JPS61197612A - Production of alpha-alkyl-substituted aromatic vinyl copolymer - Google Patents

Abstract

PURPOSE:To obtain the titled copolymer which is excellent in heat resistance and can give a molding low in coloration, by emulsion-polymerizing an alpha-alkyl- substituted aromatic vinyl monomer with a vinyl cyanide monomer in the presence of a specified emulsifier. CONSTITUTION:The titled copolymer is obtained by emulsion-polymerizing 100pts.wt. mixture comprising 70-90wt% alpha-alkyl-substituted aromatic vinyl monomer (A) (e.g., alpha-methylstyrene), 10-40wt% vinyl cyanide monomer (B) (e.g., acrylonitrile) and, optionally, 40wt% or below other vinyl monomers [e.g., (meth)acrylic acid] in the presence of 0.5-10, preferably 1-6pts.wt. emulsifier of the formula (wherein R is a 10-24C alkyl or alkylene and M is Na or K) and, optionally, a polymerization initiator, a polymerization initiator aid and a polymerization degree modifier. By mixing this copolymer with a rubber- modified graft copolymer, a heat-resistant thermoplastic resin composition more excellent in heat resistance and small in coloration during molding can be obtained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides α
- A method for producing an alkyl-substituted aromatic vinyl copolymer.

(Prior art) Today, AB8 resin, high impact polystyrene, AA13 resin, AE8 resin are used as thermoplastic resins with excellent impact resistance.
Rubber-modified thermoplastic resins, such as resins, are widely used.

However, in fields that require high heat distortion temperatures,
Since these resins lack heat resistance, their use at relatively high temperatures is limited.

A number of methods have been proposed to improve the heat resistance of special KAB8 resins, such as blending a copolymer of α-methylstyrene and acrylonitrile to create a resin composition with particularly excellent heat resistance. is a special public official in 1819.
This is described in Japanese Patent Publication No. 94, Japanese Patent Publication No. 57-605755, Japanese Patent Application Laid-Open No. 58-23810, etc.

(Problems to be Solved by the Invention) However, when attempting to produce an α-alkyl substituted aromatic vinyl copolymer for the purpose of improving the heat resistance of AB8 resin, When the amount is increased, the final 1-polymerization conversion rate tends to decrease in conventional techniques.9 If unreacted monomers are present, residual monomers are removed to reduce the heat resistance of the resulting copolymer. I needed to.

In order to remove this large amount of residual monomer, when the resulting copolymer is pelletized using an extruder, it is common to reduce the screw rotation speed, use a high vacuum vent, or increase the cylinder temperature. This will be taught on a regular basis. however,
Such methods result in reduced productivity and increased production costs. Moreover, an excessive increase in the cylinder temperature causes thermal decomposition of the copolymer, and conversely increases the amount of residual monomer, resulting in a decrease in heat resistance. Furthermore, when such a copolymer is blended with an ABS resin or the like and extrusion molded, an excessive increase in the cylinder temperature causes deterioration of the rubber component, making it difficult to obtain a resin with good impact resistance.

Furthermore, when a copolymer is produced using a large amount of an α-alkyl-substituted aromatic vinyl monomer, the polymerization stability during polymerization is poor, and long aggregates tend to be generated during the polymerization.

Furthermore, as a result of using a large amount of emulsifier for the purpose of improving the polymerization conversion rate, the emulsifier remains in the resulting copolymer, and when this is molded, there is a drawback that coloration appears to be caused by the residual emulsifier. .

(Means for Solving the Problems) As a result of intensive studies in view of the current situation as described above, the present inventors have found that at least an α-alkyl substituted aromatic vinyl monomer and a vinyl cyanide monomer are emulsion polymerized. The inventors have discovered that the above-mentioned problems can be solved by emulsion polymerization using an emulsifier having a specific structure when producing a copolymer, and have thus arrived at the present invention.

