JPH08302145A - Methacrylic resin composition and optical part produced therefrom - Google Patents

Abstract

PURPOSE: To obtain a methacrylic resin compsn. which is moldable at relatively low temps., has a good releasability, and is suitable for molded optical items by compounding a specific methacrylic resin with a higher fatty acid and a higher aliph. alcohol. CONSTITUTION: This compsn. comprises 100 pts.wt. methacrylic resin which is obtd. by subjecting a monomer mixture comprising 85-99.5wt.% methyl methacrylate and 0.5-15wt.% alkyl acrylate having a 1-8C alkyl group to bulk or soln. polymn. continuously at 100 deg.C or higher and has a reduced viscosity of 30-90ml/g in chloroform at 25 deg.C, 0.01-0.2 pt.wt. 8-22C fatty acid, and 0.01-0.5 pt.wt. 8-22C aliph. alcohol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methacrylic resin composition having extremely excellent mold release performance, and more specifically, because of its excellent mold releasability during molding, the molded product has cracks, chips or surface defects. The present invention relates to a methacrylic resin composition capable of forming a product that is less likely to have a poor appearance and that is less likely to be colored at a relatively low temperature and is less likely to be colored due to heat deterioration of the resin or to be mixed with a foreign substance.

[0002]

BACKGROUND OF THE INVENTION Since methacrylic resins are excellent in transparency, weather resistance, surface hardness, etc., they are widely used in outdoor applications such as exterior parts for automobiles and exterior products. Further, the methacrylic resin has a light transmittance in the visible light region which is equal to or better than that of glass, and the birefringence after molding is smaller than other transparent resins such as polystyrene, and is optically excellent. It is one of the plastics. Therefore, methacrylic resin has been used as various optical molding materials, and its application as optical plastic lenses and optical discs has been promoted.

In the field of these optical parts, an injection molding method is usually used, but it is necessary to transfer an optical disk, which requires accurate transfer of the signal surface of a stamper, or a precise lenticular or Fresnel lens pattern. In order to mold thin and precise optical parts such as projection television screens, it is necessary to improve the moldability and fluidity of methacrylic resin. For this purpose, a method such as reducing the molecular weight of the resin or copolymerizing a comonomer having an internal plasticizing effect is generally used.
However, the acrylic resin whose molecular weight is simply lowered to improve the fluidity is inferior in mechanical strength, while the methacrylic resin whose fluidity is improved simply by increasing the copolymerization rate of the comonomer has low heat resistance of the resin. For example, there is a problem that it is difficult to use for applications requiring heat resistance, such as a light guide plate incorporated in an in-vehicle liquid crystal panel.

Methacrylic resin is said to have a relatively strong adhesion to metals and is brittle, so cracks, cracks or surface roughness of the molded product resulting from defective release from the mold during injection molding. There is a problem that such defects are likely to occur. Also, in the molding of optical parts,
In order to suppress deterioration of color tone due to heat deterioration of resin and generation / mixing of burnt dust, it is required to perform molding at the lowest possible temperature, but in low temperature molding, the injection pressure increases, so Among them, there is a problem that a region where it is difficult to release the mold easily occurs locally. Further, if the molecular weight is lowered in order to improve the moldability of the resin in order to cope with low temperature molding, the mechanical strength is lowered, so that there is also a problem that cracks are likely to occur at the portion hitting the ejection pin at the time of mold release. That is, for example, it can be said that the need for improved releasability has emerged in an extremely sharp manner in the production of parts for optical applications in which precise thin-walled molded articles such as optical discs are injection molded at the lowest temperature possible. is there.

As a technique for improving the releasability of the acrylic resin, for example, at least one kind of ester of polyhydric alcohol and fatty acid, monovalent alkyl alcohol, fatty acid, fatty acid amide and fatty acid metal salt is added. Method (JP-A-6
No. 1-73754), a method of adding a glycerin higher fatty acid ester and a saturated aliphatic alcohol (Japanese Patent Laid-Open No. 1-31754).
No. 294763), stearic acid glyceride, behenic acid glyceride, and a method of adding at least one kind of fatty acid alkyl ester (JP-A-2-115255).
JP-A-4-53), a method in which the carbon number distribution of the alkyl group of the glycerin higher fatty acid ester is set to a specific ratio (JP-A-4-53).
No. 860, JP-A-4-253752) and the like are known, but the resin compositions disclosed therein have insufficient fluidity or low heat resistance as a resin for optical components. Was insufficient in terms of.

