JPS6317915A - Low-hygroscopic methacrylic resin - Google Patents

Abstract

PURPOSE:To provide the titled resin outputting in transparency, moldability, low birefringence, thermal stability and heat resistance, suitable for optically information recording discs, etc., consisting of a copolymer made up of p-t- butylcyclohexyl methacrylate unit and methyl methacrylate unit. CONSTITUTION:The objective resin consisting of (A) 5-95(pref. 15-50)wt% of p-t-butylcyclohexyl methacrylate unit, (B) 95-5(pref. 85-50)wt% of methyl methacrylate unit, and, preferably, (C) <=30wt% of another monomer unit copolymerizable with the components A and B [e.g. methacrylic acid, itaconic acid (alkyl ester)].

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel low hygroscopic methacrylic resin. More specifically, the present invention relates to optical information recording elements such as optical information recording discs, optical information recording cards, optical information recording sheets, optical information recording films, lenses, mirrors, prisms, etc. , optical elements such as optical transmission fibers and optical waveguides, light-transmitting plates such as signboards, displays, partitions, daylight windows, front panels of televisions, and front panels of liquid crystal display devices, and other products that perform their functions when light passes through them. The present invention relates to a novel methacrylic resin that is suitable as a material and has excellent transparency, moldability, low birefringence, and thermal stability, as well as low moisture absorption and excellent heat resistance.

Conventional technology Since methyl methacrylate resin is an optically superior resin with excellent transparency and low birefringence, it has been used for example in optical information recording elements, optical elements, transparent plates, etc. It is widely used as a material for products that function by transmitting light.

However, this methyl methacrylate resin has a high hygroscopicity, and absorption of moisture causes dimensional changes, warping, and deformation.Also, it does not have very good heat resistance, so it cannot be used in high-temperature environments. However, the actual situation is that its use is limited.

In order to improve the hygroscopicity of methyl methacrylate resin, a technique of copolymerizing styrene is known (Japanese Unexamined Patent Application Publication No. 1983-1999).
No. 33446, No. 57-162135, No. 5
7-108012). However, even if styrene is copolymerized, the effect of improving hygroscopicity is not very large, and to increase the effect, increasing the content of styrene units increases birefringence, which makes it difficult to improve the hygroscopicity of methyl methacrylate resin. There is a problem that the excellent characteristics are lost and it cannot be used for optical applications.Furthermore, copolymerizing styrene does not improve heat resistance, so applications that require higher heat resistance than that of methyl methacrylate resin. cannot be used.

On the other hand, in order to improve the hygroscopicity of methyl methacrylate resin without increasing the birefringence too much, a technique is known in which cyclohexyl methacrylate is copolymerized (JP-A-57
-186241 publication, 58-127754 publication,
Publication No. 59-1518, Publication No. 60-104110). However, even if cyclohexyl methacrylate is copolymerized, the effect of improving hygroscopicity is not so great, and
If the content of cyclohexyl methacrylate units is increased in order to greatly exhibit this effect, the heat resistance will be significantly lowered and the product will become extremely brittle, resulting in an undesirable situation in which the application is severely restricted.

In addition, in order to improve the hygroscopicity of methyl methacrylate resin without increasing birefringence, we have also used 4-isopropylcyclohexyl acrylate and dicyclohexyl fumarate in addition to cyclohexyl methacrylate (JP-A-5
7-186241), methacrylic acid-5,5,
5-) Example using remethylcyclohexyl and isobornyl methacrylate (Japanese Unexamined Patent Publication No. 104110/1983)
is disclosed.

However, in these examples, it has not been clarified which monomer is more effective than cyclohexyl methacrylate in improving the hygroscopicity of methyl methacrylate resin, and moreover, There is a problem that the heat resistance is lower than that of methyl methacrylate resin.

Furthermore, in order to improve both the hygroscopicity and heat resistance of methyl methacrylate resin, a technique is known in which isobornyl methacrylate is copolymerized (Japanese Patent Laid-Open Nos. 59-227909 and 60-115605). ).

