JPS62169836A - Production of expandable styrene polymer particle - Google Patents

Abstract

PURPOSE:To produce the titled particles of a predetermined particle diameter and a sharp particle diameter distribution in an industrially advantageous manner, by suspending an expandable styrene polymer in an aqueous medium and reacting a styrene in specified conditions by low- and high-temperature two-stage polymerization. CONSTITUTION:The titled particles are produced by suspending an expandable polymer in an aqueous medium, feeding a blowing agent to the suspension, applying a pressure to it, suspending small particles of a styrene monomer in the aqueous medium in the presence of a separately added blowing agent while the suspension is being prevented from expanding, adding thereto a low-temperature type polymerization initiator in an amount which is at least a half of the amount necessary for the polymerization of the styrene monomer, feeding thereto a blowing agent in a blowing inhiting amount during the course of heating, adding a styrene monomer to which the remaining part of the low-temperature type polymerization initiator are added, adding the remaining part of the amount of the blowing agent necessary for expansion of the finally obtained expandable styrene polymer and performing a first-stage polymerization at a temperature in the range of (the decomposition temperature for obtaining half-life of 10hr of the low-temperature polymerization type initiator minus 10 deg.C) to (said temperature plus 20 deg.C, increasing the temperature to 100-150 deg.C and performing a second-stage polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention The present invention relates to an industrially advantageous method for producing expanded styrenic polymer particles having a narrow particle size distribution.

(Industrial Application Field) When using the production method of the present invention, it is possible to obtain a desired particle size and a narrow particle size distribution without going through a suspension polymerization step of a styrene polymer that does not contain a blowing agent. Expandable styrenic polymer particles can be advantageously produced industrially.

(Prior Art) Conventionally, various methods have been proposed for producing expandable styrenic polymer particles, but they can be broadly classified into the following two methods.

■ A method in which styrenic polymer particles prepared in advance by suspension polymerization are impregnated with a blowing agent.

■ Adding a blowing agent during suspension polymerization of styrenic polymers,
A method of incorporating a blowing agent into the produced polymer particles.

The first method requires that styrenic polymer particles be produced in advance by suspension polymerization. Since the styrenic polymer particles obtained by suspension polymerization have a continuous and wide particle size distribution ranging from small particles to large particles, producing expandable particles by the first method requires such a From the styrenic polymer particles having a wide particle size distribution obtained by turbidity polymerization, only those having a desired particle size are sieved to have a uniform particle size, and the particles having a uniform particle size are impregnated with a blowing agent. Therefore, this method requires the steps of suspension polymerization of styrenic monomer, sieving step, and blowing agent impregnation step, and has the disadvantage of increasing the number of manufacturing steps.

Compared to the first method, the second method does not require a styrenic polymer suspension polymerization step (or a blowing agent impregnation step),
This has the advantage of having fewer steps, but in order to impregnate the blowing agent during the suspension polymerization process, all of the particles of four particle sizes produced are impregnated with the blowing agent, and moreover, only a few of them can be used as expandable particles. Only particles of a suitable size are used as expandable particles; the remaining particles containing blowing agent with a size unsuitable for use as expandable particles are of little use and pose a major problem in their disposal. there were. That is, among the expandable particles containing a blowing agent produced by the second method, the most commonly used expandable particles are 0.5 to 2.0.
Particles with a particle size in the following range are commercially available as standard products, but particles with particle sizes other than this are rarely commercially available as non-standard particles, which is why this method cannot be obtained. This was a major cause of increasing the production cost of expandable particles.

In addition, as a method for improving the drawbacks of the first method and the second method, small particles of a styrenic polymer that does not contain a blowing agent obtained by sieving are suspended in an aqueous medium, and the suspension system is A styrene monomer with a polymerization initiator dissolved in it is quantitatively added to the styrene monomer, the particles are grown to the desired particle size by suspension polymerization, and the particles are impregnated with a foaming agent to form an expandable styrene monomer with a uniform particle size. A method for producing polymer particles was proposed (Special Publication Publication in 1977).
-2994 publication). This method can produce expandable styrenic polymer particles with a considerably narrower particle size distribution than the conventional method described above;
There was a drawback that fine powdery polymer particles were produced at a ratio of less than 0.0%. Furthermore, this method uses styrenic polymer particles that do not contain a blowing agent and are obtained by suspension polymerization and sieving as a raw material.
As mentioned above, the drawback of increasing the number of steps is unavoidable.