[0006]

As described above, a precision thin-walled molded product is injection-molded at a relatively low temperature in order to avoid thermal deterioration of the resin, and cracks, cracks and poor appearance due to insufficient releasability are prevented. No methacrylic resin has been found that can be suitably used in optical parts such as optical discs, light guide plates for liquid crystal panels, and screens for projection televisions, which are required. Here, the required resin properties are good mechanical strength, heat resistance, fluidity that enables thin-wall molding at low temperatures, and good mold release properties.

[0007]

[Means for Solving the Problem] The present inventors have found that the acrylic resin is easily adhered to a metal and is brittle, which causes a problem in molding such as cracking, cracking, and poor appearance. For the purpose of fundamentally solving the problem, we have conducted intensive research. As a result, they have found that, by adding an appropriate amount of a specific compound to a specific methacrylic resin, a particularly remarkable effect on releasability can be obtained, and the present invention has been completed.

That is, according to the present invention, 85 to 99.5% by weight of methyl methacrylate and the number of carbon atoms of the alkyl group are 1.
Obtained by continuously bulk-polymerizing or solution-polymerizing a monomer mixture consisting of 0.5 to 15% by weight of an alkyl acrylate of 8 to 15 at a temperature of 100 ° C. or higher, and
The reduced viscosity measured at 25 ° C in chloroform is 30-9.
100 parts by weight of 0 ml / g methacrylic resin, 0.01 to 0.2 parts by weight of a fatty acid having 8 to 22 carbon atoms, and 0.01 to 0.5 of an aliphatic alcohol having 8 to 22 carbon atoms.
And a methacrylic resin composition comprising 1 part by weight, an optical disc formed by molding the same, a light guide plate for a liquid crystal panel,
The present invention relates to optical parts such as a screen for a projection television.

The methacrylic resin according to the present invention comprises a methyl methacrylate unit of 85 to 99.5% by weight and an alkyl acrylate unit of 0. 9 having an alkyl group having 1 to 8 carbon atoms.
5 to 15% by weight, preferably 1.0 to 12% by weight of alkyl acrylate units. The ratio of alkyl acrylate units in the copolymer is 1
If it exceeds 5% by weight, the heat resistance of the composition decreases, and if it is less than 0.5% by weight, thermal decomposition is large and molding defects such as silver striations are likely to occur in injection molded products. It is not preferable as a resin for use. The number of carbon atoms in the alkyl group is 1
As the alkyl acrylate having 8 to 8, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate and the like are preferable, and methyl acrylate and ethyl acrylate are particularly preferable.

The methacrylic resin in the present invention has a reduced viscosity of 30 to 90 ml measured at 25 ° C. in chloroform.
/ G, preferably 30 to 60 ml / g, 35 to 5
A range of 8 ml / g is particularly preferred. Reduced viscosity is 30m
If it is less than 1 / g, the mechanical strength of the composition is poor, while 90 m
If it exceeds 1 / g, the molding processability tends to deteriorate and the birefringence tends to increase, either of which is not preferable as a resin for molding optical parts.

It is known that high resolution H ¹ -NMR can be used to evaluate the stereoregularity of polymethylmethacrylate. That is, the absorption of the α-methyl group splits into three, and in order from the low magnetic field side, the triad of polymethylmethacrylate has isotactic (I), heterotact (H), and syndiotact (S) structures. Attributed (Polymer Experimental Science, Vol. 18, "Magnetic Resonance of Polymers", No. 25
0-252 pages, Kyoritsu Publishing Co., Ltd., 1975
Year. ). In addition, from the intensity ratio of H ¹ absorption of α-methyl group belonging to isotact (I), heterotact (H), and syndiotact (S) structure, the triad structure (I, H, S of polymethylmethacrylate) was obtained. ) Has been attempted to be quantified. In the present invention, 400
Using H ¹ -NMR of MHz, I, H of α-methyl group,
And the three absorption peaks assigned to the S structure,
The δ values are 1.15 to 1.13 ppm and 0.93 to, respectively.
The areas were compared using 1.10 ppm and 0.72 to 0.93 ppm as baselines, and the S / H area ratio was used as an index of the stereoregularity of the methacrylic resin.

