JP3118046B2 - Method for producing heat-resistant styrenic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a heat-resistant styrenic resin composition, and more particularly, to a processed article having excellent transparency, little color tone deterioration such as yellowing and good appearance. The present invention relates to a method for producing a heat-resistant styrenic resin composition improved so that it can be provided.

[0002]

2. Description of the Related Art In general, styrene polymers have high transparency,
It is a resin with excellent moldability and rigidity, and is widely used as an injection molding material for household goods and electric appliances and a sheet material for food packaging. Recently, demands for higher quality have been increasing, and styrene-based materials having heat resistance have been particularly desired.

Conventionally, methods for improving the heat resistance of styrenic polymers include (1) a method for increasing the molecular weight,
(2) a method of preparing a copolymer with a heat-resistant comonomer such as maleic anhydride, and (3) a method of kneading with a heat-resistant resin such as polyphenylene ether.

However, in the method (1), the moldability is significantly impaired, in the method (2), the production process is complicated and the cost is high, and in the method (3), the melt viscosities of the two to be kneaded are extremely high. Unless severe kneading conditions are adopted, unmelted polyphenylene ether becomes a hard spot and is unsuitable for use as a transparent material.

In order to overcome the problem of the above method (3), a method of polymerizing a styrene monomer in the presence of polyphenylene ether has been proposed (for example, Japanese Patent Application Laid-Open No. 55-137130, JP-A-58-117243.

[0006]

However, even when the styrenic resin composition obtained by the above method is used, the appearance of the processed product obtained cannot be said to be sufficient, and further improvement is required.

[0007]

The present inventors have conducted various studies on a method of polymerizing a styrene monomer in the presence of polyphenylene ether, and have obtained the following findings. In other words, when polyphenylene ether is dissolved in a styrene-based monomer in an amount necessary to exhibit the heat resistance improving effect, unmelted polyphenylene ether remains, which causes spots that affect the appearance of the processed product. However, unmelted polyphenylene ether and other solids (hereinafter referred to as “insolubles”) can be efficiently removed if a filtration step is provided at a specific stage prior to polymerization. The present invention has been completed based on the above findings, and the gist of the present invention is to provide polyphenylene ethers 5 to 5.
Dissolving 60 parts by weight of the styrene-based monomer in 40 to 95 parts by weight, filtering an insoluble substance having a particle size of 40 μm or more from the obtained solution, and filtering the polyphenylene ether and the styrene-based monomer after the filtration; A method for producing a heat-resistant styrenic resin composition comprising a step of polymerizing.

Hereinafter, the present invention will be described in detail. In the present invention, polyphenylene ether refers to a polymer having a repeating unit represented by the following chemical formula [Formula 1]. In the chemical formula [Formula 1], R ₁ and R ₂ are an alkyl group,
Represents an aryl group, a halogen atom, a hydrogen atom or the like, and n represents an integer. R ₁ and R ₂ may be the same or different from each other.

[0009]

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Specific examples of the above polyphenylene ether include poly (2,6-dimethyl-1,4-phenylene) ether and poly (2-methyl-6-ethyl-1,4).
-Phenylene) ether, poly (2-methyl-6-propyl-1,4-phenylene) ether, poly (2,6-
Dipropyl-1,4-phenylene) ether, poly (2
-Ethyl-6-propyl-1,4-phenylene) ether and the like. A particularly preferred polyphenylene ether is poly (2,6-dimethyl-1,4-phenylene) ether, which has very good compatibility with general-purpose polystyrene.

The molecular weight of the above-mentioned polyphenylene ether is not particularly limited, but from the viewpoint of moldability and strength when formed into a sheet, the weight average molecular weight is 1 × 1.
0 ⁴ to 10 × 10 ⁴ , preferably 2 × 10 ^{4 to} 7
× 10 ⁴ range.

In the present invention, the styrene monomer is
In addition to styrene alone, o-methylstyrene, m-methylstyrene, p-methylstyrene, dimethylstyrene, α-
Refers to styrene derivatives such as methylstyrene, p-chlorostyrene, and 2,4-dimethylstyrene, and mixtures thereof.

