JPH10158415A - Production of styrene polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a styrene polymer which gives an extrudate excellent in external appearance, is excellent in the balance among impact strength, tensile strength, elongation, and flowability, and allows few fish eyes to occur by subjecting a monomer mixture comprising a styrenic monomer and a (meth) acrylic ester monomer to bulk-suspension two-stage polymn. in the presence of a rubbery elastomer under specified conditions. SOLUTION: This styrene polymer is produced by subjecting 85-99 pts.wt. monomer mixture comprising a styrenic monomer and a (meth)acrylic ester monomer to bulk-suspension two-stage polymn. in the presence of 1-15 pts.wt. rubbery elastomer, the sum of the monomer mixture and the elastomer being 100 pts.wt. In the above polymn., the bulk polymn. is conducted until the sum of the elastomer and a polymer formed from a part of the monomer mixture reaches higher than 42wt.% but not higher than 80wt.% followed by suspension polymn. The content of the (meth)acrylic ester monomer in the monomer mixture is pref. 20-70wt.% in terms of product clarity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a styrene-based polymer which is excellent in strength and appearance characteristics of a molded product, and particularly excellent in appearance characteristics of a sheet and a film of an extruded product.

[0002]

2. Description of the Related Art Conventionally, polybutadiene or styrene-
There is known a process for obtaining a styrene-based polymer which is transparent and has a good balance of physical properties by subjecting styrene and methyl methacrylate to bulk-suspension two-stage polymerization in the presence of a butadiene rubber-like polymer (Japanese Patent Publication No. 46-197). No. 32748, JP-B-46-40688). However, although these methods have the effect of improving the balance between transparency and physical properties, they often produce fish eyes, which are foamy particulate matter that causes poor appearance characteristics of extruded products, especially sheet molded products. As a result, there are drawbacks that the use of the styrene-based polymer is significantly restricted and the commercial value of the resin molded product is impaired.

[0003]

DISCLOSURE OF THE INVENTION The present invention has excellent appearance characteristics of extruded sheets and films, and has excellent balance of impact strength, tensile strength, elongation characteristics and fluidity, and has less fish eyes and excellent appearance characteristics. It is an object of the present invention to provide a method for producing a styrene-based polymer.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, when polymerizing a specific monomer mixture in the presence of a rubber-like elastic material, the monomeric monomer The total amount of the polymer conversion component and the rubber-like elastic material of the body mixture is 4
It has been found that bulk polymerization is performed until the amount exceeds 2% by weight to 80% by weight or less, and then suspension polymerization is performed, whereby a styrene-based polymer having excellent strength and appearance properties can be obtained.
The present invention has been completed.

That is, the present invention relates to rubber-like elastic bodies 1 to 15
85 to 99 parts by weight of a monomer mixture composed of a styrene monomer and a (meth) acrylate monomer in the presence of parts by weight (provided that the total amount of the rubbery elastic body and the monomer mixture is 1
Of a styrene-based polymer by subjecting a styrene-based polymer to bulk-suspension two-stage polymerization in the form of a styrene-based monomer and a (meth) acrylate-based monomer. By carrying out bulk polymerization until the total amount (hereinafter referred to as “polymer content”) of the polymer exceeds 42% by weight and reaches 80% by weight or less, and then performs suspension polymerization, whereby the appearance characteristics of sheets and films of extruded articles are obtained. It is intended to provide a method for producing a styrene-based polymer having excellent balance of impact strength, tensile strength, elongation characteristics, and fluidity, and having less fish eyes and excellent appearance characteristics.

Hereinafter, the present invention will be described in detail. Examples of the rubber-like elastic material used in the present invention include polybutadiene, polyisoprene, styrene-butadiene random copolymers, and styrene-butadiene block copolymers. These rubber-like elastic bodies may be used alone or in combination of two or more. When transparency is required, styrene-butadiene random copolymers and / or styrene-butadiene block copolymers are preferred.

