JPH04132709A - Flame-retardant methacrylic resin - Google Patents

Abstract

PURPOSE:To obtain the title resin being a copolymer consisting of a specific ratio of methyl methacrylate unit, bromophenyl methacrylate unit, etc., having intrinsic viscosity being in a specific range, having excellent optical properties and heat resistance and free from problems such as stain of mold and bleeding. CONSTITUTION:The objective resin being a copolymer consisting of 55-85wt.%, preferably 60-80wt.% methyl methacrylate unit, 15-35wt.%, preferably 20-30wt.% bromophenyl methacrylate unit expressed by the formula (i is 3-5) and 0-10wt.%, preferably 2-8wt.% polymerizable other vinyl compound unit (e.g. ethyl methacrylate), being 0.35-0.60dl/g, preferably 0.40-0.55dl/g in intrinsic viscosity measured at 20 deg.C in chloroform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flame-retardant methacrylic resin, and more particularly to a flame-retardant methacrylic resin having excellent optical properties and heat resistance.

[Conventional technology]

Methacrylic resin has excellent optical properties and weather resistance,
Because it has good heat resistance and mechanical properties, it is widely used in lighting materials, electronic equipment parts, office automation equipment, automobile parts, and architectural parts such as exteriors. On the other hand, because methacrylic resin is easily flammable, it is often subject to various restrictions, such as U.S. UL regulations for home appliances and OA equipment.
(Underwriters, Laboratories) There are standards, etc.
In order to maintain combustibility suitable for such materials, a method is usually used in which a flame retardant such as a certain type of phosphorus halide compound is added in advance (Japanese Unexamined Patent Application Publications No. 49-107352, No. 51-58452). , a method of adding a halogenated flame retardant to a methacrylic acid ester copolymer having an intrinsic viscosity within a certain range (JP-A-1-217055)
Alternatively, a method has been proposed in which an organic phosphonic acid ester is added to a copolymer of methyl methacrylate and bromophenyl methacrylate (Japanese Unexamined Patent Publication No. 48-83144).

[Problem to be solved by the invention]

However, although flame retardancy can be obtained in the proposed method, the heat resistance and mechanical strength of the molded article are significantly reduced, impairing its practicality. Furthermore, when these molded products are used outdoors, there are problems such as bleeding caused by the added flame retardant and whitening caused by water absorption, and the mold being stained during molding.

Therefore, the object of the present invention is to improve the above-mentioned drawbacks of conventional flame-retardant acrylic molding materials and to obtain a composition having excellent transparency and good heat resistance and mechanical properties.

[Means to solve the problem]

As a result of intensive studies in view of the above situation, the present inventors have found that a copolymer consisting of methyl methacrylate units, bromophenyl methacrylate units and other copolymerizable vinyl compound units having a specific composition, and It was discovered that a copolymer having an intrinsic viscosity within a specific range has excellent flame retardancy and heat resistance, and retains the characteristics of methacrylic resin such as transparency and mechanical properties, leading to the completion of the present invention.

That is, the above object of the present invention is to provide a copolymer consisting of 55 to 85% by weight of methyl methacrylate units, 5 to 35% by weight of single-position bromophenyl methacrylate units, and 0 to 10% by weight of other copolymerizable vinyl compound units. and the intrinsic viscosity at 20°C in chloroform is 0.35 to 0.
Achieved by flame retardant methacrylic resin which is 60 dl/gr.

The methyl methacrylate unit used in the present invention needs to be used in an amount superior to other monomer unit components in order to maintain the excellent optical properties and well-balanced mechanical strength inherent to methacrylic resin. The content is 55-85% by weight, more preferably 60-80% by weight. If the content is less than 55% by weight, the above characteristics are not retained;
If it exceeds % by weight, the effect of improving flame retardancy will be poor, which is not preferable.

The bromophenyl methacrylate unit of the present invention is used together with methyl methacrylate, and has the effect of imparting flame retardance as well as improving heat resistance and low moisture absorption, and its content is preferably 15 to 35% by weight, more preferably is 20 to 30% by weight. If the content is less than 15% by weight, the flame retardant effect will be poor, while if it exceeds 35% by weight, the flame retardant effect will be improved, but the mechanical strength will be significantly reduced and the optical damage due to increased haze etc. This is not preferable as it will cause significant damage to the properties.

