JP2000227501A - Lens for signal device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens for a signal device with excellent transparency and heat resistance. SOLUTION: A lens for a signal device is obtained by hardening a resin composition containing the following components (A)-(C). (A) 30-60 pts.wt. of an unsaturated monomer mixture containing 20-90 wt.% unsaturated monomers consisting essentially of methyl methacrylate and 10-80 wt.% unsaturated monomers containing at least two double bonds capable of radical polymerization within a molecule is included. (B) 40-70 pts.wt. of resin particles comprising a polymer of unsaturated monomers consisting essentially of methyl methacrylate containing 20-100 wt.% partially cross-linked resin particles and 0-80 wt.% non-cross-linked resin particles is included. (C) 0.1-5 pts.wt. of a radical initiator per 100 pts.wt. of sum of components (A) and (B) is included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a signal lens having excellent transparency and heat resistance, and a method for producing the same.

[0002]

2. Description of the Related Art A methacrylic resin containing methyl methacrylate as a main component is excellent in transparency, surface gloss, weather resistance, mechanical properties and the like.
It is widely used for various purposes such as signboards and building materials.

[0003] However, when methacrylic resin is used in relatively hot places such as a meter cover of an automobile, a lamp cover of a lighting fixture, and a lens of a traffic light, problems such as insufficient heat resistance and deformation often occur. I was

As a method of imparting heat resistance, a method of adding a unsaturated monomer having at least two double bonds capable of radical polymerization in one molecule to form a crosslinked polymer when polymerizing a methacrylic resin. There is.

For example, Japanese Patent Publication No. 4-75241 proposes an acrylic resin plate having a deflection temperature under load of 115 ° C. or more obtained by adding a crosslinking agent having a specific structure in an amount of 4 to 30% and polymerizing in a mold. .

[0006]

In general, a crosslinked polymer does not melt even when heated, so that it is difficult to mold a methacrylic resin such as injection molding.

In the method described in Japanese Patent Publication No. 4-75241, it is necessary to have a viscosity by which a raw material liquid can be poured into a mold by casting polymerization. For this reason, the content of the unreacted unsaturated monomer is inevitably increased, and in the production of a three-dimensional molded product, the occurrence of defects such as sink marks and cracks due to polymerization shrinkage becomes a problem. In addition, since it is cast polymerization, the time required for curing generally takes a long time, which is industrially disadvantageous.

[0008] In view of such circumstances, the present inventor has high heat resistance,
As a result of intensive studies on a method for stably and easily producing a signal lens having excellent moldability, (A) 20 to 90% by weight of an unsaturated monomer mainly composed of methyl methacrylate was subjected to radical polymerization in one molecule. 30 to 60 parts by weight of an unsaturated monomer mixture containing 10 to 80% by weight of an unsaturated monomer having at least two possible double bonds, (B) an unsaturated monomer mainly composed of methyl methacrylate A polymer of
0-100% by weight of partially crosslinked resin particles and 0-8
0 to 40% by weight of non-crosslinked resin particles
By using 70 parts by weight of the radical polymerization initiator (C) in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total of the components (A) and (B), for a traffic light excellent in heat resistance and transparency. The present inventors have found that a lens can be manufactured stably and easily, and have reached the present invention.

[0009]

That is, the present invention is as follows. (1) A signal lens made of a resin composition containing the following components (A) to (C). (A) 20 to 90% by weight of an unsaturated monomer mainly composed of methyl methacrylate, and 10 to 8 of an unsaturated monomer having at least two radically polymerizable double bonds in one molecule.
30 to 60 parts by weight of an unsaturated monomer mixture containing 0% by weight (B) A polymer of unsaturated monomers mainly composed of methyl methacrylate, and 20 to 100% by weight of a partially crosslinked resin 40 to 70 parts by weight of resin particles composed of particles and 0 to 80% by weight of non-crosslinked resin particles (C) 0.1 parts by weight of a radical polymerization initiator based on 100 parts by weight of the total of components (A) and (B) (2) A method for manufacturing a lens for a traffic signal, comprising mixing the components (A) to (C) described in the above item (1) to form a molding material, and then heating and curing the molding material. .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The unsaturated monomer mainly composed of methyl methacrylate,
It refers to a mixture of methyl methacrylate and another copolymerizable monofunctional unsaturated monomer, wherein the content of methyl methacrylate is 50% by weight or more. Examples of the copolymerizable monofunctional unsaturated monomer include methyl acrylate, ethyl acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth) acrylate , Tetrahydrofurfuryl (meth) acrylate,
Esters of methacrylic acid or acrylic acid such as isobornyl acrylate, benzyl (meth) acrylate, and cyclohexyl acrylate with aliphatic, aromatic and alicyclic alcohols; hydroxyethyl (meth) acrylate;
(Meth) acrylic monomers such as hydroxyalkyl esters such as hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate; unsaturated acids such as acrylic acid and methacrylic acid; styrene such as styrene and α-methylstyrene Monomers: Monofunctional unsaturated monomers such as acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide, and vinyl acetate, but are not limited thereto. These can be used alone or in combination of two or more.

