JPH0745589B2 - Method for producing expandable styrenic polymer particles - Google Patents

Description

The present invention relates to a method for producing expandable styrenic polymer particles.

When the expandable styrene-based polymer particles are heated by a heating means such as steam or hot air, a large number of small bubbles are generated in the particles to become pre-expanded resin particles. When the pre-expanded resin particles are filled in a mold and heated, the pre-expanded resin particles are fused to each other to obtain a styrene resin foam molded article faithful to the mold. The foamed molded product produced in this manner is used for food containers, cushioning materials, heat insulating materials, and the like.

[Prior art]

The size of small cells (cell size) of the foamed molded product is an important factor that determines the quality characteristics of the molded product, such as surface gloss, strength, heat insulation, and heat resistance. It depends.

The cell size of the pre-expanded resin particles is also an important factor that determines the molding time.

The conventional expandable styrenic resin requires low-temperature control by means such as the following 1 to 3 in order to adjust the cell size.

1) When extracting the styrenic resin particles impregnated with the foaming agent from the impregnation tank or the polymerization tank, if the cells are extracted at a high temperature (40 to 50 ° C), the cell size is large and it is extremely uneven. Extracted at low temperature, preferably below 30 ℃. However, cooling the above-mentioned tank to a relatively low temperature in the summer requires a long time and requires the installation of a refrigerator, etc., which is extremely economically uneconomical.

2) Since the expandable styrenic resin particles produced as in 1) above are intended to make the cell size finer and more uniform,
Further, it is necessary to ripen at a room temperature or lower, preferably 15 ° C. or lower for a certain period of time, and it is usually stored in a low temperature warehouse or the like in the summer.

3) Further, even with the expandable styrenic resin particles that have been aged as in 2), if they are placed again at a high temperature (40 to 50 ° C.), the cell size becomes large and becomes non-uniform. A phenomenon occurs and it is necessary to keep the temperature relatively low during transportation.

In order to solve the above drawbacks in production and storage of expandable resin particles, USP 3,389,097, JP-B-53-2910, JP-A No.
Amides such as those found in 59-168037 and 59-166538; and JP-A-57-96029, 57-119934 and 57-141.
Surfactants as described in JP-A-5133, JP-A-59-2079
A method of using a cell adjusting agent such as a polymer as described in Japanese Patent No. 41 has been proposed.

However, these cell size regulators have a phenomenon in which only the surface cells are finely divided, and when the aged expandable resin particles are stored at a high temperature (40 to 50 ° C.), the cell size becomes coarse. Was seen.

[Specific means for solving problems]

The present inventors have found that, because of the reason that these cell size regulators have low compatibility with polymers or have low molecular weight, aggregation, precipitation, etc. occur in polystyrene particles and the cell size regulator effect is not stable. As a result of repeated in-depth investigations, a block segment of a polymer of a monovinyl-substituted aromatic hydrocarbon, which has a high compatibility with polystyrene, and a block segment of a polymer of a conjugated diene, which has a low compatibility with polystyrene, were combined. The block copolymer that has, that is, a polymer block of a monovinyl-substituted aromatic hydrocarbon such as styrene at both ends, and a block copolymer having a saturated or unsaturated conjugated diene elastomeric polymer block in the inner chain is a foamable styrene resin. It is effective as a cell size control agent for particles and has a high stability in cell size control effect. Discovered, ItaTsuta to the completion of the present invention.

That is, the present invention relates to a styrene monomer, a styrene / butadiene / styrene / block copolymer as a cell size adjuster, a styrene / isoprene / styrene / block copolymer, or a water additive thereof such as styrene / ethylene / butylene. 0.001 of at least one of the styrene block copolymers
~ 1 wt% dissolved, this solution is suspended in an aqueous medium, then the styrene monomer is subjected to suspension polymerization, an organic blowing agent is added during the polymerization, or after the polymerization step is completed It is intended to provide a method for producing expandable styrenic polymer particles by impregnating a polymer particle with a foaming agent.