The methacrylic resin in the present invention is H ^1-
By the stereoregularity evaluation method using NMR, regarding the polymethylmethacrylate chain, the H ¹ intensity (S) of the α-methyl group derived from the syndiotactic chain / the α-methyl group derived from the heterotactic chain is determined. It is a methacrylic resin in which the ratio of H ¹ strength (H) is S / H = 1.1 to 1.5. Here, when S / H exceeds 1.5, the fluidity of the methacrylic resin is slightly reduced, and S / H
When H is less than 1.1, the heat resistance of the methacrylic resin is slightly lowered, and thus both are not preferable. Although the reason why the physical properties of the methacrylic resin are affected by the S / H, which is an index of stereoregularity, is unknown, as the proportion of syndiotactic chains increases, the polymer skeleton has a stretched configuration. It is said that there is a tendency for it to become easier, and for this reason it is presumed that the heat resistance will increase slightly while the fluidity will decrease slightly. A methacrylic resin having an S / H ratio of 1.1 to 1.5 generally has a polymerization temperature of 100 to 1
It is obtained by carrying out radical polymerization in the range of 80 ° C.

The method for producing the methacrylic resin of the present invention is not particularly limited and may be carried out by a radical polymerization method which is usually carried out industrially. It is preferable to avoid as much as possible, and from this viewpoint, it is preferable to use the bulk polymerization method or the solution polymerization method without using a suspending agent or an emulsifier. In particular, a continuous bulk polymerization method or a continuous solution polymerization method, in which a polymer alone or a solution consisting of a polymer, a monomer, and a solvent is continuously extracted while continuously feeding a monomer mixture to a reactor, is suitable. is there.
Here, when a solvent is used at the time of polymerization, a chemically stable substance should be selected so as not to impair the color tone, weather resistance and light resistance of the methacrylic resin produced. From this point of view, examples of the solvent include toluene, ethylbenzene, cyclohexane, cyclohexanone, and butyl acetate.
These can be used alone or in combination of two or more.

In the production of the methacrylic resin of the present invention,
The polymerization temperature is 100 ° C. or higher, preferably 110 ° C. or higher. When a methacrylic resin is produced at a high polymerization rate by a continuous bulk polymerization method or a continuous solution polymerization method, the polymer alone or a solution consisting of the polymer, a monomer and a solvent has a high viscosity, so that the reaction temperature is 100. When the temperature is lower than 0 ° C, it becomes difficult to continuously discharge from the reactor, which is not preferable.

As the polymerization initiator used for producing the methacrylic resin of the present invention, any polymerization initiator generally used in radical polymerization can be used. For example, an azo compound such as azobisisobutyronitrile, a peroxide such as di-t-butyl peroxide, or the like can be used, and particularly when the bulk polymerization method or the solution polymerization method is performed at a high temperature of 100 ° C. or higher. Is preferably an azo compound or peroxide having a 10-hour half-life temperature of 80 ° C. or higher and soluble in a monomer mixture or a solvent, for example, 1,1-bis (t-butylperoxy) 3,3. 5-trimethylcyclohexane, cyclohexanone peroxide, 2,5-dimethyl-
2,5-di (benzoylperoxy) hexane, 1,1
-Azobis (1-cyclohexanecarbonitrile), 2
Examples thereof include- (carbamoylazo) isobutyronitrile. These initiators are used in the range of 0.005 to 1% by weight based on the monomer mixture.

In the production of the methacrylic resin of the present invention, a chain transfer agent generally used in radical polymerization can be used for controlling the molecular weight. As the chain transfer agent, for example, mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, and 2-ethylhexyl thioglycolate are preferably used. These chain transfer agents are preferably used by adding them to the monomer mixture in chloroform of the methacrylic resin of the present invention at a concentration such that the reduced viscosity at 25 ° C. is in the range of 30 to 90 ml / g.

