JPH04126754A - Flame-retardant methacrylate resin composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a flame-retardant methacrylic resin composition, and more specifically, a flame-retardant methacrylic resin composition that has excellent transparency and heat resistance, and has little dimensional change due to water absorption. The present invention relates to a thermoplastic resin composition.

(Prior art) Methacrylic resin has excellent optical properties and weather resistance, as well as good heat resistance and mechanical strength, so it is used in lighting materials, electronic equipment parts, OA equipment, automobile parts, and It is widely used for etc. On the other hand, methacrylic resin is often subject to various restrictions due to its flammability.For example, there are U.S. UL (Underwriters Laboratories) standards for home appliances, office automation equipment, etc. A method of adding various halogen-containing phosphate esters to methacrylic resin in order to maintain flame retardancy that meets the standards has been known (for example, Japanese Patent Application Laid-Open No.
-217055 Publication). In addition, these halogen-containing phosphate esters have a strong plasticizing effect and cannot provide sufficient heat resistance, so maleic anhydride is introduced into the polymer chain and halogen-containing flame retardants are added to increase heat resistance. A method of adding a halogen-containing condensed phosphoric acid ester and an acid phosphate to a methyl methacrylate-N-substituted maleimide-methacrylic acid copolymer (Japanese Unexamined Patent Publication No. 113063/1989) , JP-A-63-118358), a method of adding halogenated polyphosphate (JP-A-63-117056), and the like are already known.

(Problem to be solved by the invention) However, since water absorption is generally increased by adding a halogenated phosphorus compound, when maleic anhydride is introduced into the polymer chain, hydrolysis is accelerated and the final molded product The water absorption of these products further increases, and the water absorption also increases when methacrylic acid is introduced, so these final molded products have the disadvantage of large dimensional changes due to water absorption, and there are also restrictions on the polymerization method. The current situation is that satisfactory results have not yet been obtained.

Therefore, it is an object of the present invention to improve the above-mentioned drawbacks of conventional flame-retardant acrylic resins, to have excellent heat resistance and dimensional stability due to water absorption without impairing the excellent properties of acrylic resins such as transparency. The object of the present invention is to obtain a flame-retardant resin composition with little change.

(Means for Solving the Problems) In view of the above circumstances, the inventors of the present invention have conducted extensive studies on flame-retardant resin compositions that have excellent transparency and heat resistance, and exhibit little dimensional change due to water absorption. Should be N-
Methacrylic resins with a specific resin composition containing substituted maleimide compound units are effective in suppressing dimensional changes due to water absorption, and this effect is not lost even when halogen-containing phosphate esters and their derivatives are added, and they are heat resistant. The present invention was achieved based on the discovery that it has excellent properties and transparency.

That is, according to the present invention, the above objects are: a) 30 to 95% by weight of methyl methacrylate, b) 2 to 50% by weight of an N-substituted maleimide compound, and C) copolymerizable with these.
A flame-retardant methacrylic resin consisting of 70-92% by weight of a methacrylic resin (1) comprising 0-20% by weight of an aromatic vinyl compound and 8-30% by weight of a halogen-containing phosphoric acid ester and its derivative (II). This is achieved by the composition.

The present invention will be explained in detail below.

The methacrylic resin (1) used in the present invention can be obtained by generally known techniques such as bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization. This methacrylic resin (1
) has an intrinsic viscosity of 0.3 to 1. OdI!
, 7g, more preferably 0.5-0.8df/g
It is desirable that If the intrinsic viscosity is less than 0.3 df/g, the mechanical strength tends to decrease, making it undesirable as a molding material.On the other hand, if the intrinsic viscosity is less than 1. OdI! If it exceeds 7 g, fluidity and moldability tend to decrease, which is not preferable.

N used in copolymerization with methyl methacrylate in the present invention
-Substituted maleimide compounds include, for example, N-t
-butylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N
-o-chlorophenylmaleimide, N-dimethylphenylmaleimide, etc., and among these, N-cyclohexylmaleimide is most preferred. The proportion of copolymerization with methyl methacrylate is 5 to 50% by weight, preferably 10 to 40% by weight. If the N-substituted maleimide compound is less than 5%, no improvement in heat resistance can be expected, which is undesirable.
If it exceeds 50%, the mechanical strength will drop significantly, which is undesirable.