In the present invention, the styrene-based monomer is mainly composed of styrene-based monomers such as styrene, α-methylstyrene and vinyltoluene, and the styrene-based monomer and other vinyl monomers A mixture of a styrene monomer such as a vinyl cyanide monomer such as acrylonitrile, a methacrylate monomer such as methyl methacrylate, an acrylate monomer such as butyl acrylate, and a copolymerizable monomer. May be. There is no problem in starting the suspension polymerization by using a polymer of these monomers together with the monomers, for example, by dissolving or suspending them as seed particles.

As the dispersant, generally known polymer dispersants such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylamide; inorganic dispersants that are sparingly soluble in water, such as calcium phosphate, hydroxyapatite, and magnesium phosphate, and a dispersion aid A combination of certain surfactants such as sodium dodecylbenzene sulfonate can be used.

Examples of the polymerization initiator include polymerization initiators generally used in radical polymerization of styrene-based monomers, for example, organic peroxides such as benzoyl peroxide and butyl perbenzoate; azo compounds such as azobisisobutylnitrile. Can be used.

As the foaming agent, generally known aliphatic hydrocarbons such as propane, butane and pentane, and halogenated hydrocarbons such as trifluoromonochloroethane and difluorodichloromethane can be used.

Further, a plasticizer such as xylene or dioctyl adipate may be used in the production of the expandable styrene polymer particles.

The block copolymer having a polymer block of a monovinyl-substituted aromatic hydrocarbon at both ends and an elastomeric polymer block of a conjugated diene in the inner chain, which is used as a cell size adjuster in the present invention, is represented by the general formula (I). Is.

AB-A) _n ... (I) (where A is a polymer block of a monovinyl-substituted aromatic hydrocarbon; B is an elastomeric polymer of a conjugated diene, saturated or unsaturated, and n is 1 to 5). The total concentration of A block of the block polymer represented by the above general formula (I) is in the range of about 20 to 50% based on the total weight of the polymer.

Another notation applied to this three unit block polymer is (SSS) _n- (BBB) _n- (SSS) _n .
Here, S represents a portion derived from a vinyl-substituted aromatic hydrocarbon monomer, and B represents a portion derived from a conjugated diene monomer. Styrene is commonly used as the monovinyl aromatic hydrocarbon, while butadiene-1,3
And isoprene are most often used as conjugated diene elements. Thus, for example, styrene-butadiene-styrene block copolymers are marketed by Ciel Chemical under the tradenames "Califlex TR 1101" and "Califlex TR 1102", while styrene-isoprene-styrene block copolymers are sold under the tradename "Califlex TR 1107". And commercially available from Ciel Chemical as "Calibrex TR 1111".

Methods for making these block polymers are well known to those skilled in the art, and a typical method is USP 3,265,765 (1966).
August 9, 2012).

Further, by hydrogenating the intramolecular double bond of the block copolymer of styrene of the block polymer and the conjugated diene, an elastomer having improved thermal stability can be obtained. A method for producing such a hydrogenated block copolymer is described in, for example, Japanese Patent Publication No. 42-8704 and Japanese Patent Publication No. 43-66.
36, Japanese Patent Publication No. 45-20504, Japanese Patent Publication No. 48-3555 and the like. As a product, there is Clayton G1652 of Ciel Chemical Co., which is a styrene / ethylene / butadiene / styrene block copolymer. Such hydrogenated block copolymers can also be used as cell size regulators.

The addition amount of these block copolymers is in the range of 0.001 to 1% by weight based on the styrene monomer.
If it is less than 0.001% by weight, a sufficient bubble adjusting effect cannot be obtained, and if it is added in excess of 1% by weight, the cell size becomes excessively fine, and the melted portion in the molded product increases and the appearance deteriorates.

The expandable styrenic polymer particles obtained by carrying out the present invention have the following characteristics.

Even if the expandable styrenic polymer particles are extracted from the impregnation tank or the polymerization tank at a relatively high temperature (40 to 50 ° C) and immediately pre-expanded, the cell size is relatively fine (70 to 20
0 micron) uniform.

Further, when the expandable styrenic polymer particles are aged, the time for refining the cell size can be greatly reduced.

The expandable styrenic polymer particles that have been aged once are less likely to cause cell size disproportionation and coarsening even after being placed at a relatively high temperature (40 to 50 ° C.).

Next, examples of the present invention will be described.