The method for producing a styrenic resin composition of the present invention includes a dissolving step, a filtering step, and a polymerization step. In the dissolving step, 5 to 60 parts by weight of polyphenylene ether is dissolved in 40 to 95 parts by weight of the styrene monomer. If the amount of the polyphenylene ether is less than 5 parts by weight, a sufficiently heat-resistant styrene-based resin composition cannot be obtained, and if it exceeds 60 parts by weight, the viscosity becomes high and handling becomes difficult. The dissolution of the polyphenylene ether into the styrene monomer is performed by using an appropriate dissolution tank and
It is carried out by continuing stirring at a temperature of -100 ° C, preferably 70-90 ° C for 1-2 hours. Melting temperature is 60
When the temperature is lower than 0 ° C, the polyphenylene ether is not sufficiently dissolved to form a slurry, and when the temperature is higher than 100 ° C, thermal polymerization of styrene is promoted.

[0014] In the filtration step, 40
Insoluble matter having a particle size of μm or more is removed. The removal of insolubles is carried out by a filter.
A normal filter used for liquid separation may be used. As a material of the filter medium, a fiber-resin composite material such as cotton, polypropylene, cellulose fiber-melamine resin, cellulose fiber-phenol resin, and acrylic fiber-phenol resin is used. In addition to the filter media made of these materials, SU
A stainless steel mesh represented by S304 and a laminated sintered wire mesh filter can also be used. And
The filtration accuracy is 10 μm or less, preferably 5 μm or less.

In the polymerization step, a styrene-based monomer and polyphenylene ether are polymerized to obtain a heat-resistant styrene-based resin composition. The type of polymerization may be any of suspension polymerization, solution polymerization, bulk polymerization or a combination thereof, but bulk-suspension polymerization is advantageous. Suspension polymerization is performed by a radical polymerization initiator in an aqueous medium.

Examples of the radical polymerization initiator include, for example, t
-Butyl peroxide, di-t-butyl peroxide,
Cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane,
Organic peroxides such as 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propanone, azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile,
Methyl azobisisobutyrate, azobiscyanovaleric acid, 1-
t-butylazo-1-cyanocyclohexane, 1,1 '
Azo compounds such as -azobiscyclohexane-1-carbonitrile. The polymerization initiator can be used in an appropriate amount for polymerizing the styrene-based monomer.
0% by weight is preferred.

The amount of water in the aqueous medium may be any amount as long as the suspension of the reaction system can be improved.
70 parts by weight or more, preferably 10 parts by weight, based on 100 parts by weight of the total of the styrene monomer and the polyphenylene ether.
The range is from 0 to 300 parts by weight.

It is preferable to add a dispersion stabilizer to the aqueous medium. As a dispersion stabilizer, polyvinyl alcohol,
Examples include gelatin, agar, starch, glycerin, polyacrylic acid or its sodium salt, polyethylene glycol, ethylene glycol, polyacrylamide, and styrene-maleic anhydride copolymer. The amount of the dispersion stabilizer is not particularly limited, but is generally 0.1 to water.
001 to 3% by weight, preferably 0.01 to 1.5% by weight
It is.

If a surfactant is added to the aqueous medium, the effect of stabilizing the suspension state of the reaction system and smoothing the bead surface of the produced polymer can be obtained. As the surfactant, any cationic, anionic or nonionic surfactant may be used, and specifically, hydroxymethylcellulose, carboxymethylcellulose, methylcellulose, rosin soap, sodium glycolate, sodium dodecylbenzenesulfonate, sodium stearate. , Polyoxyethylene lauryl ether, polyoxyethylene distearate, lauryl trimethyl ammonium chloride and the like. The surfactant is not necessarily required when a dispersion stabilizer is used, but when used, is preferably used in the range of 0.0005 to 0.5% by weight based on water.

Further, if a water-insoluble inorganic compound is added to the aqueous medium as a so-called anti-adhesive agent, the beads of the produced polymer can be stabilized. As such inorganic compounds, specifically, calcium, magnesium,
Carbonates such as lead or barium, silicates, sulfates or phosphates, alumina, bentonite, talc, clay,
Oxides such as titanium oxide and lead oxide, silicates, and the like can be given. The amount of the inorganic compound is not particularly limited, but is preferably in the range of 0.01 to 5% by weight based on water. Furthermore, a water-soluble inorganic salt such as sodium sulfate can be used in combination to promote the polymerization smoothly. Each of the above-mentioned additives can be used alone or as a mixture of two or more, and a plasticizer, a lubricant, a coloring material, a stabilizer, and the like, as long as they do not adversely affect the polymerization of the styrene compound, It can be added in advance during polymerization.