In addition to the above-mentioned methyl methacrylate and N-substituted maleimide compounds, aromatic vinyl compounds copolymerizable with these may be used in the present invention. Examples of the aromatic vinyl compounds include styrene, 〇-methylstyrene, m- Examples include methylstyrene, p-methylstyrene, a-methylstyrene, and the like. By copolymerizing an appropriate amount of these aromatic vinyl compounds in addition to the above monomers, unreacted N-maleimide compounds can be effectively reduced. The copolymerization ratio of the aromatic vinyl compound with the above monomer is 0 to 20% by weight, preferably 1 to 15% by weight. Aromatic vinyl compounds may be used alone or in combination of two or more.

The halogen-containing phosphate esters and their derivatives used in the present invention are halogen-containing phosphate esters and their derivatives that are generally known as flame retardants, such as chlorine-containing phosphate esters, bromine-containing phosphate esters, and their derivatives. Derivatives such as tris (chloroethyl) phosphate, tris (dichloropropyl) phosphate, ethylene (bisthaloloethyl phosphate), bis (chloropropyl) monooctyl phosphate, polyoxyethylene bis (bischloroethyl phosphate), Di(1゜3.2-
Particularly preferred are chlorine-containing phosphoric acid esters such as dioxaphospholine, 5,5-dimethyl-2-oxide-2methyl-dichloromethylmethane, and derivatives thereof. The amount of these added is 8 to 30% by weight, preferably 9 to 25% by weight. When the amount of chlorine-containing phosphate esters and their derivatives added was 8% by weight, no flame retardant effect was observed.
- If it exceeds 30% by weight, it is undesirable because the heat resistance and mechanical strength will drop significantly.
More than one species can be used in combination.

The flame-retardant methacrylic resin composition of the present invention may contain phosphorous esters such as didecylpentaerythritol diphosphite, lubricants, ultraviolet absorbers, heat stabilizers, antioxidants, dyes and pigments, etc., as necessary. The compounding method may be either a method in which the component is dissolved in advance during preparation before polymerization and then polymerized, or a method in which the component is added to pellets after polymerization.

The methacrylic resin used in the present invention, the chlorine-containing phosphate ester and its derivatives, and the additives necessary for the present invention can be mixed by a commonly used method, such as a tumbler, Henschel mixer, The method of mixing with methacrylic resin and extrusion process to obtain pellets is efficient (high productivity), but when manufacturing methacrylic resin, it is dissolved in the monomer mixture and polymerized to achieve the desired flame retardancy. It is also possible to obtain a synthetic methacrylic resin composition.

The flame-retardant methacrylic resin thus obtained has a Bickert softening point of 100-140°C, preferably 100-140°C.
It is desirable that the temperature be in the range of 125°C. This results in 6
Volumetric expansion rate at 0°C - 24 hour hot water immersion is 1.0%
Below, it can be preferably suppressed to 0.8% or less.

(Effect of the invention) Thus, the flame-retardant methacrylic resin obtained above is
By making methacrylic resin into a specific resin composition and using a specific amount of halogen-containing phosphate ester and its derivatives, it can be used in applications where conventional flame-retardant acrylic resins could not be used due to their low heat resistance. and because the final molded product undergoes little dimensional change due to water absorption, it can be used and is useful in a wide range of fields such as light electrical fields and OA equipment.

(Examples) 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 "Part" all represent "% by weight" and "Parts by weight". Evaluation of physical properties and flame retardancy in the Examples was carried out based on the following method.

(1) Intrinsic viscosity (dj!/g) Dissolve methacrylic resin (I) at a constant concentration (g/d1) in chloroform and measure using an automatic viscometer (French
(manufactured by ica).

(2) Bickert softening temperature (VSTi”C) 20x20
A test piece of x3.2 (m) was molded using an injection molding machine and measured according to ASTM D1525.

