JPS6153363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing organic glass castings free of distortion or residual stress.

Transparent plastic materials known as organic glasses are gradually becoming popular for applications requiring transparency due to their light weight, excellent processability, and impact resistance. In particular, plastics have great merits in applications such as safety glass and large-diameter optical lenses, and are expected to replace inorganic glasses in these fields in the future. Generally, methods for producing organic glass products include cast polymerization, compression molding, and injection molding. Among these, the injection molding method has a short manufacturing time cycle and is suitable for mass production, but it has the disadvantage that the product has a lot of distortion or residual stress, and it has poor thermoplasticity and cannot produce heat-resistant products. . On the other hand, the cast polymerization method is considered to be the best method for producing products with excellent surface accuracy and dimensional accuracy, and low optical distortion or residual stress, but it has a long time cycle and is short-term. The drawback is that it is not possible to manufacture products. However, in the future, in order for organic glass to take advantage of its characteristics and advance into the field of inorganic glass, it will be necessary to have optical properties comparable to inorganic glass, dimensional accuracy, and stability of various properties and dimensions over time.
It is clear that durability will be required. Therefore, it is obvious that the cast polymerization method, which can produce products without distortion or residual stress, will become important in the future. Additionally, organic glasses are required to be improved in terms of heat resistance, chemical resistance, surface hardness, etc., which are weak points of organic glasses compared to inorganic glasses.As a result, materials with poor thermoplastic properties can be easily molded. There has been a demand for a cast polymerization method for organic glasses because of its ability to From this point of view, the only drawback of the cast polymerization method is low production efficiency,
It would be of considerable significance if the length of the time cycle could be improved and the economy improved from that point of view. An object of the present invention is to provide a cast polymerization technique that has high manufacturing efficiency and can produce products free of optical distortion and residual stress in a short period of time.

As a result of conducting research in line with these objectives, the inventors found that the viscosity of starting materials such as monomers or prepolymers was increased at relatively low temperatures, and the volume shrinkage accompanying polymerization was minimized. We have found that by performing shape polymerization, the generation of strain and stress can be reduced and cast polymerization can be performed efficiently.

At low temperatures, the density of the monomer or prepolymer increases and its volume decreases, making it possible to reduce the volumetric shrinkage associated with polymerization (particularly significant when the polymer is in a supercooled or glassy state). However, there are limits to this, and if the temperature is too low and approaches the glass transition point of the system, the polymerization rate will decrease and become impractical, and monomers or polymers that cannot achieve a stable supercooled state or glass state. In the case of polymers, if the temperature is too low, crystallization will occur and the polymerizability will be lost.

However, in order to maintain sufficient polymerizability and reduce volumetric shrinkage as much as possible without lowering the temperature too much, it is sufficient to use a prepolymer and increase the polymer concentration as much as possible, but this increases the viscosity of the system. If the viscosity is increased to a certain level or higher, workability during cast polymerization, such as pouring the prepolymer evenly into the mold or defoaming the air bubbles mixed in, becomes extremely difficult, making it impractical. Become.

Therefore, the problem is how to keep the viscosity at an appropriate level without making it excessive, and how to reduce the volumetric shrinkage accompanying polymerization. As a result of repeated efforts in this regard, the inventors arrived at the method of the present invention, which reduces polymerization shrinkage, maintains appropriate viscosity,
We succeeded in casting polymerization, which produces products with high efficiency and no distortion or stress.

