JPH0493308A - Production of rubber-modified styrene resin - Google Patents

Abstract

PURPOSE:To obtain a rubber-modified styrene resin excelling in moldability, etc., and lowly emitting a foreign odor by adding an unsaturated dimer of alpha-methylstyrene to a styrene monomer before starting polymerization, polymerizing the monomer in the presence of a butadiene rubber, and adding a mercaptan in the course of the polymerization. CONSTITUTION:After 0.2-0.5 pt.wt. unsaturated dimer of alpha-methylstyrene is added to 100 pts.wt. styrene monomer (e.g. styrene), polymerization is started in the presence of 3-10wt.% rubbery butadiene polymer (e.g. polybutadiene rubber). A rubber-modified styrene resin is obtained by adding 0.001-0.05 pts.wt., per 100 pts.wt. styrene monomer, mercaptan (e.g. n-dodecyl mercaptan) to the reaction system when the conversion of the styrene monomer is within a range of 2-10wt.% and accomplishing the polymerization. This resin is excellent in flow properties when molten by heating, can easily be molded and can desirably be used in the production of electrical appliances, food containers, etc.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a method for producing a material having excellent flow characteristics during hot melting, that is, excellent moldability.
For example, the present invention relates to a method for producing rubber-modified styrenic resin suitable for food containers, OA equipment, home appliances, etc.

[Conventional technology]

Many methods have been proposed to improve the fluidity of rubber-modified styrenic resins.

For example, JP-A-29-7892 discloses a method using mineral oil addition. However, this method requires the addition of a large amount in order to obtain the necessary fluidity, which is undesirable as it significantly reduces heat resistance and mechanical strength. Further, Japanese Patent Publication No. 481236 discloses a method of adding higher fatty acids or metal salts thereof. However, although this method improves the releasability from the mold, it has not achieved a significant effect on fluidity. Furthermore, a method of improving fluidity by lowering the molecular weight of the styrenic resin continuous phase is known. This method involves increasing the amount of mercaptans commonly used as chain transfer agents. However, in order to achieve high fluidity, adding a large amount of mercaptans causes problems such as a decrease in impact resistance and an off-odor, so the amount of mercaptans added is actually limited.

[Problem to be solved by the invention]

The present invention has been made with the object of overcoming the drawbacks of such conventional techniques and providing a rubber-modified styrenic resin that has excellent flow characteristics and can be used for various purposes.

[Means to solve the problem]

The present inventors attempted to achieve high fluidity by adding an unsaturated dimer of α-methylstyrene instead of mercaptans. However, in order to obtain high fluidity, a considerable amount is required, and although there is no off-odor, the heat resistance is significantly reduced, which is disadvantageous.

Furthermore, as a result of extensive research, we have found that by using an unsaturated dimer of α-methylstyrene in combination with mercaptans, we have created a rubber-modified styrene that has virtually no off-odor, has well-balanced physical properties, and has excellent fluidity. The present invention was completed based on the fact that a system resin could be obtained.

That is, the present invention provides a method for producing a rubber-modified styrenic resin by polymerizing a styrenic monomer in the presence of a butadiene rubbery polymer, comprising: (a) a content of the rubbery polymer; ~IO weight%, (b) per 100 parts of the styrenic monomer, α
- 0.2 to 0.5 parts by weight of an unsaturated dimer of methylstyrene is added before the start of polymerization, and (c) the polymerization rate of the styrenic monomer is 2 to 10% by weight.
It is an object of the present invention to provide a method for producing a rubber-modified styrenic resin, characterized in that 0.001 to 0.05 parts by weight of mercaptans are added per 100 parts by weight of the styrenic monomer within the range of .

The contents of the present invention will be explained in detail below.

The styrenic monomer in the present invention is styrene alone or a mixture of monomers copolymerizable with styrene. Examples of monomers copolymerizable with styrene include α-methylstyrene, vinyltoluene, etc. Aromatic monovinyl compounds, acrylonitrile, methyl methacrylate, methyl acrylate, methacrylic acid, acrylic acid, maleic anhydride, phenylmaleimide, and the like are used. These monomers may be used alone or in combination of two or more, but are usually used in a proportion of 60% by weight or less.

On the other hand, diene-based rubbery polymers include polybutadiene,
A styrene-butadiene copolymer or the like is used.

The rubber-modified styrenic resin of the present invention needs to contain the rubbery polymer in a proportion of 3 to 10% by weight. If the content of the rubbery polymer is less than 3% by weight, the impact resistance will not be improved sufficiently, and if it exceeds 10% by weight, the tensile strength will decrease, which is not preferable.

The unsaturated dimer of a-methylstyrene used in the present invention is
A commercially available chain transfer agent containing 2,4 diphenyl-4-methyl-1-pentene as a main component (content of 94% or more) can be used. The unsaturated dimer needs to be added in an amount of 0.2 to 0.5 parts by weight per 100 parts by weight of the styrenic monomer before the start of polymerization. If the amount of the unsaturated dimer is less than 0.2 parts by weight, the fluidity will not be improved sufficiently;
If it exceeds 5% by weight, the impact resistance will be significantly lowered, which is undesirable.

Examples of the mercaptans used in the present invention include n-dodecylmercaptan and t-dodecylmercaptan. The mercaptans have a polymerization rate of styrenic monomer in the range of 2 to 10% by weight,
Styrenic monomer 100% weight 0.001-0.0
It is necessary to add 5 parts by weight. When the polymerization rate is less than 2% by weight, the fluidity is significantly lowered, and when it exceeds 10% by weight, the impact resistance is undesirably lowered.