The monomer constituting the bromophenyl methacrylate unit of the present invention is a compound represented by the following formula (i represents an integer from 3 to 5), and tribromophenyl methacrylate is preferably used. If the number of bromines on the benzene ring is less than 3, a sufficient flame retardant effect cannot be obtained, which is not preferable.

Other copolymerizable vinyl compound units used as necessary in the present invention are effective in improving fluidity and flame retardant effect, and the content thereof is 0 to 10% by weight, preferably 2 to 8% by weight. Weight%. Monomers constituting other copolymerizable vinyl compound units, which are undesirable if the content exceeds 10%, will reduce heat resistance and mechanical strength.
Methacrylic acid esters such as ethyl methacrylate, isopropyl methacrylate, cyclodecyl methacrylate, benzyl methacrylate, acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, styrene, α-methylstyrene vinyl toluene, etc. Examples include aromatic vinyl compounds and nitrile compounds such as acrylonitrile and methacrylonitrile.

The intrinsic viscosity of the copolymer consisting of the above-mentioned structural units of the present invention at 20°C in chloroform solvent is 0.35 to 0.60 (
d l/g r), more preferably 0.40 to 0
．． 55 (di!, /g r). Intrinsic viscosity is 0.
If it is less than 35, it is unfavorable because the mechanical strength is low and it is impractical. On the other hand, if it exceeds 0.60, the mechanical strength is strong, but the flame retardant effect is poor because the burning part does not fall and separate during combustion. decreases and is not desirable.

The method for producing the flame-retardant methacrylic resin of the present invention is not particularly limited, and methods such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization are possible.

As the polymerization initiator used when polymerizing this flame-retardant methacrylic resin, any initiator generally used in radical polymerization can be used, such as 2,2'-azobisisobutyronitrile, 2. .2'Azobis(2,4-
azo compounds such as dimethylvaleronitrile), lauroyl peroxide, tert-butylperoxy-2-
Examples include organic peroxides such as ethylhexanoate, tert-hexylperoxy-2-ethylhexanate, and 1,1,3.3-tetramethylbutylperoxy-2-ethylhexanate.

Further, when polymerizing, a molecular weight regulator may be used as necessary. Examples of molecular weight regulators include n-octyl mercaptan, n-dodecyl mercaptan, tert-
Examples include mercaptan compounds such as dodecyl mercaptan, thiophenol, and 2-ethylhexyl thioglycolate.

The temperature at which the flame-retardant methacrylic resin of the present invention is polymerized is not particularly limited, but is selected between 50 and 150°C, particularly preferably between 60 and 130°C.

Further, the flame-retardant methacrylic resin of the present invention may contain an ultraviolet absorber, a heat stabilizer, an antioxidant, a lubricant, a mold release agent, dyes and pigments, etc., as necessary.

〔Effect of the invention〕

As mentioned above, the flame-retardant resin of the present invention is a resin copolymerized with specific monomers in a specific ratio and has a specific intrinsic viscosity, and because it does not use flame-retardant additives, it has high heat resistance. It is possible to obtain a flame-retardant methacrylic resin that does not deteriorate in properties and has fewer problems such as mold stains during injection molding and bleeding due to aging of molded products, and is useful in the field of light electrical appliances, OA equipment, etc.

〔Example〕

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

In the examples, "%" and "1 part" refer to "% by weight" and "part by weight," respectively. Physical property evaluations in Examples were conducted based on the following methods (1) to (4).

(1) Intrinsic viscosity (df/gr) Automatic viscosity needle (fica) in chloroform at 20°C
(manufactured by France).

(2) Vicart softening temperature (°C) 20x20x
3.2 (m) test piece was made by injection molding method,
Measured by ASTM D1525 method.

(3) Tensile Strength A dumbbell shape was made by injection molding according to ASTM D63B, and the tensile strength was measured.

(4) Evaluation of flame retardancy A test piece measuring 127 x 27 x 3.2 (mu) was molded by injection molding. In accordance with UL Standard No. 94, the obtained test piece is hung vertically, and a flame of a specified size generated by burning gas with a specified calorific value is applied from the bottom of the test piece. After 10 seconds of ignition, the flame is immediately removed. After confirming that the flame on the test piece was extinguished by releasing the ignited coal, the flame was applied again, and the number of seconds from when the ignited coal was released to when the flame extinguished was measured and evaluated.