(3) Tensile strength (kg-f/cj) A dumbbell test piece was molded according to ASTM D638, and the tensile strength was measured.

(4) Evaluation of flame retardancy A test piece measuring 127 x 27 x 3.2 (kaku) was molded using an injection molding machine, and in accordance with UL Standard No. 94, the test piece was hung vertically and a flame of a specified size was lit from the bottom. Immediately remove the flame after 10 seconds, and when the flame on the test piece goes out,
The flame was immediately applied again and the time taken to extinguish the flame was measured.

The evaluation standard is UL standard V-2 standard (SE-II).
), and V-2 class compliant products are flame retardant compliant products.
It was judged to be effective.

(5) Volume expansion coefficient (%) 50X50X3 (kaku) test piece at 95℃ for 24 hours
After drying for an hour, zero weight measurement was performed by immersing it in 60°C hot water for 24 hours to absorb water, and specific gravity was measured by the buoyancy method at 23°C, and the weight and specific gravity before and after immersion were calculated using the following formula.

(W/d)/ (Wo/do) Volumetric expansion coefficient (χ)=□ (We/dO) W,=Dry state weight ii (g) W=NR after water absorption (g) do-Dry state specific gravity (g/ant) d=specific gravity after water absorption (g/c1iY) Example 1 In a 75 L pressure-resistant reaction tank, 250 g of sodium polymethacrylate aqueous solution, 100 g of disodium hydrogen phosphate, and 3 g of monosodium phosphate were added as suspension stabilizers. Dissolved pure water 35
．． 6 kg and 15.12 kg of methyl methacrylate,
N-cyclohexylmaleimide 2.16 kg, styrene 0.72 kg, n-octyl mercaptan 36 g, lauroyl peroxide 54 g 3 Verhexa-C (manufactured by NOF ■) 18 g, stearyl alcohol 36 g, JF-
A monomer solution of 5.4 g of 77 (manufactured by Johoku Kagaku Kogyo ■) was charged, polymerized at 70°C for 2 hours, and after the exothermic peak was heated at 120"C for 1 hour. The resulting bead-shaped copolymer was washed with water. When the intrinsic viscosity was measured after drying, it was found to be 0.64 djl!/gte, and 'VST was 1.
The temperature was 30°C. After mixing 87% of these beads and 13% of tris (dichloropropyl) phosphate in a Henschel mixer, 0.1 part of didecyl pentaerythritol diphosphite (manufactured by Johoku Kagaku Kogyo ■; JPP-10R) was added and heated to 250°C using an extruder. pelletized. The pellets were processed into test pieces for combustion tests, VST measurements, tensile tests, etc. using an injection molding machine (manufactured by Japan Steel Works, Type N-70A) under conditions of a cylinder temperature of 250°C and a mold temperature of 60°C. It was molded and evaluated. The results are shown in Table 1.VST-1
A molded product with a temperature as high as 05°C and little discoloration in appearance was obtained. As a result of conducting a combustion test according to UL standards, it was found to comply with V-2 class.

Also, the volumetric expansion coefficient after immersion in hot water at 60°C for 24 hours is 0.4.
At 3%, it was lower than ordinary flame-retardant acrylic resins and had excellent dimensional stability.

Example 2 Using the same reaction tank as in Example 1, 10.44 kg of methyl methacrylate and 5.4 kg of N-cyclohexylmaleimide were added.
Polymerization was carried out in the same manner as in Example 1, except that the amount of styrene was changed to 2.16 kg, and a bead-shaped copolymer was obtained. The intrinsic viscosity of this bead is 0.726f/
It was g. This copolymer was pelletized by adding a flame retardant and the like in the same amounts and operations as in Example 1.

The obtained pellets were molded under the same conditions as in Example 1, and the test pieces obtained were evaluated.As shown in Table 1, ■5T=119°C, showing good heat resistance and flame retardant performance. Also ■−
It was compatible with 2. Furthermore, the volumetric expansion coefficient when immersed in hot water at 60° C. for 24 hours was 0.35%, which was lower than that of ordinary flame-retardant acrylic resins, and had excellent dimensional stability.