However, even if inbornyl methacrylate is copolymerized, the effect of improving hygroscopicity is not so great, and in order to make the effect more effective, increasing the content of inbornyl methacrylate units makes it extremely brittle.
It is not exempt from usage restrictions.

Furthermore, even if inbornyl methacrylate is copolymerized under commonly used polymerization conditions, a considerable amount of unreacted monomer remains in the resulting resin, and it is extremely difficult to remove this from the resin. It is.

If unreacted monomers remain in the resin, not only the heat resistance of the resin will be significantly reduced, but also the thermal stability will be significantly reduced. Therefore, even if you try to obtain a molded product from a resin containing a large amount of residual monomer, it may become colored or foam during molding and cannot be molded, or even if it can be molded, the resulting molded product will be colored or foamed. In some cases, the heat resistance is not as good as expected, so there are limitations in its use.

Furthermore, the resin obtained by copolymerizing inbornyl methacrylate has low thermal stability, and even resins whose residual monomer content has been reduced using special methods and conditions cannot be used to obtain high bit reproducibility in injection molding of optical discs. 28 used for
When performing melt molding at a high temperature such as 0° C., significant coloring and decomposition and foaming occur simultaneously, making it difficult to obtain a good molded product.

Furthermore, in order to simultaneously improve the hygroscopicity and heat resistance of methyl methacrylate resin, an example has been disclosed in which bornyl methacrylate, 3,5-dimethyladamantyl methacrylate, and fentyl methacrylate were copolymerized (JP-A Showa 59
-227909). However, what kind of monomer can be copolymerized to improve the hygroscopicity of methyl methacrylate resin, whether a resin with less residual monomer can be obtained, and whether it will not cause coloring or decomposition and foaming during melt molding? No specific disclosure has been made regarding this.

Problems to be Solved by the Invention The present invention has the characteristics of methyl methacrylate resin, such as excellent transparency, moldability, low birefringence, and thermal stability, as well as low hygroscopicity and excellent heat resistance. The purpose of this invention is to provide a new methacrylic resin.

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive research and found that a resin in which methyl methacrylate and at least p-tert-butylcyclohexyl methacrylate are copolymerized is methyl methacrylate. The methacrylic acid p-
Although the number of carbon atoms in tert-butylcyclohexyl is the same as that of isobornyl methacrylate,
Compared to resins copolymerized with isobornyl methacrylate, the content of residual monomers is significantly lower, the hygroscopicity is even lower, and the heat resistance is sufficiently higher than that of methyl methacrylate resins. It was discovered that even when melt-molded at high temperatures such as C, no significant coloring or decomposition and foaming occurs, and good molded products can be obtained.Based on this knowledge, the present invention was completed. I ended up doing it.

That is, the present invention provides (A) methacrylic acid p-ter
5-95% by weight of t-butylcyclohexyl units, (B)
Provides a methacrylic resin comprising a copolymer containing 95 to 5% by weight of methyl methacrylate units and optionally further (C) other copolymerizable monomer units in a proportion not exceeding 30% by weight. be.

The present invention will be explained in detail below.

The methacrylic resin of the present invention is methacrylic acid p-tθr
It is a copolymerization of t-butylcyclohexyl and methyl methacrylate, or a copolymerization of p-tert-butylcyclohexyl methacrylate, methyl methacrylate, and other monomers that can be copolymerized with these. .

In these methacrylic resins, methacrylic acid p
The ratio of -tert-butylcyclohexyl units to methyl methacrylate units is 5:95 to 95 on a weight basis.
:5 range. If the amount of p-tert-butylhexyl methacrylate units is less than the above range, the low hygroscopicity and high heat resistance, which are the characteristics of the resin of the present invention, will not be sufficiently exhibited. The preferred ratio is 10:90 to 60:40,
A more preferred ratio is selected in the range of 15:85 to 50:50.

Note that p-tert-butylcyclohexyl methacrylate exists in cis form and trans form, and in the present invention, either of them can be used, or a mixture of any proportion can be used. .

