JP2998348B2 - Method for producing heat-resistant styrenic resin composition - Google Patents

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 heat-resistant styrenic resin composition, and more particularly, to a styrene-based resin composition containing polyphenylene ether, wherein fine particles of the resin and thermal denaturation are obtained. Does not contain any material,
The present invention relates to an industrially advantageous method for producing a heat-resistant styrenic resin composition without discoloration.

[0002]

2. Description of the Related Art Sheets made of styrene resin are used for various food packaging applications because of their excellent non-toxicity, transparency and moldability, but their heat resistance is insufficient depending on the application field. Therefore, development of a sheet having improved heat resistance without impairing the original advantages of the styrene resin sheet has become an important issue. On the other hand, polyphenylene ether is
It is known that it has excellent heat resistance and is compatible with a styrene resin at an arbitrary ratio. From such a background, attention has been paid to a method of using a resin composition in which styrene-based resin is mixed with polyphenylene ether as a sheet material, as one of the methods for producing a styrene-based resin sheet with improved heat resistance. For example, as a heat-resistant polystyrene resin sheet, a biaxially stretched sheet made of a composition comprising 50 to 95% by weight of general-purpose polystyrene and 50 to 5% by weight of polyphenylene ether has been proposed (Japanese Patent Application Laid-Open No. 2-55122). ).

Conventionally, as a method for producing a resin composition containing a styrene resin and polyphenylene ether and a molded article thereof, it has been known to use a mechanical mixing method and a solution blending method represented by the following methods. I have. (B) mixing both powders or pellets in a solid state,
A method in which a molded product is obtained by directly injection molding or extrusion molding the obtained mixture. (B) Both powders or pellets are mixed in a solid state,
A method in which pellets are formed using a kneader such as a melt extruder, and the pellets are injection-molded or extruded to obtain a molded product. (C) A method in which both are dissolved in a common solvent and mixed, then recovered with a non-solvent, and the recovered composition is directly injection-molded or extruded to obtain a molded product. (D) A method in which the composition recovered by the method (c) is pelletized by using a kneader such as an extruder, and the pellet is injection-molded or extruded to obtain a molded product.

[0004]

However, originally,
Since the styrene resin and the polyphenylene ether have a large difference in the melting temperature or the melt viscosity at the same temperature, the kneading efficiency is poor in the above method (a) or (b), and depending on the kneading conditions, the kneading efficiency of the polyphenylene ether is low. Many fine particles remain or discolor, and as a result, poor appearance occurs in the molded article. If the fine article is remarkable, there are problems such as unevenness in heat resistance and mechanical strength of the molded article. Further, when the molded article is a stretched sheet, it causes sheet breakage during stretching and poor appearance of the sheet surface.

In order to eliminate fine particles of polyphenylene ether, it is conceivable to carry out mixing under severe kneading conditions. In this case, however, a large amount of low-molecular-weight substances is generated, and the mechanical properties are greatly reduced. Or a gel polymer (a polymer in which a linear polymer is partially cross-linked and swells with a solvent but does not dissolve) is formed or discolored, On the contrary, the surface appearance of the molded article is deteriorated, which is not practically preferable. On the other hand, in the above method (c) or (d), the effect of the difference in viscosity is not remarkable and mixing is easy, but a dissolving device, a device for recovering a large amount of solvent and non-solvent are required, and a utility is required. It is not economical from the point of view.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and contains a styrene resin and a polyphenylene ether, and the ratio of the styrene resin to both is more than 50% by weight and not more than 95% by weight. There is provided an industrially advantageous method for producing a heat-resistant styrene-based resin composition which is a resin composition containing substantially no resin fine particles or a gel polymer, and is suitable as a raw material for sheets and the like. Aim.