The content of methyl methacrylate in the unsaturated monomer mainly composed of methyl methacrylate is 50% or more, preferably 70% or more, more preferably 90%.
That is all.

Unsaturated monomer having at least two radically polymerizable double bonds in one molecule (polyfunctional unsaturated monomer)
Examples thereof include allyl methacrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, and 1, 3-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth)
Acrylate, divinylbenzene, diallyl phthalate, trimethylolpropane tri (meth) acrylate, tetramethylol methane tri (meth) acrylate, tetramethylol methane tetra (meth) acrylate and the like can be mentioned. It is used alone or in combination of two or more.

[0013] The unsaturated monomer mainly composed of methyl methacrylate and the unsaturated monomer having at least two radically polymerizable double bonds in one molecule are the same as those of the above.
It is preferred that the content be from 90 to 90% by weight and the latter from 10 to 80% by weight. When the content of the unsaturated monomer having at least two radical polymerizable double bonds in one molecule is less than 10% by weight, heat resistance is insufficient, and when it is more than 80% by weight, impact resistance is reduced. It is not preferable because strength and mechanical strength may be reduced.

The unsaturated monomer mixture of the component (A) is used in an amount of about 30 to 60 parts by weight based on 100 parts by weight of the total of the components (A) and (B).
Use in the range of parts by weight. If the amount is less than about 30 parts by weight, sufficient fluidity cannot be obtained when molding the resin composition. Conversely, if the amount is more than about 60 parts by weight, the handling becomes poor such that the stickiness of the surface after kneading the resin composition becomes large and the shape is difficult to maintain, which is not preferable. In addition, shrinkage due to polymerization during molding becomes large, and it becomes difficult to obtain a molded body having a smooth surface.

[0015] The resin particles comprising a polymer of an unsaturated monomer mainly composed of methyl methacrylate as the component (B) are defined as a resin of a copolymer of methyl methacrylate and another copolymerizable unsaturated monomer. Particle refers to a particle whose methyl methacrylate accounts for 50% by weight or more of its constituent components.

[0016] Examples of the unsaturated monomer copolymerizable with methyl methacrylate here include the above-mentioned polyfunctional unsaturated monomers and monofunctional unsaturated monomers.

Examples of the polyfunctional unsaturated monomer include the same as those described above, for example, allyl methacrylate,
Ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) Acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, divinylbenzene, diallyl phthalate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane Tetra (meth) acrylate and the like can be mentioned, but it is only necessary to be a monomer copolymerizable with methyl methacrylate, and it is not limited to these.

Examples of the monofunctional unsaturated monomer include the same ones as described above, for example, methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl ( Methacrylic acid or acrylic acid such as meth) acrylate, lauryl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, and aliphatic, aromatic, and fatty acids Esters with cyclic alcohols; hydroxyethyl (meth)
(Meth) acrylic monomers such as hydroxyalkyl esters such as acrylate, hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate; unsaturated acids such as acrylic acid and methacrylic acid; styrene and α-methylstyrene Styrene-based monomers: acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide,
Examples include, but are not limited to, vinyl acetate.

As the resin particles, for example, resin particles obtained by polymerization such as emulsion polymerization, suspension polymerization and dispersion polymerization are used. Resin particles obtained by pulverizing a polymer obtained by another polymerization method can also be used.

The size of the resin particles is usually about 1 to 10
Those having a thickness of 0 μm are preferably used. When resin particles smaller than about 1 μm are used, mixing and kneading with the unsaturated monomer mixture of the component (A) tend to be difficult, and conversely, when resin particles having a size exceeding about 100 μm are used. Is not preferred because the particle shape may be noticeable after molding.

[0021] Of the resin particles, about 20 to 100% by weight is a partially crosslinked resin particle, and about 0 to 80% by weight.
Uses non-crosslinked resin particles. If the proportion of the partially crosslinked resin particles in the resin particles is less than about 20% by weight, the handling properties of the molding material obtained after mixing and kneading the resin composition are not preferable.

[0022] The partially crosslinked resin particles referred to here are resin particles which generally swell but are not completely dissolved in a solvent such as acetone which can dissolve methyl methacrylate. is there.

[0023] Such resin particles contain about 50% by weight or more of methyl methacrylate, and when polymerizing a mixture thereof with a copolymerizable unsaturated monomer to produce resin particles or a polymer, It can be obtained by adding a polyfunctional unsaturated monomer.