In the resin of the present invention, there are no particular restrictions on the copolymerizable monomer used if desired, but the resin of the present invention has excellent transparency, moldability, low birefringence, thermal stability, and Monomers that do not significantly impair hygroscopicity, high heat resistance, etc. are used. Examples of such monomers include unsaturated fatty acids such as methacrylic acid and its alkyl esters, fluorinated alkyl esters, acrylic acid and its alkyl esters and fluorinated alkyl esters, itaconic acid and its alkyl esters, and fluorinated alkyl esters. and their alkyl esters and fluorinated alkyl esters; aromatic vinyl compounds such as styrene, α-methylstyrene, and p-methylstyrene; vinyl cyanide compounds such as acrylonitrile and methacrylate; Examples include saturated fatty acid amides, maleic anhydride, unsaturated dibasic acids such as cyclohexylmaleimide, and their derivatives, but they are not necessarily limited to these monomers, and molded products can be formed by direct polymerization such as cast polymerization. When obtaining the above, crosslinkable polyfunctional monomers such as urethane methacrylate, urethane acrylate, and methacrylic acid ester and acrylic ester of polyhydric alcohol can also be used. Each of these monomers may be used alone, or
Two or more types may be used in combination.

In the resin of the present invention, the content of these monomer units is 60% by weight or less, and if it exceeds 60% by weight, the characteristics of the present invention will not be fully exhibited, which is not preferable. The optimum content varies depending on the type and combination of monomers used, and also varies depending on the intended use of the resin.

In the resin of the present invention, representative examples of other copolymerizable monomers used if desired include alkyl groups such as methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, and 2-ethylhexyl acrylate. Examples include alkyl acrylates having 1 to 8 carbon atoms.

By using this alkyl acrylate having 1 to 8 carbon atoms, thermal stability and fluidity during molding can be improved, but if too much is used, the heat resistance will decrease, which is undesirable. The preferred content of the units is 20% by weight or less, and the more preferred content is 10% by weight or less.

The resin of the present invention can be produced by various commonly used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization.

Initiators used when polymerizing the resin of the present invention include:
Any initiator commonly used in radical polymerization can also be used, such as azo compounds such as azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, t-butylperoxy-2-ethylhexanoate, etc. Particularly preferred are organic peroxides. The amount used is generally 0.0 of the total amount of monomers.
It is selected within the range of 1-10 weight ratio.

As the molecular weight regulator used as necessary when polymerizing the resin of the present invention, any molecular weight regulator generally used in radical polymerization can be used, such as butyl mercaptan, octyl mercaptan, dodecyl mercaptan, thio Particularly preferred are mercaptan compounds such as 2-ethylhexyl glycolate.

There are no particular restrictions on the temperature when polymerizing the resin of the present invention, but it is usually 0 to 150°C, preferably 50 to 120°C.
Selected in the range of °C. The optimum polymerization temperature is determined in consideration of the polymerization method, polymerization equipment, polymerization initiator, molecular weight regulator, characteristics of the resulting resin, etc.

The weight average molecular weight of the resin of the present invention is not particularly limited, and is determined as necessary. When obtaining a molded article by direct polymerization, such as cast polymerization, in order to obtain a resin with high strength, a resin with a relatively high weight average molecular weight, such as 1 x 10P or more, is often preferred. When obtaining a molding material that requires melt molding, lX103 is usually used.
-IX107, and in order to obtain good moldability, a resin having a weight average molecular weight of IXl 0' - I
Preferred are resins with a weight average molecular weight of . In addition, the weight average molecular weight is determined by GPC (
It was measured by Kölpermeation chromatography).

The resin of the present invention includes random copolymers, block copolymers,
It may be any copolymer of graft copolymers,
It is not particularly limited to the form of copolymerization.

The resin of the present invention may be used in combination with other resins such as methyl metaflurate resin within the range that exhibits its characteristics such as excellent transparency, moldability, low birefringence, thermal stability, low moisture absorption, and high heat resistance. The present invention also includes a methacrylic resin composition containing the methacrylic resin described in the claims of the present invention as part of its composition.

