JPH0759659B2 - Methacrylic resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a methacrylic resin composition having excellent processability and moldability.

[Conventional technology]

Methacrylic resin is its original property, its excellent transparency,
Taking advantage of weather resistance, currently automobile parts such as meter covers,
It is used for video discs, optical components such as lenses, and lighting components such as light covers. However, when molding such parts, due to the inherent characteristics of methacrylic resin, thermal decomposition of the polymer causes a molding defect called a silver strip, and when molding a thick molded product, problems such as sink marks and internal foaming occur. was there. Further, there is a problem that crazes and cracks are generated when the molded product is subjected to post-processing such as painting.

However, in order to further expand the field of use of the methacrylic resin, a method of improving the solvent resistance by giving the methacrylic resin a specific molecular weight distribution (Japanese Patent Laid-Open Nos. 54-112987 and 54-14).
9788, JP-A-55-9614) and a method of improving solvent resistance by copolymerizing an acrylate (Japanese Patent Publication No. 54-32669).

[Problems to be solved by the invention]

However, the former has an intrinsic viscosity of 0.027 to 0.117 / g, and a poor solvent shows some effect on solvent resistance.
A good solvent was not effective and was a problem. The latter copolymerized acrylate has improved flowability and improved moldability, but has a problem of low heat distortion temperature.

On the other hand, in the field of use of methacrylic resin, the complexity and diversification of shapes have progressed due to the demand for fashionability, and molding processability in the market and solvent resistance in post-processing have become major problems, which have not yet been solved. The current situation.

[Means for solving problems]

In view of such circumstances, the present inventors have made methacrylic resin easy to mold, that is, elongation occurs during molding, does not crack during mold release, has good wall thickness moldability, and is excellent in solvent resistance. As a result of extensive studies aimed at providing the above, the present invention has been completed.

That is, the present invention comprises 80 to 99.8% by weight of methyl methacrylate and 0.2 to 20% by weight of at least one monomer copolymerizable therewith, and has an intrinsic viscosity [η] _A measured at 25 ° C. in a chloroform solvent. (A) 90 having a content of 0.03 to 0.08 / g
-99.9 parts by weight, methyl methacrylate 40-70% by weight, methyl acrylate, ethyl acrylate, butyl acrylate at least one 30-60% by weight, glass transition temperature (Tg) 20-80 ℃ And an intrinsic viscosity [μ] _B measured in a chloroform solvent at 25 ° C. of 0.10 to 0.30 / g
A methacrylic resin composition containing 0.1 to 10 parts by weight of the copolymer (B).

The use of methyl methacrylate in the copolymer (A) of the present invention plays a role of maintaining the original transparency and weather resistance of the methacrylic resin, and the proportion of methyl methacrylate in the copolymer is 80 to 99.8% by weight. %, Preferably in the range of 95 to 99.8% by weight. When the proportion of methyl methacrylate is less than 80% by weight, mechanical strength, heat distortion resistance and weather resistance are poor, and the original properties of methacrylic resin are lost. . On the other hand, when the proportion of methyl methacrylate is more than 99.8% by weight, the thermal decomposition resistance of the copolymer at the time of injection molding is inferior and molding defects such as silver strips are likely to occur, which is not preferable.

Other vinyl monomers copolymerizable with methyl methacrylate include acrylic acid esters and methacrylic acid esters having an alkyl group having 1 to 4 carbon atoms, cyclohexyl methacrylate, phenyl methacrylate, isobornyl methacrylate, styrene, vinyl. Toluene, α-methylstyrene, maleic anhydride, N-substituted maleimide and the like can be mentioned.

The intrinsic viscosity [η] _A of the copolymer (A) is in the range of 0.03 to 0.08 / g in order to achieve a balance between the mechanical strength and fluidity of the methacrylic resin, and 0.03
If it is less than / g, the mechanical strength will decrease, which is not desirable,
If it is larger than / g, the fluidity will deteriorate and a problem will occur. Preferably 0.04 to 0.07 / g, more preferably 0.04 to 0.065
/ g.