The total amount of the rubber-like elastic material used in the present invention is in the range of 1 to 15 parts by weight, preferably 1 to 10 parts by weight, particularly preferably 5 to 10 parts by weight. If the amount of the rubber-like elastic body is less than 1 part by weight, excellent impact strength cannot be obtained, and if it exceeds 15 parts by weight, fluidity,
The tensile strength is undesirably reduced. If the amount exceeds 15 parts by weight, the transparency is also reduced.

The styrene monomer used in the present invention includes styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene and the like, and is preferably styrene. These styrene monomers may be used alone or in combination of two or more.

The amount of the styrenic monomer used in the present invention is not particularly limited, but when transparency is required,
The total charge amount is 30 to 8 in the monomer mixture composed of the styrene monomer and the (meth) acrylate monomer.
It is in the range of 0% by weight, more preferably 35 to 75% by weight, particularly preferably 42 to 59% by weight. If the amount of the styrene-based monomer is out of the range of 30 to 80% by weight, the transparency of the styrene-based polymer decreases.

The (meth) acrylate monomer used in the present invention includes methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, Octyl acrylate and the like can be mentioned, and preferably methyl methacrylate or n-butyl acrylate, particularly preferably methyl methacrylate. These (meta)
The acrylate monomers may be used alone or in combination of two or more.

The amount of the (meth) acrylate monomer used in the present invention is not particularly limited. However, when transparency is required, the total amount of the styrene monomer and (meth) It is in the range of 20 to 70% by weight, more preferably 25 to 65% by weight, particularly preferably 41 to 58% by weight, based on the monomer mixture composed of an acrylate monomer.
It is. (Meth) acrylic ester monomer is 20 to
If the content is outside the range of 70% by weight, the transparency of the styrenic polymer will decrease.

In the present invention, the refractive index of a continuous phase obtained by copolymerizing a mixture of a styrene monomer and a (meth) acrylate monomer is not particularly limited, but a dispersion phase may be formed. It is preferable from the viewpoint of transparency to control the difference from the refractive index of the rubber-like elastic material to be 0.01 or less. In particular, in the case of a molded article, it is preferably within 0.005.

According to the polymerization method of the present invention, a monomer mixture composed of a styrene monomer and a (meth) acrylate monomer is subjected to bulk polymerization in the presence of a rubber-like elastic material, followed by suspension. This is performed by polymerization.

First, a rubber-like elastic material is dissolved in a mixed solution of a styrene monomer and a (meth) acrylate monomer to prepare a rubber solution. At this time, all or part of the styrene monomer and the (meth) acrylate monomer may be added during or after dissolution. next,
The rubber solution is treated with an azo compound such as azobisisobutyronitrile and azobiscyclohexanecarbonitrile, and an organic peroxide such as benzoyl peroxide, t-butylperoxybenzoate, di-t-butyl peroxide and dicumyl peroxide. In the presence of a polymerization initiator such as
Alternatively, the solution is heated with stirring in the absence of the solution to cause bulk polymerization until the polymer content exceeds 42% by weight and reaches 80% by weight or less.

Next, when the polymer content exceeds 42% by weight,
When the amount reaches 0% by weight or less, the polymerization reaction solution is suspended and dispersed in water to transfer to suspension polymerization, and suspension polymerization is performed until the polymerization is substantially completed to obtain a styrene-based polymer. The polymer content at the time of transition to suspension polymerization is more than 42% by weight and 8%.
0% by weight or less, preferably 50 to 66% by weight, particularly preferably 54 to 66% by weight. When the polymer content is 42% by weight or less, fish eyes are often formed, and it is not possible to obtain a sheeted product or an injection molded product having satisfactory appearance characteristics. On the other hand, if the polymer content exceeds 80% by weight, the viscosity of the polymerization reaction solution sharply increases, so that suspension and dispersion of the polymerization reaction solution become unstable, and normal suspension polymerization becomes difficult, which is not preferable.