(Problems to be Solved by the Invention) The second method is a method for directly obtaining expandable polymer particles, and is advantageous in terms of the number of steps. Particles containing blowing agents having a particle size unsuitable for use as
If a method is developed to convert particles of small particle size, such as less than rtrm, into particles of a particle size that can be advantageously used as expandable particles (for example, a particle size of 0.5 to 2.0 mm), the above-mentioned It is clear that the second method is industrially significantly more advantageous than the first method. The present invention provides foaming from expandable styrenic polymer particles, such as the small particles obtained by the second method, and from expandable styrenic polymer particles containing a blowing agent unsuitable for this use. The object of the present invention is to provide a method for producing expandable styrenic polymer particles having a particle size suitable for use as expandable styrenic polymer particles.

(b) Structure of the Invention (Means for Solving the Problems) As a result of repeated research in order to solve the above-mentioned problems, the present inventors have discovered that the use of expandable styrene polymer particles as a material Small particles of expandable styrenic polymer containing a blowing agent with an inappropriate particle size, arranged within a certain particle size distribution range 1, are suspended in an aqueous medium of a polymerization reaction vessel, and By supplying a blowing agent and pressurizing the reaction system! lll
@During the turbid polymerization reaction, a specific low-temperature polymerization initiator and a specific high-temperature polymerization initiator are used together under specific conditions while preventing the small particles of the expandable styrenic polymer from foaming. However, this objective could be achieved by carrying out a two-stage polymerization reaction of styrenic monomers at low and high temperatures in the presence of a separately added blowing agent.

That is, the method for producing expandable styrenic polymer particles of the present invention involves the production of small expandable styrenic polymer particles containing a blowing agent whose particle size distribution is within ±20 coefficients of the average particle size. A low-temperature polymerization initiator with a decomposition temperature of 50 to 80°C to obtain a half-life of 10 hours is added to the aqueous medium of the polymerization vessel in which the particles are suspended. It is added at a ratio of 1/2 or more of the amount required for polymerization, and is necessary to suppress the foaming of small particles of the expandable styrenic polymer in the polymerization container during heating to the first stage polymerization temperature. The remaining amount of the low temperature polymerization initiator and the decomposition temperature to obtain a half-life of 10 hours are
A styrenic monomer mainly composed of styrene with a high temperature polymerization initiator added at 0 to 120°C is added continuously or intermittently, and the final expandable styrenic polymer particles are The amount of blowing agent required for foaming is added to the polymerization reaction system, and the temperature ranges from 10°C lower than the decomposition temperature to obtain the 10-hour half-life of the low-temperature polymerization initiator to 20°C lower than the same decomposition temperature. The first stage polymerization reaction is carried out at a temperature within the range of high temperature, and then subsequently at a temperature of 100 to 15
This is a method for producing expandable styrenic polymer particles, characterized in that the second stage polymerization reaction is carried out by raising the temperature to 0°C.

By using the production method of the present invention, it is possible to use small particles of a uniform particle size of an expandable styrenic polymer containing a blowing agent that is unsuitable for use as expandable styrenic polymer particles. The amount of particles produced is extremely small, with 98% of the particles produced.
Expandable styrenic polymer particles having a desired particle size distribution (for example, particle size 0.5 to 2.0 groups) within a narrow range by weight % or more can be easily produced.

The small particles of the expandable styrenic polymer containing a blowing agent used as a raw material in the method of the present invention are particles smaller than the expandable styrenic polymer particles to be produced (for example, particles with a particle size of 0.5 ms). (below), and the particle sizes are arranged so that the particle size distribution is within 120% of the average particle size. If the range of the particle size distribution is wider than the above range, the particle size distribution of the generated expandable styrenic polymer particles will also become wider, which is not preferable. The small particles of the expandable styrenic polymer containing the foaming agent of the raw material may be those obtained by sieving the expandable styrenic polymer particles obtained by the second method, or It may be obtained by various methods, such as those obtained by sieving expandable polymer particles obtained by the method of the present invention.

