JP2002370274A - Method for manufacturing methyl methacrylate resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a methyl methacrylate resin molding having an excellent appearance and a desired ultraviolet absorbing power. SOLUTION: A method for manufacturing the methyl methacrylate resin molding comprises the steps of supplying a methyl methacrylate resin composition containing an ultraviolet absorber having a molecular weight of 200 to 400 to an extruder having a vent part, and melt molding the composition under the condition of a vent part pressure of 0.1 to 50 KPa. As the methyl methacrylate resin composition, a composition obtained by mixing a monomer containing 50 wt.% or more of methyl methacrylate or its partial polymer syrup with the absorber having the molecular weight of 200 to 400, and polymerizing the resultant mixture is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a methyl methacrylate-based resin molded product containing an ultraviolet absorbent using an extruder.

[0002]

2. Description of the Related Art Heretofore, as one of methods for improving the durability of a methyl methacrylate resin, a method of blending an ultraviolet absorber has been known. For example, in JETI, Vol. 46, No. 5, (issued in 1998), pp. 116-121, a salicylate-based, cyanoacrylate-based, or benzotriazole-based compound is used as an ultraviolet absorber for a methyl methacrylate-based resin. It is described.

[0003]

SUMMARY OF THE INVENTION The inventor of the present invention has reduced the weight of an ultraviolet absorber when producing a methyl methacrylate resin molded article containing an ultraviolet absorber by melt molding using an extruder. From the viewpoint of improving the transparency of the molded body, a UV absorber having a relatively low molecular weight is used, and from the viewpoint of suppressing the generation of bubbles and improving the appearance of the molded body, an extruder having a vent portion is used. Using, the devolatilization extrusion was studied by reducing the pressure in the vent part. As a result, according to a conventional method, a methyl methacrylate-based resin and an ultraviolet absorbent are separately supplied, or a methyl methacrylate-based resin and an ultraviolet absorber are dry-blended with a tumbler, a Henschel mixer, or the like, supplied into an extruder, and melt-kneaded. , The UV absorber volatilizes from the cylinder to the vent, causing loss of the UV absorber,
It has been found that the volatilized ultraviolet absorber stays in the vent portion and flows back to the cylinder after thermal decomposition, which may cause a problem of appearance failure such as coloring of the molded product.

[0004]

As a result of further study, the present inventor prepared a methyl methacrylate-based resin composition containing an ultraviolet absorbent in advance, and supplied this to an extruder. The present invention has been found to be able to produce a methyl methacrylate-based resin molded article having a relatively low molecular weight ultraviolet absorber, which suppresses volatilization loss during devolatilization extrusion, has excellent appearance, and has a desired ultraviolet absorption ability. Was completed.

[0005] That is, the present invention relates to a method for producing a polymer having a molecular weight of 200 to 40.
A methyl methacrylate-based resin composition containing an ultraviolet absorber of 0 is supplied to an extruder having a vent portion and melt-molded under a condition of a vent portion pressure of 0.1 to 50 KPa. The present invention relates to a method for manufacturing a resin molded body.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, the methyl methacrylate-based resin is a polymer containing 50% by weight or more of methyl methacrylate as a monomer constituting the resin, and is a polymethacrylic acid which is a substantially homopolymer of methyl methacrylate. Examples of the copolymer include methyl and methyl methacrylate of 50% by weight or more and copolymerizable unsaturated monomers of 50% by weight or less.

The unsaturated monomers copolymerizable with methyl methacrylate include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, methacrylic acid 2
-Methacrylates such as ethylhexyl, 2-hydroxyethyl methacrylate; methyl acrylate,
Acrylic esters such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate; unsaturated esters such as methacrylic acid and acrylic acid Acids; styrene, α
-Methylstyrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like, and if necessary, two or more of them can be used. Further, the copolymer may have a glutaric anhydride unit or a glutarimide unit.

