JPS608304A - Production of styrene polymer - Google Patents

Abstract

PURPOSE:To provide the titled polymer having high strength and excellent moldability, without lowering the characteristic properties of the base polymer, by polymerizing styrene at a low temperature in the presence of a specific polymerization initiator, mixing a styrene polymer having a specific viscosity to the polymerization product, and continuing the polymerization. CONSTITUTION:(A) 100pts.wt. of styrene or a mixture of styrene and a substituted styrene is mixed with (B) 0.002-0.2pts.wt. (in terms of active oxygen) of an organic peroxide decomposable at a low temperature and containing >=3 recurring units of formula I (R is bivalent organic group) (e.g. the peroxide having the recurring unit of formula II), and is subjected to the bulk polymerization or solution polymerization at 60-80 deg.C until the conversion of the component A reaches >=10wt%. The polymerization product is mixed with (C) a styrene polymer having a standard viscosity of 25-50cps, and the polymerization is continued to obtain the objective polymer having a standard viscosity of 30-60cps.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a styrenic polymer having high strength and good moldability.

Styrene polymer is a resin with excellent transparency, moldability, and rigidity, and has long been widely used as a molding material for household goods and electrical products.However, due to the recent rise in the cost of raw materials, other high-grade resins are being used. There is a tendency to switch to relatively inexpensive resins, and the demand for styrene polymers is on the rise. Along with this, in order to expand the field of application, there has been an increasing demand for simultaneously improving the impact resistance, moldability, and heat resistance of styrene polymers.

It has been known that when producing a styrene polymer by bulk polymerization or solution polymerization, in order to obtain a styrene polymer with high impact strength, the average molecular weight can be increased. Known methods for increasing the average molecular weight of styrene polymers include lowering the polymerization temperature and decreasing the amount of polymerization initiator added, but these methods do not improve the polymerization rate. This will inevitably lead to a decrease in productivity. On the other hand, if the average molecular weight of the styrene polymer is increased, the moldability will decrease and distortion will occur during molding, which will reduce the strength of the molded product. Addition of such agents is not preferable because it causes deterioration of heat resistance and other physical properties.

The present inventors have overcome the drawbacks of such conventional methods,
In order to develop a method to further improve the strength and moldability of styrene polymers without sacrificing their desirable physical properties, we have developed a method using a certain type of low-temperature decomposition organic peroxide. After polymerizing styrene at low temperature to produce a polymerization solution containing a small amount of ultra-high molecular weight styrene polymer, a styrene polymer having a normal degree of polymerization is added to this to reach a predetermined degree of polymerization. He discovered that he could achieve his goal by carrying out polymerization until
The present invention was made based on this knowledge.

That is, the present invention provides a method for producing a styrenic polymer by bulk polymerization or solution polymerization of styrene alone or a mixture of styrene and substituted styrene, in which the general formula (R in the formula is a divalent organic residue) is used. ) A low-temperature decomposition type organic peroxide containing at least three repeating units represented by is added at a ratio of 0.002 to 0.02 parts by weight in terms of active oxygen amount per 100 parts by weight of monomer, and at a temperature of 6.
Monomer conversion of at least 10 weight-iL at 0-80°C
%, then a styrenic polymer with a standard viscosity of 25 to 50 centipoise is mixed with this polymerized product, and then further polymerized to obtain a styrenic polymer with a standard viscosity of 30 to 60 centipoise. The present invention provides a method for producing a styrenic polymer.

The standard viscosity here means the viscosity of a 10% by weight toluene solution of the polymer at 25°C, and is a measure of the degree of polymerization of the polymer. can be measured.

As the monomer in the method of the present invention, styrene alone may be used, or a mixture of styrene and substituted styrene may be used. Examples of the substituted styrene used in combination with this styrene include α-methylstyrene, p-methylstyrene, vinyltoluene, and vinylxylene.

In the method of the present invention, it is first necessary to carry out the first-stage polymerization step in the presence of a polymerization initiator consisting of a specific low-temperature decomposition type organic peroxide. This low-temperature decomposition type organic peroxide contains at least 3, preferably 5 to 30, repeating units represented by the general formula (1).
It has a half-life of 10 hours at temperatures between 0 and 90°C. Examples of such organic peroxides include those having the following repeating units.

