JPS62143944A - Production of expandable styrene polymer bead - Google Patents

Abstract

PURPOSE:To obtain the titled polymer bead having narrow particle size distribution and containing a foaming agent uniformly impregnated to the core part of the bead, by adding a foaming agent, a polymerization initiator and a styrene monomer to an aqueous suspension of styrene polymer beads having uniform particle diameter and polymerizing the monomer. CONSTITUTION:Styrene polymer beads produced by suspension polymerization are sieved to collect beads having diameters falling within + or -20% from the average diameter. The sieved beads are suspended in water and the suspension is added with a polymerization initiator having a decomposition temperature of 50-80 deg.C corresponding to the half-life period of 10hr. The amount of the initiator is >=1/2 of the amount necessary for the polymerization of a styrene monomer to be added to the aqueous suspension afterwatrd. The aqueous suspension is further added with a foaming agent, a styrene monomer, a polymerization initiator having a decomposition temperature of 50-80 deg.C corresponding to the half-life period of 10hr and the remaining part of the above polymerization initiator in a state impregnated in the styrene monomer and the monomer is polymerized to obtain the objective bead.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing expandable styrenic polymer particles having a narrow particle size distribution.

[Prior art]

Conventionally, expandable styrenic polymer particles are generally produced by suspending styrene monomer that melts a polymerization initiator in water, and
Suspension polymerization is carried out at 0-120°C, and an organic blowing agent having a lung point lower than the softening temperature of the styrenic resin is added during or after the polymerization reaction to the resulting styrenic polymer particles. However, the particle size distribution of the particles obtained by this suspension polymerization is difficult to maintain even if various stirring conditions, polymerization temperature, time, styrene monomer addition method, etc. are selected. It has been considered that it is difficult to obtain a uniform product, and that it is inevitable that the foamable styrenic polymer produced has a continuous and wide particle size distribution ranging from small particles to large particles.

Expandable styrenic polymer particles with such a wide particle size distribution are filled into a mold with steam holes, and the molded foam products obtained by steam heating and foam molding have uneven bulk specific gravity and compressive strength. As a result, it becomes necessary to conduct a product qualification test.

Therefore, it is necessary to sieve the particles into particles of uniform particle size. However, it is difficult to incinerate expandable styrenic polymer particles that have been sieved as non-standard grade because the particles themselves contain organic blowing agents. It is necessary to transport and remove the blowing agent from the particles before disposal.

As a method to improve the drawbacks of this conventional method, pre-sieved styrenic polymer particles (which do not contain a blowing agent)
is suspended in water, a styrenic monomer with a polymerization initiator dissolved in it is quantitatively added to this suspension system, the particles are grown by suspension polymerization to a desired particle size, and then a blowing agent is impregnated to reduce the particle size. A method for producing uniformly uniform expandable styrenic polymer particles has been proposed (Japanese Patent Publication No. 49-2994)0 [Problems to be solved by the invention] This method has a considerably narrower particle size distribution than previous methods. Although it is possible to produce styrene-containing polymer particles,
There is a drawback when fine particles having a particle size outside the target size are produced in quantities of 8 to 13M.

In order to improve the drawbacks of these conventional methods, the present invention aims to produce expandable styrenic polymer particles with a narrow particle size distribution, which produces a small amount of fine particles, and whose theoretically obtainable target particle amount is 98% by weight or more. The present invention provides a method for manufacturing.

[Specific measures to solve the problem]

In the present invention, styrenic polymer particles obtained by suspension polymerization are sieved so that the particle size is ±20% of the average particle size.
The particles were suspended in water, and the decomposition temperature to obtain a half-life of 10 hours was between 50% and 8%.
A polymerization initiator at 0°C is required for the polymerization of styrenic monomers that are later added to the aqueous suspension system. A polymerization initiator containing a blowing agent and a styrene monomer as main components and having a decomposition temperature exceeding 80°C and below 120°C to obtain a half-life of 10 hours and the above-mentioned polymerization initiator is added to water and added to the aqueous suspension system. A styrene monomer containing a remainder of a polymerization initiator having a decomposition temperature of 50 to 80°C is added continuously or intermittently, and then the styrene monomer is polymerized. The present invention provides a method for producing expandable styrenic polymer particles.