In the present invention, the molecular weight (hereinafter, sometimes referred to as “Mw”) of the ultraviolet absorber to be added to the methyl methacrylate resin is 200 to 40.
0, preferably 200-350. If the molecular weight of the ultraviolet absorber is less than 200, it may be difficult to suppress the volatilization loss of the ultraviolet absorber during devolatilization extrusion, and if the molecular weight of the ultraviolet absorber exceeds 400, the weight per weight , The ultraviolet absorbing capacity of the molded article becomes small, the weight of the ultraviolet absorbent used increases, and the transparency of the molded article may be reduced.

As the ultraviolet absorber, 250 to 320 n
Those having a maximum absorption wavelength in the range of m are preferable, and those having a maximum absorption wavelength in the range of 250 to 800 nm (hereinafter sometimes referred to as “λmax”) suppress the coloring of the molded article. From the viewpoint of improving the transparency. Also, the molar extinction coefficient at the maximum absorption wavelength (hereinafter sometimes referred to as “εmax”) is 100.
Those having a molar mass of at least 00 mol ^-1 cm ^-1 , especially at least 15,000 mol ^-1 cm ^-1 are preferred from the viewpoint of reducing the weight used.

Examples of the type of the ultraviolet absorber include a benzophenone ultraviolet absorber, a cyanoacrylate ultraviolet absorber, a benzotriazole ultraviolet absorber, a malonic ester ultraviolet absorber, and an oxalanilide ultraviolet absorber. And two or more of them can be used as needed. Above all, a malonic ester ultraviolet absorber and an oxalanilide ultraviolet absorber are preferable.

As the benzophenone ultraviolet absorber,
For example, 2,4-dihydroxybenzophenone (Mw:
214, λmax: 288 nm, εmax: 14100 mol ^-1 c
m ^-1 ), 2-hydroxy-4-methoxybenzophenone (Mw: 228, λmax: 289 nm, εmax: 1470)
0 mol ^-1 cm ^-1 ), 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (Mw: 308, λmax: 2)
92 nm, εmax: 12,500 mol ^-1 cm ^-1 ), 2-hydroxy-4-octyloxybenzophenone (Mw: 32)
6, λmax: 291 nm, εmax: 15,300 mol ^-1 c
m ^-1 ), 4-dodecyloxy-2-hydroxybenzophenone (Mw: 383, λmax: 290 nm, εmax: 16
200 mol ^-1 cm ^-1 ), 4-benzyloxy-2-hydroxybenzophenone (Mw: 304, λmax: 289 n)
m, εmax: 15900 mol ⁻¹ cm ⁻¹ ), 2,2′-dihydroxy-4,4′-dimethoxybenzophenone (Mw:
274, λmax: 289 nm, εmax: 11,800 mol ^-1 c
m- ¹ ) and the like.

As the cyanoacrylate-based ultraviolet absorber, for example, ethyl 2-cyano-3,3-diphenylacrylate (Mw: 277, λmax: 305 nm, εm
ax: 15600 mol ^-1 cm ^-1 ), 2-ethylhexyl 2
-Cyano-3,3-diphenyl acrylate (Mw: 3
62, λmax: 307 nm, εmax: 14,400 mol ^-1 cm
^-1 ) and the like.

Examples of the benzotriazole ultraviolet absorber include 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole (Mw: 225, λma
x: 300 nm, εmax: 13,800 mol ^-1 cm ^-1 ), 5-
Chloro-2- (3,5-di-t-butyl-2-hydroxyphenyl) -2H-benzotriazole (Mw: 35
8, λmax: 312 nm, εmax: 14,600 mol ^-1 c
m ^-1 ), 2- (3-t-butyl-2-hydroxy-5-
Methylphenyl) -5-chloro-2H-benzotriazole (Mw: 316, λmax: 354 nm, εmax: 14
300 mol ^-1 cm ^-1 ), 2- (3,5-di-t-pentyl-2-hydroxyphenyl) -2H-benzotriazole (Mw: 352, λmax: 305 nm, εmax: 152)
^{00mol -1 cm - 1), 2-} (3,5- di -t- butyl -2
-Hydroxyphenyl) -2H-benzotriazole (Mw: 323, λmax: 303 nm, εmax: 1560)
0 mol ^-1 cm ^-1 ), 2- (2H-benzotriazole-2)
-Yl) -4-methyl-6- (3,4,5,6-tetrahydrophthalimidylmethyl) phenol (Mw: 38
8, λmax: 304 nm, εmax: 14100 mol ^-1 c
m ^-1 ), 2- (2-hydroxy-5-t-octylphenyl) -2H-benzotriazole (Mw: 323, λ
max: 301 nm, εmax: 14,700 mol ^-1 cm ^-1 ).