[0007]

The present inventors have conducted intensive studies to achieve the above object, and as a result, if the styrene resin and the polyphenylene ether are melt-mixed under specific kneading conditions, they can be easily obtained. We obtained the knowledge that the purpose was achieved. The present invention has been completed based on this novel finding, and the gist of the present invention is that a styrene-based resin and a polyphenylene ether are contained, and the ratio of the styrene-based resin to both of them is more than 50% by weight and 95% by weight or less. Is a method for producing a heat-resistant styrene-based resin composition by a melt-kneading method, wherein the dry-mixed composition is supplied to a melt-kneader, and the shearing of the melt-kneader without substantially external heating is performed. Heat is generated only by the action, and the outlet resin temperature is set to 310 to 3
A method for producing a heat-resistant styrenic resin composition characterized in that the temperature is controlled within a range of 40 ° C.

Hereinafter, the present invention will be described in detail. The styrenic resin used in the present invention is a homopolymer of a vinyl aromatic compound, a copolymer of one or more vinyl aromatic compounds and other monomers capable of radical copolymerization with the vinyl aromatic compound. is there. As the above vinyl aromatic compound, styrene, o-methylstyrene, m-methylstyrene, p
-Methylstyrene, dimethylstyrene, α-methylstyrene, p-chlorostyrene, 2,4-dichlorostyrene and the like. As the other copolymerizable monomer, for example, α-methylstyrene, vinyltoluene, vinylxylene, monochlorostyrene, dichlorostyrene,
Monobromostyrene, styrene derivatives such as dibromostyrene, methyl methacrylate, methacrylates such as ethyl methacrylate, acrylates such as methyl acrylate and butyl acrylate, acrylonitrile, unsaturated nitrile compounds such as methacrylonitrile, maleic anhydride, Examples include unsaturated acid anhydrides such as itaconic anhydride and unsaturated acids such as acrylic acid and methacrylic acid.
Preferred resins among the styrene resins of the present invention are polystyrene, styrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer, styrene-α-methylstyrene copolymer, styrene-maleic anhydride copolymer, styrene- A styrene-containing resin such as an acrylic acid copolymer may be used.

The polyphenylene ether used in the present invention is represented by the following chemical formula [Formula 1].

[0010]

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In the above chemical formula [1], R ₁ and R ₂ each represent an alkyl group having 1 to 4 carbon atoms or a halogen atom, and n is an integer representing the degree of polymerization and is 60 to 250.
Specific examples of the above polyphenylene ether include poly (2,6-dimethylphenylene-1,4-ether),
Poly (2,6-diethylphenylene-1,4-ether), poly (2-methyl-6-bromophenylene-1,
4-ether), poly (2-methyl-6-chlorophenylene-1,4-ether), poly (2,6-dichlorophenylene-1,4-ether), poly (2,6-di-n)
-Propylphenylene-1,4-ether) and the like. Further, a polyphenylene ether copolymer mainly composed of the chemical structure represented by the chemical formula [Formula 1] can also be used. And a specific example is 2,6-
Copolymer of disubstituted phenol and 2,4-disubstituted phenol, copolymer of 2,6-disubstituted phenol and 2,3,6-trisubstituted phenol, 2,6-dimethylphenol and 2-substituted Phenol, 3-substituted phenol or 4
-A copolymer with a substituted phenol. The polyphenylene ether used in the present invention has an intrinsic viscosity (chloroform, measured at 25 ° C.) in the range of 0.2 to 1 dl / g, preferably 0.1 to 1 from the viewpoint of the strength and moldability of the obtained resin composition. Those having a range of 3 to 0.7 dl / g are used.

In the manufacturing method according to the present invention, first,
Contains the above styrene resin and polyphenylene ether, and the ratio of the styrene resin to both is 50% by weight.
The raw material is a resin mixture which exceeds 95% by weight.
This resin mixture can be prepared by a conventionally known dry mixing method. For example, a method using any mixer such as a ribbon blender, a rotary cone mixer, and a Henschel mixer may be used.

