JPS5947698B2 - Method for improving powder properties of synthetic resin powder - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for improving powder properties of synthetic resin powder.

A commonly used method for obtaining synthetic resin powder from latex is to salt out polymerized latex with salt or acid.

However, when using conventional methods, the powder properties of the resin powder obtained are poor, and various studies have been made to improve this, such as adding improvements to the salting-out method or granulation. The reality is that no method has yet been found that fully satisfies these demands. The powder properties referred to in the present invention refer to three properties of the resin powder: ease of flow (hereinafter referred to as fluidity), ease of clumping and loosening (hereinafter referred to as cake fern), and bulk density. In view of the above drawbacks, the present inventors have conducted various studies and found that the above drawbacks can be overcome by emulsifying and mixing a lubricant into polymerized latex and then adding alkali and salts, thereby completing the present invention.

That is, in the present invention, when obtaining resin powder from emulsion polymerization latex, after adding a lubricant to the latex, salting out is carried out.
The content of the present invention is a method for improving powder characteristics of synthetic resin powder, which is characterized by adding salts and alkalis of 0.05 to 3 PHR to adjust the pH of the system to 6.5 to 8.

The lubricant employed in the present invention includes lubricants commonly used for synthetic resins, such as propylene glycol monostearate, stearyl alcohol, glycerin fatty acid ester, and the like.

These may be used alone or in combination of two or more. For example, it is preferable to emulsify them in advance with soap and mix them into the polymerized latex. The usage amount is 0.1PHR ~ 1.0PH
R) Preferably 0.1 to 0.5 PHR, which can improve the fluidity of the resin powder. Calcium compounds, magnesium compounds, aluminum compounds, etc. are used as the salts. Examples of the calcium compounds include calcium chloride, calcium sulfate, calcium carbonate, etc., and examples of the magnesium compounds used include magnesium chloride, magnesium sulfate, etc.

Best results are obtained by using these salts as an aqueous solution and adding them after salting out the polymerized latex. The amount used is an amount that does not affect the physical properties of the product, preferably 0.0
It is 5-3.0 PHR. When a small amount of salt is used as described above, the cake fern properties and bulk density of the resin powder can be significantly improved by increasing the pH of the system by adding an alkaline solution. In this case, addition of salts or alkalis alone has no effect, and a combination of both salts and alkalis is required. system P
H is considered to be the region where particle surface reactions occur at pH 6. O
The pH is preferably 6.5 to 8.0. Sodium hydroxide, potassium hydroxide, etc. are used as the alkali, and either the salt or the alkali may be added first, and in either case, a resin with good powder properties can be obtained.

On the other hand, for salting out, acids such as hydrochloric acid, acetic acid, and phosphoric acid, or salts such as sodium chloride are used.

These may be used alone or in combination. Although the effects of lubricants, salts, and alkalis are not clear, it is inferred as follows.

The lubricant in the polymerized latex is almost uniformly dispersed in the system, and when it is salted out, the lubricant is adsorbed on the surface of the salted-out particles or encapsulated in the particles, acting as an interparticle lubricant and improving fluidity. On the other hand, if salts such as the above-mentioned calcium and magnesium compounds are present in the particle atmosphere formed by salting out, and the pH of the system is within the range where surface reactions can occur, metals such as calcium and magnesium will be present on the particle surface. A chemical reaction of salt formation occurs, forming a nearly uniform surface adsorption layer and reducing interaction between particles, resulting in improved caking properties and bulk density. As mentioned above, according to the present invention, the apparent specific gravity and caking properties of the resin powder are significantly improved due to the surface modification effect of the resin powder combined with the alkali salt, and the fluidity of the resin powder is further improved due to the effect of the lubricant. Ru.

Incidentally, the present invention is applicable to all latexes obtained by emulsion polymerization. The present invention will be explained below with reference to Examples.

In addition, in the examples, the fluidity index is “Chemical En
gineering,,, January8, l63
168, 1965, the four measured values of the angle of repose, degree of compaction, angle of spatula, and degree of uniformity (or degree of cohesion) are obtained, and points are given according to the conversion table based on the values, and an index is expressed as the sum of these values. The higher the value, the better the fluidity. Also,
The caking property is evaluated by applying a certain load to the resin powder to make it into a lump, applying a certain vibration to it, and expressing the breakability of the lump itself in time (seconds). The shorter is, the better the caking property is.

Example 1 20 kg of pure water and SBR5 were placed in a 401 stainless steel reaction pot.
Kg, styrene 2.5Kg, acrylonitrile 2.5K
g, kyumene hydroperoxide 0.02K9, sodium oleate 0. IKg, EDTAO. OO3suke, F
eSO4O. 5 kg of OOl was charged, and the reaction was carried out for 2 hours while keeping the inner temperature at 50°C to obtain latex (conversion rate 95%).

Using this latex, latex treatment was performed by changing the conditions of lubricant, alkali, and salt, and the powder characteristics of the resulting resin powder were observed.

The results are shown in Table-1. Example 2 Pure water 20Kf1SBR2 in a 401 stainless steel reaction pot
．． 5K! , styrene 3.5Kf1 methyl methacrylate 2.5Kf, acrylonitrile 1.5! , sodium oleate 0.25Kf. ．． EDTA0.003Kbf1F
eS040.0015! was charged and reacted for 6 hours while maintaining the internal temperature at 60°C to obtain a polymerized latex.

Claims (1)

[Claims] 4 In obtaining resin powder from emulsion polymerization latex, after adding a lubricant to the latex, salting out is performed, and further 0.0
Add 5 to 3 PHR of salts and alkalis to reduce system p.
A method for improving powder properties of synthetic resin powder, characterized by adjusting H to 6.5 to 8.