0 0 +C! =CH20H200H2CH2-c-0-0+.

(-C-ca2cu20ca2cH200H2C!H2
-0-0-0+.

CH3 CH5 (=C-(C!H2)6.0H(C2Hs) (CH2
)9 C! OO'-1-1+ C-(CH2) t-
0-0(OH2)20 (CH2)20 (CH2)2
0- C- (OH2)4-C-0-0 An experiment was conducted in which the solution was dissolved at a concentration of 1 mol/l, sealed in a nitrogen-substituted glass tube, immersed in a constant temperature bath, and thermally decomposed by changing the temperature of the constant temperature bath. You can do it like this.

In other words, since this decomposition reaction can be approximately treated as a first-order reaction, the amount of decomposed organic peroxide (Xi, decomposition rate constant (K), time (1), and initial concentration of organic peroxide (a) The following formula holds true between:

−−K (a−x) −−−■ t tna/ −−xt −−−■ (a The decomposition rate constant @) can be calculated from the slope of the straight line.

On the other hand, regarding K, the relational expression K = Aexp(-ΔE/RT) ---, ■ (where A is the frequency factor, ΔE is the activation energy, R is the gas constant, and T is the temperature) is established, so it is different. Calculate K for the temperature set, plot the relationship between tn h and 1/T on a graph,
From the resulting straight line, a decomposition temperature indicating a 10 hour half-life ('', 4) can be obtained.

In the method of the present invention, it is advantageous to use organic peroxides with a 10-hour half-life of 40 to 90°C, and those with a half-life of less than 40°C pose dangers such as explosion during storage and handling. If the temperature is higher than 90°C, polymerization takes a long time, resulting in a significant decrease in productivity.
Not practical.

In the method of the present invention, this organic peroxide is
0.002 to 0.02 in terms of active oxygen amount per part by weight
It is necessary to use parts by weight.

The active oxygen amount here means the amount of active oxygen (-6-) in peroxide bonds present in the organic peroxide.

Polymerization in the method of the present invention is carried out by reacting a mixture of raw material monomers with a polymerization initiator and, if desired, a solvent and other necessary additives, in accordance with the bulk polymerization method or solution polymerization method used in the usual stilsin polymerization method. This can be done by charging the mixture into a container and heating it while applying pressure if necessary.

The first step of the polymerization of the process of the invention is thus carried out at a temperature of 60 to 80°C, with a monomer conversion of at least 1.
It is necessary to repeat the process until it reaches 0%. At this stage, a reaction mixture containing some ultra-high molecular weight styrenic polymer is produced. This ultra-high molecular weight styrene polymer means one having a molecular weight of 2 million or more, and can be measured using gel permeation chromatography.

If the organic peroxide monomer ioo weight part equivalent is less than 0.002 parts by weight in terms of the amount of active oxygen, the time required for polymerization will be significantly longer, resulting in a decrease in productivity, and if the amount is less than 0.002 parts by weight If the amount exceeds 100%, the formation of ultra-high molecular weight styrene polymer will be insufficient, and as a result, a styrenic polymer with high strength cannot be obtained.

On the other hand, if the polymerization temperature in the first stage is as low as 66°C, the polymerization rate will be slow, causing a decrease in overall productivity, and if it is as high as 80°C, ultra-high molecular weight styrene polymers will be produced. is not produced, and the desired high-strength styrene polymer cannot be obtained.

This first stage polymerization is carried out at a monomer conversion rate of at least 1.
It is necessary to carry out the reaction until it reaches 0% by weight, and the conversion rate is 1%.
Below 0 weight, it is not possible to obtain a reaction mixture containing a sufficient amount of ultra-high molecular weight styrenic polymer to impart high strength to the final styrenic polymer.

After the first stage polymerization has been carried out in this manner, a separately prepared styrene polymer having a standard viscosity of 25 to 50 centipoise is added to the reaction product, and a second stage polymerization is carried out.