The amount of the copolymer (A) used is 90 to 99.9 parts by weight in order to give the methacrylic resin its original mechanical strength, fluidity, weather resistance, etc. When the amount is more than 99.9 parts by weight, thermal decomposition is poor, cracking and foaming easily occur during molding, and solvent resistance during post-processing is poor, making it unusable. . Preferably 95-99.5 parts by weight, more preferably 95-
It is 99 parts by weight.

The copolymer (B), which is an important component of the composition of the present invention, is
It is effective in improving wall thickness moldability and solvent resistance.
To achieve that goal, the glass transition temperature (Tg) is 20
It is important that the intrinsic viscosity [η] _B measured at -80 ° C and 25 ° C in a chloroform solvent is 0.10 to 0.30 / g. The glass transition temperature Tg of the resulting copolymer is 20 ° C ~
The temperature of 80 ° C. is for preventing the resin from cracking at the time of releasing from the mold at the time of molding, and if it is lower than 20 ° C., the heat distortion temperature of the resin composition after mixing is lowered, which is not preferable. If the temperature is higher than 80 ° C., “porosity” will occur after kneading, and the appearance of the molded product tends to remarkably deteriorate, which is not preferable.

The most characteristic of the present invention is that the intrinsic viscosity of the copolymer (B) is 0.10 to 0.30 / g, which improves the easily moldable workability, the wall thickness moldability, and the solvent resistance of the resin after kneading. If less than 0.10 / g, the solvent resistance is inferior, 0.30
If it is larger than / g, the molded article tends to be unfavorable since it tends to be poor in appearance and has poor moldability and solvent resistance. It is preferably 0.11 / g to 0.20 / g.

The copolymer (B) is composed of 40 to 70% by weight of methyl methacrylate, 30 to 60% by weight of at least one of methyl acrylate, ethyl acrylate and butyl acrylate.

The main component of the copolymer (B) is the above-mentioned methacrylic acid and / or acrylic acid derivative in order to obtain the desired methacrylic resin by mixing with the copolymer (A). To impart transparency, weather resistance, mechanical properties, and fluidity, and is particularly preferable for the purpose of thick-wall molding.

The copolymer (B) has a composition of 40 to 70% by weight of methyl methacrylate and at least 30% to 60% by weight of at least one of methyl acrylate, ethyl acrylate and butyl acrylate. It is for improving the compatibility by mixing with, and preventing the generation of seeds after mixing and the deterioration of the appearance of the molded product.
Particularly, when the proportion of methyl methacrylate is less than 40% by weight, the heat distortion temperature of the resin composition after mixing with the copolymer (A) is lowered, while when it is more than 70% by weight, the mixing with the copolymer (A) is increased. After that, a lump occurs.

Further, other copolymerizable monomers can be added to the copolymer (B) if necessary.

The copolymerizable vinylidene and vinyl compounds include acrylate or methacrylate monomers such as cyclohexyl methacrylate, hydroxyethyl acrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, styrene, vinyltoluene, α-methylstyrene, maleic anhydride, N- Substituted maleimide and the like can be mentioned.

The mixing ratio of the copolymer (B) is 0.1 to 10 parts by weight,
If it is less than 10 parts by weight, solvent resistance and cracking during molding are likely to occur, and if it is more than 10 parts by weight, the heat distortion temperature is lowered, which is not preferable. It is more preferably 0.5 to 5 parts by weight.

When producing the methacrylic resin of the present invention, known conditions and methods can be used as individual polymerization conditions, for example, bulk polymerization method, suspension polymerization method or the like is adopted depending on the application of the resin, As the catalyst, a known azo or organic peroxide type polymerization initiator can be used.

In addition, a colorant, a stabilizer, a plasticizer, a lubricant, an ultraviolet absorber and the like can be added to the resin as long as the optical properties are not impaired.

〔Example〕

Next, specific examples for producing the methacrylic resin of the present invention will be described in detail with reference to Examples.

Parts in the examples are parts by weight, and percentages are percentages by weight.

The physical properties in the examples were evaluated as follows.

[Measurement conditions] Solvent resistance was evaluated by crazing resistance (crazing resistance) ... 4000 psi stress was applied to the fulcrum of a sample with a plate thickness of 2 mm, a width of 25 mm, and a length of 110 mm, and the fulcrum was wet with isopropyl alcohol for measurement. Measure the time from the start to the occurrence of crazes and cracks.