In the method of the present invention, the polymerization initiator is a low-temperature polymerization initiator whose decomposition temperature is 50 to 80°C to obtain a half-life of 10 hours, and a low-temperature polymerization initiator whose decomposition temperature is 80 to 80°C to obtain a half-life of 10 hours. A high temperature polymerization initiator of 120°C is used in combination.

Examples of low-temperature polymerization initiators include lauroyl peroxide (decomposition temperature is 62°C to obtain a half-life of 10 hours) and azobisisobutyronitrile (decomposition temperature is 63°C).
, t-butylperoxy-2-ethylhexanoate (
72.5℃), benzoyl peroxide (74℃)
) etc., all of which are soluble in styrene monomers are used. The low-temperature polymerization initiator is 1/2 or more of the amount required for polymerization of the styrenic monomer (it may be the entire amount)
is added to water/semi-medium, and the rest is added to the styrenic monomer for use. Even if the low-temperature polymerization initiator is liquid,
It may be in powder form, but powder form is preferable. If a liquid polymerization initiator is directly added to an aqueous medium, the liquid polymerization initiator will dissolve the styrene polymer particles and cause coagulated particles to be generated. Therefore, a liquid low-temperature polymerization initiator is added to the aqueous medium. In this case, it is desirable to add the mixture while stirring and immediately disperse it into an emulsified state.

Examples of high-temperature polymerization initiators include 7-chlorhexanone peroxide (decomposition temperature is 97°C to obtain 44JtJJ for 10 hours), t-butyl peroxypenzoate,
1- (104℃), dicumyl peroxide (11
7°C), which are soluble in styrene monomers are used. The high temperature polymerization initiator is then added to the styrenic monomer and supplied to the polymerization reaction system.

One type of each of the low-temperature polymerization initiator and the high-temperature polymerization initiator may be used, or two or more types may be used in combination.

The amount of the polymerization initiator used is 0.01 to 1.0% by weight, preferably 0.01 to 1.0% by weight, based on the styrenic monomer (ie, styrene or a monomer mixture containing styrene as a main component). The content of the high temperature initiator is 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight, based on the styrenic monomer. Note that if the amount of low-temperature polymerization initiator added to the aqueous medium is less than 1/2 of the amount required for polymerization of the styrenic monomer added to the polymerization reaction system, fine particles in the generated expandable particles Since the proportion of particles increases, in the present invention, the low-temperature polymerization initiator is added to the aqueous medium in an amount greater than 1/2 of the amount required for polymerization of the styrenic monomer.゛The amount of polymerization initiator necessary for the polymerization of styrenic monomers that can be added to the polymerization reaction system is determined so that the molecular weight of the expandable styrenic polymer particles to be produced is the optimum molecular weight for moldability during molding, expansion ratio, etc. Adjust accordingly.

In the method of the present invention, a blowing agent is added to the polymerization reaction system, and a part of the blowing agent is added to the expandable styrene suspended in the polymerization vessel system during the temperature rise to the first stage polymerization temperature. The remaining blowing agent is added in an amount that suppresses the foaming of small particles of the styrenic polymer, and the remaining blowing agent is added in an amount necessary for foaming the expandable styrenic polymer particles that are finally obtained after addition of the styrenic monomer. Added to the polymerization reaction system in gaseous form.

Part of the blowing agent is vaporized and added to the space of the polymerization reaction vessel while the temperature is raised to the first stage polymerization temperature. This is to maintain the pressure at a pressure equal to or higher than the partial pressure of the blowing agent contained in the small particles of the styrenic polymer, thereby suppressing the foaming of the small expandable particles due to temperature rise. The amount of blowing agent added to the polymerization vessel is 5 to 15% by weight of the suspended small particles of expandable styrenic polymer.

