JPH09202839A - Transparent rubber-modified styrene resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a transparent rubber-modified styrene resin having highly balanced impact strength and resistance to whitening in bending or impacting. SOLUTION: This transparent rubber-modified styrene resin having highly balanced impact strength and whitening resistance is a rigid thermoplastic resin having a continuous phase consisting of a copolymer composed mainly of an aromatic vinyl compound and a (meth)acrylic acid (ester) and a disperse phase consisting of dispersed particles of a conjugated diene elastomer. The weight-average particle diameter of the dispersed particle is 0.01-0.1μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid thermoplastic and transparent rubber-modified styrene resin, and more specifically, it is a transparent rubber having a good balance between impact strength and bleaching resistance upon bending or impact. It relates to a modified styrene resin.

[0002]

2. Description of the Related Art Rubber-modified styrenic resins are generally widely used as food containers, packaging materials, etc. because they are excellent in strength and molding processability and can maintain transparency by controlling their composition. ing. Among these, the blister container and the like are required not only to have a balance between transparency and impact strength, but also to have the property of not being whitened when bent or subjected to an impact.

As a conventional method for satisfying this requirement, there is a method of blending polystyrene with a block copolymer of styrene-butadiene, and the resin obtained by this method has a considerably low degree of whitening during bending. there were. However, in this method, the molecules are easily oriented during extrusion mixing, and the strength difference between the extrusion direction and the direction perpendicular thereto becomes large, and in order to obtain sufficient strength, the styrene-butadiene block copolymer in the resin should be aligned in the weak direction. It is necessary to further increase the polymer content. However, as the content of styrene-butadiene block copolymer in polystyrene increases, the rigidity of the resin decreases, so this is not a method that is satisfactory in terms of balance between strength and rigidity, and that it is also completely satisfactory in transparency. Was not.

On the other hand, another resin is a graft copolymer obtained by copolymerizing styrene and methyl methacrylate in the presence of a rubbery polymer. For example, Japanese Patent Laid-Open No. 4-180907
The publication discloses a method of copolymerizing styrene and methyl methacrylate in the presence of a styrene-butadiene block copolymer. The resin obtained by this method is sufficiently satisfactory in transparency and impact strength,
Since the particle size of the rubber-like polymer dispersed particles was as large as 0.3 to 1.2 μm, whitening when bent was remarkable, and it was not usable for the intended purpose.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention is to provide a transparent rubber-modified styrenic resin having an excellent balance between impact strength and whitening resistance during bending or impact.

As a result of intensive studies to solve the above-mentioned problems, the present inventors set the average particle size of the rubber-dispersed particles in the rubber-modified styrene resin to a specific range to obtain impact strength and The inventors have found that a transparent rubber-modified styrene-based resin excellent in balance with whitening resistance can be obtained, and completed the present invention.

[0007]

[Means for Solving the Problems] That is, the present invention provides a copolymer having an aromatic vinyl compound and (meth) acrylic acid (ester) as main components as a continuous phase, and conjugated diene rubber dispersed particles as a dispersed phase. In the rigid thermoplastic transparent styrene resin, the weight average particle diameter of dispersed particles is 0.0
The present invention relates to a transparent rubber-modified styrenic resin having an excellent balance between impact resistance and whitening resistance, which is characterized by having a thickness of 1 to 0.1 μm. Hereinafter, the present invention will be described in detail.

As a method for producing the rubber-modified styrene resin of the present invention, a resin (MS resin) obtained by copolymerizing styrene and methyl methacrylate by a known method and a commercially available styrene-methyl methacrylate-butadiene copolymer are used. Coalescence (MBS
Resin) with an extruder or the like, or a conjugated diene-based copolymer (for example, styrene-butadiene copolymer)
And the like, a method in which an aromatic vinyl compound (for example, styrene) and an aliphatic unsaturated carboxylic acid ester (for example, methyl methacrylate) are graft-copolymerized by suspension polymerization, solution polymerization or bulk polymerization in the presence of As a method for producing the copolymer, a commonly used method can be used. That is, in the presence of a polymerization initiator of an organic peroxide or an azo compound, polymerization is carried out at a temperature of 50 to 200 ° C. under normal pressure or pressure. Alternatively, the polymerization is carried out in the temperature range of 90 to 200 ° C. under normal pressure or under pressure without the presence of a polymerization initiator.