(Styrenic polymer particles) The styrene polymer particles used in the present invention and added to water in advance are generally resin particles obtained by suspension polymerization. It is necessary to adjust the particle size to the required range in advance by sieving. If the particle size is the same, the range is ±20% of the average particle size.
They are sieved and arranged so that The particle size of the final styrenic polymer particles obtained in the present invention is determined by the particle size of the sieved particles added in advance to water and the ratio of the particle amount to the styrene monomer. However, if the particle size range of the particles used is 120% or more of the average particle size, the particle size distribution of the produced particles will also be wide.

(M Intermediate Initiator) Next, in the present invention, the polymerization initiator used is one with a low decomposition temperature that is added to the aqueous suspension before starting the polymerization of the styrenic monomer, and one that is added to the aqueous suspension after the polymerization of the styrenic monomer. There is a type with a high decomposition temperature that is used by dissolving it in the styrene monomer added to the turbid system.

The polymerization initiator added to the suspension before the start of the first reaction must be a radical polymerization initiator with a decomposition temperature of 50 to 80°C to obtain a half-life of 10 hours, and the styrene monomer added later. Add 1/2 or more of the amount required for body weight, preferably the entire amount, to water. Examples of such polymerization initiators include lauroyl peroxide (62°C), azobisisobutylnitrile (63°C), t-butylperoxy-2-ethylhexanony (72.5°C), and benzoyl peroxide (74°C). ℃) and other styrene monomers. The polymerization initiator with a low decomposition temperature that is added to water before the start of polymerization can be either liquid or powder, but if it is liquid, it will dissolve the styrene polymer particles and cause the generation of coagulated particles. It is preferable to add it in an emulsified state or under stirring. In addition, in the case of powder, there is no need to operate the above ti, and it is preferable to use powder in the present invention.

Next, as a polymerization initiator dissolved in the styrene monomer that is added later to the aqueous suspension system, radical polymerization with a decomposition temperature exceeding 80°C and below 120°C to obtain a half-life of 10 hours is required. An initiator, specifically one that is soluble in styrene monomers, such as cyclohexanone peroxide (97°C), t-butyl peroxypene shade (104°C), dicumyl peroxide (117°C) It is.

However, if the total amount of the polymerization initiator, which has a decomposition temperature of 50 to 80°C to obtain the aforementioned 10-hour half-life, is not added in advance to the water, at this time, the remainder is used to initiate polymerization at a high decomposition temperature. It is dissolved in a styrene monomer together with the agent and added to an aqueous suspension system.

As the polymerization initiator, either a low temperature decomposition type or a high temperature decomposition type may be used in combination.

In the case of a polymerization initiator whose decomposition temperature is 50 to 80°C in order to obtain a half-life of 10 hours, the amount of the polymerization initiator added should be determined by heating the styrene monomer or styrene spinning wheel containing styrene as the main component. The weight ratio is 0.01 to 1.0% by weight, preferably 0.1 to 0.6N. In addition, in order to obtain a half-life of 10 hours, a polymerization initiator whose decomposition temperature is above 80°C and below 120°C should be 0
, O2N2.0% by weight, preferably 0.05 to 0.5% by weight.

In the present invention, the method of adding the polymerization initiator is such that the decomposition temperature of the polymerization initiator is 50-80 to obtain a half-life of 10 hours.
1/ of the amount required for polymerization of styrenic monomers to which a polymerization initiator is added later at ℃! The entire amount of the above is preferably added to water or suspension water of styrenic polymer particles before the start of polymerization. Furthermore, the amount of residue of the low-temperature decomposition type polymerization initiator and the decomposition temperature to obtain a half-life of 10 hours are 8.
A high-temperature decomposition type polymerization initiator with a temperature exceeding 0.01°C and below 120°C is used by dissolving it in a styrene monomer to be added later and adding it to an aqueous suspension system. In this case, if the amount of the low-temperature decomposition type polymerization initiator added to the water is less than 1/2 of the amount required for polymerization of the styrene monomer, fine particles will be generated.

