JP2000256527A - Methyl methacrylate-based resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a methyl methacrylate-based resin composition which is scarcely drawn down when heated and molded, and is especially suitable for the production of large moldings by an extrusion molding method, a blow- molding method or a foaming molding method. SOLUTION: This methyl methacrylate-based resin composition comprises (A) 90-99 wt.% of a methyl methacrylate-based polymer which has a weight- average mol.wt. of 80,000 400,000 and has a branched structure wherein mol.wts. between branched points are 30,000-500,000 defined using a Z-average mol.wt., and (B) 10-1 wt.% of high mol.wt. methyl methacrylate-based polymer having a weight-average mol.wt. of 1,000,000-5,000,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methyl methacrylate-based resin composition having a low drawdown during hot molding. This resin composition is particularly suitable for the production of large molded products by extrusion molding, blow molding, and foam molding.

[0002]

2. Description of the Related Art Methyl methacrylate-based polymers are rigid, have excellent transparency, and are also excellent in weather resistance.
It is widely used as molded articles such as spectacle lenses and light guides, and further extruded and formed as extruded plates such as signboards and nameplates.
On the other hand, when a general methyl methacrylate-based polymer is blow-molded, the tension of the melt-stretched resin composition is low, so that the sagging (drawdown) becomes large and only a small molded product can be obtained. In addition, foam molding can be performed only in a limited narrow range such as temperature and molding pressure. Therefore,
A resin composition having high fluidity and low drawdown is desired.

Conventionally, as a method for improving the processing characteristics at the time of molding, Japanese Patent Application Laid-Open No. 5-140411 discloses a method of adding polytetrafluoroethylene. Also,
Japanese Patent Application Laid-Open No. 8-208746 discloses a method in which the drawdown is reduced by increasing the tension during melt stretching while maintaining the melt fluidity by a methyl methacrylate polymer having a branched structure.

[0004]

However, although the method of adding polytetrafluoroethylene has the effect of lowering the drawdown, the tension required for melt-drawing required for large-size blow molding cannot be expected, and the effect is not satisfactory. It is enough. Further, since the refractive index of polytetrafluoroethylene is different from that of methyl methacrylate polymer, transparency, which is one of the characteristics of the acrylic resin, is lost. In the case of using a methyl methacrylate polymer having a branched structure, the fluidity and the tension during melt stretching can be higher than that of a normal linear methyl methacrylate polymer, but an acrylic resin can be obtained.
It is not a resin with a small drawdown that can be used for large blow molding with a parison length exceeding 40 cm,
There is a demand for a resin having a small drawdown at the time of larger melt drawing. The present invention, while maintaining the melt fluidity,
Moreover, it is an object of the present invention to provide a methyl methacrylate-based resin composition which is applicable to large-size blow molding and extrusion foam molding and has significantly improved tension at the time of melt stretching, that is, low drawdown.

[0005]

According to the present invention, there is provided a methacryl having a branched structure having a weight average molecular weight of 80,000 to 400,000 and a molecular weight between branch points defined by using the Z average molecular weight of 30,000 to 500,000. Methyl acid polymer (A) is 90 to 99% by weight
And a high-molecular-weight methyl methacrylate-based polymer (B) having a weight average molecular weight of 1,000,000 to 5,000,000 and 10 to 1% by weight.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The branched methyl methacrylate-based polymer and the high molecular weight methyl methacrylate-based polymer used in the present invention are methyl methacrylate as a constituent unit thereof.
% By weight, preferably 70% by weight or more, and as long as the methyl methacrylate unit contains 50% by weight or more, a part thereof is replaced with a monofunctional unsaturated monomer copolymerizable with methyl methacrylate. It may be what was done. The copolymerizable monofunctional unsaturated monomer is preferably contained in the polymer in an amount of 1% by weight or more, more preferably 3% by weight or more, and particularly preferably 3 to 20% by weight. . When the content of methyl methacrylate is less than 50% by weight, transparency and mechanical strength, which are characteristics of so-called polymethyl methacrylate, are hardly exhibited.

Examples of the copolymerizable monofunctional unsaturated monomer include methacrylates such as ethyl methacrylate, propyl methacrylate, butyl methacrylate, and benzyl methacrylate: methyl acrylate, ethyl acrylate, acrylic Acrylic esters such as propyl acrylate, butyl acrylate and 2-ethylhexyl acrylate:
Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, and acid anhydrides such as maleic anhydride and itaconic anhydride: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, monoglycerol acrylate, Esters having a hydroxyl group such as 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, and monoglycerol methacrylate: acrylamide, methacrylamide, and diacetone acrylamide. Further, nitriles such as acrylonitrile and methacrylonitrile; nitrogen-containing monomers such as dimethylaminoethyl methacrylate; epoxy-containing monomers such as allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate: styrene and α-methylstyrene And the like.