The methacrylic resin composition of the present invention comprises 100 parts by weight of the above methacrylic resin, 0.01 to 0.2 parts by weight of a fatty acid having 8 to 22 carbon atoms, and 8 to 2 carbon atoms.
2 of 0.01 to 0.5 parts by weight of aliphatic alcohol.

In the studies conducted by the present inventors, the reduced viscosity measured at 25 ° C. in chloroform was 30-60.
For relatively well-flowing methacrylic resin of ml / g,
It has been found that the combination of lauric acid and stearyl alcohol has a marked effect. The detailed reason for this is unknown, but the molding temperature of methacrylic resin with good flow is generally low, the temperature of the resin injected into the mold is also low, and the solidification temperature of the release agent itself and methacrylic resin It is presumed that the difference in compatibility greatly affects the release performance, and that a combination of specific release agents is particularly effective.

The fatty acids having 8 to 22 carbon atoms in the present invention include caprylic acid (n-octanoic acid), capric acid (n-decanoic acid), lauric acid, myristic acid (n-tetradecanoic acid), palmitic acid ( (n-hexadecanoic acid), stearic acid, behenic acid and the like, preferably lauric acid, myristic acid, palmitic acid and stearic acid are used, and more preferably lauric acid. These fatty acids may be used alone or in combination of two or more kinds. Here, since the fatty acid having less than 8 carbon atoms has a low boiling point, when it is added to a methacrylic resin having a relatively high molding temperature, the loss due to volatilization is large and it is not suitable. Further, a fatty acid having more than 22 carbon atoms has a high melting point and is inferior in dispersibility in a methacrylic resin, so that it is difficult to exert a releasing effect, which is not preferable. In addition, industrially available unsaturated higher fatty acids include oleic acid and linoleic acid, and these unsaturated fatty acids can be used in the methacrylic resin composition of the present invention if attention is paid to air oxidation.

The methacrylic resin composition of the present invention contains 0.01 to 0.2 part by weight of a fatty acid having 8 to 22 carbon atoms with respect to 100 parts by weight of the methacrylic resin. When the content is less than 0.01 part by weight, the mold releasing performance of the methacrylic resin composition is insufficient, while when it exceeds 0.2 part by weight, the fatty acid partially adhered to the mold causes the mold surface. May be corroded, which is not preferable.

Examples of the aliphatic alcohol having 8 to 22 carbon atoms in the present invention include n-octyl alcohol, caprin alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, lauryl alcohol,
Myristyl alcohol, cetyl alcohol, and stearyl alcohol are preferable, and stearyl alcohol is more preferable. These aliphatic alcohols may be used alone or in combination of two or more kinds. Here, since the saturated aliphatic alcohol having less than 8 carbon atoms has a low boiling point, when it is added to a methacrylic resin having a relatively high molding temperature, loss due to volatilization is large and it is not suitable. Further, an aliphatic alcohol having more than 22 carbon atoms has a high melting point and is inferior in dispersibility in a methacrylic resin, so that it is difficult to exert a releasing effect, which is not preferable.

The methacrylic resin composition of the present invention contains 0.01 to 0.5 part by weight of an aliphatic alcohol having 8 to 22 carbon atoms with respect to 100 parts by weight of the methacrylic resin. If the content is less than 0.01 parts by weight, the release performance of the methacrylic resin composition will be insufficient, while if it exceeds 0.5 parts by weight, the molded product will be formed by the aliphatic alcohol attached to the mold. Defects such as fogging on the surface are likely to occur, which is not preferable. The methacrylic resin composition of the present invention may include 0.02 to 0.5 part by weight of glycerin higher fatty acid monoester represented by the following general formula (1) with respect to 100 parts by weight of the methacrylic resin.

[0023]

Embedded image

The glycerin higher fatty acid monoester used in the present invention includes glycerin monolaurate, glycerin monomyristate, glycerin monopalmitate,
Glycerin monostearate, glycerin monobehene
And the like. These can be used alone or as a mixture of two or more kinds. Among these,
R ₁ in the general formula (1) is an alkyl group having 7 to 21 carbon atoms, and the ratio of the alkyl group having 17 carbon atoms is 80.
A high-purity glycerin monostearate of ˜99% is preferable because it is particularly excellent in the releasing effect. It is not clear why the releasability improving effect is remarkable when the ratio of the alkyl group having 17 carbon atoms is 80 to 99%, but by changing the carbon number of the alkyl group in the glycerin higher fatty acid monoester, It is presumed that this is due to a change in compatibility with the methacrylic resin. Incidentally, industrially produced glycerin higher fatty acid monoesters may contain diesters and triesters as impurities by several%, but if the amount is in this range, the effect of the present invention is not impaired. There is no.

