JPH09111073A - Styrene-based resin composition excellent in thermal stability and processability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition, comprising specific amounts of a cyclic trimer and a cyclic dimer derived from a styrene-based substance and good in processability and thermal stability by blending a radically polymerized polymer with an anionically polymerized polymer of styrene. SOLUTION: This styrene-based resin composition is obtained by blending (A) 40-95 pts.wt. resin prepared by carrying out the radical polymerization of styrene in the presence of an initiator, 1,1-bis(t-butylperoxy)-3,5,5- trimethylcyclohexane in ethylbenzene, at a polymerization temperature within the range of 60-140 deg.C with (B) 5-60 pts.wt. resin prepared by performing the anionic polymerization of styrene in the presence of an n-butyl-lithium catalyst in a 0.01% tetrahydrofuran-cyclohexane solvent at ambient temperature. The resultant composition comprises 500-15000ppm cyclic trimer, represented by formula I and derived from a styrene-based substance and <=300ppm cyclic dimer, represented by formula II and derived from the styrene-based substance and is excellent in thermal stability and processability.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a styrene resin composition having excellent processability and heat stability.

[0002]

2. Description of the Related Art Styrenic resins have many advantages such as being colorless and transparent and hard, and having excellent resistance to water and electrical properties, and moreover, molded products can be easily mass-produced. For this reason, it is molded by various molding methods such as injection molding and extrusion molding, and is widely and widely used for electric parts, sundries, food containers and the like. Styrenic resins are mainly produced by thermal initiation or radical polymerization using an initiator. Polymerization methods are mainly bulk polymerization and suspension polymerization, but bulk polymerization has become the mainstream because of the simplicity of the polymerization method and the possibility of inclusion of impurities such as suspending agents.

Review articles (Encyclopedia o
f Chemical Technology, Kir
k-Othmer, Third Edition, Jo
According to hnWiley & Sons, Vol. 21, p. 817), in the thermal initiation polymerization at 100 ° C. or higher, oligomers such as styrene dimer and styrene trimer are accompanied by-products, and the amount thereof becomes about 1% by weight, which is mainly 1 -Phenyl-4- (1'-phenylethyl) tetralin and 1,2
-Diphenylcyclobutane, with the other presence of 2,4-diphenyl-1-butene and 2,4,6-triphenyl-1-hexene.

In addition, the literature (G. Jones, II, V.
Chew, J. et al. Org. Chem. , 1974, 39
2 pp. 1447) in tetrachloroethylene solvent.
The rate of thermal decomposition of 1,2-diphenylcyclobutane to monomers at 30 ° C is described. However, no mention is made of the influence of 1,2-diphenylcyclobutane and other oligomer components present in the polymer on the thermal stability in the polystyrene production process and molding process.

From these facts, when the oligomer in the polymer is exposed to high temperature in the step of recovering unreacted monomer or solvent or in the step of granulation, it causes a part of thermal decomposition to increase the residual monomer in the pellet. It is possible that However, if the styrene resin produced by the radical polymerization method is refined in order to improve the thermal stability, there is a problem that the high temperature good flowability of the styrene resin is impaired.

On the other hand, it is known that styrene resins produced by anionic polymerization do not contain oligomers and have higher thermal stability than those of radical polymerization, but they were obtained by anionic polymerization for economic reasons. Polystyrene has not been industrially produced as much as radical polymerization except for special applications such as use as a standard resin for gel permeation chromatography.

It is easily conceivable that a composition of intermediate cost and performance can be obtained by combining the styrene resin by radical polymerization and the styrene resin by anion polymerization. Regarding the combination of polystyrene by anionic polymerization and radical polymerization, the technology is disclosed in JP-A-4-226142. Here, a composition comprising 60 to 99 parts by weight of polystyrene obtained by a radical polymerization method and 1 to 40 parts by weight of an anion-polymerized polystyrene having a specific molecular weight does not deteriorate mechanical properties and thermoforming stability, and improves processability. It will be improved. However, the thermoforming stability described here means the softening temperature, and there is no description suggesting the effect of improving the thermal stability, which means the thermal decomposition resistance intended by us.