The methyl methacrylate polymer (A) having a branched structure of the present invention is disclosed in US Pat. No. 5,726,268, and has a weight average molecular weight (Mw) of 80,000 to 40.
It is ten thousand. Preferably, it is 150,000 to 300,000. If the weight average molecular weight (Mw) is less than 80,000, the mechanical strength and solvent resistance of the polymer are not sufficient, and a methyl methacrylate resin composition comprising the polymer and a linear methyl methacrylate polymer Also, the strength and solvent resistance of the molded article obtained from the above become poor. On the other hand, if it is higher than 400,000, the melt fluidity becomes too low, and the moldability of the obtained resin composition decreases.

The methyl methacrylate polymer A having a branched structure of the present invention has a molecular weight between branch points (Mzb) defined by using its Z-average molecular weight (Mz) of 30,000 to 500,000, preferably 50,000 to 200,000. When the molecular weight between branch points (Mzb) exceeds 500,000, the obtained polymer having a branched structure has no effect on the solvent resistance to the fluidity, and this and the linear methyl methacrylate polymer A
Of the solvent resistance of the methyl methacrylate-based resin composition comprising On the other hand, when the molecular weight between the core branch points is less than 30,000, the mechanical strength of the molded article obtained from the resin composition is poor and the appearance of the molded article is also poor.

Here, the weight average molecular weight (Mw) and the Z average molecular weight (Mz) are values determined by gel permeation chromatography (GPC) and a differential refractometer. This method is described in, for example, 1984 edition, “Polymer Characteristic Analysis” (Kyoritsu Shuppan), pp. 24 to 55.

The molecular weight between branch points means an average molecular weight from a branch point to the next branch point in a polymer having a branched structure, and is defined by using a Z average molecular weight (Mz). The molecular weight between branch points (Mzb) is calculated from the following [Equation 1] and [Equation 2] based on the description in "Characterization" of the Japan Rubber Association, Vol. 45, No. 2, pages 105-118. You.

[0012]

[Equation 1] {[η ₁ ] / [η ₂ ]} ^10/6 = ｛(1 + Bz /
6) ^0.5 + 4Bz / 3π｝ ^-0.5

[0013]

## EQU2 ## Mzb = Mz / Bz

In the above [Equation ₁ ], [η ₁ ] is obtained by using a universal calibration curve showing the relationship between the intrinsic viscosity and the absolute molecular weight with respect to the GPC elution time of a standard sample of a linear methyl methacrylate polymer. In the calibration curve showing the relationship between the intrinsic viscosity and the absolute molecular weight of the polymer to be measured, the molecular weight is the intrinsic viscosity corresponding to the Mz value. [Η ₂ ] is
In the calibration curve showing the relationship between the intrinsic viscosity and the absolute molecular weight of the linear methyl methacrylate polymer standard sample, the intrinsic viscosity is the intrinsic viscosity corresponding to the same molecular weight Mz value as the polymer to be measured. Bz is the number of branch points in the Z average molecular weight Mz.

The methyl methacrylate polymer (A) having a branched structure according to the present invention has a ratio of a polymer having a molecular weight of 300,000 or more when the reduced viscosity of the polymer is 0.7 dl / g or less. Is [｛14 × the reduced viscosity value−
6.8] to [14 × the reduced viscosity value + 11 · 2]｝ (% by weight), and when the reduced viscosity is 0.7 dl / g or more,
It is preferable that {40 × the reduced viscosity value-25} to [40 × the reduced viscosity value-7}} (% by weight). In addition, the reduced viscosity of the polymer (A) represented by the present invention is a value at a solution concentration of the polymer (A) to be measured at 1 g / dl. When the ratio of the molecular weight of the methyl methacrylate polymer having a branched structure (A) of 300,000 or more is within the above range, the fluidity and solvent resistance of the methyl methacrylate polymer having a branched structure (A) In addition, the resin composition is excellent in the balance between fluidity, solvent resistance, and mechanical strength.

The degree of crosslinking of the methyl methacrylate polymer (A) having a branched structure in the present invention is usually expressed as a gel fraction (% by weight of an acetone-insoluble portion based on the total weight of the polymer), and is usually 3% or less. It is preferably at most 1%, more preferably almost 0%.