(Styrenic monomer) The styrene monomer used in the examples of the present invention includes styrene or a mixture containing styrene as a main component, such as ebastyrene and α-methylstyrene, divinylbenzene, acrylonitrile, and carbon atoms of 1 to 8. Esters obtained by reacting alcohols with acrylic acid or methacrylic acid, such as methyl methacrylate, ethyl acrylate, etc., mixtures with monomers such as monomethyl maleate, monomethyl fumarate, dimethyl maleate, monoethyl itaconate, etc. A monomer mixture containing styrene as the main component is used.

(Blowing agents, plasticizers) Examples of organic blowing agents include those having a boiling point lower than the softening point of the styrene resin, which is a styrene thread-based resin (17) fi compound, such as hexane, pemethane, butane, fluoropane, pentane, trichloromonofluoromethane,
Methyl chloride, dichlorodifluoromethane, etc. are used.

The blowing agent is used in an amount of 2 to 2 parts per 100ii parts of the styrenic polymer particles and styrenic monomer added to the aqueous suspension system.
Use in a proportion of 1 oz.

The blowing agent is added to the aqueous suspension system in an amount of 20% by weight or more of the added amount, preferably total-ff, and the temperature of the aqueous suspension system in which the styrenic monomer is dispersed has a half-life of 10 hours. It is necessary to add the polymer within 2 hours after the decomposition temperature of the polymerization initiator reaches 110 to +20°C of the decomposition temperature of the polymerization initiator, which is 50 to 80°C.

If the blowing agent is added to the aqueous suspension system after the suspension polymerization of the styrenic monomer is completed, the blowing agent may reach the center of the polymer particles due to the high molecular weight of the resulting styrenic polymer particles. The polymer particles are not impregnated and are unevenly distributed near the surface of the particles, which means that the content of the blowing agent contained in the polymer particles is low, making it impossible to obtain a molded foam product with a high expansion ratio. In order to obtain expandable polymer particles in which the center of the polymer particles is impregnated with the blowing agent using the blowing agent post-impregnation method, the molecular weight of the styrenic polymer particles obtained by shortening the polymerization time is reduced and the blowing agent is added to the foaming agent. It is conceivable that this may facilitate the impregnation of

In this case, the molecular weight of the sieved styrenic polymer particles that have been added to the aqueous suspension system in advance as the core is high, but the newly formed styrenic polymer particles in the surface portion (layer portion) have a high molecular weight. Because the molecular weight is low, when attempting to foam mold the resulting polystyrene polymer particles, the heated steam causes the surface of the expandable particles to dissolve, making it difficult to obtain a molded foam with a good appearance. Can not. Furthermore, the mechanical strength of the product is also low.

In order to facilitate impregnation with a blowing agent, a plasticizer for styrenic polymer particles such as cyclohexane, xylene, toluene, or ethylbenzene is added to 100 parts of the total of styrenic polymer particles and styrene monomer. It may be present in an aqueous suspension system in an amount of 2 to 10 weight units. This plasticizer may be added together with the styrenic monomer.

