JPH0816185B2 - Light-diffusing methacrylic resin composition having excellent flame retardancy and extruded plate thereof - Google Patents

Description

The present invention relates to a light-diffusing methacrylic resin composition having excellent flame retardancy and an extruded plate thereof, which is used for lighting covers, signboards, indicator lights, video equipment and the like. Regarding

[Conventional technology]

Methacrylic resin has excellent transparency, weather resistance, and mechanical strength, and is widely used today. For example, in the field of applications such as lighting covers and signboards, inorganic or organic fine particles with different refractive index are added. The methacrylic resin, which is originally transparent, is used after being converted into semitransparent or opaque.

However, the methacrylic resin belongs to a relatively flammable class among the resins, and due to its drawbacks, it is rarely used in applications requiring flame retardancy.

In order to impart light diffusibility, a method of blending transparent fine particles having different refractive indexes with a methacrylic resin is known. For example, in JP-A-62-273,230, barium sulfate, barium carbonate, quartz, crystalline silica, as transparent inorganic fine particles,
Amorphous silica, glass, lithium fluoride, calcium fluoride, aluminum hydroxide, and in JP-A-61-159,440, as an organic light diffusing agent, a particle diameter of alkyl methacrylate / aromatic vinyl / alkyl acrylate. 30-300μ of crosslinked polymer is mentioned.

On the other hand, many proposals have been made so far regarding flame retardation of methacrylic resin, as a method of flame retarding methacrylic resin without significantly impairing the original characteristics of methacrylic resin such as weather resistance, transparency and mechanical strength. The most proposed technology is to blend an organic compound containing a halogen element and a phosphorus element in the molecule. For example, Japanese Examined Sho 56-2
In JP 6,264, a composition comprising a polymer containing methyl methacrylate as a main component, a halogen-containing polyphosphonic acid ester, an orthophosphoric acid triester, and a halogen-containing phosphorous acid triester is also disclosed in JP-A-59-206,454. The publication discloses a composition comprising a methacrylic resin, a halogen-containing polyphosphonate, and a halogen-containing polyphosphate, and JP-A No. 61-115,950 discloses a composition comprising a methacrylic resin, a chlorine-containing phosphate ester, and tetrabromobisphenol A. The thing is disclosed.

[Problems to be Solved by the Invention]

Organic compounds containing a halogen element and a phosphorus element in these molecules have good compatibility with methacrylic resin,
A relatively transparent composition is easily obtained, and it is possible to make methacrylic resin flame-retardant. However, it is remarkably flame-retardant when fine particles, especially inorganic fine particles, are added as a light diffusing agent to impart light diffusivity. Has a problem that it is reduced.
Although it is possible to make the methacrylic resin containing fine particles flame-retardant by increasing the addition amount of the flame retardant, the heat resistance, weather resistance, and mechanical strength of the resulting composition are greatly reduced, which is unacceptable. It was Under such circumstances, there has been a strong demand for a technique for imparting a light diffusivity to a methacrylic resin, which has little or less decrease in flame retardancy.

As a result of diligent studies on the technology for imparting flame retardancy and light diffusibility to a methacrylic resin, the present inventor has found that it is more difficult than a composition containing no antimony trioxide by adding a phosphorus-based flame retardant and antimony trioxide to a methacrylic resin. The inventors have found that light diffusivity can be imparted without lowering the flammability and have completed the present invention.

[Means for solving the problem]

That is, the present invention is a methacrylic resin, phosphorus-based flame retardant,
And a light-diffusing methacrylic resin composition having excellent flame retardancy composed of antimony trioxide and an extruded plate thereof.

Examples of phosphorus-based flame retardants include triaryl phosphates, diaryl phosphates, monoaryl phosphates, arylphosphonic acid compounds, arylphosphine oxide compounds, condensed aryl phosphates, halogenated alkyl phosphates, halogen-containing condensed phosphorus. Examples thereof include acid esters, halogen-containing condensed phosphonates, halogen-containing phosphite esters, and the like, or a mixture of two or more kinds. As a concrete example,
Triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (chloroethyl) phosphate, tris (dichloropropyl) phosphate, tris (tribromoneopentyl) And compounds represented by the following structural formulas.

The addition amount of the phosphorus-based flame retardant is preferably in the range of 1 to 25 parts by weight with respect to 100 parts by weight of the methacrylic resin, and when less than 1 part by weight, the flame retardancy of the composition is low, and vice versa If it exceeds, the heat resistance, weather resistance and mechanical strength will be significantly reduced.