The gist of the present invention is that at least an α-alkyl substituted aromatic vinyl monomer and a vinyl cyanide monomer are emulsion polymerized to produce a copolymer, and as an emulsifier, an emulsifier represented by the following general formula [I] is used. This is a method for producing an α-alkyl-substituted aromatic vinyl copolymer, characterized by using an emulsifier.

. (In the formula, R is an alkyl group or an alkylene group of C8° to Ct<, and M is sodium or potassium.) As the α-alkyl substituted aromatic vinyl monomer used in carrying out the present invention, for example, α - methylstyrene,
Examples of α-ethylstyrene aloy include α-methylstyrene having a halogen or alkyl nuclear substituent, and these may be used alone or in a mixture of two or more types, but α-methylstyrene is preferred.

The amount of the α-alkyl substituted aromatic vinyl monomer used is preferably 70% by weight or more based on the total monomers, and if it is less than 70% by weight, the heat resistance of the resulting copolymer tends to decrease. Moreover, even if it is used in an amount exceeding 90% by weight, it tends to become difficult to obtain a copolymer with a high polymerization conversion rate.

Examples of vinyl noncyanide monomers include acrylonitrile, methacrylonitrile, and ethacrylonitrile, which may be used alone or in combination of two or more, but acrylonitrile is preferred.

The amount of vinyl cyanide monomer used is 10% by weight of the total monomers.
It is preferable to use more than 10% by weight, and if it is less than 10% by weight, the final polymerization conversion rate tends to decrease. Moreover, if it is used in an amount exceeding 40% by weight, the resulting copolymer tends to become colored and brittle due to heating, and its physical properties tend to deteriorate.

Furthermore, in the present invention, in addition to the above-mentioned α-alkyl-substituted aromatic vinyl monomer and vinyl cyanide monomer, other vinyl monomers that can be copolymerized with these may also be copolymerized.

Other vinyl monomers that can be copolymerized with these include, for example, maleimide monomers such as N-phenylmaleimide and maleimide, and acrylic acid monomers such as acrylic acid, methacrylic acid, acrylic esters, and methacrylic esters. body,
and fumaroni), acenaphthylene, etc., and these can be used alone or in combination of two or more. These other copolymerizable vinyl monomers are optional components, but the amount used is preferably about 40% salt by weight based on the total weight.

Next, the emulsifier used in emulsion polymerization in the present invention is an emulsifier represented by the above general formula [I], and it is most important in the present invention to use such an emulsifier.

R in general formula [I] is C3° to C24, preferably C8
, ~C4 alkyl group or alkylene group. Moreover, M in formula [I] is sodium or potassium.

The emulsifier represented by the general formula [I] has an extremely low critical micelle concentration and has the effect of increasing the number of polymer particles produced during emulsion polymerization, increasing the polymerization rate, and significantly improving the polymerization conversion rate. It also functions as a dispersant, contributes to improving polymerization stability, and has the effect of suppressing aggregates generated during emulsion polymerization to an extremely low level.

In practice of the present invention, the amount of the emulsifier represented by the above general formula [I] may be within the range used in ordinary emulsion polymerization, but preferably 1 part by weight per 100 parts by weight of the total monomers.
OQ is 5 to 10 parts by weight, more preferably 1 to 6 parts by weight. If the amount used is less than 5 parts by weight, the polymerization stability tends to decrease, and if the amount used exceeds 10 parts by weight, the resulting copolymer This is not preferable since the amount of emulsifier remaining in the coalescence increases and tends to deteriorate the physical properties of the final molded product.

Emulsion polymerization can be carried out by conventional methods.

That is, commonly known polymerization initiators, polymerization initiation aids, and polymerization degree regulators can be used as appropriate, and there are no particular limitations on their types and amounts added. After the polymerization is completed, coagulation is performed by a conventional method to obtain the desired copolymer powder.

The nine copolymer obtained by the above method has low aggregates, high polymerization conversion, very little residual monomer, and extremely excellent heat resistance, so it can be used alone. However, it may be used in blends with other polymers. The polymer to be blended can be selected as appropriate depending on the purpose of use, but AB8 resin and A
By blending it with a rubber-modified kraft copolymer containing a rubber component such as an AS resin or an Age resin, an impact-resistant thermoplastic resin composition with excellent heat resistance and little discoloration during molding can be obtained.

