JPS6253306A - Production of styrene based resin having good moldability - Google Patents

Abstract

PURPOSE:To obtain a styrene based resin having good injection and extrusion moldability and a wide molecular weight distribution, by adding another copolymerizable monomer to a process for polymerizing a styrene based monomer to complete the polymerization. CONSTITUTION:A styrene based monomer in an amount of 70-95pts.wt., based on 100pts.wt. total monomer to be used is bulk or suspension polymerized. In the process, 30-5pts.wt. monomer copolymerizable with the above-mentioned monomer, e.g. styrene based monomer, is added thereto when the polymerization conversion is >=70% to complete the polymerization and afford the aimed resin. EFFECT:The resin having preferably >=5.0 molecular weight distribution value expressed by MW/MN (MW is the weight-average molecular weight; MN is the number-average molecular weight) can be readily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a manufacturing method for obtaining a styrenic resin with excellent processing and moldability. More specifically, it relates to a method for producing styrenic resins with good injection and extrusion moldability, and more specifically, styrenic resins with a wide molecular weight distribution.

[Conventional technology and its problems]

In order to obtain styrenic resins with excellent injection and extrusion moldability, conventional methods have been to add lubricants, plasticizers, oligomers, etc., and more recently, to widen the molecular weight distribution. However, the former method of addition has the drawback of deteriorating heat resistance, tensile strength, and transparency. For the latter, methods of mixing low-molecular-weight resins and high-molecular-weight resins, and polymerization methods using a combination of low-temperature decomposition type initiators and high-temperature decomposition type initiators are known, but these methods have no effect on widening the molecular weight distribution. was insufficient, and the desired effect of improving processability was also insufficient. Furthermore, the method of mixing low molecular weight and high molecular weight materials requires a mixing step, which has the disadvantage of increasing costs. In addition, the method of combining initiators is industrially highly restricted and cannot be said to be an advantageous method from the viewpoint of the type of commercially available initiator, 1 degree of polymerization, 0 degree of polymerization, and 0 polymerization conversion rate.

By the way, the molecular weight distribution (Mw/MN,
However, My is the weight average molecular weight and MN is the number average molecular weight) is 2.3 to 2.8 for bulk polymerization and 2.7 for suspension polymerization.
~3.5.

In view of these drawbacks, the present invention provides a method for producing a styrenic resin having a wide molecular weight distribution and good moldability.

[Means and effects for solving the problem] The present invention provides 070 to 95 parts by weight of styrene monomer (however, the total amount of monomer used is 100 parts by weight, hereinafter referred to as parts only) in bulk or suspended form. During polymerization, when the polymerization conversion rate is 70% or more, preferably 80 parts or less, a monomer (2) copolymerizable with these monomers, such as a styrene monomer 30
The gist of the present invention is a production method characterized by adding ~5 parts to complete the polymerization, and the present invention can solve the above-mentioned problems. In other words, they discovered that widening the molecular weight distribution can be achieved by dividing the monomer to be polymerized and adding it to the polymerization system. By adopting the method of the present invention, values of molecular weight distribution that could not be obtained with conventional polymerization techniques, in terms of Mw 7M N values of 4.0 or higher, especially those of 5.0 or higher, can be easily obtained. You can get it.

The reason why the monomer division addition method is an effective method for widening the molecular weight distribution is not clear, but the following reasons can be considered. Generally, in polymer polymerization, a low molecular weight product is produced at the beginning of the polymerization, and a high molecular weight product is produced at the end of the polymerization, but in the method of the present invention, a relatively low molecular weight resin is produced at the beginning of the polymerization. The polymerization conversion rate is 70% or more (preferably 80%).
This is thought to be due to the fact that by adding a monomer at the point where J:> is reached and a high molecular weight product starts to be produced, this region is made longer and the production of a high molecular weight product is promoted. Here, dividing and adding the monomer has two major effects. One is that when the same amount of initiator is used, the molecular weight is higher than when it is not added separately, which is an advantageous method for obtaining a high molecular weight product. Another effect is that the present invention The objective is to obtain a resin with a wide molecular weight distribution. The amount of initiator, the amount of additional monomer, and the polymerization conversion rate during addition are important for molecular weight and molecular weight distribution, and by adjusting these amounts, molecular weight and molecular weight distribution can be controlled.

The polymerization conversion rate when monomer (2) is added is an important factor and greatly affects the molecular weight and molecular weight distribution. In other words, if the conversion rate at the time of addition is less than 70%, there is little effect on broadening the molecular weight and molecular weight distribution. The preferred conversion rate is 70 parts or more, preferably 80 parts or more, and more preferably 90 parts or more. This is because the technology of the present invention takes advantage of the fact that in polymerization, high molecular weight polymers are produced at the final stage of polymerization, when the conversion rate has sufficiently increased. Because this is the technology we are trying to create,
This is because if the conversion rate at the time of adding the monomer is not sufficiently high, the concentration of the polymer in the polymerization reaction system will decrease due to the addition of the monomer, making it impossible to produce a high molecular weight polymer.