On the other hand, the amount of the mercaptans added is 0.001% by weight.
If it is less than 0.05% by weight, an unpleasant odor may be felt, which is not preferable.

The process for producing a rubber-modified styrenic resin with excellent fluidity using the method of the present invention is not particularly limited, but a bulk-suspension polymerization method or a bulk polymerization method is preferably used.

A bulk-suspension polymerization method will be explained as an example.

A rubbery polymer is dissolved in a styrene monomer or a mixture of the styrene monomer and the monomer copolymerizable with the styrene monomer, and a predetermined amount of an unsaturated dimer of α-methylstyrene is added. , add a polymerization initiator if necessary, and heat to 100% while stirring.
Polymerization is carried out by heating to 150°C. A necessary amount of mercaptan is added so that the polymerization rate is within the range of 2 to 10% by weight, and polymerization is further carried out until the polymerization rate is 15 to 50% by weight.

Next, this polymerization solution is suspended in an aqueous phase using a combination of an inorganic salt such as tricalcium phosphate or calcium carbonate and a surfactant, or a water-soluble polymer such as polyvinyl alcohol as a suspending agent, and a polymerization initiator is added. Polymerization is carried out to a polymerization rate of nearly 100%. The suspension polymerization temperature can be arbitrarily set depending on the polymerization initiator used.

As the heavy = U initiator, organic peroxides such as benzoyl peroxide, t-butyl perbenzoate, di-t-butyl baroquinde, azobisisobutyronitrile, etc. can be used.

The polymer bead slurry thus obtained can be treated in a conventional manner, taken out, dried, and pelletized to obtain the rubber-modified styrenic resin of the present invention.

Note that the above resin contains various additives commonly used, such as lubricants, plasticizers, antioxidants, ultraviolet absorbers, flame retardants,
Antistatic agents, mold release agents, colorants, etc. may be added.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

In addition, the In2 constant of physical properties was performed by the following method.

(1) Melt flow rate: Based on JIS K6871.

(2) Vicat softening temperature 2 Same as above (3) Izot impact strength: Same as above (4) Tensile
Strength 2 Same as above.The presence or absence of an unusual odor was also determined.

Example 1 100 parts by weight of styrene monomer was charged into an autoclave having a volume of 5 g and equipped with a stirrer, and 6 parts by weight of polybutadiene rubber and 6 parts by weight of mineral oil were added and dissolved. Before starting the bulk polymerization, 0.0% of the unsaturated dimer of α-methylstyrene was added.
Add 3 parts by weight, raise the temperature while stirring, and heat to 115°C.
Time bulk polymerization was carried out. The polymerization rate of the styrene monomer at this point was 5% by weight. Adding 0.01 part by weight of n-dodecyl mercaptan and continuing polymerization for an additional 3 hours,
A pre-polymerization solution with a styrene monomer polymerization rate of 25% by weight was obtained.

Next, in an autoclave with a stirrer with a volume of 1 aloI, add 1 volume of water.
0.00 parts by weight, 0.5 parts by weight of tricalcium phosphate, and 0.001 parts by weight of sodium dodecylbenzenesulfonate, then 100 parts by weight of the prepolymerization solution, and 0.3 parts by weight of benzoyl peroxide as a polymerization initiator. and 0.2 parts by weight of t-butyl peroxybenzoate were added thereto, and suspension polymerization was carried out at 90°C for 4 hours and then at 140°C for 2 hours with stirring to obtain rubber-modified polystyrene polymer beads. The beads were made into pellets using a single screw extruder, and the pellets were subjected to physical property measurements. Table 1 shows the measurement results.

Examples 2-3, Comparative Examples 1-3 Except that the amounts of unsaturated α-methylstyrene dimer and n-dodecylmercaptan were set to the values shown in Table 1,
Polymerization was carried out in the same manner as in Example 1. Table 1 shows the physical properties of the obtained polymer.

Comparative Examples 4 and 5 Polymerization was carried out in the same manner as in Example 1, except that n-dodecylmercaptan was added in the amount shown in Table 1 before the start of polymerization. Table 1 shows the physical properties of the obtained polymer.

Comparative Example 6 Polymerization was carried out in the same manner as in Example 1, except that n-dodecylmercaptan was added at a polymerization rate of 0.5%. Table 1 shows the physical properties of the obtained polymer.

Comparative Example 7 Subpolymerization was carried out in the same manner as in Example 1, except that n-dodecylmercaptan was added at a polymerization rate of 20%.

The physical properties of the obtained polymer are shown in Table 1. vinegar.

/ [Effects of the Invention] The rubber-modified styrenic resin obtained by the method of the present invention has excellent fluidity, has a good balance of other physical properties, and has little off-odor, and is industrially useful.

Out wish Man Akira sum electric engineering KK formula Japan Polystyrene Industries Co., Ltd. teenager Reason Man

Claims (1)

[Scope of Claims] A method for producing a rubber-modified styrenic resin by polymerizing a styrenic monomer in the presence of a butadiene-based rubbery polymer, comprising: (a) a content of the rubbery polymer of 3; (b) per 100 parts by weight of the styrenic monomer, 0.2 to 0.5 parts by weight of an unsaturated dimer of α-methylstyrene is added before the start of polymerization, and ( c) mercaptans are added in an amount of 0.001 to 0.05 parts by weight per 100 parts by weight of the styrene monomer so that the polymerization rate of the styrene monomer is within the range of 2 to 10% by weight. A method for producing rubber-modified styrenic resin.