JPS61171705A - Production of styrene resin beads - Google Patents

Abstract

PURPOSE:To obtain the titled beads of high weatherability and electrical conductivity, by dispersing, in an aqueous medium, carbon black-dispersed styrene monomer followed by suspension polymerization in the presence of a specific initiator to stably incorporate the carbon black in high concentration in said beads. CONSTITUTION:A styrene monomer pref. with a pH >=2.8 and average size <=100mmu, dispersed with carbon black normally at such a level as to be 1-10wt% (e.g., styrene, alpha-methylstyrene) is dispersed in an aqueous medium followed by suspension polymerization in the presence of, as an initiator, pref. 0.1-1.0pt.wt. per 100pts.wt. of said monomer, of a benzene ring-free bifunctional organic peroxide (e.g., di-t-butyl peroxymethyl cyclohexane), thus obtaining the objective styrene resin beads.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing styrenic resin particles stably containing carbon black at a high concentration.

(Prior Art) Attempts have been made to color synthetic resins black to improve their weather resistance or to impart them with electrical conductivity by incorporating carbon into them. The following methods are available as methods for producing carbon black-containing styrenic resins.

(1) Carbon black (
A method of cross-cutting styrene resin (hereinafter abbreviated as CB) and styrene resin.

(2) A method in which CB is pretreated with a surfactant or a silane coupling agent, then dispersed in a monomer such as styrene, and suspension polymerized in an aqueous medium (Japanese Patent Publication No. 49-30
702, Japanese Patent Publication No. 50-27079).

(31 CB and monomers such as styrene are mixed and polymerized in a separate device in advance to form a polymer graft carbon black (P
GCB) is then dissolved in a monomer such as styrene and polymerized.

(A method of cross-cutting 41PGCB and styrene polymer using an extruder or the like (Japanese Patent Publication No. 46255/1983).

(Problems to be Solved by the Invention) However, methods using extruders, kneaders, etc. require high temperatures and high shearing forces, so they cannot be said to be economically advantageous manufacturing methods.
Furthermore, since the obtained cut products are in the form of pellets, there are drawbacks such as poor fluidity and lack of flexibility in adjusting the particle size.

On the other hand, PG which has been mixed and polymerized with CB and styrene monomer etc.
Suspension polymerization for CBtl is another option.

Since it requires equipment, it cannot be said to be an industrially advantageous manufacturing method. That is, it is considered to be industrially advantageous to mix CB with styrene monomer or the like and directly carry out suspension polymerization as it is.

However, the problems with this method are (a) the polymerization reaction is slow, probably due to the polymerization inhibiting property of CB, and it takes a long time to complete the double polymerization reaction; and (b) CB reacts with styrene, etc. It takes a long time for CB to change into something with a high affinity for oil-based monomers, and as a result, CB migrates into the aqueous medium and pollutes wastewater.

Furthermore, (c) the dispersion of monomer oil droplets becomes unstable, resulting in agglomeration and irregular particles.

The present invention solves these problems.

(Means for Solving the Problems) The present invention involves dispersing a styrenic monomer in which carbon black is dispersed in an aqueous medium, and suspending the monomer in the presence of a trifunctional organic peroxide having no benzene ring. The present invention relates to a method for producing styrenic resin particles characterized by polymerization.

Carbon blacks that can be used here include commonly available commercially available furnace blacks, channel blacks,
Thermal black, etc. can be used. ・The average particle diameter of the carbon black is too large (and the carbon black is poorly dispersed in the styrene monomer oil droplets, causing it to form in the water phase during suspension polymerization. Carbon black may migrate and contaminate the aqueous phase, making the dispersion unstable.Also, if the pH of carbon black is too low, polymerization will be delayed9.
Polymerization is not completed, which may result in deterioration of the properties of the final product or agglomeration of the reactants due to unstable dispersion during the polymerization. Therefore, the average particle diameter of carbon black is preferably 100 mμ or less in terms of dispersion, and the pH is preferably 18 or higher in terms of polymerizability.

