JPH0819238B2 - Styrene polymer and method for producing the same - Google Patents

Description

The present invention relates to a styrenic polymer and a method for producing the same,
More particularly, it relates to a novel styrene polymer having a branched nucleus containing a sulfur atom and having a specific sulfur content, molecular weight and molecular weight distribution, and an efficient production method thereof.

[Problems to be Solved by Prior Art and Invention]

The fluidity of the styrenic polymer can be improved by lowering its molecular weight, but it causes a sharp drop in impact strength.

As another method for improving the fluidity, it is conceivable to increase the molding temperature, but raising the molding temperature causes problems such as yellowing and molecular weight reduction due to thermal deterioration. Under such circumstances, it has been desired to develop a technique for improving the fluidity of the styrene polymer without impairing its impact resistance.

On the other hand, so-called styrenic star polymer (star polymer)
In order to produce the above, a method of anionically polymerizing a styrene-based monomer using a polymerization initiator such as metallic lithium is known (for example, J. Polym. Sci. PART, A 3 , 681 to 696 (1
965).

However, the styrene-based star polymer obtained by such an anionic polymerization method has a molecular weight distribution, that is, a weight average molecular weight / number average molecular weight (Mw / Mn) of about 1,
The molecular weight distribution is narrow, and when the styrene star polymer is made to have a high molecular weight, the moldability is remarkably lowered.

Furthermore, the method of radically polymerizing styrene-based monomers to produce styrene-based star polymers is Macromol.Che.
m., 178, 1427 (1977). However, here we are only going to pursue the reaction mechanism,
The obtained polymer has a conversion rate of only 25%,
No mention is made of a styrene-based star polymer obtained by polymerization up to a conversion rate higher than this. Further, the physical properties and moldability of the obtained styrene-based star polymer are not mentioned at all.

[Means for solving problems]

The present inventors have earnestly studied to solve the above-mentioned drawbacks of the prior art and to develop a styrene-based polymer having excellent impact resistance and fluidity. As a result, radical polymerization of styrenic monomer in the presence of a specific polyfunctional mercaptan compound until the conversion rate was 40% or more, the flowability and moldability were remarkably improved while maintaining sufficient impact resistance. It was found that a new styrenic polymer can be obtained. The present invention has been completed based on such findings.

That is, the present invention has the general formula Or [In the formula, R represents an alkyl residue having 1 to 10 carbon atoms or an aryl residue having 6 to 10 carbon atoms, S represents a sulfur atom,
St represents a styrene-based monomer unit, and A represents Represents an organic residue represented by. Here, m represents an integer of 0 to 10 and n represents an integer of 1 to 10. ] A styrene-based polymer having a branched nucleus represented by the following formula, which has a sulfur content of 6 to 550 ppm and a weight average molecular weight of 150,000 to 40.
10,000 and weight average molecular weight / number average molecular weight (Mw / Mn) 1.5 to 6.
In addition to providing a styrene-based polymer, the styrene-based monomer or the styrene-based monomer and another monomer copolymerizable with the styrene-based monomer are represented by the general formula RSH) _k or RA-SH) _k ( V) [In the Formula, R and A are the same as the above, and k shows 3 or 4. However, all k -SH or -A-SH are bonded to R. ] A polyfunctional mercaptan compound represented by the following is added at a ratio of 25 to 2000 ppm relative to the total weight of the raw material monomers, and radical polymerization is performed until the conversion becomes at least 40% by weight. A manufacturing method is provided.

The styrenic polymer of the present invention has the above-mentioned properties and can be produced by various methods, but is preferably produced by the method of the present invention. First, the method of the present invention will be described in detail as follows.

Examples of the styrene-based monomer used in the method of the present invention include not only styrene but also α-substituted styrenes such as α-methylstyrene, α-ethylstyrene and α-isopropylstyrene, p-methylstyrene, m-methylstyrene, Examples thereof include nucleus-substituted alkylstyrenes such as 2,5-dimethylstyrene, and nucleus-substituted halogenated styrenes such as p-chlorostyrene and p-bromostyrene.

