JPH0380802B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing styrenic polymer particles having a narrow particle size distribution. [Prior Art] Conventionally, styrenic polymer particles have generally been produced by suspending styrene monomer in water and carrying out suspension polymerization in the presence of a polymerization initiator and suspension stabilizer. The particle size distribution of the particles obtained by this suspension polymerization is difficult to obtain even if various stirring conditions, polymerization temperature, time, addition method of styrene monomer and polymerization initiator, etc. are selected. It has been considered that it is difficult to achieve this, and that it is unavoidable that the produced styrene polymer has a continuous and wide particle size distribution ranging from small particles to large particles. Styrenic polymer particles having such a wide particle size distribution have the following drawbacks. (1) When extrusion molding polymer particles, small diameter particles and large diameter particles are separated at a raw material supply part such as a hopper, and are not easily bitten into the screw, causing fluctuations in the extrusion rate. (1) Expandable polystyrene particles obtained by impregnating the particles with a volatile expanding agent during or after suspension polymerization are used in large and small particles depending on the purpose, so each type has a size suitable for the purpose. It is preferable to select the type and amount of the blowing agent, but when directly impregnating materials with such a wide particle size distribution, the impregnation must be carried out under the same conditions, making it difficult to obtain expandable polystyrene particles with different expansion powers. As a result, foam molded products formed using these expandable particles have disadvantages of uneven weight and non-uniform strength. In order to avoid such drawbacks, a method for producing particles with a narrow particle size distribution and a uniform particle size is desired. As a method to improve this drawback of the conventional suspension polymerization method, styrene polymer particles that have been sieved in advance are suspended in water, and styrene monomer with a polymerization initiator dissolved in this suspension system is quantitatively added. A method has been proposed in which styrenic polymer particles with uniform particle size are produced by adding styrenic polymer particles to a polymer and growing the particles to a desired particle size by suspension polymerization. (Special Publication No. 46-2987). [Problems to be solved by the invention] This method makes it possible to produce styrenic polymer particles with a considerably narrower particle size distribution than previous methods, but it is possible to produce styrenic polymer particles with a considerably narrower particle size distribution. 8
The drawback is that it is produced at ~13% by weight. In order to improve these drawbacks of the conventional methods, the present invention produces styrenic polymer particles with a narrow particle size distribution that produces a small amount of fine particles and has a theoretically obtainable target particle amount of 98% by weight or more. This provides a method to do so. [Specific means for solving the problem] The present invention provides a method of sieving styrenic polymer particles obtained by suspension polymerization so that the particle size falls within a range of ±20% of the average particle size. The particles are suspended in water, and a polymerization initiator with a decomposition temperature of 50-80°C to obtain a half-life of 10 hours is added to the aqueous suspension system. Add 1/2 or more of the amount required for polymerization to water, and add styrene monomer as the main component to this aqueous suspension system. Certain polymerization initiators and the aforementioned decomposition temperatures range from 50 to
Styrenic polymer particles with uniform particle size, characterized in that a styrene monomer containing a remainder of a polymerization initiator at 80°C is added continuously or intermittently, and then the styrene monomer is polymerized. The present invention provides a method for manufacturing. The styrenic polymer particles used in the present invention, which are added in advance to water, are generally resin particles obtained by suspension polymerization.
The resin particles must be sieved to have a particle size within a required range in advance. When adjusting the particle size, the particles are sieved to be within ±20% of the average particle size. The particle size of the final target styrenic polymer particles obtained in the present invention is determined by the particle size of the sieved particles added in advance to water,
It is determined by the ratio of particle amount and styrene monomer,
When the particle size range of the particles used is ±20% or more of the average particle size, the particle size distribution of the produced particles will be wide. Next, in the present invention, the polymerization initiator used is one with a low decomposition temperature that is added to the aqueous suspension before the start of polymerization of the styrene monomer, and a styrene initiator that is added to the aqueous suspension afterward. There are those with a high decomposition temperature that are used by dissolving them in system monomers. The polymerization initiator, which is added to the suspension before the start of polymerization, has a decomposition temperature of 50~50 to obtain a half-life of 10 hours.
It is a radical polymerization initiator at 80℃, and it contains more than 1/2 of the amount required for the polymerization of the styrene monomer that will be added later.
Preferably, the entire amount is added in water. Examples of such polymerization initiators include lauroyl peroxide (62°C) and azobisisobutylnitrile (63°C).
), t-butylperoxy-2-ethylhexanoate (72.5°C), 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. Preferably, it is added in an emulsified state or under stirring. Further, in the case of powder, the above operations are not necessary, and it is preferable to use powder in the present invention. Next, as a polymerization initiator to be used by dissolving it in the styrene monomer that is added later to the aqueous suspension system, 10
Decomposition temperature exceeds 80℃ to obtain half-life of time
It is a radical polymerization initiator of 120℃ or less, specifically, for example, cyclohexanone peroxide (97
°C), t-butyl peroxybenzoate (104
℃), dicumyl peroxide (117℃) and other styrene monomers. However, if the entire 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 remaining amount 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. The amount of polymerization initiator added is as follows:
0.01 to 0.01 to the styrenic monomer to be added or the styrenic monomer mixture containing styrene as the main component.