If the amount added is too small, it will not be possible to suppress foaming of the foamable small particles that have been clouded in advance due to the temperature rise during suspension polymerization, and the reaction system will become solidified due to foaming during the polymerization reaction, resulting in the final goal. It becomes impossible to produce expandable styrenic polymer particles. Furthermore, if the amount of the blowing agent added is too large, it may cause the generation of coagulated particles or fine particles. When to add the blowing agent in gaseous or liquid form into the polymerization vessel,
Theoretically, this is the temperature at which the glass transition temperature (TP) of the expandable styrenic polymer particles is reached. The Ty of the styrene homopolymer is 103° C., and if a blowing agent is contained, the apparent TP decreases depending on the content. For this reason, in the present invention, the temperature of the polymerization reaction system is preferably 40 to 60% during the temperature rise of the first stage polymerization reaction.
Add when it reaches °C.

The remainder of the blowing agent is added to the polymerization reaction system in liquid or gaseous form at an appropriate time after the addition of the styrene monomer, for example, from before the start of the first-stage polymerization reaction to the beginning of the second-stage polymerization reaction. It is. The amount of the blowing agent added in the latter stage is such that the amount of the blowing agent contained in the finally obtained expandable styrenic polymer particles is 2 to 107 tt%.

The blowing agent used in the production of the expandable styrenic polymer particles of the present invention, i.e. the blowing agent contained in the small particles of the raw material expandable styrenic polymer, the expandable styrenic suspended in the polymerization vessel. Various foaming agents can be used for both the foaming agent added to suppress foaming of small polymer particles and the foaming agent added to the polymerization reaction system added at a later stage. There is no problem even if different agents are used. The blowing agents used in each case include, for example, aliphatic hydrocarbons such as propane, butane, and pentane; alicyclic hydrocarbons such as cyclobutane and cyclopentane; halogenated hydrocarbons such as methyl chloride and dichlorodifluoromethane; Examples include hydrogen.

The styrenic monomer added to the polymerization reaction system in the method of the present invention is a styrene monomer or a monomer mixture containing styrene as a main component, that is, styrene alone or styrene as a main component and a small amount of other monomers. It is a monomer mixture with a monomer. Other monomers include, for example, α-methylstyrene, divinylbenzene, acrylonitrile, esters of alcohols having 1 to B carbon atoms and acrylic acid or methacrylic acid (for example, methyl methacrylate,
(ethyl acrylate, etc.), monomethyl maleate, monomethyl fumarate, dimethyl maleate, monoethyl itaconate, etc.

In the present invention, a suspension stabilizer is used to stabilize small particles of expandable styrenic polymer containing a blowing agent in an aqueous medium. Examples of the suspension stabilizer include organic suspension stabilizers such as polyvinylpyrrolidone, gelatin, carboxymethylcellulose, and hydroxy7 alkylcellulose; and inorganic suspension stabilizers such as calcium or magnesium salts of phosphoric acid or carbonate. Especially inorganic! @
Turbidity stabilizers are preferred, especially the combination of tricalcium phosphate and the anionic surfactant sodium dodecylbenzenesulfonate as a stabilizing aid.

(Examples etc.) Below, Examples and Comparative Examples will be given and further explained in detail. "%" in these examples means % by weight.

Example 1 Pure water + 000y and tribasic calcium phosphate were placed in a polymerization container with a capacity of 3t. Ojg, 2.0 y of 1% aqueous solution of sodium dodecylbenzenesulfonate, 5 y of butane as a blowing agent.
Expandable styrene polymer particles 165F containing 698% and sieved to a particle size of 0.5 to 0.37 m and benzoyl peroxide 3.3F (total amount) were added and stirred at 400 rpm to form a uniform dispersion.

4 while heating this @turbid dispersion to 85℃ under stirring.
When the temperature of 0° C. was reached, 12.92 parts of butane was liquefied and fed into the polymerization vessel in an amount corresponding to 7.5 parts of the expandable styrene polymer particles. Next, after the temperature of the polymerization system reached 85°C, it was kept at the same temperature for 7 hours, and over 5 hours after reaching 85°C, 1.65y of butyl perbenzoate and 16.5jF of dichlorohexane were added. A solution of 825y in styrene was added continuously at a rate of 165y per hour.