Here, as the styrene monomer, styrene t or α
- Substituted styrene such as methylstyrene, chlorostyrene, t-butylstyrene, etc., including acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate. may contain methacrylic acid esters such as, acrylonitrile, etc.

As the styrenic monomer, one containing 50% by weight or more of styrene or substituted styrene is preferable from the viewpoint of characteristics when used as the expandable styrenic resin particles.

The ratio of carbon black and styrene monomer can be changed depending on the blackness and conductivity of the resulting resin, but it is preferable that the carbon black be blended at 10% by weight based on the total amount. .

If the amount of carbon black is too small, the blackness will decrease,
If the amount is too large, the mechanical strength of the resulting resin tends to decrease.

It is preferable that carbon black be dispersed in a styrenic monomer before polymerization.

In the polymerization of the styrene monomer, a trifunctional organic peroxide having no benzene ring is used as a polymerization initiator. As such a polymerization initiator.

For example, di-t-butylperoxytrimethylcyclohexane, di-t-butylperoxycyclohexane, di-t-butylperoxyhexahydroterephthalate,
Di-t-butyl peroxytrimethyl adipate, di-
Examples include t-butylperoxybutane. These can be used singly or in a mixture of two or more.

When a polymerization initiator having a benzene ring such as benzoyl peroxide is used in the presence of CB, only unsatisfactory results such as one polymerization delay or termination are obtained. Furthermore, when an azobis-based compound such as azobisisobutyronitrile is used, decomposed gas is contained in the oil droplets during polymerization. This made it easy for agglomeration to occur due to the floating phenomenon of oil droplets.

In addition, the resulting resin tends to contain air bubbles. The use of monofunctional organic peroxides that do not have a benzene ring, such as t-butyl peroxyacetate, is undesirable when used alone because they tend to prolong polymerization time, but they can be used in combination with trifunctional organic peroxides. You may.

The total amount of polymerization initiator used is 0.01 to 2 parts by weight, preferably 0.1 to 1.0 parts by weight, per 100 parts by weight of the styrene monomer.
It is 0 parts by weight. If the amount of polymerization initiator is too small, the polymerization will be difficult to complete, and if it is too large, the resulting resin will tend to become brittle or have poor heat resistance.

When a monofunctional organic peroxide having no benzene ring is used in combination, the amount used is preferably 20% by weight or less based on the trifunctional organic peroxide having no benzene ring. In addition, the monofunctional organic peroxide that does not have a benzene ring and is used in combination with 1
Those with a 0-hour half-life temperature of 100 to 110°C (for example,
t-butylperoxyacetate, etc.) are preferred.

The temperature of the polymerization reaction system is determined by taking into account the decomposition temperature of the initiator used and the degree of polymerization of the resulting polymer, but it is 50 to 11
Preferably, the temperature is selected within the range of 0°C. When the polymerization progresses and the conversion rate reaches 95% or more, in order to reduce the residual monomer in the polymer, an organic peroxide that does not have a benzene ring such as t-butyl peroxyacetate is used in combination to raise the temperature of the system to 110~110℃. It is also possible to increase the temperature to 130°C. It is preferable to dissolve the polymerization initiator in the styrene monomer before polymerization, but in some cases it may be added during the polymerization.
ll L? 4 J: “o
In the present invention, suspension polymerization is carried out in an aqueous medium. At this time, calcium phosphate and magnesium pyrophosphate are used as dispersion stabilizers for suspension polymerization.

It is preferable to use a poorly soluble inorganic material such as bentonite.

When a water-soluble polymer is used as a dispersion stabilizer, carbon black added to the oil phase may migrate to the aqueous phase, contaminate the aqueous phase, and make the dispersion unstable.

When an inorganic substance is used as a dispersant, it is preferable to use a small amount of a surfactant such as sodium dodecylbenzenesulfonate. The amount used is O, O
It is preferable that S to 1.0% by weight and the surfactant be selected in the range of 5 to 100 ppm.

In the present invention, in which polymerization is carried out by containing carbon black, 9
For example, it is preferable to use about 2 to 3 times as much dispersant as in the case of general suspension polymerization of only styrene/styrene-based monomers, from the viewpoint of dispersion stability of the single polymerization system. It is also preferable to add them sequentially as the polymerization progresses.