The resin particles of the component (B) are used in an amount of about 40 to 70 parts by weight based on 100 parts by weight of the total of the components (A) and (B). When the amount is less than about 40 parts by weight, the mixture of the molding material obtained after mixing and kneading the resin composition becomes sticky, and the handleability deteriorates. When the amount is more than about 70% by weight, uniform mixing and kneading are difficult. Is not preferred.

If necessary, known additives such as an antioxidant, an ultraviolet absorber, a chain transfer agent, and the like may be added to the resin particles.
Release agents, dyes, pigments, inorganic fillers and the like can also be added.

In the present invention, a radical polymerization initiator is added to polymerize and cure the unsaturated monomer mixture of the component (A). Examples of the radical polymerization initiator include 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-
Azobis (2,4,4-trimethylpentene), 2,
2'-azobis (2-methylpropane), 2-cyano-
2-Propyrazoformamide, 2,2'-azobis (2
-Hydroxy-methylpropionate), 2,2'-azobis (2-methyl-butyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis [2-
(2-imidazolin-2-yl) propane], azo compounds such as dimethyl 2,2′-azobis (2-methylpropionate); dicumyl peroxide, t-butylcumyl peroxide, di-t-butylper oxide,
Diacyl and dialkyl peroxide initiators such as benzoyl peroxide and lauroyl peroxide;
t-butylperoxy-3,3,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisobutyrate, t-butylperoxyacetate, di-t-butylperoxyhexahydro Terephthalate, di-t-butyl peroxyazelate, t
-Butylperoxy-2-ethylhexanoate, 1,
Peroxyester initiators such as 1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-amylperoxy-2-ethylhexanoate;
percarbonate-based initiators such as t-butylperoxyallyl carbonate and t-butylperoxyisopropyl carbonate; 1,1-di-t-butylperoxycyclohexane, 1,1-di-t-butylperoxy-
3,3,5-trimethylcyclohexane, 1,1-di-
Peroxyketal initiators such as t-hexylperoxy-3,3,5-trimethylcyclohexane and the like can be mentioned. These radical polymerization initiators can be used alone or
More than one type is used in combination.

These polymerization initiators include the components (A) and (B)
Is used in an amount of about 0.1 to 5 parts by weight with respect to 100 parts by weight in total. If the amount is less than about 0.1 part by weight, it takes a long time to perform radical polymerization, and if it exceeds about 5 parts by weight, the unsaturated monomer mixture of the component (A) cannot be polymerized stably. Not preferred.

[0028] To the resin composition of the present invention, a release agent, an ultraviolet absorber, a dye, a pigment, a polymerization inhibitor, a chain transfer agent, an antioxidant, a flame retardant, a reinforcing agent, and the like can be added. .

Next, a method for molding the resin composition will be described. The production of a molded article in the present invention comprises two steps of a mixing / aging step and a polymerization / curing step.

First, in the step of mixing and aging, components (A) to
It is sufficient that (C) is mixed and a homogeneous mixture is finally obtained. As a specific method, for example, components (A) to (C)
Are mixed to obtain a slurry-like resin composition, which is aged in an appropriate container. The shape of the container is not particularly limited. Further, as the container, a cell or the like including at least two flat plates and a sealing material for sealing the periphery can be used. The material of the container is not particularly limited as long as it is not dissolved or eroded in the unsaturated monomer mixture.

After mixing the components (A) to (C), the mixture is poured into a container,
Aging is performed at about 20 ° C to 100 ° C. During the aging step, the unsaturated monomer mixture (A) is impregnated in the resin particles (B), and when non-crosslinked particles are used for the resin particles (B), the noncrosslinked particles are dissolved by (A). Is done. The appearance of the mixture is
During the aging step, the slurry changes from a slurry to a clay or a powder to obtain a molding material.

If the temperature is higher than about 100 ° C. during aging, the polymerization and curing reaction by the added radical polymerization initiator are not preferable. On the other hand, if the temperature is lower than about 20 ° C., aging takes a long time, which is not preferable. Therefore, the aging temperature is preferably in the range of about 20C to 100C. The aging conditions are appropriately selected depending on the resin particles used, the composition of the unsaturated monomer mixture, the type and amount of the polymerization initiator used, and the like.

As another method, for example, the components (A) to (A)
When mixing and kneading (C), an appropriate temperature is selected, and ripening can be performed at the same time. In that case, as a device for kneading, a known kneading device such as a twin-screw extruder, a universal mixer, a kneader, and a Banbury mixer can be used.

[0034] Next, in the step of polymerization and curing, the above-mentioned molding materials are charged into molding dies of various shapes, pressurized and heated to perform molding and curing reactions, and molded articles of various shapes are formed. obtain.

As a molding method applicable to the present invention, compression molding, injection molding, transfer molding and the like can be applied. The applicable molding method is not limited to these as long as it is a molding method in which pressing and heating are performed to perform a shaping and curing reaction.

