JPH07116261B2 - Aromatic vinyl-acrylonitrile copolymer resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aromatic vinyl-acrylonitrile copolymer resin, and more particularly to an aromatic vinyl-acrylonitrile copolymer resin having improved thermochromic properties.

[Prior Art] Aromatic vinyl-acrylonitrile copolymer resin is superior to aromatic vinyl polymer resin in mechanical properties, heat resistance, and solvent resistance, so that it can be used in automobiles, home appliances, office equipment, and foods. Widely used in containers, etc.

However, this copolymer resin, compared to aromatic vinyl resin,
Thermal discoloration is likely to occur during molding or processing, and the resulting product discolors due to heat, resulting in a drastic change in color tone, or when trying to obtain a light-transparent molded product under severe conditions such as when molding at high temperature. However, the colored part has faded, resulting in the problem that many defective products are generated.

In order to solve these problems, compositions containing an antioxidant and the like have been proposed, but in the present situation, no excellent composition has been found yet.

[Problems to be solved by the invention]

An object of the present invention is to improve the thermal stability during molding, which is a drawback of the aromatic vinyl-acrylonitrile copolymer resin, and to provide a copolymer resin with little change in color tone even under severe molding conditions.

Conventionally, it is common knowledge that a sulfur-based compound is used as a chain transfer agent in the production of an aromatic vinyl-acrylonitrile copolymer resin, and the residual amount due to this is several hundreds in terms of sulfur.
It was common sense that ppm existed. However, the present inventors have found the effect of the present invention by controlling the amount of sulfur of a specific aromatic vinyl-acrylonitrile copolymer resin within a certain limit.

[Means for solving problems]

A copolymer resin having an aromatic vinyl compound and acrylonitrile as a main component, the component due to acrylonitrile in the resin is 5 to 40% by weight, and the melt flow rate of the resin is 200 to 5 kgf under load 0.1 to 50 g / It is an aromatic vinyl-acrylonitrile copolymer resin in which the content of the sulfur compound based on the sulfur chain transfer agent in the copolymer resin in 10 minutes is controlled to 30 ppm by weight or less in terms of sulfur in the copolymer resin.

The aromatic vinyl-acrylonitrile copolymer resin of the present invention is obtained by a resin obtained by radical copolymerization of acrylonitrile and aromatic vinyl or a copolymer of acrylonitrile and aromatic vinyl and another monomer capable of radical copolymerization. It is a resin and further contains a rubber-like elastic material and a resin obtained by a mixture or block copolymerization thereof.

Here, as the aromatic vinyl, styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-
Such as methylstyrene, o-chlorostyrene, p-
It may be a halogenated aromatic vinyl such as bromo-α-methylstyrene. Other monomers that can be copolymerized with acrylonitrile and aromatic vinyl include methyl acrylate, methyl methacrylate, butyl acrylate, acrylic acid, methacrylic acid, maleic anhydride, methacrylonitrile and the like.

Rubber-like elastic material means polybutadiene, polyisoprene,
It is not particularly limited as long as it is a rubber-like one such as a butadiene-styrene copolymer and an ethylene-propylene-diene copolymer.

The aromatic vinyl-acrylonitrile copolymer resin of the present invention needs to contain at least 5% by weight of acrylonitrile as a copolymerization component. When it is less than 5% by weight, the effect of improving the thermal discoloration is small.

In addition, when acrylonitrile increases as a copolymerization component,
Since the aromatic vinyl-acrylonitrile copolymer resin is susceptible to thermal discoloration, it is preferably 40% by weight or less.

The aromatic vinyl-acrylonitrile copolymer resin of the present invention has a melt flow rate (hereinafter referred to as “M”) measured at a test temperature of 200 ° C. and a test load of 5.00 kgf shown in condition 8 of JIS K7210-1976.
FR) is required to be 0.1 to 5.0 g / 10 minutes.

If the MFR is less than 0.1 g / 10 minutes, the molding processability is unfavorably lowered, and if it exceeds 50 g / 10 minutes, the strength of the resin molded and processed is unfavorably lowered.

The method for polymerizing the aromatic vinyl-acrylonitrile copolymer resin of the present invention is not particularly limited, and various methods such as emulsion polymerization, suspension polymerization, solution polymerization and bulk polymerization are possible.

In the production of the aromatic vinyl-acrylonitrile copolymer resin according to the present invention, a sulfur chain transfer agent which is usually used is used, and a typical example thereof is a mercapto compound. The following are the mercapto compounds. Alkyl mercaptans having one or more mercapto groups in the molecule, such as methyl mercaptan, ethyl mercaptan, propyl mercaptan, butyl mercaptan, hexyl mercaptan, heptyl mercaptan, octyl mercaptan, decyl mercaptan, dodecyl mercaptan, octadecyl mercaptan, and octadecyl mercaptan. Mercaptan with chain or branch, mercaptan with cyclic structure such as cyclopentyl mercaptan, cyclohexyl mercaptan, mercaptan with unsaturated bond such as butenyl mercaptan, 1,2-ethanedithiol, 1,2-propanedithiol , 1,6-hexanedithiol, 1,10-decanedithiol and other mercaptans with two mercapto groups, 1,2,3-propanetrithiome,
It may have one or more mercapto groups such as 1,2,3,4-butenetetrathiol. Further, those having an aromatic substituent such as benzenethiol and phenylmethanethiol, mercaptoethanol, mercaptopropanol, 3-mercapto-1,2-propanediol, 2-mercapto-1,3-propanediol, 1,3- Those having a hydroxyl group such as dimercapto-2-propanol in the molecule, those having a hetero atom such as nitrogen or sulfur as a substituent, those having a carbon-carbon bond or a hetero atom in the center of the molecule, and the like. In addition, modified products of the above mercapto compounds and other compounds, and mixtures thereof are also included.