The styrenic polymer used in this case, which has a standard viscosity of 25 to 50 centipoise at 25° C. when prepared as a 10-weight toluene solution, can be prepared according to a conventional method. The standard viscosity of this material must be within the above range; if it is 25 centipoise, the strength of the resulting styrenic polymer will not be sufficiently improved, and if it exceeds 50 centipoise, This is not practical as it reduces productivity.

The styrenic polymer added in this second stage is
It can be prepared by a known method by selecting conditions that provide a predetermined viscosity.

In this second stage polymerization, adding a pre-prepared polymer of a specific viscosity is a necessary condition for obtaining a styrenic polymer with a controlled molecular weight. Although it is not necessarily impossible to obtain a styrenic polymer with a desired molecular weight by directly polymerizing the polymerization product of the first step in the second step, it is extremely difficult to control the polymerization conditions at this time. , when implemented industrially, productivity inevitably decreases.

In the second stage of polymerization, the polymer-containing solution obtained in the first stage is mixed with a separately prepared solution containing a polymer having a predetermined viscosity at a ratio of 1:5 to 2:1 based on the weight of each monomer. This can be carried out by mixing at a ratio of 100°C to 150°C in the presence of a polymerization surface initiator.

As the polymerization initiator in this case, an organic peroxide which is commonly used as a polymerization initiator in the production of styrenic polymers is used. Examples of such organic peroxides include:
2.2-bis(t-butyl-butane)butane; 2.
2-bis(1-butyl)-oxy)octane, 1.1
-Bis(t-butyl)<-Kaki7) -3,3,5-
)limethylzoclohexane, 1,J-bis(t-butyloxy)cyclohexane, 4,4-bis(1-butylperoxy)valerate n-butyl(-oxy/ Ketals, di-t-butyl peroxide, t-butylcumyl oxide, dicumyl peroxide, α, α
'-Bis(t-butyl;-oxyinopropyl)benzene, 2,5-dimethyl-2,5-di(t-butyl-oxy)hexane, 2,5-dimethyl-2,5-di(
Dialkyl peroxides such as (butylperoxy)hexyne-3, acetyl peroxide, isobutyl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, 3.5.5 -trimethylhexanoyl peroxide, 2,4-dichlorobenzoyl peroxide,
Diacyl peroxides such as m-toluoyl peroxide, diimpropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-
n-propyl peroxydicarbonate, di-n-propyl peroxydicarbonate, dimyristyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, dimethoxyisopropyl peroxydicarbonate, di(3-methyl-3 -methoxybutyl)
Peroxydicarbonates such as peroxydicarbonate, t-butylperoxyacetate, t-butylperoxyimputylate, 7-butylperoxypivalate, t-butylperoxyneodecanoate, cumylperoxy Neodecanoate, t-butylperoxy-2-ethylhexanoate, L-butylperoxy-3.5.5-trimethylhexanoate, t-butylperoxynonalate, 7-butylperoxybenzoate, G-t -butyl diperoxyisophthalate), 2
．． 5-dimethyl-2,5-di(benzoylperoxy)
Hexane, peroxy esters such as t-butylperoxyinopropyl carbonate, acetylacetone peroxide, methyl ethyl ketone oxide,
/ketone oxides such as clohexanone peroxide, 3,3.5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, t
-butyl hydroperoxide, cumene hydroperoxide, diimpropylbenzene hydroperoxide, p-
Methanehydrono-oxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1.1,3.3
- Hydroperoxides such as tetramethylbutyl hydroperoxide may be mentioned. These polymerization initiators are contained in an amount of 0.005 to 0.1% by weight based on the monomer weight.
It is added within the range of

This second stage polymerization must be carried out under conditions that will yield a styrenic polymer having a standard viscosity of 30 to 60 centivoids. In this case, if the viscosity of the styrenic polymer is less than 30 centivoids, high strength cannot be obtained. Further, even if the strength exceeds 60 centimeters, the strength remains unchanged and hardly increases, which merely causes a decrease in productivity and is practically meaningless.

From the polymerization solution thus obtained, the desired styrenic polymer can be separated by removing unreacted monomers and solvents according to a conventional method.