(Example) The present invention will be specifically explained below using examples.

Note that "parts" in each example and reference side represent "parts by weight." In addition, various measurement methods were as follows.

Final polymerization conversion rate: Calculated by determining and measuring the amount of remaining monomer using gas chromatography.

Amount of aggregates generated: The amount of aggregates generated during polymerization is the amount of aggregates generated during polymerization.
The solid matter remaining on the mesh was washed and dried, and the weight was measured, and the weight was expressed as weight (fl) based on the total amount of monomer charged.

Amount of residual monomer in pellet: After extrusion molding the copolymer powder obtained by polymerization and dissolving it in dimethylformamide, the amount of remaining monomer was determined by gas chromatography. Calculated.

Vicat softening temperature: Measured by JIBK-7206B method (load 5 to 9).

Notched Izot impact strength: , 71SK-6871.

Coloring degree of molded product (YI value): Using Hitachi Color Analyzer Model 307,
The YI value was calculated using 7103 at I8.

Example 1 The following materials were charged into a 5 t capacity reactor equipped with a stirrer.

Water 200 parts Dextrose α 5 parts Ferrous sulfate (FeSO, 7H, 0) Q, 00
5 parts Sodium pyrophosphate CLI part Potassium dispersion Q, 01 part Emulsifier
25 parts (among the emulsifiers represented by # general formula [1), R is a mixture of ('tax C11 alkyl group, M is potassium) After heating and stirring the above substance at 60°C in a nitrogen stream, α-
80 parts of methylstyrene and 4 parts of acrylonitrile were charged. After thoroughly emulsifying these, 5 parts of cumene hydroperoxide CL was added, followed by 1 part of acrylonitrile.
6 parts were continuously added dropwise for 2 hours. After finishing dropping, add 1 more
After continuing stirring for an hour, the polymerization was completed. The final polymerization conversion rate at the end of the polymerization was 95. The amount of aggregates generated during polymerization was α01% or less.

The produced copolymer latex was coagulated with an aqueous magnesium monothiosulfate solution, washed and dried to obtain a white powdery copolymer.

This white powdery copolymer was extruded using a 25%/m extruder at a cylinder temperature of 230°C and a pent pressure of 40 vmHf (absolute pressure), and the amount of residual monomer in the pellet was measured. -Methylstyrene CL03%, acrylonitrile 0%.

Test specimens for measuring the Vicat softening temperature were prepared by injection molding using the above pellet rascrill complete injection bottom molding machine (cylinder temperature 230°C, mold temperature 60°C). The Vicat softening temperature was 134°C.0 Comparative Example 1 Polymerization, coagulation, pelletization, and molding were performed under the same conditions as in Example 1 except that the emulsifier was changed to disproportionated potassium rosinate. The final polymerization conversion rate was 75%, the amount of agglomerates generated during polymerization was α5%, the α-methylstyrene remaining in the pellet was t0C4, and the amount of acrylonitrile was α2ts◇The Vicat softening temperature was 118°C. Ta.

Example 2 Polymerization, coagulation, pelletization, and molding were carried out under the same conditions as in Example 1, except that the monomer charge composition amount and the charge method were changed. That is, the amounts of water, polymerization aid, and emulsifier described in Example 1 were charged, heated and stirred at 60°C in a nitrogen stream, and then α
- 75 parts of methylstyrene and 25 parts of acrylonitrile were charged. After sufficient emulsification, 5 parts of cumene hydroperoxide Q was added and stirring was continued for 2 hours, after which the polymerization was completed. The final polymerization conversion rate was 95%, and the amount of aggregates generated during polymerization was α01% or less.

The α-methylstyrene remaining in the pellet is α02,
Acrylonitrile was Os.

Moreover, the Vicat softening temperature was 130°C.