Even if the glycerin higher fatty acid monoester is contained in an amount of more than 0.5 parts by weight, based on 100 parts by weight of the methacrylic resin composition of the present invention, no further remarkable improvement effect is observed with respect to releasability. However, it is not preferable because it is not costly. Further, if added in a too large amount, the heat resistance of the composition is lowered, and a part of the composition is deposited on the surface of the mold during processing and causes a surface defect of the molded product, so that a good molded product cannot be obtained, which is preferable. Absent.

Further, it is permissible to use a conventional releasing agent other than the fatty acid, the aliphatic alcohol, and the glycerin higher fatty acid monoester within the range that does not impair the effects of the present invention. For example, paraffin wax having 12 to 60 carbon atoms, butyl laurate, butyl stearate, octyl palmitate, octyl stearate, lauryl laurate, stearyl stearate, behenyl behenate, neopentyl polyol fatty acid ester,
Although montan wax and the like can be mentioned, it is likely to affect the color tone, heat resistance and the like of optical parts, so caution must be taken when adding them. The content of these usual lubricants and releasing agents is preferably 0.5 parts by weight or less with respect to 100 parts by weight of the methacrylic resin.

The method for producing the methacrylic resin composition of the present invention is not particularly limited, and a known method can be adopted. For example, a method of preliminarily dissolving a fatty acid and an aliphatic alcohol in a monomer mixture at the time of producing a methacrylic resin and polymerizing the mixture, a molten state, a bead-shaped or a pellet-shaped methacrylic resin with a fatty acid and an aliphatic alcohol mixer, etc. It is possible to cite, for example, a method of mixing at a desired ratio and kneading and pelletizing using an extruder. In addition, an ultraviolet absorber, an antioxidant, a light diffusing agent, a dye, a pigment or the like may be added as necessary within the range of not impairing the effects of the present invention.

The matacryl resin composition of the present invention is capable of injection-molding a precision thin-walled molded article at a relatively low temperature where thermal deterioration of the resin can be avoided, and cracks, cracks, and poor appearance due to insufficient releasability. Optical disc,
It can be suitably used for optical parts such as light guide plates for liquid crystal panels and screens for projection televisions.

[0029]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The measurements in Examples and Comparative Examples were carried out using the method described below or a measuring instrument.

(1) Composition Analysis of Methacrylic Resin A dichloromethane solution of a polymer is cast on a platinum boat.
Dry and pyrolyze in a nitrogen stream (PYR-2A made by Shimadzu)
It was decomposed at 450 ° C. inside and the monomer component produced by depolymerization was immediately introduced into a gas chromatography column and analyzed. The results were obtained by quantitative calculation using the analysis result of the polymer of known composition obtained by bulk polymerization as a standard.

(2) Analysis of stereoregularity of methacrylic resin Using a deuterated chloroform solution of a polymer sample,
The JEOL Ltd. GX-400 type NMR, give H ¹ -NMR spectra integration number 64 times. Heterotakuto (H) and from syndiotactic (S) area ratio of an H ¹ absorption of α- methyl group belonging to the structure, with respect to polymethyl methacrylate chains, H ¹ of α- methyl group derived from the syndiotactic chain The ratio of strength (S) / H ¹ strength (H) of α-methyl group derived from a heterotactic chain was determined.

(3) Reduced viscosity 0.15 g of the sample was dissolved in 50 ml of chloroform and
Measured with an Ostwald viscometer at ° C.

(4) Quantification of additive in methacrylic resin composition When a certain amount of the resin composition is dissolved in dichloromethane containing an internal standard substance and glycerin higher fatty acid monoester is used in combination, BSA (bis The glycerin ester was silylated by treatment with trimethylsilylacetamide), and then each component was quantified and analyzed by a gas chromatography method.