(Suspension Stabilizer) The suspension stability law used to suspend styrene polymer particles of uniform particle size in water is as follows:
Organic suspension stabilizers such as polyvinyl alcohol, polyvinylpyrrolidone, gelatin, carboxymethyl cellulose, hydroxyl cellulose, phosphoric acid or carbonic acid
Examples include inorganic suspension stabilizers such as a salt and Mg salt. Among them, inorganic ones are preferable, and in particular, it is preferable to use a combination of tricalcium phosphate and sodium dodecylbenzenesulfonate, which is an anionic surfactant as a stabilizing agent (suspension polymerization). The system polymer particles are suspended in water, and a polymerization initiator (low-temperature decomposition type polymerization initiator) having a decomposition temperature of 50 to 80°C to obtain a half-life of 10 hours is later added to the aqueous suspension system. 1/ of the amount required for polymerization of styrenic monomer! The above is added to water, and the aqueous suspension system contains a blowing agent and styrene monomer as main components, and the decomposition temperature exceeds 80°C to obtain a half-life of 10 hours.
The following polymerization initiator (high-temperature decomposition type polymerization initiator) and a styrenic monomer containing the remainder of the above-mentioned polymerization initiator whose decomposition temperature is 50 to 80°C are added continuously or intermittently, and the aqueous The suspension system is heated at a temperature of -10 to +20°C (usually 60 to 95°C) above the decomposition temperature of the low-temperature decomposition type polymerization initiator.
At this time, it is necessary to add at least 20% by weight of the blowing agent to the aqueous suspension system within 2 hours after the temperature for the prepolymerization is reached.) Next, the high temperature decomposition type polymerization initiator is heated to a temperature higher than the temperature at which it decomposes (usually io
o to 150°C), and the temperature is 1e1 to 150°C.
This was maintained for 5 hours to complete the polymerization of the styrene monomer.

Note that even if the blowing agent is added to the aqueous suspension system during the addition of the styrenic monomer to the aqueous suspension system, it cannot be added before the addition.
The blowing agent may be
It is necessary that at least t% by weight is added before 2 o'clock after reaching the prepolymerization temperature. Therefore, whether the blowing agent is added to the aqueous suspension system before heating to the prepolymerization temperature or during heating to the prepolymerization temperature, it should be added within 2 hours after the prepolymerization temperature is reached. It's okay.

(Expansible styrenic polymer particles) The expandable styrenic polymer particles obtained by the method of the present invention are uniformly impregnated with a blowing agent up to the center of the core, and
~50? A molded foam product with a bulk density of /l can be obtained. Moreover, its particle size distribution is narrow and there is no need for sieving.

Example 1 Into a polymerization vessel of 31, pure water, so on, and tricalcium phosphate 4. Or and 1% aqueous solution of sodium dodecylbenzenesulfonate 1.0? , 0.42-0.5 sifted styrene electrolyte particles (average particle size 0.46+111) 7
52 and benzoyl peroxide (decomposition temperature 74°C)
A total amount of 3.76 f was added and stirred at 400 rpm to uniformly disperse the mixture to obtain an aqueous suspension.

Next, while heating this aqueous suspension to t-80°C,
7. pentane at 0°C based on the total amount of styrene polymer particles and styrene monomer. 52.5 F of the percentage of OMf%
Added to aqueous suspension system. After the aqueous suspension reaches 80°C,
The temperature was kept at 80°C for 5 hours, during which time a solution of 1.25 t-butyl perbenzoate dissolved in 6252 styrene monomer was added continuously and quantitatively at a rate of 125 tons per hour over 5 hours, and then After raising the temperature of the aqueous WA suspension from 80°C to 120°C over 1.5 hours, it was further heated at 120°C for 2 hours.
The suspension polymerization of styrene was completed by heating for a certain period of time.

After completion of polymerization, the mixture was cooled, the aqueous phase was separated, and the resulting expandable styrenic polymer particles were measured for particle size distribution, volatile content, and weight average molecular weight of the particles before foaming. In addition, the expansion ratio of pre-expanded particles obtained by heating the particles with steam at 98° C. and 1.0 knots/d and the molecular IT of the surface layer and center of the pre-expanded particles were measured. Furthermore, the pre-expanded particles were
The surface condition of the foamed molded products obtained by shining a light "A" into the cavity of a mold measuring 0 m, width 100 m, and height 20 m, heating with 0.7 kp/- steam for 20 seconds, and then cooling was evaluated. 〇As shown in Table 1, the molecular weight of the expandable styrenic polymer particles is measured as follows:
The particles were heated with steam to expand them up to 50 times, and the surface layer of the foamed particles was cut to a thickness of 0.1 m, and the molecules of the particle surface layer were 1i.
(i-measurement was carried out, and then the center of the foam particles was cut out to measure the molecular weight.
RI ROTAR, polystyrene gel as filler (5h
odex A-80M), was measured using chloroform as a solvent.