As the malonic ester type ultraviolet absorber, 2- (1-arylalkylidene) malonic esters are usually used, and among them, the following general formula (1)

Embedded image (In the formula, X represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and R ¹ and R ² each independently represent an alkyl group having 1 to 6 carbon atoms. )
Are preferred. In addition, each substituent is selected such that the molecular weight of the compound represented by the general formula (1) is 400 or less.

In the general formula (1), the alkyl group represented by X and the alkyl group in the alkoxy group represented by X may be linear or branched, respectively.
For example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group and the like can be mentioned. X is preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and the substitution position of X is preferably para-position.

In the general formula (1), the alkyl groups represented by R ¹ and R ² may be linear or branched, for example, methyl, ethyl, n -Propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group and the like. R ¹
And R ² are each preferably an alkyl group having 1 to 4 carbon atoms.

Among the compounds represented by the general formula (1), dimethyl 2- (paramethoxybenzylidene) malonate (Mw: 250, λmax: 308 nm, εma
x: 24200 mol ^-1 cm ^-1 ) is preferred.

As the oxalanilide type ultraviolet absorber, 2-alkoxy-2'-alkyloxalanilides are usually used, and among them, the following general formula (2)

Embedded image (Wherein, R ³ and R ⁴ are each independently a carbon number of 1 to 6)
Represents an alkyl group. Are preferred.
In addition, each substituent is selected so that the molecular weight of the compound represented by the general formula (2) is 400 or less.

In the general formula (2), the alkyl groups represented by R ³ and R ⁴ may be linear or branched, for example, methyl, ethyl, n-propyl Group, i-propyl group, n-butyl group, i-butyl group, s
-Butyl group, t-butyl group and the like. R ³ and R ⁴ are each preferably an alkyl group having 1 to 4 carbon atoms, and the substitution positions of R ³ and R ⁴ O are preferably ortho positions.

Among the compounds represented by the general formula (2), 2-ethoxy-2'-ethyloxalanilide (Mw: 312, λmax: 298 nm, εmax: 16)
700 mol ^-1 cm ^-1 ) is preferred.

From the viewpoint of durability, the amount of the UV absorber used is 100 parts by weight of the methyl methacrylate resin.
0.0005 parts by weight or more, preferably 0.003 parts by weight or more, more preferably 0.005 parts by weight or more,
Further, from the viewpoint of transparency, the amount is 0.1 part by weight or less, preferably 0.05 part by weight or less, more preferably 0.03 part by weight or less.

In the present invention, the production of the methyl methacrylate-based resin molded article containing the above-mentioned ultraviolet absorber is performed by melt molding using an extruder having a vent portion. The prepared methyl methacrylate-based resin composition containing an ultraviolet absorber is supplied. Here, the methyl methacrylate-based resin composition containing an ultraviolet absorber is one in which the ultraviolet absorber is uniformly dispersed or dissolved in the methyl methacrylate-based resin,
As described above, by using the methyl methacrylate-based resin composition as a feed material to an extruder, the volatilization loss of the ultraviolet absorber can be suppressed even if the molecular weight of the ultraviolet absorber is relatively small. .