In the production method according to the present invention, the above-mentioned resin composition is supplied to a melt kneader, and heat is generated only by the shearing action of the melt kneader without substantially applying external heating. It has a great feature in that the resin is uniformly melt-mixed while controlling the outlet resin temperature within the above specified range.
That is, the molten state is caused by heat generated only by the shearing action of the melt kneader, and the resin temperature at the outlet of the melt kneader is 310 to 310.
It is necessary to control within the range of 340 ° C. When using means such as resistance heating or heating medium heating from the outside of the mixing and kneading section of the melt kneader, adjust the conditions of the melt kneader so that the resin temperature at the outlet of the melt kneader is within the above range. However, even if the resin fine particles remain or a gel polymer is formed, a uniform resin composition cannot be obtained.

In the production method according to the present invention, the resin temperature at the outlet of the melt-kneading machine is an important index for obtaining a uniform resin composition under the condition of substantially no external heating. Under these conditions, it is necessary to control the resin temperature at the outlet of the melt kneader within the range of 310 to 340 ° C. Because the resin temperature at the outlet is 320 ℃
When the temperature is less than 310 ° C., the tendency is more remarkable.On the other hand, when the resin temperature at the outlet exceeds 330 ° C., the melt kneading occurs. This is because a gel polymer tends to be formed, and when the temperature exceeds 340 ° C., this tendency becomes more remarkable.

Further, in the production method according to the present invention, no material deterioration phenomenon due to local heating or high shearing which is mainly observed when melt-kneading by external heating is observed. In the production method according to the present invention, various conventionally known melt kneaders can be used as long as the above conditions are satisfied. However, since it is necessary that the conditions do not substantially receive external heating, active heating of the melting / kneading unit,
For example, electric heating or heating by a heating medium from a jacket must be avoided.

Specific examples of the melt kneader that can be used in the method of the present invention include a high-speed twin-screw continuous mixer,
Examples thereof include a continuous melt kneader such as an extruder type kneader, a roll mill, a taper roll, and a continuous kneader, and a melt kneader mainly used in a batch mode such as a mixing roll, an internal mixer, and a Banbury mixer. In the case where a batch-type melt kneader is used, the above-mentioned “outlet resin temperature” means “temperature attained by temperature rise” of the melt-kneaded resin.

The proportion of the styrene-based resin in the heat-resistant resin composition is appropriately selected from the above range according to the desired physical properties of the final composition. In the method of the present invention, for the initial resin mixture as a raw material, a known stabilizer such as an antioxidant, and if necessary,
It goes without saying that a small amount of other compatible resins can be added.

In order to obtain a molded article, for example, a sheet-shaped molded article from the heat-resistant resin composition by the production method according to the present invention, the resin composition produced according to the method of the present invention is processed into pellets, and the pellet-shaped resin composition is processed. Using a product as a raw material, a product to be extruded into a sheet shape from a molding die using an extruder according to a conventionally known method is obtained. In this case, a single screw extruder having no special kneading effect can be used for pelletizing, and a single screw extruder having no special kneading effect can also be used for extrusion molding. And without using the kneading effect at all,
It is sufficient to select and manufacture only the optimum conditions for pelletizing or extrusion.

[0019]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In each of the following examples, the appearance evaluation of the obtained unstretched sheet and stretched sheet was based on the following method. (1) Number of fine particles and gel-like polymer (hereinafter, “bud”) The number of buttocks having a size of 0.2 mm ² or more present in 10 cm × 10 cm of the obtained sheet was counted and evaluated.
The number is indicated in four stages as follows. : Less than 5 △: 5 to 10 １０〜: 10 to 30 ×: 31 or more (2) Degree of discoloration The obtained sheet was evaluated by visual observation, and the following three levels were determined according to the degree of discoloration. Displayed with. ：: almost no discoloration Δ: slight discoloration ×: large discoloration

