JP3575098B2 - Manufacturing method of molded products - Google Patents

Description

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【表２】

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【表３】

[0001]
[Industrial applications]
The present invention relates to a method for diffusing and transmitting incident light and manufacturing a molded product by stretching and molding a light-diffusing methacrylic resin plate having a uniform matte surface.
[0002]
[Prior art]
Conventionally, as a light diffusing resin plate, a plate-like material in which an organic or inorganic light diffusing agent is dispersed in a transparent resin such as an acrylic resin, a styrene resin, a polycarbonate, and a vinyl chloride resin has been used. I have.
Recently, not only the performance of diffuse transmission of light but also the performance of diffuse reflection of light, that is, so-called matting, has been emphasized from the viewpoint of high-grade feeling and anti-reflection, and various proposals have been made for a plate having such properties.
For example, JP-A-58-29622 discloses that, based on 100 parts of a methyl methacrylate polymer, 1.0 to 5.0 parts of talc fine powder and 0.1 to 1.0 part of barium sulfate fine powder are blended. An acrylic resin plate having a matte surface formed by kneading and extruding and having an excellent antiglare effect is disclosed.
JP-A-61-78859 discloses an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms, an aromatic vinyl monomer, and an alkyl group having 1 to 8 carbon atoms, based on 100 parts by weight of a methyl methacrylate polymer. A non-crosslinkable monomer composed of an alkyl acrylate, a crosslinked polymer having a particle diameter of 30 to 300 μm obtained by polymerizing 0.3 to 3% by weight of a crosslinkable monomer, 1 to 20 parts by weight, and fine particles of an inorganic compound of 0.1 to A light-scattering acrylic resin composition obtained by blending 5 parts by weight is disclosed.
Conventionally, as a use of the light diffusing resin plate, a transmission type display, a lighting plate, a lighting cover, and the like have been mentioned. However, in these uses, the plate is further heated and subjected to secondary molding. is there.
Examples of the secondary molding method include free blow molding, free vacuum molding, push-up molding, ridge molding, straight molding, drape molding, reverse draw molding, air slip molding, plug assist molding, and plug assist reverse draw molding. And the like.
These molding methods involve stretching of the material, but recently, due to the complexity of the shape of the molded product such as a lighting cover and the improvement of molding technology, high stretching such that the stretching ratio partially exceeds 50%. Molding has begun to take place.
[0003]
[Problems to be solved by the invention]
In the conventional light diffusing plate, when such a molding is performed, the surface state, that is, the matting tends to be non-uniform, and the highly stretched portion tends to be easily broken.
For example, the resin plate described in JP-A-58-29622 has a non-uniform matte surface with uneven gloss when subjected to high stretching molding.
Furthermore, the impact strength after molding is also reduced.
The composition described in JP-A-61-78859 has a matte state that is uniform after high-stretch molding, but the impact strength is greatly reduced.
[0004]
Therefore, the present invention provides a light-diffusing methacrylic resin plate having a uniform matte surface and having a small decrease in impact resistance even when a high elongation ratio is formed by secondary processing.
[0005]
[Means for Solving the Problems]
The present invention relates to 100 parts by weight of a methacrylic resin containing methyl methacrylate having an intrinsic viscosity [η] of 0.25 to 1.5 dl / g as a main component,
(1) Multilayer elastic body: 5 to 50 parts by weight,
(2) Acrylic crosslinked polymer having a weight average particle diameter of 10 to 50 µm: 5 to 20 parts by weight and
(3) Light-diffusing agent particles having a weight-average particle diameter of 1 to 10 μm: a light-diffusing methacrylic resin plate in which 0.5 to 5 parts by weight is dispersed is stretch-formed at a draw ratio of more than 50%. A method for producing a molded article is provided.
[0006]
The methacrylic resin containing methyl methacrylate as a main component used in the present invention is a homopolymer of methyl methacrylate or a copolymer of 50% by weight or more of methyl methacrylate and another vinyl monomer. Examples of the vinyl monomer include methacrylates such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, and acrylic acid. Acrylates such as methyl, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc .; Saturated acids, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like. The copolymer may further contain a glutaric anhydride unit and a glutarimide unit.
In the present invention, among these methacrylic resins, those having an intrinsic viscosity [η] of 0.25 to 1.5 dl / g are suitable.
If [η] is less than 0.25 dl / g, high stretch molding becomes difficult.
Further, if the temperature during molding is slightly insufficient, peeling occurs at the interface between the base resin, the crosslinked polymer particles, and the light diffusing agent, and the impact resistance tends to decrease.
When [η] exceeds 1.5 dl / g, there is no problem in the moldability, but the mechanical properties of the molded article decrease.
[0007]