If the resin of the present invention contains a large amount of residual monomer, the high heat stability, etc., as well as the high heat resistance, which is one of the characteristics of the resin of the present invention, will be impaired. The content of residual monomers is preferably 5% by weight or less, more preferably 2% by weight or less, and most preferably 1% by weight or less. The resin of the present invention can be polymerized under commonly used polymerization conditions to have a sufficiently low residual monomer content for practical use. It is preferable to apply a method for removing residual monomers. Generally known methods for removing residual monomers include a method in which the resin is heated under an air flow, a method in which the resin is heated under reduced pressure, and a method in which the resin is vent-extruded under reduced pressure using a vented extruder.

Various properties of the resin can be improved by adding generally known additives to the resin of the present invention within a range that does not significantly impair its excellent characteristics. for example,
Added various antioxidants, heat stabilizers, ultraviolet absorbers, metal sequestering agents, lubricants, mold release agents, plasticizers, impact resistance improvers, antistatic agents, flame release agents, antifogging agents, dyes and pigments, etc. You can also.

There are no particular restrictions on the product form of the resin of the present invention, and it may be a molded product obtained directly by polymerization such as cast polymerization or cast polymerization, or it may be a solution convenient for obtaining a thin film. It may be in the form of granules, which are convenient for melt molding, or it may be in the form of powder.

Effects of the Invention The methacrylic resin of the present invention has excellent transparency, moldability, low birefringence, and thermal stability, which are characteristics of methyl methacrylate resin, and also has hygroscopicity, which is a drawback of methyl methacrylate resin. It is a new resin with significantly improved heat resistance.

Because the methacrylic resin has such excellent characteristics, it can be used for various purposes, especially optical information recording discs, optical information recording cards, optical information recording sheets, optical Optical information recording elements such as information recording films, optical elements such as lenses, mirrors, prisms, optical transmission fibers, and optical waveguides, signboards, displays, partitions, lighting windows, television front panels, liquid crystal display front panels, etc. Translucent plates are suitable for applications that function by transmitting light.

EXAMPLES Next, the present invention will be explained in more detail by examples.
The present invention is not limited in any way by this example.

The names of the monomer abbreviations listed in Tables 1 and 2 are as follows.

p-t-BCHMA=・methacrylic acid p-tert-
Buti fi'/Chlohexyl MMA...Methyl methacrylate IBA--
... Isobutyl acrylate CHMA ... Cyclohexyl methacrylate ST ... Styrene IBOMA ... Isobornyl methacrylate MA ...
...Methyl acrylate R1A...Ethyl acrylate Physical properties were measured according to the test method shown below.

(1) A sample was dissolved in acetone containing the residual monomer n-butanol as an internal standard substance, and quantified by heating temperature chromatography. The unit is (% by weight).

(2) MI AS'['M-D1238, Condition 1 (230°C, 3.
soog). The unit is [9/10 minutes]
It is.

(6) Thermal stability MI measurement Using the same equipment, the resin was allowed to stay at 280°C for 16 minutes with only the load of the extrusion rod, then extruded with an additional load, and judged by the appearance of the extruded strand. .

17-Q7 Good: Colorless, transparent, non-foamed strand Defective: Two colored foamed strands 0) Tensile strength Measured based on ASTM-D638. The test piece is 96
After annealing at .degree. C. for 2 hours, conditions were adjusted and measurements were taken. The unit is (#/d).

(5) HDT Measured based on ASTM-D648. The test piece is 96
Measurement was performed after annealing at ℃ for 2 hours. The unit is ('C).

(6) Equilibrium water absorption rate Measured at 26°C based on ASTM-D570.

The unit is [% by weight].

(7) Birefringence A flat plate obtained by injection molding was placed between two orthogonal polarizing plates, and a photograph was taken using transmitted light.

Small: Only a small area near the gate is white Medium: The entire area of the plate is white Large: The entire area of the plate is white (8) Total light transmittance Measured based on ASTM-D1005. Units(〕
It is.