Antimony trioxide is known as a flame retardant aid used together with a halogen-based flame retardant in flame retarding polyethylene or polypropylene, or a flame retardant for polyvinyl chloride. Antimony trioxide is generally said to exert a phase-retaining effect when used in combination with a halogen-based flame retardant, and its mechanism of action is such as dehydration carbonization of antimony oxyhalide produced by combustion and free radical trapping effect of antimony halide. A way of thinking has been reported (Hitoshi Nishizawa, "Polymer Flame Retardancy", published by Taisei Co., page 152).

The main function of antimony trioxide in the present invention is a light diffusion effect, and is characterized in that excellent light diffusion performance can be imparted without impairing the flame retardant effect originally possessed by the flame retardant. The particle size and amount of antimony trioxide can be selected according to the desired light diffusion performance.
0.1-5 μm, and the addition amount is preferably in the range of 0.1-5 parts by weight with respect to 100 parts by weight of methacrylic resin. If the particle size is smaller than 0.1 μm, it easily aggregates, making it difficult to uniformly disperse antimony trioxide in the methacrylic resin.
On the other hand, when it exceeds 5 μm, the light scattering effect is reduced, and it is difficult to obtain the desired light diffusion performance. Further, if the addition amount is less than 0.1 parts by weight, the light scattering performance is low, and conversely, if it is more than 5 parts by weight, the light transmittance is greatly reduced, and it is difficult to obtain a satisfactory light diffusion performance.

The methacrylic resin in the present invention includes i) a resin containing 80 to 99% by weight of a methyl methacrylate unit and 1 to 70% by weight of an alkyl acrylate unit having an alkyl group having 1 to 4 carbon atoms, and ii) a methyl methacrylate unit 30. -99% by weight and aromatic vinyl unit 1-70% by weight, iii) Methyl methacrylate unit 30-98% by weight, 6-membered cyclic anhydride unit 1-30 represented by the following structural formula [I] weight%,
Aromatic vinyl unit 0 to 50% by weight, methacrylic acid unit 1 to
Resins consisting of 10% by weight, alone or as a mixture of two or more resins.

The resin composed of a methyl methacrylate unit and an alkyl acrylate unit described in i) has excellent weather resistance and transparency, and is a known radical polymerization method, that is, a suspension polymerization method, a solution polymerization method, or a bulk polymerization method. It can be manufactured by
When the ratio of the methyl methacrylate unit is less than 80% by weight, the heat distortion resistance of the composition is largely lowered, and conversely, when it exceeds 99% by weight, thermal decomposition tends to occur, which is not preferable. A preferable range of the molecular weight is 50,000 to 500,000 in terms of weight average molecular weight, and a particularly preferable range is 100,000 to 300,000.

The resin composed of the methyl methacrylate unit and the aromatic vinyl unit described in ii) has a lower hygroscopicity than the other two types of resins and has a good moldability. Examples of aromatic vinyls include water lily, α-methylsulylene, vinyltoluene and the like. It can be produced by a known radical polymerization method, that is, a suspension polymerization method, a solution polymerization method, a bulk polymerization method, or the like. If the proportion of methyl methacrylate units is less than 30% by weight, the weather resistance of the composition is poor, and conversely, if it exceeds 99% by weight, thermal decomposition tends to occur, neither of which meets the purpose of the present invention. The preferred range of the molecular weight is 10 in terms of weight average molecular weight.
10,000 to 500,000.

iii) methyl methacrylate unit, structural formula [I]
A resin composed of a 6-membered cyclic acid anhydride unit, an aromatic vinyl unit, and a methacrylic acid unit is most excellent in heat distortion resistance,
Considering that the phosphorus-based flame retardant reduces the heat distortion temperature by plasticizing the composition at the same time as making it flame retardant, it is most effective in obtaining a light diffusible flame retardant methacrylic resin composition having excellent heat distortion resistance. Is. Here, styrene and α-methylstyrene are preferably used alone or in combination as the aromatic vinyl. The resin can be produced by the method described in JP-A-58-217,501, but the method is not limited to this method. When the ratio of the methyl methacrylate unit is less than 30% by weight, the weather resistance of the composition is poor,
On the contrary, if it exceeds 99% by weight, thermal decomposition tends to occur. Further, when the 6-membered cyclic anhydride unit represented by the structural formula [I] exceeds 30% by weight, the hygroscopicity is large, and conversely, when it is less than 1% by weight, the effect of improving heat distortion resistance cannot be recognized. Methacrylic acid unit
If it exceeds 10% by weight, the mechanical strength of the composition is greatly reduced, which is not preferable. The preferred range of the molecular weight is 50,000 to 400,000 in terms of weight average molecular weight.