Further, according to our purpose, in order to reduce the generation of a monomer during secondary processing and obtain improved thermal stability, it is necessary to devise a radically polymerized polystyrene side without
It is necessary to considerably increase the amount of styrenic resin compounded by anionic polymerization.

[0009]

DISCLOSURE OF THE INVENTION The present invention is to provide a styrene resin composition which is not easily decomposed by heat when exposed to high temperatures such as a granulation step and a processing molding step, and which is excellent in processability. To aim.

[0010]

In order to solve the above problems, the present inventors have focused their attention on styrene-derived cyclic dimers and cyclic trimers that are by-produced in the radical polymerization process, and as a result, repeated search In the polymerization of styrenic resin by radical polymerization using an agent, radical polymerization polystyrene with reduced cyclic dimer is obtained by lowering the polymerization temperature compared with thermal polymerization, and by combining this with anionic polymerization polymer, cyclic dimer By reducing the amount, a styrene resin composition having improved thermal stability was obtained. At the same time, the present inventors have completed the present invention by finding the fact that the cyclic trimer has no problem with respect to thermal stability and rather contributes as a plasticizer. That is, the present invention is a styrene-based resin mixture obtained by radical polymerization and anionic polymerization, wherein the styrene-based cyclic trimer 500 to
15000ppm, styrene-based cyclic dimer 30
A styrene resin composition containing 0 ppm or less.

It has not been known at all in the past that a styrene-based cyclic trimer is thermally stable and contributes to imparting fluidity, and based on such findings, the thermal stability and processing described in detail below. It has become possible to produce a styrene resin composition having excellent properties. The contents of the present invention will be described below step by step.

The styrene-based cyclic dimer in the present invention is 1,2-diphenylcyclobutane represented by the following formula (1).

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The styrene-based cyclic trimer in the present invention is 1-phenyl-4 represented by the following formula (2).
It is-(1'-phenylethyl) tetralin.

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The styrene resin in the present invention is obtained by polymerizing only styrene, or copolymerizing styrene with α-methylstyrene or a vinyl monomer (vinyl comonomer) copolymerizable with styrene. Examples of vinyl comonomers include acrylic acid esters such as acrylic acid, methacrylic acid and butyl acrylate, methacrylic acid esters such as methyl methacrylate, α, β-unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, and N-phenylmaleimide. Maleimide etc. are mentioned. You may use these as 1 type or a mixture of 2 or more types.

The conventional styrene resin production method is mainly based on bulk polymerization. Normally 8 in bulk polymerization process
Polymerization is performed at 0 ° C to 180 ° C, followed by devolatilization in the unreacted monomer recovery step, and the unreacted monomer and solvent are recycled to the polymerization step, but the by-produced cyclic dimer and cyclic trimer are unreacted monomers. It is recycled together with it, and finally reaches an equilibrium concentration in the system, and the amount produced as a by-product during the polymerization is contained in the polymer as it is and goes out of the devolatilization step.

The polymers produced in this way include:
For example, as a result of analysis of polystyrene, by-products in the polymerization or residues / impurities from raw materials were found to be ethylbenzene, styrene, α-methylstyrene, n-propylbenzene, i-propylbenzene, 1,3-diphenylpropane. , 2,4-diphenyl-1-butene, 1,2-
Diphenylcyclobutane, 1-phenyltetralin,
2,4,6-triphenyl-1-hexene, 1,3,5
-Triphenylbenzene, 1-phenyl-4- (1'-
It was found that phenylethyl) tetralin and the like were contained.

The content of main oligomers in the product pellets obtained by thermal polymerization is 1,3-diphenylpropane: 50 ppm, 2,4-diphenyl-1-butene: 180 ppm, 1,2-diphenyl in the dimer region. Cyclobutane:
660 ppm, 1-phenyltetralin: 10 ppm,
In the trimer region, 2,4,6-triphenyl-1-hexene: 1810 ppm and 1-phenyl-4- (1′-phenylethyl) tetralin: 12600 ppm.

Examining the thermal stability of these compounds and the effect as a radical source when contained in the polymer, 1,2-diphenylcyclobutane had the greatest effect, followed by 2,4,6-. Triphenyl-1-hexene and 2,4-diphenyl-1-butene were obtained, and the influence of 1-phenyl-4- (1′-phenylethyl) tetralin on the thermal stability was smaller than these. For example, the thermal decomposition amount at 280 ° C. for 10 min is about 50% for 1,2-diphenylcyclobutane, and about 1% for 2,4,6-triphenyl-1-hexene and 2,4-diphenyl-1-butene. The other components were lower and stable than these.