In the method of the present invention, only the above-mentioned styrene-based monomer may be used as a raw material monomer, but it is also possible to use another monomer copolymerizable with the styrene-based monomer together with the styrene-based monomer. Other monomers include acrylonitrile, methacrylonitrile,
Examples thereof include vinyl monomers such as methacrylic acid, methyl methacrylate, acrylic acid, and ester derivatives such as methyl acrylate, and maleic anhydride, maleimide, and nucleus-substituted maleimide. Therefore, the styrene-based polymer of the present invention includes homopolymers and copolymers (random, graft, etc.) of styrene-based monomers selected from the above-mentioned styrene and substituted styrene, and copolymerizable with the styrene-based monomers as described above. And other copolymers with other monomers.

In the method of the present invention, based on the total weight of the raw material monomer consisting of the above-mentioned styrene-based monomer or styrene-based monomer and other monomer copolymerizable therewith,
Polymerization is carried out by adding the polyfunctional mercaptan compound represented by the general formula (V) at a ratio of 25 to 2000 ppm before or during the polymerization.

In the general formula (V), R is an alkyl residue having 1 to 10 carbon atoms or an aryl residue having 6 to 10 carbon atoms. An alkyl residue having 1 to 10 carbon atoms is bonded from an alkyl group-S
Alternatively, it is a residue in which a hydrogen atom is removed according to the number (k) of -A-S, and for example, a hydrogen atom is 2 or It is a group with three removed. As the aryl residue having 6 to 10 carbon atoms, mention should be made of a group obtained by removing 2 or 3 hydrogen atoms from a phenyl group, a nucleus-substituted phenyl group (tolyl group, etc.), α-naphthyl group, β-naphthyl group, etc. You can In general formula (V), each of k -SH or -A-SH is bound to R.

There are various kinds of such polyfunctional mercaptan compounds, and among them, typical examples of the tetrafunctional mercaptan compounds are pentaerythritol tetrakis (2-mercaptoethanate) and pentaerythritol tetrakis (3-mercaptoprone). Pionate), pentaerythritol tetrakis (4-mercaptobutanate), pentaerythritol tetrakis (5-mercaptopentanate), pentaerythritol tetrakis (6-mercaptohexanate) and the like. As typical examples of trifunctional mercaptan compounds, trimethylolpropane tris (2-mercaptoethanate), trimethylolpropane tris (3-mercaptopropionate), trimethylolpropane tris (4-mercaptobutanate), Examples thereof include trimethylolpropane tris (5-mercaptopentanate) and trimethylolpropane tris (6-mercaptohexanate). These polyfunctional mercaptan compounds may be used alone or in combination of two or more.

The amount of the polyfunctional mercaptan compound used should be 25 to 2000 ppm with respect to the total weight of the raw material monomers. If it is less than 25 ppm, the sulfur content in the obtained styrene polymer does not reach 6 ppm, the addition effect is low, and no improvement in fluidity is observed. On the other hand, if it exceeds 2000 ppm, the sulfur content in the obtained styrene-based polymer will exceed 550 ppm, the molecular weight during molding will remarkably decrease, and the mechanical strength such as impact resistance of the molded product will decrease. From this point of view, in the method of the present invention, it is preferable to use the polyfunctional mercaptan compound in a proportion of 50 to 1500 ppm relative to the raw material monomer. Radical polymerization of the above-mentioned styrene-based monomer or a styrene-based monomer and another monomer copolymerizable therewith may be carried out by, for example, benzoyl peroxide, dikulmi peroxide, t-butylperoxyisopropyl carbonate, 2,4-dichlorobenzoyl peroxide. , By a conventionally known method using a radical polymerization initiator such as cumene hydroperoxide, for example, a suspension polymerization method, a bulk-suspension two-stage polymerization method, a bulk polymerization method, etc.
Usually, it can be carried out under normal pressure at a polymerization temperature of about 75 to 150 ° C. In the radical polymerization, various additives such as suspension stabilizers generally used in this type of polymerization reaction can be used. Further, in order to further improve the impact resistance of the obtained styrene-based polymer, a rubber-like substance such as polybutadiene may be dissolved in the raw material monomer, or may be kneaded into the polymer after polymerization. Here, examples of the rubber-like substance include polybutadiene rubber, acrylonitrile-butadiene copolymer rubber (NBR), diene rubber such as styrene-butadiene copolymer rubber (SBR), and acrylic rubber such as polybutyl acrylate and polypropyl acrylate. Rubber, and further ethylene-propylene-diene rubber (EPDM) and the like can be used.