(5) Melt flow rate (MFR) It was carried out based on JIS K7219.

(6) Releasability evaluation Using a FANUC injection molding machine T-100D, cylinder temperature 250 ° C., mold temperature 80 ° C., maximum injection pressure 67
A flat plate as shown in FIG. 1 was formed under the condition of MPa, and those having cracks, cracks and surface roughness were regarded as defective products. The number of samples is 20 in order to keep the injection molding conditions constant.
After shot-discarding, 100 shots were molded and evaluated. In the molding, the pellets were dried and the moisture content was 0.06% by weight or less.

(7) Evaluation of Mold Surface Fogging After the evaluation of (6) was carried out on each sample, the mold surface was visually observed for the cloudiness, and the degree of the haze was evaluated, and the results are shown in the following ranks. . ○: No cloudiness. Δ: There is some cloudiness. X: Remarkably cloudy.

(8) Evaluation of color tone of light guide plate The yellowness in the thickness direction of the obtained flat plate was measured by Nippon Denshoku Industries Co., Ltd.
Using a color difference meter (TC-1500MC type) manufactured by Mfg. Co., Ltd., the yellow degree (ΔYI) based on air was evaluated.

(9) Evaluation of heat resistance It was measured based on ASTM D-648 and shown as data with annealing. The abbreviations used in Examples and Comparative Examples represent the following compounds. MMA; methyl methacrylate MA; methyl acrylate LPO; lauroyl peroxide DBPMS; 1,1-di-t-butylperoxy-3,
3,5-Trimethylcyclohexane n-OM; n-octyl mercaptan EB; Ethylbenzene Unless otherwise specified, the following% and parts represent% by weight and parts by weight, respectively.

Example 1 A monomer mixture consisting of 81% by weight of MMA, 9% by weight of MA, and 10% by weight of EB,
DBPMS 150ppm and n-OM 2500ppm
Was added and mixed homogeneously. This solution was continuously supplied to a closed pressure-resistant reactor having an internal volume of 10 liters, polymerized with stirring at an average temperature of 150 ° C. and an average residence time of 2 hours, and then continuously sent to a storage tank connected to the reactor. Then, the volatile matter was removed under reduced pressure, and further transferred to the extruder in a molten state. Here, lauric acid and stearyl alcohol were quantitatively supplied in a molten state at 90 ° C. from an additive port connected to an extruder to obtain a methacrylic resin composition in the form of pellets. The reduced viscosity of this methacrylic resin (A) is
It was 44 ml / g. In addition, the composition of the methacrylic resin (A) was analyzed by a pyrolysis gas chromatography method.
The result of unit / MA unit = 90/10 (weight ratio) was obtained.
The methacrylic resin (A) was subjected to H ¹ -NMR analysis, and the S / H ratio was determined to be 1.27. Further, when lauric acid and stearyl alcohol in the resin composition were quantified, it was 0.0 per 100 parts by weight of the resin composition.
Results of 3 and 0.1 parts by weight were obtained.

The resin composition obtained was molded and evaluated. The results are shown in Table 1. Further, when using this methacrylic resin composition, 500 sheets of 300 mmφ optical disk substrates were molded at 260 ° C. by an IS100EN type injection molding machine manufactured by Toshiba Machine Co., Ltd. No mold release defect occurred.

Example 2 The procedure of Example 1 was repeated, except that the methacrylic resin composition contained 0.1 part by weight of glycerin monostearate in addition to lauric acid and stearyl alcohol. The results are shown in Table 1.

Example 3 The procedure of Example 1 was repeated except that the methacrylic resin composition contained 0.1 part by weight of lauryl laurate in addition to lauric acid and stearyl alcohol. The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that pellets were obtained without adding any additive to the methacrylic resin (A). When the releasability of the obtained resin composition was evaluated, many releasability defects of up to 63 occurred. Fogging on the surface of the mold did not occur. The results are summarized in Table 2.

Comparative Example 2 The procedure of Example 1 was repeated, except that only 0.1 part by weight of stearyl alcohol was added to the methacrylic resin (A) to obtain pellets. When the releasability of the obtained resin composition was evaluated, 22 releasability defects occurred. Fogging on the surface of the mold did not occur. The results are summarized in Table 2.