At the start of suspension polymerization and / or at the time of polymerization, a molecular weight modifier such as t-dodecyl mercaptan and a plasticizer such as butylbenzyl terephthalate may be added as required. Further, a styrene monomer and / or a (meth) acrylate monomer monomer or a polymerization initiator may be separately added during the polymerization. As a dispersant used in suspension polymerization in water, an organic dispersant such as polyvinyl alcohol and methyl cellulose, or an inorganic dispersant such as tricalcium phosphate and magnesium phosphate can be used. When an inorganic dispersant is used, the suspension stability is remarkably improved when an anionic surfactant such as potassium persulfate or sodium dodecylbenzenesulfonate is used in combination.

By washing, dehydrating, and drying the polymer obtained by the above method, a bead-like styrene-based polymer is obtained. The obtained styrene-based polymer is processed into various molded articles by a method such as injection molding, extrusion molding, compression molding and the like. Further, the styrene-based polymer is formed into a film or a biaxially stretched film, and is further provided in a sheet or injection molded product for practical use.

If necessary, additives such as an antioxidant, a lubricant, a plasticizer, a coloring agent, an antistatic agent, a mineral oil, a flame retardant, etc. may be added before the start of polymerization, during the polymerization reaction, after treatment of the polymer, May be blended at any stage such as granulation, molding and processing. Although there is no particular limitation on the method of blending the additives, for example, the styrene polymer and the additives are mixed in advance by a known blender such as a Banbury mixer or a Henschel mixer, pelletized by an extruder, injection-molded, and extruded. Various shaped articles of the styrene-based resin composition can be obtained by processing by methods such as molding and compression molding. Further, in order to improve the surface characteristics of the film or sheet, a lubricant such as an antistatic agent or silicone may be applied to the surface.

In order to prepare a sheet from the styrene-based polymer of the present invention, a general method which has been frequently used, for example, a method of melting with an extruder and extruding from a T-die or an inflation extruder is used. Can be The thickness of the sheet is not particularly limited, but is 0.05 to 4 m.
Those having a range of m are preferably used. Further, the sheet formed by the above method can be suitably used as a biaxially stretched styrene-based resin sheet having a draw ratio of 2 to 5 times using a generally known tenter method, inflation method or the like.

The molded article made of the styrenic polymer of the present invention is characterized by having excellent appearance characteristics. Although the shape of the molded article is not particularly limited, the styrenic polymer of the present invention is a large molded article, for example, a storage tray for office equipment, a paper storage tray, a copy paper tray, a costume case, an audio product storage case, a toy, a computer. It is optimally used for tape storage equipment, food storage cases, electric refrigerator crispers, office equipment parts, audio equipment parts, cosmetic storage cases, etc. It is also suitably used for storage media storage containers such as storage containers for audio tapes and video tapes, storage cases for audio cassettes, video cassettes, audio disks, video disks, floppy disks, and the like. Further, it can be used for housings of thin products, video cassette tapes, audio tapes and the like.

[0021]

The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.

Example 1 A styrene-butadiene random copolymer (styrene content: 25%, trade name: Toughden 2000, manufactured by Asahi Kasei Corporation) was added to 95 parts by weight of a monomer mixture of 42.5% by weight of styrene and 57.5% by weight of methyl methacrylate. ) 5.0 parts by weight were dissolved, and 0.04 parts by weight of benzoyl peroxide as a polymerization initiator and 0.2 parts by weight of t-dodecyl mercaptan as a chain transfer agent were added, and heated to 90 ° C with stirring. When the total amount of the converted polymer of styrene and methyl methacrylate and the styrene-butadiene copolymer (polymer content) reached 45% by weight, the mass polymerization was stopped by cooling. Next, dicumyl peroxide was newly added to the polymerization reaction solution as a polymerization initiator.
2 parts by weight were added. To 200 parts by weight of pure water, 0.001 part by weight of sodium dodecylbenzenesulfonate and 0.5 parts by weight of tribasic calcium phosphate were added as suspension stabilizers, and the mixture was dispersed with stirring. The reaction system was heated at 100 ° C. for 2 hours, at 115 ° C. for 3.5 hours, and at 130 ° C. for 2.5 hours to perform suspension polymerization. After completion of the reaction, washing, dehydration,
After drying, a beaded styrene polymer was obtained. The obtained styrenic polymer was fed to an extruder (PMS-40-28V, IG Co., Ltd.) and the cylinder temperature was set to 2
The sheet was extruded at a temperature of 00 ° C., a T-die temperature of 180 ° C., and a roll set temperature of 90 ° C. to prepare a sheet having a thickness of 2 mm and a width of 450 mm, and evaluated its properties such as transparency and fish eye. Table 1 shows the charged composition of the polymerization reaction and the polymer concentration of the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.