The method of the present invention can be carried out either batchwise or continuously. Additives commonly used for styrenic polymers, such as antioxidants, lubricants, plasticizers, and flame retardants, may be added at any stage before or after recovering unreacted monomers, solvents, etc. , a coloring agent, etc. can be added. Examples of such lubricants include stearic acid, behenic acid, lead stearate, and ethylene bisstearamide; examples of antioxidants include 2,6-di-t-phthyl-4-methylphenol β-( 3,5-di-t-butyl-4-hydroxyphenyl) flobionate, trier, tylenic 1,1 col-
Bis-3-(3-t-butyl-4~Hitoroki 7-5-J
Examples of flame retardants include l-IJ (2,4-di-1-butylphenyl) phosphite), 4,4'-butylphenyl (3-methyl-6- Examples of the binder include mineral oil recall and the like.

Styrenic polymerization obtained by the method of the present invention (Book (d).

Since it has excellent mechanical strength and good moldability, it can be suitably used as a molding material for various products.

Next, the present invention will be explained in more detail with reference to Examples.

The physical properties in each example were measured according to the method shown below.

(1) Melt flow rate It was measured according to the method of So R1133.

(2) Repeat 1 to impact strength Create a test piece (9 x 5 x sail 2 cm) f by compression molding at 200°C, and 2.5 α in the long axis direction from the center.
Fix the parts with metal fittings and %R.

A missile of 1302 was dropped from a height of f 5 C1n to its center and repeated at 1 where a crack occurred.

(3) Average polymerization rate A polymerization solution with a monomer conversion rate of C1% when polymerized for t1 hours at a low temperature using a low-temperature decomposition type organic peroxide? Polymerization liquid A2' containing a styrene-based polymer having a monomer conversion rate of 02% at fflA+2 and a polymerization time of t2 hours and a 25 to 50 centivoise.
? When a polymerization solution with a monomer conversion rate of 0.3% is obtained by mixing and polymerizing for t5 hours, the average polymerization rate is expressed by the following formula.

However, al and a2 represent the sum of the weights of the monomer and styrene polymer in A1+A2 f.

Example 1 In a 2-volume autoclave equipped with a stirrer and a temperature IW meter, styrene I K9 and a low-temperature 5+ decomposed organic peroxide * (molecular group 2380. 10 hour half-life) containing 7 repeating units represented by the formula 64.4℃,
After charging active oxygen J195:2 S'/1 mol) 1.25F and purging the inside of the autoclave with nitrogen, 75
Polymerization was carried out at ℃ for 4 hours to obtain a polymerization solution (An) with a conversion rate of 21.2%.

Separately, 0.9 kg of styrene, 0,1 K9 of ethylbenzene, and 0.52 kg of 1,1-bis(t-butylperoxy)cyclohexane were placed in a similar reactor, and after purging with nitrogen, polymerization was carried out at 125°C for 5 hours. was carried out, and the conversion rate was 5.
A 7.2% polymerization solution (B) was obtained. The standard viscosity of the styrene polymer contained therein was 28 centivoise.

Next, polymerization solution (A) 500f and polymerization solution (B) I
K9 f: Mixed and polymerized at 125°C for 1 hour to obtain a polymerization solution with a conversion rate of 58.3%. This polymerization solution was mixed with 200
1:,! After removing unreacted monomers, solvents, etc. by treating the polymer at 511 Hg for 30 minutes, the physical properties of the obtained polymer were measured. The results are shown in Table 1.

Comparative Example 1 Styrene 0,9 K9, ethylbenzene 0,1 K9 and 0.5 f of 1,1-bis(t-butylperoxy)cyclohexane were charged into the same reactor as in Example 1, and the inside of the reactor was replaced with tl-nitrogen. Thereafter, polymerization was carried out at 105° C. for 6 hours to obtain a polymerization solution with a conversion rate of 52.4%. Table 1 shows the physical properties of a polymer obtained by repeating the method of Example 1 using this polymerization solution.

Comparative Example 2 A reactor similar to Example 1 was charged with 0.9 styrene, 0.1 Kp of ethylbenzene, and 0.5 t of 1.1-bis(t-butylperoxy)cyclohexane, and the inside of the reactor was replaced with nitrogen. Thereafter, polymerization was carried out at 130° C. for 5 hours to obtain a polymerization solution (C) with a conversion rate of 63.2%. The standard viscosity of the polymer contained therein was '22 centivoise.