As a method for preparing the above-mentioned methyl methacrylate-based resin composition, methyl methacrylate is used in an amount of 50% by weight.
It is preferable to polymerize the monomer or the partially polymer syrup containing the above with a UV absorber. Examples of the polymerization method include suspension polymerization, solution polymerization, bulk polymerization, and the like. Among them, bulk polymerization is preferable, and continuous bulk polymerization is particularly preferable. The continuous bulk polymerization is described in, for example,
The method can be performed by the method described in JP-A-111408 or JP-A-7-126308. As another preparation method, for example, a method in which a methyl methacrylate-based resin prepared according to a conventional method is melt-mixed with an ultraviolet absorbent in a stirring tank and the like can be mentioned. Further, a methyl methacrylate-based resin composition having a relatively high ultraviolet absorber content may be prepared as a so-called master batch by these methods, and this may be mixed and diluted with the methyl methacrylate-based resin. Examples of the shape of the obtained methyl methacrylate-based resin composition include beads, pellets, and the like.

The above-mentioned methyl methacrylate resin composition may contain various additives as required. Examples of the additive include hindered amines (HALS) such as a compound having a 2,2,6,6-tetraalkylpiperidine skeleton, siloxane-based crosslinked resin particles, styrene-based crosslinked resin particles, acryl-based crosslinked resin particles, Light diffusing agents and matting agents such as glass particles, talc, calcium carbonate, barium sulfate; antistatic agents such as sodium alkyl sulfonate, sodium alkyl sulfate, monoglyceride stearate, and polyetheresteramide; hindered phenols Antioxidants such as;
Flame retardants such as phosphoric esters; lubricants such as palmitic acid and stearyl alcohol; and the like, and if necessary, two or more of them can be used.

The above methyl methacrylate resin composition is
When melt-molding using an extruder having a vent, the pressure of the vent is 0.1 to 50 KPa, preferably 0.1 to 50 KPa.
If it is out of this range, the appearance of the obtained molded article may be deteriorated. The temperature during melt molding is usually 180 to 300 ° C, preferably 210 to 300 ° C.
280 ° C.

Examples of melt molding using an extruder according to the method of the present invention include granulation in which beads and the like are supplied to an extruder and pellets are produced through a strand die and a strand cutter; beads and pellets; To the extruder,
Extrusion molding to produce sheets and films via T-die and roll unit; Beads and pellets, etc. are supplied to an extruder and irregular extrusion molding to produce complex molded products via sizing dies; Beads, pellets, etc. Is supplied to an extruder, and is injected into a mold to be cooled and solidified to produce various molded products, such as injection molding. Among them, extrusion molding and injection molding are preferred.

Examples of uses of the molded article include, for example, a light guide plate, a lens film, a lens sheet and a light diffusion plate in extrusion molding; a pipe in irregular extrusion molding; miscellaneous goods, optical parts, and a lamp cover in injection molding. And the like.

[0028]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. The following were used as the ultraviolet absorber. (A): dimethyl 2- (paramethoxybenzylidene) malonate [a compound of the formula (1), wherein X is a methoxy group, the substitution position thereof is para, and R ¹ and R ² are methyl groups,
Clariant, product name: Sanduvor P
R-25, Mw: 250, λmax: 308 nm, εmax:
24200 mol ^-1 cm ^-1 ]. (B): 2- (2-hydroxy-5-methylphenyl)
-2H-benzotriazole [manufactured by Sumitomo Chemical Co., Ltd.
Product name: Sumisorb 200, Mw: 225, λmax: 3
00 nm, εmax: 13,800 mol ^-1 cm ^-1 ]. (C): 1,4-bis (4-benzoyl-3-hydroxyphenoxy) -butane [Cipro Kasei Co., Ltd., trade name: Seesorb 151, Mw: 483, λmax: 290]
nm, εmax: 28500 mol ^-1 cm ^-1 ].

The structure of the extruder used for producing the sheet is as follows. Extruder: Screw diameter 40 mm, uniaxial, with vent (manufactured by Tanabe Plastics Co., Ltd.). Die: T die, lip width 250mm, lip interval 6m
m. Roll: 3 polishing rolls, vertical type.