Example 1 [Preparation of mixed composition] Intrinsic viscosity 0.52 dl / g (25
C, chloroform) poly (2,6-dimethyl-1,4)
-Phenylene ether) (in Table 1 below, "PPE"
Abbreviated. ) 25 parts by weight and a weight average molecular weight of 2.8 ×
To a resin mixture consisting of 75 parts by weight of 105 polystyrene (abbreviated as "PS" in Table 1 below), 0.5 part by weight of Irganox-1076 (trade name, phenolic antioxidant manufactured by Ciba Geigy) was added. The resulting mixture was mixed using a Henschel mixer to obtain a resin mixture. [Production of target composition]
Continuous twin-screw kneader (Kobe Steel, Model NCM-50)
And the number of rotations is 1000 to 1 without external heating.
The resin temperature at the outlet of the kneader was set to 3 in the range of 300 rpm.
The mixture was melt-kneaded while controlling the temperature at 20 ° C., and the obtained molten composition was continuously fed to a 65 mmφ single screw extruder (cylinder temperature 2).
(50 ° C.) to obtain a pelletized heat-resistant styrene resin composition. [Trial Production of Sheet] Next, the obtained pellet-like composition was subjected to a 40 mmφ vented single screw extruder (cylinder temperature 250
C.) while melting and kneading at a T-die (die temperature 260
C), the mixture was extruded into a sheet, and then cooled with a cooling roll to prepare an unstretched sheet having a thickness of about 0.9 mm. Next, using a test stretching machine, the above unstretched sheet was
The film was stretched 2.5 times in each of the biaxial directions under a temperature condition of ° C. to obtain a biaxially stretched sheet having a thickness of 0.15 mm and having good transparency. [Evaluation] The appearances of the obtained unstretched sheet and stretched sheet were evaluated by the above method. The results are shown in Table 1 below.
It was shown to.

Example 2 In the same manner as in Example 1, except that the ratio of polyphenylene ether and polystyrene was changed to 50/50 by weight, the heat-resistant styrene resin in the form of pellets was used. A composition was obtained. Next, an unstretched sheet and a biaxially stretched sheet were obtained from the pellet composition in the same manner as in the same example. The appearance of the obtained unstretched sheet and stretched sheet was evaluated in the same manner as in the same example. The results are shown in Table 1 below.

Example 3 In the same manner as in Example 1, except that the ratio of polyphenylene ether to polystyrene was changed to 10/90 by weight, the heat-resistant styrene resin in the form of pellets was used. A composition was obtained. Next, an unstretched sheet and a biaxially stretched sheet were obtained from the pellet composition in the same manner as in the same example. The appearance of the obtained unstretched sheet and stretched sheet was evaluated in the same manner as in the same example. The results are shown in Table 1 below.

Example 4 In the same manner as in Example 1, except that the resin temperature at the outlet of the continuous twin-screw kneader was controlled to 330 ° C., a pellet-like heat-resistant styrene-based resin was used. A resin composition was obtained. Next, an unstretched sheet and a biaxially stretched sheet were obtained from the pellet composition in the same manner as in the same example. The appearance of the obtained unstretched sheet and stretched sheet was evaluated in the same manner as in the same example. The results are shown in Table 1 below.

Example 5 In the same manner as in Example 1, except that the resin temperature at the outlet of the continuous twin-screw kneader was controlled to 310 ° C., a heat-resistant styrene-based pellet was obtained. A resin composition was obtained. Next, an unstretched sheet and a biaxially stretched sheet were obtained from the pellet composition in the same manner as in the same example. The appearance of the obtained unstretched sheet and stretched sheet was evaluated in the same manner as in the same example. The results are shown in Table 1 below.

Example 6 In the same manner as in Example 1, except that the resin temperature at the outlet of the continuous twin-screw kneader was controlled at 340 ° C., a pellet-like heat-resistant styrene-based A resin composition was obtained. Next, an unstretched sheet and a biaxially stretched sheet were obtained from the pellet composition in the same manner as in the same example. The appearance of the obtained unstretched sheet and stretched sheet was evaluated in the same manner as in the same example. The results are shown in Table 1 below.