That is, the method of the present invention is based on the general formula (In the formula, R is C _1-8 linear or branched alkyl or hydroxyalkyl, glycidyl,
benzyl, phenyl or _cyclohexyl ; Mixing a polymer of a monomer and/or a copolymer of two or more of the above monomers so that the amount of the polymer is 30 to 60% by weight based on the total weight of the monomer and the polymer, Dissolving or forming a polymer solution in which the proportion of the polymer is within the above range, and molding this solution into a certain shape with or without a mold or mold, A cast polymerization method characterized by obtaining an organic glass cast polymer free of distortion or residual stress by irradiating the glass with light or ionizing radiation at a temperature below room temperature while retaining its shape. or (a) general formula; (wherein R represents C _1-8 linear or branched alkyl or hydroxyalkyl, glycidyl, benzyl, phenyl or cyclohexyl, and X represents H or CH ₃ ) and (b) a mixture of monomers other than the above monomers in an amount not exceeding 50% by weight of the total amount of monomers, and (b) having a degree of polymerization in the range of 80 to 500 and being soluble in the above monomers. A polymer of the monomer of the general formula and/or a copolymer of two or more of the monomers, wherein the polymer content is 30 to 60% by weight based on the total weight of the monomer and the polymer. Mix, dissolve, or form a polymer solution in which the ratio of polymers falls within the above range, and then process this solution with or without a mold or mold. A cast polymer of organic glass without distortion or residual stress can be obtained by molding it into a certain shape and irradiating it with light or ionizing radiation at a temperature below room temperature while maintaining that shape. This is a cast polymerization method.

If such a polymer is below the polymerization degree range specified separately, its properties will become close to those of telomer and its physical properties will be significantly reduced, and it will not be able to achieve the effect of reducing polymerization shrinkage because it will resemble the properties of monomers. Moreover, when the degree of polymerization exceeds the specified range and the concentration is increased in an attempt to reduce polymerization shrinkage, the viscosity becomes excessive and workability decreases. In other words, it is not possible to obtain a sufficient concentration to reduce polymerization shrinkage.

Only when the polymer has a degree of polymerization within the appropriate range specified elsewhere can volume shrinkage accompanying polymerization be sufficiently reduced by increasing its concentration, and workability can be improved without excessive viscosity. can be maintained within a range without deteriorating.
However, if the concentration of such a polymer is too high, the viscosity will increase, and there will be virtually no difference from molding the polymer, and the characteristics of cast polymerization will be lost. The viscosity is to be reduced to the necessary degree, and the viscosity is maintained within an appropriate range, so that the production of strain and stress is significantly reduced in practical use. Therefore, in order to prepare such polymers, when using the axial polymerization method, the catalyst concentration is increased and various chain transfer agents (such as halogenated hydrocarbons, alcohols, catechol, etc.) are added. Alternatively, when producing it by irradiation with light or radiation, methods such as using an electron accelerator to increase the dose rate as much as possible and adjusting it by adding various chain transfer agents are used to achieve the degree of polymerization as specified separately. Adjust it. In addition, for cast polymerization, this may be prepared in advance as a polymer and dissolved and mixed with the monomer, or a prepolymer syrup that has been polymerized to a certain polymerization rate may be used as it is for cast polymerization. . In the present invention, this is poured into a mold, frame, etc., or is cooled without using a mold while maintaining a supercooled or glassy state, and is solidified to the extent that it loses fluidity at low temperatures. While giving a certain shape,
The cast polymerization is completed by irradiation with light or ionizing radiation. Therefore, the temperature used for irradiation may be any temperature below room temperature, and the conditions may be determined by considering the polymerization method and supercooling property at low temperatures of the system, preferably from 0°C to
-80℃ is preferable. In addition, when light or radiation polymerization is carried out at low temperatures, post-effect polymerization is large, so most of the polymerization has already been completed and strain and stress can no longer be generated, for example, after the polymerization rate has reached 80% or more. It may be removed from the light or radiation source and post-heated to complete the polymerization to 100%; such treatment methods are also included as a variant of the invention. The reason why polymerization is carried out at a low temperature below room temperature using light or radiation is that, as already mentioned, at low temperatures the volume of the prepolymer decreases, which further reduces the volume shrinkage associated with polymerization, and the strain caused by this decreases.・It is easy to prevent the generation of stress, and once it is injected into a mold or has a certain shape, there are no problems with workability.In fact, the higher the viscosity, the easier it is to maintain its shape and handle it, so it should be cooled to a low temperature. Polymerization is also important because it further increases the viscosity of the prepolymer and makes it semi-solid to prevent bubbles from being generated due to temperature rise due to the accumulation of polymerization heat, and to prevent distortion and stress from occurring due to molecular orientation due to thermal convection. This is because a relatively low temperature is desirable within a range that does not reduce the temperature.