After the addition of the styrene solution was completed, 79F butane was added in liquid form in an amount equal to 8 parts by weight based on the total amount of the raw material expandable styrene polymer particles and styrene monomer.
The temperature was raised from 85°C to 110°C over 1.5 hours, and 1
The polymerization was completed by holding at 10° C. for 4 hours.

After completion of the polymerization, the particles were cooled, water was separated, and the resulting expandable styrene polymer particles had a particle size distribution, appearance, and vapor content as shown in Table 1.

In addition, the foamed styrene polymer particles were heated at 98°C and 11.0A.
The density of the pre-expanded particles obtained by heating with I+/- steam is as shown in Table 1.
The surface condition of the foam molded product obtained by filling the cavity of a mold of 100 w x 200 cm and heating with 0.7 kg/cII steam for 20 seconds to form a foamed product was as shown in Table 1.

Example 2 In a 3 ton polymerization vessel, 100 y of pure water, 5.0 y of tertiary calcium phosphate, 2.0 y of a 1 t aqueous solution of sodium dodecylbenzenesulfonate, and a foamable styrenic polymer containing 5.63% of pentane as a blowing agent were placed. Particles 165y, which were sieved to a size of 0.5 to 0.37, and the total amount of benzoyl peroxide 3.3y were added, and the mixture was stirred at 400 rpm to uniformly disperse the particles to obtain a suspension.

Next, this hanging fJAM was heated to 40℃ while heating it to 85℃.
Then, 1 2.9 y was added in liquid form to the suspension in an amount of 7.5% by weight based on the expandable styrenic polymer particles in which pentane was suspended. After the suspension reaches 85°C,
It was kept at 5°C for 7 hours, during which time 1.65% of L-butyl perbenzoate and 16.57% of 7-chlorohexane were added to 825% of
After reaching 85° C., a solution of styrene monomer was added continuously and quantitatively at a rate of 165 P per hour over a period of 5 hours.

Next, pentane as a blowing agent was added in an amount of 8% by weight based on the total amount of the expandable styrenic polymer particles and monomer.
y was added, and then the temperature of the suspension was raised from 85°C to 110°C over 1.5 hours, and then heated at 110°C for 4 hours to complete the polymerization of the styrene monomer, forming expandable styrene polymer particles. I got it.

Thereafter, evaluation was carried out in the same manner as in Example 1 by preliminary foaming and foam molding. The results are shown in Table 1.

Example 3 In a 3t polymerization vessel, 1000ml of pure water, 5.07ml of tertiary calcium phosphate, and 1% of sodium dodecylbenzenesulfonate were added.
Aqueous solution 2.0%, pentane as blowing agent 5.44%
Expandable styrenic polymer particles containing 1.45 to 1.24
300j' of the sieved particles and a total amount of 2.4y of benzoyl peroxide were added to the solution and stirred at 400 rpm to uniformly disperse the particles to obtain a suspension.

Next, at 40°C while heating this suspension to 85°C,
Pentane was added in a liquid form in an amount of 30 pentane at a ratio of 10 parts by weight to the suspended expandable styrenic polymer particles. @After the suspension reached 85°C, it was kept at 85°C for 5 hours, during which time 1.2 f of t-butyl perbenzoate was added.
12.0 g of chlorhexane were dissolved in 600 y of styrene monomer and the solution was continuously heated at 15 g per hour.
0y was quantitatively added to the suspension over 4 hours after reaching 85°C.

Thereafter, the imaginary alloy was completed in the same manner as in Example 1, and the obtained expandable styrene-rich particles were pre-foamed and foam molded.

The results are shown in Table 1.

Example 4 In a 3I polymerization vessel, pure water 1000F and tertiary phosphorus calcium s, o? and 1% of sodium dodecylbenzenesulfonate
Aqueous solution 2. Or, 165 F particles made by sieving a foamable styrenic polymer containing 2.18% butane i as a blowing agent to a size of 0.5 to 0.37 m, and a history of benzoyl peroxide 3.
32 total t was added and stirred at 400 rpm to uniformly disperse and obtain a suspension.