Comparative Example 1 In a polymerization vessel of 31, pure water soy and tertiary calcium phosphate 4. Oy and 0')" 1% aqueous solution of sodium tesilbenzenesulfonate 1.01.0.5-0.42 m
Add 125v of sieved styrene polymer particles and 2.51ml of benzoyl peroxide to 4oOrpm.
Stir to disperse uniformly.

Next, this suspension was heated to 80°C and kept at 80°C for 5 hours, during which time 1.25% of Vct-butyl perbenzoate was added.
f dissolved in styrene monomer of 6251 was added quantitatively at 125v/hour over 5 hours, and pentane was added at a rate of 7% to the total amount of styrene polymer particles and monomer. .0 'M [percentage of 5 2.5
f was added.

Next, the temperature of the aqueous suspension was raised from 80° C. to 120° C. over 1.5 hours, and then further heated at 120° C. for 2 hours to complete suspension polymerization.

Table 1 shows the results of analyzing the expandable styrenic polymer particles after the post-treatment in the same manner as in Example 1.

Comparative Example 2 In a polymerization vessel of 31, pure water 800F and tertiary calcium phosphate 4. Of, 125 f of sieved styrene polymer particles were added to 1.02.0.5 to 42 cm of an aqueous solution of sodium dodecylbenzenesulfonate, and 2.52 x of benzoyl peroxide was added to 4 o.

Stir at rpm for uniform dispersion.

Next, this suspension was heated to SO'C and kept at 80°C for 5 hours, during which time 1.25f of t-butyl perbenzoate was added to styrene monomer 6252, and pentane was added to the styrene polymer particles and the monomer. The 5 2.5 F dissolved solution at a rate of 7.0 weight range relative to the total amount of was continuously added quantitatively at 125 f per hour to the aqueous suspension over a period of 5 hours, and then The aqueous suspension was heated from 80C to 120'C''1 over 1.5 hours, and then further heated at 120C for 2 hours to complete suspension polymerization.

Table 1 shows the results of analyzing the expandable styrenic polymer particles after the post-treatment.

Example 2 Under the same polymerization conditions as in Example 1, however, the fi of pentane added at 60°C during heating to 80°C was changed to a total amount of 52°C.
．． The remaining 39.5% is 13.1t, which is 25% by weight of 59.
After the addition of the 4 f styrene monomer was completed, expandable styrenic polymer particles were obtained in the same manner except that the addition was carried out at 80°C.

Comparative Example 3 Under the same polymerization conditions as in Example 1, however, the amount of pentane added at 60°C during heating to 80°C was changed to a total amount of 52.
7.9 tons, which is 15% by weight of 51, and the remaining 44.6 F
Expandable styrenic polymer particles were obtained in the same manner except that after the addition of the styrene monomer was completed, the mixture was added at 80°C.

Example 3 Under the same polymerization conditions as in Example 1, however, the timing of adding pentane was changed to 100°C after reaching the first stage polymerization temperature of 80°C.
Expandable styrenic polymer particles were obtained in the same manner except for the fraction.

Comparative Example 4 The same polymerization conditions as in Example 1 were used, except that the timing of adding pentane was changed to 2.2.
Expandable styrenic polymer particles were obtained in the same manner except that the heating time was changed to 5 hours.

Example 4 Polymerization conditions were the same as in Example 1, except that butane was replaced with butane in a proportion of 10% by weight based on the total amount of styrene polymer particles and styrene monomer.75. Of8
Expandable styrenic polymer particles were obtained in the same manner except that the mixture was added at 40°C during the temperature rise to 0°C.

Example 5 Under the same polymerization conditions as in Example 4, however, before the start of polymerization, cyclohexane was used as a plasticizer at a ratio of 2% by weight based on the total amount of styrene polymer particles and styrene monomer.
) was added, and further, after the addition of the styrene monomer was completed, butane was added at 52.5 F, but expandable styrenic polymer particles were obtained in the same manner.