Styrene is generally used as the aromatic vinyl compound used in the present invention, but o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4
-Dimethylstyrene, p-ethylstyrene, p-ter
Nuclear alkyl-substituted styrene such as t-butyl styrene, α-
Α-alkyl-substituted styrenes such as methyl styrene and α-methyl-p-methyl styrene, o-chlorostyrene, m-
Nuclear halogenated styrenes such as chlorostyrene, p-chlorostyrene, o-bromostyrene, m-bromochlorostyrene, p-bromostyrene, 2,4-dichlorostyrene and 2,4-dibromostyrene can be exemplified. Styrene, p-methylstyrene and α-methylstyrene are preferable, and styrene is particularly preferable. You may use these monomers individually or in mixture of 2 or more types.

Methyl methacrylate is preferred as the (meth) acrylic acid (ester) used in the present invention, but acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, methacrylic acid, Ethyl methacrylate, butyl methacrylate, etc. can also be used. You may use these monomers individually or in mixture of 2 or more types. Further, in the present invention, in addition to the above-mentioned two kinds of monomers, a small amount of another kind of monomer which can be copolymerized with them can be appropriately used.

The conjugated diene rubber used in the present invention is
It is a polymer having the properties of an elastomer for improving the impact resistance of the resin of the present invention. As such a polymer,
A styrene-butadiene block copolymer is generally used, but polybutadiene, hydrogenated (partially hydrogenated) polybutadiene, hydrogenated (partially hydrogenated) styrene-butadiene copolymer,
Examples thereof include polyisoprene, styrene-isoprene copolymer, butadiene-isoprene copolymer and the like. As the polybutadiene, any one of high cis polybutadiene having a high 1,4-cis bond content, low cis polybutadiene having a low 1,4-cis bond content, and intermediate middle cis polybutadiene can be used. As the styrene-butadiene copolymer, any of those having a block structure, those having a random structure, and those having a taper block structure can be used, but those having a block structure are most preferable.

The ratio of the conjugated diene component contained in the rubber-modified styrenic resin of the present invention is preferably 10 to 30% by weight, more preferably 15 to 20% by weight. If the content of the conjugated diene component is less than 10% by weight, the impact strength of the resin will be poor. On the other hand, if it exceeds 30% by weight, the impact strength is improved, but there is a drawback that the transparency and rigidity are lowered and the whitening property is deteriorated.

The weight average particle diameter of the conjugated diene elastomer-dispersed particles in the rubber-modified styrene resin of the present invention produced is 0.01 to 0.1 μm, preferably 0.05 to 0.1 μm.
It must be 0.1 μm. When the weight average particle diameter of the dispersed particles is less than 0.01 μm, the impact strength is insufficient, while when it exceeds 0.1 μm, the impact strength is improved, but the degree of whitening during bending or impact is increased.

The weight average particle size referred to here is ultra thin.
Permeation of resin composition dyed with osmic acid using the section method
Type electron microscope photograph was taken, and 1000 dispersed particles were exchanged.
It is a value calculated by measuring the calculated particle size and using the following formula. Average particle size = (ΣniDi^Four ) / (ΣniDi^Three) (Ni in the equation is the amount having a circle-converted particle diameter Di (μm))
Represents the number of scattered particles)

The weight average particle diameter of the conjugated diene rubber dispersion particles is determined by the stirring speed during polymerization, the type of rubber-like polymer used,
It depends on the type and amount of the chain transfer agent, the type and amount of the polymerization initiator, the polymerization temperature, etc., and can be adjusted by appropriately changing these.