The styrenic resin composition obtained by the production method of the present invention is excellent in transparency, moldability, rigidity and heat resistance, and is excellent in heat resistance for injection molding materials such as household goods and electric products, food packaging, and especially heat resistance. It can be widely used as a sheet material for lightweight containers and the like, which can be reheated or microwave heated as required.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, in the following examples, the results of the appearance and physical property measurement of the injection molded product are shown in Table 1 below, and the results of the appearance and physical property measurement of the processed sheet product are shown in Table 1 below.

Example 1 [Dissolving Step] A polyphenylene ether (weight average molecular weight 5 × 1) was placed in a 30 L dissolving tank equipped with an irrigated stirring blade.
0 ⁴⁾ 5.0 kg, was heated to 80 ° C. Put styrene 15.0 kg. Stirring was continued for 60 minutes to sufficiently dissolve the polyphenylene ether in styrene. [Filtration Step] After dissolution, the dissolved melt was transported to a 50 L autoclave (suspension polymerization vessel) by a transport pump.
Then, during transportation, insolubles were removed through a filter (filtration accuracy: 10 μm) in which cellulose fibers and a phenol resin were combined.

[Polymerization step] After transportation, heat deionized water 20k
g, sodium dodecylbenzenesulfonate 1.0 g,
450 g of a 2% aqueous solution of a polyacrylate suspension and 100 g of sodium sulfate were added, and the temperature was raised to 120 ° C. 12
After the temperature reached 0 ° C., 30 g of dicumyl peroxide was added, the temperature was raised to 150 ° C. over 5 hours, and further maintained for 1 hour to complete the reaction. [Kneading Step] After the beads obtained by the above polymerization method were dried, they were melt-kneaded in a single screw (40 mmφ) extruder at 260 ° C. for one pass to obtain pellets.

[Injection molding step] The obtained pellets were injection molded at a molding temperature of 260 ° C and a mold temperature of 50 ° C to obtain test pieces. [Sheet processing step] The obtained pellets were further extruded into a sheet shape from a T-die at 230 ° C while being melted and kneaded by an extruder equipped with a 40 mmφ vent, and then cooled by a cooling roll to a thickness of about 0.1 mm. A 9 mm unstretched sheet was produced. Then, using a test stretching machine, the above unstretched sheet is stretched 2.5 times in each of the biaxial directions under a temperature condition of 125 ° C. to obtain a biaxially stretched sheet having a thickness of 0.15 mm and having good transparency. I got

Example 2 [Dissolving Step] and [Filtration Step] The same procedure as in Example 1 was carried out except that 10.0 kg of polyphenylene ether and 10.0 kg of styrene were used. [Polymerization Step] After transportation, 20 kg of hot deionized water, 1.0 g of sodium dodecylbenzenesulfonate, 450 g of a 2% aqueous solution of a polyacrylate suspension, 10 g of sodium sulfate
0 g was added and the temperature was raised to 120 ° C. After the temperature reached 120 ° C., 20 g of dicumyl peroxide was added, the temperature was raised to 150 ° C. over 5 hours, and the reaction was maintained for 1 hour to complete the reaction.

[Kneading Step] After the bead obtained by the above polymerization method is dried, 50 parts of the bead and 50 parts of polystyrene pellets (weight average molecular weight 2.4 × 10 ⁵ ) are dry-blended with a tumbler, and are uniaxially mixed. (40 mmφ) The mixture was melt-kneaded in a single pass at 260 ° C. using an extruder to obtain pellets. [Injection Molding Step] and [Sheet Processing Step] Performed in the same manner as in Example 1.

Comparative Example 1 Example 1 was the same as Example 1 except that the filtration step was omitted.
Was performed in the same manner as described above.

Comparative Example 2 Example 2 was the same as Example 2 except that the filtration step was omitted.
Was performed in the same manner as described above.

Reference Example 1 Polyphenylene ether (weight average molecular weight 5 × 10 ⁴ )
25 parts, polystyrene (weight average molecular weight 2.4 × 1
0 ⁵ ) 75 parts were dry-blended with a tumbler and melt-kneaded in a single screw (40 mmφ) extruder at 260 ° C. for one pass to obtain pellets. The injection molding step and the sheet processing step were performed in the same manner as in Example 1. However,
In the stretching in the sheet processing step, the sheet was severely broken and no sheet was obtained.

