JPH0680083B2 - Method for producing thermoplastic resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a thermoplastic resin of a heat-resistant α-methylstyrene-acrylonitrile copolymer.

[Prior art]

As a method for improving the heat resistance of a styrene-acrylonitrile copolymer, a method in which a part or all of styrene is replaced with α-methylstyrene is generally used. Also
In order to improve the heat resistance of a rubber-modified thermoplastic resin represented by ABS resin, a method in which α-methylstyrene is used as a part of a graft monomer, or α-methylstyrene-acrylonitrile copolymer and acrylonitrile-butadiene-
A method of mixing a styrene copolymer is known.
These thermoplastic resins are used as interior materials in the fields of automobiles and weak electric fields, but their heat distortion temperatures are still insufficient. Therefore, a method for increasing the heat resistance by increasing the content of α-methylstyrene has been proposed, but in the usual emulsion polymerization method, the polymerization conversion rate sharply decreases as the amount of α-methylstyrene added increases. Therefore, for example, as disclosed in JP-B-45-33661, there is known a method of increasing the conversion rate by adding a monomer mixture composed of styrene and acrylonitrile in the second stage of polymerization. However, in this method, even if a polymer having a high α-methylstyrene content is produced by the first-stage polymerization, a considerable amount of monomers other than α-methylstyrene are polymerized in the second-stage polymerization. The content of α-methylstyrene is reduced and heat resistance is reduced.

Further, as disclosed in JP-A-57-2310, the amount of unreacted monomer at the end of the polymerization is set to 1% by weight or less, so that the total amount of unreacted monomers in the polymerization system at the end of addition of the monomer is A method is known in which the concentration of unreacted acrylonitrile is adjusted to 31% by weight or more.

The polymer obtained by this method has problems that the heat resistance is lowered and that it is colored during molding.

[Object of the Invention]

The object of the present invention is a method which is extremely easy to carry out a polymerization operation and is suitable for on-site production, and which does not reduce heat resistance and thermal stability, and which improves α-methylstyrene-polymerization rate.
An object of the present invention is to provide an improved method for producing an acrylonitrile copolymer resin.

[Structure of Invention]

The method for producing a thermoplastic resin of the present invention is α-methylstyrene
90 to 99 parts by weight of a monomer mixture consisting of 75 to 82% by weight, vinyl cyanide 25 to 18% by weight, and optionally 0 to 7% by weight of a monomer copolymerizable therewith in an emulsified state in the preceding stage. After the polymerization, the conversion of the polymerization reached 75% by weight or more, and then, in a subsequent stage, a monomer mixture (0.5 to 5 parts by weight of ethylenically unsaturated carboxylic acid ester and 0.5 to 5 parts by weight of vinyl cyanide (total unit). The total amount of the monomers is 100 parts by weight) and the polymerization is continued.

[Embodiment of the Invention]

The pre-stage polymerization of the present invention comprises 75 to 82% by weight of α-methylstyrene, 25 to 18% by weight of vinyl cyanide and 0 to 7% by weight of other copolymerizable monomers, and 90 to 99% by weight of all monomers. %,
Preferably 92-98% by weight of the monomer mixture is emulsion polymerized.

Here, if the amount of α-methylstyrene is less than 75% by weight, heat resistance cannot be improved, while if it exceeds 82% by weight, a large amount of α-methylstyrene three chains are produced, and the thermal stability of the resulting polymer resin is high. Sex decreases.

In order to obtain a thermoplastic resin having a good balance of heat resistance and thermal stability, it is desirable to produce a polymer having a composition ratio equal to or close to the charged monomer composition ratio in the pre-stage polymerization. For this reason, it is preferable to adjust the ratio of α-methylstyrene to the unreacted monomer in the emulsion polymerization system to 90% (by weight) or more and to carry out the polymerization. Such a method is achieved in the first-stage polymerization, for example, by charging the entire amount of α-methylstyrene and a part of vinyl cyanide, initiating the polymerization, and further continuously adding the vinyl cyanide to carry out the polymerization. To be done. In the first stage polymerization, the polymerization conversion rate is preferably 75% by weight or more of the charged monomers, and more preferably
Polymerization is carried out until it reaches 80% by weight or more, and then the second-stage polymerization is performed.

Although high polymerization conversion cannot be achieved by the above-mentioned first-stage polymerization having a high α-methylstyrene content, in the present invention, the conversion can be increased by performing the second-stage polymerization. In post-stage polymerization, ethylenically unsaturated carboxylic acid ester 0.5〜
5 parts by weight, preferably 1-4 parts by weight and vinyl cyanide
A monomer mixture consisting of 0.5 to 5 parts by weight, preferably 1 to 4 parts by weight (total of 100 parts by weight with the monomer in the first stage polymerization) is added to the emulsion polymerization system obtained in the first stage polymerization. . When the amount of the ethylenically unsaturated carboxylic acid ester is less than 0.5 parts by weight, the heat resistance of the thermoplastic resin produced is lowered, while when it exceeds 5 parts by weight, the thermal stability of the thermoplastic resin is lowered.