The shape and microstructure of the conjugated diene elastomer dispersion particles in the rubber-modified styrene resin of the present invention produced are not particularly limited. For example, a salami structure in which polystyrene particles are further dispersed in the elastomer-dispersed particles, a core-shell structure containing a single polystyrene particle in the elastomer-dispersed particles, a uniform structure in which the particles are all made of a conjugated diene polymer, or a salami structure and a core-shell structure. And the mixed structure thereof can be mentioned.

The polymerization initiator used in the present invention includes
For example, azobisisobutyronitrile, azobis (γ-
Azo compounds such as dimethyl valeronitrile) or lauroyl peroxide, benzoyl peroxide, t-butylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, etc. There are organic peroxides and the like.

Further, in the present invention, in order to control the molecular weight of the produced copolymer, it is preferable to add a chain transfer agent to carry out the copolymerization reaction. As the chain transfer agent, mercaptans (for example, n-butyl mercaptan, t-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, etc.), α-methylstyrene dimer, terpenes and the like are used.

The weight average molecular weight of the copolymer of the aromatic vinyl compound and (meth) acrylic acid (ester) contained in the rubber-modified styrenic resin of the present invention is preferably 10
The range is from 140,000 to 140,000, and more preferably from 120 to 140,000. When the weight average molecular weight is within this range, the balance between the fluidity during molding and the impact strength of the molded product is excellent.

Further, the molecular weight distribution of the copolymer of the aromatic vinyl compound and the (meth) acrylic acid (ester) contained in the rubber-modified styrene resin of the present invention is 1
The proportion of molecules having a molecular weight of 10,000 or less is 0.1 to 3% by weight and the molecular weight is 2
The proportion of molecules having a molecular weight of at least 0,000 is preferably in the range of 2 to 8% by weight, more preferably 0.1 to 1% by weight at a molecular weight of 10,000 and 4 to 8 at a molecular weight of 200,000 or more.
% By weight. When the molecular weight distribution is within this range, the balance between the fluidity during molding and the impact strength of the molded product is particularly excellent. In the present invention, the molecular weight distribution and the weight average molecular weight were calculated from the polystyrene-equivalent molecular weight measured by using a gel permeation chromatography device with tetrahydrofuran as a solvent.

The rubber-modified styrene resin composition of the present invention may contain a plasticizer. Examples of the plasticizer include alkyl phthalates such as dibutyl phthalate, dioctyl phthalate, and butylbenzyl phthalate, mineral oils, and the like. From the viewpoint of transparency, alkyl phthalates are preferable. Considering the balance between the fluidity during extrusion / molding and the impact strength of the molded product, the amount of the plasticizer added is preferably in the range of 0.1 to 3% by weight.

Further, the rubber-modified styrenic resin of the present invention is a lubricant such as zinc stearate, calcium stearate, ethylene bisstearylamide, a phenol-based or phosphorus-based antioxidant, and an ultraviolet absorber, if necessary. , A colorant and the like may be added.

[0023]

The rubber-modified styrene resin of the present invention has a conjugated diene elastomer in the form of fine particles in a continuous phase composed of a copolymer of an aromatic vinyl compound and (meth) acrylic acid (ester). Since it exists in a dispersed state, it is possible to obtain a transparent rubber-modified styrene resin composition having an excellent balance between impact resistance and whitening resistance.

[0024]

EXAMPLES The effects of the present invention will be described below in detail based on examples, but they do not limit the scope of the present invention. The physical properties of the rubber-modified styrenic resins obtained in Examples and Comparative Examples were measured and evaluated by the following methods. Transparency: A test piece with a thickness of 2 mm is made by injection molding and AS
According to TM D1003, the haze was measured using ethylene glycol as the immersion liquid. Impact strength: 2m thickness by DuPont drop weight impact tester
m injection test pieces were used for measurement. Fluidity (MFR): 20 according to ASTM D1238
It was measured at 0 ° C. and a load of 5 kg. Whitening resistance: A test piece having a thickness of 1 mm was prepared by injection molding, and the total light transmittance of the whitened portion when the test piece was bent 90 ° and returned was measured according to ASTM D1003.