Also, 9. It is preferable to add 0.001 to 0.1% by weight of a water-soluble inorganic salt such as sodium sulfate or sodium sulfite to the aqueous medium for the purpose of particle size adjustment.

When obtaining expandable styrenic resin particles, the content of the blowing agent is preferably 1 to 8% by weight based on the styrene resin. This amount is determined by taking into account the final density of the foam you are aiming for, but it should be between 100g/r and 20g/l! When trying to obtain a foam having a density of 2 to 6% by weight, it is preferable.

It is preferable to impregnate the foaming agent after the 9-polymerization conversion rate exceeds 65%. If the stability of the two-dispersion is more important than the impregnation speed of the blowing agent, the polymerization conversion rate is 95% when the polymerization is almost completed.
It is best to add it at the above point. Also.

The impregnation with the blowing agent may be carried out continuously after the completion of the polymerization, or it may be carried out by newly dispersing the styrenic resin particles obtained after the completion of the polymerization in an aqueous medium.

The method of impregnating the foaming agent can be carried out by adding the foaming agent into an aqueous medium (for example, by press-fitting it).

Furthermore, the styrene resin particles obtained after completion of the nine polymerizations can be impregnated with a blowing agent by other known methods.

As the blowing agent, hydrocarbons, halogenated hydrocarbons, etc. having a boiling point below the softening point of the styrene resin are used.9 For example, hexane, pentane, butane, propane, trichloromonofluoromethane.

Examples include dichlorodifluoromethane.

For the purpose of improving the physical properties of the obtained styrenic resin particles, various additives may be added as necessary during polymerization.

Particularly when obtaining expandable styrenic resin particles, a plasticizer can be added to facilitate foaming.

Such plasticizers include aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as trichloroethylene,
A substance having an affinity for styrenic resins, such as an ester compound such as dioctyl adipate, may be added. At this time, the total amount of plasticizer is 0.2 to 0.2 to the resin content of the particles.
3% by weight is preferred.

In order to impart flame retardancy to the styrene resin particles, commonly used organic halogen compounds can be contained.Also, fine metal powders such as titanium oxide and ruthenium oxide or metals can be added to improve conductivity. An oxide may be included.The amount added is 1 to 10% by weight based on the resin content of the particles.
is preferred. As other additive components, organic dyes and inorganic pigments can be used in combination to adjust the nine color tones.

These additives are added to the styrenic monomer before polymerization.

Preferably, it is dissolved or dispersed in advance.

(Example) Next, two examples of the present invention will be shown.

Example 1 In a reactor with an internal volume of 30 J and a pressure-resistant rotary stirrer.

Deionized water 20 to 9. Tricalcium phosphate (TCP
)60g, sodium dodecylbenzenesulfonate o,
4g of sodium sulfate and 20g of sodium sulfate were added to the oil phase without stirring.The oil phase was prepared by adding 9.5 kg of styrene to carbon black (Mitsubishi Chemical Corporation ■, trade name: 900: Fanes carbon black, average particle size 16 mμ, pH5.0
) 500 g, di-t-butylperoxytril
f'/°hex'''95g・t-p7
19g of ruberoxyacetate was added. Under stirring, the oil phase has a droplet diameter of approximately 0.5 to 1.
．． It was well dispersed at 5 tmn.

After 50 minutes of heating the reaction tank from the outside, the internal temperature was raised to 90'C.
(initial polymerization temperature) and then maintained at this temperature. While observing the dispersion state of the droplets in the tank, add tricalcium phosphate '1109 from time to time until the droplet diameter is 0.5 to 1.5 T.
I controlled it so that it wouldn't get too big. Six hours and 30 minutes after reaching 90°C, the reaction temperature was raised to 120°C over 60 minutes and kept at 120°C for 2 hours. After that, it was cooled and the reactant was taken out, the pH of the suspension was lowered with hydrochloric acid, dehydrated, and washed with water.