Heat resistance is evaluated by HDT (heat distortion temperature) according to ASTM D-648.

Moldability was determined by making 50 molded specimens and counting the defective specimens such as cracks and chips.

Tg measurement conditions Shimadzu thermal analyzer DT-30 system using a finger-point scanning calorimeter DSC-30 type Measurement conditions N ₂ 30 ml / min Temperature rising rate 10 ° C / min Intrinsic viscosity [η] measured in chloroform solvent at 25 ° C did.

The melt flow rate (MFR) was measured at a load of 3.8 kg and 230 ° C.

Spiral foaming temperature is injection molding machine manufactured by Mitsubishi Heavy Industries, Ltd.
125 / 75MS, gauge pressure 60kg / cm ² thickness 2mm, width 10mm
Was measured using a spiral mold of

For the wall thickness moldability, an injection machine 125 / 75MS manufactured by Mitsubishi Heavy Industries, Ltd. was used to form a square bar having a thickness of 6.5 mm, a width of 12.7 mm and a length of 127 mm, and the degree of bubbles and sink marks in the bar was visually judged.

Example 1 [Production of Copolymer A] 5000 g of deionized water in a glass separable flask with an internal volume of 10 equipped with a stirrer, a thermometer, and a monomer charging port, and methyl methacrylate and sulfoethyl methacrylate as dispersants 0.45 g of a copolymer with a sodium salt and 7.5 g of sodium sulfate were charged, and then a monomer phase having the composition shown in Table 1 was charged respectively, oxygen was substantially removed, and the mixture was vigorously stirred at 80 ° C from the outside. The suspension is heated for 3 hours to carry out suspension polymerization, then the internal temperature is raised to 95 ° C and kept for 30 minutes, then cooled, the contents are separated, washed with water, and dried to obtain a bead-like polymer (copolymer A). Got

[Production of Copolymer B]

Polymerization was performed with the composition shown in Table 2 in the same manner as the copolymer (A) to obtain a bead-shaped polymer of the copolymer (B).

Each of these beads was blended in the proportion shown in Table 3, and then extruded by using an extruder having a screw diameter of 30 mmφ at 200 to 250 ° C. under a vent vacuum pressure of −700 to −750 mmHg to form a pellet.

Next, using the injection molding machine (IS-22PN type manufactured by Toshiba Machine Co., Ltd.) with a capacity of 1 ounce, the resulting pellets were cut into a square plate with a thickness of 2 mm and 110 mm square with a mold temperature of 55 ° C and an injection pressure of 60 kg / cm ² (gauge. Molding was performed to evaluate easy moldability and solvent resistance. The results are shown in Table 3.

In addition, 0.1 part of azobisisobutyronitrile and n-octyl mercaptan as a polymerization initiator with respect to 100 parts of the monomer.
Polymerization was carried out by adding 0.23 part.

The degree of polymerization was adjusted with an initiator and mercaptan, respectively.

Examples 2 to 11 and Comparative Examples 2 to 6 The same procedure as in Example 1 was carried out except that the mixing ratios of the copolymer (A) and the copolymer (B) were changed to those shown in Tables 4 and 5. The results shown in Tables 4 and 5 were obtained.

It is clear that the resin composition of the present invention has excellent chemical resistance and moldability.

In Comparative Example 6, the fluidity was low and an evaluation sample could not be prepared.

Examples 12 to 15 and Comparative Examples 7 to 10 Production of Copolymer (A) (2) Example 1 except that a monomer solution was prepared at the ratio shown in Table 6 and the polymerization degree was adjusted with an initiator and mercaptan. Copolymer (A)
The beaded polymer shown in Table 6 was obtained in exactly the same manner as in the preparation of.

This was blended with the copolymer (B) shown in Table 2 in the proportions shown in Table 7, and otherwise the same procedure as in Example 1 was carried out to obtain the results shown in Table 7.

The copolymers (A) other than the present invention having different compositions and polymerization degrees (Comparative Examples 7 to 10) all had poor moldability,
Those of the present invention (Examples 12-15) were excellent.