1.0% by weight, preferably 0.1-0.6% by weight. Additionally, the decomposition temperature is 80°C to obtain a half-life of 10 hours.
The polymerization initiator with a temperature exceeding 120° C. or less is 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight, based on the styrenic monomer or styrene monomer mixture containing styrene as a main component. In the present invention, the method of adding a polymerization initiator is to add a polymerization initiator whose decomposition temperature is 50 to 80°C to obtain a half-life of 10 hours later. One-half or more of the amount required for polymerization, preferably the entire amount, is added to water or to water in which styrenic polymer particles are suspended before starting polymerization. Furthermore, the remaining amount of the above-mentioned low-temperature decomposition type polymerization initiator and the decomposition temperature to obtain a half-life of 10 hours exceed 80 °C and 120 °C.
A high-temperature decomposition type polymerization initiator having a temperature of 0.degree. In this case, if the amount of the low-temperature decomposition type polymerization initiator that is pre-added to the water is less than 1/2 of the amount required for polymerization of the styrenic monomer, fine particles will be generated. The styrenic monomer used in the present invention includes styrene or a mixture containing styrene as a main component, such as styrene and α-methylstyrene, divinylbenzene, acrylonitrile, and carbon atoms of 1 to 1.
Esters obtained by reacting the alcohol of No. 8 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. In the present invention, suspension stabilizers used to suspend styrenic polymer particles whose particle size has been adjusted in advance in water include polyvinyl alcohol, polyvinylpyrrolidone, gelatin, carboxymethyl cellulose, and hydroxyalkyl cellulose. Examples include organic suspension stabilizers such as phosphoric acid or carbonate, and inorganic suspension stabilizers such as phosphoric acid or carbonate Ca salt or Mg salt. Among them, inorganic ones are preferable, and in particular, it is preferable to use a combination of tricalcium phosphate and anionic surfactant sodium dodecylbenzenesulfonate as a stabilizing aid. Furthermore, it is also possible to produce expandable styrenic polymer particles by impregnating the styrenic polymer particles of uniform particle size produced in the present invention with a volatile swelling agent. Examples of volatile expanding agents to be impregnated include aliphatic hydrocarbons such as propane, butane, and pentane; alicyclic hydrocarbons such as cyclobutane and cyclopentane; and halogenated hydrocarbons such as methyl chloride and dichlorodifluorometa. . These volatile swelling agents are used in an amount of 5 to 20% by weight of the styrenic polymer particles obtained. Example 1 Into the polymerization vessel of 3, 800 g of pure water, 4.0 g of tribasic calcium phosphate, 1.0 g of a 1% aqueous solution of sodium dodecylbenzenesulfonate, and styrene polymer particles sieved to 0.42 to 0.5 mm (average particle size 0.46 mm) 75g and benzoyl peroxide (decomposition temperature 74℃)
A total amount of 3.76 g was added and stirred at 400 rpm to uniformly disperse the mixture to obtain an aqueous suspension. This aqueous suspension was then heated to 85°C;
During this holding time, 1.4 g of t-butyl peroxybenzoate (decomposition temperature 117°C) was
was dissolved in 678g of styrene.
Quantitatively added 75g per hour over 9 hours.
Next, the temperature was raised from 85°C to 120°C over 1.5 hours, and then further heated at 120°C for 2 hours to complete polymerization. After cooling, water was separated and dried, and the particle size distribution of the styrene polymer particles obtained is shown in Table 1. In the polymerization container of Comparative Examples 1 and 3, 800 g of pure water, 4.0 g of tribasic calcium phosphate, 1.0 g of a 1% aqueous solution of sodium dodecylbenzenesulfonate, and the same materials used in Example 1 were placed.