Example 1 In an autoclave equipped with a rotary stirrer of 3, distilled water 1,000
g, tricalcium phosphate (manufactured by Taihei Chemical Co., Ltd.) 4.0 g and sodium dodecylbenzenesulfonate 0.03 g,
Next, 900 g of styrene was added to styrene / ethylene / butylene / styrene block copolymer (trade name of Ciel Chemical Co .;
Kraton G1652) 0.45 g, benzoyl peroxide 0.3 g and butyl perbenzoate 0.9 g were dissolved and charged.

Next, the temperature of the reaction system was raised to 90 ° C., styrene was polymerized at 90 ° C. for 6 hours, 68 g of butane was then injected under pressure, the temperature was raised to 110 ° C., and impregnation was carried out for 4 hours. Then, the reaction system was cooled to 30 ° C. to complete the polymerization.

The resulting expandable styrene resin particles are centrifuged and dehydrated,
After drying, the particles were classified with a particle size of 0.84 to 1.19 mm and pre-expanded to a bulk ratio of 50 times without aging to obtain pre-expanded particles.

The pre-expanded particles are filled in the cavity of a 100 mm × 100 mm × 200 mm mold, heated with 0.7 kg / cm ² steam for 20 seconds, and molded to obtain a molded foam product. .

Example 2 In place of the styrene / ethylene / butylene / styrene block copolymer of the cell size adjusting agent of Example 1, styrene / butadiene / styrene block copolymer (manufactured by Shell Chemical Co., Ltd .; trade name: Califleck TR1102) was used.
The same operation as in Example 1 was performed.

Example 3 The same operation as in Example 1 was carried out except that the temperature for withdrawing from the autoclave was 45 ° C.

Example 4 The extraction temperature from the autoclave was set to 45 ° C., dry classification and aging at 5 ° C. for 3 days were performed, and then prefoaming and molding were performed.

Example 5 After the aging of Example 4, the expandable styrene resin particles were placed at 40 ° C. for 1 hour.
After storage for a day, prefoaming and molding of the molded product were performed.

Example 6 Instead of styrene / ethylene / butylene / styrene block copolymer, styrene / isoprene / styrene block copolymer (trade name of Ciel Chemicals, Califlex TR11) was used.
The same operation as in Example 1 was performed except that 11) was used.

Comparative Example 1 The same operation as in Example 1 was carried out without using the styrene / ethylene / butylene / styrene block copolymer.

Comparative Example 2 The same operation was carried out using polystyrene (weight average molecular weight 300,000) instead of the styrene / ethylene / butylene / styrene block copolymer of Example 1.

Comparative Example 3 The same operation was carried out except that the amount of the styrene / ethylene / butylene / styrene block copolymer used in Example 1 was 0.008 g.

Comparative Example 4 Example 1 was repeated except that the amount of the styrene / ethylene / butylene / styrene block copolymer used in Example 1 was 10 g.
The same operation was carried out.

Comparative Example 5 The same operation as in Example 3 was carried out without using styrene / ethylene / butylene / styrene block copolymer.

Comparative Example 6 The same operation as in Example 4 was carried out without using styrene / ethylene / butylene / styrene block copolymer.

Comparative Example 7 The same operation as in Example 5 was carried out without using styrene / ethylene / butylene / styrene block copolymer.

The following table shows the average cell size, cell uniformity and appearance of these foamed molded articles.

Claims (2)

[Claims] 1. A block copolymer having a polymer block of a monovinyl-substituted aromatic hydrocarbon at both ends and an elastomeric polymer block of a saturated or unsaturated conjugated diene in the inner chain, to a styrenic monomer. 0.001 to 1% by weight is dissolved, the solution is suspended in an aqueous medium, and then a styrene monomer is suspension polymerized, and an organic foaming agent is added during the polymerization, or an organic foaming agent is added after the polymerization step. A process for producing expandable styrene-based polymer particles, which comprises impregnating a foaming agent into the polymer particles to obtain expandable styrene-based polymer particles. 2. The method according to claim 1, wherein the block copolymer is styrene / butadiene / styrene block copolymer, styrene / isoprene / styrene block copolymer, or a water additive thereof.