Example 16, Comparative Examples 11 to 14 Production of Copolymer (B) (2) Copolymer of Example 1 except that a monomer solution was prepared at the ratio shown in Table 8 and the polymerization degree was adjusted with an initiator and mercaptan. Polymer (B)
The beaded polymer shown in Table 8 was obtained in exactly the same manner as in the preparation of.

To 2 parts of these copolymers (B), 98 parts of copolymer A-1
The mixing was carried out in the ratio of parts, and the other operations were carried out in the same manner as in Example 1 to obtain the results shown in Table 9.

Those using the copolymer (B) outside the scope of the present invention were inferior in moldability and physical properties.

It should be noted that the surfaces of the molded test pieces of Comparative Examples 11, 12 and 13 were found to have optical strain and lumps.

The fluidity of ASTM D-1238 of copolymer A-1 at 230 ° C. and a load of 10 kg was 7.7 g / 10 minutes, but the resin composition of Example 16 was
It was 8.5 g / 10 minutes, and the fluidity was excellent at about 10%. A-1
It is surprising that the fluidity is improved as compared with A-1, even though B-1 which is a higher polymer is blended.

Examples 17 to 22 and Comparative Examples 15 to 17 Copolymers of methyl methacrylate and 2-sulfoethyl methacrylate sodium salt in 1500 g of deionized water in a separable flask equipped with a stirrer, a thermometer, and a monomer charging port.
An aqueous solution containing 0.2 g and 5 g of sodium sulfate dissolved therein was charged, and then 1 g of azobisisobutyronitrile and 2.2 g of n-octyl mercaptan dissolved therein were charged respectively to substantially prepare monomer phases having the composition shown in Table 10. After removing oxygen, the mixture was heated to 80 ° C. with vigorous stirring for polymerization for 150 minutes and then cooled, the contents were separated, washed with water, and dried to obtain a copolymer (A).

On the other hand, in a separable flask equipped with a stirrer, a thermometer, and a monomer charging port, 0.5 g of a copolymer of methyl methacrylate and 2-sulfoethyl methacrylate sodium salt and 5 g of sodium sulfate were dissolved in 3000 g of deionized water. Prepared aqueous solution, and then 0.8 g of azobisisobutyronitrile and n-
Each of the monomer phases having the composition shown in Table 11 in which 0.5 g of octyl mercaptan was dissolved was charged, substantially oxygen was removed, and the mixture was heated to 80 ° C. with vigorous stirring and polymerized for 150 minutes, and then cooled. The product was separated, washed with water, and dried to obtain a copolymer (B).

Next, each of these copolymers was mixed in a ratio shown in Table 12, 0.3 g of Tinuvin P (manufactured by Ciba-Geigy, an ultraviolet absorber) and 1 g of stearic acid were added, and a twin-screw extruder (manufactured by Ikegai Tekko, (PCM-30 type) was extruded at a barrel temperature of 260 ° C. under a reduced pressure of 20 torr to be pelletized. The physical properties of the obtained pellets were evaluated. The results are shown in Table 12.

[Effects of the Invention] The methacrylic resin composition of the present invention has good molding properties and solvent resistance as compared with conventional methacrylic resins, and also has excellent transparency and weather resistance inherent to methacrylic resins. It has industrial value because it can be used effectively in the fields where methacrylic resin is currently used, such as automobile parts such as meter covers, optical parts such as video discs and lenses, lighting parts, building material parts, OA equipment parts, etc. Is big.

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Claims (1)

[Claims] 1. 80 to 99.8% by weight of methyl methacrylate and 0.2 to 20% by weight of at least one monomer copolymerizable therewith
Copolymer (A) 90 to 9 having an intrinsic viscosity [η] _A of 0.03 to 0.08 l / g measured in a chloroform solvent at 25 ° C.
9.9 parts by weight and 40 to 70% by weight of methyl methacrylate, 30 to 60% by weight of at least one of methyl acrylate, ethyl acrylate and butyl acrylate, and a glass transition temperature (Tg) of 20 to 80 ° C. A methacrylic resin composition comprising 0.1 to 10 parts by weight of a copolymer (B) having an intrinsic viscosity [η] _B of 0.10 to 0.30 l / g measured in a chloroform solvent at 25 ° C.