75g of styrene polymer particles sieved to 0.42-0.5mm
was added and stirred at 400 rpm to uniformly disperse the mixture to obtain an aqueous suspension. This aqueous suspension was then heated to 85°C;
During this holding time, a solution of 3.76 g of benzoyl peroxide and 1.4 g of t-butyl peroxybenzoate dissolved in 678 g of styrene was continuously quantitatively added at a rate of 75 g per hour over 9 hours. was added and polymerized in the same manner as in Example 1. The particle size distribution of the obtained styrene polymer particles was
Shown in the table. This product produced a much larger amount of fine particles than that of Example 1. Example 2 After suspending styrene polymer particles in the same manner as in Example 1, 1.88 g, which is half the amount of benzoyl peroxide to be added, was added to the suspension, and the remaining benzoyl peroxide, 1.88 g, was added to the suspension. g was dissolved in styrene together with 1.4 g of t-butylperoxybenzoate, and polymerization was carried out in the same manner as in Example 1. Table 1 shows the particle size distribution of the obtained styrene polymer particles. Comparative Example 2 After suspending styrene polymer particles in the same manner as in Example 1, the amount of benzoyl peroxide to be added was
A 40% amount of 1.50 g was added into the suspension and the remaining 2.26 g of benzoyl peroxide was dissolved in styrene along with 1.4 g of t-butyl peroxybenzoate and polymerized as in Example 1. The particle size distribution of the obtained styrene polymer particles was
Shown in the table. Example 3 In the polymerization container of Example 3, 800 g of pure water, 4.0 g of tribasic calcium phosphate, 1.0 g of a 1% aqueous solution of sodium dodecylbenzenesulfonate, and 0.42 g of the same amount used in Example 1 were placed.
Add the total amount of 125 g of styrene polymer particles sieved to ~0.5 mm and 2.50 g of benzoyl peroxide,
Aqueous suspension was obtained by stirring at 400 rpm for uniform dispersion. Next, this suspension was heated to 85℃, and at 85℃
During this holding time, a solution of 1.25 g of t-butyl peroxybenzoate dissolved in 625 g of styrene monomer was continuously added quantitatively to the aqueous suspension at a rate of 125 g per hour over a period of 5 hours. Then, after raising the temperature from 85℃ to 120℃ over 1.5 hours,
The mixture was further heated at 120°C for 2 hours to complete the polymerization. After cooling, water was separated and dried, and the particle size distribution of the styrene polymer particles obtained is shown in Table 1. Comparative Example 3 In the polymerization container of 3, 800 g of pure water, 4.0 g of tribasic calcium phosphate, 1.0 g of a 1% aqueous solution of sodium dodecylbenzenesulfonate, and the same materials used in Example 1 were placed.
125g of styrene polymer particles sieved to 0.42-0.5mm
was added and stirred at 400 rpm for uniform dispersion to obtain an aqueous suspension. Next, this suspension was heated to 85℃, and at 85℃
During this holding time, a solution of 2.50 g of benzoyl peroxide and 1.25 g of t-butyl peroxybenzoate dissolved in 625 g of styrene monomer was continuously added quantitatively at a rate of 125 g per hour for 5 hours. It was added to an aqueous suspension and polymerized in the same manner as in Example 1. The particle size distribution of the obtained styrene polymer particles was
Shown in the table. Example 4 The particle size distribution of styrene polymer particles obtained in the same manner as in Example 1 except that azobisisobutylnitrile was used instead of benzoyl peroxide as a polymerization initiator pre-added to the suspension before starting polymerization. Shown in Table 2. Example 5 In the same manner as in Example 1, except that instead of the styrene added to the aqueous suspension, a mixture of 80% by weight styrene and 20% by weight acrylonitrile was used,
Styrene/acrylonitrile copolymer particles were obtained. The particle size distribution of the obtained particles is shown in Table 2. Example 6 Similar to Example 1, after finishing the addition of styrene at 85°C, the styrene polymer was impregnated with 12% isobutane to produce expandable styrene polymer particles. Shown in Table 2. Example 7 Results of an example when polymerization was carried out in the same manner as in Example 3 using particles with a particle size of 0.71 to 0.84 mm (average particle size 0.78 mm) as the styrene polymer particles to be suspended first. are shown in Table 2.

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Claims (1)

[Claims] 1. 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 A polymerization initiator, suspended in water and having a decomposition temperature of 50 to 80 °C to obtain a half-life of 10 hours, is added later to the aqueous suspension system in the amount required for the polymerization of styrenic monomers. /2 or more in water, and add to this aqueous suspension system a polymerization initiator whose main component is styrene monomer and whose decomposition temperature is more than 80°C and less than 120°C to obtain a half-life of 10 hours, and the above-mentioned A method for obtaining uniform particle size characterized by continuously or intermittently adding a styrene monomer containing a polymerization initiator residue having a decomposition temperature of 50 to 80°C, and then polymerizing the styrene monomer. A method for producing styrenic polymer particles. 2. Polymerization of the styrenic monomer is carried out in advance at a decomposition temperature of -10 to +20°C in order to obtain a 10-hour half-life of the lower polymerization initiator used, and then at a higher temperature. The method according to claim 1, characterized in that the polymerization is carried out at a temperature in the range of 100 to 150°C. 3 The decomposition temperature to obtain a half-life of 10 hours is 50~
A method according to claim 1, characterized in that the entire amount of polymerization initiator at 80° C. is added in advance to the water. 4 For 100 parts by weight of styrene monomer, 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, and decomposition to obtain a half-life of 10 hours. The method according to claim 1, characterized in that the polymerization initiator whose temperature is above 80°C and below 120°C is used in an amount of 0.01 to 1 part by weight.