To perform a curing reaction by radical polymerization, about 8
This is performed by heating to a temperature of 0 to 200 ° C. When the temperature is lower than about 80 ° C., the curing reaction requires a long time, which is industrially disadvantageous. Conversely, when heated at a temperature exceeding about 200 ° C., decomposition or coloring may occur.

[0037] As the structure of the mold, it is preferable to provide a space for venting gas in the peripheral portion. If the gap is too large, the injected molding material may overflow, while if it is too small, the gas in the cavity may not be sufficiently released, which is not preferable. This venting space is
Generally, it is preferable to set the thickness in the range of about 0.01 to 0.5 mm, but it may be appropriately selected according to the viscosity of the molding material used.

Further, as another method, a method in which the inside of the mold cavity can be preliminarily reduced in pressure can be suitably used.

[0039] The molding temperature is preferably in the range of 80 to 150 ° C. If the temperature is higher than 150 ° C., the amount of the unsaturated monomer mainly composed of methyl methacrylate contained in the molding material volatilizes when the molding material comes into contact with the mold surface, which is not preferable.

The pressure at the time of molding depends on the viscosity of the molding material, the shape of the molded body, and the like, but may be any pressure that can follow the contraction of the molding material during the polymerization and curing process. In compression molding, it is generally 2070 kgf / cm ² or more, more preferably 507 kgf / cm ² or more.
What is necessary is just 0 kgf / cm ² or more.

The time of pressurization and heating in the molding depends on the composition of the unsaturated monomer mixture contained in the molding material used, the type and amount of the radical polymerization initiator, or the thickness of the molded product.
Although it is appropriately selected according to the temperature of the mold and the like, a cured product is generally obtained in less than 10 minutes.

[0042]

According to the present invention, a signal lens having high heat resistance and excellent transparency can be stably and easily manufactured.

[0043]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In addition,
The evaluation method is as follows. (1) Handleability of molding material: Judgment was made based on the degree of stickiness when wearing and touching polyethylene gloves. (2) Moldability of molding material: 40 g of molding material was charged into a disc-shaped signal lens mold having a diameter of 90 mm, and the temperature was set to 1
A molded article was produced by pressurizing and heating at 20 ° C. and a mold clamping pressure of 70 kgf / cm ² for 10 minutes, and the appearance was evaluated. (3) Heat resistance of molded article: According to JIS K7206, the temperature at which the needle penetrated 1 mm was used as an index of heat resistance. The measurement was performed up to 180 ° C, and the infiltration at 180 ° C was 1
In the case of less than mm, the amount of permeation was determined. (4) Transparency of the molded article
The total light transmittance was determined according to IS K6718.

Example 1 In a 500 ml polycup, 30 parts by weight of methyl methacrylate and neopentyl glycol dimethacrylate (NK)
15 parts by weight of ester NPG (manufactured by Shin-Nakamura Chemical Co., Ltd.), partially crosslinked resin particles (methyl methacrylate / ethylene glycol dimethacrylate = 99/1, chloroform insoluble matter 75%, average particle diameter 8 μm, swelling degree 3.8) 55 parts by weight and 0.29 parts by weight of a polymerization initiator (t-amyl peroxy-2-ethylhexanoate) were added, and the mixture was stirred and mixed to obtain a slurry resin composition.

The resin composition was poured into a polyethylene bag, sealed, and left to stand in a hot-air drying oven at 50 ° C. for 1 hour to ripen. After cooling to room temperature, a powdery molding material was obtained from the bag. This molding material exhibited low stickiness and good handleability. The molded article was transparent and had a good appearance. The heat resistance was only 0.182 mm penetration at 180 ° C. The total light transmittance was 91.3%.

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Claims (4)

[Claims] 1. A signal signal lens comprising a resin composition containing the following components (A) to (C). (A) 20 to 90% by weight of an unsaturated monomer mainly composed of methyl methacrylate, and 10 to 8 of an unsaturated monomer having at least two radically polymerizable double bonds in one molecule.
30 to 60 parts by weight of an unsaturated monomer mixture containing 0% by weight (B) A polymer of unsaturated monomers mainly composed of methyl methacrylate, and 20 to 100% by weight of a partially crosslinked resin 40 to 70 parts by weight of resin particles composed of particles and 0 to 80% by weight of non-crosslinked resin particles (C) 0.1 parts by weight of a radical polymerization initiator based on 100 parts by weight of the total of components (A) and (B) ~ 5 parts by weight 2. A method for manufacturing a lens for a traffic signal, comprising mixing the components (A) to (C) according to claim 1 to form a molding material, and then heating and curing the molding material. 3. The method according to claim 2, wherein the step of heating and curing is performed by a compression molding machine. 4. The method for producing a molded article according to claim 2, wherein the step of heating and curing is performed by an injection molding machine.