The concentration of the ultraviolet absorber in the pellet or sheet is determined by dissolving a predetermined amount of the pellet or sheet fragment in chloroform, and using a spectrophotometer [U4, manufactured by Hitachi, Ltd.]
000 with an integrating sphere], the absorbance of the ultraviolet absorbent at the maximum absorption wavelength was measured and quantified by a calibration curve. The calibration curve was prepared by dissolving a predetermined amount of an ultraviolet absorbent in chloroform and measuring the absorbance at the maximum absorption wavelength of the ultraviolet absorbent using the same spectrophotometer as described above.

For the transmittance of the sheet, the transmittance at the maximum absorption wavelength of the ultraviolet absorbent in the thickness direction was measured using a spectrophotometer [U4000, manufactured by Hitachi, Ltd., with an integrating sphere]. did.

Examples 1-3 According to the method of Example 4 of JP-A-7-126308, methyl methacrylate / methyl acrylate = 94 /
6 (weight ratio) of the monomer mixture was mixed with the types and amounts of ultraviolet absorbers shown in Table 1 and subjected to bulk polymerization in a continuous manner to prepare pellets of the methyl methacrylate resin composition.
Table 1 shows the concentration of the ultraviolet absorbent in the pellet as an initial concentration.

The obtained pellets were melt-extruded using an extruder at a resin temperature of 265 ° C. and a vent pressure of 8 KPa to produce a sheet having a thickness of 3.5 mm and a width of 20 cm. The appearance of the sheet was good. Table 1 shows the ultraviolet absorber concentration in the sheet and its residual ratio (based on the initial concentration) and the transmittance of the sheet.

Comparative Examples 1 to 4 100 parts by weight of pellets of a methyl methacrylate resin [copolymer of methyl methacrylate / methyl acrylate = 94/6 (weight ratio)] were mixed with ultraviolet rays of the types and amounts shown in Table 1. Dry blended in absorbent and plastic bag. Table 1 shows the UV absorber concentration in the mixture as an initial concentration.

The resulting mixture was melt-extruded using an extruder at a resin temperature of 265 ° C. and a vent pressure of 8 KPa to produce a sheet having a thickness of 3.5 mm and a width of 20 cm. The appearance of the sheet was good. Table 1 shows the ultraviolet absorber concentration in the sheet and its residual ratio (based on the initial concentration) and the transmittance of the sheet.

[0036]

[Table 1]

Comparative Example 5 The same operation as in Example 1 was performed except that the vent pressure was set to 80 KPa. The appearance of the resulting sheet was very poor.

[0038]

According to the present invention, an ultraviolet absorbent-containing methyl methacrylate-based resin molded article having a good appearance can be produced by a method in which the volatilization loss of the ultraviolet absorbent is suppressed.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08L 33/12 C08L 33/12 // B29K 33:04 B29K 33:04 105: 16 105: 16 105: 16 F term (reference) 4F071 AA33 AC07 AC10 AC19 AE05 AF34 AH19 BA01 BB05 BB06 BC01 BC05 4F207 AA21A AB14 AR02 KA01 KA17 KL41 KM04 KM05 KM14 KM15 4J002 BG061 EE036 EH086 EP026 ET006 EU176 FD056 GP00 4J0100 PAABA00

Claims (2)

[Claims] 1. A methyl methacrylate resin composition containing an ultraviolet absorbent having a molecular weight of 200 to 400 is supplied to an extruder having a vent portion, and the vent portion pressure is 0.1 to 50 KP.
A method for producing a methyl methacrylate-based resin molded product, which is subjected to melt molding under the condition of a. 2. A method in which a methyl methacrylate resin composition is prepared by mixing a monomer containing 50% by weight or more of methyl methacrylate or a partially polymer syrup thereof with an ultraviolet absorber having a molecular weight of 200 to 400 and polymerizing the mixture. The production method according to claim 1, which is obtained by the following method.