Drying was performed to obtain black spherical carbon black-containing polystyrene particles. In this way, suspension polymerization was carried out stably and smoothly. The resulting particles had a content of 92% by weight that passed through a HJIS sieve of 14 meshes and 32 meshes, unreacted styrene monomer was 0.1% by weight, and the weight average molecular weight of polystyrene determined by high performance liquid chromatography (in terms of standard polystyrene). showed 33×104.

Examples 2 to 9 The type and amount of carbon black used were changed as shown in Table 1. Table 1 shows the results of an experiment conducted under the same conditions as in Example 1. In all cases, suspension polymerization was carried out stably and smoothly, and carbon black-containing polystyrene particles were obtained.

Examples 10 to 15 According to the polymerization initiator, its usage amount and conditions shown in Table 2,
The results of an experiment conducted in accordance with Example 1 are shown in Table 2. In each case, suspension polymerization was carried out stably and smoothly, and carbon black-containing polystyrene particles were obtained.

Comparative Examples 1 to 2 In Example 1, benzoyl peroxide (BPO) was used instead of di-t-butylperoxytrimethylcyclohexane.
) was used in an amount of 1 weight per styrene monomer (Comparative Example f-). Three hours after reaching 90°C, the dispersion was destroyed and the mixture became agglomerated. In addition, when 3 BPO concentrations were used and the temperature was raised to 90°C, 5% BPOo was added every time to make the final concentration 6% (Comparative example t> had 9 particles with irregular diameters and a low molecular weight). The results are shown in Table 2.

Comparative example 3
φ In Example 1, N,N′-azobisisobutylnitrile (abbreviated as AIBN) was used instead of di-t-butylperoxytrimethylcyclohexane.

The amount of AIBN used is 1% by weight based on the styrene monomer.
Polymerization was carried out at an initial temperature of 80°C.

During the polymerization, oil droplets often rose to the surface, but by adding a dispersant each time, we were able to synthesize silicone beads. The resulting beads contained numerous air bubbles, and the resulting particles passed through a 14-mesh JIS sieve and stopped at 32 meshes, resulting in a poor yield of 40% by weight. Furthermore, the weight average molecular weight was as low as 13×104, which was disappointing.

The results are shown in Table 2.

Comparative Example 4 In Example 1, only t-butylperoxyacetate was used as a polymerization initiator without using di-t-butylperoxytrimethylcyclohexane. The amount of t-butyl peroxyacetate used is 1% per styrene monomer.
The polymerization was carried out at an initial temperature of 100° C. using % by weight.

The polymerization was continued for 12 hours until the conversion rate reached 95%.

The obtained particles passed through 14 meshes of a JIS sieve and only passed through 32 meshes, weighing 60%, the amount of unreacted monomer was 0.6% by weight, and the weight average molecular weight was as low as 15 x 10'.

The results are shown in Table 2.

Example 16 30I! Deionized water in a stainless steel autoclave 2
okg, 'rcp 609. Sodium dodecylbenzenesulfonate 0.49. Add sulfuric acid Noda 209 and stir at 250 rpm. Next, Mitsubishi Carbona 900 was sogged, and dioctyl adipate 2
Polymerization was carried out in the same manner as in Example 1 by adding an oil layer containing 9.5 to 9 parts of styrene monomer to 80 g of) toluene, 759 g of di-t-butylperoxytrimethylcyclohexane, and 19' of t-butylperacetate. After the polymerization was completed, 40 g of calcium carbonate, 1.0 g of sodium dodecylbenzenesulfonate, and 7009 isopentane were added to this suspension slurry, and the mixture was kept at 100° C. for 5 hours. Thereafter, the suspension was cooled, the remaining gas in the two reaction vessels was discharged, the pH of the suspension was lowered with hydrochloric acid, and the suspension was dehydrated, washed with water, and dried to obtain black spherical carbon black-containing expandable particles. In this way, suspension polymerization was carried out stably and smoothly.

The resulting expandable particles had a content of 90% by weight that passed through a JIS sieve of 14 meshes and stopped at 32 meshes, and contained 5.5% by weight of a 9-blowing agent and 0.6% by weight of toluene.