Comparative Example 1 In Example 1, the jacket of the continuous twin-screw kneader was
A heat-resistant styrene resin composition in the form of pellets was obtained in the same manner as in the example except that the heat medium oil at 50 ° C. was circulated. Next, an unstretched sheet and a biaxially stretched sheet were obtained from the pellet composition in the same manner as in the same example. About the obtained unstretched sheet and stretched sheet,
The appearance was evaluated as in the same example. The results are shown in Table 1 below.

Comparative Example 2 In the same manner as in Example 1, except that the resin temperature at the outlet of the continuous twin-screw kneader was controlled at 300 ° C., a pellet-like heat-resistant styrene-based resin was used. A resin composition was obtained. Next, an unstretched sheet and a biaxially stretched sheet were obtained from the pellet composition in the same manner as in the same example. The appearance of the obtained unstretched sheet and stretched sheet was evaluated in the same manner as in the same example. The results are shown in Table 1 below.

Comparative Example 3 In the same manner as in Example 1, except that the resin temperature at the outlet of the continuous twin-screw kneader was controlled at 350 ° C., a pellet-like heat-resistant styrene-based resin was used. A resin composition was obtained. Next, an unstretched sheet and a biaxially stretched sheet were obtained from the pellet composition in the same manner as in the same example. The appearance of the obtained unstretched sheet and stretched sheet was evaluated in the same manner as in the same example. The results are shown in Table 1 below.

[0029]

[Table 1]

The following is clear from Table 1. (1) In the case of following the production method according to the present invention, a heat-resistant resin composition in which spots and discoloration are sufficiently suppressed can be easily obtained. (2) In particular, when the resin temperature at the outlet of the melt kneader is 320 to
When the temperature is controlled in the range of 330 ° C., a heat-resistant resin composition in which spots and discoloration are suppressed to an extremely low level can be easily obtained. (3) If conditions that do not satisfy the essential requirements in the method of the present invention are adopted, it is not possible to obtain a heat-resistant resin composition in which bumps and discoloration are sufficiently suppressed.

[0031]

The present invention has a particularly remarkable effect as described below, and its industrial value is extremely large. (1) According to the production method of the present invention, a heat-resistant resin composition in which bumps and discoloration are sufficiently suppressed can be easily obtained. (2) The heat-resistant styrenic resin composition obtained by the production method according to the present invention is very suitable as a raw material for sheet production, since the lumps are satisfactorily suppressed. (3) The heat-resistant styrenic resin composition obtained by the production method according to the present invention has a low degree of discoloration upon heating, and is therefore extremely suitable as a sheet material having a good appearance.

Continuation of front page (56) References JP-A-63-256427 (JP, A) JP-A-53-65361 (JP, A) JP-A-4-117444 (JP, A) JP-A-63-309547 (JP, A) , A) JP-A-59-193928 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29B ⁷ /00-7/94 C08L 25/08

Claims (2)

(57) [Claims] A styrene resin and a polyphenylene ether are contained, and the ratio of the styrene resin to both is 5%.
A method for producing a heat-resistant styrenic resin composition having a content of more than 0% by weight and not more than 95% by weight by a melt-kneading method,
The dry-mixed composition is supplied to a melt kneader, and heat is generated only by the shearing action of the melt kneader without substantially external heating, and the outlet resin temperature is controlled within a range of 310 to 340 ° C. PROCESS FOR PRODUCING HEAT-RESISTANT STYRENE RESIN COMPOSITION 2. The resin temperature at the outlet of the melt kneader is set to 320 to 3
The method for producing a heat-resistant styrenic resin composition according to claim 1, wherein the temperature is controlled within a range of 30 ° C.