The method for producing the styrenic resin (A) by radical polymerization of the present invention is to perform polymerization at a polymerization temperature of 60 to 140 ° C. using a polymerization initiator. Only thermal polymerization without using an initiator is not preferable because there are many by-products of cyclic dimers. The initiator used is not particularly limited as long as it has a 10-hour half-life temperature in the range of 30 to 170 ° C., and the polymerization conditions can be set within the technical range known to those skilled in the art regarding the polymerization temperature and the polymerization time. Preferred initiators include azobisbutyl nitrile (AIBN), benzoyl peroxide (BPO), 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane, poly {dioxy (1,1) , 4,4-tetramethyl-
1,4-butanediyl) dioxycarbonyl-1,4-
Cyclohexanecarbonyl}, t-butylperoxyisopropyl carbonate and the like.

After the completion of the polymerization, a devolatilization treatment for recovering unreacted monomer and solvent is performed. The devolatilization device is roughly classified into a type of flushing to a vacuum tank and an extrusion evaporation type (reference: new polymer manufacturing process, edited by Saeki / Omi, published by Kogyo Kenkyukai, 1994).
Year, page 195), either of which can be used. The temperature is in the range of 180 to 260 ° C, the degree of vacuum is 0.1 to 50 Torr.
Within the range, unreacted monomers and the like are volatilized. A method is also known in which devolatilizers are connected in series and arranged in two stages, and there is also known a method in which water is added between the first stage and the second stage to increase the volatility of the second stage monomer. Has been.

However, these polymerization conditions and devising the degassing method are not sufficient to obtain the desired resin composition having high thermal stability, and the resin composition is blended with the styrene resin (B) by anionic polymerization described below. Only then can the desired composition be obtained.

Styrenic resin (B) by anionic polymerization
A known manufacturing method can be used for manufacturing the. For example, the monomer is dissolved in an inert solvent at 10 to 80 ° C., and polymerization is performed using an alkyl metal or the like as an initiator. The inert solvent may be any solvent as long as it is stable to the initiator and can dissolve the styrene resin, for example, cyclohexane, methylcyclohexane, decalin, tetralin, benzene, a hydrocarbon such as toluene. Ethers, tetrahydrofuran, dioxane, ethers such as ethylene glycol dimethyl ether, etc. are preferable, and these solvents may be mixed and used.

Alkyl lithium is preferably used as the initiator. A tertiary amine such as tetramethylethylenediamine may be added in order to increase the polymerization rate.
Further, a branched structure may be provided by using a polyfunctional initiator. After completion of the polymerization, a solvent having active hydrogen such as methanol is added to stop the active growth end. At this time, it may be stopped by using a coupling agent to give a branched structure.

The styrene resin (B) obtained by anionic polymerization of the present invention has a weight average molecular weight of 80 to 750,000, preferably 1
It is 0 to 600,000. I'm not sure about the detailed mechanism,
In order to obtain a low molecular weight resin by anionic polymerization, a large amount of anionic polymerization initiator composed of an organic metal must be used due to the restriction of the polymerization method, and the styrene resin (B) having a molecular weight of less than 80,000 is thermally stable. Insufficient in sex. Further, when it is 750,000 or more, there is a problem in fluidity, which is not suitable for the purpose of the present invention.

The composition of the present invention is obtained by blending 40 to 95 parts by weight of the resin (A) obtained by the radical polymerization and 5 to 60 parts by weight of the resin (B) obtained by the anionic polymerization. However, the blending ratio of both is not fixed, and changes depending on the amount of styrene-based cyclic dimer in the resin (A). For example, when the polymerization temperature is set low, the target composition can be obtained by mixing (A) having a small amount of cyclic dimer with a small amount (B). However, if the polymer by anionic polymerization is less than 5% by weight, the heat stabilizing effect is small,
If the content is above, the cyclic trimer content becomes insufficient, and the processability such as fluidity decreases.