(Comparative Example 3) Except that the amount of lauric acid added during the preparation of the methacrylic resin composition was 1 part by weight,
It carried out similarly to Example 1. A predetermined test piece was prepared from the obtained pellets by injection molding. The defect occurrence rate was 0%, which was extremely good, but ΔYI was 4.5.
It was a little big. The results are summarized in Table 2.

Comparative Example 4 The procedure of Example 1 was repeated, except that the amount of stearyl alcohol added during the preparation of the methacrylic resin composition was 1 part by weight. A predetermined test piece was prepared from the obtained pellets by injection molding. The defect occurrence rate was 0%, which was extremely good.
YI was 3.6, which was rather large. In addition, cloudiness occurred on the surface of the mold after the molding test. The results are summarized in Table 2.

Example 4 In the production of methacrylic resin, MMA 68.6% by weight, MA 1.4% by weight, EB3
In a monomer mixture consisting of 0 wt%, DBPMS150p
It carried out like Example 1 except having performed polymerization at 135 ° C using the solution which added pm and n-OM1500ppm. The reduced viscosity of the obtained methacrylic resin (B) was 56 ml / g, and the composition analysis using a thermal decomposition gas chromatography method revealed that MMA units / MA units = 98.0 /
A result of 2.0 (weight ratio) was obtained. Further, S / H by H ¹ -NMR was 1.33. The subsequent steps were carried out in the same manner as in Example 1, and the evaluation results are summarized in Table 1.

Example 5 In the production of methacrylic resin, MMA 68.5% by weight, MA 1.5% by weight, EB3
In a monomer mixture consisting of 0 wt%, DBPMS150p
It carried out like Example 1 except having performed polymerization at 150 ° C using the solution which added pm and n-OM2200ppm. The reduced viscosity of the obtained methacrylic resin (C) was 43 ml / g, and the composition analysis using a pyrolysis gas chromatography method revealed that MMA units / MA units = 98.0 /
A result of 2.0 (weight ratio) was obtained. Further, S / H by H ¹ -NMR was 1.27. The subsequent steps were carried out in the same manner as in Example 1, and the evaluation results are summarized in Table 1.

Example 6 In the production of methacrylic resin, MMA 65.8% by weight, MA 4.2% by weight, EB3
In a monomer mixture consisting of 0 wt%, DBPMS150p
It carried out like Example 1 except having performed polymerization at 135 ° C using the solution which added pm and n-OM1600ppm. The reduced viscosity of the obtained methacrylic resin (D) was 53 ml / g, and the composition analysis using a thermal decomposition gas chromatography method revealed that MMA units / MA units = 94.2 /
A result of 5.8 (weight ratio) was obtained. Further, S / H by H ¹ -NMR was 1.33. The subsequent steps were carried out in the same manner as in Example 1, and the evaluation results are summarized in Table 1.

Example 7 In the production of methacrylic resin, MMA 82.4% by weight, ethyl acrylate 4.6.
In a monomer mixture consisting of 1 wt% and 13 wt% EB, DB
Polymerization was carried out at 150 ° C. using a solution containing 130 ppm of PMS and 1700 ppm of n-OM,
It carried out like Example 1. The reduced viscosity of the obtained methacrylic resin (E) was 52 ml / g, and the composition analysis using a pyrolysis gas chromatography method revealed that MMA units / ethyl acrylate units = 94.9 / 5.1 (weight ratio). Got the result. In addition, S / H is 1.28 due to H ¹ -NMR
Met. The subsequent steps were carried out in the same manner as in Example 1, and the evaluation results are summarized in Table 1.

Example 8 When granulating the methacrylic resin (E), stearic acid and stearyl alcohol were quantitatively fed in a molten state at 130 ° C. from an additive charging port connected to an extruder. When the amounts of stearic acid and stearyl alcohol in the resin composition were quantified, the results were 0.05 and 0.1 parts by weight, respectively, per 100 parts by weight of the resin composition. The subsequent steps were carried out in the same manner as in Example 1, and the evaluation results are summarized in Table 1.