This material was kept at a temperature of 15° C. for 3 days, and then heated with steam in an open state to pre-foam to 50 g/l. After air-drying the pre-expanded particles for 6 hours, we molded products with complex shapes ranging from a 5 nm thin part to a 40 on thick part, but the pre-expanded particles were evenly filled into the cavity and the surface of the molded product was glossy. There was no unevenness in blackness.

Example 17 Each of the carbon black-containing polystyrene particles obtained in Examples 1 to 9 was impregnated with a blowing agent in the steps shown below. Inner volume 101! Place 5 to 9 parts of deionized water in a stainless steel autoclave. Polyvinyl alcohol (Nippon Gosei KH-20) 259 and sodium polyacrylate 2
-5g of carbon black-containing polystyrene particles were dissolved and then passed through 14 meshes and classified to stop at 32 meshes 4
kg was dispersed. The autoclave was sealed and one reaction tank was heated from the outside to 80°C with 28 g of toluene and 409 g of cyclohexane. 240g of n-butane was press-fitted and 1 hour later 110g
The temperature was raised to .degree. C. over 60 minutes and maintained for 4 hours.

After that, it was cooled and the remaining gas in the reaction tank 9 was discharged.

Dehydration, washing with water, and drying were performed to obtain black spherical carbon-containing expandable particles. These beads have a blowing agent of 5.0 to 6.0
It contained 0.65 to 0.75% by weight of toluene. Thereafter, nine foams were made in the same manner as in Example 16.

I did the molding. All molded products have a glossy surface,
There was also no unevenness in blackness.

Example 18 Each of the carbon black-containing polystyrene particles obtained in Examples 10 to 16 was impregnated with a blowing agent in the following steps.

ioI! 5k deionized water in stainless steel autoclave
g, lj tricalcium phosphate 159. Calcium carbonate 209 and sodium dodecylbenzenesulfonate o
, 7sg was dispersed or dissolved, and 9 was then dispersed in carbon black-containing polystyrene particles 5, which were classified to pass through 14 meshes and stop at 32 meshes. The autoclave was sealed, one reaction tank was heated to 100°C from the outside, and styrene 3
5g, normal hexane 75g and n-hentane 300g
The mixture was press-fitted, kept warm for 5 hours, cooled, residual gas was discharged, the pH of the suspension was lowered with hydrochloric acid, and the same operations as in Example 17 were carried out to obtain carbon black-containing expandable particles.

These beads contained 5.5 to 6.5% by weight of a blowing agent and 0.60 to 0.7% by weight of styrene, and all of the molded products obtained had glossy surfaces and uniform blackness.

Example 19 In Example 16, the conditions for impregnating the blowing agent were changed as follows. 6 hours and 30 minutes after reaching 90@CK (polymerization conversion rate of about 96 inches; determined from the relationship between the specific gravity of oil droplets and the polymerization rate), calcium carbonate 409° sodium dodecylbenzenesulfonate 1. After 1 hour, the temperature was raised to 110°C over 60 minutes, and the temperature was kept for 4 hours. After this.

The same operation as in Example 16 was performed. The obtained foam particles passed through a JIS sieve with 14 meshes and 32 meshes with a 9.
It contained 5.6% by weight of 91 blowing agent and 0.6% by weight of toluene.

The molded product obtained also had a glossy surface and uniform blackness.

(Effect of the invention) According to the present invention, in the presence of CB (carbon black),
Stable suspension polymerization is possible, and the obtained styrenic resin has a sufficiently high molecular weight in a relatively short period of time, and carbon black is well dispersed.

Claims (1)

[Claims] 1. A styrene monomer in which carbon black is dispersed is dispersed in an aqueous medium, and suspension polymerization is carried out in the presence of a bifunctional organic peroxide having no benzene ring. A method for producing styrenic resin particles. 2. The method for producing styrenic resin particles according to claim 1, wherein the carbon black has a pH of 2.8 or more. 3. The method for producing styrenic resin particles according to claim 1 or 2, wherein the carbon black has an average particle diameter of 100 mμ or less. 4. The method for producing styrenic resin particles according to claim 1, 2, or 3, wherein a poorly soluble inorganic substance is used as a dispersion stabilizer in the suspension polymerization.