The multilayered elastic body in the present invention is a powdery or granular material having at least a two-layered structure and containing 20 to 60% by weight of a rubber elastic layer or an elastomer layer, for example, Japanese Patent Publication No. 55-27576, Those described in Japanese Patent Application Laid-Open No. 1-252653 can be used.
[0008]
The amount of the multilayer elastic body is 5 to 50 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of the methacrylic resin.
If the amount is less than 5 parts by weight, the impact resistance is insufficient, and if it is more than 50 parts by weight, the rigidity is lowered, which is not preferable.
[0009]
The acrylic crosslinked polymer is defined as 50% by weight or more of an acrylic monomer, 49.9% by weight or less of another monomer having one unsaturated double bond in a molecule, and an unsaturated double bond. It is a copolymer of 0.1 to 50% by weight of a polyfunctional monomer having at least two in a molecule.
[0010]
Acrylic monomers include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, methyl acrylate, acrylic Examples include ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, acrylic acid, methacrylic acid, and the like. Two or more of these monomers may be used in combination.
[0011]
The monomer having one unsaturated double bond in the molecule is not particularly limited as long as it is other than the acrylic monomer component, but styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, anhydrous Maleic acid, phenylmaleimide, cyclohexylmaleimide and the like. Two or more of these monomers may be used in combination.
[0012]
The polyfunctional monomer is one which is copolymerizable with the above-mentioned monomer and excludes a conjugated diene. For example, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate ester, alkyl di (meth) acrylate such as neopentyl glycol di (meth) acrylic acid ester Acid esters: ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate A) alkylene glycol di (meth) acrylates such as acrylates; aromatic polyfunctional compounds such as divinylbenzene and diallyl phthalate; trimethylolpropane tri (meth) acrylate, pen Examples include (meth) acrylates of polyhydric alcohols such as taerythritol tetra (meth) acrylate and allyl methacrylate. Two or more of these monomers may be used in combination.
[0013]
The acrylic crosslinked polymer is obtained by spherically polymerizing a mixture of the above-mentioned monomers by using a method such as a suspension polymerization method or a microsuspension polymerization method.
For example, there are particles obtained by the method described in JP-A-5-155907.
[0014]
The particle size of the acrylic crosslinked polymer is 10 to 50 μm, preferably 15 to 40 μm, on a weight average.
If the particle diameter is less than 10 μm, a sufficient matte surface cannot be obtained.
On the other hand, if it exceeds 50 μm, cracks are likely to be generated from the particles during molding, and the impact resistance is reduced.
[0015]
The amount of the acrylic crosslinked polymer to be added is 5 to 20 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the methacrylic resin. If the amount is less than 5 parts by weight, uniform matting cannot be obtained, and if it exceeds 20 parts by weight, the impact resistance is reduced.
[0016]
Both organic and inorganic light diffusing agents can be used.
For example, for inorganic type, calcium carbonate, barium sulfate, aluminum hydroxide, talc, mica, glass, silica, etc., and for organic type, styrene type crosslinked polymer, silicon type crosslinked polymer, fluorine type polymer, acrylic type crosslinked polymer etc. Is mentioned.
Above all, those having a methacrylic resin as a base material having an absolute value of a difference in refractive index of 0.03 to 0.16 can be suitably used.
[0017]
The particle diameter of the light diffusing agent is 1 to 10 μm in weight average. If it is less than 1 μm, the light diffusivity is reduced, and if it is more than 10 μm, the matte after stretching becomes uneven and the impact resistance is reduced.
[0018]
The addition amount of the light diffusing agent is 0.5 to 5 parts by weight. If the amount is less than 0.5 part by weight, the light diffusibility is insufficient, and if it exceeds 5 parts by weight, the matte after stretching is affected and the impact resistance is reduced.
[0019]
As more sophisticated composition of methacrylic resin plate of the present invention, the weight of the multilayer structure elastic body (W _R), a weight average particle diameter of the acrylic crosslinked polymer (D _P), the weight of the acrylic crosslinked polymer (W _P ), some satisfy the following [Equation 2].
[0020]
(Equation 2)
^{_{(W R / W P) 2}} / D P> 0.02
[0021]
The above equation shows that the amount of the multilayer elastic body and the particle size and the amount of the acrylic cross-linked polymer greatly affect the impact resistance of the molded article. The ratio of Among (W _R) and (W _P) has been found to particularly large influence. From these findings, it was possible to specify a composition range capable of maintaining a high level of impact resistance. Note that the upper limit of the value of the above equation is 10.
[0022]
The light-diffusing methacrylic resin plate of the present invention is a so-called sheet or plate. The thickness is not particularly limited, but is generally about 0.8 mm to 10 mm.
[0023]
In order to make the light-diffusible methacrylic resin plate of the present invention from the methacrylic resin of the base material and each component to be dispersed, the two are mechanically mixed with a Henschel mixer, a tumbler or the like, and a single-screw or twin-screw extruder is used. Extrusion molding, ie, a plate-like method via a T-die and a roll unit after melt-kneading, etc .: mechanically mixing the two, pelletizing with a single-screw, twin-screw extruder, etc. There is a well-known method of forming a plate by press molding.