As the compounding method, any known method used for compounding a resin can be used.
For example, it can be produced by blending with a Henschel mixer or the like and then melt-kneading with a twin-screw extruder or the like. It is also possible to install a polymerization system in which a radical polymerization process and an anionic polymerization process are installed in parallel, and to mix both during the reaction. The styrene-based cyclic dimer reduced in this manner is 300 ppm or less, preferably 200 ppm or less in the polymer.

The concentration of cyclic trimer which gives good flowability when it is contained in the styrene resin composition of the present invention is 50.
It is 0 to 15000 ppm. Preferably 500 to 10
000, more preferably 500 to 8000 ppm. If it is less than 500 ppm, the workability cannot be greatly improved, and if it is more than 15000 ppm, problems such as lowering the heat distortion temperature occur.

Further, the styrene resin composition of the present invention is preferably a rubber-modified one or a rubber-like polymer added. As the rubber polymer, polybutadiene,
Polyisoprene, styrene-isoprene copolymer, and hydrogenated products thereof are preferably used. A rubber-modified styrene-based resin can be obtained by melt-blending these rubber-like polymers with a styrene-based resin or polymerizing styrene or the like in the presence of these rubber-like polymers.
These styrene resins may be used alone or as a mixture of two or more.

The styrene resin composition of the present invention is filled with various stabilizers, flame retardants, antistatic agents, colorants, glass fibers, etc., unless the purpose of improving processability and heat stability is violated. Any additive known to be blended with the styrenic resin such as an agent can be added.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be specifically described with reference to Examples and Comparative Examples. (Example 1) 0.9 kg of purified styrene and 0.1 kg of purified ethylbenzene were placed in a temperature-adjustable stainless steel polymerization vessel.
Initiator 1,1-bis (t-butylperoxy) -3,
Polymerization was carried out by adding 0.1 g of 5,5-trimethylcyclohexane and keeping the temperature under nitrogen gas at 140 ° C. for 8 hours while stirring. After this, 2 Torr under reduced pressure while stirring.
The temperature was raised to 50 ° C. and unreacted styrene, ethylbenzene and the like were distilled off. The obtained polymer was designated as (A). When measured by gel permeation chromatography (GPC), the weight average molecular weight was 260,000 and the molecular weight distribution was 2.4.
Met.

Next, 1 liter of a 0.01% tetrahydrofuran-cyclohexane solvent dried under nitrogen gas and purified styrene 10 were placed in a temperature controlled stainless steel polymerization vessel.
0 g was added, and 0.35 mmol of n-butyllithium was added at room temperature with stirring. After 10 hours, 10 ml of methanol was added to stop the polymerization, and then the content was dropped into 10 l of methanol to collect the precipitated polymer, which was washed with methanol and dried. The obtained polymer was designated as (B). The weight average molecular weight was 280,000 and the molecular weight distribution was 1.1.

80 g of the radically polymerized polymer (A) obtained above and 20 g of anionically polymerized polymer (B) were melt mixed using a plastomill. 200 mg of this resin composition was dissolved in 2 ml of 1,2-dichloroethane. 2 ml of methanol was added to this solution to precipitate a polymer, which was filtered through a filter having a pore size of 0.2 μm, and the filtrate was analyzed by gas chromatography. The column is TC-1 (inside diameter 0.2
5 mm, thickness 0.25 μm, length 30 m) were used. After keeping the column temperature at 50 ° C for 5 minutes, 20 ° C / mi
The temperature was raised up to 320 ° C. with n and kept for 3 minutes. The apparatus was Shimadzu GC-14B (FID detection), the injection was set at 260 ° C, and the detector was set at 330 ° C.
Anthracene was used as the internal standard. Styrene-based cyclic dimer 270ppm, the same cyclic trimer 2880pp
m.

70 mg of this styrene resin composition was placed in a glass ampoule tube, sealed under reduced pressure, and then subjected to a thermal decomposition test at 280 ° C. The generation of monomers was measured by gas chromatography as in the oligomer analysis above. The generation rate was calculated from the amount of monomer generated up to 20 minutes. The monomer generation rate was 1740 ppm / hr. The workability was measured by fluidity. Melt flow rate (MI value) was measured according to ASTM D1238 under condition G (2
It was measured at 00 ° C. and a load of 5.0 kg. As a result, MI
Was 3.2 g / 10 min.