Next, the appropriate amount of the additional monomer (2) is 30 to 5 parts, preferably 25 to 10 parts. If it exceeds 30 parts, the polymer concentration in the polymerization system will be low when monomer is added, and high molecular weight products will not be produced.If it is less than 5 parts, the additional amount will be insufficient and the overall molecular weight and molecular weight distribution will increase. This is because it does not reach that point.

The amount of initiator should be determined based on the average molecular weight of the resulting resin; for example, in the case of polystyrene, η5p
= 1.0 to 2.0. however,
Here, ηsp is the specific viscosity measured at 30°C after preparing a 1% polymer solution using toluene as a solvent. By the way, the amount of initiator is 0.05 per monomer ■
It is preferable to set it in a range of 1.0% by weight. Further, it is not necessary to use a special initiator; for example, when polystyrene is to be obtained, a general initiator used for polymerization of polystyrene can be used.

Examples of such initiators include commonly used initiators such as benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, etc. Bisisobutylene 1-,1.1'-azobiscyclohexane-1-
It is also possible to use azo initiators such as carbonitrile 9. Of course, difunctional peroxides include di-t-butylperoxyhexane hydroterephthalate, 2,5-dimethyl-2,5bis(2-ethylhexanoylperoxy)hexane, t,i'-di-t -Butyl peroxy-
Initiators such as 3°3.5-trimethylcyclohexane can also be used in the present invention. The addition of these initiators
It is preferable to add the additional monomer to the monomer (2) and not to the monomer (2) because the additional monomer is more uniformly dispersed in the polymerization system. However, in order to reduce the remaining monomer, additional monomer ■
There is no problem in adding a small amount of initiator.

Next, considering the polymerization temperature, there is no problem in changing the temperature during polymerization in order to widen the molecular weight distribution. For example, there is a method in which the first half of the polymerization is carried out at a relatively high temperature, and the second half of the polymerization, in which a high molecular weight product is produced, is carried out at a relatively low temperature.

In the present invention, the styrenic monomer refers to styrene.
It refers to a monomer system containing styrene in an amount of % or more by weight, and includes not only a monomer system containing styrene alone but also a mixture system of styrene and various monomers. Monomers other than styrene may be monomers that react with styrene, such as nuclear alkyl-substituted styrenes such as para-methylstyrene and para-t-butylstyrene; nuclear halogen-substituted styrenes such as para-chlorostyrene and ortho-para-dichlorostyrene. Styrene: In addition to styrene derivatives such as α-substituted styrene such as α-methylstyrene,
Examples include acrylonitrile, methacrylonitrile, methyl methacrylate, and ethyl methacrylate.

The monomer (2) that can be copolymerized with the styrene monomer may be any monomer that can be copolymerized with the styrene monomer (2).

Furthermore, the styrene resin referred to in the present invention refers to a resin containing 50% by weight or more of styrene structural units as a resin composition.

In the present invention, there is no problem in using a chain transfer agent for purposes such as molecular weight adjustment.

When employing suspension polymerization as the polymerization method in the present invention, known dispersants can be used. Examples of such dispersants include organic dispersants such as partially saponified polyvinyl acetate, polyvinylpyrrolidone, and methyl cellulose, as well as inorganic dispersants such as tertiary calcium phosphate, magnesium phosphate, sodium silicate, oxidized polyvinyl phosphate, and magnesium carbonate. Can be used, in which case sodium dodecylbenzenesulfonate.

When an anionic surfactant such as α-olefin sodium sulfonate is used in combination, the dispersion effect is significantly improved. Further, in the present invention, it is possible to use known lubricants having various effects of improving moldability, and in that case, a very small amount is sufficient. It is also possible to employ the polymerization method of the present invention in the presence of an elastomer to improve impact resistance.

According to the present invention, a styrenic resin having a wide molecular weight distribution and excellent processability can be advantageously produced industrially.

〔Example〕

As will be explained below using a specific example, the polymerization conversion rate was calculated by measuring the amount of residual monomer using gas chromatography. The ηsp value was determined by the method described above, and Mw/MN measured by GPC was used as an index for the molecular weight distribution targeted by the present invention. Regarding injection molding evaluation, the nozzle temperature was set to 220°C, a butter case-shaped mold was used, and the number of shots that could be continuously molded was evaluated. In other words, if the sample breaks during mold release, the resin supply gate gets clogged, or part of the runner breaks, etc., the operation must be stopped, but the number of shots that can be molded continuously without such problems was used as an index of formability.