[0024]
In addition, there is a method in which each component to be dispersed is mixed with a syrup containing a monomer constituting the methacrylic resin of the base material and a syrup containing a partial polymer thereof, and cast-polymerized and continuously cast-polymerized to form a plate.
[0025]
Further, various known additives may be added to the methacrylic light diffusing resin plate of the present invention.
[0026]
【The invention's effect】
The light-diffusing methacrylic resin plate of the present invention has a uniform matte surface even after high-stretch secondary molding, and has a higher level of impact resistance.
A highly stretched molded product molded from the resin plate can be suitably used for a lighting cover or the like that requires light diffusion, matting, and impact resistance.
[0027]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. The evaluation method is as follows.
・ Push-up molding: A 30 cm × 20 cm resin plate is heated to 170 ° C. in an oven, and a side face is formed by using a push-up molding machine (Model TF-300 manufactured by Osaka Sheet Machine Co., Ltd., push-up area 10 cm × 5 cm, push-up height 10 cm). Was drawn to a draw ratio of about 70% to prepare a drawn sample.
Press molding: The resin plate is pressed at 230 ° C. for 5 minutes using a press machine (manufactured by Shinto Metal Industry Co., Ltd., hydraulic pressure 210 kg / cm ² ) to produce a non-stretched sample having substantially the same thickness as the stretch-molded sample. did.
-Intrinsic viscosity: measured in chloroform at 25 ° C.
Average particle diameter: Measured with a light diffraction scattering particle size analyzer (manufactured by Malvern, Mastersizer), and the value of D50 was taken as the average particle diameter.
-Total light transmittance ( _Tt ): Measured with a Poic integrating sphere haze meter (SEP-HS-30D manufactured by Nippon Seimitsu Kogaku) in accordance with ASTM D1003-61.
-Opacity and light diffusivity; transmitted light intensity (I ₀ ) at a transmission angle of 0 degree due to vertically incident light, transmitted light intensity (I ₅ ) at a transmission angle of 5 degrees due to vertically incident light, and transmission angle 70 degrees due to vertically incident light Of the transmitted light (I ₇₀ ) was measured using an automatic goniophotometer GP-1R manufactured by Murakami Color Research Laboratory Co., Ltd., and I ₅ / I ₀ was made a concealing property, and I ₇₀ / I ₀ was made a wide angle. Lateral diffusion was considered.
Surface glossiness: Measured by reflection at 60 degrees with a glossmeter (UGV-4D, manufactured by Suga Test Instruments Co., Ltd.) based on the gloss measurement of JIS Z-8741.
Impact strength: A steel ball having a weight of 200 g was dropped at the center of a sample supporting 7 cm × 7 cm 2, and the cracked height (cm) was taken as impact resistance.
-Stretching ratio: The thickness of the resin plate before and after the stretching process was measured, and calculated by the formula of √ ((thickness of original plate / thickness after molding) -1) * 100 (%).
[0028]
Reference Example Production of Acrylic Cross-Linked Polymer Acrylic cross-linked polymer particles (96% methyl methacrylate / 4% methyl acrylate copolymer D) obtained by the method described in Example 4 of JP-A-5-155907. ₅₀ = 50 μm) using an air classifier (TC-15N manufactured by Nisshin Engineering Co., Ltd.) to obtain particles having D ₅₀ values of 20 μm, 35 μm, and 80 μm, respectively.
[0029]
Examples 1-4, Comparative Examples 1-3
100 parts by weight of methacrylic resin beads (methyl methacrylate 94% / methyl acrylate 6% copolymer [η] = 0.8 dl / g) were added to the acrylic cross-linked polymer particles obtained in Reference Example, having a three-layer structure. A multilayer elastic body (obtained by the method described in Example 3 of JP-B-55-27576) and the amount of light diffusing agent particles shown in Table 1 were mixed with a Henschel mixer, and then mixed with an extruder (uniaxial, After melt-kneading at a resin temperature of 265 ° C. (screw diameter: 40 mm, manufactured by Tanabe Plastics Co., Ltd.), a sheet having a thickness of 2 mm and a width of 24 cm was obtained through a T-die and three polishing rolls. The obtained sheets were subjected to bump forming and press forming, respectively, to prepare evaluation samples.
The evaluation results are shown in Tables 2 and 3.
[0030]
[Table 1]

[0031]
[Table 2]

[0032]
[Table 3]

Claims (2)

Intrinsic viscosity [η] is 100 parts by weight of a methacrylic resin containing methyl methacrylate having a main component of 0.25 to 1.5 dl / g,
(1) Multilayer elastic body: 5 to 50 parts by weight,
(2) Acrylic crosslinked polymer having a weight average particle diameter of 10 to 50 µm: 5 to 20 parts by weight and
(3) Light-diffusing agent particles having a weight-average particle diameter of 1 to 10 μm: a light-diffusing methacrylic resin plate in which 0.5 to 5 parts by weight is dispersed is stretch-formed at a draw ratio of more than 50%. Manufacturing method of molded article. The light-diffusing methacrylic resin plate has a weight of the multilayer structure elastic body (W _R ), a weight average particle diameter of the acrylic cross-linked polymer (D _P ), and a weight of the acrylic cross-linked polymer (W _P ). The method according to claim 1 , wherein the following formula (1) is satisfied.
(Equation 1)
(W _R / W _P ) ² / D _P > 0.02