Comparative Example 5 In a reactor equipped with a reflux condenser having an internal volume of 60 liters, 30 liters of ion-exchanged water, 150 g of tricalcium phosphate and 1.2 g of sodium lauryl sulfate were added and dispersed, and nitrogen was added while stirring. The temperature was raised to 75 ° C. in the atmosphere so that there was virtually no effect of oxygen. MMA18800g, MA1200g, 2,2'-
50 g of azobis (2,4-dimethylvaleronitrile),
Then, a monomer mixture consisting of and 14 g of n-OM was added all at once, and the mixture was kept at 70 ° C. for 3 hours for polymerization, then heated to 95 ° C. and kept for another hour to complete the polymerization. The reduced viscosity of the obtained bead-shaped methacrylic resin (F) is 1
It was 26 ml / g. GPC analysis of this resin showed that the weight average molecular weight was about 300,000.

When the composition of this methacrylic resin (F) was analyzed by the pyrolysis gas chromatography method, the result of MMA unit / MA unit = 94.0 / 6.0 (weight ratio) was obtained. H ¹ −
S / H by NMR was 1.63. When lauric acid and stearyl alcohol were kneaded and kneaded when granulating the methacrylic resin (F) with an extruder, the results were 0.04% by weight and 0.1% by weight, respectively. In order to evaluate the releasability of the obtained methacrylic resin composition, an attempt was made to mold a flat plate as shown in FIG. 1, but the fluidity was low and a good molded product could not be obtained.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

INDUSTRIAL APPLICABILITY The methacrylic composition of the present invention has excellent fluidity and extremely excellent releasability, and is injection molded at a relatively low temperature in order to prevent thermal deterioration of the resin. ,
Avoids defects such as cracks and cracks due to insufficient releasability,
It can be suitably used for molding good optical parts. In particular, it is suitable for applications that require precise molding, such as optical discs, light guide plates for liquid crystal panels, and screens for projection televisions. Further, it is also effective in reducing mold release defects when molding vehicle tail lamp lenses, meter covers and the like.

[Brief description of drawings]

FIG. 1 is a schematic view of a light guide plate molded to evaluate releasability and color tone in an example of the present invention.

Claims (4)

[Claims] 1. A monomer mixture comprising 85 to 99.5% by weight of methyl methacrylate and 0.5 to 15% by weight of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms at a temperature of 100 ° C. or higher. Obtained by bulk or solution polymerization, and in chloroform, 2
100 parts by weight of a methacrylic resin having a reduced viscosity of 30 to 90 ml / g measured at 5 ° C., 0.01 to 0.2 parts by weight of a fatty acid having 8 to 22 carbon atoms, and an aliphatic having 8 to 22 carbon atoms A methacrylic resin composition comprising 0.01 to 0.5 part by weight of alcohol. 2. Methyl methacrylate units 85-99.
5% by weight and 0.5 to 15% by weight of an alkyl acrylate unit in which the alkyl group has 1 to 8 carbon atoms,
The reduced viscosity measured at 25 ° C in chloroform is 30-9.
Methacrylic resin with 0 ml / g, 400 MH
The H ¹ intensity (S) of the α-methyl group derived from the syndiotactic chain with respect to the polymethylmethacrylate chain was evaluated by the stereoregularity evaluation method using H ¹ -NMR of z.
/ 100 parts by weight of a methacrylic resin having a H ¹ strength (H) ratio of α-methyl groups derived from a heterotactic chain of S / H = 1.1 to 1.5, and a carbon number of 8 to 22 A methacrylic resin composition comprising 0.01 to 0.2 part by weight of a fatty acid and 0.01 to 0.5 part by weight of an aliphatic alcohol having 8 to 22 carbon atoms. 3. A methacrylic resin in chloroform, 25
The reduced viscosity measured at ° C is 30 to 60 ml / g, the fatty acid is lauric acid, and the addition amount is 0.01 to 0.1.
3. The methacrylic resin composition according to claim 1, wherein the weight ratio of the stearic alcohol is 0.01 to 0.3 weight part, and the aliphatic alcohol is stearyl alcohol. 4. An optical component such as an optical disc formed by molding the methacrylic resin composition according to claim 1 or 2, a light guide plate for a liquid crystal panel, a screen for a projection television, or the like.