(Example 2) In Example 1, the total amount (polymer content) of the converted polymer of styrene and methyl methacrylate and the styrene-butadiene copolymer was 55.
The production was performed in the same manner as in Example 1 except that the bulk polymerization was stopped by cooling when the amount reached the weight%, to obtain a styrene-based polymer and a sheet composed of the styrene-based polymer. Table 1 shows the charged composition of the polymerization reaction and the concentration of the polymer component in the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.

Example 3 In Example 1, 90.0 parts by weight of a monomer mixture of 42.5% by weight of styrene and 57.5% by weight of methyl methacrylate was added to a random copolymer of styrene-butadiene (styrene content: 25%, Asahi Kasei Corporation). The product was manufactured in the same manner as in Example 1 except that 10.0 parts by weight of the product (Tuffden 2000, trade name, manufactured by Sharp Corporation) was dissolved to obtain a styrene-based polymer and a sheet made of the styrene-based polymer. Table 1 shows the charged composition of the polymerization reaction and the concentration of the polymer component in the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.

Example 4 94.0 parts by weight of a monomer mixture of 54.5% by weight of styrene and 45.5% by weight of methyl methacrylate was mixed with a styrene-butadiene block copolymer (styrene content 40%, trade name, manufactured by Asahi Kasei Corporation, trade name) Asaprene 670A) (6.0 parts by weight) was dissolved, and benzoyl peroxide (0.04 parts by weight) as a polymerization initiator and t-dodecyl mercaptan (0.2 parts by weight) as a chain transfer agent were added, followed by heating to 90 ° C. with stirring. When the polymer conversion amount of styrene and methyl methacrylate and the total amount of the styrene-butadiene copolymer (polymer content) reached 45% by weight, the mass polymerization was stopped by cooling. Thereafter, it was manufactured in the same manner as in Example 1 to obtain a styrene-based polymer and a sheet comprising the styrene-based polymer. Table 1 shows the charged composition of the polymerization reaction and the concentration of the polymer component in the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.

EXAMPLE 5 A styrene-butadiene block copolymer (styrene) was added to 94.0 parts by weight of a monomer mixture of 58.5% by weight of styrene, 36.0% by weight of methyl methacrylate and 5.5% by weight of n-butyl acrylate. Asaprene 670, 40% content, manufactured by Asahi Kasei Corporation
A) 6.0 parts by weight are dissolved, 0.04 parts by weight of benzoyl peroxide is used as a polymerization initiator, and t is used as a chain transfer agent.
0.2 parts by weight of dodecyl mercaptan were added and heated to 90 ° C. with stirring. Styrene, methyl methacrylate,
And the total amount of polymer conversion of n-butyl acrylate and styrene-butadiene copolymer (polymer content) is 4
When it reached 5% by weight, it was cooled to terminate the bulk polymerization.
Thereafter, it was manufactured in the same manner as in Example 1 to obtain a styrene-based polymer and a sheet comprising the styrene-based polymer. Table 1 shows the charged composition of the polymerization reaction and the concentration of the polymer component in the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.