The tension at which the thermoplastic resin is melted and drawn can be represented by a die swell ratio as an index. The die swell ratio was determined by measuring the melt flow rate using an orifice having an orifice length of 8.0 mm and an orifice diameter of 2.09 mm at a temperature of 230 ° C. and a load of 3.8 kg using a melt indexer. It can be expressed as a value obtained by dividing the strand diameter at the time by the diameter of the orifice. The die swell ratio of the methyl methacrylate polymer (A) having a branched structure of the present invention is a value of 1.2 to 2.5. Note that methyl methacrylate-based resin having no branched structure is available from Journal of Applied Polymer Science (J. Appl. Polym. Sci.) 29
(1984), 3479-3490, FIG. 9, which is about 1. That is, it is shown that the methyl methacrylate polymer (A) having a branched structure has a large die swell ratio, a large tension at the time of melt stretching, and a small drawdown. However, it is still insufficient to obtain a large molded product by blow molding or the like.

The methyl methacrylate polymer (A) having a branched structure of the present invention is obtained by adding a predetermined amount of a polyfunctional monomer, a chain transfer agent and a polymerization initiator to the above-mentioned monomer of the structural unit. Obtained by polymerization. A polyfunctional chain transfer agent can be used as the chain transfer agent, and a polyfunctional initiator can be used as the polymerization initiator. The amount of the component serving as the polyfunctional structural unit is usually 0.02 to 1% by weight based on a monofunctional monomer such as methyl methacrylate.

Examples of the polyfunctional monomer capable of being copolymerized include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, ethylene glycol such as triethylene glycol di (meth) acrylate and tetraethylene glycol di (meth) acrylate. Or those obtained by esterifying the hydroxyl groups at both ends of the oligomer with acrylic acid or methacrylic acid; dihydric alcohols such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, and butanediol di (meth) acrylate Hydroxyl groups esterified with acrylic acid or methacrylic acid; polyhydric alcohols such as trimethylolpropane and pentaerythritol or derivatives of these polyhydric alcohols with acrylic acid or methacrylic acid Those that have been etherified; aryl compound having an alkenyl group such as divinylbenzene two or more thereof.

As the chain transfer agent, those well-known for the polymerization of methyl methacrylate can be used.
The chain transfer agent includes a monofunctional chain transfer agent having one chain transfer functional group and a polyfunctional chain transfer agent having two or more chain transfer functional groups. Examples of the monofunctional chain transfer agent include alkyl mercaptans and thioglycolates, and examples of the polyfunctional chain transfer agent include ethylene glycol, neopentyl glycol, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentane Examples thereof include those obtained by esterifying a hydroxyl group of a polyhydric alcohol such as erythritol, tripentaerythritol, or sorbitol with thioglycolic acid or 3-mercaptopropionic acid.

The amount of the chain transfer agent used for the polymerization of the methyl methacrylate polymer A having a branched structure is usually from 5 × 10 ⁻⁵ mol to 5 × 10 ⁻³ per mol of the monofunctional monomer.
And the amount of the copolymerizable polyfunctional monomer is usually 1 × 10 ⁻⁵ per mole of the monofunctional monomer.
To {the chain transfer agent (mol) −2.5 × 10 ⁻⁴ } equivalent.

The weight-average molecular weight of the methyl methacrylate polymer A having a branched structure is generally governed by the concentration of the polyfunctional monomer, the concentration of the chain transfer agent and the concentration of the radical initiator which are mainly used. Adjustment of weight average molecular weight
Considering that the higher the concentration of the polyfunctional monomer, the higher the weight average molecular weight, and conversely, the lower the concentration of the chain transfer agent, the smaller the concentration, and within the above concentration range of the polyfunctional monomer and the chain transfer agent. It is performed by appropriately changing the concentration within the range.

The molecular weight between branch points can be adjusted mainly by the concentration of the polyfunctional monomer. The higher the concentration of the polyfunctional monomer, the lower the molecular weight between branch points. As for the chain transfer agent, the molecular weight at the branch point tends to be smaller when the polyfunctional chain transfer agent is used than when the same amount of the monofunctional chain transfer agent is used. When the molecular weight is 300,000 or more, the number of species having a high concentration of the polyfunctional monomer increases.