When the above-mentioned sulfur chain transfer agent is used, the sulfur compound remaining in the resin width includes the residual sulfur chain transfer agent itself, the sulfur chain transfer agent and the aromatic vinyl monomer, the acrylonitrile monomer or the acrylonitrile monomer and the aromatic compound. Examples thereof include reaction products with other monomers copolymerizable with vinyl monomers, and reaction products such as a polymerization solvent.

It is necessary that the content of the sulfur compound based on the sulfur chain transfer agent is 30 ppm by weight or less in the copolymer resin as a sulfur atom.

When the amount of sulfur atoms is more than 30 ppm by weight in the copolymer, thermal discoloration during molding is large, which is not preferable.

As a method of adjusting the content of the sulfur compound based on the sulfur-based chain transfer agent to 0 to 30 ppm by weight in the copolymerized resin as the sulfur atom, the sulfur-based chain transfer agent at the time of copolymerization is added to the resin obtained by the copolymerization. 0-30 weight pp as sulfur element
A method of obtaining a copolymer resin in which MFR is adjusted by using m and changing the temperature during copolymerization and the amount of solvent used during copolymerization is mentioned. Examples of solvents used in the copolymerization include toluene, ethylbenzene, iso-propylbenzene, n-
Propylbenzene, acetone, methyl ethyl ketone, etc. may be mentioned, and a compound having a large chain transfer effect such as an α-methylstyrene dimer may be used together with these solvents.

Further, the sulfur chain transfer agent at the time of copolymerization is used as a sulfur element in an amount of 30 ppm by weight or more based on the resin obtained by the copolymerization, and the sulfur chain transfer agent itself or the sulfur chain transfer agent remaining in the resin is used. It is also possible to use a low boiling point substance of the reaction product such as a monomer or a solvent by heating under reduced pressure and removing it to reduce the sulfur element content to 0 to 30 ppm by weight or less.

〔Example〕

 Next, the present invention will be described using examples.

Examples 1 to 3 and Comparative Examples 1 to 2 Styrene monomers and acrylonitrile monomers were completely mixed in an autoclave of 30, and copolymerization was carried out under the conditions shown in Table 1 by a method of continuously supplying monomers, solvents and the like, The polymer was vacuum dried to obtain a styrene-acrylonitrile copolymer resin.

Example 4 Copolymerization was carried out by continuously supplying a monomer, a solvent and the like to the same autoclave as in Example 1 under the conditions shown in Table 1, and using a devolatilization device equipped with a polymer and a heater for the polymerized product. After removing the residual monomer by extrusion, a copolymer resin was obtained by extrusion with an extruder. At this time, the heater was heated by a heating medium at 250 ° C., and the degree of vacuum was 50 Torr.

The resins obtained in Examples 1 to 3 and Comparative Examples 1 to 2 and Example 4 had the properties shown in Table 1.

Plates of 90 × 50 × 2.5 mm were prepared from these resins by injection molding, and the degree of yellowness was measured.

Table 1 shows the results when the molding cycle was changed to 40 seconds and the molding temperature was changed. The molding temperature was 220 ° C and the molding cycle was 4
Table 2 shows the results when 0 seconds, 180 seconds and 300 seconds were set.

The values of conversion, acrylonitrile content, sulfur content, and yellowness were based on the following measurement conditions.

a) Conversion rate The polymerization product was gradually added to methanol, the obtained precipitate was vacuum dried, the polymerization amount was determined, and the polymerization ratio of the monomer was calculated as the conversion rate.

b) Acrylonitrile content The acrylonitrile content was calculated from the nitrogen content from the elemental analysis value of the obtained copolymer resin.

c) Sulfur content By fluorescent X-ray analysis of the plate of the obtained copolymer resin,
Based on the calibration curve created in advance Was quantified.

d) Yellowness The degree of discoloration of the plate of the obtained copolymer resin is JIS K7130-1.
It was determined by the transmission method of 977.

〔The invention's effect〕

As shown in Table 1, the copolymer resin of the present invention has a small degree of discoloration even when the molding temperature rises, and the thermochromic property at the time of molding is much larger than that of the copolymer resin shown in Comparative Example. As shown in Table 2, there is little change in the value of the discoloration degree even when the molding cycle is lengthened, showing that the copolymer resin of the present invention has an excellent effect on the thermodiscoloration property. ing.

Claims (1)

[Claims] 1. A copolymer resin containing an aromatic vinyl compound and acrylonitrile as main components, wherein the acrylonitrile-derived component in the resin is 5 to 40% by weight, and the melt flow rate of the resin is 200 ° C. and a load of 5 kgf. In the copolymer resin below 0.1 to 50 g / 10 min, the sulfur compound content based on the sulfur chain transfer agent is 30 wt pp in terms of sulfur in the copolymer resin.
Aromatic vinyl-acrylonitrile copolymer resin controlled to m or less.