Reference Example 2 Polyphenylene ether (weight average molecular weight 5 × 10 ⁴ )
25 parts, polystyrene (weight average molecular weight 2.4 × 1
0 ⁵ ) 75 parts were dry-blended using a tumbler, and melt-kneaded in a two-pass extruder (30 mm) at 300 ° C. for 2 passes to obtain pellets. The injection molding step and the sheet processing step were performed in the same manner as in Example 1.

[0032]

[Table 1] Example Comparative Example Reference Example 1 2 1 2 1 2 YI ^{* 1} 12 11 12 11 13 29 Tensile strength ^{* 2} 700 700 700 700 500 670 Bee-cut softening point ^{* 3} 120 120 120 120 115 119 Melt flow rate ^{* 4} 18 15 18 16 8 6 Appearance ^{* 5} ○ △ △ × △

The meanings of the notes in Table 1 are as follows. (* 1): Yellowness according to JIS K7105 (Yeel
ow Index: white plate reflection method) (* 2): Conforms to JIS K7113 (Kg / cm ² ) (* 3): Conforms to JIS K7113 (° C) (* 4): Conforms to JIS K7210 (g / 10 minutes) Measurement Conditions: resin temperature 220 ° C, load 10Kg

(* 5) Since it is difficult to evaluate the appearance of the injection-molded article, the extruder equipped with a T-die is used to obtain a 1 mm thick sheet.
A sheet having a width of 10 cm was extruded, and its appearance was evaluated. ：: Uniformly compatible, no occurrence of bumps on the surface and no defective molding were observed. Δ: Almost uniformly compatible, but generation of lumps (unmelted solidified product) on the surface is observed. ×: Not compatible, and uneven molding due to uneven skin roughness and sheet thickness unevenness are observed.

[0035]

[Table 2] Example Comparative Example Reference Example 1 12 1 2 1 2 Sheet thickness (mm) 0.15 0.15 0.15 0.15 0.15 Orientation relaxation stress ^{* 6} 7.2 7.4 7.3 7.2 7.0 Puncture impact strength ^{* 7} 29 31 28 32 30 Heat shrinkage Starting temperature ^{* 8} 122 123 121 122 122 Sheet appearance (visual) ^{* 9} ○ ○ △ △ △ Hard spot (number) ^{* 10} 0.2 mm ² or more 400 300 1100 800 4700 0.1 mm ² or less 1100 1200 2800 2000 1200

The meanings of the notes in Table 2 are as follows. (* 6): Measured using a measuring device (DN-type stress tester manufactured by NIRI KOGYO CO., LTD.) Based on ASTM D-1504 and expressed as an average value in vertical and horizontal directions (Kg / cm ² ). (* 7): Conforms to JIS P8134 (Kg · cm)

(* 8): Indicates the temperature (° C.) measured by the following method. First, both ends of a sheet sample cut to a length of 60 mm and a width of 30 mm are held by clamps of an Instron type tensile tester (IM-500 type autograph manufactured by Shimadzu Corporation), and the clamps are immersed in a silicon oil bath. . Next, the oil bath is heated and heated at a rate of 2 ° C./min, and the temperature at which the test piece starts to rapidly shrink is read by the change in shrinkage stress appearing in a tensile tester. The above temperature was defined as the heat shrink start temperature. This heat shrinkage starting temperature can be regarded almost as it is as the heat resistant temperature of the sheet.

(* 9): Judgment was made in the same three grades as in the "appearance" evaluation shown in Table 1. (* 10): Particles (unmelted solidified material) appearing on the sheet surface were quantified by the following method. That is, an arbitrary portion (10 cm × 10 cm) of a sheet is cut out, and a loupe of 0.2 mm ² or more and 0.1 mm are used.
Divide into ² or less and count them, multiply them by 100, and
Number of hard spots per square meter.

[0039]

According to the present invention described above, by providing a filtration step between the dissolving step and the polymerization step, unmelted substances and the like in the heat-resistant styrenic resin composition can be removed. As a result, it is possible to produce a heat-resistant styrenic resin composition that is excellent in transparency, has little color tone deterioration such as yellowing, and can provide a processed product having good appearance. Therefore, the industrial utility value of the present invention is extremely large.

Claims (1)

(57) [Claims] A step of dissolving 5 to 60 parts by weight of polyphenylene ether in 40 to 95 parts by weight of a styrene monomer;
A step of filtering an insoluble substance having a particle size of 40 μm or more from the obtained solution; and a step of polymerizing polyphenylene ether and a styrene monomer after the filtration. Production method.