The polymerization initiator includes a monofunctional polymerization initiator for generating one pair of radicals in one molecule and a polyfunctional polymerization initiator for generating two or more pairs of radicals. When the polymerization is terminated at a polymerization rate of 45 to 60% by weight as in the bulk polymerization method, the use of a polyfunctional polymerization initiator having three or more functional groups makes it possible to use a polyfunctional monomer as compared with the branching using only the polyfunctional monomer. Can reduce the amount of unreacted vinyl groups. For example, tris- (t-butylperoxy) triazine as a trifunctional initiator and 2,2-bis (4,4-di-t-butylperoxycyclohexyl) as a tetrafunctional polymerization initiator
Propane can be mentioned. When a polyfunctional polymerization initiator is used, it can be replaced with part or all of the above-mentioned polyfunctional structural unit.

The amount of the polymerization initiator used may be a known and appropriate amount according to the polymerization method, and is usually about 0.001 to 1 part by weight, preferably 0 to 1 part by weight, per 100 parts by weight of the monomer or the monomer mixture. 0.01 to 0.7 parts by weight. The fact that the larger the amount of the polymerization initiator is, the smaller the weight average molecular weight is, as in the well-known general methyl methacrylate polymerization polymerization.

As a method for obtaining the methyl methacrylate polymer (A) having a branched structure in the present invention, well-known polymerization methods for producing an acrylic resin industrially, for example, a suspension polymerization method, a bulk polymerization method, and an emulsification polymerization method are used. Legal can be adapted. As the reaction conditions for the methyl methacrylate polymer (A) having a branched structure in the suspension polymerization method, for example, the reaction temperature is usually about 60 to 90 ° C., and the reaction time depends on the reaction temperature. If the temperature is about 70-85 ° C,
l. It peaks at 5 hours. 100-1 after peak
The temperature is raised to about 10 ° C., and the temperature is maintained in this range for about 10 to 30 minutes to complete the reaction. The reaction is preferably carried out in an atmosphere of an inert gas such as nitrogen, helium, argon or the like from the viewpoint of reducing the gel fraction.

The high molecular weight methyl methacrylate polymer (B) in the resin composition of the present invention has a weight average molecular weight Mw
From 1,000,000 to 5,000,000, preferably from 1.5,000,000 to 4.5,000,000. When the resin composition of the present invention obtained when the weight average molecular weight Mw is less than 1,000,000 is blow-molded, sufficient tension cannot be obtained, and no decrease in drawdown is observed. Also, in the case of extrusion foam molding, foams can be obtained only under limited conditions such as temperature and molding pressure. On the other hand, if it exceeds 5,000,000, the melt fluidity is lowered and the melt moldability is lowered.

This high molecular weight methyl methacrylate polymer (B) can be prepared by polymerizing methyl methacrylate or the above-mentioned copolymerizable monofunctional unsaturated monomer with methyl methacrylate by a known polymerization method, for example, a suspension polymerization method. It is produced by polymerization by a bulk polymerization method or an emulsion polymerization method. At this time, a polymer having a high molecular weight can be obtained by performing polymerization without using a chain transfer agent.

As a method for obtaining the methyl methacrylate polymer composition of the present invention, a known thermoplastic resin mixing method can be used. For example, there is a method of once melt-kneading each component, the melt-kneading is generally used single-screw or twin-screw extruder, using a kneading device such as various kneaders,
There is a method of pelletizing. In addition, there is a method of mixing respective components when melt-processing the final product. Also, first polymerize a monomer mixture to produce a high molecular weight polymer,
There is a method of obtaining a branched polymer by adding a component serving as a polyfunctional structural unit and a chain transfer agent to the remaining monomers. In addition, there is a method in which a previously produced high molecular weight polymer is dissolved in a monomer mixture for producing a branched polymer and then polymerized.

In the present invention, the methyl methacrylate polymer (A) having a branched structure and the high molecular weight methyl methacrylate polymer (B) in the methyl methacrylate resin composition are used.
Is about 90 to about 99% by weight, preferably about 91% by weight, of the methyl methacrylate polymer (A) having a branched structure.
About 98% by weight, and about 10% to about 1%, preferably about 9% to about 2% by weight of the high molecular weight methyl methacrylate-based polymer. When the amount of the high molecular weight methacrylic acid-based polymer (B) exceeds about 10% by weight, the melt fluidity of the composition decreases, and
If the amount is less than the percentage by weight, the drawdown during melt stretching is insufficiently reduced.