In the method of the present invention, the radical polymerization of the raw material monomers has a conversion of at least 40%, preferably at least 60%.
Carry out until%. When the conversion rate is less than 40%, a polymer having a predetermined high molecular weight cannot be obtained, and the flowability and impact resistance are not improved. Furthermore, maintaining the initial polymerization temperature at 95 to 110 ° C. is effective in obtaining a styrene polymer having a predetermined weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn).

The sulfur content of the styrene-based polymer obtained by the above-mentioned polymerization was measured by fluorescent X-ray analysis as described later. When this sulfur content was converted into the content of the mercaptan compound used, the amount of the mercaptan compound used was calculated. It turned out to be equivalent to. Further, the polymer was dissolved in chloroform, precipitated with methanol, and the methanol portion was electrotitrated, but sulfur was not detected. From the above results, it is considered that in the styrene-based polymer obtained by the method of the present invention, almost all the added mercaptan compound is incorporated in the polymer chain.

From the above, according to the method of the present invention, for example, when a trifunctional mercaptan compound is used, as shown in the following polymer schematic diagram, the trifunctional mercaptan compound residue is at the center (that is, this is a branched nucleus). It was confirmed that a styrenic polymer (branched polymer) was produced.

(In the formula, St represents a styrene-based monomer unit.) The sulfur content of the styrene-based polymer of the present invention has a correlation with the amount of the polyfunctional mercaptan compound of the general formula (V) used, and is 6 to It is 550 ppm. Sulfur content is 6ppm
If it is less than 550 ppm or more than 550 ppm, the above-mentioned unfavorable problems occur with respect to the amount of the polyfunctional mercaptan compound used. The sulfur content is particularly preferably in the range of 20 to 400 ppm.

The weight average molecular weight of the styrenic polymer of the present invention is 150,00.
It is 0 to 400,000, preferably 250,000 to 350,000. When the weight average molecular weight is less than 150,000, the impact strength is significantly decreased, while when it exceeds 400,000, the fluidity is decreased and the moldability is deteriorated.

The weight average molecular weight / number average molecular weight (Mw / Mn) showing the molecular weight distribution is 1.5 to 6.0, preferably 2 to 5. 1.5
If it is less than 1, the fluidity is lowered and the moldability is deteriorated. on the other hand,
If it exceeds 6.0, the impact strength decreases due to the formation of a low molecular weight polymer.

〔Example〕

Next, the present invention will be described more specifically by way of examples.
In the examples,% and ppm are based on weight. The sulfur content, molecular weight, molecular weight distribution, fluidity, conversion rate and impact strength of the obtained styrenic polymer were measured by the following methods.

Sulfur content The polymer was pressed and measured by X-ray fluorescence.

Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn) Monodisperse polystyrene (Pres
It was measured by gel permeation chromatography (GPC) using Sure Chemical Co., Ltd.).

Fluidity Measured by spiral flow length (SFL) (molding temperature 220 ℃, injection pressure 80kg / cm ² , mold temperature 45 ℃, wall thickness 1/8
inch).

Conversion rate The residual amount of monomers in the polymer was measured by gas chromatography, and the conversion rate was calculated from the amount of reacted monomers.

Impact strength JIS JIS for flatwise impact strength (without notch)
-Measured by K7110 (1/8 inch molding, molding temperature
230 ℃).

Example 1 Benzoyl peroxide was added to 10 polymerization tanks equipped with a stirrer.
0.2%, t-butyl peroxyisopropyl carbonate
A styrene monomer solution containing 0.25% and 40 ppm of pentaerythritol tetrakis (3-mercaptopropionate) and 1% of tribasic calcium phosphate as a suspension stabilizer.
(Against water), sodium dodecylbenzenesulfonate 0.05
% (Vs water) and ion-exchanged water were added at a volume ratio of 1: 2. 8 hours at 100 ℃ at 500 rpm under nitrogen atmosphere, 11
Polymerization was carried out at 0 ° C for 4 hours and further at 120 ° C for 4 hours. The results are shown in Table 1.

Example 2 30 pp of trimethylolpropane tris (3-mercaptopropionate) was used as a polyfunctional mercaptan compound.
Polymerization was performed in the same manner as in Example 1 except that m was added and 100 ° C was changed to 90 ° C. The results are shown in Table 1.

Example 3 Polymerization was carried out in the same manner as in Example 1 except that 400 ppm of pentaerythritol tetrakis (3-mercaptopropionate) was added and benzoyl peroxide was 0.3%. The results are shown in Table 1.