Example 2 The same procedure as in Example 1 was carried out except that 50 g of the radically polymerized polymer (A) and 50 g of the anionically polymerized polymer (B) were melt mixed using a plastomill. The contained cyclic dimer was 170
ppm, cyclic trimer is 1870 ppm, monomer generation rate is 1210 ppm / hr, MI is 3.1 g /
It was 10 minutes.

(Example 3) 0.56 kg of purified styrene, 0.26 kg of purified acrylonitrile, and 0.19 kg of purified ethylbenzene were added to a temperature-adjustable stainless steel polymerization vessel.
Polymerization was carried out by adding 0.3 g of t-butylperoxyisopropyl carbonate as an initiator and keeping the temperature under stirring at 150 ° C. for 8 hours under nitrogen gas for 2 hours while stirring. After this, 5
The temperature was raised to 250 ° C. with stirring under reduced pressure of Torr, and unreacted styrene, ethylbenzene and the like were distilled off. Obtained AS
50 g of (acrylonitrile-styrene) polymer and 50 g of the anionically polymerized polymer synthesized in Example 1 were melt mixed. The cyclic dimer contained in the obtained polymer was 210 ppm, and the cyclic trimer was 2470 ppm.
Monomer generation rate is 1070ppm / hr, MI is 26
It was g / 10 min (220 ° C., 10 kg load).

(Example 4) In Example 1, 0.5 g of BPO was added as an initiator and polymerization was carried out at 105 ° C. The weight average molecular weight of the obtained polymer (A) was 33.
The molecular weight distribution was 2.2. Other than this, Example 1
Was performed in the same manner as described above. The cyclic dimer in the obtained polystyrene was 55 ppm, and the cyclic trimer was 720 ppm. In addition, the monomer generation rate is 1080 ppm / hr.
And MI was 3.0 g / 10 min.

(Comparative Example 1) The radical-polymerized polymer obtained in Example 1 was used for the measurement. The quantification of the cyclic dimer and the cyclic trimer in the obtained polymer, the thermal decomposition test and the workability measurement were performed according to Example 1, and the content of the cyclic dimer was 350 ppm and the cyclic trimer was 3600 ppm, and the MI was 3.3 g / 10 min. The monomer generation rate was 2250 ppm / hr, which was easy to decompose.

Comparative Example 2 Using the radical-polymerized polymer obtained in Example 1, this was dissolved in tetrahydrofuran and added dropwise to methanol to obtain a purified polymer. Quantification of cyclic dimer and cyclic trimer in this polymer, thermal decomposition test and measurement of processability were carried out according to Example 1. The content of cyclic dimer was 1 ppm or less and 170 ppm of cyclic trimer, and the monomer generation rate was 110.
It was 0 ppm / hr, but MI was 2.7 g / 10 mi.
It was as low as n.

(Comparative Example 3) The measurement was carried out using the anionically polymerized polymer obtained in Example 1. Ring dimer,
No cyclic trimer was detected. Monomer generation rate 3
Excellent thermal stability of 00 ppm / hr, but MI of 2.5
It was as low as g / 10min.

Comparative Example 4 The AS polymer obtained in Example 3 contained 430 ppm of cyclic dimer, 5100 ppm of cyclic trimer, and MI of 27 g / 10.
Although it was min (220 ° C., 10 kg load), the monomer generation rate was 1500 ppm / hr, which was easy to decompose.

[0041]

Industrial Applicability According to the present invention, it is possible to provide a styrenic resin composition which is superior in thermal stability and processability to conventional styrenic resins.

Claims (3)

[Claims] 1. A styrenic resin composition obtained by radical polymerization and anionic polymerization, which comprises 500 to 15000 ppm of a styrene-derived cyclic trimer and 300 ppm or less of a styrene-derived cyclic dimer. 2. Resin (A) 40 to be obtained by radical polymerization using a polymerization initiator at a polymerization temperature of 60 to 140 ° C.
Resin (B) 5 obtained by anionic polymerization with 95 parts by weight
The styrene-based resin composition according to claim 1, which is obtained by blending -60 parts by weight. 3. The styrene resin composition according to claim 1, wherein the styrene resin obtained by anionic polymerization has a weight average molecular weight in the range of 80 to 750,000.