Example 6 A styrene-butadiene random copolymer (styrene content 25%, trade name, manufactured by Asahi Kasei Corporation) was added to 95.0 parts by weight of a monomer mixture of 42.5% by weight of styrene and 57.5% by weight of methyl methacrylate. 5.0 parts by weight of Tuffden 2000) were dissolved, and 0.04 parts by weight of benzoyl peroxide as a polymerization initiator and 0.2 parts by weight of t-dodecyl mercaptan as a chain transfer agent were added, followed by heating to 90 ° C. with stirring. When the total amount (polymer content) of the converted polymer of styrene and methyl methacrylate and the styrene-butadiene copolymer reached 65% by weight, the mass polymerization was stopped by cooling. Next, 0.2 parts by weight of dicumyl peroxide was newly added to the polymerization reaction solution as a polymerization initiator. To 400 parts by weight of pure water, 0.01 part by weight of sodium dodecylbenzenesulfonate and 5 parts by weight of tricalcium phosphate are added as suspension stabilizers,
The mixture was dispersed with stirring. The reaction system was heated at 100 ° C. for 2 hours, at 115 ° C. for 3.5 hours, and at 130 ° C. for 2.5 hours to perform suspension polymerization. After completion of the reaction, washing, dehydration and drying were performed to obtain a beaded styrene-based polymer. Example 1 below
And a sheet composed of a styrene-based polymer and a styrene-based polymer was obtained. Table 1 shows the charged composition of the polymerization reaction and the concentration of the polymer component in the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.

(Comparative Example 1) In Example 1, the total amount (polymer content) of the converted polymer of styrene and methyl methacrylate and the styrene-butadiene copolymer was 35.
The production was performed in the same manner as in Example 1 except that the bulk polymerization was stopped by cooling when the amount reached the weight%, to obtain a styrene-based polymer and a sheet composed of the styrene-based polymer. Table 1 shows the charged composition of the polymerization reaction and the concentration of the polymer component in the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.

(Comparative Example 2) In Example 1, the total amount (polymer content) of the converted polymer of styrene and methyl methacrylate and the styrene-butadiene copolymer was 90.
Except that the bulk polymerization was stopped by cooling when the weight reached% by weight, but the production was carried out in the same manner as in Example 1, but the viscosity of the bulk polymerization solution was extremely high, and the suspension / dispersion became difficult, so that the suspension polymerization could not be carried out. .

Comparative Example 3 In Example 1, 99.5 parts by weight of a monomer mixture of 42.5% by weight of styrene and 57.5% by weight of methyl methacrylate was added to a random copolymer of styrene-butadiene (styrene content: 25%, Asahi Kasei Corporation). Except for dissolving 0.5 part by weight of a commercial product (Tuffden 2000), a styrene-based polymer and a sheet made of a styrene-based polymer were obtained in the same manner as in Example 1. Table 1 shows the charged composition of the polymerization reaction and the concentration of the polymer component in the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.

Comparative Example 4 In Example 1, 80.0 parts by weight of a monomer mixture of 42.5% by weight of styrene and 57.5% by weight of methyl methacrylate was added to a random copolymer of styrene-butadiene (styrene content: 25%, Asahi Kasei Corporation). Except for dissolving 20 parts by weight of the product (Tuffden 2000, trade name, manufactured by Sharp Corporation), the same procedure as in Example 1 was carried out to obtain a styrene polymer and a sheet comprising the styrene polymer. Table 1 shows the charged composition of the polymerization reaction and the concentration of the polymer component in the polymerization reaction solution. Table 2 shows the physical properties of the obtained styrene-based polymer and the evaluation of the sheet made of the styrene-based polymer.
It was shown to.

The refractive index of the continuous phase formed by copolymerizing the mixture of the styrene monomer and the (meth) acrylate monomer obtained in the examples of the present invention, and the dispersion phase are formed. All the differences from the refractive index of the rubber-like elastic body were within 0.01.