Next, at 60° C. while heating this suspension up to 85° C., the expandable styrene thread body particles V in which butane was suspended were heated.
12.92 was added at a ratio of 7.5 liters to C.

When the suspension reached 85°C, it was kept at 85°C for 7 hours, during which time 1.659 butyl perbenzoate and 16.5 cyclohexane dissolved in a total of 8252 styrene monomers were continuously added. Quantitatively, 1651 per hour,
After reaching 85°C, the mixture was added for 5 hours.

Next, 8'N weight of 792 butane as a blowing agent was added to the total amount of polymer particles and *2 bodies, and from 85℃ to 110℃
After raising the temperature over 1.5 hours to 110°C, the polymerization was completed by heating at 110°C for 4 hours to obtain expandable styrene styrene composite particles.

Thereafter, preliminary foaming and molding @foam molding were performed in the same manner as in Example 1.

Comparative Example 1 Using expandable styrenic polymer particles, a styrene monopolymer was tested under the same conditions as in Example 1, except that no blowing agent was added to suppress foaming during the temperature rise. Normal expandable styrene polymer particles could not be obtained even when VC light foaming was carried out at 85° C.ff1J with a single humidity content and a styrene monomer was added.

Comparative Example 2 The same polymerization conditions as in Example 1 were used, except that butane, which was added to suppress foaming of cloudy expandable styrene sub-aggregate particles, was suspended) Polymerization of styrene monomer was carried out in the same manner as in Example 1, except that J4 was 4.5 mm thick relative to the body particle weight.

In this case, as in Comparative Example 1, foaming occurs before the first polymerization degree of 85°C is reached, and even if a styrene monomer is added and polymerized, normal expandable styrene polymer particles cannot be obtained. Ta.

Reference Example Under the same polymerization conditions as in Example 1, however, after adding the styrene car polymer mixture and without adding a blowing agent, monostyrene was polymerized to obtain expandable styrene polymer particles. .

Thereafter, preliminary foaming and foam molding were performed in the same manner as in Example 1.

The results are shown in Table 1.

Claims (1)

[Claims] 1) A polymerization vessel in which small particles of an expandable styrenic polymer containing a blowing agent whose particle size distribution is within ±20% of the average particle size are suspended. Add a low-temperature polymerization initiator whose decomposition temperature is 50 to 80°C to obtain a half-life of 10 hours to the aqueous medium to the polymerization reaction system. 1/2 of the amount required for polymerization of styrenic monomers. After adding the blowing agent in an amount that suppresses foaming of the small particles of the expandable styrenic polymer into the polymerization vessel during the temperature rise to the first stage polymerization temperature, the remainder of the low-temperature polymerization initiator, and 1
The decomposition temperature is 80-120℃ to obtain a half-life of 0 hours.
A styrenic monomer mainly composed of styrene with a high-temperature polymerization initiator added thereto is added continuously or intermittently, and further the necessary amount is added for foaming of the finally obtained expandable styrenic polymer particles. The remaining blowing agent is added to the polymerization reaction system, and the temperature ranges from 10°C lower than the decomposition temperature to 20°C higher than the decomposition temperature to obtain a 10-hour half-life of the low-temperature polymerization initiator. Production of expandable styrenic polymer particles characterized by carrying out a first-stage polymerization reaction at a temperature of 100 to 150°C, and then subsequently raising the temperature to a temperature of 100 to 150°C to carry out a second-stage polymerization reaction. Method. 2) A patent claim in which the blowing agent added to suppress foaming of the suspended small particles of expandable styrenic polymer is added when the temperature of the polymerization reaction system reaches 40 to 60°C. The method described in Scope 1. 3) The amount of blowing agent added to suppress foaming of the small particles of expandable styrenic polymer is 5 to 15% by weight of the small particles. Method described. 4) The method according to claim 1 or 2, wherein the blowing agent is added in an amount of 2 to 10% by weight in the finally obtained expandable styrenic polymer particles.