The resin composition of the present invention can be put to practical use by injection molding pellets or processing an extruded plate produced by extrusion molding by a method such as vacuum molding.

As a method for producing pellets, a method in which a methacrylic resin, a phosphorus-based flame retardant, and antimony trioxide are sufficiently stirred and mixed by a tumbler, a Henschel mixer or the like, and then melt-kneaded by an extruder is generally used.

Further, as a method for producing an extruded plate, a methacrylic resin, a phosphorus-based flame retardant, a tumbler of antimony trioxide,
After thoroughly stirring and mixing with a Henschel mixer, etc., directly extruding into a plate shape with an extruder equipped with a T-die, and then continuously forming an extruded plate with a desired plate thickness, width, and surface condition by rolls, or once into pellets. After that, there is a method of forming an extruded plate by the same method.

The extruded plate of the present invention is a single-layer extruded plate composed of the resin composition of the present invention, and a methacrylic resin film having a thickness of 10 to 500 μm prepared from the resin composition of the present invention on one side. , Or laminated board obtained by laminating on both sides,
And a laminate having a layer of a methacrylic resin having a thickness of 1 to 100 μm on one side or both sides of a layer of the resin composition of the present invention produced by a coextrusion method.

The resin composition of the present invention is a known antioxidant, an ultraviolet absorber, if necessary within a range not departing from the object of the present invention,
Release agents, lubricants, antistatic agents, optical brighteners, bluing agents, dyes and pigments, etc. can be included.

INDUSTRIAL APPLICABILITY The resin composition of the present invention and the extruded plate thereof are effective for applications such as lighting covers, signboards, indicator lamps and video equipment due to their excellent light diffusivity, flame retardancy, good weather resistance and mechanical strength.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The invention is in no way limited by these examples.

Example 1 A polymer mixture obtained by suspension-polymerizing a monomer mixture of methyl methacrylate / methyl acrylate / lauroyl peroxide / n-octyl mercaptan = 95/5 / 0.2 / 0.2 (weight ratio) was obtained. After thoroughly washing with water, it was dried to obtain a methacrylic resin (A). The weight average molecular weight of the obtained methacrylic resin was 150,000 as measured by bull permeation chromatography.

Next, Mitsui Miike Kakoki Co., Ltd. Henschel mixer (FM10
Methacrylic resin (A) and tris (tribromoneopentyl) phosphate by B type), antimony trioxide having an average particle size of 1.5 μm, and 2- (5
-Methyl-2-hydrooxyphenyl) benzotriazole was stirred and mixed in the ratios in Table 1 for 10 minutes. This mixture was melt-mixed with a twin-screw extruder (AS30 shoulder) manufactured by Nakata Machine Co., Ltd. to prepare milky white pellets. Further, the obtained pellets were extruded by a twin-screw extruder equipped with a T die and cooled by a metal roll to produce an extruded plate having a width of 20 cm and a thickness of 2 mm.

A test piece with a length of 125 mm and a width of 12.5 mm is cut out from the plate manufactured in this way, and the flame resistance of the test piece is measured according to the test method C specified in JIL5502 (flame resistance of synthetic resin components such as outer shells, parts, and materials). The sex was measured. Similarly, length 50 mm, width 50
A mm test piece was cut out, and the total light transmittance and haze of the test piece were measured according to the test method specified in JIS K7105 (Plastic optical property test method). The results are shown in Table 1.

[Comparative Example 1] In the same manner as in Example 1, the methacrylic resin (A), tris (ribromonepentyl) phosphate, and 2- (5) were used.
-Methyl-2-hydroxyphenyl) benzotriazole was stirred and mixed at a ratio shown in Table 1 to prepare transparent pellets, and then an extruded plate having a width of 20 cm and a thickness of 2 mm was manufactured. A predetermined test piece was prepared, and the flame resistance, total light transmittance, and haze were measured. The results are shown in Table 1.

[Comparative Examples 2.3] Methacrylic resin (A), tris (tribromoneopentyl) phosphate, average particle size 3 as in Example 1.
After stirring and mixing barium sulfate (μm) and 2- (5-methyl-2-hydroxyphenyl) benzotriazole at a ratio shown in Table 1, a milky white pellet was prepared, and then the width was 20 cm and the thickness was 20 cm.
A 2 mm extruded plate was produced. A predetermined test piece was prepared, and the flame resistance, total light transmittance, and haze were measured. The results are shown in Table 1.