The resin composition of the present invention may contain, if necessary, a releasing agent, an ultraviolet absorber, a coloring agent, an antioxidant, a heat stabilizer, a plasticizer, a filler, a dye, a pigment, a light diffusing material and the like. There is no problem even if various additives that can be added to a typical acrylic resin are mixed, and they can be added during the kneading or during the polymerization of each polymer. Further, within a range that does not impair the effects of the present invention, an impact-resistant acrylic resin other than the methyl methacrylate-based resin composition of the present invention, for example, an acrylic resin containing a small rubber-based polymer, or a rubber-based polymer alone May be mixed.

In the present invention, the drawdown is evaluated as follows. The resin pellet was dried at 85 ° C. for 4 hours, and was subjected to Capillograph (manufactured by Toyo Seiki Co., Ltd.)
Resin temperature 230 ° C, extrusion speed 0.3g / s, diameter 2mmφ
The resin is extruded downward from the orifice in the atmosphere in the air, and after extruding the resin into a strand having a length of 50 cm, the change in the length of the strand after the extrusion is stopped is measured. For a resin in which the strand elongates 10% for 0 to 5 seconds, it is difficult to produce a large molded product, and the resin exceeds 5 seconds.
The resin, preferably longer than 10 seconds, allows for the production of large molded articles.

[0033]

The resin composition of the present invention has excellent solvent resistance, high fluidity, low drawdown during blow molding, and can be used for molding large molded products. Further, when the resin composition is molded by an extruder, the meltdown during sheeting is reduced, and the extrusion processing characteristics are good. When the formed sheet or the like is formed by heating, a good product with less uneven thickness can be obtained. Further, the range of molding conditions for injection blow molding and direct blow molding is widened, and uneven wall thickness of the formed molded product is reduced. In addition, large-size blow molding has become possible, and acrylic bottles, large signboards, lighting covers, parts for automobile parts, bathtub peripheral materials, home appliance materials, and other acrylic resin materials that could not be molded with acrylic resin until now. It can be applied to materials utilizing design properties, solvent resistance, weather resistance, or surface hardness. Furthermore, while satisfactory foams cannot be obtained with conventional methacrylic resins, foams having a high expansion ratio with little outgassing during foam molding can be obtained.

[0034]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. In addition, the evaluation in an Example was performed using the following methods. (1) MFR: 230 according to JIS K7210
° C, 3.8 kg load, measured for 10 minutes (g / 10
Minutes). (2) Die swell ratio: a value obtained by dividing the strand diameter when measuring the above MFR by the orifice diameter of 2.09 mm. (3) Reduced viscosity: polymer according to JIS Z8803
The reduced viscosity of (A) is 1 g / dl and the polymer (B)
Is a value at a concentration of 0.1 g / dl, and was measured and measured at 25 ° C. in a chloroform solution (d1 / g). (4) Weight average molecular weight (Mw) and Z average molecular weight (M
z): Gel permeation chromatography with a differential refractometer and a viscometer (GPC1 manufactured by Waters)
(Molecular weight-elution time) calibration curve of standard methyl methacrylate polymer. (5) Molecular weight between branch points (Mzb): From the above calibration curve and a calibration curve showing the relationship of the intrinsic viscosity to the GPC elution time of the standard methyl methacrylate polymer, a calibration curve showing the relationship of the intrinsic viscosity to the absolute molecular weight was determined. Using this calibration curve, the intrinsic viscosity [η ₂ ] corresponding to the molecular weight Mz value was determined. Next, using a universal calibration curve showing the relationship between the absolute molecular weight and the intrinsic viscosity with respect to the elution time of the standard methyl methacrylate polymer, a calibration curve showing the relationship between the absolute molecular weight and the intrinsic viscosity of the polymer to be measured was determined. The intrinsic viscosity [η ₁ ] corresponding to the molecular weight Mz value was determined using this calibration curve. Using [η ₁ ] and [η ₂ ], the above [Equation 1]
Was calculated from the above, and then Mzb was calculated from the above [Equation 2]. (6) Draw-down evaluation: Resin pellets at 85 ° C.
After drying for an hour, using a Capillograph (manufactured by Toyo Seiki Co., Ltd.), the resin temperature was 230 ° C., the extrusion speed was 0.3 g / s, and the diameter was 2 m.
The resin was melt-extruded downward from the mφ orifice in the air, the resin was extruded into a strand having a length of 50 cm, and the change in the length of the strand after the extrusion was stopped was measured to evaluate the drawdown. Evaluation is 10 strands
% Time is 0 to 5 seconds x 1 over 5 seconds
The symbols up to 0 seconds were represented by Δ, and those exceeding 10 seconds were represented by ○.