By performing cast polymerization at a relatively low temperature and using a polymer having the degree of polymerization of the present invention at the concentration of the present invention, it is possible to achieve a high glass transition of the polymer, which has traditionally been extremely difficult to eliminate strain or stress. Even for organic glass materials that have dots and are difficult to relax, it is possible to create products without optical distortion or residual stress.

The light used in the present invention includes visible ultraviolet light from high-pressure and low-pressure mercury lamps, natural light, light from a photon factory, laser light, cold light, etc., and a photosensitizer may be added if necessary. Ionizing radiation includes X-rays, β-rays, γ-rays, α-rays, electron beams, neutron beams, mixed radiation, etc., and the dose rate is 1×
a10 ² - 1 x 10 ⁹ x rays per hour, dose 1 x 10 ³ -
It is preferable to use it within the range of 1×10 ⁷ .

Specific examples of the monomer of the present invention are as follows.

Methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, benzyl acrylate, diethylene glycol diacrylate, benzyl methacrylate, phenyl acrylate, methacrylic acid Phenyl, glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, methacrylic acid Hydroxypentyl, hydroxypentyl acrylate, hydroxyhexyl methacrylate, hydroxyhexyl acrylate, and comonomer-based mixtures of two or more of these.

Surface hardness, heat resistance, and
50% by weight of total monomers to improve tensile strength, compressive strength, solvent resistance, weathering or water resistance
The following monomers may be added within a range not exceeding .

Diethylene glycol bisallyl carbonate, ethylene glycol bisallyl carbonate, triethylene glycol bisallyl carbonate, tetraethylene glycol bisallyl carbonate, diallyl phthalate, diallyl maleate, diallyl isophthalate, diallyl itaconate, diallyl succinate, triallyl cyanurate, tri- Allyl isocyanurate, triacrylic formal, dipropargyl maleate, dipropargyl itaconate, dipropargyl phthalate, vinyl acetate, vinylbenzene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide, methacrylamide. In this case 80-500, preferably 100-
Polymers of said monomers with a degree of polymerization in the range of 300 and/or
or a copolymer of two or more of the above monomers, based on the total weight of the monomer and polymer, the polymer is 30 to 30%
60, preferably 30 to 50% by weight, is mixed and dissolved in the monomer mixture, and the resulting solution is molded into a certain shape with or without a mold or mold. By molding it into a shape and irradiating it with light or ionizing radiation at a temperature below room temperature while maintaining its shape,
Polymers without strain or residual stress may be obtained.

Example 1 1% benzoyl peroxide and 1% n-dodecyl mercaptan were added to 100 parts of methyl methacrylate.
A prepolymer was obtained by reacting at ℃ for 6 hours. The intrinsic viscosity of this polymer in a benzene solution was determined and the molecular weight was calculated to be 35,000. (ie, degree of polymerization: 350) This was dissolved in methyl methacrylate at a concentration of 42.3% to obtain a monomer-prepolymer mixture having a viscosity of 16.5 poise. Glass plate 2
Cobalt 60 (dose rate 1 x 10 ⁵ x rays per hour) is injected into a casting mold (160 mm x 80 mm x 5 mm thick) consisting of a sheet and silicone rubber packing at room temperature.
When polymerized by irradiating with gamma rays for 10 hours, a cast polymer with no optical distortion or stress was obtained. When the same sample was irradiated for 5 hours at room temperature at a dose rate of 2×10 ⁵ roentgens, distortion was generated. However, when the same sample was kept at 0° C. and irradiated for 5 hours at a dose rate of 2×10 ⁵ roentgens per hour, no strain was produced. Strain was generated when irradiation was performed for 2 hours at 0° C. with a dose rate of 5×10 ⁵ roentgens per hour.