Examples 3 to 7 Test pieces similar to those in Example 1 were obtained by changing the amount of n-octyl mercaptan and carrying out polymerization and addition at the ratios shown in Table 1, and evaluated by the same method.

The results are summarized in Table 1.

Comparative Example 1 In a 75 L pressure-resistant reaction tank, 35 g of pure water was prepared by dissolving 250 g of sodium polymethacrylate aqueous solution, 100 g of disodium hydrogen phosphate, and 3 g of sodium phosphate as suspension stabilizers.
．． 6 kg and 15.12 kg of methyl methacrylate,
2.16 kg of N-cyclohexylmaleimide, 0.72 kg of styrene, 75 g of n-octyl mercaptan, 54 g of lauroyl peroxide, 18 g of Perhex-0 (manufactured by NOF ■), 36 g of stearyl alcohol, JF-
A monomer solution 18 in which 5.4 g of 77 (manufactured by Johoku Kagaku Kogyo ■) was dissolved was charged, polymerized at 70°C for 2 hours, and after the exothermic peak was heated at 120°C for 1 hour. After washing the obtained bead-like copolymer with water and drying, the intrinsic viscosity was measured, and it was found to be 0.25 df/g, and the VST was 130°C. After mixing 87% of these beads and 3% of tris(dichloropropyl) phosphate in a Henschel mixer, 0.1 part of didecylpentaerythritol diphosphite (manufactured by Johoku Kagaku Kogyo ■; JPP-1OR) was added and heated to 250°C using an extruder. pelletized. This pellet was molded using an injection molding machine (manufactured by Japan Steel Works, Model N-70A) for combustion testing under the conditions of a cylinder temperature of 250°C and a mold temperature of 60°C.
Each test piece for measurement and tensile test was molded and evaluated. The results are shown in Table 1. ■ A molded product with a high temperature of 5T = 107°C and little discoloration in appearance was obtained, but as a result of conducting a flame test according to the UL standard, only a flame retardant effect of HB class was obtained. There wasn't.

won.

Comparative Examples 2 to 3 The amount of n-octyl mercaptan was changed and polymerization and addition were carried out at the ratios shown in Table 1 to obtain test pieces similar to those in Example 1, and evaluated by the same method.

The results are summarized in Table 1.

Comparative Examples 4 to 7 27 kg of toluene was charged into a 75 L pressure-resistant reaction tank, and 27 kg of monomers mixed in the proportions shown in Table 1 were charged, stirred to completely dissolve, and further 50 g of n-octyl mercaptan and 18 g of barhexa-C were added.

After charging and completely dissolving 36 g of stearyl alcohol and 4 g of TF-775, polymerization was carried out at 100° C. for 2 hours, and then the solution was poured into excess methanol to precipitate a copolymer, which was filtered and dried.

A flame retardant was added to the obtained copolymer in the ratio shown in Table 1, mixed in a Henschel mixer, 0.1 part of didecyl pentaerythritol diphosphite was added, and the mixture was heated at 250°C.
pelletized. This pellet was injection molded by the same method as Comparative Example 1 and evaluated. The results are shown in Table 1.

The following meeting

Claims (5)

[Claims] (1) A methacrylic resin consisting of a) 30 to 95% by weight of methyl methacrylate, b) 5 to 50% by weight of an N-substituted maleimide compound, and c) 0 to 20% by weight of an aromatic vinyl compound copolymerizable with these. (I) 70 to 92% by weight and halogen-containing phosphate esters and derivatives thereof (II) 8
~30% by weight of a flame-retardant methacrylic resin composition. (2) The resin composition according to claim 1, wherein the N-substituted maleimide compound is N-cyclohexylmaleimide. (3) Halogen-containing phosphate esters and their derivatives (I
2. The resin composition according to claim 1, wherein I) is a chlorine-containing phosphate ester or a derivative thereof. (4) The methacrylic resin according to claim 1 (
The intrinsic viscosity of I) in chloroform at 20°C is 0.
3 to 1.0 dl/g of the resin composition according to claims 1 to 3. (5) Bickert softening temperature (VST) is 100℃~14
The resin composition according to claim 4, which has a temperature of 0°C.