[Example 2] Antimony trioxide having different particle sizes (average particle size: 0.5 μ)
m, 3 μm) in the proportions shown in Table 2 in the same manner as in Example 1 to produce a milky white extruded plate, and the flame resistance, total light transmittance, and haze were measured. Table 2 shows the results.

[Comparative Example 4] In the same manner as in Example 1, the methacrylic resin (A), antimony trioxide having an average particle size of 0.5 µm, and 2- (5-methyl-2-hydroxyphenyl) benzotriazole were used in the ratios shown in Table 2. A milky white extruded plate was produced and its flame resistance, total light transmittance, and haze were measured. Table 2 shows the results.

[Example 3] 100 parts by weight of a copolymer having a composition of methyl methacrylate / styrene = 65/35 (weight ratio) and having a weight average molecular weight of 180,000 as measured by bull permeation chromatography, and the following structure 15 parts by weight of the compound [II] having the formula, 1 part by weight of antimony trioxide having an average particle size of 1.5 μm, and 2
Extruded plates were prepared from 0.05 parts by weight of-(5-methyl-2-hydroxyphenyl) benzotriazole.

When a predetermined test piece was cut out from the manufactured extruded plate and evaluated for flame resistance and optical properties, the burning rate was 33 mm / min and passed the "flame-retardant material", and the total light transmittance was 42% and the haze was It was 94%.

Example 4 72.9 parts by weight of methyl methacrylate, α-methylstyrene
13.5 parts by weight, methacrylic acid 3.6 parts by weight, ethylbenzene 1
0.0 parts by weight, 1,1-ditertiarybutylbutyloxy-3,
Prepare a mixed solution consisting of 0.025 parts by weight of 3,5-trimethylcyclohexane and 0.05 parts by weight of n-octyl mercaptan,
This mixed solution was continuously fed at a rate of 0.5 / min to a jacketed complete mixing reactor having an inner volume of 2 to carry out polymerization at a temperature of 125 ° C. Further, the polymerization liquid was set at 260 ° C. and continuously supplied to a high-temperature devolatilization apparatus to remove unreacted substances and generate a six-membered ring acid anhydride to obtain a copolymer (B). The results of compositional analysis of the copolymer (B) by neutralization titration, an infrared spectrophotometer and a nuclear magnetic resonance analyzer were as follows: methyl methacrylate unit 85% by weight, α-methylstyrene unit 8% by weight, six-membered ring anhydrous 5% by weight of the physical unit and 3% by weight of the methacrylic acid unit. The weight average molecular weight measured by gel permeation chromatography was 120,000.

In the same manner as in Example 1, the copolymer (B), phenylphosphonic acid, antimony trioxide having an average particle size of 0.5 μm, and 2- (5-methyl-2-hydroxyphenyl) benzotriazole were mixed at a ratio of Table 3 to give a milky white color. Manufactures extruded plates of
The flame resistance was measured. The results are shown in Table 3.

[Comparative Example 5] A copolymer (B) having an average particle size of 0.5 was prepared in the same manner as in Example 1.
μm antimony trioxide, and 2- (5-methyl-2)
A milky white extruded plate was produced from -hydroxyphenyl) benzotriazole in the ratio shown in Table 3 and the flame resistance was measured. The results are shown in Table 3.

[Example 5] Copolymer (B), tris (tribromoneopentyl) phosphate, phenylphosphonic acid,
Antimony trioxide having an average particle size of 1.5 μm, and 2- (5
-Methyl-2-hydroxyphenyl) benzotriazole was melt-mixed in the ratio shown in Table 4 to prepare pellets. Length by injection molding machine (IS 75S type) manufactured by Toshiba Machine Co., Ltd.
A test piece having a size of 127 mm, a width of 13 mm and a thickness of 3 mm was prepared, and the flame resistance was measured according to the test method D specified in Appendix 7 of JIL5502, and at the same time, the heat distortion temperature was measured according to ASTM D648. Further, the total light transmittance and haze were measured by the same method as in Example 1. The results are shown in Table 4.

[Effects of the Invention] The methacrylic resin composition and the extruded plate of the present invention have excellent flame retardancy and light diffusivity, and also have good weather resistance and mechanical strength, which are the original characteristics of the methacrylic resin.

Claims (1)

[Claims] 1. A methacrylic resin, a phosphorus-based flame retardant, and antimony trioxide having a particle size of 0.1 to 5 μm, which are mixed in advance and melt-kneaded by using an extruder to obtain a total light transmittance having excellent flame retardancy. Light-diffusing methacrylic resin extruded plate with 30 to 59%