For comparison, 0.5% benzoyl peroxide was added to 100 parts of methyl methacrylate and reacted at 60°C for 4 hours to obtain a prepolymer with a molecular weight of 76,000 (degree of polymerization 760). This product was added and dissolved in methyl methacrylate at a concentration of 18.7% to obtain a mixed solution with a viscosity of 35 poise. When this was poured into the same mold as above and irradiated with cobalt 60 gamma rays at room temperature, a distortion-free cast polymer could not be obtained even at a dose rate of 1×10 ⁴ Roentgen/hour. Similar results were obtained at 0°C.

Example 2 50 parts of hydroxyethyl methacrylate, 200 parts of methanol, 1% benzoyl peroxide, and 1% lauryl mercaptan were mixed and heated at 60° C. for 4 hours to produce a prepolymer. The prepolymer was separated by precipitation with ether, and the molecular weight was estimated to be 41,000 by light scattering method. This is 32
% polymer concentration, the viscosity when dissolved in hydroxyethyl methacrylate was 28 poise. This was poured into a thick lens casting mold made of inorganic glass (two glass molds connected by ring-shaped polyethylene packing) and irradiated with cobalt 60 gamma rays at room temperature, resulting in a diameter of 80 mm and a thickness of 5 mm.
In the flat lens, optical distortion was observed using a static strain meter at a dose rate of 2 x 10 ⁵ x rays per hour, but no distortion was observed at a dose rate of 1 x 10 ^{5 x} rays per hour. For comparison, we performed cast polymerization under the same conditions as above using monomers without prepolymer, and found that distortion-free cast polymers could only be obtained when the dose rate was reduced to 1 x 10 ⁴ Roentgen/hour. Ivy.

Additionally, hydroxyethyl methacrylate 50
1% of methanol and 1% of benzoyl peroxide were mixed and heated at 60°C for 4 hours to obtain a prepolymer with a molecular weight of 89,000. Add this to the monomer at a concentration of 30% and use the same mold as above at room temperature.
When casting polymerization was performed, optical distortion was observed even at a dose rate of 1×10 ⁴ Roentgen per hour.

Claims (1)

[Claims] 1. General formula (In the formula, R is C _1-8 linear or branched alkyl or hydroxyalkyl, glycidyl,
benzyl, phenyl or _cyclohexyl ; Mixing a polymer of a monomer and/or a copolymer of two or more of the above monomers so that the amount of the polymer is 30 to 60% by weight based on the total weight of the monomer and the polymer, Dissolving or forming a polymer solution in which the proportion of the polymer is within the above range, and molding this solution into a certain shape with or without a mold or mold, A cast polymerization method characterized by obtaining an organic glass cast polymer free of distortion or residual stress by irradiating the glass with light or ionizing radiation at a temperature below room temperature while retaining its shape. . 2 (a) General formula (wherein R represents C _1-8 linear or branched alkyl or hydroxyalkyl, glycidyl, benzyl, phenyl or cyclohexyl, and X represents H or CH ₃ ) and (b) a mixture of monomers other than the above monomers in an amount not exceeding 50% by weight of the total amount of monomers, and (b) having a degree of polymerization in the range from 80 to 500, A soluble polymer of the monomer of the general formula and/or a copolymer of two or more of the monomers is added in an amount of 30 to 60% by weight based on the total weight of the monomer and polymer. %, or form a polymer solution such that the proportion of the polymer falls within the above range, and then pour this solution into a mold or formwork, or by molding it using a mold or formwork. It is possible to obtain an organic glass cast polymer without strain or residual stress by molding it into a certain shape and irradiating it with light or ionizing radiation at a temperature below room temperature while maintaining that shape. Characteristic cast polymerization method.