Next, a polymer layer 11A11 prepared in the same manner as in Example 1
Mix K9 and polymerization solution (C) I Ky, and heat at 130°C.
Polymerization was carried out for 1 hour to obtain a polymerization solution with a conversion rate of 62.7%. The physical properties of the polymer recovered from this material were determined in the first
Shown in the table.

Table 1 As is clear from this table, the method of the present invention has a higher average polymerization rate than the conventional method (Comparative Example 1), improves productivity, and produces polymers with excellent moldability and strength. It will be done.

In the case of (comparative example 2), in which a droplet of polymerization solution with a standard viscosity of 25 centipoise was added in the second stage, the productivity was improved, but the strength was significantly lowered.

Example 2 Styrene l K9 and Example 1 were placed in a reactor similar to Example 1.
The same low-temperature decomposition type organic peroxide used in 1.259 was charged, the inside of the reactor was replaced with nitrogen, and polymerization was carried out at 75°C for 6 hours to obtain a polymerization solution (DJ) with a conversion rate of 28.3%. .

Separately, in the same reactor, 0.95% styrene, 0.05% ethylbenzene, 9, and 5f of 1,1-bis(t-butylperoxy)cyclohexane were charged, and after purging with nitrogen, polymerization was carried out at 110°C for 5 hours. A polymerization solution (odor) was obtained with a conversion rate of 50.4%. The standard viscosity of the polymer contained therein was 38 centivoise.

Next, the polymerization solution (KJ 1
, OK9 was added and incubated at 110°C for 2 hours until the conversion rate was 5.
A polymerized layer e of 6.4% was obtained. This material was treated in the same manner as in Example 1, and the physical properties of the obtained polymer are shown in Table 2.

Comparative Example 3 A mixture of styrene o, 9sKp ethylbenzene 0.05, and 9t1,1-HX (t-7'f rubberoxy)cyclohexane 0.52 was used as the raw material, except that the polymerization was carried out at 100°C for 7 hours. Repeating the same method as Comparative Example 1,
A polymerization solution with a conversion rate of 47.1% was obtained.

The physical properties of the polymer isolated from this are shown in Table 2.

Comparative Example 4 Styrene IK9! : Using 0.51 of 1+1-bis(t-butylperoxy)cyclohexane as a raw material, 100
A polymerization solution with a conversion rate of 48.3% was obtained by repeating the same method as in Comparative Example 1, except that the polymerization was carried out at ℃ for 7 hours.

The physical properties of this polymer are shown in Table 2.

Comparative Example 5 Polymerization solution DO, IK9 obtained in the same manner as Example 2
The polymerization solution 1, 0 K9 of Comparative Example 3 was polymerized for 2 hours at 1-1100℃, and the conversion rate was 4
A 6.7% polymerization solution was obtained. The physical properties of the polymer obtained by treating it in the same manner as in Example 1 are shown in Table 2.

Table 2 As is clear from this table, the method of the present invention is superior to the conventional method (
Productivity, moldability, and strength are significantly improved compared to Comparative Examples 3 and 4). Further, when the content of the ultra-high molecular weight styrene polymer is small (comparison 9115), no improvement effect is observed.

Patent applicant: Asahi Kasei Industries, Ltd. Agent Akira Agata

Claims (1)

[Claims] 1. A method for producing a styrenic polymer by bulk polymerization or solution polymerization of styrene alone or a mixture of styrene and substituted styrene, with the general formula % (%) (wherein R is a divalent A low-temperature decomposition type organic peroxide containing at least three repeating units represented by (organic residue) is added at a ratio of 0.002 to 0.02 parts by weight, calculated as active oxygen amount, per 100 parts by weight of monomer. and temperature 6
Polymerization is carried out at 0-80°C until the monomer conversion is at least 10% by weight, and the polymerization product is then given a standard viscosity of 25%.
1. A method for producing a styrenic polymer, which comprises mixing a styrenic polymer with a styrenic polymer having a standard viscosity of 30 to 60 centivoids, and then polymerizing the mixture to obtain a styrenic polymer having a standard viscosity of 30 to 60 centivoids.