[0033]

[Table 1]

[0034]

[Table 2]

The measuring method of each characteristic value in the above Examples and Comparative Examples is as follows. (1) Izod impact strength: Notched, ASTM D
-256. (2) Tensile strength: according to ASTM D-638. (3) Elongation: According to ASTM D-638. (4) MFR: 200 ° C, 5 kg load, JIS K-7
210. (5) Haze: 2 mm part According to ASTM D-1003. (6) Total light transmittance: AS using a 2 mm thick sheet
According to TMD-1003. (7) Fisheye: 2mm thick sheet (length 300
mm × 45 mm in width), A to A defined in Table 3
E was evaluated according to the following criteria by being ranked according to five levels. In addition, the evaluation of fish eyes was performed by comparing the rank value when the fish eye diameter was 0.2 mm or more and the rank value when the diameter of the fish eyes was 0.2 mm or less and using the rank value with a low evaluation. A: Excellent, B: Good, C: Normal, D: Bad, E: Extremely bad

[0036]

[Table 3]

(8) Total amount of polymer conversion and rubbery elastomer (polymer content): After dissolving 0.2 g of the polymerization reaction solution obtained by bulk polymerization in 30 mL of methyl ethyl ketone at 70 ° C. for 60 minutes, After precipitating in 300 mL of methanol and filtering off the insoluble matter, it was vacuum-dried to a constant weight and the weight of the insoluble matter was measured and calculated by the following formula. Polymer content (% by weight) = (weight of insoluble content / weight of polymerization liquid) ×
100 (9) Refractive index: A. Refractive index of rubber-like elastic body: 0.5 mm for rubber-like elastic body
The following slices were cut out, and the refractive index at 25 ° C. was read using an Abbe refractometer (Type 1T, manufactured by Atago Co., Ltd.). B. Refractive index of continuous phase: A styrene-based monomer or (meth) acrylate-based monomer forming a continuous phase is sealed in an ampoule tube (made of glass), and about 130 ° C. in an oil bath.
, And the contents of the ampule were dissolved in methyl ethyl ketone, and the dissolved product was precipitated in a large amount of methanol to obtain a homopolymer of the monomer.
The homopolymer was sliced into pieces having a size of 0.5 mm or less by a press molding machine, and the refractive index of the homopolymer obtained by polymerizing each monomer was read by the above refractometer. The refractive index of the continuous phase was calculated by the following equation. Refractive index of continuous phase = {(constituent weight fraction of each monomer constituting continuous phase) × (refractive index of homopolymer composed of each monomer)}

[0038]

According to the present invention, an extruded sheet,
Excellent film appearance characteristics, impact strength, tensile strength,
A styrene-based polymer having an excellent balance between elongation characteristics and fluidity, having few fish eyes, and having excellent appearance characteristics can be produced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // (C08F 279/06 212: 06 220: 10)

Claims (4)

[Claims] 1. A monomer mixture consisting of a styrene monomer and a (meth) acrylate ester monomer in the presence of 1 to 15 parts by weight of a rubber-like elastic body, 85 to 99 parts by weight (provided that rubber-like The method for producing a styrene polymer by bulk-suspension two-stage polymerization of an elastomer and a monomer mixture (100 parts by weight in total) comprises a styrene monomer and a (meth) acrylate monomer. Wherein the bulk polymerization is carried out until the total amount of the converted polymer and the rubber-like elastic material exceeds 42% by weight and reaches 80% by weight or less, and then the suspension polymerization is carried out. . 2. The amount of the (meth) acrylate monomer contained in the monomer mixture comprising the styrene monomer and the (meth) acrylate monomer is 20% in the monomer mixture. 2. The method for producing a styrenic polymer according to claim 1, wherein the amount is in the range of from 70 to 70% by weight. 3. A styrenic polymer obtained by the production method according to claim 1. 4. A styrene-based resin sheet comprising a styrene-based polymer obtained by the production method according to claim 1 and having improved appearance.