Reference Example 1 Manufacture of MS resin Styrene monomer and methyl methacrylate monomer were charged in a weight ratio of 40/60, and then Perbutyl Z manufactured by NOF CORPORATION was chain-transferred as a polymerization initiator. Polymerization was carried out by adding NOFMA-MSD manufactured by NOF CORPORATION as an agent. The polymerization conditions and the molecular weight characteristics of the obtained MS resin are shown in [Table 1].

[Table 1] Polymerization conditions and molecular weight characteristics of the obtained MS resin

Examples 1 to 5 MBS resin B-58 manufactured by Kanegafuchi Chemical Industry Co., Ltd. was mixed with the MS resin obtained in Reference Example 1, and dioctyl phthalate was used as a plasticizer for some of the resins. Add and extrude mix using a twin screw extruder at 230 ° C. The obtained resin was molded using an injection molding machine, and the applied physical properties were evaluated. The composition, structural characteristic value and applied physical property evaluation result of each resin are summarized in [Table 2].

[Table 2] Composition, structural characteristic value and applied physical property value of each resin

COMPARATIVE EXAMPLE 1 SBS resin (KR-03) manufactured by Nippon Steel Chemical Co., Ltd. and polystyrene resin Daicel Styro manufactured by Daicel Chemical Industries Ltd.
(# 51) with a twin screw extruder
Extruded and mixed at ° C. The obtained resin was molded using an injection molding machine and the physical properties were evaluated. The mixing ratio (parts by weight) of each resin and the evaluation results are shown in [Table 3]. Comparative Examples 2 to 4 10 parts by weight of Tuffden 2003 manufactured by Asahi Kasei Co., Ltd., 38.7 parts by weight of a styrene monomer, 51.
To a monomer solution of rubber dissolved in 3 parts by weight, 0.03 parts by weight of polymerization initiator Perbutyl Z manufactured by NOF CORPORATION was added as an initiator, and the mixture was heated with stirring at 125 ° C. until the conversion rate reached 30%. After exceeding 30%, polymerization was carried out at 140 ° C., and after completion of the polymerization, heating was carried out under vacuum to remove residual monomers to obtain a resin. Three kinds of resins having different particle diameters were obtained by changing the stirring speed in the same manner. The obtained resin was molded using an injection molding machine and the physical properties were evaluated. The results are shown in Table 3.

[Table 3]

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C08L 51/04 LKY C08L 51/04 LKY

Claims (6)

[Claims] 1. A continuous phase comprising a copolymer containing an aromatic vinyl compound and (meth) acrylic acid (ester) as main components,
In a hard thermoplastic transparent rubber-modified styrene resin having a dispersed phase of conjugated diene elastomer dispersed particles, the dispersed particles have a weight average particle diameter of 0.01 to 0.1 μm and impact resistance. A transparent rubber-modified styrenic resin that has a good balance with whitening resistance. 2. The ratio of the conjugated diene component contained in the resin is 10 to 30% by weight.
The rubber-modified styrenic resin according to. 3. The rubber-modified styrenic resin according to claim 1, wherein the copolymer forming the continuous phase has a weight average molecular weight of 100,000 to 140,000. 4. Among the copolymer molecules forming a continuous phase,
The ratio of molecules having a molecular weight of 10,000 or less is 0.1 to 3% by weight, and 2
The rubber-modified styrenic resin according to any one of claims 1 to 3, wherein the proportion of the molecules of 0,000 or more is 2 to 8% by weight. 5. The rubber-modified styrenic resin according to claim 1, wherein the resin contains 0.1 to 3% by weight of phthalic acid alkyl ester. 6. The aromatic vinyl compound is styrene,
6. The rubber-modified styrenic resin according to claim 1, wherein the (meth) acrylic acid (ester) is methyl methacrylate, and the conjugated diene rubber is a styrene-butadiene copolymer.