Example 1 751 with stirrer! , 250 g of polypotassium methacrylate aqueous solution and 2 hydrogen phosphate as a suspension stabilizer in a pressure-resistant reaction tank.
N-octyl mercaptan is added to 100 parts of a monomer mixture of 75% methyl methacrylate, 5% methyl acrylate, and 20% tribromophenyl methacrylate with 32.4 kg of deionized water in which 15 g of sodium and 30 g of sodium dihydrogen phosphate are dissolved. A monomer mixture in which 0.2 parts of t-butylperoxy-2-ethylhexanony), 0.1 parts of stearyl alcohol, and 0.01 parts of JF77 (manufactured by Taika Kagaku) as an ultraviolet absorber were dissolved 21. Insert 6kg and N! After the substitution, polymerization was carried out at 80°C with stirring, and after the exothermic peak was reached, the polymerization was carried out by heating at 120°C for 1 hour. After washing the resulting bead-shaped copolymer with water and drying it,
It was pelletized using an extruder (manufactured by Nakayo Kikai) with a cylinder diameter of 40 mm. The intrinsic viscosity of this pellet is 0.50 dl/
It was gr. This pellet is molded into injection molding machine N-70.
Each test piece was molded and evaluated using Type A (Japan Steel Works Type) under the conditions of a cylinder temperature of 220°C and a mold temperature of 60°C. The results are shown in Table 1, and the physical properties such as tensile strength and heat resistance were good, and a molded product with no coloration in appearance was obtained. As a result of the combustion test, it complies with UL standard ■2 class.

Comparative Examples 1 to 2 Copolymerization components and n-octyl mercaptan as a polymerization degree regulator were prepared to have the composition and intrinsic viscosity shown in Table 1, and polymerization, pelletization, and injection were carried out under the same conditions as in Example 1. The test pieces obtained through molding were evaluated.

In Comparative Example 1, even if the composition is within the claimed range, when the intrinsic viscosity is high, the flame retardant effect is low and does not reach the UL standard v-2 class. In addition, when the intrinsic viscosity is too small as in Comparative Example 2, the flame retardant performance is sufficient and UL standard v-2
class, but its strength is low and its practicality is poor, making it undesirable.

Examples 2 to 5 In Example 2, the copolymer components were prepared as shown in Table 1,
Polymerization, pelletization, and injection molding were carried out under exactly the same conditions as in Example 1 and evaluated. Even if other vinyl compounds are copolymerized, as long as the composition and intrinsic viscosity are within the claimed range, there will be no decrease in strength and heat resistance, and the flame retardant performance will be UL standard V-2 class.

Examples 3 and 4 use bromophenyl methacrylate and pentabromophenyl methacrylate, but as long as the copolymer composition and intrinsic viscosity are within the claimed range, they have good physical properties and flame retardancy as in Example 1. You can get sex.

In Example 5, good strength, heat resistance, and flame retardant performance were obtained even when no other copolymerizable vinyl compound was used.

Comparative Example 3 A test piece prepared with the composition shown in Table 1 and polymerized, pelletized, and injection molded under the same conditions as Example 1 was evaluated. As a result, the strength and heat resistance were sufficient. However, if the proportion of the copolymerized components does not reach the claimed range, sufficient flame retardance cannot be obtained and the product falls within the UL standard HB class.

Example 6 0.25 parts of n-dodecyl mercaptan, 0.2 parts of stearic acid monoglyceride, 03 parts of JF770, and 0.1 parts of lauroyl peroxide were added to 100 parts by weight of a monomer mixture prepared in the proportions shown in Table 1. was dissolved and injected into a cell consisting of a vinyl chloride tube between two glass plates, and polymerized at 70"C. After the exothermic peak, the temperature was 130°C.
Thermal polymerization was carried out for 60 minutes, and the mixture was taken out after cooling. The intrinsic viscosity of the obtained casting plate was 0.52 (dj!/gr). After crushing this cast plate with a crusher, it was pelletized and injection molded under the same conditions as in Example 1, and the obtained test pieces were evaluated. As a result, the strength and heat resistance were good, and the flame retardance was also sufficient. DeU
It was L standard V-2 class.

Margin below

Claims (1)

[Claims] A copolymer consisting of 55 to 85% by weight of methyl methacrylate units, 5 to 35% by weight of single-position bromophenyl methacrylate units, and 0 to 10% by weight of other copolymerizable vinyl compound units, and which is produced in chloroform at 20°C. A flame-retardant methacrylic resin having an intrinsic viscosity of 0.35 to 0.60 dl/gr.