On the other hand, if the amount of vinyl cyanide is less than 0.5 part by weight, a large number of unreacted α-methylstyrene and ethylenically unsaturated carboxylic acid ester bond chains remaining in the prepolymerization are produced, which is not preferable. On the other hand, if it exceeds 5 parts by weight, the bonding chain of only vinyl cyanide increases and the thermal stability decreases.

As described above, by using the ethylenically unsaturated carboxylic acid ester and vinyl cyanide in the amount in the above range in the second-stage polymerization, the polymerization conversion rate is improved, and both heat resistance and thermal stability are improved as compared with the conventional method. Can be improved.

Among the monomers used in the present invention, examples of vinyl cyanide include acrylonitrile and methacrylonitrile,
Acrylonitrile is particularly preferable.

Examples of the ethylenically unsaturated carboxylic acid ester include methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate, and methyl methacrylate is particularly preferable.

Other copolymerizable monomers include aromatic vinyl compounds such as styrene, p-methylstyrene, chlorostyrene, bromstyrene, etc .; the ethylenically unsaturated carboxylic acid esters shown above; ethylenically unsaturated carboxylic acids, such as Acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, etc .; crosslinkable monomers such as divinylbenzene, trimethylolpropane trimethacrylate,
Trimethylolpropane triacrylate or the like can be used.

The emulsifier used in the present invention is not particularly limited, and examples thereof include organic carboxylic acid salts such as sodium stearate, potassium oleate, and disproportionated potassium rosinate, sulfonic acid such as sodium lauryl sulfate, and sodium dodecylbenzenesulfonate. Salt or the like can be used.

As the initiator used in the present invention, an initiator usually used in emulsion polymerization, for example, a redox type initiator such as a sulfoxylate formulation or a sugar-containing pyrophosphate formulation, and potassium persulfate or ammonium persulfate can be used. It is also possible to increase the polymerization rate by adding these initiators during the first-stage polymerization.

Next, the heat-resistant resin of the present invention is a resin obtained by graft-copolymerizing an aromatic vinyl compound and optionally a vinyl cyanide compound and / or a monomer selected from (meth) acrylic acid ester into a rubber component. By mixing, a resin composition having impact resistance can be obtained.

Polybutadiene rubber, styrene-butadiene rubber, ethylene-propylene rubber, acrylic rubber and the like can be used as the rubber component used in such a resin.

As the aromatic vinyl compound, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, chlorostyrene, dichlorostyrene, bromstyrene, dibromostyrene, α-methylstyrene, α-ethylstyrene, methyl- Examples include α-methylstyrene, dimethylstyrene, vinylnaphthalene and the like. Preferred compounds are styrene, α-methylstyrene, p-methylstyrene.

Examples of the vinyl cyan compound include acrylonitrile and methacrylonitrile.

Examples of the (meth) acrylic acid ester include methacrylate, ethyl acrylate, butyl acrylate,
Examples thereof include methyl methacrylate, ethyl methacrylate, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate and the like. A preferred compound is methyl methacrylate.

The preferred monomer combination of the graft monomer component to the rubber component is styrene and / or α-methylstyrene-acrylonitrile, styrene and / or α-methylstyrene-methylmethacrylate, styrene and / or α-methylstyrene- Acrylonitrile-methylmethacrylate, and the content of styrene and / or α-methylstyrene in all graft monomer components is preferably 50% by weight to
90% by weight.

The preferred graft copolymer has a rubber component content of 20.
~ 70% by weight, grafting ratio 25% or more, non-grafting component (methyl ethyl ketone soluble content) has an intrinsic viscosity [η] of 0.2
To 1.0 dl / g (in methyl ethyl ketone, 30 ° C), more preferably the content of rubber component is 30 to 70% by weight, and the graft ratio
30% or more, the intrinsic viscosity [η] of the non-grafted component is 0.25 to 0.
8 On the other hand, the preferable mixing ratio of the heat resistant resin of the present invention and the graft copolymer is 50 to 80/20 to 50% by weight.

By blending the graft copolymer in the above range, the excellent heat resistance and thermal stability of the heat resistant resin of the present invention can be more effectively imparted to the impact resistant resin.

Further, a thermoplastic resin having heat resistance to the thermoplastic resin obtained by mixing the above graft copolymer, for example, polyphenylene oxide, polyethylene terephthalate, polypropylene terephthalate, polyacetal, polyamide, styrene-maleic anhydride copolymer, polycarbonate Etc. may be mixed.

The heat-resistant resin thus obtained can be used in fields requiring heat resistance such as automobile interior parts and electric products.

The present invention will be specifically described below with reference to examples.