Comparative Example 2 Polymerization, coagulation, pelletization, and molding were carried out under the same conditions as in Example 2 except that the emulsifier was changed to disproportionated potassium rosinate. The final polymerization conversion rate was 83, and the number of aggregates generated during polymerization was 18. The amount of α-methylstyrene remaining in the pellet was 8% and the amount of acrylonitrile was 11%. In addition, the Vicat softening temperature was 117°C.0 Examples 5 to 8 Other than making various changes in Example 1, such as the type and amount of emulsifier added, the amount of monomer charged, and the method of preparation as shown in Table 1. was polymerized, solidified, and coagulated under the same conditions as in Example 1.
Pelletization and molding were performed. Note that Examples 5 and 8
In this case, the polymerization method of Example 2 was used.

Table 1 shows the results of the final polymerization conversion, the amount of aggregates generated during polymerization, the amount of monomer remaining in the pellets, and the Vicat softening temperature.

Comparative Examples 3 to 7 Polymerization, coagulation, pelletization, and molding were carried out under the same conditions as in Example 1, except that the type and amount of emulsifier added, the monomer charge composition, and the preparation method 1 were changed as shown in Table 2. In the case of Comparative Example 7, the polymerization method of Example 20 was used.

Table 2 shows the results of the final polymerization conversion, the amount of aggregates generated during polymerization, the amount of monomer remaining in the pellet, and the Vicat softening temperature.

Reference Example Production of diene-based rubber-modified graft copolymer The following materials were charged into a reactor equipped with a stirrer and having a capacity of 251 kg.

Water 140 parts Dextrose 13 parts Ferrous sulfate (Fe804.7H!O) αoo
S part Sodium pyrophosphate (L2 part Polybutadiene latex 120 parts (solid content 50 cm, average particle size α 3 μm) After heating and stirring the above material at 60°C in a nitrogen stream, 28 parts of styrene, 12 parts of acrylonitrile and cumene hydrochloride were added. 2 continuously with 0.5 parts of peroxide
dripped for an hour. After the addition was completed, the mixture was stirred at 60°C for an additional hour to ensure that the polymerization was complete. Two parts of butylated hydroxytoluene was added as an antioxidant to the obtained graft copolymer latex, which was coagulated with a 5S sulfuric acid aqueous solution, washed and dried to obtain a white powdery graft copolymer.

Table 3 shows the obtained diene rubber-modified graft copolymers and the copolymers obtained in Examples 1 to 8 and Comparative Examples 1 to 7.
Sample 1 was mixed at the weight ratio shown in Table 1, and further added 1 part of phosphite stabilizer (L1 part) to each of these, mixed in a Henschel mixer at 300 Or, pom for 5 minutes, extruded at a cylinder temperature of 230°C, and pelletized. ~15
I got it. These pellet samples were injection molded using a screw set injection molding machine (cylinder temperature 230°C, mold temperature 60°C) to prepare notched Izot impact measurement test pieces and Vicat softening temperature measurement test pieces. Impact strength and Vicat softening temperature were measured. The degree of coloration (YI value) ft of the molded product was also measured. These results are shown in Table 3.

The results in Table 3 show that when the copolymer obtained by the method of the present invention is blended with the diene rubber-modified graft copolymer, a molded article with excellent heat resistance and little coloring can be obtained.

(Effects of the Invention) By using a specific emulsifier in the method for producing an α-alkyl-substituted aromatic vinyl copolymer of the present invention, a copolymer that can provide molded products with excellent heat resistance and less coloring can be obtained. It has excellent effects such as being able to produce it stably and at a high polymerization conversion rate.

Claims (1)

[Claims] When producing a copolymer by emulsion polymerization of at least an α-alkyl substituted aromatic vinyl monomer and a vinyl cyanide monomer, an emulsifier represented by the following general formula [I] is used as an emulsifier. A method for producing an α-alkyl-substituted aromatic vinyl copolymer. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] (In the formula, R is an alkyl group or alkylene group of C_1_0 to C_2_4, and M is sodium or potassium.)