained.

Example 6 500 g of sericite and 10 g of methyl hydrogen polysiloxane were dry-mixed for 30 minutes with a Henschel mixer. Then, while introducing steam into the Henschel mixer at a rate of 1 kg / cm ² , a mixing treatment was performed for 30 minutes, and then a heat treatment was carried out at 120 ° C. for 2 hours in a hot air circulation dryer to obtain a surface-coated powder. It was

Example 7 Titanium oxide 500 was used for the composition charged in the kneader.
A surface-coated powder was obtained in the same manner as in Example 2, except that the amount of talc was changed to 500 g and the amount of methylhydrogenpolysiloxane was changed from 10 g to 5 g.

Example 8 A composition coated in a kneader was treated in the same manner as in Example 1 except that 10 g of methylhydrogenpolysiloxane was changed to 10 g of tetramethylcyclotetrasiloxane to obtain a surface-coated powder.

Example 9 Titanium oxide (500 g), methylhydrogenpolysiloxane (5 g) and toluene (1,000 g) were placed in a kneader capable of heating and reducing the pressure, and the mixture was heated and reduced in pressure with stirring to remove the solvent. Next, after heating the inside of the apparatus to 120 ° C., 50 g of IPA (isopropyl alcohol) was added, and stirring was performed for 2 hours while maintaining the temperature. Next, the degree of vacuum was further increased to remove IPA. After that, it was pulverized with a pulverizer to obtain a surface-coated powder.

Example 10 500 g of fine particle titanium oxide, 10 g of methylhydrogenpolysiloxane and 1,000 g of toluene were put into a kneader capable of heating and depressurizing, and heating and depressurizing was performed with stirring to remove the solvent. Then 200 as pressure gas
Using superheated steam at 6 ° C. and 6 kg / cm ^2, the powder was pulverized by a jet mill at a rate of 500 g / min to obtain a surface-coated powder.

Example 11 500 g of fine particle titanium oxide, 10 g of methylhydrogenpolysiloxane and 1,000 g of toluene were put into a kneader capable of heating and reducing the pressure, and the solvent was removed by heating and reducing the pressure while stirring. Then take out the powder, 110
The mixture was allowed to stand for 2 hours together with a beaker containing 100 ml of water in a hot-air circulation type dryer kept at 0 ° C. Then, it was crushed by a jet mill using compressed air to obtain a surface-coated powder.

Example 12 Titanium oxide 500 was used for the composition charged in the kneader.
Example 7 except that g was 500 g of particulate titanium oxide, the amount of methylhydrogenpolysiloxane was 5 g to 10 g, and 50 g of water was 50 g of ethanol.
The same treatment as described above was performed to obtain a surface-coated powder.

Comparative Examples 1 to 12 The surface treatment was carried out in the same manner as in each of the corresponding Examples, but in each case, the treatment was carried out without adding water (steam) or alcohol, and each surface coating treatment was carried out. A powder was obtained. In Comparative Example 10, jet mill grinding was performed using compressed air of 6 kg / cm ² as the pressure gas.

[0047]

Results: The amount of hydrogen gas generated in the surface-coated powder obtained in each of the examples and comparative examples was measured by the following method.

Method for measuring hydrogen gas generation amount Methanol: triethylamine: ion-exchanged water: surface-coated powder: methanol, triethylamine, ion-exchanged water, and each of the surface-coated powders obtained in Examples and Comparative Examples A slurry is prepared by stirring and mixing in a weight ratio of body = 10: 2: 1: 1.

The above-mentioned slurry was put into a syringe with a needle tip whose weight was measured in advance, the air bubbles in the cylinder were completely pushed out, and then the weight was measured to calculate the weight of the separated slurry, The amount of surface-coated powder inside is calculated.

After fixing the piston part of the syringe and leaving the cylinder sideways for one day (24 hours), the weight was measured again to calculate the weight of the slurry expelled from the syringe due to hydrogen gas generation. From this value and the amount of the surface-coated powder in the syringe, 1 g of the surface-coated powder was obtained.
Calculate the amount of hydrogen gas generated per unit.

Further, the amount of hydrogen gas generated per 1 g of the surface-coated powder and the hydrogen atom content of the Si-H group originally contained in the organohydrogenpolysiloxane compound present per 1 g of the surface-coated powder, From the above, the ratio of unreacted hydrogen atoms remaining in the surface-coated powder was calculated and calculated as the unreacted ratio.

Table 1 shows the values of the unreacted rate in the surface-coated powders obtained in the respective Examples and Comparative Examples.
The smaller the amount of unreacted hydrogen atoms in the Si—H bond, which is a source of hydrogen gas generation, the smaller the value of the unreacted ratio, which is preferable.

[0053]

[Table 1]

As is clear from Table 1, the surface-coated powder treated by the method of the present invention has a very low ratio of unreacted hydrogen atoms, which is a source of hydrogen gas generation, and can be used in various applications without any problems. it can.

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C09C 3/12 PCH (72) Inventor Ikuo Yoshida 1-3-47 Funamachi, Taisho-ku, Osaka, Osaka Teika Co., Ltd. Within

Claims (1)

[Applicant reference number] TAYCA0004 [Claims] 1. A surface of a powder is reacted with an organohydrogenpolysiloxane compound to carry out a surface coating treatment, and then one or more compounds selected from water and lower alcohols are contacted with the surface coated powder. Then, the hydrogen atom of the Si—H bond in the organohydrogenpolysiloxane compound remaining in the coating layer is replaced with another functional group, which is a method for treating a surface-coated powder.