Abbreviations of various monomers and chain transfer agents used in the examples are as follows. MMA: methyl methacrylate MA: methyl acrylate BA: butyl acrylate HDA: 1,6-hexanediol diacrylate LRSH: lauryl mercaptan DDSH: n-dodecyl mercaptan LRPO: lauroyl peroxide DBSN: sodium dodecylbenzene sulfonate

Reference Example 1 "Production of methyl methacrylate polymer having branched structure (A)" Methyl methacrylate, methyl acrylate, lauroyl peroxide, 1,6 hexanediol diacrylate and lauryl mercaptan were placed in an SUS autoclave. The amounts shown in Table 1, 200 parts by weight of ion-exchanged water, and 1 part by weight of polysodium methacrylate were added and mixed, heated and heated to start polymerization at 80 ° C.
Polymerization was carried out at 0 ° C. for 60 minutes. After the polymerization, washing, dehydration and drying were performed to obtain a beaded polymer (A1). The obtained polymer was evaluated. Table 1 shows the evaluation results.

[0037]

[Table 1]

Reference Examples 2 to 4 "Production of high molecular weight methyl methacrylate polymer (B)" A solution of methyl methacrylate, butyl acrylate or methyl acrylate, and lauryl mercaptan, sodium carbonate, sodium dodecylbenzenesulfonate and An aqueous solution of 100 parts by weight of ion-exchanged water was mixed at a ratio shown in Table 2, heated, a potassium persulfate aqueous solution was added at 40 ° C, and polymerized at 83 ° C for 3 hours. After the polymerization, drying was performed by a freeze drying method to obtain a beaded polymer. The obtained polymer was evaluated. The evaluation results are shown in Table 2 (B1, B2). Further, methyl methacrylate, methyl acrylate, lauroyl peroxide and lauryl mercaptan were mixed in the amounts shown in Table 2, 200 parts by weight of ion-exchanged water, and 1 part by weight of polysodium methacrylate. The polymerization was started at 90 ° C., and after 90 minutes, the polymerization was further performed at 100 ° C. for 60 minutes. After polymerization, washing,
Dehydration and drying were performed to obtain a beaded polymer. The obtained polymer was evaluated. The evaluation results are shown in Table 2 (B3, B
4).

[0039]

[Table 2]

Examples 1-4, Comparative Examples 1-3 Methyl methacrylate polymers having a branched structure (A) prepared in Reference Example 1 and high molecular weight methyl methacrylate polymers prepared in Reference Examples 2-4 ( After B) was uniformly dry-blended using a mixer at the mixing ratio shown in Table 3, 3
Using a twin screw kneading extruder of 0 mm, cylinder temperature 25
The obtained pellets were melt-kneaded at 0 ° C. and pelletized, and the obtained pellets were evaluated for drawdown and the like. Table 3 shows the evaluation results.

[0041]

[Table 3] * 1: Means failure due to the occurrence of melt fracture.

Claims (4)

[Claims] (1) a weight average molecular weight of 80,000 to 400,000, and a molecular weight between branch points defined by using a Z average molecular weight of 30,000 to 5
90-99% by weight of a methyl methacrylate-based polymer (A) having a branched structure of 100,000 and a weight average molecular weight of 1
A methyl methacrylate-based resin composition comprising 10 to 1% by weight of a high-molecular-weight methyl methacrylate-based polymer (B) having a molecular weight of from 500,000 to 5,000,000. 2. The methyl methacrylate-based polymer (A) having a branched structure may have a molecular weight of 300,000 or more, and the reduced viscosity of the polymer may be 0.7 dl / g.
In the following cases, Δ [14 × the reduced viscosity value−6.8] to [1
4 × the reduced viscosity value + 11.2]｝ (wt%), and when the reduced viscosity is 0.7 or more, {40 × the reduced viscosity value−
The methyl methacrylate-based resin composition according to claim 1, wherein the ratio is 25] to [40 x reduced viscosity value-7] (% by weight). 3. A methyl methacrylate polymer having a branched structure (A) comprises methyl methacrylate, a monofunctional monomer copolymerizable therewith, a polyfunctional monomer, a chain transfer agent and a polymerization initiator. 3. The methyl methacrylate resin composition according to claim 1, which is obtained by polymerization. 4. The methyl methacrylate according to claim 1, wherein the high molecular weight methyl methacrylate polymer (B) is obtained by polymerizing methyl methacrylate, a monofunctional monomer copolymerizable therewith, and a polymerization initiator. -Based resin composition.