Example 1 Contents: 10I! In a separable glass flask, add 5 liters of water.
/, 50 g of potassium polyacrylate and 1.5 g of disodium hydrogen phosphate were added and stirred at 30-35°C to form an aqueous phase. Meanwhile, in another glass container, 400 J of p-tert-butylcyclohexyl methacrylate, 1,560 J of methyl methacrylate, 40 J of isobutyl acrylate,
g, 6 g of azobisisobutyronitrile, and 6 g of n-octylmercaptan were added and stirred to form a monomer phase.

This monomer phase was added to the aqueous phase, stirred, and suspended. After replacing the air in the separable flask with nitrogen, polymerization was carried out by keeping the monomer phase at a temperature of 75°C for 2 hours without stirring. Ta. In order to further complete the reaction, the temperature was raised to 95°C and kept at this temperature for 2 hours. The mixture was then cooled to room temperature, and the contents were filtered, washed, and dried to obtain a colorless, free-flowing bead-like polymer. The obtained bead-like polymer was heated at 230°C using a vented twin-screw extruder with a screw diameter of 60mm and a vent vacuum degree of 760mm.
Granular resin (pellets) were obtained by extruding into strands at 11 MRg or more and cutting. The obtained pellets were molded into 2 pieces using a 3oz screw injection molding machine.
Test pieces were obtained by injection molding at 30°C. Table 1 shows the results of measuring the physical properties of the obtained bead-shaped polymer, pellets, and test pieces.

Injection molding was also carried out at 280°C, and a good colorless and transparent molded piece was obtained.

Examples 2-5 p-tert-butylcyclohexyl methacrylate,
Total amount of methyl methacrylate and isobutyl acrylate2. For ODD fi, methacrylic acid p-ter
Bead-shaped polymers, pellets, and test pieces were obtained in the same manner as in Example 1, except that the composition of t-butylcyclohexyl and methyl methacrylate was changed and the amount of n-octyl mercaptan added. was measured. The results obtained are shown in Table 1.

Comparative Examples 1 to 4 Beads were prepared in the same manner as in Example 4, except that p-tert-butylcyclohexyl methacrylate was replaced with methyl methacrylate, cyclohexyl methacrylate, styrene, and isobornyl methacrylate, respectively. A polymer, pellets, and test pieces were obtained, and their physical properties were measured. The results obtained are shown in Table 1.

Comparative Example 5 Beads obtained in the same manner as Comparative Example 4 were immersed in 4 times the amount of methanol, heated at a temperature of 50°C or less for 2 hours while stirring, and then filtered to remove residual monomers. After repeating the extraction and removal operation three times, it was dried at 70°C for 48 hours.

The obtained dried beads were pelletized in the same manner as in Example 1 to obtain a test piece, and the physical properties were measured. The obtained results are the first
Shown in the table.

Examples 6-10 p-tert-butylcyclohexyl methacrylate,
Total amount of methyl methacrylate and isobutyl acrylate 2
,00011, the composition of methyl methacrylate and isobutyl acrylate was changed (Example 6),
Using methyl acrylate (Example 7) or ethyl acrylate (Example 9) instead of isobutyl acrylate, using methyl acrylate or ethyl acrylate instead of isobutyl acrylate, and using methyl methacrylate and these acrylates. Changing the composition of the alkyl acid (Example day,
Example 10) A bead-shaped polymer, a pellet, and a test piece were obtained in the same manner as in Example 1, and their physical properties were measured.

The results obtained are shown in Table 2.

Example 11

Claims (1)

[Scope of Claims] 1. A methacrylic resin comprising a copolymer of (A) 5 to 95% by weight of p-tert-butylcyclohexyl methacrylate units and (B) 95 to 5% by weight of methyl methacrylate units. 2 (A) p-tert-butylcyclohexyl methacrylate units and (B) methyl methacrylate units in a ratio of 5:95 to 95:5 on a weight basis, and further contains (C
) A methacrylic resin comprising a copolymer containing other monomer units copolymerizable with the above monomer in a proportion not exceeding 30% by weight.