Examples 1-4: 200 parts ion-exchanged water, sodium dodecylbenzesulfonate
2.5 times, charged amounts of α-methylstyrene and acrylonitrile shown in Table 1 and 0.4 part of t-dodecyl mercaptan were charged in a reactor substituted with nitrogen, and emulsified while stirring under a nitrogen stream. Then sodium formaldehyde 0.2
Parts, 0.1 parts of ethylenediaminetetraacetic acid sodium salt, and 0.003 parts of ferrous sulfate in 20 parts of ion-exchanged water were added, and then 0.1 part of cumene hydroperoxide was added to initiate polymerization. One hour after the initiation of polymerization, acrylonitrile shown in Table 1 was continuously added over 6 hours.

Next, as a second-stage polymerization, the monomer mixture of mail methacrylate and acrylonitrile shown in Table 1 was added, and at the same time, 1/6 amount of the above-mentioned initiator was added and the polymerization was continued for another 2 hours. The polymerization temperature was 70 ° C.

The obtained latex was coagulated with an aqueous calcium chloride solution, washed with water and dried. This powder is pelletized and
A test piece was prepared with an injection molding machine in which the cylinder temperature was set to ℃, and the Vicat softening temperature was measured. Next, the cylinder temperature of the injection molding machine was set to 280 ° C., the pellets were allowed to stay in the cylinder for 15 minutes, and then injection molding was performed. A test piece similar to the above was prepared and the Vicat softening temperature was measured. The results are shown in Table 1. It is recognized that all of them have high polymerization conversion and good heat resistance. It also has good thermal stability.

Comparative Examples 1 to 4: Table 1 shows examples of copolymers obtained by a method outside the scope of the present invention. Comparative Example 1 is a case where the second-stage polymerization is not carried out,
Heat resistance is good, but polymerization conversion is low. Comparative example 2 is α
-The amount of methylstyrene is outside the range of the present invention, and the polymerization conversion is high, but the heat resistance is low. In Comparative Example 3, the post-polymerization methyl methacrylate exceeds the range of the present invention. Although the polymerization conversion rate and heat resistance are high, the Vicat softening temperature when retained at 280 ° C. for 15 minutes is greatly reduced, indicating that the thermal stability is poor. Comparative Example 4 is a case where the acrylonitrile is the only monomer for the second-stage polymerization, and the polymerization conversion is within the range of the object of the present invention, but the heat resistance and thermal stability are inferior to those of the present invention.

Example 5: Preparation of graft copolymer: 60 parts ion-exchanged water, 28 parts styrene, 12 acrylonitrile
Part, potassium oleate 1 part, 1/3 amount of the solution (a) obtained by emulsifying t-dodecyl mercaptan 0.2 part and deionized water 80 parts, polybutadiene latex (solid content) 60 parts with a stirrer with nitrogen substitution. The mixture was charged into a reactor equipped with it and emulsified. After raising the temperature to 40 ° C while stirring under a nitrogen stream,
20 parts of ion-exchanged water, 0.2 parts of sodium pyrophosphate, glucose
0.4 parts, a solution of 0.01 parts of ferrous sulfate and 0.1 parts of cumene hydroperoxide were added, and the jacket was heated to 70 ° C.
It was kept for 1 hour and reacted. Then, the rest of the emulsified solution (a) of the above monomers and cumene hydroperoxide.
One part was continuously added into the polymerization system over 3 hours. After completion of the addition, 0.025 parts of cumene hydroperoxide was added to a solution prepared by dissolving 0.05 parts of sodium pyrophosphate, 0.1 parts of glucose and 0.0025 parts of ferrous sulfate in 5 parts of ion-exchanged water, and further stirred for 1 hour to complete the polymerization. It was

The copolymer obtained in Example 1 and the above graft copolymer were mixed in a latex state so that the solid content weight ratio was 67:33 (the diene rubber-like polymer in the mixed composition was about 20%). ,
Antioxidant was added and coagulated with calcium chloride.
The coagulated product was filtered, washed, dried, and then pelletized. Table 2 shows the results of measuring the physical properties of the obtained pellets by using an injection molding machine in which the cylinder temperature was set to 230 ° C.

Was 48%, and [η] of the non-grafted component was 0.35 dl / g.

As shown in Table 2, it has high heat resistance and excellent impact resistance as an ABS resin.

Table 2 HDT (1/2 ″ 264psi) 120 ℃ Izod impact (kg cm / cm) 12 High-performance flow tester 10 ^-3 cc / sec 10

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Claims (1)

[Claims] 1. A monomer mixture 90-containing 75-82% by weight of α-methylstyrene, 25-18% by weight of vinyl cyanide, and optionally 0-7% by weight of a monomer copolymerizable therewith. 99
In the former stage, parts by weight are polymerized in an emulsified state, and the polymerization conversion rate is
After 75 wt% or more, then in the subsequent stage, a monomer mixture consisting of 0.5 to 5 parts by weight of ethylenically unsaturated carboxylic acid ester and 0.5 to 5 parts by weight of vinyl cyanide (total amount of all monomers is 100 parts by weight) Part) is added and the polymerization is continued to produce a thermoplastic resin.