Example 4 1500 is trimethylolpropane tris (3-mercaptopropionate) as a polyfunctional mercaptan compound.
Polymerization was performed in the same manner as in Example 3 except that ppm was added. The results are shown in Table 1.

Example 5 40% of pentaerythritol tetrakis (3-mercaptopropionate) was used as a polyfunctional mercaptan compound.
Polymerization was performed in the same manner as in Example 1 except that 0 ppm was added. However, the polymerization was interrupted at a conversion of 75%. First result
Shown in the table.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that mercaptan was not added. The results are shown in Table 1.

Example 6 8% by weight of polybutadiene rubber was completely dissolved in the styrene monomer solution of Example 1. This styrene monomer solution was placed in a bulk polymerization tank No. 5 equipped with a double helical blade and reacted at 500 ° C. under a nitrogen atmosphere at 100 ° C. for 4 hours to produce a prepolymer.

Next, this prepolymer and polyvinyl alcohol 0.2% (vs. water), which is a suspension stabilizer, were dissolved in ion-exchanged water at a volume ratio of 1: 2 into a suspension polymerization tank of 10 and under a nitrogen atmosphere at 500 rpm. , 100 ℃ for 4 hours, 110 ℃ for 4 hours, 120 ℃
And reacted for 4 hours.

Comparative Example 2 Polymerization was carried out in the same manner as in Comparative Example 1 except that the reaction was carried out at 90 ° C. for 10 hours without adding mercaptan. The results are shown in Table 1.

Comparative Example 3 Polymerization was carried out in the same manner as in Example 5 except that the reaction was stopped at 85 ° C. for 3 hours. The results are shown in Table 1.

Comparative Example 4 Polymerization was carried out in the same manner as in Example 1 except that 1000 ppm of trimethylolpropane tris (3-mercaptopropionate) was added and 0.3 wt% of benzoyl peroxide was added. The results are shown in Table 1.

[Advantages of the Invention] As described above, the styrene-based polymer of the present invention is excellent in impact resistance, fluidity, and moldability, and can be molded by general injection or extrusion molding to obtain a molded product having excellent mechanical strength. You can Moreover, according to the method of the present invention, the styrene polymer can be obtained very efficiently.

Therefore, the present invention can be widely and effectively utilized as a raw material in the fields of general injection or extrusion molding of styrene resins and sheet molding.

Claims (2)

[Claims] 1. A general formula [In the formula, R represents an alkyl residue having 1 to 10 carbon atoms or an aryl residue having 6 to 10 carbon atoms, S represents a sulfur atom,
St represents a styrene-based monomer unit, and A represents Represents an organic residue represented by. Here, m represents an integer of 0 to 10 and n represents an integer of 1 to 10. ] A styrene-based polymer having a branched nucleus represented by the following formula, which has a sulfur content of 6 to 550 ppm and a weight average molecular weight of 150,000 to 40.
10,000 and weight average molecular weight / number average molecular weight (Mw / Mn) 1.5 to 6.
A styrenic polymer characterized by being 0. 2. A styrene-based monomer or a styrene-based monomer and another monomer copolymerizable therewith are represented by the general formula RSH) _k or RA-SH) _k (V) [wherein R represents 1 to 10 carbon atoms]. Represents an alkyl residue or an aryl residue having 6 to 10 carbon atoms, wherein A is Represents an organic residue represented by. Here, m represents an integer of 0 to 10 and n represents an integer of 1 to 10. Further, S represents a sulfur atom, and k represents 3 or 4. However, all k -SH or -A-SH are bonded to R. ] A polyfunctional mercaptan compound represented by the following is added at a ratio of 25 to 2000 ppm with respect to the total weight of the raw material monomers, and radical polymerization is carried out until the conversion becomes at least 40% by weight, a general formula [In the formula, R represents an alkyl residue having 1 to 10 carbon atoms or an aryl residue having 6 to 10 carbon atoms, S represents a sulfur atom,
St represents a styrene-based monomer unit, and A represents Represents an organic residue represented by. Here, m represents an integer of 0 to 10 and n represents an integer of 1 to 10. ] A styrene-based polymer having a branched nucleus represented by the following formula, which has a sulfur content of 6 to 550 ppm and a weight average molecular weight of 150,000 to 40.
10,000 and weight average molecular weight / number average molecular weight (Mw / Mn) 1.5 to 6.
A method for producing a styrene-based polymer, which is 0.