Examples 1 to 3 110 parts of water, parts of tertiary calcium phosphate o, ao, 0.005 parts of sodium dodecylbenzenesulfonate, and 0.3 parts of sodium chloride were placed in an autoclave equipped with a stirrer, and then benzoyl peroxide was added under stirring. 0.28 parts of oxide, di-
A system consisting of 0.15 parts of t-butylperoxy-3.5-1-dimethylcyclohexane and 75 parts of styrene was introduced, the temperature was raised to 98°C, and polymerization was carried out for 3 hours and 30 minutes. The polymerization conversion rate at this point was 83%. 25 parts of styrene was introduced into this system, and polymerization was further carried out for 2 hours.
Further, the temperature was raised to 115°C and a heat treatment was performed for 4 hours, followed by cooling, dehydration, and drying to obtain Resin A. Also, instead of performing polymerization at 98°C for 3 hours and 30 minutes, polymerization was performed for 4 hours and 30 minutes, 5
Resin B, 0 was obtained in the same manner as Resin A except that styrene was added after 30 minutes of polymerization. in this case,
The conversion rate upon addition was 90% for each.

It was 95%. The physical properties and moldability of the obtained resin are shown in Table-
As shown in 1.

Examples 4 to 6 In Examples 1 to 3, 80 parts of styrene was initially charged,
Polymerization was carried out at 98° C. for 4 hours, 5 hours, and 6 hours,
Resins E and F were obtained by the same treatment except that 20 parts of styrene was added. The conversion rate when adding styrene was 88% in each case.
, 93% and 96%. The results are shown in Table-1.

Examples 7 to 8 According to Examples 1 to 3, 0.23 parts of benzoyl peroxide was used, 90 parts of styrene was initially added, and polymerization was carried out at 98°C for 4 hours and 30 minutes and 5 hours and 30 minutes. I did it. The polymerization conversion rates at this point were 89% and 95%, respectively.
%Met. Add 10 parts of styrene to this system and
Polymerization was carried out for a period of time, followed by raising the temperature to 115° C. and treating in the same manner to obtain resins G and )I. The results are shown in Table-1.

Comparative Example-1 In Examples 1 to 3, 100 parts of styrene was used instead of 75 parts, polymerization was carried out at 98°C for 4 hours, and polymerization was carried out by raising the temperature to 115°C without adding styrene. was completed and designated as comparative resin A. The physical properties and moldability of this product are shown in Table 1.

Comparative Example-2 In Comparative Example-1, 0.16 parts of benzoyl peroxide was used instead of 0.28 parts, and instead of polymerizing at 98°C for 4 hours, polymerization was performed at 98°C for 4 hours and 30 minutes. Comparative resin B was obtained in exactly the same manner except for the following procedure. The physical properties and moldability of this product are shown in Table 1.

Comparative Example 3 To obtain Resin A, polymerization was carried out for 2 hours instead of 3 hours and 30 minutes at 98°C.

The polymerization conversion rate at this point was 65%. Thereafter, 25 parts of styrene was added and polymerization was carried out for 2 hours, followed by a post-heat treatment to complete the polymerization to obtain comparative resin C. The physical properties and moldability of this product are shown in Table 1.

Comparative Example-4 In Examples 4 to 6, 96 parts of styrene was used instead of 80 parts of the initial styrene.
Polymerization was carried out at 98° C. for 4 hours and 30 minutes using 0.18 parts of benzoyl peroxide instead of 0.28 parts. The conversion rate at this point was 85%. This system was treated in the same manner with 4 parts of styrene added, and the resulting resin was used as a comparative resin. The results are shown in Table-1.

Ratio shell examples-1 and 2 are examples in which monomer is not added.・Mv/
The MN value is low and the moldability is also poor. In Comparative Example 3, since the conversion rate when adding styrene was low, neither ηSp nor MW/MN increased, and the moldability was also poor. In Comparative Example 4, the amount of additional styrene was small, the Mw1MN value did not increase, and the moldability was poor.

Claims (3)

[Claims] (1) When carrying out bulk or suspension polymerization of 70 to 95 parts by weight of the styrene monomer (A), 30% of the monomer (B) that can be copolymerized with these monomers when the polymerization conversion rate is 70% or more.
A method for producing a styrenic resin, characterized by adding ~5 parts by weight to complete the polymerization (provided that the total amount of monomers used is 100 parts by weight). (2) The manufacturing method according to claim 1, wherein the monomer (B) is a styrene monomer. (3) Claim 1, wherein the styrenic monomer (A) and the monomer copolymerizable therewith (B) are styrene.
Manufacturing method described in section.