Example 6 The same polymerization conditions as in Example 5 were used, except that cyclohexane was used as a plasticizer at a ratio of 2.0 weight 152 to the total amount of styrene polymer particles and styrene monomer, and butane was added as a blowing agent. Expandable styrene obtained in the same manner except that 52.5 F at a ratio of 7.0 weight range to the total amount of styrene polymer and styrene monomer was added at 60 °C during heating to 80 °C. The results for the polymer particles are shown in Table 1.

(Margin below)

Claims (1)

[Claims] 1) The styrenic polymer particles obtained by suspension polymerization are sieved so that the particle size is within ±20% of the average particle size, and the particles are immersed in water. suspend,
The decomposition temperature is 50-80℃ to obtain a half-life of 10 hours.
A polymerization initiator is added to water in an amount of 1/2 or more of the amount required for polymerizing the styrenic monomer that will be added later to the aqueous suspension system, and a blowing agent and styrene monomer are added to the aqueous suspension system. The decomposition temperature is 80℃ to obtain a half-life of 10 hours.
and a styrenic monomer containing the remainder of the polymerization initiator whose decomposition temperature is 50 to 80°C is added continuously or intermittently, and then the styrene monomer is added continuously or intermittently. 1. A method for producing expandable styrenic polymer particles with uniform particle size, the method comprising polymerizing the following: 2), sifting the styrenic polymer particles obtained by suspension polymerization so that the particle size is within ±20% of the average particle size, and suspending the particles in water;
The decomposition temperature is 50-80℃ to obtain a half-life of 10 hours.
A polymerization initiator is added to water in an amount of 1/2 or more of the amount required for polymerization of styrenic monomers that will be added to the aqueous suspension system later, and a blowing agent, a plasticizer, and styrene are added to the aqueous suspension system. Contains a polymerization initiator whose decomposition temperature is above 80°C and 120°C or less to obtain a half-life of 10 hours using monomer as a product, and the remainder of the polymerization initiator whose decomposition temperature is 50 to 80°C. 1. A method for producing expandable styrenic polymer particles of uniform particle size, comprising adding a styrene monomer continuously or intermittently, and then polymerizing the styrene monomer. 3) The styrenic monomer is polymerized in advance at a decomposition temperature range of -10 to +20°C to obtain a 10-hour half-life of the lower polymerization initiator used, and then 3. The method according to claim 1 or 2, wherein the polymerization is carried out at a higher temperature in the range of 100 to 150°C. 4), the decomposition temperature to obtain a half-life of 10 hours is 50~
3. A method according to claim 1 or 2, characterized in that the entire amount of the polymerization initiator at 80° C. is added in advance to the water. 5) 0.01 to 1 part by weight of a polymerization initiator whose decomposition temperature is 50 to 80°C to obtain a half-life of 10 hours per 100 parts by weight of the styrene monomer, and a half-life of 10 hours. The method according to claim 1 or 2, characterized in that a polymerization initiator whose decomposition temperature is more than 80°C and less than 120°C is used in an amount of 0.01 to 1 part by weight. . 6) The addition of a blowing agent or a blowing agent and a plasticizer is carried out at a temperature in the range of -10 to +20 °C above the decomposition temperature to obtain a 10-hour half-life of the polymerization initiator, whichever is lower in the temperature of the aqueous suspension system. 4. The method according to claim 3, wherein the method is added to the aqueous suspension system in an amount of 20% by weight or more within 2 hours from the time of arrival. 7) The foaming agent is used in a proportion of 2 to 10 parts by weight based on 100 parts by weight of the styrenic polymer and styrene monomer to be added. the method of. 8) Claims characterized in that the blowing agent is added to the aqueous suspension system after the addition of the styrenic monomer to the aqueous suspension system is started and during the addition of the styrenic monomer to the aqueous suspension system. The method according to item 1 or 2. 9) Claims characterized in that the plasticizer is added to the aqueous suspension system after the addition of the styrenic monomer to the aqueous suspension system is started and during the addition of the styrenic monomer to the aqueous suspension system. The method described in Section 2. 10) The method according to claim 1 or 2, wherein the blowing agent is gaseous at 20°C and atmospheric pressure.